β2AR against myocarditis-lipid deposition depends on estrogenic environment in stress.

Cardiac lipid accumulation and inflammation have been linked to stress. There is mounting evidence that estrogen reduces lipid deposition and has anti-inflammatory properties; however, the exact mechanism is unknown. Recent studies showed that NLRP3 inflammasome is a key trigger of cardiac inflammation, and it is also involved in the progression of metabolic diseases. This study investigated the crucial role of the NLRP3 inflammasome in lipid accumulation during stress and the regulatory mechanism of estrogen in this process. Stress models were established by isoproterenol treatments in mice and H9c2 cells. With 5 mM isoproterenol, NLRP3 inflammasome activation was observed earlier at 0.5 h than that of lipid accumulation at 1 h in H9c2 cells. At 1 h after stress, the isoproterenol concentration required for NLRP3 inflammasome activation was lower compared to the concentration required for lipid deposition in mice myocardia and H9c2 cells; the former required 210 mg/kg or 10 μM for activation while the latter required 280 mg/kg or 5 mM. Knocking out or inhibiting NLRP3 inflammasome reduced myocardial lipid accumulation caused by stress in the mice myocardia and H9c2 cells. Estrogen downregulated NLRP3 inflammasome and reduced lipid accumulation in cardiomyocytes during stress. Finally, the anti-inflammatory and lipid-lowering effect of estrogen disappeared in β2ARKO mice and H9c2 cells pre-treated with ICI118,551. In conclusion, the upregulation of NLRP3 inflammasome induced by stress led to myocardial lipid accumulation, and β2AR downregulated NLRP3 inflammasome thereby reducing lipid accumulation which was dependent on the estrogenic environment.