Severe burn induces NLRP3 inflammasome activation in rat myocardium

AIM To study the expression and effect of NLRP3 inflammasome in severely burned rat myocardium. METHODSTwenty-four rats were randomly divided into three groups: sham group, burn group and BAY11-7082 treatment group. Animals were subjected to full-thickness burn injury of a 40% total body surface area via exposure to water maintained at 95°C for 18 sec. Rats in burn group received an intraperitoneal injection of 10 ml normal saline for resuscitation and rats in treatment group received 10 ml normal saline and 10 μl BAY11-7082 (0.2 mg/ml, 10 mg/kg). Rats in the sham group were immersed in room temperature water for 18 sec. Rats were sacrificed 8 h after burn and myocardial tissues and serums were sampled. Protein expressions of NLRP3 and caspase-1 were examined by Western blot and mRNA levels of NLRP3, caspase-1, IL-1β and TNF-α were tested by RT-PCR. Histomorphological images were also observed by H&E staining and levels of CK-MB and LDH were detected by ELISA. RESULTSProtein expressions of myocardial NLRP3 and caspase-1 in the burn group were significantly higher than in the sham group (P<0.01). When treated with BAY11-7082, expressions of NLRP3 and caspase-1 were significantly decreased (P<0.01). mRNA values of myocardial NLRP3, caspase-1, IL-1β and TNF-α in the burn group were 3.15±0.46, 2.47±0.24, 3.26±0.22 and 2.17±0.32, respectively, much higher than 1.00±0.09, 1.00±0.06, 1.00±0.08 and 1.00±0.07 in the sham group (P<0.01). When treated with BAY11-7082, mRNA values changed to 1.68±0.37, 1.55±0.17, 1.21±0.15 and 1.38±0.23, respectively, significantly lower compared with those in the burn group (P<0.01). In the sham group, myocardial fibers were in a well-arranged irregular stripe shape and the transverse striation was distinct. In the burn group, part of the myocardial fibers were arranged in a disordered manner with edema of the myocardial interstitium. Part of the myocardial fibers dissolved and inflammatory cells were infiltrated. In the treatment group, myocardial fibers were disordered and myocardial interstitial edema and inflammatory cell infiltration were alleviated. The values of CK-MB and LDH in serum of in burned rats were (2753±825) U/L and (2618±238) U/L, respectively, much higher than (247±76) U/L and (721±59) U/L in the sham rats (P<0.01). When treated with BAY11-7082, the values changed to (1267±248) U/L and 1982±183 U/L, respectively, significantly lower compared to those in the burn group (P<0.01). CONCLUSIONNLRP3 inflammasome is activated in severely burned rat myocardium. When treated with BAY11-7082, the activity of NLRP3 is inhibited, with myocardial injury alleviated and myocardial inflammatory response relieved.