Beneficial effects of low doses of the phytoestrogen quercetin on osteoblastic cells

Abstract

Currently, there is a global trend to use natural bioactive compounds such as phytoestrogens (PEs), present in a wide variety of foods, for their beneficial biological effects demonstrated in vitro and in vivo including antioxidant, anti-inflammatory, anticancer, and antidiabetic activities. PEs are plant-derived non-steroidal compounds that bind to estrogen receptors and have estrogen-like activity. Given that the increase in life expectancy of the population has led to bone health becoming a major concern, in this work we investigated the effects of the PE quercetin (QUE) on the estrogen receptor-positive murine osteoblastic cell line MC3T3-E1. A dose dependent effect of QUE was observed on cell viability after 48 h of exposure, determined by MTS assay; with inhibition of cell viability at 20-100 µM concentrations and no change at lower concentrations. In parallel, by trypan blue assay a significant increase in cell number was obtained at 1 µM QUE. The wound healing assay show that low doses of QUE stimulate osteoblastic cell migration, with a significant closure at 12h, which further increases after 24h of treatment. Cell migration and proliferation are specific cell functions that require cell attachment and spreading. Using a cell adhesion assay we found a 60% increase in cellular adhesion when cells were treated with 1 µM of QUE, and no changes were observed with higher concentrations. QUE is generally considered to have strong antioxidant potency and provides protection against oxidative injury in cultured cells. We found that the pretreatment with 1 or 10 µM of QUE for 48h protects against H2O2-induced toxicity in MC3T3-E1 cells. Altogether, these results indicate that the beneficial effects of QUE on bone formation cells are observed at low doses while high doses of QUE have shown to be deleterious for MC3T3-E1 cells. Furthermore, QUE at high doses increases Erk1/2 and decreases Akt activation, with the consequent increase in the levels of active pro-apoptotic protein BAD, as assessed by Western blot analysis; and blockade of Erk1/2 activity with PD98059 decreases cell death induced by QUE. Based on these findings, we conclude that QUE has positive effects on migration, proliferation, adhesion and antioxidation of osteoblastic cells when it is used at doses lower than 20 µM; and may be consider a potential natural therapeutic alternative for bone healing repair in osteopathologies.