Resveratrol protects osteoblasts against dexamethasone-induced cytotoxicity through activation of amp-activated protein kinase

Abstract

Purpose: Glucocorticoids are used for the treatment of inflammatory diseases, but gluco-corticoid treatment is associated with bone damage. Resveratrol is a phytoalexin found in many plants, and we investigated its protective role on dexamethasone-induced dysfunction in MC3T3-E1 cells and primary osteoblasts. Materials and Methods: MC3T3-E1 cells and primary osteoblasts were treated with dexa-methasone in the presence/absence of different doses of resveratrol for 24 or 48 h. Then, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium (MTT) and lactate dehydrogenase (LDH) assays were used to evaluate cell viability. Apoptosis was analyzed by a flow cytometry. An alkaline phosphatase (ALP) activity assay and Alizarin Red S staining were used to study osteoblast differentiation. Expression of osteoblast-related genes was measured by real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The AMP-activated protein kinase (AMPK) signaling pathway and mitochondrial expression of superoxide dismutase were evaluated by Western blotting. Intracellular reactive oxygen species (ROS), adenosine triphosphate (ATP) content, mitochondrial-complex activity, and mitochondrial DNA content were measured to evaluate mitochondrial function. Results: Resveratrol induced the proliferation and inhibited apoptosis of osteoblasts in the presence of dexamethasone. Resveratrol increased the ALP activity and mineraliza-tion of osteoblasts. Resveratrol also attenuated dexamethasone-induced inhibition of mRNA expression of osteogenesis maker genes, including bone morphogenetic protein-2, osteoprotegerin, runt-related transcription factor-2, and bone Gla protein. Resveratrol alleviated dexamethasone-induced mitochondrial dysfunction. Resveratrol strongly stimu-lated expression of peroxisome proliferator–activated receptor-γ coactivator 1α and sir-tuin-3 genes, as well as their downstream target gene superoxide dismutase-2. Resveratrol induced phosphorylation of AMPK and acetyl-CoA carboxylase (ACC). Blockade of AMPK signaling using compound C reversed the protective effects of resveratrol against dexamethasone. Conclusion: Resveratrol showed protective effects against dexamethasone-induced dysfunction of osteoblasts by activating AMPK signaling.