Induction of apoptosis of RAW 264.7 cells by the cytostatic macrolide apicularen A

Abstract

In RAW 264.7 cells, a mouse leukaemic monocyte cell line, apicularen A decreased cell growth and survival as assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in a concentration-dependent manner at 10-1000 nM. Apicularen B, an N-acetyl-glucosamine glycoside of apicularen A, was 10-100-fold less effective than apicularen A. Apicularen A induced a DNA ladder, an increase in the percentage of sub-G(1) cells and annexin V-binding cells, and promoted the activation of caspase as revealed by the cleavage of poly(ADP-ribose) polymerase, indicating that apicularen A induced apoptosis in RAW 264.7 cells. In addition, apicularen A phosphorylated p44/42 mitogen-activated protein kinase (MAPK) and p38 MAPK. The p44/42 MAPK inhibitor PD98059 rescued the cells from apicularen-induced decrease in cell growth and survival as determined by the MTT assay, while the p38 MAPK inhibitor SB203580 augmented the effect of apicularen A. This suggested the activation of p44/42 MAPK to be pro-apoptotic and the activation of p38 MAPK antiapoptotic in apicularen A-treated RAW 264.7 cells.