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Biomedical subjects

P Vadas

Publications and source records attributed to P Vadas.

At least 55 records · Page 3Linked to original sources
PubMed1991

Interleukin-1 alpha stimulates the release of prostaglandin E2 and phospholipase A2 from fetal rat calvarial cells in vitro: relationship to bone nodule formation.

We have shown previously that interleukin-1 (IL-1) has biphasic effects on the formation of bone nodules in long-term cultures of fetal rat calvarial (RC) cells (Ellies and Aubin, Cytokine 2:430-437, 1990). To determine the role of arachidonic acid metabolism in this process, we have examined the release of prostaglandin E2 (PGE2) and phospholipase A2 (PLA2) from RC cells under conditions that allowed concomitant analysis of the formation of bone nodules. Recombinant human IL-1 alpha (rhIL-1 alpha) stimulated PGE2 and PLA2 release in a time- and dose-dependent manner. PGE2 release was highest in preconfluent cultures (days 1-6) and was stimulated up to 8.5-fold in response to 50 U/ml of rhIL-1 alpha. In contrast, extracellular PLA2 activity was maximal in postconfluent cultures, with 50 U/ml of rhIL-1 alpha causing a 20-fold increase by day 15. PLA2 release by RC cells was not significantly affected by PGE2, the glucocorticoid dexamethasone, or the cyclooxygenase inhibitor indomethacin. Indomethacin partially blocked the inhibition of bone nodule formation caused by rhIL-1 alpha, and exogenous PGE2 reversed this effect. Addition of group I PLA2 from Naja naja venom to RC cells had no effect on bone nodule development; however, group II PLA2 from Crotalus adamanteus venom inhibited the formation of bone nodules in a dose range similar to that induced by rhIL-1 alpha. These results indicate that PGE2 release does not have a direct temporal correlation with increases in PLA2 activity. In addition, the data show that only part of the inhibition of bone formation seen with rhIL-1 alpha is mediated by PGE2 and suggest that extracellular PLA2 also accounts for part of the inhibition.

Animals↗
PubMed1991

Comparison of group I and II soluble phospholipases A2 activities on phagocytic functions of human polymorphonuclear and mononuclear phagocytes.

Soluble phospholipase A2 (PLA2) purified from rheumatoid synovial fluid (group II) and repurified Naja naja venom PLA2 (group I) were compared for their influence on phagocytic activity of human polymorphonuclear (PMN) and mononuclear (MO) phagocytes. Group II PLA2 reduced chemotaxis, adhesiveness, and intracellular bactericidal activity (ICBA) and induced release of muramidase from PMNs. Group I PLA2 suppressed chemotaxis, and enhanced ICBA but had no influence on other phagocytic functions. Group II PLA2 purified from synovial fluid or from placenta caused marked spontaneous superoxide generation followed by inhibition of phagocytosis-induced burst of energy. Group I Naja naja and porcine pancreatic PLA2 had no effect on superoxide generation. Group II but not group I PLA2 reduced markedly ICBA of monocytes. It may be concluded that human group II soluble PLA2, in concentrations comparable to those present in inflamed joints or in sera of patients with active arthritis or septic shock, causes spontaneous formation of the oxygen radical superoxide and release of lysosomal enzymes, and suppresses conventional phagocytic activities of PMNs and monocytes. Marked differences between group I and group II PLA2s may mean that these enzymes exert different influences on cell membrane.

Arthritis, Rheumatoid↗
PubMed1991

Enzymatic activity and distribution of phospholipase A2 in human cartilage.

Extracellular phospholipase A2 (PLA2) with proinflammatory activity has recently been discovered in synovial fluids in inflammatory arthritides. In the search for the sources of synovial fluid PLA2, human synovium and articular cartilage were found to contain large quantities of the enzyme. In rheumatoid arthritis (RA), PLA2 activity in synovium, superficial and deep layers of articular cartilage was 20 +/- 14 (SEM), 168 +/- 62 and 533 +/- 176 nmol/min/mg protein respectively. Corresponding values in osteoarthritis (OA) were 49 +/- 11, 569 +/- 109 and 1709 +/- 243 nmol/min/mg protein, all significantly higher (p less than .01) than in RA. Nasal septal cartilage contained much less PLA2, 19 +/- 5.6. PLA2 in human articular and nasal cartilage has sn-2 specificity, a neutral pH optimum and absolute calcium dependence. High PLA2 concentration in articular cartilage may imply that, at least in part, cartilage is the source of PLA2 in the joint space. Since RA cartilage and synovium have less PLA2 activity than the corresponding OA tissues, additional sources of PLA2 in RA synovial fluids are implicated.

Arthritis, Rheumatoid↗
PubMed1991

Extracellular phospholipase A2 secretion is a common effector pathway of interleukin-1 and tumour necrosis factor action.

Inflammatory processes are characterized by increased levels of extracellular phospholipase A2 (PLA2) and cytokines such as interleukin 1 (IL-1) and tumour necrosis factor (TNF). IL-1, TNF and PLA2 share a number of proinflammatory, arthritogenic effects. The sequential induction, first of the cytokines followed by PLA2, suggests that these cytokines may regulate synthesis and secretion of PLA2. To test this postulate, foetal rat calvarial bone-forming cells (FRCC) were treated with recombinant human IL-1 and TNF and extracellular PLA2 release was quantitated. Both IL-1 and TNF induced the de novo synthesis of PLA2 in a concentration-dependent manner. Continuous exposure of FRCC in primary culture to IL-1 (50 units/ml) over 15 days resulted in as much as 100-fold increase in PLA2 secretion. IL-1 (50 units/ml) added to post-confluent cultures for a 48-h pulse increased PLA2 activity 9.4-fold. The combination of IL-1 (50 units/ml) and TNF (500 units/ml) was synergistic with an observed increase in extracellular PLA2 secretion of 146-fold following a 48-h pulse. Interleukin-6, alone or in combination with IL-1 or TNF, did not further enhance PLA2 synthesis of secretion. Cytokine-induced synthesis of PLA2 was inhibited 80% by 10 microM cycloheximide but not by dexamethasone over the range of 10(-6) to 10(-8) M. FRCC-derived PLA2 was neutral-active with a pH optimum of 6-7.5 and was calcium-dependent with optimal activity in the presence of 2-7 mM calcium. It had absolute 2-acyl specificity using micellar phosphatidylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Acute lung injury induced by phospholipase A2. Structural and functional changes.

On the basis of the observation that serum levels of phospholipase A2 (PLA2) are elevated in pancreatitis and systemic sepsis, and the association of these conditions with the subsequent development of acute lung injury, the present investigation examined the structural and physiologic consequences of intratracheal administration of PLA2 to adult male rats. Rats received direct intratracheal instillation of either control vehicle or 40,000 units/kg of PLA2 repurified from Naja naja venom. Animals treated with PLA2 showed higher cumulative mortality (33% versus 0%, n = 79; p less than 0.01) than did their control littermates. The PLA2-treated animals showed histologic evidence of acute lung injury characterized by interstitial and alveolar edema, accumulation of inflammatory cells, and alveolar wall thickening, which reached maximal severity 48 h after enzyme instillation. Forty-eight hours after PLA2 administration experimental animals had lower arterial oxygen tensions (73.9 +/- 7.66 mm Hg versus 96.7 +/- 2.52 mm Hg, mean +/- SEM; p less than 0.01), higher alveolar-arterial oxygen gradients (35.3 +/- 6.3 mm Hg versus 18.8 +/- 1.42 mm Hg, p less than 0.01), and higher wet-dry lung weight ratios (5.08 +/- 0.26, mean +/- SEM, n = 7 versus 3.29 +/- 0.08, n = 3; p less than 0.002) than did control animals. Lung lavage from experimental animals 48 h after PLA2 instillation showed increased total cell counts [(26.6 +/- 5.04) x 10(6) cells versus (4.69 +/- 1.48) x 10(6) cells; p less than 0.01], an increased percentage of neutrophils (34.2 +/- 4.6% versus 1.25 +/- 0.25%, mean +/- SEM; p less than 0.01), and increased protein concentrations in lavage fluid (0.38 +/- 0.06 mg/ml, mean +/- SEM, n = 4 versus 0.27 +/- 0.02 mg/ml, n = 5; p less than 0.05). The histologic and physiologic abnormalities had largely resolved by 240 h. These results suggest that PLA2 may be a potent mediator of lung inflammation and that intratracheal administration of PLA2 to adult rats may provide a useful experimental model of acute lung injury.

Acute-Phase Reaction↗
PubMed1991

A predictive model for the clearance of soluble phospholipase A2 during septic shock.

Circulating phospholipase A2 (PLA2) has been recognized as a mediator of cardiovascular collapse in septic shock. Proximal mediators of endotoxemia, including tumor necrosis factor and interleukin 1, induce PLA2 synthesis and release, but the factors regulating PLA2 elimination are unknown. Similarly, the kinetics of PLA2 clearance during recovery from septic shock have not been examined. An autoregressive mathematical model was developed to describe the rate of PLA2 clearance during the recovery phase of septic shock. This model (which estimates that the current day's PLA2 level is 77% of the previous day's level), accounted for 89% of the variability seen in the data. The estimated circulating half-life of soluble PLA2 in septic shock in man was 32 hours. Since elevation in serum PLA2 activity is closely associated with bacteremia or endotoxemia, a significant deviation from predicted PLA2 values may denote impending relapse.

Adult↗
PubMed1991

The role of phospholipase A2 in the physiopathology of osteoarthritis.

High activity of phospholipase A2 (PLA2) was found in 58 synovial fluids of patients with osteoarthritis (OA), with a range of 2.2-75.1 nmol/min/ml and mean +/- SEM of 22.0 +/- 1.4 nmol/min/ml. This PLA2 was a calcium dependent enzyme composed of 2 isoforms called A and B. Twelve of 25 patients with OA (48%) were found to have high circulating PLA2, but no correlation to the numbers or size of affected joints was found. High concentrations of PLA2 were detected in human articular cartilage ranging from 33 to 4257 nmol/min/mg protein. The deep layers of the cartilage contained on average 3-fold more PLA2 than the superficial layers. Also synovial cells cultures and chondrocyte cultures that derived from OA joints synthesized and released PLA2 extracellularly. Since PLA2 is proinflammatory, its role in the inflammation that complicates OA process is highly probable. Further studies of PLA2 impact on OA joints and clinical trials with PLA2 inhibitors in OA are warranted.

Cartilage, Articular↗
PubMed1990

Phospholipase A2 activation is the pivotal step in the effector pathway of inflammation.

Our understanding of the mechanisms of initiation and propagation of local and systemic inflammatory processes is clearly imperfect if one uses the available therapeutic modalities as a yardstick. While glucocorticoids are potent anti-inflammatory drugs, the pharmacologic target of this class of agents has not been identified with certainty, and the use of steroids is fraught with the risk of considerable and potentially dangerous side effects. On the other hand, non-steroidal anti-inflammatory drugs (NSAIDS), while more specific, are relatively weak anti-inflammatory compounds and frequently require the addition of more potent agents. Cytotoxic drugs or anti-metabolites effectively suppress acute and chronic inflammatory reactions, but also predispose to infection and initiate the development of neoplasms following long-term exposure. The inadequacy and relative non-specificity of these approaches underscore the deficiencies in our understanding of the principles that govern these responses. A better understanding of these processes will be applicable to broad categories of human disease including autoimmunity, the collagen vascular diseases, aberrations in host defense and the response to trauma and infection.

Animals↗
PubMed1990

Compartmental heterogeneity of soluble phospholipases A.

Multiple forms of soluble phospholipase A2 (PLA2) are known to coexist in venoms of individual reptilian species. While similar observations in several mammalian species suggest that this is a common phenomenon, the functional implications are not yet understood. In attempting to devise therapeutic strategies for treatment of inflammatory disorders by inhibition of PLA2, it is imperative to define the various PLA2 species in the relevant compartments. Herein, we report the presence of three PLA2 isotypes in rheumatoid arthritis serum, one pancreatic and two nonpancreatic phospholipases A2. The pancreatic and one of the nonpancreatic forms were optimally active in 7 mM calcium at pH 7.5. The other nonpancreatic form was calcium-independent and optimally active at pH 7.0. Only the calcium-dependent nonpancreatic form was observed in rheumatoid synovial fluid. Of the three serum isotypes, only the calcium-dependent nonpancreatic form correlated with markers of disease activity, such as the joint count and Landsbury index. Therefore, not all soluble or circulating phospholipases A2 are relevant to inflammatory processes. Selective inhibition of the proinflammatory form of PLA2 may prove to have some therapeutic benefit while minimizing the possible adverse effects of this form of intervention.

Arthritis, Rheumatoid↗
PubMed1990

Synthesis and release of phospholipase A2 by unstimulated human articular chondrocytes.

High activity of proinflammatory, type II phospholipase A2 (PLA2) was found in synovial fluids (SF) in inflammatory arthritis. In search for the sources of this PLA2, we cultured human articular chondrocytes and cartilage explants from healthy, osteoarthritic and rheumatoid joints. All cultures, unstimulated by cytokines, released PLA2 extracellularly. Cultures obtained from the deep layers of the cartilage released more PLA2 than those obtained from the superficial layers. Deep layer explants released 0.38 to 18.16 pmol/min/mg protein PLA2/day, whereas superficial layer explants released 0.39-3.18 pmol/min/mg/day. Chondrocyte cell cultures continuously released PLA2, in the first day 909-46347 pmol/min/(10)6 cells and after 9-26 days of culture 166-2115 pmol/min/10(6) cells. PLA2 released from chondrocytes was calcium dependent and had optimum activity at pH 7.5. Cycloheximide markedly inhibited its release. Chondrocyte cultures also released muramidase (LZM) but there was no correlation between PLA2 and LZM release. It may be concluded that cytokine unstimulated human articular chondrocytes synthesize and release PLA2 extracellularly which is similar to that found in the SF. Thus, chondrocytes may possibly serve as one of the sources of intraarticular PLA2.

Arthritis, Rheumatoid↗
PubMed1990

Hypophospholipasemia A2 in systemic sclerosis.

Phospholipase A2 (PLA2), total and pancreatic, were quantitated in 91 sera of patients with systemic sclerosis (SSc). The mean total PLA2 of 216 +/- 161 U/ml (SD) was significantly lower (p less than 0.001) than in controls (317 +/- 128 U/ml). In 55 of 91 patients (60%) PLA2 was more than 1 SD and in 6 (7%) more than 2 SD below the normal mean. Serum pancreatic PLA2 was also significantly lower in SSc. The prevalence of low serum total PLA2 was significantly greater (p less than 0.001) than in healthy adults, or in patients with rheumatoid arthritis, systemic lupus erythematosus or vasculitis. Repeat assays of PLA2 activity in 10 patients with SSc documented persistence of low PLA2. Among 76 patients with SSc with complete clinical and laboratory assessment, there were 48 with low and 28 with normal (or slightly elevated) PLA2. These 2 groups showed no differences in disease manifestation or therapy. The group with low serum PLA2 had lower erythrocyte sedimentation rates (p less than 0.0005) and lower neutrophil (p less than 0.05) and monocyte counts (p less than 0.025) in the peripheral blood. The finding of low serum PLA2 activity adds to the spectrum of arachidonic acid pathway abnormalities associated with SSc, and may in part be related to the paucity of inflammatory changes observed in this disease.

Adult↗
PubMed1989

Cloning and recombinant expression of phospholipase A2 present in rheumatoid arthritic synovial fluid.

Synovial fluid from arthritic patients contains multiple forms of phospholipase A2 (PLA2), as resolved by high performance liquid chromatography (Seilhamer, J.J., Plant, S., Pruzanski, W., Schilling, J., Stefanski, E., Vadas, P., and Johnson, L. K. (1989) J. Biochem. (Tokyo), submitted for publication). Here we describe the cloning of a human 4.5-kilobase gene and 800-base pair cDNA encoding the form representing the major peak of activity and protein mass (peak A). The clones encode a mature peptide of 124 amino acids, which follows a prepeptide of 20 residues. The deduced amino acid sequence constitutes an enzyme of the "Type II" class of PLA2s, and resembles PLA2s from other mammalian sources. This represents the first report of a full length mammalian non-pancreatic PLA2 sequence. Active transcription of this PLA2 gene was detected in two different inflammatory cell sources. Recombinant human peak A PLA2 was expressed in vaccinia as a secreted protein which accumulated in conditioned medium.

Amino Acid Sequence↗