Pancreatic pseudocysts: a biochemical evaluation of proteases and protease inhibitors in plasma

Complement in Pancreatic Disease-Perpetrator or Savior?

The complement system is a major pillar of the humoral innate immune system. As a first line of defense against pathogens, it mediates early inflammatory response and links different branches of humoral and cellular immunity. Disorders affecting the exocrine pancreas, such as acute pancreatitis, potentially lead to a life-threatening systemic inflammatory response with aberrant activation of complement and coagulation cascades. Pancreatic proteases can activate key effectors of the complement system, which in turn drive local and systemic inflammation. Beyond that, the extent of pancreas–complement interaction covers complex pro- and anti-inflammatory mechanisms, which to this day remain to be fully elucidated. This review provides a comprehensive overview of the pathophysiological role of complement in diseases of the exocrine pancreas, based on existing experimental and clinical data. Participation of complement in acute and chronic pancreatitis is addressed, as well as its role in tumor immunology. Therapeutic strategies targeting complement in these diseases have long been proposed but have not yet arrived in the clinical setting.

Advances in the enzyme diagnosis of pancreatic diseases

This paper reviews recent developments of analytical methods for the determination of alpha-amylase, of its isoenzymes, and of lipase. The evaluation of severity and etiology of acute pancreatitis by enzyme assays, e.g., pancreatic elastase 1, phospholipase A2, and routine enzymes are discussed. The limited significance of enzyme determinations as compared to imaging and endoscopic procedures for the diagnosis of chronic pancreatitis is demonstrated. Indirect "tubeless" tests for the evaluation of pancreatic exocrine insufficiency with respect to the secretion of chymotrypsin (chymotrypsin in stool and NBT-PABA test) and cholesterol esterase (pancreolauryl test) are reviewed. Finally, the superiority of morphologic investigations over biochemical tests for the timely detection of pancreatic carcinoma is shown.

Pancreatic pseudocyst fluid--a mixture of plasma proteins and pancreatic juice possessing a high proteolytic activity

Pancreatic pseudocyst fluid from eight patients was examined biochemically. The fluid was found to be a mixture of plasma proteins and pancreatic juice, possessing a high proteolytic activity against high- as well as low-molecular-weight proteins. The proteolytic activity was found to be trypsin-, kallikrein- and plasmin-like. Gel filtration studies showed proteolytic activity to be present corresponding to alpha-2-macroglobulin-bound proteases and also to free proteases. Quantitative immunochemical levels were about 30-100% of normal plasma levels for alpha-2-macroglobulin, C1 inhibitor, antithrombin III and alpha-2-antiplasmin. However, there was practically no functional inhibitory capacity left in the pseudocyst fluid, except for alpha-1-protease inhibitor, which retained its inhibitory capacity. Neither native kininogen nor complement factor C3 was found: this was probably a result of the proteolytic activity. It is concluded, that a continuing proteolytic activity within the pseudocyst, although decreasing with aging of the cyst, could explain symptoms and complications caused by the pseudocyst.

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

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 x 10(3) U/min/100 microliters). 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.