Background/Purpose: Cyclic phosphatidic acid (cPA) is one of bioactive lipid, has been implicated as an mediator of various biological effects including inhibitory effects of proliferation, invasion and metastasis of cancer cells. We have previously confirmed that cPA stimulated HAS-2 production on human osteoarthritic chondrocytes and synovial fibroblasts (SFs) in vitro. Furthermore, intra-articular administration of cPA has shown its suppressing effect of pain, swelling, and articular cartilage destruction in rabbit experimental osteoarthritis. We have shown that cPA might had direct inhibitory effect of cartilage degrading enzymes on rheumatoid synovial fibroblasts (SFs) in vitro. Inflammatory arthritis such as rheumatoid arthritis and early stage of OA involves synovial inflammation and subsequent production of cartilage degrading enzymes. cPA is naturally occurring mediator even exists in human serum. cPA may be possible another therapeutic option for degenerative arthritis.  The aim of this study was to evaluate the direct effects of cPA on cartilage matrix degrading enzymes using SFs and articular chondrocytes under influence of inflammatory cytokines. 

Methods: In vitro studies were performed using SFs and chondrocytes obtained from arthritis patients at joint replacement surgery.  cPA 0-25 μM was added to cell cultures and effects of cPA on ADAMTS-4, -5, MMP-3, -13, TIMP-3 expression were assessed by real time PCR using specific primers to corresponding genes. SFs or chondrocytes were also cultured with IL-1β (2.5ng/ml) and/or TNF-α (10 ng/ml), to study attenuated effect of cPA. Beta-actin was used as endogenous expression control for PCR. Newly synthesized MMP-3, -13, TIMP-3 from SFs or chondrocytes in cultured media were measured by sandwich ELISA.

Results: cPA itself repressed cartilage degrading enzymes, ADAMTS-4, ADAMTS-5, MMP-3, and MMP-13 expression in both SFs and chondrocytes was all repressed by low dose of cPA, even after these expressions was stimulated by cytokines. Expression of these enzymes were repressed more in chondrocytes by cPA. ELISA results also confirmed the inhibitory effect of cPA on MMP-3, MMP-13, and PGE2 production.

Conclusion: The in vitro results confirmed that cPA had suppressing effect of cartilage degrading enzymes on SFs and chondrocytes, supports the hypothesis that cPA might have played direct role to suppress inflammation and also protect articular cartilage in arthritic condition. Molecular mechanism of cPA to prevent cartilage degradation remains to be elucidated, however, further study should be warranted for cPA as a novel candidate for therapeutic agent of arthritis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cyclic-phosphatidic-acid-cpa-suppresses-expression-of-cartilage-degrading-enzymes-such-as-mmp-3-mmp-13-and-adamts-4-in-inflammatory-synovial-fibroblasts-and-articular-chondrocytes-induced-by-il-1-b/