AZT treatment induces molecular and ultrastructural oxidative damage to muscle mitochondria. Prevention by antioxidant vitamins

Oxidant Stress and Peripheral Neuropathy During Antiretroviral Therapy

BACKGROUND

Peripheral neuropathy that complicates HIV nucleoside reverse transcriptase inhibitor (NRTI) therapy is likely caused by mitochondrial injury. Mitochondria play a central role in regulating oxidant stress. We explored the relationships between oxidant stress and NRTI-induced peripheral neuropathy.

METHODS

The AIDS Clinical Trials Group (ACTG) studied the cases of 384 antiretroviral-naive individuals randomized to receive didanosine/stavudine or zidovudine/lamivudine, plus efavirenz, nelfinavir, or both. The participants were followed for up to 3 years. Peripheral neuropathy was ascertained by signs and symptoms. We performed a case-control study of ACTG 384 participants. Peripheral neuropathy cases and nonneuropathy control subjects were selected from didanosine/stavudine recipients. Alternate control subjects were selected from zidovudine/lamivudine recipients who developed peripheral neuropathy. Oxidant stress was assessed by quantifying F2-isoprostanes (F2-IsoPs) in cryopreserved plasma.

RESULTS

Seventy-five cases, 71 control subjects, and 18 alternate control subjects were identified. The median baseline F2-IsoP values were 53 (interquartile range [IQR], 40-85), 57 (IQR, 41-77), and 53 (IQR, 47-101) pg/mL, respectively, and did not differ between cases and control subjects (P = 0.78) or alternate control subjects (P = 0.60). Changes in F2-IsoPs from baseline to time of peripheral neuropathy did not differ significantly between cases (median, 10 [IQR, -17 to 26] pg/mL) and control subjects (median, 4 [IQR, -11 to 17] pg/mL; P = 0.48) or alternate control subjects (median, 1 [IQR, -48 to 10] pg/mL; P = 0.21).

CONCLUSIONS

Peripheral neuropathy that complicates antiretroviral therapy with NRTIs was not associated with increased systemic oxidant stress assessed by plasma F2-IsoPs.

[Mitochondrial cytopathies associated with HIV infection]

The tremendous progress achieved during the last few years with the use of highly active antiretroviral therapy in suppressing HIV replication together with improvements in immunity have been tempered by a growing number of new adverse effects. Mitochondrial toxicity is one aspect of these long-term toxicities of antiretroviral drugs, with the role of nucleoside analogs particularly underlined. Some cases of impaired mitochondrial function have been clearly identified, such as pancreatitis due to didanosine, neuropathy due to zalcitabine, myopathy due to zidovudine, and lactic acidosis due to stavudine. These mitochondrial toxicities can affect several organs, presenting different patterns of symptoms: from asymptomatic to states with few symptoms despite huge metabolic abnormalities whose prognosis is immediately life-threatening. Beyond the inhibition of DNA polymerase gamma using nucleoside analogs, responsible for decreasing mitochondrial DNA in certain targeted organs, it appears that several physiopathologic mechanisms interact to explain this observed toxicity, HIV itself plays a role, and the underlying genetic pool needs to be better identified. Such cases mean that, it is imperative to avoid cumulated toxicities caused by associated treatments. With serious cases, or persistent symptoms despite discontinuing the nucleoside analogs responsible for such toxicity, one must propose vitamins, mitochondrial co-factors, or anti-oxidants. However, the future lies in the use of potent, less toxic nucleoside analogs, and in developing compounds belonging to other classes of antiretrovirals.

Mitochondrial dysfunction in NASH: causes, consequences and possible means to prevent it

Calorie-enriched diet and lack of exercise are causing a worldwide surge of obesity, insulin resistance and lipid accretion in liver (i.e. hepatic steatosis), which can lead to steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs, including stavudine and zidovudine. There is accumulating evidence that mitochondrial dysfunction (more particularly respiratory chain deficiency) plays a key role in the physiopathology of NASH whatever its initial cause. In contrast, the mitochondrial beta-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, generation of reactive oxygen species (ROS) by the damaged respiratory chain can be augmented. ROS generation in an environment enriched in lipids in turn induces lipid peroxidation which releases highly reactive aldehydic derivatives (e.g. malondialdehyde) that have diverse detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS, reactive nitrogen species and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This consequently leads to the generation of more ROS and a vicious cycle occurs. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also increase the generation of several cytokines (TNF-alpha, TGF-beta, Fas ligand) playing a key role in cell death, inflammation and fibrosis. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. Interestingly, most of these drugs could exert their beneficial effects by improving directly or indirectly mitochondrial function in liver. Finding a drug, which could fully prevent oxidative stress and mitochondrial dysfunction in NASH is a major challenge for the next decade.

Complications musculaires de l’infection par le virus de l’immunodéficience humaine (VIH) à l’ère des trithérapies

Introduction of highly active antiretroviral therapy (HAART) has dramatically modified the natural history of HIV disease, but lengthening the survival of HIV-infected individuals has been associated with an increasing prevalence of iatrogenic conditions. Muscular complications of HIV infection are classified as follows: (1) HIV-associated myopathies and related conditions including polymyositis, inclusion-body myositis, nemaline myopathy, diffuse infiltrative lymphocytosis syndrome (DILS), HIV-wasting syndrome, vasculitis, myasthenic syndromes, and chronic fatigue; (2) iatrogenic conditions including mitochondrial myopathies, HIV-associated lipodystrophy syndrome, and immune restoration syndrome; (3) opportunistic infections and tumor infiltrations of skeletal muscle; and (4) rhabdomyolysis. These features are described in the present review.

Skeletal muscle involvement in human immunodeficiency virus (HIV)-infected patients in the era of highly active antiretroviral therapy (HAART)

Skeletal muscle involvement can occur at all stages of human immunodeficiency virus (HIV) infection, and may represent the first manifestation of the disease. Myopathies in HIV-infected patients are classified as follows: (1) HIV-associated myopathies and related conditions, including HIV polymyositis, inclusion-body myositis, nemaline myopathy, diffuse infiltrative lymphocytosis syndrome (DILS), HIV-wasting syndrome, vasculitic processes, myasthenic syndromes, and chronic fatigue; (2) muscle complications of antiretroviral therapy, including zidovudine and toxic mitochondrial myopathies related to other nucleoside-analogue reverse-transcriptase inhibitors (NRTIs), HIV-associated lipodystrophy syndrome, and immune restoration syndrome related to highly active antiretroviral therapy (HAART); (3) opportunistic infections and tumor infiltrations of skeletal muscle; and (4) rhabdomyolysis. Introduction of HAART has dramatically modified the natural history of HIV disease by controlling viral replication, but, in turn, lengthening of the survival of HIV-infected individuals has been associated with an increasing prevalence of iatrogenic conditions.

Tratamiento de la hiperlactatemia sintomática y de la acidosis láctica en pacientes con infección por el virus de la inmunodeficiencia humana en tratamiento con inhibidores de la transcriptasa inversa análogos de los nucleósidos

BACKGROUND AND OBJECTIVE

We intended to find out the effectiveness of lactic acidosis therapy for mitochondrial toxicity.

PATIENTS AND METHOD

HIV-patients receiving nucleoside reverse transcriptase inhibitors (NRTIs), hospitalized with lactic acidosis or symptomatic hyperlactatemia. Venous hyperlactatemia was considered at > 2.2 mmol/l. Treatment consisted of a daily vitamin regime of L-carnitine, thiamine, vitamin B6, hydroxicobalamine, and vitamin C; any glucose intake was discontinued. NRTIs treatment was stopped immediately.

RESULTS

Nine patients on current therapy were identified who had symptomatic hyperlactatemia (n = 4) or lactic acidosis (n = 5) from 1/2001 to 9/2002. All were patients with AIDS, receiving NRTIs with a mean duration of 5 years: ddI (n = 7), d4T (n = 5), AZT(n = 3), 3TC (n = 2), abacavir (n = 1). Most common symptoms were tachypnea, slight fever, abdominal pain, nausea, vomiting and diarrhea. All patients had a favourable prognosis after administration of L-carnitine and vitamin complexes, with discontinuation of NRTIs and glucose intake. Clinical features lasted 7 days. After 15 (5) months of follow up, none had a recurrence of the syndrome.

CONCLUSION

The application of this therapy could play a role in the treatment of NRTI - related lactic acidosis.

Zidovudine-induced diaphragmatic contractile dysfunction: Impact of an antioxidant diet

OBJECTIVE

Zidovudine (AZT) is a primary drug therapy used to treat HIV-infected individuals. While AZT inhibits replication of HIV, it also induces a drug-specific myopathy resulting in altered muscle mitochondria, increased oxidative stress and muscle contractile dysfunction. The purpose of this study was to assess the impact of an antioxidant diet (high in vitamins C and E) on AZT-mediated diaphragmatic contractile dysfunction in rodents.

METHODOLOGY

Adult, Sprague-Dawley rats were assigned to feeding groups: control (CON, n = 9), AZT-treatment (AZT, n = 8), antioxidant diet only (Anti-Ox, n = 6), and AZT + antioxidant diet (AZT + Anti, n = 9). Two costal diaphragm strips were removed from each animal (under surgical anaesthesia) and evaluated for force-frequency relationship, maximal specific tension, and fatigue resistance using an in vitro preparation.

RESULTS

Results indicate significant reductions in normalized force production (20-200 Hz), including maximal specific tension, between AZT animals and all other groups. While AZT reduced diaphragm contractility, the addition of an antioxidant diet eliminated this decrease.

CONCLUSION

These data suggest that an increase in oxidative stress mediated by AZT may contribute to AZT-induced muscle contractile dysfunction, and that antioxidant vitamin supplementation may help ameliorate this effect.

Uridine in the Prevention and Treatment of Nrti-Related Mitochondrial Toxicity

Long-term side effects of antiretroviral therapy are attributed to the mitochondrial (mt) toxicity of nucleoside analogue reverse transcriptase inhibitors (NRTIs) and their ability to deplete mtDNA. Studies in hepatocytes suggest that uridine is able to prevent and treat mtDNA depletion by pyrimidine NRTIs [zalcitabine (ddC) and stavudine (d4T)] and to fully abrogate hepatocyte death, elevated lactate production and intracellular steatosis. Uridine was also found to improve the liver and haematopoietic toxicities of zidovudine (AZT), which are unrelated to mtDNA depletion, and to prevent neuronal cell death induced by ddC. Most recently, uridine was found to prevent the onset of a lipoatrophic phenotype (reduced intracellular lipids, increased apoptosis, mtDNA depletion and mt depolarization) in adipocytes incubated long-term with d4T and AZT. Various steps of mt nucleoside utilization may be involved in the protective effect, but competition of uridine metabolites with NRTIs at polymerase y or other enzymes is a plausible explanation. Pharmacokinetic studies suggest that uridine serum levels can be safely increased in humans to achieve concentrations which are protective in vitro (50–200 μM). Uridine was not found to interfere with the antiretroviral activity of NRTIs. Mitocnol, a sugar cane extract which effectively increases uridine in human serum, was beneficial in individual HIV patients with mt toxicity and is now being tested in placebo-controlled randomized trials. Until these data become available, the risk-benefit calculation of using uridine should be individualized. The current safety data justify the closely monitored use of uridine in individuals who suffer from mt toxicity but who cannot be switched to less toxic NRTIs.

AZT induces oxidative damage to cardiac mitochondria: Protective effect of vitamins C and E

AZT (zidovudine) is a potent inhibitor of HIV replication and a major antiretroviral drug used for AIDS treatment. A major limitation in the use of AZT is the occurrence of severe side effects. The aim of this work was to test whether AZT causes oxidative damage to heart mitochondria and whether this can be prevented by supranutritional doses of antioxidant vitamins. An experimental animal model was used in which mice were treated with AZT for 35 days (10 mg/kg/day) in drinking water. Animals treated with antioxidant vitamins were fed the same diet as controls but supplemented with vitamins C (ascorbic acid, 10 g/ kg diet) and E (alpha-dl-tocopherol, 0.6 g/kg diet) for 65 days before sacrifice. This resulted in a daily intake of 1250 mg/kg/day (vitamin C) and 75 mg/kg/day (vitamin E). Cardiac mitochondrial DNA (mtDNA) of mice treated with AZT had over 120% more oxo-dG (8-oxo-7,8-dihydro-2'-deoxyguanosine, which is a biomarker of oxidative damage to DNA) in their mitochondrial DNA than untreated controls. AZT treatment also caused an increase in mitochondrial lipid peroxidation and an oxidation of mitochondrial glutathione. Dietary supplementation with supranutritional doses of the antioxidant vitamins C and E protected against these signs of mitochondrial oxidative stress. The oxidative effects of AZT are probably due to an increase in production of reactive oxygen species by mitochondria of AZT-treated animals, raising the possibility that oxidative stress may play an important role in the cardiotoxicity of AZT.

Antiretrovirals, Part II: Focus on Non-Protease Inhibitor Antiretrovirals (NRTIs, NNRTIs, and Fusion Inhibitors)

The second in a series reviewing the HIV/AIDS antiretroviral drugs. This review summarizes the non-protease inhibitor antiretrovirals: nucleoside and nucleotide analogue reverse transcriptase inhibitors (NRTIs), the nonnucleoside reverse transcriptase inhibitors (NNRTIs), and cell membrane fusion inhibitors. In an overview format for primary care physicians and psychiatrists, this review presents the mechanism of action, side effects, toxicities, and drug interactions of these agents.

Oxidative DNA damage and disease: induction, repair and significance

The generation of reactive oxygen species may be both beneficial to cells, performing a function in inter- and intracellular signalling, and detrimental, modifying cellular biomolecules, accumulation of which has been associated with numerous diseases. Of the molecules subject to oxidative modification, DNA has received the greatest attention, with biomarkers of exposure and effect closest to validation. Despite nearly a quarter of a century of study, and a large number of base- and sugar-derived DNA lesions having been identified, the majority of studies have focussed upon the guanine modification, 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-OH-dG). For the most part, the biological significance of other lesions has not, as yet, been investigated. In contrast, the description and characterisation of enzyme systems responsible for repairing oxidative DNA base damage is growing rapidly, being the subject of intense study. However, there remain notable gaps in our knowledge of which repair proteins remove which lesions, plus, as more lesions identified, new processes/substrates need to be determined. There are many reports describing elevated levels of oxidatively modified DNA lesions, in various biological matrices, in a plethora of diseases; however, for the majority of these the association could merely be coincidental, and more detailed studies are required. Nevertheless, even based simply upon reports of studies investigating the potential role of 8-OH-dG in disease, the weight of evidence strongly suggests a link between such damage and the pathogenesis of disease. However, exact roles remain to be elucidated.

The ins and outs of mitochondrial dysfunction in NASH

Rich diet and lack of exercise are causing a surge in obesity, insulin resistance and steatosis, which can evolve into steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs. There is growing evidence that mitochondrial dysfunction, and more specifically respiratory chain deficiency, plays a role in the pathophysiology of NASH whatever its initial cause. In contrast, the B-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, the generation of reactive oxygen species (ROS) by the damaged respiratory chain is augmented, as components of this chain are over-reduced by electrons, which then abnormally react with oxygen to form increased amounts of ROS. Concomitantly, ROS oxidize fat deposits to release lipid peroxidation products that have detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This, in turn, leads to the generation of more ROS and a vicious cycle ensues. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also activate stellate cells, thus resulting in fibrosis. Finally, ROS and lipid peroxidation increase the generation of several cytokines (TNF-alpha, TGF-B, Fas ligand) that play sundry roles in the pathogenesis of NASH. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. For the next decade, reducing the incidence of NASH will be a major challenge for hepatologists.

Azidothymidine promotes free radical generation by activated macrophages and hydrogen peroxide-iron-mediated oxidation in a cell-free system

Azidothymidine (AZT) and AZT monophosphate (AZT-MP) in concentrations as low as 10 and 50 microM, respectively, promote oxidation of chemically deacetylated 2',7'-dichlorodihydrofluorescein (DCDHF) to 2',7'-dichlorofluorescein (DCF) by rat peritoneal macrophages activated with latex. Cells were incubated with AZT and AZT-MP for 18 h, washed out from residual AZT or AZT-MP and activated with latex for 30 or 60 min in the presence of DCDHF. Latex-activated cells oxidize DCDHF extracellularly due to release of hydrogen peroxide and low-molecular iron complexes, which is verified using catalase, desferal and the peroxidase inhibitor sodium azide. AZT and AZT-MP increase DCDHF oxidation due to additional release of hydrogen peroxide as demonstrated by catalase inhibition of DCDHF oxidation and direct H(2)O(2) measurement. Thymidine and thymidine phosphates did not show any effect on macrophage activation. In separate experiments we evaluated the in vitro prooxidant activity of AZT, AZT-MP, AZT triphosphate (AZT-TP), AZT glucuronide (GAZT) and 3'-amino-3'-deoxythymidine (AMT) in a cell-free system using the hydrogen peroxide-iron-mediated oxidation of DCDHF. Under these conditions, AZT and AZT phosphates exhibit a prooxidant effect in concentrations as low as 100 microM. Furthermore, GAZT is a less effective prooxidant and AMT acts like an antioxidant. Thymidine did not show any effect.

Impaired oxygen on-kinetics in persons with human immunodeficiency virus are not due to highly active antiretroviral therapy

OBJECTIVE

To determine the effects of human immunodeficiency virus (HIV) and highly active antiretroviral therapy (HAART) on oxygen on-kinetics in HIV-positive persons.

DESIGN

Quasi-experimental cross-sectional.

SETTING

Infectious disease clinic and exercise laboratory.

PARTICIPANTS

Referred participants (N=39) included 13 HIV-positive participants taking HAART, 13 HIV-positive participants not taking HAART, and 13 noninfected controls.

INTERVENTIONS

Participants performed 1 submaximal exercise treadmill test below the ventilatory threshold, 1 above the ventilatory threshold, and 1 maximal treadmill exercise test to exhaustion.

MAIN OUTCOME MEASURES

Change in oxygen consumption (Delta.VO2) and oxidative response index (Delta.VO2/mean response time).

RESULTS

Delta.VO2 was significantly lower in both HIV-positive participants taking (946.5+/-68.1mL) and not taking (871.6+/-119.6mL) HAART than in controls (1265.3+/-99.8mL) during submaximal exercise above the ventilatory threshold. The oxidative response index was also significantly lower (P<.05) in HIV-positive participants both taking (15.0+/-1.3mL/s) and not taking (15.1+/-1.7mL/s) HAART than in controls (20.8+/-2.1mL/s) during exercise above the ventilatory threshold.

CONCLUSION

Oxygen on-kinetics during submaximal exercise above the ventilatory threshold was impaired in HIV-positive participants compared with a control group, and it appeared that the attenuated oxygen on-kinetic response was primarily caused by HIV infection rather than HAART.

Decreased peak arteriovenous oxygen difference during treadmill exercise testing in individuals infected with the human immunodeficiency virus

OBJECTIVE

To determine if arteriovenous oxygen difference was lower in asymptomatic individuals with human immunodeficiency virus (HIV) infection than in sedentary but otherwise healthy controls.

DESIGN

Quasi-experimental cross-sectional.

SETTING

Clinical exercise laboratory.

PARTICIPANTS

Fifteen subjects (10 men, 5 women) with HIV and 15 healthy gender- and activity level-matched controls (total N=30).

INTERVENTION

Participants performed an incremental maximal exercise treadmill test to exhaustion. Electrocardiogram, metabolic, and noninvasive cardiac output measurements were evaluated at rest and throughout the tests. Data were analyzed by using analysis of covariance.

MAIN OUTCOME MEASURES

Peak oxygen consumption (Vo(2)), cardiac output, stroke volume, and arteriovenous oxygen difference. The arteriovenous oxygen difference was determined indirectly using the Fick equation.

RESULTS

Peak VO(2) was significantly lower (P<.0005) in participants with HIV (24.6+/-1.2mL.kg(-1).min(-1)) compared with controls (32.0+/-1.2mL.kg(-1).min(-1)). There were no significant intergroup differences in cardiac output or stroke volume at peak exercise. Peak arteriovenous oxygen difference was significantly lower (P<.04) in those infected with HIV (10.8+/-0.5 volume %) than in controls (12.4+/-0.5 volume %).

CONCLUSION

The observed deficit in aerobic capacity in the participants with HIV appeared to be the result of a peripheral tissue oxygen extraction or utilization limitation. In addition to deconditioning, potential mechanisms for this significant attenuation may include HIV infection and inflammation, highly active antiretroviral therapy medication regimens, or a combination of these factors.

Mitochondrial toxicity of NRTI antiviral drugs: an integrated cellular perspective

Highly active antiretroviral therapy (HAART) regimes based on nucleoside reverse transcriptase inhibitors (NRTIs) have revolutionized the treatment of AIDS in recent years. Although HAART can successfully suppress viral replication in the long term, it is not without significant toxicity, which can seriously compromise treatment effectiveness. A major toxicity that has been recognized for more than a decade is NRTI-related mitochondrial toxicity, which manifests as serious side effects such as hepatic failure and lactic acidosis. However, a lack of understanding of the mechanisms underlying mitochondrial toxicity has hampered efforts to develop novel drugs with better side-effect profiles. This review characterizes the pharmacological mechanisms and pathways that are involved in mitochondrial dysfunction caused by NRTIs, and suggests opportunities for future pharmacological research.

Lipid oxidative markers are significantly increased in lipoatrophy but not in sustained asymptomatic hyperlactatemia

The exact mechanism of lipoatrophy remains unclear. One hypothesized mechanism is accumulation of reactive oxygen free radicals, which is possibly related to dysfunctional mitochondria. We evaluated plasma levels of F2-isoprostanes-the most accurate method to measure oxidant stress in vivo-in a group of 59 nucleoside reverse transcriptase inhibitor-treated HIV-1-infected subjects. All had serial measurements of venous lactate levels as well as clinical evaluations for assessment of lipoatrophy and symptoms of mitochondrial toxicity. Overall, 16 subjects had sustained hyperlactatemia (4 of whom were symptomatic) and 43 had serial normal lactate levels. We found a significant increase in circulating products of lipid peroxidation, F2-isoprostanes (nanograms per milliliter), in subjects with lipoatrophy when compared with subjects without lipoatrophy (0.060 +/- 0.025 vs. 0.0420 +/- 0.02, respectively; P = 0.02). Interestingly, there was no significant difference in F2-isoprostane levels (nanograms per milliliter) between patients with persistently normal lactate and those who exhibited a sustained asymptomatic hyperlactatemia (0.053 +/- 0.027 vs. 0.053 +/- 0.021, respectively; P > 0.05). This could be explained by the yet unclear significance of asymptomatic hyperlactatemia, even in a setting like ours, where lactate levels were measured with close attention to the method of collection and processing. In contrast, the 4 subjects with symptomatic hyperlactatemia/lactic acidosis had a significant increase in their F2-isoprostanes compared with subjects with asymptomatic sustained hyperlactatemia (0.082 +/- 0.021 vs. 0.053 +/- 0.021, respectively; P < 0.05).

Oxidative DNA damage induced by photodegradation products of 3(')-azido-3(')-deoxythymidine

3(')-Azido-3(')-deoxythymidine (AZT) is carcinogenic to experimental animals and can cause the formation of 8-oxo-7,8-dihydro-2(')-deoxyguanosine (8-oxodG) in humans and animals. To clarify the mechanism of carcinogenesis by AZT, we investigated DNA damage induced by its photodegradation products, using 32P-5(')-end-labeled DNA fragments obtained from human genes. Following exposure to UVB, AZT induced DNA damage in the presence of Cu(II). Catalase inhibited DNA damage, indicating the involvement of H(2)O(2). UVB-exposed AZT plus Cu(II) induced 8-oxodG formation in a dose-dependent manner. Mass spectrum of UVB-exposed AZT demonstrated the generation of a hydroxylamine derivative. The colorimetric determination suggested that AZT was converted into the hydroxylamine derivative depending on UVB doses. UVB-exposed AZT induced double base damage at the 5(')-ACG-3(') sequence, complementary to a hot spot of the p53 gene. The basic compound, hydroxylamine, showed similar site specificity. The hydroxylamine derivative produced by photodegradation and/or possible metabolism of AZT induces oxidative DNA damage, which may participate in carcinogenesis.

Effect of antioxidants on glucose metabolism and plasma lipids in HIV-infected subjects with lipoatrophy

Ten HIV-infected nucleoside reverse transcriptase inhibitor-treated subjects with lipoatrophy or sustained hyperlactatemia were given antioxidants: vitamins C, E, and N-acetyl cysteine. After 24 weeks, anthropometrics did not change significantly, except for a modest decrease in the waist-to-hip ratio. Fasting low-density lipoprotein cholesterol trended toward lower values. Fasting glucose significantly increased along with a significant increase in homeostatic model assessment values, reflecting an increase in insulin resistance. Controlled trials are required to evaluate directly the effects of these agents on lipid and glucose metabolism.

Lactic acidosis related to nucleoside therapy in HIV-infected patients

The incidence of nucleoside analogue-related lactic acidosis has been estimated in 0.57 - 8.5 cases/1000 person years of antiretroviral therapy. The onset of lactic acidosis is usually insidious and patients complain of nausea, vomiting, abdominal pain, fatigue and weight loss. When lactate levels are high enough, a catastropic clinical situation develops, resulting in multiorgan failure. The mortality rate of patients with lactic acidosis related to nucleoside therapy is very high, 33 - 60%. Although all nucleoside analogues have been implicated in lactic acidosis, most cases are associated with stavudine. At present, there are no controlled trials to evaluate the treatment of nucleoside-induced lactic acidosis. Therapy is based on supportive measures and discontinuation of all antiretroviral drugs. Administration of essential vitamin coenzymes, electron acceptors and L-carnitine may be useful in some cases.

A comparison of Qt and a-vO2 in individuals with HIV taking and not taking HAART

PURPOSE

The aim of this study was to determine whether highly active antiretroviral therapy (HAART), rather than the direct effect of HIV infection, limits peripheral muscle oxygen extraction-utilization (a-vO(2)) in individuals infected with the human immunodeficiency virus (HIV).

METHODS

Fifteen subjects (6 female and 9 male) with HIV taking HAART, 15 subjects infected with HIV not taking HAART, and 15 healthy gender and activity level matched non-HIV infected controls (N = 45) performed an maximal treadmill exercise test to exhaustion. Noninvasive cardiac output Qt was measured at each stage and at peak exercise using the indirect Fick method based on the exponential rise carbon dioxide rebreathing method. Intergroup comparisons were adjusted for interactions of peak oxygen consumption ([V02), body surface area, and [V02]t using ANCOVA.

RESULTS

Peak a-vO(2) was significantly lower (P < 0.05) in subjects with HIV taking HAART (10.0 +/- 0.5 vol%) compared with subjects with HIV not taking HAART (11.7 +/- 0.5 vol%) and noninfected controls (12.7 +/- 0.5 vol%). In subjects with HIV taking HAART, peak heart rate (HR) (170.5 +/- 3.9 bpm) was lower than (P < 0.05) and stroke volume (Vs) (123.0 +/- 3.9 mL x beat-1) at peak exercise was higher (P < 0.05) than subjects with HIV not taking HAART (179.9 +/- 3.5 bpm) (106.6 +/- 3.9 mL x beat-1) and noninfected controls (185.4 +/- 3.8 bpm) (100.6 +/- 4.0 mL.beat-1) upon ANCOVA. There were no significant differences in peak [VO2]t between groups.

CONCLUSION

Peak a-vO(2) was diminished in subjects infected with HIV taking HAART compared with HIV-infected subjects not taking HAART and noninfected controls matched for age, gender, and physical activity level. Findings of the current study implicated HAART as a primary contributor to decreased muscle oxygen extraction-utilization in individuals infected with HIV.

Hyperlactataemia syndromes associated with HIV therapy

Hyperlactataemia is seen in 8-18.3% of HIV-infected patients taking nucleoside-analogue reverse transcriptase inhibitors (NRTIs). Recent epidemiological studies suggest that most episodes are transient and subclinical. However, symptomatic and occasionally life-threatening cases accompanied by metabolic acidosis and hepatic steatosis (ie, lactic acidosis syndrome) have also been described. Though yet to be fully elucidated, the proposed mechanism is NRTI-induced inhibition of mitochondrial DNA polymerase culminating in derangements in oxidative phosphorylation and lactate homeostasis. Signs and symptoms range from mild hyperlactataemia accompanied by nausea, abdominal discomfort, and weight loss to severe, intractable lactic acidosis complicated by coma and multi-organ failure. Significant progress has recently been made with regard to the natural history of NRTI-related hyperlactataemia. However, other important aspects of the disorder, such as its pathogenesis, predisposing conditions, and management, remain poorly understood. This article reviews the current published work on these issues, identifies areas of controversy, and addresses directions for future research.

Could antioxidant supplementation reduce antiretroviral therapy-induced chronic stable hyperlactatemia?

OBJECTIVE

To determine if asymptomatic stable chronic hyperlactatemia in human immunodeficiency virus (HIV)-infected patients under highly active antiretroviral therapy (HAART, including nucleoside analog reverse transcriptase inhibitors (NRTI)) could be improved by antioxidant supplementation.

DESIGN

To match two groups of patients taking NRTI for at least 24 months: 15 without and 15 with antioxidant supplementation (vitamin E, beta-carotene, N-acetylcysteine, selenium, Gingko biloba extracts and nutritional supplements). For both the groups, the supplementation by antioxidants or its lack was carefully assessed. Venous lactatemia, blood oxidative stress markers (plasma lipid peroxidation, enzymatic and non-enzymatic antioxidants), CDC revisited classification, CD4 count and viral load, NRTI (with or without stavudine) and other antiretroviral drugs used, lipoatrophy, central fat accumulation were assessed.

RESULTS

Patients were not statistically different with respect to the CDC classification, CD4 count, viral load and characteristics of antiretroviral therapy. Blood oxidative stress markers, i.e. vitamin E, vitamin A and beta-carotene tended to be higher in the supplemented group. The difference observed in venous lactate concentration between the two groups was significant (1.37 +/- 0.10 vs. 1.82 +/- 0.19 mmol/l in the supplemented and non-supplemented groups, respectively P = 0.04).

CONCLUSION

Antioxidant supplementation improves the asymptomatic stable chronic hyperlactatemia observed in HIV-infected patients taking HAART including NRTI for a long time. Controlled studies are needed to demonstrate the efficacy of this supplementation on mitochondrial toxicity observed during HAART and the possible usefulness of its combination with mitochondrial cofactors like carnitine, riboflavine, coenzyme Q, alpha-lipoic acid.

Mitochondrial dysfunction and nucleoside reverse transcriptase inhibitor therapy: experimental clarifications and persistent clinical questions

Nucleoside reverse transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are critical in current AIDS therapy, but mitochondrial side effects have come to light with the increased use of these compounds. Clinical experience, pharmacological, cell and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in specific target tissues are observed. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself. With increased use of NRTIs, mtDNA mutations may become increasingly important pathophysiologically. One important future goal is to prevent or attenuate the side effects so that improved efficacy is achieved.

Mitochondrial DNA replication, nucleoside reverse-transcriptase inhibitors, and AIDS cardiomyopathy

Nucleoside reverse-transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are the cornerstones of current AIDS therapy, but extensive use brought mitochondrial side effects to light. Clinical experience, pharmacological, cell, and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in target tissues are observed. Organ-specific pathological changes or diverse systemic effects result from and are frequently attributed to HAART in which NRTIs are included. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself.

Nucleoside reverse transcriptase inhibitors impair endothelium-dependent relaxation by increasing superoxide

Nucleoside reverse transcriptase inhibitors (NRTIs) have been used successfully to reduce acquired immunodeficiency syndrome mortality. However, the use of these compounds is associated with numerous tissue toxicities, including cardiomyopathy. These studies address the effects of NRTIs on vascular function. Functional assays of contraction and relaxation were performed on isolated mouse aorta segments obtained from FVB/n mice exposed to zidovudine (AZT), stavudine, or water for 35 days. AZT and stavudine treatment impaired sensitivity to endothelium-dependent relaxation by acetylcholine. Dihydroethidium staining revealed that AZT treatment was associated with an increase in superoxide levels. Pretreatment of AZT-treated vessels with tiron (1 mM), a free radical scavenger, restored endothelium-dependent relaxation in mice. In cellular preparations, electron spin resonance measurements revealed elevated superoxide in cultured endothelial cells exposed to AZT; elevation was dependent on the length of exposure. These results indicate that NRTIs impair endothelium-dependent relaxation by increasing superoxide levels and suggest that NRTI therapy contributes to cardiovascular complications in acquired immunodeficiency syndrome.

Mitochondrial damage associated with long-term antiretroviral treatment: associated alteration or causal disorder?

Combination of antiretroviral drugs has dramatically improved the prognosis of human HIV infection but is also associated with many adverse effects, the mitochondrial origin of which is discussed. In this study using extensive diagnostic procedures set up for inherited mitochondrial disorders, we analyzed HIV patients under active antiretroviral therapy who complained of severe adverse symptoms unexplained by HIV. All these patients had been treated for at least 5 years. They all had significant mitochondrial damage as evidenced by the diverse combination of lactate accumulation in blood or cerebrospinal fluid, mitochondrial morphologic alterations in muscle, and biochemical defects in muscle and liver, which designated mitochondrial DNA (mtDNA) as the main target of the toxic mechanisms. Southern blot and/or polymerase chain reaction -based analyses disclosed multiple deletions of the muscle mtDNA and reduction of the muscle and/or liver mtDNA copy number in a majority of the patients. In opposition to muscle and liver, blood mononuclear cells were devoid of significant biochemical or genetic alterations. Whether the mitochondrial toxicity is directly responsible for the patients' adverse symptoms remains disputable, because the investigations were transversal. Its severity argues for its clinical relevance, however. The skewed tissue distribution of mitochondrial alterations indicates potential pitfalls in the needed future prospective studies.

Immunomodulatory effect of zidovudine (ZDV) on cytotoxic T lymphocytes previously exposed to ZDV

In a previous study, zidovudine (ZDV) was shown to cause a concentration-dependent inhibition of antigen-specific cytotoxic T-lymphocyte (CTL) clonal expansion (S. Francke, C. G. Orosz, K. A. Hayes, and L. E. Mathes, Antimicrob. Agents Chemother. 44:1900-1905, 2000). However, this suppressive effect was lost if exposure to ZDV was delayed for 24 to 48 h during the antigen sensitization period, suggesting that antigen-primed CTL may be less susceptible than naive T lymphocytes to the suppressive effects of ZDV. The present study was undertaken to determine if naive T lymphocytes were more sensitive to the suppressive effects of ZDV than T lymphocytes previously exposed to antigen. The 50% inhibitory concentration (IC(50)) values of ZDV were determined on naive and antigen-primed T-cell responses in an alloantigen system. Lymphocyte cultures with continuous antigen exposure (double prime) were more resistant to ZDV suppression (IC(50) = 316 micro M) than were naive lymphocytes (IC(50) = 87.5 micro M). Interestingly, lymphocytes that were antigen primed but deprived of antigen during the final 7 days of culture (prime/hold) were exquisitely sensitive to ZDV suppression (IC(50) = 29.3 micro M). The addition of 80 micro M ZDV during the initial priming of the single-prime (prime/hold) and double-prime cultures did not select for a more drug-resistant cell population. The differences in ZDV sensitivities are likely a reflection of the physiological properties of the lymphocytes related to their activation state.

Protective role of melatonin and a combination of vitamin C and vitamin E on lung toxicity induced by chlorpyrifos-ethyl in rats

The ameliorating effects of melatonin and vitamin C plus vitamin E were examined histologically and biochemically in lung tissues in rats exposed to chlorpyriphos-ethyl (CE). Experimental groups were as follows: Control group (C), CE treated group (CE), vitamin C plus vitamin E treated group (Vit), melatonin treated group (Mel), vitamin C plus vitamin E plus CE treated group (Vit + CE), and melatonin plus CE treated group (Mel + CE). Vitamin E and vitamin C were administered intramuscularly at the rates of 150 and 200 mg per kg body weight, respectively, in Vit and Vit + CE groups, once a day for 6 consecutive days. Melatonin was administered intramuscularly at the rate of 10 mg per kg body weight in Mel and Mel + CE groups, once a day for 6 consecutive days. At the end of the fifth day, the rats of CE, Vit + CE and Mel + CE groups were treated orally with CE dissolved in corn oil with two equal doses of 41 mg CE per kg body weight at zero and twenty-first hours. Tissue samples of lungs were taken by using appropriate techniques for biochemical and histological examinations under anesthesia at the twenty-fourth hours of CE administration, at the end of the sixth day of the experiment. In tissue homogenates, the level of thiobarbituric acid reactive substances (TBARS), antioxidant potential (AOP), and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined. TBARS was significantly high (p < 0.05) in CE group compared to control group, while TBARS was found to significantly decrease (p < 0.05) with Vit and Mel groups compared to control. On the other hand, TBARS was seen to significantly decrease (p < 0.05) in both groups of Vit + CE and Mel + CE compared to CE group. In comparison with CE group, SOD activity was significantly high (p < 0.05) with the groups of Vit, Mel, Vit + CE and Mel + CE. GSH-Px activity was found to significantly decrease (p < 0.05) with CE group, compared with both C and Vit groups. AOP was significantly lower (p < 0.01) in CE group than C group. Although there was an increased AOP with Vit + CE and Mel + CE groups compared to CE group, the increase in AOP was only seen to be significant (p < 0.05) in Mel + CE group. In comparison with C group, AOP significantly (p < 0.05) increased with Vit group. There was also a significant (p < 0.05) increase in AOP with Mel + CE group, compared with CE group. Additionally, AOP was significantly lower (p < 0.05) in Vit + CE group than Mel + CE group. Lungs were examined histologically at the end of sixth day. There were remarkable changes in the histomorphology of peribronchial and perivascular area in the lung of rats treated with CE. These were infiltration of mononuclear cells (such as lymphocytes, plasmocytes, macrophages), hyperplasia of type II pneumocyte, and thickened and increased connective tissue. Damage to the lung tissue such as increased inflammatory mononuclear cells in peribronchial and perivascular areas were more pronounced for the CE group than Vit + CE and Mel + CE groups in which these changes were higher than C, Vit and Mel groups. These results suggest that CE increases lipid peroxidation and decreases antioxidant enzymes activities and AOP due to increasing oxidative stress induced by CE, and high doses of vitamin C plus vitamin E and melatonin considerably reduce CE toxicity in lung tissues of rats.

Inhibition of phosphate transport in rat heart mitochondria by 3'-azido-3'-deoxythymidine due to stimulation of superoxide anion mitochondrial production

In order to gain some insight into the mechanism by which 3'-azido-3'-deoxythymidine (AZT) damages mitochondria, we investigated whether externally added AZT can stimulate reactive oxygen species (ROS) production by rat heart mitochondria (RHM). An increase in superoxide anion ((O(2)(.-)) production was measured in RHM added with AZT, by using a photometrically method which allows an early O(2)(.-) detection by following the absorbance increase at 550 nm due to the ferricytochrome c reduction. Such an increase was found to be prevented from externally added superoxide dismutase. The stimulation of O(2)(.-) mitochondrial production induced by AZT was found to occur under conditions in which mitochondrial oxygen consumption was prevented by both inhibitors of electron flow and ATP synthesis. Since ROS can cause mitochondrial carrier impairment, we investigated whether AZT can affect mitochondrial permeability in virtue of its capability to stimulate ROS production. In this regard, we studied the transport of phosphate (P(i)), by measuring the mitochondrial shrinkage that takes place as a result of P(i) uptake by RHM previously swollen in a calcium acetate medium. As a result of the AZT-dependent O(2)(.-) production, uncompetitive inhibition of the rate of P(i) transport in RHM was found (K(i) of about 10 microM), consistently, such an inhibition was found to prevent by certain known ROS scavengers, i.e. superoxide dismutase, the antioxidant Vitamin C and reduced gluthatione.

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.

Mitochondrial dysfunction and antiretroviral nucleoside analog toxicities: what is the evidence?

Mitochondrial dysfunction has been associated with long-term toxicities of human immunodeficiency virus (HIV) therapy, particularly with the nucleoside analog reverse transcriptase inhibitors (NRTIs). Lactic acidosis, hepatic steatosis, myopathies, cardiomyopathies, neuropathies, and lipodystrophy are frequently attributed to mitochondrial toxicity. Since mitochondrial toxicity could pose a major threat to the long-term success of HIV therapy, the scientific evidence underlying an association between mitochondrial toxicity and antiretroviral therapies, must be carefully examined. There is some data to support the association between NRTIs and mitochondria dysfunction. In this review, we examine human, animal, and in vitro data implicating mitochondrial dysfunction as the causal mechanism of NRTI-associated toxicity in HIV-infected patients.

Xanthine oxidase is involved in free radical production in type 1 diabetes: protection by allopurinol

The aim of this work was to study the mechanism of free radical formation in type 1 diabetes and its possible prevention. We have found oxidation of blood glutathione and an increase in plasma lipoperoxide levels in both human type 1 diabetes and experimental diabetes. Peroxide production by mitochondria does not increase in diabetes. On the contrary, the activity of xanthine oxidase, a superoxide-generating enzyme, increases in liver and plasma of diabetic animals. The increase in plasma xanthine oxidase activity may be explained by the increase in the hepatic release of this enzyme, which is not due to nonspecific membrane damage: release of other hepatic enzymes, such as the amino transferases, does not increase in diabetes. Superoxide formation by aortic rings of rabbits increases significantly in diabetes. This is completely inhibited by allopurinol, an inhibitor of xanthine oxidase. Heparin, which releases xanthine oxidase from the vessel wall, also decreases superoxide formation by aortic rings of diabetic animals. Treatment with allopurinol decreases oxidative stress in type 1 diabetic patients: hemoglobin glycation, glutathione oxidation, and the increase in lipid peroxidation are prevented. These results may have clinical significance in the prevention of late-onset vascular complications of diabetes.

Oral administration of pharmacological doses of vitamins C and E reduces reproductive fitness and impairs the ovarian and uterine functions of female mice

This study aims to ascertain whether oral administration of pharmacological doses of Vitamins C and E has any detrimental effect on reproductive fitness of female mice. We fed hybrid female mice from the first day of weaning a standard diet supplemented or not supplemented with pharmacological doses of Vitamins C and E. At the age of 28 weeks, we individually caged females with a male for the rest of their reproductive life. We performed a series of mating experiments to ascertain the number of oocytes ovulated and the potential for embryo development in vitro to the blastocyst stage and in vivo to Day 12 of gestation. The antioxidant diet decreased the frequency of litters, litter size, total number of offspring born and survival of male pups to weaning. This effect was associated with lower number of corpora lutea in the left ovary, decreased percentage of viable fetuses, and higher number of fetal resorptions in the left uterine horn when compared to the control group. The strategy of supplementing the diet with antioxidant vitamins to prevent the age associated decrease in reproductive potential should not be implemented in human beings until a safe and efficient diet is designed.

Assessment of mitochondrial toxicity in human cells treated with tenofovir: comparison with other nucleoside reverse transcriptase inhibitors

Drug-associated dysfunction of mitochondria is believed to play a role in the etiology of the various adverse symptoms that occur in human immunodeficiency virus (HIV)-infected patients treated with the nucleoside reverse transcriptase inhibitors (NRTIs). Tenofovir, a nucleotide analog recently approved for use in the treatment of HIV infection, was evaluated in vitro for its potential to cause mitochondrial toxicity and was compared to currently used NRTIs. Treatment with tenofovir (3 to 300 microM) for up to 3 weeks produced no significant changes in mitochondrial DNA (mtDNA) levels in human hepatoblastoma (HepG2) cells, skeletal muscle cells (SkMCs), or renal proximal tubule epithelial cells. The potencies of inhibition of mtDNA synthesis by the NRTIs tested were zalcitabine (ddC) > didanosine (ddI) > stavudine > zidovudine (ZDV) > lamivudine = abacavir = tenofovir, with comparable relative effects in the three cell types. Unlike ddC and ddI, tenofovir did not affect cellular expression of COX II and COX IV, two components of the mitochondrial cytochrome c oxidase complex. Lactate production was elevated by less than 20% in HepG2 cells or SkMCs following treatment with 300 microM tenofovir. In contrast, lactate synthesis increased by >200% in the presence of 300 microM ZDV. Thus, treatment of various human cell types with tenofovir at concentrations that greatly exceed those required for it both to have in vitro anti-HIV type 1 activity in peripheral blood mononuclear cells (50% effective concentration, 0.2 microM) and to achieve therapeutically relevant levels in plasma (maximum concentrations in plasma, 0.8 to 1.3 microM) is not associated with mitochondrial toxicity.

Oral antioxidants counteract the negative effects of female aging on oocyte quantity and quality in the mouse

This study aims to compare the effect of early and late onset administration of oral antioxidants on number and quality of oocytes retrieved from aged mice after exogenous ovarian stimulation. Control hybrid females were fed a standard diet supplemented or not supplemented with pharmacological doses of vitamins C and E either from the first day of weaning or from the age of 32 weeks until they were autopsied at the age 40-42, 50-52, or 57-62 weeks after exogenous ovarian stimulation. Analysis of chromosomal distribution, DNA organization and cellular morphology was performed in ovulated cumulus-enclosed and -free oocytes, ovarian non-germinal vesicle oocytes enclosed by or free of mucous cumulus cells and in vitro-matured ovarian germinal-vesicle oocytes. Both early and late onset administration of oral antioxidants counteracted the negative effects of female aging on number of ovarian oocytes and total percentage of oocytes retrieved from oviducts and ovaries exhibiting a normal distribution of chromosomes in the metaphase-II plate and/or morphological traits of apoptosis. Although both early and late onset administration of oral antioxidants can counteract the negative effects of female aging on number and quality of oocytes, transference of these results to human beings should be made with caution because of the potential side effects of high doses of vitamins on reproductive function as well as many other undesirable systemic disorders.

Effect of dietary supplementation with a mixture of Vitamins C and E on fertilization of tertiary butyl hydroperoxide-treated oocytes and parthenogenetic activation in the mouse

The present study aims to analyze the effect of dietary supplementation with a mixture of Vitamins C and E on fertilization and later development of tertiary butyl hydroperoxide (tBH)-treated mouse oocytes and on parthenogenetic activation of freshly ovulated mouse oocytes. We fed hybrid mice a standard diet supplemented or not supplemented with Vitamins C and E from the first day of weaning until the age of 12 weeks. We noted no significant effect of diet on fertilization rate, percentage of total and hatching blastocysts, total number of cells, mitotic index and percentage of apoptotic nuclei at 120 h post-insemination of oocytes incubated for 15 min in the presence of 0, 1, 5 and 10 microM tBH. Furthermore, diet did not affect the percentage of activated oocytes after treatment with Ca2+ ionophore, acid Tyrode's solution or ethanol. The percentage of parthenogenetically activated oocytes that progressed to the pronuclear stage was significantly higher in the antioxidant group. Oocytes from antioxidant females exhibited a significantly lower mitogen-activated protein kinase (MAPK) activity than oocytes from control females. We detected no significant differences between groups in M-phase-promoting factor (MPF) activity. These results show that oral administration of antioxidants decreases MAPK activity and increases the probability of reaching the pronuclear stage after parthenogenetic activation.

Hyperlactatemia and antiretroviral therapy: the Swiss HIV Cohort Study

The prevalence, clinical presentation, and risk factors for hyperlactatemia among patients receiving antiretroviral therapy was determined during a 1-month period for patients in the Swiss HIV Cohort Study. Overall, 73 (8.3%) of 880 patients presented an increase in serum lactate of >1.1 times the upper normal limit (UNL). For 9 patients (1%), lactate elevation was moderate or severe (>2.2 times the UNL). Patients who presented with hyperlactatemia were more likely to be receiving stavudine with or without didanosine (odds ratio, 2.7; 95% confidence interval, 1.5-4.8), as compared with patients who received zidovudine-based regimens. The risk increased with increasing time receiving stavudine with or without didanosine. The association between hyperlactatemia and stavudine with or without didanosine was not biased by these medications being more recently available and, therefore, being given preferentially to patients who had prolonged use of nucleoside analog reverse-transcriptase inhibitors. Hyperlactatemia was associated with lipoatrophy, hyperlipidemia, and hyperglycemia. Age, sex, or stage of infection with human immunodeficiency virus were not predictive of hyperlactatemia. Determination of lactate levels may prove useful in the screening for mitochondrial toxicity.

Mitochondrial toxin 3-nitropropionic acid induces cardiac and neurotoxicity differentially in mice

We investigated the effects of 3-nitropropionic acid (3NPA), a previously characterized neurotoxin, in four strains of mice to better understand the molecular basis of variable host responses to this agent. Unexpectedly, we found significant cardiac toxicity that always accompanied the neurotoxicity in all strains of mice in acute and subacute/chronic toxicity testing. Caudate putamen infarction never occurred without cardiac toxicity. All mouse strains tested are sensitive to 3NPA although the C57BL/6 and BALB/c mice require more exposure than 129SVEMS and FVB/n mice. Cardiac toxicity alone was found in 50% of symptomatic mice tested and morphologically, the cardiac toxicity is characterized by diffuse swelling of cardiomyocytes and multifocal coagulative contraction band necrosis. In subacute to chronic exposure, atrial thrombosis, cardiac mineralization, cell loss, and fibrosis are combined with cardiomyocyte swelling and necrosis. Ultrastructurally, mitochondrial swelling occurs initially, followed by disruption of myofilaments. Biochemically, isolated heart mitochondria from the highly sensitive 129SVEMS mice have a significant reduction of succinate dehydrogenase activity, succinate oxygen consumption rates, and heart adenosine triphosphate after 3NPA treatment. The severity of morphological changes parallels the biochemical alterations caused by 3NPA, consistent with cardiac toxicity being a consequence of the effects of 3NPA on succinate dehydrogenase. These experiments show, for the first time, that 3NPA has important cardiotoxic effects as well as neurotoxic effects, and that cardiac toxicity possibly resulting from inhibition of the succinate dehydrogenase in heart mitochondria, contributes to the cause of death in 3NPA poisoning in acute and subacute/chronic studies in mice.