Subject(s)
Dermatomyositis , Myositis , Creatine Kinase/blood , Dermatomyositis/complications , Dermatomyositis/diagnosis , Dermatomyositis/immunology , Dermatomyositis/physiopathology , Dermatomyositis/therapy , Humans , Myositis/complications , Myositis/diagnosis , Myositis/immunology , Myositis/physiopathology , Myositis/therapy , Neoplasms/complications , PrognosisABSTRACT
The hydrolysis of radiolabelled Escherichia coli phospholipids, and micellar dispersions of phosphatidylethanolamine and phosphatidylcholine, were used to characterise the phospholipase A2 activity in synovial fluid from patients with rheumatoid arthritis. Cell free fractions of synovial fluid contain a phospholipase A2 enzyme that preferentially releases [14C]oleic acid from E coli biomembranes (specific activity 291.3 (SEM 27.6) pmol/min/mg). This enzyme requires calcium and is optimally active at neutral pH. Purified dispersions of phosphatidylethanolamine are also readily degraded by the soluble enzyme, but it is not active against phosphatidylcholine. The substitution of [14C]oleic acid by [3H]arachidonic acid for the labelling of E coli allowed differentiation between the soluble phospholipase A2 and the cell associated phospholipase A2 present in sonicates of mononuclear cells and neutrophils from peripheral blood and synovial fluid. The cell associated phospholipase A2 preferentially releases [3H]arachidonic acid from E coli cardiolipin. In this paper the phospholipid substrate specificity of phospholipase A2 from rheumatoid synovial fluid, the optimal assay conditions for its detection, and a standardised expression of activity in terms of pmol per minute per mg of protein are established.
Subject(s)
Arthritis, Rheumatoid/enzymology , Phospholipases A/metabolism , Phospholipases/metabolism , Synovial Fluid/enzymology , Humans , Leukocytes, Mononuclear/enzymology , Neutrophils/enzymology , Phospholipases A2 , Solubility , Substrate Specificity , Synovial Fluid/cytologyABSTRACT
Radiolabeled E. coli, Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC), were used to characterize the phospholipase A2 (PLA2) activity in synovial fluid (SF) from rheumatoid arthritis (RA) patients. Cell-free fractions of SF contain a PLA2 enzyme that preferentially releases [14C]oleic acid from E. coli, requires calcium and is optimally active at neutral pH. Purified PE, but not PC is also readily degraded by the soluble enzyme. A cell-associated PLA2 present in sonicates of SF mononuclear cells and neutrophils preferentially releases [3H]AA from E. coli. These studies suggest the presence of at least two different enzymes with activity of PLA2 in rheumatoid SF.
Subject(s)
Arthritis, Rheumatoid/enzymology , Phospholipases A/metabolism , Phospholipases/metabolism , Synovial Fluid/enzymology , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Calcium/pharmacology , Edetic Acid/pharmacology , Escherichia coli/metabolism , Humans , Hydrogen-Ion Concentration , Micelles , Phosphatidylcholines/metabolism , Phosphatidylethanolamines/metabolism , Phospholipases A2 , Phospholipids/metabolism , Substrate SpecificityABSTRACT
The activation of phospholipase A2 is believed to have an important role in the inflammatory process owing to its induction of eicosanoids, platelet activating factor, and other mediators. Soluble phospholipase A2 has been associated with exudates in different inflammatory conditions. In this review the general physiology and control of this enzyme and, in particular, the most recent findings on human synovial fluid phospholipase A2s are discussed.