Comparison of the effect of alpha-lipoic acid and alpha-tocopherol supplementation on measures of oxidative stress

Mitochondrial dysfunction in the pathophysiology of renal diseases

Mitochondria are essential organelles in the human body, serving as the metabolic factory of the whole organism. When mitochondria are dysfunctional, it can affect all organs of the body. The kidney is rich in mitochondria, and its function is closely related to the development of kidney diseases. Studying the relationship between mitochondria and kidney disease progression is of great interest. In the past decade, scientists have made inspiring progress in investigating the role of mitochondria in the pathophysiology of renal diseases. This article discusses various mechanisms for maintaining mitochondrial quality, including mitochondrial energetics, mitochondrial biogenesis, mitochondrial dynamics, mitochondrial DNA repair, mitochondrial proteolysis and the unfolded protein response, mitochondrial autophagy, mitochondria-derived vesicles, and mitocytosis. The article also highlights the cross talk between mitochondria and other organelles, with a focus on kidney diseases. Finally, the article concludes with an overview of mitochondria-related clinical research.

Alpha-lipoic acid for diabetic peripheral neuropathy

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a frequent complication in people living with type 1 or type 2 diabetes. There is currently no effective treatment for DPN. Although alpha-lipoic acid (ALA, also known as thioctic acid) is widely used, there is no consensus about its benefits and harms.

OBJECTIVES

To assess the effects of alpha-lipoic acid as a disease-modifying agent in people with diabetic peripheral neuropathy.

SEARCH METHODS

On 11 September 2022, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, and two clinical trials registers. We also searched the reference lists of the included studies and relevant review articles for additional references not identified by the electronic searches.

SELECTION CRITERIA

We included randomised clinical trials (RCTs) that compared ALA with placebo in adults (aged 18 years or older) and that applied the study interventions for at least six months. There were no language restrictions.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane. The primary outcome was change in neuropathy symptoms expressed as changes in the Total Symptom Score (TSS) at six months after randomisation. Secondary outcomes were change in neuropathy symptoms at six to 12 months and at 12 to 24 months, change in impairment, change in any validated quality of life total score, complications of DPN, and adverse events. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

Our analysis incorporated three trials involving 816 participants. Two studies included people with type 1 or type 2 diabetes, while one study included only people with type 2 diabetes. The duration of treatment was between six months and 48 months. We judged all studies at high risk of overall bias due to attrition. ALA compared with placebo probably has little or no effect on neuropathy symptoms measured by TSS (lower score is better) after six months (mean difference (MD) -0.16 points, 95% confidence interval (CI) -0.83 to 0.51; 1 study, 330 participants; moderate-certainty evidence). The CI of this effect estimate did not contain the minimal clinically important difference (MCID) of 0.97 points. ALA compared with placebo may have little or no effect on impairment measured by the Neuropathy Impairment Score-Lower Limbs (NIS-LL; lower score is better) after six months (MD -1.02 points, 95% CI -2.93 to 0.89; 1 study, 245 participants; low-certainty evidence). However, we cannot rule out a significant benefit, because the lower limit of the CI surpassed the MCID of 2 points. There is probably little or no difference between ALA and placebo in terms of adverse events leading to cessation of treatment within six months (risk ratio (RR) 1.48, 95% CI 0.50 to 4.35; 3 studies, 1090 participants; moderate-certainty evidence). No studies reported quality of life or complications associated with DPN.

AUTHORS' CONCLUSIONS

Our analysis suggests that ALA probably has little or no effect on neuropathy symptoms or adverse events at six months, and may have little or no effect on impairment at six months. All the studies were at high risk of attrition bias. Therefore, future RCTs should ensure complete follow-up and transparent reporting of any participants missing from the analyses.

Effect of Alpha Lipoic Acid Supplementation on Oxidative Stress and Lipid Parameters in Women Diagnosed with Low-Grade Squamous Intraepithelial Lesions (LSILs): A Double-Blind, Randomized, Placebo-Controlled Trial

Limited scientific evidence shows that alpha lipoic acid (ALA) can induce regression rates of low-grade squamous intraepithelial lesions (LSILs), but the mechanisms of these effects have not been elucidated. To gain a broader insight into its therapeutic potential and mechanisms of action, the effects of 3 months of supplementation with 600 mg of ALA on antioxidant and lipid status parameters in 100 patients with LSILs were investigated in a randomized, placebo-controlled study. The obtained results are discussed in terms of patients' initial metabolic status and diet quality (particularly nutritional intake of antioxidants). The obtained results showed that oxidative status biomarkers were not significantly affected by ALA supplementation. However, serum superoxide dismutase (SOD) activity was positively affected in the subgroup of patients with higher dietary antioxidant intake. Surprisingly, ALA supplementation resulted in a small but statistically significant increase in serum low density lipoprotein (LDL), and the observed effect was significantly affected by the initial lipid status of the participants. Larger studies are necessary to gain additional insights on the clinical significance of ALA as an antioxidant and hypolipemic agent and to optimize its potential application in LSIL treatment.

Recent advances in small molecules for improving mitochondrial disorders

Mitochondrial disorders are observed in various human diseases, including rare genetic disorders and complex acquired pathologies. Recent advances in molecular biological techniques have dramatically expanded the understanding of multiple pathomechanisms involving mitochondrial disorders. However, the therapeutic methods for mitochondrial disorders are limited. For this reason, there is increasing interest in identifying safe and effective strategies to mitigate mitochondrial impairments. Small-molecule therapies hold promise for improving mitochondrial performance. This review focuses on the latest advances in developing bioactive compounds for treating mitochondrial disease, aiming to provide a broader perspective of fundamental studies that have been carried out to evaluate the effects of small molecules in regulating mitochondrial function. Novel-designed small molecules ameliorating mitochondrial functions are urgent for further research.

Alpha lipoic acid-loaded electrospun fibrous patch films protect heart in acute myocardial infarction mice by inhibiting oxidative stress

Oxidative stress, characterized by excessive accumulation of reactive oxygen species (ROS), is involved in acute myocardial infarction (AMI)-related pathological processes and vascular reperfusion therapy injury. Alpha lipoic acid (LA) exhibits excellent antioxidant properties, however, its application is limited by inherent characteristics, including rapid clearance and extensive volume distribution. In this study, we hypothesized that scavenging cardiac ROS using adequately delivered LA could promote heart repair. Here, we report a new strategy for dynamic-release LA to treat AMI disease. In particular, this involves using poly(lactic-co-glycolic) (PLGA) copolymers as carriers to form a thin film (LA@PLGA) via electrospinning technology to achieve controlled release of LA, which essentially blocking local ROS production in damaged hearts. The drug-loading capacity and capsulation efficiency of this compound film could be regulated by determining the dose proportions of LA and PLGA. The incubation of LA@PLGA showed strong anti-oxidative activity and anti-apoptosis effect in hydrogen peroxide-administered primary cardiomyocytes. Patching LA@PLGA on the infarcted cardiac surfaces of AMI mice dramatically improved heart functions and reduced cardiac fibrosis throughout ventricular remodeling process. Importantly, the attenuation of detrimental pathologies was observed, including oxidative stress, senescence, DNA damage, cytokine-related processes, apoptosis, and ferroptosis. These results suggest that PLGA-carried LA can reduce ROS damage and restore heart function after myocardial damage, demonstrating a great potential for LA drugs in treating AMI disease.

Molecular and Therapeutic Insights of Alpha-Lipoic Acid as a Potential Molecule for Disease Prevention

Alpha-lipoic acid is an organic, sulfate-based compound produced by plants, humans, and animals. As a potent antioxidant and a natural dithiol compound, it performs a crucial role in mitochondrial bioenergetic reactions. A healthy human body, on the other hand, can synthesize enough α-lipoic acid to scavenge reactive oxygen species and increase endogenous antioxidants; however, the amount of α-lipoic acid inside the body decreases significantly with age, resulting in endothelial dysfunction. Molecular orbital energy and spin density analysis indicate that the sulfhydryl (-SH) group of molecules has the greatest electron donating activity, which would be responsible for the antioxidant potential and free radical scavenging activity. α-Lipoic acid acts as a chelating agent for metal ions, a quenching agent for reactive oxygen species, and a reducing agent for the oxidized form of glutathione and vitamins C and E. α-Lipoic acid enantiomers and its reduced form have antioxidant, cognitive, cardiovascular, detoxifying, anti-aging, dietary supplement, anti-cancer, neuroprotective, antimicrobial, and anti-inflammatory properties. α-Lipoic acid has cytotoxic and antiproliferative effects on several cancers, including polycystic ovarian syndrome. It also has usefulness in the context of female and male infertility. Although α-lipoic acid has numerous clinical applications, the majority of them stem from its antioxidant properties; however, its bioavailability in its pure form is low (approximately 30%). However, nanoformulations have shown promise in this regard. The proton affinity and electron donating activity, as a redox-active agent, would be responsible for the antioxidant potential and free radical scavenging activity of the molecule. This review discusses the most recent clinical data on α-lipoic acid in the prevention, management, and treatment of a variety of diseases, including coronavirus disease 2019. Based on current evidence, the preclinical and clinical potential of this molecule is discussed.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43450-023-00370-1.

Positive Aspects of Oxidative Stress at Different Levels of the Human Body: A Review

Oxidative stress is the subject of numerous studies, most of them focusing on the negative effects exerted at both molecular and cellular levels, ignoring the possible benefits of free radicals. More and more people admit to having heard of the term "oxidative stress", but few of them understand the meaning of it. We summarized and analyzed the published literature data in order to emphasize the importance and adaptation mechanisms of basal oxidative stress. This review aims to provide an overview of the mechanisms underlying the positive effects of oxidative stress, highlighting these effects, as well as the risks for the population consuming higher doses than the recommended daily intake of antioxidants. The biological dose-response curve in oxidative stress is unpredictable as reactive species are clearly responsible for cellular degradation, whereas antioxidant therapies can alleviate senescence by maintaining redox balance; nevertheless, excessive doses of the latter can modify the redox balance of the cell, leading to a negative outcome. It can be stated that the presence of oxidative status or oxidative stress is a physiological condition with well-defined roles, yet these have been insufficiently researched and explored. The involvement of reactive oxygen species in the pathophysiology of some associated diseases is well-known and the involvement of antioxidant therapies in the processes of senescence, apoptosis, autophagy, and the maintenance of cellular homeostasis cannot be denied. All data in this review support the idea that oxidative stress is an undesirable phenomenon in high and long-term concentrations, but regular exposure is consistent with the hormetic theory.

Lipoic Acid Metabolism as a Potential Chemotherapeutic Target Against Plasmodium falciparum and Staphylococcus aureus

Lipoic acid (LA) is an organic compound that plays a key role in cellular metabolism. It participates in a posttranslational modification (PTM) named lipoylation, an event that is highly conserved and that occurs in multimeric metabolic enzymes of very distinct microorganisms such as Plasmodium sp. and Staphylococcus aureus, including pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase (KDH). In this mini review, we revisit the recent literature regarding LA metabolism in Plasmodium sp. and Staphylococcus aureus, by covering the lipoate ligase proteins in both microorganisms, the role of lipoate ligase proteins and insights for possible inhibitors of lipoate ligases.

Alpha-Lipoic Acid as a Nutritive Supplement for Humans and Animals: An Overview of Its Use in Dog Food

Simple Summary

A review of human and animal studies involving alpha-lipoic acid supplementation was conducted to determine the utility of alpha-lipoic acid in dog food. The present literature shows that alpha-lipoic acid has utility as a nutritive additive at concentrations of 2.7–4.94 mg/kg body weight/day and improves antioxidant capacity in dogs.

Abstract

Alpha-lipoic acid (a-LA) is used as a nutritive additive in dog food. Therefore, we performed a systematic review of studies published to date in PubMed, Google Scholar, Cochrane Library and MedlinePlus involving alpha-lipoic acid supplementation, which included human clinical trials as well as animal studies, to evaluate its utility as a supplement in foods for healthy, adult dogs. While an upper limit of alpha-lipoic acid intake in humans has not been conclusively determined, the levels for oral intake of a-LA have been better defined in animals, and distinct differences based on species have been described. The maximum tolerated oral dose of a-LA in dogs has been reported as 126 mg/kg body weight and the LD₅₀ as 400 to 500 mg/kg body weight. The antioxidant, anti-inflammatory and neuro-protective benefits of alpha-lipoic acid in dogs were observed at concentrations much lower than the maximum tolerated dose or proposed LD₅₀. At concentrations of 2.7–4.94 mg/kg body weight/day, alpha-lipoic acid is well tolerated and posed no health risks to dogs while providing improved antioxidant capacity. This review thereby supports the utility of alpha-lipoic acid as an effective nutritive additive in dog food.

Mechanisms of Toxicity and Modulation of Hemoglobin-based Oxygen Carriers

Several adverse events have been associated with the infusion of hemoglobin-based oxygen carriers (HBOCs), including transient hypertension, gastrointestinal, pancreatic/liver enzyme elevation, and cardiac/renal injury in humans. Although several mechanisms have been suggested, the basis of HBOC toxicity is still poorly understood. Scavenging of vascular endothelial nitric oxide (NO) and heme-mediated oxidative side reactions are thought to be the major causes of toxicity. However, based on more recent preclinical studies, oxidative pathways (driven by the heme prosthetic group) seem to play a more prominent role in the overall toxicity of free Hb or HBOCs. HBOCs display a diversity of physicochemical properties, including molecular size/cross-linking characteristics leading to differences in oxygen affinity, allosteric, redox properties, and even oxidative inactivation by protein/heme clearing mechanisms. These diverse characteristics can therefore be manipulated independently, leaving open the possibility of engineering a safe and effective HBOC. To date, several antioxidative strategies have been proposed to counteract the redox side reactions of current generation HBOCs.

Advances in drug therapy for mitochondrial diseases

Mitochondrial diseases are a group of clinically and genetically heterogeneous disorders driven by oxidative phosphorylation dysfunction of the mitochondrial respiratory chain which due to pathogenic mutations of mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). Recent progress in molecular genetics and biochemical methodologies has provided a better understanding of the etiology and pathogenesis of mitochondrial diseases, and this has expanded the clinical spectrum of this conditions. But the treatment of mitochondrial diseases is largely symptomatic and thus does not significantly change the course of the disease. Few clinical trials have led to the design of drugs aiming at enhancing mitochondrial function or reversing the consequences of mitochondrial dysfunction which are now used in the clinical treatment of mitochondrial diseases. Several other drugs are currently being evaluated for clinical management of patients with mitochondrial diseases. In this review, the current status of treatments for mitochondrial diseases is described systematically, and newer potential treatment strategies for mitochondrial diseases are also discussed.

Metabolic effects of α-lipoic acid supplementation in pre-diabetics: a randomized, placebo-controlled pilot study

Supplementation of health promoting nutraceuticals may be an effective adjunct strategy with other lifestyle and drug approaches to impede disease progression in prediabetic subjects. α-Lipoic acid, a naturally occurring short-chain fatty acid, has been extensively evaluated for its antioxidant and glycemic control properties but has rarely been investigated as a lipid-lowering strategy. We conducted a pilot study to examine the effects of α-lipoic acid supplementation on glycemic control and lipid profile in pre-diabetic, overweight/obese adults. The study was designed as a free-living, randomized, two-phase, placebo-controlled cross-over study with 12 pre-diabetic, dyslipidemic subjects. Eligible subjects completed two thirty-day phases (in random order) consisting of a placebo (600 mg cellulose per day) and α-lipoic acid treatment (600 mg day^-1). Although no change (p < 0.05) in serum glucose was observed, α-lipoic acid-supplemented subjects demonstrated reduced fasting serum insulin (p = 0.04) and HOMA-IR (p = 0.07) compared with the placebo group. However, no change (p > 0.05) in serum lipids (including total cholesterol, LDL-C, HDL-C, triglycerides, LDL-C/HDL-C, and TC/HDL-C) were observed. Study results suggest that α-lipoic acid supplementation may be a useful strategy to improve insulin sensitivity in pre-diabetic subjects but is not effective in modulating serum lipids.

Evaluating the Lipid-Lowering Effects of α-lipoic Acid Supplementation: A Systematic Review

Dietary supplementation of α-lipoic acid, an 8-carbon organosulfur compound, has been widely reported to lower blood glucose concentration and/or improve insulin sensitivity in previous randomized controlled trials. Although animal model studies further report fairly consistent lipid lowering in both blood and tissue pools in response to α-lipoic acid supplementation, results from human studies are mixed. According to PRISMA guidelines, we conducted a systematic review of published randomized controlled studies (RCTs) to assess the efficacy of α-lipoic acid supplementation as a strategy to improve dyslipidemia, with a focus on serum lipid endpoints including TC, low density lipoprotein cholesterol (LDL-C), HDL-C, and TG. PubMed, EMBASE, Cochrane Evidence-Based Medicine Reviews, Proquest, Web of Science, and Scopus were searched to identify RCTs that reported the effects of α-lipoic acid on blood lipid concentrations from 1970 to 2017. We included RCTs reporting blood lipid responses in adults supplemented with oral α-lipoic acid versus a placebo or control for at least one month. Studies were reviewed and data were extracted by two independent study authors. Seventeen studies were deemed eligible for inclusion. Overall, mean percent changes in blood lipid endpoints in response to α-lipoic acid varied considerably between studies for total cholesterol (-10.5 to +13.9), low-density lipoprotein cholesterol (-19.67 to +9.06), high-density lipoprotein cholesterol (-12.5 to +29.20), and triglycerides (-38.57 to +17.0). Results of this systematic review suggest little consistent benefit on serum lipids in response to α-lipoic acid supplementation. Further well-controlled studies designed and powered to detect improvements in blood lipids in hypercholesterolemic individuals are warranted (PROSPERO registration number: CRD42018105933).

Progesterone, Lipoic Acid, and Sulforaphane as Promising Antioxidants for Retinal Diseases: A Review

Oxidative stress has been documented to be a key factor in the cause and progression of different retinal diseases. Oxidative cellular unbalance triggers a sequence of reactions which prompt cell degeneration and retinal dysfunction, both hallmarks of several retinal pathologies. There is no effective treatment, yet, for many retinal diseases. Antioxidant treatment have been pointed out to be an encouraging palliative treatment; the beneficial effects documented involve slowing the progression of the disease, a reduction of cell degeneration, and improvement of retinal functions. There is a vast information corpus on antioxidant candidates. In this review, we expose three of the main antioxidant treatments, selected for their promising results that has been reported to date. Recently, the sulforaphane, an isothiocyanate molecule, has been unveiled as a neuroprotective candidate, by its antioxidant properties. Progesterone, a neurosteroid has been proposed to be a solid and effective neuroprotective agent. Finally, the lipoic acid, an organosulfur compound, is a well-recognized antioxidant. All of them, have been tested and studied on different retinal disease models. In this review, we summarized the published results of these works, to offer a general view of the current antioxidant treatment advances, including the main effects and mechanisms described.

Chronic co-exposure to chlorpyrifos and deltamethrin pesticides induces alterations in serum lipids and oxidative stress in Wistar rats: mitigating role of alpha-lipoic acid

The study evaluated the effect of combination of chlorpyrifos (CPF) and deltamethrin (DLT) on serum lipid profiles and oxidative stress in rats, and the mitigating role of alpha-lipoic acid (ALA). Thirty male rats were used for the 120-day study. Serum samples obtained at termination were evaluated for the levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL), malondialdehyde (MDA), and the activities of antioxidant enzymes. The levels of low-density lipoprotein-cholesterol (LDL), very low-density lipoprotein-cholesterol (VLDL), and atherogenic index (AI) were calculated. The pesticide combination elevated the levels of TG, TC, LDL, VLDL, AI, and MDA, and decreased HDL level, and activities of CAT, SOD, and GPx. The alterations induced by CPF and DLT were alleviated by ALA, partly through its antioxidant properties. In conclusion, co-exposure to DLT and CPF altered serum lipids and increased oxidative stress changes in the rats, which were ameliorated by ALA.

Advantages of the Alpha-lipoic Acid Association with Chlorpromazine in a Model of Schizophrenia Induced by Ketamine in Rats: Behavioral and Oxidative Stress evidences

Schizophrenia is a chronic mental disorder reported to compromise about 1% of the world's population. Although its pathophysiological process is not completely elucidated, evidence showing the presence of an oxidative imbalance has been increasingly highlighted in the literature. Thus, the use of antioxidant substances may be of importance for schizophrenia treatment. The objective of this study was to evaluate the behavioral and oxidative alterations by the combination of chlorpromazine (CP) and alpha-lipoic acid (ALA), a potent antioxidant, in the ketamine (KET) model of schizophrenia in rats. Male Wistar rats (200-300 g) were treated for 10 days with saline, CP or ALA alone or in combination with CP previous to KET and the behavioral (open field, Y-maze and PPI tests) and oxidative tests were performed on the last day of treatment. The results showed that KET induced hyperlocomotion, impaired working memory and decreased PPI. CP alone or in combination with ALA prevented KET-induced behavioral effects. In addition, the administration of KET decreased GSH and increased nitrite, lipid peroxidation and myeloperoxidase activity. CP alone or combined with ALA prevented the oxidative alterations induced by KET. In conclusion, the treatment with KET in rats induced behavioral impairments accompanied by hippocampal oxidative alterations, possibly related to NMDA receptors hypofunction. Besides that, CP alone or combined with ALA prevented these effects, showing a beneficial activity as antipsychotic agents.

The effects of vitamin E or lipoic acid supplementation on oxyphytosterols in subjects with elevated oxidative stress: a randomized trial

Despite increased serum plant sterol concentrations after consumption of plant sterol enriched margarines, plasma oxyphytosterol concentrations were not increased in healthy subjects. Here, we assessed plasma oxyphytosterol concentrations and whether they are affected by antioxidants in subjects with elevated oxidative stress. Twenty subjects with impaired glucose tolerance (IGT) or type 2 diabetes (DM2) consumed for 4 weeks placebo, vitamin E (804 mg/d) or lipoic acid capsules (600 mg/d). Plasma and blood cell oxyphytosterol and oxycholesterol concentrations were determined in butylated hydroxytoluene-enriched EDTA plasma via GC-MS. Also, markers reflecting oxidative stress and antioxidant capacity were measured. Plasma oxycampesterol and oxysitosterol concentrations were 122% and 83% higher in IGT or DM2 subjects than in healthy subjects, as determined in an earlier study. Vitamin E or lipoic acid supplementation did not reduce plasma oxyphytosterol and oxycholesterol concentrations, or other markers reflecting oxidative stress or antioxidative capacity. Concentrations of different oxyphytosterols correlated within plasma, and within red blood cells and platelets. However, plasma and blood cell oxyphytosterol levels did not correlate. Although plasma oxyphytosterol concentrations are higher in IGT or DM2 subjects than in healthy subjects, 4-weeks vitamin E or lipoic acid supplementation does not lower plasma oxycholesterol or oxyphytosterol concentrations.

Therapies for mitochondrial diseases and current clinical trials

Mitochondrial diseases are a clinically and genetically heterogeneous group of disorders that result from dysfunction of the mitochondrial oxidative phosphorylation due to molecular defects in genes encoding mitochondrial proteins. Despite the advances in molecular and biochemical methodologies leading to better understanding of the etiology and mechanism of these diseases, there are still no satisfactory therapies available for mitochondrial disorders. Treatment for mitochondrial diseases remains largely symptomatic and does not significantly alter the course of the disease. Based on limited number of clinical trials, several agents aiming at enhancing mitochondrial function or treating the consequences of mitochondrial dysfunction have been used. Several agents are currently being evaluated for mitochondrial diseases. Therapeutic strategies for mitochondrial diseases include the use of agents enhancing electron transfer chain function (coenzyme Q₁₀, idebenone, riboflavin, dichloroacetate, and thiamine), agents acting as energy buffer (creatine), antioxidants (vitamin C, vitamin E, lipoic acid, cysteine donors, and EPI-743), amino acids restoring nitric oxide production (arginine and citrulline), cardiolipin protector (elamipretide), agents enhancing mitochondrial biogenesis (bezafibrate, epicatechin, and RTA 408), nucleotide bypass therapy, liver transplantation, and gene therapy. Although, there is a lack of curative therapies for mitochondrial disorders at the current time, the increased number of clinical research evaluating agents that target different aspects of mitochondrial dysfunction is promising and is expected to generate more therapeutic options for these diseases in the future.

Oxidative pathways in the sickle cell and beyond

Polymerization of deoxy sickle cell hemoglobin (HbS) is well recognized as the primary event that triggers the classic cycles of sickling/unsickling of patients red blood cells (RBCs). RBCs are also subjected to continuous endogenous and exogenous oxidative onslaughts resulting in hemolytic rate increases which contribute to the evolution of vasculopathies associated with this disease. Compared to steady-state conditions, the occurrences of vaso-occlusive crises increase the levels of both RBC-derived microparticles as well as extracellular Hb in circulation. Common byproduct resulting from free Hb oxidation and from Hb-laden microparticles is heme (now recognized as damage associated molecular pattern (DAMP) molecule) which has been shown to initiate inflammatory responses. This review provides new insights into the interplay between microparticles, free Hb and heme focusing on Hb's pseudoperoxidative activity that drives RBC's cytosolic, membrane changes as well as oxidative toxicity towards the vascular system. Emerging antioxidative strategies that include the use of protein and heme scavengers in controlling Hb oxidative pathways are discussed.

Chronic treatment of (R)-α-lipoic acid reduces blood glucose and lipid levels in high-fat diet and low-dose streptozotocin-induced metabolic syndrome and type 2 diabetes in Sprague-Dawley rats

(R)‐ α ‐lipoic acid (ALA), an essential cofactor in mitochondrial respiration and a potential antioxidant, possesses a wide array of metabolic benefits including anti‐obesity, glucose lowering, insulin‐sensitizing, and lipid‐lowering effects. In this study, the curative effects of ALA (100 mg/kg) on a spectrum of conditions related to metabolic syndrome and type 2 diabetes (T2D) were investigated in a high‐fat diet (HFD)‐fed and low‐dose streptozotocin (STZ)‐induced rat model of metabolic syndrome and T2D. The marked rise in the levels of glucose, triglycerides, total‐cholesterol, LDL‐cholesterol, and VLDL‐cholesterol in the blood of HFD‐fed and low‐dose STZ‐injected rats were significantly reduced by ALA treatment. Furthermore, ALA treatment significantly increased the serum HDL‐cholesterol levels and tended to inhibit diabetes‐induced weight reduction. Mathematical computational analysis revealed that ALA also significantly improved insulin sensitivity and reduced the risk of atherosclerotic lesions and coronary atherogenesis. This study provides scientific evidence to substantiate the use of ALA to mitigate the glucose and lipid abnormality in metabolic syndrome and T2D.

Cisplatin-Induced Nephrotoxicity; Protective Supplements and Gender Differences

Cisplatin (CDDP) has been widely used as a chemotherapeutic agent for solid tumors. The most common side effect of CDDP is nephrotoxicity, and many efforts have been made in the laboratory and the clinic to employ candidate adjuvants to CDDP to minimize this adverse influence. Many synthetic and herbal antioxidants as well as trace elements have been investigated for this purpose in recent years and a variety of positive and negative results have been yielded. However, no definitive supplement has so far been proposed to prevent CDDP-induced nephrotoxicity; however, this condition is gender related and the sex hormone estrogen may protect the kidney against CDDP damage. In this review, the results of research related to the effect of different synthetic and herbal antioxidants supplements are presented and discussed with suggestions included for future work.

α-Tocopherol and Atherosclerosis

Cardiovascular disease is the leading cause of morbidity and mortality in the Western world. There is compelling evidence incriminating oxidative stress in the pathogenesis of the atherosclerotic lesion. Several lines of evidence suggest that antioxidants, especially α-tocopherol, have potential beneficial effects with regard to cardiovascular disease. In vitro, α-tocopherol has been shown to inhibit platelet adhesion and aggregation and smooth muscle cell proliferation, exert anti-inflammatory effects on monocytes, and improve endothelial function. Also, supplementation with α-tocopherol has been shown to decrease lipid peroxidation, platelet aggregation, and pro-inflammatory activity of monocytes. However, clinical trials with α-tocopherol supplementation to date have been equivocal. Thus, although mounting in vitro evidence and animal models provide a sound scientific basis for α-tocopherol supplementation, further clinical trials are required before a definitive recommendation can be made with respect to the primary and secondary prevention of heart disease.

Review: Targeting therapeutics against glutathione depletion in diabetes and its complications

Glutathione (GSH) is the most abundant intracellular antioxidant, the dysregulation of which is widely implicated in disease states. There is in vitro and clinical evidence that abnormal glutathione status is involved in β-cell dysfunction and in the pathogenesis of long-term complications of diabetes. Interest has developed in the potential for therapeutic modification of glutathione status in the treatment of diabetes. There is evidence which supports the use of glutathione pro-drugs, lipoic acid and vitamin supplementation but further studies are required before these enter widespread use. Studies into the role of oxidative stress in diabetes rely heavily on the ability to measure glutathione, which has been a problematic analyte to measure in the laboratory. New electrochemical methods being developed should speed up the rate at which data can be accumulated and will help define clinical utility for its measurement.

Vitamin E and a-Lipoic Acid Supplementation Increase Bleeding Tendency via an Intrinsic Coagulation Pathway

Vitamin E and a-lipoic acid are potent nutritional antioxidants, and when used together, their antioxidant capabilities are improved as a-lipoic acid recycles vitamin E. Supplementation of vitamin E has been shown to prolong platelet aggregation but the effects of vitamin E and a-lipoic acid supplementation on bleeding tendency have yet to be reported. Young, male rats consumed either control diet (n=5) or vitamin E and a-lipoic acid-supplemented diet (n=5) for 14 weeks. Activated partial thromboplastin time (APTT) and prothrombin time (PT) were measured as markers of intrinsic and extrinsic coagulation pathways respectively in addition to lipid peroxidation (malondialdehyde). Supplementation significantly prolonged APTT (23.8±1.5 vs 31.4±1.2s, p<0.05) compared to the control diet; however, there was no significant difference in PT (27.8±1.5 vs 26.6±0.9s, p>0.05). While vitamin E was increased (p<0.05), there was no significant difference in plasma levels of malondialdehyde (p>0.05). Dietary supplementation of vitamin E and a-lipoic acid increases bleeding tendency via inhibition of the intrinsic coagulation pathway with no change in markers of lipid peroxidation. Such supplementation could benefit patients with cardiovascular disease who exhibit elevated levels of coagulation and oxidative stress.

Alpha-lipoic acid: molecular mechanisms and therapeutic potential in diabetes

Diabetes is a chronic metabolic disease with a high prevalence worldwide. Diabetes and insulin resistance are associated with the development of cardiovascular and nervous diseases. The development of these disorders reflects complex pathological processes in which the oxidative stress caused by reactive oxygen species (ROS) and reactive nitrogen species (RNS) plays a pivotal role. It is widely accepted that diabetes impairs endothelial nitric oxide synthase (eNOS) activity and increases the production of ROS, thus resulting in diminished NO bioavailability and increased oxidative stress. Alpha-lipoic acid (LA) possesses beneficial effects both in the prevention and in the treatment of diabetes. LA is a potent antioxidant with insulin-mimetic and anti-inflammatory activity. LA in the diet is quickly absorbed, transported to the intracellular compartments, and reduced to dihydrolipoic acid (DHLA) under the action of enzymes. LA, which plays an essential role in mitochondrial bioenergetic reactions, has drawn considerable attention as an antioxidant for use in managing diabetic complications such as retinopathy, neuropathy and other vascular diseases.

Effects of Dietary L-carnosine and Alpha-lipoic Acid on Growth Performance, Blood Thyroid Hormones and Lipid Profiles in Finishing Pigs

The present study was conducted to determine the effects of L-carnosine (LC) and/or alpha-lipoic acid (ALA) supplementation on growth performance, blood thyroid hormones and lipid profiles in finishing pigs. A total of 40 (Landrace×Yorkshire) pigs with an initial body weight of 57.93±3.14 kg were randomly allocated to 4 experimental diets using a 2×2 factorial arrangement with 2 LC supplemental levels (0 or 0.1%) and 2 ALA supplemental levels (0 or 0.03%) in basal diets. The results showed that pigs fed LC-supplemented diets increased final live weight, average daily gain, and average daily feed intake compared to those of pigs fed without LC-supplemented diets (p<0.05). Dietary supplementation with ALA did not affect the growth performance and carcass traits of pigs (p>0.05). Additionally, LC supplementation increased serum triiodothyronine, thyroxine levels, and ALA supplementation increased serum triiodothyronine levels (p<0.05). Serum total cholesterol and triglycerides levels were significantly decreased in LC and ALA supplemented groups, respectively (p<0.05). Moreover, serum low density lipoprotein cholesterol levels were lower in the ALA-supplemented groups than those of pigs fed without ALA-supplemented diets (p<0.05). However, no significant LC×ALA interaction effect on growth performance, blood thyroid hormones and lipid profiles was found. This study suggested that dietary supplementation of LC resulted in better growth performance compared to that of ALA supplementation. L-carnosine and/or ALA supplementation positively modified blood lipid profiles, which may have the potential to prevent cardiovascular diseases.

Influence of α-tocopherol and α-lipoic acid on bisphenol-A-induced oxidative damage in liver and ovarian tissue of rats

Bisphenol A (BPA) is a commonly used material in daily life, and it is argued to cause oxidative stress in liver and ovarian tissue. α-Lipoic acid (ALA) and α-tocopherol (ATF), two of the most effective antioxidants, may play a role in preventing the toxic effect. Therefore, the purpose of this study was to examine the beneficial effects of ALA, ATF, and that of ALA + ATF combination on oxidative damage induced by BPA. Female Wistar rats were divided into five groups (control, BPA, BPA + ALA, BPA + ATF, and BPA + ALA + ATF). BPA (25 mg/kg/day), ALA (100 mg/kg/day), and ATF (20 mg/kg/day) were administered for 30 days.  The levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), liver malondialdehyde (L-MDA) and glutathione peroxidase (L-GPx), and ovarian malondialdehyde (Ov-MDA) and nitric oxide (Ov-NO) were significantly higher in the BPA-treated groups compared with the control group. The levels of AST and ALT decreased in the BPA + ALA, BPA + ATF, and BPA + ALA + ATF groups compared with the BPA group. Similarly, BPA + ALA or BPA + ATF led to decreases in L-MDA and Ov-MDA levels compared with the BPA group. However, the BPA + ALA + ATF group showed a significant decrease in L-MDA levels compared with the BPA + ALA group and the BPA + ATF group. The levels of L-GPx decreased in the BPA + ATF and the BPA + ALA + ATF groups compared with the BPA group. The administration of ATF and ALA + ATF significantly decreased the Ov-NO levels.  This study demonstrates that BPA causes oxidative damage in liver and ovarian tissues. ALA, ATF, or their combination were found to be beneficial in preventing BPA-induced oxidative stress.

In vivo detection of a novel endogenous etheno-DNA adduct derived from arachidonic acid and the effects of antioxidants on its formation

Previous studies showed that 7-(1',2'-dihydroxyheptyl)-substituted etheno DNA adducts are products of reactions with the epoxide of (E)-4-hydroxy-2-nonenal, an oxidation product of ω-6 polyunsaturated fatty acids (PUFAs). In this work, we report the detection of 7-(1',2'-dihydroxyheptyl)-1,N(6)-ethenodeoxyadenosine (DHHedA) in rodent and human tissues by two independent methods: a (32)P-postlabeling/HPLC method and an isotope dilution liquid chromatography-electrospray ionization-tandem mass spectrometry method, demonstrating for the first time that DHHedA is a background DNA lesion in vivo. We showed that DHHedA can be formed upon incubation of arachidonic acid with deoxyadenosine, supporting the notion that ω-6 PUFAs are the endogenous source of DHHedA formation. Because cyclic adducts are derived from the oxidation of PUFAs, we subsequently examined the effects of antioxidants, α-lipoic acid, Polyphenon E, and vitamin E, on the formation of DHHedA and γ-hydroxy-1,N(2)-propanodeoxyguanosine (γ-OHPdG), a widely studied acrolein-derived adduct arising from oxidized PUFAs, in the livers of Long Evans Cinnamon (LEC) rats. LEC rats are afflicted with elevated lipid peroxidation and prone to the development of hepatocellular carcinomas. The results showed that although the survival of LEC rats was increased significantly by α-lipoic acid, none of the antioxidants inhibited the formation of DHHedA, and only Polyphenon E decreased the formation of γ-OHPdG. In contrast, vitamin E caused a significant increase in the formation of both γ-OHPdG and DHHedA in the livers of LEC rats.

Treatment of mitochondrial disorders

OPINION STATEMENT

While numerous treatments for mitochondrial disorders have been suggested, relatively few have undergone controlled clinical trials. Treatment of these disorders is challenging, as only symptomatic therapy is available. In this review we will focus on newer drugs and treatment trials in mitochondrial diseases, with a special focus on medications to avoid in treating epilepsy and ICU patient with mitochondrial disease, which has not been included in such a review. Readers are also referred to the opinion statement in A Modern Approach to the Treatment of Mitochondrial Disease published in Current Treatment Options in Neurology 2009. Many of the supplements used for treatment were reviewed in the previous abstract, and dosing guidelines were provided. The focus of this review is on items not previously covered in depth, and our discussion includes more recently studied compounds as well as any relevant updates on older compounds . We review a variety of vitamins and xenobiotics, including dichloroacetate (DCA), arginine, coenzyme Q10, idebenone, EPI-743, and exercise training. Treatment of epilepsy, which is a common feature in many mitochondrial phenotypes, warrants special consideration due to the added toxicity of certain medications, and we provide a discussion of these unique treatment challenges. Interesting, however, with only a few exceptions, the treatment strategies for epilepsy in mitochondrial cytopathies are the same as for epilepsy without mitochondrial dysfunction. We also discuss intensive care management, building upon similar reviews, adding new dimensions, and demonstrating the complexity of overall care of these patients.

Biological Effects of Space Radiation and Development of Effective Countermeasures

As part of a program to assess the adverse biological effects expected from astronaut exposure to space radiation, numerous different biological effects relating to astronaut health have been evaluated. There has been major focus recently on the assessment of risks related to exposure to solar particle event (SPE) radiation. The effects related to various types of space radiation exposure that have been evaluated are: gene expression changes (primarily associated with programmed cell death and extracellular matrix (ECM) remodeling), oxidative stress, gastrointestinal tract bacterial translocation and immune system activation, peripheral hematopoietic cell counts, emesis, blood coagulation, skin, behavior/fatigue (including social exploration, submaximal exercise treadmill and spontaneous locomotor activity), heart functions, alterations in biological endpoints related to astronaut vision problems (lumbar puncture/intracranial pressure, ocular ultrasound and histopathology studies), and survival, as well as long-term effects such as cancer and cataract development. A number of different countermeasures have been identified that can potentially mitigate or prevent the adverse biological effects resulting from exposure to space radiation.

Effect of α -Lipoic Acid on Oxidative Stress in End-Stage Renal Disease Patients Receiving Intravenous Iron

Oxidative stress is associated with increased risk of cardiovascular disease in end-stage renal disease (ESRD) patients. Intravenous (IV) iron has been shown to increase oxidative stress. The aim of the study was to evaluate changes in oxidative stress markers following administration of IV sodium ferric gluconate (SFG) to ESRD patients with and without administration of the antioxidant, α -lipoic acid. This is an open-label, crossover study. 125 mg of IV SFG was administered during control (C) and intervention (I) visits. During the I visit, 600 mg of α -lipoic acid was given orally prior to IV SFG. Blood samples were collected at defined time periods for F2-isoprostane (FIP), lipid hydroperoxide (LHP), malondialdehyde (MDA), and iron indices. We recruited ten African-American ESRD subjects: 50% male; mean age 45 ± 9 years; mean hemoglobin 13 ± 1 g/dL; ferritin 449 ± 145 ng/mL; transferrin saturation 27 ± 4%. There were no significant differences in iron indices between the two visits after IV SFG. MDA, FIP, and LHP increased significantly for both C and I visits with a greater increase in the I group. Administration of IV SFG results in an acute rise in oxidative stress in ESRD patients. In contrast to previous studies, administration of α -lipoic acid was associated with a greater increase in oxidative stress.

Oxidative stress in sickle cell disease: an overview of erythrocyte redox metabolism and current antioxidant therapeutic strategies

Erythrocytes have an environment of continuous pro-oxidant generation due to the presence of hemoglobin (Hb), which represents an additional and quantitatively significant source of superoxide (O2(-)) generation in biological systems. To counteract oxidative stress, erythrocytes have a self-sustaining antioxidant defense system. Thus, red blood cells uniquely function to protect Hb via a selective barrier allowing gaseous and other ligand transport as well as providing antioxidant protection not only to themselves but also to other tissues and organs in the body. Sickle hemoglobin molecules suffer repeated polymerization/depolymerization generating greater amounts of reactive oxygen species, which can lead to a cyclic cascade characterized by blood cell adhesion, hemolysis, vaso-occlusion, and ischemia-reperfusion injury. In other words, sickle cell disease is intimately linked to a pathophysiologic condition of multiple sources of pro-oxidant processes with consequent chronic and systemic oxidative stress. For this reason, newer therapeutic agents that can target oxidative stress may constitute a valuable means for preventing or delaying the development of organ complications.

Wheat germ oil and α-lipoic acid predominantly improve the lipid profile of broiler meat

In response to recent assertions that synthetic antioxidants may have the potential to cause toxic effects and to consumers' increased attention to consuming natural products, the poultry industry has been seeking sources of natural antioxidants, alone or in combination with synthetic antioxidants that are currently being used by the industry. The present study was conducted to determine the effect of α-lipoic acid, α-tocopherol, and wheat germ oil on the status of antioxidant enzymes, fatty acid profile, and serum biochemical profile of broiler blood. One-day-old (180) broiler birds were fed six different feeds varying in their antioxidant content: no addition (T1), natural α-tocopherol (wheat germ oil, T2), synthetic α-tocopherol (T3), α-lipoic acid (T4), α-lipoic acid together with natural α-tocopherol (T5), and α-lipoic acid together with synthetic α-tocopherol (T6). The composition of saturated and unsaturated fatty acids in the breast and leg meat was positively influenced by the different dietary supplements. The content of fatty acid was significantly greater in broilers receiving T2 both in breast (23.92%) and in leg (25.82%) meat, whereas lower fatty acid levels was found in broilers receiving diets containing T6 in the breast (19.57%) and leg (21.30%) meat. Serum total cholesterol (113.42 mg/dL) and triglycerides (52.29 mg/dL) were lowest in the group given natural α-tocopherol and α-lipoic acid. Wheat germ oil containing natural α-tocopherol alone or with α-lipoic acid was more effective than synthetic α-tocopherol in raising levels of antioxidant enzymes superoxide dismutase, catalase, and glutathione reductase while lowering plasma total cholesterol, low-density lipoprotein, and triglycerides and raising high-density lipoprotein and plasma protein significantly. It was concluded that the combination of wheat germ oil and α-lipoic acid is helpful in improving the lipid profile of broilers.

Direct and indirect antioxidant properties of α-lipoic acid and therapeutic potential

Diabetes has emerged as a major threat to worldwide health. The exact mechanisms underlying the disease are unknown; however, there is growing evidence that the excess generation of reactive oxygen species (ROS) associated with hyperglycemia, causes oxidative stress in a variety of tissues. In this context, various natural compounds with pleiotropic actions like α-lipoic acid (LA) are of interest, especially in metabolic diseases such as diabetes. LA, either as a dietary supplement or a therapeutic agent, modulates redox potential because of its ability to match the redox status between different subcellular compartments as well as extracellularly. Both the oxidized (disulfide) and reduced (di-thiol: dihydro-lipoic acid, DHLA) forms of LA show antioxidant properties. LA exerts antioxidant effects in biological systems through ROS quenching but also via an action on transition metal chelation. Dietary supplementation with LA has been successfully employed in a variety of in vivo models of disease associated with an imbalance of redox status: diabetes and cardiovascular diseases. The complex and intimate association between increased oxidative stress and increased inflammation in related disorders such as diabetes, makes it difficult to establish the temporal sequence of the relationship.

Pesticide-induced decrease in rat testicular steroidogenesis is differentially prevented by lipoate and tocopherol

We have previously demonstrated that the sub-chronic administration of low doses of Toc or α-Toc, glyphosate and zineb to rats (i.p. 1/250 LD50, three times a week for 5 weeks) provoked severe oxidative stress (OS) in testicles. These effects were also reflected in plasma. Lipoic acid (LA) and α-tocopherol are considered as antioxidants due to their ability to neutralize reactive oxygenated species (ROS) and reset endogenous antioxidant levels. To investigate the possible protective effect on reproductive function, LA and Toc (i.p. 25, 50 and 100mg/kg) were administered simultaneously with the pesticide mixture (PM) for 5 weeks. Both drugs prevented OS and the damage to proteins and lipids caused by PM in a dose-dependent manner. The PM-induced increase levels of prostaglandins E2 and F2α was completely restored by LA but not by Toc. Similarly, only LA was able to restore the inhibition of testosterone production, the decrease of 3β- and 17β-hydroxysteroid dehydrogenases activities, and the elevation of gonatropins (FSH and LH) levels produced by PM. Furthermore, LA was more efficient than Toc in normalizing the histological alterations produced by PM administration, suggesting that pesticides act though other mechanisms that generate oxidative stress. In our experimental model LA displayed a higher protective role against pesticide-induced damage than that observed by Toc administration. Our results suggest that LA administration is a promising therapeutic strategy for coping with disorders suspected to be caused by OS generators - such as pesticides - in male reproductive system.

The effect of alpha-lipoic acid on mitochondrial superoxide and glucocorticoid-induced hypertension

Aims. To examine the effect of alpha-lipoic acid, an antioxidant with mitochondrial superoxide inhibitory properties, on adrenocorticotrophic hormone- (ACTH-HT) and dexamethasone-induced hypertensions (DEX-HT) in rats and if any antihypertensive effect is mediated via mitochondrial superoxide inhibition. Methods. In a prevention study, rats received ground food or alpha-lipoic-acid-laced food (10 mg/rat/day) for 15 nights. Saline, adrenocorticotrophic hormone (ACTH, 0.2 mg/kg/day), or dexamethasone (DEX, 10 μg/rat/day) was injected subcutaneously from day 5 to day 11. In a reversal study, rats received alpha-lipoic-acid-laced food 4 days after commencement of saline or DEX. Tail-cuff systolic blood pressure (SBP) was measured second daily. Kidney mitochondrial superoxide was examined using (MitoSOX) Red (MitoSOX) via flow cytometry. Results. SBP was increased by ACTH (P < 0.0005) and DEX (P < 0.0005). Alpha-lipoic acid alone did not alter SBP. With alpha-lipoic acid pretreatment, SBP was increased by ACTH (P′ < 0.005) but not by DEX. Alpha-lipoic partially prevented ACTH-HT (P′ < 0.0005) and fully prevented DEX-HT (P′ < 0.0005) but failed to reverse DEX-HT. ACTH and DEX did not increase MitoSOX signal. In ACTH-hypertensive rats, high-dose alpha-lipoic acid (100 mg/rat/day) did not decrease SBP further but raised MitoSOX signal (P < 0.001), suggesting prooxidant activity. Conclusion. Glucocorticoid-induced hypertension in rats is prevented by alpha-lipoic acid via mechanisms other than mitochondrial superoxide reduction.

The effect of the ALAnerv nutritional supplement on some oxidative stress markers in postacute stroke patients undergoing rehabilitation

Stroke is a pathologic condition associated with redox imbalance. This pilot study was designed to evaluate the effect of the consumption of the nutritional supplement ALAnerv on some oxidative stress markers in postacute stroke patients undergoing rehabilitation. To achieve this goal, we assigned 28 patients to 2 study groups: (-)ALA and (+)ALA. Patients in both groups participated in the same rehabilitation program and received comparable standard medications; however, patients in the (+)ALA group received ALAnerv for 2 weeks (2 pills per day). We assessed total and nonproteic thiols, protein carbonyls, ceruloplasmin, oxidized low-density lipoprotein (LDL) particles, lipid hydroperoxide concentrations, gamma-glutamyl transpeptidase activity, and total antioxidant capacity. Regression analysis indicated that supplementation with ALAnerv was responsible for the significant decrease in glucose (p = 0.002) and oxidized LDL particles (p < 0.001) during the study period. For both parameters, the variation in the percent of concentration between the 2 groups during the study period reached statistical significance (p = 0.012 and p < 0.001, respectively). Moreover, Barthel Index values at discharge were significantly influenced by ALAnerv treatment. These preliminary results indicate that ALAnerv might be helpful because it rapidly corrects plasma fasting glucose and corrects serum oxidized LDL particle concentrations, suggesting the need for longer treatment with 2 pills or more per day.

Inhibition by polyphenolic phytochemicals and sulfurous compounds of the formation of 8-chloroguanosine mediated by hypochlorous acid, human myeloperoxidase, and activated human neutrophils

Hypochlorous acid (HOCl) produced by myeloperoxidase (MPO) of activated neutrophils can react with nucleic acid bases to form chlorinated nucleosides such as 8-chloroguanosine (Cl-Guo). Chlorination is enhanced by nicotine. We investigated the effects of various natural antioxidants including polyphenolic phytochemicals on the formation of Cl-Guo by HOCl in the presence and the absence of nicotine. Polyphenols, including catechins, curcumin, resveratrol, silibinin, and sulfurous compound α-lipoic acid, were found to inhibit both HOCl- and human MPO-induced Cl-Guo formation dose-dependently. Among the test compounds, (-)-epigallocatechin gallate (EGCG) showed the strongest inhibitory effect. Cl-Guo formation, mediated by activated human neutrophils in the presence of nicotine, was inhibited by EGCG, silibinin, and α-lipoic acid. These results suggest that polyphenols and sulfurous compounds have the potential to inhibit the induction of nucleobase damage mediated by chlorination, with possible application to reducing DNA damage associated with inflammation and cigarette-smoke inhalation.