Brett Jones

Alcohol Metabolism Increases the Replication of Hepatitis C Virus and Attenuates the Antiviral Action of Interferon

The interactions between hepatitis C virus (HCV) and alcohol metabolism are not well understood. To determine the effect that alcohol metabolism has on HCV replication and the antiviral action of interferon (IFN), Huh-7 cells that harbor HCV replication and metabolize ethanol via the introduced expression of cytochrome P450 2E1 (Cyp2e1) were treated with ethanol and IFN-alpha. Treatment of these cells with ethanol (0-100 mmol/L) significantly increased HCV replication. This effect was dependent on Cyp2e1 expression and alcohol-metabolized oxidative stress (OS), because the antioxidant N-acetylcysteine blocked this effect. Furthermore, the anti-HCV action of IFN-alpha was attenuated in the presence of ethanol metabolism, most likely via attenuation of Stat1 tyrosine-701 phosphorylation. These in vitro results mimic what is often noted clinically, and further dissection of this model system will aid in our understanding of interactions between HCV and alcohol metabolism.

Entecavir versus lamivudine for hepatitis B prophylaxis in patients with haematological disease.

Hepatitis B reactivation in patients receiving immunosuppressive therapy or chemotherapy may be associated with acute hepatitis, liver failure and/or death.

Age-Related Pseudocapillarization of the Liver Sinusoidal Endothelium Impairs the Hepatic Clearance of Acetaminophen in Rats

We investigated the effect of age-related pseudocapillarization of the liver sinusoidal endothelium on the hepatic disposition of acetaminophen. The multiple indicator dilution technique assessed the hepatic disposition of tracer (14)C-acetaminophen and reference markers in isolated perfused livers of young (n = 11) and old (n = 12) rats. Electron microscopy confirmed defenestration of the sinusoidal endothelium in old rats compared with young rats. Acetaminophen recovery following a single pass through the liver was significantly increased in old rats (0.64 ± 0.04, old; 0.59 ± 0.05, young; p < .05). In old age, there was significant reduction of the intercompartmental rate constant k(1) (0.34 ± 0.10 s(-1), old; 0.61 ± 0.38 s(-1), young; p < .05) and the permeability-surface area product for the transfer of acetaminophen across the sinusoidal endothelium (0.034 ± 0.006 mL/s/g, old; 0.048 ± 0.014 mL/s/g, young; p < .005). There was no difference in k(3), the measure of sequestration of acetaminophen that reflects enzyme activity. Age-related pseudocapillarization of the liver sinusoid resulted in increased acetaminophen recovery and decreased transfer of acetaminophen into the liver.

The Effect of Aging on Acetaminophen Pharmacokinetics, Toxicity and Nrf2 in Fischer 344 Rats

We investigated the effect of aging on hepatic pharmacokinetics and the degree of hepatotoxicity following a toxic dose of acetaminophen. Young and old male Fischer 344 rats were treated with 800 mg/kg acetaminophen (young n = 8, old n = 5) or saline (young n = 9, old n = 9). Serum measurements showed old rats treated with acetaminophen had significantly lower serum alanine aminotransferase and higher acetaminophen and acetaminophen glucuronide levels and creatinine, compared with acetaminophen treated young rats (p < .05). Immunoblotting and activity assays showed old saline-treated rats had twofold lower cytochrome P450 2E1 activity and threefold higher NAD(P)H quinone oxireductase 1 protein expression and activity than young saline-treated rats (p < .05), although Nrf2, glutathione cysteine ligase-modulatory subunit, glutathione cysteine ligase-catalytic subunit, and cytochrome P450 2E1 protein expressions were unchanged. Primary hepatocytes isolated from young rats treated with 10 mM acetaminophen had lower survival than those from old rats (52.4% ± 5.8%, young; 83.6% ± 1.7%, old, p < .05). The pharmacokinetic changes described may decrease susceptibility to acetaminophen-induced hepatotoxicity but may increase risk of nephrotoxicity in old age.

Acetaminophen hepatotoxicity in mice: Effect of age, frailty and exposure type.

Acetaminophen is a commonly used analgesic that can cause severe hepatotoxicity in overdose. Despite old age and frailty being associated with extensive and long-term utilization of acetaminophen and a high prevalence of adverse drug reactions, there is limited information on the risks of toxicity from acetaminophen in old age and frailty. This study aimed to assess changes in the risk and mechanisms of hepatotoxicity from acute, chronic and sub-acute acetaminophen exposure with old age and frailty in mice. Young and old male C57BL/6 mice were exposed to either acute (300 mg/kg via oral gavage), chronic (100 mg/kg/day in diet for six weeks) or sub-acute (250 mg/kg, t.i.d., for three days) acetaminophen, or saline control. Pre-dosing mice were scored for the mouse clinical frailty index, and after dosing serum and liver tissue were collected for assessment of toxicity and mechanisms. There were no differences with old age or frailty in the degree of hepatotoxicity induced by acute, chronic or subacute acetaminophen exposure as assessed by serum liver enzymes and histology. Age-related changes in the acetaminophen toxicity pathways included increased liver GSH concentrations, increased NQO1 activity and an increased pro- and anti-inflammatory response to acetaminophen in old age. Frailty-related changes included a negative correlation between frailty index and serum protein, albumin and ALP concentrations for some mouse groups. In conclusion, although there were changes in some pathways that would be expected to influence susceptibility to acetaminophen toxicity, there was no overall increase in acetaminophen hepatotoxicity with old age or frailty in mice.

The Influence of Old Age and Poloxamer-407 on the Hepatic Disposition of Diazepam in the Isolated Perfused Rat Liver

Background and Purpose: The normal liver sinusoidal endothelium is thin and punctuated with fenestrations 50–200 nm in diameter that filter endobiotics and xenobiotics. Defenestration of the liver sinusoidal endothelium in old age and after pre-treatment with poloxamer-407 (P407) has been shown to prevent the transfer of small chylomicrons across the liver sinusoidal endothelium. The aim of this study was to investigate the impact of liver sinusoidal endothelium fenestrations on the hepatic uptake of the highly protein-bound drug diazepam. We hypothesized that defenestration will reduce the hepatic extraction of drugs which are highly bound to albumin. Methodology: The isolated perfused rat liver (IPRL) model and multiple indicator dilution technique were used to investigate the effect of fenestrations in the liver sinusoidal endothelium on the hepatic disposition of diazepam in old and young rats, and in young rats treated with P407 or vehicle. A bolus dose of 14C-diazpeam and non-extracted tracers (3H-sucrose and Evans blue) was injected into the portal vein. The single-pass recovery of diazepam and markers and the apparent volume of distribution were determined. Results: Scanning electron microscopy confirmed reduced porosity of the liver sinusoidal endothelial cells in P407-treated rats and old rats compared to young and control rats. The fractional recovery of diazepam was significantly increased in P407-treated rats compared to controls (0.20 ± 0.16, n = 12, P407; 0.08 ± 0.05, n = 8, controls; p = 0.0029), and in old rats compared to young rats (0.15 ± 0.03, n = 11, old; 0.10 ± 0.02, n = 11, young; p = 0.0004) following a single pass. Conclusion: Defenestration due to age-related pseudocapillarization and treatment with P407 resulted in reduced hepatic extraction of diazepam after a single pass through the IPRL. These results highlight the importance of the liver sinusoidal endothelium in the ultrafiltration of highly protein-bound drugs, and may also provide an additional mechanism for reduced hepatic clearance of diazepam in conditions associated with defenestration.

Lumiracoxib-induced cholestatic liver injury.

Lumiracoxib is a novel cyclo-oxygenase 2 inhibitor with gastrointestinal safety benefits over conventional non-steroidal anti-inflammatories. The Australian Therapeutic Goods Administration (TGA) approved lumiracoxib at 200-mg and 400-mg doses; however, clinical efficacy is not dose dependent with therapeutic equivalency shown between 50-mg, 200-mg and 400-mg doses. Hinz et al. also suggested that hepatotoxicity can be avoided at a lower dose of 50 mg with preserved clinical efficacy. This case report looks at a cholestatic pattern of liver injury with lumiracoxib and reviews available histological information to date from the Australian TGA. An 83-year-old woman was referred for assessment of progressive, cholestatic liver enzyme abnormalities. She was of good health, with no significant smoking or drinking history. Her past history included hysterectomy, cholecystectomy, appendicectomy, segmental colectomy for an extensive polyp, hypertension, osteoporosis, gastro-oesophageal reflux, chronic bronchitis, trigeminal neuralgia and osteoarthritis of left knee. There was no past or familial liver disease. The patient was initiated on lumiracoxib from November 2006 to September 2007 by her local practitioner for osteoarthritis. This was in addition to a regular medication list taken over >2 years of risedronate, irbesartan, omeprazole, fish oil, paracetamol, glucosamine, simvastatin and psyllium husks, with no recent antibiotic use. Her liver enzymes were then noted to be progressively cholestatic over an 8-month period between mid-2007 and early 2008. Liver enzymes were normal in May 2006, with isolated elevation of gamma-glutamyl transpeptidase (gGT) to 86 u/L (normal range 0–45 u/L) first noticed in June 2007. Worsening of liver function tests followed with an asymptomatic clinical picture and preserved liver function (alkaline phosphatase 1174 u/L gGT 2114 u/L alanine transaminase 208 u/L and aspartate transaminase 186 U/L). Physical examination was normal. A full liver screening panel was ordered to exclude autoimmune, infectious and metabolic causes. These tests were normal, with the exception of anti-nuclear antibody 1:80 and cytoplasmic anti-neutrophil cytoplasmic antibody 1:20. Simvastatin was ceased without an improvement to her hepatic test results. Computer tomography scanning of the abdomen found prominence of the common bile duct, and the patient referred for endoscopic retrograde cholangiopancreatogram (ERCP). ERCP was normal, with a temporary 10-Fr plastic stent placed into a 9-mm common bile duct. This failed to improve her liver function tests (LFT), and the stent was removed 8 weeks after. A percutaneous liver biopsy was done in August 2008. The biopsy showed preserved hepatic lobular architecture without necrosis, mild expansion of all portal tracts and ductular proliferation with occasional ductopaenia. These portal tracts had heavy inflammatory cell infiltrates, predominantly of neutrophils and lymphocytes with occasional eosinophils and plasma cells (Fig. 1). There was no lymphocytic piecemeal necrosis. Granulomas were not present. The biopsy was consistent with a cholestatic drug-induced liver injury correlating with a predominantly cholestatic liver function test. The chronology of drug use and the complete normalisation of the patient’s LFT following drug discontinuation suggest the presentation to be a probable hepatotoxic reaction to lumiracoxib. The Australian TGA to date had documented 53 cases of adverse drug reactions for lumiracoxib, of which 44 were classified possible adverse drug reactions and nine probable. Histology was available only in four; the first poorly documented; the second a chronic active hepatitis with piecemeal necrosis, extensive cholestasis, cirrhosis and abundant polymorphonuclear cells; the third a severe acute hepatitis with extensive multi-acinar dropout and lastly a chronic active hepatitis with mononuclear cells in abundance. Only one was deemed a probable adverse drug reaction with a predominant acinar injury pattern observed. Between lumiracoxib’s approval in 2006 and market withdrawal in August 2007, five patients had developed life-threatening hepatotoxicity, with two dead and three receiving a liver transplant. Although significant hepatotoxicity has been noted for lumiracoxib, there is a paucity of histopathological Figure 1 The portal tract is expanded and inflamed, with prominent ductular proliferation at its margin. A damaged bile duct is present centrally. The hepatocytes show little abnormality. bs_bs_banner

The effect of ageing on isoniazid pharmacokinetics and hepatotoxicity in Fischer 344 rats.

Isoniazid is the first‐line treatment for tuberculosis; however, its use is limited by hepatotoxicity. Age‐related differences in isoniazid pharmacokinetics and hepatotoxicity are uncertain. We aimed to investigate these in young (3 ± 0 months, n = 26) and old (23.0 ± 0.2 months, n = 27) male Fischer 344 rats following a low‐ or high‐dose toxic regimen of isoniazid or vehicle (4 doses/day over 2 days; low: 100, 75, 75, 75 mg/kg; high: 150, 105, 105, 105 mg/kg i.p. every 3 h). Fifteen hours after the last dose, animals were euthanized and sera and livers were prepared for analysis. Isoniazid treatment increased serum hepatotoxicity markers (alanine and aspartate transaminase) in young animals but not in old animals, and only reached significance with the high dose in young animals. Isoniazid treatment caused a trend towards an increase in necrosis in young animals with both doses. In contrast, microvesicular steatosis was increased in old isoniazid‐treated animals, reaching significance only with the low dose (steatosis prevalence in old: vehicle 1/9, isoniazid 4/5; P < 0.05). Among isoniazid‐treated animals, concentrations of toxic intermediates acetylhydrazine and hydrazine were higher in old than young animals (P < 0.05). With both doses, hepatic cytochrome P450 2E1 activity was higher in young animals compared with old (P < 0.05). There were no other age effects seen on any of the other measured enzymes involved in isoniazid metabolism (N‐acetyl transferase, amidase, glutathione‐S‐transferase). These results show age‐related changes in isoniazid pharmacokinetics may contribute towards differential patterns of toxicity and confirm that standard hepatotoxicity markers do not detect isoniazid‐induced microvesicular steatosis.

Sustained virological response following chronic hepatitis C treatment is associated with improvement in insulin resistance

Insulin resistance (IR) is a key factor in the development of hepatic steatosis and fibrosis in chronic hepatitis C virus infection. Little is known about the impact of viral clearance on IR.

Hepatitis C virus and oxidative stress: a dangerous liaison

Chronic hepatitis C infection persists in more than 170 million people worldwide and is one of the major causes of hepatic failure and liver transplantation. Recent studies have demonstrated that hepatitis C virus (HCV)-derived proteins have the capacity to generate substantial oxidative stress within the hepatocyte. Subsequently, oxidative stress has been identified as a significant mechanistic pathway culminating in the development of hepatic cirrhosis, liver failure and liver cancer. In vitro HCV-induced oxidative stress has been demonstrated to activate cellular signaling pathways involved in both inflammatory and fibrogenic responses. In addition, oxidative stress has also been shown to play a role in HCV replication. Preliminary data from small clinical trials have implicated oxidative stress as a risk factor for liver fibrosis and increased HCV viral load. Although conclusive evidence from large-scale clinical trials is lacking, it is possible that antioxidant co-therapies may improve hepatic infla...