Digestive enzymes and protease inhibitors in plasma from patients with acute pancreatitis

Action of tacrolimus in arginine induced experimental acute pancreatitis

OBJECTIVE

To determine whether tacrolimus administered to rats, in the presence of pancreatitis induced by L-Arginine, interferes with the serum levels of amylase and glucose and the histological pattern of the pancreatic parenchyma.

METHODS

Forty Wistar rats were divided into four groups with 10 rats each: control group (C), tacrolimus group (T), pancreatitis group (P) and pancreatitis-tacrolimus group (PT). We evaluated serum levels of amylase, glucose, and tacrolimus and made histological assessments of the pancreas. Induction of pancreatitis was made by inoculation of L-Arginine at a dose of 500 mg/100g body weight intraperitoneally, and tacrolimus treatment at a dose of 1ìg/kg subcutaneously for four days.

RESULTS

Serum amylase was higher (p = 0.0000) in groups PT, P and T than in the control group. The PT group mean was higher (p = 0.0009) than in the T group, but did not differ (p = 0.6802) from the average of the P group. There was no difference between groups P and T (p = 0.2568). Neither in mean blood glucose between the groups (p = 0.4920); serum levels of tacrolimus were similar in PT and T groups (p = 0.7112). There were no histological changes in groups T and C and no hemorrhage in the pancreas of rats in groups P and PT. In group P, there was no edema in 30%, mild edema in 20% and in 50%, moderate; as for inflammatory infiltration, it was moderate in 80% and absent in 20%, and atrophy of the parenchyma was moderate in 60% and severe in 40%. In the PT group, there was edema, inflammatory infiltration or atrophy in the pancreas in all rats.

CONCLUSION

Treatment with Tacrolimus induced an increase in serum amylase in normal mice, but did not affect blood glucose or the histological pattern of the pancreatic parenchyma. In the presence of pancreatitis induced by L-Arginine tacrolimus induced edema, inflammatory infiltration and more severe atrophy in the pancreatic parenchyma.

Compartmentalization of the protease-antiprotease balance in early severe acute pancreatitis

OBJECTIVE

To assess the balance between trypsin and protease inhibitors simultaneously in the systemic circulation and in the thoracic lymph and peritoneal exudate.

METHODS

Twenty patients with early severe acute pancreatitis were studied. Enzymatically active and immunoreactive trypsin in conjunction with its major inhibitors were measured in the 3 compartments at the onset of end-organ failure(s). The molecular forms of trypsin were determined in the lymph and ascites by gel filtration chromatography to separate trypsinogen and free-and inhibitor-bound trypsin.

RESULTS

Both enzymatically active trypsin and immunoreactive trypsin levels were highest in ascites and lymph compared with the systemic circulation. Intracompartmental alpha1- protease inhibitor gradient moved in the opposite direction, whereas alpha2 macroglobulin concentration was highest in ascites and lowest in the lymph. Although most of the enzymatically and immunoreactive material in ascites and lymph consisted of trypsin complexed with alpha2 macroglobulin and trypsinogen, respectively, free active trypsin was detected in more than 80% of the samples.

CONCLUSIONS

In patients with early severe acute pancreatitis, there is a significant trypsinogen activation resulting in protease-antiprotease imbalance and thereby free enzymatically active trypsin in the 2 body fluid compartments in close vicinity to the inflammatory process. This may be involved in the pathophysiology of local and distant tissue damage.

Pathophysiological effects of nicotine on the pancreas: an update

Epidemiological evidence strongly suggests an association between cigarette smoking and pancreatic diseases. It is well recognized that nicotine, a major component in cigarette smoke, is an addictive agent and, therefore, reinforces smoking behavior. The current review update focuses on the genetics of nicotine dependence and its role on the development of pancreatic diseases. The role of smoking and nicotine in pancreatitis and pancreatic cancer development is also discussed. Exposure of laboratory animals to nicotine clearly supports the notion that nicotine can induce pancreatic injury. The mechanism by which nicotine induces such effects is perhaps mediated via signal transduction pathways in the pancreatic acinar cell, leading to enhanced levels of intracellular calcium release, resulting in cytotoxicity and eventual cell death. The induction of pancreatic injury by nicotine may also involve activation and expression of protooncogene, H-ras, which can increase cytosolic calcium via second messenger pathways. Development of pancreatic carcinoma in cigarette smokers as observed in human populations may be the result of activation and mutation of the H-ras gene. A possible pathogenetic mechanism of nicotine in the pancreas activating multiple signal transduction pathways is schematically summarized in Figure 1.

New laboratory tests in acute pancreatitis

Acute pancreatitis (AP) is a common disease with wide variation of severity. The diagnosis of AP is usually based on high serum amylase or lipase values but the accuracy of these methods is considered unsatisfactory. One in five of the patients develops a severe disease and carries a considerable risk of development of organ failure and high mortality. Early detection of patients with severe AP and especially those with increased risk of organ failure is importance since such patients seem to benefit from treatment in an intensive care unit started as soon as possible after presentation. In addition to enzymological methods, increasing interest has been focused on laboratory markers reflecting the level of inflammatory response in AP. At present, in routine clinical work the most commonly used severity marker is serum C-reactive protein, the concentration of which rises too slowly to be used for early prediction of severity. New therapies aiming at modifying the course of systemic inflammation in AP are being developed and therefore monitoring the patient's immune inflammatory status is needed. In this review article we present the current knowledge of laboratory tests, which has been evaluated for diagnostic and prognostic purposes in AP.

alpha2-macroglobulin- and murinoglobulin-1- deficient mice. A mouse model for acute pancreatitis

Mice deficient in either or both mouse alpha2-macroglobulin (MAM) and murinoglobulin-1 (MUG1) were generated and proved phenotypically normal under standard conditions. Acute pancreatitis was induced with a diet deficient in choline and methionine, supplemented with ethionine. The mortality was less than 25% in wild-type mice, as opposed to at least 56% in knockout mice, and was highest (70%) in MAM-/- mice, with earliest onset at 2 days. Plasma amylase and lipase levels were increased, but pancreatic tissue appeared histologically variable in individual mice. The clinical symptoms were most severe in MAM-/- mice and, surprisingly, were not aggravated in the double knockout mice, suggesting that the lack of proteinase inhibition capacity was not the major problem. Therefore, we analyzed the expression of 21 different cytokines and polypeptide factors in the pancreas of all experimental groups of mice. Interleukin-1-receptor antagonist mRNA was consistently induced by the diet in the pancreas of MAM-/- mice, and transforming growth factor-beta, tumor necrosis factor-alpha, tumor necrosis factor-beta, beta-lymphotoxin, and interferon-gamma mRNA levels were also increased. The data demonstrate the important role of alpha2-macroglobulin (A2M) in acute pancreatitis as both a proteinase inhibitor and a cytokine carrier. Mice deficient in MAM and/or MUG thus offer new experimental models for defining in vivo the role of the macroglobulins in pancreatitis and in other normal and pathological processes.

Polyclonal pancreatic elastase assay is superior to monoclonal assay for diagnosis of acute pancreatitis

We compared the clinical values for diagnosis of acute pancreatitis of two commercial assays for pancreatic elastase: an ELISA procedure with monoclonal antibodies and a RIA technique with polyclonal antibodies. In 14 patients with acute pancreatitis, serum concentrations of elastase determined by ELISA (ELISA-elastase) decreased much faster (half-life 0.4 days) than those of elastase determined by RIA (RIA-elastase) (2.2 days), amylase (0.8 days), or lipase (0.9 days). Serum samples from 253 additional patients with abdominal pain (32 of these with acute pancreatitis) were analyzed. In sera collected up to 48 h after the onset of disease, the ROC curves showed a slightly higher diagnostic value of RIA-elastase. In samples taken later, at a sensitivity of 90% the specificity of RIA-elastase was 95% (ELISA-elastase 40%). We conclude that serum ELISA-elastase is of much lower clinical value than RIA-elastase for diagnosis of acute pancreatitis.

Serum amylase and lipase concentrations and lipase/amylase ratio in assessment of etiology and severity of acute pancreatitis

We studied the behavior of serum amylase and lipase in 66 consecutive patients with acute pancreatitis in order to assess the ability of these tests and of the serum lipase-amylase ratio to establish the etiology and predict the severity of acute pancreatitis. Forty-two patients had biliary acute pancreatitis, 14 had alcoholic acute pancreatitis, and the remaining 10 nonbiliary, nonalcoholic (NBNA) acute pancreatitis. Serum amylase and lipase were abnormally high in all patients. The elevations of both serum amylase and lipase were significantly lower in patients with alcoholic pancreatitis than in those with biliary pancreatitis, although a considerable overlap was observed between the two groups. No statistically significant differences were found between NBNA patients and those with either biliary or alcoholic forms of the disease. The serum lipase-amylase ratios in patients with alcoholic pancreatitis ranged from 0.2 to 5.6, in those with biliary pancreatitis from 0.1 to 7.9, and in those with NBNA pancreatitis from 0.1 to 4.4. These differences were not statistically significant. No differences in serum enzyme levels were observed among patients without apparent imaging signs of acute pancreatitis (N = 20), those with signs of pancreatic edema (N = 36), and those with necrotizing pancreatitis (N = 10). The results indicate that serum amylase and lipase concentrations are not able to establish either the etiology or to predict the severity of acute pancreatitis as assessed by imaging techniques. Furthermore, the serum lipase-amylase ratio is not useful in distinguishing acute episodes of alcoholic from nonalcoholic acute pancreatitis.

Impaired mononuclear phagocyte function in patients with severe acute pancreatitis: evidence from studies of plasma clearance of trypsin and monocyte phagocytosis

Activated proteases in plasma are complexed by alpha 2-macroglobulin. Although the complexes retain peptidase activity, they are usually eliminated promptly by mononuclear phagocytes. In severe acute pancreatitis, almost 30% of plasma alpha 2-macroglobulin becomes complexed, suggesting impaired clearance. In the present study, plasma [methyl-14C]trypsin clearance and monocyte phagocytosis were investigated. Attacks complicated by major organ-system failure, pancreatic pseudocyst, abscess, or necrosis were graded severe (median Ranson score 5.5). Plasma [methyl-14C]trypsin half-life was significantly increased in severe attacks (N = 7, median 21.1 min), compared to mild attacks (N = 14, median 15.4 min, P < 0.05) and healthy controls (N = 4, median 10.8 min, P < 0.02). Monocyte phagocytosis was significantly lower in severe attacks (N = 9, median 3.6%) compared to mild attacks (N = 20, median 20.8%, P < 0.01) and healthy controls (N = 8, median 26.9%, P < 0.01). Plasma [methyl-14C]trypsin half-life and monocyte phagocytosis were significantly inversely correlated (r = -0.51, P < 0.01). Impaired clearance of circulating trypsin in acute pancreatitis is potentially deleterious but may be reversed by stimulating mononuclear phagocytes.

Histopathologic correlates of serum amylase activity in acute experimental pancreatitis

The association of serum amylase activity with the extent of pancreatic injury in acute pancreatitis is unclear. To clarify this relationship, we induced acute pancreatitis ranging from mild to lethal in 118 Sprague-Dawley rats (350-450 g). This was achieved by controlled intraductal infusion of low- or high-dose bile salt, with or without enterokinase, followed by intravenous cerulein or saline for 6 hr. Serum amylase was measured at baseline and 6 hr. Pancreatic histopathology was evaluated by two blinded pathologists employing total surface scoring (N = 118) and morphometric 20-field documentation (N = 22). Serum amylase correlated best with edema (r = 0.61) and fat necrosis (r = 0.58), less well with acinar necrosis (r = 0.53) and inflammation (r = 0.50), and poorly with hemorrhage (r = 0.33) and perivascular infiltrate (r = 0.31). Inasmuch as edema and fat necrosis are not important determinants of severity, these observations could explain the poor prognostic value of serum amylase activity in patients with acute pancreatitis.

Plasma disappearance of homologous and heterologous pancreatic enzymes in dogs

Homologous and heterologous (human) pure pancreatic juice was infused into dogs to compare the behaviour of pancreatic enzymes in the circulation. This was achieved by estimating the magnitude of elevation and speed of disappearance of pancreatic enzymes in plasma. The half-lives of the plasma enzymes did not differ significantly between dogs and humans. However the half-lives of other enzymes (longest for amylase and shortest for trypsinogen) did differ. The magnitude of elevation expressed as a ratio of peak (5 min) to basal level was greatest for trypsinogen (28 times) and least for amylase (1.4 times). However, 289% and 410% of the initial lipase enzyme activity was recovered 5 min after infusion of dog and human pure pancreatic juice, respectively (44% when measured by immunoreactive human lipase activity). The excess recovery requires re-evaluation of diagnostic value of turbidimetric activity of plasma pancreatic lipase.

Trypsinogen-activation peptides in experimental rat pancreatitis: prognostic implications and histopathologic correlates

Intrapancreatic activation of trypsinogens is believed to occur either as a cause or a consequence of acute pancreatitis and to be associated with the more severe forms of the disease. Trypsinogen-activation peptides (TAPs) were measured in plasma, urine, and ascites of rats (n = 54) assigned to different pancreatitis-inducing regimens reproducing the entire spectrum of severity. Compared with survivors, nonsurvivors at 9 hours had significantly higher TAP levels in plasma at 3 hours (P = 0.0001), urine (peak, 1-4 hours) (P = 0.004), and ascites (P = 0.0001) after death. Stepwise discriminant analysis showed that TAP in urine and plasma were the most accurate predictors of outcome (88.2% of animals) compared with other routine laboratory parameters. Morphometric analysis showed that the best histopathologic correlates of TAP elevation were acinar necrosis and intrapancreatic hemorrhage. In a second series of experiments using a homogeneous technique of induction producing pancreatitis with a mortality of 55% at 48 hours, plasma TAP level at 3 hours (cutoff, 0.5 nmol/L) and/or urinary TAP level (peak, 1-6 hours; cutoff, 25 nmol/L) accurately predicted outcome in 85% of animals. It is concluded that the TAP assay gives an accurate early prediction of outcome in different pancreatitis models and correlates best with acinar necrosis and hemorrhage.

Involvement of heparin cofactor II in chymotrypsin neutralization and in the pancreatic proteinase-antiproteinase interaction during acute pancreatitis in man

Heparin cofactor II is a proteinase inhibitor which inhibits both chymotrypsin and thrombin, and displays great similarities with antithrombin III, the main inhibitor of thrombin in human plasma. Since acute pancreatitis is known to be associated with modification of the proteinase-antiproteinase equilibrium, we studied heparin cofactor II and antithrombin III as well as other biochemical and haematological parameters in 10 patients experiencing attacks of acute pancreatitis. Heparin cofactor II activity decreased during the first week of illness, while its antigen concentration remained subnormal. This discrepancy between antigen concentration and activity which persisted during the first week of illness was due both to complex formation of heparin cofactor II with its target proteinases and to partial proteolysis of the inhibitor. Heparin cofactor II was shown to form a complex with chymotrypsin in the plasma of such patients. Antithrombin III levels remained unchanged throughout the study, with no discrepancy between its activity and antigen concentration. No modification of haemostasis was shown either, except for a rise in the fibrinogen level during the first days of illness. It is concluded that, unlike antithrombin III, heparin cofactor II is involved in the proteinase-inhibitor equilibrium in patients with acute pancreatitis, and that heparin cofactor II might react as an inhibitor of pancreatic proteinases rather than an inhibitor of thrombin.

Serum enzymes and other laboratory tests in acute pancreatitis

This review evaluates selective enzymes and blood tests available for the diagnosis and prognosis of acute pancreatitis. It is concluded that serum amylase and lipase measurements represent the best available diagnostic methods. Newer alternative assays still require careful evaluation.

Role of serum pancreatic enzyme assays in diagnosis of pancreatic disease

The serum behavior of amylase, pancreatic isoamylase, lipase, trypsinogen, and elastase 1 was studied in 145 patients with pancreatic disease and in 66 patients with abdominal pain of nonpancreatic origin, for the purpose of evaluating the relative diagnostic utility of their assays. In 34 patients with acute pancreatitis, serum lipase, trypsinogen, and elastase 1 were elevated in all 34, pancreatic isoamylase in 33 (97%) and amylase in 30 (88%). Ten of these acute pancreatitis patients were followed sequentially for seven days: the variations in their serum enzyme levels were parallel, although the lipase, trypsinogen, and particularly the elastase 1 elevations persisted longer than did those of amylase and pancreatic isoamylase. Among the patients with chronic pancreatitis, either in painful relapse (N = 19) or with pancreatic cysts (N = 15), the respective percentages of enzymes elevations were: 79 and 80% for elastase 1, 68 and 67% for trypsinogen, 63 and 73% for pancreatic isoamylase, 58 and 60% for lipase, 53 and 60% for amylase. In the 52 chronic pancreatitis patients studied during clinical remission, serum enzyme behavior varied greatly, and a majority of the assays (60%) were normal; even in the case of severe pancreatic exocrine insufficiency, normal as well as abnormally high and low enzyme values were seen. Highly variable enzyme behavior was also seen in the 40 patients with pancreatic cancer, and elastase I was the most frequently (35%) elevated enzyme in this group as well. Among the patients with abdominal pain of nonpancreatic origin, abnormally high enzyme levels were present in percentages ranging from 6% for lipase to 21% for trypsinogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the role of pancreatic proteases in human abdominal aortic aneurysms and occlusive disease

Previous studies on the pathogenesis of abdominal aortic aneurysms have shown both elastase-like activity in the aortic wall and a decreased elastin content. The present study, using specific radioimmunoassays for pancreatic elastase 2 (IRE2) and cationic trypsin(ogen) (IRCT), investigates the concentrations of these proteases which are known to circulate in blood, in abdominal aortic aneurysms. Aortic specimens were obtained from 32 patients with aneurysms and 21 patients with atherosclerotic occlusive disease. Aortic tissue, obtained at autopsy from young adults, served as controls. Elastase-like activity was 300% and 800% higher, respectively, in aortic homogenates from aneurysms in comparison to occlusive disease and control aortic tissue. This was associated with 1.4-fold higher level of IRE2 and 2.7-fold higher levels of IRCT as compared to occlusive disease. Although there was no significant difference in the aortic collagen concentration among all 3 groups, the elastin content of aneurysmal aorta was 85% and 74% lower, respectively, in comparison to control and occlusive aorta. The results of this investigation demonstrate the presence of pancreatic elastase 2 and cationic trypsin(ogen) in abdominal aortic aneurysmal tissue and suggest that circulating pancreatic proteases contribute to the pathophysiology of aneurysms of the infrarenal aorta.