Relationship between delayed cardioprotection effect of 11,12-EET and phosphorylated ERK during ischemia and reperfusion in the rat myocardium

AIM:In order to study the relationship of the activation of ERK and delayed cardioprotection of 11,12-EET . METHODS:A rat ischemia/reperfusion (I/R) model was replicated by ligating left anterior descending coronary artery 30 min followed by 60 min. The expression of ERK was detected with Western blotting, and the change of heart function during reperfusion was observed. RESULTS:The difference of myocardial function was prominent at 24 h in I/R group compared with sham group, EET+I/R and EET+PD098059+I/R group. The activity of ERK at 24 h in EET+I/R group was higher than sham group, and the activity of ERK in EET+PD098059+I/R group was lower than that in EET+I/R group;the expression of phosphorylated ERK1/ERK2 at 24 h in EET+I/R group was more than that in I/R group, and the expression of phosphorylated ERK1/ERK2 in EET+PD098059+I/R group was less than EET+I/R group. CONCLUSION:11, 12-EET has a delayed cardioprotection effect, and this protection effect is involved in the activity of ERK and expression of phosphorylated ERK1/ERK2.     

Effect of pretreatment with 11,12-EET on myocardial ischemia/reperfusion injury in rats

AIM: To examine the effect of pretreatment with low-concentration of 11, 12-epoxyeicosatrienoic acid(EET) on myocardial ischemia/reperfusion injury in rats. METHODS: After tracheotomy, myocardial ischemia/reperfusion was produced by occlusion and release of the left anterior descending artery(LAD) of the rats. Ischemic preconditioning(IP) was made by two times of ischemia(5 min)/reperfusion(5 min). The experiment was conducted in three groups: control,IP and pretreatment with 11,12-EET(6.24×10^-8 mol/L), and each group was subdivided into two subgroups:A,the rats were subjected to ischemia(10 min)/reperfusion(10 min) and arrhythmias during the whole periods were monitored; The rats in B were subjected to ischemia(60 min)/reperfusion(30 min) and arrhythmias, cardiac funtion and myocardial infarction size were documented. RESULTS: Both IP and pretreatment with 11,12-EET could protect the heart against arrhythmias, cardiac disfunction and myocardial infarction. CONCLUSION: Pretreatment with 11,12-EET had protective effect on myocardium in case of ischemia/reperfusion, which was similar to ischemic preconditioning.     

Pretreatment with Sini decoction induces delayed preconditioning in rat heart and role of p38 MAP kinase

AIM: The present study was designed to determine whether Sini decoction (SND), a traditional Chinese medicine, induces delayed preconditioning-like effect in rat heart and the possible mechanism by which ischemia myocardium is protected. METHODS: Sprage－Dawleyt rats underwent three 5 min episodes of preconditioning ischemia 24 h prior to the global ischemia and reperfusion in ischemic preconditioning/second window of protection (IPC/SWOP) group or were pretreated with Sini decoction (5 mL·kg-1·d-1 for 3 days, the last treatment 24 h before global ischemia and reperfusion) in SND group. Myocardial infarct size, CK, LDH and NO were examined. p38 MAPK and PKC were determined by immunohistochemisty. RESULTS: Myocardial infarct size was significantly decreased, CK and LDH were decreased in the serum, NO2-/NO3- was increased in myocardial tissue in SND group as well as in IPC/SWOP group (there was no difference between the two groups). The expression of p38 MAPK and PKC were upregulated in myocardial tissue in SND and IPC/SWOP groups. CONCLUSION: These results suggest that Sini decoction induces delayed preconditioning-like effect in the rat heart, possibly via inducing p38 MAPK activation.     

Ischemic preconditioning protects against hepatic ischemia-reperfusion injury by attenuating leukotriene C4 production

AIM：To investigate the effect of ischemic preconditioning (IP) on leukotriene C4 (LTC4) generation during hepatic ischemia-reperfusion(I/R) injury.METHODS：Adult male Sprague-Dawley rats were randomly divided into sham (control) group, I/R group and IP+I/R group. The rat liver was subject to 60 min of partial hepatic ischemia followed by 5 h of reperfusion. LTC4 content was measured by reversed-phase high-performance liquid chromatography (RP-HPLC). The activity of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was determined, and the changes of histological structures were observed to assess the tissue injury. The reduced glutathione (GSH) level in the liver tissues was also examined by biochemical methods.RESULTS：IP markedly decreased LTC4 content in rat livers compared with I/R group. The activity of serum ALT and AST in I/R group and IP+I/R group was higher than that in control group. Compared with I/R group, the levels of serum ALT and AST were markedly decreased, and the level of GSH in hepatic tissues was elevated in IP+I/R group. In addition, the structural damage of the rat liver tissues in IP+I/R group displayed slighter than that in I/R group.CONCLUSION：IP treatment reduces LTC4 production accompanied with improving the liver function and histological structure during I/R injury, suggesting that the beneficial effects of IP may be involved in its repressing LTC4 generation during hepatic I/R injury.     

Effect of diazoxide postconditioning on cardiac function and mitochondrial cardiolipin in isolated rat heart

AIM: To investigate the effect of diazoxide (D) postconditioning on Cardiac function and mitochondrial cardiolipin in isolated rat heart and to explore the protective effect of ATP sensitive potassium channel on diazo-xide postconditioning myocardium. METHODS: The myocardial ischemia/reperfusion injury model in isolated rat hearts was established by Langendorff apparatus. The isolated rat hearts were randomized into 4 groups (n=8): control group (control), myocardial ischemia/reperfusion injury group (I/R), diazoxide postconditioning group (I/R+D), 5- hydroxy decanoic acid (5-HD) plus diazoxide postconditioning group (I/R+5-HD+D). The hearts in each group were started with 20 min perfusion for equilibration. The hearts in control group perfused for 70 min; The hearts in I/R group was global ischemia for 40 min after ischemia reperfusion at 4 ℃ ST. Thomas cardioplegia, then reperfusion for 30 min; The hearts in I/R+D group were treated with diazoxide (50 μmol/L) in K-H perfusion for 5 min after global ischemia for 40 min, then reperfusion for 25 min; The hearts in I/R+5-HD+D group were treated with 5-HD (100 μmol/L) in K-H perfusion for 5 min before diazoxide postconditioning, then reperfusion for 20 min. The heart rate, coronary outflow volume, heart function, myocardial enzymes and myocardial mitochondrial cardiolipin at the end of perfusion in each group were determined. RESULTS: Compared with control group and I/R+D group, the heart rate, the concentration of heart phospholipid and the coronary outflow volume were reduced, the heart function was significantly impaired the contents of myocardial enzymes were increased in I/R group. However, no significant difference between I/R group and I/R+5-HD+D group was observed. CONCLUSION: The diazoxide postconditioning protects the myocardium by increasing mitochondrial cardiolipin content, reducing the release of myocardial enzymes, improving heart function and reducing myocardial reperfusion injury. The myocardial protective effect of diazoxide is completely blocked by 5- hydroxy decanoic acid.     

Xinshuaikang inhibits myocardial autophagy and MAPK/ERK1/2 signaling pathway in rats with chronic heart failure

AIM:To explore the effect of Xinshuaikang on myocardial autophagy in the rats with chronic heart failure and its relationship with the MAPK/ERK1/2 signaling pathway. METHODS:The rats were divided into sham group, model group (rat model of chronic heart failure was established by ligation of anterior descending branch of left coronary artery), low-, middle-, and high-dose Xinshuaikang treatment (TL, TM and TH) groups and captopril group (treated with captopril as positive control), with 12 in each group. Doppler echocardiography was used to evaluate the cardiac function. The morphological changes of the myocardium were observed by HE staining. TUNEL staining was used to detect cardiomyocyte apoptosis. The expression of microtubule-associated protein 1 light chain 3-Ⅱ (LC3-Ⅱ) in the myocardium was detected by immunofluorescence labeling. The protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ, beclin-1 and p62 in the myocardium were determined by Western blot. RESULTS:Compared with sham group, left ventricular end-diastolic dia-meter (LVEDD) and left ventricular end-systolic diameter (LVESD) in model group were increased, while left ventricular posterior wall thickness at end-diastole (LVPWTd), left ventricular posterior wall thickness at end-systole (LVPWTs), left ventricular ejection fraction (LVEF), cardiac output (CO), left ventricular diastolic pressure (LVDP), left ventricular systolic pressure (LVSP) and maximum rate of rise/decrease of left ventricular pressure (+dp/dt_max/-dp/dt_max) were decreased (P<0.05). The myocardial cells were deformed and necrotic, and the myocardial fibers were broken, with inflammatory cell infiltration. The apoptotic rate, the positive rate of LC3-Ⅱ, and the protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ/LC3-I and beclin-1 were increased, and the protein expression of p62 was decreased (P<0.05). Compared with model group, the levels of LVEDD and LVESD were decreased, LVPWTd, LVPWTs, LVEF, CO, LVSP, LVDP, +dp/dt_max and -dp/dt_max were increased in Xinshuaikang groups and captopril group (P<0.05). The morphological changes of myocardial cells were gradually returned to normal, and inflammatory cell infiltration, the apoptotic rate and the positive rate of LC3-Ⅱ were decreased. The protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ/LC3-I and beclin-1 were decreased, and the protein expression of p62 was increased (P<0.05). CONCLUSION:Xinshuaikang inhibits myocardial auto-phagy to play a role of cardiac protection in the rats with chronic heart failure, and its mechanism may be related to inhibition of MAPK/ERK1/2 signaling pathway.     

Endogenous basic fibroblst growth factor is a protective factor against myocardial ischemia/reperfusion injury of rats

AIM: To observe the role of exogenous and endogenous basic fibroblst growth factor (bFGF) on myocardial ischemia/reperfusion(I/R) injury of rats.METHODS:bFGF and bFGF antiserum were applied to rat isolated I/R heart. Myocardial function, coronary effluent volume,protein and myoglobin content as well as LDH activity in coronary effluent fluid, myocardial calcium, MDA and ATP concentration as well as PKC, MAPK activity were measured. RESULTS:Compared with control, myocardial function in I/R group significantly decreased. Protein, myoglobin content and LDH activity in coronary effluent liquid as well as myocardial MDA and calcium content increased, while myocardial ATP concentration decreased(all P＜0.01). Compared with I/R group, ±LV dp/dt_max in bFGF group increased by 43% and 26%, respectively. LVEDP decreased by 40%. HRr/HRi and B/A augmented by 42% and 20%, respectively. Protein and myoglobin content as well as LDH activity lowered by 29%,30％ (all P＜0.01) and 33％ (P＜0.05) respectively. Myocardial MDA and calcium content decreased by 44% and 35%, respectively, while myocardial ATP level as well as PKC and MAPK activity increased by 34%,41％ and 10% (all P＜0.01), respectively. In bFGF antiserum group, ±LV dp/dt_max were 35% and 38% lower than those in I/R group. LVEDP increased by 93%. HRr/HRi and B/A decreased by 36% and 45%, respectively. Protein and myoglobin content as well as LDH activity augmented by 54%,96％ (all P＜0.01) and 34％ (P＜0.05) respectively. Myocardial MDA and calcium content increased by 24% and 50%, respectively, while myocardial ATP level as well as PKC and MAPK activity lowered by 28%,21％ and 8% (all P＜0.01), respectively. CONCLUSION:Endogenous bFGF is a protective factor against myocardial ischemia/reperfusion injury of rats.     

Intestinal ischemic postconditioning attenuates acute lung injury induced by intestinal ischemia/reperfusion in rats

AIM: Previous study has shown that brief period of repetitive superior mesenteric artery (SMA) occlusion and reperfusion applied at the onset of reperfusion, ischemic postconditioning (IPo), attenuates intestinal injury after intestinal ischemia/reperfusion (I/R). This study tested the hypothesis that IPo would attenuate intestinal I/R-induced acute lung injury which is comparable to ischemic preconditioning (IPC) and the brief period of postconditioning applied at the onset of reperfusion is critical to pulmonary protection by IPo. METHODS: Rat intestinal I/R injury was produced by clamping SMA for 60 min followed by 60 min of reperfusion. The rats were randomly allocated into one of five groups based upon the intervention (n=8): sham operation (sham): sham surgical preparation including isolation of the SMA without occlusion was performed; injury: there was no intervention either before or after SMA occlusion; ischemia preconditioning (IPC): the SMA was occluded for 10 min followed by 10 min of reperfusion before prolonged occlusion; ischemia postconditioning (IPo): 3 cycles of 30 s reperfusion-30 s reocclusion were imposed immediately upon reperfusion (3 min total intervention); delayed postconditioning (delay): clamping was completely released for full reperfusion for 3 min (the duration of the IPo algorithm), after which 3 cycles of 30 s occlusion and reperfusion were applied. RESULTS: Histological results showed severe damages in rat lungs in the injury group evidenced by increased lung wet/dry weight ratio and pulmonary permeability index, which was accompanied by increases in the levels of plasma TNF-α and IL-6, the pulmonary malondialdehyde (MDA), and the pulmonary myeloperoxidase (MPO) activity, and a decrease in superoxide dismutase (SOD) activity. IPo, not delayed IPo, significantly attenuated lung injury and improved the above variables, which was comparable to IPC. CONCLUSION: IPo at onset of reperfusion reduces acute lung injury induced by intestinal I/R, which may be mediated, in part, by inhibiting oxidant generation, filtration of neutrophils and releases of proinflammatory mediators. The early period of reperfusion in the rat model is critical to pulmonary protection by IPo. IPo may improve outcome in clinical conditions associated with intestinal I/R.     

Establishment and evaluation of rat heart ischemia-reperfusion injury model in vivo

AIM: To establish and evaluate a rat model of heart ischemia-reperfusion injury in vivo. METHODS: Seventy-two male Sprague-Dawley rats weighing(250±50)g were randomly divided into sham operation group(sham), ischemia-reperfusion group(I/R) and normal group. The animals were anesthetized and heparinized. Myocardial ischemia-reperfusion was induced by ligating the left anterior descending coronary artery with "U-shape tube" for 35 min followed by 120 min or 240 min reperfusion in vivo. The heart infarct size was measured by triphenyltetrazolium chloride(TTC) staining. The myocardial cell apoptotic index was determined by the method of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling(TUNEL). Immunohistochemical method was used to detect the expression of Bcl-2 and Bax in rat ischemia myocardium. The blood level of MB isoenzyme of creatine kinase(CK-MB),cardiac troponin I(cTnI),nitric oxide(NO),malondialdehyde(MDA), total superoxide dismutase(T-SOD)and glutathione peroxidase(GSH-Px) were detected after reperfusion for 2 h and 4 h. RESULTS: Compared with normal group and sham group, there were obvious changes of ST-T segment and Q wave in the electrocardiogram of I/R group. The blood level of CK-MB, cTnI, NO, MDA and GSH-Px in I/R group increased(P<0.05,P<0.01) after reperfusion for 2 h and 4 h, and the blood level of T-SOD in I/R group after reperfusion for 2 h and 4 h also increased(P<0.05). The heart infarct size in I/R group was the largest as compared to other groups. Among these groups, the apoptotic index of I/R group was the highest and the Bcl-2/Bax ratio in I/R group decreased(P<0.01).CONCLUSION: The rat model of heart ischemia-reperfusion injury in vivo can be successfully established with the "U-shape tube". There are obviously changes of heart infarct size, blood level of CK-MB, cTnI, NO, MDA, T-SOD and GSH-Px, myocardial apoptotic index and Bcl-2/Bax ratio between I/R rats and control animals.     

Riboflavin preconditioning alleviates hepatic ischemia/reperfusion injury in rats

AIM: To explore the protective effect of riboflavin preconditioning on hepatic ischemia/reperfusion injury in rats. METHODS: Twenty-four Sprague-Dawley rats wererandomly divided into 3 groups (n=8): sham group, ischemia/reperfusion (I/R) group and riboflavin preconditioning (R+I/R) group. The rats in sham group and I/R group received a standard chow,while the rats in R+I/R group received a chow supplemented with riboflavin. After 4 weeks, portal vein and hepatic artery supplying the middle and left hepatic lobes were clamped with a traumatic vascular clip for induction of partial hepatic ischemia in the rats in I/R group and R+I/R group. After 1 h of ischemia, 1 h of reperfusion was conducted by removal of the clip. The activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum,the activity of superoxide dismutase (SOD) and the level of malondialdehyde (MDA) in serum and liver were measured. Western blotting was employed to examine the protein expression of heme oxygenase-1(HO-1) in the liver. RESULTS: The results showed that ischemia/reperfusion injury markedly increased the activity of AST and ALT in serum, decreased the activity of SOD, and elevated the level of MDA and the activity of HO-1 in the liver as compared with sham group (P<0.01). The riboflavin pretreatment significantly decreased the activity of AST and ALT in serum, increased the activity of SOD and decreased the levels of MDA in serum and liver as compared with I/R group (P<0.01). In addition, the protein expression of HO-1 and the activity of HO-1 were elevated in R+I/R group (P<0.01). Cytoplasmic vacuolation and swelling of the hepatocytes were observed in I/R group. Treatment with riboflavin markedly alleviated the changes of liver structure. CONCLUSION: Riboflavin preconditioning has protective effect on hepatic ischemia/reperfusion injury. The mechanism may be correlated with enhancing the anti-oxidation and alleviating the reaction of lipid peroxidation.     

Protection of Glycyl-L-Glutamine against myocardial ischemia-reperfusion injury in the isolated rat heart

AIM: To study the protection of Glycyl-L-Glutamine(Gly-Gln) against myocardial ischemia/reperfusion(I/R) injury in the isolated rat heart.METHODS: A model of myocardial ischemia-reperfusion injury was established with a Langendorff apparatus. Thirty male SD rats were randomly divided into four groups: control group, Gly-Gln group, I/R group and I/R+Gly-Gln group. Both I/R and I/R+Gly-Gln group were pre-perfused for 30 min, followed by 20 min ischemia and 40 min reperfusion. During reperfusion I/R+Gly-Gln group was perfused with Gly-Gln perfusate. Control group was kept perfused for 90 min. Gly-Gln group Gly-Gln perfusate was also kept perfused for 90 min. The left ventricular end-diastolic pressure(LVEDP), left ventricular developed pressure (LVDP), ±dp/dtmax, heart rate (HR), monophasic action potentials(MAP) was measured during perfusion. The coronary effluent fluid was collected at different certain times. The activities of lactic dehydrogenase (LDH) and creatine kinase(CK) were determined.RESULTS: The isolated rat heart function decreased severely after 20 min ischemia and 40 min reperfusion(I/R): the LVEDP increased and the LVDP, ±dp/dtmax decreased. But the LVEDP decreased and the LVDP, ±dp/dtmax increased in I/R+Gly-Gln group compared with I/R group. Moreover, the activities of LDH and CK in the coronary effluent fluid decreased remarkably in I/R+Gly-Gln group compared with I/R group.CONCLUSION: Gly-Gln can play a protective role against myocardial I/R injury in isolated rat hearts via maintaining the left ventricular function and decreasing the release of LDH and CK.     

Significance and changes of serum interleukin-8 and 10 in human myocardium ischemic preconditioning

AIM: To explore the mechanism of myocardium protection after ischemia/reperfusion (I/R) injury by preconditioning with ischemia in human. METHODS: Thirty-six patients underwent valve replacement were divided into ischemic preconditioning group (IP group, 20 cases) and non-ischemic preconditioning group (control group, 16 cases) according to whether they were given single cycle reperfusion before cardioplegia or not. Serum levels of interleukin-8 and 10 were measured with ELISA. Expressions of myocardial Bcl-2 and caspase-3 were analyzed. RESULTS: The inflammatory factors IL-8 and IL-10 increased to the highest level in serum at 6 h after declamping and recovered to normal level on 5 d after declamping. On 6 h, 1 d and 2 d after declamping, serum level of IL-8 was significantly lower in IP group than that in control group (P<0.05), but serum level of IL-10 was higher in IP group (P<0.05). Expression of myocardial Bcl-2 and caspase-3 increased in both groups after reperfusion, and Bcl-2 was lower in the control group than that in IP group while the level of caspase-3 was higher (P<0.05). Expression of myocardial Bcl-2 had positive correlation with IL-10 and negative correlation with IL-8. CONCLUSION: Ischemic preconditioning has the effect of protection of human myocardial cells after ischemia/reperfusion injury through decreasing systemic inflammatory response following ischemia reperfusion injury.     

Inhibitory effect of ginkgo-dipyridamole injection on ischemia/reperfusion injury in rat hearts in vitro

AIM：To investigate the effect of ginkgo-dipyridamole injection (GD) on ischemia/reperfusion (I/R) injury in rat hearts in vitro and its possible mechanism. METHODS：Forty male Sprague-Dawley rats were randomly divided into 5 groups (n=8): normal control (NC) group, I/R group, ischemic preconditioning (IPC)+I/R group, GD+I/R group and GD+LaCl3+I/R group. Cardiac function indexes, including heart rate (HR), left ventricular systolic pressure (LVSP) and the maximal rise/fall rate of left ventricular pressure (±dp/dtmax), were detected at 5 time points, including stabilizing point, 30 min after ischemia, and 5, 30 and 60 min after reperfusion. The activity of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent at the five time points was assayed. The concentration of Ca2+ and the content of α-ketoglutarate dehydrogenase (α-OGDH) in myocardial mitochondria were determined at the end of the whole experiment. RESULTS：Compared with I/R group, the cardiac function indexes in IPC+I/R and GD+I/R groups were improved at the reperfusion period (P<0.05), the activity of LDH and CK in coronary effluent and the concentration of Ca2+ in mitochondria were significant reduced (P<0.01), and the content of α-OGDH was increased (P<0.05). However, the protective effect of GD was inhibited by LaCl3 (P<0.05). CONCLUSION：GD protects rat hearts against I/R injury by inhibiting calcium overload and improving mitochondrial enzyme activity to stabilize mitochondrial energy metabolism.     

X-ray irradiation increases sensitivity of myocardium to ischemia/reperfusion injury in rats

AIM：To observe the sensitivity of myocardium to ischemia/reperfusion (I/R) injury in the rats with chest radiotherapy. METHODS：The radiation-induced heart disease model was established by local 20 Gy of X-ray irradiation in the chest. Male Wistar rats (n=42) were randomly divided into 6 groups:sham trauma group, trauma group, sham trauma+sham operation group, sham trauma +I/R group, trauma+sham operation group and trauma+I/R group. The rats were subjected to 30 min of ischemia and 1 h of reperfusion 2 week after trauma. The left ventricular developed pressure (LVDP) and ±dp/dtmax were recorded by BL-410 biological signal recording and analysis system. The serum cardiac troponin I (cTnI) and creatine kinase isoenzyme (CK-MB) were measured by ELISA. The myocardial infarct size was determined by nitroblue tetrazolium(NBT) staining method and BI2000 image analysis software. RESULTS：Compared with sham trauma+I/R group, significant decreases in LVDP and ±dp/dtmax were observed in trauma+I/R group (P<0.01) with significant increases in the infarct size and the concentrations of cTnI and CK-MB (P<0.01). CONCLUSION:Chest X-ray irradiation increases the sensitivity of myocardium to I/R injury in rats.     

Upregulative effect of CGRP on expression of CREB and phospho-CREB protein during focal cerebral ischemia/reperfusion in rat parietal cortex

AIM: To investigate the effect of calcitonin gene related peptide (CGRP) on the expression of cyclic AMP response element binding protein (CREB) and phosphorylated-CREB in rat parietal cortex during focal cerebral ischemia/reperfusion (I/R).METHODS: Focal cerebral ischemia/reperfusion model was induced by occlusion of the right middle cerebral artery using the intraluminal suture method. The expressions of CREB and phospho-CREB in the parietal cortex in different groups (sham group, focal cerebral ischemia/reperfusion group and CGRP group) were detected with immunohistochemistry and Western blotting, and the positive products were analyzed by image analysis system.RESULTS: There was definite expression of CREB in right parietal cortex in sham group, while it was lesser in I/R group than that in sham group, but it became more in CGRP group than that in I/R group (P<0.05). Phospho-CREB was barely detected in right parietal cortex in sham group and it became more in I/R group than that in sham group. The expression of phospho-CREB increased in CGRP group than that in I/R group of the right parietal cortex (P<0.05).CONCLUSION: CGRP upregulates the expression of CREB and phospho-CREB in the ischemic neurons of the parietal cortex during focal cerebral ischemia/reperfusion and CREB probably involves in the mechanism of protective role of CGRP to ischemic neurons.     

Changes of cardiac energy metabolism and structure during ischemia/reperfusion injury of liver in rats

AIM: To investigate the effect and mechanism of liver ischemia/reperfusion (I/R) injury on the changes of cardiac energy metabolism and structure.METHODS: 48 healthy Wistar male rats were randomly divided into 6 groups as follows (n=8 in each group): control group (CTL), simply ischemia for 30 min without reperfusion(I group); reperfusion following ischemia for 30 min (I/R group); 2 h reperfusion following ischemia for 30 min (I/R 2 h group); 4 h reperfusion following ischemia for 30 min (I/R 4 h group) and 6 h reperfusion following ischemia for 30 min (I/R 6 h group). The level of serum endotoxin was measured. The levels of insulin and insulin antibody in heart were detected by radioimmunoassay. The contents of MDA, MPO and lactic acid in heart were also determined. RESULTS: During the process of liver I/R injury, the level of endotoxin increased in I group and I/R group and declined gradually for long time during reperfusion, but was still longer than that in CTL group (P<0.05). The level of MDA obviously increased in I group and in all reperfusion groups compared to CTL (P<0.05). The obvious significant differences among I/R 2 h group, I/R 4 h group, I/R 6 h group with CTL were observed (P<0.05). The activities of MPO obviously increased in all reperfusion groups, there was also an obvious significant difference compared with CTL and I group (P<0.05). The level of lactic acid obviously increased with prolongation in reperfusion (P<0.05), but decreased in I/R 6 h group (P<0.05). The level of insulin decreased in I/R 4 h group and I/R 6 h group (P<0.05). No difference of insulin antibody was observed among all groups (P>0.05). CONCLUSION: During the process of liver I/R injury, endotoxin is absorbed from intestine and impairment of liver detoxication leads to endotoxemia, which might play a role in the changes of the energy metabolism and structure in heart.     

p38 MAPK-Pim-3 signal pathway may be involved in cardiomyocyte anoxia preconditioning against anoxia/reoxygenation injury

AIM: To investigate the role of mitogen-activated protein kinases (MAPKs) pathways and the molecular mechanism by which the proto-oncogene Pim-3 protects cardiomyocyte against anoxia/reoxygenation (A/R) injury. METHODS: The primarily cultured neonatal rat ventricular cardiomyocytes were randomly divided into 4 groups: control group; A/R group; APC+A/R group; SB203850, U0126 or SP600125+APC+A/R group. The cells were pre-incubated with U0126 (ERK1/2 inhibitor), SP600125 (SAPK/JNK inhibitor), or SB203850 (p38 MAPK inhibitor) at concentration of 10 μmol/L for 30 min before the APC. The activities of p38 MAPK, JNK and ERK1/2 were detected by Western blotting. The viability of cardiomyocytes was assayed by MTT and the apoptosis of cardiomyocyte was detected by TUNEL. RESULTS: U0126, SB203850, and SP600125 abolished the increased expression of ERK1/2, p38-MAPK, and JNK proteins induced by APC+A/R or A/R, respectively. The expression level of Pim-3 protein significantly decreased when the p38 MAPK signal pathway was inhibited. Meanwhile, the activity of LDH and the apoptosis index increased, and the viability of cardiomyocytes decreased. CONCLUSION: Pim-3 expression through a p38 MAPK signaling pathway may protect cardiomyocytes from A/R injury.     

Effects of norepinephrine preconditioning and ischemic preconditioning on apoptosis and Bcl-2, Bax expression in rat myocardial cells during myocardial ischemic reperfusion

AIM: To study the effects of norepinephrine preconditioning(NE-P) and ischemic preconditioning (IP)on apoptosis and Bcl-2, Bax expression in rat myocardial cells in myocardial ischemic reperfusion (I/R). METHODS: The model of rat ischemic-reperfusion was used to conduct NE-preconditioning. Apoptotic myocytes were detected with TUNEL. Bcl-2, Bax expression were detected with immunohistochemistry. RESULTS: The rate of apoptosis cells in I/R group was higher, the rate of apoptosis cells in NE-P group and IP was lower significantly than that in I/R group(P＜0.01). The expression of Bcl-2 in I/R group was lower, but the expression of Bax was higher, the expression of Bcl-2 in NE-P group was higher significantly than that in I/R group(P＜0.01), the expression of Bax in NE-P group was lower than that in I/R group(P＜0.01). There was no significantly difference between NE-P and IP group in the above parameters (P＞0.05). CONCLUSION: NE-P reduced myocyte apoptosis by I/R in rats; The expression of Bcl-2 ,Bax genes played an important role in myocardial apoptosis.     

Remote preconditioning provides myocardial protection against myocardial ischemia/reperfusion injury through downregulating the expression of calreticulin in rats

AIM: To evaluate the role of calreticulin (CRT) in myocardial protection of remote preconditioning against myocardial ischemia/reperfusion injury. METHODS: Thirty SD rats were randomly divided into 5 groups: ischemia reperfusion group (IR), ischemia preconditioning group (IP), remote preconditioning group Ⅰ (RPI), remote preconditioning group Ⅱ (RPII) and pseudo-operation group (PO). The ischemia/reperfusion model was established in vivo. Hemodynamic changes of heart function were observed. Serum cardiac troponin T (cTnT), superoxide dismutase (SOD), malondialdehyde (MDA) and the expression of calreticulin in myocardium were detected. RESULTS: Hemodynamic data, serum cTnT, DA, SOD and the expression of CRT in RPI and IR group were not statistically different (P>0.05). SOD level in IP and RPII group was higher than that in IR group (P<0.05). Accordingly, cTnT, MDA and the expression of CRT in these two groups were lower than those in IR group (P<0.05). CONCLUSION: Remote preconditioning may mimic the protective effect of ischemic preconditioning. Remote preconditioning attenuates myocardial ischemia/reperfusion injury in vivo possibly through down-regulation of CRT expression in rats.     

Role of nitric oxide in ischemia/reperfusion injury and ischemic preconditioning

AIM: To clarify the role of nitric oxide(NO) in ischemic preconditioning(IP) and its effects on apoptosis. METHODS: Seventy-two male Wistar rats were divided into the following six groups:ischemia/reperfusion (IR) group,IP group,IR+L-arg group,IP+L-arg group,IR+L-NAME group and IP+L-NAME group,The following changes were measured:cardiac hemodynamic parameters,infarct size,PMNs counting myocardial MPO activity and TUNEL staining.RESULTS: ①L-arg significantly attenuated ischemia/reperfusion-induced heart injury,reduced PMNs infiltration and cardiomyocyte apoptosis.②L-NAME also significantly reduced infarct size,PMNs infiltration and cardiomyocyte apoptosis compared with IR group,however,L-NAME aggravated ischemia/reperfusions-induced cardiac functional injury.③L-arg or L-NAME did not significantly alter the protective effect of ischemic preconditioning. CONCLUSION: Increased production of endogenous NO before prolonged ischemic period can protect hearts and inhibit apoptosis.L-NAME can inhibit iNOS activity and ONOO^- production in reperfusion period to protect heart.