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

Abstract

Aim: Sirtuin 1 (Sirt1) is the class III histone/protein deacetylase that interferes with the NF-B signaling pathway, thereby has anti-inflammatory 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-B was examined using NF-B 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-B activation, followed by reducing the expression of iNOS and NO formation. Sirt1 activator resveratrol (10mol/L) mimicked the protection of the cells by Sirt1 overexpression against TNF-α-induced injury, which was reversed by the Sirt1 inhibitor EX-527 (5mol/L).Conclusion:Overexpression of Sirt1 protects MC3T3-E1 osteoblasts aganst TNF-α-induced cell injury in vitro, at least in part, via suppressing NF-B signaling. Sirt1 may be a novel therapeutic target for treating rheumatoid arthritis-related bone loss. © 2012 CPS and SIMM. All rights reserved.