Objective:To evaluate the role of peptidylarginine deiminase 4 (PAD4)-mediated development of neutrophil extracellular traps (NETs) in lung ischemia-reperfusion injury (LIRI) in mice.Methods:Ninety-six clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups ( n=24 each) using a table of random numbers: sham operation group (group S), sham operation + PAD4 specific inhibitor GSK484 group (group S+ G), lung ischemia-reperfusion group (group L), and lung ischemia-reperfusion + GSK484 group (group L+ G). After anesthesia and mechanical ventilation, mice were subjected to left hilum occlusion for 1 h followed by 2 h of reperfusion to establish the LIRI model in L and L+ G groups. Mice underwent thoracotomy for 3 h without left hilum occlusion in S and S+ G groups. In S+ G and L+ G groups, GSK484 4 mg/kg was intraperitoneally injected once a day for 3 days before developing the model. At the end of reperfusion, blood samples were collected from the abdominal aorta for blood gas analysis to record arterial partial pressure of oxygen (PaO 2). Mice were then sacrificed to collect bronchoalveolar lavage fluid (BALF) and to obtain lung tissues. The concentrations of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and myeloperoxidase (MPO) in BALF were measured using enzyme-linked immunosorbent assay. The wet/dry lung weight (W/D) ratio was calculated. The lung tissues were obtained for microscopic examination of pathological changes (with a light microscope) which were scored after hematoxylin-eosin staining and for determination of the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) (by colorimetric assay) and expression of PAD4, neutrophil elastase (NE), high-mobility group box 1 (HMGB1), and citrullinated histone 3 (Cit-H3) (by Western blot). Results:Compared with group S, lung injury scores and W/D ratios were significantly increased, PaO 2 was decreased, the concentrations of IL-1β, IL-6, TNF-α and MPO in BALF were increased, the content of SOD was decreased, the content of MDA was increased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was up-regulated in L and L+ G groups ( P<0.05), and no significant changes were observed in the aforementioned parameters in group S+ G ( P>0.05). Compared with group L, lung injury scores and W/D ratios were significantly decreased, PaO 2 was increased, concentrations of IL-1β, IL-6, TNF-α, and MPO in BALF were decreased, the content of SOD was increased, the content of MDA was decreased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was down-regulated in group L+ G ( P<0.05). Conclusions:Up-regulated PAD4 expression can promote the development of NETs and aggravate oxidative stress and inflammatory responses in lung tissues, thereby participating in LIRI in mice.

Objective:To evaluate the role of peptidylarginine deiminase 4 (PAD4)-mediated development of neutrophil extracellular traps (NETs) in lung ischemia-reperfusion injury (LIRI) in mice.Methods:Ninety-six clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups ( n=24 each) using a table of random numbers: sham operation group (group S), sham operation + PAD4 specific inhibitor GSK484 group (group S+ G), lung ischemia-reperfusion group (group L), and lung ischemia-reperfusion + GSK484 group (group L+ G). After anesthesia and mechanical ventilation, mice were subjected to left hilum occlusion for 1 h followed by 2 h of reperfusion to establish the LIRI model in L and L+ G groups. Mice underwent thoracotomy for 3 h without left hilum occlusion in S and S+ G groups. In S+ G and L+ G groups, GSK484 4 mg/kg was intraperitoneally injected once a day for 3 days before developing the model. At the end of reperfusion, blood samples were collected from the abdominal aorta for blood gas analysis to record arterial partial pressure of oxygen (PaO 2). Mice were then sacrificed to collect bronchoalveolar lavage fluid (BALF) and to obtain lung tissues. The concentrations of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and myeloperoxidase (MPO) in BALF were measured using enzyme-linked immunosorbent assay. The wet/dry lung weight (W/D) ratio was calculated. The lung tissues were obtained for microscopic examination of pathological changes (with a light microscope) which were scored after hematoxylin-eosin staining and for determination of the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) (by colorimetric assay) and expression of PAD4, neutrophil elastase (NE), high-mobility group box 1 (HMGB1), and citrullinated histone 3 (Cit-H3) (by Western blot). Results:Compared with group S, lung injury scores and W/D ratios were significantly increased, PaO 2 was decreased, the concentrations of IL-1β, IL-6, TNF-α and MPO in BALF were increased, the content of SOD was decreased, the content of MDA was increased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was up-regulated in L and L+ G groups ( P<0.05), and no significant changes were observed in the aforementioned parameters in group S+ G ( P>0.05). Compared with group L, lung injury scores and W/D ratios were significantly decreased, PaO 2 was increased, concentrations of IL-1β, IL-6, TNF-α, and MPO in BALF were decreased, the content of SOD was increased, the content of MDA was decreased, and the expression of PAD4, NE, HMGB1 and Cit-H3 was down-regulated in group L+ G ( P<0.05). Conclusions:Up-regulated PAD4 expression can promote the development of NETs and aggravate oxidative stress and inflammatory responses in lung tissues, thereby participating in LIRI in mice.