Biomedical subjects

Manfred Bilzer

Publications and source records attributed to Manfred Bilzer.

At least 19 recordsLinked to original sources

PubMed2007

IL-22-mediated liver cell regeneration is abrogated by SOCS-1/3 overexpression in vitro.

The IL-10-like cytokine IL-22 is produced by activated T cells. In this study, we analyzed the role of this cytokine system in hepatic cells. Expression studies were performed by RT-PCR and quantitative PCR. Signal transduction was analyzed by Western blot experiments and ELISA. Cell proliferation was measured by MTS and [(3)H]thymidine incorporation assays. Hepatocyte regeneration was studied in in vitro restitution assays. Binding of IL-22 to its receptor complex expressed on human hepatic cells and primary human hepatocytes resulted in the activation of MAPKs, Akt, and STAT proteins. IL-22 stimulated cell proliferation and migration, which were both significantly inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin. IL-22 increased the mRNA expression of suppressor of cytokine signaling (SOCS)-3 and the proinflammatory cytokines IL-6, IL-8, and TNF-alpha. SOCS-1/3 overexpression abrogated IL-22-induced STAT activation and decreased IL-22-mediated liver cell regeneration. Hepatic IL-22 mRNA expression was detectable in different forms of human hepatitis, and hepatic IL-22 mRNA levels were increased in murine T cell-mediated hepatitis in vivo following cytomegalovirus infection, whereas no significant differences were seen in an in vivo model of ischemia-reperfusion injury. In conclusion, IL-22 promotes liver cell regeneration by increasing hepatic cell proliferation and hepatocyte migration through the activation of Akt and STAT signaling, which is abrogated by SOCS-1/3 overexpression.

Animals↗

PubMed2006

PI 3-kinase pathway is responsible for antiapoptotic effects of atrial natriuretic peptide in rat liver transplantation.

AIM: To investigate the in vivo effect of atrial natriuretic peptide (ANP) and its signaling pathway during orthotopic rat liver transplantation. METHODS: Rats were infused with NaCl, ANP (5 microg/kg), wortmannin (WM, 16 microg/kg), or a combination of both for 20 min. Livers were stored in UW solution (4 degrees C) for 24 h, transplanted and reperfused. Apoptosis was examined by caspase-3 activity and TUNEL staining. Phosphorylation of Akt and Bad was visualized by Western blotting and phospho-Akt-localization by confocal microscopy. RESULTS: ANP-pretreatment decreased caspase-3 activity and TUNEL-positive cells after cold ischemia, indicating antiapoptotic effects of ANP in vivo. The antiapoptotic signaling of ANP was most likely caused by phosphorylation of Akt and Bad, since pretreatment with PI 3-kinase inhibitor WM abrogated the ANP-induced reduction of caspase-3 activity. Interestingly, analysis of liver tissue by confocal microscopy showed translocation of phosphorylated Akt to the plasma membrane of hepatocytes evoked by ANP. CONCLUSION: ANP activates the PI-3-kinase pathway in the liver in vivo leading to phosphorylation of Bad, an event triggering antiapoptotic signaling cascade in ischemic liver.

Animals↗

PubMed2006

Role of Kupffer cells in host defense and liver disease.

Kupffer cells (KC) constitute 80-90% of the tissue macrophages present in the body. They reside within the lumen of the liver sinusoids, and are therefore constantly exposed to gut-derived bacteria, microbial debris and bacterial endotoxins, known to activate macrophages. Upon activation KC release various products, including cytokines, prostanoides, nitric oxide and reactive oxygen species. These factors regulate the phenotype of KC themselves, and the phenotypes of neighboring cells, such as hepatocytes, stellate cells, endothelial cells and other immune cells that traffic through the liver. Therefore, KC are intimately involved in the liver's response to infection, toxins, ischemia, resection and other stresses. This review summarizes established basic concepts of KC function as well as their role in the pathogenesis of various liver diseases.

Acetaminophen↗

PubMed2005

Characterization of organic anion transporter regulation, glutathione metabolism and bile formation in the obese Zucker rat.

BACKGROUND/AIMS: Alterations in hepatobiliary transporters may render fatty livers more vulnerable against various toxic insults. METHODS: We therefore studied expression and function of key organic anion transporters and their transactivators in 8-week-old obese Zucker rats, an established model for non-alcoholic fatty liver disease. RESULTS: Compared to their heterozygous littermates, obese animals showed a significant reduction in canalicular bile salt secretion, which was paralleled by significantly diminished Oatp2 mRNA and protein levels together with reduced nuclear HNF3beta, while expression of bile salt export pump, organic anion transporter (Oatp) 1 and multidrug resistance-associated protein (Mrp) 4 were unchanged. Impaired bile salt-independent bile flow in obese rats was associated with a 50% reduction of biliary secretion of the Mrp 2 model-substrates glutathione disulfide and S-(2,4-dinitrophenyl)glutathione. In line Mrp2 protein expression was reduced by 50% in obese rats. CONCLUSIONS: Oatp2 and Mrp2 expression is decreased in fatty liver and may impair metabolism and biliary secretion of numerous xenobiotics. Reduction of bile salt secretion and absence of biliary GSH excretion may contribute to impaired bile flow and posthepatic disorders associated with biliary GSH depletion.

ATP-Binding Cassette Transporters↗

PubMed2004

Suramin inhibits death receptor-induced apoptosis in vitro and fulminant apoptotic liver damage in mice.

Suramin is a polysulfonated derivative of urea and has been widely used both to treat infections and as a chemotherapeutic drug. Suramin has been shown to inhibit growth factor signaling pathways; however, its effect on apoptosis is unknown. Here we show that suramin inhibits apoptosis induced through death receptors in hepatoma and lymphoma cells. It also inhibits the proapoptotic effect of chemotherapeutic drugs. The antiapoptotic mechanism is specific to cell type and is caused by reduced activation, but not altered composition, of the death-inducing signaling complex (DISC), and by inhibition of the initiator caspases 8, 9 and 10. Suramin also shows similar effects in in vivo models: apoptotic liver damage induced by CD95 stimulation and endotoxic shock mediated by tumor-necrosis factor (TNF) are inhibited in mice, but necrotic liver damage is not inhibited in a rat model of liver transplantation. Thus, the antiapoptotic property of suramin in the liver may be therapeutically exploited.

Animals↗

PubMed2004

ANP-induced decrease of iron regulatory protein activity is independent of HO-1 induction.

Atrial natriuretic peptide (ANP)-preconditioned livers are protected from ischemia-reperfusion injury. ANP-treated organs show increased expression of heme oxygenase (HO)-1. Because HO-1 liberates bound iron, the aim of our study was to determine whether ANP affects iron regulatory protein (IRP) activity and, thus, the levels of ferritin. Rat livers were perfused with Krebs-Henseleit buffer [+/-ANP, 8-bromo-cGMP (8-Br-cGMP), and tin protoporphyrin, 20 min], stored in University of Wisconsin solution (4 degrees C, 24 h), and reperfused (120 min). IRP activity was assessed by gel-shift assays, and ferritin, IRP phosphorylation, and PKC localization were assessed by Western blot. Control livers displayed decreased IRP activity at the end of ischemia but no change in ferritin content during ischemia and reperfusion. ANP-pretreated livers showed reduced IRP activity, an effect mimicked by 8-Br-cGMP. Ferritin levels were increased in ANP-pretreated organs. Simultaneous perfusion of livers with ANP and tin protoporphyrin did not reduce ANP-induced action, arguing against a role for HO-1 in changes in IRP activity. ANP and 8-Br-cGMP decreased membrane localization of PKC-alpha and PKC-epsilon, but this modulation of PKC seems unrelated to inhibition of IRP binding. This work shows the cGMP-mediated attenuation of IRP binding activity by ANP, which results in increased hepatic ferritin levels. This change in IRPs is independent of ANP-induced HO-1 and reduced PKC activation.

Animals↗

PubMed2004

Intravenous administration of glutathione protects parenchymal and non-parenchymal liver cells against reperfusion injury following rat liver transplantation.

AIM: To investigated the effects of intravenous administration of the antioxidant glutathione (GSH) on reperfusion injury following liver transplantation. METHODS: Livers of male Lewis rats were transplanted after 24 h of hypothermic preservation in University of Wisconsin solution in a syngeneic setting. During a 2-h reperfusion period either saline (controls, n=8) or GSH (50 or 100 micromol/(h/kg), n=5 each) was continuously administered via the jugular vein. RESULTS: Two hours after starting reperfusion plasma ALT increased to 1457+/-281 U/L (mean+/-SE) in controls but to only 908+/-187 U/L (P<0.05) in animals treated with 100 microGSH/(h/kg). No protection was conveyed by 50 micromol GSH(h/kg). Cytoprotection was confirmed by morphological findings on electron microscopy: GSH treatment prevented detachment of sinusoidal endothelial cells (SEC) as well as loss of microvilli and mitochondrial swelling of hepatocytes. Accordingly, postischemic bile flow increased 2-fold. Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow and a significant reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Following infusion of 50 micromol and 100 micromol GSH/(h/kg), plasma GSH increased to 65+/-7 mol/L and 97+/-18 mol/L, but to only 20+/-3 mol/L in untreated recipients. Furthermore, plasma glutathione disulfide (GSSG) increased to 7.5+/-1.0 mol/L in animals treated with 100 micro(h/kg) GSH but did not raise levels of untreated controls (1.8+/-0.5 mol/L) following infusion of 50 microGSH/(h/kg) (2.2+/-0.2 mol/L). CONCLUSION: Plasma GSH levels above a critical level may act as a "sink" for ROS produced in the hepatic vasculature during reperfusion of liver grafts. Therefore, GSH can be considered a candidate antioxidant for the prevention of reperfusion injury after liver transplantation, in particular since it has a low toxicity in humans.

Animals↗

PubMed2004

Selective retroinfusion of GSH and cariporide attenuates myocardial ischemia-reperfusion injury in a preclinical pig model.

OBJECTIVE: Reperfusion after ischemia may contribute to loss of myocardial function and increase in infarct size. Scavenging of reactive oxygen species (ROS) by glutathione (GSH) and inhibition of the sodium-proton-exchanger by cariporide are both capable of reducing myocardial reperfusion injury. We tested the efficacy of both agents applied regionally into the myocardium immediately before reperfusion. METHODS: Neonatal rat cardiomyocytes (NRCMs) were exposed to either hypoxia (H, 8 h)/reoxygenation (R, 1 h) or H2O2 (300 microM) in the presence or absence of GSH (10 mg/ml). In pigs (n=5 per group), percutaneous LAD occlusion was performed for 60 min. Application of GSH (250 mg/kg) and/or cariporide (1 mg/kg) was achieved by pressure-regulated retroinfusion of the anterior cardiac vein draining the ischemic area starting 5 min before reopening of the occluded LAD. Seven days later, subendocardial segment shortening (SES) was analyzed by sonomicrometry. Infarct size was determined by methylene-blue staining of the non-ischemic area and tetrazolium red staining of the viable myocardium in the area at risk (AAR). RESULTS: NRCM incubated with GSH (10 mg/ml) survived H/R or H2O2 (0.3 mM) to a larger extent than untreated cells. In pigs, infarct size of untreated hearts (51 +/- 6% of the AAR) was not significantly altered by GSH or cariporide retroinfusion alone (41 +/- 3% and 42 +/- 6%). In contrast, combined retroinfusion of cariporide and GSH significantly reduced infarct size (29 +/- 3%). SES of the infarcted area was improved only after cariporide/GSH retroinfusion as compared to untreated hearts. Additional systemic application of CD18-antibody IB4 (1.5 mg/kg) did not alter infarct size or SES in comparison to GSH/cariporide retroinfusion alone. CONCLUSION: Timely application of GSH scavenging ROS and cariporide targeting ion imbalance provides cardioprotection to the postischemic heart, which is superior to either treatment alone. The lack of an effect of additional IB4 treatment may indicate that GSH/cariporide retroinfusion itself affects leukocyte-dependent reperfusion injury.

Animals↗

PubMed2004

Glutathione protects the rat liver against reperfusion injury after prolonged warm ischemia.

OBJECTIVE: To evaluate the potential of postischemic intravenous infusion of the endogenous antioxidant glutathione (GSH) to protect the liver from reperfusion injury following prolonged warm ischemia. BACKGROUND DATA: The release of reactive oxygen species (ROS) by activated Kupffer cells (KC) and leukocytes causes reperfusion injury of the liver after warm ischemia. Therefore, safe and cost-effective antioxidant strategies would appear a promising approach to prevent hepatic reperfusion injury during liver resection, but need to be developed. METHODS: Livers of male Lewis rats were subjected to 60, 90, or 120 minutes of normothermic ischemia. During a 120 minutes reperfusion period either GSH (50, 100 or 200 micromol/h/kg; n= 6-8) or saline (n= 8) was continuously administered via the jugular vein. RESULTS: Postischemic GSH treatment significantly prevented necrotic injury to hepatocytes as indicated by a 50-60% reduction of serum ALT and AST. After 1 hour of ischemia and 2 hours of reperfusion apoptotic hepatocytes were rare (0.50 +/- 0.10%; mean +/- SD) and not different in GSH-treated animals (0.65 +/- 0.20%). GSH (200 micromol GSH/h/kg) improved survival following 2 hours of ischemia (6 of 9 versus 3 of 9 rats; P < 0.05). Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow. This was paralleled by a reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Intravenous GSH administration resulted in a 10- to 40-fold increase of plasma GSH levels, whereas intracellular GSH contents were unaffected. Plasma concentrations of oxidized glutathione (GSSG) increased up to 5-fold in GSH-treated animals suggesting counteraction of the vascular oxidant stress produced by activated KC. CONCLUSIONS: Intravenous GSH administration during reperfusion of ischemic livers prevents reperfusion injury in rats. Because GSH is well tolerable also in man, this novel approach could be introduced to human liver surgery.

Animals↗

PubMed2003

Rapid development of esophageal squamous cell carcinoma after liver transplantation for alcohol-induced cirrhosis.

Liver transplant recipients have an increased risk of developing de novo malignancies. It is generally accepted that chronic alcohol abuse is a contributive factor in the pathogenesis of several malignancies, in particular, of oropharyngeal squamous cell carcinoma (SCC). Thus, patients with end-stage alcohol-induced cirrhosis could be at risk of esophageal SCC following orthotopic liver transplantation (OLT). From January 1986 to December 1997 a total of 313 patients underwent OLT for various indications. Of these patients, 72 had alcohol-related cirrhosis. Oropharyngeal and esophageal malignancies after OLT were not observed in non-alcoholic patients. In contrast, these malignancies were diagnosed in three male patients who underwent transplantation for alcohol-induced cirrhosis (incidence 4.2%). Furthermore, all patients had a history of tobacco abuse. The tumors were located in the tongue of one patient and in the esophagus of two patients. While SCC of the tongue became apparent 5 years after OLT, esophageal SCC was detected 8 and 16 months after transplantation. Shortly before transplantation, endoscopy of the esophagus had not revealed evidence of pre-malignant dysplastic lesions in any of these patients. Thus, esophageal SCC may develop rapidly in patients undergoing transplantation for alcohol-related cirrhosis with a history of tobacco abuse before liver transplantation, which warrants careful post-transplant screening of these patients.

Adult↗

PubMed2003

Kupffer-cell specific induction of heme oxygenase 1 (hsp32) by the atrial natriuretic peptide--role of cGMP.

BACKGROUND/AIMS: Pretreatment with atrial natriuretic peptide (ANP) attenuates ischemia-reperfusion injury of livers via cGMP. Heme oxygenase-1 (HO-1) is known as a protective mediator in ischemia-reperfusion injury. The aim of this study was to investigate whether ANP affects the expression of HO-1. METHODS: Rat livers were perfused with KH-buffer with/without ANP or 8-Br-cGMP, kept in UW solution (4 degrees C, 24 h), and reperfused. HO-1 mRNA and protein was determined by Northern and Western blot, in situ hybridization, and immunohistochemistry in livers or isolated liver cells. RESULTS: ANP significantly elevated HO-1 mRNA expression at the end of the preconditioning period and was without effects at the end of ischemia and during reperfusion. 8-Br-cGMP did not affect HO-1 mRNA expression. In situ hybridization as well as immunohistological double-staining revealed that Kupffer cells but not hepatocytes showed HO-1 mRNA and protein expression. Hepatocytes revealed no changes in HO-1 protein whereas Kupffer cells showed a marked increase in HO-1 protein after ANP treatment. Inhibition of HO-1 did not abrogate hepatoprotection conveyed by ANP. CONCLUSION: Our data show the potency of ANP to specifically induce HO-1 in Kupffer cells independently of cGMP. This increased expression of HO-1 is not involved in hepatoprotection conferred by ANP being in line with the knowledge that ANP mediates hepatoprotection via cGMP.

Animals↗

PubMed2003

Atrial natriuretic peptide preconditioning protects against hepatic preservation injury by attenuating necrotic and apoptotic cell death.

BACKGROUND/AIMS: Preconditioning of livers with the atrial natriuretic peptide (ANP) markedly reduces hepatic ischemia-reperfusion injury. Aim of this study was to characterize the influence of ANP preconditioning on necrotic and apoptotic cell death and on proliferation. METHODS: Rat livers were perfused with Krebs-Henseleit buffer with or without ANP or its second messenger analogue 8-Bromo cyclic guanosine monophosphate (8-Br cGMP) for 20 min, stored in cold University of Wisconsin solution (24 h), and reperfused for up to 120 min. Apoptosis and necrosis were determined using biochemical and morphological criteria, proliferation was assessed by Ki67 histochemistry. RESULTS: Apoptosis peaked after 24 h of cold ischemia. Preconditioning with both ANP and 8-Br-cGMP significantly reduced caspase-3-like activity and the number of triphosphate nick-end labelling-positive cells. Reduction of apoptosis was significant for hepatocytes, but not for endothelial cells. After ischemia, degenerative cell changes were clearly reduced in ANP pretreated livers. After reperfusion, ANP preconditioning led to a significant reduction of necrotic hepatocytes and endothelial cells in periportal zones. Cell proliferation was not affected by preconditioning. CONCLUSIONS: ANP reduces necrotic and apoptotic cell death without affecting the proliferation status. The protection takes place mainly in the periportal area and seems to be most prominent against necrosis of hepatocytes and endothelial cells during reperfusion.

Animals↗

PubMed2003

Induction of cellular resistance against Kupffer cell-derived oxidant stress: a novel concept of hepatoprotection by ischemic preconditioning.

Ischemic preconditioning (IP) triggers protection of the liver from prolonged subsequent ischemia. However, the underlying protective mechanisms are largely unknown. We investigated whether and how IP protects the liver against reperfusion injury caused by Kupffer cell (KC)-derived oxidants. IP before 90 minutes of warm ischemia of rat livers in vivo significantly reduced serum alanine aminotransferase (AST) levels and leukocyte adherence to sinusoids and postsinusoidal venules during reperfusion. This protective effect was mimicked by postischemic intravenous infusion of glutathione (GSH), an antioxidative strategy against KC-derived H(2)O(2). Interestingly, no additional protection was achieved by infusion of GSH to preconditioned animals. These findings and several additional experiments strongly suggest IP mediated antioxidative effects: IP prevented oxidant cell injury in isolated perfused rat livers after selective KC activation by zymosan. Moreover, IP prevented cell injury and pertubations of the intracellular GSH/GSSG redox system caused by direct infusion of H(2)O(2) (0.5 mmol/L). IP-mediated resistance against H(2)O(2) could neither be blocked by the adenosine A2a antagonist DMPX nor mimicked by A2a agonist CGS21680. In contrast, H(2)O(2) resistance was abolished by the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580, but induced when p38 MAPK was directly activated by anisomycin. In conclusion, we propose a novel concept of hepatoprotection by IP: protection of liver cells by enhancing their resistance against KC-derived H(2)O(2). Activation of p38 MAPK and preservation of the intracellular GSH/oxidized glutathione (GSSG) redox system, but not adenosine A2a receptor stimulation, seems to be pivotal for the development of H(2)O(2) resistance in preconditioned livers.

Animals↗

PubMed2002

Short-term treatment with mycophenolic acid increases bile flow in continuously perfused and cold-preserved rat livers and does not affect hepatic ischemia-reperfusion injury.

Mycophenolate mofetil (MMF) is a new immunosuppressive agent which has been used successfully after kidney and heart transplantation. Experience with MMF after liver transplantation is still limited. In particular, there is no information about influence on ischemia-reperfusion injury (IRI). Therefore, the aim of this investigation was to assess the effects of mycophenolic acid (MPA), the pharmacologically active metabolite of MMF, in the cold-preserved or normal rat liver. Livers of male Sprague-Dawley rats were subjected to cold ischemia in University of Wisconsin (UW) solution (24 h, 4 degrees C) and reperfused for 2 h in the absence or presence of MPA (100 microg/ml, n=5-6 each). Another group received MPA pretreatment for 20 min prior to ischemia ( n=7). In further experiments, livers were perfused with a bile salt-free Krebs-Henseleit buffer in a continuous fashion (controls, n=5). MPA was infused from 20-40 min after starting perfusion in therapeutic concentrations (5 microg/ml, 10 microg/ml, 40 microg/ml, and 100 microg/ml; n=3-6 each). There was no significant influence of MPA on portal pressure nor on postischemic efflux rates of LDH. MPA pretreatment resulted in a significant improvement of bile flow during reperfusion (0.32+/-0.05 microl/min x g liver) compared with controls (0.17+/-0.04 microl/min x g liver, mean+/-SEM). In contrast, postischemic bile flow was not influenced by continuous administration of MPA during the reperfusion period only (0.18+/-0.07 microl/min x g liver). In continuously perfused livers, MPA increased bile salt-independent bile flow (1.00+/-0.06 microl/min x g liver) in a dose-dependent manner, reaching half-maximal effects around 5 microg/ml (1.66+/-0.15 microl/min x g liver) and maximal effects at 40 microg/ml (2.61+/-0.28 microl/min x g liver). In conclusion, neither preischemic nor postischemic administration of MPA influences IRI to hepatocytes significantly after hypothermic liver preservation in UW solution. In contrast to other immunosuppressive agents, MPA exhibits strong choleretic effects, which are related to a stimulation of bile salt-independent bile formation.

Animals↗

PubMed2002

The atrial natriuretic peptide and cGMP: novel activators of the heat shock response in rat livers.

Preischemic treatment with atrial natriuretic peptide (ANP) attenuates ischemia-reperfusion injury of the rat liver via cyclic guanosine monophosphate (cGMP). The attenuated activation of nuclear factor kappaB (NF-kappaB) seems to contribute to this effect. The aim of this study was to determine whether heat shock proteins are involved in these molecular pathways. Livers of male Sprague-Dawley rats were continuously perfused with Krebs-Henseleit (KH) buffer with or without ANP or 8-Br-cGMP. In different experiments livers were perfused with or without ANP for 20 minutes, kept in cold storage solution for 24 hours, and reperfused. Activation of heat shock transcription factor (HSF) (by electrophoretic mobility shift assay), heat shock protein 70 (HSP70), and glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA (by reverse transcription polymerase chain reaction [RT-PCR]), as well as HSP70 (by Western blot) were investigated in freeze-clamped liver samples. During continuous perfusion ANP as well as 8-Br-cGMP activated HSF, HSP70 protein concentrations paralleled HSF-activation. ANP pretreated livers exhibited elevated HSF after 24 hours of ischemia and elevated HSP70 mRNA levels during reperfusion. ANP prevented the marked decrease of HSP70 protein during reperfusion. Coimmunoprecipitation studies showed increased binding of HSP70 to inhibitory factor kappaB (IkappaB) in ANP-treated livers. In conclusion, we showed the cGMP-mediated activation of HSF by ANP, which resulted in elevated HSP70 mRNA and protein concentrations and correlated with enhanced binding of HSP70 to IkappaB. This could be an important mechanism of ANP-mediated prevention of hepatic preservation damage.

Adhesins, Bacterial↗

PubMed2002

The atrial natriuretic peptide as a regulator of Kupffer cell functions.

Kupffer cells (KCs), the resident macrophages of the liver, contribute prominently to liver injury by inflammatory mediators. Pre-conditioning with the atrial natriuretic peptide (ANP), known also as a regulator of macrophage functions, attenuates hepatic ischemia-reperfusion injury. Therefore, the aim of this study was to determine the presence of functional ANP receptors on isolated KCs and to investigate whether this hepatoprotective hormone influences the activation of KCs. KCs were isolated by collagenase/pronase digestion followed by elutrial centrifugation and cultured for 1 to 3 days. Intracellular cyclic guanosine 3'5'-monophosphate (cGMP) concentrations were measured by radioimmunoassay after treating the cells with sodium nitroprusside or ANP. KCs were stimulated with bacterial lipopolysaccharide in the presence or absence of ANP, and inflammatory mediators were determined. Phagocytosis was assayed using Coumarin-labeled latex particles and flow cytometric analysis. Treatment of KCs with ANP but not with sodium nitroprusside resulted in a significant elevation of intracellular cGMP levels indicating functional type A natriuretic peptide receptors (NPR-As). ANP significantly reduced lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNFalpha) secretion, paralleled by an increased cell-associated TNFalpha. LPS-induced TNFalpha mRNA expression was not affected. ANP significantly increased phagocytotic activity of KCs via NPR-A. No effect of ANP on LPS-activated inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 protein levels, iNOS mRNA expression, nitric oxide, and PGE2-production was observed. We demonstrated functional cGMP-dependent ANP receptors in isolated rat KCs. ANP reduced TNFalpha release possibly by influencing post-translational processing of TNFalpha in LPS-activated KCs. In addition, we demonstrated that ANP enhances phagocytosis in KCs. These effects may contribute to the hepatoprotective actions of ANP.

Animals↗

PubMed2002

Glutathione treatment protects the rat liver against injury after warm ischemia and Kupffer cell activation.

BACKGROUND/AIM: The generation of reactive oxygen species by activated Kupffer cells (KC) may contribute to reperfusion injury of the liver during liver transplantation or resection. The aim of our present studies was to investigate (1) prevention of hepatic reperfusion injury after warm ischemia by administration of the antioxidant glutathione (GSH) and (2) whether GSH confers protection through influences on KC toxicity. METHODS: Isolated perfused rat livers were subjected to 1 h of warm ischemia followed by 90 min of reperfusion without (n = 5) or with GSH or catalase (n = 4-5 each). Selective KC activation by zymosan (150 micro g/ml) in continuously perfused rat livers was used to investigate KC-related liver injury. RESULTS: Postischemic infusion of 0.1, 0.5, 1.0 and 2.0 mM GSH, but not 0.05 mM GSH prevented reperfusion injury after warm ischemia as indicated by a marked reduction of sinusoidal LDH efflux by up to 83 +/- 13% (mean +/- SD; p < 0.05) and a concomitant significant improvement of postischemic bile flow by 58 +/- 27% (p < 0.05). A similar protection was conveyed by KC blockade with gadolinium chloride indicating prevention of KC-related reperfusion injury by postischemic GSH treatment. Postischemic treatment with catalase (150 U/ml) resulted in a reduction of LDH efflux by 40 +/- 9% (p < 0.05). Accordingly, catalase as well as GSH (0.1-2.0 mM) nearly completely prevented the increase in LDH efflux following selective KC activation by zymosan in continously perfused rat livers. CONCLUSION: Postischemic administration of GSH protects the liver against reperfusion injury after warm ischemia. Detoxification of KC-derived hydrogen peroxide seem to be an important feature of the protective mechanisms.

Animals↗

PubMed2002

Improved quality of life in patients with refractory or recidivant ascites after insertion of transjugular intrahepatic portosystemic shunts.

BACKGROUND: We have recently shown that the transjugular intrahepatic portosystemic shunt (TIPS) is more effective than paracentesis in the treatment of cirrhotic patients with severe ascites and can prolong survival in selected patients. Although an improved quality of life (QOL) has been suggested in these patients after the TIPS procedure, so far there are no data available to substantiate this assumption. Therefore, the aim of this study was to determine the effect of TIPS on the QOL in cirrhotic patients with refractory or recidivant ascites. METHODS: 21 cirrhotic patients who underwent TIPS for refractory or recidivant ascites were investigated. All patients were pretreated with repeated paracentesis for at least 1 year. Before the procedure and at 3 and 6 months during follow-up, the patients themselves rated QOL, fatigue and physical performance on a visual analogue scale (range 0-100). Furthermore, QOL was determined by the QOL index (range 0-10) according to Spitzer. RESULTS: Patients' rating of the QOL on the visual analogue scale significantly increased from 35 +/- 25 (baseline) to 64 +/- 28 (3 months), and 66 +/- 24 (6 months; p = 0.02). Similarly, the QOL index significantly increased from 6.9 +/- 2.0 (baseline) to 8.3 +/- 2.1 (3 months), and 8.6 +/- 1.7 (6 months; p < 0.001). The increase of QOL was more pronounced in patients with complete response to TIPS. CONCLUSIONS: We demonstrate that TIPS for refractory or recidivant ascites improves the QOL in patients with cirrhosis. Our data indicates that this improvement is dependent on the response to therapy.

Ascites↗