Objective: To investigate the protective effects of insulin on burn serum-challenged cardiocyte apoptosis and its mechanism.
Methods: Burn-serum challenged cardiocytes were pretreated with insulin and inhibitors to pathway SB203580 and LY294002. The expression of cardiac myofilament proteins cleaved-caspase-3, Bax and phosphorylation nuclear factor-ΚB inhibitive factor α (p-IΚBα) were examined by Western blotting. The mRNA expression of tumor necrosis factor-α (TNF-α) was determined by real-time reverse transcription-polymerase chain reaction (RT-PCR). Apoptosis of cardiocyte was observed after Hoechst 33258 staining. Further blocking experiments were used to investigate the cytoprotective pathway of insulin.
Results: Insulin could significantly decrease the expression of cleaved-caspase-3 (2.22 ± 0.30 vs. 4.84 ± 0.74, P < 0.01), Bax (1.33 ± 0.35 vs. 3.74 ± 0.65, P < 0.01), p-IΚBα (1.43 ± 0.62 vs. 3.62 ± 0.74, P < 0.01), TNF-α (0.72 ± 0.27 vs. 2.02 ± 0.63, P < 0.01) and the cardiocyte apoptosis rate [(9.4 ± 3.4)% vs. (19.1 ± 5.6)%, P < 0.01] in cardiocytes challenged by burn serum. Further blocking experiments showed that LY294002, phosphatidylinositol-3-kinase (PI3K)/Akt activation inhibitor, could mitigate the protective effects of insulin. Meanwhile, SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38MAPK) pathway, was able to inhibit cardiocyte injury challenged by burn serum, and it was as effective as insulin.
Conclusion: For cardiocytes challenged by burn serum, insulin may decrease inflammatory cytokine expression and apoptosis via regulating PI3K/Akt and p38MAPK pathway.