Linking alcohol use to Alzheimer’s disease: Interactions with aging and APOE along immune pathways

Abstract

Although it is known that APOE genotype is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD), AD development is a multifactorial process. Alcohol use is a contributor to the epidemic of AD and related dementias in the US and globally, yet mechanisms are not fully understood. Carriers of the APOE ε4 allele show elevated risk of dementia in relation to several lifestyle factors, including alcohol use. In this review, we describe how alcohol interacts with APOE genotype and aging with potential implications for AD promotion. Age-related immune senescence and “inflammaging” (i.e., low-grade inflammation associated with aging) are increasingly recognized as contributors to age-related disease. We focus on three immune pathways that are likely contributors to AD development, centering on alcohol and APOE genotype interactions, specifically: 1) microbial translocation and immune activation, 2) the senescence associated secretory phenotype (SASP), and 3) neuroinflammation. First, microbial translocation, the unphysiological movement of gut products into systemic circulation, elicits a proinflammatory response and increases with aging, with proposed links to AD. Second, the SASP is a set of intercellular signaling factors, e.g., proinflammatory cytokines and chemokines, growth regulators, and proteases, that drives cellular aging when senescent cells remain metabolically active. The SASP can drive development of aging-diseases such as AD. Third, neuroinflammation occurs via numerous mechanisms such as microglial activation and is gaining recognition as an etiological factor in the development of AD. This review focuses on interactions of alcohol with APOE genotype and aging along these three pathways that may promote AD. Further research on these processes may inform development of strategies to prevent onset and progression of AD and to delay associated cognitive decline.