title: Suppression of human synovial cell proliferation by dihomo-gamma-linolenic acid.
abstract: Prostaglandin E1 (PGE1) and oils enriched in its precursor fatty acids suppress inflammation and joint tissue injury in several animal models. Since synovial cell proliferation is a hallmark of rheumatoid arthritis, we studied the effect of dihomo-gamma-linolenic acid (DGLA), an immediate precursor of PGE1, on the growth of human adherent synovial cells (ASC) in tissue culture. When stimulated by appropriate concentrations of recombinant interleukin-1 beta (rIL-1 beta), ASC proliferate and produce PGE. DGLA-enriched medium suppressed both baseline and rIL-1 beta-stimulated ASC growth fivefold, compared with medium supplemented with arachidonic acid. Indomethacin reduced the effect of the DGLA. Synovial cells incorporated the DGLA, and rIL-1 beta-stimulated cells that were incubated with DGLA exhibited a 14-fold increase in PGE1 (to 25.2 +/- 6.0 ng/ml, mean +/- SD) and a 70% decrease in PGE2 (to 25.2 +/- 4.2 ng/ml) compared with cells in control medium. At equivalent concentrations (5 x 10(-7) M), PGE1 increased the level of cellular cAMP to a greater extent than did PGE2 (16.8 +/- 2.0 pmoles versus 4.3 +/- 1.9 pmoles, mean +/- SEM). Exogenous PGE1 was also a more effective inhibitor of cell growth. Similarly, cAMP concentrations in cells exposed to DGLA for 6 hours were greater than concentrations in arachidonic acid-enriched cultures (17.8 +/- 3.3 pmoles versus 2.1 +/- 2.0 pmoles). These observations suggest that DGLA can restrain ASC growth, an effect which may be due to its capacity to increase PGE1 production and subsequent cellular cAMP concentration.
authors.affiliation: Department of Medicine (Rheumatology Section), University of Pennsylvania, Philadelphia.
authors.forename: D G
authors.initials: DG
authors.lastname: Baker
authors.forename: K A
authors.initials: KA
authors.lastname: Krakauer
authors.forename: G
authors.initials: G
authors.lastname: Tate
authors.forename: M
authors.initials: M
authors.lastname: Laposata
authors.forename: R B
authors.initials: RB
authors.lastname: Zurier
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000494:pharmacology*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D011458:Prostaglandins E / Q000096:biosynthesis / Q000494:pharmacology; D013583:Synovial Membrane / Q000166:cytology*
chemical_list: D001095:Arachidonic Acids; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D007375:Interleukin-1; D011458:Prostaglandins E; D016718:Arachidonic Acid; D000242:Cyclic AMP; D015126:8,11,14-Eicosatrienoic Acid; D007213:Indomethacin