Role of p38MAPK signaling pathway in up-regulation of heme oxygenase-1 expression in lung tissues in rats with acute lung injury induced by endotoxic shock

Abstract

Objective To evaluate the role of p38MAPK signaling pathway in the up-regulation of heme oxygenase-1 (HO-1) expression in the lung tissue in rats with acute lung injury (AL1) induced by endotoxic shock.Methods Forty-eight male SD rats,aged 8 weeks,weighing 180-200 g,were randomly divided into 4 groups ( n =12 each):control group ( group C ) ; endotoxic shock group ( group LS );endotoxic shock +SB203580 (a specific p38MAPK inhibitor) group (group LSS) and SB203580 group (group SB).Normal saline 0.5ml was injected via the femoral vein in groups C and SB,while LPS 10 mg/kg (in 0.5 ml normal saline) was injected via the femoral vein in groups LS and LSS.When MAP was decreased to 75％ of baseline value,10％ dimethyl sulfoxide (DMSO) 0.1 ml was infused via the femoral vein in groups C and LS,while SB203580 5 mol/kg (in 10％ DMSO 0.1 ml) was infused via the femoral vein at a rate of 0.01 ml/min in groups LSS and SB.Arterial blood samples were obtained at 6 h after LPS or normal saline was given for blood gas analysis and oxygenation index (PaO2/FiO2) was calculated.Then the rats were sacrificed and the lungs were removed for microscopic examination.The pathological changes of the lung were scored.The lung water content was calculated.The MDA content,SOD activity,and expression of HO-1 mRNA and protein,p38MAPK protein and phospharylated p38MAPK (p-p38MAPK) protein were determined.Results Compared with group C,the oxygenation index and SOD activity were significantly decreased,the pathological score,lung water content and MDA content were significantly increased,and the expression of HO-1 mRNA and protein and p-p38MAPK protein was significantly up-regulated ( P＜0.05),while no significant change was found in p38MAPK protein expression in groups LS and LSS,and no significant change was found in the indexes mentioned above in group SB (P＞0.05).Compared with group LS,the oxygenation index and SOD activity were significantly increased,the pathological score,lung water content and MDA content were significantly decreased,the expression of HO-1 mRNA and protein was significantly up-regulated,and p-p38MAPK protein expression was down-regulated ( P＜0.05),and no significant change was found in p38MAPK protein expression in group LSS ( P＞0.05).Conclusion The inhibition of p38MAPK signaling pathway can lead to the up-regulation of HO-1 expression in lung tissues in rats with ALI induced by endotoxic shock. Key words: p38 Mitogen-activated protein kinases; Hemne oxygenase-1; Lung; Shock,septic; Respiratory distress syndrome,adult