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Sirtuin 1 (SIRT1), also known as NAD-dependent deacetylase, has been reported to increase in vivo osteoclast-mediated bone resorption. However, its effects on osteoclastogenesis or bone loss in vitro have not been widely examined. Therefore, the effects and underlying mechanism of SIRT1 on osteoclast differentiation in mice in vitro were studied. During RANKL-induced osteoclastogenesis in differentiated bone marrow-derived macrophages (BMMs), SIRT1 downregulation was observed. The use of resveratrol (SIRT1 activator) and SIRT1 overexpression was found to inhibit osteoclastogenesis, which was confirmed by TRAP staining and activity loss, reduced expression of osteoclast markers and related genes, and a decrease in the number of multinuclear cells. In contrast, treatment with EX-527 (SIRT1 inhibitor) as well as SIRT1 silencing promoted osteoclastogenesis. Furthermore, the tumor necrosis factor (TNF)-α level was reduced by resveratrol treatment and SIRT1 overexpression but increased following EX-527 incubation and SIRT1 depletion. TNF-α silencing blocked the osteoclastogenesis of BMMs promoted by SIRT1 depletion. Moreover, transient receptor potential vanilloid 1 (TRPV1) channel activation and reactive oxygen species (ROS) production, which are associated with osteoclastogenesis, were impaired by TNF-α silencing. These data demonstrate that SIRT1 directly inhibits osteoclastogenesis by inhibiting ROS generation and TRPV1 channel activation under mediation of TNF-α.

As a deacetylase relying on NAD, sirtuin 1 (SIRT1) has been proven to inhibit osteoclastogenesis directly by repressing reactive oxygen species (ROS) production and TRPV1 channel stimulation modulated by TNF‐α. MicroRNAs do not have coding functions, but they influence the expression of particular genes after transcription. Nevertheless, the current understanding of the impact of SIRT1 on osteoclastogenesis is insufficient. Our research explored whether and how miRNAs contributed to osteoclast differentiation modulated by SIRT1 in vitro. In osteoclastogenesis induced by RANKL in bone marrow‐derived macrophages (BMMs), repression of SIRT1 expression and enhancement of miR‐506 expression were discovered. Transfection with an miR‐506 inhibitor repressed miR‐506 concentration in BMMs treated with RANKL. Additional research revealed that BMMs with repressed miR‐506 treated with RANKL displayed phenotypes with suppressed osteoclastogenesis, as demonstrated by TRAP staining, reduced function, decreased expression of osteoclast markers and correlated genes, and reduced multinuclear cell quantity. Bioinformatics prediction outcomes and the dual‐luciferase reporter test suggested that miR‐506 targeted the SIRT1 3′‐UTR for silencing. Decreased miR‐506 in BMMs induced by RANKL caused SIRT1 upregulation. Additionally, treatment with EX‐527 (SIRT1 repressor) or SIRT1 silencing attenuated repression caused by miR‐506 depletion in BMMs treated with RANKL. Furthermore, TNF‐α was repressed via miR‐506 inhibition but was enhanced following EX‐527 incubation as well as SIRT1 depletion. TRPV1 channel stimulation and ROS generation, which was related to osteoclastogenesis, were reduced via miR‐506 depletion. miR‐506 modulated osteoclastogenesis by targeting SIRT1 expression in part through modulation of the TRPV1 channel, ROS production, and TNF‐α. [ABSTRACT FROM AUTHOR]