Oxidative Stress in Pediatric Asthma: Sources, Mechanisms, and Therapeutic Potential of Antioxidants

Abstract

Pediatric asthma is a common respiratory condition in children, characterized by a complex interplay of environmental and genetic factors. Evidence shows that the airways of stimulated asthmatic patients have increased oxidative stress, but the exact mechanisms through which this stress contributes to asthma progression are not fully understood. Oxidative stress originates from inflammatory cells in the airways, producing significant amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS). External factors such as cigarette smoke, particulate matter, and atmospheric pollutants also contribute to ROS and RNS levels. The accumulation of these reactive species disrupts the cellular redox balance, leading to heightened oxidative stress, which activates cellular signaling pathways and modulates the release of inflammatory factors, worsening asthma inflammation. Therefore, understanding the sources and impacts of oxidative stress in pediatric asthma is crucial to developing antioxidant-based treatments. This review examines the sources of oxidative stress in children with asthma, the role of oxidative stress in asthma development, and the potential of antioxidants as a therapeutic strategy for pediatric asthma.

Graphical abstract

Keywords

pediatric asthma / oxidative stress / inflammatory / antioxidant

1. Introduction

Asthma is a chronic respiratory disease characterized by recurrent coughing, shortness of breath, and chest tightness [1]. According to the Centers for Disease Control and Prevention [2], nearly 25 million asthma people in the US had asthma in 2021, including 4.6 million children under 18 years old. Studies have shown that many children with clinically well-controlled asthma still exhibit persistent bronchial hyperresponsiveness. Severe asthma in children poses a significant health burden, as it often leads to medication-related side effects and impaired quality of life [3, 4, 5]. Asthma that begins in early life and persists into school age usually continues into adulthood, affecting lung function and increasing the risk of chronic obstructive pulmonary disease [6].

The primary pathological features of asthma include airway inflammation, hyperresponsiveness (exaggerated response to exercise, air pollutants, allergens, etc., leading to airway spasms and narrowing), remodeling (thickening of the airway wall and hypertrophy of smooth muscles), and airway obstruction due to excessive mucus secretion. Asthma is diverse and challenging to categorize: It can be classified based on phenotypes (clinical observations) and endotypes (etiological observations) [7]. Research indicates that one phenotype corresponds to multiple endotypes [8]. Common phenotypes include allergen-induced asthma, non-allergic asthma, infection-exacerbated asthma, aspirin-exacerbated respiratory disease, and exercise-induced asthma [9].

The incidence of adult-onset asthma is similar to childhood asthma. However, adult-onset asthma tends to be more severe and progressive, whereas childhood asthma is generally milder and often goes into remission [10]. Both types share many common triggers, and evidence suggests that asthma results from the interaction of environmental factors with genetic and atopic predispositions. Most childhood-onset asthma cases exhibit an allergic phenotype, whereas adult-onset asthma is predominantly non-allergic [11]. Asthma during adolescence is more common in males, likely due to relatively poorer lung development in male fetuses. [12]. A study of 3622 asthma cases indicated that the rise in asthma prevalence between 1964 and 1983 was primarily driven by an increased incidence among children aged 1 to 14 years [13]. Clinical and lung function outcomes in adulthood are closely linked to the severity of childhood asthma [14], highlighting the importance of early diagnosis and treatment. Environmental factors, including mode of birth delivery, antibiotic use, exposure to tobacco smoke, and an industrialized lifestyle, significantly contribute to childhood asthma exacerbation [15]. The inflammatory phenotype of asthma differs in adults and children, with neutrophilic inflammation predominating in adults and eosinophil inflammation in children [16]. Research indicates that children with allergic sensitization showed significant lung function impairment, suggesting a crucial relationship between allergic reactions and childhood asthma. [17]. Allergy plays a key role in the early development of childhood asthma and is closely related to allergic inflammation cascade reactions [18].

Oxidative environments leading to redox imbalance are closely related to the asthma pathophysiology of asthma, causing airway constriction, hyper-reactivity, and airway remodeling [19]. Pulmonary cells produce reactive oxygen species (ROS) and reactive nitrogen species (RNS), contributing to oxidative stress. Additionally, reactive substances inhaled from the environment elevate oxidative stress, which disrupts the cellular redox balance, exacerbating inflammation and intensifying asthma symptoms in children. This article reviews the generation of oxidative stress in pediatric asthma and explores how elevated oxidative stress leads to cellular inflammation. Furthermore, it aims to promote research on the relationship between oxidative stress and pediatric asthma progression, facilitating the development of antioxidant treatments.

2. Oxidative Stress from Cellular and Environmental Sources and Its Impact on Asthma

Many studies have demonstrated that elevated oxidative stress levels exacerbate the risk of childhood asthma [20, 21, 22]. Respiratory inflammation is a major source of oxidative stress, with research indicating a significant increase in the number of inflammatory cells and the production of ROS in asthma patients compared to the control [23]. As shown in Fig. 1, oxidative stress can be categorized into endogenous and exogenous, with endogenous oxidative stress resulting from ROS and RNS [24] and exogenous oxidative stress originating from air pollutants, particulate matter, and cigarette smoke [25]. The antioxidant system in lung cells responds to increased oxidative stress to maintain redox balance. However, once this homeostasis is disrupted, excessive oxidative stress can damage biological molecules such as lipids, proteins, and DNA, impairing cellular functions [26]. Elevated oxidative stress also activates intracellular inflammatory pathways, exacerbating the release of proinflammatory cytokines and enhancing the inflammatory response [27].

In summary, increased oxidative stress impairs lung cell function and is closely associated with the development of inflammation. Lung function and pulmonary inflammation are critical to the progression of childhood asthma. Therefore, this section focuses on the production of endogenous and exogenous oxidative stress in the lungs and its impact on pediatric asthma.

2.1 Origins and Production of Reactive Oxygen and Nitrogen Species in Asthma

2.1.1 The Production of ROS

Oxidative stress arises from an imbalance between the production of ROS and the capacity of the antioxidant system. In the lungs, ROS primarily originate from inflammatory cells such as macrophages, eosinophils, and neutrophils, as well as bronchial epithelial cells, which produce dual oxidase 1 [28]. Additionally, myofibroblasts, influenced by terminal end proteins, generate ROS by increasing the expression of transforming growth factor-beta [29].

ROS includes superoxide anion, hydrogen peroxide, and hydroxyl radicals. Within cells, ROS generation is primarily derived from mitochondria. While mitochondria supply energy through the electron transport chain, they also produce a significant amount of superoxide anion. Mitochondrial superoxide anion production relies on the reduced form of nicotinamide adenine dinucleotide/ the oxidized form of nicotinamide adenine dinucleotide (NADH/NAD⁺) and the ubiquinol/ubiquinone (UQH2/UQ) isopotential pools [30]. The former involves flavin-dependent dehydrogenases that oxidize or reduce nicotinamide, generating the superoxide anion. The latter involves enzymes that oxidize mitochondrial coenzyme Q, producing superoxide anion through coenzyme Q oxidation. The mitochondrial-generated superoxide anion is unstable and interacts with NADH oxidoreductase and, to a lesser extent, with hydrogen peroxide, significantly decreasing its activity [31, 32]. To prevent sustained damage, the superoxide anion is catalyzed by superoxide dismutase (SOD) into hydrogen peroxide [33], which is then reduced to hydroxyl radicals in the presence of ferrous ions. Hydroxyl radicals are highly reactive, causing immediate oxidative damage to surrounding proteins or lipids [34]. Eosinophil peroxidase catalyzes the reaction of hydrogen peroxide with chloride, bromide, and thiocyanate to produce hypohalous acids, exacerbating tissue oxidative damage under inflammatory conditions and promoting the onset of asthma [35].

Numerous research findings link the rise in ROS with increased levels of inflammatory cells in asthma patients. For instance, Sanders et al. [36] observed a notable increase in the eosinophil count and superoxide anion production in asthmatic patients exposed to antigens. Subsequent experiments involving density gradient centrifugation confirmed that the heightened production of ROS was primarily attributed to the expanded eosinophil population, suggesting a key role of superoxide anions in airway damage associated with allergic inflammation [36]. Furthermore, 48 hours after antigen stimulation, there was a notable increase in alveolar macrophages, exacerbating superoxide anion production [37]. Asthma severity is directly associated with increased ROS. Hoshino et al. [38] reported a significant increase in inflammatory cells in the airways of asthmatic patients compared to healthy individuals, with these cells releasing a substantial amount of ROS and RNS. In mice asthma models, Human thioredoxin 1 (TRX1), a peptide with reducing properties, significantly attenuates airway hyperresponsiveness and inflammatory cell proliferation, thereby reducing pulmonary inflammation and alleviating airway remodeling [38].

2.1.2 The Production of RNS

In addition to ROS, RNS also contributes to oxidative stress in the lungs. The primary RNS generated in the lungs is nitric oxide (•NO), produced through the oxidative reaction of L-arginine to L-citrulline, involving NO synthase (NOS) [39]. There are three main types of NOS: Neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3) [40]. NOS1 and NOS3 are constitutively expressed in neurons and endothelial cells, respectively, and are activated calcium ions that bind to calmodulin [41]. NOS2 is typically induced under conditions involving cytokines and proinflammatory factors and is also calcium-dependent [42, 43]. NOS2 is expressed in lung epithelial cells of both normal individuals and asthma patients, with higher expression levels in asthma patients. Studies indicate that higher levels of peroxynitrite, a potent oxidant formed by the reaction of free NO radicals and superoxide, are detected in the airway epithelial cells of asthma patients [44, 45], suggesting a curial role for NOS2 in promoting airway epithelial cell damage. All three NOS isoforms are present in the lungs, predominantly in lung epithelial cells, endothelial cells, neurons, eosinophils, neutrophils, macrophages, and smooth muscle cells [46].

Asthma is closely related to the production of •NO in the airways, with levels of •NO in asthmatic patients exceeding those in healthy individuals [47]. This elevation is attributed to increased transcription of NOS2 in airway epithelial cells and an increase in L-arginine, the substrate for NOS [42]. •NO exists in a dynamic metabolic balance in the airways, with different metabolic products determining its role in asthma. For example, the reaction of •NO with thiols generates S-nitrosothiols, which have bronchodilatory and antibacterial effects, meaning low-dose inhaled •NO gas can be used to treat asthmatic patients [48]. However, •NO can also react with superoxide to generate cytotoxic peroxynitrite and nitrosamines and with nucleotides, proteins, and lipids, disrupting their function [49]. Upon antigen stimulation, the nitrate (NO^3-) content in the airways of asthmatic patients significantly increases, suggesting that in the early stages of asthmatic response, •NO exerts a toxic effect, forming nitrate. Subsequently, the S-nitrosothiol levels rise over time, indicating that in the later stages of asthma, •NO may mitigate its toxic effects by generating S-nitrosothiols [50].

2.2 Oxidative Stress Arising from the Environment

Direct exposure of the lungs to the external environment makes them vulnerable to oxidative substances in air pollutants, such as oxidizing gases and particulate matter. Children with incomplete lung development are particularly susceptible to lung damage from the pollutants [51].

2.2.1 Air Pollution Gases

One significant gaseous pollutant is ozone, a potent oxidant that exacerbates inflammatory responses [20]. Ozone primarily affects pulmonary tissues, and even trace amounts can worsen the symptoms of pediatric asthma patients [52, 53]. Ozone is a photochemical gaseous pollutant generated from volatile organic compounds in the presence of nitrogen oxides and sunlight [54]. It can react with nitric acid in fossil fuels, producing NO and NO₂, which, although less oxidizing than ozone, still induce mild airway inflammation [20]. Ozone can also react with unsaturated fatty acids and cell membranes in airway epithelial cells, producing lipid ozonation products (LOPs). Increasing the LOP concentration activates phosphorylated enzymes in airway epithelial cells, promoting lung inflammation [55].

Research has shown that inhaling ozone damages the lungs [52, 54]. In areas with low ozone concentrations, outdoor exposure and physical activity do not significantly increase the risk of childhood asthma. However, in regions with high ozone concentrations, prolonged outdoor exposure and physical activity significantly exacerbate the likelihood of childhood asthma, suggesting ozone has a role in promoting asthma development [56]. Ozone increases airway hyperresponsiveness and neutrophil count in allergic asthma patients, an effect worsened by allergens such as dust mites, ragweed, and Aspergillus fumigatus (DRA). This exacerbation likely results from DRA disrupting the immune response and antioxidant systems, weakening the immune response and intensifying ozone’s proinflammatory effect. Thus, ozone contributes to lung injury by disrupting the body’s antioxidant and anti-inflammatory defense systems [57].

2.2.2 Particle Matter Pollution

Particle matter (PM) pollution significantly contributes to atmospheric pollution, particularly particles with a diameter of less than 10 micrometers (PM10), which negatively impact health and increase the incidence and mortality of respiratory diseases [58]. The specific components of PM that are detrimental to health are not fully understood, but the health effects are due to various active components [59]. One important characteristic of PM is its oxidative potential, which has received increasing attention. Research by Strak et al. [60] suggests that the oxidative potential of PM2.5 (particles with a diameter less than 2.5 micrometers) is more strongly correlated with health than its mass. Common methods for characterizing the oxidative potential of PM include the macrophage-based method [61], ascorbic acid, dithiothreitol (DTT), and glutathione assays [62]. The DTT method is widely used to characterize the relationship between oxidative stress and PM-induced inflammation [63, 64]. Epidemiological analysis by Bates et al. [65] found that biomass combustion contributed to 45% of the total DTT activity during the study period, and DTT activity showed a significant link with asthma hospitalization compared to PM2.5. The study by Scott Weichenthal et al. [66] also indicated that oxidative stress correlates with lung cancer mortality more strongly than the mass concentration of PM2.5. Notably, different methods of characterizing oxidative stress show varying correlations with lung cancer mortality. Oxidative stress characterized by glutathione activity demonstrated a clear correlation, whereas that characterized by ascorbic acid activity did not [66]. The oxidative stress burden also varies with particle size; smaller PM fractions exhibit stronger ROS activity, possibly due to their higher content of transition metal ions (such as Ni, Cr, Cu) and water-soluble organic compounds involved in redox reactions [67, 68].

2.2.3 Cigarette Smoke

Cigarette smoke contains over a thousand chemical compounds, most of which are detrimental to the respiratory system. Studies show that maternal smoking exposes fetuses or newborns to nicotine, which adversely affects lung development and accelerates the genetic aging process. This makes offspring more susceptible to lung diseases and accelerates pulmonary aging [69, 70]. Nicotine binds to nicotinic acetylcholine receptors in developing beta cells, increasing intracellular ROS and causing significant mitochondrial protein and beta cell apoptosis in newborns [71]. Research on lactating mice indicates that maternal nicotine exposure reduces the expression of antioxidant enzymes such as SOD and catalase (CAT), elevates malondialdehyde (MDA) levels, and induces pulmonary interstitial inflammation [72]. Numerous studies also show a significant increase in oxidative stress after smoking [73, 74, 75]. For example, 8-isoprostane, a lipid peroxidation product, is found to be 2.2 times higher in the breath condensate of smokers compared to non-smokers [76]. Exhaled hydrogen peroxide levels increase significantly half an hour after smoking [77]. Exposure of rat tracheal segments to cigarette smoke results in noticeable epithelial cell damage, which is alleviated by superoxide dismutase. The hydrogen peroxide and superoxide anions levels in tracheal segments significantly correlate with cigarette smoke exposure [78]. Additionally, endothelial cells in smokers show activation of the pentose phosphate pathway and increased cellular glutathione secretion, indicating significant oxidative stress [79].

2.2.4 Indoor Allergens

Exposure to indoor allergens can trigger early allergic reactions in children, leading to the development of childhood asthma [80]. Early-life contact with allergens such as cat and dust mite allergens significantly increases the risk of sensitization by the age of four, with cat allergens particularly linked to persistent wheezing [81]. Study indicates that children aged 5–17 exposed to indoor allergens (e.g., dust mites, cat, and dog allergens) have a higher asthma incidence than the control group; however, the association between dog allergens and asthma is weaker than that of cat allergens [82]. Custovic et al. [83] found a significant association between cat ownership and sensitization to cats in infants, whereas dog ownership was not linked to sensitization to either cats or dogs. This suggests a difference in how allergens from various pets relate to childhood asthma.

Pet-derived allergens, such as the cat allergen Fel d 1, can provoke severe allergic reactions [84]. Fel d 1 significantly enhances the signaling of innate immune receptors Toll-like receptor 4 (TLR4) and TLR2 through interactions with the TLR4 agonist, lipopolysaccharide (LPS) [85]. Moreover, TLR4 activation is widely reported to be involved in the production of ROS, which contributes to oxidative stress and inflammation [86, 87].

3. Mechanisms of Oxidative Stress in Pediatric Asthma Pathogenesis

Oxidative stress plays a crucial role in the pathogenesis of asthma by promoting inflammation, airway remodeling, and airway hyperresponsiveness. Various environmental cytokines bind to cell membrane receptors, activating downstream signaling pathways that increase ROS and RNS, thereby facilitating inflammation. As shown in Fig. 2, this process involves the activation of transcription factor nuclear factor kappa B (NF-\kappaB), TLR signaling pathways, and disruption of endoplasmic reticulum (ER) homeostasis. Therefore, understanding these mechanisms can enhance our asthma knowledge and aid in developing antioxidant therapies.

3.1 Oxidative Stress and Activation of NF-\kappaB

Inflammatory mediators play a pivotal role in inflammation by activating inflammatory cells. Structural airway cells, such as epithelial cells, also release inflammatory mediators [88], perpetuating airway inflammation by inducing the expression of downstream genes; NF-\kappaB is a crucial transcription factor in this process [89].

Studies suggest an association between NF-\kappaB activation and increased oxidative stress [90, 91]. Li et al. [92] demonstrated that low concentrations of hydrogen peroxide activate NF-\kappaB inducing kinase (NIK), promoting NF-\kappaB activation in response to interleukin-1\beta stimulation. Higher concentrations of hydrogen peroxide, however, inhibit NIK. The effects of interleukin-1\beta are suppressed by clearing hydrogen peroxide and inhibiting Rac1 RNA, implying the involvement of Rac-dependent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in NF-\kappaB activation [92]. Similarly, Han et al. [93] found that p47-deficient mice with inhibited ROS generation exhibited upregulated NF-\kappaB activity compared to wild-type mice. This was accompanied by a significant increase in intracellular reduced glutathione/glutathione disulfide ratio and nuclear redox factor 1 (Ref-1) levels, suggesting that NADPH oxidase modulates NF-\kappaB activity by regulating intracellular redox levels. Treatment with hydrogen peroxide and a Ref-1 inhibitor suppressed NF-\kappaB activation in these mice, indicating that elevated oxidative stress can inhibit NF-\kappaB activation [93]. Schreck et al. [94] reported that ROS promotes the release of NF-\kappaB inhibitor I\kappaB, thereby suppressing NF-\kappaB activation. Increased oxidative stress disrupts thiols in the nuclear binding subunit of NF-\kappaB [95], preventing it from binding to nuclear DNA [96]. These studies suggest that while the NF-\kappaB pathway plays a role in early ROS-induced inflammation, the oxidative environment inhibits it at later stages, indicating a complex relationship between oxidative stress and NF-\kappaB-induced inflammation. Further investigation is needed to understand this dynamic fully.

3.2 Oxidative Stress-Activated TLR Pathways

Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen-associated and damage-associated molecular patterns, activating immune cells and proinflammatory cytokines [97]. Ten TLR family members (TLR1-10) have been identified in humans, [98] each playing various roles in the development of childhood asthma.

Studies in mice models show that low-dose treatment with TLR agonists increases neutrophils, while high TLR7 and TLR9 doses significantly reduce eosinophil levels. Conversely, TLR2 and TLR4 agonists increase airway eosinophils and release inflammatory cytokines [99]. TLR2 and TLR4 activation are closely related to ROS and RNS [100, 101]. For instance, interleukin 6 (IL-6) expression and airway hyperresponsiveness induced by ozone are suppressed in mice lacking TLR2 or TLR4 genes [87], indicating their role in promoting inflammation.

In the lung epithelium, TLR4-mediated inflammatory responses prevail over TLR2. Allergens activate TLR4 on epithelial cells, catalyzing inflammation [102]. Elevated TLR4 expression is observed in mice exposed to ozone and ozone-sensitive mice [103]. Activated TLR4 stimulates ROS production via the MyD88-B4 receptor 2 (BLT2) pathway and NADPH oxidase 1, activating NF-\kappaB and promoting IL-13 production [104]. Singh et al. [105] found that MyD88 knockout mice do not exhibit calcium/calmodulin-dependent protein kinase II (CaMKII) oxidation. In contrast, wild-type mice show TLR4-dependent CaMKII and oxidation, which activates NF-\kappaB and intensifies cellular inflammation. CaMKII also activates the nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in macrophages via the JNK pathway [106]. A high-fat diet is significantly associated with asthma prevalence, with polyunsaturated fatty acid intake during childhood increasing the risk of adult asthma [107]. Asthmatic patients on a high-fat diet exhibit elevated NLRP3 inflammasome and TLR4 receptor levels in the sputum. NLRP3 inflammasome activation increases IL-1\beta protein levels, exacerbating airway inflammation [108], linking the NLRP3 inflammasome with the TLR4 pathway. This suggests that the NLRP3 inflammasome is a potential therapeutic target for childhood asthma induced by obesity and plays a role in the oxidative stress-activated TLR4 pathway.

3.3 ER Stress and Pediatric Asthma

The ER serves as critical for protein synthesis and secretion in cells. ER stress occurs when it is overloaded with unfolded proteins, disrupting the redox balance. Using RNA sequencing, researchers discovered that airway epithelial cells influenced by IL-13 exhibit significant ER stress and apoptosis characteristics, mirroring the transcriptional features of nasal airway epithelium in children with high and low type 2 cytokine asthma [109]. Orosomucoid 1-like protein 3 (ORMDL3), a protein targeting the ER, induces ER stress. Subsequently, ORMDL3 overexpression in mice leads to airway remodeling and increased airway hyperreactivity [110]. Children with upregulated ORMDL3 gene expression have a significantly increased risk of asthma [111]. Elevated ER stress markers were found in the ovalbumin and LPS-induced bronchial mice model and in the bronchoalveolar lavage fluid of asthma patients [112]. Treatment with 4-phenyl butyric acid, a chemical chaperone that alleviates ER stress, significantly downregulated inflammatory cytokines, TLR4 receptors, and NF-\kappaB expression and eventual reduction in asthmatic features [112], indicating that inhibiting ER stress can alleviate asthma by modulating the TLR4–NF-\kappaB pathway.

Environmental ROS, such as hydrogen peroxide, exacerbate ER stress and cellular inflammation [113]. Proteins in the ER form disulfide bonds with the help of protein disulfide isomerase and ER oxidoreductase, releasing hydrogen peroxide and increasing oxidative stress [114]. This disrupts the ER’s redox balance, inactivating disulfide isomerase and preventing proper protein folding, leading to ER stress [115, 116], which activates the unfolded protein response, triggering downstream inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6), and pancreatic ER kinase (PERK) signaling pathways [117]. Inhibitors of inositol-requiring enzyme 1 (IRE1) could suppress transforming growth factor beta (TGF\beta)-induced inflammatory pathways [118]. Higher levels of TGF\beta1 linked with higher airway concentrations of 8-isoprostane, malondialdehyde, and IL-13 are found in children with asthma, suggesting ER stress exacerbates asthma severity through TGF\beta1-mediated inflammation [119]. Activation of the IRE1, ATF6, and PERK signaling pathways also activates NF-\kappaB, promoting cellular inflammation [118, 120, 121].

3.4 Nrf2/HO-1 Signaling Pathway and Antioxidation

Cells respond to excessive oxidative stress by regulating gene expression to counteract the damage. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor in the cellular response to oxidative stress and in maintaining antioxidant defenses [122]. Nrf2 consists of six functional domains, Nrf2 – ECH homology (Neh)1–Neh6. Under normal physiological conditions, the Neh2 domain of Nrf2 binds to Kelch-like ECH-associated protein 1 (Keap1), retaining Nrf2 in the cytoplasm and promoting its degradation through ubiquitination. When oxidative stress occurs, Keap1 releases Nrf2, which then translocates into the nucleus. In the nucleus, Nrf2 forms heterodimers with Maf proteins via its Neh1 domain and binds to antioxidant response elements (AREs), activating antioxidant genes such as SOD, CAT, and heme oxygenase-1 (HO-1) [123]. SOD catalyzes the conversion of superoxide anions into hydrogen peroxide, which CAT then converts to water, thus eliminating ROS [124]. HO-1, a phase II detoxifying enzyme, can bind to NADPH and cytochrome P450, regulating various cellular activities, including oxidative stress [125]. HO-1 also interacts with Nrf2, stabilizing and enhancing its antioxidant capacity [126].

Activation of the Nrf2 pathway alleviates airway hyperresponsiveness. Studies have shown that the Nrf2/HO-1 pathway significantly improves PM2.5-induced bronchial epithelial cell damage and reduces ROS generation, thereby inhibiting cell apoptosis; for instance, Shan et al. [127] found that activating the Nrf2/HO-1 pathway mitigated PM2.5-induced damage in bronchial epithelial cells. Similarly, Ge et al. [128] reported that vitamin D alleviated airway hyperresponsiveness in PM-exposed mice. This improvement was attenuated in HO-1 knockout cell lines, confirming the crucial role of the Nrf2/HO-1 signaling pathway in asthma development.

4. Antioxidants in the Treatment of Pediatric Asthma

Oxidative stress disrupts the redox balance, leading to airway epithelial cell damage, inflammation, and immune dysregulation in pediatric asthma. This highlights the potential of antioxidants in mitigating these effects and improving asthma outcomes. As shown in Table 1 (Ref. [86, 107, 127, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147]), both natural and synthetic antioxidants have been investigated for their therapeutic potential in managing pediatric asthma.

4.1 Antioxidants from Daily Food Sources

Natural antioxidants, particularly those found in vegetables and fruits, play a role in reducing oxidative stress. Increased vegetable intake is associated with lower airway inflammation rates and asthma in school-aged children [148]. Key food-derived antioxidants include vitamins C, D, and E. Some studies suggest vitamin C can help prevent and manage childhood asthma, although the evidence is inconsistent [129, 130, 131]. While vitamin D supplementation has shown therapeutic benefits in mice models [132, 133, 134], clinical studies in children have not demonstrated significant improvements in lung function, asthma control, or quality of life [132, 135]. Therefore, it is not recommended for treating childhood asthma. Similarly, vitamin E has not shown therapeutic benefits for childhood asthma [136, 137], though maternal supplementation during pregnancy may reduce the incidence of asthma in infants, suggesting a potential preventive effect [138].

Fruits contain antioxidant compounds such as polyphenols. Low levels of pure fruit juice intake are associated with higher asthma incidence in 11-year-olds, but increasing pure fruit juice intake does not improve asthma at any age [139]. Clinical studies have shown that pomegranate extract, rich in polyphenols, can improve asthma symptoms [149]. Dietary intake of n-3 and n-6 polyunsaturated fatty acids (PUFAs) is also associated with pediatric asthma risk. Higher plasma levels of very-long-chain n-3 PUFAs, arachidonic acid, and n-3 PUFA \alpha-linolenic acid at age 8 negatively correlate with asthma risk at age 24. In contrast, higher plasma levels of n-6 PUFA linoleic acid were positively associated with asthma risk [107].

Metal ions such as magnesium and selenium, which are cofactors for antioxidant enzymes, including SOD and glutathione peroxidase (GPx), enhance antioxidant capacity [150, 151, 152]. Lower levels of these ions have been observed in children with asthma [153, 154], suggesting a role in the development of childhood asthma. Intravenous administration of these ions significantly improves more than inhalation [140].

4.2 Plant Extracts and Chemically Synthesized Small Molecule Antioxidants

Current asthma treatments often involve corticosteroids to reduce inflammation [155]. Corticosteroids decrease the release of superoxide anions from blood mononuclear cells in asthma patients and can restore the activity of antioxidant enzymes such as Cu and Zn-SOD in the bronchial epithelium [141, 142]. For example, prednisone significantly increases plasma selenium concentrations, providing a positive antioxidant effect in asthma patients [143]. Plant-derived active extracts, such as ginger ketone and salidroside, have shown potential in asthma treatment by activating Nrf2, reducing ROS, and alleviating airway hyperresponsiveness [127, 144]. Isoquinoline alkaloid protopine activates the TLR4 pathway, reducing oxidative stress and inhibiting apoptosis in airway epithelial cells [86].

N-acetylcysteine (NAC), a glutathione precursor, significantly reduces eosinophilic airway inflammation and hyperresponsiveness in asthmatic mice [156]. Clinical studies have confirmed the therapeutic value of NAC in shortening the duration of cough and asthma symptoms in children [145].

Although there is a strong link between oxidative stress and pediatric asthma, long-term research is needed to better understand and apply antioxidants in clinical treatment. Further investigation into the relationship between asthma and oxidative stress will help promote the clinical application of antioxidants in asthma management.

5. Conclusion

Childhood asthma is a chronic inflammatory respiratory tract disease arising from the interplay between genetic predispositions and environmental exposures. In pediatric asthma, cells produce a substantial volume of ROS and RNS, leading to an imbalance in redox homeostasis. Environmental air pollutants, particulate matter, and components of cigarette smoke contain oxidative elements that, when inhaled, increase oxidative stress. This heightened oxidative stress facilitates the release of inflammatory cytokines through pathways such as NF-\kappaB and TLRs, thereby intensifying airway inflammation. While antioxidants have shown potential in managing pediatric asthma, their effectiveness remains to be conclusively proven. Therefore, further research into the generation and mechanistic pathways of oxidative stress is essential to establish a solid foundation for the therapeutic use of antioxidants in treating pediatric asthma.

References

[1] Mims JW. Asthma: definitions and pathophysiology. International Forum of Allergy & Rhinology. 2015; 5: S2–S6.

[2] Pate CA, Zahran HS, Qin X, Johnson C, Hummelman E, Malilay J. Asthma Surveillance - United States, 2006-2018. Morbidity and Mortality Weekly Report. Surveillance Summaries (Washington, D.C.: 2002). 2021; 70: 1–32.

[3] Haktanir Abul M, Phipatanakul W. Severe asthma in children: Evaluation and management. Allergology International: Official Journal of the Japanese Society of Allergology. 2019; 68: 150–157.

[4] Fleming L, Murray C, Bansal AT, Hashimoto S, Bisgaard H, Bush A, et al. The burden of severe asthma in childhood and adolescence: results from the paediatric U-BIOPRED cohorts. The European Respiratory Journal. 2015; 46: 1322–1333.

[5] Zhang L, Fu Z, Deng H, Xie Q, Wu W. Identification and treatment of persistent small airway dysfunction in paediatric patients with asthma: a retrospective cohort study. BMC Pulmonary Medicine. 2024; 24: 94.

[6] Grad R, Morgan WJ. Long-term outcomes of early-onset wheeze and asthma. The Journal of Allergy and Clinical Immunology. 2012; 130: 299–307.

[7] Padem N, Saltoun C. Classification of asthma. Allergy and Asthma Proceedings. 2019; 40: 385–388.

[8] Lötvall J, Akdis CA, Bacharier LB, Bjermer L, Casale TB, Custovic A, et al. Asthma endotypes: a new approach to classification of disease entities within the asthma syndrome. The Journal of Allergy and Clinical Immunology. 2011; 127: 355–360.

[9] Jesenak M, Zelieskova M, Babusikova E. Oxidative Stress and Bronchial Asthma in Children-Causes or Consequences? Frontiers in Pediatrics. 2017; 5: 162.

[10] Trivedi M, Denton E. Asthma in Children and Adults-What Are the Differences and What Can They Tell us About Asthma? Frontiers in Pediatrics. 2019; 7: 256.

[11] Dharmage SC, Perret JL, Custovic A. Epidemiology of Asthma in Children and Adults. Frontiers in Pediatrics. 2019; 7: 246.

[12] Becklake MR, Kauffmann F. Gender differences in airway behaviour over the human life span. Thorax. 1999; 54: 1119–1138.

[13] Yunginger JW, Reed CE, O’Connell EJ, Melton LJ, 3rd, O’Fallon WM, Silverstein MD. A community-based study of the epidemiology of asthma. Incidence rates, 1964-1983. The American Review of Respiratory Disease. 1992; 146: 888–894.

[14] Tai A, Tran H, Roberts M, Clarke N, Gibson AM, Vidmar S, et al. Outcomes of childhood asthma to the age of 50 years. The Journal of Allergy and Clinical Immunology. 2014; 133: 1572–1578.e3.

[15] Noutsios GT, Floros J. Childhood asthma: causes, risks, and protective factors; a role of innate immunity. Swiss Medical Weekly. 2014; 144: w14036.

[16] Wang F, He XY, Baines KJ, Gunawardhana LP, Simpson JL, Li F, et al. Different inflammatory phenotypes in adults and children with acute asthma. The European Respiratory Journal. 2011; 38: 567–574.

[17] Illi S, von Mutius E, Lau S, Niggemann B, Grüber C, Wahn U, et al. Perennial allergen sensitisation early in life and chronic asthma in children: a birth cohort study. Lancet (London, England). 2006; 368: 763–770.

[18] Dodig S, Richter D, Zrinski-Topić R. Inflammatory markers in childhood asthma. Clinical Chemistry and Laboratory Medicine. 2011; 49: 587–599.

[19] Comhair SAA, Erzurum SC. Redox control of asthma: molecular mechanisms and therapeutic opportunities. Antioxidants & Redox Signaling. 2010; 12: 93–124.

[20] Dondi A, Carbone C, Manieri E, Zama D, Del Bono C, Betti L, et al. Outdoor Air Pollution and Childhood Respiratory Disease: The Role of Oxidative Stress. International Journal of Molecular Sciences. 2023; 24: 4345.

[21] To T, Terebessy E, Zhu J, Zhang K, Lakey PS, Shiraiwa M, et al. Does early life exposure to exogenous sources of reactive oxygen species (ROS) increase the risk of respiratory and allergic diseases in children? A longitudinal cohort study. Environmental Health: a Global Access Science Source. 2022; 21: 90.

[22] Sackesen C, Ercan H, Dizdar E, Soyer O, Gumus P, Tosun BN, et al. A comprehensive evaluation of the enzymatic and nonenzymatic antioxidant systems in childhood asthma. The Journal of Allergy and Clinical Immunology. 2008; 122: 78–85.

[23] Lewis BW, Ford ML, Rogers LK, Britt RD, Jr. Oxidative Stress Promotes Corticosteroid Insensitivity in Asthma and COPD. Antioxidants (Basel, Switzerland). 2021; 10: 1335.

[24] Vincenzo SD, Ferrante G, Ferraro M, Cascio C, Malizia V, Licari A, et al. Oxidative Stress, Environmental Pollution, and Lifestyle as Determinants of Asthma in Children. Biology. 2023; 12: 133.

[25] Michaeloudes C, Abubakar-Waziri H, Lakhdar R, Raby K, Dixey P, Adcock IM, et al. Molecular mechanisms of oxidative stress in asthma. Molecular Aspects of Medicine. 2022; 85: 101026.

[26] Andreadis AA, Hazen SL, Comhair SAA, Erzurum SC. Oxidative and nitrosative events in asthma. Free Radical Biology & Medicine. 2003; 35: 213–225.

[27] Kostenko V, Akimov O, Gutnik O, Kostenko H, Kostenko V, Romantseva T, et al. Modulation of redox-sensitive transcription factors with polyphenols as pathogenetically grounded approach in therapy of systemic inflammatory response. Heliyon. 2023; 9: e15551.

[28] Geiszt M, Witta J, Baffi J, Lekstrom K, Leto TL. Dual oxidases represent novel hydrogen peroxide sources supporting mucosal surface host defense. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 2003; 17: 1502–1504.

[29] Stock CJW, Michaeloudes C, Leoni P, Durham AL, Mumby S, Wells AU, et al. Bromodomain and Extraterminal (BET) Protein Inhibition Restores Redox Balance and Inhibits Myofibroblast Activation. BioMed Research International. 2019; 2019: 1484736.

[30] Wen L, Tao SH, Guo F, Li LZ, Yang HL, Liang Y, et al. Selective EZH2 inhibitor zld1039 alleviates inflammation in cisplatin-induced acute kidney injury partially by enhancing RKIP and suppressing NF-κB p65 pathway. Acta Pharmacologica Sinica. 2022; 43: 2067–2080.

[31] De Biasi S, Gibellini L, Bianchini E, Nasi M, Pinti M, Salvioli S, et al. Quantification of mitochondrial reactive oxygen species in living cells by using multi-laser polychromatic flow cytometry. Cytometry. Part a: the Journal of the International Society for Analytical Cytology. 2016; 89: 1106–1110.

[32] Zhang Y, Marcillat O, Giulivi C, Ernster L, Davies KJ. The oxidative inactivation of mitochondrial electron transport chain components and ATPase. The Journal of Biological Chemistry. 1990; 265: 16330–16336.

[33] Zorov DB, Juhaszova M, Sollott SJ. Mitochondrial reactive oxygen species (ROS) and ROS-induced ROS release. Physiological Reviews. 2014; 94: 909–950.

[34] Sharma G, Banerjee R, Srivastava S. Molecular Mechanisms and the Interplay of Important Chronic Obstructive Pulmonary Disease Biomarkers Reveals Novel Therapeutic Targets. ACS Omega. 2023; 8: 46376–46389.

[35] Davis KU, Sheats MK. The Role of Neutrophils in the Pathophysiology of Asthma in Humans and Horses. Inflammation. 2021; 44: 450–465.

[36] Sanders SP, Zweier JL, Harrison SJ, Trush MA, Rembish SJ, Liu MC. Spontaneous oxygen radical production at sites of antigen challenge in allergic subjects. American Journal of Respiratory and Critical Care Medicine. 1995; 151: 1725–1733.

[37] Breiteneder H, Peng YQ, Agache I, Diamant Z, Eiwegger T, Fokkens WJ, et al. Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma. Allergy. 2020; 75: 3039–3068.

[38] Hoshino T, Okamoto M, Takei S, Sakazaki Y, Iwanaga T, Aizawa H. Redox-regulated mechanisms in asthma. Antioxidants & Redox Signaling. 2008; 10: 769–783.

[39] Hosseini N, Kourosh-Arami M, Nadjafi S, Ashtari B. Structure, Distribution, Regulation, and Function of Splice Variant Isoforms of Nitric Oxide Synthase Family in the Nervous System. Current Protein & Peptide Science. 2022; 23: 510–534.

[40] Cinelli MA, Do HT, Miley GP, Silverman RB. Inducible nitric oxide synthase: Regulation, structure, and inhibition. Medicinal Research Reviews. 2020; 40: 158–189.

[41] Stuehr DJ. Mammalian nitric oxide synthases. Biochimica et Biophysica Acta. 1999; 1411: 217–230.

[42] Guo FH, Comhair SA, Zheng S, Dweik RA, Eissa NT, Thomassen MJ, et al. Molecular mechanisms of increased nitric oxide (NO) in asthma: evidence for transcriptional and post-translational regulation of NO synthesis. Journal of Immunology (Baltimore, Md.: 1950). 2000; 164: 5970–5980.

[43] Seki M, Takeuchi E, Fukui E, Matsumoto H. Upregulation of iNOS and phosphorylated eNOS in the implantation-induced blastocysts of mice. Reproductive Medicine and Biology. 2023; 22: e12545.

[44] Saleh D, Ernst P, Lim S, Barnes PJ, Giaid A. Increased formation of the potent oxidant peroxynitrite in the airways of asthmatic patients is associated with induction of nitric oxide synthase: effect of inhaled glucocorticoid. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 1998; 12: 929–937.

[45] Wood LG, Gibson PG, Garg ML. Biomarkers of lipid peroxidation, airway inflammation and asthma. The European Respiratory Journal. 2003; 21: 177–186.

[46] Sanders SP. Nitric oxide in asthma. Pathogenic, therapeutic, or diagnostic? American journal of respiratory cell and molecular biology. 1999; 21: 147–149.

[47] Khatri SB, Iaccarino JM, Barochia A, Soghier I, Akuthota P, Brady A, et al. Use of Fractional Exhaled Nitric Oxide to Guide the Treatment of Asthma: An Official American Thoracic Society Clinical Practice Guideline. American Journal of Respiratory and Critical Care Medicine. 2021; 204: e97–e109.

[48] Weitoft T, Lind A, Larsson A, Rönnelid J, Högman M. Exhaled nitric oxide in early rheumatoid arthritis and effects of methotrexate treatment. Scientific Reports. 2022; 12: 6489.

[49] Gaston B, Drazen JM, Loscalzo J, Stamler JS. The biology of nitrogen oxides in the airways. American Journal of Respiratory and Critical Care Medicine. 1994; 149: 538–551.

[50] Dweik RA, Comhair SA, Gaston B, Thunnissen FB, Farver C, Thomassen MJ, et al. NO chemical events in the human airway during the immediate and late antigen-induced asthmatic response. Proceedings of the National Academy of Sciences of the United States of America. 2001; 98: 2622–2627.

[51] Schwartz J. Air pollution and children’s health. Pediatrics. 2004; 113: 1037–1043.

[52] Mudway IS, Kelly FJ. Ozone and the lung: a sensitive issue. Molecular Aspects of Medicine. 2000; 21: 1–48.

[53] Ierodiakonou D, Zanobetti A, Coull BA, Melly S, Postma DS, Boezen HM, et al. Ambient air pollution, lung function, and airway responsiveness in asthmatic children. The Journal of Allergy and Clinical Immunology. 2016; 137: 390–399.

[54] Tapak M, Sadeghi S, Ghazanfari T, Mosaffa N. Chemical exposure and alveolar macrophages responses: ‘the role of pulmonary defense mechanism in inhalation injuries’. BMJ Open Respiratory Research. 2023; 10: e001589.

[55] Chmielewska-Krzesińska M, Wąsowicz K. Local and Systemic Influence of Toxic Levels of Airborne Ozone on The Inflammatory Response in Rats. Journal of Veterinary Research. 2021; 65: 513–517.

[56] McConnell R, Berhane K, Gilliland F, London SJ, Islam T, Gauderman WJ, et al. Asthma in exercising children exposed to ozone: a cohort study. Lancet (London, England). 2002; 359: 386–391.

[57] Ho K, Weimar D, Torres-Matias G, Lee H, Shamsi S, Shalosky E, et al. Ozone impairs endogenous compensatory responses in allergic asthma. Toxicology and Applied Pharmacology. 2023; 459: 116341.

[58] Sarnat JA, Schwartz J, Suh HH. Fine particulate air pollution and mortality in 20 U.S. cities. The New England Journal of Medicine. 2001; 344: 1253–1254.

[59] Kelly FJ. Oxidative stress: its role in air pollution and adverse health effects. Occupational and Environmental Medicine. 2003; 60: 612–616.

[60] Strak M, Janssen N, Beelen R, Schmitz O, Vaartjes I, Karssenberg D, et al. Long-term exposure to particulate matter, NO₂ and the oxidative potential of particulates and diabetes prevalence in a large national health survey. Environment International. 2017; 108: 228–236.

[61] Landreman AP, Shafer MM, Hemming JC, Hannigan MP, Schauer JJ. A Macrophage-Based Method for the Assessment of the Reactive Oxygen Species (ROS) Activity of Atmospheric Particulate Matter (PM) and Application to Routine (Daily-24 h) Aerosol Monitoring Studies. Aerosol Science and Technology. 2008; 42: 946–957.

[62] Guo H, Jin L, Huang S. Effect of PM characterization on PM oxidative potential by acellular assays: a review. Reviews on Environmental Health. 2020; 35: 461–470.

[63] Delfino RJ, Staimer N, Tjoa T, Gillen DL, Schauer JJ, Shafer MM. Airway inflammation and oxidative potential of air pollutant particles in a pediatric asthma panel. Journal of Exposure Science & Environmental Epidemiology. 2013; 23: 466–473.

[64] Engels SM, Kamat P, Pafilis GS, Li Y, Agrawal A, Haller DJ, et al. Particulate matter composition drives differential molecular and morphological responses in lung epithelial cells. PNAS Nexus. 2023; 3: pgad415.

[65] Bates JT, Weber RJ, Abrams J, Verma V, Fang T, Klein M, et al. Reactive Oxygen Species Generation Linked to Sources of Atmospheric Particulate Matter and Cardiorespiratory Effects. Environmental Science & Technology. 2015; 49: 13605–13612.

[66] Weichenthal S, Crouse DL, Pinault L, Godri-Pollitt K, Lavigne E, Evans G, et al. Oxidative burden of fine particulate air pollution and risk of cause-specific mortality in the Canadian Census Health and Environment Cohort (CanCHEC). Environmental Research. 2016; 146: 92–99.

[67] Shafer MM, Perkins DA, Antkiewicz DS, Stone EA, Quraishi TA, Schauer JJ. Reactive oxygen species activity and chemical speciation of size-fractionated atmospheric particulate matter from Lahore, Pakistan: an important role for transition metals. Journal of Environmental Monitoring: JEM. 2010; 12: 704–715.

[68] Saffari A, Daher N, Shafer MM, Schauer JJ, Sioutas C. Seasonal and spatial variation in reactive oxygen species activity of quasi-ultrafine particles (PM0.25) in the Los Angeles metropolitan area and its association with chemical composition. Atmospheric Environment. 2013; 79: 566–575.

[69] Maritz GS, Harding R. Life-long programming implications of exposure to tobacco smoking and nicotine before and soon after birth: evidence for altered lung development. International Journal of Environmental Research and Public Health. 2011; 8: 875–898.

[70] De Queiroz Andrade E, Da Silva Sena CR, Collison A, Murphy VE, Gould GS, Bonevski B, et al. Association between active tobacco use during pregnancy and infant respiratory health: a systematic review and meta-analysis. BMJ Open. 2020; 10: e037819.

[71] Bruin JE, Petre MA, Lehman MA, Raha S, Gerstein HC, Morrison KM, et al. Maternal nicotine exposure increases oxidative stress in the offspring. Free Radical Biology & Medicine. 2008; 44: 1919–1925.

[72] Primo CC, Ruela PBF, Brotto LDDA, Garcia TR, Lima EDF. Effects of maternal nicotine on breastfeeding infants. Revista Paulista De Pediatria: Orgao Oficial Da Sociedade De Pediatria De Sao Paulo. 2013; 31: 392–397.

[73] Emma R, Bansal AT, Kolmert J, Wheelock CE, Dahlen SE, Loza MJ, et al. Enhanced oxidative stress in smoking and ex-smoking severe asthma in the U-BIOPRED cohort. PloS One. 2018; 13: e0203874.

[74] Comhair SA, Gaston BM, Ricci KS, Hammel J, Dweik RA, Teague WG, et al. Detrimental effects of environmental tobacco smoke in relation to asthma severity. PloS One. 2011; 6: e18574.

[75] Xue J, Li Z, Li X, Hua C, Shang P, Zhao J, et al. Evaluation of cigarette smoke-induced oxidative stress and inflammation in BEAS-2B cells based on a lung microfluidic chip. Food and Chemical Toxicology. 2023; 176: 113787.

[76] Montuschi P, Collins JV, Ciabattoni G, Lazzeri N, Corradi M, Kharitonov SA, et al. Exhaled 8-isoprostane as an in vivo biomarker of lung oxidative stress in patients with COPD and healthy smokers. American Journal of Respiratory and Critical Care Medicine. 2000; 162: 1175–1177.

[77] Guatura SB, Martinez JA, Santos Bueno PC, Santos ML. Increased exhalation of hydrogen peroxide in healthy subjects following cigarette consumption. Sao Paulo Medical Journal. 2000; 118: 93–98.

[78] Hobson J, Wright J, Churg A. Histochemical evidence for generation of active oxygen species on the apical surface of cigarette-smoke-exposed tracheal explants. The American Journal of Pathology. 1991; 139: 573–580.

[79] Silva H. Tobacco Use and Periodontal Disease-The Role of Microvascular Dysfunction. Biology. 2021; 10: 441.

[80] Arshad SH. Does exposure to indoor allergens contribute to the development of asthma and allergy? Current Allergy and Asthma Reports. 2010; 10: 49–55.

[81] Brussee JE, Smit HA, van Strien RT, Corver K, Kerkhof M, Wijga AH, et al. Allergen exposure in infancy and the development of sensitization, wheeze, and asthma at 4 years. The Journal of Allergy and Clinical Immunology. 2005; 115: 946–952.

[82] Lin S, Jones R, Munsie JP, Nayak SG, Fitzgerald EF, Hwang SA. Childhood asthma and indoor allergen exposure and sensitization in Buffalo, New York. International Journal of Hygiene and Environmental Health. 2012; 215: 297–305.

[83] Custovic A, Simpson BM, Simpson A, Kissen P, Woodcock A, NAC Manchester Asthma and Allergy Study Group. Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial. Lancet (London, England). 2001; 358: 188–193.

[84] Bonnet B, Messaoudi K, Jacomet F, Michaud E, Fauquert JL, Caillaud D, et al. An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen. Allergy, Asthma, and Clinical Immunology: Official Journal of the Canadian Society of Allergy and Clinical Immunology. 2018; 14: 14.

[85] Herre J, Grönlund H, Brooks H, Hopkins L, Waggoner L, Murton B, et al. Allergens as immunomodulatory proteins: the cat dander protein Fel d 1 enhances TLR activation by lipid ligands. Journal of Immunology (Baltimore, Md.: 1950). 2013; 191: 1529–1535.

[86] Yang J, Zhang M, Luo Y, Xu F, Gao F, Sun Y, et al. Protopine ameliorates OVA-induced asthma through modulatingTLR4/MyD88/NF-κB pathway and NLRP3 inflammasome-mediated pyroptosis. Phytomedicine: International Journal of Phytotherapy and Phytopharmacology. 2024; 126: 155410.

[87] Williams AS, Leung SY, Nath P, Khorasani NM, Bhavsar P, Issa R, et al. Role of TLR2, TLR4, and MyD88 in murine ozone-induced airway hyperresponsiveness and neutrophilia. Journal of Applied Physiology (Bethesda, Md.: 1985). 2007; 103: 1189–1195.

[88] Watanabe N, Fujita Y, Nakayama J, Mori Y, Kadota T, Hayashi Y, et al. Anomalous Epithelial Variations and Ectopic Inflammatory Response in Chronic Obstructive Pulmonary Disease. American Journal of Respiratory Cell and Molecular Biology. 2022; 67: 708–719.

[89] Ming S, Tian J, Ma K, Pei C, Li L, Wang Z, et al. Oxalate-induced apoptosis through ERS-ROS-NF-κB signalling pathway in renal tubular epithelial cell. Molecular Medicine (Cambridge, Mass.). 2022; 28: 88.

[90] Rahman I, MacNee W. Role of transcription factors in inflammatory lung diseases. Thorax. 1998; 53: 601–612.

[91] Manea A, Manea SA, Gafencu AV, Raicu M. Regulation of NADPH oxidase subunit p22(phox) by NF-kB in human aortic smooth muscle cells. Archives of Physiology and Biochemistry. 2007; 113: 163–172.

[92] Li Q, Engelhardt JF. Interleukin-1beta induction of NFkappaB is partially regulated by H2O2-mediated activation of NFkappaB-inducing kinase. The Journal of Biological Chemistry. 2006; 281: 1495–1505.

[93] Han W, Li H, Cai J, Gleaves LA, Polosukhin VV, Segal BH, et al. NADPH oxidase limits lipopolysaccharide-induced lung inflammation and injury in mice through reduction-oxidation regulation of NF-κB activity. Journal of Immunology (Baltimore, Md.: 1950). 2013; 190: 4786–4794.

[94] Schreck R, Rieber P, Baeuerle PA. Reactive oxygen intermediates as apparently widely used messengers in the activation of the NF-kappa B transcription factor and HIV-1. The EMBO Journal. 1991; 10: 2247–2258.

[95] Toledano MB, Leonard WJ. Modulation of transcription factor NF-kappa B binding activity by oxidation-reduction in vitro. Proceedings of the National Academy of Sciences of the United States of America. 1991; 88: 4328–4332.

[96] Machado IF, Miranda RG, Dorta DJ, Rolo AP, Palmeira CM. Targeting Oxidative Stress with Polyphenols to Fight Liver Diseases. Antioxidants (Basel, Switzerland). 2023; 12: 1212.

[97] Li M, Li M, Hou Y, He H, Jiang R, Wang C, et al. Ferroptosis triggers airway inflammation in asthma. Therapeutic Advances in Respiratory Disease. 2023; 17: 17534666231208628.

[98] Fitzgerald KA, Kagan JC. Toll-like Receptors and the Control of Immunity. Cell. 2020; 180: 1044–1066.

[99] Duechs MJ, Hahn C, Benediktus E, Werner-Klein M, Braun A, Hoymann HG, et al. TLR agonist mediated suppression of allergic responses is associated with increased innate inflammation in the airways. Pulmonary Pharmacology & Therapeutics. 2011; 24: 203–214.

[100] Clemente-Suárez VJ, Mielgo-Ayuso J, Ramos-Campo DJ, Beltran-Velasco AI, Martínez-Guardado I, Navarro Jimenez E, et al. Basis of preventive and non-pharmacological interventions in asthma. Frontiers in Public Health. 2023; 11: 1172391.

[101] Erzurum SC. New Insights in Oxidant Biology in Asthma. Annals of the American Thoracic Society. 2016; 13: S35–S39.

[102] Ryu JH, Yoo JY, Kim MJ, Hwang SG, Ahn KC, Ryu JC, et al. Distinct TLR-mediated pathways regulate house dust mite-induced allergic disease in the upper and lower airways. The Journal of Allergy and Clinical Immunology. 2013; 131: 549–561.

[103] Kleeberger SR, Reddy S, Zhang LY, Jedlicka AE. Genetic susceptibility to ozone-induced lung hyperpermeability: role of toll-like receptor 4. American Journal of Respiratory Cell and Molecular Biology. 2000; 22: 620–627.

[104] Lee AJ, Ro M, Cho KJ, Kim JH. Lipopolysaccharide/TLR4 Stimulates IL-13 Production through a MyD88-BLT2-Linked Cascade in Mast Cells, Potentially Contributing to the Allergic Response. Journal of Immunology (Baltimore, Md.: 1950). 2017; 199: 409–417.

[105] Singh MV, Swaminathan PD, Luczak ED, Kutschke W, Weiss RM, Anderson ME. MyD88 mediated inflammatory signaling leads to CaMKII oxidation, cardiac hypertrophy and death after myocardial infarction. Journal of Molecular and Cellular Cardiology. 2012; 52: 1135–1144.

[106] Okada M, Matsuzawa A, Yoshimura A, Ichijo H. The lysosome rupture-activated TAK1-JNK pathway regulates NLRP3 inflammasome activation. The Journal of Biological Chemistry. 2014; 289: 32926–32936.

[107] Ekström S, Sdona E, Klevebro S, Hallberg J, Georgelis A, Kull I, et al. Dietary intake and plasma concentrations of PUFAs in childhood and adolescence in relation to asthma and lung function up to adulthood. The American Journal of Clinical Nutrition. 2022; 115: 886–896.

[108] Wood LG, Li Q, Scott HA, Rutting S, Berthon BS, Gibson PG, et al. Saturated fatty acids, obesity, and the nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in asthmatic patients. The Journal of Allergy and Clinical Immunology. 2019; 143: 305–315.

[109] Jackson ND, Everman JL, Chioccioli M, Feriani L, Goldfarbmuren KC, Sajuthi SP, et al. Single-Cell and Population Transcriptomics Reveal Pan-epithelial Remodeling in Type 2-High Asthma. Cell Reports. 2020; 32: 107872.

[110] Worgall TS. Sphingolipids, ORMDL3 and asthma: what is the evidence? Current Opinion in Clinical Nutrition and Metabolic Care. 2017; 20: 99–103.

[111] Calışkan M, Bochkov YA, Kreiner-Møller E, Bønnelykke K, Stein MM, Du G, et al. Rhinovirus wheezing illness and genetic risk of childhood-onset asthma. The New England Journal of Medicine. 2013; 368: 1398–1407.

[112] Kim SR, Kim DI, Kang MR, Lee KS, Park SY, Jeong JS, et al. Endoplasmic reticulum stress influences bronchial asthma pathogenesis by modulating nuclear factor κB activation. The Journal of Allergy and Clinical Immunology. 2013; 132: 1397–1408.

[113] Tang Y, Zhou X, Cao T, Chen E, Li Y, Lei W, et al. Endoplasmic Reticulum Stress and Oxidative Stress in Inflammatory Diseases. DNA and Cell Biology. 2022; 41: 924–934.

[114] Wu Z, Wang H, Fang S, Xu C. Roles of endoplasmic reticulum stress and autophagy on H2O2 induced oxidative stress injury in HepG2 cells. Molecular Medicine Reports. 2018; 18: 4163–4174.

[115] Kowalczyk M, Kowalczyk E, Kwiatkowski P, Łopusiewicz Ł Talarowska M, Sienkiewicz M. Cellular Response to Unfolded Proteins in Depression. Life (Basel, Switzerland). 2021; 11: 1376.

[116] Burman A, Tanjore H, Blackwell TS. Endoplasmic reticulum stress in pulmonary fibrosis. Matrix Biology: Journal of the International Society for Matrix Biology. 2018; 68–69: 355–365.

[117] Wei J, Rahman S, Ayaub EA, Dickhout JG, Ask K. Protein misfolding and endoplasmic reticulum stress in chronic lung disease. Chest. 2013; 143: 1098–1105.

[118] Heindryckx F, Binet F, Ponticos M, Rombouts K, Lau J, Kreuger J, et al. Endoplasmic reticulum stress enhances fibrosis through IRE1α-mediated degradation of miR-150 and XBP-1 splicing. EMBO Molecular Medicine. 2016; 8: 729–744.

[119] Brown SD, Baxter KM, Stephenson ST, Esper AM, Brown LAS, Fitzpatrick AM. Airway TGF-β1 and oxidant stress in children with severe asthma: association with airflow limitation. The Journal of Allergy and Clinical Immunology. 2012; 129: 388–396, 396.e1–396.e 8.

[120] Yamazaki H, Hiramatsu N, Hayakawa K, Tagawa Y, Okamura M, Ogata R, et al. Activation of the Akt-NF-kappaB pathway by subtilase cytotoxin through the ATF6 branch of the unfolded protein response. Journal of Immunology (Baltimore, Md.: 1950). 2009; 183: 1480–1487.

[121] Zhu S, Liu H, Sha H, Qi L, Gao DS, Zhang W. PERK and XBP1 differentially regulate CXCL10 and CCL2 production. Experimental Eye Research. 2017; 155: 1–14.

[122] Zhang X, Ding M, Zhu P, Huang H, Zhuang Q, Shen J, et al. New Insights into the Nrf-2/HO-1 Signaling Axis and Its Application in Pediatric Respiratory Diseases. Oxidative Medicine and Cellular Longevity. 2019; 2019: 3214196.

[123] Loboda A, Damulewicz M, Pyza E, Jozkowicz A, Dulak J. Role of Nrf2/HO-1 system in development, oxidative stress response and diseases: an evolutionarily conserved mechanism. Cellular and Molecular Life Sciences: CMLS. 2016; 73: 3221–3247.

[124] Fernández-Sánchez A, Madrigal-Santillán E, Bautista M, Esquivel-Soto J, Morales-González A, Esquivel-Chirino C, et al. Inflammation, oxidative stress, and obesity. International Journal of Molecular Sciences. 2011; 12: 3117–3132.

[125] Canning P, Sorrell FJ, Bullock AN. Structural basis of Keap1 interactions with Nrf2. Free Radical Biology & Medicine. 2015; 88: 101–107.

[126] Biswas C, Shah N, Muthu M, La P, Fernando AP, Sengupta S, et al. Nuclear heme oxygenase-1 (HO-1) modulates subcellular distribution and activation of Nrf2, impacting metabolic and anti-oxidant defenses. The Journal of Biological Chemistry. 2014; 289: 26882–26894.

[127] Shan H, Li X, Ouyang C, Ke H, Yu X, Tan J, et al. Salidroside prevents PM2.5-induced BEAS-2B cell apoptosis via SIRT1-dependent regulation of ROS and mitochondrial function. Ecotoxicology and Environmental Safety. 2022; 231: 113170.

[128] Ge D, Chen Q, Xie X, Li Q, Yang Y. Unveiling the potent effect of vitamin D: harnessing Nrf2/HO-1 signaling pathways as molecular targets to alleviate urban particulate matter-induced asthma inflammation. BMC Pulmonary Medicine. 2024; 24: 55.

[129] Yieh L, McEvoy CT, Hoffman SW, Caughey AB, MacDonald KD, Dukhovny D. Cost effectiveness of vitamin c supplementation for pregnant smokers to improve offspring lung function at birth and reduce childhood wheeze/asthma. Journal of Perinatology: Official Journal of the California Perinatal Association. 2018; 38: 820–827.

[130] Wilkinson M, Hart A, Milan SJ, Sugumar K. Vitamins C and E for asthma and exercise-induced bronchoconstriction. The Cochrane Database of Systematic Reviews. 2014; 2014: CD010749.

[131] Chang HH, Chen CS, Lin JY. High dose vitamin C supplementation increases the Th1/Th2 cytokine secretion ratio, but decreases eosinophilic infiltration in bronchoalveolar lavage fluid of ovalbumin-sensitized and challenged mice. Journal of Agricultural and Food Chemistry. 2009; 57: 10471–10476.

[132] Han YY, Forno E, Bacharier LB, Phipatanakul W, Guilbert TW, Cabana MD, et al. Vitamin D supplementation, lung function and asthma control in children with asthma and low vitamin D levels. The European Respiratory Journal. 2021; 58: 2100989.

[133] Agrawal T, Gupta GK, Agrawal DK. Vitamin D supplementation reduces airway hyperresponsiveness and allergic airway inflammation in a murine model. Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology. 2013; 43: 672–683.

[134] Gorman S, Weeden CE, Tan DHW, Scott NM, Hart J, Foong RE, et al. Reversible control by vitamin D of granulocytes and bacteria in the lungs of mice: an ovalbumin-induced model of allergic airway disease. PloS One. 2013; 8: e67823.

[135] Hall SC, Agrawal DK. Vitamin D and Bronchial Asthma: An Overview of Data From the Past 5 Years. Clinical Therapeutics. 2017; 39: 917–929.

[136] Rubin RN, Navon L, Cassano PA. Relationship of serum antioxidants to asthma prevalence in youth. American Journal of Respiratory and Critical Care Medicine. 2004; 169: 393–398.

[137] Nwaru BI, Virtanen SM, Alfthan G, Karvonen AM, Genuneit J, Lauener RP, et al. Serum vitamin E concentrations at 1 year and risk of atopy, atopic dermatitis, wheezing, and asthma in childhood: the PASTURE study. Allergy. 2014; 69: 87–94.

[138] Wu H, Zhang C, Wang Y, Li Y. Does vitamin E prevent asthma or wheeze in children: A systematic review and meta-analysis. Paediatric Respiratory Reviews. 2018; 27: 60–68.

[139] Scheffers FR, Boer JMA, Gehring U, Koppelman GH, Vonk J, Smit HA, et al. The association of pure fruit juice, sugar-sweetened beverages and fruit consumption with asthma prevalence in adolescents growing up from 11 to 20 years: The PIAMA birth cohort study. Preventive Medicine Reports. 2022; 28: 101877.

[140] Mohammed S, Goodacre S. Intravenous and nebulised magnesium sulphate for acute asthma: systematic review and meta-analysis. Emergency Medicine Journal: EMJ. 2007; 24: 823–830.

[141] Majori M, Vachier I, Godard P, Farce M, Bousquet J, Chanez P. Superoxide anion production by monocytes of corticosteroid-treated asthmatic patients. The European Respiratory Journal. 1998; 11: 133–138.

[142] De Raeve HR, Thunnissen FB, Kaneko FT, Guo FH, Lewis M, Kavuru MS, et al. Decreased Cu,Zn-SOD activity in asthmatic airway epithelium: correction by inhaled corticosteroid in vivo. The American Journal of Physiology. 1997; 272: L148–L154.

[143] Fenech AG, Ellul-Micallef R. Selenium, glutathione peroxidase and superoxide dismutase in maltese asthmatic patients: effect of glucocorticoid administration. Pulmonary Pharmacology & Therapeutics. 1998; 11: 301–308.

[144] Zhu Y, Wang C, Luo J, Hua S, Li D, Peng L, et al. The protective role of Zingerone in a murine asthma model via activation of the AMPK/Nrf2/HO-1 pathway. Food & Function. 2021; 12: 3120–3131.

[145] Liu H, Wang W, Gao X. Comparison of the efficacy of ambroxol hydrochloride and N -acetylcysteine in the treatment of children with bronchopneumonia and their influence on prognosis. Experimental and Therapeutic Medicine. 2020; 20: 130.

[146] Adam-Bonci TI, Bonci EA, Pârvu AE, Herdean AI, Moț A, Taulescu M, et al. Vitamin D Supplementation: Oxidative Stress Modulation in a Mouse Model of Ovalbumin-Induced Acute Asthmatic Airway Inflammation. International Journal of Molecular Sciences. 2021; 22: 7089.

[147] Rosenlund H, Magnusson J, Kull I, Håkansson N, Wolk A, Pershagen G, et al. Antioxidant intake and allergic disease in children. Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology. 2012; 42: 1491–1500.

[148] Mendes FDC, Paciência I, Cavaleiro Rufo J, Farraia M, Silva D, Padrão P, et al. Higher diversity of vegetable consumption is associated with less airway inflammation and prevalence of asthma in school-aged children. Pediatric Allergy and Immunology: Official Publication of the European Society of Pediatric Allergy and Immunology. 2021; 32: 925–936.

[149] Hosseini SA, Shateri Z, Abolnezhadian F, Maraghi E, Haddadzadeh Shoushtari M, Zilaee M. Does pomegranate extract supplementation improve the clinical symptoms of patients with allergic asthma? A double-blind, randomized, placebo-controlled trial. Frontiers in Pharmacology. 2023; 14: 1109966.

[150] Ojeda ML, Nogales F. Dietary Selenium and Its Antioxidant Properties Related to Growth, Lipid and Energy Metabolism. Antioxidants (Basel, Switzerland). 2022; 11: 1402.

[151] Zhang Q, Qian ZY, Zhou PH, Zhou XL, Zhang DL, He N, et al. Effects of oral selenium and magnesium co-supplementation on lipid metabolism, antioxidative status, histopathological lesions, and related gene expression in rats fed a high-fat diet. Lipids in Health and Disease. 2018; 17: 165.

[152] Bjørklund G, Shanaida M, Lysiuk R, Antonyak H, Klishch I, Shanaida V, et al. Selenium: An Antioxidant with a Critical Role in Anti-Aging. Molecules (Basel, Switzerland). 2022; 27: 6613.

[153] Kuti BP, Kuti DK, Smith OS. Serum Zinc, Selenium and Total Antioxidant Contents of Nigerian Children with Asthma: Association with Disease Severity and Symptoms Control. Journal of Tropical Pediatrics. 2020; 66: 395–402.

[154] Flatt A, Pearce N, Thomson CD, Sears MR, Robinson MF, Beasley R. Reduced selenium in asthmatic subjects in New Zealand. Thorax. 1990; 45: 95–99.

[155] Sahiner UM, Birben E, Erzurum S, Sackesen C, Kalayci O. Oxidative stress in asthma. The World Allergy Organization Journal. 2011; 4: 151–158.

[156] Shalaby KH, Allard-Coutu A, O’Sullivan MJ, Nakada E, Qureshi ST, Day BJ, et al. Inhaled birch pollen extract induces airway hyperresponsiveness via oxidative stress but independently of pollen-intrinsic NADPH oxidase activity, or the TLR4-TRIF pathway. Journal of Immunology (Baltimore, Md.: 1950). 2013; 191: 922–933.