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PubMed1999

Glutathione homeostasis in response to exercise training and nutritional supplements.

Glutathione plays a central role in the maintenance of tissue antioxidant defenses and in the regulation of redox sensitive signal transduction. In muscle cells, the level and redox status of GSH regulates activity of the redox sensitive transcription factor NF-kappaB. Physical exercise may cause oxidation of GSH in tissues such as the blood, skeletal muscle and liver. Endurance training strengthened GSH dependent tissue antioxidant defenses in most studies. Although studies investigating the effect of sprint training are few, current results show that sprint training may also have a beneficial effect on tissue GSH homeostasis. Skeletal muscle GSH level appears to be tightly regulated by the state of physical activity. Regular exercise enhances and chronic inactivity decreases the level of GSH in this tissue. N-acetyl-L-cysteine (NAC) and alpha-lipoic acid (LA) are two antioxidant dietary supplements that are able to enhance cellular GSH levels. Because LA can be recycled to its potent dithiol form, dihydrolipoate, by enzymes present in the human cell it has a clear advantage over NAC. Recently an improved form of LA, a positively charged analogue (LA-Plus), has been discovered. LA-Plus has more potent immuno-modulatory activity compared to LA. Both LA and NAC have been shown to have beneficial effects in protecting tissue GSH homeostasis against exercise induced oxidative stress.

Dietary Supplements↗
PubMed1999

Separation of structurally related flavonoids by GC/MS technique and determination of their polarographic parameters and potential carcinogenicity.

The present study deals with the investigation of the naturally occurring derivatives of the benzo[b]pyran-4-one - flavonoids - chrysin, tectochrysin and galangin, and with the effect of minor changes in their chemical structure on their separation using GC/MS. In the relation to their close chemical structure, their basic polarographic parameters were also investigated. Their potential carcinogenicity index tg alpha was determined by DC polarography experiments in the presence of alpha-lipoic acid. The tg alpha values for chrysin, tectochrysin and galangin were all under 0.180. This indicates a very minor carcinogenic potential that does not prevent the use of the investigated flavonoids in human.

Carcinogens↗
PubMed1999

Ototoxicity. Amelioration by protective agents.

The findings of studies from this laboratory are summarized to compare the efficacy of four chemoprotective agents against the effects of cisplatin-induced hearing loss and biochemical damage in the rat cochlea. A number of studies have shown that cisplatin is ototoxic, resulting in hearing loss, morphologic damage, and biochemical changes in the cochlea. These studies used Wistar rats, which underwent pre- and posttreatment ABR testing using clicks and tonebursts stimuli at 8, 16, and 32 kHz. Controls received i.p. saline injection. Cisplatin-treated rats were given 16 mg/kg cisplatin i.p. Animals received protective agents in the following dosage: DDTC protected rats received 600 mg/kg subcutaneously an hour after cisplatin. MTBA-protected animals were given 250 mg/kg i.p. 30 minutes before cisplatin. Animals protected with ebselen received 16 mg/kg i.p. an hour before cisplatin. One hundred mg/kg of alpha-lipoic acid was injected i.p. 30 minutes before cisplatin. Rats were sacrificed three days after treatment and the cochleae were harvested and frozen in liquid nitrogen and stored at -80 degrees C until analysis of glutathione (GSH), the activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) and malondialdehyde was performed. Cisplatin-treated rats were found to have ABR threshold shifts of 27-40 dB, and rats treated with chemoprotective agents plus cisplatin all had ABR thresholds shifts of less than 10 dB. Significant depletion of glutathione and decrease of the activities of the antioxidant enzymes were observed in cisplatin-treated rats. These changes were accompanied by a marked elevation of malondialdehyde. These changes were almost completely prevented by the use of the chemoprotective agents. These findings suggest that cisplatin ototoxicity is related to lipid peroxidation and that the use of protective agents prevents hearing loss and lipid peroxidation by sparing the antioxidant defense system in the cochlea.

Animals↗
PubMed2000

Alternative therapies: Part I. Depression, diabetes, obesity.

Natural supplements are widely used in the United States and, while claims of their therapeutic effects abound, medical research does not always support their effectiveness. St. John's wort acts as a weak selective serotonin reuptake inhibitor with fewer side effects. S-Adenosylmethionine (SAMe) has enough of an antidepressant effect to warrant further research. More human studies are needed before garlic, bitter melon, soy and fenugreek supplements can be recommended for the management of diabetes, although chromium may be a promising treatment in some cases. Alpha lipoic acid is used in the treatment of diabetic neuropathy. The effects of ma huang/guarana combinations in obesity have not been well studied. These combinations may have potentially serious side effects but may also offer some benefit. The combination of hydroxycitric acid and garcinia has proved no more effective than placebo.

Complementary Therapies↗
PubMed2000

Therapeutic potential of glutathione.

Reactive oxygen species, formed in various biochemical reactions, are normally scavenged by antioxidants. Glutathione in its reduced form (GSH) is the most powerful intracellular antioxidant, and the ratio of reduced to oxidised glutathione (GSH:GSSG) serves as a representative marker of the antioxidative capacity of the cell. Several clinical conditions are associated with reduced GSH levels which as a consequence can result in a lowered cellular redox potential. GSH and the redox potential of the cell are components of the cell signaling system influencing the translocation of the transcription factor NF kappa B which regulates the synthesis of cytokines and adhesion molecules. Therefore, one possibility to protect cells from damage caused by reactive oxygen species is to restore the intracellular glutathione levels. Cellular GSH concentration can be influenced by exogenous administration of GSH (as intravenous infusion or as aerosol), of glutathione esters or of GSH precursors such as glutamine or cysteine (in form of N-acetyl-L-cysteine, alpha-lipoic acid). The modulation of GSH metabolism might present a useful adjuvant therapy in many pathologies such as intoxication, diabetes, uremia, sepsis, inflammatory lung processes, coronary disease, cancer and immunodeficiency states.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Immunotherapy (recombinant interleukin 2), hormone therapy (medroxyprogesterone acetate) and antioxidant agents as combined maintenance treatment of responders to previous chemotherapy.

An open, non-randomized phase II study was carried out including all patients treated with whatever chemotherapy or combined modality regimen for whatever cancer who were in clinical objective response or stable disease (SD) for more than three months, to receive maintenance treatment with recombinant interleukin-2 (rIL-2) plus medroxyprogesterone acetate (MPA) plus antioxidant agents alpha-lipoic acid (ALA) and N-acetyl cysteine (NAC). The main study endpoints were clinical outcome and toxicity. The secondary endpoints were effects of treatment on cancer-related anorexia/cachexia syndrome (CACS) symptoms, on serum levels of proinflammatory cytokines, IL-2, C-reactive protein (CRP) and leptin as well as the evaluation of quality of life (QL). rIL-2 was administered at a dose of 1.8 MIU subcutaneously three times/week on alternate days for the first two weeks of every month and MPA was given orally at a dose of 500 mg once a day at alternate days without interruption. ALA 300 mg/day orally and NAC 1800 mg/day orally were also administered. The treatment was administered until progression of disease or appearance of toxicity. From July 1998 to May 2000, 16 patients were enrolled in the study (M/F ratio: 15/1; mean age: 62 years, range 45-71). The median duration of maintenance treatment was 10 months (range 5-22). The response to maintenance treatment at September 2000 was: CR (persistent throughout the treatment) 4 patients (25%); SD 1 patient (6.2%); PD 11 patients (68.8%). The median duration of response was 9.8 months (range: 5-22+). The median follow-up duration was 19 months (range: 8-102). The median OS was not reached. The median PFS was 14 months (range 1-29). The 1-year survival rate was 25%. At September 2000, 9 patients are still surviving. No grade 3/4 toxicity was observed. One Grade 2 skin toxicity was observed and Grade 1: 2 fever, 2 thrombocytopenia, 1 neutropenia and 1 skin were observed. The ECOG PS did worsen significantly, the body weight and BMI increased significantly after treatment, whereas the appetite did not change significantly. The QL evaluation showed a significant amelioration of cognitive functions and a borderline significant amelioration of emotional functions after treatment, whereas a borderline worsening of dyspnea was observed. The absolute lymphocyte count increased significantly after the maintenance treatment, as well as the serum IL-2, TNFalpha decreased at borderline statistical significance; the serum levels of leptin did not change significantly. The evaluation of patient subgroups showed that responders/survivors had a pattern superimposable to that of whole patient population, the patients who rapidly progressed and died exhibited no significant changes of these parameters during treatment. The results of the present study suggest that the host immune response, evaluated by several parameters, after IL-2 administration, (e.g. lymphocytosis), are worth further study as potential markers for the major end points of cancer treatment, i.e. OS and QL, in an adequate number of patients.

Aged↗
PubMed2001

Potential for creatine and other therapies targeting cellular energy dysfunction in neurological disorders.

Substantial evidence indicates that bioenergetic dysfunction plays either a primary or secondary role in the pathophysiology of cell death in neurodegenerative and neuromuscular disorders, and even in normal aging. Agents that ameliorate bioenergetic defects may therefore be useful in therapy. Creatine, which increases muscle and brain phosphocreatine concentrations, and may inhibit the activation of the mitochondrial permeability transition, protects against neuronal degeneration in transgenic murine models of amyotrophic lateral sclerosis and Huntington's disease and in chemically mediated neurotoxicity. Initial studies of creatine use in humans appear promising; however, further long-term, well-designed trials are needed. Coenzyme Q10, Gingko biloba, nicotinamide, riboflavin, carnitine, lipoic acid, and dichloroacetate are other agents which may have beneficial effects on energy metabolism, but the preclinical and clinical evidence for efficacy in neurological diseases remains limited. These compounds are widely used as dietary supplements; however, they must be subjected to rigorous evaluation through randomized, double-blinded trials to establish efficacy, cost-effectiveness and safety in neurological disorders.

Animals↗
PubMed2001

Chronic fatigue syndrome: oxidative stress and dietary modifications.

Chronic fatigue syndrome (CFS) is an illness characterized by persistent and relapsing fatigue, often accompanied by numerous symptoms involving various body systems. The etiology of CFS remains unclear; however, a number of recent studies have shown oxidative stress may be involved in its pathogenesis. The role of oxidative stress in CFS is an important area for current and future research as it suggests the use of antioxidants in the management of CFS. Specifically, the dietary supplements glutathione, N-acetylcysteine, alpha-lipoic acid, oligomeric proanthocyanidins, Ginkgo biloba, and Vaccinium myrtillus (bilberry) may be beneficial. In addition, research on food intolerance is discussed, since food intolerance may be involved in CFS symptom presentation and in oxidation via cytokine induction. Finally, recent evidence suggests celiac disease can present with neurological symptoms in the absence of gastrointestinal symptoms; therefore, celiac disease should be included in the differential diagnosis of CFS.

Antioxidants↗
PubMedDate not supplied

Prevention of benznidazole-induced prolonging effect on the pentobarbital sleeping time of rats using different thiol-containing compounds.

Benznidazole (BZ) is a nitroimidazolic chemotherapeutic agent employed against the acute and indeterminate phase of Chagas' disease, a tropical sickness afflicting more than twenty million people in Latin America. BZ has serious toxic side effects forcing people to stop treatment. These effects were attributed to the nitroreductive metabolic activation of BZ to a hydronitroxide radical or the hydroxylamine, which would covalently bind to cellular components. One of these deleterious effects is the prolongation on the pentobarbital sleeping time of rats. This results from the covalent binding of BZ reactive metabolites, arisen during its nitroreductive metabolism, to the phospholipid component of the mixed function oxidase which biotransform the barbiturate. In this study, the potential ability of different thiol containing drugs to trap BZ reactive metabolites and to prevent BZ effect on the pentobarbital sleeping time was tested. Our HPLC studies evidenced that cysteine, N-acetylcysteine, penicillamine and glutathione were able to trap BZ reactive metabolites in vitro to produce one or two adducts. Reduced lipoic acid instead, decreased the intensity of the nitroreductive process without leading to detectable adducts. The in vivo administration of the thiol drugs, at dosage regimes available in literature, was able to markedly prevent the BZ prolongation effect on the sleeping time. Whether these thiols might prevent other BZ toxic effects without harming its chemotherapeutic actions remains to be established.

Animals↗
PubMed2001

Neuronal death in the rat hippocampus in experimental diabetes and cerebral ischaemia treated with antioxidants.

Male Wistar rats were subjected to intraperitoneal (i.p.) streptozotocin (STZ) administration (85 mg/kg) to evoke diabetes. Cerebral ischaemia was produced by injection of 0.03 ml of air into the left carotid followed by bilateral common carotid ligation. We studied the effect of application of two antioxidants--coenzyme Q10 (CoQ10, 10 mg/kg b.w., i.p. for seven days) and lipoic acid (LA, 100 mg/kg b.w., i.p. for seven days) on neurones and on the apoptosis-related enzyme--caspase-3 activity in the hippocampus and dentate gyrus. Ischaemia and diabetes lead to a decrease of nuclear and perikaryon diameters as well as neuronal density in the CA1, CA2, CA3 and dentate gyrus. Application of CoQ10 or LA for seven days improved the mean nucleus area and perikaryon area in almost all investigated structures. Both antioxidants diminished neuronal loss in the diabetes complicated with ischaemia but not in the animals with diabetes only. Activity of one of the key enzymes in apoptotic cell death, caspase-3 (CPP32), increased in hippocampus in the diabetic rats, in the animals with cerebral ischaemia and in the rats with both diabetes and ischaemia by about 80%, 33% and 53%, respectively. Either the CoQ10 or the LA treatment led to a significant decrease of the CPP32 activity in all experimental groups. Our results confirm the presence of neuronal damage and death in the hippocampus and dentate gyrus in the experimental STZ-diabetes and its aggravation by the additional cerebral ischaemia. The effects of the antioxidative treatment support the hypothesis of an important role of oxidative stress and free radicals in neuronal pathology in diabetes and ischaemia. The above results of CPP32 activity suggest an important role of apoptosis as a mechanism of cell death and demonstrate the positive effect of the CoQ10 and the LA treatment.

Animals↗
PubMed2001

[Detection and treatment of lower extremity neuropathy in patients with diabetic foot].

Possibilities of diagnosis and treatment of the lower extremities neuropathy were studied in 118 patients with diabetes mellitus (DM). Neurological examination, investigation of algesic, vibratory and temperature sensibility, thermography of feet were done in each patient. Electrostimulation treatment using therapeutic-diagnostic complex "Salut 11" was applied in 47 patients. Algesic syndrome and paresthesia occurs in the absence of the ulcerative-necrotic changes of foot or together with disorders of passability of the lower extremity main arteries. Ulcerative-necrotic changes of the foot tissues, caused by diabetic microangiopathy, are observed in the absence of pain and paresthesia, witnessing the presence of various mechanisms of the diabetic neuropathy occurrence. Application of the alpha-lipoic acid preparations had promoted the reduction of the pain and paresthesia intensity in 63% of patients. Usage of the lower extremities electromyoneurostimulation with the help of permanent impulsive current promotes the healing improvement of the purulent-necrotic wounds and ulcers of foot in patients with DM.

Adult↗
PubMed2002

Antioxidant supplementation decreases lipid peroxidation biomarker F(2)-isoprostanes in plasma of smokers.

Free radicals in cigarette smoke (CS) cause oxidative damage to proteins, DNA, and lipids, contributing to the pathobiology of atherosclerosis, heart disease, and cancer. In vitro studies have shown that antioxidants quench free radicals and ameliorate certain aspects of biomolecular damage caused by CS. It is hypothesized that a combination of antioxidants is more effective than a single antioxidant, due to their interactions. To investigate whether supplemental antioxidants reduce CS-related lipid peroxidation in vivo and whether they are more effective in combination, we conducted an intervention study in smokers. In a randomized double-blind placebo-controlled trial, we investigated whether vitamin C or an antioxidant mixture containing vitamin C, alpha-lipoic acid, and vitamin E decreases plasma F(2)-isoprostane levels, an index of oxidant stress, in smokers. Plasma of 126 smokers (mean age, 46 years; age range, 20-78 years) was analyzed for F(2)-isoprostanes at baseline and after intervention with antioxidants and placebo. In smokers with a body mass index (BMI) above the median, 2 months of daily supplementation with 500 mg of vitamin C decreased plasma F(2)-isoprostane levels by 28.8 pmol/liter when compared with the placebo group (P = 0.001); levels in the mixture group were 7.45 pmol/liter lower after treatment, but this difference was not statistically significant (P = 0.14). There was no treatment effect in smokers with a low BMI. BMI was significantly positively associated with plasma F(2)-isoprostane levels (trend P = 0.001). Antioxidants decrease smoking-related lipid peroxidation markers of oxidative stress in humans with high BMI. Our results do not indicate that an antioxidant combination is more effective than vitamin C alone. The intake of antioxidants may help prevent smoking-related diseases. Smoking cessation should still be considered the most effective way to prevent smoking-related diseases.

Adult↗
PubMedDate not supplied

Dose-intense phase II study of weekly cisplatin and epidoxorubicin plus medroxyprogesterone acetate and recombinant interleukin 2 in stage IIIB-IV non-small cell lung cancer.

The purpose of the study was to evaluate the effectiveness in terms of response rates, toxicity and survival of the combination chemotherapy regimen cisplatin and epidoxorubicin (epirubicin) including medroxyprogesterone acetate (MPA), recombinant IL-2 (rIL-2) and antioxidants in patients with advanced (stage IIIB-IV) non-small cell lung cancer (NSCLC). Thirty-three chemotherapy-naive patients with NSCLC were enrolled in the study and 30 of them were evaluable. The mean age of the patients was 61 years. Twenty (66.7%) out of 30 patients were >or=60 years, and 5 (16.7%) patients were >or=70 years. The ECOG performance status was 0 to 1 in 30 patients and 2 in 3 patients. Twenty-six patients (78.8%) had stage IIIB disease and 7 (21.2%) had stage IV; histology was mainly squamous cell carcinoma (72.7%). The treatment consisted of cisplatin 40 mg/m2/week and epirubicin 40 mg/m2/week both intravenously on day 1, rIL-2 1.8 MIU/day subcutaneously, MPA 1 g/day orally, alpha-lipoic acid 300 mg/day orally and N-acetyl cysteine 1.8 g/day orally. The treatment was administered for 6 weeks. Patients with a complete response (CR), partial response (PR) or stable disease (SD) continued the treatment, according to response re-evaluation, until 15 weeks. The present study reports the results of 6, 9, 12 and 15-week treatment. After 6 weeks, 30 patients were assessable for response: no CR was observed, a PR was achieved in 15 patients (50%; ORR 50%). After 15 weeks, 1 CR and 8 PR were observed (ORR 30.0%). The median follow-up period was 13 months. The median duration of response was 9 months. The median overall survival (OS) was 15 months. The one-year survival rate was 55.8%. The median progression-free survival (PFS) was 10 months. The toxicity was, as expected, mainly hematologic: neutropenia was the most significant symptom. The non-hematologic toxicity was quite low. Therefore, the treatment's toxicity was quite acceptable. There was no toxic death. The 30.0% ORR, the 15 month OS and the 10 month PFS obtained in this study are comparable with those observed with cisplatin plus epirubicin (ORR 39-54%) in phase II studies and in a previous phase III study (ORR 33%, OS 10.5 months). Moreover, the toxicity was acceptable and it was mainly hematologic. Serum levels of proinflammatory cytokines significantly decreased after treatment.

Adult↗
PubMedDate not supplied

Phase II study of subcutaneously administered interleukin-2 in combination with medroxyprogesterone acetate and antioxidant agents as maintenance treatment in advanced cancer responders to previous chemotherapy.

An open, non-randomized phase II study was carried out including patients with advanced solid tumors who achieved an objective response or disease stabilization as a result of previous chemotherapy, to receive a maintenance treatment with recombinant interleukin-2 (rIL-2) plus medroxyprogesterone acetate (MPA) plus antioxidant agents alpha-lipoic acid (ALA) and N-acetyl cysteine (NAC). The first study endpoints were to define clinical outcome and toxicity as well as the evaluation of quality of life. As secondary endpoints we measured the changes of lymphocyte absolute count, the serum levels of proinflammatory cytokines, IL-2, C-reactive protein (CRP) and leptin after treatment. rIL-2 was administered at a dose of 1.8 MIU subcutaneously 3 times/week on alternate days for the first two weeks of every month and MPA was given orally at a dose of 500 mg/day at alternate days without interruption. ALA 300 mg/day orally and NAC 1800 mg/day orally were also administered continuously. Twenty-eight patients were enrolled in the study. The median duration of maintenance treatment was 10 months (6-30+). The response to maintenance treatment at September 15, 2001 was: CR 11 patients (39.3%); SD 2 patients (7.1%); PD 15 patients (53.6%). The median duration of response was 11 months (6-34+). The median follow-up duration was 11 months (6-34+). The median OS was not reached. The median PFS was 21.5 months (1-40+). The 1-year survival rate was 72.2%. At September 15, 2001, 16 patients were still surviving. No grade 3/4 toxicity and one grade 2 skin toxicity were observed. We found a significant increase of the absolute lymphocyte count and serum levels of IL-2 and a significant decrease of TNF alpha after treatment. The evaluation of patient subgroups showed the following: the patients alive at the end of study had a significant increase of lymphocyte count, IL-2 and leptin, and a significant decrease of IL-1 beta, IL-6 and TNF alpha, whereas the patients who had died had only a significant increase of lymphocyte count and IL-2. Among the patients alive, those in objective clinical response (CR + PR) + those in SD had a significant increase of lymphocyte count, IL-2 and leptin and a significant decrease of IL-1 beta, IL-6 and TNFalpha, whereas those with PD had no significant changes in any of the above values. We conclude that the combination of s.c. rIL-2 with oral MPA and anti-oxidant agents ALA and NAC in an intermittent schedule, repeated for a long-term period, is feasible, has a very low toxicity and results in the improvement of biological markers which are predictive for patient outcome.

Acetylcysteine↗
PubMed2002

[Autonomic neuropathy in diabetics, treatment possibilities].

Diabetic neuropathy is a chronic complication of diabetes. It involves non-inflammatory damage of the function and structure of peripheral nerves by metabolic vascular pathogenic processes. In case of affection of vegetative nerves (small non-myelinated C fibres) autonomic neuropathy develops. It is a relatively frequent form of neuropathy which remains for a long time without clinical symptoms and therefore is rarely diagnosed and treated. Manifestations of the affection are encountered in all organs which are supplied by vegetative nerves. The presence of this complication of diabetes is signalized by tachycardia at rest, deterioration of gastric evacuation, diabetic diarrhoea or constipation, erectile dysfunction, impaired function of the sweat glans or impaired pupillary reaction. The advanced form involves the danger of latent myocardial ischaemia, serious postural hypotension and sudden death. It increases significantly the mortality of the affected patients. Similarly as the treatment of other complication of diabetes, treatment of autonomic neuropathy is difficult. The objective of the present paper is to review contemporary therapeutic possibilities. An essential prerequisite remain efforts to achieve optimal compensation. The authors draw attention to the effect of alpha-lipoic acid which exerts a positive effect not only on subjective symptoms but also on the objective finding. The other mentioned drugs are used either only experimentally or for purely symptomatic treatment.

Diabetic Neuropathies↗
PubMed2003

Comparison of the carcinogenic potential of streptozotocin by polarography and alkaline elution.

The carcinogenic potential of streptozotocin (STZ) was evaluated by the polarographic determination of its reduction potential in the presence of alpha-lipoic acid and detection of DNA single-strand brakes by alkaline elution. After STZ electrochemical reduction in an anhydrous solvent, the half-wave potential (E1/2 ) was determined to be -1.340 V. The parameter of the carcinogenic potential (tg alpha) for STZ was 0.400. This is in good agreement with WHO data regarding STZ carcinogenicity. Additionally, it is in the good agreement with the tg alpha value determined for the positive control used, N-nitroso-N-methylurea (NMU), which was found to be 0.459. The 3 hours exposure of A549 human lung tumor cells to 250, 500, and 1000 nmol/ml STZ was followed by DNA single-strand brakes detection using the alkaline elution method. NMU, the positive control, was tested under identical experimental conditions at the same concentrations. Without metabolic activation, NMU induced a significant formation of DNA single-strand brakes only at 1000 nmol/ml. In the presence of the metabolic activation, NMU caused a significant, concentration-dependent formation of DNA single-strand brakes. In the absence of metabolic activation, STZ induced no significant formation of DNA single-strand brakes at any concentration used. In the presence of metabolic activation, STZ caused a significant, concentration-dependent formation of DNA single-strand brakes. The results of this study underline the crucial role of using a metabolic activation system when carcinogenic potential of drugs and chemicals is investigated in vitro studies. Results of polarographic experiments and alkaline elution correlate well with each other and they indicate that these methods are useful to early predict the carcinogenic potential of STZ and other xenobiotics.

Carcinogens↗
PubMed2003

Toxic metals and antioxidants: Part II. The role of antioxidants in arsenic and cadmium toxicity.

Exposure to toxic metals has become an increasingly recognized source of illness worldwide. Both cadmium and arsenic are ubiquitous in the environment, and exposure through food and water as well as occupational sources can contribute to a well-defined spectrum of disease. The symptom picture of arsenic toxicity is characterized by dermal lesions, anemia, and an increased risk for cardiovascular disease, diabetes, and liver damage. Cadmium has a significant effect on renal function, and as a result alters bone metabolism, leading to osteoporosis and osteomalacia. Cadmium-induced genotoxicity also increases risk for several cancers. The mechanisms of arsenic- and cadmium-induced damage include the production of free radicals that alter mitochondrial activity and genetic information. The metabolism and excretion of these heavy metals depend on the presence of antioxidants and thiols that aid arsenic methylation and both arsenic and cadmium metallothionein-binding. S-adenosylmethionine, lipoic acid, glutathione, selenium, zinc, N-acetylcysteine (NAC), methionine, cysteine, alpha-tocopherol, and ascorbic acid have specific roles in the mitigation of heavy metal toxicity. Several antioxidants including NAC, zinc, methionine, and cysteine, when used in conjunction with standard chelating agents, can improve the mobilization and excretion of arsenic and cadmium.

Antioxidants↗
PubMed2003

Human enzymes involved in the metabolic activation of the environmental contaminant 3-nitrobenzanthrone: evidence for reductive activation by human NADPH:cytochrome p450 reductase.

Determining the capability of humans to metabolize the suspected carcinogen 3-nitrobenzanthrone (3-NBA) and understanding which human enzymes are involved in its activation are important in the assessment of individual susceptibility to this environmental contaminant found in diesel exhaust and ambient air pollution. We compared the ability of eight human hepatic microsomal samples to catalyze DNA adduct formation by 3-NBA. Using two enrichment procedures of the (32)P-postlabeling method, nuclease P1 digestion and butanol extraction, we found that all hepatic microsomes were competent to activate 3-NBA. DNA adduct patterns with multiple adducts, qualitatively similar to those found recently in vivo in rats, were observed. Additionally one major DNA adduct generated by human microsomes was detected. The role of specific cytochromes p450 (p450) and NADPH:p450 reductase in the human hepatic microsomal samples in 3-NBA activation was investigated by correlating the p450- and NADPH: p450 reductase-linked catalytic activities in each microsomal sample with the level of DNA adducts formed by the same microsomes. On the basis of this analysis, most of the hepatic microsomal activation of 3-NBA was attributed to NADPH: p450 reductase. Inhibition of DNA adduct formation in human liver microsomes by alpha-lipoic acid, an inhibitor of NADPH: p450 reductase, supported this finding. Using the purified rabbit enzyme and recombinant human NADPH: p450 reductase expressed in Chinese hamster V79 cells, we confirmed the participation of this enzyme in the formation of 3-NBA-derived DNA adducts. Moreover, essentially the same DNA adduct pattern found in microsomes was detected in metabolically competent human lymphoblastoid MCL-5 cells. The role of individual human recombinant p450s 1A1, 1A2, 1B1, 2A6, 2B6, 2D6, 2C9, 2E1, and 3A4 and of NADPH: p450 reductase in the metabolic activation of 3-NBA, catalyzing DNA adduct formation, was also examined using microsomes of baculovirus-transfected insect cells containing the recombinant enzymes (Supersomes). DNA adducts were observed in all Supersomes preparations, essentially similar to those found with human hepatic microsomes and in human cells. Of all of the recombinant human p450s, p450 2B6 and -2D6 were the most efficient to activate 3-NBA, followed by p450 1A1 and -1A2. These results demonstrate for the first time the potential of human NADPH: p450 reductase and recombinant p450s to contribute to the metabolic activation of 3-NBA by nitroreduction.

Animals↗