[The protective effects of Astragaloside â £ on diastolic function of rat thoracic aortic rings impaired by microvesicles].

OBJECTIVES: To investigate the effects of Astragaloside IV (AST) on diastolic function of rat thoracic aorta rings which was injured by microvesicles derived from hypoxia/reoxygenation (H/R)-treated human umbilical vein endothelial cells (HUVECs), and the mechanism of AST. METHODS: H/R-induced endothelial microvesicles (H/R-EMVs) were generated from cultured HUVECs in vitro under the condition of hypoxia for 12 hour/Reoxygenation for 4 hour, H/R-EMVs were stored in D-Hank's solution. Male Wistar rats were underwent thoracotomy, the thoracic aorta with intact endothelium were carefully removed and cut into 3~4 mm rings. The experiment was divided into six groups. H/R-EMVs group:thoracic aortic rings of rats were incubated in culture medium and treated with H/R-EMVs in a final concentration of 10µg/ml; different doses of AST groups:thoracic aortic rings of rats were treated with 10, 20, 40, 60 mg/L AST co-incubated with 10µg/ml H/R-EMVs respectively; control group were treated with the same volume of D-Hank's solution. Duration of incubation was 4 h, each group was tested in five replicate aortic rings. Effects of AST on endothelium-dependent relaxation were detected. The production of nitric oxide (NO) and the level of endothelial NO synthase (eNOS), phosphorylated eNOS (p-eNOS, Ser-1177), serine/threonine kinase (Akt), phosphorylated Akt (p-Akt, Ser-473), extracellular regulated protein kinases (ERK1/2) and phosphorylated ERK1/2 (p-ERK1/2, Thr202/Tyr204) of rat thoracic aortic rings were detected. RESULTS: Tenµg/ml H/R-EMVs could impaire the relaxation of rat thoracic aortic rings significantly (P<0.01). Compared with H/R-EMVs group, relaxation of rat thoracic aortic rings was increased by 20, 40 and 60 mg/L AST in a concentration-dependent manner (P<0.01), the level of NO production was also enhanced (P<0.05, P<0.01). The level of t-eNOS, t-Akt and ERK1/2 was not changed, but the level of p-eNOS, p-Akt and p-ERK1/2 increased by the treatment with AST (P<0.01). CONCLUSIONS: AST could effectively ameliorate endotheliumdependent relaxation of rat thoracic aortic rings impaired by H/R-EMVs in a concentration-dependent manner, the mechanism might involve the increase in production of NO, and the protein level of p-eNOS, p-Akt and p-ERK1/2.

Protective effects of circulating microvesicles derived from myocardial ischemic rats on apoptosis of cardiomyocytes in myocardial ischemia/reperfusion injury.

OBJECTIVE: To investigate the effects of circulating microvesicles derived from myocardial ischemia (I-MVs) on apoptosis in myocardial ischemia/reperfusion (I/R) injury in rats. METHODS: I-MVs from rats undergoing myocardial left anterior descending (LAD) coronary artery ligation were isolated by ultracentrifugation from circulating blood and characterized by flow cytometry. I-MVs were administered intravenously (4.8 mg/kg) at 5 min before reperfusion procedure in I/R injury model which was induced by 30-min of ischemia and 120-min of reperfusion of LAD in rats. RESULTS: Treatment with I-MVssignificantly reduced the size of myocardial infarction, the activities of serum CK-MB and LDH, and the number of apoptotic cardiomyocytes. The activities of caspase 3, caspase 9 and caspase 12 in myocardium were also decreased significantly with I-MVs treatment. Moreover, the expression of Bax was decreased but Bcl-2 was increased. The expression of glucose regulated protein 78 (GRP78), sarco/endoplasmic reticulum Ca2+-ATPase 2 (SERCA2) and phosphorylated phospholamban (p-PLB) were increased after being treated with I-MVs. CONCLUSION: I-MVs could protect hearts from I/R injury in rats through SERCA2 and p-PLB of calcium regulatory proteins to alleviate intrinsic myocardial apoptosis including mitochondrial and endoplasmic reticulum pathways.

[Effects of circulating microvesicles derived from myocardial ischemic preconditioning on myocardial ischemia/reperfusion injury in rats].

OBJECTIVE: To investigate the effects of circulating microvesicles (MVs) derived from ischemic preconditioning (IPC) on myocardial ischemia/reperfusion (I/R) injury in rats and explore the underlying mechanism. METHODS: To establish the IPC model, the rats were subjected to brief cycles of left anterior descending (LAD) coronary occlusion and reperfusion. The blood was drawn from abdominal aorta once the operation was finished. IPC-MVs were isolated by ultracentrifugation from the peripheral blood and characterized by flow cytometry. The myocardial I/R model of rats was established in vivo. Rats were injected via the femoral vein with IPC-MVs at 7 mg/kg. Morphological changes of myocardium were observed microscopically after HE staining. Apoptosis of myocardial cells was detected with TUNEL assay. Myocardial infarct size was detected by TTC staining. Moreover, activity of plasma lactate dehydrogenase (LDH) was tested by colorimetry. The activity of caspase 3 in myocardium was assayed with spectrophotometry. Expression levels of Bcl-2 and Bax protein were examined with Western blot. RESULTS: The concentration of IPC-MVs, which was detected by flow cytometry, was 4380±745 cells/µl. Compared with I/R group, IPC-MVs alleviated the damage of tissues in I/R injured rats significantly. The myocardial infarct size and the cardiomyocyte apoptotic index were obviously decreased after IPC-MVs treatment (P<0.01, respectively). The activity of plasma LDH was significantly decreased in IPC-MVs treated rats (P<0.01). Moreover, the activity of caspase 3 was markedly decreased after IPC-MVs treatment (P<0.01). In addition, the expression of Bcl-2 was increased (P<0.01), the expression of Bax was decreased (P<0.01), the ratio of Bcl-2/Bax was significantly increased after IPC-MVs treatment (P<0.01). CONCLUSIONS: IPC-MVs protected myocardial against I/R injury by up-regulating the expression of Bcl-2 protein, down-regulating the expression of Bax protein, increasing the ratio of Bcl-2/Bax and decreasing cleavage of caspase 3.

Flow cytometric analysis of circulating microvesicles derived from myocardial Ischemic preconditioning and cardioprotection of Ischemia/reperfusion Injury in rats.

OBJECTIVE: To establish a flow cytometric method to detect the alteration of phenotypes and concentration of circulating microvesicles (MVs) from myocardial ischemic preconditioning (IPC) treated rats (IPC-MVs), and to investigate the effects of IPC-MVs on ischemia/reperfusion (I/R) injury in rats. METHODS: Myocardial IPC was elicited by three.cycles of 5-min ischemia and 5-min reperfusion of the left anterior descending (LAD) coronary artery. Platelet-free plasma (PFP) was isolated through two steps of centrifugation at room temperature from the peripheral blood, and IPC-MVs were isolated by ultracentrifugation from PFR PFP was incubated with anti-CD61, anti-CD144, anti-CD45 and anti-Erythroid Cells, and added 1, 2 µm latex beads to calibrate and absolutely count by flow cytometry. For functional research, I/R injury was induced by 30-min ischemia and 120-min reperfusion of LAD. IPC-MVs 7 mg/kg were infused via the femoral vein in myocardial I/R injured rats. Mean arterial blood pressure (MAP), heart rate (HR) and ST-segment of electro-cardiogram (ECG) were monitored throughout the experiment. Changes of myocardial morphology were observed after hematoxylin-eosin (HE) staining. The activity of plasma lactate dehydrogenase (LDH) was tested by Microplate Reader. Myocardial infarct size was measured by TTC staining. RESULTS: Total IPC-MVs and different phenotypes, including platelet-derived MVs (PMVs), endothelial cell-derived MVs (EMVs), leucocyte-derived MVs (LMVs) and erythrocyte-derived MVs (RMVs) were all isolated which were identified membrane vesicles (<1 Vm) with corresponding antibody positive. The numbers of PMVs, EMVs and RMVs were significantly increased in circulation of IPC treated rats (P<0.05, respectively). In addition, at the end of 120-min reperfusion in I/R injured rats, IPC-MVs markedly increased HR (P<0.01), decreased ST-segment and LDH activity (P < 0.05, P < 0.01). The damage of myocardium was obviously alleviated and myocardial infarct size was significantly lowered after IPC-MVs treatment (P < 0.01). CONCLUSION: The method of flow cytometry was successfully established to detect the phenotypes and concentration alteration of IPC-MVs, including PMVs, EMVs, LMVs and RMVs. Furthermore, circulating IPC-MVs protected myocardium against I/R injury in rats.

Microvesicles derived from hypoxia/reoxygenation-treated human umbilical vein endothelial cells impair relaxation of rat thoracic aortic rings.

OBJECTIVE: To investigate the effects of microvesicles (MVs) derived from hypoxia/reoxygenation (H/R)-treated human umbilical vein endothelial cells (HUVECs) on endothelium-dependent relaxation of rat thoracic aortic rings. METHODS: H/R injury model was established to induce HUVECs to release H/R-EMVs. H/R-EMVs from HUVECs were isolated by ultracentrifugation from the conditioned culture medium. H/R-EMVs were characterized using 1 µm latex beads and anti-PE-CD144 by flow cytometry. Thoracic aortic rings of rats were incubated with 2.5, 5, 10, 20 µg/ml H/R-EMVs derived from H/R-treated HUVECs for 4 hours, and their endothelium-dependent relaxation in response to acetylcholine (ACh) or endothelium-independent relaxation in response to sodium nitroprusside (SNP) was recorded in vitro. The nitric oxide (NO) production of ACh-treated thoracic aortic rings of rats was measured using Griess reagent. The expression of endothelial NO synthase (eNOS) and phosphorylated eNOS (p-eNOS, Ser-1177) in the thoracic aortic rings of rats was detected by Western blotting. Furthermore, the levels of SOD and MDA in H/R-EMVs-treated thoracic aortic rings of rats were measured using SOD and MDA kit. RESULTS: H/R-EMVs were induced by H/R-treated HUVECs and isolated by ultracentrifugation. The membrane vesicles (< 1 µm) induced by H/R were CD144 positive. ACh-induced relaxation and NO production of rat thoracic aortic rings were impaired by H/R-EMVs treatment in a concentration-dependent manner (P < 0.05, P < 0.01). The expression of total eNOS (t-eNOS) was not affected by H/R-EMVs. However, the expression of p-eNOS decreased after treated with H/R-EMVs. The activity of SOD decreased and the level of MDA increased in H/R-EMVs treated rat thoracic aortic rings (P < 0.01). CONCLUSION: ACh induced endothelium-dependent relaxation of thoracic aortic rings of rats was impaired by H/R-EMVs in a concentration-dependent manner. The mechanisms included a decrease in NO production, p-eNOS expression and an increase in oxidative stress.

Effects of endothelial microvesicles induced by A23187 on H9c2 cardiomyocytes.

OBJECTIVE: To investigate the effects of endothelial microvesicles (EMVs) induced by calcium ionophore A23187 on H9c2 cardiomyocytes. METHODS: Human umbilical vein endothelial cells (HUVECs) were treated with 10 micromol/L A23187 for 30 min. EMVs from HUVECs were isolated by ultracentrifugation from the conditioned culture medium. EMVs were characterized using 1 and 2 microm latex beads and anti-PE-CD144 antibody by flow cytometry. For functional research, EMVs at different concentrations were cocultured with H9c2 cardiomyocytes for 6 h. Cell viability of H9c2 cells and the activity of LDH leaked from H9c2 cells were tested by colorimetry. Moreover, apoptosis of H9c2 cells was observed through Hoechst 33258 staining and tested by FITC-Annexin V/PI double staining. RESULTS: EMVs were induced by A23187 on HUVECs, and isolated by ultracentrifugation. We identified the membrane vesicles (< 1 microm) induced by A23187 were CD144 positive. In addition, the EMVs could significantly reduce the viability of H9c2 cells, and increase LDH leakage from H9c2 cells in a dose dependent manner (P < 0.05). Condensed nuclei could be observed with the increasing concentrations of EMVs through Hoechst 33258 staining. Furthermore, increased apoptosis rates of H9c2 cells could be assessed through FITC-Annexin V/PI double staining by flow cytometry. CONCLUSION: Microvesicles could be released from HUVECs after induced by A23187 through calcium influx, and these EMVs exerted a pro-apoptotic effect on H9c2 cells by induction of apoptosis.

Extracellular signal-regulated kinase 1/2 activation is involved in intermedin1-53 attenuating myocardial oxidative stress injury induced by ischemia/reperfusion.

Intermedin (IMD)(1-53) is a novel member of the calcitonin gene-related peptide superfamily and has potent cardioprotective effects against myocardial injury induced by ischemia-reperfusion (I/R). To explore the mechanism of the IMD(1-53) cardioprotective effect, we studied the anti-oxidant effects of IMD(1-53) on myocardial injury induced by I/R in vivo in rat and H(2)O(2) treatment in vitro in rat cardiomyocytes. Compared with sham treatment, I/R treatment induced severe lipid peroxidation injury in rat myocardium: plasma malondialdehyde (MDA) content and myocardial LDH activity was increased by 34% and 85% (all P<0.01); Mn-superoxide dismutase (Mn-SOD) and catalase (CAT) activity was reduced 80% and 86% (all P<0.01), respectively, and the protein levels of the NADPH oxidase complex subunits gp91(phox) and p47(phox) were markedly increased, by 86% (P<0.05) and 95% (P<0.01), respectively; IMD(1-53) treatment ameliorated lipid peroxidation injury: plasma MDA content and myocardial LDH activity was decreased by 30% (P<0.05) and 36% (P<0.01); Mn-SOD and CAT activity was elevated 1.0- and 4.3-fold (all P<0.01), respectively; and the protein levels of gp91(phox) and p47(phox) were reduced, by 28% and 36% (both P<0.05), respectively. Concurrently, IMD(1-53) treatment markedly promoted cell viability and inhibited apoptosis in cardiomyocytes as compared with H(2)O(2) treatment alone. Furthermore, IMD(1-53) increased the ratio of p-ERK to ERK by 66% (P<0.05) as compared with I/R alone, and the protective effect of IMD(1-53) on H(2)O(2)-induced apoptosis was abolished by preincubation with PD98059, a MEK inhibitor. IMD(1-53) may improve the oxidative stress injury induced by I/R via inhibiting the production of reactive oxygen species and enhancing ERK phosphorylation.

Insulin resistance induces medial artery calcification in fructose-fed rats.

Osteogenic differentiation of vascular smooth muscle cells (VSMCs) results in medial artery calcification, which is common in diabetes, but the pathogenesis is poorly understood. We aimed to explore the pathophysiological roles of insulin resistance (IR) on medial artery calcification in rats with 10% fructose in drinking water. After 12 weeks of fructose feeding, rats showed severe IR, with increased levels of fasting blood glucose, serum insulin and oral glucose tolerance test (OGTT). Fructose-fed rats showed aortic calcification, increased aortic calcium deposition and irregular elastic fibers in the medial layer of the vessel wall. Moreover, plasma phosphorus concentration, calcium × phosphorus product and alkaline phosphatase (ALP) activity, and aortic calcium content and ALP activity were significantly increased. Fructose feeding increased mRNA levels of osteopontin, type III sodium-dependent phosphate co-transporter, bone morphogenetic protein-2 and the key transcription factor core binding factor alpha 1 in aortic tissue and downregulated mRNA levels of osteoprotegerin and matrix γ-carboxyglutamic acid protein. Fructose feeding decreased protein levels of smooth-muscle lineage markers and induced severe lipid peroxidation injury. IR induced by high fructose feeding could evoke osteogenic transdifferentiation of VSMCs and promote vascular calcification.

[Effect of ERK1/2 signaling pathway on astragaloside IV protects H9c2 cells against H2O2-induced oxidative injury].

OBJECTIVE: To investigate whether Astragaloside IV(AST) protects H9c2 cells against H2O2-induced oxidative injury partly through ERK1/2 signaling pathway. METHODS: H9c2 cells oxidative injury was induced by 200 tmol/L H2O2 for 6 hours to establish the H2O2-induced injury model of H9c2 cells. The viability of H9c2 cells was detected using MTf method. Activity of lactate dehydrogenase(LDH), total-superoxide dismutase (T-SOD), manganese-superoxide dismutase (Mn-SOD) and content of MDA (malondialdehyde) in the culture medium were detected using colorimetric method. Western blot was performed to exam expression of p-ERK1/2 and ERK1/2 in H9c2 cells respectively. RESULTS: Under 200 micromol/L H2O2 treatment for 6 hours, the vaibility of H9c2 cells was suitable for the following study. Compared with H2O2 group, the cell viability was increased significantly in AST10 + H2O2 and AST2O + H2O2 groups (P < 0.01). The activity of LDH in the culture medium was decreased significantly (P < 0.01). The activity of T-SOD and Mn-SOD was increased significantly (P < 0.01), the content of MDA was decreased significantly (P < 0.01). Treated with 10 mg/L or 20 mg/L of AST, expression of p-ERK1/2 in H9c2 cells injured from H2O2 was increased significantly (P < 0.01), when PD98059 (inhibitor of ERK1/2) was added, the effects of AST were cancelled. CONCLUSION: AST protects H9c2 cells against H2O2-induced oxidative injury partly through ERK1/2 signaling pathway.

[Effect of age on vascular calcification induced by vitamin D3 and nicotine].

OBJECTIVE: To explore the effect of age on vascular calcification induced by vitamin D3 and nicotine. METHODS: Vascular calcification in rats was induced by administration of vitamin D3 plus nicotine (VDN treatment). After six weeks, Von Kossa staining, calcium content, alkaline phosphatase activity, phosphorus and calcium content in plasma were assayed. Carotid blood pressure, cardiac function and the relative amounts of osteopontin (OPN), osteoprotegerin (OPG), matrix Gla protein (MGP), bone morphogenetic protein-2 (BMP2) mRNA level and smooth muscle actin-alpha (alpha-SMA)protein level were measured. RESULTS: Compared with control group, the systolic blood pressure(SBP)of the rats of 2,8 and 16 months with vascular calcification respectively increased by 20.7%, 29.4% and 22.2% (P<0.05); the left ventricular systolic pressure (LVSP) respectively increased by 13.6%, 21.1% and 16.2% (P<0.05); + LVdP/dtmax respectively increased by 49.1% (P<0.01), 21.4% and 13.1% (P<0.05); -LVdP/dtmax respectively increased by 56.3% (P<0.01), 24.4% and 11.3% (P<0.05). Aortic calcium contents of the 2-, 8- and 16-month calcified rats were respectively 2.62-fold (P<0.05), 24.87-fold (P<0.01) and 10.01-fold (P<0.05) of the age-matched control group. As compared with the aortic calcium contents of calcified groups at different ages, the calcification group of 8 months had higher aortic calcium content than those of 2 and 16 months, which were respectively, 5.28-fold and 2.63-fold (P<0.05). Compared with the control groups, alkaline phosphatases activity (ALP) of calcification groups increased respectively by 126.6%, 115.2% and 227.9% (P<0.01) in the 2-, 8- and 16-month rats. As compared with the ALP activity of calcified groups at different ages, ALP activity of aortic calcification group of the 8-month-old rats was higher than that of the 2-month-old and 16-month-old rats, which increased by 176% and 75% respectively (all P<0.01). Von kossa staining for calcification showed positive staining as black/brown areas within the main, large, nodular structures as shown in extracellular matrix and cytoplasma in VDN groups at different ages, especially in the 8-month-old VDN group, with the most dispersed calcific nodules deposited and a few of the elastic fibers of the medial layer collapse. The mRNA expressions of OPN, OPG, MGP, BMP2 were up-regulated (P<0.01 or P<0.05) and protein levels of alpha-SMA were down-regulated in different calcification groups(P<0.05). The mRNA levels of OPN in 8-month-old calcification group increased by 3.41-fold (P<0.01) and 1.34-fold (P<0.05) respectively compared with the 2-month-old and 16-month-old calcification groups. And the alpha-SMA protein expression levels were lower at calcification groups in different ages, which were respectively equivalent to 17.6% of the 2-month-old control group (P<0.01), 11% of the 8-month-old control group (P<0.05) and 41.7% of 16-month-old control group (P<0.01). CONCLUSION: SD rats of 2, 8 and 16 months can all be used to duplicate vascular calcification model induced by vitamin D3 plus nicotine and the 8-month-old rat has the most sensitivity to the calcification treatment, which means that the 8-month-old rat may be the most appropriate age for the study of vascular calcification.

Cortistatin attenuates vascular calcification in rats.

Cortistatin (CST) is a newly discovered polypeptide with multiple biological activities that plays a regulatory role in the nervous, endocrine and immune systems. However, the role of CST in the pathogenesis of cardiovascular diseases remains unclear. In this study, we investigated in rats whether CST inhibits vascular calcification induced by vitamin D3 and nicotine treatment in vivo and calcification of cultured rat vascular smooth muscular cells (VSMCs) induced by beta-glycerophosphate in vitro and the underlying mechanism. We measured rat hemodynamic variables, alkaline phosphatase (ALP) activity, calcium deposition and pathological changes in aortic tissues and cultured VSMCs. CST treatment significantly improved hemodynamic values and arterial compliance in rats with vascular calcification, by decreasing systolic blood pressure, pulse pressure, left ventricular end-systolic pressure and left ventricular end-diastolic pressure. CST also significantly decreased ALP activity and calcium deposition, alleviated pathological injury and down-regulated the mRNA expression of type III sodium-dependent phosphate co-transporter-1 (Pit-1) in aortic tissues. It dose-independently inhibited the calcification of VSMCs by decreasing ALP activity and calcium deposition, alleviating pathologic injury and down-regulating Pit-1 mRNA expression. As with CST treatment, ALP activation and calcium deposition were decreased significantly on treatment with ghrelin, the endogenous agonist of growth hormone secretagogue receptor 1a (GHSR1a), but not significantly with somatostatin-14 or proadrenomedullin N-terminal 20 peptide in VSMCs. Further, growth hormone-releasing peptide-6[D-lys], the endogenous antagonist of GHSR1a, markedly reversed the increased ALP activity and calcium deposition in VSMCs. CST could be a new target molecule for the prevention and therapy of vascular calcification, whose effects are mediated by GHSR1a rather than SSTRs or Mrg X2.

Activation of Akt/GSK-3beta signaling pathway is involved in intermedin(1-53) protection against myocardial apoptosis induced by ischemia/reperfusion.

Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide family. We investigated the cardioprotective mechanism of IMD(1-53) in the in vivo rat model of myocardial ischemia/reperfusion (I/R) injury and in vitro primary neonatal cardiomyocyte model of hypoxia/reoxygenation (H/R). Myocardial infarct size was measured by 2,3,5-triphenyl tetrazolium chloride staining. Cardiomyocyte viability was determined by trypan blue staining, cell injury by lactate dehydrogenase (LDH) leakage, and cardiomyocyte apoptosis by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling assay, Hoechst staining, gel electrophoresis and caspase 3 activity. The translocation of mitochondrial cytochrome c of myocardia and expression of apoptosis-related factors Bcl-2 and Bax, phosphorylated Akt and phosphorylated GSK-3beta were determined by western blot analysis. IMD(1-53) (20 nmol/kg) limited the myocardial infarct size in rats with I/R; the infarct size was decreased by 54%, the apoptotic index by 30%, and caspase 3 activity by 32%; and the translocation of cytochrome c from mitochondria to cytosol was attenuated. IMD(1-53) increased the mRNA and protein expression of Bcl-2 and ratio of Bcl-2 to Bax by 81 and 261%, respectively. IMD(1-53) (1 x 10(-7) mol/L) inhibited the H/R effect in cardiomyocytes by reducing cell death by 43% and LDH leakage by 16%; diminishing cellular apoptosis; decreasing caspase 3 activity by 50%; and increasing the phosphorylated Akt and GSK-3beta by 41 and 90%, respectively. The cytoprotection of IMD(1-53) was abolished with LY294002, a PI3K inhibitor. In conclusion, IMD(1-53) exerts cardioprotective effect against myocardial I/R injury through the activation of the Akt/GSK-3beta signaling pathway to inhibit mitochondria-mediated myocardial apoptosis.

Activation of Akt/GSK-3beta signaling pathway is involved in intermedin(1-53) protection against myocardial apoptosis induced by ischemia/reperfusion.

Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide family. We investigated the cardioprotective mechanism of IMD(1-53) in the in vivo rat model of myocardial ischemia/reperfusion (I/R) injury and in vitro primary neonatal cardiomyocyte model of hypoxia/reoxygenation (H/R). Myocardial infarct size was measured by 2,3,5-triphenyl tetrazolium chloride staining. Cardiomyocyte viability was determined by trypan blue staining, cell injury by lactate dehydrogenase (LDH) leakage, and cardiomyocyte apoptosis by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling assay, Hoechst staining, gel electrophoresis and caspase 3 activity. The translocation of mitochondrial cytochrome c of myocardia and expression of apoptosis-related factors Bcl-2 and Bax, phosphorylated Akt and phosphorylated GSK-3beta were determined by western blot analysis. IMD(1-53) (20 nmol/kg) limited the myocardial infarct size in rats with I/R; the infarct size was decreased by 54%, the apoptotic index by 30%, and caspase 3 activity by 32%; and the translocation of cytochrome c from mitochondria to cytosol was attenuated. IMD(1-53) increased the mRNA and protein expression of Bcl-2 and ratio of Bcl-2 to Bax by 81 and 261%, respectively. IMD(1-53) (1 x 10(-7) mol/L) inhibited the H/R effect in cardiomyocytes by reducing cell death by 43% and LDH leakage by 16%; diminishing cellular apoptosis; decreasing caspase 3 activity by 50%; and increasing the phosphorylated Akt and GSK-3beta by 41 and 90%, respectively. The cytoprotection of IMD(1-53) was abolished with LY294002, a PI3K inhibitor. In conclusion, IMD(1-53) exerts cardioprotective effect against myocardial I/R injury through the activation of the Akt/GSK-3beta signaling pathway to inhibit mitochondria-mediated myocardial apoptosis.

Inhibition of endoplasm reticulum stress by ghrelin protects against ischemia/reperfusion injury in rat heart.

Ghrelin is a multi-functional polypeptide with cardiovascular protective effects. We aimed to explore whether the cardioprotective effect of ghrelin is mediated by inhibiting myocardial endoplasmic reticulum stress (ERS). A Langendorff model of isolated rat heart was used with ischemia/reperfusion (I/R; 40/120 min). Cardiac function was monitored, and histomorphologic features, degree of myocardial injury, level of ERS markers, and number of apoptotic cardiomyocytes were determined. Compared with control group, the I/R group showed significantly decreased cardiac function, seriously damaged myocardial tissue, increased number of apoptotic cells, and overexpression of mRNA and protein of ERS markers. However, preadministration of ghrelin in vivo (10(-8)mol/kg, intraperitoneal injection, every 12h, twice in all) greatly ameliorated the damaged heart function, attenuated myocardial injury and apoptosis, and decreased the expression of ERS markers: it decreased the mRNA and protein levels of glucose-regulated protein78 (GRP78) and C/EBP homologous protein (CHOP), with reduced caspase-12 protein expression. Furthermore, in vitro, ghrelin directly inhibited the myocardial ERS response induced by tunicamycin or dithiothreitol in rat cardiac tissue. Ghrelin could protect the heart against I/R injury, at least in part, through inhibiting myocardial ERS.

[Cardioprotection of ramipril and BQ-123 against myocardial ischemia/reperfusion injury in vivo in rats].

AIM: To study the protective effects of ramipril in combination with BQ-123 on myocardial ischemia/reperfusion (I/R) injury in vivo in anesthetized rats. METHODS: Healthy male Wistar rats were divided into 5 groups randomly and subjected to 30 min of myocardial ischemia followed by 120 min reperfusion. Ramipril, BQ-123 and their combination were given to rats respectively. To observe the protection of their combination against myocardial I/R injury. HR, MAP and the change of ST-segment were observed. Ventricular arrthymias were monitored. The activity of creatine kinase (CK) and lactate dehydrogenase (LDH) in plasma, the infarct size and morphologic change were examined. RESULTS: Compared with I/R group, the elevation of ST-segment was decreased. Onsets of VPC and VT were delayed, durations of VPC and VT were shortened, especially their combination. Incidences of VPC, VT and VF were decreased. Activity of plasma CK and LDH was decreased, especially their combination. IS, IS/AAR and the morphology of myocardium were improved, especially their combination. CONCLUSION: Ramipril, BQ-123 and combined using these two agents protected myocardium from I/R injury in vivo. The protective effects on delaying onset of VA, shortening duration of VA, decreasing the activities of CK and LDH, decreasing infrarct size and improving morphology of myocardium were better than using ramipril and BQ-123 alone.