Alpha lipoic acid changes iron uptake and storage in lens epithelial cells

The Protective Effect of α-Lipoic Acid against Gold Nanoparticles (AuNPs)-Mediated Liver Damage Is Associated with Upregulating Nrf2 and Suppressing NF-κB

This study examined if regulating the keap-1? Nrf2 antioxidant pathway mediated gold nanoparticles (AuNPs) induced liver damage, and examined the protective effect of co-supplement of α-lipoic acid (α-LA). Rats were separated into 4 groups (n = 8/each) as control, α-LA (200 mg/kg), AuNPs (5 µg/2.85 × 10¹¹), and AuNPs (5 µg/2.85 × 10¹¹) + α-LA (200 mg/kg). After 7 days, AuNPs induced severe degeneration in the livers of rats with the appearance of some fatty changes. In addition, it increased serum levels of alanine aminotransferase (ALT) and gamma-glutamyl transferase (ɣ-GTT), and aspartate aminotransferase (AST), as well as liver levels of malondialdehyde (MDA). Concomitantly, AuNPs significantly depleted hepatic levels of total glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) but increased hepatic levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). It also reduced mRNA levels of B-cell lymphoma 2 (Bcl2) and heme oxygenase-1 (HO-1) but significantly increased those of Bax and cleaved caspase-3, as well as the ratio of Bax/Bcl2. In addition, AuNPs enhanced the total and nuclear levels of NF-κB p65 but reduced the mRNA and total and nuclear protein levels of Nrf2. Of note, AuNPs did not affect the mRNA levels of keap-1. All these events were reversed by α-LA in the AuNPs-treated rats. In conclusion, α-LA attenuated AuNPs-mediated liver damage in rats by suppressing oxidative stress and inflammation, effects that are associated with upregulation/activation of Nrf2.

Decrypting the potential role of α-lipoic acid in Alzheimer's disease

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases with motor disturbances, cognitive decline, and behavioral impairment. It is characterized by the extracellular aggregation of amyloid-β plaques and the intracellular accumulation of tau protein. AD patients show a cognitive decline, which has been associated with oxidative stress, as well as mitochondrial dysfunction. Alpha-lipoic acid (α-LA), a natural antioxidant present in food and used as a dietary supplement, has been considered a promising agent for the prevention or treatment of neurodegenerative disorders. Despite multiple preclinical studies indicating beneficial effects of α-LA in memory functioning, and pointing to its neuroprotective effects, to date only a few studies have examined its effects in humans. Studies performed in animal models of memory loss associated with aging and AD have shown that α-LA improves memory in a variety of behavioral paradigms. Furthermore, molecular mechanisms underlying α-LA effects have also been investigated. Accordingly, α-LA shows antioxidant, antiapoptotic, anti-inflammatory, glioprotective, metal chelating properties in both in vivo and in vitro studies. In addition, it has been shown that α-LA reverses age-associated loss of neurotransmitters and their receptors. The review article aimed at summarizing and discussing the main studies investigating the neuroprotective effects of α-LA on cognition as well as its molecular effects, to improve the understanding of the therapeutic potential of α-LA in patients suffering from neurodegenerative disorders, supporting the development of clinical trials with α-LA.

Therapeutic Potential of Alpha-Lipoic Acid in Viral Infections, including COVID-19

Oxidative stress (OS), resulting from a disrupted balance between reactive oxygen species (ROS) and protective antioxidants, is thought to play an important pathogenetic role in several diseases, including viral infections. Alpha-lipoic acid (LA) is one of the most-studied and used natural compounds, as it is endowed with a well-defined antioxidant and immunomodulatory profile. Owing to these properties, LA has been tested in several chronic immunoinflammatory conditions, such as diabetic neuropathy and metabolic syndrome. In addition, a pharmacological antiviral profile of LA is emerging, that has attracted attention on the possible use of this compound for the cotreatment of several viral infections. Here, we will review the emerging literature on the potential use of LA in viral infections, including COVID-19.

Effects of alpha lipoic acid on iron overload, lipid profile and oxidative stress indices in β-thalassemia major patients: A cross-over randomised controlled clinical trial

AIMS

β-Thalassemia major (β-TM) is associated with iron overload, abnormal lipid levels and oxidative stress. Alpha lipoic acid (ALA) showed anti-oxidant and iron chelating properties, but its effect in β-TM patients is unclear. We investigated the effects of ALA on iron levels, lipid profile and oxidative stress.

METHODS

In this cross-over randomised clinical trial, 26 β-TM patients were assigned to receive 600 mg/d ALA or placebo (corn starch), for 8 weeks with a 21-days washout period. Serum ferritin, total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), LDL-C/HDL-C, total antioxidant capacity, malondialdehyde (MDA) and MDA/LDL-C were assessed at baseline and the end of each intervention phase.

RESULTS

Twenty-two patients completed the study. Serum ferritin (P = .004), MDA (P = .025) and MDA/LDL-C ratio (P =.002) were decreased and HDL-C (P =.035) increased significantly during ALA consumption. In comparison with placebo, ALA decreased the serum ferritin significantly (P = .02). Also, the changes in serum ferritin between ALA and placebo (-123.1 ± 40.0 vs -34.3 ± 21.0, P =.03) was significant in women subgroup. ALA had no significant effects on the other biomarkers.

CONCLUSION

The results of this study indicated that supplementation with 600 mg/d ALA may decrease serum ferritin in β-TM. Further studies are needed to confirm the findings.

Alpha-Lipoic Acid Mediates Clearance of Iron Accumulation by Regulating Iron Metabolism in a Parkinson's Disease Model Induced by 6-OHDA

The disruption of neuronal iron homeostasis and oxidative stress are related to the pathogenesis of Parkinson's disease (PD). Alpha-lipoic acid (ALA) is a naturally occurring enzyme cofactor with antioxidant and iron chelator properties and has many known effects. ALA has neuroprotective effects on PD. However, its underlying mechanism remains unclear. In the present study, we established PD models induced by 6-hydroxydopamine (6-OHDA) to explore the neuroprotective ability of ALA and its underlying mechanism in vivo and in vitro. Our results showed that ALA could provide significant protection from 6-OHDA-induced cell damage in vitro by decreasing the levels of intracellular reactive oxygen species and iron. ALA significantly promoted the survival of the dopaminergic neuron in the 6-OHDA-induced PD rat model and remarkably ameliorated motor deficits by dramatically inhibiting the decrease in tyrosine hydroxylase expression and superoxide dismutase activity in the substantia nigra. Interestingly, ALA attenuated 6-OHDA-induced iron accumulation both in vivo and in vitro by antagonizing the 6-OHDA-induced upregulation of iron regulatory protein 2 and divalent metal transporter 1. These results indicated that the neuroprotective mechanism of ALA against neurological injury induced by 6-OHDA may be related to the regulation of iron homeostasis and reduced oxidative stress levels. Therefore, ALA may provide neuroprotective therapy for PD and other diseases related to iron metabolism disorder.

Renoprotective Effects of Alpha Lipoic Acid on Iron Overload-Induced Kidney Injury in Rats by Suppressing NADPH Oxidase 4 and p38 MAPK Signaling

We aimed to investigate the protective effect of alpha lipoic acid (ALA), a powerful antioxidant, against oxidative kidney damage induced by iron overload in rats. Male Wistar albino rats were separated into groups: control (n = 7), ALA (100 mg/kg (n = 7), iron sucrose (IS) (40 mg/kg) (n = 7), and IS + ALA (40 mg/kg IS administration followed by 100 mg/kg ALA) (n = 7). IS and ALA were injected weekly for 4 weeks via the tail vein. Blood and kidneys were collected at sacrification on day 29. Serum creatinine and iron levels were analyzed. Tubular injury and iron deposits were evaluated histopathologically. Additionally, iron, malondialdehyde (MDA), superoxide dismutase (SOD), catalase, and glutathione (GSH) levels and mRNA expressions of the subunits of NADPH oxidase, known as NOX4 and p22^phox, tumor necrosis factor (TNF)-α, kidney injury molecule-1 (KIM-1), and also p38 MAPK signaling in the kidneys, were evaluated biochemically. In the IS group, serum creatinine and iron level, tubular dilation, and loss of brush border in the kidneys were significantly higher than those of the control. Although those changes were reduced by ALA, the differences were not statistically significant. However, ALA reduced significantly MDA level and increased SOD activity in the kidney during IS administration. ALA also significantly reduced mRNA expressions of NOX4 and p22^phox induced by IS, which was parallel to significant decreases of TNF-α and KIM-1 mRNA expressions. Moreover, ALA could suppress the activation of p38 MAPK during IS administration. In conclusion, ALA may be an effective strategy to attenuate in IS-induced oxidative kidney injury.

Insights on the Use of α-Lipoic Acid for Therapeutic Purposes

α-lipoic acid (ALA, thioctic acid) is an organosulfur component produced from plants, animals, and humans. It has various properties, among them great antioxidant potential and is widely used as a racemic drug for diabetic polyneuropathy-associated pain and paresthesia. Naturally, ALA is located in mitochondria, where it is used as a cofactor for pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase complexes. Despite its various potentials, ALA therapeutic efficacy is relatively low due to its pharmacokinetic profile. Data suggests that ALA has a short half-life and bioavailability (about 30%) triggered by its hepatic degradation, reduced solubility as well as instability in the stomach. However, the use of various innovative formulations has greatly improved ALA bioavailability. The R enantiomer of ALA shows better pharmacokinetic parameters, including increased bioavailability as compared to its S enantiomer. Indeed, the use of amphiphilic matrices has capability to improve ALA bioavailability and intestinal absorption. Also, ALA's liquid formulations are associated with greater plasma concentration and bioavailability as compared to its solidified dosage form. Thus, improved formulations can increase both ALA absorption and bioavailability, leading to a raise in therapeutic efficacy. Interestingly, ALA bioavailability will be dependent on age, while no difference has been found for gender. The present review aims to provide an updated on studies from preclinical to clinical trials assessing ALA's usages in diabetic patients with neuropathy, obesity, central nervous system-related diseases and abnormalities in pregnancy.

Oxidative/nitrative stress in the pathogenesis of systemic sclerosis: are antioxidants beneficial?

Systemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future.

Iron and Alzheimer's Disease: From Pathogenesis to Therapeutic Implications

As people age, iron deposits in different areas of the brain may impair normal cognitive function and behavior. Abnormal iron metabolism generates hydroxyl radicals through the Fenton reaction, triggers oxidative stress reactions, damages cell lipids, protein and DNA structure and function, and ultimately leads to cell death. There is an imbalance in iron homeostasis in Alzheimer's disease (AD). Excessive iron contributes to the deposition of β-amyloid and the formation of neurofibrillary tangles, which in turn, promotes the development of AD. Therefore, iron-targeted therapeutic strategies have become a new direction. Iron chelators, such as desferoxamine, deferiprone, deferasirox, and clioquinol, have received a great deal of attention and have obtained good results in scientific experiments and some clinical trials. Given the limitations and side effects of the long-term application of traditional iron chelators, alpha-lipoic acid and lactoferrin, as self-synthesized naturally small molecules, have shown very intriguing biological activities in blocking Aβ-aggregation, tauopathy and neuronal damage. Despite a lack of evidence for any clinical benefits, the conjecture that therapeutic chelation, with a special focus on iron ions, is a valuable approach for treating AD remains widespread.

Effects of alpha-lipoic acid on expression of iron transport and storage proteins in BV-2 microglia cells

BACKGROUND

The antioxidant properties of alpha-lipoic acid (ALA) are associated with its ability to reduce iron in cells and tissues, which is partly due to its inhibiting effect on iron uptake from transferrin and its promoting effect on iron deposition into ferritin. However, the relevant mechanisms are unknown.

METHODS

We therefore investigated the effects of ALA on the expression of transferrin receptor 1 (TfR1), divalent metal transporter 1 (DMT1), ferroportin 1 (Fpn1) and ferritin in BV-2 microglia cells.

RESULTS

We demonstrated that ALA significantly inhibited DMT1 expression, lowered ferritin-light-chain (Ft-L) and ferritin-heavy-chain (Ft-H) content, and had no effect on TfR1 and Fpn1 in BV-2 microglia cells. This indicated that the inhibiting effect of ALA on DMT1 might be one of the causes of the ALA-induced reduction in cellular transferrin-bound-iron uptake. We also demonstrated that ALA enhanced DMT1 and TfR1 expression in ferric ammonium citrate (FAC)-treated cells. FAC treatment led to a significant increase in Ft-L, Ft-H and Fpn1, and pre-treatment with ALA resulted in a further increase in the contents of Ft-L and Ft-H but not Fpn1 in cells.

CONCLUSIONS

ALA could up-regulate TfR1, DMT1 and ferritin expression when iron is increased outside of the cell, promoting iron deposition into ferritin by increasing cell iron uptake, and then reducing free iron both inside and outside of the cell.

Alpha lipoic acid induces hepatic fibroblast growth factor 21 expression via up-regulation of CREBH

Hepatic expression of fibroblast growth factor 21 (FGF21), one of the most promising therapeutic candidates for metabolic syndrome, is induced by multiple factors associated with fasting, including cyclic AMP response element-binding protein H (CREBH). Alpha lipoic acid (ALA), a naturally occurring thiol antioxidant, has been shown to induce metabolic changes that are similar to those induced by FGF21, including weight loss and increased energy expenditure. Here, we investigated the effect of ALA on hepatic FGF21 expression. ALA treatment enhanced CREBH and FGF21 mRNA expression and protein abundance in cultured hepatocytes. ALA increased FGF21 promoter activity by up-regulating CREBH expression and increasing CREBH binding to the FGF21 promoter, indicating that ALA up-regulates FGF21 at the transcriptional level. Moreover, inhibition of endogenous CREBH expression by siRNA attenuated ALA-induced FGF21 expression. Finally, treatment of mice with ALA enhanced fasting-induced up-regulation of CREBH and FGF21 in the liver and inhibited feeding-induced suppression of their expression. Consistently, ALA increased serum FGF21 levels in both fasted and fed mice. Collectively, these results indicate that ALA increases hepatic FGF21 expression via up-regulation of CREBH, identifying ALA as a novel positive regulator of FGF21.

Systemic administration of the antioxidant/iron chelator α-lipoic acid protects against light-induced photoreceptor degeneration in the mouse retina

PURPOSE

Oxidative stress and inflammation have key roles in the light damage (LD) model of retinal degeneration as well as in age-related macular degeneration (AMD). We sought to determine if lipoic acid (LA), an antioxidant and iron chelator, protects the retina against LD.

METHODS

Balb/c mice were treated with LA or control saline via intraperitoneal injection, and then were placed in constant cool white light-emitting diode (LED) light (10,000 lux) for 4 hours. Retinas were evaluated at several time points after LD. Photoreceptor apoptosis was assessed using the TUNEL assay. Retinal function was analyzed via electroretinography (ERG). Retinal degeneration was assessed after LD by optical coherence tomography (OCT), TUNEL analysis, and histology. The mRNAs of several oxidative stress, inflammation, and iron-related genes were quantified by quantitative PCR (qPCR).

RESULTS

The LD resulted in substantial photoreceptor-specific cell death. Dosing with LA protected photoreceptors, decreasing the numbers of TUNEL-positive photoreceptors and increasing the number of surviving photoreceptors. The retinal mRNA levels of genes indicating oxidative stress, inflammation, and iron accumulation were lower following LD in mice treated with LA than in control mice. The ERG analysis demonstrated functional protection by LA.

CONCLUSIONS

Systemic LA is protective against light-induced retinal degeneration. Since this agent already has proven protective in other retinal degeneration models, and is safe and protective against diabetic neuropathy in patients, it is worthy of consideration for a human clinical trial against retinal degeneration or AMD.

Antioxidant and toxicological effects elicited by alpha-lipoic acid in aquatic organisms

Lipoic acid (LA) is a disulfide-containing compound derived from octanoic acid that is synthesized in mitochondria. This molecule acts as a co-factor for mitochondrial enzymes that catalyze oxidative decarboxylation reactions. Several antioxidant properties of LA enable it to be considered as an "ideal antioxidant", having diverse benefits that allow it to deal with environmental or biological stress. Some of the effects induced by LA in aquatic organisms render it suitable for use in aquaculture. However, it is necessary to determine the appropriate dose(s) to be used with different species and even organs to maximize the beneficial antioxidant and detoxifying effects and to minimize the pro-oxidant toxic effects. This review analyzes and compiles existing data from aquatic organisms in which both benefits and drawbacks of LA have been described.

Dietary supplementation with (R)-α-lipoic acid reverses the age-related accumulation of iron and depletion of antioxidants in the rat cerebral cortex

Accumulation of divalent metal ions (e.g. iron and copper) has been proposed to contribute to heightened oxidative stress evident in aging and neurodegenerative disorders. To understand the extent of iron accumulation and its effect on antioxidant status, we monitored iron content in the cerebral cortex of F344 rats by inductively coupled plasma atomic emission spectrometry (ICP-AES) and found that the cerebral iron levels in 24-28-month-old rats were increased by 80% (p<0.01) relative to 3-month-old rats. Iron accumulation correlated with a decline in glutathione (GSH) and the GSH/GSSG ratio, indicating that iron accumulation altered antioxidant capacity and thiol redox state in aged animals. Because (R)-alpha-Lipoic acid (LA) is a potent chelator of divalent metal ions in vitro and also regenerates other antioxidants, we monitored whether feeding LA (0.2% [w/w]; 2 weeks) could lower cortical iron and improve antioxidant status. Results show that cerebral iron levels in old LA-fed animals were lower when compared to controls and were similar to levels seen in young rats. Antioxidant status and thiol redox state also improved markedly in old LA-fed rats versus controls. These results thus show that LA supplementation may be a means to modulate the age-related accumulation of cortical iron content, thereby lowering oxidative stress associated with aging.

Quantum-chemical investigation of the structure and the antioxidant properties of α-lipoic acid and its metabolites

Quantum-chemical computations were used to investigate the structure-antioxidant parameter relationships of α-lipoic acid and its natural metabolites bisnorlipoic acid and tetranorlipoic acid in their oxidized and reduced forms. The enantiomers of lipoic and dihydrolipoic acid were optimized using the B3LYP/6-311+G(3df,2p), B3LYP/aug-cc-pVDZ and MP2(full)/6-31+G(d,p) levels of theory as isolated molecules and in the presence of water. The geometries of the metabolites and the values of their antioxidant parameters (proton affinity, bond dissociation enthalpy, adiabatic ionization potential, spin density, and the highest occupied molecular orbital energy) were calculated at the B3LYP/6-311+G(3df,2p) level of theory. The results obtained reveal similarities between these structures: a pentatomic, nonaromatic ring is present in the oxidized forms, while an unbranched aliphatic chain (as found in saturated fatty acids) is present in both the oxidized and the reduced forms. Analysis of the spin density and the highest occupied molecular orbital energy revealed that the SH groups exhibited the greatest electron-donating activities. The values obtained for the proton affinity, bond dissociation enthalpy and adiabatic ionization potential indicate that the preferred antioxidant mechanisms for α-lipoic acid and its metabolites are sequential proton loss electron transfer in polar media and hydrogen atom transfer in vacuum.

Diabetes and alpha lipoic Acid

Diabetes mellitus is a multi-faceted metabolic disorder where there is increased oxidative stress that contributes to the pathogenesis of this debilitating disease. This has prompted several investigations into the use of antioxidants as a complementary therapeutic approach. Alpha lipoic acid, a naturally occurring dithiol compound which plays an essential role in mitochondrial bioenergetic reactions, has gained considerable attention as an antioxidant for use in managing diabetic complications. Lipoic acid quenches reactive oxygen species, chelates metal ions, and reduces the oxidized forms of other antioxidants such as vitamin C, vitamin E, and glutathione. It also boosts antioxidant defense system through Nrf-2-mediated antioxidant gene expression and by modulation of peroxisome proliferator activated receptors-regulated genes. ALA inhibits nuclear factor kappa B and activates AMPK in skeletal muscles, which in turn have a plethora of metabolic consequences. These diverse actions suggest that lipoic acid acts by multiple mechanisms, many of which have only been uncovered recently. In this review we briefly summarize the known biochemical properties of lipoic acid and then discussed the oxidative mechanisms implicated in diabetic complications and the mechanisms by which lipoic acid may ameliorate these reactions. The findings of some of the clinical trials in which lipoic acid administration has been tested in diabetic patients during the last 10 years are summarized. It appears that the clearest benefit of lipoic acid supplementation is in patients with diabetic neuropathy.

Biodegradable microspheres loaded with an anti-Parkinson prodrug: an in vivo pharmacokinetic study

During chronic treatment with L-dopa (LD), Parkinsonian patients often experience uncontrolled motor complications due to fluctuations of the plasmatic levels of LD that result in pulsatile dopaminergic stimulation. To overcome these plasmatic fluctuations, a novel prodrug of LD, L-dopa-α-lipoic acid (LD-LA), has been proposed as a tool for achieving continuous dopaminergic stimulation. Due to slower susceptibility toward enzymatic conversion by LD-degrading enzymes (such as catechol-O-methyltransferase and monoamine oxidase), the plasma half-life of this prodrug is longer than that of LD. Moreover, the higher lipophilicity of LD-LA over LD promotes its delivery to the CNS, where the resulting levels of dopamine (DA) are kept high for a longer time than after equimolar administration of LD. To further reduce fluctuations in plasma levels of LD, LD-LA has been entrapped into biodegradable polymeric microspheres to be used as a depot system with the aim to prevent prodrug degradation and to obtain a sustained release of the intact compound. In the present work, a formulation of LD-LA loaded microspheres (characterized for drug loading, size, morphology, thermal properties, and in vitro prodrug release) has been administered subcutaneously to rats, and the resulting levels of LD and DA in plasma and striatal tissue, respectively, have been monitored. A good correlation between the in vitro release kinetics and the time range during which the formulation alters the LD/DA tissue levels in vivo was observed, suggesting that the polymeric microsphere matrix protects the loaded prodrug from chemical and enzymatic degradation and controls its release. Interestingly, LD-LA microspheres provided sustained levels of DA neurotransmitter in the striatum nucleus for up to 4 days after a single administration. In conclusion, a polymeric microsphere formulation of LD-LA is an attractive medicine for treating Parkinson's disease (PD) symptoms, avoiding motor complications.

Alpha-lipoic acid as a dietary supplement: molecular mechanisms and therapeutic potential

Alpha-lipoic acid (LA) has become a common ingredient in multivitamin formulas, anti-aging supplements, and even pet food. It is well-defined as a therapy for preventing diabetic polyneuropathies, and scavenges free radicals, chelates metals, and restores intracellular glutathione levels which otherwise decline with age. How do the biochemical properties of LA relate to its biological effects? Herein, we review the molecular mechanisms of LA discovered using cell and animal models, and the effects of LA on human subjects. Though LA has long been touted as an antioxidant, it has also been shown to improve glucose and ascorbate handling, increase eNOS activity, activate Phase II detoxification via the transcription factor Nrf2, and lower expression of MMP-9 and VCAM-1 through repression of NF-kappa B. LA and its reduced form, dihydrolipoic acid, may use their chemical properties as a redox couple to alter protein conformations by forming mixed disulfides. Beneficial effects are achieved with low micromolar levels of LA, suggesting that some of its therapeutic potential extends beyond the strict definition of an antioxidant. Current trials are investigating whether these beneficial properties of LA make it an appropriate treatment not just for diabetes, but also for the prevention of vascular disease, hypertension, and inflammation.

Iron metabolism in the eye: a review

This review article covers all aspects of iron metabolism, which include studies of iron levels within the eye and the processes used to maintain normal levels of iron in ocular tissues. In addition, the involvement of iron in ocular pathology is explored. In each section there is a short introduction to a specific metabolic process responsible for iron homeostasis, which for the most part has been studied in non-ocular tissues. This is followed by a summary of our current knowledge of the process in ocular tissues.

Reactive Oxygen Species Mediate Caspase Activation and Apoptosis Induced by Lipoic Acid in Human Lung Epithelial Cancer Cells through Bcl-2 Down-Regulation

The antioxidant alpha-lipoic acid (LA) is a naturally occurring compound that has been shown to possess promising anticancer activity because of its ability to preferentially induce apoptosis and inhibit proliferation of cancer cells relative to normal cells. However, the molecular mechanisms underlying the apoptotic effect of LA are not well understood. We report here that LA induced reactive oxygen species (ROS) generation and a concomitant increase in apoptosis of human lung epithelial cancer H460 cells. Inhibition of ROS generation by ROS scavengers or by overexpression of antioxidant enzymes glutathione peroxidase and superoxide dismutase effectively inhibited LA-induced apoptosis, indicating the role of ROS, especially hydroperoxide and superoxide anion, in the apoptotic process. Apoptosis induced by LA was found to be mediated through the mitochondrial death pathway, which requires caspase-9 activation. Inhibition of caspase activity by the pan-caspase inhibitor (z-VAD-FMK) or caspase-9-specific inhibitor (z-LEHD-FMK) completely inhibited the apoptotic effect of LA. Likewise, the mitochondrial respiratory chain inhibitor rotenone potently inhibited the apoptotic and ROS-inducing effects of LA, supporting the role of mitochondrial ROS in LA-induced cell death. LA induced down-regulation of mitochondrial Bcl-2 protein through peroxide-dependent proteasomal degradation, and overexpression of the Bcl-2 protein prevented the apoptotic effect of LA. Together, our findings indicate a novel pro-oxidant role of LA in apoptosis induction and its regulation by Bcl-2, which may be exploited for the treatment of cancer and related apoptosis disorders.

Iron-binding drugs targeted to lysosomes: a potential strategy to treat inflammatory lung disorders

In many inflammatory lung disorders, an abnormal assimilation of redox-active iron will exacerbate oxidative tissue damage. It may be that the most important cellular pool of redox-active iron exists within lysosomes, making these organelles vulnerable to oxidative stress. In experiments employing respiratory epithelial cells and macrophages, the chelation of intra-lysosomal iron efficiently prevented lysosomal rupture and the ensuing cell death induced by hydrogen peroxide, ionising radiation or silica particles. Furthermore, cell-permeable iron-binding agents (weak bases) that accumulate within lysosomes due to proton trapping were much more efficient for cytoprotection than the chelator, desferrioxamine. On a molar basis, the weak base alpha-lipoic acid plus was 5000 times more effective than desferrioxamine at preventing lysosomal rupture and apoptotic cell death in cell cultures exposed to hydrogen peroxide. Thus, iron-chelating therapy that targets the lysosome might be a future treatment strategy for inflammatory pulmonary diseases.

L-Dopa− and Dopamine−(R)-α-Lipoic Acid Conjugates as Multifunctional Codrugs with Antioxidant Properties

A series of multifunctional codrugs (1-4), obtained by joining L-Dopa (LD) and dopamine (DA) with (R)-alpha-lipoic acid (LA), was synthesized and evaluated as potential codrugs with antioxidant and iron-chelating properties. These multifunctional molecules were synthesized to overcome the pro-oxidant effect associated with LD therapy. The physicochemical properties, together with the chemical and enzymatic stabilities of synthesized compounds, were evaluated in order to determine both their stability in aqueous medium and their sensitivity in undergoing enzymatic cleavage by rat and human plasma to regenerate the original drugs. The new compounds were tested for their radical scavenging activities, using a test involving the Fe (II)-H2O2-induced degradation of deoxyribose, and to evaluate peripheral markers of oxidative stress such as plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the plasma. Furthermore, we showed the central effects of compounds 1 and 2 on spontaneous locomotor activity of rats in comparison with LD-treated animals. From the results obtained, compounds 1-4 appeared stable at a pH of 1.3 and in 7.4 buffered solution; in 80% human plasma they were turned into DA and LD. Codrugs 1-4 possess good lipophilicity (log P > 2 for all tested compounds). Compounds 1 and 2 seem to protect partially against the oxidative stress deriving from auto-oxidation and MAO-mediated metabolism of DA. This evidence, together with the "in vivo" dopaminergic activity and a sustained release of the parent drug in human plasma, allowed us to point out the potential advantages of using 1 and 2 rather than LD in treating pathologies such as Parkinson's disease, characterized by an evident decrease of DA concentration in the brain.

(R)-alpha-lipoic acid protects retinal pigment epithelial cells from oxidative damage

PURPOSE

To determine whether (R)-alpha-lipoic acid (LA) protects cultured human fetal retinal pigment epithelial (hfRPE) cells against oxidative injury and identify the pathways that may mediate protection.

METHODS

Cultured hfRPE cells were pretreated with various concentrations of LA for 14 to 16 hours followed by treatment with a chemical oxidant, tert-butylhydroperoxide (t-BuOOH; 0.8 mM, 3 hours). Reactive oxygen species (ROS) production and cell viability were measured using H(2)DCF and MTT assays, respectively. RPE cells were evaluated with fluorescent dyes (SYTOX Orange and SYTO Green; Molecular Probes, Eugene, OR), which differentiate between live and dead cells. Apoptosis was visualized by using the TUNEL assay. Changes in mitochondrial membrane potential were detected by JC-1 dye. Intracellular levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) were measured by HPLC. Regulation of gamma-glutamylcysteine ligase (GCL), the rate-controlling enzyme of GSH production, was assayed by RT-PCR.

RESULTS

Pretreatment of hfRPE cells with LA, 0.2 mM and 0.5 mM, significantly reduced the levels of t-BuOOH-induced intracellular ROS, by 23% and 49%, respectively. LA (0.5 mM) prevented oxidant-induced cell death and apoptosis and also increased the viability of oxidant-treated hfRPE cells from 38% to 90% of control. LA upregulated the mRNA expression of GCL, and was protective against t-BuOOH-induced decreases in both mitochondrial membrane potential and intracellular levels of GSH and GSH/GSSG.

CONCLUSIONS

The present study suggests that the protective effect of LA involves multiple pathways and that LA could be effective against age-associated increase in oxidative stress and mitochondrial dysfunction in RPE cells.

Plasma protein oxidation in aging rats after alpha-lipoic acid administration

In the present study, we investigated whether alpha-lipoic acid administration could have prooxidant or antioxidant effect on oxidative protein damage parameters such as protein carbonyl, nitrotyrosine, advanced oxidation protein products, and protein thiol, as well as oxidative stress parameters such as total thiol, nonprotein thiol, and lipid hydroperoxide in the plasma proteins of aged rats. Alpha-lipoic acid (100 mg/kg body wt/day) was administrated intraperitoneally to the Sprague-Dawley rats for 14 days. Protein carbonyl, nitrotyrosine, and advanced oxidation protein products levels were increased, protein thiol, nonprotein thiol, and total thiol levels were not changed in the plasma proteins of aged rats with alpha-lipoic acid administration. In aging rats with and without alpha-lipoic acid administration, plasma lipid hydroperoxide levels were significantly increased compared with those of the control group. The increased levels of protein oxidation markers such as protein carbonyl, nitrotyrosine and advanced oxidation protein products in the plasma proteins of alpha-lipoic acid-administrated aged rats compared with nonadministrated aged rats suggests that protein oxidation is increased in alpha-lipoic acid-administrated aged rats. We assume that an explanation for our findings regarding alpha-lipoic acid administration on protein oxidation markers in the plasma proteins of aged rats may be due to the prooxidant effects of alpha-lipoic acid.

Thioctic acid for patients with symptomatic diabetic polyneuropathy: a critical review

Diabetic neuropathy represents a major health problem, as it is responsible for substantial morbidity, increased mortality, and impaired quality of life. Near-normoglycemia is now generally accepted as the primary approach to prevention of diabetic neuropathy, but is not achievable in a considerable number of patients. A growing body of evidence suggests that oxidative stress resulting from enhanced free-radical formation and/or defects in antioxidant defense is implicated in the pathogenesis of diabetic neuropathy. Markers of oxidative stress such as superoxide anion and peroxynitrite production are increased in diabetic patients in relation to the severity of polyneuropathy. In experimental diabetic neuropathy, oxygen free-radical activity in the sciatic nerve is increased, and treatment with thioctic acid, a potent lipophilic antioxidant, results in prevention or improvement of the diabetes-induced neurovascular and metabolic abnormalities in various organ systems. Pharmacodynamic studies have shown that thioctic acid favorably influences the vascular abnormalities of diabetic polyneuropathy such as impaired microcirculation, increased indices of oxidative stress, and increased levels of markers for vascular dysfunction, such as thrombomodulin, albuminuria, and nuclear factor-kappaB. Thus far, seven controlled randomized clinical trials of thioctic acid in patients with diabetic neuropathy have been completed (Alpha-Lipoic Acid in Diabetic Neuropathy [ALADIN I-III], Deutsche Kardiale Autonome Neuropathie [DEKAN], Oral Pilot [ORPIL], Symptomatic Diabetic Neuropathy [SYDNEY], Neurological Assessment of Thioctic Acid in Neuropathy [NATHAN] II) using different study designs, durations of treatment, doses, sample sizes, and patient populations. Recently, a comprehensive analysis was undertaken of trials with comparable designs that met specific eligibility criteria for a meta-analysis to obtain a more precise estimate of the efficacy and safety of thioctic acid (600mg intravenously for 3 weeks) in diabetic patients with symptomatic polyneuropathy. This meta-analysis included the largest sample of diabetic patients (n = 1258) ever to have been treated with a single drug or class of drugs to reduce neuropathic symptoms, and confirmed the favorable effects of thioctic acid based on the highest level of evidence (Class Ia: evidence from meta-analyses of randomized, controlled trials). The following conclusions can be drawn from these trials: (i) short-term treatment for 3 weeks using intravenous thioctic acid 600 mg/day reduces the chief symptoms of diabetic polyneuropathy to a clinically meaningful degree; (ii) this effect on neuropathic symptoms is accompanied by an improvement of neuropathic deficits, suggesting potential for the drug to favorably influence underlying neuropathy; (iii) oral treatment for 4-7 months tends to reduce neuropathic deficits and improve cardiac autonomic neuropathy; and (iv) clinical and postmarketing surveillance studies have revealed a highly favorable safety profile of the drug. Based on these findings, a pivotal long-term multicenter trial of oral treatment with thioctic acid (NATHAN I) is being conducted in North America and Europe to investigate effects on progression of diabetic polyneuropathy, using a clinically meaningful and reliable primary outcome measure that combines clinical and neurophysiological assessment.

Pro-oxidant actions of alpha-lipoic acid and dihydrolipoic acid

There is strong accumulating evidence that a alpha-lipoic acid (LA) supplement is good insurance, and would markedly improve human health. LA is readily absorbed from the diet, transported to cells and reduced to dihydrolipoic acid (DHLA). Of the two compounds, DHLA evidently has greater antioxidant activity. Much research has focused on the antioxidant properties of these compounds. Aside from its antioxidant role, in vitro and in vivo studies suggest that LA and its reduced form DHLA also act as a pro-oxidant properties. Limited number of studies concerning the pro-oxidant potential of LA and DHLA were performed only in recent years. The ability of LA and/or DHLA to function as either anti- or pro-oxidants, at least in part, is determined by the type of oxidant stress and the physiological circumstances. These pro-oxidant actions suggest that LA and DHLA act by multiple mechanisms, many of which are only now being explored. LA has been reported to have a number of potentially beneficial effects in both prevention and treatment of oxygen-related diseases. Selection of appropriate pharmacological doses of LA for use in oxygen-related diseases is critical. On the other hand, much of the discussion in clinical studies has been devoted to the pro-oxidant role of LA. This aspect remains to be elucidated. In further studies, careful evaluation will be necessary for the decision in the biological system whether LA administration is beneficial or harmful.

Prooxidant activities of alpha-lipoic acid on oxidative protein damage in the aging rat heart muscle

In the present study, we investigated whether alpha-lipoic acid (ALA) supplementation could have prooxidant or antioxidant effects on protein oxidation parameters such as protein carbonyl (PCO), nitrotyrosine (NT), advanced oxidation protein products (AOPP), and protein thiol (P-SH), as well as oxidative stress parameters such as total thiol (T-SH), non-protein thiol (Np-SH), and lipid hydroperoxide (LHP) in the heart muscle tissue of aged rats. ALA (100 mg/kg body wt/day) was administered intraperitoneally to the experimental animals for 14 days. PCO, NT, AOPP, and P-SH levels were increased, T-SH and Np-SH levels were not changed, and only LHP levels were decreased in the heart muscle tissue of aged rats with ALA supplementation. When compared with non-supplemented aged rats, increasing levels of protein oxidation markers such as PCO, NT, and AOPP in ALA-supplemented aged rats may suggest that oxidative protein damage is increased in ALA-supplemented aged rats. We assume that an explanation for our findings regarding ALA supplementation on protein oxidation markers in the heart muscle tissue of aged rats may be due to the prooxidant effects of ALA. The prooxidant effects of ALA supplementation should be considered in future studies.

The protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation

PURPOSE

The purpose of this study was to determine the protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation.

METHODS

20 rabbits weighing 2,500- 3,000 g were used, and we divided them into 4 groups with 5 randomly selected rabbits. The rabbits were exposed to 2 J/cm(2)/h of ultraviolet A radiation (UVA) in the range of 320-405 nm for 12 h per day within 90 days. The control group did not undergo any procedure, the UVA group was only exposed to UVA radiation. The PUVA group was treated with 8-methoxypsoralen and UVA. The alpha-lipoic acid group was administered 8-methoxypsoralen + UVA + alpha-lipoic acid. At the end of 90 days, the rabbits were killed by decapitation, and the eyes were enucleated. Both eyes of each rabbit were used for biochemical evaluation. Conjunctival and corneal free malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) levels were compared among the groups.

RESULTS

Conjunctival free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.05, p < 0.001, respectively). Both conjunctival SOD levels (p < 0.05, p < 0.01, respectively) and conjunctival GSH-PX levels (p < 0.01, p < 0.001, respectively) were higher in the alpha-lipoic acid group compared with other groups. Corneal free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.01, p < 0.001, respectively). Both corneal SOD levels (p < 0.01, p < 0.01, respectively) and corneal GSH-PX levels (p < 0.01, p < 0.01, respectively) were higher in the alpha-lipoic acid group compared with the other groups.

CONCLUSION

alpha-Lipoic acid which is considered as potent antioxidant protects the eye from the damaging effect of ultraviolet exposure.

Effect of alpha-lipoic acid supplementation on markers of protein oxidation in post-mitotic tissues of ageing rat

In the present study, we investigated whether DL-alpha-lipoic acid (LA) supplementation could have prooxidant or antioxidant effects on oxidative protein damage parameters such as protein carbonyl (PCO), nitrotyrosine (NT), advanced oxidation protein products (AOPP), and protein thiol (P-SH), as well as oxidative stress parameters such as total thiol (T-SH), non-protein thiol (Np-SH), and lipid hydroperoxide (LHP) in the brain and the skeletal muscle tissue of aged rats. PCO, and NT levels were increased, AOPP and P-SH levels were not changed in the brain tissue of aged rats given LA supplementation. On the other hand, TSH, Np-SH, and LHP levels were decreased in the brain tissue of aged rats given LA supplementation. The levels of the same parameters were not significantly different in the skeletal muscle tissue of aged rats given LA supplementation. The increased levels of protein oxidation markers such as PCO, and NT in the brain tissue of LA-supplemented aged rats compared with non-supplemented aged rats may suggest that oxidative protein damage is increased in LA-supplemented aged rats. We assume that an explanation for our findings regarding LA supplementation on protein oxidation markers in the brain tissue of aged rats may be due to the prooxidant effects of LA. Depending on post-mitotic tissue type and dosage of LA, the prooxidant effects of LA supplementation, should be considered in future studies.

The effects of oxidative stress on telomerase activity and other stress-related proteins in lens epithelial cells

Telomerase is a ribonucleoprotein complex responsible for maintaining the ends of chromosomes and for repair of DNA strand breaks. While telomerase activity is generally found in cells that have unlimited proliferative potential such as neoplastic cells, germline cells and some stem cells, lens epithelial cells (though not highly proliferative) have telomerase activity. Our previous studies indicated that lens epithelial cells express high levels of telomerase despite their low proliferative potential, thus we hypothesized that telomerase expression protects lens epithelial cells from oxidative stress. We also determined levels of the stress proteins gadd45 and p16 and the stress and proliferation-related protein, proliferating cell nuclear antigen (PCNA). In acute studies, lenses were exposed to TBHP for 0-120 min. In recovery studies, lenses were exposed to TBHP for 1 hr, then allowed to recover for up to 18 hr. In acute studies, telomerase activity was increased, p16 initially decreased then normalized, PCNA levels did not change significantly even in the overnight recovery groups, and gadd45 was decreased in some TBHP exposed groups. In recovery studies, telomerase activity was increased in all groups, gadd45 decreased then became elevated, and p16 levels were decreased at later recovery times. PCNA levels remained constant during the studies, indicating that there was no change in proliferation. These studies showed that elevated telomerase activity did not correlate with increased proliferation in lens epithelial cells; instead, increased telomerase activity was associated with increased levels of the stress-related protein gadd45 only in the later recovery times. These findings support the hypothesis that telomerase plays a protective rather than a proliferative role in lens epithelial cells.