α-MSH inhibits TNF-α-induced matrix metalloproteinase-13 expression by modulating p38 kinase and nuclear factor κB signaling in human chondrosarcoma HTB-94 cells
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OBJECTIVE: Proinflammatory cytokine-induced expression of matrix metalloproteinases (MMPs) is a major cause of arthritic cartilage destruction. The neuropeptide, alpha-melanocyte-stimulating hormone (alpha-MSH), has been detected in the synovial fluid of arthritis patients, where it is thought to play an anti-inflammatory role. Here, we examined whether alpha-MSH acts via downregulation of MMP expression, and sought to elucidate the intracellular signal pathways underlying this effect. DESIGN: Human chondrosarcoma cell line, HTB-94 (SW1353) was pretreated with or without alpha-MSH and then treated with tumor necrosis factor-alpha (TNF-alpha). The effect of alpha-MSH on TNF-alpha-induced MMP-13 expression and mitogen-activated protein kinases' (MAPKs) activation were determined by reverse transcriptase-polymerase chain reaction and Western blot analysis. Additionally, the intracellular signaling of alpha-MSH was investigated using the inhibitors of MAPK and nuclear factor kappaB (NF-kappaB) and plasmids encoding dominant negative (dn) forms of inhibitor kappaB kinase-alpha (IKKalpha) and inhibitor kappaB kinase-beta (IKKbeta). RESULTS: We found that alpha-MSH pretreatment inhibited TNF-alpha-induced MMP-13 expression and p38 kinase phosphorylation in HTB-94 human chondrosarcoma cells. TNF-alpha-induced MMP-13 expression was not suppressed by extracellular signal-regulated kinase (ERK) inhibitors (PD98059 and U0126) or a c-jun terminal kinase (JNK) inhibitor (SP600125), but was inhibited by inhibitors of p38 kinase (SB203580) and NF-kappaB (SN-50 peptide) and dnIKKalpha and dnIKKbeta. CONCLUSIONS: Our results suggest that alpha-MSH regulates TNF-alpha-induced MMP-13 expression by decreasing p38 kinase phosphorylation and subsequent NF-kappaB activation in human chondrocytes and may be an effective inhibitor of MMP-13-mediated collagen degradation, providing new potential opportunities for the development of anti-arthritis therapeutics.
