Oral vancomycin treatment alters levels of indole derivatives and secondary bile acids modulating the expression of mTOR pathway genes in astrocytes during EAE

Astrocytes play important roles in the central nervous system (CNS) during health and disease. Prior studies have shown that gut commensals derived indole derivatives as well as secondary bile acids modulate astrocyte function during the late stage of EAE (recovery phase). Here we show that administering vancomycin to mice starting during the early stage of EAE improved disease recovery, an effect that is mediated by the gut microbiota. We observed that 6 taxa within the Clostridia vadin BB60 group were enriched in vancomycin treated mice compared to untreated EAE mice. Vancomycin-treated EAE mice also had elevated serum levels of the anti-inflammatory tryptophan derived metabolite, indole-3-lactic acid and decreased levels of deoxycholic acid, a pro-inflammatory secondary bile acid. RNA sequencing revealed altered expression of several genes belonging to the mammalian target of rapamycin (mTOR) pathway in astrocytes obtained during the late stage of EAE from vancomycin treated EAE mice. Furthermore, we observed a link between serum levels of indole derivatives and bile acids and expression of several genes belonging to the mTOR pathway. Interestingly, the mTOR signaling cascades have been implicated in several key biological processes including innate (e.g., astrocyte) immune responses as well as neuronal toxicity/degeneration. In addition, rapamycin, a specific inhibitor of mTOR, has been shown to inhibit the induction and progression of established EAE. Collectively, our findings suggest that the neuroprotective effect of vancomycin is at least partially mediated by indole derivatives and secondary bile acids modulating the expression of mTOR pathway genes in astrocytes. HIGHLIGHTSO_LIVancomycin attenuated established EAE through regulation of the microbiota C_LIO_LIVancomycin induced increased serum levels of indole-3-lactic acid, decreased serum levels of indoxyl-3-sulfate, p-cresol and decreased stool levels of deoxycholic acid C_LIO_LIVancomycin modulated the expression of mTOR pathway genes in astrocytes C_LIO_LILactobacillus reuteri regulated the expression of mTOR pathway genes in astrocytes C_LIO_LISerum levels of indole-3-lactic acid, indoxyl-3-sulfate, p-cresol and deoxycholic acid correlated with expression of mTOR pathway genes in astrocytes C_LI