bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosynthesis of heparan sulphate with diverse structures and functions: two alternatively spliced forms of human heparan sulphate 6-O-sulphotransferase-2 having different expression patterns and properties
Authors: HABUCHI Hiroko , MIYAKE Goichiro , NOGAMI Ken , KUROIWA Asato , MATSUDA Yoichi , KUSCHE-GULLBERG Marion , HABUCHI Osami , TANAKA Masayuki , KIMATA Koji
Published: March 2003

Heparan sulphate 6-O-sulphotransferase (HS6ST) catalyses the transfer of sulphate from adenosine 3′-phosphate, 5′-phosphosulphate to the 6th position of the N-sulphoglucosamine residue in HS. We previously described the occurrence of three isoforms of mouse HS6ST, mHS6ST-1, −2, and −3 [Habuchi, Tanaka, Habuchi, Yoshida, Suzuki, Ban and Kimata (2000) J. Biol. Chem. 275, 2859—2868]. In the present study, we have characterized HS6ST-2 and HS6ST-1 human isologues, including their chromosomal localizations. In the process of their cDNA cloning, we found two forms of HS6ST-2: the original (hHS6ST-2) and a short form (hHS6ST-2S) with 40 amino acids deleted. Both hHS6ST-2 and hHS6ST-2S catalysed the same sulphation reaction, but their preferences for sulphation sites in HS substrates were different. Dot-blot analysis of the two forms showed that the original form was exclusively expressed in adult and foetal brain tissues, whereas the short form was expressed preferentially in ovary, placenta and foetal kidney, suggesting that the expression of two forms of hHS6ST-2 is strictly regulated to yield tissue-dependent differences in the fine structure of HS. A refined analysis of their reaction products has led us to another finding, that HS6STs could also transfer sulphate to N-sulphoglucosamine residues located at the non-reducing terminal of HS with high affinity.
Granular gland transcriptomes in stimulated amphibian skin secretions
Authors: CHEN Tianbao , FARRAGHER Susan , BJOURSON Anthony J. , ORR David F. , RAO Pingfan , SHAW Chris
Published: March 2003

Amphibian defensive skin secretions are complex, species-specific cocktails of biologically active molecules, including many uncharacterized peptides. The study of such secretions for novel peptide discovery is time-limited, as amphibians are in rapid global decline. While secretion proteome analysis is non-lethal, transcriptome analysis has until now required killing of specimens prior to skin dissection for cDNA library construction. Here we present the discovery that polyadenylated mRNAs encoding dermal granular gland peptides are present in defensive skin secretions, stabilized by endogenous nucleic acid-binding amphipathic peptides. Thus parallel secretory proteome and transcriptome analyses can be performed without killing the specimen in this model amphibian system—a finding that has important implications in conservation of biodiversity within this threatened vertebrate taxon and whose mechanistics may have broader implications in biomolecular science.
Regulation of the epithelial sodium channel by accessory proteins
Authors: GORMLEY Kelly , DONG Yanbin , SAGNELLA Giuseppe A.
Published: March 2003

The epithelial sodium channel (ENaC) is of fundamental importance in the control of sodium fluxes in epithelial cells. Modulation of sodium reabsorption through the distal nephron ENaC is an important component in the overall control of sodium balance, blood volume and thereby of blood pressure. This is clearly demonstrated by rare genetic disorders of sodium-channel activity (Liddle's syndrome and pseudohypoaldosteronism type 1), associated with contrasting effects on blood pressure. The mineralocorticoid aldosterone is a well-established modulator of sodium-channel activity. Considerable insight has now been gained into the intracellular signalling pathways linking aldosterone-mediated changes in gene transcription with changes in ion transport. Activating pathways include aldosterone-induced proteins and especially the serum- and glucocorticoid-inducible kinase (SGK) and the small G-protein, K-Ras 2A. Targeting of the ENaC for endocytosis and degradation is now emerging as a major mechanism for the down-regulation of channel activity. Several proteins acting in concert are an intrinsic part of this process but Nedd4 (neural precursor cell expressed developmentally down-regulated 4) is of central importance. Other mechanisms known to interact with ENaC and affect sodium transport include channel-activating protease 1 (CAP-1), a membrane-anchored protein, and the cystic fibrosis transmembrane regulator. The implications of research on accessory factors controlling ENaC activity are wide-ranging. Understanding cellular mechanisms controlling ENaC activity may provide a more detailed insight not only of ion-channel abnormalities in cystic fibrosis but also of the link between abnormal renal sodium transport and essential hypertension.
1-Methyl-4-phenylpyridinium (MPP+)-induced apoptosis and mitochondrial oxidant generation: role of transferrin-receptor-dependent iron and hydrogen peroxide
Authors: KALIVENDI Shasi V. , KOTAMRAJU Srigiridhar , CUNNINGHAM Sonya , SHANG Tiesong , HILLARD Cecilia J. , KALYANARAMAN B.
Published: March 2003

1-Methyl-4-phenylpyridinium (MPP+) is a neurotoxin used in cellular models of Parkinson's Disease. Although intracellular iron plays a crucial role in MPP+-induced apoptosis, the molecular signalling mechanisms linking iron, reactive oxygen species (ROS) and apoptosis are still unknown. We investigated these aspects using cerebellar granule neurons (CGNs) and human SH-SY5Y neuroblastoma cells. MPP+ enhanced caspase 3 activity after 24h with significant increases as early as 12h after treatment of cells. Pre-treatment of CGNs and neuroblastoma cells with the metalloporphyrin antioxidant enzyme mimic, Fe(III)tetrakis(4-benzoic acid)porphyrin (FeTBAP), completely prevented the MPP+-induced caspase 3 activity as did overexpression of glutathione peroxidase (GPx1) and pre-treatment with a lipophilic, cell-permeable iron chelator [N,N′-bis-(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid, HBED]. MPP+ treatment increased the number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labelling)-positive cells which was completely blocked by pre-treatment with FeTBAP. MPP+ treatment significantly decreased the aconitase and mitochondrial complex I activities; pre-treatment with FeTBAP, HBED and GPx1 overexpression reversed this effect. MPP+ treatment increased the intracellular oxidative stress by 2—3-fold, as determined by oxidation of dichlorodihydrofluorescein and dihydroethidium (hydroethidine). These effects were reversed by pre-treatment of cells with FeTBAP and HBED and by GPx1 overexpression. MPP+-treatment enhanced the cell-surface transferrin receptor (TfR) expression, suggesting a role for TfR-induced iron uptake in MPP+ toxicity. Treatment of cells with anti-TfR antibody (IgA class) inhibited MPP+-induced caspase activation. Inhibition of nitric oxide synthase activity did not affect caspase 3 activity, apoptotic cell death or ROS generation by MPP+. Overall, these results suggest that MPP+-induced cell death in CGNs and neuroblastoma cells proceeds via apoptosis and involves mitochondrial release of ROS and TfR-dependent iron.
The specificities of protein kinase inhibitors: an update
Authors: BAIN Jenny , McLAUCHLAN Hilary , ELLIOTT Matthew , COHEN Philip
Published: March 2003

We have previously examined the specificities of 28 commercially available compounds, reported to be relatively selective inhibitors of particular serine/threonine-specific protein kinases [Davies, Reddy, Caivano and Cohen (2000) Biochem. J. 351, 95—105]. In the present study, we have extended this analysis to a further 14 compounds. Of these, indirubin-3′-monoxime, SP 600125, KT 5823 and ML-9 were found to inhibit a number of protein kinases and conclusions drawn from their use in cell-based assays are likely to be erroneous. Kenpaullone, Alsterpaullone, Purvalanol, Roscovitine, pyrazolopyrimidine 1 (PP1), PP2 and ML-7 were more specific, but still inhibited two or more protein kinases with similar potency. Our results suggest that the combined use of Roscovitine and Kenpaullone may be useful for identifying substrates and physiological roles of cyclin-dependent protein kinases, whereas the combined use of Kenpaullone and LiCl may be useful for identifying substrates and physiological roles of glycogen synthase kinase 3. The combined use of SU 6656 and either PP1 or PP2 may be useful for identifying substrates of Src family members. Epigallocatechin 3-gallate, one of the main polyphenolic constituents of tea, inhibited two of the 28 protein kinases in the panel, dual-specificity, tyrosine-phosphorylated and regulated kinase 1A (DYRK1A; IC50 = 0.33μM) and p38-regulated/activated kinase (PRAK; IC50 = 1.0μM).
Murine serpin 2A is a redox-sensitive intracellular protein
Authors: MORRIS Emma C. , DAFFORN Timothy R. , FORSYTH Sharon L. , MISSEN Melinda A. , HORVATH Anita J. , HAMPSON Lynne , HAMPSON Ian N. , CURRIE Graeme , CARRELL Robin W. , COUGHLIN Paul B.
Published: March 2003

Murine serpin 2A is expressed at high levels in haemopoietic progenitors and down-regulated on differentiation. When it is constitutively expressed in the multipotent haemopoietic cell line, FDCP-Mix, it causes a delay in differentiation and increased clonogenic potential. The serpin is also dramatically up-regulated on T-cell activation. It has an unusual reactive site Cys-Cys sequence, a unique C-terminal extension and lacks a typical cleavable N-terminal signal sequence. In spite of these features, the protein is not a member of the ovalbumin—serpin family, but is instead most closely related to human antichymotrypsin. We have shown that the serpin is intracellular with prominent nuclear localization. Transverse urea gradient gels and CD studies show that the protein undergoes the stressed—relaxed conformational change typical of inhibitory serpins. However, we have not detected complex-forming activity with a set of proteases. Thermal denaturation studies also show that the protein has decreased structural stability under reducing conditions, although it lacks disulphide bonds within the core of the molecule. Our results show that serpin 2A is an intracellular protein with the potential to mediate its biological effects via interaction with non-protease intracellular targets. Furthermore, the results presented suggest a model whereby the serpin interactions could be modulated by redox conditions or conformational change induced by cleavage of the reactive-site loop.
Positive and negative regulation of T-cell activation through kinases and phosphatases
Authors: MUSTELIN Tomas , TASKÉN Kjetil
Published: March 2003

The sequence of events in T-cell antigen receptor (TCR) signalling leading to T-cell activation involves regulation of a number of protein tyrosine kinases (PTKs) and the phosphorylation status of many of their substrates. Proximal signalling pathways involve PTKs of the Src, Syk, Csk and Tec families, adapter proteins and effector enzymes in a highly organized tyrosine-phosphorylation cascade. In intact cells, tyrosine phosphorylation is rapidly reversible and generally of a very low stoichiometry even under induced conditions due to the fact that the enzymes removing phosphate from tyrosine-phosphorylated substrates, the protein tyrosine phosphatases (PTPases), have a capacity that is several orders of magnitude higher than that of the PTKs. It follows that a relatively minor change in the PTK/PTPase balance can have a major impact on net tyrosine phosphorylation and thereby on activation and proliferation of T-cells. This review focuses on the involvement of PTKs and PTPases in positive and negative regulation of T-cell activation, the emerging theme of reciprocal regulation of each type of enzyme by the other, as well as regulation of phosphotyrosine turnover by Ser/Thr phosphorylation and regulation of localization of signal components.
The metabolism of S-nitrosothiols in the trypanosomatids: the role of ovothiol A and trypanothione
Authors: VOGT Ryan N. , STEENKAMP Daniel J.
Published: March 2003

It has recently been established that nitrosoglutathione is the preferred substrate of the glutathione-dependent formaldehyde dehydrogenase from divergent organisms. Trypanosomatids produce not only glutathione, but also glutathionylspermidine, trypanothione and ovothiol A. The formaldehyde dehydrogenase activity of Crithidia fasciculata was independent of these thiols and extracts possessed very low levels of nitrosothiol reductase activity with glutathione or its spermidine conjugates as the thiol component. Although ovothiol A did not form a stable nitrosothiol, it decomposed the S-nitroso groups of nitrosoglutathione (GSNO) and dinitrotrypanothione [T(SNO)2] with second-order rate constants of 19.12M-1·s-1 and 8.67M-1·s-1 respectively. The reaction of T(SNO)2 with ovothiol A, however, accelerated to a rate similar to that seen with GSNO. Ovothiol A can act catalytically to decompose these nitrosothiols, although non-productive mechanisms exist. The catalytic phase of the reaction was dependent on the production of thiyl radicals, since it was abolished in the presence of 5,5-dimethyl-1-pyrroline-N-oxide and the formation of nitric oxide could be detected by means of the conversion of oxyhaemoglobin into methaemoglobin. The rate-limiting step in the catalytic process was the reduction of oxidized ovothiol species and, in this respect, T(SNO)2 is a more efficient substrate than GSNO. Trypanothione decomposed GSNO with a second-order rate constant of 0.786M-1·s-1 and the major nitrogenous end product changed from nitrite to ammonia as the ratio of thiol to nitrosothiol increased. The results indicate that ovothiol A acts in synergy with trypanothione in the decomposition of T(SNO)2.
The anti-apoptotic effect of leukotriene D4 involves the prevention of caspase 8 activation and Bid cleavage
Authors: WIKSTRÖM Katarina , JUHAS Maria , SJÖLANDER Anita
Published: March 2003

We have shown in a previous study that leukotriene D4 (LTD4) signalling increases cell survival and proliferation in intestinal epithelial cells [Öhd, Wikström and Sjölander (2000) Gastroenterology 119, 1007—1018]. This is highly interesting since inflammatory conditions of the bowel are associated with an increased risk of developing colon cancer. The enzyme cyclo-oxygenase 2 (COX-2) is important in this context since it is up-regulated in colon cancer tissues and in tumour cell lines. Treatment with the COX-2-specific inhibitor N-(2-cyclohexyloxy-4-nitrophenyl)methane sulphonamide has been shown previously to cause apoptosis in intestinal epithelial cells. In the present study, we attempted to elucidate the underlying mechanisms and we can now show that a mitochondrial pathway is employed. Inhibition of COX-2 causes release of cytochrome c, as shown by both Western-blot and microscopy studies, and as with apoptosis, this is significantly decreased by LTD4. Since previous studies showed increased Bcl-2 levels on LTD4 stimulation, we further studied apoptotic regulation at the mitochondrial level. From this we could exclude the involvement of the anti-apoptotic protein Bcl-XL as well as its pro-apoptotic counterpart Bax, since they are not expressed. Furthermore, the activity of the pro-apoptotic protein Bad (Bcl-2/Bcl-XL-antagonist, causing cell death) was completely unaffected. However, inhibition of COX-2 caused cleavage of caspase 8 into a 41kDa fragment associated with activation and caused the appearance of an activated 15kDa fragment of Bid. This indicates that N-(2-cyclohexyloxy-4-nitrophenyl)methane sulphonamide-induced apoptosis is mediated by the activation of caspase 8, via generation of truncated Bid, and thereafter release of cytochrome c. Interestingly, LTD4 not only reverses the effects induced by inhibition of COX-2 but also reduces the apoptotic potential by lowering the basal level of caspase 8 activation and truncated Bid generation.
Effects of prenatal glucocorticoid exposure on cardiac calreticulin and calsequestrin protein expression during early development and in adulthood
Authors: LANGDOWN Maria L. , HOLNESS Mark J. , SUGDEN Mary C.
Published: March 2003

Overexpression of the conserved Ca2+-binding proteins calreticulin and calsequestrin impairs cardiac function, leading to premature death. Calreticulin is vital for embryonic development, but also impairs glucocorticoid action. Glucocorticoid overexposure during late fetal life causes intra-uterine growth retardation and programmed hypertension in adulthood. To determine whether intra-uterine growth retardation or programmed hypertension was associated with altered calreticulin or calsequestrin expression, effects of prenatal glucocorticoid overexposure (maternal dexamethasone treatment on days 15—21 of pregnancy) were examined during fetal life and postnatal development until adulthood (24 weeks). Dexamethasone (100 or 200μg/kg of maternal body weight) was administered via osmotic pump. Calreticulin was detected as a 55kDa band and calsequestrin as 55 and 63kDa bands in 21 day fetal hearts. Only the 55kDa calsequestrin band was detected postnatally. Prenatal glucocorticoid overexposure at the higher dose decreased calreticulin protein expression (26%; P<0.05) but increased calsequestrin protein expression, both 55 and 63kDa bands, by 87% (P<0.01) and 78% (P<0.01); only the 55kDa calsequestrin band was increased at the lower dose (66%; P<0.05). Offspring of dams treated at the lower dexamethasone dose were studied further. In control offspring, cardiac calreticulin protein expression declined between 2 and 3 weeks of age, and remained suppressed until adulthood. Cardiac calsequestrin protein expression increased 2-fold between fetal day 21 and postnatal day 1 and continued to increase until adulthood, at which time it was 3.4-fold higher (P<0.001). Prenatal dexamethasone exposure minimally affected postnatal calsequestrin protein expression, but the postnatal decline in calreticulin protein expression was abrogated and calreticulin protein expression in adulthood was 2.2-fold increased (P<0.001) compared with adult controls. In view of the known associations between cardiac calreticulin overexpression and impaired cardiac function, targeted up-regulation of calreticulin may contribute to the increased risk of adult heart disease introduced as a result of prenatal overexposure to glucocorticoids.
Mastoparan binds to glycogen phosphorylase to regulate sarcoplasmic reticular Ca2+ release in skeletal muscle
Authors: HIRATA Yutaka , ATSUMI Masanori , OHIZUMI Yasushi , NAKAHATA Norimichi
Published: March 2003

The ryanodine receptor, a Ca2+-releasing channel in sarcoplasmic reticulum (SR), plays an important role in the excitation—contraction coupling of skeletal muscle. In a previous study [Hirata, Nakahata and Ohizumi (2000) Mol. Pharmacol. 57, 1235—1242], we reported that mastoparan caused Ca2+ release through ryanodine receptor from the heavy fraction of SR (HSR) isolated from rabbit skeletal muscle, and that it specifically bound to a 97kDa protein which was distinct from Ca2+-pump or triadin. The present study was undertaken to identify and characterize the 97kDa mastoparan-binding protein. The 97kDa protein was purified from solubilized HSR by DEAE-Sepharose column chromatography and preparative SDS/PAGE. The partial amino acid sequence of the purified 97kDa protein was matched with that of glycogen phosphorylase (GP). The proteolytic cleavage pattern of the 97kDa protein was identical with that of GP. Furthermore, [125I-Tyr3]mastoparan specifically bound to GP. Interestingly, mastoparan-induced Ca2+ release was inhibited by exogenous addition of GP-a, and mastoparan dissociated GP from HSR. These results indicate that the 97kDa mastoparan-binding protein is GP, which negatively regulates Ca2+ release from HSR. There may be a functional cross-talk between Ca2+ release from HSR and glycogenolysis for energy supply mediated through GP in skeletal muscles.
Imbalanced intrahepatic expression of interleukin 12, interferon gamma, and interleukin 10 in fulminant hepatitis B
Authors: Leifeld Ludger , Cheng Silvia , Ramakers Jan , Dumoulin Franz-Ludwig , Trautwein Christian , Sauerbruch Tilman , Spengler Ulrich
Published: March 2003

In murine models, overexpression of interleukin (IL)-12 and interferon (IFN)-γ can induce severe liver damage, whereas IL-10 has anti-inflammatory and hepatoprotective properties. To analyze the potential role of these cytokines in human fulminant hepatitis B, we used immunohistochemistry to study expression of IL-12, IFN-γ, and IL-10 in explant livers of 11 patients with fulminant hepatitis B, 5 patients with fulminant hepatitis due to other etiologies, 37 patients with chronic liver disease (CLD; hepatitis B virus, n = 15; hepatitis C virus, n = 10; primary biliary cirrhosis, n = 12), and 10 normal controls (NCs). Furthermore, cytokine messenger RNA (mRNA) levels were determined in the liver specimens by quantitative real-time polymerase chain reaction (PCR). In NCs, faint IL-12 expression was detected in only a few Kupffer cells, whereas sinusoidal endothelial cells, hepatic stellate cells, bile ducts, and lymphocytes expressed IL-12 in CLD and, more conspicuously, in fulminant hepatitis B. In contrast, expression of IFN-γ and IL-10 was restricted to lymphocytes and Kupffer cells, respectively. In fulminant hepatitis B, numbers of IL-12- and IFN-γ-positive cells markedly exceeded those found in CLD and NCs. A close correlation existed between IL-12 and IFN-γ expression (r = 0.68; P < .001). In contrast, IL-10 expression was not significantly different in CLD and fulminant hepatitis. The quantitative differences in immunohistologic cytokine expression closely corresponded to the mRNA levels. In conclusion, our data indicate massive induction of the proinflammatory cytokines IL-12 and IFN-γ in fulminant hepatitis B, which is apparently not counterbalanced by the anti-inflammatory cytokine IL-10. This cytokine imbalance may play an important role in promoting inflammatory reactions leading to massive liver damage in fulminant hepatitis B.
Fractal dimension can distinguish models and pharmacologic changes in liver fibrosis in rats
Authors: Moal Frédéric , Chappard Daniel , Wang Jianhua , Vuillemin Eric , Michalak-Provost Sophie , Rousselet Marie Christine , Oberti Frédéric , Calès Paul
Published: March 2003

Fractal analysis measures the complexity of geometric structures. The aim of this study was to evaluate the feasibility and accuracy of fractal analysis in liver fibrosis. A total of 77 rats were included: 10 sham, 46 with fibrosis secondary to bile duct ligation (BDL), and 21 with fibrosis due to CCl4 intoxication. Measurements included the fractal dimension of Kolmogorov (Dk), histologic lesions, the area of fibrosis by image analysis, liver hydroxyproline content, messenger RNA fibronectin, serum hyaluronate level, and portal pressure. Fibrotic rats were given placebo, octreotide, or O2-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO). Intraobserver agreement of Dk was excellent with the intraclass (ic) correlation coefficient r
ic = 0.91 (P < .0001) as well as the interobserver agreement with r
ic = 0.88 (P < .001). Dk was correlated with other measurements or markers of fibrosis: the area of fibrosis (r = 0.75; P < .0001), hydroxyproline content (r = 0.51; P < .001), serum hyaluronate level (r = 0.52; P < .001), and portal pressure (r = 0.52; P < .01). Dk was significantly different between the 2 models of fibrosis (P < .0001), unlike the area of fibrosis, and this relationship was independent of other histologic lesions. The significant decrease in fibrosis observed with octreotide or V-PYRRO/NO was similarly reflected by Dk or the area of fibrosis. The diagnostic accuracy for the fibrosis model was 97% with the 5 main measurements or markers of fibrosis studied, with Dk isolated at the first step by stepwise analysis. In conclusion, fractal analysis is suitable for analyzing liver fibrosis and has excellent reproducibility. This is the only quantitative morphometric method that can discriminate among the models of fibrosis and is sensitive enough to detect pharmacologically induced changes in liver fibrosis.
Liver disease in pediatric patients with cystic fibrosis is associated with glutathione S-transferase P1 polymorphism
Authors: Henrion-Caude Alexandra , Flamant Cyril , Roussey Michel , Housset Chantal , Flahault Antoine , Fryer Anthony A. , Chadelat Katarina , Strange Richard C. , Clement Annick
Published: March 2003

Liver disease in patients with cystic fibrosis (CF) is inconstant and has not yet been clearly related to any specific risk factor. While the expression of cystic fibrosis transmembrane conductance regulator (CFTR) is restricted to the biliary epithelium in the liver, recent findings indicate that CFTR modulates reduced glutathione (GSH) transport and that CFTR dysfunction creates an imbalance in the antioxidant defense. Among liver detoxifying enzymes, the glutathione S-transferases (GSTs) play a key role in the protection against oxidative stress. Because oxidative injury contributes to the development of liver disease, we hypothesized that 2 members of the GST superfamily, GSTM1 and GSTP1, which are expressed in the biliary epithelium, could influence the hepatic status in patients with CF. The potential impact of GSTM1 and GSTP1 gene polymorphisms was assessed in 106 children with CF (mean age, 11.5 years). Based on polymerase chain reaction/restriction fragment length polymorphism analysis, we found that the frequency of GSTP1-Ile105/Ile105 genotype was significantly higher in patients with CF with liver disease than in those without (P < .03). Among the youngest patients, aged 6 years, GSTP1-Ile105/Ile105 genotype was associated with a 8-fold increase in the risk of liver disease compared with other GSTP1 genotypes (P = .002). No association between the GSTM1 genotype and liver status was documented. In conclusion, GSTP1-Ile105-encoding allele contributes to hepatic dysfunction in CF. Identification of this polymorphism may have prognostic value and prompt early treatment in patients with CF with an increased risk of liver disease.
Cold ischemia decreases liver regeneration after partial liver transplantation in the rat: A TNF-α/IL-6-dependent mechanism
Authors: Selzner Nazia , Selzner Markus , Tian Yinghua , Kadry Zakiyah , Clavien Pierre-Alain
Published: March 2003

New strategies of partial liver transplantation such as cadaveric split or living related liver transplantation have been developed to overcome organ shortage. Thus, studies on the ability of small partial grafts to regenerate to normal size while maintaining adequate function have become important. Here, we evaluated the effects of cold preservation on hepatocyte proliferation and function in a novel model of partial liver transplantation in rats. Lewis rats subjected to 70% liver resection (control) were compared with rats that underwent total hepatectomy and 30% partial liver transplantation (recipient). Livers were preserved at 4°C for 30 minutes, 10 hours, or 16 hours in University of Wisconsin solution. Seventy percent liver resection was associated with 100% survival, whereas 30-minute, 10-hour, and 16-hour preservation before 30% transplantation resulted in 80%, 40%, and 20% animal survival, respectively. Prolonged time of cold preservation (10 and 16 hours) was associated with a dramatic decrease of all markers of regeneration (P < .05). Tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) levels were also significantly decreased in recipient rats compared with the control group. Finally, pretreatment of recipients with recombinant IL-6 (rIL-6) normalized all markers of regeneration and significantly improved survival in the 10-hour group (90% vs. 40%; P < .05). In conclusion, sustained periods of cold preservation significantly impaired TNF-α and IL-6 production, the regenerative ability of the liver, and animal survival. rIL-6 reversed impaired regeneration in the 10-hour cold ischemia group and suggests a primary role of nonparenchymal cells in modulating hepatocyte proliferation in the ischemic liver.
Prevention of bile acid-induced apoptosis by betaine in rat liver
Authors: Graf Dirk , Kurz Anna Kordelia , Reinehr Roland , Fischer Richard , Kircheis Gerald , Häussinger Dieter
Published: March 2003

Bile acid-induced apoptosis plays an important role in the pathogenesis of cholestatic liver disease, and its prevention is of therapeutic interest. The effects of betaine were studied on taurolithocholate 3-sulfate (TLCS) and glycochenodeoxycholate (GCDC)-induced apoptosis in rat hepatocytes in vitro and in vivo. Hepatocyte apoptosis, caspase activation, and poly (ADP-ribose) polymerase (PARP) cleavage, which are normally observed in response to both bile acids, were largely prevented after preincubation of hepatocytes with betaine. Betaine uptake was required for this protective effect, which was already observed at betaine concentrations of 1 mmol/L. Betaine did not affect the TLCS-induced membrane trafficking of CD95 and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) receptor 2 to the plasma membrane or the TLCS-induced recruitment of Fas-associated death domain (FADD) and caspase 8 to the CD95 receptor. However, betaine largely prevented cytochrome c release and oxidative stress exerted otherwise by TLCS. Inhibition of caspase 9 strongly blunted TLCS-induced caspase-8 activation. Further betaine did not prevent the TLCS-induced c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (Erk), and p38 mitogen-activated protein kinase (p38MAPK) activation or TLCS-induced protein kinase B (PKB) dephosphorylation. The protective betaine effect was insensitive to inhibition of Erks by PD089059, of p38MAPK by SB203580, or of phosphatidylinositol 3-kinase (PI3-kinase) by LY294002. Betaine supplementation in the drinking water significantly ameliorated in vivo hepatocyte apoptosis following bile duct ligation. In conclusion, this study identifies betaine as a potent protectant against bile acid-induced apoptosis in vivo and in vitro, and its antiapoptotic action largely resides on an inhibition of the proapoptotic mitochondrial pathway.
Analysis of TCR antagonism and molecular mimicry of an HLA-A*0201-restricted CTL epitope in primary biliary cirrhosis
Authors: Kita Hiroto , Matsumura Shuji , He Xiao-Song , Ansari Aftab A. , Lian Zhe-Xiong , Van de Water Judy , Coppel Ross L. , Kaplan Marshall M. , Gershwin Eric M.
Published: March 2003

Although the etiology and mechanism of primary biliary cirrhosis (PBC) is unknown, growing evidence suggests a major role for T cells. We have recently identified the first CD8 T-cell epitope, amino acid 159-167 of the E2 component of pyruvate dehydrogenase complexes (PDC-E2). To seek for analogue peptide-antagonizing effector function of CTLs specific for this autoantigen, we examined the effector functions of the PDC-E2-specific CTLs against alanine substituted peptides. Furthermore, because molecular mimicry has been postulated as a possible cause of initiating PBC, we carried out studies aimed at identifying naturally occurring peptides for the 159-167 peptide of PDC-E2 that may serve as agonists. An alanine substitution at position 5 of this epitope significantly reduced peptide-specific effector functions of CTLs. Moreover, this analogue peptide inhibited effector functions of the CTLs to the prototype peptide, including cytotoxicity and IFN-γ production. We also identified a peptide derived from Pseudomonas aeruginosa, which showed a higher binding affinity to the HLA-A*0201 than the prototype peptide. This homologous peptide was recognized by CTLs specific for the prototype epitope on PDC-E2. In conclusion, a modification of the immunodominant autoepitope can be utilized to manipulate the CD8 T-cell responses against the autoantigen PDC-E2. Our finding also supports the thesis that molecular mimicry may be implicated in the initiation of the autoreactive CD8 T-cell responses and has implications for the use of such peptides for immunotherapy.
Relevance of Niemann-Pick type C1 protein expression in controlling plasma cholesterol and biliary lipid secretion in mice
Authors: Amigo Ludwig , Mendoza Hegaly , Castro Juan , Quiñones Verónica , Miquel Juan Francisco , Zanlungo Silvana
Published: March 2003

Receptor-mediated endocytosis is one of the major mechanisms for uptake of lipoprotein cholesterol in the liver. Because Niemann-Pick C1 (NPC1) protein is a key component in the intracellular distribution of cholesterol obtained from lipoproteins by the endocytic pathway, it may play a critical role in controlling plasma lipoprotein cholesterol and its biliary secretion. A murine model of Niemann-Pick type C disease (NPC), the NPC1-deficient [NPC1 (−/−)] mouse, was used to evaluate the relevance of hepatic NPC1 expression in regulating plasma lipoprotein cholesterol profile and biliary lipid secretion under chow and high-cholesterol diets. Total plasma cholesterol concentrations were increased in NPC1 (−/−) mice compared with wild-type mice when both mouse strains were fed chow or high-cholesterol diets. The increased plasma cholesterol levels found in NPC1 (−/−) mice were mostly due to elevated cholesterol content in larger and more heterogeneous HDL particles. On the chow diet, biliary lipid secretion was not impaired by NPC1 deficiency. Furthermore, chow-fed NPC1 (−/−) mice showed a small, but significant, increase in biliary cholesterol secretion. On the high-cholesterol diet, wild-type mice increased biliary cholesterol output, whereas NPC1 (−/−) mice did not. Finally, hepatic NPC1 overexpression by adenovirus-mediated gene transfer increased biliary cholesterol secretion by 100% to 150% in both wild-type mice and cholesterol-fed NPC1 (−/−) mice. In conclusion, hepatic NPC1 expression is an important factor for regulating plasma HDL cholesterol levels and biliary cholesterol secretion in mice.
Reversal of drug resistance of hepatocellular carcinoma cells by adenoviral delivery of anti-MDR1 ribozymes
Authors: Huesker Matthes , Folmer Yvonne , Schneider Michaela , Fulda Christine , Blum Hubert E. , Hafkemeyer Peter
Published: March 2003

Human cancers, including hepatocellular carcinoma (HCC), are characterized by a high degree of drug resistance. The multidrug resistance (MDR) transporters MDR1-P-glycoprotein and MRP2 (multidrug-associated protein 2) are expressed in almost 50% of human cancers, including HCCs. In this study, we analyzed the effect of anti-MDR1 ribozymes, especially AFP promoter-driven anti-MDR1 ribozymes, to specifically chemosensitize HCC cells. Epirubicin-selected HB8065/R cells were used as MDR1-P-glycoprotein-overexpressing cells. Adenoviral vectors were constructed to allow an efficient gene transfer of anti-MDR1 ribozyme constructs. AFP promoter-driven anti-MDR1 ribozymes reduced the IC50 30-fold for epirubicin in HCC cells, whereas human colorectal cancer cells were unaffected. Target sequences were either the translational start site or codon 196 of the human MDR1 gene. Adenoviral delivery of CMV promoter-driven anti-MDR1 ribozymes resulted in a reduced IC50 for epirubicin and doxorubicin (60- and 20-fold, respectively). They completely restored chemosensitivity in stably transfected anti-MDR1 ribozyme-expressing HCC cells as well as in HCC cells transduced with adenoviruses expressing wild-type anti-MDR1 ribozymes. Adenoviral delivery of ribozymes was so efficient that chemosensitization of HCC cells could be demonstrated in cell cultures without further selection of transduced cells for single anti-MDR1 ribozyme-expressing HCC cell clones. Northern blots showed a decreased MDR1 mRNA expression, and fluorescence-activated cell sorting (FACS) analysis revealed a significantly reduced expression of MDR1-P-glycoprotein on the cell surface of HB8065/R cells after transduction with the anti-MDR1 ribozymes. In conclusion, our data demonstrate that adenoviral delivery of ribozymes can chemosensitize HCC cells and that chemosensitization can be specifically achieved by ribozymes driven by an AFP promoter directed against human MDR1.
Hepatitis C, cryoglobulinemia, and cirrhosis: A meta-analysis
Authors: Kayali Zeid , Buckwold Victor E. , Zimmerman Bridget , Schmidt Warren N.
Published: March 2003

Approximately 40% of patients with chronic hepatitis C virus (HCV) infection develop detectable serum cryoglobulins or cryoprecipitates (CP), although most do not show clinical or physical signs of syndromic cryoglobulinemia. Although association of HCV with the extrahepatic complications of cryoglobulinemia is widely recognized, the relationship of cryoglobulinemia with liver disease is unclear. We wished to study the relationship between CP and cirrhosis and to determine whether the development of CP is a true covariate for progressive liver disease or a confounding variable that impacts cirrhosis because of patient age, duration of disease, or differences in gender. We undertook a meta-analysis of 19 studies published between 1994 and 2001. The incidence of cirrhosis was compared in patients with and without CP after logistic regression adjustments for accepted risk factors for progressive liver disease, including age, gender, and estimated duration of disease (EDD). A total of 2,323 patients with chronic hepatitis C were identified, with 1,022 (44%) having detectable CP. Cirrhosis was present in 40% of patients with CP but only 17% of patients without CP (total χ2 = 141.69, P < .001). After adjusting for age, gender, and estimated duration of disease by logistic regression, the combined odds ratio for incidence of cirrhosis in patients CP positive versus CP negative was 4.87, (95% CI: 3.32, 7.15), indicating a highly significant association between cirrhosis and cryoglobulinemia. In conclusion, cryoglobulins may be a useful prognostic indicator for increased risk of cirrhosis with chronic hepatitis C.
Regulation of endothelin-A receptor sensitivity by cyclic adenosine monophosphate in rat hepatic stellate cells
Authors: Reinehr Roland , Fischer Richard , Häussinger Dieter
Published: March 2003

Sensitization of the endothelin-A receptor (ETA) occurs during HSC transdifferentiation, but the underlying mechanisms remained unclear. Sensitization of ETA was studied in quiescent and activated hepatic stellate cells (HSC) at the levels of receptor phosphorylation, localization, endothelin (ET)-1-induced Ca2+ signals, and cell contraction. The endothelin-1 (ET-1) concentrations required to obtain an ETA-mediated Ca2+ signal in 50% of HSC cultured for 1 to 2 or 10 days were approximately 1.2 and 0.012 nmol/L, respectively. This transdifferentiation-dependent sensitization of ETA was accompanied by receptor translocation to the plasma membrane. Cyclic AMP rapidly desensitized ETA in activated HSC and shifted their ET-1 responsiveness from picomolar to nanomolar concentrations with respect to Ca2+ signals and HSC contraction. ETA desensitization also occurred in response to prostaglandin E2, adenosine, or ETB stimulation. Desensitization by cAMP in activated HSC was accompanied by an increased Ser/Thr phosphorylation of ETA and their rapid internalization. Quiescent HSC exhibited Ser/Thr phosphorylation of the ETA protein, which was not affected by cAMP. In conclusion, the ETA response in HSC is regulated by protein kinase A (PKA)-dependent receptor phosphorylation and internalization. This may explain the transdifferentiation-dependent sensitization of HSC towards ET-1 and its reversal by cAMP and ETB activation.
Increasing intra-abdominal pressure increases pressure, volume, and wall tension in esophageal varices
Authors: Escorsell Angels , Ginès Angels , Llach Josep , García-Pagán Joan C. , Bordas Josep M. , Bosch Jaume , Rodés Joan
Published: March 2003

Many daily activities cause acute elevations of intra-abdominal pressure (IAP). In portal hypertensive cirrhotic patients, increased IAP increases absolute portal pressure and azygos blood flow, suggesting that it may have detrimental consequences at the esophageal varices. The aim of this study was to investigate the effects of increased IAP on variceal pressure, size, and wall tension. Endosonography and a noninvasive endoscopic pressure gauge were used to measure variceal pressure, radius, wall tension, and volume in baseline conditions and after increasing IAP by 10 mm Hg using an inflatable girdle in 14 patients with cirrhosis and esophageal varices. Increasing IAP markedly increased variceal pressure (from 13.3 ± 4.2 to 17.4 ± 4.6 mm Hg; P = .0001) and radius (from 2.9 ± 1.0 to 3.9 ± 1.1 mm; P = .0001). Consequently, wall tension dramatically increased (from 38.7 ± 13.6 to 65.9 ± 23.8 mm Hg · mm, +78%; P = .0001). Variceal volume increased significantly from 1,264 ± 759 to 2,025 ± 1,129 mm3 (P = .0001). In conclusion, in portal hypertensive cirrhotic patients, increases in IAP have deleterious effects on variceal hemodynamics, markedly increasing the volume, pressure, and wall tension of the varices. Increases in IAP may contribute to the progressive dilatation that precedes the rupture of the varices in portal hypertension.
Inducible differentiation and morphogenesis of bipotential liver cell lines from wild-type mouse embryos
Authors: Strick-Marchand Hélène , Weiss Mary C.
Published: March 2003

This work shows that hepatic cell lines reproducibly can be derived from E14 embryos of many mouse inbred strains. These bipotential mouse embryonic liver (BMEL) cell lines present a mixed morphology, containing both epithelial and palmate-like cells, and an uncoupled phenotype, expressing hepatocyte transcription factors (HNF1α, HNF4α, GATA4) but not functions (apolipoproteins, albumin). BMEL cells are bipotential: under inducing conditions they express hepatocyte and bile duct functions. In addition, they can undergo morphogenesis in Matrigel culture to form bile duct units. When returned to basal culture conditions, the differentiated cells revert, within a few days, to an undifferentiated state. The ensemble of markers expressed by BMEL cells implies that they originate from hepatoblasts, the endodermal precursors of the liver. In conclusion, the establishment of a simple and reproducible method to isolate from any mouse embryo bipotential hepatic cell lines that exhibit the properties of transit stem cells provides a novel paradigm for investigation of hepatic cell lineage relationships.
Proapoptotic and antiproliferative potential of selective cyclooxygenase-2 inhibitors in human liver tumor cells
Authors: Kern Michael André , Schubert Dominic , Sahi Dina , Schöneweiβ Mirja Mareike , Moll Ilona , Haugg Anke Maria , Dienes Hans Peter , Breuhahn Kai , Schirmacher Peter
Published: March 2003

Recent studies have shown increased levels of cyclooxygenase-2 (COX-2) in a variety of human malignancies, including hepatocellular carcinoma (HCC), but so far it is unknown whether COX-2 contributes to the malignant growth and whether inhibition of COX-2 function modifies the malignant potential of liver tumors. COX-1 and COX-2 expression was determined in 4 liver tumor cell lines (Hep 3B, HuH-7, Hep G2, Sk-hep1) by Northern hybridization and Western immunoblot. The functional effects of the nonselective inhibitor sulindac sulfide and the COX-2 selective inhibitors SC-58635 and meloxicam were examined by 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoliumbromide (MTT)-assays and BrdU uptake, morphology, and TUNEL analysis of apoptosis. Apoptosis regulating proteins were analyzed by Western immunoblot. COX-1 and COX-2 expression was demonstrable in all tested liver tumor cell lines. Sulindac sulfide (50 to 400 μmol/L), SC-58635 (6,25 to 400 μmol/L), and meloxicam (6.25 to 400 μmol/L) led to a significant time- and dose-dependent reduction of cell numbers of up to 80% (P < .05). At equimolar concentrations the effect was more pronounced when COX-2 was selectively blocked. COX-2 inhibition induced apoptosis and reduced tumor cell proliferation. Apoptosis after COX-2 inhibition with SC-58635 (50 μmol/L) was independent of BCL-2, BAX, and the phosphorylation status of AKT/PKB and BAD, but correlated with activation of caspase-9, caspase-3, and caspase-6. In conclusion, selective inhibition of COX-2 leads to a marked growth inhibition of human liver tumor cells, based on the induction of apoptosis and inhibition of proliferation and, thus, may offer therapeutic and preventive potential in human hepatocarcinogenesis.
Outcome of an outbreak of acute hepatitis C among healthy volunteers participating in pharmacokinetics studies
Authors: Larghi Alberto , Zuin Massimo , Crosignani Andrea , Ribero Maria Lisa , Pipia Cristina , Battezzati Pier Maria , Binelli Giorgio , Donato Francesco , Zanetti Alessandro Remo , Podda Mauro , Tagger Alessandro
Published: March 2003

We identified 15 patients with acute hepatitis C (AHC) among 29 healthy volunteers participating in 2 consecutive pharmacokinetics studies. Molecular techniques were used to determine the relatedness of viral strains, whereas clinical and virologic follow-up was started to establish the course and outcome of the acute infection. After presentation, serum liver enzymes and HCV RNA were monitored weekly for 4 months, then monthly for at least 12 months. Liver biopsy was performed 6 to 12 months after AHC diagnosis. Phylogenetic analysis of coding regions for the envelope glycoproteins E1 and E2 was performed. At presentation, all 15 patients tested HCV RNA-positive and had HCV genotype 2c. Phylogenetic analysis indicated a common source of infection. Fourteen patients agreed to be followed prospectively. Infection resolved spontaneously in 8 patients, HCV RNA becoming undetectable by 4 to 5 months after the presumed time of infection in 5 of them and by 8, 13, and 24 months in the remaining 3. Six patients developed chronic infection. Liver biopsies performed in 9 subjects who were HCV RNA-positive 6 months after AHC diagnosis revealed that the prevalent histologic finding was lobular inflammation. In conclusion, our homogeneous cohort showed a wide spectrum of clinical, virologic and histologic features, and, more importantly, short-term outcome differed noticeably despite the common source of infection.
Albumin dialysis in cirrhosis with superimposed acute liver injury: A prospective, controlled study
Authors: Heemann Uwe , Treichel Ulrich , Loock Jan , Philipp Thomas , Gerken Guido , Malago Massimo , Klammt Sebastian , Loehr Matthias , Liebe Stephan , Mitzner Steffen , Schmidt Reinhardt , Stange Jan
Published: March 2003

Patients with liver cirrhosis and a superimposed acute injury with progressive hyperbilirubinemia have a high mortality. A prospective, controlled study was performed to test whether hyperbilirubinemia, 30-day survival, and encephalopathy would be improved by extracorporeal albumin dialysis (ECAD). Twenty-four patients were studied; 23 patients had cirrhosis; 1 had a prolonged cholestatic drug reaction and was excluded from per protocol (PP) analysis. Patients had a plasma bilirubin greater than 20 mg/dL and had not responded to prior standard medical therapy (SMT). Patients were randomized to receive SMT with ECAD or without (control). ECAD was performed with an extracorporeal device that dialyzes blood in a hollow fiber dialyzer (MW cutoff < 60 kd) against 15% albumin. Albumin-bound molecules transfer to dialysate albumin that is regenerated continuously by passage through a charcoal and anion exchange column and a conventional dialyzer. ECAD was associated with improved 30-day survival (PP, 11 of 12 ECAD, 6 of 11 controls; log rank P < .05). Plasma bile acids and bilirubin decreased on average by 43% and 29%, respectively, in the ECAD group after 1 week of treatment, but not in the control group. Renal dysfunction and hepatic encephalopathy improved in the ECAD group, but worsened significantly in the control group. ECAD was safe, with adverse events being rare and identical in both groups. In conclusion, ECAD appears to be effective and safe for the short-term treatment of patients with cirrhosis and superimposed acute injury associated with progressive hyperbilirubinemia and may be useful for increasing survival in such patients awaiting liver transplantation.