Azidothymidine causes functional and structural destruction of mitochondria, glutathione deficiency and HIV-1...

Mitochondrial functional and structural impairment and generation of oxidative stress have been implicated in aging, various diseases and chemotherapies. This study analyzed azidothymidine (AZT)-caused failures in mitochondrial functions, in redox regulation and activation of the HIV-1 gene expression. We monitored intracellular concentrations of ATP and glutathione (GSH) as the indicators of energy production and redox conditions, respectively, during the time-course experiments with U937 and MOLT4 human lymphoid cells in the presence of AZT (0.05 mg x mL(-1)) or H(2)O(2) (0.01 mm) for 15-25 days. Mitochondrial DNA integrity and NF-kappa B-driven HIV-1 promoter activity were also assessed. ATP concentration began to decrease within several days after exposure to AZT or H(2)O(2), and the decrease continued to reach 30-40% of the normal level. However, decline of GSH was detectable after a retention period for at least 5-6 days, and progressed likewise. PCR analyses found that mitochondrial DNA destruction occurred when the ATP and GSH depletion had progressed, detecting a difference in the deletion pattern between AZT and H(2)O(2)-treated cells. The GSH decrease coincided with HIV-1 promoter sensitization detected by enhanced DNA binding ability of NF-kappa B and induction of the gene expression upon H(2)O(2)-rechallenge. Our results suggest that, in the process of AIDS myopathy development, AZT or oxidative agents directly impair the energy-producing system of mitochondria, causing dysfunction of cellular redox control, which eventually leads to loss of the mitochondrial DNA integrity. The mechanism of cellular redox condition-mediated NF-kappa B activation is discussed.