The investigation of HO-1 in mechanical stretch induced inflammation

Objectives: It is known that mechanical stress induces the production of inflammatory cytokines which are involved in TMJ disease, such as internal derangement and osteoarthritis and enhances the production of inflammatory mediators. Heme oxygenase-1 (HO-1) is an inducible enzyme in response to stress including mechanical stress, oxidative stress and cytokines. However, the transduction mechanism responsible for the evolution of molecular events between inflammation and HO-1 caused by mechanical stress remains unknown. The purpose of this study is to investigate the expression of HO-1 in mechanical stretch. Methods: Human Fibroblast-Like Syobiocytes (HFLS) cells and Human Fibroblast-Like Synoviocytes-Osteoarthritis (HFLS-OA) cells isolated from human knee joints were cultured with human syovial growth medium. The fibronectin-coated silicon chambers were attached to a stretching apparatus that was used to apply a uniaxial sinusoidal stretch (2%, 10% and 20% peak-to-peak) for 12 h. Cox-2 selective inhibitor, NS-398 (50 ìM), was added 24 h before mechanical stretch. The gene expression of COX-2, HO-1 and inflammatory cytokines were analyzed by Real Time RT-PCR. The protein expression of COX-2 and HO-1 were determined by western blotting analysis. The amount of PGE2 released into culture medium was measured by ELISA. Results: Mechanical stretch increased the expression levels of IL-1â, IL-6, COX-2 and HO-1 in Real Time RT-PCR. Furthermore mechanical stretch enhanced the release of PGE2 through COX-2 expression. NS-398 significantly suppressed the expression of HO-1 and the release of PGE2. 10% stretch induced the highest expression of HO-1 and COX-2 among the stretch strength. Conclusion: The present study indicated that mechanical stretch induced the expression of IL-1â, IL-6, COX-2 and HO-1. Furthermore the proper stretch was found to enhance the expression of COX-2 and HO-1. These findings suggest the mechanical stretch regulates the inflammation through COX-2 and HO-1.