| The incidence, mutilation rate and lethality rate of cardiovascular diseases turn on the increasing trends all over the world in recent years. Ischemic heart disease (IHD) is one of the most common cardiovascular diseases in clinical practice. IHD is caused by coronary blood circulation changes resulting in the imbalance of myocardial supply and demand. Acute myocardial ischemia or acute myocardial infarction happened when coronary artery was occluded suddenly and for a long time. Drug therapy is one of important ways to cure myocardial ischemia. Although nitrate, calcium-channel blocker andβ-receptor antagonist are effective in the therapy of myocardial ischemia, they all have some adverse reactions. Studies on the new agents used to treat myocardium ischemia are still a pivotal issue.Tribulus terrestris is also called Bai Jili and Ci Jili. It refers to the dry, ripe fruit of the plant caltrop. Its main chemical ingredients are saponins, ketone, alkaloid. The gross saponins of Tribulus terrestris(GSTT) was one of the effective group ingredients which was exracted from the whole plant of caltrop. It is a mixture of over 10 kinds of saponins, mainly steroid saponins. It mainly includes furan-strol and spiral -strol. It is a powder and dissolvable in water. Domestic research materials showed that GSTT had: the effect of lowering blood pressure and stimulating anti-hypoxia,sheeting blood vessels,lowering cholesterol, inhibiting fat deposition on arteries, myocardium and liver. It also inhibited atherosclerotic occurrence and development, protecting the isolated heart from the ishemai/reperfusion(I/R)injury. It had positive effects on brain ishemia, lowered blood sugar, improved micro-circulation, showed anti-aging properties and imporved sex function. It was well studied abroad too. The materials showed that it was mainly about improving sexual function but no records about research on cardio-vascular system .To investigate the mechanism of protection of reperfused ischemic heart by Gross Saponin Tribulus Terrestris (GSTT). The hearts of rats were isolated, linked to Langendorff perfusion apparatus, and randomly divided into 5 equal groups.The heart rate,mean aortic pressure and CK-MB were measured 20 min after the stabilization of perfusion, and 60 and 120 min after reperfusion. After the stop of reperfusion, hearts were sliced into 1-mm-thick transverse sections and incubated in triphenyltetrazolium chloride solution (TTC) to determine infarct size. The phosphorylation level and translocation of PKCεand ERK1/2 from the heart was determined by western blot analysis. From the results we can see GSTT significantly reduced infarct size and can reinforce PKCεtranslocate from cytoplasm to cellular membrane . In addition, GSTT can reinforce the abundance of phosph-PKCεand ERK1/2.and Chelerythrine can partly abolish these effects.The primary cultured cardiac myocytes in neonatal rats damaged by 0.3mmol/L hydrogen peroside (H2O2) simulated the oxidative stress model. The survival ability was detected by Methyl thiazolyl tetrazolium (MTT) method. The apoptosis cells morphous were observed by hoechst33258 through fluorescence microscope, and intracellular calcium change by Fluo-3/AM staining before and after H2O2 damage was observed by laser-confocal-microscopy system. Cell apoptosis rate was detected by flowcytomety. The phosphorylation level and translocation of PKCεand ERK1/2 from the cell was determined by western blot analysis and laser confocal microscopy system. Meanwhile, the protein and mRNA expression of Bcl-2, Bax were analyzed by Western-blotting and RT-PCR. The results in vitro experiments showed that GSTT could increase the survival rate of cardiac myocytes, reduce apoptosis percentage, reduce the intracellular calcium overload, increace the content of Bcl-2 mRNA, increase the protein expression of Bcl-2 and decrease the protein expression of Bax. GSTT can up-regulated p-PKCεand p-ERK1/2 expressions. And GSTT can reinforce ERK1/2 translocate from cytoplasm to cellular nucleus.Considerable data demonstrated that PKCεmight be important for cardiac protection. The isozyme selective peptide inhibitors and activators were used to test for the abilities of different PKCs to protect cardiocytes from ischemic damage in a variety of models, including isolated neonatal and adult cardiocytes and intact hearts. It found that ischemic preconditioning activates PKCε, as well as treatments that mimic preconditioning such as arachidonic acid, exposure to low amounts of ethanol, or by directly applying the PKCεagonist peptide. Moreover, selective inhibition of PKCεduring preconditioning results in loss of cardiac protection, indicating that PKCεactivation is required and sufficient to mediate cardiac protection from ischemic damage. Our study shows that the GSTT stimulation doesn't lead to significant difference of reduction in the abundance of PKCεand phosph-PKCεin the cytosolic fraction; but PKCεand phosph-PKCεabundance in the particulate fraction is increased than that is exposed to H2O2 only. This result indicates a potential role of PKCεand phosph-PKCεfor GSTT stimulation effects in cardiocytes. It shows that GSTT may be PKCεactivators or mimicing preconditioning. PKCεactivation was found to induce the phosphorylation of BAD indirectly, which is a pro-apoptotic Bcl-2-related protein. So it renders BAD unable to participate in apoptosis. This may help explain how PKCεis cardiacprotective during preconditioning. PKCεmay also regulate the expression of anti-apoptotic Bcl-2.The subcellular localization and t ranslocation of signaling proteins have raisen large interest in the studyof cellular signal transduction. MAP kinase pathways are key signaling systems in eukaryotic cells. ERK1/2 have relatively specific localization in cells, and translocate into nucleus upon appropriate stimuli, leading to consequent physiological effects. It has been shown that the phosphorylation state of MAPKs as well as the interactions between MAP kinases and other proteins such as the up stream kinases, phosphatases, and down stream substrates may play a role in their specific localization and translocation. The elucidation of the mechanisms of localization and translocation of ERK1/2 will be helpful to understand their in vivo functions. In conclusion, GSTT protected from the ishemai/reperfusion(I/R)injury in rats and oxidative stress in the primary cultured cardiac myocytes in neonatal rats damaged by H2O2. Based on the above experiments in vivo and in vitro, it has been proven GSTT protected the cardiac myocyte from hypoxia damage probably owing to activating PKCε-ERK1/2 pathway. Reducing free radical damnification, decreasing intracellular calcium overload, protecting the mitochondrion and inhibiting cardiomyocyte apoptosis. |
PDF Full Text Request