u-0126 and myricetin

Myricetin has been reported to promote osteogenic differentiation and inhibit osteoclastogenesis. The aim of this study was to investigate the potential effects of myricetin on glucocorticoid-induced osteoporosis (GIOP) both in vivo and in vitro. Male Sprague-Dawley (SD) rats were given dexamethasone (DEX, 0.1 mg/kg, s.c.) once daily and myricetin (1 mg/kg or 2.5 mg/kg, i.p.) once every other day for a total of five weeks. Body weight was recorded once a week. Bone mineral density (BMD), the activities or levels of bone turnover markers, and histological changes were assessed. MC3T3-E1 cells were incubated with DEX (1 μM) and myricetin (20 μM). Osteoblast proliferation, differentiation and mineralization were evaluated. U0126 was added to evaluate the involvement of the ERK signaling pathway. The results showed that myricetin increased body weight gain and inhibited DEX-induced reduction in BMD, enhanced alkaline phosphatase (ALP) activity, and upregulated osteocalcin (OCN), bone morphogenetic protein 2 (BMP2) and runt-related transcription factor 2 (Runx2) levels, whereas reduced tartrate-resistant acid phosphatase (TRAP) activity and C-terminal telopeptide of type I collagen (CTx) level. In addition, myricetin ameliorated histological changes in the femurs. In our in vitro studies, myricetin promoted osteoblast differentiation and mineralization in DEX-treated MC3T3-E1 cells, accompanied by increases in BMP2, Runx2, ALP, OCN, collagen type I alpha 1 (COL1A1) and osteopontin (OPN) levels. The promotion effects of myricetin on osteogenic differentiation and matrix mineralization were reversed by U0126. These results suggest that myricetin may alleviate DEX-induced osteoporosis by promoting osteogenic differentiation and matrix mineralization via the ERK signaling pathway.

Topics: 3T3 Cells; Alkaline Phosphatase; Animals; Body Weight; Bone Morphogenetic Protein 2; Butadienes; Cell Differentiation; Cell Proliferation; Core Binding Factor Alpha 1 Subunit; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Glucocorticoids; Male; MAP Kinase Signaling System; Mice; Nitriles; Osteoblasts; Osteocalcin; Osteogenesis; Osteoporosis; Rats; Rats, Sprague-Dawley; Signal Transduction

Acrylamide is formed during cooking processes and is present in many foods. Accumulating evidence suggests that AA is carcinogenic, but the underlying mechanism remains unclear. Here, we investigated the carcinogenesis mechanisms of AA. AA increased the COX-2 expression. Two major transcription factors, AP-1 and NF-κB, were activated by AA treatment. AA induced the ERK phosphorylation, and this was abolished by the treatment of U0126, a pharmacological inhibitor of MEK, an upstream kinase of ERK. AA-induced expression and promoter activity of COX-2 were suppressed by U0126. U0126 treatment attenuated AA-induced transactivation of AP-1 and NF-κB, suggesting that the MEK/ERK signaling pathway regulates COX-2 expression. In addition, myricetin, a natural inhibitor of the MEK/ERK signal pathway, reduced AA-induced activation of the COX-2 promoter as well as activation of AP-1 and NF-κB. Collectively, these results suggest that the ability of AA to up-regulate COX-2 expression through the MEK/ERK signaling pathway underlies AA carcinogenicity.

Topics: Acrylamide; Animals; Anticarcinogenic Agents; Butadienes; Carcinogens; Cell Line; Cyclooxygenase 2; Enzyme Inhibitors; Epidermis; Extracellular Signal-Regulated MAP Kinases; Flavonoids; MAP Kinase Kinase Kinases; Mice; NF-kappa B; Nitriles; Signal Transduction; Transcription Factor AP-1; Up-Regulation