Oxysterols, the major components of oxidized
low-density lipoproteins (ox-LDLs), are present in
atherosclerotic plaque and are suggested to play an active role in plaque development. The formation of an atherosclerotic lesion occurs through activation of cellular events that include vascular smooth muscle cell (SMC) migration and proliferation. Therefore, we investigated the roles of two common
oxysterols,
7-ketocholesterol (7-keto) and cholesterol-5alpha,6alpha-epoxide (alpha-
epoxide) on SMCs. Our results showed that 7-keto and alpha-
epoxide promoted SMC migration by a chemotactic assay, and induced mitogenic effects by MTT assay and
BrdU assay. Specific inhibitors confirmed that
MMPs, EGFR and PI3K are involved in
oxysterol-induced SMC migration, while EGFR, ERK, Akt, and
sphingomyelin/
ceramide pathways might play a role in SMC proliferation. More, the co-immunoprecipitation study indicated that 7-keto and alpha-
epoxide caused EGFR phosphorylation and there was an interaction between EGFR and PI3K. At
protein expression level, Akt and ERK were activated, at
messenger RNA level,
MMP-2/9
mRNA was transcribed, at
enzyme activity level, the
MMP-2/9
enzyme activity were increased in SMCs treated with 7-keto and alpha-
epoxide according to Western bolt, RT-PCR and a
fluorogenic substrate. Taken together, we concluded that 7-keto and alpha-
epoxide may be an atherogenic factor by stimulating SMC migration and proliferation.