Effects of ethanol feeding on collagen synthesizing and degrading enzymes in rat pancreas

Assessment of the protective effects of oral tocotrienols in arginine chronic-like pancreatitis

Tocotrienols exhibit anti-inflammatory properties over macrophages and promote cytotoxicity in activated pancreatic stellate cells, suggesting that they may limit chronic pancreatitis progression. We aimed to quantitate the effect of oral tocotrienols on a rat model of chronic pancreatic injury. Chronic-like pancreatitis was induced by repeated arginine pancreatitis. Palm oil tocotrienol-rich fraction (TRF) was given by gavage before and after pancreatitis inductions. Amylase and hydroxyproline were determined in pancreatic homogenates; collagen, fibronectin, α-smooth muscle actin (SMA), glial fibrillary acidic protein (GFAP), and phosphorylated Smad3 were assessed by Western blotting. Transforming growth factor (TGF)-β1 was measured in plasma. Morphological assessment included light microscopy, fibrosis area fraction, and collagen network fractal analysis. Arginine pancreatitis induced pancreatic atrophy and increased hydroxyproline that ameliorated after TRF. Arginine increased TGF-β1 (185 ± 40 vs. 15 ± 2 ng/ml; P <0.01) that was blunted by TRF (53 ± 19; P < 0.01). TRF reduced protease and Smad3 activation, collagen, and fibronectin. α-SMA increased and GFAP diminished in arginine pancreatitis, consistent with long-term stellate cell activation, and TRF reverted these changes to basal. Arginine pancreatitis increased fibrosis area fraction (4.5 ± 0.3% vs. 0.2 ± 0.2%), collagen network complexity (fractal dimension 1.52 ± 0.03 vs. 1.42 ± 0.01; P < 0.001), and inhomogeneity (lacunarity 0.63 ± 0.03 vs. 0.40 ± 0.02; P < 0.001), which were all reduced by TRF (1.3 ± 0.4%, 1.43 ± 0.02%, and 0.51 ± 0.03%, respectively; P < 0.01). Best correlation coefficients were obtained when comparing fibrosis area fraction with lacunarity (r = 0.88) and both parameters with pancreatic weight (r = -0.91 and -0.79, respectively). TRF administered only before pancreatitis best, but not fully, recapitulated the beneficial effects of TRF. Tocotrienols improve quantitative measures of chronic pancreatic damage. They may be of benefit in human chronic pancreatitis.

Progression of pancreatitis prior to diabetes onset in WBN/Kob-Lepr(fa) rats

We established the WBN/Kob-Lepr(fa) rat as a new congenic strain for the fa allele of the leptin receptor gene (Lepr). Homozygous (fa/fa) WBN/Kob-Lepr(fa) rats provide a model of non-insulin-dependent diabetes, although its onset is secondary to pancreatitis. In the present study, we compared histopathological observations of pancreatitis in each genotype of this rat, to examine its suitability as a model of pancreatitis. The histopathological findings of the pancreatitis revealed intense changes dependent on age, such as hemorrhage or hemosiderin deposition. The pancreatitis in homozygous (fa/fa) WBN/Kob-Lepr(fa) rats were more severe than those of WBN/Kob rats.

Activated perilobular, not periacinar, pancreatic stellate cells contribute to fibrogenesis in chronic alcoholic pancreatitis

The authors investigated the role of activated perilobular, not periacinar, pancreatic stellate cells, in fibrogenesis in chronic pancreatitis, based on the distribution of myofibroblasts. Twenty-four patients with clinically diagnosed chronic alcoholic pancreatitis were studied histopathologically, immunohistochemically and quantitatively. In all cases, fibrosis was patchily distributed in the perilobular, or interlobular, areas, accompanied by a cirrhosis-like appearance; it had extended into the intralobular area in advanced cases. Seven patients had a massive or confluent loss of exocrine tissue, resulting in extensive interlobular fibrosis; the more extensive the interlobular fibrosis, the smaller the lobules. Immunoreactivity to alpha-smooth muscle actin, a myofibroblast marker, was found mostly in the same areas of the fibrosis, mainly the interlobular, and less often the periacinar, areas; the average percentage area of perilobular myofibroblasts was significantly higher than that of periacinar myofibroblasts in 20 randomly selected lobules (P > 0.001), in which the average value for the former was 38.03% (range: 13.54-61.32%; SD, 13.8%) and that for the latter was 4.85% (range 0.90-9.57%; SD, 2.22%). Fibrosis also immunostained positive for collagen types I and III. In conclusion, activated perilobular, not periacinar, pancreatic stellate cell contribute to fibrogenesis in chronic pancreatitis.

Camostat, an oral trypsin inhibitor, reduces pancreatic fibrosis induced by repeated administration of a superoxide dismutase inhibitor in rats

BACKGROUND AND AIM

An oral trypsin inhibitor, camostat (CM), has a beneficial effect on chronic pancreatitis, but its mechanism is not yet fully understood. Recently, pancreatic stellate cells (PSC) have been reported to play an essential role in pancreatic fibrosis. An experimental model of pancreatic fibrosis induced by a superoxide dismutase (SOD) inhibitor (diethyldithiocarbamate [DDC]) was developed in rats. Thus, the effect of an oral trypsin inhibitor on pancreatic fibrosis and PSC was investigated.

METHODS

Pancreatic fibrosis was induced in rats using DDC (DDC rats). DDC + CM rats were administered DDC, and subsequently were fed a diet containing CM. Immunohistochemistry of the pancreas was performed with monoclonal anti-alpha-smooth muscle actin (alpha-SMA) antibody and anti-desmin antibody.

RESULTS

The DDC rats showed a significant increase in alpha-SMA-positive cells or desmin-positive cells compared with control rats. These significant increases in the fibrotic area improved after treatment with CM. The level of prolyl hydroxylase in the pancreas, which significantly increased as a result of DDC, decreased after treatment with CM.

CONCLUSION

Camostat has a beneficial effect on pancreatic fibrosis induced by the administration of a SOD inhibitor, which inhibits the proliferation and activation of PSC.

Histopathologic difference between chronic pancreatitis animal models and human chronic pancreatitis

OBJECTIVES

There are many experimental models for chronic pancreatitis. However, it remains unclear which animal models of pancreatic fibrosis can be categorized as chronic pancreatitis models. We compared the histologic features of some animal models of pancreatic fibrosis/chronic pancreatitis and chronic pancreatitis in humans.

METHODS AND RESULTS

Human chronic pancreatitis due to chronic alcohol abuse and unknown etiology showed interlobular fibrosis and a cirrhosis-like appearance. Histopathologically, spontaneous pancreatitis models, WBN/Kob rats and OLETF rats, showed localized/nodular fibrotic lesions, which consisted of swollen, aggregated, atrophic islets of Langerhans; loss of the exocrine parenchyma and hemosiderin deposition that was seldom distributed in the interlobular area. On the other hand, fibrosis in the canine model, which was produced by combining alcohol administration with incomplete pancreatic duct obstruction, was characterized by interlobular fibrosis admixed with a cirrhosis-like appearance very similar to that in human chronic pancreatitis.

CONCLUSION

Most experimental models for chronic pancreatitis, except alcohol administration combined with other procedures such as incomplete pancreatic duct obstruction, are different from human chronic pancreatitis.

Ethanol feeding aggravates morphological and biochemical parameters in experimental chronic pancreatitis

BACKGROUND AND AIMS

Instillation of trinitrobenzene sulfonic acid (TNBS) into the rat pancreatic ducts induces morphological changes resembling human chronic pancreatitis. In humans, alcoholism is commonly associated with chronic pancreatitis, but ethanol feeding fails to induce pancreatitis in experimental animals. We hypothesized that ethanol would manifest its pathogenetic effects on a duct-injured pancreas.

METHODS

Chronic pancreatitis was induced in rats by instillation of TNBS into pancreatic ducts. Thereafter, rats were fed a normal chow diet with or without ethanol supplementation. Control rats received vehicle and a normal diet. A separate group of vehicle-treated rats were also fed with ethanol. At 2 and 4 weeks pancreata were excised and processed for morphological examination or for biochemical assays. From crude homogenates, protein and hydroxyproline were quantified. After sonication, homogenates were also assayed for amylase and DNA. An oral glucose tolerance test was performed on the fourth week.

RESULTS

TNBS induced chronic fibrogenic pancreatitis that was associated with a reduction in pancreatic weight, DNA, protein and amylase as compared to control rats. Ethanol feeding to TNBS-treated animals slowed weight gain, increased fasting glucose and impaired glucose tolerance test. Larger areas of gland atrophy were observed with a striking disruption of the normal architecture of the islets. Ethanol accelerated pancreatic involution and collagen deposition as measured by total amylase, protein, DNA and hydroxyproline content.

CONCLUSIONS

In TNBS chronic pancreatitis, active fibrogenesis is associated with progressive atrophy of glandular elements. Morphological and biochemical parameters are aggravated by sustained ethanol intake.

Effects of ethanol feeding and malnutrition on collagen synthesizing and degrading enzymes in rat pancreas

This study was performed to delineate the combined effects of a low-fat diet and chronic ethanol ingestion on collagen metabolism in rat pancreas. Rats fed a very low-fat diet (5% of total calories as lipid) for 12 weeks developed malnutrition as judged by weight loss (-33% of the initial body weight) and low serum albumin and amylase levels. The pancreas of malnourished rats showed increased collagenase activity with respect to animals fed a 35% lipid diet (p < 0.05). Hydroxyproline content was higher in the pancreas of malnourished rats and collagenase activity correlated well with hydroxyproline content (r = 0.57, p = 0.0013). Ethanol feeding for 12 weeks, regardless of the nutritional state of the rats, did not change the synthesis and degradation rates of collagen in the pancreas. The present study suggests that malnutrition may have profound effects on collagen metabolism.

Aprotinin inhibits unspecific degradation of collagen in rat and human pancreas

CONCLUSION

Addition of aprotinin in human and rat pancreatic extracts inactivates nonspecific proteases that completely degrade collagen.

BACKGROUND

We sought to clarify the relative roles of collagenase and nonspecific proteases in the breakdown of collagen by the pancreas.

METHODS

The degradation of [3H] collagen fibrils by pancreatic extracts to small fragments of low molecular weight was determined by SDS-electrophoresis and autoradiography. Aprotinin (0.14 mg/mL) was added to inhibit nonspecific protease activity.

RESULTS

Rat and human pancreas extracts contained a high collagenolytic activity that was demonstrated to be the result of the combined action of collagenase and other pancreatic proteases. Seventy percent of the total collagenolytic activity in rat pancreas extracts was inhibited by aprotinin. The same aprotinin concentration had no effect on two commercially available collagenases. The electrophoretic pattern obtained from [3H] collagen treated with rat and human pancreatic extracts containing aprotinin confirmed the presence of a true specific collagenase in the pancreas.

Collagenolytic activity in human pancreatic tissue with different degrees of fibrosis

The present study was designed to establish a valid method for expressing collagenolytic activity in pancreatic tissue with different degrees of fibrosis. Collagenolytic activity was measured in pancreatic tissue of control and alcoholic chronic pancreatitis (CP) patients and data were expressed as percent digestion/mg tissue or as percent digestion/mg protein obtaining different results. The values were 18.4 +/- 4.7% digestion/mg tissue in the control group, and 8.4 +/- 3.2% digestion/mg tissue in the chronic pancreatitis group (p < 0.001). When collagenolytic activity was expressed as percent digestion/mg protein, measured by the Bradford assay, the values of the control group were 190.2 +/- 69.0% digestion/mg protein, and those of chronic pancreatitis patients were 187.2 +/- 61.7% digestion/mg protein (p = ns). Protein determination in pancreatic tissue of control and CP patients was seen to be influenced by the method assayed. Protein content per mg of fresh tissue, measured by the methods of Lowry, Bradford, and Bradford-SDS, were similar and twofold higher in controls than in CP samples. However, the Kjeldahl assay showed that protein content per mg of dry tissue was the same in both groups. The high degree of fibrosis in the pancreas of CP patients (60.2 +/- 28.0%) with regard to controls (4.7 +/- 1.8%) (p < 0.001) and the low response of collagen proteins to the Lowry and Bradford assays could explain the differences observed in protein content of human samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase in lipoperoxides and prolyl hydroxylase activity in rat liver following chronic ethanol feeding

The effect of lipid peroxidation on hepatic collagen synthesis was investigated in male Wistar strain rats after 7 weeks of ethanol feeding. Compared with control rats, the ethanol-fed rats had a significantly higher lipoperoxide content and a significantly lower reduced glutathione content al all times following ethanol treatment. Except for the earliest time (2 days), hepatic prolyl hydroxylase activity was also significantly increased and finally reached up to 214% of the control level. Hepatic hydroxyproline content was slightly increased, but not statistically significant. The lipoperoxides content was significantly correlated with prolyl hydroxylase activity and inversely correlated with reduced glutathione content. These findings were also confirmed in ethanol-pyrazole-treated rats. These results suggest that elevated lipoperoxides mediate an acceleration of collagen synthesis, even at an early stage, in ethanol-induced hepatic injury.

Nonoxidative metabolism of ethanol in the pancreas; implication in alcoholic pancreatic damage

Alcohol dehydrogenase activity and fatty acid ethyl ester synthase activity were measured in various organs of male Wistar strain rats. The mean (+/- SE) values of alcohol dehydrogenase activity in liver, testis, pancreas and brain were 223 +/- 34, 35 +/- 13, 27 +/- 17 and 24 +/- 15 nmol/hr/mg protein, respectively, but not detectable in heart and skeletal muscle. Fatty acid ethyl ester synthase activity in pancreas, liver, testis and heart were 1348 +/- 263, 23 +/- 14, 17 +/- 3 and 2 +/- 1 nmol/hr/mg protein, respectively, but not detectable in brain and skeletal muscle. Alcohol dehydrogenase activity, fatty acid ethyl ester synthase activity, fatty acid ethyl ester content and amylase activity were measured in pancreas of rat after 7 weeks of ethanol feeding. Compared with control rats, ethanol-fed rats had normal fatty acid ethyl ester synthase activity and alcohol dehydrogenase activity. However, fatty acid ethyl ester content increased five-fold and amylase activity decreased up to 20% of the control group. Fatty acid ethyl ester content was inversely correlated with amylase activity. These results suggest that fatty acid ethyl ester may be responsible for the development of pancreatic damage by ethanol.