Induction of apoptosis and change of bcl-2 expression in macrophage Ana-1 cells by all-trans retinoic acid

Abstract

Macrophage cells play an important role in the initiation and regulation of the immune response. All-trans retinoic acid (ATRA) and its natural and synthetic analogs (retinoids) affect a large number of biological processes. Recently, retinoids have been shown promise in the therapy and prevention of various cancers. However, many interesting questions related to the activities of retinoids remain to be answered: (I) Molecular mechanisms by which retinoids exert their effects; (II) why the clinical uses of retinoids give undesirable side effects of varying severity with a higher frequency of blood system symptoms; (III) little is known for its impacts on macrophage cells etc. We set up this experiment, therefore, to examine the apoptosis of ATRA on macrophage Ana-1 cell line. Apoptosis of the cells was quantitated, after staining cells with propidium iodide (PI), by both accounting nuclear condensation and flow cytometry. When the cells were treated with ATRA at or higher than l μM for more than 24 h, significant amount of the apoptotic cells was observed. Induction of apoptosis of Ana-1 cells by ATRA was in time- and dose-dependent manners, exhibiting the similar pattern as the apoptosis induced by actinomycin D (ACTD). ATRA treatment of Ana-1 cells also caused the changes of the mRNA levels of apoptosis-associated gene bcl-2, as detected by Northern blot analysis. The temporal changes of bcl-2 expression by ATRA was also parallel to that by ACTD. In conclusion, ATRA can induce apoptosis in macrophage cells, which may be helpful in understanding of immunological functions retinoids.