[ ABSTRACT] AIM: To study the protective effect of ischemia preconditioning ( IPC ) on ischemia/reperfusion ( IR)-damaged myocardium in young and old rats .METHODS: Male Wistar rats aged at 3 months ( young ) and 20 months ( old) were used to establish myocardial IPC model and IR model with the method of Langendorff heart perfusion . The rats were divided into young ischemia/reperfusion ( YIR) group, young ischemic preconditioning ( YPC) group, old ischemia/reperfusion ( OIR) group and old ischemic preconditioning ( OPC) group.Transmission electron microscopy was used to observe the ultrastructural changes of myocardial tissue and myocardial mitochondria .The myocardial infarction area was determined by TTC staining .The lactate dehydrogenase ( LDH) content in coronary effluent fluid and the levels of su-peroxide dismutase ( SOD) and malondialdehyde ( MDA) in myocardial tissues were detected by the method of colorimetry . The levels of nitrated and carbonylated proteins in myocardial tissue were measured by ELISA .The myocardial cell apopto-sis was analyzed by TUNEL assay .The mitochondrial respiratory function and mitochondrial permeability transition pore o-pening induced by calcium load were evaluated by oxygen electrode method .RESULTS: Compared with YIR group , the myocardial infarction area in YPC group was obviously smaller , SOD activity in myocardial tissues increased , LDH activity in coronary effluent fluid and the content of MDA decreased , and the levels of nitrated and carbonylated proteins in the car-diac tissues reduced .In YPC group, the mitochondrial membrane structure appeared intact , cristae of the mitochondria showed close arrangement , and the matrix was compressed under the electron microscope .Myocardial mitochondrial respir-atory control rate , state Ⅲoxygen consumption and the P/O ratio in YIR group all significantly increased , proton leak de-creased, mitochondrial swelling induced by calcium distinctly reduced , and myocardial apoptosis rate declined .No signifi-cant difference of the above indexes between OIR group and OPC group was observed .Compared with YPC group , myocar-dial ultrastructural damage increased clearly , cardiac oxidative stress increased , mitochondrial respiratory function de-clined, and cell apoptosis and necrosis increased in OPC group .CONCLUSION:Ischemic preconditioning has protective effect against myocardial IR injury in young rat hearts , while old rat hearts were less sensitive to ischemic preconditioning , leading to bluntness of cardioprotection with IPC in aging hearts .This may be related to mitochondrial injury and severe cel-lular apoptosis caused by increase of cardiac oxidative stress levels in the aging ischemic preconditioning heart .

Objective To investigate whether advanced glycation end products (AGEs) can induce the expression of Ros,JC-1 and its apoptosis-related proteins in glomerular mesangial cells under high glucose environment,induce apoptosis and injury of glomerular mesangial cells.Methods Rat glomerular mesangial cell line HBZY-1 was cultured in vitro.The cells were cultured with different concentrations of AGEs for 0,12,24 and 48 hours respectively.MTT assay was used to observe the cell proliferation ability.After the optimal time and concentration of AGEs were selected,the caspase enzyme inhibitor Z-VAD-fmk and reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC) were cultured and the apoptosis rate was detected by cell death detection apoptosis ELISA plus and Annexin V-FITC/PI kit.JC-1 staining was used to detect the changes of mitochondrial membrane potential (MMP).Cell ROX deep red flow cytometry was used to detect the total ROS level.The expression of anti-apoptotic protein Bcl-2,pro-apoptotic protein BAX,caspase-9,caspase-3 and poly ADP-ribose polymerase (PARP)-activated fragments was detected by Western blotting.Results AGEs could decrease the activity of glomerular mesangial cells in a time and concentration-dependent manner,and induce cell death.The percentage of apoptotic cells in glomerular mesangial cells was significantly increased after treatment with 250 mg/L AGEs for 24 h (P ＜ 0.01),and Z-VAD-fmk could significantly alleviate AGEs-induced glomerular mesangial cell apoptosis (P ＜ 0.01).Compared with the control group,AGEs increased the level of intracellular reactive oxygen species and decreased MMP in a time-dependent manner,and the two time points that AGEs significantly caused the change were 1 h and 2 h (all P ＜ 0.01).AGEs also reduced the expression of antiapoptotic protein Bcl-2 and increased the expression of pro-apoptotic protein Bax,cleaved caspase-9,cleaved caspase-3 and cleaved PARP (all P ＜ 0.01).Compared with AGEs group,NAC could significantly stabilize MMP (P ＜ 0.01),increase Bcl-2 expression (P ＜ 0.01),and decrease the expression of BAX,cleaved caspase-9,cleaved caspase-3 and cleaved PARP (all P ＜ 0.01).Conclusion AGEs induce mitochondrial pathway apoptosis in glomerular mesangial cells by increasing intracellular ROS level and destroying MMP.