Protective Effects Of Ischemic Preconditioning On Lung Injury And Its Mechanism In Rats Undergoing Cardiopulmonary Bypass

Objective To research the protective effects of remote ischemic preconditioning (RIPC) on lung injury and its concrete mechanism in rats undergoing cardiopulmonary bypass (CPB).Methods Sixty male Sprague-Dawley rats were randomly divided into 3 groups, the number of each group is 20:Sham-operated group (group S), Cardiopulmonary bypass group (group CPB) and Remote ischemic preconditioning group (group RIPC+CPB). Rats in group S did not undergoing CPB; rats in group CPB were induced the lung injury by CPB; rats in group RIPC+CPB were subjected to RIPC before CPB. RIPC was used by compressing the two hindlimbs alternately with a tourniquet for three cycles of 15 min ischaemia followed by 15 min reperfusion. At 2h after anesthesia resuscitation, the bronchoalveolar lavage fluid (BALF) samples were collected for determination of the leucocyte count, albumin and IL-6, TNF-α and the pulmonary tissue were obtained for observe the wet to dry weight raito (W/D raito)、the Evan’S blue (EB)、activity of glutathione per oxidase (GSH-px) and the concentrations of malondialdehyde (MDA). The histopathological changes by hematoxylin-eosin (HE) of lung tissue were also observed.The apoptosis of alveolar epithelial cell by TUNEL method, and the protein expression of Bal-2 and Bax were calculated by Western blot.Results Compared with group S, the leucocyte count, albumin, IL-6 and TNF-ain BALF, W/D ratio and the EB content,the apoptosis index of alveolar epithelial cell, the concentrations of MDA and ratio of Bax/Bcl-2 in lung tissues were increased, while activity of GSH-px in lung tissues was decreased in group CPB and group RIPC+CPB (P<0.05). Compared with group CPB, the leucocyte count, albumin, IL-6 and TNF-a in BALF, the W/D ratio and EB content, the apoptosis index of alveolar epithelial cell, the concentrations of MDA and ratio of Bax/Bcl-2 in lung tissues were significantly lower, while activity of GSH-px in lung tissues was higher in group RIPC+CPB (P<0.05). Compared with group CPB, the morphological injury of pulmonary tissue was alleviated in group RIPC+CPB under HE staining.Conclusions RIPC can reduce the lung injury in rats undergoing CPB, the mechanism is closely related to inhibiting the inflammatory reaction,lipid peroxidation and apoptosis by adjusting the expression of apoptosis-related proteins Bax and Bal-2.