Coexpression of Microsomal Prostaglandin E Synthase with Cyclooxygenase-2 in Human Rheumatoid Synovial Cells

FUMIAKI KOJIMA, HIROAKI NARABA, YASUHARU SASAKI, RENZO OKAMOTO, TOMIHISA KOSHINO, and SHINICHI KAWAI

ABSTRACT.

Objective. Recently, microsomal prostaglandin (PG) E synthase (mPGES) was cloned as a terminal enzyme catalyzing PGH₂ to PGE₂. We investigated mPGES as well as cyclooxygenase (COX)-2, catalyzing arachidonic acid to PGH₂, in synovial cells from patients with rheumatoid arthritis (RA). The effect of dexamethasone on mPGES expression was also studied.

Methods. Synovial cells were treated with interleukin 1ß (IL-1ß) and dexamethasone under various conditions, and expression of mPGES mRNA and protein was analyzed by Northern blot and Western blot, respectively. Conversions of arachidonic acid or PGH₂ to PGE₂ were measured by ELISA. Subcellular localization of mPGES and COX-2 was determined by immunofluorescent microscopic analysis.

Results. mPGES mRNA and protein expression were significantly upregulated by IL-1ß in synovial cells. COX-2 mRNA and protein were also upregulated by IL-1ß, but with a different time course from that of mPGES. Conversion of PGH₂ to PGE₂ was increased by IL-1ß and was correlated with mPGES expression. Increased conversion of arachidonic acid to PGE₂ was maintained when mPGES and COX-2 were coexpressed. Subcellular localization of mPGES and COX-2 overlapped in the perinuclear region in IL-1ß stimulated synovial cells. Dexamethasone inhibited mRNA and protein expression for mPGES and increased conversion of arachidonic acid to PGE₂, but inhibition of mPGES was weaker compared with that of COX-2 in IL-1ß stimulated cells.

Conclusion. The results suggest that abundant PGE₂ production at inflammation sites such as rheumatoid synovia is caused by the coordinated upregulation of mPGES and COX-2. Thus mPGES might be a potential new target for therapeutic strategies to control PGE₂ synthesis specifically in patients with RA and other inflammatory diseases. (J Rheumatol 2002;29:1836-42)

Key Indexing Terms:

PROSTAGLANDIN E SYNTHASE
CYCLOOXYGENASE
SYNOVIAL CELLS
RHEUMATOID ARTHRITIS
INTERLEUKIN 1ß
DEXAMETHASONE

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From the Department of Pharmacology, School of Pharmaceutical Sciences, Kitasato University, Tokyo; Department of Orthopedics, Yokohama City University School of Medicine, Yokohama; and Institute of Medical Science, St. Marianna University School of Medicine, Kawasaki, Japan.

Supported in part by a research grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

F. Kojima, MS; H. Naraba, PhD; Y. Sasaki, PhD, School of Pharmaceutical Sciences, Kitasato University; R. Okamoto, MD, PhD; T. Koshino, MD, PhD, Department of Orthopedics, Yokohama City University School of Medicine; S. Kawai, MD, PhD, Institute of Medical Science, St. Marianna University School of Medicine.

Address reprint requests to: Dr. H. Naraba, current address, Department of Pharmacology, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka, 565-8565, Japan. E-mail: naraba@ri.ncvc.go.jp

Submitted August 6, 2001; revision accepted February 7, 2002.

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