A Study On The Effect And Mechanism Of Small Heat Shock Protein 20 In Aged Rats After Myocardial Ischemia/reperfusion Injury

Objective: The small heat shock protein 20 (sHSP20) can suppress platelet aggregation, stabilize cystoskeleton and inhibite apoptosis, et al. However, there is no study on the effect and mechanism of sHSP20 in aged rats after myocardial ischemia/reperfusion injury (MIRI). MIRI is one of important causes that impact prognostic of coronary heart disease (CHD) patients and the incidence of MIRI in aged is higher than non-aged peoples. Additionally, presby-myocardium present different characteristics in morphosis and function from young myocardial. So, we prepare MIRI model and investigate the effect and potential mechanism of sHSP20 in aged rats through technique of molecular biology and immunofluorescence. The destination is to provide new idea and approach which can prevention and cure MIRI in the aged.Material and methods:Juvenile (3 month old), adult (9 month old) and aged (24 month old) male wistar rats were randomly divided into two groups: controlled group (Ctrl) and MIRI group. In the Ctrl group, rat's breast were opened with continuous perfusing for 160 minutes, while in the MIRI group, rats were treated with ischemia 40 minutes by ligating anterior descending coronary and reperfused for 120 minutes. After that, ischemic left ventricular wall was taken and putted into liquid nitrogen. After 5 minutes, samples were frozen into -80℃refrigerator and to provide to inspect.The mRNA expression of sHSP20 in different groups was detected by semi-quantitative RT-PCR. The synthesis and distribution of sHSP20 was detected by western blot. The location of sHSP20 in the myocardial tissues was detected by immunofluorescence technique. Results:RT-PCR showed that the expression of sHSP20 mRNA did not change among three Ctrl groups, but the expression of sHSP20 mRNA increased after MIRI among three experimental groups.Western blot demonstrated that the expression of sHSP20 in aged was decreased before and after MIRI. Compared juvenile and adult groups, it was higher in aged groups that sHSP20 shifted from endochylem to cellular nucleus.Immunohistology indicated sHSP20 shifted to Z line and I band after MIRI. But it attenuated obviously in aged rats compared other two groups.Conclusion:Our study demonstrated that the aged rats still had ability of sHSP20 genetic transcription. But the synthesis of sHSP20 decreased before and after MIRI. It indicated that aged rats may lack sHSP20 protection in normal and stringent state. At the same time, the distribution of sHSP20 in cellular nucleus was higher and reduced in Z line and I band after MIRI in aged rats. It might explain why aged rats heart partially loss the protection after MIRI.