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PubMed2006

Hepatic gene expression profile associated with non-alcoholic steatohepatitis protection by S-nitroso-N-acetylcysteine in ob/ob mice.

BACKGROUND/AIMS: To understand the molecular mechanisms underlying non-alcoholic steatohepatitis (NASH) prevention by S-nitroso-N-acetylcysteine (SNAC), an NO donor that inhibits lipid peroxidation, we examined hepatic differentially expressed genes between ob/ob mice receiving or not SNAC treatment concomitantly with a methionine-choline deficient (MCD) diet. METHODS: Ob/ob mice were assigned to receive oral SNAC fed solution (MCD+SNAC group) or vehicle (MCD group) by gavage. After four weeks, histopathological analysis and microarray hybridizations were conducted in liver tissues from groups. GeneSifter system was used to identify differentially expressed genes and pathways according to Gene Ontology. RESULTS: NASH was absent in the MCD+SNAC group and no significant changes in food intake or body weight were observed in comparison to MCD group. After SNAC treatment, several genes belonging to oxidative phosphorylation, fatty acid biosynthesis, fatty acid metabolism and glutathione metabolism pathways were down-regulated in comparison to the MCD group. CONCLUSIONS: SNAC treatment promotes down regulation of several genes from fatty acid (FA) metabolism related pathways, possibly through abrogation of the cytotoxic effects of reactive oxygen species and lipid peroxides with consequent prevention of mitochondrial overload. Further studies are required to investigate the clinical implications of these findings, in attempt to develop novel therapeutic strategies for NAFLD treatment.

Acetylcysteine↗
PubMed1989

[Study of microcirculatory changes in experimental dietary fatty liver].

UNLABELLED: Regional hepatic blood flow in SD rats with fatty liver was measured by electrolytic regional blood flow meter (Biomedical Sci. Co. Ltd. model RBF-2) and compared with areas of sinusoids histologically calculated by CONTRON MOP-AM 03. METHODS: SD male rats, weighing around 240 g, fed on the choline deficient diet, were anaesthetized with ethyl ether and rough regional hepatic blood flow were measured after 3, 5 and 7 weeks. Furthermore, after 15 min. from death, they were measured (death regional flow) in order to determine the simple diffusion of hydrogen gas in liver tissue. Real regional blood flow was got by subtraction of death regional flow from rough regional blood flow. The degree of fatty liver was histologically divided into 3 groups, as it were, slight, moderate and severe. The lipid was extracted from fatty liver in 3 groups using the combined liquids of methanol and chloroform, and the weight of the lipid was measured to compare with fatty changes. The area of sinusoids in fatty liver was analyzed from microscopic pictures using CONTRON MOP-AM 03. RESULTS: There was no difference of rough regional hepatic blood flow among 3 groups as shown Figure.: (table; see text) But the real regional blood flow was decreased in the moderate or severe groups. And the lipid weights of the liver tissues were increased according to severe fatty changes. The values of real regional blood flow were well-correlated with decrease of the areas of sinusoids histologically analyzed. These facts suggested that fat vacuoles narrowed the lumen of sinusoid and decreased the hepatic blood flow.

Animals↗
PubMed1989

Involvement of cholecystokinin receptors in the adverse effect of glucocorticoids on diet-induced necrotizing pancreatitis.

The mechanism that explains the association between corticoids and acute pancreatitis is unknown. Our hypothesis was that chronic glucocorticoid treatment could adversely affect the course of hemorrhagic pancreatitis by acting through cholecystokinin (CCK) receptors. Acute necrotizing pancreatitis was induced by feeding young female mice a choline-deficient, ethionine-supplemented (CDE) diet for 60 hours. Treatment with hydrocortisone (10 mg/kg/day) was begun 1 week before pancreatitis. At the onset of the CDE diet, a group of hydrocortisone-treated mice were also given the CCK receptor antagonist CR-1409 (5 mg/kg three times a day). Control mice received injections of saline solution. A follow-up of 336 hours was conducted for survival analysis. Hydrocortisone given alone did not produce pancreatitis. Hydrocortisone, however, did increase the pancreatic necrosis caused by the CDE diet (from 40% to 70%) and significantly reduce survival (from 40% to 9%). CR-1409 completely abolished the adverse effects of hydrocortisone on pancreatitis. We measured amylase release by dispersed pancreatic acini from mice chronically treated with hydrocortisone in response to CCK-8. Treatment with hydrocortisone increased both the sensitivity and the responsiveness of the pancreas to CCK-8. We conclude that glucocorticoids alone may not induce acute pancreatitis, but they can increase the risk of a more severe form of pancreatitis developing. The glucocorticoid effect appears to be attributable to a CCK receptor-mediated sensitization of the pancreas to endogenous CCK. Thus, CCK-receptor blockade may improve survival in necrotizing pancreatitis associated with chronic glucocorticoid treatments.

Amylases↗
PubMed1994

A possible role for rat intestinal surfactant-like particles in transepithelial triacylglycerol transport.

To further examine whether surfactant-like particles (DeSchryver-Kecskemeti, K., R. Eliakim, S. Carroll, W. F. Stenson, M. A. Moxley, and D. H. Alpers. 1989. J. Clin. Invest. 84:1355-1361) were involved in the transepithelial transport of lipid, alkaline phosphatase activity and surfactant-like particle content were measured in apical mucosal scrapings, enterocytes, lamina propria, and serum after inhibition of chylomicron transport. Serum triacylglycerol levels were decreased 60-76% by Pluronic L-81, fenfluramine, and choline deficiency compared with fat-fed controls. 5 h after triacylglycerol feed, alkaline phosphatase activity in all three experimental groups was decreased compared with controls by 52-69% in mucosal scrapings and by 33-72% in serum. A parallel decline (60%) in alkaline phosphatase activity occurred in the lamina propria of Pluronic-treated animals. Total particle content (measured by an ELISA using antiserum against purified particle) after Pluronic treatment was decreased in mucosal scrapings, lamina propria, and serum by 16, 22, and 29% at 3 h and by 33, 40, and 8%, respectively, at 5 h after fat feeding. In contrast, particle content was increased in enterocytes by 29% 3 h and by 8% 5 h after fat feeding. By electron microscopy, enterocytes from Pluronic- and fenfluramine-treated animals exhibited a two- to threefold increase in large intracellular cytoplasmic lipid globules and the appearance of lamellae in apposition, with a marked decrease in the number of surfactant-like particles overlying the brush border. These changes, produced by inhibition of chylomicron transport, in the distribution of surfactant-like particles and particle-bound alkaline phosphatase are consistent with a role for these particles in transepithelial triacylglycerol transport across and out of the enterocyte.

Animals↗
PubMed2006

The role of the nuclear receptor constitutive androstane receptor in the pathogenesis of non-alcoholic steatohepatitis.

BACKGROUND: Non-alcoholic fatty liver disease is a common liver injury, but the pathophysiological mechanisms leading to the development of non-alcoholic steatohepatitis (NASH) remain unclear. The pathological roles of the nuclear receptor constitutive androstane receptor (CAR), a key regulator of drug-metabolising enzymes, in the development of NASH were investigated. METHODS AND RESULTS: CAR(+/+) and CAR(-/-) mice were given a methionine and choline-deficient (MCD) diet to establish a dietary model of NASH. Increases in serum alanine aminotransferase (ALT) and in infiltration of inflammatory cells were dominant in CAR(+/+) mice at 8 weeks. There was no significant difference in the lipid concentration of the liver - namely, the first hit between CAR(+/+) and CAR(-/-) mice. The index of lipid peroxidation increased in liver of the CAR(+/+) mice, as demonstrated by 8-iso-prostaglandin F2alpha (F2-isoprostanes). Western blotting analysis showed that nuclear translocation of CAR occurred in CAR(+/+) mice fed the MCD diet. As a result, the CAR activation caused the lipid peroxidation - namely, the second hit. The expressions of cytochrome P450 (CYP)2B10, 2C29, 3A11 all increased considerably in the CAR(+/+) mice. Furthermore, alpha smooth muscle actin immunohistochemistry and Sirius red staining showed an increase in the degree of fibrosis in CAR(+/+) mice fed the MCD diet at 16 weeks. The mRNA expressions of collagen alpha1(1) and the tissue inhibitor of metalloproteinase-1 were found to be elevated in CAR(+/+) mice. CONCLUSION: CAR caused the worsening of the hepatic injury and fibrosis in the dietary model of NASH. Our results suggest that the CAR nuclear receptor may thus play a critical role in the pathogenesis of NASH.

Alanine Transaminase↗
PubMed1999

Ischemia-reperfusion injury in rat fatty liver: role of nutritional status.

Fatty livers are more sensitive to the deleterious effects of ischemia-reperfusion than normal livers. Nutritional status greatly modulates this injury in normal livers, but its role in the specific setting of fatty liver is unknown. This study aimed to determine the effect of nutritional status on warm ischemia-reperfusion injury in rat fatty livers. Fed and fasted rats with normal or fatty liver induced by a choline deficient diet underwent 1 hour of lobar ischemia and reperfusion. Rat survival was determined for 7 days. Serum transaminases, liver histology and cell ultrastructure were assessed before and after ischemia, and at 30 minutes, 2 hours, 8 hours, and 24 hours after reperfusion. Survival was also determined in fatty fasted rats supplemented with glucose before surgery. The preischemic hepatic glycogen was measured in all groups. Whereas survival was similar in fasted and fed rats with normal liver (90% vs. 100%), fasting dramatically reduced survival in rats with fatty liver (14% vs. 64%, P <.01). Accordingly, fasting and fatty degeneration had a synergistic effect in exacerbating liver injury. Mitochondrial damage was a predominant feature of ultrastructural hepatocyte injury in fasted fatty livers. Glucose supplementation partially prevented the fasting-induced depletion of glycogen and improved the 7-day rat survival to 45%. These data indicate that rat fatty livers exposed to normothermic ischemia-reperfusion injury are much more sensitive to fasting than histologically normal livers. Because glucose supplementation improves both the hepatic glycogen stores and the rat survival, a nutritional repletion procedure may be part of a treatment strategy aimed to prevent ischemia-reperfusion injury in fatty livers.

Alanine Transaminase↗
PubMed1990

Pancreatic exocrine secretion in acute experimental pancreatitis.

Little is known about exocrine pancreatic secretory function in patients with acute pancreatitis, in particular during the early phase of the disease. Therefore, this study evaluates basal and stimulated pancreatic secretion in vivo and in vitro in four different models of acute pancreatitis which reflect its clinical spectrum of severity: (a) edematous pancreatitis induced in the rat by seven IP injections of 50 micrograms/kg cerulein at hourly intervals; (b) edematous pancreatitis with cellular necrosis induced in the mouse by seven IP injections of 50 micrograms/kg cerulein at hourly intervals; (c) hemorrhagic pancreatitis induced in the mouse by feeding an ethionine-supplemented, choline-deficient diet for 66 hours; and (d) hemorrhagic pancreatitis induced in the rat by retrograde infusion of 0.6 mL 5% sodium taurocholate into the pancreatic duct. Secretory studies were performed in vivo and in vitro at various times after onset of pancreatitis. The results show that the exocrine pancreas gradually became resistant to cholecystokinin stimulation after the onset of acute pancreatitis in all four animal models. Cholecystokinin-stimulated secretion was almost abolished in vivo and in vitro at the time of maximal histological damage. In vivo basal secretion was also reduced. In vitro there was an increase in basal release of amylase from isolated acini that was not caused by an increase in luminal secretion but by enzyme release from damaged cells. The time course of improvement of secretory function after acute experimental pancreatitis depended on the severity of the pancreatitis. Recovery of secretory capacity took longer after severe necrotizing pancreatitis than after edematous pancreatitis. However, the ultimate resolution of secretory function was remarkable, in particular after severe hemorrhagic pancreatitis. In all four models, secretory capacity became indistinguishable from normal before the morphological alterations had completely resolved. The present experimental data suggest that pancreatic secretion, and particularly pancreatic secretory response to cholecystokinin, may also be reduced in patients early after the onset of acute pancreatitis.

Acute Disease↗
PubMed2006

Protective effect of portal vein arterialization in acute liver failure induced by hepatectomy in normal and fatty liver rat.

AIM: We sought to determine whether an additional supply of oxygenated blood achieved by partial portal vein arterialization (PPVA) was protective on normal or fatty liver (FL) in rats with acute liver failure (ALF) induced by hepatectomy. METHODS: Sprague-Dawley rats with normal or FL were segregated either to receive or not to undergo PPVA after hepatectomy. FL was induced by feeding a choline-deficient diet (5 days). PPVA was performed by anactamasing the left renal artery to the splenic vein with a stent following a left nephrectomy and splenectomy; the control rats underwent left nephrectomy and splenectomy only. Liver injury was evaluated by the serum alanine aminotransferase (ALT) level. The animals were sacrificed at 24 hours, 48 hours, and 7 days to collect blood and liver tissue samples for biochemical analysis. The 7-day survival was assessed in separate experimental groups. RESULTS: PPVA significantly increased Po2 and oxygen saturation in the portal blood compared to non PPVA rats. PPVA significantly improved the 7-day survival compared with controls in both groups: hepatectomy of normal liver (90% vs 30%) and hepatectomy of FL (75% vs 25%). Serum ALT levels were slightly lower in the PPVA groups compared with the non-PPVA groups without a significant difference. Prothrombin activity decreased soon after hepatectomy in the normal and the FL liver groups but recovered rapidly thereafter without differences between the PPVA and non-PPVA treated animals. CONCLUSION: An additional supply of arterial oxygenated blood through a PPVA promotes rapid resolution of ALF after partial hepatectomy in rats with normal or fatty livers, significantly improving 7-day survivals compared to hepatectomy controls.

Anastomosis, Surgical↗
PubMed1987

Free radical injury and liver tumor promotion.

One of the underlying mechanisms of tumor promotion both in the skin and liver involves free radical mediated injury to informational macromolecules of target cells. A choline-deficient (CD) diet, which is an efficient liver tumor promoter, induces peroxidative damage of liver cell membrane lipids. By modifying components of a CD diet, we have shown that the efficacy of the promotion is correlated with the extent of lipid peroxidation. The substitution of fats in a CD diet with predominantly polyunsaturated fat and the addition of methapyrilene to a CD diet enhances membrane lipid peroxidation and the promoting effects. An antioxidant (BHT) and hypolipidemic peroxisome proliferators (BR931 and DEHP) suppress both of these effects. Contrary to these findings, phenobarbital did not induce membrane lipid peroxidation, and its addition to a CD diet inhibited the diet-induced lipid peroxidation, though such a combination exerted a stronger promoting action. Thus, a CD diet and phenobarbital exert their promoting actions through different mechanisms. The consequence of membrane lipid peroxidation in the liver cells induced by a CD diet may be multiple. Our recent study of surface membrane insulin receptors of liver cells of rats fed a CD diet showed a decrease in number and an enhanced binding affinity leading to altered responsiveness of liver cells to insulin mediated glycogen synthesis. It is suggested that CD diet-induced lipid peroxidation leads to functional alterations of membrane receptors involved in cell growth control and may thereby exert its promoting action.

Animals↗
PubMed2004

Organ-specific stress induces mouse pancreatic keratin overexpression in association with NF-kappaB activation.

Keratin polypeptides 8 and 18 (K8/K18) are the major intermediate filament proteins of pancreatic acinar cells and hepatocytes. Pancreatic keratin function is unknown, whereas hepatocyte keratins protect from mechanical and non-mechanical forms of stress. We characterized steady-state pancreatic keratin expression in Balb/c mice after caerulein and choline-deficient ethionine-supplemented diet (CDD), or on exposure to the generalized stresses of heat and water immersion. Keratins were studied at the protein, RNA and organizational levels. Isolated acini were used to study the role of nuclear factor (NF)-kappaB using selective inhibitors. Keratins were found to be abundant proteins making up 0.2%, 0.3% and 0.5% of the total cellular protein of pancreas, liver and small intestine, respectively. Caerulein and CDD caused a threefold transcription-mediated overall increase in K8/K18/K19/K20 proteins. Keratin overexpression begins on tissue recovery, peaks 2 days after caerulein injection, or 1 day after CDD discontinuation, and returns to basal levels after 10 days. K19/K20-containing cytoplasmic filaments are nearly absent pre-injury but form post-injury then return to their original membrane-proximal distribution after 10 days. By contrast, generalized stresses of heat or water-immersion stress do not alter keratin expression levels. Caerulein-induced keratin overexpression is associated with NF-kappaB activation when tested using ex vivo acinar cell cultures. In conclusion, keratins are abundant proteins that can behave as stress proteins in response to tissue-specific but not generalized forms of injury. Pancreatic keratin overexpression is associated with NF-kappaB activation and may serve unique functions in acinar or ductal cell response to injury.

Animals↗
PubMed1980

Acute hemorrhagic pancreatic necrosis in mice: the activity of lysosomal enzymes in the pancreas and the liver.

The activity of lysosomal enzymes of the pancreas and the liver has been studied during induction and onset of acute hemorrhagic pancreatic necrosis with fat necrosis (AHPN) in mice. We induced AHPN by feeding the animals a choline-deficient (CD) diet containing 0.5% DL-ethionine (CDE). Control animals were fed either laboratory chow or a plain CD DIET. Increased total activities of cathespin B1, beta-galactosidase, and acid phosphatase were found to occur in pancreas homogenates of mice fed the CDE diet for 2 and 3 days. Release of cathespin B1 into pancreas cytosol was observed after 1 day of feeding. beta-galactosidase and acid phosphatase were increased in pancreas cytosol after 2 and 3 days of feeding. Changes in total activity and location of the lysosomal enzymes did not occur in the liver. Feeding the CD and CDE diets resulted in an increase in the free activity of lysosomal enzymes of both the pancreas and the liver, suggesting the existence of alterations in the lysosomal membrane. Pancreas and liver homogenates were stored on ice up to 3 hours, and the free activity of acid phosphatase and beta-galactosidase were determined at various time intervals. The free activity of both enzymes increased progressively for 3 hours in the pancreas but not in the liver. It is concluded that: 1) induction of AHPN in mice is accompanied by an increase in the activity of lysosomal enzymes of the acinar cells of the pancreas; 2) cathepsin B1 may be responsible for triggering an intraparenchymal activation of zymogens, and 3) pancreatic lysosomes are labilized more easily than liver lysosomes.

Acid Phosphatase↗
PubMed1991

Effects of the seleno-organic substance Ebselen in two different models of acute pancreatitis.

This study evaluated the effects of the seleno-organic substance Ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one] in two models of acute hemorrhagic and acute edematous pancreatitis. Ebselen is known to catalyze glutathione peroxidase-like reactions and to inhibit lipid peroxidation. Hemorrhagic pancreatitis was induced by feeding a choline-deficient, ethionine-supplemented (CDE) diet to mice for 66 h. Edematous pancreatitis was induced by 7-h subcutaneous injections of 50 micrograms/kg of cerulein in mice. Ebselen was given from the beginning of the CDE diet either as a subcutaneous injection of 100 mg/kg at 6-h intervals or was mixed in with the CDE diet to yield a daily dose of 100 mg/kg of Ebselen. In further experiments, Ebselen was given at various time intervals after the beginning of the CDE diet as subcutaneous injections of 100 mg/kg at 6-h intervals. In the cerulein model, Ebselen was given 5 min prior to each cerulein injection at doses from 10-500 mg/kg. Prophylactic administration of Ebselen given orally or subcutaneously significantly improved survival from 38.5% in the control group of saline-injected CDE-fed mice to 61.9 and 65.0%, respectively. Ebselen also reduced increases in serum amylase and pancreatic weight in the diet model. Therapeutic administration of Ebselen significantly increased survival only when injections were started 20 h after the beginning of the CDE diet (64%), but not when started after 40 h (44%). Similarly, increases in serum amylase and pancreatic weight due to the CDE diet were significantly reduced by Ebselen only when injections were started after 20 h but not when started after 40 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1984

Isolation of oval cells by centrifugal elutriation and comparison with other cell types purified from normal and preneoplastic livers.

Oval cells and biliary epithelial cells were isolated from livers of rats fed a choline-deficient diet containing 0.1% ethionine and from normal rat livers, respectively. Nonparenchymal cell suspensions prepared from these livers by collagenase perfusion followed by digestion of undissociated tissue with 0.1% collagenase, 0.1% Pronase, and 0.004% DNase I were separated into six fractions by centrifugal elutriation. Cells in each fraction were characterized histochemically for gamma-glutamyl transpeptidase, peroxidase, alkaline phosphatase, and glucose-6-phosphatase activities, and for albumin and alpha-fetoprotein by immunocytochemical methods. Cells from Fraction 5 of the elutriation procedure had various features predicted for oval cells and were selected for further studies. The cell yield in this fraction, from each preneoplastic liver, was 5.7 X 10(7) cells, 93 +/- 2% of which were gamma-glutamyl transpeptidase positive, 6 +/- 1% peroxidase positive, 61% albumin positive, and 29% alpha-fetoprotein positive. Cells in this fraction have a median diameter of 13.1 micron and are diploid and cycling. The majority of these cells has morphological features characteristic of biliary epithelial cells, although some cells display features intermediate between duct cells and hepatocytes. Nucleic acid hybridization using specific probes revealed that these cells contain albumin and alpha-fetoprotein messenger RNAs, while hepatocytes from normal and preneoplastic liver contain only albumin messenger RNA. Biliary cells obtained from normal livers do not contain albumin messenger RNA. The large-scale purification and characterization of cell populations from preneoplastic livers is an important step in elucidating the cellular derivation of liver tumors.

Animals↗
PubMed1986

Diminished agonist-stimulated inositol trisphosphate generation blocks stimulus-secretion coupling in mouse pancreatic acini during diet-induced experimental pancreatitis.

Young female mice fed a choline-deficient, ethionine-supplemented (CDE) diet rapidly develop acute hemorrhagic pancreatitis. We have observed that pancreatic acini prepared from these mice are unable to secrete amylase in response to addition of the cholinergic agonist carbachol, although they retain the ability to secrete amylase in response to the Ca2+ ionophore A23187. The CDE diet does not alter the binding characteristics (Kd or the maximal number of binding sites) for muscarinic cholinergic receptors as tested using the antagonist [3H]N-methylscopolamine nor the competition for this binding by carbachol. Addition of carbachol to acini prepared from mice fed the CDE diet does not result in as marked an increase in cytosolic free Ca2+ levels as that noted in control samples (evaluated using quin2 fluorescence). These observations indicate that the CDE diet interferes with stimulus-secretion coupling in mouse pancreatic acini at a step subsequent to hormone-receptor binding and prior to Ca2+ release. This conclusion is confirmed by our finding that the hormone-stimulated generation of [3H]inositol phosphates (inositol trisphosphate, inositol bisphosphate, and inositol monophosphate) from acini labeled with [3H]myoinositol is markedly reduced in acini prepared from mice fed the CDE diet. This reduction is not due to a decrease in phosphatidylinositol-4,5-bisphosphate. This communication represents the first report of a system in which a blockade of inositol phosphate generation can be related to a physiologic defect and pathologic lesion.

Aminoquinolines↗
PubMed2005

NF-kappaB activation, rather than TNF, mediates hepatic inflammation in a murine dietary model of steatohepatitis.

BACKGROUND & AIMS: We explored the roles of nuclear factor-kappaB (NF-kappaB) and tumor necrosis factor (TNF) alpha (TNF-alpha) as mediators of inflammation in a nutritional model of steatohepatitis. METHODS: Wild-type (wt), TNF null -/-, and TNF receptor (R)-1-/- mice were fed a methionine- and choline-deficient (MCD) diet for up to 5 weeks. Liver injury (serum alanine aminotransferase [ALT]), hepatic inflammation, triglycerides, and lipid peroxide levels were determined. Hepatic NF-kappaB activation and expression of TNF and intercellular adhesion molecule-1 (ICAM-1) were assayed. RESULTS: Irrespective of genotype, MCD diet-fed mice developed hepatic lipid peroxidation and serum ALT elevation; at day 10, livers from wt, TNF-/-, and TNFR-1-/- mice showed equivalent steatohepatitis. NF-kappaB/DNA binding was enhanced in hepatic nuclear fractions from MCD diet-fed wt mice compared with dietary controls; there were corresponding increases of ICAM-1 and TNF messenger RNA (mRNA). Likewise, NF-kappaB activation and ICAM-1 expression were enhanced by MCD dietary feeding in TNF-/- and TNFR-1-/- mice compared with respective controls. To establish whether NF-kappaB is a primary mediator of inflammation in experimental steatohepatitis, we over-expressed a mutant, nondegradable IkappaB (mIkappaB), delivered by adenovirus in vivo. As expected, hepatic mIkappaB expression reduced NF-kappaB/DNA binding induced by MCD dietary feeding, with resultant abrogation of ICAM-1 and TNF synthesis. Such blockade of NF-kappaB transcriptional activation substantially protected against development of steatohepatitis, with significant reductions in liver injury and hepatic inflammation. CONCLUSIONS: In the MCD dietary model of steatohepatitis, NF-kappaB is activated early and is an important proinflammatory mediator of lesion development, but steatohepatitis occurs independently of TNF synthesis and TNFR-1 activation.

Animals↗
PubMed1996

Transgenic animals demonstrate a role for the IL-1 receptor in regulating IL-1beta gene expression at steady-state and during the systemic stress induced by acute pancreatitis.

Interleukin-1 (IL-1) gene expression is selectively induced in tissues involved in multisystem organ failure during acute pancreatitis, suggesting a role in the pathogenesis of distant organ dysfunction. This study was undertaken to investigate the mechanism of pancreatitis-induced end organ cytokine production and to better understand the processes by which IL-1 production is regulated. Seventy adult male transgenic mice in which the type 1 IL-1 receptor had been deleted by gene targeting in embryonic stem cells were utilized (homozygous -/- IL-1R knockout). Acute pancreatitis was induced by one of two methods: (A) IP injections of caerulein (50 microgram/kg/hr x 4) with animals sacrificed at 0, .5, 1, 2, 4, 6, and 8 hr; (B) 48-hr exposure to a choline deficient ethionine supplemented (CDE) diet with animals sacrificed at 0 and 72 hr. Knockout animals were compared to strain-specific control mice expressing the normal wild-type IL-1 receptor gene in which pancreatitis was similarly induced. The severity of pancreatitis was stratified by serum amylase, lipase, and blind histologic grading. IL-1 mRNA production was determined within the pancreas, lungs, liver, and spleen by quantitative differential RT-PCR. Deletion of the IL-1R1 attenuated the severity of pancreatitis, reaching statistical significance in the less severe edematous model. There was little or no constitutive expression of IL-1 mRNA within any of the tissues examined from wild-type animals; however, knockout animals showed elevated steady-state levels in each tissue. IL-1 mRNA became detectable in all tissues of wild-type animals shortly after either form of pancreatitis became apparent and increased significantly with worsening pancreatitis. Despite the attenuated pancreatitis, knockout animals produced significantly greater levels of IL-1 mRNA in each tissue, typically demonstrating a 30-50% increase over time matched IL-1 mRNA production in wild-type animals which was not pancreatitis model dependent. We conclude that genetic deletion of IL-1 receptors results in the overproduction of IL-1 mRNA in organs known to produce cytokines during pancreatitis even when the severity of pancreatitis is lessened. This suggests that a negative feedback loop exists between the IL-1 receptor and IL-1 gene expression.

Acute Disease↗
PubMed2006

Effect of insulin-sensitizing agents in combination with ezetimibe, and valsartan in rats with non-alcoholic fatty liver disease.

AIM: To assess whether treatment with insulin-sensitizing agents (ISAs) in combination with ezetimibe and valsartan have greater effect on hepatic fat content and lipid peroxidation compared to monotherapy in the methionine choline-deficient diet (MCDD) rat model of non-alcoholic fatty liver disease (NAFLD). METHODS: Rats (n = 6 per group) were treated with different drugs, including MCDD only, MCDD diet with either metformin (200 mg/kg), rosiglitazone (3 mg/kg), metformin plus rosiglitazone (M+R), ezetimibe (2 mg/kg), valsartan (2 mg/kg), or combination of all drugs for a total of 15 wk. Liver histology, lipids, parameters of oxidative stress and TNF-alpha were measured. RESULTS: Fatty liver (FL) rats demonstrated severe hepatic fatty infiltration (> 91% fat), with an increase in hepatic TG (+ 1263%, P < 0.001), hepatic cholesterol (+ 245%, P < 0.03), hepatic MDA levels (+ 225%, P < 0.001), serum TNF-alpha (17.8 +/- 10 vs 7.8 +/- 0.0, P < 0.001), but a decrease in hepatic alpha tocopherol (-74%, P<0.001) as compared to the control rats. Combination therapy with all drugs produced a significant decrease in liver steatosis (-54%), hepatic TG (-64%), hepatic cholesterol (-31%) and hepatic MDA (-70%), but increased hepatic alpha tocopherol (+ 443%) as compared to FL rats. Combination therapy with ISA alone produced a smaller decrease in liver steatosis (-32% vs -54%, P < 0.001) and in hepatic MDA levels (-55% vs -70%, P < 0.01), but a similar decrease in hepatic lipids when compared with the all drugs combination. TNF-alpha levels decreased significantly in all treatment groups except in ISA group. CONCLUSION: Combination therapies have a greater effect on liver fat content as compared to monotherapy. Rosiglitazone appears to improve hepatic steatosis to a greater extent than metformin.

Animals↗
PubMed1986

A structural analysis of gap and tight junctions in the rat liver during a dietary treatment that induces oval cell proliferation.

The authors have investigated early changes in liver cell gap and tight junctions that occur when rats are fed a carcinogenic diet. Animals were fed a choline-deficient diet that contained 0.1% ethionine (CDE) for periods up to 6 weeks. Short-term feeding of this diet results in the rapid proliferation of so-called "oval cells" within the liver, which is reversible upon returning the rats to a normal diet. Livers from animals fed the diet were removed at various times during feeding and during recovery from the diet and were analyzed by light and electron microscopy. The freeze-fracture technique was used to produce extended views of the internal structure of liver cell membranes at each stage under study. The characteristic junctional complex surrounding canalicular regions in normal liver disappears after only 2 weeks of the CDE regimen. Gap junctions were not found after 4 weeks of the diet, and tight junctions became increasingly disorganized. Tight junction elements were observed, however, between hepatocytes and oval cells, which indicated that these two cell types do interact directly. Changes occur in the structural complexity of tight junction elements between hepatocytes and between hepatocytes and oval cells. Recovery from the CDE diet results in a rapid increase in junctional complexity, and the large gap junction plaques characteristic of normal liver are visible within 2 weeks after cessation of the CDE regimen. These and other observations demonstrate that reversible alterations in hepatocyte gap and tight junctions occur as a result of administration of a diet that induces oval cell proliferation. The relationship of these changes to those that have been reported during other processes of cell proliferation are discussed.

Animals↗