OBJECTIVETo investigate whether p53 pathway participates in the effect of emodin on vascular smooth muscle cell proliferation.

METHODSThe effects of emodin on vascular smooth muscle cell proliferation were evaluated by cell count, senescent-associated beta-galactosidase staining, and annexin V staining. DNA synthesis was determined by (3)H-thymidine corporation, cell cycle was analyzed by FACS, the p53 protein level was measured by Western blot and cDNA expression array technology was used to demonstrate the effect of emodin on the simultaneous expression of a large number of genes in cultured vascular smooth muscle cells.

RESULTSEmodin at 1.6-3.1 microg/ml inhibited VSMC growth, at 6.3-12.5 microg/ml promoted VSMC aging and induced VSMC apoptosis at 25.0 microg/ml 24 hours after exposure. Unscheduled DNA synthesis, which was a sensitive indicator for DNA injury, was observed in VSMC following 24 hours emodin exposure. The mRNA and protein levels of p53 were up-regulated in a concentration-dependent manner. Proliferation/carcinogenesis-related genes were down-regulated and other genes related to cell senescence, apoptosis, and DNA damage/repair were up-regulated in VSMC after exposure to emodin for 24 hours. Emodin readily permeated VSMC membrane and mostly located in the cytoplasm and few of them in the nucleus.

CONCLUSIONSThe p53 pathway in VSMC was activated post emodin exposure in a concentration-dependent manner and which might be responsible for the observed antiproliferative effects of emodin in vascular smooth muscle cells.