Urinary Trypsin Inhibitor Exerts Multifaceted Regulation of Angiopoietin 2 in Septic Cardiomyopathy

Septic cardiomyopathy (SCM) represents one of the life-threatening manifestations of sepsis, for which specific therapies are currently lacking. The mechanism of action of urinary trypsin inhibitor (UTI), widely employed in treating acute inflammatory disorders, on SCM has remained elusive. Here, we observed that UTI alleviated cardiac function, reduced myocardial injury, and improved cardiac permeability in a cecum ligation and puncture (CLP)-induced sepsis mouse model. In addition, UTI significantly decreased serum and myocardial angiopoietin 2 (ANG2) levels in CLP mice, which is a biomarker associated with sepsis prognosis. In vitro experiments utilizing mouse myocardial microvascular endothelial cells (MMVECs) were conducted to explore the molecular mechanisms underlying UTI-mediated regulation of ANG2 expression, secretion, and its impacts on endothelial permeability and neutrophil adhesion. UTI mitigated endothelial barrier dysfunction and reduced neutrophil adherence following thrombin stimulation and ANG2 overexpression. The experiments further demonstrated that UTI-induced inhibition of ANG2 expression was related to the blockade of forkhead box O1 (FOXO1) and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) nuclear transcription and that UTI disrupted ANG2 exocytosis by reducing intracellular Ca 2+ concentration, a mechanism distinct from other serine protease inhibitors. In addition, UTI ameliorated barrier impairment and neutrophil adhesion in ANG2 overexpression cells by restoring tyrosine kinase receptor 2 Tie2)/protein kinase B (AKT) pathway phosphorylation. Docking predictions and surface plasmon resonance (SPR) further corroborated that UTI is strongly bound to ANG2. Altogether, our findings revealed a novel perspective wherein UTI functions as a multifaceted ANG2 inhibitor in SCM. Thus, ANG2 constitutes a promising therapeutic target for septic cardiomyopathy.