Chronic methanol exposure induces cognitive impairment and Alzheimer's-like pathology in rhesus monkeys

Abstract

Background: The absence of effective animal models for sporadic Alzheimer's disease (AD) remains a pivotal barrier to therapy development. Because methanol metabolism produces endogenous formaldehyde, a neurotoxic agent linked to cognitive decline, this study investigated whether chronic, low-dose methanol exposure could recapitulate AD-like pathology and cognitive deficits in rhesus monkey, thereby establishing a nonhuman primate animal model driven by this environmental-metabolic insult.

Methods: Adult rhesus monkeys received low-concentration methanol for 9 months. Behavioral tests for cognition, locomotion, sleep, and vision were conducted. Postmortem analyses involved histopathological examination, immunohistochemistry, immunofluorescence, and Western blot to evaluate neuronal integrity, microglial activation, and the expression of key proteins associated with AD (amyloid-β [Aβ], phosphorylated tau, TAR DNA-binding protein 43 [TDP-43]) and cellular stress (synaptic markers, mitochondrial fission, autophagy, and apoptosis-related proteins).

Results: Chronic methanol exposure led to progressive cognitive and memory impairment without significant motor or visual deficits. Neuropathology revealed brain atrophy, neuronal loss, synaptic damage, microglial activation, and mitochondrial structural disorganization. Critically, the exposed animals exhibited hallmark AD-like molecular alterations, including increased Aβ deposition, tau hyperphosphorylation, and TDP-43 dysregulation. Furthermore, neurotoxicity was associated with elevated urinary formaldehyde, enhanced mitochondrial fission, increased autophagy, and elevated apoptosis.

Conclusion: Chronic low-dose methanol exposure in rhesus monkeys recapitulates progressive cognitive deficits and AD-like neuropathological features. This model, driven by endogenous formaldehyde toxicity, effectively mimics key aspects of sporadic AD. Our findings shed light on the neurotoxic mechanisms of methanol and propose a reproducible and translationally relevant nonhuman primate model for studying AD pathogenesis and evaluating potential therapeutics.

Keywords

Alzheimer's disease (AD) / amyloid-β (Aβ) / animal model / cognitive impairment / methanol

References

[1] Nurieva O, Hubacek JA, Urban P, et al. Clinical and genetic determinants of chronic visual pathway changes after methanol—induced optic neuropathy: four-year follow-up study. Clin Toxicol (Phila). 2019; 57(6): 387-397.

[2] Manuchehri AA, Alijanpour E, Daghmechi M, et al. A case of methanol poisoning leading to prolonged respirator dependency with consequent blindness and irreversible brain damage. Caspian J Intern Med. 2015; 6(3): 180-183.

[3] Dorokhov YL, Shindyapina AV, Sheshukova EV, Komarova TV. Metabolic methanol: molecular pathways and physiological roles. Physiol Rev. 2015; 95(2): 603-644.

[4] Zhai R, Zheng N, Rizak J, Hu X. Evidence for conversion of methanol to formaldehyde in nonhuman primate brain. Anal Cell Pathol (Amst). 2016; 2016:4598454.

[5] Wakayama K, Yamaguchi S, Takeuchi A, et al. Regulation of intracellular formaldehyde toxicity during methanol metabolism of the methylotrophic yeast Pichia methanolica. J Biosci Bioeng. 2016; 122(5): 545-549.

[6] Yang M, Miao J, Rizak J, et al. Alzheimer's disease and methanol toxicity (part 2): lessons from four rhesus macaques (Macaca mulatta) chronically fed methanol. J Alzheimer's Dis. 2014; 41(4): 1131-1147.

[7] Wang T, Yan S, Lu J. The effects of noninvasive brain stimulation on cognitive function in patients with mild cognitive impairment and Alzheimer's disease using resting-state functional magnetic resonance imaging: a systematic review and meta-analysis. CNS Neurosci Ther. 2023; 29(11): 3160-3172.

[8] Brookmeyer R, Johnson E, Ziegler-Graham K, Arrighi HM. Forecasting the global burden of Alzheimer's disease. Alzheimers Dement. 2007; 3(3): 186-191.

[9] He Y, Li C, Yang Y, et al. Meta-analysis of the rs2075650 polymorphism and risk of Alzheimer disease. Aging Clin Exp Res. 2016; 28(5): 805-811.

[10] Lee YJ, Lin SY, Peng SW, et al. Predictive utility of plasma amyloid and tau for cognitive decline in cognitively normal adults. J Prev Alzheimers Dis. 2023; 10(2): 178-185.

[11] Hsieh CH, Ko CA, Liang CS, et al. Longitudinal assessment of plasma biomarkers for early detection of cognitive changes in subjective cognitive decline. Front Aging Neurosci. 2024; 16:1389595.

[12] DeTure MA, Dickson DW. The neuropathological diagnosis of Alzheimer's disease. Mol Neurodegener. 2019; 14(1):32.

[13] Jonathan Graff-Radford K, Yong KXX, Apostolova LG, et al. New insights into atypical Alzheimer's disease in the era of biomarkers. Lancet Neurol. 2021; 20(3): 222-234.

[14] Lao K, Ji N, Zhang X, Qiao W, Tang Z, Gou X. Drug development for Alzheimer's disease: review. J Drug Target. 2019; 27(2): 164-173.

[15] Briggs R, Kennelly SP, O'Neill D. Drug treatments in Alzheimer's disease. Clin Med (Lond). 2016; 16(3): 247-253.

[16] Liu N, Yue F, Tang WP, Chan P. An objective measurement of locomotion behavior for hemiparkinsonian cynomolgus monkeys. J Neurosci Methods. 2009; 183(2): 188-194.

[17] Durand E, Petit O, Tremblay L, et al. Social behavioral changes in MPTP-treated monkey model of Parkinson's disease. Front Behav Neurosci. 2015; 9:42.

[18] Tong Z, Wang W, Luo W, et al. Urine formaldehyde predicts cognitive impairment in post-stroke dementia and Alzheimer's disease. J Alzheimer's Dis. 2017; 55(3): 1031-1038.

[19] Sanchez-Varo R, Mejias-Ortega M, Fernandez-Valenzuela JJ, et al. Transgenic mouse models of Alzheimer's disease: an integrative analysis. Int J Mol Sci. 2022; 23(10):5404.

[20] Chouliaras L, Lardenoije R, Kenis G, et al. Age-related disturbances in DNA (hydroxy)methylation in APP/PS1 mice. Transl Neurosci. 2018; 9: 190-202.

[21] Li HW, Zhang L, Qin C. Current state of research on non-human primate models of Alzheimer's disease. Animal Model Exp Med. 2019; 2(4): 227-238.

[22] Rogers Flattery CN, Rosen RF, Farberg AS, et al. Quantification of neurons in the hippocampal formation of chimpanzees: comparison to rhesus monkeys and humans. Brain Struct Funct. 2020; 225(8): 2521-2531.

[23] Honda Y, Shimokawa T, Matsuda S, Kobayashi Y, Moriya-Ito K. Hippocampal connectivity of the Presubiculum in the common marmoset (Callithrix jacchus). Front Neural Circuits. 2022; 16:863478.

[24] Gonzalez-Arnay E, Perez-Santos I, Jimenez-Sanchez L, et al. Immunohistochemical field parcellation of the human hippocampus along its antero-posterior axis. Brain Struct Funct. 2024; 229(2): 359-385.

[25] Kou Y, Zhao H, Cui D, Han H, Tong Z. Formaldehyde toxicity in age-related neurological dementia. Ageing Res Rev. 2022; 73:101512.

[26] Zhiqian Tong J, Wenhong L, et al. Urine formaldehyde level is inversely correlated to mini mental state examination scores in senile dementia. Neurobiol Aging. 2011; 32(1): 31-41.

[27] Tong Z, Han C, Luo W, et al. Aging-associated excess formaldehyde leads to spatial memory deficits. Sci Rep. 2013; 3:1807.

[28] Qiang M, Xiao R, Su T, et al. A novel mechanism for endogenous formaldehyde elevation in SAMP8 mouse. J Alzheimer's Dis. 2014; 40(4): 1039-1053.

[29] Dourlen P, Kilinc D, Malmanche N, Chapuis J, Lambert JC. The new genetic landscape of Alzheimer's disease: from amyloid cascade to genetically driven synaptic failure hypothesis? Acta Neuropathol. 2019; 138(2): 221-236.

[30] Burke E, Gunstad J, Pavlenko O, Hamrick P. Distinguishable features of spontaneous speech in Alzheimer's clinical syndrome and healthy controls. Neuropsychol Dev Cogn B Aging Neuropsychol Cogn. 2024; 31(3): 575-586.

[31] Tong Z, Han C, Luo W, et al. Accumulated hippocampal formaldehyde induces age-dependent memory decline. Age (Dordr). 2013; 35(3): 583-596.

[32] Boyle PA, Yu L, Schneider JA, Wilson RS, Bennett DA. Scam awareness related to incident Alzheimer dementia and mild cognitive impairment: a prospective cohort study. Ann Intern Med. 2019; 170(10): 702-709.

[33] He X, Li Z, Rizak JD, et al. Resveratrol attenuates formaldehyde induced hyperphosphorylation of tau protein and cytotoxicity in N2a cells. Front Neurosci. 2016; 10:598.

[34] Scheltens P, De Strooper B, Kivipelto M, et al. Alzheimer's disease. Lancet. 2021; 397(10284): 1577-1590.

[35] Seress L. Comparative anatomy of the hippocampal dentate gyrus in adult and developing rodents, non-human primates and humans. Prog Brain Res. 2007; 163: 23-41.

[36] Tzioras M, McGeachan RI, Durrant CS, Spires-Jones TL. Synaptic degeneration in Alzheimer disease. Nat Rev Neurol. 2023; 19(1): 19-38.

[37] Sato C, Barthélemy NR, Mawuenyega KG, et al. Tau kinetics in neurons and the human central nervous system. Neuron. 2018; 97(6): 1284-1298.

[38] Barthélemy NR, Mallipeddi N, Moiseyev P, Sato C, Bateman RJ. Tau phosphorylation rates measured by mass spectrometry differ in the intracellular brain vs. extracellular cerebrospinal fluid compartments and are differentially affected by Alzheimer's disease. Front Aging Neurosci. 2019.

[39] Serrano-Pozo A, Frosch MP, Masliah E, Hyman BT. Neuropathological alterations in Alzheimer disease. Cold Spring Harb Perspect Med. 2011; 1(1):a006189.

[40] Dionisio-Santos DA, Olschowka JA, O'Banion MK. Exploiting microglial and peripheral immune cell crosstalk to treat Alzheimer's disease. J Neuroinflammation. 2019; 16(1):74.

[41] Webers A, Heneka MT, Gleeson PA. The role of innate immune responses and neuroinflammation in amyloid accumulation and progression of Alzheimer's disease. Immunol Cell Biol. 2020; 98(1): 28-41.

[42] Tong Z, Han C, Qiang M, et al. Age-related formaldehyde interferes with DNA methyltransferase function, causing memory loss in Alzheimer's disease. Neurobiol Aging. 2015; 36(1): 100-110.

[43] Manczak M, Calkins MJ, Reddy PH. Impaired mitochondrial dynamics and abnormal interaction of amyloid beta with mitochondrial protein Drp1 in neurons from patients with Alzheimer's disease: implications for neuronal damage. Hum Mol Genet. 2011; 20(13): 2495-2509.

[44] Hatsuta H, Takao M, Nogami A, et al. Tau and TDP-43 accumulation of the basal nucleus of Meynert in individuals with cerebral lobar infarcts or hemorrhage. Acta Neuropathol Commun. 2019; 7(1):49.

[45] Lopez-Carbonero JI, Garcia-Toledo I, Fernandez-Hernandez L, et al. In vivo diagnosis of TDP-43 proteinopathies: in search of biomarkers of clinical use. Transl Neurodegener. 2024; 13(1):29.

[46] Manuela Neumann D, Kwong LK. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science. 2006; 314(5796): 130-133.

[47] Xie M, Liu YU, Zhao S, et al. TREM2 interacts with TDP-43 and mediates microglial neuroprotection against TDP-43-related neurodegeneration. Nat Neurosci. 2022; 25(1): 26-38.

[48] Meneses A, Koga S, O'Leary J, Dickson DW, Bu G, Zhao N. TDP-43 pathology in Alzheimer's disease. Mol Neurodegener. 2021; 16(1):84.

[49] Bryan D, James RSW, Patricia AB. TDP-43 stage, mixed pathologies, and clinical Alzheimer's-type dementia. Brain. 2016; 139(11): 2983-2993.

[50] Amador-Ortiz C, Lin WL, Ahmed Z, et al. TDP-43 immunoreactivity in hippocampal sclerosis and Alzheimer's disease. Ann Neurol. 2007; 61(5): 435-445.

[51] Nelson PT, Dickson DW, Trojanowski JQ, et al. Limbic-predominant age-related TDP-43 encephalopathy (LATE): consensus working group report. Brain. 2019; 142(6): 1503-1527.

[52] Phan TX, Malkani RG. Sleep and circadian rhythm disruption and stress intersect in Alzheimer's disease. Neurobiol Stress. 2019; 10:100133.

[53] Leroy V, Ayers E, Adhikari D, Verghese J. Association of sleep disturbances with prevalent and incident motoric cognitive risk syndrome in community-residing older adults. Neurology. 2024; 103(11):e210054.

[54] Rulisek J, Waldauf P, Belohlavek J, et al. Health-related quality of life determinants in survivors of a mass methanol poisoning outbreak: six-year prospective cohort study. Clin Toxicol (Phila). 2020; 58(9): 870-880.

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2026 The Author(s). Animal Models and Experimental Medicine published by John Wiley & Sons Australia, Ltd on behalf of The Chinese Association for Laboratory Animal Sciences.