This project defines in vivo mechanisms of acquired mitochondria! (mt-) DNA depletion caused by nucleoside reverse transcriptase inhibitors (NRTI) for HIV/AIDS. Survival with HIV/AIDS improved because of pyrimidine NRTIs like zidovudine (AZT) and stavudine (d4T), but NRTI mitochondrial toxicity limits therapy and mani- fests as mtDNA depletion and organ dysfunction. The """"""""DNA pol y hypothesis"""""""" underscores NRTI phosphor- ylation (to active moieties) and inhibition of DNA pol y (the mtDNA replicase) by NRTI triphosphates (-TP) in the mechanism of acquired mtDNA depletion. Cellular kinases control mitochondrial nucleotide and NRTI phosphorylations. Pyrimidine NRTIs compete with dThd for phosphorylation to monophosphates (-MP) by thymidine kinase (cytoplasmic TK1 and mitochondrial TK2 isoforms) and to diphosphates (-DP) by thymidylate kinase (TMPK). The working hypothesis states: Transgenic (TG) over-expression of wild type (WT) TK2 or WT TMPK promotes mtDNA replication by increasing the mitochondrial dTTP mass in parallel with increased enzyme abundance. TGs with TMPK mutants (""""""""gain of function"""""""") are active with dTMP phosphorylation, but exhibit enhanced activity with AZTMP. In absence of AZT, these TGs each increases dTTP abundance. With AZT therapy, AZT-DP abundance increases dramatically and is imported into mito- chondria for phosphorylation to AZT-TP. Conversely, TGs harboring specific TK2 point mutations decrease TK2 activity (""""""""loss of function""""""""). These latter TGs deplete mtDNA by limiting mitochondrial dTMP for down- stream intra-mitochondrial processing. AZT treatment here enhances mtDNA depletion by AZT's competition with dThd for phosphorylation by TK2. Mitochondrial AZT-TP competes with dTTP for incorporation into mtDNA by DNA pol y. This inhibits mtDNA replication, causes mtDNA depletion and mutation, mitochondrial dysfunction, and organ dysfunction.
AIM 1 defines molecular, pathological and physiological events in mtDNA depletion from NRTIs (like AZT) using TGs with cardiac targeted, conditional, overexpression of WT TMPK, chimeric TMPK, and mutant TMPK.
AIM 2 defines molecular, pathological, and physiological events in mtDNA depletion from NRTIs (like AZT) using TGs with cardiac targeted, conditional, overexpressionof WT TK2 and mutant TK2. Experiments offer insights into improving therapy with antiretrovirals used in AIDS.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Study Section
AIDS Discovery and Development of Therapeutics Study Section (ADDT)
Program Officer
Reid, Diane M
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Emory University
Schools of Medicine
United States
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Koczor, Christopher A; White, Richard C; Zhao, Peter et al. (2012) p53 and mitochondrial DNA: their role in mitochondrial homeostasis and toxicity of antiretrovirals. Am J Pathol 180:2276-83
Kohler, James J; Hosseini, Seyed H (2011) Subcellular renal proximal tubular mitochondrial toxicity with tenofovir treatment. Methods Mol Biol 755:267-77
Kushnir, Vitaly A; Lewis, William (2011) Human immunodeficiency virus/acquired immunodeficiency syndrome and infertility: emerging problems in the era of highly active antiretrovirals. Fertil Steril 96:546-53
Kohler, James J; Hosseini, Seyed H; Green, Elgin et al. (2011) Tenofovir renal proximal tubular toxicity is regulated by OAT1 and MRP4 transporters. Lab Invest 91:852-8
Kohler, James J; Hosseini, Seyed H; Green, Elgin et al. (2010) Absence of mitochondrial toxicity in hearts of transgenic mice treated with abacavir. Cardiovasc Toxicol 10:146-51
Kohler, James J; Hosseini, Seyed H; Cucoranu, Ioan et al. (2010) Transgenic cardiac-targeted overexpression of human thymidylate kinase. Lab Invest 90:383-90
Kohler, James J; Cucoranu, Ioan; Fields, Earl et al. (2009) Transgenic mitochondrial superoxide dismutase and mitochondrially targeted catalase prevent antiretroviral-induced oxidative stress and cardiomyopathy. Lab Invest 89:782-90
Kohler, James J; Hosseini, Seyed H; Hoying-Brandt, Amy et al. (2009) Tenofovir renal toxicity targets mitochondria of renal proximal tubules. Lab Invest 89:513-9
Kohler, James J; Hosseini, Seyed H; Cucoranu, Ioan et al. (2009) Murine cardiac mtDNA: effects of transgenic manipulation of nucleoside phosphorylation. Lab Invest 89:122-30
Kohler, James J; Hosseini, Seyed H; Lewis, William (2008) Mitochondrial DNA impairment in nucleoside reverse transcriptase inhibitor-associated cardiomyopathy. Chem Res Toxicol 21:990-6

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