| BackgroundIschemia-reperfusion injury (IRI) exists during liver resections performed undertemporary inflow occlusion commonly used to reduce intraoperative blood loss, and during storage and implantation of livers for transplantation. IRI then induces the cell apoptosis, which is the main method of cell death after IRI. Both IRI and apoptosis result in significant parenchymal cell injury and organ dysfunction. In the last several years, many investigations have focused on the intervention of IRI. Ischemic preconditioning (IPC) has been demonstrated promising approach to effectively minimize hepatic IRI in animals and humans. Furthermore, recent researches have proved that several brief cycles of ischemia and reperfiision at the onset of sustained reperfusion after a prolonged period of ischemia, termed ischemic postconditioning (IPO), provided effective cardioprotection on IRI. The objective of the present study was to determine the effects of IPO on the IRI and apoptosis in rat liver via a comparative analysis with IPC and IPC combined IPO (IPC-IPO).Part 1Protective effects and mechanisms of ischemic postconditioning onwarm/cold ischemia-reperfusion injury and apoptosisObjective To evaluate the protective effect of IPO on warm/cold ischemia-reperfusion injury (IRI) and apoptosis in rat liver. MethodsWarm IRI model (with 30-minute inflow occlusion according to Nauta's method) and cold IRI model (orthotopic liver transplantation according to Kamada's method with 2-hour cold storage) were established. The rats were divided into 5 groups.1. Sham group, duodenohepatic ligament was dissected only, without inflow occlusion;2. Warm IRI model2.1 IRI group, 30-minute warm ischemia only, without additional intervention;2.2 IPO group, 30-second reperfusion followed by 30-second reocclusion for three times at the onset of reperfusion after warm ischemia;3. Cold IRI model3.1 IRI group, OLT was performed normally, without additional intervention;3.2 IPO group, 30-second reperfusion followed by 30-second reocclusion for three times at the onset of reperfusion after cold ischemia.The blood from the inferior vena cava, bile and liver tissue were collected at 3 hours after long-time reperfusion, which were used to analyze the serum transaminase levels, biliary glucose and GGT levels, histopathologic examination, the levels of tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-α) in blood, levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in hepatic tissue were measured. The expression of Fas protein was measured by immunohistochemical techniques and the apoptotic cells were detected by flow cytometry. In each model, the indexes were compared.Results1. In both models, the levels of AST and ALT in IRI group and IPO group were higher than in Sham group (P<0.01), and the levels of AST and ALT in IPO group were lower than in IRI group (P<0.05).2. In both models, biliary glucose and GGT levels in IRI group and IPO group were significant higher than in Sham group (P<0.01), and the levels of biliary glucose and GGT in IPO group were lower than in IRI group (P<0.05).3. In both models, the damage of hepatic histology and ultramicrostructure in IRI group were serious. And the damage was less in IPO group.4. In both models, the levels of TNF-αand IL-1βin IRI group and IPO group were higher than in Sham group (P<0.01), and the levels of TNF-αand IL-ipin IPO group were lower than in IRI group (P<0.05).5. In both models, the levels of SOD in IRI group and IPO group were lower than in Sham group (P<0.05), and the levels of SOD in IPO group were higher than IRI group (P<0.05). And the levels of MDA in IRI group and IPO group were higher than in Sham group (P<0.05), and the levels of MDA in IPO group were lower than IRI group (P<0.05).6. In both models, the positive express index (PEI) in IRI group and IPO group were higher than in Sham group (P<0.05), and the PEI in IPO group were lower than in IRI group (P<0.05).7. In both models, the apoptotic index (AI) in IRI group and IPO group were higher than in Sham group (P<0.05), and the AI in IPO group were lower than in IRI group (P<0.05).Conclusions1. IPO is associated with protective effect on warm/cold ischemia-reperfusion injury in liver.2. IPO protects hepatic cells by inhibiting the infiltration of heterophil granulocyte; inducing the release of TNF-αand IL-1βdecreasing the inactivation of SOD and the production of MDA,.3. IPO protects hepatic cells by inhibiting cell apoptosis via the release of TNF-αand IL-1β, decreasing the inactivation of SOD and the production of MDA, preventing the express of Fas protein. Part 2Comparative study of the protective effects on warm/cold ischemia-reperfusion injury among IPO, IPC and IPC-IPOObjectiveTo study comparatively the protective mechanisms on warm/cold ischemia-reperfiision injury (IRI) between IPO and IPC in rat liver and to evaluate whether the protective effects of IPO combined IPC (IPC-IPO) is additive of IPO and IPC.MethodsWarm IRI model (with 30-minute inflow occlusion according to Nauta's method) and cold IRI model (orthotopic liver transplantation according to Kamada's method with 2-hour cold storage) were established. Each model consisted of 4 groups:1) Control group, warm or cold IRI was performed normally, without additional intervention;2) IPC group, 5-minute ischemia followed by 5-minute reperfusion prior to warm or cold IRI;3) IPO group, 30-second reperfusion followed by 30-second reocclusion for three times at the onset of long-time reperfusion after warm or cold IRI;4) IPC-IPO group, 5-minute ischemia followed by 5-minute reperfusion twice prior to warm/cold IRI, and 30-second reperfusion followed by 30-second reocclusion for three times at the onset of long-time reperfusion after warm or cold IRI.The blood from the inferior vena cava, bile and liver tissue were collected at 3 hours after long-time reperfusion in half of the rats, which were used to analyze the serum transaminase levels, biliary glucose and GGT levels, histopathologic examination, the levels of tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-1β) in blood, levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in hepatic tissue were measured. The expression of Fas protein was measured by immunohistochemical techniques and the apoptotic cells were detected by flow cytometry. In each model, the indexes were compared among 4 groups.Results1. In both models, the levels of AST and ALT in IPC group, IPO group and IPC-IPO group were comparable (P>0.05), but were all lower as compared to valve in Control group (P<0.05).2. In both models, biliary glucose and GGT levels in IPC group, IPO group and IPC-IPO group were lower than valve in Control group (P<0.05). In Warm IRI model, biliary glucose and GGT levels in IPC-IPO group were comparable with the values in IPC group, IPO group (P>0.05). In cold IRI model, GGT level in IPC-IPO group was lower than in IPC group and IPO group(P<0.05); but the biliary glucose were similar in 3 groups (P>0.05).3. In both models, the damage of hepatic histology in Control group were serious. But the damage was less in IPC group, IPO group and IPC-IPO group than in Control group.4. In both models, the levels of TNF-αand IL-1βin IPC group, IPO group and IPC-IPO group were comparable (P>0.05), but were all lower as compared to valve in Control group (P<0.05).5. In both models, the levels of SOD in IPC group, IPO group and IPC-IPO group were comparable (P>0.05), but were all higher as compared to valve in Control group (P<0.05). And the levels of MDA in IPC group, IPO group and IPC-IPO group were comparable (P>0.05), but were all lower as compared to valve in Control group (P<0.05)6. In both models, the positive express index (PEI) of Fas were comparable in IPC group, IPO group and IPC-IPO group(P>0.05), and were all lower as compared to valve in Control group (P<0.05).7. In both models, the apoptotic index (AI) in IPC group, IPO group and IPC-IPO group were all lower as compared to AI in Control group (P<0.05). And there no difference in AI between IPC group, IPO group and IPC-IPO group (P>0.05).8. In both models, most loss of the recipients was within 3 days. In Warm IRI model, The survival rates at 7th day in IPC .group, IPO group, IPC-IPO group were 87.5% (7 of 8),75% (6 of 8), and 87.5% (7 of 8) respectively, which were without statistical significance (P>0.05), but were higher than that in Control group(37.5%, 3of 8, P<0.05). In cold IRI model, The survival rates at 7th day in IPC group, IPO group, IPC-IPO group were 62.5% (5 of 8),75% (6 of 8), and 87.5% (7 of 8) respectively, which were without statistical significance (P>0.05), but were higher than that in Control group(25%, 2of 8, P<0.05).Conclusions1. IPO and IPC are associated with comparable effective to protect rat liver from warm and cold IRI and apoptosis.2. Inhibiting the infiltration of heterophil granulocyte, inducing the release of TNF-αand IL-1β, decreasing the inactivation of SOD and the production of MDA, preventing the express of Fas protein are the common path of the protection of IPO and IPC.3. The combined protective effects of IPC and IPO do not appear to be additive, which is equal to IPC or IPO alone. |
PDF Full Text Request