KIAA1199 aggravates sepsis-induced lung injury by promoting complement activation.

Sepsis-induced acute lung injury (ALI) is a life-threatening condition associated with high mortality rates. While emerging evidence suggests that KIAA1199 (also known as cell migration-inducing protein, CEMIP) contributes to the pathogenesis of bacterial infections, its specific role in sepsis-induced ALI remains largely unexplored. In this study, we find that serum levels of KIAA1199 are significantly elevated in sepsis patients compared to healthy individuals, demonstrating a positive correlation with the SOFA scores. Additionally, we observe the expression of KIAA1199 increased in the lung tissue of septic mice, particularly in alveolar epithelial Type II (AT2) cells. We further generate AT2-specific KIAA1199 knockout mice on a male C57BL/6 J background and establish LPS-induced ALI model. The results indicate that KIAA1199-deficient mice exhibit improved survival rates, reduced lung injury, and decreased levels of proinflammatory cytokines. Transcriptomic analysis and functional validation reveal that KIAA1199 promotes pulmonary complement activation by downregulating complement factor H (CFH), a critical regulator of the alternative complement pathway. Mechanistically, KIAA1199 downregulates CFH expression by enhancing the ubiquitinated degradation of its transcription factor of p53. In conclusion, our data demonstrate that KIAA1199 exacerbates sepsis-induced ALI via promoting local complement activation through CFH suppression, which may serve as a potential therapeutic target for sepsis-induced ALI.