Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019158 (hepatitis)
 30,205 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The two ribozymes of hepatitis delta virus (HDV) cleave faster in divalent metal ions than in monovalent cations, and a variety of divalent metal ions can act as catalysts in supporting these higher rates. Although the ribozymes are closely related in sequence and structure, they display a different metal ion preference; the genomic form cleaves moderately faster in Mg2+ than in Ca2+ while the reverse is true for the antigenomic ribozyme. This difference raises questions about understanding the catalytic role of the metal ion in the reaction. We found that the metal ion reactivity preference correlated with the identity of a single nucleotide 5' of the cleavage site (-1 position). It is a U in the genomic sequence and a C in the antigenomic sequence. With both ribozymes, the reactivity preference for Mg2+ and Ca2+ could be reversed with a change at this position (C to U or U to C). Moreover, with an A at position -1, there was a relative increase in cleavage rates in low concentrations of Mn2+ for both ribozymes. Metal ion reactivity preference was also linked to changes in pH, and the pH-rate profiles could be shifted with nucleotide changes at position -1. Together, the data provide biochemical evidence in support of an organized active site, as seen in the crystal structures, where at least one metal ion, an ionizable group, and the conformation of the phosphate backbone at the cleavage site interact in concert to promote cleavage.
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PMID:A single nucleotide linked to a switch in metal ion reactivity preference in the HDV ribozymes. 1741 76

Woodchuck hepatitis virus (WHV)-infected woodchucks have been used for preclinical development of drugs against hepatitis B virus (HBV). However, there is no simple in vivo model to evaluate small amounts of compounds against HBV. To develop such a model, HepAD38 cells, in which HBV replication is regulated by tetracycline (tet), were grown as subcutaneous tumours in nude mice. Mice developing viraemia were then left untreated or given tet in the drinking water. In some of the mice given tet, it was removed and the mice were injected intraperitoneally with phosphate buffer saline (PBS), lamivudine (3TC), clevudine (CLV) or tenofovir dipivoxil fumarate (TDF). Virus DNA titres were measured by real-time PCR during and after drug treatment. In water-fed and PBS-injected mice, virus titres reached approximately 10(9) copies/ml serum within 35 days of HepAD38 injection, whereas in tet-treated mice, virus titres remained at 10(4)-10(5) copies/ml. HBV DNA levels were suppressed by 3TC, TDF and CLV, with the latter two drugs showing more sustained virus suppression compared with 3TC. Combination therapy with CLV plus TDF was much more effective than either drug alone in suppressing virus titre for at least 3 weeks after the end of treatment. There was no demonstrable toxicity to HepAD38 cells in drug-treated mice. Hence, a robust tet-controlled system for HBV replication in vivo was demonstrated, validated with monotherapies against HBV and shown to be useful in assessing combination therapy. This system will be useful for preclinical assessment of small amounts of single or multiple compounds against HBV in vivo.
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PMID:Development of a novel mouse model to evaluate drug candidates against hepatitis B virus. 1790 79

Conserved molecular patterns of microbial pathogens, such as lipopolysaccharide (LPS) and cytosine-phosphate-guanine (CpG) DNA motifs are important signals for receptor-mediated activation of innate immune cells. It has been shown that the liver-specific transcription-blocking d-galactosamine (D-GalN) severely sensitizes to the lethal effects of LPS and CpG DNA. Lethality of LPS or CpG DNA in GalN-treated mice is entirely due to TNF-alpha, which leads to liver cell apoptosis and acute liver failure. We report that also polyinosinic-polycytidylic acid [poly(I:C)], a TLR-3 agonist, induces systemic TNF in mice. The increases of hepatic enzymes and induction of death induced by LPS, CpG DNA, and poly(I:C) in D-GalN sensitized mice are completely blocked by neutralizing anti-TNF-alpha antibodies and absent in TNF receptor p55-knockout mice. Our results provide direct evidence that poly(I:C) induces TNF-alpha in d-GalN sensitized mice, which leads to severe, acute, and TNF-dependent lethal hepatitis.
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PMID:Tumor necrosis factor alpha mediates the lethal hepatotoxic effects of poly(I:C) in D-galactosamine-sensitized mice. 1833 98

A Raman microscope and Raman difference spectroscopy are used to detect the vibrational signature of RNA-bound magnesium hydrate in crystals of hepatitis delta virus (HDV) ribozyme and to follow the effects of magnesium hydrate binding to the nonbridging phosphate oxygens in the phosphodiester backbone. There is a correlation between the Raman intensity of the innersphere magnesium hydrate signature peak, near 322 cm-1, and the intensity of the PO2- symmetric stretch, near 1100 cm-1, perturbed by magnesium binding, demonstrating direct observation of -PO2-...Mg2+(H2O)x innersphere complexes. The complexes may be pentahydrates (x = 5) and tetrahydrates (x = 4). The assignment of the Raman feature near 322 cm-1 to a magnesium hydrate species is confirmed by isotope shifts observed in D2O and H218O that are semiquantitatively reproduced by calculations. The standardized intensity changes in the 1100 cm-1 PO2- feature seen upon magnesium hydrate binding indicates that there are approximately 5 innersphere Mg2+...-O2P contacts per HDV molecule when the crystal is exposed to a solution containing 20 mM magnesium.
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PMID:Detection of innersphere interactions between magnesium hydrate and the phosphate backbone of the HDV ribozyme using Raman crystallography. 1859 25

[Structure: see text]. Five naturally occurring nucleolytic ribozymes have been identified: the hammerhead, hairpin, glmS, hepatitis delta virus (HDV), and Varkud satellite (VS) ribozymes. All of these RNA enzymes catalyze self-scission of the RNA backbone using a chemical mechanism equivalent to that of RNase A. RNase A uses four basic strategies to promote this reaction: geometric constraints, activation of the nucleophile, transition-state stabilization, and leaving group protonation. In this Account, we discuss the current thinking on how nucleolytic ribozymes harness RNase A's four sources of catalytic power. The geometry of the phosphodiester cleavage reaction constrains the nucleotides flanking the scissile phosphate so that they are unstacked from a canonical A-form helix and thus require alternative stabilization. Crystal structures and mutational analysis reveal that cross-strand base pairing, along with unconventional stacking and tertiary hydrogen-bonding interactions, work to stabilize the splayed conformation in nucleolytic ribozymes. Deprotonation of the 2'-OH nucleophile greatly increases its nucleophilicity in the strand scission reaction. Crystal structures of the hammerhead, hairpin, and glmS ribozymes reveal the N1 of a G residue within hydrogen-bonding distance of the 2'-OH. In each case, this residue has also been shown to be important for catalysis. In the HDV ribozyme, a hydrated magnesium has been implicated as the general base. Catalysis by the VS ribozyme requires both an A and a G, but the precise role of either has not been elucidated. Enzymes can lower the energy of a chemical reaction by binding more tightly to the transition state than to the ground states. Comparison of the hairpin ground- and transition-state mimic structures reveal greater hydrogen bonding to the transition-state mimic structure, suggesting transition-state stabilization as a possible catalytic strategy. However, the hydrogen-bonding pattern in the glmS ribozyme transition-state mimic structure and the ground-state structures are equivalent. Protonation of the 5'-O leaving group by a variety of functional groups can promote the cleavage reaction. In the HDV ribozyme, the general acid is a conserved C residue. In the hairpin ribozyme, a G residue has been implicated in protonation of the leaving group. An A in the hammerhead ribozyme probably plays a similar role. In the glmS ribozyme, an exogenous cofactor may provide the general acid. This diversity is in contrast to the relatively small number of functional groups that serve as a general base, where at least three of the nucleolytic ribozymes may use the N1 of a G.
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PMID:Catalytic strategies of self-cleaving ribozymes. 1865 94

Functional and crystallographic analyses of catalytically active RNA molecules ('ribozymes') have revealed a multitude of different routes by which nature accomplishes cleavage reactions of the RNA sugar-phosphate backbone. While there is agreement that these reactions involve general acid-base chemistry, the choice of 'acid' and of 'base' appears to be quite versatile. Among the numerous surprises that have emerged from these studies in recent years is the phenomenon of 'shifted pK(a) values' of nucleobases, hence, the fact that pK(a) values of isolated nucleobases in H(2)O can be shifted in either direction--upward or downward--into the physiological pH range, and that consequently allows these nucleobases to function as 'acids' or 'bases'. Another change in paradigm in recent years relates to the role of divalent metal ions in these catalytic reactions, which points to the possibility of an indirect involvement in the catalytic cycle rather than necessarily to a direct participation, as in the case with the hepatitis delta virus ribozyme. In this review, basic features of nucleobases and/or aqua ligand pK(a) shifts caused by metal coordination and H-bonding are discussed.
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PMID:Ligand-pKa shifts through metals: potential relevance to ribozyme chemistry. 1872 8

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. Some reports also suggest that it causes extragastric disease, including hepatitis. In this study, the pathological changes in the liver and gall bladder in H. pylori-colonized C57BL/6 mice were investigated. Twenty mice were inoculated orally with H. pylori strain SS1, and ten controls were injected with phosphate-buffered saline. Gastric colonization with H. pylori was assessed at 2 months after inoculation. Mice were examined at 8 months by histopathology, culture for H. pylori, and PCR for specific H. pylori genes. All C57BL/6 mice infected with H. pylori for 8 months developed severe gastric mucosal inflammation. Three mice showed mild-to-moderate multifocal hepatitis. The gall bladder mucosa of one H. pylori-infected mouse showed thickening of the mucous membrane with mild submucosal lymphocytic infiltration. H. pylori was observed morphologically in four liver specimens and six gall bladders from infected mice by immunohistochemistry. Specific H. pylori genes were also detected in six liver samples from infected mice, six samples of bile, and two blood samples by nested PCR. Thus, H. pylori inoculated orally may reach the hepatobiliary system and cause inflammation as an independent aetiological factor. The pathway to the liver may be via the blood or the biliary system.
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PMID:The pathological effect of Helicobacter pylori infection on liver tissues in mice. 1939 1

Coronaviruses are positive-strand RNA viruses with features attractive for oncolytic therapy. To investigate this potential, we redirected the coronavirus murine hepatitis virus (MHV), which is normally unable to infect human cells, to human tumor cells by using a soluble receptor (soR)-based expression construct fused to an epidermal growth factor (EGF) receptor targeting moiety. Addition of this adapter protein to MHV allowed infection of otherwise nonsusceptible, EGF receptor (EGFR)-expressing cell cultures. We introduced the sequence encoding the adaptor protein soR-EGF into the MHV genome to generate a self-targeted virus capable of multiround infection. The resulting recombinant MHV was viable and had indeed acquired the ability to infect all glioblastoma cell lines tested in vitro. Infection of malignant human glioblastoma U87DeltaEGFR cells gave rise to release of progeny virus and efficient cell killing in vitro. To investigate the oncolytic capacity of the virus in vivo, we used an orthotopic U87DeltaEGFR xenograft mouse model. Treatment of mice bearing a lethal intracranial U87DeltaEGFR tumor by injection with MHVsoR-EGF significantly prolonged survival compared to phosphate-buffered saline-treated (P = 0.001) and control virus-treated (P = 0.004) animals, and no recurrent tumor load was observed. However, some adverse effects were seen in normal mouse brain tissues that were likely caused by the natural murine tropism of MHV. This is the first demonstration of oncolytic activity of a coronavirus in vivo. It suggests that nonhuman coronaviruses may be attractive new therapeutic agents against human tumors.
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PMID:Coronavirus genetically redirected to the epidermal growth factor receptor exhibits effective antitumor activity against a malignant glioblastoma. 1943 66

Activities of sphingomyelinase and ceramidase decreased in the liver in chronic toxic hepatitis and the balance between the levels of proapoptotic ceramide and antiapoptotic sphyngosine-1-phosphate shifts towards the latter substance. Pronounced changes in the qualitative and quantitative composition of fatty acids in the sphingomyelin cycle effector molecules were revealed.
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PMID:Functional activity of sphingomyelin cycle in rat liver in chronic toxic hepatitis. 1951 67

A 24-year-old man was referred to our clinic in August 2003 with complaints of weakness, dizziness, and bilateral knee pain of 3 years' duration. Bilateral digital clubbing had been found on routine physical examination during his military service 4 years earlier. There were no cardiorespiratory or abdominal symptoms. There was no compromise in the activities of everyday life. The patient was not a chronic smoker. In the family history of the patient, his brother had been diagnosed with pachydermoperiostosis in another center 2 years earlier, but did not return to the hospital for a follow-up investigation of myelofibrosis. On physical examination, the patient showed marked drumstick clubbing of the hands (Fig. 1), and a pale general appearance. The causes of digital clubbing are shown in Table 1 (Fawcett RS, Linford S, Stulberg DL. Nail abnormalities: clues to systemic disease. Am Fam Physician 2004; 69: 1417-1424). Deep nasolabial folds were seen on the face. Skin hypertrophy, cutis verticis gyrata, and seborrhea on the face were also observed. The patient also complained of hyperhidrosis. Examination of the cardiovascular system was normal. There was bilateral swelling of the ankle and knee (Fig. 2). Hepatosplenomegaly was found on abdominal examination. Investigations showed hypochromic microcytic anemia [hemoglobin, 8.58 g/dL (normal, 12.2-18.1 g/dL); hematocrit, 28.1% (normal, 37.7-53.7%); white blood cell count, 3430/mm(3) (normal, 4600-10,200/mm(3)); neutrophils, 2470/mm(3) (normal, 2000-6900/mm(3)); lymphocytes, 820/mm(3) (normal, 600-3400/mm(3)); platelets, 162,000/mm(3) (normal, 142,000-424,000 mm(3)); mean corpuscular volume, 73.7 fL (normal, 80-97 fL)]. Anisocytosis, poikilocytosis, microcytosis, and hypochromia were observed on peripheral blood examination, and the erythrocyte sedimentation rate was 37 mm/h. The serum C-reactive protein level was 50.1 mg/L (normal, 0-5 mg/L). Biochemical parameters, including serum calcium, phosphate, alkaline phosphates and liver function tests, were found to be within the normal range. The causes of secondary hypertrophic osteoarthropathy associated with pulmonary, rheumatologic, endocrine, cardiac, and gastroenterologic disorders were excluded. Growth hormone level and thyroid function tests were normal. Antinuclear antibody, TORCH [Toxoplasma immunoglobulin M (IgM), rubella IgM, cytomegalovirus IgM, herpes simplex IgM] panel, and markers of hepatitis were negative. Serum Igs and rheumatoid factor were found to be within the normal range. There was subperiosteal new bone formation on bilateral knee X-ray (Fig. 3). Radiography of the chest, pulmonary function tests, arterial blood gas, and echocardiography were normal. Abdominal ultrasonography revealed hepatosplenomegaly. Amyloid deposition was not determined in rectal biopsy. Reticulin-type myelofibrosis was found on bone marrow biopsy (Figs 4 and 5). In the cytogenetic study, monosomy 22 was detected in four of 20 metaphase plates.
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PMID:An interesting case of pachydermoperiostosis with idiopathic myelofibrosis associated with monosomy 22. 1965 69


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