Decreased expression of prohibitin 1 mediates high-mobility group protein 1-induced pulmonary artery endothelial cell injury.

OBJECTIVES There is a significant increase of high-mobility group protein B1 (HMGB1) in plasma levels of patients with pulmonary hypertension, but the biological significance is still unclear. Anti-proliferative protein 1 (prohibitin 1, PHB1) is an important protein that maintains the homeostasis of vascular cells. This study aimed to investigate the effect of HMGB1 on pulmonary artery endothelial cells and the role of PHB1. METHODS In vivo experiment: A rat model of pulmonary hypertension induced by monocrotaline (MCT) was constructed. The right ventricular systolic pressure (RVSP), and the weight ratio of right ventricle to left ventricle plus ventricular septum were used to evaluate the success of model. ELISA was used to detect the level of HMGB1 in rat's plasma. Western blotting was used to detect the level of PHB1 in rat's lung tissues. CD31 immunofluorescence was used to detect the integrity of pulmonary vascular endothelium. In vitro experiments: Pulmonary artery endothelial cell (PAEC) was incubated with HMGB1 to observe the effect of HMGB1 on PAEC injury. Overexpression and knockdown of PHB1 were conducted, and the role of PHB1 was investigated by detecting the levels of reative oxygen species and cytochrome c (cyto-c), and the activation of caspase-3. RESULTS Compared with the control group, the level of HMGB1 in the plasma of rats with pulmonary hypertension was significantly increased (P<0.05), and the expression of PHB1 in the lung tissue was decreased accompanied with endothelial dysfunction (P<0.05); HMGB1 incubation damaged the pulmonary artery endothelium and down-regulated PHB1 expression (P<0.05), while overexpression of PHB1 reduced the PAEC damage and oxidative stress induced by HMGB1 (P<0.05). Meanwhile, PHB1 reduced HMGB1-induced cyto-c expression and caspase-3 cleavage by inhibiting oxidative stress (P<0.05). CONCLUSIONS The down-regulation of PHB1 expression mediates HMGB1-induced PAEC injury, which is related to the induction of oxidative stress, the increase of cyto-c release, and the promotion of caspase-3 cleavage.