Takafumi Naiki

TNF-α-Induced Sphingosine 1-Phosphate Inhibits Apoptosis Through a Phosphatidylinositol 3-Kinase/Akt Pathway in Human Hepatocytes

Human hepatocytes usually are resistant to TNF-α cytotoxicity. In mouse or rat hepatocytes, repression of NF-κB activation is sufficient to induce TNF-α-mediated apoptosis. However, in both Huh-7 human hepatoma cells and Hc human normal hepatocytes, when infected with an adenovirus expressing a mutated form of IκBα (Ad5IκB), which almost completely blocks NF-κB activation, >80% of the cells survived 24 h after TNF-α stimulation. Here, we report that TNF-α activates other antiapoptotic factors, such as sphingosine kinase (SphK), phosphatidylinositol 3-kinase (PI3K), and Akt kinase. Pretreatment of cells with N,N-dimethylsphingosine (DMS), an inhibitor of SphK, or LY 294002, an inhibitor of PI3K that acts upstream of Akt, increased the number of apoptotic cells induced by TNF-α in Ad5IκB-infected Huh-7 and Hc cells. TNF-α-induced activations of PI3K and Akt were inhibited by DMS. In contrast, exogenous sphingosine 1-phosphate, a product of SphK, was found to activate Akt and partially rescued the cells from TNF-α-induced apoptosis. Although Akt has been reported to activate NF-κB, DMS and LY 294002 failed to prevent TNF-α-induced NF-κB activation, suggesting that the antiapoptotic effects of SphK and Akt are independent of NF-κB. Furthermore, apoptosis mediated by Fas ligand (FasL) involving Akt activation also was potentiated by DMS pretreatment in Hc cells. Sphingosine 1-phosphate administration partially protected cells from FasL-mediated apoptosis. These results indicate that not only NF-κB but also SphK and PI3K/Akt are involved in the signaling pathway(s) for protection of human hepatocytes from the apoptotic action of TNF-α and probably FasL.

High Levels of Serum Interleukin-10 and Tumor Necrosis Factor—α Are Associated with Fatality in Fulminant Hepatitis

Serum pro- and anti-inflammatory mediators in patients with acute liver diseases were assessed to clarify the clinical significance of these measurements in relation to disease severity. Concentrations of circulating tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-10, IL-12, and soluble TNF receptors (sTNFR) p55 and p75 were measured at admission in patients with fulminant hepatitis (FH; n=19), severe acute hepatitis (AHS, n=15), or acute hepatitis (AH, n=7). Serum concentrations of TNF-alpha, IL-10, and sTNFR-55 were significantly higher in patients with FH than in those with AHS (P<.05, <.05, and <.01, respectively) or AH (P<.05). Serum IL-10 and TNF-alpha levels were higher in patients who died of FH (n=13) than in FH survivors (n=6; P<.05). The ratios between TNF-alpha and IL-10 and sTNFR-55 or sTNFR-75 were not valuable in predicting mortality and disease severity. However, both proinflammatory cytokine TNF-alpha and anti-inflammatory cytokine IL-10 levels at admission were associated with fatal outcome among patients with FH.

Etiology and prognosis of fulminant hepatitis and late-onset hepatic failure in Japan : Summary of the annual nationwide survey between 2004 and 2009

To summarize the annual nationwide survey on fulminant hepatitis (FH) and late‐onset hepatic failure (LOHF) between 2004 and 2009 in Japan.

Diagnostic criteria of acute liver failure: A report by the Intractable Hepato-Biliary Diseases Study Group of Japan

The diagnostic criteria of fulminant hepatitis in Japan are different from those of acute liver failure in Europe and the United States, both in regard to the histological features in the liver and the cutoff values of the prothrombin time. Thus, the Intractable Hepato‐Biliary Disease Study Group established novel diagnostic criteria for “acute liver failure” in Japan based on the demographic and clinical features of the patients. Patients showing prothrombin time values of 40% or less of the standardized values or international normalized ratios of 1.5 or more caused by severe liver damage within 8 weeks of onset of the symptoms are diagnosed as having “acute liver failure”, where the liver function prior to the current onset of liver damage is estimated to be normal. Acute liver failure is classified into “acute liver failure without hepatic coma” and “acute liver failure with hepatic coma,” depending on the severity of the hepatic encephalopathy; the latter is further classified into two types, the “acute type” and the “subacute type”, in which grade II or more severe hepatic coma develops within 10 days and between 11 and 56 days, respectively, after the onset of disease symptoms. Patients without histological findings of hepatitis, such as those with liver damage caused by drug toxicity, circulatory disturbance or metabolic disease, are also included in the disease entity of “acute liver failure”, while acute‐on‐chronic liver injuries, such as liver injury caused by alcohol, are excluded. A nationwide survey of “acute liver failure” in Japan based on the novel criteria is proposed.

Lethal hepatic apoptosis mediated by tumor necrosis factor receptor, unlike Fas-mediated apoptosis, requires hepatocyte sensitization in mice

BACKGROUND/AIMS Tumor necrosis factor a (TNF-alpha) and Fas ligand are apoptotic cell-death mediators that act by binding to their responsive receptors. The aims of this study were to assess the differences between liver cell deaths induced by TNF-alpha and anti-Fas antibody, and to investigate the mechanism by which GalN sensitizes the hepatocyte to injury by TNF-alpha. METHODS TNF-alpha or anti-Fas antibody was injected into BALB/c mice sensitized or unsensitized by D-galactosamine (GalN). Liver injury was assessed biochemically and histologically. The expressions of TNF receptor (TNFR)1 and TNFR2 mRNA in the liver were determined by Northern blot analysis. Nuclear factor-kappaB (NF-kappaB) DNA binding activity was determined by gel shift assay. RESULTS In GalN-sensitized mice, hepatocyte apoptosis and liver failure were observed after TNF-alpha injection, but neither occurred in unsensitized mice. Microscopically, GalN preceding TNF-alpha caused massive hemorrhagic liver damage with fragmented hepatocyte nuclei resembling effects of anti-Fas antibody, but GalN largely failed to sensitize to injury by this antibody. TNFR1 mRNA expression in the liver was upregulated within 3 h after GalN administration, and anti-TNFR1 antibody protected GalN-sensitized mice from hepatotoxic effects of TNF-alpha. GalN treatment failed to affect TNF-alpha-induced NF-kappaB activation. CONCLUSIONS Unlike Fas-related apoptosis, TNFR-mediated apoptosis requires hepatocyte sensitization involving TNFR1 upregulation.

Long-term outcome of branched-chain amino acid treatment in patients with liver cirrhosis

Clinical impact of protein‐energy malnutrition (PEM) on the outcome of liver cirrhosis is well documented. As a candidate interventional modality to improve PEM in cirrhosis, effects of branched‐chain amino acid (BCAA) supplementation on event‐free survival and quality of life (QOL) was first reported by Yoshida et al. in 1989. Although critical arguments still continue regarding the effects of BCAA, several randomized trials in the last 5 years have brought positive results, and seem to have settled the discussion in a favorable direction for the efficacy of BCAA in liver cirrhosis. Actually, The European Society for Clinical Nutrition and Metabolism (ESPEN) upgraded the recommendation of BCAA supplementation in decompensated liver cirrhosis in the latest revision of its guidelines in 2006, by referring to the literatures from Italy and Japan. Particularly in these two long‐term randomized studies with 1–2 years‐supplementation, event‐free survival was estimated by employing composite endpoints such as aggravation of hepatic failure (ascites, peripheral edema, hepatic encephalopathy, and jaundice), rupture of esophageal or gastric varices, development of liver cancer, and death from any cause. Both trials agreed on the effect of BCAA to reduce the incidence of hepatic failure, thus contributing to the rise in the event‐free survival. Quality of life is another essential marker of outcome survey. Marchesini, Muto, and Nakaya reported the improved QOL in cirrhotics with BCAA supplementation. In particular, quantitative analysis of QOL measured by Short Form 36 (SF‐36) questionnaire demonstrated a significant recovery of general heath perception score in BCAA supplemented patients in a randomized trial. In this article, the long‐term outcome of BCAA treatment in liver cirrhosis will be reviewed with its action mechanisms. In addition, the effects of BCAA treatment on the incidence of liver cancer in obese patients with type C liver cirrhosis, significance of obesity as a risk factor for type C liver cancer, and a possible role of Body Mass Index to estimate the histological grade of fat deposition in the liver will be briefly discussed.

Leflunomide protects from T‐cell–mediated liver injury in mice through inhibition of nuclear factor κB

Leflunomide is a novel immunosuppressive and anti‐inflammatory agent for the treatment of autoimmune disease. The aim of this study was to investigate whether leflunomide protects from liver injury induced by concanavalin A (Con A), a T‐cell–dependent model of liver damage. BALB/c mice were injected with 25 mg/kg Con A in the presence or absence of 30 mg/kg leflunomide. Liver injury was assessed biochemically and histologically. Levels of circulating cytokines and expressions of cytokine messenger RNA (mRNA) in the liver and the spleen were determined. Treatment with leflunomide markedly reduced serum transaminase activities and the numbers of dead liver cells. Leflunomide significantly inhibited increases in plasma tumor necrosis factor alpha (TNF‐α) and interleukin 2 concentrations, and also reduced TNF‐α mRNA expression in the liver after administration of Con A. These findings were supported by the results in which leflunomide administration decreased the number of T lymphocytes infiltrating the liver as well as inhibiting their production of TNF‐α. Activation of nuclear factor κB (NF‐κB), which regulates TNF‐α production, was inhibited in the liver of mice treated with leflunomide, resulting in a reduction of TNF‐α production from lymphocytes infiltrating the liver. In conclusion, leflunomide is capable of regulating T‐cell–mediated liver injury in vivo and that this event may depend on the decrease of TNF‐α production in the liver through inhibition of NF‐κB activation caused by leflunomide. (HEPATOLOGY 2004.)

Insulin resistance raises the risk for recurrence of stage I hepatocellular carcinoma after curative radiofrequency ablation in hepatitis C virus‐positive patients: A prospective, case series study

Aim:  Several studies have reported that insulin resistance raises the risk of primary hepatocellular carcinoma (HCC). We conducted a prospective, case series study to test the impact of insulin resistance on the recurrence after curative radiofrequency ablation (RFA) of stage I HCC in HCV‐positive patients.

Novel scoring system as a useful model to predict the outcome of patients with acute liver failure: Application to indication criteria for liver transplantation.

Aim:  In Japan, the indication for liver transplantation in patients with acute liver failure (ALF) is currently determined according to the guideline published in 1996. However, its predictive accuracy has fallen in recent patients. Thus, we attempted to establish a new guideline.

Normal liver regeneration and liver cell apoptosis after partial hepatectomy in tumor necrosis factor-α-deficient mice

Abstract: Aims/Background: Tumor necrosis factor‐α (TNF‐α) is known as a proinflammatory cytokine that has been implicated as a contributing factor in a number of disease processes. TNF‐α also influences liver repair following hepatotoxic damage, and regeneration following partial hepatectomy (PH). The aim of this study was to assess the mechanism by which TNF‐α influences liver cell apoptosis and regeneration following PH in TNF‐α‐deficient (TNF‐α−/−) mice.