Pyrimidine Nucleoside Depletion Sensitizes to the Mitochondrial Hepatotoxicity of the Reverse Transcriptase Inhibitor Stavudine

Abstract

Stavudine is a hepatotoxic antiretroviral nucleoside analogue that also inhibits the replication of mitochondrial DNA (mtDNA). To elucidate the mechanism and consequences of mtDNA depletion, we treated HepG2 cells with stavudine and either redoxal, an inhibitor of de novo pyrimidine synthesis, or uridine, from which pyrimidine pools are salvaged. Compared with treatment with stavudine alone, co-treatment with redoxal accelerated mtDNA depletion, impaired cell division, and activated caspase 3. These adverse effects were completely abrogated by uridine. Intracellular ATP levels were unaffected. Transcriptosome profiling demonstrated that redoxal and stavudine acted synergistically to induce CDKN2A and p21, indicating cell cycle arrest in G 1 , as well as genes involved in intrinsic and extrinsic apoptosis. Moreover, redoxal and stavudine showed synergistic interaction in the up-regulation of transcripts encoded by mtDNA and the induction of nuclear transcripts participating in energy metabolism, mitochondrial biogenesis, oxidative stress, and DNA repair. Genes involved in nucleotide metabolism were also synergistically up-regulated by both agents; this effect was completely antagonized by uridine. Thus, pyrimidine depletion sensitizes cells to stavudine-mediated mtDNA depletion and enhances secondary cell toxicity. Our results indicate that drugs that diminish pyrimidine pools should be avoided in stavudine-treated human immunodeficiency virus patients. Uridine supplementation reverses this toxicity and, because of its good tolerability, has potential clinical value for the treatment of side effects associated with pyrimidine depletion. (Am J Pathol 2008, 172:681-690;

Mitochondrial and Oxidative Stress Response in HepG2 Cells Following Acute and Prolonged Exposure to Antiretroviral Drugs

“…PGC-1α regulates mt gene transcription via interaction with nuclear respiratory factor 1 (NRF1) and 2, which in turn activates mt transcription factor A (TFAM) [Mallon et al, 2005]. Previous studies found that both PGC-1α and TFAM expressions were elevated in the presence of NRTIs, suggesting a nuclear response to mt toxicity [Mallon et al, 2005;Setzer et al, 2008]. Aside from its role in mt biogenesis, PGC-1α also acts as a modulator of mt AO response by increasing expression of oxidative stress protective genes [Valle et al, 2005;StPierre et al, 2006].…”

“…This opened up investigations into alternate mechanisms of mt toxicity. Other proposed targets of NRTI toxicity include ATP synthesis, mt biogenesis, depleted native nucleotide pools, transcription of mtDNA, mt membrane integrity and transport and protein synthesis [Setzer et al, 2008;Cohen, 2010].…”

“…The liver being the metabolic hub of humans is abundant in mitochondria. The HepG2 cell line has been widely used in previous studies evaluating the effect of antiretroviral drugs on mitochondrial toxicity [Birkus et al, 2002;Walker et al, 2002;Velsor et al, 2004;de Baar et al, 2007;Setzer et al, 2008]. HepG2 cells possess cytochrome P 450 activity and has hence been identified as an early model for xenobiotic metabolism [Roe et al, 1993].…”

Seguimiento fármaco-terapéutico en pacientes ambulatorios con tratamiento anti-retroviral

“…Además se observó aumento en los niveles de transaminasas producto del uso de efavirenz, que alcanzó grado 1 y 2 en nuestros pacientes. Sin embargo, es importante mencionar que existen informaciones sobre hepatotoxicidad grado 3 ó 4 asociada a este medicamento por lo que la monitorización de estos parámetros permitirá su detección precoz y la retirada del medicamento sospechoso de toxicidad 10,32,33 .…”

Drug-Induced Liver Injury

“…13 Dideoxynucleotide analogs, often used in the treatment of HIV, may impair mitochondrial DNA replication. 13,14 Drug toxicity may also result from the opening of the mitochondrial permeability transition pore (MPTP), which is strongly associated with cell death. 15 ROS generation, ATP depletion, and the aforementioned mitochondrial insults may combine to induce intracellular damage.…”