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PubMed1993

Allosteric modulation of the NMDA receptor by dihydrolipoic and lipoic acid in rat cortical neurons in vitro.

The mitochondrial cofactor dihydrolipoic acid (DHLA) was observed to potentiate N-methyl-D-aspartate (NMDA), but not non-NMDA, receptor-mediated whole-cell responses in cultured neurons. This potentiation was readily reversed by the oxidizing agent 5,5'-dithio-bis-(2-nitro-benzoic acid) (DTNB). DHLA was unable to increase NMDA responses previously potentiated by dithiothreitol, nor did it have an effect on NMDA receptors alkylated with N-ethylmaleimide. Single-channel recordings revealed that DHLA produced an increase in NMDA channel open frequency, with no change in single-channel conductance or open time. In contrast, lipoic acid reversed the potentiation of NMDA-evoked responses produced by dithiothreitol and had no effect on NMDA receptors previously oxidized by DTNB. DHLA and lipoic acid are pervasively found substances that readily permeate cellular membranes and thus may influence NMDA receptor activity in vivo by modifying its redox site.

Animals↗
PubMed1978

[Microbial metabolic activity and transmembrane transport phenomena by potentiometric analysis of lipoic acid oxidation-reduction, in a minimal culture medium].

A method of measuring and studying metabolic bacterial activity is proposed, by following the kinetic evolution of the ratio of the oxidized and reduced forms of an electron transporter as a consequence of decreasing oxidizing power--due to oxygen consumption in the culture,--and increasing. Reduction power of bacterial activity. Namely, with minimum composition using salts and glucose the oxido-reduction of lipoic acid is well indicated by a gold electrode without any major bio-or electrochemical interference. A kinetic diffusion reaction theory takes into account the passive or active transmembrane transport of lipoic acid in good agreement with the experimentally observed shapes of the electrical signal. The various types of antibiotic activities are well reflected by the modifications of the signal.

Bacteria↗
PubMed2003

Redox balance in patients with Down's syndrome before and after dietary supplementation with alpha-lipoic acid and L-cysteine.

The aim of the present study was to investigate the possible normalizing effect of antioxidants on certain parameters indicative of oxidative stress in Down's syndrome (DS). The study was performed in pediatric patients with DS with proven redox imbalance, who were advised to take a dietary supplementation composed of alpha-lipoic acid and L-cysteine for several treatment cycles (one treatment cycle = 30 days dietary supplementation plus 30 days wash-out). Serum thiol groups, serum total and septic reactive oxygen species (ROS) and total antioxidant status of serum were determined before and after dietary supplementation, using commercially available kits. In all the evaluable patients (n = 20), after 3.8 +/- 1.1 treatment cycles, thiol group serum concentrations and total antioxidant status of serum significantly increased (p < 0.0001 for both parameters) in comparison with basal values, while serum total and septic ROS significantly decreased (p < 0.0001 for both parameters). On the basis of these results it is impossible to demonstrate the clinical effects of the biochemical normalization obtained in patients with DS after supplying alpha-lipoic acid and L-cysteine. These data suggest that delaying the clinical expression of redox imbalance in patients with DS might be feasible by normalizing their redox balance.

Adolescent↗
PubMed2001

Effects of an inhibitor of poly(ADP-ribose) polymerase, desmethylselegiline, trientine, and lipoic acid in transgenic ALS mice.

The development of transgenic mouse models of amyotrophic lateral sclerosis (ALS) allows the testing of neuroprotective agents. We evaluated the effects of five agents in transgenic mice with the G93A Cu,Zn superoxide dismutase mutation. A novel inhibitor of poly(ADP-ribose) polymerase showed no effects on survival. Desmethylselegiline and CGP3466 are agents that exert antiapoptotic effects in vitro by preventing nuclear translocation of glyceraldehyde-3-phosphate dehydrogenase. They had no significant effects on survival in the G93A mice. Trientine, a copper chelator, produced a modest significant increase in survival. Similarly administration of lipoic acid in the diet produced a significant improvement in survival. These results therefore provide evidence for potential therapeutic effects of copper chelators and lipoic acid in the treatment of ALS.

Amphetamines↗
PubMed1999

Endogenous and new synthetic antioxidants for peroxynitrite: selective inhibitory effect of 5-methoxytryptamine and lipoic acid on tyrosine nitration by peroxynitrite.

The inhibitory effects of endogenous and synthetic compounds on the nitration and oxidation of L-tyrosine by peroxynitrite were examined. Nitration and oxidation activities of L-tyrosine by peroxynitrite were estimated by monitoring the formation of 3-nitrotyrosine and dityrosine with a high-performance liquid chromatography-ultraviolet (HPLC-UV)-fluorescence detector system. Glutathione and synthetic compounds ((2S,3R,4S)-N-ethylmercapto-3,4-dihydroxy-2-hydroxymethylpyrrolidine, L-N-dithiocarboxyproline) inhibited both the nitration and the oxidation reactions of L-tyrosine effectively. On the other hand, 5-methoxytryptamine and lipoic acid inhibited only the nitration reaction of L-tyrosine, and instead increased the oxidation reaction. It was assumed that 5-methoxytryptamine and lipoic acid reacted only with the nitrating species of peroxynitrite. This is the first report of a selective inhibitor for the nitrating reaction of peroxynitrite.

5-Methoxytryptamine↗
PubMed1999

The effect of alpha-lipoic acid on the neurovascular reflex arc in patients with diabetic neuropathy assessed by capillary microscopy.

Patients with diabetic polyneuropathy are known to have an impaired neurovascular reflex arc compared to healthy controls. This is seen in a delayed decrease in microcirculation of the ipsilateral hand after cooling of the contralateral hand. The aim of this pilot study was to investigate whether intravenous alpha-lipoic acid (ALA) (Thioctacid, Asta Medica) therapy might be able to improve this impaired neurovascular reflex arc in patients with diabetic neuropathy. In addition, clinical effects were evaluated with the aid of the neuropathy symptom score (NSS) and the neuropathy disability score (NDS). Ten patients with diabetes mellitus and polyneuropathy (5 females, 5 males, 2 smokers, 5 IDDM, 5 NIDDM, body mass index 26.1 +/- 1.0 kg/m2, age 58.3 +/- 9.5 years, diabetes duration 15.7 +/- 11.2 years, Hb A1c 6.8 +/- 0.3%) were investigated by nail-fold capillaroscopy after contralateral cooling before and after intravenous therapy with 600 mg alpha-lipoic acid per day over 3 weeks. Cardiac autonomic neuropathy was excluded by beat-to-beat variation analysis. Symptoms of diabetic neuropathy were evaluated before and after therapy with the aid of the NSS and NDS. Capillary blood cell velocity (CBV) of the hand was determined before, during, and for the following 30 min after cooling (3 min at 15 degrees C) of the contralateral hand. Blood pressure, heart rate, and local skin temperature were monitored at 2-min intervals. ALA therapy resulted in a significant improvement of the microcirculatory response to cooling, as seen by an immediate decrease in CBV of 12. 3% (P < 0.02 vs before treatment), which was absent before therapy. Blood pressure, heart rate, and local skin temperature were not different between investigations. There was a significant improvement of the NSS after therapy (5.4 +/- 1.1 vs 8.6 +/- 1.1 points, P < 0.01). These results demonstrate that intravenous therapy with ALA has a positive influence on the impaired neurovascular reflex arc in patients with diabetic neuropathy.

Adult↗
PubMed2006

Mitigation of age-dependent oxidative damage to DNA in rat heart by carnitine and lipoic acid.

Endogenous damage to mtDNA by free radicals is believed to be a major contributory factor to aging. Mitochondrial DNA exists in a highly genotoxic environment created by exposure to reactive oxygen species and thus are more vulnerable to free radical attack. In the present study we have focused on the age associated alterations to DNA during aging and in parallel investigated the efficacy of carnitine (300 mg/kg bw) and lipoic acid (100 mg/kg bw) for 28 days in altering these changes. We observed a decline in the content of both mitochondrial and nuclear DNA during aging with an exponential increase in the 8-OHdG levels. We also observed an age-dependent increase in DNA protein crosslinks and double strand and single strand breaks. Supplementation of carnitine and lipoic acid during aging process decreased the incidence of these DNA damage, therefore suggesting that this feeding regimen inhibits the accumulation of age-associated oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2006

Chronic systemic D-galactose exposure induces memory loss, neurodegeneration, and oxidative damage in mice: protective effects of R-alpha-lipoic acid.

Chronic systemic exposure of mice, rats, and Drosophila to D-galactose causes the acceleration of senescence and has been used as an aging model. The underlying mechanism is yet unclear. To investigate the mechanisms of neurodegeneration in this model, we studied cognitive function, hippocampal neuronal apoptosis and neurogenesis, and peripheral oxidative stress biomarkers, and also the protective effects of the antioxidant R-alpha-lipoic acid. Chronic systemic exposure of D-galactose (100 mg/kg, s.c., 7 weeks) to mice induced a spatial memory deficit, an increase in cell karyopyknosis, apoptosis and caspase-3 protein levels in hippocampal neurons, a decrease in the number of new neurons in the subgranular zone in the dentate gyrus, a reduction of migration of neural progenitor cells, and an increase in death of newly formed neurons in granular cell layer. The D-galactose exposure also induced an increase in peripheral oxidative stress, including an increase in malondialdehyde, a decrease in total anti-oxidative capabilities (T-AOC), total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-Px) activities. A concomitant treatment with lipoic acid ameliorated cognitive dysfunction and neurodegeneration in the hippocampus, and also reduced peripheral oxidative damage by decreasing malondialdehyde and increasing T-AOC and T-SOD, without an effect on GSH-Px. These findings suggest that chronic D-galactose exposure induces neurodegeneration by enhancing caspase-mediated apoptosis and inhibiting neurogenesis and neuron migration, as well as increasing oxidative damage. In addition, D-galactose-induced toxicity in mice is a useful model for studying the mechanisms of neurodegeneration and neuroprotective drugs and agents.

Aging↗
PubMed2006

Chronic systemic D-galactose exposure induces memory loss, neurodegeneration, and oxidative damage in mice: protective effects of R-alpha-lipoic acid.

Chronic systemic exposure of D-galactose to mice, rats, and Drosophila causes the acceleration of senescence and has been used as an aging model. However, the underlying mechanism is as yet unclear. To investigate the mechanisms of neurodegeneration in this model, we studied cognitive function, hippocampal neuronal apoptosis and neurogenesis, and peripheral oxidative stress biomarkers and also the protective effects of the antioxidant R-alpha-lipoic acid. Chronic systemic exposure of mice to D-galactose (100 mg/kg, s.c., 7 weeks) induced a spatial memory deficit, an increase in cell karyopyknosis, apoptosis, and caspase-3 protein levels in hippocampal neurons, a decrease in the number of new neurons in the subgranular zone in the dentate gyrus, a reduction of migration of neural progenitor cells, and an increase in death of newly formed neurons in the granular cell layer. The D-galactose exposure also induced an increase in peripheral oxidative stress, including an increase in malondialdehyde and decreases in total antioxidative capabilities (T-AOC), total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-Px) activities. A concomitant treatment with lipoic acid ameliorated cognitive dysfunction and neurodegeneration in the hippocampus and also reduced peripheral oxidative damage by decreasing malondialdehyde and increasing T-AOC and T-SOD, without an effect on GSH-Px. These findings suggest that chronic D-galactose exposure induces neurodegeneration by enhancing caspase-mediated apoptosis and inhibiting neurogenesis and neuron migration, as well as increasing oxidative damage. In addition, D-galactose-induced toxicity in mice is a useful model for studying the mechanisms of neurodegeneration and neuroprotective drugs and agents.

Animals↗
PubMed2000

Magnetic fields and lipoic acid influence the respiratory burst in activated rat peritoneal neutrophils.

When rat (Sprague-Dawley, male) peritoneal neutrophils are exposed to 60 Hz, 1 Gauss, magnetic fields and activated by phorbor 12-myristate 13-acetate they undergo an enhanced respiratory burst (S. Roy, Y. Noda, V. Eckert, M.G. Traber, A. Mori, R.P. Liburdy, L. Packer, The phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst in rat peritoneal neutrophils is increased by a 0. 1 mT (60 Hz) magnetic field, FEBS Lett. 376 (1996) 164-6). In the present study, the reproducibility of these previous findings was confirmed using a new dual-monochrometer exposure system; a 1 Gauss, 60 Hz magnetic field enhanced the production of fluorescence during the respiratory burst. Dose-response studies employed static DC magnetic fields of up to 20 Gauss. Both static DC fields (2.5 and 20 Gauss) showed enhancement of fluorescence production during the respiratory burst. Pre-treatment of neutrophil cells for 10 min at 37 degrees C with an antioxidant, lipoic acid (1-100 µM), significantly elevates fluorescence production in a dose-response manner. The combination of lipoic acid pre-treatment and DC field (2.5 Gauss) exposure further enhanced fluorescence.

Journal Article↗
PubMed2001

alpha-Lipoic acid prevents the development of glucose-induced insulin resistance in 3T3-L1 adipocytes and accelerates the decline in immunoreactive insulin during cell incubation.

Oxidative stress has been implicated in glucose toxicity. We tested the hypothesis that certain antioxidants may prevent insulin-resistant glucose transport that develops in adipocytes after sustained exposure to high glucose, provided insulin is present. The antioxidant alpha-lipoic acid has been proposed as an insulin sensitizer. 3T3-L1 adipocytes were preincubated 18 hours in media containing insulin (0.6 nmol/L) with low (5 mmol/L) or high (25 mmol/L) glucose with or without alpha-lipoate, dihydrolipoate (each 0.1 to 0.5 mmol/L), or N-acetylcysteine (1 to 5 mmol/L). After extensive re-equilibration in insulin and antioxidant-free media, basal and maximally insulin-stimulated (100 nmol/L) glucose transport was measured. Insulin was quantified by radioimmunoassay. Preincubation with alpha-lipoate and dihydrolipoate but not N-acetylcysteine increased subsequent basal glucose transport; the effect was much smaller than that of acute maximal insulin stimulation. Preincubation in high glucose without antioxidants inhibited acutely insulin-stimulated glucose transport by 40% to 50% compared with low glucose. This down- regulation was partially or completely prevented by each antioxidant. In cell-free media, the 2 reductants, dihydrolipoate and N-acetylcysteine, rapidly decreased immunoreactive insulin, but alpha-lipoate was ineffective. However, during incubation with adipocytes, alpha-lipoate, and dihydrolipoate promoted the decline in immunoreactive insulin nearly equally. Because insulin and high glucose are synergistic in inducing insulin resistance in this model, the reduction in immunoreactive insulin probably contributed to the protective effect of the antioxidants. 3T3-L1 adipocytes efficiently metabolize alpha-lipoate to dihydrolipoate, which may be released into the medium. The stimulation of glucose transport by alpha-lipoic acid may represent redox effects in subcellular compartments that are accessible to dihydrolipoate.

3T3 Cells↗
PubMedDate not supplied

Effect of lipoic acid administration on gentamicin-induced lipid peroxidation in rats.

The intraperitoneal administration of gentamicin (100 mg kg[-1] day[-1]) to rats is associated with an increased production of malondialdehyde (MDA), which is an end product of lipid peroxidation in the kidney. The level of glutathione (GSH) and the activity of three antioxidant systems--superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)--were also decreased in the kidney. The liver, however, did not show any such alterations. Gentamicin (100 mg kg[-1] day[-1]) plus lipoic acid administration (25 mg kg[-1] day[-1]) by gastric intubation brought about a decrease in the degree of lipid peroxidation. An increase in the GSH level and in the activity of SOD, CAT and GPx was also observed. From these observations it can be concluded that administration of DL-alpha-lipoic acid prevents lipid peroxidation, which may, at least partly, play an important role in the injury cascade of gentamicin-induced nephrotoxicity.

Administration, Oral↗
PubMed1994

Effects of alpha-lipoic acid and dihydrolipoic acid on expression of proto-oncogene c-fos.

The transcription factor AP-1 is an important human mediator of the cellular response to serum, growth factors, and phorbol esters such as 12-O-tetradecanoyl-phorbol-13 acetate (TPA). The AP-1 complex consists of distinct protein heterodimers encoded by the proto-oncogene c-fos and c-jun mRNA whose gene expression can be induced by TPA, cyclic AMP and growth factors. Recent findings suggest an involvement of reactive oxygen species in the pathway of TPA and protein kinase C leading to expression of c-fos and c-jun mRNA. To investigate the role of reactive oxygen species we studied the effects of alpha-lipoic acid and dihydrolipoic acid (natural thiol antioxidants) on the expression of c-fos mRNA in human Jurkat T cells. When cells were preincubated with dihydrolipoic acid (0.2 mM) the expression of c-fos mRNA was suppressed at 30 min after stimulation of TPA (0.5 microM) whereas in the case of preincubation of alpha-lipoic acid (0.2 microM), the expression was enhanced at 30 min. These studies support the idea that superoxide anion radical plays a role in the expression of c-fos mRNA.

Base Sequence↗
PubMed2005

Efficacy of levo carnitine and alpha lipoic acid in ameliorating the decline in mitochondrial enzymes during aging.

BACKGROUND: Mitochondria are central to energy production and are therefore fully integrated into the rest of the cell's physiological responses to stress. The age-related decline of capacity of each cell to manufacture energy (as ATP) is due to the progressive loss of structural integrity of mitochondria. It is apparent that as the body ages, the cells become less and less able to maintain threshold levels of cellular energy production. METHODS: In the present study we have evaluated the efficacy of carnitine, a mitochondrial metabolite and lipoic acid, a potent antioxidant on the activities of the tri carboxylic acid (TCA) cycle enzymes like succinate dehydrogenase, malate dehydrogenase, alpha-ketoglutarate dehydrogenase, Isocitrate dehydrogenase and electron transport complex I-IV in young and aged heart mitochondria. RESULT: We observed that there was an age-dependent decrement in the levels of the TCA cycle enzymes and electron transport chain complexes. Supplementation of carnitine (300 mg/kg bw/day) and lipoic acid (100 mg/kg bw/day) for 30 days brought the activities of these enzymes to almost near normal levels. CONCLUSION: These findings suggest that the combination of these drugs raises the mitochondrial energy producing capabilities by reversing the age-associated decline in mitochondrial enzyme activities and thereby protecting mitochondria from aging.

Age Factors↗
PubMed2000

Restoration of functional defects in peripheral blood mononuclear cells isolated from cancer patients by thiol antioxidants alpha-lipoic acid and N-acetyl cysteine.

The ability of Alpha-Lipoic Acid (ALA) and N-Acetyl Cysteine (NAC), two active antioxidant agents, to correct in vitro the most significant functional defects of peripheral blood mononuclear cells (PBMC) isolated from advanced stage cancer patients was studied. The proliferative response of PBMC isolated from cancer patients to anti-CD3 monoclonal antibody (MAb) and the expression of CD25 (IL-2R) and CD95 (Fas) on unstimulated and anti-CD3 MAb-stimulated PBMC were studied, and the serum levels of proinflammatory cytokines IL-1, IL-6, TNFalpha as markers of pro-cachectic activity in cancer patients, and the serum levels of IL-2 and sIL-2R were assessed. Twenty patients (mean age 64.6 years) with cancer of lung, ovary, endometrium, and head and neck, all in advanced (III, IV) stage of disease, were studied. The serum levels of IL-1beta, IL-2, IL-6, TNFalpha, and sIL-2R were significantly higher in cancer patients than in normal subjects. The response of PBMC isolated from cancer patients to anti-CD3 MAb was significantly lower than that of controls. The addition of either ALA 0.001 mM or NAC 0.004 mM in the PBMC cultures stimulated with anti-CD3 MAb significantly increased the response of PBMC isolated from cancer patients and normal subjects. After 24 and 72 hr of culture with anti-CD3 MAb, the expression of CD25 and CD95 on PBMC isolated from cancer patients was significantly lower than that of PBMC isolated from normal subjects. The addition of either ALA or NAC into cultures of PBMC isolated from cancer patients significantly increased the percentage of cells expressing CD25 as well as those expressing CD95. The results of the present study show a favorable effect of antioxidant agents ALA and NAC on several important T-cell functions in vitro in advanced-stage cancer patients.

Acetylcysteine↗
PubMed1976

Spin-label study of the mobility of enzyme-bound lipoic acid in the pyruvate dehydrogenase multienzyme complex of Escherichia coli.

The lipoic acid residues covalently bound to the transacetylase component of the pyruvate dehydrogenase multienzyme complex of Escherichia coli were selectively modified by reaction with 4-maleimido-2,2,6,6-tetramethylpiperidino-oxyl. The electron-spin-resonance spectrum of the spin-labelled enzyme indicates that the bound nitroxide groups have high mobilities relative to the protein molecule. This physicochemical evidence is consistent with the view that the dithiolane ring of a lipoyl residue is capable of rapid migration between the active sites of the component enzymes in the catalytic mechanism.

Escherichia coli↗
PubMed1997

A new metabolic link. The acyl carrier protein of lipid synthesis donates lipoic acid to the pyruvate dehydrogenase complex in Escherichia coli and mitochondria.

Lipoic acid is an essential enzyme cofactor that requires covalent attachment to its cognate proteins to confer biological activity. The major lipoylated proteins are highly conserved enzymes of central metabolism, the pyruvate and alpha-ketoglutarate dehydrogenase complexes. The classical lipoate ligase uses ATP to activate the lipoate carboxyl group followed by attachment of the cofactor to a specific subunit of each dehydrogenase complex, and it was assumed that all lipoate attachment proceeded by this mechanism. However, our previous work indicated that Escherichia coli could form lipoylated proteins in the absence of detectable ATP-dependent ligase activity raising the possibility of a class of enzyme that attaches lipoate to the dehydrogenase complexes by a different mechanism. We now report that E. coli and mitochondria contain lipoate transferases that use lipoyl-acyl carrier protein as the lipoate donor. This finding demonstrates a direct link between fatty acid synthesis and lipoate attachment and also provides the first direct demonstration of a role for the enigmatic acyl carrier proteins of mitochondria.

Acyl Carrier Protein↗
PubMedDate not supplied

Alpha-lipoic acid modulates NF-kappaB activity in human monocytic cells by direct interaction with DNA.

The constitutive activity of the redox-sensitive transcription factor, NF-kappaB, which regulates the production of many inflammatory cytokines and adhesion molecules, appears to be up-regulated in an age-associated manner and it is thought this might contribute to the increased incidence of chronic inflammatory conditions observed with increasing age. As some antioxidants have demonstrated protective effects against rheumatoid arthritis, we are investigating the effects of vitamin E, vitamin C and alpha-lipoic acid (ALA) on NF-kappaB activity and on the expression of intracellular adhesion molecule (ICAM)-1. MonoMac6 cells (a human monocytic cell line) stimulated with tumour necrosis factor-alpha (TNF-alpha) were treated with antioxidants at physiological achievable levels and ICAM-1 mRNA levels investigated. Both vitamin E and vitamin C had no effect on ICAM-1 expression at the doses used, but ALA reduced the TNF-alpha-stimulated ICAM-1 expression in a dose-dependent manner, to levels observed in unstimulated cells. Alpha-lipoic acid also reduced NF-kappaB activity in these cells in a dose-dependent manner. Addition of ALA to the binding reaction of nuclear extract with DNA prior to gel-shift analysis showed that it caused inhibition at this level. These initial results suggest that antioxidant modulation of monocyte activity might have potential benefits in inhibiting the dysregulated activity of redox-sensitive transcription factors that occurs with increasing age.

Antioxidants↗