The NLRP3 inflammasome is an intracellular multiple-protein complex that controls the maturation and release of interleukin (IL)-1β and IL-18. Endogenous carbon monoxide (CO) is anti-inflammatory. The aim of this study was to assess the effects/mechanisms of CO-releasing molecule-3 (CORM-3)-dependent modulation of the NLRP3 inflammasome in cardiac fibroblasts (CF) and its effect on myocardial function in sepsis. CF were treated with CORM-3 or inactive CORM-3 (iCORM-3) before NLRP3 inflammasome priming with lipopolysaccharides (LPS) or following activation with adenosine triphosphate (ATP). In parallel, cardiomyocytes (CM) were challenged with supernatants of LPS/ATP-stimulated CF or a cytokine mixture (Cyto-mix) containing IL-1β, IL-18, and HMGB1. In vivo, mice were treated with CORM-3 before or after LPS to induce sepsis (endotoxemia). Pretreatment of CF with CORM-3 prevented an LPS-induced increase in NLRP3 and pro-IL-1β expression. Treatment of CF with CORM-3 before ATP prevented ATP-induced activation of the NLRP3 inflammasome. Challenging CF with LPS/ATP promoted NLRP3 interactions with adaptor ASC (apoptosis-associated speck-like protein containing a caspase-recruitment domain), which was prevented by CORM-3. Challenging CM with supernatants of CF with LPS/ATP or Cyto-mix (IL-1β, IL-18, and HMGB1) resulted in CM apoptosis, which was attenuated with either a CORM-3 or IL-1 receptor antagonist. Finally, myocardial NLRP3 inflammasome activation and myocardial dysfunction in septic mice were abolished by CORM-3. In NLRP3-deficient mice with sepsis, CORM-3 did not show additional benefits in improving myocardial function. Our results indicate that CORM-3 suppresses NLRP3 inflammasome activation by blocking NLRP3 interactions with the adaptor protein ASC and attenuates myocardial dysfunction in mice with sepsis.
Diabetic cardiomyopathy (DiCM) is characterized by myocardial fibrosis and dysfunction. In rodent models of diabetes myocardial HMGB1 increases while IL-33 decreases. The major cardiac cell type expressing HMGB1 is the myocyte while the primary IL-33 expressing cell is the fibroblast. The aim of this study was to delineate the extracellular communication pathway(s) between cardiomyocytes and fibroblasts that contributes to murine DiCM. The streptozotocin (STZ)-induced murine model of diabetes and a cardiomyocyte/fibroblast co-culture challenged with high glucose were used. In STZ mice, myocardial HMGB1 expression was increased while IL-33 expression decreased (immunofluorescence and Western blot). In addition, STZ mice had an increased myocardial collagen deposition and myocardial dysfunction (pressure-volume loop analysis). An HMGB1 inhibitor (A-box) or exogenous IL-33 prevented the myocardial collagen deposition and dysfunction. In the cardiomyocyte/fibroblast co-culture model, HG increased cardiomyocyte HMGB1 secretion, decreased fibroblast IL-33 expression, and increased fibroblast collagen I production. Further, using A-box and HMGB1 shRNA transfected myocytes, we found that cardiomyocyte-derived HMGB1 dramatically potentiated the HG-induced down-regulation of IL-33 and the increase in collagen I expression in the fibroblasts. The potentiating effects of the cardiomyocytes was diminished when toll-like receptor 4 deficient (TLR4(-/-)) fibroblasts were co-cultured with wild-type myocytes. Finally, TLR4(-/-) mice with diabetes had increased myocardial expression of HMGB1, but failed to down-regulate IL-33. The diabetes-induced myocardial collagen deposition and cardiac dysfunction were significantly attenuated in TLR4(-/-) mice. In conclusion, our findings support a role for "cardiomyocyte HMGB1-fibroblast TLR4/IL-33 axis" in the development of myocardial fibrosis and dysfunction in a murine model of diabetes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.