Prostaglandin E2 downregulates TNF-α-induced production of matrix metalloproteinase-1 in HCS-2/8 chondrocytes by inhibiting Raf-1/MEK/ERK cascade through EP4 prostanoid receptor activation
✍ Scribed by Kazunari Fushimi; Shigeru Nakashima; Fukka You; Masaharu Takigawa; Katsuji Shimizu
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 250 KB
- Volume
- 100
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
Matrix metalloproteinase‐1 (MMP‐1, collagenase‐1) plays a pivotal role in the process of joint destruction in degenerative joint diseases. We have examined the regulation of MMP‐1 production in human chondrocytic HCS‐2/8 cells stimulated by tumor necrosis factor‐α (TNF‐α). In response to TNF‐α, MMP‐1 is induced and actively released from HCS‐2/8 cells. The induction of MMP‐1 expression correlates with activation of ERK1/2, MEK, and Raf‐1, and is potently prevented by U0126, a selective inhibitor of MEK1/2 activation. In contrast, SB203580, a selective p38 mitogen‐activated protein kinases (MAPK) inhibitor, had no effects on TNF‐α‐induced MMP‐1 release. A serine/threonine kinase, Akt was not activated in TNF‐α‐stimulated HCS‐2/8 cells. TNF‐α stimulated the production of PGE~2~ in addition to MMP‐1 in HCS‐2/8 cells. Exogenously added PGE~2~ potently inhibited TNF‐α‐induced both MMP‐1 production and activation of ERK1/2. The effects of PGE~2~ were mimicked by ONO‐AE1‐329, a selective EP4 receptor agonist but not by butaprost, a selective EP2 agonist. In contrast, blockade of endogenously produced PGE~2~ signaling by ONO‐AE3‐208, a selective EP4 receptor antagonist, enhanced TNF‐α‐induced MMP‐1 production. Furthermore, the suppression of MMP‐1 production by exogenously added PGE~2~ was reversed by ONO‐AE3‐208. Activation of EP4 receptor resulted in cAMP‐mediated phosphorylation of Raf‐1 on Ser259, a negative regulatory site, and blocked activation of Raf‐1/MEK/ERK cascade. Taken together, these findings indicate that Raf‐1/MEK/ERK signaling pathway plays a crucial role in the production of MMP‐1 in HCS‐2/8 cells in response to TNF‐α, and that the produced PGE~2~ downregulates the expression of MMP‐1 by blockage of TNF‐α‐induced Raf‐1 activation through EP4‐PGE~2~ receptor activation. J. Cell. Biochem. 100: 783–793, 2007. © 2006 Wiley‐Liss, Inc.