Neutrophils, macrophages, CD3⁺, CD4⁺, and CD8⁺ T lymphocytes express µ-, δ-, and κ-opioid receptors (ORs) with varying affinities for opioids. Mast cells express the atypical OR Mas-related G-protein-coupled receptor X2 (MRGPRX2), which has a low affinity for morphine. Neutrophils and macrophages can synthesize and release endogenous opioid peptides. Activation of ORs enhances the synthesis of proinflammatory cytokines and the production of reactive oxygen species (ROS) in unstimulated leukocytes. Conversely, OR activation reduces proinflammatory cytokine synthesis in stimulated neutrophils and macrophages. Morphine inhibits Toll-like receptor 4 (TLR4) expression in macrophages, thereby attenuating inflammation, whereas methadone induces ROS production in mast cells through TLR4 activation. Stimulation of TLR4 triggers β-endorphin synthesis in macrophages. The production of proinflammatory cytokines and ROS contributes to cardiac reperfusion injury. Importantly, activation of κ₁- and µ-ORs suppresses proinflammatory cytokine production by leukocytes, thereby mitigating inflammatory injury to the heart and other organs.

Neuromuscular electrical stimulation (NMES) is a well-established therapeutic approach for chronic wounds. Conventionally, NMES involves direct electrode contact with wounds or adjacent healthy skin; however, it is limited by the need for wound exposure and by increased pain. Our preliminary study demonstrated the innovative application of remote NMES (rNMES) to the skeletal muscle of the distal calf, which showed the potential to accelerate wound healing in remote areas. rNMES was effective in human clinical trials in our previous work, although the underlying mechanisms remain unclear. As rNMES is often used to stimulate muscle contraction in long-term bedridden patients, we analyzed data from the Gene Expression Omnibus (GEO) database and found that exercise promotes midkine (MDK) expression in muscle. MDK is a small secreted heparin-binding protein that interacts with multiple cell surface receptors to promote growth. In the present study, we found that MDK significantly enhanced macrophage efferocytosis in a low-density lipoprotein receptor-related protein 1 (LRP1)-dependent manner. Our findings demonstrate that rNMES upregulates MDK expression in skeletal muscles through the AMPK-ERK axis, facilitating its delivery to wounds through the circulatory system and promoting LRP1-mediated efferocytosis of apoptotic cells, thereby expediting wound healing.

Articular cartilage maintains joint homeostasis by adapting to mechanical loading, but both insufficient and excessive loading can impair cartilage integrity. Whether mechanical activity should be restricted in early osteoarthritis (OA), particularly among exercise enthusiasts, remains controversial. Here, we established in vitro and in vivo models of prolonged moderate mechanical loading (7.5% strain, 1 Hz) and analyzed human cartilage from weight-bearing and non-weight-bearing regions using RNA sequencing. Prolonged exposure (≥ 12 h) significantly increased chondrocyte apoptosis (2.3-fold), reduced expression of the chondrogenic transcription factor SOX9 and the matrix markers COL2A1, and elevated nerve growth factor (NGF) expression (1.8-fold), accompanied by enrichment of neural sensitization and inflammatory pathways. Immunofluorescence staining revealed NGF accumulation in mechanically stressed cartilage. Unlike high-intensity stress, which led to immediate apoptosis, moderate loading induced a delayed pro-apoptotic response after 12 h. These findings indicate that prolonged moderate mechanical loading may promote chondrocyte apoptosis through an NGF-mediated inflammatory microenvironment and provide mechanistic evidence suggesting that patients with early OA may benefit from limiting high-impact or prolonged moderate-intensity exercise sessions to prevent cartilage damage and guide rehabilitation.

Activation of neutrophil membrane receptors initiates intracellular signal transduction cascades that orchestrate the cell's effector functions, including phagocytosis, production of reactive oxygen and halogen species, degranulation, and NETosis (formation of neutrophil extracellular traps [NETs]). NETs, which contain antimicrobial compounds such as myeloperoxidase (MPO), represent a strategy to combat infection. However, excessive production of NETs promotes thrombosis, diabetes mellitus, and other diseases. Therefore, investigations into the mechanisms of NETosis and the identification of modulators of this process are critical for developing strategies to address NETosis-related disorders. Here, we identified a novel NETosis inducer, human serum albumin (HSA) modified by the MPO product hypochlorous acid (HSA_HOCl), whose accumulation in vivo was correlated with inflammatory processes. Using human blood neutrophils, we investigated HSA_HOCl-induced NETosis and detected NET formation by flow cytometry. The results showed that the mechanism of HSA_HOCl-induced NETosis involved MPO, NADPH oxidase, and phosphatidylinositol 3-kinases (PI3Ks), and that HSA_HOCl activated a reactive oxygen species-dependent suicidal type of NETosis. Moreover, HSA_HOCl-induced NETosis was inhibited by an anti-HSA_HOCl monoclonal antibody. Thus, our findings may facilitate the development of strategies to modulate NETosis in inflammation associated with elevated MPO activity.

Mosquito-borne diseases pose a significant global health threat, necessitating the development of innovative vector control strategies. In this study, we investigated the potential of harnessing host immunity against mosquitoes through vaccination. Using Culex pipiens (C. pipiens) as a model, we demonstrated that polyclonal antibodies against C. pipiens abdominal protein extracts significantly impaired oviposition and increased mosquito mortality, primarily through the classical complement activation pathways. However, repeated exposure led to resistance, indicating potential adaptation. Proteomic analysis identified metabolic proteins as key targets, with Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses highlighting their roles in carboxylic acid metabolism, tyrosine degradation, and the proteasome pathways. Notably, cross-species reactivity was revealed by Western blotting, showing strong binding of Culex-specific antibodies to Anopheles and Aedes abdominal proteins. This study provides mechanistic insights into antibody-based mosquito suppression, highlighting its potential as an innovative vector control strategy while underscoring the need for further research on resistance management and ecological impacts.

The comorbidity of skin and gastrointestinal tract (GIT) diseases, primarily driven by the gut-skin axis (GSA), is well established. However, the genetic contribution to the GSA remains unclear. Here, using genome-wide association study (GWAS) summary statistics from European populations, we performed a genome-wide pleiotropic analysis to investigate the shared genetic basis and causal associations between skin and GIT diseases. We observed extensive genetic correlations and overlaps between skin and GIT diseases. A total of 298 pleiotropic loci were identified, 75 of which were colocalized, and 61 exhibited pleiotropic effects across multiple trait pairs, including 2p16.1 (PUS10), 6p21.32 (HLA-DRB1), 10q21.2 (ZNF365), and 19q13.11 (SLC7A10). Additionally, five novel loci were identified based on the pleiotropic analysis; among them, the 15q22.2 locus harboring RORA was validated by the latest inflammatory bowel disease GWAS. Gene-based analysis identified 394 unique pleiotropic genes, which were enriched in GSA-associated tissues and the immune system, and protein-protein interaction analysis further revealed that the GPCR-cAMP, chromatin remodeling, JAK-STAT, and HLA-mediated immunity pathways were involved in GSA comorbidity. Notably, the JAK-STAT pathway showed strong potential for drug repurposing, with adalimumab targeting tumor necrosis factor and ustekinumab targeting interleukin-12 subunit beta already being used to treat both skin and GIT diseases. Finally, Mendelian randomization analysis identified five significant causal associations, and subsequent mediation analysis identified three potential microbiota-GIT-skin pathways. Taken together, our study demonstrated that the shared genetic factors between skin and GIT diseases were widely distributed across the genome. These findings will enhance our understanding of the genetic mechanisms underlying GSA comorbidity.

The highly conserved human leukocyte antigen-A2 (HLA-A2)-restricted epitope NS3-1073 represents a promising candidate for a therapeutic vaccine against hepatitis C virus (HCV). In this study, we engineered a set of fusion proteins based on the artificial self-assembling peptide (SAP), which were expressed in Escherichia coli and spontaneously self-assembled into nanosized particles displaying HCV epitopes, including NS3-1073. To enhance immunogenicity, we incorporated the T helper epitope PADRE into the construct. Alpha-helical linkers were introduced between SAP and the epitopes to facilitate proper protein folding. Notably, a helical linker with a high supercoiling propensity enabled soluble expression of the fusion protein containing both the NS3-1073 and PADRE epitopes, allowing purification of the in vivo-formed nanoparticles by metal affinity chromatography. Human dendritic cells derived from peripheral blood monocytes showed robust activation in response to the fusion proteins and preferentially stimulated T lymphocytes toward a Th1-biased immune response. In mice, immunization with nanoparticles carrying NS3-1073 induced splenocyte proliferation in response to in vitro stimulation with a mixture of NS3 peptides. These results demonstrate that recombinant nanoparticle-based carriers presenting the NS3-1073 epitope can be produced in bacterial systems and hold strong potential as a foundation for a therapeutic HCV vaccine.

Severe fever with thrombocytopenia syndrome (SFTS), caused by Dabie bandavirus (DBV), triggers aberrant immune activation and cytokine storms, contributing to poor prognosis; however, its immune dysfunction mechanism remains unclear. Current management relies on symptomatic treatment and glucocorticoids, but no standardized treatment guidelines exist. This study investigated the mechanisms of abnormal lymphocyte function in acute-phase SFTS and the effects of glucocorticoid treatment on lymphoid cells using single-cell RNA sequencing (scRNA-seq) and bioinformatics analysis. We enrolled three healthy volunteers and 13 patients with acute SFTS and divided them into four groups. ScRNA-seq was performed on peripheral blood mononuclear cells from all 16 participants, capturing transcripts from the 3′ ends of mRNA. Bioinformatics analyses were used to profile patient immunological signatures, characterize subpopulation compositions, infer developmental trajectories, and assess lymphoid cell interactions. We obtained 120886 lymphoid cells, which were clustered into 23 functionally heterogeneous subsets. Results showed that patients with severe SFTS exhibited stronger inflammatory and adaptive immune responses. Glucocorticoid treatment suppressed inflammation and the interferon response but also inhibited the production of virus-specific antibodies. These findings suggest that appropriate glucocorticoid administration may alleviate the hyperinflammatory state in severe SFTS during the acute phase, although it is not recommended as a conventional treatment because of its potential to suppress antiviral immunity. This study provides insights into SFTS immunopathology and informs the optimized clinical use of glucocorticoids.

Neutralizing antibodies are essential tools in antiviral therapy and epidemic preparedness, capable of directly inhibiting viral entry and limiting disease progression. However, traditional antibody discovery strategies—such as animal immunization or B cell isolation from infected individuals—are often hindered by biosafety concerns, lengthy development timelines, and limited adaptability during outbreaks. In the present study, we aimed to establish a robust and rapid in vitro platform for the efficient isolation of neutralizing antibodies targeting conserved viral epitopes. We developed an epitope-guided negative screening strategy that integrates phage display technology with rational antigen mutagenesis to exclude antibodies against variable regions while enriching for those that recognize functionally constrained epitopes. When applied to the receptor-binding domain of severe acute respiratory syndrome coronavirus 2, this method enabled the identification of six neutralizing antibodies (one IgG and five nanobodies) exhibiting broad-spectrum neutralizing activity across multiple viral variants. Notably, antibodies recognizing distinct epitopes demonstrated significant synergistic neutralization when used in combination (P < 0.05). This screening approach facilitates the rapid discovery of potent and mutation-resistant antibodies and holds promise for application to other emerging pathogens. Our findings underscore the potential of epitope-guided, in vitro platforms in expediting therapeutic antibody development under conditions of high biosafety requirements.