A prenylation inhibitor prevents production of infectious hepatitis delta virus particles

Hepatitis delta virus (HDV) causes both acute and chronic liver disease throughout the world. Effective medical therapy is lacking. Previous work has shown that the assembly of HDV virus-like particles (VLPs) could be abolished by BZA-5B, a compound with farnesyltransferase inhibitory activity. Here we show that FTI-277, another farnesyltransferase inhibitor, prevented the production of complete, infectious HDV virions of two different genotypes. Thus, in spite of the added complexity and assembly determinants of infectious HDV virions compared to VLPs, the former are also sensitive to pharmacological prenylation inhibition. Moreover, production of HDV genotype III virions, which is associated with particularly severe clinical disease, was as sensitive to prenylation inhibition as was that of HDV genotype I virions. Farnesyltransferase inhibitors thus represent an attractive potential class of novel antiviral agents for use against HDV, including the genotypes associated with most severe disease.     

Mechanism of asymmetric hydrogenation by rhodium complexes with unsymmetrical P-chirogenic bisphosphine ligands

Using a series of the rhodium complexes with (1S,2S)-1-(R(1))methylphosphino-2-(R(2))(R(3))phosphinoethane (R(1), R(2) and R(3) = 1-adamantyl, t-butyl, cyclohexyl, cyclopentyl, methyl; abbreviated as unsymmetrical BisP*), very high enantioselectivities were observed when the di- or tri- substituted and tetra-substituted dehydro-alpha-amino acid derivatives were used as the substrates. The main factor to give high enantioselectivity is the repulsive interaction between the functional groups of the substrate and the bulky substituents of the unsymmetrical BisP*. Since the unsymmetrical BisP* has two independent chiral phosphorous atoms in the vicinity of the active site, the higher enantioselectivity than those by the C2 symmetric BisP* complexes can be obtained. Moreover, the fine-tuning to obtain extremely high enantioselectivity may be possible by changing the combination of the substituents on the two phosphorous atoms of the unsymmetrical BisP*.     

Kinetic analysis of the effect of (-)-epigallocatechin gallate on the DNA scission induced by Fe(II)

The DNA strand scission induced by Fe(II) in a citrate buffer solution and the effect of (-)-epigallocatechin gallate (EGCg) were kinetically analyzed. The rate of consumption of dissolved oxygen by Fe(II) in each of these solutions was measured and paralleled that DNA scission. Coordinated EGCg accelerated these reactions. Curves of the time-course characteristics of DNA scission were simulated by using the rate constant of oxygen consumption and by assuming that scission with the hydroxyl radical (OH), which was formed from the dissolved oxygen, proceeded competitively with the scavenging of OH by citrate, Cl- ions and EGCg added. Free EGCg acted as a DNA scission inhibitor to scavenge OH, in contrast to the case of the coordinated one. This analysis is useful for estimating the rate constant of the reaction between an antioxidant and OH, and might provide a new method for measuring the OH-scavenging activity.     

Activation of ribosomal S6 kinase (RSK) during porcine oocyte maturation

The normal kinetics of ribosomal S6 kinase (RSK) during the meiotic maturation of porcine oocytes were examined. The phosphorylation states of RSK and extracellular signal-regulated kinase (ERK), major mitogen-activated protein (MAP) kinases in maturating porcine oocytes, were detected by Western blotting analysis. The S6 protein kinase activity was assayed using a specific substrate peptide which contained the major phosphorylation sites of S6 kinase. Full phosphorylation of RSK was correlated with ERK phosphorylation and was observed before germinal vesicle breakdown. S6 kinase activity was low in both freshly isolated and 20 h cultured oocytes. S6 kinase activity was significantly elevated in matured oocytes to a level about 6 times higher than that in freshly isolated oocytes. Furthermore, full phosphorylation of RSK was inhibited when oocytes were treated with U0126, a specific MAP kinase kinase inhibitor, in dose-dependent manner, indicating that RSK is one of the substrates of MAP kinase. These results suggest that the activation of RSK is involved in the regulation of meiotic maturation of porcine oocytes.     

Translesion replication of benzo[a]pyrene and benzo[c]phenanthrene diol epoxide adducts of deoxyadenosine and deoxyguanosine by human DNA polymerase iota

Human DNA polymerase ι (polι) is a Y-family polymerase whose cellular function is presently unknown. Here, we report on the ability of polι to bypass various stereoisomers of benzo[a]pyrene (BaP) diol epoxide (DE) and benzo[c]phenanthrene (BcPh) DE adducts at deoxyadenosine (dA) or deoxyguanosine (dG) bases in four different template sequence contexts in vitro. We find that the BaP DE dG adducts pose a strong block to polι-dependent replication and result in a high frequency of base misincorporations. In contrast, misincorporations opposite BaP DE and BcPh DE dA adducts generally occurred with a frequency ranging between 2 × 10^–3 and 6 × 10^–4. Although dTMP was inserted efficiently opposite all dA adducts, further extension was relatively poor, with one exception (a cis opened adduct derived from BcPh DE) where up to 58% extension past the lesion was observed. Interestingly, another human Y-family polymerase, polκ, was able to extend dTMP inserted opposite a BaP DE dA adduct. We suggest that polι might therefore participate in the error-free bypass of DE-adducted dA in vivo by predominantly incorporating dTMP opposite the damaged base. In many cases, elongation would, however, require the participation of another polymerase more specialized in extension, such as polκ.     

iNOS enhances rat intestinal apoptosis after ischemia-reperfusion

The aim of this study was to demonstrate (i) the role of iNOS (inducible nitric oxide synthase) on apoptosis in the rat intestinal mucosa after ischemia-reperfusion, and (ii) the effect of iNOS on the release of cytochrome c from mitochondria. The superior mesenteric artery was occluded for 60 min and was followed by a 60 min reperfusion. Rats were pretreated with an intraperitoneal injection of the following iNOS inhibitors: N-nitro-L-arginine methyl ester, aminoguanidine, and (1S,5S,6R,7R)-7- chloro-3-imino-5-methyl-2-azabicyclo [4. 1. 0] heptane hydrochloride (ONO-1714). Apoptosis was evaluated and NO(X) in the portal vein was assayed. The amount of iNOS, caspase-3, and cytochrome c were determined by a Western blot analysis. Intestinal mucosal epithelial mitochondrial dehydrogenase activity was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoilium bromide. Ischemia-reperfusion increased intestinal mucosal apoptosis, NO(X) production in the portal vein, the amount of iNOS protein, and the release of cytochrome c, but not caspase-3. Inhibitors of iNOS significantly attenuated the induction of apoptosis, increased NO(X) production, and release of cytochrome c. Mitochondrial dysfunction was induced by ischemia-reperfusion, which was ameliorated by iNOS inhibitors. Our results indicate that iNOS is related to increased mucosal apoptosis in the rat small intestine after ischemia-reperfusion, which is partly explained by the release of cytochrome c from mitochondria to cytosols following mitochondrial dysfunction.     

Relative biological effectiveness and tolerance dose of fission neutrons in canine skin for a potential combination of neutron capture therapy and fast-neutron therapy

To investigate the potential efficacy of fission neutrons from a fast-neutron reactor for the treatment of radioresistant tumors, the relative biological effectiveness (RBE) and tolerance dose of fission neutrons in canine skin were determined. The forelimbs of 34 healthy mongrel dogs received a single dose of fission neutrons (5.6, 6.8, 8.2, 9.6 or 11 Gy) or 137Cs gamma rays (10, 15, 20, 25 or 30 Gy). Based on observations of radiodermatitis for each radiation, the single-fraction RBE of fission neutrons in the sixth month was calculated as approximately 3. The tolerance doses of fission neutrons and gamma rays, defined as the highest doses giving no moist desquamation on the irradiated skin in the recovery phase, were estimated as 7.6 Gy and 20 Gy, respectively. The tolerance dose of 7.6 Gy of fission neutrons included 5.0 Gy of fast neutrons possessing high anti-tumor effects and 1.4 x 10(12) n/cm2 of thermal neutrons, which could be applicable to neutron capture therapy (NCT). The combination of fast-neutron therapy and NCT using a fast-neutron reactor might be useful for the treatment of radioresistant tumors.