Objective: To study the protective role of heat shock protein (HSP)70 expression in the myocardial cells undergoing anoxia/reoxygeneration.
Methods: Myocardiocytes of neonatal SD rats were cultured and randomly divided into 4 groups: anoxia/reperfusion (A/R) group undergoing anoxia/reperfusion; A/R + HS group, undergoing transfection of HS and A/R, pCDNA HSP70 + A/R group, undergoing transfection of liposome-coated HSP70 pCDNA and A/R, and control group. RT-PCR and Western blotting were used to detect the mRNA and protein expression of HSP70 in the cells. The cell viability was examined by MTT method. The levels of lactic dehydrogenase (LDH), and serum creatine phosphokinase isoenzyme (CPK) were detected. Transmission electronic microscopy was used to observe the ultrastructure of the cells. Apoptosis rate was measured.
Results: The cell viability rates of the HS + A/R group and pCDNA HSP70 + A/R group were (71.8 +/- 10.3)% and (73.4 +/- 12.2)% respectively, both significantly higher than that of the A/R group [(35.2 +/- 6.8)%, both P < 0.01]. The LDH activity levels of the HS + A/R and pCDNA HSP70 + A/R groups were (14.3 +/- 2.6) and (14. 6 +/- 2.9) IU/L respectively, both significantly lower than that of the A/R group [22.9 +/- 4.0 IU/L, P < 0.01]. The cell ultrastructure was abnormal in the A/R group e, whereas nearly normal in the HS + A/R and pCDNA HSP70 + A/R groups. The HSP70 mRNA land protein were only slightly expressed in the myocardiocytes of the A/R group; However, the expressions of HSP70 mRNA and protein were of the HS + A/R and pCDNA HSP70 + A/R groups were significantly higher than those of the A/R group (both P < 0.01). The apoptosis rates of the A/R group was (12.84 +/- 2.17), significantly higher than that of the control group [(2.16 +/- 0.15), P < 0.01], and the apoptotic rates of the HS + A/R and pCDNA HSP70 + A/R groups were (5.23 +/- 1.04) and (4.42 +/- 0.93) respectively, both significantly lower than that of the A/R group (P < 0.01).
Conclusion: Overexpression of HSP70 alone can provide protection, related to the anti-apoptosis effect, for cardiomyocytes against anoxia-reoxygeneration.