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

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.