Punicalagin suppresses inflammation in ventilator‐induced lung injury through protease‐activated receptor‐2 inhibition‐induced inhibition of NLR family pyrin domain containing‐3 inflammasome activation

Abstract Punicalagin is recorded to be a potent anti‐inflammatory drug, while its effect on inflammation existing in ventilator‐induced lung injury (VILI) requires further verification. Rats were pretreated with punicalagin, followed by VILI modeling. Lung histopathological examination was performed with hematoxylin–eosin staining accompanied by the lung injury score. The lung wet/dry (W/D) weight ratio and total bronchoalveolar lavage fluid (BALF) protein level were measured. After transfection with protease‐activated receptor‐2 (PAR2) overexpression plasmids, mouse alveolar epithelial MLE‐12 cells were treated with punicalagin and then subjected to cyclic stretching. Punicalagin's cytotoxicity to MLE‐12 cells were measured by MTT assay. The levels of inflammatory cytokines (tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, and IL‐6), PAR2, NLR family pyrin domain containing‐3 (NLRP3), and apoptosis‐associated speck‐like protein containing a CARD (ASC) in the BALF, lung tissues or cells were analyzed by enzyme‐linked immune‐sorbent assay (ELISA), qRT‐PCR or/and western blot. Punicalagin treatment attenuated VILI‐induced lung histopathological changes and counteracted VILI‐induced increases in the lung injury score, W/D weight ratio and total protein level in BALF. Also, punicalagin treatment counteracted in vivo VILI/cyclic stretching‐induced increases in the levels of PAR2, inflammatory cytokines, NLRP3, and ASC. PAR2 overexpression potentiated the cyclic stretching‐induced effects, while punicalagin treatment revoked this PAR2 overexpression‐induced potentiation effect. In turn, PAR2 overexpression partly resisted the punicalagin treatment‐induced counteractive effects on the cyclic stretching‐induced effects. Punicalagin suppresses inflammation in VILI through PAR2 inhibition‐induced inhibition of NLRP3 inflammasome activation.