XBP1-mediated mitochondrial damage activates the mtDNA/STING/NLRP3 pathway to delay diabetic wound healing

BACKGROUND: Diabetic wounds (DBW) are characterized by high levels of reactive oxygen species (ROS) and pro-inflammatory factors; reducing inflammation is therefore a key strategy in the treatment of chronic diabetic wounds. X-box binding protein-1 (XBP1), a crucial transcription factor activated during endoplasmic reticulum stress, has been found to mediate mitochondrial damage, thereby activating the mitochondrial deoxyribonucleic acid/cyclic GMP-AMP synthase/stimulator of interferon genes (mtDNA/cGAS/STING) pathway and inducing Kupffer cell M1 polarization, which leads to excessive secretion of inflammatory cytokine. However, its role in regulating DBW healing remains unclear. Therefore, this study aims to explore the underlying mechanism of XBP1 in diabetic wound healing. METHODS: Human skin samples were collected from diabetic and non-diabetic patients at the First Affiliated Hospital with Nanjing Medical University between January 2021 and December 2023 to evaluate XBP1 expression. A wound model was constructed using macrophage-specific knockout and wild-type diabetic mice. Wound healing rate, inflammatory cytokine levels, macrophage polarization, mitochondrial integrity, and activation of the mtDNA/cGAS/STING/NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) pathway were assessed. Statistical analyses were performed using GraphPad Prism 10.0 software (GraphPad, La Jolla, USA), and a P value <0.05 was considered statistically significant difference. RESULTS: We found that XBP1 was highly expressed in macrophages within DBW(P <0.0001). Specific deletion of XBP1 in macrophages significantly reduced inflammatory cytokine secretion, increased M2 macrophage polarization, and accelerated wound healing. Further investigation revealed that knocking out Xbp1 in macrophages restored mitochondrial integrity, promoted ROS and mtDNA clearance, and inhibited the cGAS/STING/NLRP3 inflammatory pathway. Additionally, treatment with the XBP1 inhibitor toyocamycin markedly accelerated DBW healing. CONCLUSIONS: In summary, under hyperglycemic stress, XBP1-induced mitochondrial damage and activation of the mtDNA/cGAS/STING/NLRP3 pathway are a key mechanism underlying DBW healing impairment. Thus, XBP1 may serve as a promising therapeutic target for DBW treatment.