The Potential Role And Mechanism Of Poly(ADP-Ribose) Polymerase 1 In Diabetic Cardiomyopathy

IntroductionDiabetes is a chronic, progressive metabolic disorder characterized by insulin deficiency and/or resistance, resulting in elevated plasma glucose levels, and it is firmly established as a major threat to human health in the 21 st century due to its alarming rise in incidence over the past two decades, which has attracted considerable attention.Diabetic cardiomyopathy(DCM) is diagnosed when ventricular dysfunction develops in patients with diabetes who do not exhibit coronary atherosclerosis and hypertension. It is also a major threat to human health, but also is an urgent clinical problem to solve.According to the results of our team previous research before, High glucose(HG) can induce apoptosis in rat cardiomyocytes. We use glucose in rat cardiomyocytes to build high glucose on cell model.Whether high glucose stimulation of cellular oxidative stress and DNA damage, and affect the expression of PARP-1 activity. What roles do PARP-1 play in inflammatory response and cardiomyocytes apoptosis.PARP-1 play a significant role in oxidative stress and DNA damage.In this study, PARP-1 intervene in order to clarify potential mechanism of action the PARP-1 in diabetic cardiomyopathy and provide a feasible strategy for the treatment of diabetic cardiomyopathy.ObjectiveConstruction diabetic mouse model of diabetic cardiomyopathy, study the PARP-1 potential mechanism in diabetic cardiomyopathy, at the same time high glucose on cell model was constructed for to futher clarify the regulatory mechanisms of PARP-1 in myocardial apoptosis.MethodsTo induce diabetes, 20 males C57BL/6(WT) mice or 20 PARP-1-/- mice(10 weeks old, Jackson Laboratories, ME, USA) were treated with STZ(sigma, 50mg/kg in citrate buffer, pH 4.5) by intraperitoneal injection for 5 consecutive days, while the control animals(male C57BL/6 mice) received the same volume of citrate buffer. Mouse tail vein blood glucose levels were monitored by analysis with theRoche Accu-Chek Active blood glucose monitor. The mice with random blood glucose concentration >16.7mmol/l were considered diabetic. Mice were housed in a pathogen-free animal care facility and allowed free access to food and water. PARP-1-/-mice were genotyped by PCR. Cardiac diameter and function were measured by use of the Vevo 770 imaging system(VisualSonics, Toronto, Canada). Left ventricular(LV)ejection fraction(LVEF), fractional shortening(FS), ratio of early to late mitral inflow velocity(E/A), and left ventricular end-diastolic dimension(LVEDd) were measured. All measurements were performed by the same observer and were the average of five consecutive cardiac cycles. Heart rate, systolic blood pressure,and diastolic blood pressure were measured with a noninvasive tail-cuff system(Softron BP-98A; Softron,Tokyo, Japan) as described previously. Meanwhile, harvesting cardiac musle specimens for Western Bolt and RT-PCR experiments, detect the gene and protein expression. Using HE-staining and immunohistochemical methods observed morphological changes of cardiac musle. Cell culture and stimulate with high glucose and use PARP-1 to interfere in cardiomyocytes using Western Blot and Real time-PCR to detect expression of inflammatory factors and apoptosis factors, and to charify the potential mechanism of PARP-1 in diabetic cardiomyopathy.Results(1)HG increased PARP-1 expression and activity by induction of DNA damage.(2)PARP-1 inhibition alleviated HG-increased inflammatory response in vitro.(3)PARP-1 inhibition suppressed HG-induced cell apoptosis.(4)PARP-1 inhibition increased IGF-1R/Akt phosphorylation in vitro.(5)PARP-1 deletion restore cardiac function in DM and alleviated hyperglycemia induced heart remodeling.(6)Hyperglycemia increased nitrotyrosine as well as PARP-1 expression and activity.Conclusions1.In vitro, high glucose(HG) stimulation increased oxidative stress and induced DNA damage to upregulate PARP-1 expression and activity.PARP-1 siRNA significantly reduced HG-induced inflammatory response, including TNF-?, IL-1? and IL-6 secretion, and ICAM-1 and iNOS expression. Meanwhile,PARP-1 inhibition reduced HG-induced cardiomyocytes apoptosis through downregulation of cleavaged caspase and activation of IGF-1R/Akt pathway.2.In vivo, hyperglycemia increased the protein expression of nitrotyrosine and PARP-1 as well as PARP-1 activity. PARP-1 gene deletion significantly decreased the inflammatory response, accompanied by decreasing cardiac apoptosis, and improved histological abnormalities and cardiac dysfunction without affecting hyperglycemia.