Alteration of the bile acid pool attenuates neuroinflammation in the EAE mouse model of Multiple Sclerosis

Abstract

Bile acids are critical signaling molecules that mediate gut crosstalk with other organs, including the brain. The primary bile acids, such as chenodeoxycholic acid (CDCA), are synthesized in the liver and modified by gut bacteria to generate secondary bile acids like the 12α-hydroxylated deoxycholic acid (DCA). Bile acids are effciently absorbed in the distal ileum, and recent studies have implicated them in neuroinflammation and the pathophysiology of several neurological diseases such as Multiple Sclerosis (MS). However, the specific effects of different types of bile acids on MS have not been thoroughly investigated. We hypothesize that bile acids differentially affect neuroinflammation and that treatment with cholestyramine (bile acid sequestrant) modulates astrocyte activation in a mouse model of MS. Methods: Primary astrocyte cultures were prepared from 6-10-week-old C57BL/6 mice and incubated with cytokines in the presence and absence of bile acids. The expression of inflammatory and astrocyte activation markers was assessed by real-time qPCR. The effects of blocking bile acid absorption on MS were examined using the established Experimental Autoimmune Encephalomyelitis (EAE) mouse model of MS in 8-week-old female mice (C57BL/6). Mice were fed either a standard chow diet or a standard chow diet supplemented with 2% cholestyramine, a bile acid sequestrant, to block bile acid absorption. Statistical significance between groups was determined by an unpaired T-test. Results: Astrocytes treated with cytokines (TNF-α, 10 ng/mL, IL1-β, 10 ng/mL, 24 h) significantly increased the mRNA expression of TNF-α and IL1-β and markers of astrocyte activation, lipocalin 2 (LCN2), and Serpina3n. Co-treatment with cytokines and CDCA but not DCA (50 μM, 24 h) significantly decreased TNF-α (~56%, p<0.01), IL1-β (~40%, p<0.01), LCN2 (~26%, p<.001), and Serpina3n (~44%, p<.001), vs cytokines alone. The taurine-conjugate, TCDCA, also resulted in significant decreases in the expression of TNF-α (~72%, p<0.001), IL1-β (~53%, p<.001), LCN2 (~30%, p<0.05), and Serpina3n (~16%, p<0.01), suggesting an anti-inflammatory effect specific to CDCA and its taurine conjugate on astrocytes. Cholestyramine treatment in EAE mice was associated with significant reductions in the mRNA expression of TNF-α (~40%, p<0.05) and Serpina3n (~30%, p= 0.217) in the frontal cortex of the brain. Together, these data imply that altering the composition of the bile acid pool may be a viable therapeutic strategy for MS patients by attenuating neuroinflammation. University of Illinois at Chicago, JBVMC, Chicago, IL. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.