Exposure to Traffic-Generated Pollutants Exacerbates the Expression of Factors Associated with the Pathophysiology of Alzheimer’s Disease in Aged C57BL/6 Wild-Type Mice

Article type: Research Article

Authors: Armstrong, Tyler D.^{; 1} | Suwannasual, Usa^{; 1} | Kennedy, Conner L. | Thasma, Akshaykumar | Schneider, Leah J. | Phillippi, Danielle | Lund, Amie K.^{; *}

Affiliations: Advanced Environmental Research Institute, Department of Biological Sciences, University of North Texas, Denton, TX, USA

Correspondence: [*] Correspondence to: Amie Lund, PhD, 1704 W. Mulberry St, Denton, TX 76201, USA. Tel.: +1 940 369 8946; Fax: +1 940 565 4297; E-mail: [email protected].

Note: [1] These authors contributed equally to this manuscript.

Abstract: Background:Multiple studies report a strong correlation between traffic-generated air pollution-exposure and detrimental outcomes in the central nervous system (CNS), including Alzheimer’s disease (AD). Incidence of AD is rapidly increasing and, worldwide, many live in regions where pollutants exceed regulatory standards. Thus, it is imperative to identify environmental pollutants that contribute to AD, and the mechanisms involved. Objective:We investigated the effects of mixed gasoline and diesel engine emissions (MVE) on the expression of factors involved in progression of AD in the hippocampus and cerebrum in a young versus aged mouse model. Methods:Young (2 months old) and aged (18 months old) male C57BL/6 mice were exposed to either MVE (300μg/m3 PM) or filtered air (FA) for 6 h/d, 7 d/wk, for 50 d. Immunofluorescence and RT-qPCR were used to quantify oxidative stress (8-OHdG) and expression of amyloid-β protein precursor (AβPP), β secretase (BACE1), amyloid-β (Aβ), aryl hydrocarbon receptor (AhR), cytochrome P450 (CYP) 1B1, angiotensin-converting enzyme (ACE1), and angiotensin II type 1 (AT1) receptor in the cerebrum and hippocampus, in addition to cerebral microvascular tight junction (TJ) protein expression. Results:We observed age-related increases in oxidative stress, AhR, CYP1B1, Aβ, BACE1, and AT1 receptor in the CA1 region of the hippocampus, and elevation of cerebral AβPP, AhR, and CYP1B1 mRNA, associated with decreased cerebral microvascular TJ protein claudin-5. MVE-exposure resulted in further promotion of oxidative stress, and significant increases in AhR, CYP1B1, BACE1, ACE1, and Aβ, compared to the young and aged FA-exposed mice. Conclusion:Such findings suggest that MVE-exposure exacerbates the expression of factors in the CNS associated with AD pathogenesis in aged populations.

Keywords: Air pollution, Alzheimer’s disease, amyloid-β , AT1 receptor, reactive oxygen species

DOI: 10.3233/JAD-200929

Journal: Journal of Alzheimer's Disease, vol. 78, no. 4, pp. 1453-1471, 2020