Epithelial Glutamate Retention Protects against Colitis
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that encompasses ulcerative colitis and Crohns disease. Here we identify the cystine/glutamate antiporter xCT as being markedly upregulated in the inflamed intestinal epithelium of patients with IBD. To clarify its functional contribution to disease pathogenesis, we performed genetic loss-of-function study and found that inhibition of xCT confers robust protection against dextran sulfate sodium (DSS)-induced colitis in mice. Intestinal epithelial cell (IEC)-specific deletion of xCT markedly attenuated colitis severity, demonstrating that epithelial xCT upregulation acts as a disease-exacerbating factor in IBD. Mechanistically, xCT deficiency preserved intracellular glutamate levels and protein polyglutamylation, thereby maintaining epithelial barrier integrity and protecting IECs from inflammatory injury. Consistently, pharmacological inhibition of glutamine synthetase, which increases intracellular glutamate, exerted a potent anti-inflammatory effect on the DSS-induced colitis. These findings identify intracellular glutamate retention in IECs as a previously unrecognized mechanism of epithelial protection and highlight both inhibition of xCT-dependent glutamate efflux and suppression of glutamine synthetase as potential therapeutic strategies for IBD.