5-OH-TMT mitigates colitis through HTRA2 binding–mediated activation of the Dectin-1 signaling pathway

Abstract Inflammatory bowel disease (IBD) is a debilitating condition driven by the dual pathologies of chronic inflammation and impaired intestinal barrier function. A significant clinical need exists for therapies that can effectively target both issues simultaneously. In this study, we investigated the therapeutic potential and mechanism of 5-hydroxy- N,N,N -trimethyltryptamine (5-OH-TMT), a quaternary ammonium salt derivative of bufotenine. We demonstrate that oral administration of 5-OH-TMT significantly ameliorates disease in two distinct murine models of experimental colitis (dextran sulfate sodium-induced and 2,4,6-trinitrobenzene sulfonic acid-induced colitis). The 5-OH-TMT treatment markedly improved clinical symptoms, potently suppressed pro-inflammatory cytokine production, and promoted a vital restoration of intestinal barrier integrity. Further exploration of the molecular basis of action of 5-OH-TMT using an unbiased proteomic screen revealed that 5-OH-TMT directly binds to and inhibits the mitochondrial serine protease high-temperature requirement A2 (HTRA2) protein. Additional mechanistic studies demonstrated that this inhibition of HTRA2 activates the Dectin-1/CARD9 signaling pathway, a key axis in mucosal defense. Subsequent work confirmed that siRNA-mediated silencing of HTRA2 could phenocopy the drug’s effects, including the suppression of pro-inflammatory NF-κB phosphorylation. In conclusion, our findings establish that 5-OH-TMT mitigates colitis through a newly identified mechanism involving direct HTRA2 inhibition. This inhibition unleashes a protective Dectin-1-dependent program that both suppresses inflammation and restores barrier function. This work identifies the HTRA2-Dectin-1 axis as a promising new therapeutic target for IBD.