Dihydrolipoate reduces neuronal injury after cerebral ischemia

Effects of Alpha Lipoic Acid Supplementation on Serum Levels of Oxidative Stress, Inflammatory Markers and Clinical Prognosis among Acute Ischemic Stroke Patients: A Randomized, Double Blind, TNS Trial

Purpose: Stroke is one of the most common conditions causing death. There have been few studies examining the effects of alpha lipoic acid (ALA) on stroke patients. In this regard, the present randomized controlled clinical trial was conducted to examine the effects of ALA supplementation on serum albumin, and inflammatory and oxidative stress markers in stroke patients.

Methods: The present paralleled randomized controlled clinical trial involved 42 stroke patients who were over 40 years and under enteral feeding. The participants were randomly assigned into two groups and finally 40 patients completed the study. Patients in alpha lipoic acid group (n=19) took 1200 mg ALA supplement daily along with their meal, and participants in control group (n=21) underwent the routine hospital diet for 3 weeks. Fasting blood samples were obtained and albumin, oxidative stress, and inflammatory indices were assessed at baseline, as well as at the end of the trial.

Results: After 3 weeks, treatment of patients with ALA led to a significant decrease in tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) levels (P=0.01) compared to baseline. But serum levels of albumin, total antioxidant capacity (TAC), malondialdehyde (MDA), highsensitivity C-reactive protein (hs-CRP), IL-6 and TNF-α did not change significantly vs. control group (P>0.05).

Conclusion: ALA did not significantly change the serum levels of albumin and inflammatory as well as antioxidant capacity indices in stroke patients compared with the control group. More clinical trials with large sample sizes and long duration are needed to clarify the effects of ALA on these patients.

Achieving Life through Death: Redox Biology of Lipid Peroxidation in Ferroptosis

Redox balance is essential for normal brain, hence dis-coordinated oxidative reactions leading to neuronal death, including programs of regulated death, are commonly viewed as an inevitable pathogenic penalty for acute neuro-injury and neurodegenerative diseases. Ferroptosis is one of these programs triggered by dyshomeostasis of three metabolic pillars: iron, thiols, and polyunsaturated phospholipids. This review focuses on: (1) lipid peroxidation (LPO) as the major instrument of cell demise, (2) iron as its catalytic mechanism, and (3) thiols as regulators of pro-ferroptotic signals, hydroperoxy lipids. Given the central role of LPO, we discuss the engagement of selective and specific enzymatic pathways versus random free radical chemical reactions in the context of the phospholipid substrates, their biosynthesis, intracellular location, and related oxygenating machinery as participants in ferroptotic cascades. These concepts are discussed in the light of emerging neuro-therapeutic approaches controlling intracellular production of pro-ferroptotic phospholipid signals and their non-cell-autonomous spreading, leading to ferroptosis-associated necroinflammation.

Nutraceuticals against Neurodegeneration: A Mechanistic Insight

The mechanisms underlying neurodegenerative disorders are complex and multifactorial; however, accumulating evidences suggest few common shared pathways. These common pathways include mitochondrial dysfunction, intracellular Ca²⁺ overload, oxidative stress and inflammation. Often multiple pathways co-exist, and therefore limit the benefits of therapeutic interventions. Nutraceuticals have recently gained importance owing to their multifaceted effects. These food-based approaches are believed to target multiple pathways in a slow but more physiological manner without causing severe adverse effects. Available information strongly supports the notion that apart from preventing the onset of neuronal damage, nutraceuticals can potentially attenuate the continued progression of neuronal destruction. In this article, we i) review the common pathways involved in the pathogenesis of the toxicants-induced neurotoxicity and neurodegenerative disorders with special emphasis on Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Multiple sclerosis (MS) and Amyotrophic lateral sclerosis (ALS), and ii) summarize current research advancements on the effects of nutraceuticals against these detrimental pathways.

The antioxidative property of melatonin against brain ischemia

INTRODUCTION

This review briefly summarizes some of the large amount of data documenting the ability of melatonin to limit molecular and organ tissue damage in neural ischemia-reperfusion injury (stroke), where free radicals are generally considered as being responsible for much of the resulting tissue destruction.

AREA COVERED

Melatonin actions that have been identified include its ability to directly neutralize a number of toxic reactants and stimulate antioxidative enzymes. Furthermore, several of its metabolites such as N(1)-acetyl-N(2)-formyl-5- methoxykynuramine (AFMK) and N(1)-acetyl-5-methoxykynuramine (AMF), are themselves scavengers suggesting that there is a cascade of reactions that greatly increase the efficacy of melatonin. Expert Commentary: However, the mechanisms by which melatonin is protective in such widely diverse areas of the cell and different organs are likely not yet all identified.

Antioxidants: The new frontier for translational research in cerebroprotection

It is important for the anesthesiologist to understand the etiology of free radical damage and how free-radical scavengers attenuate this, so that this knowledge can be applied to diverse neuro-pathological conditions. This review will concentrate on the role of reactive species of oxygen in the pathophysiology of organ dysfunction, specifically sub arachnoid hemorrhage (SAH), traumatic brain injury (TBI) as well as global central nervous system (CNS) hypoxic, ischemic and reperfusion states. We enumerate potential therapeutic modalities that are been currently investigated and of interest for future trials. Antioxidants are perhaps the next frontier of translational research, especially in neuro-anesthesiology.

Cellular mechanisms by which lipoic acid confers protection during the early stages of cerebral ischemia: a possible role for calcium

Lipoic acid (LA) is a naturally occurring compound and dietary supplement with powerful antioxidant properties. Although LA is neuroprotective in models of stroke, little is known about the cellular mechanisms by which it confers protection during the early stages of ischemia. Here, using a rat model of permanent middle cerebral artery occlusion (MCAO), we demonstrated that administration of LA 30 min prior to stroke, reduces infarct volume in a dose dependent manner. Whole-cell patch clamp techniques in rat brain slices were used to determine if LA causes any electrophysiological alterations in either healthy neurons or neurons exposed to oxygen and glucose deprivation (OGD). In healthy neurons, LA (0.005 mg/ml and 0.05 mg/ml) did not significantly change resting membrane potential, threshold or frequency of action potentials or synaptic transmission, as determined by amplitude of excitatory post synaptic currents (EPSCs). Similarly, in neurons exposed to OGD, LA did not alter the time course to loss of EPSCs. However, there was a significant delay the onset of anoxic depolarization as well as in the time course of the depolarization. Next, intracellular calcium (Ca(2+)) levels were monitored in isolated neurons using fura-2. Pretreatment with 0.005 mg/ml and 0.05 mg/ml LA for 30 min and 6 h did not significantly alter resting Ca(2+) levels or Ca(2+) response to glutamate (250 μM). However, pretreatment with 0.5 mg/ml LA for 6 h significantly increased resting Ca(2+) levels and significantly decreased the Ca(2+) response to glutamate. In summary, these findings suggest that LA does not affect neuronal physiology under normal conditions, but can protect cells from an ischemic event.

Anti-apoptotic and neuroprotective effects of α-lipoic acid on spinal cord ischemia-reperfusion injury in rabbits

PURPOSE

Radical oxygen species produced after injury counteracts antioxidant activity and frequently causes severe oxidative stress for the tissues. Alpha-lipoic acid is a powerful metabolic antioxidant with immunomodulatory effects which provides neuroprotection. The aim of this study is to investigate the neuroprotective and anti-apoptotic effects of alpha-lipoic acid on spinal cord ischemia-reperfusion.

METHODS

Twenty-four adult, male, New Zealand rabbits were divided into sham (n = 8), control (n = 8), and treatment groups (n = 8). The abdominal aorta was clamped for 30 min by an aneurysm clip, approximately 1 cm below the renal artery and 1 cm above the iliac bifurcation in control and treatment groups. Only laparotomy was performed in the sham group. Twenty-five cubic centimeters of saline in control group and 100 mg/kg lipoic acid were administered intraperitoneally in the treatment group after closure of the incision. The animals were killed 48 h later. Spinal cord segments between L2 and S1 were harvested for analysis. Levels of nitric oxide, glutathione, malondialdehyde, advanced oxidation protein products, and superoxide dismutase were analyzed as markers of oxidative stress and inflammation. Caspase-3 activity was analyzed to detect the effect of lipoic acid on apoptosis.

RESULTS

In all measured parameters of oxidative stress, administration of lipoic acid significantly demonstrated favorable effects. Both plasma and tissue levels of nitric oxide, glutathione, malondialdehyde, and advanced oxidation protein products significantly changed in favor of antioxidant activity. There was no significant difference between the plasma superoxide dismutase levels of the groups. Histopathological evaluation of the tissues also demonstrated significant decrease in cellular degeneration and infiltration parameters after lipoic acid administration. However, lipoic acid has no effect on caspase-3 activity.

CONCLUSIONS

Although further studies considering different dose regimens and time intervals are required, the results of the present study prove that alpha-lipoic acid has favorable effects on experimental spinal cord ischemia-reperfusion injury.

The energy-redox axis in aging and age-related neurodegeneration

Decrease in mitochondrial energy-transducing capacity is a feature of the aging process that accompanies redox alterations, such as increased generation of mitochondrial oxidants, altered GSH status, and increased protein oxidation. The decrease in mitochondrial energy-transducing capacity and altered redox status should be viewed as a concerted process that embodies the mitochondrial energy-redox axis and is linked through various mechanisms including: (a) an inter-convertible reducing equivalents pool (i.e., NAD(P)(+)/NAD(P)H) and (b) redox-mediated protein post-translational modifications involved in energy metabolism. The energy-redox axis provides the rationale for therapeutic approaches targeted to each or both component(s) of the axis that effectively preserves or improve mitochondrial function and that have implications for aging and age-related neurodegenerative disorders.

An alpha-lipoic acid–vitamin E mixture reduces post-embolism lipid peroxidation, cerebral infarction, and neurological deficit in rats

Oxidative stress increases delayed neuronal death in the brain following ischemia. As a consequence, many attempts to reduce the damage resulting from cerebral ischemia under more highly oxidized conditions have focused on treatments aimed at maintaining the redox equilibrium of the local environment. This study demonstrates the synergistic effects of combining treatments with alpha-lipoic acid (LA) and vitamin E (VE) as an efficient measure to reduce the damage caused by cerebral ischemia. Two oral therapeutic protocols were examined: intensive treatment (100 mg/kg LA and 140 mg/kg VE for 7 days after ischemia) and prophylactic treatment (20 mg/kg LA and 50 mg/kg VE from 30 days before infarction up to the day of sacrifice). The prophylactic treatment reduced serum lipid peroxidation, and diminished brain infarct volume by approximately 50%. Furthermore, prophylactically treated rats showed a reduction in post-ischemia neurological scores. No significant differences were found in the intensively treated group. Our data indicate that pre-ischemia administration of the LA-VE antioxidant mixture reduced the volume of brain damaged and the functional consequences of embolic infarction. These findings suggest that prophylaxis with an LA-VE mixture may be valuable in reducing cerebral damage levels in patients with a high risk of stroke.

Protective role of DLalpha-lipoic acid against adriamycin-induced cardiac lipid peroxidation

The cytoprotective activity of alpha-lipoic acid against free radical toxicity manifested during adriamycin (ADR)-induced cardiotoxicity has been investigated. ADR is a potent antitumour drug known to cause severe cardiotoxicity. Although ADR generates free radicals, the role of these radicals in the development of cardiac toxicity is still not well understood. In the present study, we evaluated the influence of chronic ADR treatment on the cellular defence mechanism against free radicals and the effect of alpha-lipoic acid supplementation on ADR-induced cardiotoxicity in male Wistar rats. The increase in lipid peroxidation (LPO) and activities of serum myocardial enzymes, namely lactate dehydrogenase (LDH) and creatinephosphokinase, associated with the decrease in activities of enzymatic (SOD, CAT, GPx, G6PD and GR) and non-enzymatic (GSH, Vit C and Vit E) antioxidants levels were the salient features observed in ADR-induced cardiotoxicity. Lipoic acid pretreated groups showed significant increase in activities of both enzymatic and non-enzymatic antioxidant levels. These observations highlight the antioxidant property of alpha-lipoic acid and its cytoprotective action against ADR-induced cardiotoxicity.

Melatonin ameliorates neurologic damage and neurophysiologic deficits in experimental models of stroke

This review summarizes the numerous reports that have documented the neuroprotective actions of melatonin in experimental models of ischemia/reperfusion injury (stroke). In these investigations, which have used three species (rat, gerbil, and cat), melatonin was universally found to reduce brain damage that normally occurs as a consequence of the temporary interruption of blood flow followed by the reflow of oxygenated blood to the brain. The exogenous administration of melatonin in these experimental stroke models reduced infarct volume, lowered the frequency of apoptosis, increased the number of surviving neurons, reduced reactive gliosis, lowered the oxidation of neural lipids and oxidatively damaged DNA, induced bcl-2 gene expression (the activity of which improves cell survival), upregulated excision repair cross-complementing factor 6 (an essential gene for preferential DNA excision repair), restrained poly(ADP ribose) synthetase (which depletes cellular NAD resulting in the loss of ATP) activity, and improved neurophysiologic outcomes. Under no circumstances did melatonin exacerbate the damage associated with ischemia/reperfusion injury. As well as the beneficial pharmacologic actions of melatonin, several studies show that a relative deficiency of endogenous melatonin exaggerates neural damage due to stroke; this suggests that even physiologic concentrations of melatonin normally serve to protect the brain against damage. The primary action to explain melatonin's protective effects may relate to its ubiquitous direct and indirect antioxidative actions, although other beneficial functions of melatonin are not precluded.

In vitro neuroprotection against oxidative stress by pre-treatment with a combination of dihydrolipoic acid and phenyl-butyl nitrones

One consequence of trauma to the CNS is the production and liberation, from damaged tissue, of large amounts of oxygen-centered free radicals or reactive oxygen species (ROS). An excessive production of ROS can overwhelm the endogenous antioxidant defense system resulting in lipid peroxidation, DNA strand breaks, protein denaturation and cross-linking. The brain is particularly vulnerable to oxidative injury, because it contains high concentrations of readily oxidizable poly-unsaturated fatty acids, has a high rate of oxygen consumption per unit mass, and has only a relatively modest antioxidant defense system. We have conducted studies in vitro to determine the feasibility of reducing ROS-mediated damage in neurons by bolstering endogenous neuronal antioxidant defenses. Primary cultures of neurons derived from embryonic rat forebrain were pre-treated with the free radical scavenger dihydrolipoic acid (DHLA), the reduced form of Alpha-lipoic acid (ALA), and then subjected to H(2)O(2)-mediated oxidative stress. Neuroprotection was determined using the colorimetric MTT reduction assay. As has been reported by others, pre-treatment of neurons with DHLA (4 h) provided dose-dependent neuroprotection against a subsequent exposure to H(2)O(2). The addition of spin trapping nitrones N-tert-butyl-Alpha-phenyl-nitrone (PBN) or its sulfonated analog N-tert-butyl-Alpha(2-sulfophenyl)-nitrone (SPBN) to the pre-treatment cocktail enhanced neuroprotection at every dihydrolipoate concentration. Greater therapeutic efficacy in antioxidant treatment might be realized by employing combinations of complementary antioxidants.

Modification of brain aging and neurodegenerative disorders by genes, diet, and behavior

Multiple molecular, cellular, structural, and functional changes occur in the brain during aging. Neural cells may respond to these changes adaptively, or they may succumb to neurodegenerative cascades that result in disorders such as Alzheimer's and Parkinson's diseases. Multiple mechanisms are employed to maintain the integrity of nerve cell circuits and to facilitate responses to environmental demands and promote recovery of function after injury. The mechanisms include production of neurotrophic factors and cytokines, expression of various cell survival-promoting proteins (e.g., protein chaperones, antioxidant enzymes, Bcl-2 and inhibitor of apoptosis proteins), preservation of genomic integrity by telomerase and DNA repair proteins, and mobilization of neural stem cells to replace damaged neurons and glia. The aging process challenges such neuroprotective and neurorestorative mechanisms. Genetic and environmental factors superimposed upon the aging process can determine whether brain aging is successful or unsuccessful. Mutations in genes that cause inherited forms of Alzheimer's disease (amyloid precursor protein and presenilins), Parkinson's disease (alpha-synuclein and Parkin), and trinucleotide repeat disorders (huntingtin, androgen receptor, ataxin, and others) overwhelm endogenous neuroprotective mechanisms; other genes, such as those encoding apolipoprotein E(4), have more subtle effects on brain aging. On the other hand, neuroprotective mechanisms can be bolstered by dietary (caloric restriction and folate and antioxidant supplementation) and behavioral (intellectual and physical activities) modifications. At the cellular and molecular levels, successful brain aging can be facilitated by activating a hormesis response in which neurons increase production of neurotrophic factors and stress proteins. Neural stem cells that reside in the adult brain are also responsive to environmental demands and appear capable of replacing lost or dysfunctional neurons and glial cells, perhaps even in the aging brain. The recent application of modern methods of molecular and cellular biology to the problem of brain aging is revealing a remarkable capacity within brain cells for adaptation to aging and resistance to disease.

Increased protein oxidation and decreased creatine kinase BB expression and activity after spinal cord contusion injury

Traumatic injury to the spinal cord triggers several secondary effects, including oxidative stress and compromised energy metabolism, which play a major role in biochemical and pathological changes in spinal cord tissue. Free radical generation and lipid peroxidation have been shown to be early events subsequent to spinal cord injury. In the present study, we demonstrated that protein oxidation increases in rat spinal cord tissue after experimental injury. As early as h after injury, the level of protein carbonyls at the injury epicenter was significantly higher than in control (169%, p < 0.05) and increased gradually over the next 4 weeks to 1260% of control level. Both caudal and rostral parts of the injured spinal cord demonstrated a mild increase of protein carbonyls by 4 weeks postinjury (135-138%, p < 0.05). Immunocytochemical analysis of protein carbonyls in the spinal cord cross-sections showed increased protein carbonyl immunoreactivity in the epicenter section compared to rostral and caudal sections of the same animal or control laminectomy animals. Increased protein carbonyl formation in damaged spinal cord tissue was associated with changes in activity and expression of an oxidative sensitive enzyme, creatine kinase BB, which plays an important role in the maintenance of ATP level in the CNS tissue. Damage to CK function in the CNS may severely aggravate the impairment of energy metabolism. The results of our study indicate that events associated with oxidative damage are triggered immediately after spinal cord trauma but continue to occur over the subsequent 4 weeks. These results suggest that antioxidant therapeutic strategies may be beneficial to lessen the consequences of the injury and potentially improve the restoration of neurological function.

Beneficial effects of alpha-lipoic acid plus vitamin E on neurological deficit, reactive gliosis and neuronal remodeling in the penumbra of the ischemic rat brain

During cerebral ischemia-reperfusion, the enhanced production of oxygen-derived free radicals contributes to neuronal death. The antioxidants alpha-lipoic acid and vitamin E have shown synergistic effects against lipid peroxidation by oxidant radicals in several pathological conditions. A thromboembolic stroke model in rats was used to analyze the effects of this mixture under two oral treatments: intensive and prophylactic. Neurological functions, glial reactivity and neuronal remodeling were assessed after experimental infarction. Neurological recovery was only found in the prophylactic group, and both antioxidant schemes produced down-regulation of astrocytic and microglial reactivity, as well as higher neuronal remodeling in the penumbra area, as compared with controls. The beneficial effects of this antioxidant mixture suggest that it may be valuable for the treatment of cerebral ischemia in humans.

Early effects on restoration of evoked field potentials in the hippocampal CA(1) region after reversible hypoxia/hypoglycemia by the radical scavenger N-tert.-butyl-alpha-phenylnitron

In transverse hippocampus slices a short period of hypoxia/hypoglycemia induced by perfusion with an O(2)/glucose-free medium caused early loss and incomplete restoration of evoked field potentials in the CA(1) region. In the present study a search was made for whether the formation of free oxoradicals immediately after starting the hypoxic phase could be part of the breakdown and incomplete restoration of the excitatory potentials (EPs). It was shown that preincubation and postischemic incubation with the radical scavenger PBN did not prevent the potential breakdown but significantly enhances potential restoration, even when PBN was added to the perfusion medium 40 min after hypoxia. Thus, free oxoradicals may damage membrane constituents such as receptors or channel proteins at a very early phase, before neuronal death is pronounced. The results also show that treatment with radical scavengers has a beneficial effect on early hypoxic damage.

Sulfur-centered radical formation from the antioxidant dihydrolipoic acid

Lipoic acid and its reduced form, dihydrolipoic acid, are thought to be strong antioxidants. There are also reports of dihydrolipoic acid acting as a pro-oxidant under certain circumstances. This article reports the direct observation by ESR spectrometry of the disulfide radical anion and the spin trapping of the primary thiyl radical formed from the oxidation of dihydrolipoic acid through thiol pumping with phenol and horseradish peroxidase. The disulfide radical anion reacts rapidly with oxygen to form the reactive radical superoxide, which is also trapped. The radical species formed show a potential for pro-oxidant activity of this compound. Although antioxidants, in general, have been shown to have pro-oxidant potential, the pro-oxidant chemistry of dihydrolipoic acid has not been well characterized.

Versatile cytoprotective activity of lipoic acid may reflect its ability to activate signalling intermediates that trigger the heat-shock and phase II responses

Although lipoic acid (LA) and its reduced derivative (DHLA) have broad antioxidant activity, it seems unlikely that this can adequately explain the remarkable neuroprotective effects of LA observed in rodents and in diabetic patients. It is proposed that this protection is mediated, in large measure, by induction of various protective proteins. More specifically, there is some reason to suspect that LA can trigger both heat-shock and phase II responses, and that LA may achieve this by catalyzing the formation of intramolecular disulfides in certain signalling proteins that function as detectors of oxidants and/or electrophiles. This hypothesis is readily testable, and, if true, would suggest that LA may have general utility for preventing or treating neurodegenerative disorders, and possibly also may retard the adverse impact of aging on brain function. This model also predicts that LA should have anticarcinogenic activity.

Efficacy of antioxidant therapies in transient focal ischemia in mice

BACKGROUND AND PURPOSE

Ginkgo biloba extract (EGb) and alpha-lipoic acid (LA) are commercially available "antioxidant supplements" with a variety of actions that may be beneficial during acute stroke. These actions include inhibiting platelet and leukocyte activation and adhesion, reducing free radical generation, and increasing cerebral blood flow. Both EGb and LA have been shown to be neuroprotective in cell culture and global central nervous system ischemia models. In this study we investigated the neuroprotective efficacy of EGb and LA in a clinically relevant, transient focal central nervous system ischemic model.

METHODS

In the EGb study, 60 adult C57blk mice were randomized to treatment with EGb given orally (via gavage) for 7 days: low dose, 50 EGb mg/kg daily; high dose, 100 mg/kg daily; matched placebo. On day 7, reversible middle cerebral artery occlusion was produced by advancing a silicone-coated 8-0 filament into the internal carotid artery for 45 minutes followed by reperfusion. At 24 hours, the animals were evaluated on a 28-point clinical scale, and infarct volume was determined with the use of triphenyltetrazolium chloride. In the LA study, 24 C57blk mice were treated with 100 mg/kg SC of LA or placebo 1.5 hours before transient MCAO, as in the EGb study.

RESULTS

In the EGb study, values for infarct volume at 24 hours were as follows (mean+/-SD): low dose (n=18), 13+/-5 mm(3); high dose (n=22), 22+/-12 mm(3); placebo (n=20), 20+/-10 mm(3) (P:=0.03 overall; P=0.02, low dose versus placebo). Infarct percentage of hemisphere values were as follows: low dose, 14+/-5%; high dose, 21+/-11%; placebo, 20+/-9% (P=0.03 overall; P=0.02, low dose versus placebo). Ten percent of the high-dose group showed significant intracerebral hemorrhage (ICH) within the infarct, while no ICH was seen in the other groups. Neurological function scores were as follows: low dose, 11.8+/-1.5; high dose, 11.4+/-1.7; placebo, 11.3+/-1.8 (P=NS). In the LA study, infarct volume was as follows: 100 mg/kg LA (n=12), 16.8+/-8.3 mm(3); placebo (n=12), 27.2+/-14.6 mm(3) (P<0.05). LA also produced a significant improvement in neurological function at 24 hours: LA, 9.5+/-1.2; placebo, 11.2+/-1.8 (P=0.02). There was no evidence of ICH in any of the animals.

CONCLUSIONS

Both oral EGb and LA therapies produced significant reductions in stroke infarct volume. However, for EGb this beneficial effect appears to be dose related, with higher doses potentially increasing the risk of ICH.

A conservative triple antioxidant approach to the treatment of hepatitis C. Combination of alpha lipoic acid (thioctic acid), silymarin, and selenium: three case histories

BACKGROUND

There has been an increase in the number of adults seeking liver transplantation for hepatitis C in the last few years and the count is going up rapidly. There is no reliable and effective therapy for chronic hepatitis C since interferon and antivirals work no more than 30% of the time, and liver transplant surgery is uncertain and tentative over the long run. This is because, ultimately, residual hepatitis C viremia infects the new liver. Furthermore, liver transplantation can be painful, disabling and extremely costly.

TREATMENT PROGRAM

The author describes a low cost and efficacious treatment program in 3 patients with cirrhosis, portal hypertension and esophageal varices secondary to chronic hepatitis C infection. This effective and conservative regimen combines 3 potent antioxidants (alpha-lipoic acid [thioctic acid], silymarin, and selenium) that possess antiviral, free radical quenching and immune boosting qualities.

CONCLUSION

There are no remarkably effective treatments for chronic hepatitis C in general use. Interferon and antivirals have less than a 30% response rate and because of the residual viremia, a newly transplanted liver usually becomes infected again. The triple antioxidant combination of alpha-lipoic acid, silymarin and selenium was chosen for a conservative treatment of hepatitis C because these substances protect the liver from free radical damage, increase the levels of other fundamental antioxidants, and interfere with viral proliferation. The 3 patients presented in this paper followed the triple antioxidant program and recovered quickly and their laboratory values remarkably improved. Furthermore, liver transplantation was avoided and the patients are back at work, carrying out their normal activities, and feeling healthy. The author offers a more conservative approach to the treatment of hepatitis C, that is exceedingly less expensive. One year of the triple antioxidant therapy described in this paper costs less than $2,000, as compared to mor than $300,000 a year for liver transplant surgery. It appears reasonable, that prior to liver transplant surgery evaluation, or during the transplant evaluation process, the conservative triple antioxidant treatment approach should be considered. If these is a significant betterment in the patient's condition, liver transplant surgery may be avoided.

Chromatographic analysis of lipoic acid and related compounds

The analysis of lipoic acid and related compounds, such as its reduced form dihydrolipoic acid, its amide form lipoamide and other analogues, in biological and food samples is important in biochemistry, nutritional and clinical chemistry. This review summarizes the chromatographic methods for the determination of lipoic acid and related compounds, and their applications to various samples such as bacteria, tissues, drugs and food. Gas chromatographic methods with flame ionization detection and flame photometric detection are commonly used for the quantification of lipoic acid present as its protein-bound form, after acid or base hydrolysis of these samples. High-performance liquid chromatographic methods with ultraviolet, fluorescence and electrochemical detection are mainly used for the determination of free lipoic acid and related compounds, such as dihydrolipoic acid, lipoamide and other analogues. Moreover, gas chromatography-mass spectrometry and capillary electrophoresis methods are also developed.

alpha-Lipoic acid: a metabolic antioxidant which regulates NF-kappa B signal transduction and protects against oxidative injury

Although the metabolic role of alpha-lipoic acid has been known for over 40 years, it is only recently that its effects when supplied exogenously have become known. Exogenous alpha-lipoic acid is reduced intracellularly by at least two and possibly three enzymes, and through the actions of its reduced form, it influences a number of cell process. These include direct radical scavenging, recycling of other antioxidants, accelerating GSH synthesis, and modulating transcription factor activity, especially that of NF-kappa B (Fig. 12). These mechanisms may account for the sometimes dramatic effects of alpha-lipoic acid in oxidative stress conditions (e.g., brain ischemia-reperfusion), and point the way toward its therapeutic use.

NMDA-induced superoxide production and neurotoxicity in cultured rat hippocampal neurons: role of mitochondria

Excitotoxic mechanisms are believed to be involved in the death of neurons after trauma, epileptic seizures and cerebral ischaemia. We investigated the role of mitochondrial superoxide production in excitotoxic cell death of cultured rat hippocampal neurons. Brief exposure to the selective glutamate agonist N-methyl-D-aspartate (NMDA; 100-300 microM, 10 min) induced significant neuronal death, which was sensitive to cycloheximide (1 microM) and the caspase-1 inhibitor, acetyl-Tyr-Val-Ala-Asp-chloromethylketone (10 microM). Intracellular superoxide production was monitored semiquantitatively on sister cultures from the same platings using the oxidation-sensitive probe, hydroethidine. Brief exposures to toxic NMDA concentrations induced significant increases in superoxide production which correlated with the degree of neuronal injury. However, subtoxic NMDA exposures also produced moderate, yet statistically significant increases in superoxide production. Both NMDA-induced superoxide production and neurotoxicity were reduced by inhibition of mitochondrial electron transport using either sodium cyanide (1 mM), or a combination of rotenone (2 microM) and oligomycin (2 microM). The mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP, 1 microM) mimicked the effect of NMDA on mitochondrial superoxide production. Both NMDA-induced superoxide production and neurotoxicity were potentiated by FCCP (1 microM). Exposure to FCCP alone (1-10 microM, 10 min), however, failed to produce any toxicity. Our data suggest that mitochondrial superoxide production per se is not sufficient to trigger the degeneration of cultured hippocampal neurons, but that manipulation of mitochondrial activity alters NMDA-induced superoxide production and neurotoxicity.

Lipoic acid reduces the activities of biotin-dependent carboxylases in rat liver

In the past, lipoic acid has been administered to patients and test animals as therapy for diabetic neuropathy and various intoxications. Lipoic acid and the vitamin biotin have structural similarities. We sought to determine whether the chronic administration of lipoic acid affects the activities of biotin-dependent carboxylases. For 28 d, rats received daily intraperitoneal injections of one of the following: 1) a small dose of lipoic acid [4.3 micromol/( kg.d)]; 2) a large dose of lipoic acid [15.6 micromol/(kg.d)]; or 3) a large dose of lipoic acid plus biotin [15.6 and 2.0 micromol/(kg.d), respectively]. Another group received n-hexanoic acid [14.5 micromol/(kg.d)], which has structural similarities to lipoic acid and biotin and thus served as a control for the specificity of lipoic acid. A fifth group received phosphatidylcholine in saline injections and served as the vehicle control. The rat livers were assayed for the activities of acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, and beta-methylcrotonyl-CoA carboxylase. Urine was analyzed for lipoic acid; serum was analyzed for indicators of liver damage and metabolic aberrations. The mean activities of pyruvate carboxylase and beta-methylcrotonyl-CoA carboxylase were 28-36% lower in the lipoic acid-treated rats compared with vehicle controls (P < 0.05). Rats treated with lipoic acid plus biotin had normal carboxylase activities. Carboxylase activities in livers of n-hexanoic acid-treated rats were normal despite some evidence of liver injury. Propionyl-CoA carboxylase and acetyl-CoA carboxylase were not significantly affected by administration of lipoic acid. This study provides evidence consistent with the hypothesis that chronic administration of lipoic acid lowers the activities of pyruvate carboxylase and beta-methylcrotonyl-CoA carboxylase in vivo by competing with biotin.

Fused 2-thiohydantoin derivatives: evaluation as potential antioxidants

A series of fused 5,5-diphenyl and 5-arylidene-2-thiohydantoin derivatives were examined for their oxygen free radical inhibitory and radical scavenging properties (RSC) using both an enzymic and non-enzymic biological generators of free radicals. Non-enzymic lipid peroxidation (OH. radicals) was assayed as the amount of malondialdehyde (MDA) that had been formed during incubation of boiled rat liver microsomes in the presence of ascorbic acid and ferric ions. Superoxide anions (.O2- anion radicals) were generated enzymatically in the xanthine-xanthine oxidase system. Among the 20 investigated compounds only four fused arylidene 2-thiohydantoin derivatives showed weak antioxidant activity scavenging OH. radicals. There is a relationship between the electrophilic OH. radical scavenging properties (RSC) of the tested molecules and the value of their HOMO energy derived from semiempirical MO calculations.

Neuroprotection by the metabolic antioxidant alpha-lipoic acid

Reactive oxygen species are thought to be involved in a number of types of acute and chronic pathologic conditions in the brain and neural tissue. The metabolic antioxidant alpha-lipoate (thioctic acid, 1, 2-dithiolane-3-pentanoic acid; 1, 2-dithiolane-3 valeric acid; and 6, 8-dithiooctanoic acid) is a low molecular weight substance that is absorbed from the diet and crosses the blood-brain barrier. alpha-Lipoate is taken up and reduced in cells and tissues to dihydrolipoate, which is also exported to the extracellular medium; hence, protection is afforded to both intracellular and extracellular environments. Both alpha-lipoate and especially dihydrolipoate have been shown to be potent antioxidants, to regenerate through redox cycling other antioxidants like vitamin C and vitamin E, and to raise intracellular glutathione levels. Thus, it would seem an ideal substance in the treatment of oxidative brain and neural disorders involving free radical processes. Examination of current research reveals protective effects of these compounds in cerebral ischemia-reperfusion, excitotoxic amino acid brain injury, mitochondrial dysfunction, diabetes and diabetic neuropathy, inborn errors of metabolism, and other causes of acute or chronic damage to brain or neural tissue. Very few neuropharmacological intervention strategies are currently available for the treatment of stroke and numerous other brain disorders involving free radical injury. We propose that the various metabolic antioxidant properties of alpha-lipoate relate to its possible therapeutic roles in a variety of brain and neuronal tissue pathologies: thiols are central to antioxidant defense in brain and other tissues. The most important thiol antioxidant, glutathione, cannot be directly administered, whereas alpha-lipoic acid can. In vitro, animal, and preliminary human studies indicate that alpha-lipoate may be effective in numerous neurodegenerative disorders.

Cytosolic and mitochondrial systems for NADH- and NADPH-dependent reduction of alpha-lipoic acid

In cellular, tissue, and organismal systems, exogenously supplied alpha-lipoic acid (thioctic acid) has a variety of significant effects, including direct radical scavenging, redox modulation of cell metabolism, and potential to inhibit oxidatively-induced injury. Because reduction of lipoate to dihydrolipoate is a crucial step in many of these processes, we investigated mechanisms of its reduction. The mitochondrial NADH-dependent dihydrolipoamide dehydrogenase exhibits a marked preference for R(+)-lipoate, whereas NADPH-dependent glutathione reductase shows slightly greater activity toward the S(-)-lipoate stereoisomer. Rat liver mitochondria also reduced exogenous lipoic acid. The rate of reduction was stimulated by substrates which increased the NADH content of the mitochondria, and was inhibited by methoxyindole-2-carboxylic acid, a dihydrolipoamide dehydrogenase inhibitor. In rat liver cytosol, NADPH-dependent reduction was greater than NADH, and lipoate reduction was inhibited by glutathione disulfide. In rat heart, kidney, and brain whole cell-soluble fractions, NADH contributed more to reduction (70-90%) than NADPH, whereas with liver, NADH and NADPH were about equally active. An intact organ, the isolated perfused rat heart, reduced R-lipoate six to eight times more rapidly than S-lipoate, consistent with high mitochondrial dihydrolipoamide dehydrogenase activity and results with isolated cardiac mitochondria. On the other hand, erythrocytes, which lack mitochondria, somewhat more actively reduced S- than R-lipoate. These results demonstrate differing stereospecific reduction by intact cells and tissues. Thus, mechanisms of reduction of alpha-lipoate are highly tissue-specific and effects of exogenously supplied alpha-lipoate are determined by tissue glutathione reductase and dihydrolipoamide dehydrogenase activity.

alpha-Lipoic acid protects against reperfusion injury following cerebral ischemia in rats

Ischemic-reperfusion injury in humans occurs in conditions such as stroke, cardiac arrest, subarachnoid hemorrhage or head trauma. Maximal tissue damage is observed during reperfusion, which is primarily attributed to oxidative injury resulting from production of oxygen free radicals. One of the major consequences of such damage is the depletion of the cellular antioxidant, glutathione (GSH) leading to oxidation of protein thiols to disulfides and the loss of activity of critical enzymes having active thiol group(s). Thus, the maintenance of thiol homeostasis is an important factor in cell survival. The effect of thiol antioxidants like alpha-lipoic acid and the isopropyl ester of GSH was examined on the morbidity and mortality of rats subjected to reperfusion following cerebral ischemia induced by bilateral carotid artery occlusion and hypotension. While the GSH isopropyl ester had no significant protective effect; after pretreatment of rats, alpha-lipoic acid was detected in the rat brain and it dramatically reduced the mortality rate from 78% to 26% during 24 h of reperfusion. The natural thiol antioxidant, alpha-lipoic acid is effective in improving survival and protecting the rat brain against reperfusion injury following cerebral ischemia.

Neuroprotective effects of alpha-lipoic acid and its enantiomers demonstrated in rodent models of focal cerebral ischemia

The purpose of this study was to investigate whether alpha-lipoic acid (LA), the oxidized form of the radical scavenger dihydrolipoic acid (DLA), protected brain tissue against ischemic damage and whether there were differences in the neuroprotective potencies between its enantiomers. We used the models of focal cerebral ischemia in mice and rats. The infarct area on the mouse brain surface and the infarct volume of the rat brain were determined by means of an image analyzing system. The LA was capable of reducing the infarct area only when it was administered subcutaneously, but not when it was administered intraperitoneally or into the cisterna magna. Both the R- and the S-enantiomer of LA protected brain tissue against ischemic damage, but their protective activities seemed to be related to the time period of pretreatment. In mice, both enantiomers revealed a similar neuroprotective potency when they were administered subcutaneously 1 or 2 hr before occlusion of the middle cerebral artery (MCA), whereas a longer time period of pretreatment (4 or 6 hr) failed to exert neuroprotection. In rats, subcutaneous pretreatment with R- or S-LA for 2 hr before ischemia significantly diminished the infarct volume. We assume that LA has to be reduced to DLA which finally causes neuroprotection.

Neuroprotective efficacy of microvascularly-localized versus brain-penetrating antioxidants

The 21-aminosteroid (lazaroid) tirilazad mesylate has been demonstrated to be a potent inhibitor of lipid peroxidation and to reduce traumatic and ischemic damage in a number of experimental models. Currently, tirilazad is being actively investigated in phase III clinical trials in head and spinal cord injury, ischemic stroke and subarachnoid hemorrhage. This compound acts in large part to protect the microvascular endothelium and consequently to maintain normal blood-brain barrier (BBB) permeability and cerebral blood flow autoregulatory mechanisms. However, due to its limited penetration into brain parenchyma, tirilazad has generally failed to affect delayed neuronal damage to the selectively vulnerable hippocampal CA1 and striatal regions. Recently, we have discovered a new group of antioxidant compounds, the pyrrolopyrimidines, which possess significantly improved ability to penetrate the BBB and gain direct access to neural tissue. Several compounds in the series, such as U-101033E, have demonstrated greater ability to protect the CA1 region in the gerbil transient forebrain ischemia model with a post-ischemic therapeutic window of at least four hours. In addition, U-101033E has been found to reduce infarct size in the mouse permanent middle cerebral artery occlusion model in contrast to tirilazad which is minimally effective. These results suggest that antioxidant compounds with improved brain parenchymal penetration are better able to limit certain types of ischemic brain damage compared to those which are localized in the cerebral microvasculature. On the other hand, microvascularly-localized agents like tirilazad appear to have better ability to limit BBB damage.

The free radical scavenger, alpha-lipoic acid, protects against cerebral ischemia-reperfusion injury in gerbils

alpha-Lipoic acid (thioctic acid) was tested for its neuroprotective activity in a Mongolian gerbil model of forebrain ischemia/reperfusion. Adult gerbils were treated for 7 days with two intraperitoneal injections per day of alpha-lipoic acid (20 mg/kg), vehicle or saline and on the 7th day the animals were subjected to 5 min of forebrain ischemia. Ischemic injury was assessed by monitoring the increases in locomotor activity and from the extent of damage to the CA1 hippocampal pyramidal cell layer after 5 days of recovery. By both criteria, alpha-lipoic acid was neuroprotective against ischemia/reperfusion evoked cerebral injury.

Chronic treatment with thioctic acid does not protect against malonate toxicity in vivo

We reported previously that short-term systemic pretreatment with thioctic acid is protective against NMDA and malonate lesions of the striatum. In the current study, we examined the effects of 3 weeks of pretreatment with various doses of thioctic acid (5-60 mg/kg per day) on malonate-induced striatal degeneration in adult rats. In this paradigm, we were unable to demonstrate protection against malonate toxicity. The reasons for the difference in efficacy between subacute and chronic treatment remain to be defined.

alpha-Lipoic acid as a biological antioxidant

alpha-Lipoic acid, which plays an essential role in mitochondrial dehydrogenase reactions, has recently gained considerable attention as an antioxidant. Lipoate, or its reduced form, dihydrolipoate, reacts with reactive oxygen species such as superoxide radicals, hydroxyl radicals, hypochlorous acid, peroxyl radicals, and singlet oxygen. It also protects membranes by interacting with vitamin C and glutathione, which may in turn recycle vitamin E. In addition to its antioxidant activities, dihydrolipoate may exert prooxidant actions through reduction of iron. alpha-Lipoic acid administration has been shown to be beneficial in a number of oxidative stress models such as ischemia-reperfusion injury, diabetes (both alpha-lipoic acid and dihydrolipoic acid exhibit hydrophobic binding to proteins such as albumin, which can prevent glycation reactions), cataract formation, HIV activation, neurodegeneration, and radiation injury. Furthermore, lipoate can function as a redox regulator of proteins such as myoglobin, prolactin, thioredoxin and NF-kappa B transcription factor. We review the properties of lipoate in terms of (1) reactions with reactive oxygen species; (2) interactions with other antioxidants; (3) beneficial effects in oxidative stress models or clinical conditions.

Prolonged pretreatment with alpha-lipoic acid protects cultured neurons against hypoxic, glutamate-, or iron-induced injury

The antioxidant dihydrolipoic acid has been shown to reduce hypoxic and excitotoxic neuronal damage in vitro. In the present study, we tested whether pretreatment with alpha-lipoic acid, which presumably allows endogenous formation of dihydrolipoic acid, can protect cultured neurons against injury caused by cyanide, glutamate, or iron ions, using the trypan blue exclusion method to determine neuronal damage. One hour of preincubation with dihydrolipoic acid (1 microM), but not with alpha-lipoic acid, reduced damage of neurons from chick embryo telencephalon caused by 1 mM sodium cyanide or iron ions. alpha-Lipoic acid (1 microM) reduced cyanide-induced neuronal damage when added 24 h before hypoxia, and pretreatment with alpha-lipoic acid for > 24 h enhanced this neuroprotective effect. Both the R- and the S-enantiomer of alpha-lipoic acid exerted a similar neuroprotective effect. Pretreatment with alpha-lipoic acid (1 microM) from the day of plating onward prevented the degeneration of chick embryo telencephalic neurons that had been exposed to Fe2+/Fe3+. alpha-Lipoic acid (1 microM) added to the culture medium the day of plating also reduced neuronal injury induced by 1 mM L-glutamate in rat hippocampal cultures, whereas 30 min of preincubation with alpha-lipoic acid failed to attenuate glutamate-induced neuronal damage. Our results indicate that neuroprotection by prolonged pretreatment with alpha-lipoic acid is probably due to the radical scavenger properties of endogenously formed dihydrolipoic acid.

Biochemical changes associated with selective neuronal death following short-term cerebral ischaemia

A brief interruption of blood flow to the brain results in the selective loss of specific subpopulations of neurons. Important advances have been made in recent years in defining the biochemical changes associated with cerebral ischaemia and reperfusion and in identifying physical and chemical interventions capable of modifying the extent of neuronal loss. Neuronal death is not irreversibly determined by the ischaemic period but develops during recirculation over a period of hours or even days in different susceptible neuronal populations. The onset of ischaemia produces a rapid decline in ATP production and an associated major redistribution of ions across the plasma membrane including a large intracellular accumulation of Ca2+ in many neurons. Alterations subsequently develop in many other metabolites. These include a marked and progressive release of neurotransmitters and a rapid accumulation of free fatty acids. Most of these alterations are reversed within the first 20 min to 1 hr of recirculation. The changes essential for initiating damage in neurons destined to die have not been definitively identified although there is some evidence suggesting roles for the intracellular Ca2+ accumulation, the release of the neurotransmitter glutamate and a brief burst of free radical production which occurs during early recirculation. During further recirculation, there are reductions in oxidative glucose metabolism and protein synthesis in many brain regions. Few changes have been detected which distinguish tissue containing ischaemia-susceptible neurons from ischaemia-resistant regions until the development of advanced degeneration and neuronal loss. Subtle changes in cytoplasmic Ca2+ content and a decrease in the respiratory capacity of mitochondria are two changes apparently selectively affecting ischaemia-susceptible regions which could contribute to neuronal loss. The mitochondrial change may be one indicator of a slowly developing post-ischaemic increase in susceptibility to oxidative damage in some cells.

N-tert-butyl-alpha-phenylnitrone improves recovery of brain energy state in rats following transient focal ischemia

Recent results have demonstrated that the spin trapping agent N-tert-butyl-alpha-phenylnitrone (PBN) reduces infarct size due to middle cerebral artery occlusion (MCAO), even when given after ischemia. The objective of the present study was to explore whether PBN influences recovery of energy metabolism. MCAO of 2-hr duration was induced in rats by an intraluminal filament technique. Brains were frozen in situ at the end of ischemia and after 1, 2, and 4 hr of recirculation. PBN was given 1 hr after recirculation. Neocortical focal and perifocal ("penumbra") areas were sampled for analyses of phosphocreatine (PCr), creatine, ATP, ADP, AMP, glycogen, glucose, and lactate. The penumbra showed a moderate-to-marked decrease and the focus showed a marked decrease in PCr and ATP concentrations, a decline in the sum of adenine nucleotides, near-depletion of glycogen, and an increase in lactate concentration after 2 hr of ischemia. Recirculation for 1 hr led to only a partial recovery of energy state, with little further improvement after 2 hr and signs of secondary deterioration after 4 hr, particularly in the focus. After 4 hr of recirculation, PBN-treated animals showed pronounced recovery of energy state, with ATP and lactate contents in both focus and penumbra approaching normal values. Although an effect of PBN on mitochondria cannot be excluded, the results suggest that PBN acts by preventing a gradual compromise of microcirculation. The results justify a reevaluation of current views on the pathophysiology of focal ischemic damage and suggest that a therapeutic window of many hours exists in stroke.

Inhibitors of lipid peroxidation protect cultured neurons against cyanide-induced injury

We tested the 21-aminosteroid U-74500A and the 2-methylaminochroman U-83836E, two potent inhibitors of lipid peroxidation, for their protective efficacy against cyanide- or Fe2+/Fe(3+)-induced damage of cultured neurons from chick embryo telencephalon. U-74500A (0.1-10 microM) as well as U-83836E (0.01-10 microM) reduced cyanide-induced neurotoxicity, indicating that lipid peroxidation plays an important role in the genesis of cyanide-induced neuronal injury. Both U-74500A and U-83836E, but not the NMDA antagonist dizocilpine (1 microM, prevented Fe2+/Fe(3+)-induced neuronal degeneration.

[Pharmacologic brain protection: specific agents]

Dysfunctional sodium influx is the first step in the ischaemic cascade. It has been recently demonstrated that reducing ionic flux through voltagegated Na channels shortens the NMDA receptor activity of cultured hippocampal slices in which oxidative phosphorylation and glycolysis have been blocked. The implication of this finding is that blocking initial events in the ischaemic cascade, events which do not directly cause neuronal damage, will reduce the damage done by downstream events. It also seems intuitively reasonable to suppose that truncating initial steps of the ischaemic cascade, as distinct from blocking glutamate receptors and scavening free radicals, will reduce the probability of interfering with endogenous mechanisms of repair. Clinically useful, substantive, prophylactic, pharmacological cerebral protection will come from drugs that work upstream. And for pharmacological protection that can only be initiated subsequent to an ischaemic event, the more we learn about endogenous repair, or genetic pharmacology, the closer we will come to maximizing the benefits and minimizing the costs of downstream intervention.

The endogenous cofactors, thioctic acid and dihydrolipoic acid, are neuroprotective against NMDA and malonic acid lesions of striatum

Thioctic acid (alpha-lipoic acid) and dihydrolipoic acid are endogenous, interconvertible cofactors of the mitochondrial pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase complexes. These compounds help to maintain glutathione and alpha-tocopherol in their reduced states, and they possess intrinsic free radical scavenging properties. We examined whether systemic treatment with thioctic acid or dihydrolipoic acid is protective against direct- and indirect-acting excitotoxins. Adult rats were treated for 10 days with intraperitoneal injections of vehicle, thioctic acid or dihydrolipoic acid, and on day 7 of treatment animals received unilateral stereotaxic injections of NMDA or malonic acid into the striatum. Histological assessment 3 days after the stereotaxic injections revealed a marked reduction in lesion volume in animals treated with thioctic acid or dihydrolipoic acid. We conclude that thioctic acid and dihydrolipoic acid are neuroprotective against direct and indirect excitotoxic insults.

Lipoic and dihydrolipoic acids as antioxidants. A critical evaluation

A detailed evaluation of the antioxidant and pro-oxidant properties of lipoic acid (LA) and dihydrolipoic acid (DHLA) was performed. Both compounds are powerful scavengers of hypochlorous acid, able to protect alpha 1-antiproteinase against inactivation by HOCl. LA was a powerful scavenger of hydroxyl radicals (OH.) and could inhibit both iron-dependent OH. generation and peroxidation of ox-brain phospholipid liposomes in the presence of FeCl3-ascorbate, presumably by binding iron ions and rendering them redox-inactive. By contrast, DHLA accelerated iron-dependent OH. generation and lipid peroxidation, probably by reducing Fe3+ to Fe2+. LA inhibited this pro-oxidant action of DHLA. However, DHLA did not accelerate DNA degradation by a ferric bleomycin complex and slightly inhibited peroxidation of arachidonic acid by the myoglobin-H2O2 system. Under certain circumstances, DHLA accelerated the loss of activity of alpha-antiproteinase exposed to ionizing radiation under a N2O/O2 atmosphere and also the loss of creatine kinase activity in human plasma exposed to gas-phase cigarette smoke. Neither LA nor DHLA reacted with superoxide radical (O.2-) or H2O2 at significant rates, but both were good scavengers of trichloromethylperoxyl radical (CCl3O2.). We conclude that LA and DHLA have powerful antioxidant properties. However, DHLA can also exert pro-oxidant properties, both by its iron ion-reducing ability and probably by its ability to generate reactive sulphur-containing radicals that can damage certain proteins, such as alpha 1-antiproteinase and creatine kinase.

Primary cultures of neurons for testing neuroprotective drug effects

Primary cultures of neurons are widely used for the investigation of pathomechanisms of neuronal damage and for the evaluation of neuroprotective drug effects. The present paper gives a short survey of frequently used primary neuronal culture systems and of experimental measures for the induction of defined neuronal damage with particular respect to the pathomechanisms of cerebral ischemia. Neuroprotective drug effects as achieved under these conditions are reviewed, and the neuroprotective effects of glutamate antagonists, radical scavengers, and neural growth factors are discussed in some more detail.

Mechanisms of drug actions against neuronal damage caused by ischemia--an overview

1. Oxygen and energy deficits induces a cascade of pathological processes which lead to neuronal dysfunction and cell death. 2. The pathogenesis of ischemia-induced neuronal damage includes a disturbed calcium homeostasis, an excessive release of EAA and an enhanced formation of free oxygen radicals. 3. Calcium antagonists inhibit Ca2+ influx into the neuronal cell via VSCC. 4. Glutamate antagonists reduce intracellular Ca2+ concentration by inactivation of NMDA receptor-associated calcium channels (NMDA antagonists) or AMPA/quisqualate receptor-linked sodium channels (non-NMDA antagonists). 5. Furthermore, oxygen radical scavengers can avoid neuronal damage. 6. Agonists of the adenosinergic and serotonergic transmitter systems contribute to neuroprotection by hyperpolarization of the neuronal membrane due to an increase of K+ permeability.