Trypsin and activation of circulating trypsinogen contribute to pancreatitis-associated lung injury. (1/24)

Pancreatic proteases are secreted in acute pancreatitis, but their contribution to associated lung injury is unclear. Applying models of mild edematous (intravenous caerulein) and severe necrotizing (intraductal glycodeoxycholic acid) pancreatitis in rats, we showed that both trypsinogen and trypsin concentrations in peripheral blood, as well as lung injury, correlate with the severity of the disease. To isolate the potential contribution of proteases to lung injury, trypsin or trypsinogen was injected into healthy rats or trypsinogen secreted in caerulein pancreatitis was activated by intravenous enterokinase. Pulmonary injury induced by protease infusions was dose dependent and was ameliorated by neutrophil depletion. Trypsinogen activation worsened lung injury in mild pancreatitis. In vitro incubation of leukocytes with trypsinogen showed that stimulated leukocytes can convert trypsinogen to trypsin. In conclusion, this study demonstrates that the occurrence and severity of pancreatitis-associated lung injury (PALI) corresponds to the levels of circulating trypsinogen and its activation to trypsin. Neutrophils are involved in both protease activation and development of pulmonary injury.  (+info)

Comparison of the effects of bile acids on cell viability and DNA synthesis by rat hepatocytes in primary culture. (2/24)

Bile acid-induced inhibition of DNA synthesis by the regenerating rat liver in the absence of other manifestation of impairment in liver cell viability has been reported. Because in experiments carried out on in vivo models bile acids are rapidly taken up and secreted into bile, it is difficult to establish steady concentrations to which the hepatocytes are exposed. Thus, in this work, a dose-response study was carried out to investigate the in vitro cytotoxic effect of major unconjugated and tauro- (T) or glyco- (G) conjugated bile acids and to compare this as regards their ability to inhibit DNA synthesis. Viability of hepatocytes in primary culture was measured by Neutral red uptake and formazan formation after 6 h exposure of cells to bile acids. The rate of DNA synthesis was determined by radiolabeled thymidine incorporation into DNA. Incubation of hepatocytes with different bile acid species - cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), in the range of 10-1000 microM - revealed that toxicity was stronger for the unconjugated forms of CDCA and DCA than for CA and UDCA. Conjugation markedly reduced the effects of bile acids on cell viability. By contrast, the ability to inhibit radiolabeled thymidine incorporation into DNA was only slightly lower for taurodeoxycholic acid (TDCA) and glycodeoxycholic acid (GDCA) than for DCA. When the effect of these bile acids on DNA synthesis and cell viability was compared, a clear dissociation was observed. Radiolabeled thymidine incorporation into DNA was significantly decreased (-50%) at TDCA concentrations at which cell viability was not affected. Lack of a cause-effect relationship between both processes was further supported by the fact that well-known hepatoprotective compounds, such as tauroursodeoxycholic acid (TUDCA) and S-adenosylmethionine (SAMe) failed to prevent the effect of bile acids on DNA synthesis. In summary, our results indicate that bile acid-induced reduction of DNA synthesis does not require previous decreases in hepatocyte viability. This suggests the existence of a high sensitivity to bile acids of cellular mechanisms that may affect the rate of DNA repair and/or proliferation, which is of particular interest regarding the role of bile acids in the etiology of certain types of cancer.  (+info)

cAMP inhibits bile acid-induced apoptosis by blocking caspase activation and cytochrome c release. (3/24)

We have previously shown that cAMP protects against bile acid-induced apoptosis in cultured rat hepatocytes in a phosphoinositide 3-kinase (PI3K)-dependent manner. In the present studies, we investigated the mechanisms involved in this anti-apoptotic effect. Hepatocyte apoptosis induced by glycodeoxycholate (GCDC) was associated with mitochondrial depolarization, activation of caspases, the release of cytochrome c from the mitochondria, and translocation of BAX from the cytosol to the mitochondria. cAMP inhibited GCDC-induced apoptosis, caspase 3 and caspase 9 activation, and cytochrome c release in a PI3K-dependent manner. cAMP activated PI3K in p85 immunoprecipitates and resulted in PI3K-dependent activation of the survival kinase Akt. Chemical inhibition of Akt phosphorylation with SB-203580 partially blocked the protective effect of cAMP. cAMP resulted in wortmannin-independent phosphorylation of BAD and was associated with translocation of BAD from the mitochondria to the cytosol. These results suggest that GCDC-induced apoptosis in cultured rat hepatocytes proceeds through a caspase-dependent intracellular stress pathway and that the survival effect of cAMP is mediated in part by PI3K-dependent Akt activation at the level of the mitochondria.  (+info)

Pulmonary injury in acute experimental pancreatitis correlates with elevated levels of free fatty acids in rats. (4/24)

Since some authors have stated a certain role for so-called "free fatty acids" (FFA) in the pathogenesis of AP and the subsequent systemic complications we tried to find possible correlations between FFA, pancreatitis and lung injury using a rat model. AP was induced by intraductal infusion of two different concentrations of glycodeoxycholic acid (GDOC 17 mmol and 34 mmol). An equal number of animals had only cannulation of the pancreatic duct without infusion and served as controls (GDOC-control). In another experimental model iv.-infusion of oleic acid (OA) was used to create severe lung injury comparable to human ARDS. In this model control animals received iv.-infusion of saline solution only (SAL). At 2, 6, 12, 24 and 48 hours the animals were sacrificed and blood was collected for determination of FFA, amylase and pO2. The pancreas and lungs were removed for histologic examination and the lungs were weighed. GDOC-34 animals developed severe pancreatitis with hemorrhage and necrosis. Histology of the lungs showed edema, inflammatory infiltrates, hemorrhage and thickening of the alveolar membrane in GDOC-34 rats as well as in OA-animals. In contrast, there was only pancreatic edema until 24 hours in the GDOC 17 group and less severe histological changes in the lungs. Amylase, FFA, pO2 and lung weight were directly influenced by the different kinds of treatment. Furthermore, FFA correlated positively with the levels of amylase and lung weight and negatively with pO2. Infusion of OA alone also caused an increase in levels of amylase with pancreatic edema and focal necroses in some animals. These results show that it was possible to create different degrees of severity of AP which was in concordance with different degrees of morphologic changes and dysfunction in the lungs. FFA values correlated significantly with the clinical course as well as with increasing amylase, lung weight and decreasing pO2.  (+info)

Effect of tamoxifen and raloxifene on the conjugation of bile acids with taurine and glycine in ovariectomized rats. (5/24)

The selective estrogen receptor modulators tamoxifen and raloxifene represent a major therapeutic advance for clinical practice. Unlike estrogens, which are uniformly agonists, tamoxifen and raloxifene exert selective agonistic or antagonistic effects on various estrogen target tissues. The aim of the study was to evaluate the influence of tamoxifen and raloxifene on the conversion of cholesterol to bile acids in estrogen deficiency in rats. The study included 40 female Wistar rats. The animals were divided into four groups: sham operated control, ovariectomized control, ovariectomized rats treated with tamoxifen ovariectomized rats treated with raloxifene. After 42 days of drug administration, bile was collected under anesthesia after administration of radioactive 4-(14)C cholesterol. Bile was assayed for concentration of (14)C bile acids conjugated with taurine and glycine after thin-layer chromatography separation by the use of isotopic technique. In rats treated with tamoxifen and raloxifene, the statistically significant increase in concentration of bile acids conjugated with glycine was observed as compared to ovariectomized animals from control group. Moreover, in rats treated with tamoxifen the concentration of bile acids conjugated with taurine significantly increased. The results of the present study suggest that tamoxifen and raloxifene increase the concentrations of conjugated bile acids in bile.  (+info)

Interaction of complement and leukocytes in severe acute pancreatitis: potential for therapeutic intervention. (6/24)

In acute pancreatitis, local as well as systemic organ complications are mediated by the activation of various inflammatory cascades. The role of complement in this setting is unclear. The aim of the present study was to determine the level of complement activation in experimental pancreatitis, to evaluate the interaction of complement and leukocyte-endothelium activation, and to assess the effects of complement inhibition by soluble complement receptor 1 (sCR1) in this setting. Necrotizing pancreatitis was induced in Wistar rats by the combination of intravenous cerulein and retrograde infusion of glycodeoxycholic acid into the biliopancreatic duct; edematous pancreatitis was induced by intravenous cerulein only. In control animals, a sham operation (midline laparotomy) was performed. Complement activation, leukocyte sequestration, and pancreatic as well as pulmonary injury were assessed in the presence/absence of sCR1. Increased levels of C3a were found in necrotizing but not in edematous pancreatitis. When complement activation in necrotizing pancreatitis was blocked by sCR1, levels of C3a and total hemolytic activity (CH50) were decreased. Leukocyte-endothelial interaction, as assessed by intravital microscopy, and pancreatic as well as pulmonary organ injury (wet-to-dry weight ratio, MPO activity, and histology) were ameliorated by sCR1. As a result of the present study, necrotizing but not edematous pancreatitis is characterized by significant and early complement activation. Based on the interaction of complement and leukocytes, complement inhibition by sCR1 may be a valuable option in the treatment of leukocyte-associated organ injury in severe pancreatitis.  (+info)

A better model of acute pancreatitis for evaluating therapy. (7/24)

Existing models of acute pancreatitis have limitations to studying novel therapy. Whereas some produce mild self-limited pancreatitis, others result in sudden necrotizing injury. The authors developed an improved model providing homogeneous moderately severe injury by superimposing secretory hyperstimulation on minimal intraductal bile acid exposure. Sprague-Dawley rats (n = 231) received low-pressure intraductal glycodeoxycholic acid (GDOC) at very low (5 or 10 mmol/L) concentrations followed by intravenous cerulein. Cerulein or GDOC alone caused only very mild inflammation. However, GDOC combined with cerulein was uniformly associated with more edema (p less than 0.0005), acinar necrosis (p less than 0.01), inflammation (p less than 0.006), and hemorrhage (p less than 0.01). Pancreatic injury was further increased and death was potentiated by increasing volume and duration of intraductal low-dose GDOC infusion. There was significant morphologic progression between 6 and 24 hours. The authors conclude that (1) combining minimal intraductal bile acid exposure with intravenous hyperstimulation produces homogeneous pancreatitis of intermediate severity that can be modulated at will; (2) the injury is progressive over at least 24 hours with finite mortality rate; (3) the model provides superior opportunity to study innovative therapy.  (+info)

Biosynthesis of bile acids in a variety of marine bacterial taxa. (8/24)

Several marine bacterial strains, which were isolated from seawater off the island Dokdo, Korea, were screened to find new bioactive compounds such as antibiotics. Among them, Donghaeana dokdonensis strain DSW-6 was found to produce antibacterial agents, and the agents were then purified and analyzed by LC-MS/MS and 1D- and 2D-NMR spectrometries. The bioactive compounds were successfully identified as cholic acid and glycine-conjugated glycocholic acid, the 7alpha-dehydroxylated derivatives (deoxycholic acid and glycodeoxycholic acid) of which were also detected in relatively small amounts. Other masine isolates, taxonomically different from DSW-6, were also able to produce the compounds in a quite different production ratio from DSW-6. As far as we are aware of, these bile acids are produced by specific members of the genus Streptomyces and Myroides, and thought to be general secondary metabolites produced by a variety of bacterial taxa that are widely distributed in the sea.  (+info)

• 1
• 2
• 3