Role of SIRT1 in Heat Stress- and Lipopolysaccharide-induced Immune and Defense Gene Expression in Human Dental Pulp Cells

Introduction: Although bacterial infection and heat stress are common causes of injury in human dental pulp cells (HDPCs), little is known about the potential defense mechanisms mediating their effects. This study examined the role of SIRT1 in mediating heat stress and lipopolysaccharide (LPS)-induced immune and defense gene expression in HDPCs. Methods: HDPCs were exposed to heat stress (42 degrees C) for 30 minutes after stimulation with LPS (1 mu g/mL) for 48 hours. The expression of defense genes was evaluated by reverse-transcriptase polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assay. Results: LPS and heat stress synergistically increased the expression of SIRT1 and immune and defense genes such as interleukin (IL)-8, hemeoxygenase-1 (HO-1), and human beta-defensin 2 (hBD-2). Resveratrol enhanced LPS- and heat stress induced expression of HO-1 and hBD-2 but reduced IL-8 messenger RNA levels. The stimulation of HO-1 and hBD-2 messenger RNA expression by LPS and heat stress was inhibited by sirtinol; SIRT1 small interfering RNA; and inhibitors of p38, ERK, JNK, and nuclear factor kappa B. Conclusions: These results show for the first time that SIRT1 mediates the induction of immune and defense gene expression in HDPCs by LPS and heat stress. SIRT1 may play a pivotal role in host immune defense system in HDPCS. (J Endod 2011;37:1525-1530)