Abstract: Objective: To test whether Notch1 attenuates myocardial ischemia/reperfusion (MI/R) injury after diabetes, and clarify the role of TNF-α inhibitor in it. Methods: A mice model of type 2 diabetes mellitus was induced by STZ intraperitoneal injection along with a high fat diet. And Notch1 specific small interfering RNA (siRNA, 20 μg) was delivered through intramyocardial injection to knockdown cardiac Notch1 levels. After 48 hours, myocardial ischemia/reperfusion (30 minutes) mice model was prepared. Then, etanercept (8 mg/kg) was administrated by intraperitoneal injection 10 minute before reperfusion. Mice were subjected to 30 minutes of myocardial ischemia followed by 3 hours (for TNF-α contents determined by ELISA, Notch1 activation and LDH release measured by western blot and cell apoptosis detected by caspase-3 activity assay) or 24 hours (for myocardial infarct size assessed by Evans blue/ (TTC) doubles staining and cardiac function determined by ultrasound) reperfusion. Results: TNF-α level of plasma and the myocardial tissue in diabetes mice was increased, while cardiac Notch1 was significantly suppressed (P<0.05). Etanercept apparently mitigated MI/R injury in mice subjected to diabetic, evidenced by decreased release of LDH, improved cardiac function, lessened myocardial infarct size and reduced myocardial apoptosis (P<0.01). In addition, etanercept obviously reduced the contents of TNF-α in both plasma and myocardium, in contrast, enhanced the expression of Notch1 intracellular domain (Notch1 ICD) in cardiac tissues (P<0.05). The disturbance of Notch1 pathway partly reversed etanercept's cardioprotection. Conclusion: TNF-α inhibitor attenuates myocardial ischemia/reperfusion injury via activating Notch1 in diabetic mice.

Key words: diabetes, myocardial reperfusion injury, Notch1, TNF-α inhibitor