Activated MMP-3 Enhances sIL-6R Production in Macrophage Like Differentiated THP-1Cells

Objective: Inteleukin-6 (IL-6) is one of inflammatory cytokines associated with periodontitis, and soluble form of IL-6 receptor (sIL-6R) plays important roles as an agonist to IL-6 signals (IL-6 trans-signaling). sIL-6R is produced via alternative splicing or shedding of IL-6R on the cell membrane (mIL-6R). Although it has been reported that TNF-α converting enzyme (TACE) is involved in the cleavage of mIL-6R, the precise mechanisms are still unknown. Matrix metalloproteinase-3 (MMP-3) is known to be an abundant enzyme in periodontal tissue, and is also known as a cleavage for several membrane proteins such as Fas ligand. In this study, we hypothesized that exogenous MMP-3 is involved in the shedding of mIL-6R, and investigated the effects of MMP-3 on sIL-6R production. Methods: Macrophage like differentiated THP-1 cells were cultured with MMP-3 inhibitor (100 nM), TNF-α proteinase inhibitor (TAPI-1: 10 µM) or recombinant activated MMP-3 (0-500 ng/ml) for 0-48 h. Both mIL-6R and sIL-6R mRNA expression were examined by real-time PCR. Productivity of sIL-6R was measured by ELISA. Expression of mIL-6R on the cell surface was analyzed by FACS analysis. Results: MMP-3 inhibitor and TAPI-1 did not affect on mIL-6R and sIL-6R mRNA expression. MMP-3 inhibitor blocks sIL-6R production (p<0.05), whereas activated MMP-3 enhanced sIL-6R production significantly (p<0.05) in THP-1 macrophage. Furthermore, activated MMP-3 (100 or 500 ng/ml) reduced mIL-6R protein expression on the cell surface. As expected, MMP-3 inhibitor or TAPI-1 induced mIL-6R expression on the cell surface. Conclusion: These data suggest that exogenous MMP-3 increases sIL-6R production via shedding of mIL-6R in THP-1 macrophage, resulting in progression of periodontal inflammation as an IL-6 agonist. This study was supported by Grants-in Aid for Young Scientists B (22792083) from JSPS.