Biomedical subjects

E Stefanski

Publications and source records attributed to E Stefanski.

45 records · Page 3Linked to original sources

PubMed1986

Influence of plasma proteins on activity of proinflammatory enzyme phospholipase A2.

The influence of plasma proteins on quantitation of the proinflammatory enzyme phospholipase A2 (PLA2) from rheumatoid synovial fluid was studied using two different assays. Human and bovine serum albumins increased the rate of PLA2 hydrolysis of membrane-associated phospholipid substrates. In contrast, albumin profoundly inhibited the PLA2 hydrolysis of synthetic phospholipids in micellar dispersion. Other plasma proteins (alpha, beta and gamma-globulins) had minimal effect on PLA2 activity in either assay system. Since the presence of albumin may compromise estimation of PLA2 and of phospholipase-inhibitory proteins, the appropriate selection of assay conditions is obligatory for the accurate quantitation of their respective activities.

Arthritis, Rheumatoid↗

PubMed1986

Potential therapeutic efficacy of inhibitors of human phospholipase A2 in septic shock.

Soluble phospholipase A2 has been implicated in the pathogenesis of local and systemic inflammatory reactions. Elevated levels of circulating phospholipase A2 (PLA2) correlate with the severity of circulatory collapse and pulmonary dysfunction in gram-negative septic shock. Characterization of septic shock serum PLA2 revealed a calcium-dependent enzyme with absolute 2-acyl specificity with a pH optimum of 7.5. We tested a number of therapeutic agents for their ability to inhibit PLA2 from human septic shock serum. Chloroquine, chlorpromazine, dexamethasone base, dexamethasone sodium phosphate, indomethacin, lidocaine, oleic acid, palmitic acid, promethazine, trans-retinoic acid, rutin and dl-alpha-tocopherol were all studied over the range of 10(-2) to 10(-7) M. All agents, with the sole exception of dexamethasone base, inhibited PLA2 activity at concentrations greater than 10(-3) M. PLA2 inhibition by dexamethasone sodium phosphate was factitious, due to the formation of calcium-phosphate complexes. Of the 11 agents studied, chlorpromazine was the most effective, with an IC50 of 7.5 X 10(-5) M, a membrane concentration achievable within its therapeutic range. Inhibition was non-competitive with an apparent Ki of 5 nM. Since serum PLA2 levels correlate with mortality in both experimental endotoxemia and clinical gram-negative septic shock, and chlorpromazine was previously shown to improve survival in these conditions, we postulate that its therapeutic efficacy resides at least in part in its PLA2-inhibitory activity.

Dexamethasone↗

PubMed1986

Purification of a soluble phospholipase A2 from synovial fluid in rheumatoid arthritis.

A soluble phospholipase A2 (PLA2) was purified 4,500-fold from human rheumatoid synovial fluid. Preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis yielded two bands of PLA2 activity of molecular weights 15,000 and 17,000 and pl 4.2-5.0. Purified PLA2 had absolute 2-acyl specificity, and hydrolyzed phosphatidylcholine with optimal activity at pH 7.5-8.0 and phosphatidylethanolamine with optimal activity at pH 7.0. Human synovial fluid PLA2 did not cross-react with anti-human pancreatic PLA2, as tested by radioimmunoassay.

Arthritis, Rheumatoid↗

PubMed1985

Characterization of extracellular phospholipase A2 in rheumatoid synovial fluid.

Phospholipase A2 (PLA2) activity has now been identified in rheumatoid synovial fluids. This PLA2 is a calcium-requiring protein of MW 11,000 with a neutral pH optimum. Its activity was inhibited by high concentrations of Mg2+, and by the active site-directed histidine reagent p-bromophenacyl bromide. Ionic and nonionic detergents, or the sulfhydryl reagent dithiothreitol caused loss of enzyme activity. Synovial fluid PLA2 did not interact with sulphated mucopolysaccharides such as heparin or chondroitin sulphate. Release and sequestration of PLA2 in the joint space may contribute to the characteristic rheumatoid inflammatory changes.

Acetophenones↗

PubMed1985

Phospholipase A2 activity in sera and synovial fluids in rheumatoid arthritis and osteoarthritis. Its possible role as a proinflammatory enzyme.

Phospholipase A2 (PLA2) activity was found in the sera and synovial fluids (SF) in rheumatoid arthritis (RA) and osteoarthritis (OA). PLA2 activity in RA SF was 6158 +/- 549 (SEM) U/ml (n = 48) and in RA sera 554 +/- 175 U/ml (normal sera-115 +/- 12 U/ml). In OA SF PLA2 activity was 5069 +/- 542 U/ml (n = 28), and in OA sera 268 +/- 55 U/ml. There was no significant difference between SF PLA2 activity in RA and OA. PLA2 activity in SF did not correlate with muramidase (lysozyme), beta-glucuronidase, total protein or white cell count, which were all significantly higher in RA SF than OA. A positive correlation between PLA2 in SF and matched sera was found in both RA and OA. It may be concluded that significant elevation of extracellular PLA2 occurs in both RA and OA, especially in the SF. The fact that high PLA2 did not correlate with other enzymes such as lysozyme and beta-glucuronidase, which are usually high in RA and low in OA SF, may mean that the handling of PLA2 in the joint space is different from other enzymes.

Arthritis, Rheumatoid↗

PubMed1974