Azidothymidine causes functional and structural destruction of mitochondria, glutathione deficiency and HIV‐1 promoter sensitization

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.