Abstract

Sinomenine (SN) a component from Sinomenium acutum, widely used as an anti-inflammatory agent in Chinese traditional medicine, was reported to have anti-tumor activities. This study aims to examine the anti-leukemic activity of SN with or without aclarubicin (Acla) on leukemia cells and its molecular mechanism. HL-60 cells were treated with SN (5 to 20 ng/ml) with or without Acla (0.05 to 0.25 µg/ml). To study apoptosis, the cells were stained with Annexin V - propidium iodide (PI) and assessed by flow cytometry. To investigate the molecular mechanism, Caspase 3, Caspase 9 and cyclooxygenase-2 (Cox-2) were assessed by Western blot, NF-kB activity and prostaglandin E2 (PGE2) were tested by ELISA. Exposure to Acla (even at 0.25 µg/ml) alone or SN alone (20 ng/ml) for 20 h did not induce significant apoptosis. However, SN (5 to 20 ng/ml) promoted apoptosis induced by 0.1 µg/ml Acla in a dose-dependent manner. Increased Caspase 3 and 9 protein expression correlated positively with SN concentration when combined with 0.1 µg/ml Acla. In addition, SN significantly inhibited Acla-induced NF-kB activation, Cox-2 gene expression and PGE2 production. In summary, SN most likely enhances apoptosis by suppressing NF-kB activation, and Cox-2 and PGE2 expression. In the future, this natural agent may provide a new avenue for anti-leukemia treatment.

Key words: Sinomenine, Aclarubicin, apoptosis, nuclear factor-kappa B, prostaglandin E2 (PGE2), cyclo-oxygenase (Cox)-2.