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1.  Evaluation of Mitochondrial Toxicity in Marmota himalayana Treated with Metacavir, a Novel 2′,3′-Dideoxyguanosine Prodrug for Treatment of Hepatitis B Virus▿ 
Metacavir (PNA) is a novel synthetic nucleoside analogue for the treatment of hepatitis B virus (HBV). Our recent studies showed that PNA, a prodrug of 2′,3′-dideoxyguanosine (ddG), exhibited lower mitochondrial toxicity in long-term cultures of HepG2 cells. In the current study, we examined the long-term effects of PNA on mitochondrial toxicity in Marmota himalayana (Himalayan marmot). Himalayan marmots were treated daily with oral PNA (50 or 100 mg/kg), ziduvidine (AZT) (100 mg/kg), or water (control) for 90 days. PNA treatment did not alter the body weight or plasma lactate acid level. In livers from the animals treated with PNA at 100 mg/kg/day, histopathology showed mild steatosis or small focal liver cell necrosis. Electron microscopy also showed minor proliferation and partial mitochondrial swelling with crista reduction. Measurement of respiratory chain complex enzyme activity and mitochondrial DNA (mtDNA) content revealed no significant differences in skeletal muscle, liver, and kidney tissues between animals treated with PNA and controls. In contrast, in Himalayan marmots treated with AZT we observed delayed toxicity, including lactic acidosis, severe hepatic steatosis, obvious mitochondrial damage, and significant decreases in respiratory chain complex enzyme activity and mtDNA content. This is similar to the delayed toxicity syndrome observed previously in animals and humans. In summary, PNA treatment did not alter mitochondrial enzyme activity or mtDNA content. This suggests that PNA could pose a very low risk for adverse mitochondrion-related effects. However, long-term hepatotoxic effects of PNA were observed, and this indicates a need for continued monitoring of PNA-associated hepatotoxicity in clinical trials.
doi:10.1128/AAC.01520-10
PMCID: PMC3088222  PMID: 21282436
2.  In Vitro Mitochondrial Toxicity of Metacavir, a New Nucleoside Reverse Transcriptase Inhibitor for Treatment of Hepatitis B Virus ▿  
Antimicrobial Agents and Chemotherapy  2010;54(11):4887-4892.
Therapy with nucleoside reverse transcriptase inhibitors (NRTIs) can be associated with mitochondrial toxicity. In vitro studies have been used to predict the predisposition for and characterize the mechanisms causing mitochondrial toxicity. Metacavir (PNA) is a novel synthetic nucleoside analog for oral administration with potent and specific antiviral activity against hepatitis B virus (HBV). We assessed the potential for mitochondrial toxicity of PNA in long-term cultures of HepG2 hepatoma cells by measuring mitochondrial function (through lactate secretion), levels of mitochondrial DNA (mtDNA), and the activities of respiratory-chain complexes I to IV. Exposure of HepG2 cells to PNA at concentrations up to 50 μM for 15 days resulted in no deleterious effect on cell proliferation, levels of lactate or mtDNA, or enzyme activities of respiratory-chain complexes I to IV. In contrast, dideoxycytosine at 10 μM and zidovudine at 50 μM have significant effects on cell proliferation, levels of lactate and mtDNA, and enzyme activities of respiratory-chain complexes I to IV. However, PNA at a supratherapeutic concentration of 250 μM could result in significant alterations in the levels of mtDNA and the activities of respiratory-chain complex enzymes, revealing evidence of the potential mitochondrial toxicity of PNA. In summary, these in vitro results indicate that the potential for PNA to interfere with mitochondrial functions is low.
doi:10.1128/AAC.00794-10
PMCID: PMC2976109  PMID: 20805401
3.  A Novel Genotype H9N2 Influenza Virus Possessing Human H5N1 Internal Genomes Has Been Circulating in Poultry in Eastern China since 1998 ▿ †  
Journal of Virology  2009;83(17):8428-8438.
Many novel reassortant influenza viruses of the H9N2 genotype have emerged in aquatic birds in southern China since their initial isolation in this region in 1994. However, the genesis and evolution of H9N2 viruses in poultry in eastern China have not been investigated systematically. In the current study, H9N2 influenza viruses isolated from poultry in eastern China during the past 10 years were characterized genetically and antigenically. Phylogenetic analysis revealed that these H9N2 viruses have undergone extensive reassortment to generate multiple novel genotypes, including four genotypes (J, F, K, and L) that have never been recognized before. The major H9N2 influenza viruses represented by A/Chicken/Beijing/1/1994 (Ck/BJ/1/94)-like viruses circulating in poultry in eastern China before 1998 have been gradually replaced by A/Chicken/Shanghai/F/1998 (Ck/SH/F/98)-like viruses, which have a genotype different from that of viruses isolated in southern China. The similarity of the internal genes of these H9N2 viruses to those of the H5N1 influenza viruses isolated from 2001 onwards suggests that the Ck/SH/F/98-like virus may have been the donor of internal genes of human and poultry H5N1 influenza viruses circulating in Eurasia. Experimental studies showed that some of these H9N2 viruses could be efficiently transmitted by the respiratory tract in chicken flocks. Our study provides new insight into the genesis and evolution of H9N2 influenza viruses and supports the notion that some of these viruses may have been the donors of internal genes found in H5N1 viruses.
doi:10.1128/JVI.00659-09
PMCID: PMC2738149  PMID: 19553328

Results 1-3 (3)