Timo J. Nevalainen

Experimental pancreatitis in the rat. Sodium taurocholate-induced acute haemorrhagic pancreatitis.

Sodium taurocholate injected into the pancreatic duct system of the rat caused acute haemorrhagic pancreatitis. The pancreatic lesions were immediate and characterized by interstitial oedema, extensive necrotic changes of the acinar cells, and haemorrhages during the first 24 h after the injection. In animals surviving 72 h there were marked acinar atrophy and pancreatic fibrosis. The mortality increased according to the amount of sodium taurocholate injected. Except for necrosis of occasional liver cells, other organs examined were histologically normal. This investigation created an experimental model for studying the pathogenesis of acute pancreatitis. The results support the hypothesis that bile can initiate acute haemorrhagic pancreatitis.

Importance of group X–secreted phospholipase A2 in allergen-induced airway inflammation and remodeling in a mouse asthma model

Arachidonic acid metabolites, the eicosanoids, are key mediators of allergen-induced airway inflammation and remodeling in asthma. The availability of free arachidonate in cells for subsequent eicosanoid biosynthesis is controlled by phospholipase A2s (PLA2s), most notably cytosolic PLA2-α. 10 secreted PLA2s (sPLA2s) have also been identified, but their function in eicosanoid generation is poorly understood. We investigated the role of group X sPLA2 (sPLA2-X), the sPLA2 with the highest in vitro cellular phospholipolysis activity, in acute and chronic mouse asthma models in vivo. The lungs of sPLA2-X−/− mice, compared with those of sPLA2-X+/+ littermates, had significant reduction in ovalbumin-induced infiltration by CD4+ and CD8+ T cells and eosinophils, goblet cell metaplasia, smooth muscle cell layer thickening, subepithelial fibrosis, and levels of T helper type 2 cell cytokines and eicosanoids. These data direct attention to sPLA2-X as a novel therapeutic target for asthma.

Epidemiology of intestinal and diffuse types of gastric carcinoma a time‐trend study in finland with comparison between studies from high‐ and low‐risk areas

The incidence of gastric cancer has declined markedly in Finland during the last 4 decades. To document the changes caused by that in the ratio of the intestinal type (IT) to the diffuse type (DT) of gastric carcinoma we compared the 367 cases diagnosed from southwestern Finland at the Department of Pathology, Turku University, from 1950–1959 and 1076 cases from 1980–1989. IT virtually disappeared in the male and female populations younger than 50 years, and in patients younger than 60 years, DT became more common than IT (P < 0.001). The transitional age, the time at which IT exceeds DT in frequency, shifted by 20 years to older age groups. In patients older than 60 years, IT remained the dominant type, but the ratio of IT to DT (IT:DT) decreased in men from 3.8 to 2.1 (P < 0.05) and in women from 4.4 to 2.1 (P < 0.001). No decrease in the frequency of DT could be demonstrated in the material studied. The disappearance of the male‐dominant IT in the younger male population changed the male‐to‐female ratio of patients reported to the Finnish Cancer Registry. When the ratio IT:DT in Finland was compared with the ratios reported by the authors in data from other continents and by other investigators, regional variations in basal level of IT:DT emerged. This phenomenon seems to be based on the differing genetic susceptibility to DT of various races. The decrease of IT, seen in reports from regions with declining incidence of gastric carcinoma, seems to be connected to a diminished rate of severe chronic gastritis.

Acinar cell carcinoma of the pancreas

Pancreatic acinar cell carcinoma is a rare neoplasm (comprising about 1% of pancreatic tumours). We studied three cases (61‐year‐old female; 42‐year‐old male; 57‐year‐old male), whose survival after diagnosis ranged from 1 year 2 months to 6 years 8 months. There were widespread metastases in each case. The tumours had acinar, trabecular and solid growth patterns. By immunohistochemistry, pancreatic acinar cell markers including carboxyl ester lipase, pancreatic secretory trypsin inhibitor and pancreatic phospholipase A2 (group I PLA2) gave a strong positive reaction in all three cases. By electron microscopy, zymogen granules were seen in the cytoplasm of the tumour cells. Immunostaining for prostate‐specific antigen was positive in all three cases. Above‐normal concentrations of pancreatic PLA2 were measured in the serum of one patient and the values decreased during chemotherapy concomitantly with the reduction in the size of the tumour mass. In conclusion, immunohisto‐chemical demonstration of the secretory products of acinar cells including the new marker pancreatic PLA2 is useful in the differential diagnosis of pancreatic acinar cell carcinoma. Determination of the concentration of pancreatic group I PLA2 in serum may be helpful in the evaluation of therapy.

Antibacterial actions of secreted phospholipases A2. Review

Antibacterial properties of secreted phospholipases A2 (PLA2) have emerged gradually. Group (G) IIA PLA2 is the most potent among mammalian secreted (s) PLA2s against Gram-positive bacteria, but additional antibacterial compounds, e.g. the bactericidal/permeability-increasing protein, are needed to kill Gram-negative bacteria. The mechanisms of binding to the bacterial surface and the killing of bacteria by sPLA2s are based on the positive charge of the PLA2 protein and its phospholipolytic enzymatic activity, respectively. The concentration of GIIA PLA2 is highly elevated in serum of patients with bacterial sepsis, and overexpression of GIIA PLA(2) protects transgenic mice against experimental Gram-positive infection. The synthesis and secretion of GIIA PLA2 are stimulated by the cytokines TNF-alpha, IL-1 and IL-6. Secreted PLA2s may be potentially useful new endogenous antibiotics to combat infections including those caused by antibiotic-resistant bacteria such as methicillin-resistant staphylococci and vancomysin-resistant enterococci.

Pathophysiologic role of oxygen free radicals in acute pancreatitis: initiating event or mediator of tissue damage?

BACKGROUND AND OBJECTIVE Oxidative stress is an important factor in the pathogenesis of acute pancreatitis, as shown in vivo by the beneficial effects of scavenger treatment and in vitro by the potential of free radicals to induce acinar cell damage. However, it is still unclear whether oxygen free radicals (OFR) act only as mediators of tissue damage or represent the initiating event in acute pancreatitis in vivo as well. In the present study the authors aimed to address this issue in an experimental set-up. MATERIALS AND METHODS Two hundred male Wistar rats were randomly assigned to one of the following experimental groups. In two groups, acute necrotizing pancreatitis was induced by retrograde intraductal infusion of 3% sodium taurocholate. Through the abdominal aorta, a catheter was advanced to the origin of the celiac artery for continuous regional arterial (CRA) pretreatment with isotonic saline (NP-S group) or superoxide dismutase/catalase (NP-SOD/CAT group). In another group, oxidative stress was generated by CRA administration of xanthine oxidase and intravenous administration of hypoxanthine (HX/XOD group). Sham-operated rats received isotonic saline both arterially and intraductally. After observation periods of 5 and 30 minutes and 3 and 6 hours, the pancreas was removed for light microscopy and determination of reduced glutathione (GSH), oxidized glutathione (GSSG), conjugated dienes (CD), and malondialdehyde as a marker for OFR-induced lipid peroxidation as well as myeloperoxidase as a parameter for polymorphonuclear leukocyte accumulation. RESULTS A significant decrease of GSH was paralleled by an increased ratio of GSSG per total glutathione and elevated CD levels after 5 minutes in the NP-S group versus the sham-operated group. Thereafter, the percentage of GSSG and GSH returned to normal levels until the 6-hour time point. After a temporary decrease after 30 minutes, CD levels increased again at 3 hours and were significantly higher at 6 hours in contrast to sham-operated rats. Myeloperoxidase levels were significantly elevated at 3 and 6 hours after pancreatitis induction. In contrast to NP-S rats, treatment with SOD/CAT significantly attenuated the changes in glutathione metabolism within the first 30 minutes and the increase of CDs after 6 hours. HX/XOD administration lead to changes in levels of GSH, GSSG, and CDs at 5 minutes as well as to increased myeloperoxidase levels at 3 hours; these changes were similar to those observed in NP-S rats. Acinar cell damage including necrosis was present after 5 minutes in both NP groups, but did not develop in HX/XOD rats. In addition, serum amylase and lipase levels did not increase in the latter group. SOD/CAT treatment significantly attenuated acinar cell damage and inflammatory infiltrate compared with NP-S animals during the later time intervals. CONCLUSION OFRs are important mediators of tissue damage. However, extracellular OFR generation alone does not induce the typical enzymatic and morphologic changes of acute pancreatitis. Factors other than OFRs must be involved for triggering acute pancreatitis in vivo.

Distribution of pancreatic (group I) and synovial-type (group II) phospholipases A2 in human tissues.

The catalytic activity of phospholipase A2 (cat-PLA2) and the concentration of pancreatic (group I) phospholipase A2 (pan-PLA2) and synovial-type (group II) phospholipase A, (syn-PLA2) were studied in 19 human tissues in order to find potential sources of circulating phospholipase A2. Five specimens of each tissue were collected at autopsies or from normal deliveries (placentas and amnionic membranes). The concentrations of pan-PLA2 and syn-PLA2 were measured by specific timeresolved fluoroimmuncassays. The cat-PLA2 was measured by radioactive dipalmitoyl phosphatidylcholine as substrate. The concentration of pan-PLA2 was negligible in all tissue homogenales except the pancreas. Immunoreactive syn-PLA2 was found in the homogenates of the digestive tract, cartilage, and prostatic and parotid glands. By immunohistochemistry, syn-PLA2 was localized in Paneth cell secretory granules, chondrocytes, cartilage: matrix, and glandular cells of prostate.

Experimental pancreatitis in the rat. Ultrastructure of sodium taurocholate-induced pancreatic lesions.

Necrotic lesions caused by the intraductal injection of sodium taurocholate in rat pancreas were studied by electron microscopy. The early (1 and 15 min after the injection) ductal cells were often necrotic. The acinar cell damage was characterized by mitochondrial swelling, vesiculation of the granular endoplasmic reticulum, and dissolution of cellular membranes. At later time intervals (1, 3, and 6 h) there were necrotic acinar cells with heterogeneous cytoplasmic inclusions representing degenerative cell organelles and their remnants. At 6, 12, and 24 h there were autophagic vacuoles in sublethally damaged acinar cells. The zymogen granules seemed relatively well preserved throughout the experiment. The vascular lesions consisted of endothelial detachment, extravasation of erythrocytes, thrombosis, and poikilocytosis. It was concluded that the initial cell injury was caused by the detergent action of the injected bile salt.

Phospholipase A2 in Acute Pancreatitis

Acute pancreatitis is an autodigestive disease, in which digestive enzymes produced by the pancreas destroy the gland. Opie and Meakins [29] proposed that it is trypsin that causes the tissue injury. However, it seems more probable that phospholipase A2 might be the enzyme responsible for autodigestion in acute pancreatitis [26]. Accordingly, increased catalytic activities of this enzyme [33] as well as above-normal concentrations of immunoreactive phospholipase A2 [27] have been detected in sera of patients suffering from acute pancreatitis.

Human acute pancreatitis: a light and electron microscopic study.

The histology and ultrastructure of resected pancreas from seven patients suffering from acute haemorrhagic pancreatitis were studied. Special attention was paid to necrotic acini and zymogen granules. Acinar cells in the border of necrotic and non-necrotic parenchyma contained lipid droplets, autophagic vacuoles, bundles of intermediate filaments and degenerated cell organelles, including zymogen granules, PAS-positive material derived from secretory proteins was situated in dilated acinar lumina and in the interstitium, and proved to be fibrillar in fine structure. There were thrombosed vessels and extravasated erythrocytes at the border of the parenchymal necrosis. Bundles of intermediate filaments were often the only identifiable structures in the severely necrotic acinar cells. The amount of lipid was decreased in damaged fat cells. Older fat necroses were surrounded by myofibroblasts. It was concluded that acinar and fat cells undergo concomitant necrosis in the inflamed pancreas, zymogen granules degenerate in the acinar cells at the border of necrotic and non-necrotic areas, and secretory proteins may be displaced in the interstitium outside acinar lumina. Myofibroblasts participate in the healing of autodigestive injuries.