Effects And Mechanisms Of Propofol On Myocardium Ischemia/Reperfusion Injury In Diabatic Rats

In recent years, the prevalence of diabetes mellitus is rapidly increasing . Diabetes is one of the main causes for increased incidence of complication during perioperative period. Clinically, diabetes represents an important risk factor for cardiovascular accident and poor outcomes after coronary revascularization. Diabetes is thought as an independent predictor of low output syndrome after coronary artery bypass graft (CABG) surgery.Myocardium ischemia/reperfusion (I/R) injury is not only a commonly occurred perioperative cardiac problem, but also a main early complication of coronary revascularization. So it has become a focus in basal and clinical study on how to relieve or avoid the myocardium ischemia-reperfusion injury in diabetic patients. Propofol, 2,6-diisopropylphenol, an intravenous anaesthetic with a rapid and short anesthesia, is frequently used during cardiac surgery and in postoperative sedation. There are reports that propofol can protect myocardium against the I/R injury in isolated rat hearts. It has been proposed that this action of propofol may be mediated by its ability to act as a free radical scavenger conferred by the phenolichydroxyl group in its structure or through inhibition of trans-membrane calcium channel, but the effects and the mechanisms of propofol against myocardial I/R injury in diabetes are not known or understood. In the present study, we investigated the effects of propofol on myocardium I/R injury in diabetic rats in vivo and explored the possible mechanisms at cellular and molecular level.PartⅠEffects of propofol on oxidative stress induced by myocardium ischemia/reperfusion in diabetic ratsObjective: To investigate effects of propofol on myocardium ischemia/ reperfusion injury in diabetic rats and clarify the possible molecular mechanism from oxidative stress.Methods: A total of 100 SD rats were randomly divided into two groups: non-diabetics group (n=24) and diabetics group (n=76). Diabetes mellitus was induced by intraperitoneal injection of streptozotocin (STZ) 55 mg/kg, rats serving as controls were injected the same volume of sodium citrate. Finally, 60 diabetics rat models were successfully reproduced. The myocardium I/R model was reproduced by ligation of the left anterior descending coronary artery for 30 min and reperfusing for 120 min. The rats in non-diabetic group were randomly reassigned into sham-operated group(NS), I/R group(NI/R) , the rats in diabetic group were randomly reassigned into sham-operated group(DS), I/R group(DI/R) and propofol 3, 6, 12mg/kg/h(DI/R+PL, DI /R+PM, DI/R+PH) groups (n=12). Propofol(3, 6, 12mg/kg/h) was intravenously infused respectively at 10min before ischemia in rats of propofol groups. The blood glucose and weight were determined. The cardiac function indexes such as the left ventricular developed pressure (LVDP), the left ventricular end diastolic pressure (LVEDP), heart rate (HR),±dp/dtmax were recorded at the end of reperfusion. The lactate dehydrogenase (LDH), MB isoenzyme of creatine kinase (CK-MB) activities in the serum and the activities of SOD and the contents of malondialdehyde (MDA) in myocardium during the reperfusion period were measured. The pathological changes of myocardium mitochondria were obersved by electron microscope.Results:1. The blood glucose of rats in diabetic groups was much higher and the weight was much lower than that of non-diabetics group after 3 week injected STZ(P﹤0.05, P﹤0.01).2. Compared respectively with those of NS or DS group, the cardiac function parameters (HR, LVDP,±dp/dtmax) were significantly decreased in NI/R group and DI/R group at the end of reperfusion, the LVEDP was markedly increased(P﹤0.05, P﹤0.01), the values of above parameters were more severe in diabetic rats than in non-diabetes rats(P﹤0.05, P﹤0.01). Compared with that of DI/R group, administration of propofol (6, 12mg/kg/h) could ameliorate the HR, LVDP, LVEDP and±dp/dtmax(P﹤0.05,P﹤0.01).3. Compared respectively with those of NS or DS group, the activities of LDH, CK and content of malondialdehyde (MDA) in myocardium were increased, the activities of SOD in myocardium were decreased in NI/R group and DI/R group(P﹤0.05, P﹤0.01), the values of above parameters were more severe in diabetic rats than in non-diabetic rats(P﹤0.05, P﹤0.01), administration of propofol (6, 12mg/kg/h) could decrease the activities of LDH, CK in serum and content of MDA in myocardium respectively and significantly enhance the activities of SOD in myocardium(P﹤0.05, P﹤0.01).4. In DI/R group, the pathological changes of mitochondria induced by I/R injury, such as membrane swelling, cristae disruption, dissolution or disappearance, glycogen granule reduction, were significantly worse than that of NI/R group, and could be alleviated by propofol (12 mg/kg/h).Conclusion: Myocardium ischemia/reperfusion injury was aggravated by diabetes. Propofol has a beneficial myocardial protection against the ischemia/reperfusion injury in the diabetic rats. It could be concluded that the protection is related to diminishing oxidative stress, protecting mitochondria from peroxidative injury. Further studies will be needed to investigate the exact signal pathway.PartⅡEffects of propofol on inflammatory response induced by myocardium ischemia/reperfusion in diabetic ratsObjective: To explore the molecular mechanisms of propofol in cardioprotection, the activation of NF-κB and its regulated inflammatory mediators expression were examined in the present experiment with the model of myocardial ischemia/reperfusion in diabetic rat .Methods: A total of 100 SD rats were randomly divided into two groups: non-diabetics group (n=24) and diabetics group (n=76). Diabetes mellitus was induced by intraperitoneal injection of streptozotocin (STZ) 55 mg/kg, rats serving as controls were injected the same volume of sodium citrate. Finally, 60 diabetics rat models were successfully reproduced. The myocardium I/R model was reproduced by ligation of the left anterior descending coronary artery for 30 min and reperfusing for 120 min. The rats in non-diabetic group were randomly reassigned into sham-operated group(NS), I/R group(NI/R), the rats in diabetic group were randomly reassigned into sham-operated group(DS), I/R group(DI/R) and propofol 3, 6, 12mg/kg/h(DI/R+PL, DI/R+PM, DI/R+PH)groups (n=12). Propofol (3,6,12mg/kg/h) was intravenously infused respectively at 10min before ischemia in rats of propofol groups. Heart rate(HR), mean arterial blood pressure(MAP) and blood pressure-heart rate index (PRI) were recorded under basal conditions, during occlusion and at the end of reperfusion, respectively. The translocation of NF-κB in the cardiomyocytes was detected by immunohistochemistry and NF-κB expression were determined by Westernblotting. The concentrations of TNF-α, IL-6, IL-1βin serum and myocardium were evaluated by ELISA respectively. The cardiac amount of mRNA codifying for TNF-α, IL-6, IL-1βwere investigated by RT-PCR.Results:1. Compared with that of non-diabetic group, before ischemia the cardiac function parameters (HR, MAP, PRI) were decreased in diabetic group(P﹤0.05, P﹤0.01). At the end of reperfusion, the cardiac function parameters in NI/R group and DI/R group were lower than those of NS group or DS group and the value of the parameters were lower in DI/R group(P﹤0.05, P﹤0.01). Compared with those of DI/R group, administration of propofol (6, 12 mg/kg/h) resulted in improvement in HR, MAP and PRI, respectively(P﹤0.05, P﹤0.01).2. Compared with that of NS group, the concentrations of TNF-α, IL-6, IL-1βin serum were increased in DS group(P﹤0.05). Compared with those of NS or DS group, the concentrations of TNF-α, IL-6, IL-1βin serum and myocardium, the expression of TNF-α, IL-6, IL-1βmRNA in myocardium were significantly increased in NIR and DI/R group respectively(P﹤0.05, P﹤0.01),In DI/R group, NF-κB was significantly translocated from the cytoplasm into the nucleus; however, NF-κB remained in the cytoplasm of cardiomyocyte in the sham group. And the expression of NF-κB in the nuclei in DI/R group was markedly higher than that of in the sham group(P﹤0.01).Compared with those of DI/R group, administration of propofol at 6, 12mg/kg/h significantly inhibited the NF-κB translocation into nucleus and attenuated the expression of NF-κB in the nuclei(P﹤0.05), decreased the concentrations of TNF-α, IL-6, IL-1βin serum and myocardium and the expression of TNF-α, IL-6, IL-1βmRNA respectively(P﹤0.05, P﹤0.05).Conclusion: Propofol inhibits NF-κB activation, subsequent leads to down-regulation of NF-κB-dependent inflammatory gene expression and thus reduces the inflammatory response in myocardial ischemia reperfusion injury in the diabetic rats, which may be one of the molecular mechanisms of its cardioprotection.PartⅢEffects of propofol on ischemia/reperfusion-induced cardiocyte apoptosis in diabetic ratsObjective: To investigate the effects of propofol on ischemia/reperfusion -induced cardiocyte apoptosis in diabetic rats and explore the possible mechanism.Methods: A total of 100 SD rats were randomly divided into two groups: non-diabetics group (n=24) and diabetics group (n=76). Diabetes mellitus was induced by intraperitoneal injection of streptozotocin (STZ) 55 mg/kg , rats serving as controls were injected the same volume of sodium citrate. Finally, 60 diabetics rat models were successfully reproduced. The myocardial I/R model was reproduced by ligation of the left anterior descending coronary artery for 30 min and reperfusing for 120 min. The rats in non-diabetic group were randomly reassigned into sham-operated group(NS), I /R group(NI/R) , the rats in diabetic group were randomly reassigned into sham-operated group(DS), I /R group(DI/R) and propofol 3, 6, 12mg/kg/h(DI /R+PL, DI/R+PM, DI/R+PH) groups (n=12). Propofol (3, 6, 12mg/kg/h) was intravenously infused respectively at 10min before ischemia in rats of propofol groups. The apoptotic rate of cardiomyocytes was evaluated by Flow Cytometry. The positive expressions of Bcl-2, Bax, caspase-3 in cardiomyocytes were respectively detected by immunohistochemistry and westernblotting.Results: The apoptotic rates of cardiomyocytes in NI/R and DI/R group (18.18±2.12, 27.01±2.06) was significantly higher than that of NS or DS group (5.61±1.04,8.37±2.64)(P<0.01), and it is higher in DI/R group than in NI/R group(P<0.01). The apoptotic rates of cardiomyocytes in the three propofol groups were 24.03±5.05, 17.08±2.00, 13.67±3.07, respectively. The percentage of apoptosis cardiomyocytes in propofol 6, 12mg/kg/h group was markedly lower than that of DI/R group, respectively(P﹤0.01). Compared with those of DI/R group, the expression of Bax and casepase-3 were significantly decreased and the expression of Bcl-2 was markedly increased in propofol( 6,12mg/kg/h) group (P<0.05, P<0.01).Conclusion: It could be concluded that diabetes exacerbates cardiocyte apoptosis induced by I/R , propofol has a beneficial myocardial protection against the I/R injury in diabetic rats by decreasing the expression of bax, caspase-3 and rate of cardiomyocytes apoptosis and increasing the expression of Bcl-2.PartⅣEffect of propofol on mitochondria injury after myocardial ischemic/reperfusion in diabetic ratsObjective: To investigate effects of propofol on mitochondria structure and function after myocardial I/R injury in diabetic rats and explore the possible mechanism.Methods: A total of 100 SD rats were randomly divided into two groups: non-diabetics group (n=24) and diabetics group (n=76). Diabetes mellitus was induced by intraperitoneal injection of STZ at 55 mg/kg, rats serving as controls were injected the same volume of sodium citrate. Finally, 60 diabetics rat models were successfully reproduced. The myocardium I/R model was reproduced by ligation of the left anterior descending coronary artery for 30 min and reperfusing for 120 min. The rats in non-diabetic group were randomly reassigned into sham-operated group(NS), I/R group(NI/R) , the rats in diabetic group were randomly reassigned into sham-operated group(DS), I /R group(DI/R) and propofol 3, 6, 12mg/kg/h(DI/R+PL, DI/R+PM, DI/R+PH) groups(n=12). Propofol(3, 6, 12mg/kg/h) was intravenously infused respectively at 10min before ischemia in rats of propofol groups. The pathological changes of myocardium mitochondria were obersved by electron microscope. The mitochondria were prepared by differential centrifugation. The activities of SOD, GSH-PX, ATPase and the contents of malondialdehyde (MDA) in myocardial mitochondria during the reperfusion period were measured. The swelling and activity of mitochondria were also determined.Results:1. The pathological changes of mitochondria induced by I/R injury, such as membrane swelling, cristae disruption, dissolution or disappearance, glycogen granule reduction, were significantly alleviated by propofol at 6, 12mg/kg/h.2. In NI/R and DI/R group, the swelling of mitochondria was markedly increased and the activity of mitochondria was decreased (P﹤0.05), and the activities of SOD, GSH-PX, ATPase were decreased and the content of malondialdehyde (MDA) in myocardial mitochondria was increased(P﹤0.05) compared with those of NS and DS group, respectively. Compared with those of DI/R group, administration of propofol at the concentrations 6, 12mg/kg/h significantly enhanced the activities of SOD, GSH-Px and ATPase and the activity of myocardium mitochondria, ameliorated the mitochondria swelling and decreased the MDA contents, respectively(P﹤0.05).Conclusion: Diabetes exacerbates the mitochondria damages induced by I/R. Propofol has a beneficial myocardial protection against the I/R injury in diabetic rats by increasing the activities of SOD, GSH-Px, ATPase and diminishing oxidative stress.