Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LIPOIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMedDate not supplied

Structure and dynamics of a lipoic acid-arsenical adduct.

The lipoic acid-phenyldichloroarsine adduct was prepared in methanol, and the structure and molecular motions of this adduct were studied. The results showed that a six-membered heteroatom adduct was formed. One-dimensional and two-dimensional NMR spectroscopy was used to confirm the structure and assign some of the resonances in the proton and carbon spectra. Spin-lattice relaxation times of the various carbon atoms indicated that the overall molecular reorientation time (tau R) of the molecule is 0.02 ns at 30 degrees C. An Arrhenius plot of the data showed that the activation energy (Ea) for molecular tumbling is 13.4 kJ/mol.

Arsenicals↗
PubMed2006

Cellular disulfide-reducing capacity: an integrated measure of cell redox capacity.

To assess the disulfide reduction capacity of intact cells, EA.hy926 endothelial cells were incubated with alpha-lipoic acid in the presence of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). Alpha-lipoic acid was reduced within cells to dihydrolipoic acid, which could be quantified upon efflux from the cells as reduction of DTNB. Uptake of both alpha-lipoic acid and alpha-lipoamide occurred at least in part via a medium chain fatty acid transporter, based on inhibition by octanoate. Alpha-lipoic acid was reduced within cells by pyridine nucleotide-disulfide oxidoreductases, since it is not reduced by GSH and since its reduction was inhibited by carmustine. Nonetheless, reduction was also dependent on the cellular redox environment, since it was inhibited by the redox cycling of menadione, by decreasing intracellular GSH, and by reduction of dehydroascorbate. Together, these results show that alpha-lipoic acid-dependent DTNB reduction provides a simple method to assess the disulfide-reducing capacity of intact cells, especially as determined by pyridine nucleotide-disulfide oxidoreductases.

Cell Line↗
PubMed1997

Synthesis and characterization of selenolipoylated H-protein of the glycine cleavage system.

H-protein of the glycine cleavage system has a lipoic acid prosthetic group. Selenolipoic acid is a lipoic acid analog in which both sulfur atoms are replaced by selenium atoms. Two isoforms of bovine lipoyltransferase that are responsible for the attachment of lipoic acid to H-protein had an affinity for selenolipoyl-AMP and transferred the selenolipoyl moiety to bovine apoH-protein comparable to lipoyl-AMP. Selenolipoylated H-protein was overexpressed in Escherichia coli and purified. Selenolipoylated H-protein was 26% as effective as lipoylated H-protein in the glycine decarboxylation reaction, in which reduction of the diselenide bond of selenolipoylated H-protein is catalyzed by P-protein. The diselenide form of selenolipoylated H-protein was a poor substrate for L-protein, and the rate of reduction was 0.5% of that of lipoylated H-protein. The rate of the overall glycine cleavage reaction with selenolipoylated H-protein was <1% of that with lipoylated H-protein. These results are consistent with the difference in the redox potential between the diselenide and disulfide bonds. In contrast, selenolipoylated H-protein showed three times as high glycine-14CO2 exchange activity as lipoylated H-protein, presumably because the rate of reoxidation of reduced selenolipoylated H-protein is much higher than that of lipoylated H-protein.

Acyltransferases↗
PubMed1988

Vitamin contents of archaebacteria.

The levels of six water-soluble vitamins of seven archaebacterial species were determined and compared with the levels found in a eubacterium, Escherichia coli. Biotin, riboflavin, pantothenic acid, nicotinic acid, pyridoxine, and lipoic acid contents of Halobacterium volcanii, Methanobacterium thermoautotrophicum delta H, "Archaeoglobus fulgidus" VC-16, Thermococcus celer, Pyrodictium occultum, Thermoproteus tenax, and Sulfolobus solfataricus were measured by using bioassays. The archaebacteria examined were found to contain these vitamins at levels similar to or significantly below the levels found in in E. coli. Riboflavin was found at levels comparable to those in E. coli. Pyridoxine was as abundant among the archaebacteria of the methanogenhalophile branch as in E. coli. It was only one-half as abundant in the sulfur-metabolizing branch. "A. fulgidus," however, contained only 4% as much pyridoxine as E. coli. Nicotinic and pantothenic acids were approximately 10-fold less abundant (except for a 200-fold-lower nicotinic acid level in "A. fulgidus"). Nicotinic acid may be replaced by an 8-hydroxy-5-deazaflavin coenzyme (factor F420) in some archaebacteria (such as "A. fulgidus"). Compared with the level in E. coli, biotin was equally as abundant in Thermococcus celer and Methanobacterium thermoautotrophicum, about one-fourth less abundant in P. occultum and "A. fulgidus," and 25 to over 100 times less abundant in the others. The level of lipoic acid was up to 20 times lower in H. volcanii, Methanobacterium thermoautotrophicum, and Thermococcus celer. It was over two orders of magnitude lower among the remaining organisms. With the exception of "A. fulgidus," lipoic acid, pantothenic acid, and pyridoxine were more abundant in the members of the methanogen-halophile branch of the archaebacteria than in the sulfur-metabolizing branch.

Archaea↗
PubMed2005

Preincubation of rat and human hepatocytes with cytoprotectants prior to cryopreservation can improve viability and function upon thawing.

Cryopreservation of human hepatocytes is important for the treatment of liver disease by hepatocyte transplantation and also for the use of hepatocytes as an in vitro model of the liver. One factor in the success of cryopreservation is the quality of cells before freezing. Preincubation of hepatocytes with cytoprotective compounds to allow recovery from the isolation process prior to cryopreservation, such as those that will boost cellular adenosine triphosphate (ATP) content or antioxidants, may improve the viability and function of cells upon thawing. Rat hepatocytes were used to investigate the effects of preincubation with 10 compounds: precursors (glucose, fructose, glutathione, and S-adenosyl-L-methionine), antioxidants (ascorbic acid and alpha-lipoic acid), and compounds with multiple effects (N-acetylcysteine, pentoxifylline, prostaglandin E(1), and tauroursodeoxycholic acid). Human hepatocytes were then used to investigate 5 of the original 10 compounds (glucose, fructose, alpha-lipoic acid, S-adenosyl-L-methionine, and pentoxifylline). Glucose preincubation (100-300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the viability and reduced lactate dehydrogenase (LDH) leakage of human hepatocytes. Fructose preincubation (100-300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the attachment efficiency of human hepatocytes. alpha-lipoic acid preincubation (0.5-5 mM) improved the viability and attachment efficiency of both rat and human hepatocytes. At a concentration of 2.5 mM alpha-lipoic acid also improved the albumin production of human hepatocytes. In conclusion, preincubation of hepatocytes prior to cryopreservation can improve the viability and function of thawed cells and may provide a method of obtaining better-quality cryopreserved hepatocytes for transplantation.

Animals↗
PubMed2006

Preincubation of rat and human hepatocytes with cytoprotectants prior to cryopreservation can improve viability and function upon thawing.

Cryopreservation of human hepatocytes is important for the treatment of liver disease by hepatocyte transplantation and also for the use of hepatocytes as an in vitro model of the liver. One factor in the success of cryopreservation is the quality of cells before freezing. Preincubation of hepatocytes with cytoprotective compounds to allow recovery from the isolation process prior to cryopreservation, such as those that will boost cellular adenosine triphosphate (ATP) content or antioxidants, may improve the viability and function of cells upon thawing. Rat hepatocytes were used to investigate the effects of preincubation with 10 compounds: precursors (glucose, fructose, glutathione, and S-adenosyl-L-methionine), antioxidants (ascorbic acid and alpha-lipoic acid), and compounds with multiple effects (N-acetylcysteine, pentoxifylline, prostaglandin E1, and tauroursodeoxycholic acid). Human hepatocytes were then used to investigate 5 of the original 10 compounds (glucose, fructose, alpha-lipoic acid, S-adenosyl-L-methionine, and pentoxifylline). Glucose preincubation (100 - 300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the viability and reduced lactate dehydrogenase (LDH) leakage of human hepatocytes. Fructose preincubation (100 - 300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the attachment efficiency of human hepatocytes. alpha-lipoic acid preincubation (0.5 - 5 mM) improved the viability and attachment efficiency of both rat and human hepatocytes. At a concentration of 2.5 mM alpha-lipoic acid also improved the albumin production of human hepatocytes. In conclusion, preincubation of hepatocytes prior to cryopreservation can improve the viability and function of thawed cells and may provide a method of obtaining better-quality cryopreserved hepatocytes for transplantation.

Animals↗
PubMed2004

The human malaria parasite Plasmodium falciparum has distinct organelle-specific lipoylation pathways.

Lipoic acid is an essential cofactor of alpha-keto acid dehydrogenase complexes (KADHCs). This study shows that Plasmodium falciparum possesses two distinct lipoylation pathways that are found in separate subcellular localizations. Lipoic acid synthesis comprising lipoic acid synthase and lipoyl-ACP:protein N-lipoyl transferase is present in the parasite's apicoplast, whereas the second pathway consisting of lipoic acid protein ligase is located in the parasite's mitochondrion. The two localizations were established by overexpressing green fluorescent protein fusions of the N-terminal sequences of lipoic acid synthase and lipoic acid protein ligase in intraerythrocytic stages of P. falciparum. Northern and Western blot analyses revealed that the genes/proteins encoding lipoic acid synthase, lipoyl-ACP:protein N-lipoyl transferase and lipoic acid protein ligase are expressed maximally in the early and late stages of P. falciparum erythrocytic development. The functionality of the three proteins was proven by complementation of bacteria deficient in lipA and lipB. Our results show that P. falciparum possesses two independent pathways, with different locations, responsible for the post-translational modification of KADHCs. Both pathways fundamentally differ from those in the human host. As KADHCs provide metabolites that are required for essential biosynthetic processes such as fatty acid biosynthesis and haem biosynthesis, the two lipoylation pathways of P. falciparum might be attractive therapeutic targets against malaria.

Animals↗
PubMed2007

Increased ROS generation and p53 activation in alpha-lipoic acid-induced apoptosis of hepatoma cells.

Alpha-lipoic acid (alpha-LA) is an antioxidant used for the treatment of a variety of diseases, including liver cirrhosis, heavy metal poisoining, and diabetic polyneuropathy. In addition to its protective effect against oxidative stress, alpha-LA induces apoptosis in different cancer cells types. However, whether alpha-LA acid induces apoptosis of hepatoma cells is unknown. Herein, we investigated whether alpha-LA induces apoptosis in two different hepatoma cell lines FaO and HepG2. The results showed that alpha-LA inhibits the growth of both cell lines as indicated by the reduction in cell number, the reduced expression of cyclin A and the increased levels of the cyclin/CDKs inhibitors, p27(Kip1) and p21(Cip1). Cell cycle arrest was associated with cell loss, and DNA laddering indicative of apoptosis. Apoptosis was preceded by increased generation of reactive oxygen species, and associated with p53 activation, increased expression of Bax, release of cytochrome c from mitochondria, caspases activation, decreased levels of survivin, induction of pro-apoptotic signaling (i.e JNK) and inhibition of anti-apoptotic signaling (i.e. PKB/Akt) pathways. In conclusion, this study provides evidence that alpha-LA induces apoptosis in hepatoma cells, describes a possible sequence of molecular events underlying its lethal effect, and suggests that it may prove useful in liver cancer therapy.

Acetylcysteine↗
PubMedDate not supplied

Evaluation of the antioxidant capacity of ubiquinol and dihydrolipoic acid.

Ubiquinone and alpha-lipoic acid are natural constituents which are involved in mitochondrial energy metabolism. Their bioenergetic activities require redox-cycling. In the case of alpha-lipoic acid redox-cycling leads to dihydrolipoic acid which occurs in multienzyme complexes involved in the citric acid cycle while UQ recycles through semi- and divalently reduced ubiquinones in the respiratory chain. We have proved the validity of the concept about the antioxidant function of these natural compounds in their reduced form. Ubiquinol was found to interfere with lipid peroxidation of liposomal membranes being itself degradated by two consecutive oxidation steps. Dihydrolipoic acid was found to totally recycle ubiquinone to the antioxidant active divalently reduced form. In contrast to the antioxidative derived reaction products of ubiquinols which in turn promoted lipid peroxidation, the antioxidant derived reaction product of dihydrolipoic acid was the unreactive two electron oxidation product alpha-lipoic acid. Our experiments demonstrate the existence of an dihydrolipoic acid driven recycling of UQ to the antioxidative-active UQH2. The efficiency of the antioxidative capacity of the latter was found to be diminished through prooxidant activities of the antioxidant-derived metabolites.

Antioxidants↗
PubMed1999

Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kappaB.

Increased oxidative stress and subsequent activation of the transcription factor NF-kappaB has been linked to the development of late diabetic complications. To determine whether oxidative stress dependent NF-kappaB activation is evident in patients with diabetic nephropathy we used an Electrophoretic Mobility Shift Assay based semiquantitative detection system which enabled us to determine NF-kappaB activation in ex vivo isolated peripheral blood mononuclear cells. We examined 33 patients with diabetes mellitus (Type I and Type II). Patients with diabetic nephropathy showed higher NF-kappaB binding activity in Electrophoretic Mobility Shift Assays and stronger immunohistological staining for activated NF-kappaBp65 than patients without renal complications. NF-kappaB binding activity correlated with the degree of albuminuria (r = 0.316) and with thrombomodulin plasma concentrations (r = 0.33), indicative for albuminuria associated endothelial dysfunction. In a 3 day intervention study in which 600 mg of the antioxidant thioctic acid (alpha-lipoic acid) per day were given to nine patients with diabetic nephropathy oxidative stress in plasma samples was decreased by 48% and NF-kappaB binding activity in ex vivo isolated peripheral blood mononuclear cells by 38%. In conclusion, activation of the transcription factor NF-kappaB in ex vivo isolated peripheral blood mononuclear cells of patients with diabetes mellitus correlates with the degree of diabetic nephropathy. NF-kappaB activation is at least in part dependent on oxidative stress since thioctic acid (alpha-lipoic acid) reduced NF-kappaB binding activity.

Adult↗
PubMed2002

Differential effects of short-chain fatty acids on head and neck squamous carcinoma cells.

OBJECTIVES/HYPOTHESIS: Head and neck squamous cell carcinoma (HNSCC) is a major cause of mortality. Despite advances in therapeutic modalities, recurrences and second primaries are commonly observed. Biological agents that can suppress growth of tumors that are otherwise difficult to treat are greatly needed. The present study examined the effects of short-chain fatty acids on HNSCC cell lines. STUDY DESIGN: The effects of short-chain fatty acids on HNSCC cells was examined using tissue culture and immunoblotting techniques. METHODS: The effects of four short-chain fatty acids, arginine butyrate, alpha-methyl hydrocinnamic acid, 2,2-dimethylbutyrate, and alpha-lipoic acid, were evaluated on four HNSCC cell lines (FaDu, SCC9, SCC25, and Detroit-562). Proliferation assays were performed by means of spectrophotometric techniques. Histone deacetylase activity was assessed by identifying the amount of acetylated histone H4. Involucrin expression was determined to assess cellular differentiation. RESULTS: Inhibition of cellular proliferation was determined after 5 days of incubation with increasing doses with short-chain fatty acids. Arginine butyrate and alpha-lipoic acid were most effective in suppressing growth. Arginine butyrate demonstrated strong histone deacetylase inhibition in FaDu cells, while not inducing cellular differentiation. The short-chain fatty acid alpha-lipoic acid demonstrated weak histone deacetylase inhibition but was the only short-chain fatty acid that induced involucrin expression in at least two of the cell lines. Histone deacetylase inhibitory activity or induction of involucrin expression correlated with suppression of cell growth. CONCLUSIONS: Short-chain fatty acids have variable effects on HNSCC cells. Arginine butyrate and alpha-lipoic acid are the most effective in suppressing growth and appear to do so through different biochemical mechanisms. These compounds warrant further research as chemotherapeutic or chemopreventive agents in HNSCC.

Blotting, Western↗
PubMed1995

Lipoic (thioctic) acid increases brain energy availability and skeletal muscle performance as shown by in vivo 31P-MRS in a patient with mitochondrial cytopathy.

A woman affected by chronic progressive external ophthalmoplegia and muscle mitochondrial DNA deletion was studied by phosphorus magnetic resonance spectroscopy (31P-MRS) prior to and after 1 and 7 months of treatment with oral lipoic acid. Before treatment a decreased phosphocreatine (PCr) content was found in the occipital lobes, accompanied by normal inorganic phosphate (Pi) level and cytosolic pH. Based on these findings, we found a high cytosolic adenosine diphosphate concentration [ADP] and high relative rate of energy metabolism together with a low phosphorylation potential. Muscle MRS showed an abnormal work-energy cost transfer function and a low rate of PCr recovery during the post-exercise period. All of these findings indicated a deficit of mitochondrial function in both brain and muscle. Treatment with 600 mg lipoic acid daily for 1 month resulted in a 55% increase of brain [PCr], 72% increase of phosphorylation potential, and a decrease of calculated [ADP] and rate of energy metabolism. After 7 months of treatment MRS data and mitochondrial function had improved further. Treatment with lipoate also led to a 64% increase in the initial slope of the work-energy cost transfer function in the working calf muscle and worsened the rate of PCr resynthesis during recovery. The patient reported subjective improvement of general conditions and muscle performance after therapy. Our results indicate that treatment with lipoate caused a relevant increase in levels of energy available in brain and skeletal muscle during exercise.

Adenosine Diphosphate↗
PubMed1997

Protection against glutamate-induced cytotoxicity in C6 glial cells by thiol antioxidants.

In many cell lines, glutamate cytotoxicity is known to be medicated by an inhibition of cystine transport. Because glutamate and cystine share the same transporter, elevated levels of extracellular glutamate competitively inhibit cystine transport leading to depletion of intracellular glutathione. A glutathione-depleted state impairs cellular antioxidant defenses resulting in oxidative stress. It was therefore of interest to investigate whether proglutathione agents, e.g., N-acetylcysteine and lipoic acid, are able to protect against glutamate cytotoxicity. Both lipoic acid (100 microM-1 mM) and N-acetylcysteine (100 microM-1 mM) completely protected C6 cells from the glutamate-induced cell death. Both agents facilitate extracellular supply of cysteine, the reduced form of cystine, that is transported into the cell by a glutamate-insensitive transport mechanism. Protection by lipoic acid and N-acetylcysteine corresponded with a sparing effect on cellular glutathione, which is usually depleted after glutamate treatment. In the presence of L-buthionine-(S,R)-sulfoximine, a gamma-glutamylcysteine synthetase inhibitor, low doses (< 100 microM) of lipoic acid and N-acetylcysteine did not protect cells against glutamate-induced cytotoxicity. At higher concentrations (> 500 microM), however, both lipoic acid and N-acetylcysteine provided partial protection against glutamate cytotoxicity even in glutathione synthesis-arrested cells. These results indicate that at low concentrations the primary mechanism of protection by the thiol antioxidants was mediated by their proglutathione property rather than direct scavenging of reactive oxygen. At higher concentrations (> 500 microM), a GSH-independent direct antioxidant effect of lipoic and N-acetylcysteine was observed. Dichlorofluorescin fluorescence, a measure of intracellular peroxides, increased sixfold after glutamate treatment of C6 cells. Lipoic acid and N-acetylcysteine treatment significantly lowered glutamate-induced dichlorofluorescin fluorescence compared with that of controls. Interestingly, alpha-tocopherol (50 microM) also suppressed glutamate-induced dichlorofluorescin fluorescence, indicating the peroxides detected by dichlorofluorescin were likely lipid hydroperoxides. Both thiol antioxidants, particularly lipoic acid, appear to have remarkable therapeutic potential in protecting against neurological injuries involving glutamate and oxidative stress.

Acetylcysteine↗
PubMed2000

Lipoic acid-derived amphiphiles for redox-controlled DNA delivery.

BACKGROUND: Intracellular release of free DNA from the vector complex is one of the critical steps limiting the efficiency of non-viral gene delivery. The complex should be stable enough to prevent DNA degradation but it should be destabilized inside the cell to allow DNA release and transcription. Destabilization and degradation of synthetic vectors is also required to reduce their cytotoxicity and augment the life-time of transfected cells. RESULTS: Here we describe new cationic amphiphiles made from the natural pro-vitamin, lipoic acid, that reversibly binds and releases DNA, depending on the redox state of the lipoate moieties. In the oxidized state these amphiphiles condense DNA into homogeneous spherical particles, which, upon reduction, swell into DNA toroids with subsequent release of free DNA. Complex reduction and DNA release can be induced by various thiols as well as enzymatically, by thioredoxin reductase. Transfection with amphiphile-DNA complexes in vitro shows a several fold increase of transgene expression compared with DOTAP, and can be further augmented by attachment of the nucleus-targeting peptide to the amphiphile. The increase of transfection efficiency results from GSH- and NAD(P)H-dependent complex reduction and release of free DNA inside the cells. CONCLUSIONS: The present work demonstrates the principle of a redox-controlled gene delivery system that uses the reversibility of thiol-disulfide exchange reaction. Our data suggest that the efficiency of synthetic vectors can be augmented by their controlled destabilization inside the cells. Being formed from the natural non-toxic compound lipoic acid, these cationic amphiphiles provide a new promising class of synthetic vectors for gene delivery.

Benzoxazoles↗
PubMed2005

The plasmodial apicoplast was retained under evolutionary selective pressure to assuage blood stage oxidative stress.

Malaria, the clinical disease resulting from infection with Plasmodium, has haunted mankind with illness and death for thousands of years. As Plasmodia's ancient ancestor evolved from a mixotroph to an intracellular parasite, subsiding on amino acids obtained from hemoglobin, it encountered increased oxidative stress. To compensate for this oxidative stress, Plasmodia reduced its own production of reactive oxygen species by becoming largely fermentative and adapted novel methods to assuage oxidative injury. One such method appears to have been accomplished through the acquisition, retention and exploitation of an ancient red algal endosymbiote, now denoted the apicoplast. The apicoplast, located in close proximity to mitochondria, appears to synthesize the potent antioxidant lipoic acid. Lipoic acid may be utilized by Plasmodium as an antioxidant, a shuttle for reducing potentials and as a mitochondrial cofactor. Inhibition or alteration of the apicoplast leads to a curious phenomena known as "delayed death", whereby parasites die not in the present generation but in the ensuing one. Apicoplast inhibition may produce lipoic acid "starvation", increasing oxidative stress/mitochondrial injury during the subsequent asexual reproductive cycle. Collectively, data available to date indicate that the apicoplast was retained as an obligate endosymbiote, under evolutionary selective pressure, to assuage oxidative stress and plays a critical role in maintaining parasite viability during the Plasmodial shizont blood stage.

Animals↗
PubMed1964

INDUCTION AND MECHANISMS OF ARSENITE RESISTANCE IN PSEUDOMONAS PSEUDOMALLEI.

Arima, Kei (University of Tokyo, Tokyo, Japan), and Michiko Beppu. Induction and mechanisms of arsenite resistance in Pseudomonas pseudomallei. J. Bacteriol. 88:143-150. 1964.-Pseudomonas pseudomallei strain 54, able to grow in the presence of 2 x 10(-2)m arsenite, was isolated from soil. After a short lag period, it grew at a normal growth rate. In the organisms grown with 10(-2)m arsenite, oxidation of alpha-ketoglutarate and other substrates proceeded in the presence of the same concentration of the drug. The concentration of arsenite which was half-inhibitory to alpha-ketoglutarate oxidation was 1.6 x 10(-3)m in the sensitive bacteria and 3.3 x 10(-2)m in the resistant ones. Cells capable of oxidizing alpha-ketoglutarate in the presence of arsenite were induced rapidly by contact with arsenite in growing cultures; when the drug was removed from the cultures, resistance was maintained for about two generations and then gradually disappeared. From the data presented, it was concluded that resistance in this organism is a physiological change and not a hereditary one. Further studies were carried out to investigate the arsenite-resistance mechanisms. alpha-Ketoglutarate dehydrogenase activity in the cell-free extracts of the resistant bacteria was sensitive to arsenite. An increase in the contents of this enzyme and sulfhydryl compounds, involving lipoic acid, was not observed in the resistant bacteria. The possibility of detoxication of arsenite was ruled out. Treatment of the resistant cells with cetyl-trimethylammonium bromide made them susceptible to 2 x 10(-2)m arsenite, although untreated cells were resistant to the same concentration of the drug. These data suggest the decreased permeability to arsenite of the resistant bacteria as a main mechanism of resistance.

Ammonium Compounds↗
PubMed2003

Synthesis and pharmacological evaluation of new 1,2-dithiolane based antioxidants.

Molecules containing a dithiolane moiety are widely investigated due to their antioxidant properties. The archetypal representative of this class of compounds is lipoic acid and indeed the lipoic acid-dihydrolipoic acid couple is part of the antioxidant defence system of the cell. In the course of a program aiming to find improved antioxidants effective in vivo, we designed, synthesised and pharmacologically investigated new lipoic acid analogs. The salient feature of these structures is the connection, via a thioamide or a thiocarbamate, of a 1,2-dithiolane moiety bearing a carbon chain and a N-alkyl-substituted morpholine ring. It was expected that the antioxidant and chelating properties of these functional groups combined with the basicity of the morpholine ring will impact on the antioxidant as well as on the partition and solubility characteristics of the compounds. Indeed in vitro and in vivo pharmacological investigation showed that these new molecules and especially those containing a thiocarbamate linker possess superior antioxidant properties compared with alpha-lipoic acid and to the amide or carbamate linker analogs. In particular, some of these compounds efficiently cross the blood brain barrier (BBB) thus providing efficient protection from lethality in a situation of induced oxidative stress. Moreover the absence of the 1,2-dithiolane moiety does not completely abolish antioxidant effects thus demonstrating that these compounds are distinct new chemical entities and not merely lipoic acid prodrugs. The chemical and pharmacological features of these new antioxidants are presented and discussed in the following paper.

Alloxan↗
PubMed1998

Rickettsia rickettsii infection of the EA.hy 926 endothelial cell line: morphological response to infection and evidence for oxidative injury.

EA.hy 926 is a permanent human cell line that expresses highly differentiated functions characteristic of human vascular endothelium. Rickettsia rickettsii can efficiently infect and cause a cytopathic effect in EA.hy 926 cells. R. rickettsii produced visible lytic plaques in EA.hy 926 cells at 10 d post-infection (p.i.) following application of a secondary agarose overlay containing 2 micrograms emetine ml-1 and 40 micrograms NaF ml-1 on day 2. Rickettsial growth in EA.hy 926 cells had a similar profile to that occurring in human umbilical vein endothelial cells (HUVEC) and rickettsiae catalysed polymerization of actin tails. Intracellular multiplication of R. rickettsii resulted in significant changes in the internal morphology of EA.hy 926 cells, most notably extensive dilatation of the membranes of the endoplasmic reticulum and outer nuclear envelope by 72 h p.i. These events correlated with significant alterations in the host-cell antioxidant system, including decreased levels of intracellular reduced glutathione and glutathione peroxidase activity and increased amounts of intracellular peroxide through to 96 h of infection. These findings are similar to the changes described previously for R. rickettsii-infected HUVEC and suggest that common mechanisms associated with rickettsia-induced oxidative injury occur in the two cell lines. EA.hy 926 cells were also used to investigate the influence of the antioxidant alpha-lipoic acid on rickettsial infection. Overnight pretreatment with 1-500 microM alpha-lipoic acid did not prevent cells from being destroyed following infection with rickettsiae. Supplementation of the culture medium with 1 and 10 microM alpha-lipoic acid 2 h after rickettsial inoculation also did not provide any protective effect. However, 100, 200 and 500 microM alpha-lipoic acid increased the viability of infected cells at 96 h to 45, 51 and 70%, respectively compared with 26% for untreated, infected samples. Thiol levels and glutathione peroxidase activity in treated, infected cells increased and peroxide content decreased proportionally to increasing alpha-lipoic acid concentrations. Furthermore, treatment with 500 microM alpha-lipoic acid for 72 h p.i. completely prevented ultrastructural changes in infected cells. In conclusion, the permanent endothelial cell line EA.hy 926 is susceptible to injury induced by R. rickettsii infection. Although the cellular changes resulting from infection are not identical in all aspects to that demonstrated previously in HUVEC, the increased reproducibility and convenience of EA.hy 926 cells make them suitable for biochemical and morphological studies.

Actins↗