Hepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide. The current standard therapy for chronic hepatitis C (CHC) consists of a combination of pegylated IFN alpha (pegIFN␣) and ribavirin. It achieves a sustained viral clearance in only 50 -60% of patients. To learn more about molecular mechanisms underlying treatment failure, we investigated IFN-induced signaling in paired liver biopsies collected from CHC patients before and after administration of pegIFN␣. In patients with a rapid virological response to treatment, pegIFN␣ induced a strong up-regulation of IFN-stimulated genes (ISGs). As shown previously, nonresponders had high expression levels of ISGs before therapy. Analysis of posttreatment biopsies of these patients revealed that pegIFN␣ did not induce expression of ISGs above the pretreatment levels. In accordance with ISG expression data, phosphorylation, DNA binding, and nuclear localization of STAT1 indicated that the IFN signaling pathway in nonresponsive patients is preactivated and refractory to further stimulation. Some features characteristic of nonresponders were more accentuated in patients infected with HCV genotypes 1 and 4 compared with genotypes 2 and 3, providing a possible explanation for the poor response of the former group to therapy. Taken together with previous findings, our data support the concept that activation of the endogenous IFN system in CHC not only is ineffective in clearing the infection but also may impede the response to therapy, most likely by inducing a refractory state of the IFN signaling pathway.Jak-STAT signaling ͉ liver ͉ viral hepatitis

Neonicotinoids are implicated in the decline of bee populations. As agonists of nicotinic acetylcholine receptors, they disturb acetylcholine receptor signaling leading to neurotoxicity. Several behavioral studies showed the link between neonicotinoid exposure and adverse effects on foraging activity and reproduction. However, molecular effects underlying these effects are poorly understood. Here we elucidated molecular effects at environmental realistic levels of three neonicotinoids and nicotine, and compared laboratory studies to field exposures with acetamiprid. We assessed transcriptional alterations of eight selected genes in caged honey bees exposed to different concentrations of the neonicotinoids acetamiprid, clothianidin, imidacloporid, and thiamethoxam, as well as nicotine. We determined transcripts of several targets, including nicotinic acetylcholine receptor α 1 and α 2 subunit, the multifunctional gene vitellogenin, immune system genes apidaecin and defensin-1, stress-related gene catalase and two genes linked to memory formation, pka and creb. Vitellogenin showed a strong increase upon neonicotinoid exposures in the laboratory and field, while creb and pka transcripts were down-regulated. The induction of vitellogenin suggests adverse effects on foraging activity, whereas creb and pka down-regulation may be implicated in decreased long-term memory formation. Transcriptional alterations occurred at environmental concentrations and provide an explanation for the molecular basis of observed adverse effects of neonicotinoids to bees.

The up-regulation of protein phosphatase 2 A (PP2A) is an important factor leading to an inhibition of IFN␣ signaling caused by viral protein expression. Here, we describe the molecular mechanism involved in PP2Ac up-regulation by HCV and HBV. HCV and HBV protein expression in cells induces an ER stress response leading to calcium release from the ER. HCV protein expression induces CREB activation, probably through calcium/calmodulin-dependent protein kinase. CREB binds to a CRE element in the promoter of PP2Ac and induces its transcriptional up-regulation. Because PP2Ac is involved in many important cellular processes including cell-cycle regulation, apoptosis, cell morphology, development, signal transduction and translation, its up-regulation during ER stress has potentially important implications. (HEPATOLOGY 2007;46:558-565.)

Alpha interferon (IFN-␣) and pegylated IFN-␣ (pegIFN-␣) are used for the treatment of chronic hepatitis B (CHB). Unfortunately, only a minority of patients can be cured. The mechanisms responsible for hepatitis B virus (HBV) resistance to pegIFN-␣ treatment are not known. pegIFN-␣ is also used to treat patients with chronic hepatitis C (CHC). As with chronic hepatitis B, many patients with chronic hepatitis C cannot be cured. In CHC, IFN-␣ signaling has been found to be inhibited by an upregulation of protein phosphatase 2A (PP2A). PP2A inhibits protein arginine methyltransferase 1 (PRMT1), the enzyme that catalyzes the methylation of the important IFN-␣ signal transducer STAT1. Hypomethylated STAT1 is less active because it is bound by its inhibitor, PIAS1. In the present work, we investigated whether similar molecular mechanisms are also responsible for the IFN-␣ resistance found in many patients with chronic hepatitis B. We analyzed the expression of PP2A, the enzymatic activity of PRMT1 (methylation assays), the phosphorylation and methylation of STAT1, the association of STAT1 with PIAS1 (via coimmunoprecipitation assays), the binding of activated STAT1 to interferon-stimulated response elements (via electrophoretic mobility shift assays), and the induction of interferon target genes (via real-time RT-PCR) in human hepatoma cells expressing HBV proteins as well as in liver biopsies from patients with chronic hepatitis B and from controls. We found an increased expression of PP2A and an inhibition of IFN-␣ signaling in cells expressing HBV proteins and in liver biopsies of patients with CHB. The molecular mechanisms involved are similar to those found in chronic hepatitis C.More than 350 million people worldwide are chronically infected with hepatitis B virus (HBV) (19,21). Chronic hepatitis B (CHB) can progress to cirrhosis and hepatocellular carcinoma. Approved treatments for CHB include a few nucleos(t)ide analogues, such as lamivudine and adefovir, or alpha interferon (IFN-␣), recently in pegylated form (pegIFN-␣) (19). pegIFN-␣2a given for 48 weeks can induce the seroconversion of hepatitis B e antigen (HBeAg) in 32% of patients (20). However, over 60% of patients will continue to suffer from chronic active hepatitis B despite pegIFN-␣2a therapy. The molecular mechanisms responsible for the ineffectiveness of IFN-␣ treatments in CHB are not known. pegIFN-␣ (in combination with ribavirin) is also the current standard therapy for chronic hepatitis C (CHC). Interestingly, as with CHB, pegIFN-␣ is not effective in many patients with CHC. Over the last years, several molecular mechanisms responsible for viral evasion of the type I IFN system have been studied (10,14). One of these mechanisms involved in the evasion of hepatitis C virus (HCV) has been elucidated in our laboratory over the last years: HCV proteins interfere with IFN-␣-induced signaling through the Jak-STAT pathway (3,8,15).The interferon system is an important component of the host response against viruses, and mice with deficiencies of IFN re...

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