Morphine-induced apoptosis in PC12 cells: role of Bax and Bcl2

Introduction: It was reported that morphine could induce apoptosis in neurons. However, its specific mechanistic pathways remain elusive. The present study was undertaken to determine whether morphine could induce apoptosis in PC12 cells, a neuronal cell line, and the involvement of Bax and Bcl-2, as upstream factors of mitochondrial pathway. Methods: In an experimental study, the viability of PC12 cells exposed to morphine was measured by MTT assay. Subsequently, to confirm whether morphine could induce apoptosis, analysis of DNA fragmentation in PC12 cells was carried out. Moreover, the alteration in expression of pro- apoptotic, Bax and anti-apoptotic, Bcl-2, proteins were measured by Western blotting. Results: The results showed that morphine (1mM) significantly reduced the cell viability after 96 h and induced apoptosis in PC12 cells, as evidenced by a DNA ladder pattern, a hallmark of apoptosis. In Western blot analysis, the Bax pro-apoptotic expression in treated rats was significantly increased while there was no change in Bcl2 expression, so that the ratio of Bax/Bcl-2 protein expression in cells treated with morphine was significantly increased compared to controls. Conclusion: These data support the idea that morphine can induce apoptosis in PC12 cells, possibly by the mitochondrial pathway through higher expression of Bax pro-apoptotic protein.