Sirt1 overexpression protects murine osteoblasts against TNF-α-induced injury in vitro by suppressing the NF-κB signaling pathway

Abstract

Aim: Sirtuin 1 (Sirt1) is the class III histone/protein deacetylase that interferes with the NF-κB signaling pathway, thereby has antiinflammatory function. This study was undertaken to investigate whether Sirt1 could protect osteoblasts against TNF-α-induced injury in vitro. Methods: Murine osteoblastic cell line, MC3T3-E1, was used. Overexpress of Sirt1 protein in MC3T3-E1 cells was made by transfection the cells with Sirt1-overexpressing adenovirus. The levels of mRNAs and proteins were determined with qRT-PCR and Western blotting, respectively. The activity of NF-κB was examined using NF-κB luciferase assay. The NO concentration was measured using the Griess method. Results: Treatment of MC3T3-E1 cells with TNF-α (2.5-10 ng/mL) suppressed Sirt1 protein expression in a concentration-dependent manner. TNF-α (5 ng/mL) resulted in an increase in apoptosis and a reduction in ALP activity in the cells. Overexpression of Sirt1 in the cells significantly attenuated TNF-α-induced injury through suppressing apoptosis, increasing ALP activity, and increasing the expression of Runx2 and osteocalcin mRNAs. Furthermore, overexpression of Sirt1 in the cells significantly suppressed TNF-α-induced NF-κB activation, followed by reducing the expression of iNOS and NO formation. Sirt1 activator resveratrol (10 µmol/L) mimicked the protection of the cells by Sirt1 overexpression against TNF-α-induced injury, which was reversed by the Sirt1 inhibitor EX-527 (5 µmol/L). Conclusion: Overexpression of Sirt1 protects MC3T3-E1 osteoblasts aganst TNF-α-induced cell injury in vitro, at least in part, via suppressing NF-κB signaling. Sirt1 may be a novel therapeutic target for treating rheumatoid arthritis-related bone loss.

The metal nanoparticle-induced inflammatory response is regulated by SIRT1 through NF-κB deacetylation in aseptic loosening

“…41 For example, SIRT1 was able to activate runt-related transcription factor 2 (RUNX2) and suppress NF-κB signaling in bone, leading to the stimulation of osteoblastogenesis and the inhibition of osteoclastogenesis. [42][43][44][45] In this study, the expression of SIRT1 was decreased in macrophages treated …”

Sirt3–MnSOD axis represses nicotine-induced mitochondrial oxidative stress and mtDNA damage in osteoblasts

“…However, when exposed to risk factors, such as smoking or ageing, Sirt3 knockout mice will have high oxidative stress level and may be more sensitive to osteoporosis Among the Sirtuin family, Sirt1, Sirt2, and Sirt6 are reported to regulate bone homeostasis in vivo [24][25][26]. Sirt1 regulates differentiation of MSCs and represses osteoblast injury [27,28], while Sirt2 and Sirt6 protect mice from arthritis [25,26]. Sirt3 is the first mitochondrial Sirtuin that has been shown to participate in maintaining bone hemostasis.…”

Epigenetic mechanisms in bone

“…It is important to note that SIRT1 action is not limited to epigenetic mechanisms as it exerts its multiple activities by interacting not only with histones but also with numerous transcription factors, enzymes and other protein species [52]. Additional studies, for example, have shown that SIRT1 promotes the activation of RUNX2 and the suppression of NFκB signaling, thus stimulating osteoblastogenesis while also inhibiting osteoclastogenesis; this indicates that it plays an important role in the coupling of bone formation and resorption with a possible contribution to bone quality and a reduction in bone frailty ( Figure 4) [51,[53][54][55].…”

“…In the bone environment, SIRT1 causes the deacetylation of histones at the SOST promoter, thus repressing SOST expression and preventing its negative regulation of osteoblast activity. In addition, SIRT1 promotes the activation of RUNX2 and suppression of NFκB signaling, thereby both stimulating osteoblastogenesis and inhibiting osteoclastogenesis [51,[53][54][55]. It is also positively linked to estrogen signaling, an essential regulator of bone mass, both upstream and downstream of the estrogen receptor.…”