Abstract
BACKGROUND: Vascular leakage is a major cause of multiple organ failure and mortality in sepsis, and factors that regulate endothelial integrity could serve as promising biomarkers of septic shock development. Copine family members (CPNEs) are well-characterized as soluble membrane-binding proteins, whether CPNEs play a critical role in maintaining vascular integrity during sepsis, however, remains unclear. METHODS: Human aorta single-nucleus RNA-sequencing data were analyzed for the expression profile of all Copine family members (CPNE1-9). Plasma levels of CPNE5, Ang-II, sICAM-1, and SDC-1 were measured in human sepsis patients at admission and healthy donors as well as in septic mice induced by injection i.p. with cecal slurry. The correlation of CPNE5 levels to other three factors (Ang-II, sICAM-1, SDC-1) were analyzed. CPNE5-knockdown endothelial cells (ECs) and global CPNE5-knockout (KO) mice were utilized to determine the critical role of CPNE5 in sepsis-triggered vascular leakage, organ damage and mortality. RESULTS: Among nine CPNEs, only CPNE5 is predominantly expressed in human aorta endothelial cells. In sepsis patients (n = 77), plasma levels of CPNE5 were significantly reduced, whereas plasma levels of Ang-II, sICAM-1, and SDC-1 were markedly elevated, compared to healthy donors (n = 44; p < 0.01). Similar findings were also observed in a murine sepsis model induced by cecal slurry (CS)-injection intraperitoneally. Furthermore, in the supernatants of cultured ECs treated with LPS or pro-inflammatory cytokine mixture (Cytomix: TNFα/IL-1β/IFNγ, each 10 ng/mL), the concentrations of CPNE5 were significantly lower, which was negatively correlated with the higher EC permeability, compared to the control group. Accordingly, siRNA-mediated knockdown of CPNE5 in ECs caused hyperpermeability upon stimulation with LPS or Cytomix. In vivo, we observed that loss of CPNE5 increased vascular leakage, leading to severe organ injury and higher mortality, compared to WT mice upon septic conditions. The initial mechanistic analysis showed that the reduction of CPNE5 in cardiac and pulmonary ECs was linked to the increased cleavage of membrane tight junctions and adherens junctions. CONCLUSIONS: These observations from human sepsis patients and a murine sepsis model suggest that reduced plasma levels of CPNE5 may contribute to sepsis-induced vascular leakage and mortality.