KARAP Deficiency Alleviates Intestinal Mucosal Barrier Dysfunction by Regulating Mitochondrial Homeostasis in Macrophages

Abstract Background Killer cell activating receptor-associated protein (KARAP) has been implicated in the progression of various inflammatory and immune-mediated diseases, including ulcerative colitis (UC). Although macrophages play a pivotal role in UC pathogenesis, how KARAP regulates macrophage immune responses remains poorly understood. Methods In this study, KARAP expression was assessed in peripheral blood mononuclear cells (PBMCs) and colonic tissues from patients with UC using quantitative real-time PCR and immunofluorescence. Dextran sulfate sodium (DSS)-induced colitis was established in KARAP knockout (KARAP⁻/⁻) and wild-type (WT) mice. In addition, macrophages isolated from KARAP⁻/⁻ and WT mice were cocultured with intestinal epithelial cells. Results KARAP expression was increased in PBMCs from patients with UC and was particularly high in macrophages. In the DSS-induced colitis model, KARAP deficiency improved intestinal barrier integrity by preserving macrophage mitochondrial homeostasis. KARAP blockade also increased interleukin (IL)-10 expression, thereby further preserving intestinal mucosal barrier integrity. Mechanistically, increased IL-10 expression depended on enhanced mTOR/mitophagy-mediated mitochondrial homeostasis in KARAP⁻/⁻ macrophages. Conclusions Our findings indicate that KARAP contributes to the regulation of intestinal mucosal barrier integrity by modulating macrophage mitochondrial homeostasis and IL-10 expression. Overall, these results offer new insight into the potential of KARAP as a new target for UC treatment strategies.