The Impact Of Advanced GlyCation End Products On The Platelet Activity Of Acute Coronary Syndrome And Its Mechanism

Atherogenesis is critical in the pathogenesis of coronary artery disease. The instability of atherosclerotic plaque and the acute formation of thrombosis are the key links in acute coronary artery syndrome. Diabetes is an independent risk factor of coronary artery disease. It was suggested in our study that the blood glucose level of acute coronary syndrome with diabetes was significantly higher than that of stable angina with diabetes. The abnormalities of blood glucose parameters were found to be most closely associated with cardiac enzyme abnormalities among various risk factors of coronary artery disease such as age, blood pressure and blood lipid level. These results indicated that patients of coronary artery disease with diabetes had significantly higher chances to undergo acute coronary syndrome than those without diabetes. High blood glucose was found to be more closely associated with unstable angina or non-ST elevation myocardial infarction than stable angina and ST elevation myocardial infarction. Furthermore, the blood glucose levels of patients with thrombosis were significantly higher than those without thrombosis under coronary angiography. Hence, it was suggested that hyperglycemia could enhance the platelet activity and promote acute thrombogenesis. Advanced glycation end products (AGEs) play a critical role in the vascular complications of diabetes. AGEs mediate the downstream signaling pathways via their specific receptors RAGE (receptors for advanced glycation end products). It was demonstrated by Western blot in our study that RAGE were expressed on the membrane of platelets. AGEs could does-dependently enhance the platelet activity. The expression of RAGE on platelets increased and then decreased as the AGEs concentration increased, however, without statistic significance, which further indicated that AGEs could enhance the platelet activity. AGEs could does-dependently induce the expression and phosphorylation of PKCa as revealed by Western blot in our study. Furthermore, AGEs could does-dependently promote the expression and phosphorylation of JNK and the cleavage of Caspase3, indicating that AGEs might mediate the activation of platelets via JNK-Caspase3apoptotic signaling pathway. We also found that PKCa inhibitor could significantly reverse the activation of platelets induced by AGEs, however, had no effect on the RAGE expression on platelets. Meanwhile, PKCa inhibitor could suppress the phosphorylation of JNK as well as the cleavage of Caspase3induced by AGEs. Therefore, it was suggested that PKCa, the signaling element downstream to AGEs-RAGE, might mediate the platelet activity via the phosphorylation of its downstream JNK and the cleavage of Caspase3. To sum up, AGEs might mediate the platelet activity via the RAGE-PKCa-JNK-Caspase3signaling pathway, which provided an explanation from the perspective of molecular mechanism for the acute thrombogenesis in acute coronary syndrome promoted by diabetes.Part1Diabetes Promoted the Advancement of Acute Coronary SyndromeObjective:To elucidate the role of diabetes in the advancement of acute coronary syndrome.Methods:142patients with stable angina, unstable angina, non-ST elevation myocardial infarction and ST elevation myocardial infarction were selected and then-clinical data were collected and analyzed. The causal relationship between acute coronary syndrome and diabetes was investigated by retrospective analysis. The relationships between blood glucose parameters including fasting blood glucose,2hour postprandial blood glucose, random blood glucose, glycosylated hemoglobin and coronary artery disease of different types were investigated by ANOVA analysis. The relationships between blood glucose parameters and cardiac enzymes or cardiac function parameters were investigated by correlation analysis. The impact of blood glucose level on acute coronary syndrome among various risk factors of coronary artery disease was investigated by regression analysi. The causal relationship between acute coronary syndrome and fasting blood glucose level under anti-hyperglycemic treatment was investigated by retrospective analysis according to the ORIGIN fasting blood glucose target range (4-5.3mmol/L).Results:The ratios of non-diabetic to diabetic patients were not significantly different among stable angina, unstable angina, non-ST elevation myocardial infarction and ST elevation myocardial infarction (P>0.05) as revealed by chi-square test. The fasting blood glucose level of non-ST elevation myocardial infarction was significantly higher than those of stable angina and unstable angina (P<0.05), however, was not significantly different from that of ST elevation myocardial infarction (P>0.05), as indicated by ANOVA analysis. Statistic analysis revealed significant difference in fasting blood glucose levels (P<0.05) but no significant difference in the ratios of non-diabetic to diabetic patients (P>0.05) between patients with and without thrombosis under coronary angiography. The Kendall and Spearman correlation analysis revealed statistic correlation between fasting blood glucose and CK-MB, cTnT, LDH, BNP (P<0.01), CK, LA (P<0.05). Regression analysis revealed that blood glucose, especially fasting blood glucose, had more significant effect on cardiac enzyme changes than other risk factors of coronary artery disease. The retrospective analysis according to the ORIGIN fasting blood glucose target range (4-5.3mmol/L) revealed that the fasting blood glucose level of acute coronary artery syndrome was significantly higher than that of stable coronary artery disease under anti-hyperglycemic treatment (P<0.05).Conclusion:Hyperglycemia promoted the advancement of acute coronary syndrome and acute thrombogenesis. Part2Advanced glycation end products enhanced the platelet activity of acute coronary syndrome with diabetes and its mechanismObjective:To investigate the effect of AGEs on platelet activity and its signaling transduction.Methods:Fasting venous whole blood was drawn from acute coronary syndrome patients with diabetes and platelet rich plasma (PRP) was prepared. PRP was divided into groups as followed:control group, low-concentration AGEs group (20ug/ml), moderate-concentration AGEs group (100ug/ml) and high-concentration AGEs group (500ug/ml). Platelet aggregation rate was measured by platelet aggregation test. The expression of RAGE, the expressions and phosphorylations of PKCα, PKCβ1, PKCβ2and JNK, and the cleavage of Caspase3were detected by Western blot. Then, platelets were treated with PKCa inhibitor Ro-32-0432alone or with Ro-32-0432and AGEs, which was followed by platelet aggregation rate measurement and Western blot detection of RAGE expression, PKCa and JNK expressions and phosphorylations, and Caspase3cleavage. Finally, platelets were treated with PKC02inhibitor CGP53353alone or with CGP53353and AGEs, which was followed by platelet aggregation rate measurement and Western blot detection of RAGE expression, PKCβ2and JNK expressions and phosphorylations, and Caspase3cleavage.Results:AGEs could does-dependently enhance the platelet activity. RAGE expression on platelets increased and then decreased as AGEs concentration increased (P>0.05). AGEs could does-dependently promote the expression and phosphorylation of PKCa (P<0.05), however, had no significant effect on PKCβ1and PKCβ2(P>0.05). AGEs could does-dependently promote the expression and phosphorylation of JNK and the cleavage of Caspase3(P<0.05). PKCa inhibitor Ro-32-0432could significantly reverse the activation of platelets by AGEs, however, had no significant effect on RAGE expression (P>0.05). Ro-32-0432could significantly suppress the phosphorylation of JNK and the cleavage of Caspase3induced by AGEs (P<0.05). PKCβ2inhibitor CGP53353had no significant effect on the platelet activity, RAGE expression, JNK activation and Caspase3cleavage (P>0.05).Conclusion:AGEs might mediate the platelet activity via the RAGE-PKCa-JNK-Caspase3signaling pathway. Conclusion1. Hyperglycemia promoted the advancement of acute coronary syndrome and acute thrombogenesis.2. AGEs might mediate the platelet activity via the RAGE-PKCa-JNK-Caspase3signaling pathway.The Potential Application and Novelty1. It was suggested in our study that enhancement of platelet activity might be one of the mechanisms involved in the advancement of acute coronary syndrome in diabetes. Platelets, as an important source of inflammatory cells, might play an important role in the instability of atherosclerotic plaque and acute thrombogenesis. 2. It was proposed for the first time in our study that high blood glucose of diabetic patients might enhance the platelet activity via the activation of RAGE-PKCa-JNK-Caspase3signaling pathway by AGEs.3. The present study revealed a brand-new signaling pathway involved in the platelet activation, which was different from the typical molecular mechanisms such as ADP receptor associated signaling transduction. It provided new molecular targets for the anti-platelet therapy for acute coronary syndrome with diabetes.