Liver X receptors attenuate myocardial ischemia-reperfusion injury through modulating GLUT-4

AIM：To investigate whether liver X receptors (LXRs) attenuate myocardial ischemia-reperfusion (I/R) injury in isolated rat heart through modulating glucose transporter 4 (GLUT-4). METHODS：Isolated rat hearts were used to establish the model of ischemia-reperfusion injury using Langendorff apparatus. The hearts were divided into 7 groups: LXR agonist T0901317 (0.1, 0.5 and 10 μmol/L) pretreatment groups, ischemic preconditioning group, control group, control+DMSO group, and I/R group. The releases of lactate dehydrogenase (LDH) and creatine kinase (CK), the infarct size, the hemodynamic parameters (left ventricle developed pressure,left ventricle end-diastolic pressure, coronary flow and ±dp/dt max), the relative mRNA level of GLUT-4 and the protein content of GLUT-4 in the myocardial cell membrane were compared between these groups. RESULTS：Besides producing hemodynamic disorders, I/R increased the activities of LDH and CK, and the infarct size in model groups. Treatment with T0901317 significantly suppressed ischemia-reperfusion injury-induced increases in LDH and CK, and reduced the infarct size. T0901317 also significantly ameliorated the parameters of haemodynamics. Treatment with T0901317 significantly increased GLUT-4 expression at mRNA and protein levels in the myocardial cell membrane. CONCLUSION：Liver X receptors may attenuate myocardial ischemia-reperfusion injury in isolated rat heart by modulating the expression of GLUT-4.     

Effects of diabetes on ischemic/reperfusion injury and cell apoptosis in rats myocardium via alterations in peroxynitrite

AIM: To determine the effects of different-term streptozotocin(STZ)-induced diabetes on ischemia/reperfusion (I/R) injury and cell apoptosis in rats myocardial via alterations in myocardial peroxynitrite.METHODS: The models of I/R injury were induced by occlusion and reperfusion of the left descending coronary artery (LDCA) in rats.I/R-induced infarct size was determined using triphenyltetrazolium chloride (TTC) staining.Quantified caspase-3 expression was used to represent apoptosis by Western blotting analysis.Peroxynitrite formation as indicated by nitrotyrosine level was measured by morphometric analysis.RESULTS: Two weeks after STZ treatment,infarct size (35.00%±3.00%) was smaller in 2 weeks diabetic hearts (2WKD) as compared with time-matched control group (2WKC) (51.00%±3.30%),whereas after 16 weeks of diabetes (16WKD),the infarct size (61.00%±3.00%) was bigger in the diabetic hearts as compared with the 16WKC group (50.00%±2.00%,P<0.05).After I/R,caspase-3 expression was lower in 2WKD+I/R group (A value：481±77) than that in 2WKC+I/R group (A value：1033±46),while caspase-3 was higher in the 16WKD+I/R group (A value：1206±78) than that in 16WKC+I/R group (A value：940±72,P<0.05).Nitrotyrosine was lower in 2WKD hearts (A value：211±13) than that in controls (A value：409±12),but was higher in 16WKD group (A value：506±37) compared with controls (A value：378±46,P<0.05).CONCLUSION: Short- and long-term STZ induced diabetes exerts opposite influences on myocardial I/R injury and cell apoptosis,and these contradictory influences may depend on different alterations in myocardial peroxynitrite.     

Effect of limb ischemic postconditioning on brain focal ischemia and reperfusion injury in mice

AIM: To establish the mouse model in which the limbic ischemic postconditionning (LIPostC) enhances the tolerance against brain ischemia, and to investigate the effects of LIPostC on the ischemic extent and roles of heat shock protein 70 (HSP70) in ischemia and reperfusion injury. METHODS: The male Kunming mice were used in the study. The brain ischemia reperfusion (I/R) model was made by middle cerebral artery occlusion (MCAO). In the first test, the male mice were randomly divided into 9 groups (n=10): sham group, ischemia/reperfusion (I/R) groups (with ischemia for 0.5 h, 1 h,1.5 h and 2 h) and LIPostC+I/R groups (0.5 h+LIPostC,1 h+LIPostC,1.5 h+LIPostC,2 h+LIPostC). The reperfusion was performed after LIPostC for 24 h. After the neurologic deficit scores were evaluated, the brains were taken out to measure the infarct volume with TTC staining and to observe the pathological changes of cerebral cortex with HE staining. The neuronal apoptosis was determined by TUNEL. In the second test, the male mice were randomized into 4 groups (n=6): sham group, I/R group, LIPostC+I/R group and LIPostC+I/R+quercetin group (2 h ischemia). The neurological deficit scores were evaluated at 24 h after operation. The expression of HSP70 was determined by Western blotting.RESULTS: The duration of brain ischemia was related to the motor behavior and degree of brain injury. The longer the ischemic duration of the brain was performed, the more severe the pathological and behavioral changes were observed. The brain injury in 2 h MCAO mice was more severe than that in 1 h and 1.5 h MCAO mice (P<0.05). Compared to I/R group, each LIPostC group showed lower neurological score, less infarct volume and TUNEL positive neuron. The expression of HSP70 protein was increased and neurological functions were improved significantly in the mice with LIPostC. However, the neuroprotective role of LIPostC was attenuated by treating with quercetin, an inhibitor of HSP70.CONCLUSION: LIPostC promotes the expression of HSP 70, improves the neurological functions and attenuates the ischemia and reperfusion injury in MCAO mice. HSP70 produces a marked effect on the ischemic tolerance induced by LIPostC in MCAO mice.     

Nitric oxide opens the second window of protection in ischemic preconditioning via induction of heat shock protein 72

AIM:To examine the inhibition of nitric oxide (NO) synthesis during ischemic preconditioning (IP) on the induction of heat shock protein 72 (HSP72) and infarct size-limiting effect of the second window of protection. METHODS:Rabbits were subjected to 4 cycles of 5 min of coronary artery occlusion separated by 10 min reperfusion, or received a sham operation. During this procedure, N^G-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) was injected intravenously 5 min before IP followed by its continuous infusion. Twenty-four hours later, the hearts were rapidly excised for assaying HSP72 expression or were subjected to 30 min coronary artery occlusion followed by 120 min reperfusion and then measured infarct size (IS). RESULTS:Twenty-four hours later, immunoblotting revealed an increase in HSP72 protein levels in the IP group, and this was blocked by L-NAME. IS of the IP rabbits was reduced as compared with the control (29.8%±3.7% vs 50.8%±4.3%, P＜0.01). IS in the IP rabbits was elevtated as a result of L-NAME treatment (46.0%±5.1%). Administration of L-arginine reversed the effects of L-NAME on the induction of HSP72 and IS (33.5%±4.0%). The intravenous administration of S-nitroso-N-acetylpenicillamine (SNAP, a NO donor) increased the induction of HSP72 and reduced IS (31.3%±5.7%, P＜0.01vs control) 24 h later. CONCLUSION:These findings suggest that NO may be involved in the induction of HSP72 and the opening of the second window of protection of IP.     

Inhibition of calcineurin is involved in cardioprotection induced by ischemic postconditioning in rats

AIM: To demonstrate the mechanisms underlying cardioprotection induced by ischemic postconditioning (I-postC) via studying the alteration of calreticulin (CRT)/calcineurin (CaN) signaling pathway in rat heart subjected to ischemia/reperfusion (I/R).METHODS: The model of myocardial I/R injury in vivo was made by occluding the left anterior descending artery for 45 min followed by 24 h of reperfusion in Wistar rats.Hemodynamics and activity of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) in plasma were measured.Myocardial infarct size was measured by 2,3,5- triphenyltetrazolium chloride (TTC) staining and cardiomyocyte apoptosis was detected using in situ TDT-mediated dUTP nick end labeling (TUNEL).The activity of CaN,the expressions of CaN and CRT in myocardium were detected by enzyme reaction phosphorus measurement and Western blotting analysis,respectively.RESULTS: Cyclosporin A,the inhibitor of CaN,limited significantly myocardial infarct size and cardiomyocyte apoptosis induced by I/R,but had no significant effect on cardiac function.I-postC ameliorated significantly the cardiac dysfunction induced by I/R.Compared with those in I/R group,the myocardial infarct size,the LDH and CK-MB activities in plasma and the cardiomyocyte apoptotic index were significantly reduced in I-postC group.In addition,I/R-induced upregulation of CaN activity,CaN and CRT expression were relieved by I-postC.No significant difference was found between I-postC and ischemic preconditioning groups.I-postC had stronger protective effect on the reperfused heart compared with cyclosporin A.CONCLUSION: The findings indicate that I-postC protects myocardium against I/R injury,at least in part,via inhibiting the CRT/CaN signaling pathway.     

Protective effects of glutamine pretreatment on occludin protein in rats with intestinal ischemia-reperfusion injury

AIM: To determine the effects of glutamine(Gln) pretreatment on occludin protein in the rats with intestinal ischemia-reperfusion(I/R) injury. METHODS: Male Wistar rats(n=30) were randomly divided into 3 groups(n=10):sham group, I/R group and Gln pretreatment group. The rats in Gln pretreatment group were pretreated with Gln at dose of 1 g·kg^-1·d^-1 by orogastric route for 7 d, and those in the other 2 groups were pretreated with the same volume of normal saline. Intestinal I/R was induced by 30-min occlusion of the superior mesenteric artery followed by 24 h of reperfusion. After the operation, the levels of IL-10, IL-2, TNF-α, SOD and MDA were measured. The occludin protein was determined by the methods of immunohistochemistry and Western blotting. RESULTS: The occludin protein level in I/R group was significantly lower than that in sham group and Gln group(P<0.05). The levels of MDA and TNF-α in I/R group were significantly higher than those in sham group and Gln group(P<0.05). The levels of SOD, IL-10 and IL-2 in I/R group were significantly lower than those in sham group and Gln group(P<0.05). CONCLUSION: Glutamine has a protective effect on occludin protein in intestinal ischemia-reperfusion injury. The mechanism may be rela-ted to oxidative stress response and inflammatory inhibition.     

Protective effect of heat-shock pretreatment on rat ischemia-reperfusion myocardium

AIM:To investigate the changes of expression of P-selectin (Ps) in ischemia-reperfusion myocardium and to observe the effects of heat shock protein (HSP) on the expression of Ps and apoptosis. METHODS:Mature female Wistar rats (n=40) were divided into three groups at random. Under general anesthesia, the rats in heat-shock group were subjected to whole-body hyperthermia, and those in the other two groups were treated with anesthetic alone. Twenty-four hours later, the animals in heat-shock group and in control group were subjected to surgical operative ligation of coronary left anterior descending branch (LAD) for 1 h, then accepted reperfusion for 2 h. Those in sham operation group were also performed surgical operation without LAD ligation for 3 h. After operation, the CK-MB in blood serum, infarct size of left ventricles, HSP70, Bax, Bcl-2, Ps and apoptosis cells were measured. RESULTS:The amount of HSP70 in heat-shock group was significant higher than that in control group and in sham operation group (P<0.05). There was no difference between control group and sham operation group (P>0.05). Compared with control group, the infarct size, CK-MB, apoptosis cells, Bax and Ps in heat-shock group were significantly reduced (P<0.05). However, expression of Bcl-2 was similar (P>0.05). No expression of Ps in sham operation group was detected. CONCLUSIONS:HSP70 may reduce myocardial apoptosis during ischemia-reperfusion. One of the mechanisms is that HSP70 restraines the expression of Bax and Bax/Bcl-2. Ps plays an injurious role in ischemia-reperfusion myocardium. HSP70 is likely to restrain Ps from expression, which may be one of the mechanisms by which heat-shock pretreatment plays a protective role in ischemia- reperfusion myocardium.     

Effects of human urotensin II on ischemia/reperfusion injury in isolated perfused rat hearts

AIM: To investigate the effects of human urotensin II (hUII) on ischemia/reperfusion (I/R) injury in isolated rat hearts. METHODS: In the ischemia/reperfusion (I/R) model of isolated perfused rat hearts, the effects of hUII pretreatment on cardiac function was monitored with cardiac function software of MFL Lab200. ATP, total calcium, and malondialdehyde (MDA) content in myocardium were detected. The coronary perfusion flow (CPF) and lactate dehydrogenase (LDH) activity in coronary effluent were measured during reperfusion. RESULTS: In the hUII pretreated group, the release of LDH from myocardium was lower [(78.3±18.1)U/L] than I/R group [(109.3±23.9) U/L, P< 0.05], with decreased contents of MDA and calcium in myocardium (decreased by 24% and 27%, respectively, P< 0.05) and an increased myocardial ATP content [(3.8±0.4)μmol/g dw vs (2.2±0.4)μmol/g dw, P< 0.05)]. At the same time, hUII pretreatment increased CPF [(5.4±0.7) mL/min vs (3.8±0.8) mL/min in I/R group, P< 0.05], reduced left ventricular end-diastolic pressure (LVEDP) by 20% ( P< 0.05) with increased±d p /d t max [(217±38) kPa/s and (119±18) kPa/s vs (173±29) kPa/s and (82±25) kPa/s in I/R groups, respectively, P< 0.05]. hUII pretreatment also increased natrite/natrate (NO₂^-/NO₃^-) content in coronary effluent [(52.2±12.0)μmol/L vs (32.1±10.2)μmol/L in I/R group, P< 0.05)]. CONCLUSION: hUII pretreatment attenuated I/R injury in isolated perfused rat hearts. The protective mechanism might be associated with NO-mediated coronary vasodilation.     

Knockdown of Atg5 aggravates cerebral ischemia and reperfusion injury in mice

AIM: To study the role of autophagy-related gene 5 (Atg5) in cerebral ischemia and reperfusion injury in mice. METHODS: BALB/c male mice (weighing 18~22 g) were randomly divided into sham group, ischemia/reperfusion (I/R) group, Atg5 siRNA group and control siRNA group. Focal cerebral ischemia was performed using the method of middle cerebral artery occlusion (MCAO) for 60 min and reperfusion for 24 h. In siRNA group and control group, 5 μL Atg5 siRNA or scrambled siRNA was administered by intracerebroventricular injection 24 h before MCAO. The expression of Atg5 at mRNA and protein levels in ischemic cortex at 24 h after reperfusion was determined by real-time PCR and Western blot. The infarct volume and edema were evaluated by TTC staining, and motor deficits were evaluated by neurological scoring. RESULTS: The expression of Atg5 at mRNA and protein levels was significantly increased 24 h after reperfusion in I/R group compared with sham group. Atg5 siRNA obviously decreased the expression of Atg5 at mRNA and protein levels induced by I/R. Inhibition of Atg5 exacerbated the infarct volume and ameliorated the neurological symptoms. CONCLUSION: Atg5 has neuroprotective effect on focal cerebral ischemia and reperfusion injury.     

Role of mitochondrial permeability transition pore in TNFα-induced cardioprotection in isolated rat hearts subjected to hypoxia and reoxygenation

AIM: To investigate whether tumor necrosis factor α (TNFα) pretreatment can inhibit mitochondrial permeability transition pore opening in isolated rat hearts subjected to hypoxia and reoxygenation. METHODS: Isolated perfused rat hearts were subjected to 30 min regional hypoxia (occlusion of left anterior descending artery) and 120 min reoxygenation. The infarct size, lactate dehydrogenase (LDH) release during reoxygenation and ventricular hemodynamic parameters were measured. RESULTS: Pretreatment with TNFα at concentration of 1×104 U/L for 7 min followed by 10 min washout reduced the infarct size and LDH release, and improved the left ventricular performance (left ventricular developed pressure and rate-pressure product) and left ventricular end-diastolic pressure during hypoxia and reoxygenation. Administration of atractyloside (Atr, an opener of mitochondrial permeability transition pore, 20 μmol/L) for 20 min (last 5 min of hypoxia and first 15 min of reoxygenation) and paxilline (Pax, a calcium activated potassium channel antagonist, 1 μmol/L) for 5 min before hypoxia attenuated the reduction of infarct size and LDH release and improved the left ventricular performance induced by TNFα. CONCLUSION: The findings indicate that in the isolated rat heart model, TNFα protects myocardium against hypoxia and reoxygenation injury via inhibiting mitochondrial permeability transition pore opening as well as activating calcium, activated potassium channel.     

Panax quinquefolium saponins protect rat myocardium from ischemia/reperfusion injury through attenuating excessive endoplasmic reticulum stress

AIM: To investigate whether excessive endoplasmic reticulum stress (ERS) is involved in the protective mechanism of Panax quinquefolium saponins (PQS) against ischemia/reperfusion (I/R) injury in rat myocardium. METHODS: The model of myocardial I/R injury in vivo was made by ligating the left anterior descending artery for 45 min followed by 24 h of reperfusion in SD rats. The hemodynamics and serum content of cardiac troponin T (cTnT) were measured. The myocardial infarct size was measured by Evans blue and 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Cardiomyocyte apoptosis was detected using in situ TDT-mediated dUTP nick end labeling (TUNEL). The protein levels of glucose-regulated protein 78 (GRP78), calreticulin (CRT), C/EBP homologous protein (CHOP), caspase-12, apoptosis-associated proteins Bax and Bcl-2 were determined by Western blotting. RESULTS: Compared with I/R group, the mean arterial pressure in PQR+IR group was decreased by 32.0%, and left ventricular±dp/dtmax was increased by 64.0% and 35.0%, respectively.The serum content of cTnT was decreased by 53.3%, the percentage of area of necrosis (AN)/area at risk (AAR) was reduced by 65.5% and the apoptosis rate was decreased by 54.9%.The myocardial pathological changes were improved. Bcl-2 protein expression was increased by 110.0% and that of Bax was decreased by 47.8%. CRT protein expression was decreased by 43.4 %, CHOP protein expression and the protein level of cleaved caspase-12 were decreased by 38.6% and 23.7% in PQS+I/R group. CONCLUSION: PQS alleviates I/R injury in myocardium by inhibition of excessive ERS.     

Effects of Panax quinquefolium saponin on mitochondrial membrane potential and cardiomyocyte apoptosis in ischemia/reperfusion rats

AIM：To investigate whether mitochondrial membrane potential (ΔΨm) and the mitochondrial apoptotic pathway are involved in the protective mechanism of Panax quinquefolium saponin (PQS) against cardiomyocyte apoptosis after ischemia/reperfusion (I/R) injury in rat myocardium. METHODS：Ninety healthy male SD rats were randomly divided into sham group, I/R group, PQS (200 mg·kg-1·d-1) +I/R group, cyclosporine A (CsA) group, CsA (10 mg·kg-1) +I/R group and PQS +CsA +I/R group. The model of myocardial I/R injury in vivo was established by ligating the left anterior descending artery (LAD) for 30 min followed by 120 min of reperfusion in the rats. The serum activity of lactate dehydrogenase (LDH) was measured by automatic chemistry analyzer. The myocardial infarct size was measured by Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining. Cardiomyocyte apoptosis was detected by in situ TDT-mediated dUTP nick end labeling (TUNEL). The protein levels of Bcl-2, Bax, cleaved caspase-3 and cytosolic cytochrome C were determined by Western blotting. ΔΨm was measured by laser scanning confocal microscopy and fluorescence microplate reader. RESULTS：Compared with I/R group, the serum content of LDH,the infarction size in PQS+I/R group, CsA+I/R group and PQS+CsA+I/R group and the myocardial apoptotic index were decreased. Compared with I/R group, the fluorescence intensity of mitochondria after JC-1 staining was enhanced in PQS+I/R group, CsA+I/R group and PQS+CsA+I/R group, and the relative fluorescence units (RFU) of ΔΨm were improved in those 3 groups. In PQS+I/R group, CsA+I/R group and PQS+CsA+I/R group, the protein expression of Bcl-2 was increased, and that of Bax was decreased compared with I/R group. Moreover, in those 3 groups, the protein levels of cleaved-caspase-3 and cytosolic cytochrome C were decreased compared to I/R group, respectively. CONCLUSION：PQS attenuates myocardial injury and cardiomyocyte apoptosis during I/R, and the protective mechanisms of PQS were associated with the modulation of ΔΨm and the inhibition of mitochondrial apoptosis pathway.     

Ischemia reperfusion-induced proteomic changes in rat skeletal muscle

AIM: To investigate ischemia reperfusion (I/R)-induced proteomic changes in rat skeletal muscle. METHODS: Healthy male Wistar rats were randomly divided into two groups as follows (n=6): sham group and I/R group. I/R of right hind limb was induced by 4 h ischemia followed by 24 h reperfusion. The 2-DE was applied to separate the proteins extracted from skeletal muscle tissue at the end of experiment, followed by Coomassie Brillant blue R-250 staining. Computer image analysis was used to determine the differential expression of proteins between the two groups, and 7 protein spots expressed differentially were picked out and subjected to in-gel digest and MALDI-TOP for identification. RESULTS: 354±13 proteins were detected and the match rate was (78.7±1.4)%. 10 proteins displayed significant changes after I/R, of which, 6 proteins increased and 3 proteins decreased in expression. Moreover, 2 spots in I/R group were observed, only 1 spots of which in control. 5 proteins were identified after mass spectrometry. Mitochondrial aldehyde dehydrogenase (ALDH) precursor, heat shock 27 kD protein (HSP27), an unnamed protein product (increased in I/R group), α-actin (decreased in I/R group), and nuclear transport factor 2 (NTF-2) W7a mutant were found in I/R group. CONCLUSION: I/R injury induced differential proteomic changes in rat skeletal muscle. ALDH, α-actin and HSP27 expression, and NTF-2 mutation are involved in I/R injury.     

Effects of pretreatment with captopril on the infarct size and myocardial cell apoptosis in experimental rabbits

AIM:To investigate the effects of pretreatment of captopril on the infarct size and myocardial cell apoptosis in rabbits. METHODS:Rabbits were randomly divided into sham-operated control group (SO), acute infarct group (AI) and captopril pretreatment group (CP). The rabbits of CP group were treated with captopril (25 mg·kg^-1.d^-1) for 1 week before harvest. The left circumflex branch of coronary (LCX) was ligated to develop acute ischemic model. The systolic and diastolic function of left ventricle(LV) was measured before and at 15, 30, 60 min after ligating LCX, and the blood viscosity and hematocrit before and at 60 min after ligating LCX were measured also. 6 hours later LCX ligation, the hearts were harvested for determining the infarction size, which was expressed as the ratio of infarct area to the total ischemic area, and evaluating apoptosis index expressed as the percentage of myocardial cells with TUNEL positive staining. RESULTS:1.Compared with AI group, captopril pretreatment significantly reduced the infarction size (16.60%±0.94% vs 36.24%±1.94%, P＜0.05), and improved the LV function and viscosity of blood. 2. Apoptosis of myocardial cell was found in the myocardium surrounding to the infarction area, however, the apoptosis index of CP group was significantly lower than that of AI group (26.30%±0.71% vs 42.44%±2.32%,P＜0.05).CONCLUSION:Apoptosis of myocardial cell exists in the area surrounding the infarction. Captopril pretreatment can reduce infarction size and myocardial apoptosis index, and improve the LV function as well as blood viscosity in this acute ischemic model.     

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.     

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.     

The relationship between delayed preconditioning mediated by R-PIA and myocardial nuclear factor-kappa B

AIM:To investigate the role of myocardial nuclear factor kappa B (NF-κB)and manganese superoxide dismutase (Mn-SOD) in the mechanism underlying cardioprotective effect of delayed preconditioning mediated by adenosine A₁ receptor agonist R-phenylisopropyladenosine ( R-PIA). METHODS:Male Wistar rats were randomly divided into three groups(n=12), Group normal saline, Group R-PIA and Group R-PIA plus DPCPX (an adenosine A₁ receptor antagonist). Twenty four hours after administration of above drug, left ventricular myocardial samples of 4 rats in each group were obtained for assessment of myocardial Mn-SOD content (ELISA) and NF-κB binding activity (EMSA). Eight rats in each group, 24 hours after pretreatment as above, were subjected to chest-open and subjected to 30 min of regional myocardial ischemia followed by 120 min of reperfusion, and then the hearts of the rats were isolated to determine the infarct size (TTC stain ). RESULTS: The infarct size in group R-PIA was significantly less than that in group normal saline (P＜0.01), and there was no significant difference between group R-PIA+DPCPX and group normal saline in infarct size (P＞0.05). Myocardial NF-kappa B binding activity and Mn-SOD content in group R-PIA were all higher than those in group normal saline. There was no significant difference between group R-PIA+DPCPX and group normal saline in NF-κB binding activity and Mn-SOD content (P＞0.05). CONCLUSIONS:This study suggested that there might be a close relationship between delayed preconditioning mediated by adenosine A₁ receptor agonist R-PIA and myocardial nuclear factor-kappa B binding activity and Mn-SOD protein expression.     

Effects of heat shock protein 70 on inflammation after hepatic local ischemia/reperfusion in rats

AIM:To study the effects of heat shock protein 70 (HSP70) induced by the heat stress pretreatment on inflammation after hepatic ischemia/resperfusion.METHODS:With the hepatic local ischemia/reperfusion model (IR group),heat stress pretreatment (H+IR group) and injecting quercetin before heat stress pretreatment (Q+H+IR group) were performed.The HSP70,intercellular adhesion molecule-1 (ICAM-1) and the myeloperoxidase (MPO) activity were detected.The levels of serum ALT and AST and histological changes of the hepatocytes were also observed.RESULTS:In H+IR group,the HSP70 expression was higher than that in other groups at each time point,after performing ischemia-perfusion,hepatic injury was slighter.The levels of serum ALT and AST were increased slightly (P<0.01).The expression of ICAM-1 and the changes of MPO activity increased and peaked respectively at 6 h and 12 h after reperfusion.However,they were lower in H+IR group than those in IR group and Q+H+IR group.CONCLUSION:The HSP70 induced by heat stress pretreament reduces the expression of ICAM-1 and the changes of MPO activity during hepatic ischemia-reperfusion,then hepatic injury is depressed from the inflammation.     

Effects of ischemic postconditioning on sizes of myocardial infarction induced by ischemia/reperfusion and PKCα expression in rats

AIM: To observe the effects of ischemic postconditioning on the sizes of myocardial infarction induced by ischemia/reperfusion (I/R) and expression of protein kinase C-α (PKCα) in rats. METHODS: The infarction sizes (IS) were measured with Evan’s and TTC dye, and the expression of PKCα in myocardial tissue was investigated by immunohistochemistry. RESULTS: Compared with the I/R group, the IS was reduced significantly (P<0.01), and the expression of PKCα increased significantly in IPC and IPTC groups (P<0.01). There was no significant difference between IPC and IPTC groups. CONCLUSIONS: The postconditioning is as effective as preconditioning in reducing infarct size, and the expression of PKCα may be one of the potential mechanisms of reducing the infarction sizes.     

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.