Identification of a calcium-independent phospholipase A2 in rat lung cytosol and differentiation from acetylhydrolase for 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF-acether)

Nijssen, Jik; Roosenboom, C.F.P.; Bosch, H. van den

doi:10.1016/0005-2760(86)90050-0

Cited by 61 publications

(16 citation statements)

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“…Therefore, PAF may be involved in a variety of immunopathological reactions trig gered by several effector cells. However, the potent bi ological effect of PAF in vivo is under strict control of multiple regulatory mechanisms [24][25][26][27][28][29][30][31]. The concen tration of PAF in the biological environment is in fact regulated by the rate of biosynthesis and degradation.…”

Section: Discussionmentioning

confidence: 99%

“…In vivo the enhanced synthesis may be balanced by plasma inhibitors that prevent the increased activity of bio synthetic enzymes [23]. Once formed, however, PAF may be inactivated intracellularly or in biological fluids by the specific PAF acetylhydrolase [24][25][26][27][28][29]. Therefore, the biological relevance of PAF may be re lated to an increased synthesis due to appropriate stimulation and/or inactivation of plasma inhibitors of PAF biosynthesis or to reduced degradation.…”

Section: Discussionmentioning

confidence: 99%

“…The regu lation of the PAF concentration in biological fluids and in cells is related to several factors; first, the re quirement of an appropriate stimulus to trigger the biosynthetic pathway [22]; second, the presence in plasma of proteins that act as specific inhibitors of bi osynthetic pathways [23] and third, its degradation by a specific PAF acetylhydrolase to form the biologi cally inactive lyso-PAF [24,25]. Both an intracellular [26,27] and a plasma [28] form of the enzyme have been described. In human plasma, this enzyme has been characterized as acid-labile and Ca2+-independent, and is inactivated by heating at 65 °C for 30 min, and by pronase and trypsin, but is insensitive to pa pain [24,25,29], PAF acetylhydrolase activity has been reported to be mainly associated with lipopro teins [24,25].…”

Section: Introductionmentioning

confidence: 99%

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Release of Platelet-Activating Factor in Systemic Lupus erythematosus

Tetta

Bussolino

Modena

et al. 1990

Int Arch Allergy Immunol

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The biologically active 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (platelet-activating factor; PAF) is inactivated in plasma mainly by a specific PAF acetylhydrolase (1-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine acetylhydrolase; EC 3.1.1.48). In the present study, PAF was released in detectable amounts (5.4 ± 2.9 ng/ml; mean ± 1 SD) in the plasma of 8 out of 10 patients with systemic lupus erythematosus (SLE) during the most active phases of the disease. PAF was never detectable in the plasma of patients with inactive SLE or of healthy subjects. PAF acetylhydrolase activity was markedly reduced in sera of 10 patients with active SLE as compared to 7 patients with inactive SLE, 16 patients with rheumatoid arthritis (RA), 5 patients with nephrotic syndrome (NS) and 15 healthy subjects. A kinetic study of the enzyme in patients with active SLE suggested an overall reduced activity rather than an intrinsic defect of the enzyme. PAF acetylhydrolase in sera of patients with active SLE shared with that of healthy subjects the same substrate specificity, sensitivity to enzymatic and chemicophysical treatments and association to low-density lipoprotein (LDL), acting as carrier of PAF acetylhydrolase in plasma. However, the protein concentration of LDL was significantly reduced in patients with active SLE as compared to patients with inactive SLE, RA and NS and to healthy subjects, thereby suggesting that the reduction of PAF acetylhydrolase activity in active SLE might be due at least in part to a carrier defect related to the activity of the disease. In addition, experiments in which serum of patients with active SLE and serum of healthy subjects were mixed in different combinations indicated the absence of factors inhibiting PAF acetylhydrolase activity in SLE patients.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Release of Platelet-Activating Factor in Systemic Lupus erythematosus

Tetta

Bussolino

Modena

et al. 1990

Int Arch Allergy Immunol

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“…After centrifugation at 600 x g and 12000 x g the supernatant was centrifuged 1 hat 100000 x g. The cytosol thus obtained was concentrated in a dialysis bag with Aquacide 111, dialyzed against buffer for AcA 54 gel filtration (20 mM Tris/HCl, pH 7.4, 10 mM 2-mercaptoethanol, 2 mM EDTA, lo%, v/v, glycerol and 1 M KCI) and filtered over an AcA 54 column (47 x 1.7 cm) as described previously for rat lung cytosol [15]. As this phospholipase appeared to be stimulated by deoxycholate, 0.1 Yo (w/v) of this detergent was included in the assays.…”

Section: Purification Of Rat Liver Cytosol Phospholipase Amentioning

confidence: 99%

Monoclonal antibodies against an intracellular phospholipase A2 from rat liver and their cross-reactivity with other phospholipases A2

Jong

Amesz²,

Aarsman

et al. 1987

Eur J Biochem

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The membrane-associated phospholipase A2 from rat liver mitochondria was solubilized and partially purified by AcA 54 gel filtration and Matrex gel blue A chromatography. The approximately 2500-fold purified preparation was injected into mice to prepare monoclonal antibodies against phospholipase A2 after fusion of spleen cells and mouse SP2/0 myeloma cells. Hybridoma supernatants were assayed for antibody production in enzymelinked immunosorbent assay with partially purified phospholipase A2 as antigen. Positive clones were tested for their ability to bind phospholipase A2 in a specific immunoprecipitation assay involving protein-A -Sepharose to which rabbit anti-(mouse immunoglobulins) and monoclonal antibodies from hybridoma supernatants were complexed. Twelve clones producing antibodies that bound mitochondrial phospholipase A2 were identified. The binding of all of these antibodies to protein fractions eluted from AcA 54 and Matrex gel blue A columns coincided with the phospholipase A2 activity in these fractions. All monoclonal antibodies showed cross-reactivity with rat liver cytosolic and solubilized rat platelet phospholipase A2. Extracellular phospholipase A2 from rat and pig pancreas or Crotalus atrox were not recognized by the anti-(mitochondria1 phospholipase A2) antibodies.Phospholipases A2 are widespread in nature. The digestive enzyme from pancreas has been purified and analyzed for many mammalian species and much is known about the molecular mechanisms of its enzyme action 111. Also the other secreted phospholipases A2 from bee, snake, wasp and scorpion venoms are easily accessible for investigation as all these enzymes are soluble proteins and can be purified in reasonable quantities.Intracellular phospholipases A2 have been described for many cell types and within the cell their occurrence is often not restricted to one compartment. Investigation of these phospholipases is not only hampered by the low concentration within the cell and the low specific activity of the enzyme, but also by the diversity of their localization. The enzyme can be found in soluble form in the cytosol and membrane-bound in many of the subcellular compartments [2, 31. Little is known about the structural relationship between the enzymes with different subcellular localization and between the intracellular phospholipases A2 from the various tissues. It is even not clear to what extent these intracellular phospholipases from the various organs can be compared with the secreted enzymes from pancreas, bee, snake, wasp and scorpion venoms. Only a few of the intracellular phospholipases A2 have been purified to homogeneity [3]. With some exceptions most of the purified intracellular phospholipases A2 have similar molecular masses (about 14 kDa). They all need calcium and have a basic or neutral pH optimum. They share these properties with secreted phospholipases A2, although their biological Enzyme. Phospholipase A2 (EC 3.1.1.4).function is completely different. The specific activities measured for the intracellular enzymes ...

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“…The degradation of PAF occurs through the hydrolysis of the acetyl group at the sn-2 position of PAF and produces biologically inactive lyso-PAF. PAF-acetylhydrolase catalyzes the hydrolytic reaction, and this enzyme is present in mammalian blood (2)(3)(4), blood cells (5-7), and various tissues (5,8,9). Also, PAF-acetylhydrolase has been isolated from the peritoneal cavity of guinea pigs after endotoxin shock (10).…”

mentioning

confidence: 99%

Cell-specific Regulation of Expression of Plasma-type Platelet-activating Factor Acetylhydrolase in the Liver

Howard

Miller

Miwa

et al. 1997

Journal of Biological Chemistry

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Platelet-activating factor (PAF) is a potent proinflammatory phospholipid mediator that causes hypotension, increases vascular permeability, and has been implicated in anaphylaxis, septic shock and several other inflammatory responses. PAF is hydrolyzed and inactivated by the enzyme PAF-acetylhydrolase. In the intact rat, a mesenteric vein infusion of lipopolysaccharide (LPS) served as an acute, liver-focused model of endotoxemia. Plasma PAF-acetylhydrolase activity increased 2-fold by 24 h following LPS administration. Ribonuclease protection experiments demonstrated very low levels of plasma-type PAF-acetylhydrolase mRNA transcripts in the livers of saline-infused rats; however, 24 h following LPS exposure, a 20-fold induction of PAF-acetylhydrolase mRNA was detected. In cells isolated from endotoxin-exposed rat livers, Northern blot analyses demonstrated that Kupffer cells but not hepatocytes or endothelial cells were responsible for the increased PAF-acetylhydrolase mRNA levels. In Kupffer cells, plasma-type PAF-acetylhydrolase mRNA was induced by 12 h, peaked at 24 h, and remained substantially elevated at 48 h. Induction of neutropenia prior to LPS administration had no effect on the increase in PAF-acetylhydrolase mRNA seen at 24 h. Although freshly isolated Kupffer cells contain barely detectable levels of plasma-type PAF-acetylhydrolase mRNA, when Kupffer cells were established in culture, PAF-acetylhydrolase expression became constitutively activated concomitant with cell adherence to the culture plates. Alterations in plasma-type PAF-acetylhydrolase expression may constitute an important mechanism for elevating plasma PAF-acetylhydrolase levels and an important component in minimizing PAF-mediated pathophysiology in livers exposed to endotoxemia.

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Identification of a calcium-independent phospholipase A2 in rat lung cytosol and differentiation from acetylhydrolase for 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF-acether)

Cited by 61 publications

References 44 publications

Release of Platelet-Activating Factor in Systemic Lupus erythematosus

Release of Platelet-Activating Factor in Systemic Lupus erythematosus

Monoclonal antibodies against an intracellular phospholipase A2 from rat liver and their cross-reactivity with other phospholipases A2

Cell-specific Regulation of Expression of Plasma-type Platelet-activating Factor Acetylhydrolase in the Liver

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