Role of haeme oxygenase-1 in remote limb ischemic preconditioning-induced attenuation of lung ischemia-reperfusion injury in rabbits

Abstract

Objective To evaluate the role of haeme oxygenase-1 (HO-1) in remote limb ischemic preconditioning (RLIP)-induced attenuation of lung ischemia-reperfusion (I/R) injury in rabbits.Methods Twenty-four Japanese White Rabbits,aged 4-5 months,weighing 2.0-2.5 kg,were randomly divided into 4 groups (n =6 each) using a random number table:sham operation group (S group),I/R group,RLIP group and zinc protoporphyrin (ZnPP,an inhibitor of HO-1) plus RLIP group (ZnPP + RLIP group).Lung I/R was produced by 60 min occlusion of the left lung hilum followed by 180 min of reperfusion in I/R,RLIP and ZnPP + RLIP groups.RLIP and ZnPP + RLIP groups received 3 cycles of 10 min ischemia followed by 10 min reperfusion in the bilateral hind limbs immediately before occlusion of the left lung hilum.In ZnPP + RLIP group,ZnPP 10 μmol/kg was injected intravenously 10 min prior to hind limb ischemia and the rest of the procedures were similar to those previously described in RLIP group.At the end of reperfusion,arterial blood samples were collected for blood gas analysis.The animals were then sacrificed and pulmonary specimens were obtained for microscopic examination of the pathological changes which were scored (lung injury score,LIS) and for determination of wet/dry lung weight ratio (W/D ratio),myleoperoxidase (MPO) activity,malondialdehyde (MDA) content and expression and activity of HO-1 in the lung tissues.Results Compared with group S,PaO2 was significantly decreased,and LIS,W/D ratio,MPO activity,MDA content,and HO-1 expression and activity were increased in I/R group (P ＜ 0.01).Compared with I/R group,PaO2 and HO-1 expression and activity were significantly increased,and LIS,W/D ratio,MPO activity and MDA content were decreased in RLIP group (P ＜ 0.01).Compared with RLIP group,PaO2 and HO-1 expression and activity were significantly decreased,and LIS,W/D ratio,MPO activity and MDA content were increased in ZnPP + RLIP group (P ＜ 0.01).Conclusion RLIP up-regulates HO-1 expression and enhances HO-1 activity,thus reducing lung I/R injury in rabbits. Key words: Heme oxygenase-1 ; Ischemic preconditioning ; Extremities ; Reperfusion injury ; Lung