Diagnostic value of immunoreactive phospholipase A2 in acute pancreatitis

Summary In a prospective clinical trial 85 patients with acute pancreatitis were analysed for serum total amylase, pancreatic amylase, pancreatic lipase, trypsin, elastase 1, and immunoreactive phospholipase A₂ (IR-PLA₂). The diagnostic sensitivity of serum IR-PLA₂ was comparable to that of serum total amylase, pancreatic amylase, and trypsin. The specificity of IR-PLA₂ is superior to that of serum total amylase determination due to the fact that the IR-PLA₂ determination is based on an antibody against human pancreatic PLA₂.     

Serum phospholipase A2 in intensive care patients with peritonitis,multiple injury,and necrotizing pancreatitis

Summary To study the source and role of circulating phospholipase A₂ (PLA₂) catalytic activity we monitored the serum from patients with necrotizing pancreatitis (n=8), diffuse peritonitis (n=6), and multiple injuries (n=11). Immunoreactive PLA₂ serum protein concentration was analysed using a fluoroimmunoassay based on an antibody against human pancreatic PLA₂. Serum PLA₂ catalytic activity was analysed using a radiochemical method based on a substrate with tritiated palmitic acid in beta position. In necrotizing pancreatitis immunoreactive PLA₂ and PLA₂ catalytic activity both increased. Obviously, in necrotizing pancreatitis the major part of serum catalytic activity stems from the pancreas. In patients with diffuse peritonitis and multiple injuries, as a rule, immunoreactive phospholipase A₂ serum concentration appears to be within the normal range. In contrast, in these patients we demonstrated high serum catalytic PLA₂ activity comparable to that in necrotizing pancreatitis. The source of catalytic PLA₂ activity in peritonitis and multiple injuries seems not to be the pancreas. There was a correlation between pulmonary insufficiency and serum PLA₂ catalytic activity in patients with necrotizing pancreatitis, peritonitis, and multiple injuries.     

The role of phospholipase A2 in human acute pancreatitis

Summary Several studies suggest that the activation of pancreatic phospholipase A₂ (PLA₂) and its release from injured acinar cells play an important role in the pathogenesis of acute pancreatitis. Elevated catalytic activity of PLA₂ in serum is associated especially with severe forms of the disease. PLA₂ has been purified from human cadaver pancreas and an antiserum raised against the enzyme in rabbits. Immuno-histochemical localization of PLA₂ in pancreatic tissue was abnormal in acute pancreatitis. A time-resolved fluoroimmunoassay for human pancreatic PLA₂ has been developed. Increased serum concentrations of immunoreactive PLA₂ were found in acute pancreatitis during the first week after hospital admission. The values returned to normal somewhat more slowly than corresponding serum amylase values. The immunochemical determination of PLA₂ in serum provides a fast and specific detection of injury to pancreatic acinar cells. The pancreas is not the only source of PLA₂ in acute pancreatitis. The nonpancreatic PLA₂ may originate from various inflammatory cells, but this hypothesis remains to be proven.     

Lysolecithin concentration in pancreatic tissue during therapy with phospholipase A2-inhibitors in acute necrotizing pancreatitis

Summary Four hours after hemorrhagic necrotizing pancreatitis was induced in experimental animals the concentration of lysolecithin in pancreatic tissue rose (p=0.0025). Parenteral administration of unspecific inhibitors of phospholipase A₂, such as chlorpromazine, gabexat mesilat and CaNa₂ EDTA, can neither inhibit elevation of the enzyme nor influence the course of the disease.     

Involvement of oxygen radicals and phospholipase A2 in acute pancreatitis of the rat

Summary The purpose of this study was to assess the involvement of oxygen radicals and phospholipase A₂ in acute pancreatitis. Acute pancreatitis was induced in rats by the CCK-analogue cerulein (5 µg/kg · h) for 30 min, 3.5 h, and 12 h. At the end of the infusion, serum enzymes and the lipid peroxidation products conjugated dienes and malondialdehyde in the tissue were measured. Moreover, tissue samples underwent lightmicroscopical examination. After 3.5 h cerulein, an interstitial edema and a beginning accumulation of granulocytes in the pancreatic gland is observed. These changes are aggravating within 12 h, leading to tissue necrosis and migration of the granulocytes into the tissue. Concomitantly amylase and lipase increase by 15 and 35 times, respectively. Conjugated dienes and malondialdehyde increase already after 30 min cerulein and reach their highest levels after 3.5 h cerulein. At the same time the tissue activity of phospholipase A₂ is elevated three fold. Rats were treated with superoxide dismutase and catalase before cerulein infusion. Treatment significantly prevents tissue necrosis, granulocyte accumulation, and edema formation. The enhanced activity of phospholipase A₂, however, is unaffected by the treatment. Oxygen radicals seem to be instrumental in the development of the disease.     

A radiochemical test for phospholipase A2 catalytic activity

Summary A position-specifically labelled phosphatidylcholine is the substrate for the selective determination of Phospholipase A₂ in serum, ascites and tissue samples. Optimal reaction conditions and simplifications of handling are discussed.A control group of human serum samples ranged up to 2.1 U/l. The maximum serum activity in samples of patients with acute pancreatitis was 126 U/l. In human ascites activities up to 380 U/l were measured. The method described here turned out to be a practicable instrument for the determination of phospholipase A₂ activity using only commercially available reagents.Abbreviation PlA₂ Phospholipase A₂     

Phospolipase a activities in ascites,serum, lymph,and urine in acute pancreatitis following pancreas stimulation with secretin-ceruletid

Summary As a result of pancreas stimulation with secretin-ceruletid we were able to measure the release of phospholipase A in ascites, serum, lymph, and urine in acute experimental pancreatitis in the dog. After induction of acute pancreatitis we found no increase over the normal range in serum, lymph, and urine phospholipase A activities. In addition, the stimulation of the exocrine pancreas did not show a significant change in phospholipase A activity. The excessively high phospholipase A activity in ascites following induction of acute pancreatitis fell significantly after pancreas stimulation with secretin-ceruletid.     

Characterization of phospholipase A2 activity in aspirates of human pancreatic pseudocysts after isolation by reversed-phase high performance liquid chromatography

Summary Phospholipase A (PLA) is able to attack membrane phospholipids and thereby plays a putative role in the pathogenesis of pancreatic pseudocysts. We looked for PLA₂-like activity in aspirates from human pancreatic pseudocysts. In material originating from one cyst which occurred shortly after an acute pancreatitis attack, hydrolyzing enzymatic activity measured by a sensitive bioassay system for PLA₂ activity was found without prior trypsin activation (67×10³ U/min/100 µl). A biochemical characterization of this hydrolyzing enzymatic activity was provided after resolution of the respective proteins contained in the cyst fluid by HPLC. High hydrolyzing activities were found in correspondence to one specific, early eluting peak. The purified enzyme had pH optima at 3.5 and 6. Addition of EDTA (5 mM) to the test system abolished the enzymatic activity which mirrored the requirement for calcium ions. The activity was optimal at calcium concentrations ranging from 1–2 mM. Higher calcium concentrations reduced the enzymatic activity. The enzyme showed high heat stability. SDS-gel analysis of the peak showed one single band with a molecular weight of about 20,000 Daltons. Our findings demonstrate the possibility of activated, PLA-like activity in human pancreatic pseudocyst fluid. We speculate that an inappropriate activation of this enzyme in peri- or intrapancreatic fluid collections could account for pseudocyst formation after an acute pancreatitis attack.     

Immunocytochemical evidence of phospholipase A2 in pancreatic tumors — Diagnostic values

Summary Phospholipase A₂ is an enzyme which is produced in acinar cells, and persists even in regressive states of chronic pancreatitis, when the production of other enzymes diminishes. We therefore tested this enzyme as a marker of acinar descent in various pancreatic tumors. This enzyme could be seen in 50% of the acinar-cell carcinomas, in 60% of solid and papillary pancreatic tumors, and in 50% of microglandular carcinomas. Ductal cancers and isletcell cancers were negative. In contrast to other markers of acinar matrix (amylase, antitrypsin), phospholipase A₂ gave fewer false-positive or false-negative results.Supported by a grant of the J. and F. Marohn Stiftung at the University of Erlangen/Nürnberg     

Inhibition of porcine pancreas phospholipase A2 activation by gabexate mesilate

Summary We investigated the effect of gabexate mesilate on the catalytic activity of phospholipase A₂ in homogenized porcine pancreatic tissue. Gabexate mesilate is a potent inhibitor of serine proteases. There is no direct inhibition of phospholipase A₂ catalytic activity in concentrations up to 6 mmol/l. Preincubation of homogenized pancreatic tissue with gabexate mesilate leads to a reduction of phospholipase A₂ activity even in concentrations as low as 6 µmol/l. The activation of purified porcine prophospholipase A₂ added to pancreatic tissue can be completely inhibited. Thus, gabexate mesilate might influence the activation of phospholipase A₂ administered in therapeutic concentrations in inflamed pancreatic tissue.Abbreviations PLA₂ Phospholipase A₂ - ProPLA₂ Prophospholipase A₂     

Serum phospholipase — Regulatory and pathophysiological aspects

Summary The development of a photometric procedure to measure phospholipase A activity has extended previous observations that this enzyme activity increases in several pathological states including pancreatic and inflammatory diseases. Serum phospholipase A in pancreatitis was characterized as a mixture of the pancreatic enzyme and a different phospholipase with a pH optimum at 8.0. The latter enzyme was also observed in nonpancreatic diseases like septicemia and acute lung failure which are characterized by an increase in tissue phagocyte activity. The possible pathogenic role of phospholipase(s) A, their intracellular regulation and the proposed mechanisms of release into the blood stream are discussed with respect to the present pathobiochemical knowledge. This includes the mechanism of activation of phagocytosis and the possible role of lipocortins known to be stimulated by glucocorticoid treatment.Abbreviation PLA Phospholipase A     

Effect of serum from cardiovascular patients on catalytic activity of secretory phospholipase A2 (IIA)

Incubation of patients’ serum catalytically active by type IIA secretory phospholipase A₂ (SP-IIA) with serum containing the enzyme in a high concentration but exhibiting no catalytic activity in 1:1 volume ratio led to a significant inhibition of SP-IIA catalytic activity. Donor and patient sera with low levels of SP-IIA had no effect on the serum with SP-IIA activity under these conditions. However, the increase in the content of patients’ serum with a low level of SP-IIA in the incubation mixture to 1:2 (v/v) and of donor serum to 1:3 (v/v) also led to blockade of SP-IIA catalytic activity. These results indicate that human serum contains an SP-IIA inhibitor and its concentration decreases significantly in sera with SP-IIA activity. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 11, pp. 525–527, November, 2006     

A rapid phospholipase A2 bioassay using14C-oleate-labelledE. coli bacterias

Summary Two methods of phospholipase A₂ determination using¹⁴C-labelledE. coli bacterias as substrate were compared. One method works with a filter membrane for separation of cleaved¹⁴C-oleate from remaining phospholipids, the other uses the well-known thin-layer chromatography for lipid analysis. Some features of human serum phospholipase A₂ regarding pH and Ca²⁺ dependency were investigated. Possible sources of errors were discussed. It was shown that either method can differentiate between normal and pathologically elevated phospholipase A₂ levels, but that the filter method is superior in terms of sensitivity and workload.Abbreviations PLA₂ phospholipase A₂ - BSA bovine serum albumin - (F)FA (free) fatty acid - TLC thin-layer chromatography     

In vitro inhibition of phospholipase A2 by gabexate mesilate,camostate, and aprotinine

Summary Gabexate mesilate (FOY, ethyl-p-(6-guanidino-hexanoyl-oxy)-benzoate-methansulfonate), camostate (N,N-dimethyl-carb-amoylmethyl-4-(guanidinobenzoyloxy)-phenyl-acetate) methansulfonate and aprotinine (Trasylol) were tested for possible inhibition of phospholipase A₂. Gabexate mesilate at a concentration of 5×10^–4 mol/l and camostate at a concentration of 10^–3 mol/l caused a 50% reduction in enzyme activity. There was almost no inhibition by aprotinine at clinical doses; 40 million KIU/l were necessary to reduce phospholipase A₂ activity by 20%. From the therapeutic dose (4,000 mg/day per i.v. infusion) and the half-life of gabexate mesilate in blood circulation (1 min) it can be calculated that the in vitro concentration of gabexate mesilate is only 10^–6 to 10^–7 mol/l. Under these conditions gabexate mesilate cannot diminish the in vivo enzyme activity of phospholipase A₂.     

Acid phospholipase A1 in liver — A brief survey

Summary Acid phospholipase A₁ activity in liver (rat, human) is predominantly localized in lysosomes. A minor proportion (less than 3% of the total activity) is also present in the Golgi apparatus and the endoplasmic reticulum, presumably due to enzymatically active precursors of the corresponding lysosomal enzyme. Lysosomal phospholipase A₁ is the most important enzyme initiating the intralysosomal catabolism of diacylphosphoglycerides. It has been purified 50,600-fold, with a yield of about 26%. The enzyme prefers phosphatidylethanolamine as a substrate, which at 200 µM and pH 4.5, is hydrolysed at a rate of approximately 8.2 U/mg. Lysosomal phospholipase A₁ is a glycoprotein of about 29 kDa with an isoelectric point of pH 5.3. Unspecific extralysosomal endogenous inhibitors of this enzyme are pH range, inorganic cations, and various proteins. Divalent cations are more potent inhibitors than monovalent ones. Most endogenous intra- and extracellular proteins inhibit the enzyme, the cationic species exhibiting high inhibitory potencies, glycoproteins only little. Inhibitory proteins act through their binding to the substrate. Lysosomal phospholipase A₁ seems to be an important target in drug-induced lipidosis. This lipid storage disease is caused by various cationic amphiphilic drugs that are trapped intralysosomally by protonation. In lysosomes such compounds raise the pH, interact with the polar lipids to be degraded and the lysosomal lipolytic enzymes, such as phospholipase A₁. These mechanisms result in impaired intralysosomal phospholipid degradation and hence in intralysosomal phospholipid accumulation.Dedicated to Professor Walther Vogt on the occasion of his 70th birthday     

Crucial role of group IIA phospholipase A2 in pancreatitis-associated adrenal injury in acute necrotizing pancreatitis

This study investigated the mechanistic role of group IIA phospholipase A2 (sPLA2-IIA) in the process of pancreatitis-associated adrenal injury in acute necrotizing pancreatitis.     

Action of lipases on low-density serum lipoproteins

During the action of phospholipase A₂ on low-density serum lipoproteins (LDL) in the presence of serum albumin as adsorbent for low-molecular-weight products of lipolysis a change takes place in the physicochemical properties of the LDL, expressed as a decrease in their flotation coefficients. Lipase hydrolyzes the triglycerides of LDL after preliminary treatment of the latter with phospholipase A₂. Under the influence of lipases the LDL residue becomes insoluble and a cholesterol-rich precipitate is formed. Loss of solubility of lipoproteins following treatment with lipases and proteases may take place in certain states in vivo and may provide the basis for the formation of atheromas, i.e., it may be one of the factors in the pathogenesis of atherosclerosis.Laboratory of Physical Chemistry of Biopolymers, Institute of Biological and Medical Chemistry, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Orekhovich.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 173–175, August, 1977.     

IL-6 release from mouse glia caused by MeHg requires cytosolic phospholipase A2 activation

Methylmercury is a potent neurotoxin that causes severe neurological disorders in fetuses and young children. Recent studies indicated that MeHg could alter levels of immune mediators produced by cells of the central nervous system. Results from this study indicated that MeHg could greatly induce IL-6 release from primary mouse glial cultures. This property was not shared by other cytotoxic heavy metals, such as CdCl₂ or HgCl₂. MeHg was known to induce cytosolic phospholipase A₂ (PLA₂) activation and expression, and this enzyme was required for IL-6 induction in some experimental systems. Further experiments using structurally distinct pharmacological agents were performed to test the hypothesis that MeHg induced PLA₂ activation was necessary for MeHg induced IL-6 release. Results indicated that AACOCF₃ (≥10 μM), MAFP (≥0.625 μM) and BEL (≥0.625 μM) significantly reduced MeHg induced IL-6 release in glia. However, these PLA₂ inhibitors did not block MeHg induced GSH depletion. These results suggested that PLA₂ activation was required for MeHg to induce glial IL-6 release.     

Effect of phospholipase A2 on development of pulmonary edema and on the pulmonary hemodynamics in intact and vagotomized animals

Laboratory of Pathophysiology of Respiration and Bioengineering Laboratory, Research Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Department of Pathophysiology, Yaroslavl' Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR B. I. Tkachenko.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 110, No. 9, pp. 254–257 September, 1990.