Objective:To evaluate the role of NOD-like receptor 3 (NLRP3) inflammasome activation-mediated macrophage polarization in myocardial injury after ischemic stroke in diabetic mice.Methods:Wild-type C57BL/6J mice and NLRP3 -/- mice, aged 4-6 weeks, were fed a high fat diet combined with streptozotocin administration to develop the diabetic model. Twenty-four diabetic wild type C57BL/6J mice and 23 diabetic NLRP3 -/- mice were divided into wild type sham operation group (WT D-SHAM group, n=9) , wild type ischemic stroke group (WT D-MCAO group, n=15) , NLRP3 -/- sham operation group (NLRP3 -/-D-SHAM group, n=9) and NLRP3 -/- ischemic stroke group (NLRP3 -/-D-MCAO group, n=14). The ischemic stroke model was developed by middle cerebral artery occlusion in the animals anesthetized with isoflurane. Echocardiography and electrocardiography were carried out at 3, 7, 14 and 28 days after developing the model. Mice were sacrificed under deep anesthesia, and myocardial tissues were taken at 28 days after surgery for determination of the expression of macrophage marker F4/80 and M2 type macrophage marker CD206 mRNA (by real-time fluorescence quantitative polymerase chain reaction). Results:Compared with WT D-SHAM group, the cardiac output, mass of left ventricle and corrected mass of left ventricle were significantly decreased at 28 days after surgery, and QT interval and QTc interval were prolonged at 14 and 28 days after developing the model in WT D-MCAO group ( P<0.05). Compared with NLRP3 -/-D-SHAM group, the cardiac output, mass of left ventricle and corrected mass of left ventricle were significantly decreased, and QT interval and QTc interval were prolonged at 3 days after surgery in NLRP3 -/-D-MCAO group ( P<0.05). There was no significant difference in CD206 and F4/80 mRNA expression between WT D-SHAM group and WT D-MCAO group and between NLRP3 -/-D-SHAM group and NLRP3 -/-D-MCAO group ( P>0.05). Compared with WT D-MCAO group, the QT interval and QTC interval were significantly shortened at 14 and 28 days after developing the model, and the expression of F4/80 mRNA was down-regulated and the expression of CD206 mRNA was up-regulated at 28 days after developing the model in NLRP3 -/-D-MCAO group ( P<0.05). Conclusions:NLRP3 inflammasome activation-mediated polarization of macrophages to M2 phenotype is involved in myocardial injury after ischemic stroke in diabetic mice.