Acute Particulate Matter (PM ₁₀ ) Exposure Selectively Triggers Behavioral Alterations in the Presymptomatic Experimental Autoimmune Encephalomyelitis (EAE) Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disease of the central nervous system, where neuroinflammation and autoimmune response against myelin lead to functional impairments, cognitive and psychiatric symptoms. Exposure to air pollution-in particular to peaks of particulate matter (PM)-has been associated with an increase in hospital admissions for MS onset and relapses and exacerbated neuroinflammation in MS patients. Here, in the MOG_35-55-induced experimental autoimmune encephalomyelitis (EAE) mouse model of MS, we tested the hypothesis that exposure to PM₁₀ might influence the disease course and severity in individuals with a predisposing background. Short-term PM₁₀ exposures-occurring either before immunization or during the presymptomatic phase-did not modify disease manifestation in EAE mice, as assessed by clinical and neuropathological analyses. Yet, presymptomatic EAE-but not healthy-mice selectively showed increased disinhibited, risk-taking, and novelty-seeking behaviors early after being exposed to PM₁₀. These data show a selective vulnerability of immunologically primed mice toward the effects of PM₁₀, occurring before the emergence of overt motor impairment and presenting as specific behavioral alterations.