Role Of NLRP3 Inflammasome In Burn Wound Progression And Its Regulation By Autophagy

Objective:1. Excessive inflammation in burn wounds is one of the most important contributors to early burn wound progression. NLRP3 inflammasome plays important role in innate immunity and inflammatory response. However, the role of NLRP3 inflammasome in burn wound progression remains unclear. So the first part of this study is to investigate the expression and the role of NLRP3 inflammaosme in burn wound progression in a rat deep-second degree burn model.2. Autophagy is a highly conserved lysosome-dependent degradation pathway. Our previous studies have demonstrated that autophagy is protective in burn wound progression. However, the exact mechanisms are unknown. Are there any relations between autophagy and NLRP3 inflammasome in the background of burn wound progression? Does autophagy inhibit burn wound inflammation and protect from burn wound progression through regulating NLRP3 inflammasome mediated inflammatory pathway? This is the main object to be discussed in the second part of the study.Methods:This study is divided into two parts. The fisrt part is to investigate the expression and the role of NLRP3 inflammasome in burn wound progression. A deep-second degree burn model was eastablished on the back of Wistar rats. The expresssion and change pattern of the NLRP3 inflammasome in burn wounds at 1h,24h,48h, and 72h post burn were observed. Then a specific NLRP3 inflammasome inhibitor, MNS, was used to inhibit the activation of NLRP3 inflammasome. The NLRP3 inflammasome activity in burn wounds, the blood perfusion, inflammatory infiltration, burn depth, and the time to wound healing were observed. The second part is to discuss the regulatory effects of autophagy on NLRP3 inflammasome in burn wounds and the influence of autophagy on burn wound progression. The burned rats were randomly divided into three groups: treated with either vehicle control, rapamycin, or chloroquine. Then the autophagy level, activity of NLRP3 inflammsome, inflammatory cytokines production, free radical injuries. H&E staining and Masson staining in burn wounds were assayed.Results:First part results:The activity of NLRP3 inflammasome in burn wounds were significanlty elevated as compared to sham burn control. The NLRP3 inflammasome was mainly observed in macrophages of the zone of stasis. MNS significantly inhibited the NLRP3 inflammasome activation in burn wounds, and consequently reduced the inflammatoy infiltrations in burn wounds, enhanced the blood perfusion, ameliorated the progression of burn injury, and accelerated burn wound healing process.Second part results:Comparing with the control group, the autophagy level in burn wounds of rapamycin treated rats was signifcantly enhanced, the NLRP3 inflammsome activity was remarkably decreased, the infiammtory infiltration in burn wound were ameliorated, the free radical injury was reduced and the wound progression was ameliorated. Whereas comparing with the control group, the autophagy level in burn wounds of chloroquine treated rats was signifcantly decreased, the NLRP3 inflammsome activity was remarkably increased, the infiammtory infiltration in burn wound were exacerbated, the free radical injury was worsened and the wound progression was exacerbated.Conclusion:1. The NLRP3 inflammasome activation in burn wounds was significantly increased after burn injury in this rat second-degree burn model. The NLRP3 inflammasome was mainly expressed in macrophages of the zone of stasis. Inhibiting the activity of NLRP3 inflammasome can ameliorate burn wound progression and accelerate burn wound healing.2. Activating or inhibiting autophagy level can regulate the NLRP3 inflammasome activity in burn wounds, and then influence the burn wound depth. The protective role of autophagy on early burn wound progression is at least partly mediated by inhibiting the NLRP3 inflammsome activity in burn wounds.