ABSTRACT
Objective To explore the effects of daidzein (DA) on the expressions of estrogen receptors (ER) and peroxisome proliferator-activated recepor γ (PPARγ) in osteoblasts and the influence of estrogen on these effects.Methods A mouse osteoblastic cell line MC3T3-E1 cultured in α-MEM containing 2％ FBS was treated by 0.1 and 10 μmol/L DA.ER antagonist ICI182780 and PPARγ antagonist GW9662 in 0.1 μmol/L was added as required,and an equivalent amount of phosphate buffer solution (PBS) was used as control.For the study on estrogen effect,the cells were treated by DA in the serum-free medium with or without 10 nmol/L 17β-estradiol (E2).The expressions of ERa,ERβ and PPARγ were determined by real-time RT-PCR and Western blot analysis,respectively.Results DA inhibited ER,expression but stimulated PPARγ expression in the cells at the concentration of 0.1 and 10 μmol/L.The down-regulation of ERα by DA could be blocked by ICI182780,whereas the up-regulation of PPARγ could be repressed by GW9662 in transcription levels.Furthermore,the inhibitory effect of DA on ERβ expression was markedly enhanced,while its stimulatory effect on PPARγ expression was almost lost in serum-free medium with 10 nmol/L 17βestradiol as determined by real-time RT-PCR.Conclusions Besides its direct roles in ERs and PPARγ mediated gene transcriptions,DA could exert indirect effect on cellular pharmacological responses by altering ER and PPARγ expressions.The predominant influence on receptors expression probably involved in the time-related biphasic effects of DA on osteogenesis,which was supposedly influenced by estrogen level.