Efficacy of interferon therapy in patients with chronic hepatitis C. Comparison between non-drinkers and drinkers

Expression of interferon alfa signaling components in human alcoholic liver disease

Interferon alfa (IFN-alpha) is currently the only well-established therapy for viral hepatitis. However, its effectiveness is much reduced (<10%) in alcoholic patients. The mechanism underlying this resistance is not fully understood. In this study, we examined the expression of IFN-alpha signaling components and its inhibitory factors in 9 alcoholic liver disease (ALD) and 8 healthy control liver tissues. In comparison with normal control livers, expression of IFN-beta, IFN-alpha receptor 1/2, Jak1, and Tyk2 remained unchanged in ALD livers, whereas expression of IFN-alpha, signal transducer and activator of transcription factor 1 (STAT1), and p48 were up-regulated and expression of STAT2 was down-regulated. Expression of antiviral MxA a karyophilic 75 kd protein induced by IFN in mouse cells carrying the influenza virus resistance allele Mx(+) and 2'-5' oligoadenylate synthetase (OAS) proteins was not regulated, whereas expression of double-stranded RNA-activated protein kinase (PKR) was decreased by 55% in ALD livers. Three families of inhibitory factors for the JAK-STAT signaling pathway were examined in ALD livers. Members of the suppressor of cytokine signaling (SOCS) family, including SOCS 1, 2, 3, and CIS, and the protein tyrosine phosphatases, including Shp-1, Shp-2, and CD45, were not up-regulated in ALD livers, whereas the phosphorylation of and protein levels of p42/44 mitogen-activated protein kinase (p42/44MAP kinase) were increased about 3.9- and 3.2-fold in ALD livers in comparison with normal control livers, respectively. In conclusion, these findings suggest that chronic alcohol consumption down-regulates STAT2 and PKR, but up-regulates p42/44 mitogen-activated protein kinase (p42/44MAP kinase), which may cause down-regulation of IFN-alpha signaling in the liver of ALD patients.

Ethanol inhibits the JAK-STAT signaling pathway in freshly isolated rat hepatocytes but not in cultured hepatocytes or HepG2 cells: evidence for a lack of involvement of ethanol metabolism

OBJECTIVES

To understand the molecular mechanism underlying alcoholic liver injury, effects of acute ethanol on the Janus kinase-signal transducer and activator transcription factor (JAK-STAT) signaling in hepatic cells were studied.

DESIGNS AND METHODS

Effects of acute ethanol on the JAK-STAT signaling in freshly isolated, cultured rat hepatocytes, and HepG2 cells were explored.

RESULTS

Acute ethanol exposure inhibited IL-6- or IFN-activated STAT in freshly isolated hepatocytes but not in cultured hepatocytes, HepG2 cells, or HepG2 cells transfected with alcohol dehydrogenase (ADH) or cytochrome P450(2E1). The inhibitory action of ethanol in freshly isolated hepatocytes was not antagonized by the ADH inhibitor 4-methylpyrazole (4-MP). Acute exposure of hepatocytes to acetaldehyde or hydrogen peroxide did not suppress STAT activation. Further studies indicated that the loss of response to the inhibitory effect of ethanol was not due to hepatocyte proliferation and collagen contact.

CONCLUSIONS

Freshly isolated hepatocytes are more susceptible to the inhibitory action of ethanol on the JAK-STAT signaling than cultured hepatocytes or HepG2 cells, which may be implicated in pathogenesis and progression of alcoholic liver disease.

Commercial tattooing as a potentially important source of hepatitis C infection. Clinical epidemiology of 626 consecutive patients unaware of their hepatitis C serologic status

Tattooing in commercial tattoo parlors is known to transmit blood-borne viral infections, including hepatitis C virus (HCV), in other countries, but its contribution to the high population prevalence of HCV infection in the United States has been incompletely evaluated. Risk factors for blood-borne infection were assessed by physician's interview of 626 consecutive patients undergoing medical evaluation for spinal problems in 1991 and 1992 while unaware of their HCV status. Later all were screened for HCV infection with enzyme-linked immunosorbent assay (EIA-1 and EIA-2), and positives were confirmed with second-generation recombinant immunoblot assay (RIBA). Forty-three patients were seropositive for HCV (sample prevalence 6.9%, population-standardized prevalence 2.8%). Logistic regression analysis identified 4 independent risk factors for HCV infection: injection-drug use (adjusted prevalence odds ratio [OR] = 23.0; 95% confidence intervals [CI] = 7.5-70.6), ancillary hospital jobs held by men (OR = 9.6; 95% CI = 3.8-24.3), tattoos from commercial tattoo parlors (OR = 6.5; 95% CI = 2.9-14.8), and drinking > or = 3 6-packs of beer per month (OR = 4.0; 95% CI = 1.8-8.7). If causal, these 4 risk factors account for 91% of HCV infections, with tattooing explaining 41%, heavy beer drinking 23%, injection-drug use 17%, and ancillary health care jobs for men 8%. Transfusions, promiscuous sexual activity, bone grafts, acupuncture, perinatal or intimate transmission in families, and other modes were not independently associated with serologic evidence of HCV infection. Unlikely to be explained by confounding or incomplete disclosure of other risk factors, tattooing in commercial tattoo parlors may have been responsible for more HCV infections than injection-drug use.

IL-1 beta attenuates IFN-alpha beta-induced antiviral activity and STAT1 activation in the liver: involvement of proteasome-dependent pathway

IFN-alphabeta is the only established treatment for viral hepatitis; however, more than 60% of patients are poorly responsive. Because viral hepatitis is associated with inflammation, we hypothesized that inflammation may attenuate the efficacy of IFN therapy. To test this hypothesis, the effect of IL-1beta, one of the major proinflammatory cytokines, on IFN signaling pathway in the liver was examined. Administration of IL-1beta in vivo attenuated IFN-alphabeta-induced STAT1 tyrosine phosphorylation in the liver but not in the spleen. The inhibitory action of IL-1beta in vivo was not affected by depleting hepatic Kupffer cells, suggesting that IL-1beta may directly target IFN-alphabeta signaling in hepatocytes. Indeed, pretreatment of human hepatocellular carcinoma HepG2 cells with IL-1beta suppressed IFN-alphabeta-induced antiviral activity and antiviral protein MxA mRNA expression. Furthermore, IL-1beta attenuated IFN-alphabeta-induced STAT1 binding and tyrosine phosphorylation without affecting the level of STAT1 protein. This inhibitory effect can be reversed by pretreatment with either proteasome inhibitors or transfection of dominant negative NF-kappaB inducing kinase mutants. Taken together, these findings suggest that IL-1beta attenuates IFN-alphabeta-induced STAT1 activation by a proteasome-dependent mechanism. In view of high levels of IL-1beta in the serum or within the liver of patients with chronic liver diseases, attenuation of IFN-alphabeta signaling in the liver by IL-1beta could be one of the mechanisms underlying the resistance to IFN therapy in chronic hepatitis C, and IL-1beta could be a potential therapeutic target for improving the efficacy of IFN therapy.

Interferons activate the p42/44 mitogen-activated protein kinase and JAK-STAT (Janus kinase-signal transducer and activator transcription factor) signalling pathways in hepatocytes: differential regulation by acute ethanol via a protein kinase C-dependent mechanism

Interferons (IFNs) have been used in the treatment of viral hepatitis. However, their effectiveness is much reduced (<10%) in alcoholics. The mechanism underlying this resistance remains unknown. Here, we report that IFN-alpha/beta and IFN-gamma rapidly activate the JAK-STAT1 (Janus kinase-signal transducer and activator transcription factor 1) and p42/44 mitogen-activated protein kinase (p42/44 MAPK) in freshly isolated rat hepatocytes. Treatment of hepatocytes with 25-100 mM ethanol for 30 min inhibited IFN-beta- or IFN-gamma-induced STAT1 activation and tyrosine phosphorylation. The inhibitory effect of ethanol was not reversed by pretreatment with either sodium vanadate, a non-selective tyrosine phosphatase inhibitor, or with MG132, a specific proteasome inhibitor. This suggests that protein tyrosine phosphatases or the ubiquitin-proteasome pathway are not involved in the inhibitory action of ethanol. In contrast with the JAK-STAT signalling pathway, acute ethanol exposure significantly potentiated IFN-beta or IFN-gamma-induced activation of p42/44 MAPK, and caused marked activation of protein kinase C (PKC). Inhibition of PKC partially antagonized ethanol attenuation of IFN-induced STAT1 activation, suggesting that PKC may be involved. Taken together, these findings suggest that the ability of biologically relevant concentrations of ethanol (less than 100 mM) to markedly inhibit IFN-activated STAT1 is one of the cellular mechanisms responsible for the observed resistance of IFN therapy in alcoholics.

Alcohol-induced liver disease

Hepatic changes resulting from the regular ingestion of alcohol are many and include fat infiltration, alcoholic hepatitis, and cirrhosis. Only 10% to 15% of chronic alcoholics develop liver disease. Women are more susceptible. An area of considerable importance is the high prevalence of concomitant infection with hepatitis C virus in chronic alcoholics. Patients who have hepatitis C and alcohol-induced liver injury are much more likely to develop progressive liver disease and cirrhosis. Corticosteroid therapy has proven useful in the treatment of patients with severe acute alcoholic hepatitis.

Hepatitis C and alcohol

A close relationship and possible interaction has been noted between alcohol intake and hepatitis C virus infection, since the discovery of HCV markers. It is not understood whether these are additive or synergistic effects in causing liver injury. Interactions between alcohol and HCV may be studied at several levels, including epidemiology, virology (including viral load), histology (effect on the severity of liver lesions), carcinogenesis (the role of alcohol in the occurrence of hepatocellular carcinoma), and the effect on the extrahepatic manifestations or severity of HCV infection. At the epidemiological level, a high prevalence of HCV infection was noted in patients with alcoholic liver diseases (14-37%), also characterized by a high rate of viral replication as detected by PCR, which was present in over 90% of patients tested. Moreover, the prevalence of anti-HCV antibodies increased proportionally with the severity of liver lesions. Virological analysis based on the determination of HCV RNA levels in the serum showed variations of HCV RNA levels with diet, and a clear relationship between self reported alcohol consumption and the levels of serum HCV RNA (r = .26, p = .001). At the histologic level the role of alcohol may be evaluated either through the development of fibrosis or by determination of the incidence of cirrhosis. A study on the effect of alcohol intake below or over 40 g per day on the histologic progression of liver lesions has confirmed a more rapid increase in fibrosis and a doubling in the incidence of cirrhosis in patients admitting to alcohol consumption >40 g per day. The role of alcohol in the occurrence of hepatocellular carcinoma in patients with cirrhosis due to HCV infection has been extensively studied with controversial results. A recent case control study performed in Italy showed that the relative risk of HCC in patients with HCV infection and heavy alcohol consumption doubled. Finally, alcohol consumption potentially worsens the evolution of dermatological diseases associated with HCV infection such as porphyria cutanea tarda. All of the above are strong arguments which should be used to advise HCV patients against alcohol consumption, regardless of the degree of liver injury. However, the deleterious effect of the occasional intake of small amounts of alcohol has not been demonstrated and therefore an occasional drink may be allowed in some cases.

The alcoholic patient with hepatitis C virus infection

Chronic alcoholism in patients with chronic hepatitis C hastens disease progression toward development of cirrhosis and hepatocellular carcinoma. Approximately 30% of alcoholic patients with liver disease are infected with the hepatitis C virus (HCV), the primary risk factor being a history of injection drug use. The histologic pattern in alcoholics is typically indistinguishable from nonalcoholic patients similarly infected with chronic hepatitis C. The mechanism(s) involved in alcohol-induced enhancement of chronic hepatitis C have not entirely been established but may involve increased viral replication, iron overload, and immune suppression. Still to be determined is the minimum amount of daily alcohol intake, if any, that can be ingested without enhancing progressive liver injury. However, chronic hepatitis C patients undergoing treatment with interferon must abstain from any alcohol intake, because the efficacy of interferon therapy is significantly lower in those who continue to drink. Future research efforts are needed in order to further delineate the epidemiology and pathogenesis of chronic hepatitis C in the alcoholic patient.

Interrelationship between alcohol intake, hepatitis C, liver cirrhosis, and hepatocellular carcinoma

The discovery of a cDNA clone of hepatitis C virus (HCV) genome in 1989 has resulted in numerous reports of high rates of the prevalence of HCV antibody in patients with alcoholic liver disease, in particular, alcoholic liver cirrhosis and hepatocellular carcinoma. Thus, the interaction between alcohol intake and HCV infection has become of great importance. In terms of the effect of alcohol on HCV-RNA levels, the data are controversial; in some reports, alcohol increases HCV-RNA levels, and in the other reports it does not. There are several reports suggesting the possibility of an elevated quasi-species of hypervariable region 1 in the HCV genome caused by alcohol drinking. Recent studies have documented that alcohol intake exaggerates the responsiveness of interferon therapy for chronic hepatitis C; however, its mechanism is still obscure. Several studies have suggested the promoting effect of alcohol on the development of hepatocellular carcinoma in type C liver cirrhosis, which has been similarly observed in type B chronic liver disease, whereas its mechanism is limited to speculations.

Review article: interferon and hepatitis C--factors predicting therapeutic outcome

Hepatitis C chronically infects approximately 1.5% of Americans and is the most common clinical problem facing hepatologists. Since the virus was initially described in 1989, development of an effective therapy has been challenging. Although several different therapeutic agents have been used, no therapy has been shown to reliably eradicate the virus. Interferon-alpha, a cytokine with immunostimulatory and anti-viral properties, has become the therapy of choice for patients with chronic hepatitis C infection. Trials assessing the efficacy of interferon-alpha have characterized host and viral factors predictive of responses to treatment. A thorough understanding of these predictive factors is requisite to providing cost-effective therapeutic decisions for the patient with chronic hepatitis C infection.

Hepatitis C virus infection in patients with clinically diagnosed alcoholic liver diseases

To determine the incidence of hepatitis C virus (HCV) infection in patients with alcoholic liver disease (ALD), serum samples from 252 patients with ALD were tested for anti-HCV and HCV RNA. Serial sera of these patients were collected and stored under optimal conditions to allow exact quantification of HCV RNA. Fifteen patients who visited our hospital during the same period of time with chronic HCV infections served as controls. In those with ALD, anti-HCV and HCV RNA were positive in 55.5% and 41.2%, respectively. Patients with histologically diagnosed chronic hepatitis and hepatocellular carcinoma had much higher prevalence rates of HCV RNA (84% and 100%, respectively) compared to those with fatty liver (4.3%), hepatic fibrosis (10.1%) and alcoholic hepatitis (22.2%) (P < 0.01). Although no difference in serum HCV RNA levels was observed between the patients with both ALD and chronic HCV infection and those with chronic HCV infection alone, HCV RNA levels significantly (10-fold) dropped after abstinence in nearly half of the patients (P < 0.01). These data indicate that HCV infection in patients with ALD promotes progression of liver disease, and abstinence from alcohol is associated with a reduction in serum HCV RNA levels.

Progression of type C chronic hepatitis to liver cirrhosis and hepatocellular carcinoma--its relationship to alcohol drinking and the age of transfusion

Alcohol drinking has been reported to be an important factor that modulates the development and prognosis of chronic hepatitis B; however, little is known about an interrelationship between alcohol intake and the progression of chronic hepatitis C to liver cirrhosis (LC) and hepatocellular carcinoma (HCC). We attempted to clarify this interrelationship in patients with hepatitis C and history of blood transfusion. Thirty LC and 85 HCC patients were enrolled. In patients with LC, no significant correlation was observed between the amount of alcohol intake and the period from transfusion to diagnosis. The period from transfusion to diagnosis in HCC patients with alcohol intake > or = 46 g/day and < 46 g/day were 26 +/- 6 and 31 +/- 9 years, respectively, resulting in a significant difference (p < 0.05). The period from transfusion to diagnosis of LC and/or HCC showed significant negative correlation with the age of transfusion (r = 0.82, Y = -0.67X + 48.0, p < 0.01; r = 0.76, Y = -0.70X + 54.1, p < 0.001, respectively). This correlation was also observed in patients with HCC, regardless of the amount of alcohol intake. In conclusion, these data suggest that alcohol drinking might be an important factor that promotes an occurrence of HCC in patients with hepatitis C, and that hepatitis C virus infection in the elderly promotes development of liver disease via LC to HCC.