Insights into exazaphosphorine resistance and possible approaches to its circumvention

The oxazaphosphorines cyclophosphamide, ifosfamide and trofosfamide remain a clinically useful class of anticancer drugs with substantial antitumour activity against a variety of solid tumors and hematological malignancies. A major limitation to their use is tumour resistance, which is due to multiple mechanisms that include increased DNA repair, increased cellular thiol levels, glutathione S-transferase and aldehyde dehydrogenase activities, and altered cell-death response to DNA damage. These mechanisms have been recently re-examined with the aid of sensitive analytical techniques, high-throughput proteomic and genomic approaches, and powerful pharmacogenetic tools. Oxazaphosphorine resistance, together with dose-limiting toxicity (mainly neutropenia and neurotoxicity), significantly hinders chemotherapy in patients, and hence, there is compelling need to find ways to overcome it. Four major approaches are currently being explored in preclinical models, some also in patients: combination with agents that modulate cellular response and disposition of oxazaphosphorines; antisense oligonucleotides directed against specific target genes; introduction of an activating gene (CYP3A4) into tumor tissue; and modification of dosing regimens. Of these approaches, antisense oligonucleotides and gene therapy are perhaps more speculative, requiring detailed safety and efficacy studies in preclinical models and in patients. A fifth approach is the design of novel oxazaphosphorines that have favourable pharmacokinetic and pharmacodynamic properties and are less vulnerable to resistance. Oxazaphosphorines not requiring hepatic CYP-mediated activation (for example, NSC 613060 and mafosfamide) or having additional targets (for example, glufosfamide that also targets glucose transport) have been synthesized and are being evaluated for safety and efficacy. Characterization of the molecular targets associated with oxazaphosphorine resistance may lead to a deeper understanding of the factors critical to the optimal use of these agents in chemotherapy and may allow the development of strategies to overcome resistance.

Changes in bacterial concentration in the liver correlate with that in the hepaticojejunostomy after bile duct reconstruction: implication in the pathogenesis of postoperative cholangitis

Postoperative cholangitis is a frequent and unpredictable complication of unknown etiology following bile duct reconstruction (BDR), particularly for biliary atresia. This study was undertaken to correlate the growth of bacteria in the hepaticojejunostomy with that in the liver after BDR. Quantitative bacterial culture was done on the specimens taken from the liver and from the hepaticojejunostomy at 1 week (group 1, n = 7), 1 month (group 2, n = 7), and 2 months (group 3, n = 7) following BDR with Roux-en-Y hepaticojejunostomy in piglets after 2 weeks of common bile duct ligation. The histological examination of the liver and the hepaticojejunostomy, as well as serial monitoring of hemogram and liver function tests, were performed to correlate the findings with the bacterial concentration of the liver and the hepaticojejunostomy following BDR. The bacterial concentration of the hepaticojejunostomy, expressed as log10 colony-forming units per gram (log10 CFU/g) of the hepaticojejunostomy, showed a progressive decrease from 8.38 ± 1.36 in group 1, 7.07 ± 2.54 in group 2, to 3.56 ± 1.31 in group 3 (p = 0.001). The log10 CFU/g of the liver also showed a progressive decrease from 5.02 ± 1.59 in group 1, 3.16 ± 1.56 in group 2, to 2.19 ± 1.09 in group 3 (p = 0.006). There was a significant positive correlation of the log10 CFU/g of the liver (n = 21) with that of the hepaticojejunostomy (n = 21) following BDR (r = 0.600, p = 0.004). Most of the infectious pathogens isolated from the liver were also isolated from the hepaticojejunostomy. The changes in hemoglobin, bilirubin, albumin, and ammonia significantly correlated with the changes of the bacterial concentration of the liver. The results of the study suggests that hepatic bacterial proliferation after BDR is significantly affected by microbial overgrowth in the bilioenteric anastomosis and is associated with deteriorated liver function and hemogram.

A genomic approach to understanding the cause and effect of annual ryegrass toxicity

Annual Ryegrass Toxicity (ARGT) is a potentially lethal disease affecting livestock grazing on pastures or consuming fodder that include annual ryegrass (Lolium rigidum) contaminated with corynetoxins. The corynetoxins (CTs), among the most lethal toxins produced in nature, are produced by the bacterium Rathayibacter toxicus that uses a nematode vector to attach to and infect the seedheads of L.rigidum. There is little known of the factors that control toxin production. Several studies have speculated that a bacteriophage specific to R.toxicus may be implicated in CT production. We have developed a PCR-based assay to test for both bacterium and phage in ryegrass material and results indicate that there is a correlation between phage and bacterial presence in all toxic ryegrass samples tested so far. This PCR-based technique may ultimately allow for a rapid, high-throughput screening assay to identify potentially toxic pastures and feed in the field. Currently, ~80% of the 45 Kb genome has been sequenced an investigation to further elucidate its potential role in toxin production.Furthermore, specific alterations in gene expression as a result of exposure to CTs or the closely related tunicamycins (TMs), which are commercially available and considered biologically indistinguishable from CTs, will be evaluated for use as biomarkers of exposure. The effects of both toxins will be analysed in vitro using a rat hepatocyte cell line and screened on a low-density DNA micro array “CT-Chip” that contains <100 selected rat hepatic genes. The results are expected to further define the bioequivalence of CTs and TMs and to identify levels of exposure that are related to specific toxic effects or have no adverse effect on livestock.

Vascular distribution of nitric oxide synthase and vasodilation in the Australian lungfish, Neoceratodus forsteri

The presence of nitric oxide synthase (NOS) and role of nitric oxide (NO) in vascular regulation was investigated in the Australian lungfish, Neoceratodus forsteri. No evidence was found for NOS in the endothelium of large and small blood vessels following processing for NADPH-diaphorase histochemistry. However, both NADPH-diaphorase histochemistry and neural NOS immunohistochemistry demonstrated a sparse network of nitrergic nerves in the dorsal aorta, hepatic artery, and branchial arteries, but there were no nitrergic nerves in small blood vessels in tissues. In contrast, nitrergic nerves were found in non-vascular tissues of the lung, gut and kidney. Dual-wire myography was used to determine if NO signalling occurred in the branchial artery of N. forsteri. Both SNP and SIN-1 had no effect on the pre-constricted branchial artery, but the particulate guanylyl cyclase (GC) activator, C-type natriuretic peptide, always caused vasodilation. Nicotine mediated a dilation that was not inhibited by the soluble GC inhibitor, ODQ, or the NOS inhibitor, L-NNA, but was blocked by the cyclooxygenase inhibitor, indomethacin. These data suggest that NO control of the branchial artery is lacking, but that prostaglandins could be endothelial relaxing factors in the vasculature of lungfish.

Copper is taken up efficiently from albumin and α2-macroglobulin by cultured human cells by more than one mechanism

Ionic copper entering blood plasma binds tightly to albumin and the macroglobulin transcuprein. It then goes primarily to the liver and kidney except in lactation, where a large portion goes directly to the mammary gland. Little is known about how this copper is taken up from these plasma proteins. To examine this, the kinetics of uptake from purified human  albumin and α2-macroglobulin, and the effects of inhibitors, were measured using human hepatic (HepG2) and mammary epithelial (PMC42) cell lines. At physiological concentrations (3–6 µM), both cell types took up copper from these proteins independently and at rates similar to each other and to those for Cu-dihistidine or Cu-nitrilotriacetate (NTA). Uptakes from   α2-macroglobulin indicated a single saturable system in each cell type, but with different kinetics, and 65–80% inhibition by Ag(I) in HepG2 cells but not PMC42 cells. Uptake kinetics for Cu-albumin were more complex and also differed with cell type (as was the case for Cu-histidine and NTA), and there was little or no inhibition by Ag(I). High Fe(II) concentrations (100–500 µM) inhibited copper uptake from albumin by 20–30% in both cell types and that from {alpha}2-macroglobulin by 0–30%, and there was no inhibition of the latter by Mn(II) or Zn(II). We conclude that the proteins mainly responsible for the plasma-exchangeable copper pool deliver the metal to mammalian cells efficiently and by several different mechanisms.α2-Macroglobulin delivers it primarily to copper transporter 1 in hepatic cells but not mammary epithelial cells, and additional as-yet-unidentified copper transporters or systems for uptake from these proteins remain to be identified.

Pharmaceutical ecomonics and politics vs. patient safety : Lumiracoxib in Australia

Lumiracoxib (Prexige©) 200 mg was listed in Australia’s Pharmaceutical Benefits Scheme (PBS) schedules on 01 August 2006. The listing was intended as a cost-minimisation strategy, as lumiracoxib 200 mg was deemed equivalent in therapeutic effect to celecoxib (Celebrex©) 200 mg, and was available at a lower cost. By the time of listing on the PBS, a safety re-evaluation of the recommended daily dose of lumiracoxib was being considered in other national regulatory jurisdictions. Within 3 months of listing, the manufacturer revised the recommended dosage to half that of the PBS-listed dosage. However, the PBS listing was neither revoked nor modified. At the time of listing on the PBS, lumiracoxib was known to be 17 times as biochemically selective in inhibiting the COX-2 isoform as celecoxib, and twice as selective as rofecoxib, already withdrawn for safety reasons. Safety concerns had already been raised about adverse hepatic outcomes on daily doses of lumiracoxib 200 mg. Communication of information about the risk potential of lumiracoxib was inadequate. Economic and political considerations were prioritised over patient safety, and lumiracoxib 200 mg remained available via the PBS until 10 August 2007, when it was withdrawn for safety reasons following cases of hepatic morbidity and mortality.

The measurement of GLUT4 translocation in 3T3-L1 adipocytes

Type 2 diabetes (T2D) is one of the fastest growing threats to human health in westernised and developing countries and is associated with central obesity, atherosclerosis, dyslipidaemia, hyperinsulinaemia and  hypertension. Insulin resistance, defined as a diminished response to ordinary levels of circulating insulin in one or more peripheral tissues, is an integral feature of T2D pathophysiology. This includes an impairment of insulin to inhibit hepatic glucose output and to stimulate glucose disposal into muscle and fat. While insulin is responsible for a number of specific biological responses, stimulation of glucose transport is critical for the maintenance of glucose homeostasis. The primary mechanism for insulin stimulation of glucose uptake into muscle and fat is the translocation of glucose transporter 4 (GLUT4) to the cell surface from intracellular storage vesicles within the cell. A major advantage in focussing on insulin regulation of glucose transport is that this represents the endpoint of multiple upstream signalling pathways. This chapter describes the measurement of GLUT4 translocation in cultured cells and its potential application for both  mechanistic and therapeutic studies.

The use of auricular examination for screening heaptic disorders

Researches on auricular acupuncture (AA) have examined mainly its treatment effects. This study aimed to investigate the accuracy and precision of using auricular examination (AE) as a complementary diagnostic tool for screening hepatic disorders. Twenty patients suffering from liver dysfunction and 25 controls aged 18–60 years were recruited from an acute hospital. Participants were examined using three AE methods including visual inspection, electrical skin resistance measurement, and tenderness testing on the liver AA zone of both ears. Significant differences were found in visual inspection and electrical skin resistance on the AA zones between the two groups. Patients suffering from liver dysfunction tended to have at least one abnormality in skin color, appearance, presence of papules, abundance of capillary and desquamation on the ear (Relative Risk—Right ear: RR = 2.9, 95% confidence interval (CI) 1.4, 6.2; Left: RR = 1.8, 95% CI, 1.01, 3.1). The sensitivity for visual inspection was 0.7 for both ears; specificity was 0.76 for the (R) and 0.6 for the (L) ear. The mean difference in electrical skin resistance was 4.3 MΩ (95% CI, 1.7, 6.9) for the (L) ear; 4.5 MΩ (95% CI, 1.5, 7.6) for the (R) ear. Our results suggest that malfunction of the liver appeared to be reflected by the presence of morphological changes on the liver AA zone. Visual inspection and electrical skin resistance on the liver AA zone are potentially sensitive to screen hepatic disorders.

Green tea, black tea, and epigallocatechin modify body composition, improve glucose tolerance, and differentially alter metabolic gene expression in rats fed a high-fat diet

The mechanisms of how tea and epigallocatechin-3-gallate (EGCG) lower body fat are not completely understood. This study investigated long-term administration of green tea (GT), black tea (BT), or isolated EGCG (1 mg/kg per day) on body composition, glucose tolerance, and gene expression related to energy metabolism and lipid homeostasis; it was hypothesized that all treatments would improve the indicators of metabolic syndrome. Rats were fed a 15% fat diet for 6 months from 4 weeks of age and were supplied GT, BT, EGCG, or water. GT and BT reduced body fat, whereas GT and EGCG increased lean mass. At 16 weeks GT, BT, and EGCG improved glucose tolerance. In the liver, GT and BT increased the expression of genes involved in fatty acid synthesis (SREBP-1c, FAS, MCD, ACC) and oxidation (PPAR-α, CPT-1, ACO); however, EGCG had no effect. In perirenal fat, genes that mediate adipocyte differentiation were suppressed by GT (Pref-1, C/EBP-β, and PPAR-γ) and BT (C/EBP-β), while decreasing LPL, HSL, and UCP-2 expression; EGCG increased expression of UCP-2 and PPAR-γ genes. Liver triacylglycerol content was unchanged. The results suggest that GT and BT suppressed adipocyte differentiation and fatty acid uptake into adipose tissue, while increasing fat synthesis and oxidation by the liver, without inducing hepatic fat accumulation. In contrast, EGCG increased markers of thermogenesis and differentiation in adipose tissue, while having no effect on liver or muscle tissues at this dose. These results show novel and separate mechanisms by which tea and EGCG may improve glucose tolerance and support a role for these compounds in obesity prevention.

Histological assessment of intermediate - and long-term creatine monohydrate supplementation in mice and rats

Creatine monohydrate (CrM) supplementation appears to be relatively safe based on data from short-term and intermediate-term human studies and results from several therapeutic trials. The purpose of the current study was to characterize pathological changes after intermediate-term and long-term CrM supplementation in mice [healthy control and SOD1 (G93A) transgenic] and rats (prednisolone and nonprednisolone treated). Histological assessment (18-20 organs/tissues) was performed on G93A mice after 159 days, and in Sprague-Dawley rats after 365 days, of CrM supplementation (2% wt/wt) compared with control feed. Liver histology was also evaluated in CD-1 mice after 300 days of low-dose CrM supplementation (0.025 and 0.05 g · kg^-1 · day^-1) and in Sprague-Dawley rats after 52 days of CrM supplementation (2% wt/wt) with and without prednisolone. Areas of hepatitis were observed in the livers of the CrM-supplemented G93A mice (P < 0.05), with no significant inflammatory lesions in any of the other 18-20 tissues/organs that were evaluated. The CD-1 mice also showed significant hepatic inflammatory lesions (P < 0.05), yet there was no negative effect of CrM on liver histology in the Sprague-Dawley rats after intermediate-term or long-term supplementation nor was inflammation seen in any other tissues/organs (P = not significant). Dietary CrM supplementation can induce inflammatory changes in the liver of mice, but not rats. The observed inflammatory changes in the murine liver must be considered in the evaluation of hepatic metabolism in CrM-supplemented mice. Species differences must be considered in the evaluation of toxicological and physiological studies.

Novel genes in the liver of diabetic Psammomys obesus

Type 2 diabetes mellitus is a metabolic disease characterised by defects in insulin secretion and insulin action and disturbances in carbohydrate, fat and protein metabolism. Hepatic insulin resistance contributes to hyperglycemia and also leads to disturbances in fat metabolism in type 2 diabetes. Psammomys obesus is a unique poly genie animal model of type 2 diabetes and obesity, ideally suited for studies examining physiological and genetic aspects of these diseases. To identify metabolic abnormalities potentially contributing to the obesity and diabetes phenotype in P. obesus, indirect calorimetry was used to characterise whole body energy expenditure and substrate utilisation. Lean-NGT, obese-IGT and obese-diabetic animals were examined in fed and fasted states and following 14 days of dietary energy restriction. Energy expenditure and fat oxidation were elevated in the obese-IGT and obese-diabetic groups in proportion to body weight. Glucose oxidation was not different between groups. Obese-diabetic P. obesus displayed elevated nocturnal blood glucose levels and fat oxidation. Following 14 days of dietary energy restriction, body weight was reduced and plasma insulin and blood glucose levels were normalised in all groups. Glucose oxidation was reduced and fat oxidation was increased. After 24 hours of fasting, plasma insulin and blood glucose levels were normalised in all groups. Energy expenditure and glucose oxidation were greatly reduced and fat oxidation was increased. Following either dietary energy restriction or fasting, energy expenditure, glucose oxidation and fat oxidation were not different between groups of P. obesus. Energy expenditure and whole body substrate utilisation in P. obesus was similar to that seen in humans. P. obesus responded normally to short term fasting and dietary energy restriction. Elevated nocturnal fat oxidation rates and plasma glucose levels in obese-diabetic P. obesus may be an important factor in the pathogenesis of obesity and type 2 diabetes in these animals. These studies have further validated P. obesus as an ideal animal model of type 2 diabetes and obesity. It was hypothesised that many genes in the liver of P. obesus involved in glucose and fat metabolism would be differentially expressed between lean-NGT and obese-diabetic animals. These genes may represent significant factors in the pathophysiology of type 2 diabetes. Two gene discovery experiments were conducted using suppression subtractive hybridisation (SSH) to enrich a cDNA library for differentially expressed genes. Experiment 1 used cDNA dot blots to screen 576 clones with cDNA derived from lean-NGT and obese-diabetic animals. 6 clones were identified as overexpressed in lean-NGT animals and 6 were overexpressed in obese-diabetic animals. These 12 clones were sequenced and SYBR-Green PCR was used to confirm differential gene expression. 4 genes were overexpressed (≥1.5 fold) in lean-NGT animals and 4 genes were overexpressed (≥1.5 fold) in obese-diabetic animals. To explore the physiological role of these genes, hepatic gene expression was examined in several physiological conditions. One gene, encoding thyroxine binding globulin (TBG), was confirmed as overexpressed in lean-NGT P. obesus with ad libitum access to food, relative to both obese-IGT and obese-diabetic animals. TBG expression decreased with fasting in all animals. Fasting TBG expression remained greater in lean-NGT animals than obese-IGT and obese-diabetic animals. TBG expression was not significantly affected by dietary energy restriction. TBG is involved in thyroid metabolism and is potentially involved in the regulation of energy expenditure. Fasting increased hepatic site 1 protease (SIP) expression in lean-NGT animals but was not significantly affected in obese-IGT and obese-diabetic animals. SIP expression was not significantly affected by dietary energy restriction. SIP is involved in the proteolytic processing of steroid response element binding proteins (SREBP). SREBPs are insulin responsive and are known to be involved in lipid metabolism. Gene expression studies found TBG and SIP were associated with obesity and diabetes. Future research will determine whether TBG and SIP are important in the pathogenesis of these diseases. Experiment 2 used SSH and cDNA microarray to screen 8064 clones. 223 clones were identified as overexpressed in lean-NGT P. obesus and 274 clones were overexpressed in obese-diabetic P. obesus (p ≤0.05). The 9 most significantly differentially expressed clones identified from the microarray screen were sequenced (p ≤0.01). 7 novel genes were identified as well as; sulfotransferase related protein and albumin. These 2 genes have not previously been associated with either type 2 diabetes or obesity. It is unclear why hepatic expression of these genes may differ between lean-NGT and obese-diabetic groups of P. obesus. Subsequent studies will explore the potential role of these novel and known genes in the pathophysiology of type 2 diabetes.

Liver fat metabolism, obesity and diabetes in Psammomys obesis

Defects in fat metabolism are central to the aetiology and pathogenesis of obesity and type II diabetes. The liver plays a central role in these disease states via its regulation of glucose and fat metabolism. In addition, accumulation of fat within the liver has been associated with changes in key pathways of carbohydrate and fat metabolism. However a number of questions remain. It is hypothesised that fat accumulation within the liver is a primary defect in the aetiology and pathogenesis of obesity and type II diabetes. Fat accumulating in the liver is the result of changes in the gene expression of key enzymes and proteins involved with fat uptake, fat transport, fat oxidation, fat re-esterification or storage and export of fat from the liver and these changes are regulated by key lipid responsive transcription factors. To study these questions Psammomys obesus was utilised. This polygenic rodent model of obesity and type II diabetes develops obesity and diabetes in a similar pattern to susceptible human populations. In addition dietary and environmental changes to Psammomys obesus were employed to create different states of energy balance, which allowed the regulation of liver fat gene expression to be examined. These investigations include: 1) Measurement of fat accumulation and fatty acid binding proteins in lean, obese and diabetic Psammomys obesus. 2) Characterisation of hepatic lipid enzymes, transport protein and lipid responsive transcription factor gene expression in lean, obese and diabetic Paammomys obesus. 3) The effect of acute and chronic energy restriction on hepatic lipid metabolism in Psammomys obesus. 4) The effect of sucrose feeding on the development of obesity and type II diabetes in Psammomys obesus. 5) The effect of nicotine treatment in lean and obese Psammomys obesus, 6) The effect of high dose leptin administration on hepatic fat metabolism in Psammomys obesus. The results of these studies demonstrated that fat accumulation within the liver was not a primary defect in the aetiology and pathogenesis of obesity and type II diabetes. Fat accumulating in the liver was not the result of changes in the gene expression of key enzymes and proteins involved in hepatic fat metabolism. However changes in the mRNA level of the transcription factors PPAR∝ and SREBP-1C was associated with the development of diabetes and the gene expression of these two transcription factors was associated with changes in diabetic status.

Adrenergic regulation of carbohydrate metabolism during exercise

1. This series of studies was undertaken to examine the adrenergic regulation of carbohydrate metabolism during exercise. Recreationally active males were tested during moderate to intense exercise on a stationary cycle ergometer. Venous and arterial plasma obtained from indwelling catheters was analysed for hormonal and metabolite responses, and hepatic glucose production and glucose uptake were measured using the tracer-dilution method with stable isotopes. Muscle samples were obtained by the needle biopsy technique to examine muscle glycogen utilisation and the flux of related muscle metabolites using enzymatic, fluorometric and radioisotopic techniques. 2. During moderate exercise adrenaline infusion induced a marked hyperglycemia and this was due to reduced glucose uptake rather than enhanced hepatic glucose production. The reduction in glucose uptake was most likely mediated by a decrease in glucose phosphorylation, as indicated by the accumulation of glucose 6-phosphate with adrenaline infusion. 3. The hyperglycemic response to intense exercise was prevented by the administration of α- and β-adrenergic antagonists. Adrenergic blockade was without effect on hepatic glucose production whereas glucose uptake was enhanced when compared with control subjects. These data support the notion that adrenergic mechanisms are more important in restraining glucose uptake than enhancing hepatic glucose production during intense exercise. Other glucoregulatory factors are responsible for the increase in glucose production during intense exercise. 4. Elevated plasma adrenaline levels during moderate exercise in untrained men increases skeletal muscle glycogen breakdown and PDH activation which results

Natural history of hepatitis B in perinatally infected carriers

Objectives: To establish natural seroconversion rates and incidence of hepatic pathology in perinatally infected hepatitis B carriers.

Methods: Seventy three perinatally infected hepatitis B carriers identified through maternal screening were evaluated. Fifty three were born to parents from the Indian subcontinent, nine were Oriental, six were Afro-Caribbean, and five were white. Median follow up was 10.24 (range 2.02–20.16) years.

Results: Only three of the children followed up had cleared hepatitis B surface antigen during this period, and 30% of the children had seroconverted to anti-HBe. Seroconversions to anti-HBe were observed in Asian (18/50) and white (4/5) children, but not in Oriental or Afro-Caribbean children. More girls (40%) than boys (23%) had seroconverted, but the difference was not significant. All children were asymptomatic with normal physical examination, growth, and development. Almost half (48%) of the hepatitis B e antigen (HBeAg) positive children had normal hepatic transaminases and liver function. Thirty five liver biopsies were performed in children with active virus replication (HBeAg or hepatitis B virus DNA positive) who were being considered for antiviral treatment as part of a clinical trial and were scored using the Ishak method. Two thirds (62%) of the children had mild hepatitis, 60% had mild fibrosis, and 18% had moderate to severe fibrosis. There was a weak correlation between histological evidence of hepatitis and hepatic transaminase activity, implying that biochemical monitoring of hepatic disease activity may be ineffective.

Conclusions: These asymptomatic hepatitis B virus carrier children remain infectious in the medium to long term with notable liver pathology. They should receive antiviral treatment to reduce infectivity and to prevent further progression of liver disease. Hepatic transaminases alone are not a reliable marker of liver pathology, and liver histology is essential before consideration for antiviral treatment.

Hydrogen sulfide attenuates carbon tetrachloride-induced hepatotoxicity, liver cirrhosis and portal hypertension in rats

BACKGROUND : Hydrogen sulfide (H(2)S) displays vasodilative, anti-oxidative, anti-inflammatory and cytoprotective activities. Impaired production of H(2)S contributes to the increased intrahepatic resistance in cirrhotic livers. The study aimed to investigate the roles of H(2)S in carbon tetrachloride (CCl(4))-induced hepatotoxicity, cirrhosis and portal hypertension.

METHODS AND FINDINGS : Sodium hydrosulfide (NaHS), a donor of H(2)S, and DL-propargylglycine (PAG), an irreversible inhibitor of cystathionine γ-lyase (CSE), were applied to the rats to investigate the effects of H(2)S on CCl(4)-induced acute hepatotoxicity, cirrhosis and portal hypertension by measuring serum levels of H(2)S, hepatic H(2)S producing activity and CSE expression, liver function, activity of cytochrome P450 (CYP) 2E1, oxidative and inflammatory parameters, liver fibrosis and portal pressure. CCl(4) significantly reduced serum levels of H(2)S, hepatic H(2)S production and CSE expression. NaHS attenuated CCl(4)-induced acute hepatotoxicity by supplementing exogenous H(2)S, which displayed anti-oxidative activities and inhibited the CYP2E1 activity. NaHS protected liver function, attenuated liver fibrosis, inhibited inflammation, and reduced the portal pressure, evidenced by the alterations of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), albumin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and soluble intercellular adhesion molecule (ICAM)-1, liver histology, hepatic hydroxyproline content and α-smooth muscle actin (SMA) expression. PAG showed opposing effects to NaHS on most of the above parameters.

CONCLUSIONS :  Exogenous H2S attenuates CCl4-induced hepatotoxicity, liver cirrhosis and portal hypertension by its multiple functions including anti-oxidation, anti-inflammation, cytoprotection and anti-fibrosis, indicating that targeting H2S may present a promising approach, particularly for its prophylactic effects, against liver cirrhosis and portal hypertension.