A suppressive effect of prostaglandin E2 on the expression of SERPINE1/plasminogen activator inhibitor-1 in human articular chondrocytes: An in vitro pilot study

Abstract

Kayo Masuko1, Minako Murata2, Naoya Suematsu1, Kazuki Okamoto1, Kazuo Yudoh2, Hiroyuki Shimizu3, Moroe Beppu3, Hiroshi Nakamura4, Tomohiro Kato11Department of Biochemistry; 2Department of Frontier Medicine, Institute of Medical Science; 3Department of Orthopedic Surgery, St. Marianna University School of Medicine, Kawasaki-shi, Kanagawa, Japan; 4Department of Joint Disease and Rheumatism, Nippon Medical School, Bunkyo-ku, Tokyo, JapanAbstract: Prostaglandin E2 (PGE2) is expressed in articular joints with inflammatory arthropathy and may exert catabolic effects leading to cartilage degradation. As we observed in a preliminary experiment that PGE2 suppressed the expression of SERPINE1/plasminogen activator inhibitor (PAI)-1 mRNA in chondrocytes, we focused on the effect of PGE2 on PAI-1 in a panel of cultured chondrocytes obtained from osteoarthritic patients. Specifically, articular cartilage specimens were obtained from patients with osteoarthritis who underwent joint surgery. Isolated chondrocytes were cultured in vitro as a monolayer and stimulated with PGE2. Stimulated cells and culture supernatants were analyzed using Western blotting and enzyme-linked immunosorbent assay. The results confirmed that the in vitro PGE2 stimulation suppressed the expression of PAI-1 in the tested chondrocyte samples. The inhibitory effect was partly abrogated by an antagonist of EP4 receptor of PGE2, but not by an EP2 antagonist. Although PGE2 induced activations of mitogen-activated protein kinases (MAPK), blocking of the MAPK did not abrogate the suppressive effect of PGE2, implying a distinct signaling pathway. In summary, prostaglandin is suggested to modulate the plasminogen system in chondrocytes. Further elucidation of the interaction might open a new avenue to understand the degradative process of cartilage.Keywords: chondrocyte, prostaglandin, PGE2, PAI-1