LAUSR

BACKGROUND Sepsis is a life-threatening condition caused by bacterially-induced systemic inflammation that can result in septic cardiomyopathy. Bacterial lipopolysaccharide (LPS) stimulates the Toll-like receptor 4 (TLR4, Tlr4)-induced inflammatory response and intracellular reactive oxygen species (ROS) accumulation, causing sarcoplasmic reticulum (SR) Ca2+ leakage and impairing myocardial contractility. Hydroxysafflor yellow A (HSYA), a quinochalcone C-glycoside pigment derived from flowers of Carthamus tinctorius L or safflower, suppresses the inflammatory response in myocardial ischemia-reperfusion by inhibiting TLR4 signaling. OBJECTIVE Therefore, we hypothesized that HSYA may display therapeutic efficacy against septic cardiomyopathy. METHOD In silico docking simulation and in vitro assays were used to characterize HSYA's binding to Md2, LPS-Md2 interactivity, and Tlr4/Md2 complex formation. An in vitro murine cardiomyocyte model using small-interfering RNAs (siRNAs) targeting Tlr4 or Md2 was used to investigate HSYA's cellular effects. An LPS-induced rat model of sepsis and a cecum ligation and puncture (CLP) murine model of polymicrobial sepsis in WT or Tlr4-/- animals were employed to test HSYA's in vivo efficacy. RESULTS HSYA directly interacts with the Ser120 residue in Md2's hydrophobic pocket, thereby interfering with LPS-Md2 interactivity and Tlr4/Md2 complex formation. In vitro, HSYA rescued LPS-induced mitoROS and intracellular ROS accumulation, SR Ca2+ leakage, NFκB p65 activation, NFκB p65-mediated Il-6 secretion, and apoptosis in a Tlr4/Md2-dependent manner. In both in vivo models, HSYA improved sepsis-induced cardiac dysfunction, SR Ca2+ leakage, NFκB p65 activation, NFκB p65-mediated Il-6 secretion, and apoptosis in a Tlr4-dependent manner. CONCLUSION This evidence suggests that HSYA may be a viable therapeutic strategy in treating septic cardiomyopathy.