Acute Liver Failure of Indeterminate Etiology: A Comprehensive Systematic Approach by An Expert Committee to Establish Causality.

OBJECTIVES: In the United States, the Acute Liver Failure Study Group (ALFSG) registry lists approximately 11% of cases as of indeterminate etiology (IND-ALF) as determined by the respective local site principal investigator (PI). Traditionally, IND-ALF has prompted concern that other viruses or toxins might be implicated. We hypothesized that many IND- ALF cases would have an identifiable etiology upon further investigation. Improving the identification process should reduce the number of truly indeterminate cases. METHODS: Specific definitions for each etiology ("etiology-specific algorithms") were developed by a Causality Adjudication Committee that included six reviewers (each with 20 or more years of experience). Of 2718 patients with ALF, 303 initially deemed IND-ALF by site PIs underwent committee review guided by the algorithms. Acetaminophen (APAP) protein adducts were measured in sera when available, additional HEV testing was performed, and viral sequences sought by microarray analysis and metagenomic next-generation sequencing (mNGS). Study sites were asked to provide liver biopsy and/or explant reports and to update serological findings not reported previously. RESULTS: Nearly half (142, 46.9%) of the 303 IND-ALF cases could be reassigned to a single, defined etiology and rated as highly likely or probable; 11 additional cases, upon review, did not meet ALF criteria. Amongst reassigned etiologies, 45 were previously unrecognized APAP, 34 autoimmune hepatitis (AIH), 24 drug-induced liver injury (DILI), 13 various viral causes, 12 ischemia, and 14 miscellaneous other etiologies. The remaining 150, deemed true IND-ALF, represented just 5.5%. CONCLUSIONS: The indeterminate etiology in ALF includes patients with a diagnosis that is discernible after closer examination. Revision of etiologic diagnoses of indeterminate cases using added testing and expert opinion is useful in understanding all aspects of ALF.

The Natural History of Severe Acute Liver Injury.

OBJECTIVES: Acute liver failure (ALF) is classically defined by coagulopathy and hepatic encephalopathy (HE); however, acute liver injury (ALI), i.e., severe acute hepatocyte necrosis without HE, has not been carefully defined nor studied. Our aim is to describe the clinical course of specifically defined ALI, including the risk and clinical predictors of poor outcomes, namely progression to ALF, the need for liver transplantation (LT) and death. METHODS: 386 subjects prospectively enrolled in the Acute Liver Failure Study Group registry between 1 September 2008 through 25 October 2013, met criteria for ALI: International Normalized Ratio (INR)≥2.0 and alanine aminotransferase (ALT)≥10 × elevated (irrespective of bilirubin level) for acetaminophen (N-acetyl-p-aminophenol, APAP) ALI, or INR≥2.0, ALT≥10x elevated, and bilirubin≥3.0 mg/dl for non-APAP ALI, both groups without any discernible HE. Subjects who progressed to poor outcomes (ALF, death, LT) were compared, by univariate analysis, with those who recovered. A model to predict poor outcome was developed using the random forest (RF) procedure. RESULTS: Progression to a poor outcome occurred in 90/386 (23%), primarily in non-APAP (71/179, 40%) vs. only 14/194 (7.2%) in APAP patients comprising 52% of all cases (13 cases did not have an etiology assigned; 5 of whom had a poor outcome). Of 82 variables entered into the RF procedure: etiology, bilirubin, INR, APAP level and duration of jaundice were the most predictive of progression to ALF, LT, or death. CONCLUSIONS: A majority of ALI cases are due to APAP, 93% of whom will improve rapidly and fully recover, while non-APAP patients have a far greater risk of poor outcome and should be targeted for early referral to a liver transplant center.

Review article: medical management of the liver transplant recipient - a primer for non-transplant doctors.

BACKGROUND: Survival 10 years after orthotopic liver transplantation now approaches 65%. Consequently, community doctors must manage the metabolic and neoplastic complications of orthotopic liver transplantation in an ageing population. AIMS: To review common sources of morbidity and mortality in long-term orthotopic liver transplantation recipients, and to make evidence-based recommendations regarding their management. METHODS: Pertinent studies and reviews were identified by literature search through PubMed. Where evidence-based recommendations could not be gleaned from the literature, expert opinion was obtained from syllabi of national meetings. RESULTS: The two most common causes of morbidity and mortality in orthotopic liver transplantation recipients are atherosclerotic vascular disease and de novo malignancy. The pathogenesis of many complications begins before orthotopic liver transplantation, and many are potentially modifiable. Most complications, however, can be directly ascribed to immunosuppressive agents. Despite improvements in our understanding of the pathogenesis and epidemiology of the metabolic and neoplastic complications of orthotopic liver transplantation, remarkably few randomized-controlled studies exist to define their optimal management. CONCLUSIONS: Orthotopic liver transplantation recipients experience and succumb to the same afflictions of old age as non-transplant patients, but with greater frequency and at an earlier age. Most recommendations regarding surveillance for, and treatment of, medical complications of orthotopic liver transplantation remain based upon expert opinion rather than evidence-based medicine.

Multimodality therapy and liver transplantation in patients with cirrhosis and hepatocellular carcinoma: 6 years, single-center experience.

The treatment of patients with cirrhosis and hepatocellular carcinoma (HCC) has improved dramatically over the past 10 years. We conducted a 6-year prospective study, using multimodality ablation therapy (MMT) combined with liver transplantation (LTx) for patients with cirrhosis and unresectable HCC. Subjects were classified as: group 1 (n = 35), intention to treat with MMT + LTx; group 2 (n = 16), contemporaneous LTx with "incidental" HCC on explants; group 3 (n = 94), MMT alone; and group 4 (n = 19), palliative care alone. MMT included trans-arterial chemo-embolization (54.4%), trans-arterial chemo-infusion (28.6%), and radio frequency ablation (17%). Group 1, with a mean wait time of 11.6 months pre-MELD era and 5.4 months post-MELD era, had a mean of 2.4 +/- 1.2 MMTs and achieved 1- 3-, and 5-year patient survivals of 100, 100, and 76%, respectively, which was not different from group 2 (incidental HCC), namely 93, 93, and 93%, respectively; or to a contemporaneous non-HCC LTx group: namely 84.3, 78.7, and 73.9%, respectively. Despite careful pretransplant HCC staging, 22.8% (8 of 35) group 1 subjects were understaged. Those subjects in group 1 with true T1-2 stage HCC achieved 100% cancer-free survival at 5 years. Only three cases of HCC recurrence occurred in our series, all of whom were understaged. Our data suggest that pretransplant MMT followed by timely LTx provides excellent disease-free survival at 5 years for patients with true T1-2 stage HCC and cirrhosis. Pretransplant HCC understaging contributes to posttransplant HCC recurrence after LTx.

Evaluation of Arteriovenous Shunting in Patients With End-Stage Liver Disease: Potential Role of Early Right Heart Catheterization.

BACKGROUND: In patients with end-stage liver disease (ESLD), the presence of hypoxemia suggests the presence of intrapulmonary oxygen shunting (IPS) and/or transatrial shunting. Early identification of each is imperative to avoid potentially fatal peritransplantation complications and appropriately prioritize patients for liver transplantation (LT). The aim of this work was to compare the sensitivity of transthoracic echocardiography (TTE) and right heart catheterization (RHC) with intracardiac echocardiography (ICE) for identifying the etiologies of resting hypoxemia in patients with ESLD being evaluated for LT. METHODS: Records of 28 patients with ESLD and resting hypoxemia who underwent TTE with bubble study and RHC/ICE were reviewed. Patients with a patent foramen ovale (PFO) were compared with non-PFO patients to determine diagnostic accuracy of TTE with bubble study versus RHC/ICE. RESULTS: TTE with bubble study diagnosed PFO, IPS, and pulmonary hypertension (PH), respectively, with sensitivities of 46%, 41%, and 25% and specificities of 46%, 45%, and 80% compared with RHC/ICE. Although IPS detected by RHC/ICE was more common in patients without a PFO (92%), 5 patients with a PFO (33%) also had IPS (P = .002). Isolated PH was detected exclusively in patients with a PFO (5/15; 33%). CONCLUSIONS: TTE with bubble study is neither sensitive nor specific to exclude a PFO in patients with ESLD. RHC/ICE is a safe and accurate diagnostic/interventional modality in this group of patients and is useful to diagnose other comorbidities, such as IPS and PH, that may coexist and contribute to resting hypoxemia.

A prospective, randomized-controlled pilot study of ursodeoxycholic acid combined with mycophenolate mofetil in the treatment of primary sclerosing cholangitis.

BACKGROUND: Ursodeoxycholic acid has been ineffective in the treatment of primary sclerosing cholangitis. Because the pathogenesis of primary sclerosing cholangitis is related to immune destruction of bile duct epithelium, several immune suppressive agents have been evaluated. Mycophenolate mofetil is a potent immunosuppressant that is now widely used in organ transplantation. AIM: In this pilot study to determine if mycophenolate mofetil when combined with ursodeoxycholic acid could prevent evidence of clinical progression and improve the biochemical, histological and/or cholangiographic features of primary sclerosing cholangitis compared with patients treated with ursodeoxycholic acid alone. METHODS: Twenty-five patients with well-defined primary sclerosing cholangitis were randomized to ursodeoxycholic acid (13-15 mg/kg/day) with or without mycophenolate mofetil (1000 mg b.d.). Cholangiography and liver biopsy were performed at study entry and after 2 years of treatment. Symptoms, clinical features of liver disease and biochemical tests were monitored at 3-month intervals. RESULTS: The mean age 44 years, 58% male, 84% Caucasian and 64% had ulcerative colitis. After 2 years, there were no differences in laboratory values, histological stage or cholangiograms between patients treated with ursodeoxycholic acid alone and those treated with mycophenolate mofetil + ursodeoxycholic acid. CONCLUSIONS: Mycophenolate mofetil combined with ursodeoxycholic acid does not appear to provide additional benefit compared with standard doses of ursodeoxycholic acid alone in the treatment of primary sclerosing cholangitis.

Regulation of sterol 27-hydroxylase and an alternative pathway of bile acid biosynthesis in primary cultures of rat hepatocytes.

In man, hepatic mitochondrial sterol 27-hydroxylase and microsomal cholesterol 7alpha-hydroxylase initiate distinct pathways of bile acid biosynthesis from cholesterol, the "acidic" and "neutral" pathways, respectively. A similar acidic pathway in the rat has been hypothesized, but its quantitative importance and ability to be regulated at the level of sterol 27-hydroxylase are uncertain. In this study, we explored the molecular regulation of sterol 27-hydroxylase and the acidic pathway of bile acid biosynthesis in primary cultures of adult rat hepatocytes. mRNA and protein turnover rates were approximately 10-fold slower for sterol 27-hydroxylase than for cholesterol 7alpha-hydroxylase. Sterol 27-hydroxylase mRNA was not spontaneously expressed in culture. The sole requirement for preserving sterol 27-hydroxylase mRNA at the level of freshly isolated hepatocytes (0 h) after 72 h was the addition of dexamethasone (0.1 microM; > 7-fold induction). Sterol 27-hydroxylase mRNA, mass and specific activity were not affected by thyroxine (1.0 microM), dibutyryl-cAMP (5O microM), nor squalestatin 1 (15O nM-1.0 microM), an inhibitor of cholesterol biosynthesis. Taurocholate (50 microM), however, repressed sterol 27-hydroxylase mRNA levels by 55%. Sterol 27-hydroxylase specific activity in isolated mitochondria was increased > 10-fold by the addition of 2-hydroxypropyl-beta-cyclodextrin. Under culture conditions designed to maximally repress cholesterol 7alpha-hydroxylase and bile acid synthesis from the neutral pathway but maintain sterol 27-hydroxylase mRNA and activity near 0 h levels, bile acid synthesis from [14C]cholesterol remained relatively high and consisted of beta-muricholate, the product of chenodeoxycholate in the rat. We conclude that rat liver harbors a quantitatively important alternative pathway of bile acid biosynthesis and that its initiating enzyme, sterol 27-hydroxylase, may be slowly regulated by glucocorticoids and bile acids.

Down-regulation of the rat hepatic sterol 27-hydroxylase gene by bile acids in transfected primary hepatocytes: possible role of hepatic nuclear factor 1alpha.

In vitro and in vivo studies have shown that the sterol 27-hydroxylase (CYP27) gene is transcriptionally repressed by hydrophobic bile acids. The molecular mechanism(s) of repression of CYP27 by bile acids is unknown. To identify the bile acid responsive element (BARE) and transcription factor(s) that mediate the repression of CYP27 by bile acids, constructs of the CYP27 5'-flanking DNA were linked to either the CAT or luciferase reporter gene and transiently transfected into primary rat hepatocytes. Taurocholate (TCA), taurodeoxycholate (TDCA) and taurochenodeoxycholate (TCDCA) significantly reduced CAT activities of the -840/+23, -329/+23, and -195/+23 mCAT constructs. A -76/+23 construct showed no regulation by bile acids. When a DNA fragment (-110/-86) from this region was cloned in front of an SV 40 promoter it showed down-regulation by TDCA. 'Super'-electrophoretic mobility shift assays (EMSA) indicated that both HNF1alpha and C/EBP bind to the -110 to -86 bp DNA fragment. Recombinant rat HNF1alpha and C/EBPalpha competitively bound to this DNA fragment. 'Super'-EMSA showed that TDCA addition to hepatocytes in culture decreased HNF1alpha, but not C/EBP, binding to the -110/-86 bp DNA fragment. A four base pair substitution mutation (-103 to -99) in this sequence eliminated TCA and TDCA regulation of the (-840/+23) construct. The substitution mutation also eliminated (>95%) HNF1alpha, but not C/EBP, binding to this DNA fragment. We conclude that bile acids repress CYP27 transcription through a putative BARE located between -110 and -86 bp of the CYP27 promoter. The data suggest that bile acids repress CYP27 transcriptional activity by decreasing HNF1alpha binding to the CYP27 promoter.

Randomised clinical trial: Lactobacillus GG modulates gut microbiome, metabolome and endotoxemia in patients with cirrhosis.

BACKGROUND: Safety of individual probiotic strains approved under Investigational New Drug (IND) policies in cirrhosis with minimal hepatic encephalopathy (MHE) is not clear. AIM: The primary aim of this phase I study was to evaluate the safety, tolerability of probiotic Lactobacillus GG (LGG) compared to placebo, while secondary ones were to explore its mechanism of action using cognitive, microbiome, metabolome and endotoxin analysis in MHE patients. METHODS: Cirrhotic patients with MHE patients were randomised 1:1 into LGG or placebo BID after being prescribed a standard diet and multi-vitamin regimen and were followed up for 8 weeks. Serum, urine and stool samples were collected at baseline and study end. Safety was assessed at Weeks 4 and 8. Endotoxin and systemic inflammation, microbiome using multi-tagged pyrosequencing, serum/urine metabolome were analysed between groups using correlation networks. RESULTS: Thirty MHE patients (14 LGG and 16 placebo) completed the study without any differences in serious adverse events. However, self-limited diarrhoea was more frequent in LGG patients. A standard diet was maintained and LGG batches were comparable throughout. Only in the LGG-randomised group, endotoxemia and TNF-α decreased, microbiome changed (reduced Enterobacteriaceae and increased Clostridiales Incertae Sedis XIV and Lachnospiraceae relative abundance) with changes in metabolite/microbiome correlations pertaining to amino acid, vitamin and secondary BA metabolism. No change in cognition was found. CONCLUSIONS: In this phase I study, Lactobacillus GG is safe and well-tolerated in cirrhosis and is associated with a reduction in endotoxemia and dysbiosis.

Intact thrombin generation and decreased fibrinolytic capacity in patients with acute liver injury or acute liver failure.

BACKGROUND: It has been well established that hemostatic potential in patients with chronic liver disease is in a rebalanced status due to a concomitant decrease in pro- and antihemostatic drivers. The hemostatic changes in patients with acute liver injury/failure (ALI/ALF) are similar but not identical to the changes in patients with chronic liver disease and have not been studied in great detail. OBJECTIVE: To assess thrombin generation and fibrinolytic potential in patients with ALI/ALF. METHODS: We performed thrombin generation tests and clot lysis assays in platelet-poor plasma from 50 patients with ALI/ALF. Results were compared with values obtained in plasma from 40 healthy volunteers. RESULTS AND CONCLUSION: The thrombin generation capacity of plasma from patients with ALI/ALF sampled on the day of admission to hospital was indistinguishable from that of healthy controls, provided thrombomodulin was added to the test mixture. Fibrinolytic capacity was profoundly impaired in patients with ALI/ALF on admission (no lysis in 73.5% of patients, compared with 2.5% of the healthy controls), which was associated with decreased levels of the plasminogen and increased levels of plasminogen activator inhibitor type 1. The intact thrombin generating capacity and the hypofibrinolytic status persisted during the first week of admission. Patients with ALI/ALF have a normal thrombin generating capacity and a decreased capacity to remove fibrin clots. These results contrast with routine laboratory tests such as the PT/INR, which are by definition prolonged in patients with ALI/ALF and suggest a bleeding tendency.

Modified-orientation log to assess hepatic encephalopathy.

BACKGROUND: The subjectivity of the West-Haven criteria (WHC) hinders hepatic encephalopathy (HE) evaluation. The new HE classification has emphasised assessment of orientation. The modified-orientation log (MO-log, eight questions, scores 0-24; 24 normal) is adapted from a validated brain injury measure. AIM: To validate MO-log for HE assessment in cirrhosis. METHODS: Cirrhotics admitted with/without HE were administered MO-log. We collected cirrhosis/HE details, admission/daily MO-logs and WHC (performed by different examiners), time to reach normal mentation (MO-log ≥23) and MO-log/WHC change (Δ) over day 1. Outcomes were in-hospital mortality, duration to normal mentation and length-of-stay (LOS). Regressions were performed for each outcome. MO-log inter-rater reliability was measured. RESULTS: Ninety-six HE (55 ± 8 years, MELD 21) and 20 non-HE (54 ± 5 years, MELD 19) in-patients were included. In HE patients, median admission WHC was 3 (range 1-4). Mean MO-log was 12 ± 8 (range 0-22). Their LOS was 6 ± 5 days and 13% died. Time to reach normal mentation was 2.4 ± 1.7 days. Concurrent validity: there was a significant negative correlation between admission MO-log and WHC (r = -0.79, P < 0.0001). Discriminant validity: admission MO-logs were significantly lower in those who died (7 vs. 12, P = 0.03) and higher in those admitted without HE (23.6 vs. 12, P < 0.0001). MO-log improved in 69% on day 1 (ΔMO-log 4 ± 8) which was associated with lower duration to normal mentation (2 vs. 3.5 days, P = 0.03) and mortality (3% vs.43%, P < 0.0001), not ΔWHC. Regression models for all outcomes included admission/ΔMO-log but not WHC as a predictor. Inter-rater reliability: ICC for MO-log inter-rater observations was 0.991. CONCLUSIONS: Modified-orientation log is a valid tool for assessing severity and is better than West-Haven criteria in predicting outcomes in hospitalised hepatic encephalopathy patients.

PROMIS computerised adaptive tests are dynamic instruments to measure health-related quality of life in patients with cirrhosis.

BACKGROUND: Cirrhotic patients have an impaired health-related quality of life (HRQOL), which is usually analysed using static paper-pencil questionnaires. The Patient Reported Outcomes Measurement Information System (PROMIS) computerised adaptive testing (CAT) are flexible, freely available, noncopyrighted, HRQOL instruments with US-based norms across 11 domains. CAT presents five to seven questions/domain depending on the patient's response, from large validated question banks. This provides brevity and precision equivalent to the entire question bank. AIM: To evaluate PROMIS CAT tools against 'legacy instruments' for cirrhotics and their informal caregivers. METHODS: A total of 200 subjects: 100 cirrhotics (70 men, 53% decompensated) and 100 caregivers were administered the PROMIS and legacy instruments [Sickness Impact Profile (SIP), Beck depression/anxiety inventories, Pittsburgh Sleep-Quality Index (PSQI) and Epworth Sleepiness scale (ESS)] concurrently. Both legacy and PROMIS results for patients were compared with caregivers and US norms. These were also compared between compensated and decompensated patients. Preference for SIP or PROMIS was inquired of a selected group (n = 70, 50% patients). Test - retest reliability was assessed in another group of 20 patients. RESULTS: Patients had significant impairment on all PROMIS domains apart from anger and anxiety compared with caregivers and US norms (P < 0.02 to <0.0001). Decompensated patients had significantly worse sleep, pain, social and physical function scores compared with compensated ones, similar to legacy instruments. There was a statistically significant correlation between PROMIS and their corresponding legacy instruments. The majority (71%) preferred PROMIS over SIP. PROMIS tools had significant test - retest reliability (ICC range 0.759-0.985) when administered 12 ± 6 days apart. CONCLUSION: PROMIS computerised adaptive testing tools had significant concurrent and discriminant validity, test - retest reliability and subject preference for assessing HRQOL in cirrhotic patients.

Percutaneous liver biopsy in adult haemophiliacs with hepatitis C virus: safety of outpatient procedure and impact of human immunodeficiency virus coinfection on the spectrum of liver disease.

Both HCV and HIV are common in haemophiliacs previously treated with non-viral-inactivated clotting factor concentrates. Because of increased bleeding risks, little data are available on the safety of percutaneous outpatient liver biopsy (LBx) and impact of HIV coinfection in this population. This study aims at reporting our experience with percutaneous LBx in a cohort of haemophiliacs infected with HCV and describe the spectrum of disease and impact of HIV coinfection. A retrospective review of consecutive patients with haemophilia and HCV who underwent percutaneous LBx was performed. All patients were positive for HCV RNA by commercial assay and received factor concentrate prior to biopsy. A total of 29 male patients (mean age 36, 24 haemophilia A, five haemophilia B, and 44% coinfected with HIV) underwent successful outpatient percutaneous LBx without bleeding complication. Histologic activity index was 6.44 with advanced fibrosis (bridging fibrosis/cirrhosis) in 31%. When patients were stratified by HIV positive (n = 13) vs. HIV negative (n = 16), coinfected patients had higher fibrosis scores and higher proportion advanced fibrosis (54% vs. 12%; P = 0.0167) with no differences in age, demographic or other laboratory parameters. Multivariate logistic regression found that HIV positivity was independently associated with advanced fibrosis (OR = 3.7; 95% CI: 1.17-11.8; P = 0.026). Outpatient percutaneous LBx can be safely performed in patients with haemophilia. Despite similar age, HIV coinfection was an independent predictor of advanced fibrosis. These data support the hypothesis that HIV accelerates fibrosis progression in those coinfected with HCV and highlights the importance of liver histology in this population.

Regulation of bile acid biosynthesis.

This article provides a review of the pathways through which cholesterol is degraded to bile acids. Regulation of key enzymes in the bile acid biosynthestic pathways is discussed. The important role of these pathways in the maintenance of cholesterol homeostasis and the possible therapeutic implications for the treatment of hypercholesterolemia are emphasized.

Hep G2 cells: a model for studies on regulation of human cholesterol 7alpha-hydroxylase at the molecular level.

The present study examines the feedback control governing human cholesterol 7alpha-hydroxylase mRNA expression in the human hepatoblastoma cell line, Hep G2. Glycochenodeoxycholate (GCDC) and glycodeoxycholate, hydrophobic bile salts, decreased cholesterol 7alpha-hydroxylase mRNA levels and bile acid synthesis in a concentration-dependent (76 +/- 8%, P<0.001, and 48 +/- 3%, P<0.01, respectively) and time-dependent manner. Cholesterol 7alpha-hydroxylase mRNA levels were repressed with a half-maximal inhibitory concentration of <12.5 microM by GCDC and a half-life of 30 min by 100 microM of the bile acid. The addition of actinomycin D (10 microgram/ml) alone or in combination with GCDC (100 microM) led to similar concentration-and time-dependent suppression of cholesterol 7alpha-hydroxylase mRNA. Glycocholate (100 microM), not internalized based on lack of uptake of a fluorescent cholate analogue, had no effect on cholesterol 7alpha-hydroxylase mRNA or total bile acid synthesis. In cultures transfected with a rat cholesterol 7alpha-hydroxylase promoter construct, reporter gene activity was decreased (31%, P<0.01) by GCDC (100 microM). Hep G2 cells maintain the intracellular machinery to express and rapidly regulate human cholesterol 7alpha-hydroxylase by hydrophobic bile acids. These data suggest that Hep G2 cells will support functional studies of the human cholesterol 7alpha-hydroxylase gene.

Repression of cholesterol 7 alpha-hydroxylase transcription by bile acids is mediated through protein kinase C in primary cultures of rat hepatocytes.

Inhibitors of protein kinases were screened for the ability to prevent the repression of cholesterol 7 alpha-hydroxylase mRNA by taurocholate in primary cultures of adult rat hepatocytes. The addition of taurocholate (25 microM) for 6 h decreased cholesterol 7 alpha-hydroxylase mRNA by 64 +/- 3%. However, after a preincubation with the protein kinase C inhibitors calphostin C or chelerythrine, taurocholate had no significant effect on cholesterol 7 alpha-hydroxylase mRNA, or decreased levels by only 23 +/- 8%, respectively. Protein kinase C activation with phorbol 12-myristate, 13-acetate (100 nM) decreased cholesterol 7 alpha-hydroxylase mRNA and transcriptional activity by 71 +/- 5% and 60 +/- 16%, respectively, within 3 h. mRNA levels recovered to control levels by 18-24 h, however, consistent with downregulation of protein kinase C. Furthermore, after depletion of protein kinase C with a 24-h preincubation with phorbol diesters, taurocholate (25 microM) repressed cholesterol 7 alpha-hydroxylase mRNA by only 14 +/- 17%. The addition of taurocholate (50 microM) to the culture medium transiently increased membrane-associated protein kinase C activity by approximately twofold, while causing a concomitant decrease in cytosolic activity. Other bile acids increased membrane-associated protein kinase C activity in approximate proportion to their relative hydrophobicity. Finally, immunoblotting experiments revealed translocation of the alpha isoform of protein kinase C to hepatocyte membranes in response to taurocholate. These data suggest that hydrophobic bile acids repress cholesterol 7 alpha-hydroxylase transcription through a protein kinase C-dependent mechanism.

Bile salt-induced apoptosis of hepatocytes involves activation of protein kinase C.

Toxic bile salts induce hepatocyte apoptosis, a model relevant to liver injury during cholestasis. However, the signaling mechanisms culminating in bile salt-induced apoptosis remain unclear. Because protein kinase C (PKC) is activated by bile salts in hepatocytes and causes apoptosis in other cells, we tested the hypothesis that bile salt-induced hepatocyte apoptosis is mediated by PKC. The PKC inhibitors chelerythrine and Gö-6976 reduced, whereas a PKC agonist, phorbol 12-myristate 13-acetate (PMA), increased glycochenodeoxycholate (GCDC)-induced hepatocyte apoptosis. Membrane-associated total PKC activity was increased in GCDC-treated hepatocytes. Quantitative immunoblot analysis demonstrated membrane translocation of PKC-alpha, PKC-delta, and PKC-epsilon to hepatocyte membranes after administration of GCDC. Direct activation of PKC-alpha and PKC-delta by GCDC was also demonstrated using recombinant, baculovirus-expressed PKC isoforms in a medium of defined lipid composition. Chelerythrine and Gö-6976 reduced, whereas PMA enhanced, cathepsin B activity during treatment of hepatocytes with GCDC, demonstrating coupling of PKC activity to the protease effector mechanisms of apoptosis. In conclusion, our data suggest for the first time that PKC-dependent signaling pathways play a critical role in bile salt-induced hepatocyte apoptosis.

Down-regulation of cholesterol 7alpha-hydroxylase (CYP7A1) gene expression by bile acids in primary rat hepatocytes is mediated by the c-Jun N-terminal kinase pathway.

Cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in the neutral pathway of bile acid biosynthesis, is feedback-inhibited at the transcriptional level by hydrophobic bile acids. Recent studies show that bile acids are physiological ligands for farnesoid X receptor (FXR). Activated FXR indirectly represses CYP7A1 transcription through induction of small heterodimer protein (SHP-1). In this study, we provide evidence that bile acids rapidly down-regulate CYP7A1 transcription via activation of the JNK/c-Jun pathway. Furthermore, we demonstrate that SHP-1 is also a direct target of activated c-Jun. In primary rat hepatocyte cultures, taurocholate (TCA) strongly activated JNK in a time- and concentration-dependent manner. Tumor necrosis factor-alpha, a potent activator of JNK, also rapidly activated JNK and down-regulated CYP7A1 mRNA levels. Overexpression of dominant-negative JNK1 or a transactivating domain mutant of c-Jun significantly blocked the ability of TCA to down-regulate CYP7A1 mRNA. In contrast, overexpression of wild-type c-Jun (c-Jun(wt)) enhanced the repression of CYP7A1 by TCA. Moreover, overexpression of c-Jun(wt) resulted in increased SHP-1 promoter activity. Mutation of a putative AP-1 (c-Jun) element suppressed c-Jun-mediated activation of the SHP-1 promoter construct. These results indicate that the bile acid-activated JNK pathway plays a pivotal role in regulating CYP7A1 levels in primary rat hepatocytes.

Regulation of rat hepatic 3 alpha-hydroxysteroid dehydrogenase in vivo and in primary cultures of rat hepatocytes.

In the bile acid biosynthetic pathways of humans and the rat, hepatic 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSDH) catalyzes the stereospecific reduction of the 3-oxo group of bile acid precursors. In addition, 3 alpha-HSDH may serve to shuttle bile acids from sinusoidal to apical (cannalicular) membranes of the rat hepatocyte. The objective of the present study was to define the molecular regulation of rat hepatic 3 alpha-HSDH in response to the key effectors of cholesterol 7 alpha-hydroxylase, the rate-determining enzyme in bile acid biosynthesis. Steady-state 3 alpha-HSDH mRNA levels in primary cultures of rat hepatocytes fell to 16 +/- 1% of whole liver levels after 72 h in culture, indicating that the gene is not spontaneously expressed in isolated hepatocytes. However, the addition of thyroxine (1.0 microM) or dexamethasone (1.0 microM) to the culture medium resulted in steady-state mRNA levels of 34 +/- 4% and 102 +/- 20% of whole liver levels, respectively. Moreover, the combination of thyroxine and dexamethasone (each 1.0 microM) induced mRNA to levels 2-fold higher than whole liver. 3 alpha-HSDH specific activity in cultured hepatocyte cytosol increased from 3.0 +/- 0.7 to 10.4 +/- 1.3 nmol/min per mg protein in no-addition and thyroxine plus dexamethasone-treated cultures, respectively; protein mass underwent similar changes. Whole liver 3 alpha-HSDH mRNA levels decreased in thyroidectomized, adrenalectomized, and hypophysectomized rats, to 60 +/- 6%, 51 +/- 4%, and 29 +/- 5% of sham-operated rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocellular protein kinase C activation by bile acids: implications for regulation of cholesterol 7 alpha-hydroxylase.

We have recently shown that taurocholate (TCA) represses the transcriptional activity of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme of the bile acid biosynthetic pathway, through a protein kinase C (PKC)-dependent mechanism in primary cultures of rat hepatocytes. The present studies sought to determine the mechanisms by which bile acids activate hepatic PKC activity and the consequences of this activation on isoform distribution and cholesterol 7 alpha-hydroxylase mRNA levels. TCA (12.5-100 microM for 15 min) increased membrane-associated "classic" isoenzyme cPKC-alpha and "novel" isoenzymes nPKC-delta, and nPKC by two- to sixfold. Membrane-associated PKC progressively increased, and cytosolic PKC decreased, for 1 h after the addition of TCA (50 microM); after 24 h whole cell cPKC-alpha, nPKC-delta, and nPKC were downregulated by 35-55% compared with untreated controls. In a reconstituted assay system, TCA or taurodeoxycholate (10-100 microM) increased calcium-dependent and -independent PKC activity by three- and fourfold, respectively. Taurine-conjugated bile acids stimulated PKC activity in proportion to their hydrophobicity index (r = 0.99). Finally, cholesterol 7 alpha-hydroxylase mRNA was repressed > 75% by phorbol 12-myristate 13-acetate (100 nM for 3 h), a nonselective activator of PKC isoforms. In contrast, selective cPKC-alpha activation with thymeleatoxin (100 nM for 3 h) had no significant effect on cholesterol 7 alpha-hydroxylase mRNA levels. We conclude that bile acids activate hepatocellular PKC, resulting in sequential redistribution and down-regulation of calcium-dependent and -independent isoforms. The calcium-independent PKC isoforms may mediate the repression of cholesterol 7 alpha-hydroxylase mRNA by TCA.