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Biomedical subjects

P Vadas

Publications and source records attributed to P Vadas.

At least 19 recordsLinked to original sources

Detection of peanut allergens in breast milk of lactating women.

CONTEXT: Most individuals who react to peanuts do so on their first known exposure. A potential but unproven route of occult exposure resulting in sensitization to peanut is via breast milk during lactation. OBJECTIVE: To investigate the ability of maternal dietary peanut protein to pass into breast milk during lactation. DESIGN AND SETTING: Clinical investigation conducted at 2 North American hospitals from March 1999 to October 2000. PATIENTS: Twenty-three healthy, lactating women aged 21 to 35 years. INTERVENTION: Each woman consumed 50 g of dry roasted peanuts, after which breast milk samples were collected at hourly intervals. MAIN OUTCOME MEASURES: Presence in breast milk of total peanut protein, analyzed by a sandwich enzyme-linked immunosorbent assay, and 2 major peanut allergens, Ara h 1 and Ara h 2, detected by immunoblot analysis. RESULTS: Peanut protein was detected in 11 of 23 subjects. It was detected in 10 subjects within 2 hours of ingestion and in 1 subject within 6 hours. The median peak peanut protein concentration in breast milk was 200 ng/mL (mean, 222 ng/mL; range, 120-430 ng/mL). Both major peanut allergens Ara h 1 and Ara h 2 were detected. CONCLUSIONS: Peanut protein is secreted into breast milk of lactating women following maternal dietary ingestion. Exposure to peanut protein during breastfeeding is a route of occult exposure that may result in sensitization of at-risk infants.

2S Albumins, Plant↗

Regulation of the cellular expression of secretory and cytosolic phospholipases A2, and cyclooxygenase-2 by peptide growth factors.

Secretory group II (sPLA2) and cytosolic (cPLA2) phospholipases A2 and cyclooxygenase-2 (Cox-2) play a pivotal role in release of proinflammatory eicosanoids. Excessive activity of sPLA2 per se can also propagate inflammation. Endogenous control of the above enzymes has not been completely elucidated. We investigated the combined impact of promoting cytokines and inhibitory peptide growth factors on the expression of mRNA of the above enzymes, on protein content and extracellular release of sPLA2 and on PGE2 production in osteoblasts (FRCO). The synthesis and release of sPLA2 were enhanced by about 20-fold by 0.5 ng/ml IL-1beta or by 50 ng/ml of TNFalpha. Coaddition of both cytokines resulted in synergistic 150-fold increase in the release of sPLA2 implying the existence of two paths of induction. IL-1beta and TNFalpha markedly enhanced the transcription of sPLA2 mRNA. Kinetic study showed that IL-1/TNF initiated sPLA2 release after 12 h, reaching maximum at 48 h. IL-1alpha was a weak stimulator of sPLA2 release, whereas IL-6, IL-8, IGF, IFN-gamma, growth hormone, insulin and GM-CSF were not stimulatory. Peptide growth hormones TGFbeta, PDGF-BB, EGF and bFGF markedly inhibited the extracellular release of sPLA2. TGFbeta and PDGF-BB significantly reduced the level of sPLA2 mRNA, thus acting upon transcription whereas EGF and bFGF were not inhibitory, acting rather upon the translational or posttranslational steps. IL-1/TNF and growth factors had no significant effect on cPLA2 mRNA expression. Cox-2 mRNA expression was markedly enhanced by IL-1/TNF and suppressed by all growth factors tested. Cytokines enhanced the extracellular release of PGE2 and further enhancement was induced by growth factors with the exception of TGFbeta. Cycloheximide abolished completely the release of sPLA2 and markedly reduced the release of PGE2 from cytokine-stimulated FRCO, regardless of whether growth factors were present or not. NS-398, a specific inhibitor of Cox-2 abolished almost completely the release of PGE2 from cytokine-stimulated cells, regardless of the presence of growth factors. Thus, different signalling mechanisms are involved in the impact of growth factors on mRNA expression of sPLA2, cPLA2 and Cox-2. The differences between the impact on FRCO sPLA2 and that reported in other cells, imply that endogenous control of arachidonic acid cascade is cell-specific.

Animals↗

Inhibition of type I and type II phospholipase A2 by phosphatidyl-ethanolamine linked to polymeric carriers.

We have previously shown that cell surface proteoglycans protect the cell membrane from the action of extracellular phospholipase A2 (PLA2) enzymes [Dan, P., Nitzan, D. W., Dagan, A., Ginsburg, I., and Yedgar, S. (1996) FEBS Lett. 383, 75-78]. Cell-impermeable PLA2 inhibitors (ExPLIs) were prepared by linking phosphatidylethanolamine (PE) to polymeric carriers, specifically, carboxymethylcellulose, heparin, or hyaluronic acid. The structure of these inhibitors enables the incorporation of their PE moiety into the membrane while the polymer remains at the membrane surface. In the present study, we show that the ExPLIs are effective inhibitors of the hydrolysis of different phospholipids in biological (Escherichia coli) and model (phospholipid vesicle) membranes, by diverse types of PLA2 enzymes, specifically human recombinant synovial fluid and C. atrox (type II), as well as Naja mocambique and porcine pancreatic (type I) PLA2. It is proposed that the external polymers of the ExPLIs, which are anchored to the membrane by the PE, mimic the naturally occurring cell surface proteoglycans and similarly protect membranes from the action of exogenous PLA2.

Animals↗

Induction of secretory phospholipase A2 confirms the systemic inflammatory nature of adjuvant arthritis.

Adjuvant arthritis (AA) is an accepted model of inflammatory arthritis. Until now, however, there is little information about inflammatory mediators, specifically in relation to the arachidonic acid cascade in AA. Our objective was to study the expression of secretory (sPLA2) and cytosolic (cPLA2) phospholipases A2 in various organs during the course of AA. AA was induced in Lewis rats which were sacrificed at days 0, 7, 14, 21, 28 and 42. Expression of sPLA2 mRNA and protein and mRNA of cPLA2 in paws, regional lymph nodes, spleen, liver, lungs and aorta was investigated. Serum sPLA2 activity increased from 15213 +/- 1131 to a maximum of 32,455 +/- 4109 nmol/30' on day 21. Maximal increase in sPLA2 mRNA in paws, lung and aorta was observed on day 14, and in the lymph nodes and spleen on day 28. In the liver, trace levels were found with no corresponding protein expression. In paws, lung, aorta and lymph nodes maximum increase in sPLA2 protein was noted on day 14 whereas the spleen showed constant sPLA2 protein level during AA. cPLA2 mRNA detected in all organs, did not significantly change during the course of AA, with the exception of regional lymph nodes where the message increased between 14 and 28 day. Induction of mRNA and protein of sPLA2 in several organs is an evidence that AA is a systemic inflammatory process. The parallelity of the sPLA2 expression to the severity of inflammatory process, implies that sPLA2 may play pathogenic role in AA. Lack of enhancement of cPLA2 mRNA may mean that this enzyme is either not induced in AA, or it increases earlier in the course of the inflammatory process.

Animals↗

Chemically modified non-antimicrobial tetracyclines inhibit activity of phospholipases A2.

OBJECTIVE: Tetracyclines have been recognized as useful agents for therapy of inflammatory arthritides. However, prolonged use of tetracyclines is limited by their detrimental antimicrobial properties. Recently, a group of chemically modified tetracyclines (CMT) devoid of antimicrobial properties has been synthesized. Some CMT were found to inhibit various matrix metalloproteinases (MMP). We reported previously that antimicrobial tetracyclines inhibit the activity of proinflammatory secretory group II phospholipase A2 (sPLA2). The objective of this study was to detect whether non-antimicrobial CMT also inhibit sPLA2 and other phospholipases A2. METHODS: Ten synthetic CMT were tested for inhibition of sPLA2 human and porcine PLA2, and Naja naja PLA2. PLA2 activity was assessed by radiolabeled Escherichia coli assay using standard and high calcium concentrations. RESULTS: Six of 10 CMT inhibited sPLA2 activity at concentrations close to or lower than 50 microg/ml. All 6 CMT had identical C1-3 and C10-12a positions in the 4-ringed nucleus of the tetracycline molecule. Calcium concentrations up to 20 mM did not eliminate the inhibitory activity of CMT. Inhibition of other PLA2 was induced by some CMT, all but one (CMT-9) belonging to the group of strong inhibitors of sPLA2. Thus, inhibition of PLA2 different from sPLA2 does not necessarily require identical C1-3/C10-12a residues. CONCLUSION: Since CMT, which inhibit proinflammatory sPLA2, are also inhibitors of some MMP, they may be useful for therapy of inflammatory diseases in which both MMP and sPLA2 are overexpressed.

Animals↗

Lipoproteins are substrates for human secretory group IIA phospholipase A2: preferential hydrolysis of acute phase HDL.

Group IIA secretory phospholipase A2 is an acute phase enzyme, co-expressed with serum amyloid A protein. Both are present in atherosclerotic lesions. We report that human normal and acute phase high density lipoproteins and low density lipoprotein are effective substrates for human group IIA phospholipase A2. The enzyme hydrolyzed choline and ethanolamine glycerophospholipids at the sn -2 position resulting in an accumulation of the corresponding lysophospholipids, including the unhydrolyzed alkyl and alkenyl ether derivatives. The hydrolysis of acute phase high density lipoprotein was 2- to 3-fold more rapid and intensive than of normal high density lipoprotein. The hydrolysis of lipoproteins was noted at enzyme concentration as low as 0.05 microgram/mg protein, which was within the range observed in the circulation in acute and chronic inflammatory diseases. The enzyme hydrolyzed the different molecular species of the residual glycerophospholipids in proportion to their mass, showing no preference for the release of arachidonic acid. Group IIA phospholipase A2 preferentially attacked the hydroxy and hydroperoxy linoleates and possibly other oxygenated fatty acids, which were released from the glycerophospholipids at early times of incubation. There was no effect on the content or molecular species composition of the sphingomyelins or neutral lipids of the lipoproteins. In conclusion, human plasma lipoproteins are the first reported natural biological substrates for human group IIA phospholipase A2. The enhanced hydrolysis of acute phase high density lipoproteins is probably due to its association with serum amyloid A protein, which enhances the activity of the enzyme and may promote its penetration to the lipid monolayer. As sPLA2-induced hydrolysis of the lipoproteins leads to accumulation of lysophosphatidylcholine and potentially toxic oxygenated fatty acids, overexpression of this enzyme may be proatherogenic.

Acute-Phase Reaction↗

Inhibition of extracellular release of proinflammatory secretory phospholipase A2 (sPLA2) by sulfasalazine: a novel mechanism of anti-inflammatory activity.

Sulfasalazine is widely used in rheumatoid arthritis and inflammatory bowel diseases. The mechanisms of its activity have not been elucidated. In leukocytes, sulfasalazine and its analogue, CL 42A, inhibited the formation of leukotrienes and possibly of the second messenger compounds at the level of phospholipase C. Partial inhibition of interleukin-lbeta (IL-1beta), IL-6 and tumor necrosis factor-alpha (TNF-alpha) was also found. Since the synthesis of eicosanoids is induced by phospholipase A2 and since secretory phospholipase A2 (sPLA2) is proinflammatory, we investigated the impact of sulfasalazine and related compounds on mRNA, protein synthesis, and release of sPLA2 from osteoblasts. Sulfasalazine and CL 42A markedly inhibited extracellular release of sPLA2. The impact of sulfasalazine was evident at 50 microM (P < 0.001) and maximal at 400 microM, and that of CL 42A at 10 microM (P < 0.001) and 200 microM, respectively. Split products of sulfasalazine, 5-aminosalicylic acid (400 microM) and sulfapyridine (400 microM), had no impact. The effect of sulfasalazine and CL 42A was evident regardless of whether the cells were stimulated with IL-1beta/TNF-alpha, lipopolysaccharide/forskolin, or dibutyryl-cAMP. Sulfasalazine and CL 42A did not alter the level of sPLA2 mRNA. Exposure of stimulated fetal rat calvaria osteoblasts (FRCO) to sulfasalazine did not show accumulation of the intracellular sPLA2 protein as tested by western blot; however, enzymatic activity of PLA2 in disrupted cells was definitely increased. Thus, the impact is on the post-transcriptional release of sPLA2 rather than on the synthesis. There was also an increase in the extracellular release of prostaglandin E2 from FRCO exposed to sulfasalazine or to CL 42A. In contrast, sulfasalazine had no effect on the extracellular release of gelatinase from the cells or on mRNA of cytosolic PLA2 or cyclooxygenase 2. We conclude that the anti-inflammatory activity of sulfasalazine may be related, in part, to the selective inhibition of the extracellular release of proinflammatory sPLA2.

Anti-Inflammatory Agents↗

Group II phospholipases A2 are indirectly cytolytic in the presence of exogenous phospholipid.

Systemic inflammatory response syndromes including septic shock and salicylate poisoning are associated with high circulating levels of secretory phospholipase A2 (sPLA2). In septic shock, sPLA2 has been implicated in the pathogenesis of multisystem organ failure, presumably by a direct cytotoxic effect on cells. The cytotoxicity of recombinant human sPLA2 and a venom PLA2 were examined on human erythrocytes, erythroleukemia cells and U937 cells. Neither the human nor venom PLA2's were directly injurious to target cells. However, in the presence of liposomal phospholipids, both PLA2's induced irreversible cell injury. Whereas venom PLA2 was cytolytic in the presence of either phosphatidylcholine or phosphatidylethanolamine (PE), rh-sPLA2 caused cell death only in the presence of PE. These data show that normal unperturbed cells are resistant to injury from PLA2, and that additional cofactors such as PE are required to induce cell injury.

Cell Survival↗

Coordinate expression of group II phospholipase A2 and the acute-phase proteins haptoglobin (HP) and alpha1-anti-chymotrypsin (ACH) by HepG2 cells.

The early response to inflammation is characterized by the synthesis of a variety of proteins under cytokine and glucocorticoid control. During episodes of infection or inflammation, a secretory phospholipase A2 (sPLA2) appears in the circulation along with a variety of acute-phase proteins (APP), suggesting possible common regulatory elements amongst sPLA2 and APP. Using the human hepatoma line, HepG2, regulation of sPLA2 expression was examined in relation to synthesis of HP and ACH. The patterns of induction of sPLA2, HP and ACH were distinct for each of IL- 1, tumour necrosis factor (TNF) and IL-6, oncostatin M, IL-11 and leukaemia inhibitory factor. Dexamethasone had an enhancing effect on IL-6-induced expression of HP and ACH, but inhibited sPLA2 expression by 50%. Both 8-bromo-cAMP and dibutyryl cAMP increased sPLA2 expression (48.8-fold and 64.2-fold, respectively), whereas KT5720, an inhibitor of protein kinase A, down-regulated cytokine-induced sPLA2 synthesis by 51%. These data show that a panel of cytokines induced varying patterns of up-regulation of sPLA2, ACH and HP. Although dexamethasone potentiated IL-6-induced APP expression in HepG2 cells, it suppressed sPLA2 expression in a dose-dependent manner. In several respects, sPLA2 regulation is similar to that of HP and ACH, but a notable difference is the reciprocal effect of glucocorticoids on sPLA2 expression compared with that of ACH and HP.

Acute-Phase Proteins↗

Microtubule depolymerization selectively down-regulates the synthesis of proinflammatory secretory nonpancreatic phospholipase A2.

Microtubule depolymerizing agents (MTD) diminish the expression of cell surface receptors for TNF-alpha. Because TNF-alpha along with IL-1 beta markedly enhance the gene expression and extracellular release of proinflammatory secretory nonpancreatic phospholipase A2 (sPLA2), we tested the impact of MTD on the expression of sPLA2. We report that MTD markedly inhibit the expression and release of sPLA2 by fetal rat calvarial osteoblasts (FRCO), which synthesize and release sPLA2. When FRCO were pretreated with colchicine and then stimulated with IL-1 beta 0.2 ng/ml and TNF-alpha 25 ng/ml (IL-1/TNF), minute quantities of colchicine (1.25 nM) reduced the released sPLA2 activity to 11% of that in controls. IC50 was 0.75 nM. When IL-1/TNF and colchicine were added simultaneously, similar inhibition (8% of that in controls) required higher concentrations of colchicine (0.125 microM). IC50 was 68.75 nM. When FRCO were prestimulated by IL-1/TNF, much higher concentrations of colchicine were required to reduce sPLA2 activity. MTD inhibited the expression of sPLA2 by a mechanism(s) different from the way in which they impact TNF surface receptors, because they inhibited sPLA2 expression in FRCO stimulated by IL-1 beta or by cell-permeable cAMP analogs. Colchicine (1 microM) reduced the expression of sPLA2 induced by dibutyryl cAMP (2 mM) and 8-bromo-cAMP (4 mM) to 38% and 58% of that n controls, respectively. Photoinactivated lumicolchicines beta and gamma were noninhibitory. Microtubular stabilizer taxol (5 microM) abolished inhibitory activity of colchicine, increasing the expression of sPLA2 3.2-fold compared with that in control cells cultured without taxol. Other MTD, such as vinblastine (0.01 microM), inhibited sPLA2 release to 27% of the controls, whereas nocodazole (10 microM) was less inhibitory. Northern blot analysis of FRCO showed that sPLA2 mRNA was greatly induced by IL-1/TNF. The induction of sPLA2 mRNA by IL-1/TNF was nearly completely abolished by colchicine in a dose-related manner. Western blot analysis of intra- and extracellular sPLA2 protein showed complete inhibition of the synthesis by MTD. To determine whether the inhibition of sPLA2 is selective, mRNA levels of cytosolic PLA2 and of inducible cyclooxygenase-2 were investigated. Colchicine had no effect on the mRNA levels of these two enzymes, which suggests that the inhibitory effect of MTD on sPLA2 expression is selective and occurs at the transcriptional level. Thus, the microtubular system plays a significant role in the synthesis of proinflammatory sPLA2, a fact that may explain in part the anti-inflammatory activity of microtubular disrupters.

Animals↗

Anaphylactic shock induced by intraarticular injection of methylprednisolone acetate.

There are numerous reports of hypersensitivity reactions to corticosteroids. However, cases of anaphylactic shock after intraarticular injection of corticosteroids are exceedingly rare. We describe a case of anaphylaxis in a 31-year-old woman after intraarticular injection of synthetic methylprednisolone acetate. Immediately after injection she developed sneezing, angioedema, tachycardia, and marked hypotension. She responded promptly to treatment with subcutaneous epinephrine. She had received uneventfully one intraarticular injection of the same compound 4 years earlier. Intradermal skin testing showed strong reactivity to methylprednisolone acetate suspension, moderate reactivity to hydrocortisone, and weak reactivity to betamethasone. Tests with dexamethasone, triamcinolone, lidocaine, latex and nonsteroid constituents of the injected suspension including polyethylene glycol, polysorbate 80, mono and dibasic sodium phosphate, and myristyl-gamma-picolinium chloride were negative. This patient had developed anaphylaxis due to methylprednisolone acetate alone. Although such events are very rare, it is advisable to keep injectable epinephrine in the offices of rheumatologists.

Adrenal Cortex Hormones↗

Secretory non-pancreatic phospholipase A2 and cyclooxygenase-2 expression by tracheobronchial smooth muscle cells.

Lipid mediators of inflammation, contribute to airway hyper-reactivity in asthma. Since production of lipid mediators is largely regulated by phospholipase A2 (PLA2), and since PLA2 expression in mesenchymal cells is induced by cytokines and other signals, we examined PLA2 expression by rat tracheobronchial smooth muscle cells (TBSMC). PLA2 expression in TBSMC cultures was markedly increased by tumour-necrosis factor (TNF) alpha (130-fold) and interleukin-1beta (IL-1beta) (7.4-fold). Lipopolysaccharide (LPS;100 ng/ml) resulted in a 51-fold increase in extracellular PLA2 activity. PLA2 expression by LPS-stimulated or cytokine-stimulated cells was downregulated by dexamethasone. Whereas forskolin or dibutyrl cAMP increased PLA2 activity, inhibition of protein kinase A but not tyrosine kinase reduced PLA2 expression. Northern blot analysis showed that TNF alpha and IL-1beta increased both PLA2 and inducible cyclooxygenase (Cox-2) mRNA transcription. Addition of dexamethasone substantially blunted the increase in PLA2 and Cox-2 mRNA. In contrast, the level of Cox-1 mRNA was very low and did not change with the various treatments. Since proinflammatory lipid mediators have been implicated in the pathogenesis of asthma and PLA2 activity regulates generation of these lipid mediators, cytokine-stimulated synthesis and release of PLA2 by airway smooth cells may contribute to the potentiation of airway inflammation in asthma.

Animals↗

Secretory phospholipase A2 as an index of disease activity in rheumatoid arthritis. Prospective double blind study of 212 patients.

OBJECTIVE: A limited retrospective study of patients with rheumatoid arthritis (RA) found that serum secreted phospholipase A2 (sPLA2) activity correlates with disease activity (J Rheumatol 1988; 15:1351-5). To assess the strength of this relationship we investigated prospectively 212 patients with RA using a double blind approach. METHODS: 212 patients who fulfilled the 1987 ACR criteria for RA had 420 clinical and laboratory assessments. 65 patients were assessed on one occasion and 147 on multiple occasions (a mean of 2.41 visits/patient). sPLA2 was tested by an independent investigator. RESULTS: sPLA2 activity assessed as a dichotomous variable (less or more than mean +/- 2 SD) correlated highly (p < 0.005) with Lansbury index, number of effusions, number of damaged joints, erythrocyte sedimentation rate (ESR), platelet count, and low hemoglobin. Univariate and multivariate regression analyses showed significant correlations with Lansbury index, active and effused joints, hemoglobin, platelet count, and ESR. The best correlation was observed in a multivariate model that included Lansbury index, ESR, and platelet count (r = 0.60). Analysis of longitudinal changes in sPLA2 activity in 147 patients assessed more than once showed that sPLA2 correlates significantly with Lansbury index, active and effused joints, and hemoglobin. CONCLUSION: Serum sPLA2 activity correlates significantly with Lansbury index, active and effused joints, ESR, platelet court, and hemoglobin. Thus, sPLA2 can serve as an index of disease activity in RA.

Adolescent↗

A natural disruption of the secretory group II phospholipase A2 gene in inbred mouse strains.

The synovial fluid or group II secretory phospholipase A2 (sPLA2) has been implicated as an important agent involved in a number of inflammatory processes. In an attempt to determine the role of sPLA2 in inflammation, we set out to generate sPLA2-deficient mice. During this investigation, we observed that in a number of inbred mouse strains, the sPLA2 gene was already disrupted by a frameshift mutation in exon 3. This mutation, a T insertion at position 166 from the ATG of the cDNA, terminates out of frame in exon 4, resulting in the disruption of the calcium binding domain in exon 3 and loss of both activity domains coded by exons 4 and 5. The mouse strains C57BL/6, 129/Sv, and B10.RIII were found to be homozygous for the defective sPLA2 gene, whereas outbred CD-1:SW mice had variable genotype at this locus. BALB/c, C3H/HE, DBA/1, DBA/2, NZB/BIN, and MRL lpr/lpr mice had a normal sPLA2 genotype. The sPLA2 mRNA was expressed at very high levels in the BALB/c mouse small intestine, whereas in the small intestine of the sPLA2 mutant mouse strains, sPLA2 mRNA was undetectable. In addition, PLA2 activity in acid extracts of the small intestine were approximately 40 times higher in BALB/c than in the mutant mice. Transcription of the mutant sPLA2 gene resulted in multiple transcripts due to exon skipping. None of the resulting mutant mRNAs encoded an active product. The identification of this mutation should not only help define the physiological role of sPLA2 but also has important implications in mouse inflammatory models developed by targeted mutagenesis.

Amino Acid Sequence↗

Serum amyloid A protein enhances the activity of secretory non-pancreatic phospholipase A2.

The acute-phase proteins serum amyloid A protein (SAA) and secretory phospholipase A2 (sPLA2) are simultaneously expressed during inflammatory conditions. SAA associates with high-density lipoprotein (HDL) altering its physicochemical composition. We found that purified acute-phase SAA, but not the constitutive form, markedly enhances the lipolytic activity of sPLA2 in a dose-related manner with phosphatidylcholine/lysophosphatidylcholine or phosphatidylethanolamine/lysophosphatidylethanolamine liposomal substrates. Normal HDL was found to reduce activity of sPLA2 in a dose-dependent manner, but when acute-phase HDL containing 27% SAA was tested, it enhanced sPLA2 activity. Immunopurified monospecific antibodies against SAA completely abolished the enhancing activity of SAA and acute-phase HDL. Given the central role of HDL in lipoprotein metabolism, the interaction between HDL, SAA and sPLA2 may account for changes detected in lipoprotein metabolism during the acute phase.

Acute-Phase Proteins↗