Phospholipase A2 inhibitors and their possible clinical use in the treatment of acute pancreatitis

A laboratory method was established for measurement of phospholipase A2 activity in buffer and serum. A series of different phospholipase A2 inhibitors was tested. The most effective inhibitors were Ca2+ chelating compounds like EDTA, DTPA, EGTA, and phytic acid. The calcium salt of EDTA also has some inhibitory effect. Serum phospholipase A2 activity in normal healthy control patients was measured. The activity in 27 patients with acute pancreatitis was tested. The activity was abnormally high in five patients. This activity was in vitro inhibited by EDTA and partly by CaNa2EDTA. The clinical picture of these patients did not differ from that of phospholipase-A2-negative patients. Six patients with acute pancreatitis were treated by intravenous infusion of CaNA2EDTA. Two of them had haemorrhagic pancreatitis and two were suspected of having early haemorrhagic pancreatitis. During the CaNa2EDTA infusion serum amylase and phospholipase A2 activities decreased. All patients recovered. No harmful side effects were noticed.     

Phospholipase A2 inhibitors in hemorrhagic-necrotizing pancreatitis. Animal experiment evaluation of a new treatment concept

In mongrel dogs with induced pancreatitis we studied the effects of the nonspecific phospholipase A2-inhibitors chlorpromazine, gabexate mesilate and CaNa2EDTA on the course of pancreatogenic shock and the intrapancreatic lysolecithin production. The local level of lysolecithine the metabolite of phospholipase A2 was lower in the treated than in the untreated control groups. Gabexate mesilate was the most active inhibitor. However, none of the drugs had a beneficial influence on hemodynamics, chlorpromazine made it even worse. Morphologically no difference was seen between the treated and untreated groups.     

Role of phospholipase A2 in human acute pancreatitis

In a prospective clinical trial, 85 patients with acute pancreatitis, including 50 with acute interstitial-edematous pancreatitis and 35 with necrotizing pancreatitis, were recruited. Serum pancreatic immunoreactive phospholipase A2 (IR-PLA2), serum phospholipase A catalytic activity (CA-PLA), and serum phospholipase A2 catalytic activity (CA-PLA2) were determined daily between day 1 and day 10 after the onset of the disease. The serum course of IR-PLA2 values for patients with acute interstitial-edematous pancreatitis was comparable to that for patients with necrotizing pancreatitis. In contrast, the determination of CA-PLA and of CA-PLA2 specific activity in the serum revealed a high differentiation between patients with interstitial edematous and those with necrotizing pancreatitis. The overall accuracy for differentiating patients with necrotizing pancreatitis from those with the interstitial-edematous type was 79% for CA-PLA and 77% for CA-PLA2 (cut-off level: CA-PLA, 15 U/L, day 1-5; CA-PLA2, 3.5 U/L, day 1-5). Patients with pancreatitis-associated pulmonary complications showed significantly higher CA-PLA and CA-PLA2 values in the serum. This study demonstrates the role of serum catalytic phospholipase A2 in human acute pancreatitis where the development of pancreatic necrosis and pulmonary failure is concerned.     

Usefulness of determination of serum immunoreactive pancreatic phospholipase A2 content for early identification of severe acute pancreatitis

To investigate the correlation between the initial levels of serum pancreatic enzymes and the severity of acute pancreatitis, serum amylase activity, immunoreactive trypsin content, phospholipase A2 activity and immunoreactive pancreatic phospholipase A2 content were comparatively measured in 22 patients with acute pancreatitis. Serum immunoreactive pancreatic phospholipase A2 content and phospholipase A2 activity in the severe group were significantly elevated as compared with those in the group of moderate pancreatitis on the first day of onset. The elevation of the initial immunoreactive phospholipase A2 content in the severe group was far greater than that of amylase activity, trypsin content and phospholipase A2 activity. The difference between immunoreactive phospholipase A2 content and phospholipase A2 activity was, in part, due to the presence of prophospholipase A2 in severe acute pancreatitis sera, but the phospholipase A2 content measured by radioimmunoassay was still about 5 times higher than that calculated from fully activated phospholipase A2 activity by trypsin.     

Increased concentrations of synovial-type phospholipase A2 in serum and pulmonary and renal complications in acute pancreatitis.

The most important fatal complications of acute pancreatitis are respiratory dysfunction and anuria. Phospholipase A2 has been postulated to be associated with pathologies of various diseases, such as acute pancreatitis, septic shock and multiple injuries. We have recently developed immunoassays for the measurement of pancreatic and nonpancreatic synovial-type phospholipase A2. The present prospective study on 35 consecutive patients with acute pancreatitis indicated that the concentration of synovial-type phospholipase A2, the catalytic activity of phospholipase A2 and the concentration of C-reactive protein in serum were significantly higher in those patients suffering from acute pancreatitis who needed respirator treatment than in those who managed with spontaneous breathing, while there was no difference between these groups in the concentration of pancreatic phospholipase A2. The only significant difference between patients whose highest creatinine concentration rose up to 140 mumol/l and those whose highest creatinine concentration remained below this cutoff value was in their synovial-type phospholipase A2 values. The increased concentration of nonpancreatic synovial-type phospholipase A2 in serum was associated with pulmonary and renal complications. These results emphasize the role of synovial-type phospholipase A2 in the pathophysiology of acute pancreatitis.     

C-reactive protein (CRP) and serum phospholipase A2 in the assessment of the severity of acute pancreatitis.

The present study examines the value of C-reactive protein (CRP) determinations in the assessment of the severity of acute pancreatitis and the correlation of CRP with serum phospholipase A2 activity and the clinical status. Fifty three patients with acute pancreatitis were studied; 17 with haemorrhagic pancreatitis and 36 with a mild form of the disease. S-phospholipase A2 activity increased significantly (p less than 0.05) in patients with fatal pancreatitis but not in those with mild disease. Phospholipase A2 concentrations were below 10 nmol FFA/ml min in mild, while they rose to 20-40 nmol FFA/ml min in haemorrhagic pancreatitis. In fatal cases very high (up to 50-60 nmol FFA/ml min) serum phospholipase A2 concentrations were recorded. The increase in CRP was greater in the patients with severe pancreatitis. One day after admission mean CRP was 280 mg/l in patients with haemorrhagic and 45 mg/l in those with the mild pancreatitis (p less than 0.001). High CRP values also correlated with the prognostic signs indicative of severe pancreatitis. CRP and S-phospholipase A2 determinations are valuable in the early assessment of the severity of acute pancreatitis, but the CRP assay is much easier to include in hospital routine.     

Phospholipase A2 activity in taurocholate-induced acute pancreatitis in the rat model

The activity of phospholipase A2 (PA2) was measured in the plasma of rats after the induction of acute pancreatitis. Buffered sodium taurocholate (3.75% w/v), injected into the pancreatico-biliary duct, was used to induce acute pancreatitis. Blood was taken at 1-h intervals for the measurement of phospholipase A2, glucose, lipase, and arterial gases. Plasma lipase was markedly elevated in the test groups, indicating acute pancreatitis, but no significant difference in PA2 activity was seen between the controls and the test group. However, in four animals the PA2 activity was elevated and in all cases this was accompanied by a low arterial pO2. This supports the theoretical role of PA2 in the pathogenesis of the respiratory complications observed in severe acute pancreatitis.     

Study of phospholipase A2 in serum, ascitic exudate and pancreatic tissue in acute pancreatitis in rats

Serum and ascitic phospholipase A2 (PLA2) activity was assayed in rat model of acute pancreatitis. Serum PLA2 activity was increased at the onset of acute pancreatitis, but had no correlation with severity of disease. The increase of PLA2 in ascites was, on the other hand, correlated well with severity of disease. Pancreatic PLA2 activity was also increased in the course of acute pancreatitis, which reflects increase in particulate fraction and showed obviously different pattern from amylase activity. Increase of PLA2 activity on particulate fraction was due to activation of membrane bound PLA2. These data suggest that activated membrane bound PLA2 exacerbates pancreatitis. The possibility of participation of endotoxin was also to be considered.     

Clinical studies of serum phospholipase A2 immunoreactivity

We tested the new radioimmunoassay method of serum phospholipase A2 (PLA2). In healthy individuals, serum PLA2 concentrations were 301 +/- 65.6 ng/dl (mean +/- SD), and in patients with acute pancreatitis, significant elevations of serum PLA2 concentrations were observed. In clinical course of acute pancreatitis, serum PLA2 was maintained high level more longer than serum amylase and elastase 1. In patients with chronic pancreatitis, serum PLA2 concentration were low at a stage of severe exocrine dysfunction, and high at a stage of acute exacerbation. In patients with pancreatic cancer, serum PLA2 concentration were changed in accord with severity of disease states. After endoscopic retrograde pancreatography, serum PLA2 levels immediately elevated significantly, and returned to basal levels 24 hours later. Serum PLA2 concentrations were within normal range in patients with other malignant tumors, diabetes mellitus, chronic liver diseases, and hypertension, whereas in patients with chronic renal failure serum PLA2 concentrations were elevated. These results suggest that measurement of serum PLA2 can be clinically useful for diagnosis of pancreatitis and monitoring of mild and severe stage of pancreatitis.     

Serum and ascitic phospholipase A2 activities and their heat stabilities in taurocholate induced rat acute pancreatitis]

Serum and ascitic phospholipase A2 (PLA2) activities in rat acute pancreatitis induced by sodium taurocholate (TCA) were investigated with special reference to their heat stabilities and were compared to those in serum of carrageenan induced granuloma in rats. PLA2 activity was measured by previously reported radiochemical method and was separated into two forms, heat stable and labile PLA2, based on the stability to preincubation at 55 degrees C for 5 minutes. While a heat stable PLA2 predominantly increased in ascitic fluid, the elevations of both heat stable and labile PLA2 activities in serum were observed in TCA induced pancreatitis. On the other hand, serum PLA2, which was mainly composed of heat labile form, elevated with the increase of leukocyte count in carrageenan induced granuloma rats. These facts suggested that serum PLA2 activity might increase in acute inflammatory changes other than in pancreatic diseases. And it is assumed that PLA2 derived from extrapancreatic origins as well as pancreatic secretory PLA2 may also contribute to high PLA2 level in acute pancreatitis, because pancreatic secretory PLA2 was generally accepted to be heat stable.     

Human pancreatic phospholipase A2 in acute necrotizing pancreatitis

The activity and the content of phospholipase A2 (PLA2), a potential 'toxin' in pancreatitis, were determined separately by respective methods in pancreatic tissue resected from 22 patients treated for acute necrotizing pancreatitis. Correspondent enzyme assays were analyzed in the serum of 6 last patients. In cases with total necrosis in the tissue resected, the pancreatic PLA2 activity, but not the content, was almost totally lost. Serum PLA2 activity slightly decreased within the extension of pancreatic necrosis. The timing of sampling, number of positive Ranson signs or the course of the disease had no influence on the tissue PLA2 results. Serum PLA2 activity showed a correlation with tissue PLA2 activity.     

Phospholipase A2 activity and concentration in several body fluids in patients with acute pancreatitis

According to recent studies, phospholipase A2 (PLA2) may be an important factor in the pathogenesis and pathophysiology of acute pancreatitis. Increased serum PLA2 activities and concentrations have been measured in patients with acute pancreatitis. Serum PLA2 activities have been shown to correlate with the severity and prognosis of the disease. To study the different methods of PLA2 determination, we measured the PLA2 activity by means of an isotopic assay method and the concentration by a radioimmunologic method in several body fluids of 52 consecutive patients with acute pancreatitis. PLA2 activity and concentration were detected in all of the patient body fluids. The serum PLA2 activities were 2.5-fold higher (mean +/- SD, 7.6 +/- 6.0) than normal activities, and the concentrations were 9.6-fold higher (mean +/- SD, 41 +/- 88). The enzyme activities and concentrations correlated well in ascites, fluids from the pleural cavity, and peritoneal lavation and poorly in serum, urine, and fluid from pancreatic pseudocyst.     

The role of ascites and phospholipase A2 on peritoneal permeability changes in acute experimental pancreatitis.

Peritoneal permeability to fluorescein-isothiocyanate-conjugated (FITC) dextran, mol wt 10,000 was studied in acute experimental pancreatitis (AEP) in rats. The aim of the study was to elucidate the role of the pancreatitis ascites and its phospholipase A2 activity on the observed peritoneal permeability increase during AEP. Phospholipase A2 activity of ascites was 40 U/microL 1 h after the induction of AEP and decreased during the next 3 h gradually to a plateau of about 20 U/microL, where it remained to the end of the experiment at 24 h. A similar pattern was seen for protein, amylase, and lipase although the initial peak was most pronounced for lipase. Pancreatitis ascites did not--irrespective of its age (1 or 20 h) or incubation time (3-20 h)--affect the peritoneal transport of FITC dextran 10,000 in healthy rats. Similarly, intravenously-administered ascites and intraperitoneal instillation of pancreatic phospholipase A2 dissolved in saline were without effects. On the other hand, in another group of healthy animals, phospholipase dissolved in fresh pancreatitis ascites caused a statistically significant increase of peritoneal transport, as defined. In rats with pancreatitis, the addition of phospholipase A2 to the peritoneal fluid increased peritoneal transport of FITC dextran 10,000 as well as phospholipase A2 itself. We conclude that phospholipase A2 when instilled into the peritoneal cavity in the presence of pancreatitis ascites, has the ability to increase peritoneal permeability to FITC dextran 10,000 in healthy, as well as in pancreatitis rats. However, the phospholipase A2 activity of rat pancreatitis ascites is not sufficient for this mechanism to work. This, however, does not exclude its existence in other species, including humans.     

Clinical usefulness of serum phospholipase A2 determination in patients with pancreatic diseases

A new kit for radioimmunoassay of serum phospholipase A2 (PLA2) with monoclonal antibody (S-0932, Shionogi, Osaka, Japan) was used to examine PLA2 levels in patients with various diseases. Patients with acute pancreatitis showed significantly increased serum PLA2 levels. In patients with chronic pancreatitis, significant correlations were observed between the levels of factors evaluated by the secretin test and serum PLA2 levels. In patients with pancreatic cancer, serum PLA2 levels varied with disease severity. Serum PLA2 concentrations were within the normal range in patients with other malignant tumors, diabetes mellitus, and chronic liver diseases but were increased in patients with chronic renal failure. S-Sepharose column analysis of sera showed a small peak of pro-PLA2 and a large peak of PLA2 in sera from patients with severe acute pancreatitis, but a large peak of pro-PLA2 in healthy controls and patients with other diseases. On G-100 gel filtration, high-molecular-weight PLA2 immunoreactivity was detected in sera of patients with chronic renal failure, whereas a single peak of PLA2 immunoreactivity coinciding with that of standard PLA2 was detected in sera of patients with acute pancreatitis. These results suggest that (a) measurement of serum PLA2 is clinically useful for diagnosis and monitoring of pancreatitis, (b) active PLA2 in the circulation is dominant in severe acute pancreatitis, and (c) the kidney may be the main site of PLA2 degradation or excretion.     

The diagnostic value of serum pancreatic phospholipase A2 (PLA2) in pancreatic diseases.

The diagnostic significance of serum immunoreactive pancreatic phospholipase A2 (PLA2) was studied in 119 patients with pancreatic disease, 200 with various non-pancreatic disease, and 203 healthy controls using radioimmunoassay (RIA) specific to human pancreatic PLA2. This newly developed RIA using monoclonal antibody was satisfactorily sensitive and reliable. Serum PLA2 was elevated in all six patients with acute pancreatitis. Frequency of abnormal serum PLA2 levels was 60% in chronic pancreatitis (n = 52) and 67% in pancreatic cancer (n = 61). Serum PLA2 levels were low in chronic pancreatitis with severe exocrine insufficiency and advanced pancreatic cancer. In chronic pancreatitis, patients with low serum PLA2 level showed lower enzyme output in secretin test than patients with normal or high serum PLA2 level. Frequency of abnormal PLA2 levels was 27% in non-pancreatic disease and, in particular, patients with renal failure showed high PLA2 levels. Sensitivity (62%) and efficiency (69%) of serum PLA2 assay in pancreatic disease were superior to those of amylase. In conclusion, serum PLA2 determination using RIA was useful for the diagnosis of acute pancreatitis by high serum PLA2 levels and the diagnosis of severe exocrine pancreatic insufficiency by low serum PLA2 levels.     

Pathophysiological role of secretory type I and II phospholipase A2 in acute pancreatitis: an experimental study in rats.

BACKGROUND: In human acute pancreatitis two different types of secretory phospholipase A2 (PLA2) have been found. AIM: To analyse the specific pattern of distribution of these PLA2 activities and their pathophysiological role in experimental acute pancreatitis. SUBJECTS AND METHODS: Catalytic activities of secretory type I (pancreatic) and type II (non-pancreatic) PLA2 and the protein concentration of immunoreactive pancreatic PLA2 (IR-PLA2) in serum and pancreatic tissue of rats with cerulein (mild form) and sodium taurocholate (severe form) induced acute pancreatitis were determined. RESULTS: Cerulein infusion caused a significant increase in type I PLA2 activity (p < 0.01) and IR-PLA2 protein concentration (p < 0.01) in serum and pancreas, whereas type II PLA2 activity remained unchanged during the 12 hour observation period. Histology showed no significant tissue destruction. In sodium taurocholate induced acute pancreatitis type II PLA2 activity significantly increased, reaching values over 10-fold higher than controls (p < 0.01), whereas IR-PLA2 protein concentration and type I PLA2 activity were only marginally increased. In this severe model of acute pancreatitis significantly lower values were detected than in the control pancreas (p < 0.002) for PLA2 activity and IR-PLA2 protein concentration. Histology showed parenchymal and fat necroses with haemorrhage, oedema, and inflammatory cell infiltration. CONCLUSIONS: Type I PLA2 activity is dependent on the IR-PLA2 protein concentration in serum and pancreatic tissue. The type II PLA2 activity is not stimulated by cerulein, which indicates an extra-acinar origin of this enzyme. Type II PLA2 activity is significantly increased in sodium taurocholate induced acute pancreatitis indicating its role in the local necrotising process and involvement in the systemic effects in severe acute pancreatitis.     

Inhibition of local hemorrhage and dermonecrosis induced by Bothrops asper snake venom: effectiveness of early in situ administration of the peptidomimetic metalloproteinase inhibitor batimastat and the chelating agent CaNa2EDTA.

The effectiveness of the chelating agent CaNa2EDTA and the peptidomimetic matrix metalloproteinase inhibitor batimastat (BB-94) to inhibit local tissue damage induced by Bothrops asper snake venom was studied in mice. Both compounds totally inhibited proteolytic, hemorrhagic, and dermonecrotic effects, and partially reduced edema-forming activity, when incubated with venom prior to injection. Much lower concentrations of batimastat than of CaNa2EDTA were required to inhibit these effects. In addition, batimastat, but not CaNa2EDTA, partially reduced myotoxic activity of the venom. When the inhibitors were administered at various time intervals after envenomation at the same site of venom injection, both compounds were effective in neutralizing local hemorrhage and dermonecrosis if administered rapidly after venom. Inhibition was not as effective as the time lapse between venom and inhibitor injections increased. Owing to the relevance of metalloproteinases in the pathogenesis of local tissue damage induced by B. asper and other pit viper venoms, it is suggested that administration of peptidomimetic metalloproteinase inhibitors or CaNa2EDTA at the site of venom injection may represent a useful alternative to complement antivenoms in the neutralization of venom-induced local tissue damage.     

Urinary phospholipase A2 excretion in chronic pancreatic diseases.

This study was performed to investigate the behavior of phospholipase A2 (PLA2) in serum and urine of patients with chronic pancreatic diseases and to ascertain whether any factors influenced the results. In 30 controls, 45 patients with pancreatic cancer, 54 with chronic pancreatitis, and 64 with extrapancreatic diseases, serum and urinary PLA2, pancreatic isoamylase and RNase, and urinary N-acetylglucosaminidase (NAG) were measured. Serum PLA2 levels were higher in patients with chronic pancreatitis than in all the other groups. In our patients, only occasionally was urinary PLA2 elevated, the increase occurring almost exclusively in the presence of an acute inflammatory disease, e.g., relapsed chronic pancreatitis or active inflammatory bowel disease. A correlation was found between serum PLA2 and serum RNase, an indicator of tissue damage, but not between serum PLA2 and pancreatic isoamylase. Urinary PLA2 output was correlated with its renal input and with RNase output. No correlation was found between PLA2 output and pancreatic isoamylase or NAG urinary excretion. In conclusion, (1) the determination of serum PLA2 activity may be an aspecific test of pancreatic disease; (2) PLA2 urinary excretion occasionally increases, especially in the presence of severe phlogosis, which occurs in chronic pancreatitis, in particular during relapse; and (3) irrespective of the tissue origin of urinary PLA2, its increased excretion may be accounted for in part by its increased circulating levels. It is, however, more likely the consequence of a renal tubular dysfunction, which is sometimes found in patients with pancreatic diseases.     

Role of interleukin-6 in acute pancreatitis. Comparison with C-reactive protein and phospholipase A.

Plasma values of immunoreactive interleukin-6, C-reactive protein and phospholipase A have been determined in serial samples from 24 patients with acute pancreatitis ('mild' pancreatitis nine, 'severe' pancreatitis 15). Median plasma concentrations of interleukin-6, C-reactive protein, and phospholipase A activity were significantly higher in patients with 'severe' illness (p < 0.001) than those with 'mild' illness. A particularly marked increase in interleukin-6 was found in two patients with necrotising pancreatitis and fatal outcome. Significant correlations between plasma concentrations of interleukin-6 and phospholipase A (p = 0.0218) and C-reactive protein and phospholipase A activity (p < 0.0001) were found in patients with 'severe' disease. These findings in a limited number of patients with acute pancreatitis are promising in that raised interleukin-6 correlated with clinical severity and with two other established markers, C-reactive protein, and phospholipase A activity.     

Phospholipase Activity in Pancreatic Exudate in Experimental Acute Pancreatitis

Acute pancreatitis was induced in dogs by injecting into the pancreatic duct a mixture of taurocholate and trypsin. Exudate from pancreas was collected outside the body by a special technique in separate portions each covering one hour.

All exudates were found to possess ability to break down lecithin by phospholipase and lysophospholipase action. Calcium, bile, and taurocholate stimulated and EDTA inhibited the degradation of lecithin. The phospholipase activity was studied in the hourly collected portions of pancreatic exudate. It was very high and had a maximum in the portion collected during the first hour, being lower and levelling out in the portions collected during the 4 to 7 hour periods. Amylase activity paralleled the phospholipase activity of the exudate.

The demonstration of an early release in acute pancreatitis of lecithin-hydrolyzing enzyme systems in pancreatic exudate may have bearings on the pathogenesis of acute pancreatitis.