| Backgroud Pulmonary ischemia-reperfusion (I/R) injury is one of the most important complications following lung transplantation and cardiopulmonary bypass and may occur in many pulmonary disorders such as pulmonary artery thromboendarterectomy, thrombolysis after pulmonary embolism, etc. The development of I/R injury is associated with a higher mortality rate. The precise pathophysiological process of lung I/R injury has not been fully elucidated. Experimental studies revealed that production of endogenous H2S altered during chronic obstructive pulmonary disease, inflammatory lung injury and bleomycin-induced lung fibrosis, which suggested CSE/H2S pathway was involved in the pathogenesis of these diseases. It is not yet clear whether the CSE/H2S pathway is involved in the pathogenesis of lung I/R injury.Objective The present study was performed to explore the changes in endogenous hydrogen sulfide (H2S) generation and the role of H2S in the pathogenesis of pulmonary I/R injury in rats; To study the changes of A549 cell viability after treatment with NaHS at different concentrations for 24 h.Methods We prepared an isolated rat lung I/R model. Control group lungs were constantly perfused with Krebs-Henseleit solution; experimental lungs underwent 45-min ischemia followed by 45-min reperfusion. Additionally, treated lungs were perfused with different doses of H2S (50 umol/L or 100 umol/L) or propargylglycine (PPG; H2S inhibitor)(2 mmol/L) before ischemia. Rats underwent intraperitoneal injection of 75 umol/kg hemin solution 24 hr before lung harvest in Hemin group. We examined indices of lung injury: lung histological change, perfusion flow rate, ratio of lung wet weight to dry weight (W/D), and lung compliance. H2S content, CSE activity and CSE protein expression in lung tissues were measured by sulfide-sensitive electrode and western blotting, respectively. Malondialdehyde (MDA) content, activities of superoxide dismutase (SOD) and catalase (CAT), and restraint of superoxide anion (O2(.|-) ) production in lung tissues were measured to reflect oxidative stress. After incubation with NaHS at different concentrations in FBS-free DMEM at 37℃for 24 h, cell viability was determined by a slightly modified MTT assay.Results These results showed that H2S content and CSE activity in lungs after I/R were significantly higher than those in the control group (all P<0.05), while Western blot analysis revealed no change in the expression of pulmonary CSE protein after I/R. I/R induced lung edema, increased lung w/d ratio, increased alveolar thickening, marked neutrophil infiltration, slowed perfusion flow rate (thereby increasing pulmonary vascular resistance), and reduced lung compliance. PPG pretreatment aggravated the lung I/R injury. Pre-treatment with exogenous H2S or Hemin produced pulmonary protection in terms of lung morphology and function during pulmonary I/R: it attenuated I/R-induced lung histological injury, decreased pulmonary vascular resistance (increased lung perfusion flow rate), ameliorated pulmonary edema (lowered lung w/d ratio), and improved lung compliance. There were no difference in w/d ratio and pulmonary compliance between control and H2S-alone groups. MDA content was increased in lung tissues after I/R, and the activities of SOD and CAT and the restraint of O2(.|-) production in lung were lower after I/R than in the control group. H2S or Hemin preperfusion has been shown to attenuate lung oxidative injury, by reducing MDA production, attenuating the inhibition of SOD and CAT activities and potentiating the restraint of O2(.|-) production in the lung subjected to I/R, which attenuated lung oxidative injury. Pulmonary MDA content, SOD and CAT activities, and restraint of O2(.|-) production did not differ between the H2S-alone and control groups. Cell viability 24 h after NaHS (0.5-1 mM) administration was significantly reduced, this effect was not observed in A549 cells treated at lower concentrations (0.03-0.2 mM) of NaHS.Conclusion On the basis of these results, we assumed that the endogenous CSE/H2S pathway was involved in the pathogenesis of lung I/R injury, which suggests that intervening in the pulmonary CSE/H2S pathway may be a new preventive and therapeutic strategy for lung I/R injury. |
PDF Full Text Request