Antti J. Hietaranta

Inhibition of ubiquitin-proteasome pathway–mediated IκBα degradation by a naturally occurring antibacterial peptide

Induction of NF-kappaB-dependent gene expression plays an important role in a number of biological processes including inflammation and ischemia-reperfusion injury. However, few attempts aimed at selective regulation of this transcription factor have been successful. We report here that a naturally occurring antibacterial peptide PR39 reversibly binds to the alpha 7 subunit of the 26S proteasome and blocks degradation of NF-kappa B inhibitor I kappa B alpha by the ubiquitin-proteasome pathway without affecting overall proteasome activity. I kappa B alpha phosphorylation and ubiquitination occur normally after PR39 treatment, and binding of valosin-containing proteins is not impaired. The inhibition of I kappa B alpha degradation abolishes induction of NF-kappa B-dependent gene expression in cell culture and in mouse models of acute pancreatitis and myocardial infarction, including upregulation of endothelial adhesion proteins VCAM-1 and ICAM-1. In the latter model, sustained infusion of PR39 peptide resulted in significant reduction of myocardial infarct size. PR39 and related peptides may provide novel means to regulate cellular function and to control of NF-kappa B-dependent gene expression for therapeutic purposes.

Severe acute pancreatitis: prognostic factors in 270 consecutive patients.

Acute pancreatitis (AP) is a common abdominal disorder with severity varying from mild to fatal disease. Predicting a patients outcome remains problematic. The aim of this study was to analyze a large consecutive series of patients with severe AP and to identify prognostic factors for hospital mortality. Between 1989 and 1997, a consecutive series of 270 patients with severe AP were included in the study. All patients fulfilled the criteria of Atlanta classification for severe AP. Retrospectively and prospectively collected data included age, gender, etiology, number of previous episodes of pancreatitis, medication history, type of admission, body-mass index (BMI), respiratory failure, renal failure, need for pressor support, and abdominal surgery performed during hospitalization. The overall mortality rate was 24.4%. In univariate survival analysis advanced age, history of continuous medication, patient transferred from other hospital, high BMI, respiratory or renal failure, need for pressor support, and need for abdominal surgery were significant prognostic factors for hospital mortality. In a multivariate stepwise logistic regression analysis, the need of pressor support, renal failure requiring dialysis, advanced age, history of continuous medication and need for abdominal surgery were identified as independent prognostic factors for mortality. A logistic regression analysis of variables available on admission (the first seven above mentioned variables) showed that transferral admission, advanced age, and history of continuous medication were independent prognostic factors for mortality. In patients with severe AP, advanced age, history of continuous medication, and need for dialysis, mechanical ventilator support, and pressor support predict fatal outcome and thus should be taken into account in clinical evaluation.

Heat shock protein 70 prevents secretagogue-induced cell injury in the pancreas by preventing intracellular trypsinogen activation.

Rodents given a supramaximally stimulating dose of cholecystokinin or its analogue cerulein develop acute pancreatitis with acinar cell injury, pancreatic inflammation, and intrapancreatic digestive enzyme (i.e., trypsinogen) activation. Prior thermal stress is associated with heat shock protein 70 (HSP70) expression and protection against cerulein-induced pancreatitis. However, thermal stress can also induce expression of other HSPs. The current studies were performed using an in vitro system to determine whether HSP70 can actually mediate protection against pancreatitis and, if so, to define the mechanism underlying that protection. We show that in vitro exposure of freshly prepared rat pancreas fragments to a supramaximally stimulating dose of cerulein results in changes similar to those noted in cerulein-induced pancreatitis, i.e., intra-acinar cell trypsinogen activation and acinar cell injury. Short-term culture of the fragments results in HSP70 expression and loss of the pancreatitis-like changes noted after addition of cerulein. The culture-induced enhanced HSP70 expression can be prevented by addition of either the flavonoid antioxidant quercetin or an antisense oligonucleotide to HSP70. Under these latter conditions, addition of a supramaximally stimulating concentration of cerulein results in trypsinogen activation and acinar cell injury. These findings indicate that the protection against cerulein-induced pancreatitis that follows culture-induced (and possibly thermal) stress is mediated by HSP70. They suggest that the HSP acts by preventing trypsinogen activation within acinar cells.

Both thermal and non-thermal stress protect against caerulein induced pancreatitis and prevent trypsinogen activation in the pancreas

Background and aim: Recent studies have indicated that prior thermal stress causes upregulation of heat shock protein 70 (HSP70) expression in the pancreas and protects against secretagogue induced pancreatitis. The mechanisms responsible for the protective effect are not known. Similarly, the effects of prior non-thermal stress on HSP70 expression and pancreatitis are not known. The current studies were designed to specifically address these issues. Methods: In the current studies pancreatitis was induced by administration of a supramaximally stimulating dose of caerulein 12 hours after thermal stress and 24 hours after non-thermal (that is, β adrenergic stimulation) stress. Results: Both thermal and non-thermal stresses caused pancreatic HSP70 levels to rise and resulted in increased expression of HSP70 in acinar cells. Both forms of stresses protected against caerulein induced pancreatitis and prevented the early intrapancreatic activation of trypsinogen which occurs in this model of pancreatitis. Conclusions: These results suggest that both thermal and non-thermal stresses protect against pancreatitis by preventing intrapancreatic digestive enzyme activation and that HSP70 may mediate this protective effect.

Extracellular phospholipases A2 in relation to systemic inflammatory response syndrome (SIRS) and systemic complications in severe acute pancreatitis.

The pathophysiology of severe acute pancreatitis (AP) resembles other conditions with systemic inflammatory response syndrome (SIRS) such as sepsis predisposing to remote organ failure. Because extracellular phospholipases A2 (PLA2) have been implicated in AP, their serum concentrations were analyzed with respect to SIRS and systemic complications in patients with severe AP. The serum samples were collected daily for 12 days in 57 patients with severe AP. SIRS, early organ complications, local complications, and outcome of AP were recorded. Time-resolved fluoroimmunoassays were used for group I and group II PLA2 measurements. Thirty-nine (68.4%) patients fulfilled the criteria of SIRS within 12 days from admission. Pancreatic necrosis was detected in 43 (75.4%) patients. Infected necrosis was found preoperatively or at operation in five (8.8%) patients. Twenty-six (45.6%) and eight (14.0%) patients had respiratory or renal failure, respectively. Seven (12.3%) patients died of their disease. All patients with systemic complications fulfilled the criteria of SIRS. The increasing number of positive SIRS criteria was associated with increased frequency of systemic complications. Pancreatic necrosis was not significantly associated with SIRS. The serum concentration of group II PLA2 was significantly higher in patients with SIRS (p < 0.05) compared with patients without from day 7 onward. The concentration of group II PLA2 increased (p < 0.01) in patients with SIRS but decreased in patients without. The serum concentration of group II PLA2 did not differ significantly with respect to systemic complications. The concentration of group I PLA2 decreased (p < 0.05) similarly in patients with and without SIRS or systemic complications during follow-up, respectively. Early systemic complications of severe AP are associated with SIRS with increasing frequency as the number of positive SIRS criteria increases. Group II PLA2 but not group I PLA2 may have pathophysiologic importance in severe AP-associated SIRS. Increasing serum concentration of group II PLA2 seems to reflect the ongoing systemic inflammation in severe AP-associated SIRS.

Rat pancreatic phospholipase A2

SummaryPhospholipase A2 (PLA2, E.C. 3.1.1.4) was purified from rat pancreatic tissue by heat treatment of the homogenate and use of cation-exchange chromatography on a CM-Sepharose column. The enzyme was apparently homogenous on SDS polyacrylamide gel electrophoresis, and its mol wt was estimated to be 14,400. An antiserum raised against rat pancreatic PLA2 in a rabbit was used in a solid-phase enzyme immunoassay employing inorganic pyrophosphatase (E.C. 3.6.1.1) as the enzyme label. As measured by this assay, the concentration of pancreatic PLA2 in plasma was found to be above normal in rats with hemorrhagic pancreatitis induced by an intraductal injection of sodium taurocholate. PLA2 was localized in pancreatic acinar cells and in the chief cells in the mucosa of the glandular stomach by immunohistochemistry. By immunoelectron microscopy, the immunogold conjugates were mainly located on profiles of zymogen granules in acinar cells.

Pancreatic phospholipase A2 in proximal tubules of rat kidney in experimental acute pancreatitis and after intravenous injection of the enzyme

Kinetics and distribution of i.v. human pancreatic phospholipase A2 (h-PLA2) were determined in intact and nephrectomized rats, and tissue localization of rat pancreatic PLA2 (r-PLA2) was studied by immunohistochemistry in experimental acute pancreatitis. The concentration of h-PLA2 and the catalytic activity of phospholipase A2 in plasma decreased exponentially in intact and nephrectomized animals after the injection. The initial 15-min half-life was considerably longer in nephrectomized animals, and higher h-PLA2 concentrations and PLA2 catalytic activities were found in plasma. h-PLA2 was localized in endocytotic vesicles and apical cytoplasmic vacuoles in proximal tubule cells of the kidney. The intensity of the immunoreaction decreased considerably between 15 and 50 min in these cells. No signs of tubular damage were seen by light microscopy. Neither immunoreactive h-PLA2 nor PLA2 catalytic activity was found in urine. r-PLA2 was observed in proximal tubule cells 15 min after an injection of sodium taurocholate (necrotizing pancreatitis group) or saline (edematous pancreatitis group) into the pancreatic duct. Signs of tubular damage were present in necrotizing pancreatitis, but tubular morphology was normal in the animals with edematous pancreatitis. We conclude that the proximal tubule cells of the kidney participate in the metabolism of circulating pancreatic PLA2, and considerably higher PLA, levels persist in plasma in nephrectomized animals. Endogenous pancreatic PLA, is detected in kidneys in acute pancreatitis.

The role of phospholipase a2 in pancreatic acinar cell injury

SummaryThe integrity of rat pancreatic acinar cells under the influence of human phospholipase A2 (PLA2) was studied. Isolated pancreatic acini showed no increased discharge of aspartylaminotransferase (ASAT) when incubated either in solutions containing human pancreatic PLA2 or the bile salt sodium deoxycholate (DEC), the latter in concentrations that augment PLA2 activity but have no destructive detergent effect. When human pancreatic PLA2 was injected into the rat pancreatic duct, uneven distribution was observed at 15 min and 3 h in immunohistochemical sections. Edema and a mild inflammatory reaction were the main changes in the pancreas. The necrotic areas seen by light and electron microscopy were quite small and located mostly at the periphery of lobules corresponding the spread of the injected material. Necrosis was of the coagulation type and showed equal extent after the injection of PLA2 with or without DEC. Internalized human pancreatic PLA2 was present already 15 min after the injection in the cytoplasm of some intact acinar cells, indicating a functioning protective mechanism. It was concluded that pancreatic acinar cells are quite resistant to PLA2-catalyzed hydrolysis of membrane phospholipids in vitro, but additional trauma, e.g., pressure caused by intraductal injection, and tissue related factors, such as the mediators of the inflammatory reaction, make acinar cells susceptible to the effect of PLA2.

Pancreatic phospholipase A2 in cerulein-induced acute pancreatitis in the rat

SummaryWe investigated the concentration of immunoreactive pancreatic phospholipase A2 (pan-PLA2) and the catalytic activity of phospholipase A2 (CA-PLA2) in plasma and pancreases of rats with cerulein-induced acute pancreatitis. Edematous pancreatitis with ascites and fat necroses in the abdominal cavity developed after 8 h infusion of cerulein (5 μg/kg/h). Large vacuoles were found in acinar cells and there were small areas of acinar cell necrosis. No pathological changes were seen in saline-infused control animals. Pancreatic PLA2 was localized by immunohistochemistry in pancreatic acinar cells in both groups of animals and in the proximal tubular cells of the kidney in cerulein-infused animals. The lungs and kidneys appeared normal by light microscopy in all animals. The pan-PLA2 values increased markedly, whereas the CA-PLA2 values did not change during the cerulein-infusion. The CA-PLA2 values in the homogenates of pancreatic tissue of cerulein-infused animals did not differ significantly from those of saline-infused controls. The results indicate that the CA-PLA2 in plasma is independent from the concentration of pan-PLA2 in cerulein-induced acute pancreatitis in rat.

Early acinar cell changes in caerulein-induced interstitial acute pancreatitis in the rat

Early ultrastructural and immunohistochemical changes caused by supramaximal secretory stimulation with caerulein were studied in the rat pancreas. The morphological basis for the earlier reported decrease of pancreatic juice secretion after supramaximal caerulein was the appearance of swollen and irregular zymogen-like material containing structures with short segments of budding bristle-coated membranes in the apical parts of acinar cells. Images of exocytosis of zymogen granules were only few. Later, marked vacuolization and signs of autophagocytosis are seen in the basal cytoplasm. Immunohistochemistry showed that the large zymogen containing structures were intensively labelled for trypsin at the early stages of the experiment (4-30 min). Later (1-2 h), the vacuoles were empty or contained occasional, small-labelled granules only. The pancreozymin-receptor antagonist proglumide as well as cycloleucine that inhibits protein synthesis by inhibiting the synthesis of S-adenosylmethionine, effectively prevented the caerulein induced acinar cell changes. The irregular zymogen containing structures with coated pits on their surface indicate disturbed zymogen granule formation leading to the accumulation of large lakes of zymogen material and finally to marked autophagocytosis in acinar cells. The effects of caerulein are receptor-mediated and depend on the process of methylation in the formation of zymogen granules.