Objective:To explore the molecules mechanism of Pin1 in severe heat stroke induced acute lung injury by observing Pin1 regulate oxidative stress and apoptosis formation in pulmonary microvascular endothelial cells (PMVECs) and lung tissue in heat stressed mice.Methods:In vitro, a PMVECs heat stress (HS) model was established. In the control group, PMVECs were placed in a standard 37 °C, 5% CO 2 cell incubator; in the HS group, PMVECs were placed in a 43 °C cell incubator for 2 h, then the cells were further incubated at 37 °C for 1, 3, 6 or 12 h. PMVECs were pretreated with Pin1 inhibitor Juglone (1 μmol/L) 1 h before 43 °C of HS. In vivo, a severe heat stroke mouse model was established. In the HS group, the mice were kept at the simulation of climate chamber with temperature (35.5±0.5) °C, humidity (60±5)%, the rectum temperature in mice was measured by the anal rectal temperature table, when the temperature reached 42 °C, the heat exposure was stopped, and the mice were sacrificed at 1, 3, 6 or 12 h after HS. In the control group, the mice were kept at room temperature (25±0.5) °C. Mice received daily intraperitoneal administration of Pin1 inhibitor Juglone (1 mg/kg) for 3 d before HS. The protein level of Pin1, cleaved caspase-9 and cleaved caspase-3 were analyzed by Western blot, the level of O 2-˙ in cells was observed by DHE staining and fluorescence microscopy, the levels of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) in lung tissue were measured by ELISA, the pathological changes of mice in different group were detected by HE staining, and the expression of Pin1 in the lung tissue of different groups was detected by immunohistochemical staining, the apoptosis rate of the lung tissue in different groups was tested by TUNEL staining. Results:At 1 h after HS, the protein expression of Pin1 in PMVECs and lung tissue began to increase in a rewarming time-dependent manner ( F=771.6, P<0.05; F=1 035, P<0.05). Cleaved caspase-9 protein in PMVECs and lung tissue started to increase at 3 h post-HS, then increased with a rewarming time-dependent manner ( F=729.8, P<0.05; F=1 773, P<0.05). The protein expression of cleaved caspase-3 in PMVECs and lung tissue also started to increase at 3 h after HS and the expression continued to be increased with prolonged rewarming time, and the trend was consistent with cleaved caspase-9 ( F=1 084, P<0.05; F=1 252, P<0.05). In addition, HS induced the increased release of O 2-˙ from PMVECs, HS induced the imbalance of oxidation-antioxidant system in lung tissue of mice after HS which verified by the continuous release of MDA ( F=114.2, P<0.05) and the continuous inhibition of SOD activity ( F=99.15, P<0.05). Compared with the HS group, pretreatment with Pin1 inhibitor Juglone in PMVECs and mice before HS significantly inhibited the protein expression of Pin1, cleaved caspase-9 and cleaved caspase-3 (all P<0.05), pretreatment with Pin1 inhibitor greatly reduced the release of O 2-˙ in PMVECs after HS, and promoted the restore of the oxidation-antioxidant system balance of lung tissue in mice with severe heat stroke. In addition, compared with the HS group, inhibiting the expression of Pin1 significantly decreased HS induced MDA release [(11.53±0.84) nmol/mL vs (9.65±0.69) nmol/mL, t=12.52, P<0.05], promoted the restore of SOD activity [(41.18±3.45) U/mL vs (57.52±4.83) U/mL, t=5.57, P<0.05] and improved the pathological damage of lung tissue as well as decreased the occurrence of apoptosis in post-HS mice. Conclusion:It was confirmed that Pin1 is involved in heat stress induced acute lung injury mainly through mediating oxidative stress response and apoptosis.