Interferon and cyclosporin A in the treatment of fulminant viral hepatitis

The Mitochondrial Permeability Transition Pore: Channel Formation by F-ATP Synthase, Integration in Signal Transduction, and Role in Pathophysiology

The mitochondrial permeability transition (PT) is a permeability increase of the inner mitochondrial membrane mediated by a channel, the permeability transition pore (PTP). After a brief historical introduction, we cover the key regulatory features of the PTP and provide a critical assessment of putative protein components that have been tested by genetic analysis. The discovery that under conditions of oxidative stress the F-ATP synthases of mammals, yeast, and Drosophila can be turned into Ca(2+)-dependent channels, whose electrophysiological properties match those of the corresponding PTPs, opens new perspectives to the field. We discuss structural and functional features of F-ATP synthases that may provide clues to its transition from an energy-conserving into an energy-dissipating device as well as recent advances on signal transduction to the PTP and on its role in cellular pathophysiology.

Efficacy of high-dose corticosteroid in the early stage of viral acute liver failure

AIM

Acute liver failure (ALF) is a worldwide problem despite its rare incidence because of its extremely high mortality. There are no beneficial therapies except for emergency liver transplantation for ALF. However, in Japan where the problem of a shortage of donor livers still remains, therapies other than transplantation must be further investigated for patients with ALF. Our aim was to elucidate the efficacy of high-dose corticosteroid (CS) in decreasing liver enzyme levels in the early stage of ALF.

METHODS

Thirty-one consecutive Japanese patients with viral ALF in the early stage were prospectively examined for their clinical and biochemical features and treatment responses during 2 weeks after the start of treatment. Nineteen were treated with high-dose methylprednisolone, and 12 having clinical and biochemical backgrounds with no significant difference were treated without CS.

RESULTS

The aspartate aminotransferase : alanine aminotransferase ratio became lower in patients treated with CS than in controls (P < 0.05). Fifteen of 19 patients in the CS group and eight of 12 in the control group recovered (P = 0.36). Hepatitis B viral infection and advanced liver damage at the start of treatment were associated with poor prognosis (P < 0.05). Complications during the therapy were not greater in the CS group than control (P = 0.64).

CONCLUSION

The introduction of high-dose CS in the early stage of ALF was effective in suppressing the destruction of hepatocytes. CS-treated patients showed slightly higher survival rates and slightly more improved liver regeneration than controls, although the differences were not statistically significant.

The mitochondrial permeability transition pore and its involvement in cell death and in disease pathogenesis

Current research on the mitochondrial permeability transition pore (PTP) and its role in cell death faces a paradox. Initially considered as an in vitro artifact of little pathophysiological relevance, in recent years the PTP has received considerable attention as a potential mechanism for the execution of cell death. The recent successful use of PTP desensitizers in several disease paradigms leaves little doubt about its relevance in pathophysiology; and emerging findings that link the PTP to key cellular signalling pathways are increasing the interest on the pore as a pharmacological target. Yet, recent genetic data have challenged popular views on the molecular nature of the PTP, and called into question many early conclusions about its structure. Here we review basic concepts about PTP structure, function and regulation within the framework of intracellular death signalling, and its role in disease pathogenesis.

Calcium and cell death: the mitochondrial connection

Physiological stimuli causing an increase of cytosolic free Ca2+ [Ca2+], or the release of Ca2+ from the endoplasmic reticulum invariably induce mitochondrial Ca2+ uptake, with a rise of mitochondrial matrix free [Ca2+] ([Ca2+]m). The [Ca2+]m rise occurs despite the low affinity of the mitochondrial Ca2+ uptake systems measured in vitro and the often limited amplitude of the cytoplasmic [Ca2+]c increases. The [Ca2+]m increase is typically in the 0.2-3 microM range, which allows the activation of Ca2(+)-regulated enzymes of the Krebs cycle; and it rapidly returns to the resting level if the [Ca2+], rise recedes due to activation of mitochondrial efflux mechanisms and matrix Ca2+ buffering. Mitochondria thus accumulate Ca2+ and efficiently control the spatial and temporal shape of cellular Ca2+ signals, yet this situation exposes them to the hazards of Ca2+ overload. Indeed, mitochondrial Ca2+, which is so important for metabolic regulation, can become a death factor by inducing opening of the permeability transition pore (PTP), a high conductance inner membrane channel. Persistent PTP opening is followed by depolarization with Ca2+ release, cessation of oxidative phosphorylation, matrix swelling with inner'membrane remodeling and eventually outer membrane rupture with release of cytochrome c and other apoptogenic proteins. Understanding the mechanisms through which the Ca2+ signal can be shifted from a physiological signal into a pathological effector is an unresolved problem of modern pathophysiology that holds great promise for disease treatment.

The mitochondrial permeability transition from in vitro artifact to disease target

The mitochondrial permeability transition pore is a high conductance channel whose opening leads to an increase of mitochondrial inner membrane permeability to solutes with molecular masses up to approximately 1500 Da. In this review we trace the rise of the permeability transition pore from the status of in vitro artifact to that of effector mechanism of cell death. We then cover recent results based on genetic inactivation of putative permeability transition pore components, and discuss their meaning for our understanding of pore structure. Finally, we discuss evidence indicating that the permeability transition pore plays a role in pathophysiology, with specific emphasis on in vivo models of disease.

Reactivation of hepatitis B virus with rituximab

Rituximab has become a useful drug for the treatment of non-Hodgkin's lymphoma (NHL) and such autoimmune diseases as idiopathic thrombocytopenic purpura and rheumatoid arthritis. When combined with cytotoxic agents, rituximab showed synergistic effects for the treatment of NHL. In such treatment, hepatitis B virus (HBV) reactivation is a crucial complication when patients are treated with immunosuppressive or chemotherapeutic agents. Despite its treatment efficacy, several studies have pointed out unusual viral infections after its administration that resulted in fatal hepatitis due to HBV reactivation. In the cases at the authors' institute, the authors analysed the kinetics of HBV antibodies, HBV-reactivation timing, and the prophylactic efficacy of lamivudine. The authors reviewed their cases and the previous literature to clarify the characteristics of HBV-reactivated patients who were administered rituximab.

Desensitization of the Permeability Transition Pore by Cyclosporin A Prevents Activation of the Mitochondrial Apoptotic Pathway and Liver Damage by Tumor Necrosis Factor-α

We studied the effects of cyclosporin A (CsA) administration 1) on the properties of the permeability transition pore (PTP) in mitochondria isolated from the liver and 2) on the susceptibility to hepatotoxicity induced by lipopolysaccharide of Escherichia coli (LPS) plus D-galactosamine (D-GalN) in rats. CsA exerted a marked PTP inhibition ex vivo, with an effect that peaked between 2 and 9 h of drug treatment and decayed with an apparent half-time of about 13 h. Administration of LPS plus D-GalN to naive rats caused the expected increased serum levels of tumor necrosis factor (TNF)-alpha, liver inflammation with BID cleavage, activation of caspase 3, appearance of terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling-positive nuclei, and release of alanine aminotransferase and aspartate aminotransferase into the bloodstream. Treatment with CsA before or within 5 h of the administration of LPS plus D-GalN protected rats from hepatotoxicity despite the normal increase of serum TNF-alpha and BID cleavage. These results indicate that CsA prevents the hepatotoxic effects of TNF-alpha by blocking the mitochondrial proapoptotic pathway through inhibition of the PTP and provides a viable strategy for the treatment of liver diseases that depend on increased production and/or liver sensitization to TNF-alpha.

Reactivation of replication of hepatitis B and C viruses after immunosuppressive therapy: an unresolved issue

The liver is susceptible to the toxic effects of many cytotoxic or immunosuppressive treatments. However, in carriers of hepatitis B virus (HBV) and, less frequently, of hepatitis C virus, liver damage due to reactivation of viral replication can occur after withdrawal of immunosuppressive drugs. These reactivations, which are associated with fulminant forms of hepatitis in up to 25% of cases, are observed both in symptom-free chronic carriers of hepatitis B surface antigen and in patients who have chronic hepatitis B or C and concurrent haematological tumours or solid neoplasms or who have received transplants. HBV-related complications may cause delays or modifications of therapy, and the chance of cure is reduced. In this review, we analyse clinical, biochemical, and serological issues in reactivation of viral replication and examine the role of immune reactions in the pathogenesis and the possible toxicity of immunosuppressive drugs. We emphasise the importance of identifying predictive markers of a clinically relevant reactivation, review difficulties in drug prevention and treatment, indicate studies that are needed to address the key clinical issues, and give practical recommendations to practising physicians and oncologists.

Mannose-binding lectin and the prognosis of fulminant hepatic failure caused by HBV infection

BACKGROUND/AIMS

The mannose-binding lectin (MBL) gene was reported to play an important role in determining the clinical outcome of persistent hepatitis B virus (HBV) infection. We investigated serum MBL concentrations and MBL gene mutations to determine whether they were related to the prognosis of patients with fulminant hepatic failure (FHF) caused by HBV infection.

METHODS

We investigated serum MBL concentrations and MBL gene mutations in 43 HBV-infected Japanese patients with FHF and 260 HBsAg-negative healthy controls. Serum MBL concentrations were measured by an enzyme-linked immunosorbent assay, and mutations in the MBL gene were analysed by nested PCR and direct DNA sequencing.

RESULTS

Only a mutation in codon 54 of the MBL gene was found. The frequency of this mutation in nonsurvivors (40%, 8/20) was higher than in survivors (13%, 3/23), and the difference was slightly significant (p = 0.043). The H allele frequency in survivors (70.5%, 31/44) was higher than in nonsurvivors (39.5%, 15/38) (p = 0.0048). Because of these factors the mean serum MBL concentration in survivors, 1.61 ,micro/ml (range 0.3-3.86), was significantly higher than in nonsurvivors, 0.79 microg/ml (range 0.04-1.51) (p < 0.0001). The likelihood ratio for nonsurvival was 0 for over 2.0 microg/ml, 0.67 for 1.0-2.0 microg/ml, and 2.24 for 0-1.0 microg/ml.

CONCLUSIONS

The mutation in codon 54 of the MBL gene tended to be higher in nonsurvivors than in survivors. The H allele frequency (high producing allele in H/Y) in survivors was higher than that in nonsurvivors. High levels of serum MBL correlated with the survival of patients with FHF due to HBV infection. Serum MBL may be useful as a predictive factor for the survival of patients with FHF caused by HBV.

Fulminant hepatitis is significantly increased in hepatitis B carriers after allogeneic bone marrow transplantation

BACKGROUND

Bone marrow transplantation (BMT) is effective treatment for many hematologic disease, but performed in a population with a high endemic hepatitis B virus carrier rate, the incidence of liver function impairment and fulminant hepatitis (FH) is expected to be raised.

METHODS

Forty-three hepatitis B virus carriers received high-dose chemotherapy and BMT, 32 patients received an allogeneic graft, and 11 patients autologous marrow. Acute graft-versus-host disease prophylaxis consisted of methotrexate on day 1, 3, 6, and 11 and cyclosporine for 6 months.

RESULTS

After a median follow-up period of 68 months (range: 1-11.5 years), 26 (81.3%) allogeneic BMT patients developed impaired liver function (LF), 5 progressed to FH on day 93, 169, 170, 180, and 468, respectively, and died after an average of 13.8 days (range: 1-45 days). Whereas only 4 (36.4%) autologous BMT patients developed impaired LF, and none FH. Impaired LF (P=0.026, chi-square), and FH (odds ratio=12.86, P=0.009 for coefficient) were significantly related to an allogeneic marrow graft, and the timing of liver function impairment coincided with cyclosporine withdrawal. Hepatitis B surface antigen (HbsAg) disappeared from the serum in 4/14 (28.6%) patients receiving a marrow graft from an HbsAg+ donor. HbsAg was not detected in the serum after BMT in 2/11 (18.2%) autologous BMT patients.

CONCLUSIONS

Hepatitis B virus carriers receiving a marrow graft from an HbsAg+ donor have a significantly increased risk of FH.

Long-term administration of cyclosporin A to HCV-antibody-positive patients with dermatologic diseases

BACKGROUND

Cyclosporine A (CYA) is an immunosuppressive agent which is being used in the treatment of an increasingly wide range of dermatologic diseases, but its use has been avoided in carriers of hepatitis C virus (HCV).

METHODS

We administered small doses of CYA (maximum, 3 mg/kg/day) for a long time to treat dermatologic diseases in one HCV-antibody-positive patient with no HCV-RNA in the blood, one patient with a small amount of HCV-RNA in the blood, and two patients with large amounts of HCV-RNA in the blood.

RESULTS

Skin lesions improved in all patients, but recurred upon complete or partial withdrawal of CYA. In the absence of HCV-RNA in the blood, or when only a small quantity of HCV-RNA was present in the blood, HCV-RNA load showed no apparent change. In one patient with a large blood HCV-RNA load, CYA dosage reduction was followed by increases in alanine aminotransferase (ALT) levels and decreases in blood HCV-RNA. Aggravation of hepatitis due to immunologic reactivation was suspected in this patient.

CONCLUSIONS

The reduction of CYA dosage is a key element in the use of this agent for cutaneous diseases.

Transplantation for acute hepatic failure in children

BACKGROUND/PURPOSE

Acute liver failure in the pediatric population is a rare but highly lethal health problem. Sometimes it is difficult to predict who will benefit from liver transplantation. The authors report on their experience in the past 8 years at a pediatric transplant center.

METHODS

A retrospective chart review was performed on all children referred to the liver transplant (TX) service with the diagnosis of acute hepatocellular dysfunction (AHD) from 1988 to 1996. Presentation, chemistries, and clinical course were evaluated. Statistical analysis was performed using analysis of variance.

RESULTS

Twenty-six children underwent evaluation. Seventeen patients fulfilled the criteria for fulminant hepatic failure (FHF). Eleven patients recovered without TX, 14 received a TX, and one died awaiting TX. Of those that received a TX, four died in the early postoperative period and 10 survived (mean follow-up of 4.2 years). There was a wide range in most laboratory values. Serum bilirubin levels, ammonia levels, and coagulation parameters, however, reached statistical significance in patients requiring transplant. The most consistent discriminators of need for transplantation and outcome were neurological findings and multisystem organ failure. Children who recovered without TX had no seizures and minimal encephalopathy. Of the 15 children who were recommended for TX, six had seizures and all had encephalopathy, 12 having grade III or IV. All five nonsurvivors had respiratory failure early in their clinical course, and four of five nonsurvivors also had renal failure.

CONCLUSIONS

There is significant overlap in the presentation and laboratory findings of children who present with AHD or FHF. Neurological status was an important discriminator of need for transplantation. Patients who presented with multisystem organ failure, including renal failure and respiratory failure, had 100% mortality rate despite liver transplantation.

Favorable effect of new artificial liver support on survival of patients with fulminant hepatic failure

The two most serious symptoms of fulminant hepatic failure are bleeding and hepatic coma. To overcome these problems, we developed an artificial liver support system comprising a combination of plasma exchange and hemodiafiltration using a high performance membrane. We treated 67 patients with fulminant hepatic failure. Of these, 65 patients (97.0%) regained normal consciousness, and 55 patients (80.9%) were kept alert as long as we continued to apply this system. All 7 patients (100%) with fulminant hepatitis caused by hepatitis A virus infection and 9 of 12 patients (75%) with fulminant hepatitis caused by acute hepatitis B (HB) virus infection survived. In addition, 7 of 15 HB virus carriers (46.7%) who developed fulminant hepatitis and 11 of 29 patients (37.9%) with fulminant hepatitis caused by non-A, non-B hepatitis viruses survived. The overall survival rate was 37 of 67 patients (55.2%). Our artificial liver support system allows as high a survival rate as liver transplantation.