Hypoxia-reoxygenation-induced apoptosis in cultured neonatal rat cardiomyocytes and the protective effect of prostaglandin E1

1. The aim of the present study was to investigate the effect of prostaglandin (PG) E-1 on hypoxia/re-oxygenation (H/R) apoptosis and the expression of bcl-2 and bax in cultured neonatal rat cardiomyocytes. 2. The H/R model was made using the first generation of cultured neonatal rat cardiomyocytes. Hypoxia/re-oxygenation apoptosis was studied by electron microscopy and agarose gel electrophoresis. The percentage of apoptotic cells was measured by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL). The expression of bcl-2 and bax was detected by in situ hybridization and immunohistochemical staining. 3. Most cells of the H/R group tested by electron microscopy showed cytoplasmic concentration, nuclear chromatin condensation and margination. Prostaglandin E-1 (5, 15 and 45 mu g/L) relieved the injury. The results of DNA electrophoresis in the H/R group showed a typical DNA ladder and the DNA ladder decreased gradually corresponding with increasing doses of PGE(1). 4. The TUNEL staining showed that the total number of apoptotic cells in the H/R group was much more than that in the PGE(1) (45 mu g/L) group. 5. The results of in situ hybridization and immunohistochemical staining showed that the bcl-2 content in the H/R group was lower than that in the control group; bax content showed the reverse. Compared with the H/R group, bcl-2 content was significantly higher in the PGE(1) (5, 15 and 45 mu g/L) groups. However, bax content in the PGE(1) (5, 15 and 45 mu g/L) groups was significantly lower than that in the H/R group. 6. In conclusion, H/R injury can induce cardiomyocyte apoptosis. Prostaglandin E-1 obviously has anti-apoptotic effects on cardiomyocytes and the mechanisms probably involve the inhibition of bax expression and increased expression of bcl-2.