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.
Keywords: apoptosis; microvesicles; myocardial ischemia/reperfusion; myocardial ischemic preconditioning; rats.