Desulfovibrio spp. are sulfate-reducing bacteria (SRB) associated with conditions such as inflammatory bowel disease (IBD) that are linked to intestinal barrier dysfunction (leaky gut). Previously, we reported that Desulfovibrio vulgaris (DSV) caused increased intestinal permeability by upregulating nuclear transcription factor Snail. However, the signaling mechanisms underlying this effect remain unclear. Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that maintains intestinal barrier integrity and negatively regulates Snail and promotes its degradation by proteasomes. Rapamycin has been shown to protect the intestinal barrier and is also known to activate GSK-3. In this study, we investigated whether DSV disrupts intestinal barrier function through modulation of GSK-3 signaling and whether rapamycin could counteract these effects. Using a previously established DSV-induced paracellular permeability model using polarized Caco-2 monolayers, here, we showed that DSV induced inhibitory phosphorylation of GSK-3. Pretreatment of cells with rapamycin prevented DSV- induced phospho- inactivation of GSK-3, suppressed Snail expression and nuclear localization, and significantly reduced DSV-induced barrier permeability. Inhibition of proteasomal degradation with MG132 abolished the protective effects of rapamycin on barrier permeability, supporting a role for GSK-3–mediated proteasomal regulation of Snail. Together, these findings identify GSK-3 signaling as a novel mechanism underlying DSV-induced intestinal barrier dysfunction and highlight rapamycin as a potential therapeutic approach strategy to protect intestinal barrier integrity in response to DSV. Specifically, targeting the GSK-3/Snail pathway may represent a promising strategy to mitigate SRB-associated intestinal barrier disruption.
Singh et al. (Mon,) studied this question.