Characterization of a mouse neuropathic pain model caused by the highly active antiviral therapy (HAART) Stavudine.

BACKGROUND: Although highly active antiviral therapies (HAART) exert control over viral replication in persons with Acquired Immunodeficiency Syndrome (AIDS), neuropathic pain is a side effect. Symptoms include hyperalgesia and allodynia. Stavudine, also known as D4T, is a HAART used to treat Human Immunodeficiency Virus (HIV). This study examined the extent to which D4T produces neuropathic pain and examined pharmacological management with a standard opioid analgesic. METHODS: Male and female C57BL/6 J mice were injected intraperitoneally with one dose of vehicle or D4T (10-56 mg/kg). Mice were tested through day 92 post injection for mechanical allodynia, assessed with von Frey filaments, and thermal hyperalgesia, assessed via the hotplate test. Separate cohorts received vehicle or 56 mg/kg D4T, the presence of allodynia and thermal hyperalgesia confirmed, and mice received intraperitoneal vehicle, morphine, or 0.032 mg/kg naltrexone + morphine. RESULTS: D4T produced dose- and time-dependent mechanical allodynia and thermal hyperalgesia. The smallest effective D4T dose was 17.8 mg/kg. This dose produced mechanical allodynia but not thermal hyperalgesia. Larger D4T doses (32 and 56 mg/kg) produced mechanical allodynia and thermal hyperalgesia lasting 92 days. Morphine dose-dependently alleviated both mechanical allodynia and thermal hyperalgesia in D4T-treated mice with ED50 values of 4.4 and 1.2 mg/kg, respectively. Naltrexone produced a rightward shift of the morphine dose-response function, i.e., increased the ED50 value of morphine by at least 3.8-fold. CONCLUSION: Stavudine produced neuropathic pain as a function of dose and time in mice. Opioid analgesics appear to be effective in alleviating neuropathic pain in a D4T-induced mouse model.

Stavudine exposure results in developmental abnormalities by causing DNA damage, inhibiting cell proliferation and inducing apoptosis in mouse embryos.

Stavudine is an anti-AIDS drug widely used to prevent HIV transmission from pregnant mothers to the fetuses in underdeveloped countries for its low price. However, there is still a controversy on whether stavudine affects embryo development. In the current study, embryotoxicity of stavudine was evaluated using cultured mouse embryos with the concentrations: 5, 10, 15 µM and vehicle control. The data indicated that the effect of stavudine was dose-dependent at early neurogenesis. Stavudine exposure reduced somite numbers, yolk sac diameter, crown-rump length, and increased the rate of embryonic degeneration compared with the control. We chose the lowest but clearly toxic concentration: 5 µM to investigate the molecular mechanisms of the damage. At the molecular level, stavudine produced DNA damage, increased the levels of the phospho-CHK1 and cleaved-caspase-3, and decreased the expression level of proliferating cell nuclear antigen. These changes indicated that stavudine caused a coordinated DNA damage response, inhibited cell proliferation, and induced apoptosis in the embryos. Collectively these results suggest that stavudine exposure disturbs the embryonic development, and its use in pregnant mothers should be re-examined.

Reasons for first line ART modification over the years during the ART scale up in Uganda.

BACKGROUND: During the initial scale up of ART in sub-Saharan Africa, prescribed regimens included drugs with high potential for toxicity (particularly stavudine). More recently a growing number of patients requires second line treatment due to treatment failure, especially following the expansion of viral load testing. We aim to determine the reasons and risk factors for modification of first line ART across the years. METHODS: We included patients started on standard first line ART (2NRTI + 1 NNRTI) between 2005 and 2016 at the Infectious Diseases Institute, Kampala, Uganda. We described the reasons for treatment modification categorized in (1) toxicity (2) treatment failure (3) other reason (new TB treatment, new pregnancy). We used Cox proportional hazard to identify factors associated with treatment modification due to toxicity. RESULTS: We included 14,261 patients; 9114 (63.9%), were female, the median age was 34 years (IQR: 29-40), 60.8% were in WHO stage 3 and 4. The median BMI and CD4 count were 21.9 (IQR: 19.6-24.8) and 188 cell/µL (IQR: 65-353) respectively; 27.5% were started on stavudine, 46% on zidovudine, and 26.5% on a tenofovir containing regimens. We observed 6248 ART modifications in 4868/14,261 patients (34.1%); 1615 were due to toxicity, 1077 to treatment failure, 1330 to contraindications, and 1860 patients following WHO recommendation of phasing out stavudine and substituting with another NRTI. Modification for drug toxicity declined rapidly after the phase out of stavudine (2008), while switches to second line regimes increased after the implementation of viral load monitoring (2015). Patients with normal BMI compared to underweight, (HR: 0.79, CI 0.69-0.91), with CD4 counts 200-350 cells/µL compared to < 200 cells/µL (HR: 0.81- CI 0.71-0.93), and started on zidovudine (HR: 0.51 CI 0.44-0.59) and tenofovir (HR: 0.16, CI 0.14-0.22) compared to stavudine were less likely to have ART modification due to toxicity. Older patients (HR: 1.14 per 5-year increase CI 1.11-1.18), those in WHO stage 3 and 4 (HR: 1.19, CI 1.06-1.34) were more likely to have ART modification due to toxicity. CONCLUSIONS: Toxicity as reason for drugs substitution decreased over time mirroring the phase out of stavudine, while viral load expansion identified more patients in need of second line treatment.

Removal of antiretroviral drugs stavudine and zidovudine in water under UV254 and UV254/H2O2 processes: Quantum yields, kinetics and ecotoxicology assessment.

The concentration of antiretroviral drugs in wastewater treatment plants (WWTP) effluents and surface waters of many countries has increased significantly due to their widespread use for HIV treatment. In this study, the removal of stavudine and zidovudine under UV254 photolysis or UV254/H2O2 was investigated in a microcapillary film (MCF) photoreactor, using minimal water samples quantities. The UV254 quantum yield of zidovudine, (2.357 ±â€¯0.0589)·10-2 mol ein-1 (pH 4.0-8.0), was 28-fold higher that the yield of stavudine (8.34 ±â€¯0.334)·10-4 mol ein-1 (pH 6.0-8.0). The second-order rate constant kOH,iof reaction of hydroxyl radical with the antiretrovirals (UV254/H2O2 process) were determined by kinetics modeling: (9.98 ±â€¯0.68)·108 M-1 s-1 (pH 4.0-8.0) for zidovudine and (2.03 ±â€¯0.18)·109 M-1 s-1 (pH 6.0-8.0) for stavudine. A battery of ecotoxicological tests (i.e. inhibition growth, bioluminescence, mutagenic and genotoxic activity) using bacteria (Aliivibrio fischeri, Salmonella typhimurium), crustacean (Daphnia magna) and algae (Raphidocelis subcapitata) revealed a marked influence of the UV dose on the ecotoxicological activity. The UV254/H2O2 treatment process reduced the ecotoxicological risk associated to direct photolysis of the antiretrovirals aqueous solutions, but required significantly higher UV254 doses (≥2000 mJ cm-2) in comparison to common water UV disinfection processes.

A Direct Comparison of the Effects of the Antiretroviral Drugs Stavudine, Tenofovir and the Combination Lopinavir/Ritonavir on Bone Metabolism in a Rat Model.

Antiretroviral (ARV) treatment may induce metabolic complications in HIV patients on long-term therapy that can affect bone health. In this study, the effects of the ARVs Stavudine (d4T), Tenofovir (TDF) and Lopinavir/ritonavir (LPV/r) on bone metabolism and lipodystrophy were directly compared in rats to negate the consequences of HIV-associated confounding factors. Healthy 12-14-week-old male Wistar rats (n = 40) were divided into four treatment groups and received an oral animal equivalent dose of either Stavudine (6.2 mg/kg/day), TDF (26.6 mg/kg/day), LPV/r (70.8 mg/kg/day) or water (Control 1.5 mL water/day) for a period of 9 weeks. Whole-body DXA measurements, a biomechanical three-point breaking test and histomorphometric analysis were performed on the femurs and tibias at the end of the treatment period. Stavudine monotherapy was found to be associated with decreased femoral bone mineral density that translated into reduced bone strength, whereas histomorphometric analysis demonstrated that Stavudine induces an imbalance in bone metabolism at tissue level, evident in higher resorption (eroded surfaces, osteoclast surfaces and osteoclast number) and lower formation parameters (osteoblast surfaces and osteoid surfaces). This was less clear in the rats treated with either TDF or LPV/r. Furthermore, both Stavudine and TDF treatment resulted in significant bone marrow adiposity, although no significant redistribution of body fat was noted in the treated rats compared to controls. The data from this study suggest that in the absence of HIV-associated factors, LPV/r is less detrimental to bone metabolism compared to Stavudine and TDF.

Niflumic acid, a TRPV1 channel modulator, ameliorates stavudine-induced neuropathic pain.

TRP channels have been discovered as a specialized group of somatosensory neurons involved in the detection of noxious stimuli. Desensitization of TRPV1 located on dorsal root and trigeminal ganglia exhibits analgesic effect and makes it potential therapeutic target for treatment of neuropathic pain. With this background, the present study was aimed to investigate the protective effect of niflumic acid, a TRPV1 modulator, on stavudine (STV)-induced neuropathic pain in rats. Stavudine (50 mg/kg) was administered intravenously via tail vein in rats to induce neuropathic pain. Various behavioral tests were performed to access neuropathic pain (hyperalgesia and allodynia) on 7th, 14th, 21st, and 28th days. Electrophysiology (motor nerve conduction velocity; MNCV) and biochemical estimations were conducted after 28th day. Niflumic acid (10, 15, and 20 mg/kg) was administered intraperitoneally and evaluated against behavioral, electrophysiological (MNCV), and biochemical alterations in stavudine-treated rats. Pregabalin (30 mg/kg) was taken as reference standard and administered intraperitoneally. Four weeks after stavudine injection, rats developed behavioral, electrophysiological (MNCV), and biochemical (oxidative, nitrosative stress, and inflammatory cytokines, TRPV1) alterations. Niflumic acid restored core and associated symptoms of peripheral neuropathy by suppressing oxidative-nitrosative stress, inflammatory cytokines (TNF-α, IL-1ß) and TRPV1 level in stavudine-induced neuropathic pain in rats. Pharmacological efficacy of niflumic acid (20 mg/kg) was equivalent to pregabalin (30 mg/kg). In conclusion, niflumic acid attenuates STV-induced behavioral, electrophysiological and biochemical alterations by manipulating TRP channel activity in two manners: (1) direct antagonistic action against TRPV1 channels and (2) indirect inhibition of TRP channels by blocking oxidative and inflammatory surge. Therefore, NA can be developed as a potential pharmacotherapeutic adjunct for antiretroviral drug-induced neuropathy.

Behavioral and electrophysiological abnormalities in two rat models of antiretroviral drug-induced neuropathy.

Painful peripheral neuropathy due to the antiretroviral therapy used to treat HIV is one of the most prevalent side effects occurring in at least 30% of patients living with this infection. We have evaluated the electrophysiological and behavioral effects of d4T and ddC on peripheral large and small nerve fibers in male rats treated with d4T (Sprague-Dawley, 50 mg/kg, twice within 1 week), ddC (Wistar, 50 mg/kg, 3 times per week for 3 weeks), or vehicle. The effect of the interventions was assessed using behavioral measures of mechanical sensitivity, conventional nerve conduction studies, and microneurographic single nerve C-fiber recordings. To mimic as much as possible the human clinical condition, all treated animals were included in the study. No statistically significant differences were observed in behavioral parameters of mechanical sensitivity. Nerve conduction studies did not reveal any significant change in the ddC-treated group. In contrast, we observed electrophysiological evidence of significant demyelinating neuropathy 1 week after the start of d4T treatment. Additionally, spontaneous activity in mechanoinsensitive C-nociceptors was observed in both drug-treated groups. No relationship could be established between measures of spontaneous activity in C-nociceptors and the results of the behavioral tests. Our results show that both models of antiretroviral-induced neuropathy differ in their effects on peripheral nerves. However, both groups present abnormal spontaneous activity in mechanoinsensitive C-nociceptors that can be used as a model for pharmacological intervention.

Caenorhabditis elegans as a Model System for Studying Drug Induced Mitochondrial Toxicity.

Today HIV-1 infection is recognized as a chronic disease with obligatory lifelong treatment to keep viral titers below detectable levels. The continuous intake of antiretroviral drugs however, leads to severe and even life-threatening side effects, supposedly by the deleterious impact of nucleoside-analogue type compounds on the functioning of the mitochondrial DNA polymerase. For detailed investigation of the yet partially understood underlying mechanisms, the availability of a versatile model system is crucial. We therefore set out to develop the use of Caenorhabditis elegans to study drug induced mitochondrial toxicity. Using a combination of molecular-biological and functional assays, combined with a quantitative analysis of mitochondrial network morphology, we conclude that anti-retroviral drugs with similar working mechanisms can be classified into distinct groups based on their effects on mitochondrial morphology and biochemistry. Additionally we show that mitochondrial toxicity of antiretroviral drugs cannot be exclusively attributed to interference with the mitochondrial DNA polymerase.

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

Chronic HIV treatment with antiretroviral drugs has been associated with adverse health outcomes. Mitochondrial toxicity exhibited by nucleoside reverse transcriptase inhibitors (NRTIs) is pinpointed as a molecular mechanism of toxicity. This study evaluated the effect of NRTIs: Zidovudine (AZT, 7.1 µM), Stavudine (d4T, 4 µM) and Tenofovir (TFV, 1.2 µM), on mitochondrial (mt) stress response, mtDNA integrity and oxidative stress response in human hepatoma cells at 24 and 120 h. Markers for mt function, mt biogenesis, oxidative stress parameters, and antioxidant response were evaluated by spectrophotometry, luminometry, flow cytometry, qPCR and western blots. We found that AZT and d4T reduced mtDNA integrity (120 h, AZT: 76.1%; d4T:36.1%, P < 0.05) and remained unchanged with TFV. All three NRTIs, however, reduced ATP levels (AZT: 38%; d4T: 56.4%; TFV: 27.4%, P = 0.01) and mt membrane potential at 120 h (P < 0.005). Oxidative damage and reactive oxygen species (ROS) were increased by TFV and AZT at 24 h, and by d4T at 120 h (P < 0.05). Antioxidant response molecules and mt biogenesis markers were elevated by all NRTIs, with TFV causing the most significant increase (P < 0.05). Data from this study suggest that AZT, d4T and TFV alter mt function. TFV, however, achieves this independently of mtDNA depletion. Furthermore, AZT exerts toxicity soon after exposure as noted from changes at 24 h and d4T exerts greater toxicity over prolonged exposure (120 h).

Peripheral blood mitochondrial DNA/nuclear DNA (mtDNA/nDNA) ratio as a marker of mitochondrial toxicities of stavudine containing antiretroviral therapy in HIV-infected Malawian patients.

Mitochondrial toxicity is a major concern related to nucleoside reverse transcriptase inhibitors. Common manifestations are peripheral neuropathy and lipodystrophy. Depletion of mitochondria has been associated with mitochondrial dysfunction. We investigated whether mitochondria DNA (mtDNA) levels in peripheral blood can be used as biomarker of stavudine-associated mitochondrial toxicities. We enrolled 203 HIV-infected Malawian adult patients on stavudine-containing ART and 64 healthy controls of Bantu origin in a cross-sectional study. Total DNA was extracted from whole blood.The glyceraldehyde-3-phosphate dehydrogenase gene was used to estimate nuclear DNA (nDNA) levels and the ATP synthase-8 mitochondrial DNA gene to estimate mtDNA levels, from which mtDNA/nDNA ratios were determined. MtDNA subhaplogroups were established by sequencing. Among patients, peripheral neuropathy was present in 21% (43/203), lipodystrophy in 18% (20/112), elevated lactate level (>2.5 mmol/L) in 17% (19/113). Healthy controls had a higher median mtDNA/nDNA ratio when compared to HIV/AIDS patients (6.64 vs. 5.08; p=0.05), patients presenting with peripheral neuropathy (6.64 vs. 3.40, p=0.039), and patients with high lactate levels (6.64 vs. 0.68, p=0.024), respectively. Significant differences in median mtDNA/nDNA ratios were observed between patients with high and normal lactate levels (5.88 vs. 0.68, p=0.018). The median mtDNA/nDNA ratio of patients in subhaplogroup L0a2 was much lower (0.62 vs. 8.50, p=0.01) than that of those in subhaplogroup L2a. Our data indicate that peripheral blood mtDNA/nDNA ratio is a marker of mitochondrial toxicities of stavudine and is associated with elevated lactate levels and mtDNA subhaplogroups. This could open the prospect to select a substantial group of patients who will not have problematic side effects from stavudine, an affordable and effective antiretroviral drug that is being phased out in Africa due to its toxicity.

Myristoylated derivatives of 2',3'-didehydro-2',3'-dideoxythymidine (stavudine) bi-functional prodrugs with potent anti-HIV-1 activity and low cytotoxicity.

BACKGROUND: To improve in vitro antiviral activity and selectivity of stavudine (d4T), a range of its bi-functional prodrugs, 5'-O-myristoylated derivatives, have been synthesized. METHODS: Stavudine 5'-O-myristoylated esters were synthesized using modified Parang's procedure. The cytotoxicity and anti-HIV activity was evaluated in the established MT-4 cell line. The level of p24 protein in culture medium was assayed, and EC50 and EC90 values were determined. RESULTS: Excellent anti-HIV activity was obtained for stavudine derivatives 2',3'-didehydro-2',3'-dideoxy-5'-O-(11-thioethylundecanoyl) thymidine, 2',3'-didehydro-2',3'-dideoxy-5'-O-(12-thioethyldodecanoyl) thymidine and 5'-O-(12-azidododecanoyl)-2',3'-didehydro-2',3'-dideoxythymidine with C10 and C11 alkyl chains bearing thioethyl- and azido- substituents. These prodrugs were more potent than the parent stavudine, as is clear from their EC50 values: 2',3'-didehydro-2',3'-dideoxy-5'-O-(11-thioethylundecanoyl) thymidine (R=CO(CH2)10SC2H5, EC50 0.06 µM), 2',3'-didehydro-2',3'-dideoxy-5'-O-(12-thioethyldodecanoyl) thymidine (R=CO(CH2)11SC2H5, EC50 0.09 µM) and 5'-O-(12-azidododecanoyl)-2',3'-didehydro-2',3'-dideoxythymidine (R=CO(CH2)11N3, EC50 0.06 µM), while 50% cytotoxic concentration was >16.65 µM, >7.5 µM and >18.53 µM, respectively. CONCLUSIONS: Overall data demonstrate that compounds 2',3'-didehydro-2',3'-dideoxy-5'-O-(11-thioethylundecanoyl) thymidine, 2',3'-didehydro-2',3'-dideoxy-5'-O-(12-thioethyldodecanoyl) thymidine and 5'-O-(12-azidododecanoyl)-2',3'-didehydro-2',3'-dideoxythymidine are very potent and selective anti-HIV agents and could be useful in treatment of HIV infections of the central nervous system.

Estimation of intracellular concentration of stavudine triphosphate in HIV-infected children given a reduced dose of 0.5 milligrams per kilogram twice daily.

The antiviral efficacy of stavudine depends on the trough concentration of its intracellular metabolite, stavudine-triphosphate (d4T-TP), while the degree of stavudine's mitochondrial toxicity depends on its peak concentration. Rates of mitochondrial toxicity are high when stavudine is used at the current standard pediatric dose (1 mg/kg twice daily [BID]). Evidence from adult work suggests that half of the original standard adult dose (i.e., 20 mg BID) may be equally effective, with markedly less mitochondrial toxicity. We present a population pharmacokinetic model to predict intracellular d4T-TP concentrations in pediatric HIV-infected patients administered a dose of 0.5 mg/kg BID. Our model predicted that the reduced pediatric dose would result in a trough intracellular d4T-TP concentration above that of the reduced 20-mg adult dose and a peak concentration below that of the 20-mg adult dose. The simulated pediatric intracellular d4T-TP at 0.5 mg/kg BID resulted in median peak and trough values of approximately 23.9 fmol/10(6) cells (95% prediction interval [PI], 14.2 to 41 fmol/10(6) cells) and 14.8 fmol/10(6) cells (95% PI, 7.2 to 31 fmol/10(6) cells), respectively. The peak and trough concentrations resulting from a 20-mg BID adult dose were 28.4 fmol/10(6) cells (95% PI, 17.3 to 45.5 fmol/10(6) cells) and 13 fmol/10(6) cells (95% PI, 6.8 to 28.6 fmol/10(6) cells), respectively. Halving the current standard pediatric dose should therefore not compromise antiviral efficacy, while markedly reducing mitochondrial toxicity.

BMS-986001, an HIV nucleoside reverse transcriptase inhibitor, does not degrade mitochondrial DNA in long-term primary cultures of cells isolated from human kidney, muscle, and adipose tissue.

Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) remain the cornerstone of HIV treatment; however, they are associated with toxicities attributed in part to inhibition of mitochondrial DNA (mtDNA) polymerase γ. In this study, we compared the in vitro toxicity profiles of structurally similar NRTIs (BMS-986001 to stavudine and tenofovir to adefovir) that differ by the presence of an acetylene or methyl group, respectively. Primary cultures of human renal proximal tubule epithelium, skeletal muscle myotubes, and differentiated adipocytes were exposed to the NRTIs at the maximum concentration (Cmax) reported for the clinically approved dose (investigational dose for BMS-986001, 600 mg) and a high equimolar concentration (200 µM) for 19 days. After 19 days, BMS-986001 did not significantly decrease mtDNA or cell protein at either concentration in any cell line. In contrast, stavudine significantly decreased mtDNA in all cultures (1.5- to 2.5-fold) (except at Cmax in renal cells) and cell protein in renal cells (1.4- to 2.4-fold). By day 19, at 200 µM, tenofovir significantly reduced mtDNA in adipocytes (1.9-fold) and adefovir significantly decreased mtDNA in all cultures (3.7- to 10.2-fold); however, no significant reduction in mtDNA was observed at Cmax in any cell line. Adefovir also significantly reduced cell protein at both concentrations in renal cells (2.2- to 2.8-fold) and at 200 µM in muscle cells (2.0-fold). In conclusion, BMS-986001 and tenofovir were considerably less cytotoxic than their respective structural analogs, demonstrating that small structural differences can contribute to significant differences in toxicity.

Resultados de una intervencion de farmacovigilancia en pacientes con VIH/SIDA tratados con estavudina / Pharmacosurveillance regarding Colombian patients beingtreated with stavudine

Objetivos Dado que la estavudina se ha asociado a toxicidad acumulativa e irreversible, se pretendió reducir la aparición de resultados negativos asociados al uso de estavudina mediante la notificación del riesgo a diferentes responsables de la atención sanitaria de pacientes con VIH/SIDA en Colombia. Métodos A partir de la base de datos de dispensación de medicamentos de Audifarma S.A a unos 4,5 millones de personas, se identificaron todos los usuarios de estavudina, se notificó el riesgo a los prestadores del servicio de salud y se recomendó la sustitución por zidovudina o tenofovir. Resultados En 2010 se identificaron 1 410 pacientes en tratamiento antirretroviral, de los cuales 109 (7,5 %) recibían estavudina, distribuidos en 20 ciudades del país y atendidos por 19 instituciones diferentes. Tras la intervención se consiguió en 28 meses reducir su empleo en 94,6 %. El medicamento más empleado en la sustitución fue zidovudina. Discusión Se consiguió exitosamente reemplazar estavudina siguiendo las recomendaciones de la Organización Mundial de la Salud, con lo cual se puede evitar la aparición de lipodistrofia y neuropatía periférica asociada a su empleo.(AU)

Objectives Reducing the occurrence of negative stavudine use-associated outcomes by reporting such risk to doctors responsible for the care of HIV/AIDS patients in Colombia as stavudine has been associated with cumulative and irreversible toxicity. Methods All stavudine users were identified from Audifarma S.A. (drug suppliers) databases (covering about 4.5million people). The risk was then reported to health service providers and the substitution of stavudine for zidovudine or tenofovir was recommended. Results It was found that 1,410 patients registered in the afore mentioned databases were receiving antiretroviral therapy during 2010, of whom 109 (7.5 %) were receiving stavudine; these patients were living in 20 cities and being attended by 19 institutions. Stavudine use became reduced by 94.6 % during the 28 months following the intervention. Zidovudine was the most commonly used replacement drug. Discussion Stavudine was successfully replaced following World Health Organization recommendations aimed at preventing the occurrence of lipodystrophy and the peripheral neuropathy associated with its use.(AU)

Brain-derived neurotrophic factor modulates antiretroviral-induced mechanical allodynia in the mouse.

Nucleoside reverse transcriptase inhibitors (NRTIs) are key components of HIV/AIDS treatment to reduce viral load. However, these drugs can induce chronic neuropathic pain, leading to increased morbidity in HIV patients. This study examines the role of brain-derived neurotrophic factor (BDNF) in the spinal dorsal horn (SDH) in development of mechanical allodynia in male C57BL/6J mice treated with the NRTI stavudine (d4T). After d4T administration, mice developed increased neuronal activity and BDNF expression in the SDH and hind paw mechanical allodynia that was exacerbated by intrathecal BDNF administration. Intrathecal BDNF alone also increased neuronal activity and caused mechanical allodynia. Because excess BDNF amplified d4T-induced mechanical allodynia and neuronal activity, the impact of decreasing BDNF in the SDH was investigated. After d4T, BDNF heterozygous mice were less allodynic than wild-type littermates, which was negated by intrathecal BDNF administration. Finally, pretreatment with intrathecal trkB-Fc chimera prior to d4T or administration of the tyrosine kinase inhibitor K252a 3 days after d4T blocked BDNF-mediated signaling, significantly attenuated the development of mechanical allodynia (trkB-Fc), and decreased neuronal activity (trkB-Fc and K252a). Taken together, these findings provide evidence that BDNF in the SDH contributes to the development of NRTI-induced painful peripheral neuropathy and may represent a new therapeutic opportunity.

Progressive mitochondrial compromise in brains and livers of primates exposed in utero to nucleoside reverse transcriptase inhibitors (NRTIs).

Mitochondrial compromise has been documented in infants born to women infected with the human immunodeficiency virus (HIV-1) who received nucleoside reverse transcriptase inhibitor (NRTI) therapy during pregnancy. To model these human exposures, we examined mitochondrial integrity at birth and 1 year in brain cortex and liver from offspring of retroviral-free Erythrocebus patas dams-administered human-equivalent NRTI doses for the last half (10 weeks) of gestation. Additional infants, followed for 1 year, were given the same drugs as their mothers for the first 6 weeks of life. Exposures included: no drug, Zidovudine (AZT), Lamivudine (3TC), AZT/3TC, AZT/Didanosine (ddI), and Stavudine (d4T)/3TC. In brain and liver, oxidative phosphorylation (OXPHOS) enzyme activities (complexes I, II, and IV) showed minimal differences between unexposed and NRTI-exposed offspring at both times. Brain and liver mitochondria from most NRTI-exposed patas, both at birth and 1 year of age, contained significant (p < 0.05) morphological damage observed by electron microscopy (EM), based on scoring of coded photomicrographs. Brain and liver mitochondrial DNA (mtDNA) levels in NRTI-exposed patas were depleted significantly in the 3TC and d4T/3TC groups at birth and were depleted significantly (p < 0.05) at 1 year in all NRTI-exposed groups. In 1-year-old infants exposed in utero to NRTIs, mtDNA depletion was 28.8-51.8% in brain and 37.4-56.5% in liver. These investigations suggest that some NRTI-exposed human infants may sustain similar mitochondrial compromise in brain and liver and should be followed long term for cognitive integrity and liver function.

The genetic toxicity effects of lamivudine and stavudine antiretroviral agents.

IMPORTANCE OF THE FIELD: The nucleoside reverse transcriptase inhibitors (NRTIs) are used in antiretroviral therapy worldwide for the treatment of HIV infections. These drugs act by blocking reverse transcriptase enzyme activity, causing pro-viral DNA chain termination. As a consequence, NRTIs could cause genomic instability and loss of heterozygosity. AREAS COVERED IN THIS REVIEW: This review highlights the toxic and genotoxic effects of NRTIs, particularly lamivudine (3TC) and stavudine (d4T) analogues. In addition, a battery of short-term in vitro and in vivo systems are described to explain the potential genotoxic effects of these NRTIs as a single drug or a complexity of highly active antiretroviral therapy. WHAT THE READER WILL GAIN: The readers will gain an understanding of a secondary effect that could be induced by 3TC and d4T treatments. TAKE HOME MESSAGE: Considering that AIDS has become a chronic disease, more comprehensive toxic genetic studies are needed, with particular attention to the genetic alterations induced by NRTIs. These alterations play a primary role in carcinogenesis and are also involved in secondary and subsequent steps of carcinogenesis.

Ubisol-Aqua: coenzyme Q10 prevents antiretroviral toxic neuropathy in an in vitro model.

BACKGROUND: Peripheral neuropathy is the dose-limiting toxicity of stavudine and didanosine (nucleoside analogs used in HIV treatment) and is attributed to mitochondrial toxicity from these drugs. Acetyl L-carnitine (ALC) and co-enzyme Q(10) are proposed as neuropathy treatments, but evidence to support these is limited. METHODS: We examined ALC and a water-soluble formulation of co-enzyme Q(10) (H(Q)O) for the prevention of d4T and ddI neurotoxicity using cultured fetal rat DRG as an in vitro model. RESULTS: DdI (33microM) and d4T (50microM) caused clear toxicity (impaired neurite growth) by day 8 of DRG culture. H(Q)O at concentrations 1-100microM completely prevented the toxicity of 33microM ddI in vitro and ALC at concentrations 1-100 microM substantially (but incompletely) prevented ddI toxicity in this model. In contrast, ALC was ineffective at all concentrations tested for preventing the toxicity of 50microM d4T. H(Q)O showed dose-dependent efficacy for preventing d4T toxicity. H(Q)O (1microM) partially prevented d4T toxicity while 10 and 100microM H(Q)O completely prevented d4T toxicity in this model. CONCLUSIONS: We find H(Q)O is superior to ALC for preventing the neurotoxicity of d4T (the HIV treatment most associated with neuropathy) and ddI in vitro. Further study is needed to clarify any clinical role for co-enzyme Q(10) co-administration with d4T and ddI and to assess whether this compound may have a role in treating established cases of neuropathy.

Construction and validation of a yeast model system for studying in vivo the susceptibility to nucleoside analogues of DNA polymerase gamma allelic variants.

Mitochondrial dysfunctions have been observed in subjects treated with antiretroviral nucleoside analogues, such as stavudine, as they can interfere with the activity of DNA polymerase gamma. Recently, stavudine-induced mitochondrial toxicity was associated to POLG mutations R964C and E1143G. A yeast model system useful to evaluate the association between D4T toxicity and mutations in MIP1, the yeast ortholog of POLG, was constructed and validated as a tool for pharmacogenetics research. We showed that mutant Mip1p(R964C) and possibly Mip1p(E1143G) are more sensitive to stavudine, and that stavudine has the potential to cause mitochondrial toxicity in heterozygous subjects harboring recessive mutations.