Molecular Mechanisms Underlying the Regulation of VCAM-1 Expression by the Short-Chain Fatty Acid Butyrate

Over the past decade, cerebrovascular inflammation has been increasingly recognized as a contributor to the progression of neurodegenerative diseases, particularly Alzheimer's disease (AD). One of the molecular hallmarks of cerebrovascular inflammation is the increased expression of vascular cell adhesion molecule (VCAM)-1 on blood-brain barrier (BBB) endothelial cells. Exposure to amyloid beta (Aβ) peptides, one of the primary hallmarks of AD, and pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) induces VCAM-1 expression on the BBB endothelium, which facilitates extravasation of leukocytes into the brain thereby promoting an inflammatory response. Therefore, it is crucial to explore therapeutic agents that can inhibit VCAM-1 expression induced by Aβ and TNF-α. Short-chain fatty acids, such as butyrate, produced by the gut microbiota as byproducts of dietary fiber metabolism, are recognized for their anti-inflammatory properties. In this study, we successfully tested the hypothesis that butyrate mitigates Aβ and TNF-α-induced VCAM-1 expression in polarized human cerebral microvascular endothelial cell monolayers, a widely used BBB in vitro model. Our findings indicated that pre-treatment with butyrate significantly reduced Aβ42 and TNF-α mediated upregulation of VCAM-1. Furthermore, we have shown STAT3/GATA6 axis as a key mediator of anti-inflammatory effects of butyrate. These findings provide mechanistic insight into butyrate's protective role and highlight its potential to mitigate Aβ and TNF-α-induced cerebrovascular inflammation in AD.