Procyanidin B2 protects rats from paraquat-induced acute lung injury by inhibiting NLRP3 inflammasome activation.

Paraquat is a commonly used heterocyclic herbicide and has high toxicity by causing acute lung injury. There is no effective treatment for paraquat poisoning. We evaluated the effects of procyanidin B2, a natural dietary phytochemical, on paraquat-induced lung injury in rats. Paraquat was used to induce acute lung injury of rats, which were administered with procyanidin B2. The lung injury was evaluated by measuring the lung/body weight ratio, the histology and PMNs count. The oxidative stress was assessed by detecting ROS-mediated indices in the BALF. The expression of IL-1β and IL-18 were detected by RT-PCR and ELISA. The levels of NLRP3 inflammasome components including NLRP3, ASC and caspase-1 were detected by western blot. The lung injury in the paraquat-induced models in NLRP3 gene silenced animals was compared with the same lung injury model treated with procyanidin B2. Administration of procyanidin B2 significantly reduced paraquat-induced lung injury with lower BALF PMNs count, MPO activity, MDA level and elevated SOD activity. Procyanidin B2 suppressed expression of IL-1β and IL-18 at both RNA and protein levels, similar to the NLRP3 gene silenced rats. Compared to paraquat-induced group, procyanidin B2 showed remarkably decreased NLRP3, ASC and caspase-1 signals in the lung tissues in a dose-dependent manner. Procyanidin B2 significantly suppressed the activation of NLRP3 inflammasome in the lung tissue induced by paraquat in the rat model. This finding revealed a novel mechanism by which procyanidin B2 exerts anti-inflammatory effects and their clinical benefits in health.