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Mitochondrial reactive oxygen species (ROS) play a central role in most aging-related diseases. ROS are produced at the respiratory chain that demands NADH for electron transport and are eliminated by enzymes that require NADPH. The nicotinamide nucleotide transhydrogenase (Nnt) is considered a key antioxidative enzyme based on its ability to regenerate NADPH from NADH. Here, we show that pathological metabolic demand reverses the direction of the Nnt, consuming NADPH to support NADH and ATP production, but at the cost of NADPH-linked antioxidative capacity. In heart, reverse-mode Nnt is the dominant source for ROS during pressure overload. Due to a mutation of the Nnt gene, the inbred mouse strain C57BL/6J is protected from oxidative stress, heart failure, and death, making its use in cardiovascular research problematic. Targeting Nnt-mediated ROS with the tetrapeptide SS-31 rescued mortality in pressure overload-induced heart failure and could therefore have therapeutic potential in patients with this syndrome.

Plasma from 173 patients with HCV genotype 1 infection was analyzed for IP-10 levels prior to treatment with pegylated interferon-␣-2a and ribavirin. Significantly lower IP-10 levels were observed in patients achieving a rapid viral response (RVR) (P < .0001), even in those with body mass index (BMI) > 25 kg/m 2 (P ‫؍‬ .004) and with baseline viral load > 2 million IU/mL (P ‫؍‬ .001). Similarly, significantly lower IP-10 levels were observed in patients obtaining a sustained viral response (SVR) (P ‫؍‬ .0002), including those having higher BMI (P < .05), higher viral load (P ‫؍‬ .0005), and both higher BMI and viral load (P < .03). In multivariate logistic regression analyses, a low IP-10 value was independently predictive of both RVR and SVR. A baseline cutoff IP-10 value of 600 pg/mL yielded a negative predictive value (NPV) of 79% (19/24) for all genotype 1-infected patients, which was comparable with that observed using a reduction in HCV-RNA by at least 2 logs after 12 weeks of therapy (NPV 86%; 19/22); by combining the two, 30 of 38 patients (NPV 79%) potentially could have been spared unnecessary therapy. In patients having both higher BMI and viral load, cut-off levels of 150 and 600 pg/mL yielded a positive predictive value (PPV) of 71% and NPV of 100%, respectively. In conclusion, pretreatment IP-10 levels predict RVR and SVR in patients infected with HCV genotype 1, even in those with higher BMI and viral load. A substantial proportion of the latter patients may achieve SVR in spite of unfavorable baseline characteristics if their pretreatment IP-10 level is low. Thus, pretreatment IP-10 analysis may prove helpful in decision-making regarding pharmaceutical intervention. (HEPATOLOGY 2006;44:1617-1625

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Delayed-rectifier K؉ currents (I DR ) in pancreatic ␤-cells are thought to contribute to action potential repolarization and thereby modulate insulin secretion. The voltagegated K ؉ channel, K V 2.1, is expressed in ␤-cells, and the biophysical characteristics of heterologously expressed channels are similar to those of I DR in rodent ␤-cells. A novel peptidyl inhibitor of K V 2.1/K V 2.2 channels, guangxitoxin (GxTX)-1 (half-maximal concentration ϳ1 nmol/l), has been purified, characterized, and used to probe the contribution of these channels to ␤-cell physiology. In mouse ␤-cells, GxTX-1 inhibits 90% of I DR and, as for K V 2.1, shifts the voltage dependence of channel activation to more depolarized potentials, a characteristic of gating-modifier peptides. GxTX-1 broadens the ␤-cell action potential, enhances glucose-stimulated intracellular calcium oscillations, and enhances insulin secretion from mouse pancreatic islets in a glucose-dependent manner. These data point to a mechanism for specific enhancement of glucose-dependent insulin secretion by applying blockers of the ␤-cell I DR , which may provide advantages over currently used therapies for the treatment of type 2 diabetes.

In patients with heart failure, reactivation of a fetal gene program, including atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), is a hallmark for maladaptive remodeling of the LV. The mechanisms that regulate this reactivation are incompletely understood. Histone acetylation and methylation affect the conformation of chromatin, which in turn governs the accessibility of DNA for transcription factors. Using human LV myocardium, we found that, despite nuclear export of histone deacetylase 4 (HDAC4), upregulation of ANP and BNP in failing hearts did not require increased histone acetylation in the promoter regions of these genes. In contrast, di-and trimethylation of lysine 9 of histone 3 (H3K9) and binding of heterochromatin protein 1 (HP1) in the promoter regions of these genes were substantially reduced. In isolated working murine hearts, an acute increase of cardiac preload induced HDAC4 nuclear export, H3K9 demethylation, HP1 dissociation from the promoter region, and activation of the ANP gene. These processes were reversed in hearts with myocytespecific deletion of Hdac4. We conclude that HDAC4 plays a central role for rapid modifications of histone methylation in response to variations in cardiac load and may represent a target for pharmacological interventions to prevent maladaptive remodeling in patients with heart failure.

Treatment of patients with chronic hepatitis C with recombinant interferon alfa (rIFN-␣) can achieve clearance of the hepatitis C virus (HCV) from serum and liver. However, the overall sustained virological response to IFN-␣ monotherapy is less than 20%. 1,2 Additional clinical trials have been conducted to evaluate alternative treatment modalities in chronic hepatitis C, including therapy with ribavirin. While ribavirin monotherapy revealed no consistent effect on HCV RNA relative to placebo, 3,4 results of combination therapy with subcutaneously administered rIFN-␣ and orally administered ribavirin suggested a potential synergistic effect. [5][6][7] Ribavirin (1-␤-D-ribofuranosyl-1H-1,2,4-triazole-3-carboxamide) is a synthetic purine nucleoside that is structurally similar to guanosine. The drug rapidly enters eukaryotic cells, and after intracellular phosphorylation exhibits virustatic activity against a broad spectrum of DNA and RNA viruses. Several possible mechanisms of action have been proposed, including depletion of the intracellular guanosine triphosphate pools, synthesis of RNA with abnormal 5Јcap structures, and inhibition of viral polymerase activity. Furthermore, ribavirin has detectable effects on host immune responses. The detailed mechanism of action, however, is unknown. 4,8 In the present study, we treated patients chronically infected with HCV with either 3 ϫ 3 MU rIFN-␣ per week, 3 ϫ 6 MU rIFN-␣ per week, or 3 ϫ 6 MU rIFN-␣ per week plus 14 mg/kg of body weight ribavirin per day to perturb the balance between virus production and clearance. From serial measurements of changes in viremia in patients responding to antiviral therapy, we obtained kinetic information on the dynamics of HCV replication in vivo. Numerical data modeling was performed to compare the direct antiviral efficacy of the three different treatment schedules. PATIENTS AND METHODSIn this study, 26 patients chronically infected with HCV were treated with 3 MU rIFN-␣ three times per week subcutaneously. In a different cohort of 37 patients, we administered 6 MU rIFN-␣ three times per week subcutaneously. Eighteen patients of this cohort were randomized to receive ribavirin (14 mg per kg of body weight, i.e., 900-1,200 mg) in two divided doses orally per day. Duration of treatment is scheduled for 12 months; the trials are ongoing. All patients were previously untreated, and the diagnosis of chronic hepatitis C was based on elevated serum transaminase levels, histological examination, and the consistent detection of anti-HCV antibodies (third-generation assay) and HCV RNA. All patients were hepatitis B surface antigen-negative and negative for the antibody to the human immunodeficiency virus type 1 and type 2. Blood samples were obtained 4 and 1 week before initiation of treatment and subsequently at days 0, 1, 3, 7, 14, 21, 28, and 56. Serum was prepared under a laminar flow bench and frozen at Ϫ80°C. Serum HCV RNA levels were quantified as recently described in detail. [9][10][11] Abbreviations: rIFN-␣, recombinant interferon ...