EPICERTIN, an engineered variant of cholera toxin B subunit, promotes survival and a pro-remodeling macrophage phenotype for mucosal healing in colitis

Abstract

EPICERTIN, a modified cholera toxin B subunit (CTB), facilitates mucosal healing in preclinical colitis models, but its anti-inflammatory mechanisms remain unclear. Here, we investigated EPICERTIN's effects on macrophages. In a dextran sulfate sodium-induced colitis mouse model, oral administration of EPICERTIN reduced neutrophil infiltration and increased CX3CR1⁺MHCII^lo/- (M2-like) over CX3CR1⁺MHCII^hi (M1-like) macrophages in the colon lamina propria. This was concurrent with upregulation of colony-stimulating factor 2 (Csf2) and growth factors (Egf, TgfA, Fgf, Pdgf) involved in mucosal remodeling. Similarly, in colon tissue from a human with active colitis, EPICERTIN significantly upregulated CSF2 and tissue repair-associated genes while downregulating proinflammatory genes (IL1B, IL6ST). In vitro, EPICERTIN promoted macrophage survival under serum-free conditions, whereas CTB induced apoptosis in murine RAW264.7 cells, peritoneal macrophages, and human THP-1 cells. Remarkably, EPICERTIN protected macrophages from apoptosis induced by chemical ER-stressors or lipopolysaccharides. Additionally, EPICERTIN downregulated cell surface molecules HLA-DR, CD14, CD80, and CD86 in THP-1 cells and modestly upregulated chemokines and proinflammatory cytokines genes as well as TGFB1 in human PBMC-derived macrophages. In contrast, CTB strongly increased proinflammatory genes and activation markers. These findings indicate that EPICERTIN promotes macrophage homeostasis by inducing a less inflammatory, pro-remodeling phenotype, whereas CTB may trigger activation-induced cell death.

Keywords: M2-like macrophage; apoptosis; cholera toxin B subunit; colitis; mucosal healing.