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PubMed1989

High-performance liquid chromatography/chemiluminescence determination of biological thiols with N-[4-(6-dimethylamino-2-benzofuranyl)phenyl]maleimide.

The peroxyoxalate chemiluminescence detection of biological thiols combined with high-performance liquid chromatography (HPLC) is described. SH groups of the thiol compounds including glutathione (GSH), cysteine, N-acetylcysteine, cysteamine, and D-penicillamine were labelled with N-[4-(6-dimethylamino-2-benzofuranyl)phenyl]maleimide (DBPM), a specific fluorogenic reagent for SH group. The labelling reaction was carried out at 60 degrees C for 30 min and at pH 8.5 and a sample of the resulting reaction mixture was subjected to HPLC. Five kinds of labelled thiols were separated within 12 min on ODS-80 column (150 x 4.6 mm ID; 5 microns) and detected in the ranges from 500 fmol to 2 pmol/100 microL (cysteamine and N-acetylcysteine), to 3 pmol/100 microL (cysteine) and to 5 pmol/100 microL (GSH and D-penicillamine). The lower detection limits were from 7 fmol (cysteamine) to 113 fmol (GSH) per 100 microL (S/N = 2). The method was applied to the determination of thiols in a rat liver. The amounts of glutathione and cysteine were 1.23 +/- 0.15 mumol/g (n = 5) and 0.15 +/- 0.04 mumol/g (n = 5), respectively.

Animals↗
PubMed1986

Apolipoprotein E3-Leiden. A new variant of human apolipoprotein E associated with familial type III hyperlipoproteinemia.

A variant of apolipoprotein E, denoted apo E3-Leiden, has been identified in a 41-year-old male suffering from type III hyperlipoproteinemia with xanthomatosis. Apo E3-Leiden focus in the E3 position. In contrast with normal apo E3, apo E3-Leiden is defective in binding to the low density lipoprotein (LDL) receptor and does not contain cysteine as evaluated by cysteamine treatment of very low density lipoprotein followed by isoelectric focusing and conventional protein staining and by amino acid analysis. On sodium dodecyl sulfate polyacrylamide gel electrophoresis, apo E3-Leiden displays an electrophoretic mobility intermediate to that of normal apo E3 and apo E2 (Arg158----Cys). The mother and four siblings of the proband also have apo E3-Leiden and hyperlipoproteinemia type III; three of them with xanthomatosis. Two siblings do not show apo E3-Leiden in their VLDL fraction and do not have hyperlipoproteinemia type III. In the VLDL fractions of all affected family members only the presence of apo E3-Leiden could be detected after cysteamine treatment and isoelectric focusing followed by conventional protein staining. However, isoelectric focusing of cysteamine-treated sera followed by immunoblotting, using anti-apo E antiserum as first antiserum, demonstrates the presence of low amounts of normal apo E3 in addition to apo E3-Leiden in serum of the affected family members. These results indicate that all affected family members are heterozygotes E3/E3-Leiden and suggest that in this family type III hyperlipoproteinemia is transmitted as a dominant trait.

Adult↗
PubMed1982

A quantitative cytochemical method for the measurement of beta-hydroxyacyl CoA dehydrogenase activity in rat heart muscle.

Although cytochemical methods exist for measuring dehydrogenases that act on substrates involved in the production of chemical energy from sugars, virtually no methods exist for measuring the dehydrogenases that act on fatty acids. Yet the oxidation of fatty acids accounts for over 60% of the oxidative activity of cardiac muscle. Consequently a new quantitative cytochemical method, based on a new substrate (DL-S-beta-hydroxybutyryl-N-acetyl cysteamine), has been developed for measuring the activity of hydroxy-acyl coenzyme A dehydrogenase, which is the penultimate step of the beta-oxidation of fatty acids to acetyl-coenzyme A that is used in the Krebs' cycle. Menadione or phenazine methosulphate is used as the intermediate hydrogen-acceptor, with neotetrazolium chloride as the final acceptor. The medium contains nitroprusside, ostensibly to react with any cysteamine liberated by hydrolysis of the substrate. As a control, cysteamine is substituted for the substrate. The concentrations of reactants have been optimized for cardiac muscle; the reaction is linear with thickness of the sections and with time of reaction from 15 to 60 min.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2006

Protective effects of nedocromil sodium and sodium cromoglycate on gastroduodenal ulcers: a comparative study in rats.

Stabilization of mast cells plays a key mechanism to protect gastrointestinal tract from injury. This study presents a comparative evaluation of mast cell stabilizers nedocromil sodium (NDS) and sodium cromoglycate (SCG) in experimental gastric and duodenal ulcers in rats. Wistar rats of either sex were used in this study. Both NDS and SCG, in the doses of 10, 30 and 100 mg/kg were given intraperitoneally for gastric secretion studies and by gavage for antiulcer studies. Acid secretion studies were undertaken in pylorus-ligated rats. Gastric lesions were induced by water immersion restraint stress (WIRS), indomethacin and ethanol whereas duodenal ulcers were produced by cysteamine. The level of glutathione (GSH) and gastric wall mucus were measured in glandular stomach of rats following ethanol-induced gastric lesions. SCG was more effective than NDS in preventing WIRS- and indomethacin-induced gastric lesions whereas reverse was true in ethanol- and cysteamine-induced ulcers. All the 3 doses of SCG offered almost equal protection against WIRS-induced gastric lesions whereas only medium and high dose of NDS provided significant protection in this model of ulcer. NDS significantly inhibited cysteamine-induced duodenal ulcers whereas SCG failed to do so. Pretreatment with NDS or SCG significantly and dose-dependently protected gastric mucosa against ethanol-induced injury, while the former drug appeared to be more effective. The cytoprotective effects of these two drugs were accompanied by the attenuation of ethanol-induced depletion of gastric wall mucus and GSH. The differential effects of NDS and SCG against various gastric lesions rationalize the possible benefits of a combined therapy (NDS+SCG) for the treatment of complex gastroduodenal ulcers.

Animals↗
PubMed1989

Pantethine, a somatostatin depleting agent, increases food intake in rats.

During the course of studies of the effects of pantethine, a cysteamine precursor known to deplete tissue concentration of immunoreactive somatostatin, we observed that the subject rats continued to eat despite marked distension of the stomach. To determine whether this effect was caused by drug-altered food intake, we have measured food and water intake in pantethine-injected rats in the fed and fasting state. In three separate experiments, rats allowed free access to food until the morning of study showed significant increased food intake accompanied by an increased stomach content (at 4 hr) of both food and water following the IP injection of pantethine. In one experiment, intake at 3 hours was 0.60 g/100 g b.wt. (pantethine dose 0.74 g/kg b.wt.) and 0.64 g/100 g b.wt. (pantethine dose 1.47 g/kg b.wt.) compared with 0.24 g/100 g b.wt. in saline-treated animals (p less than 0.05). In contrast, pantethine, 1.47 g/kg b.wt., when administered to overnight-fasted rats, significantly inhibited food intake (3-hr intake 1.54 +/- 0.16 g/100 g b.wt. in rats injected with pantethine 1.47 g/kg b.wt. as compared with 3.3 +/- 0.21 g/100 g b.wt. in saline-injected controls). The intake-stimulating effect of pantethine in ad lib-fed rats was not demonstrable when the drug was administered shortly before the "lights out"-induced feeding at night. These findings indicate that pantethine, a cysteamine precursor, stimulates food intake in satiated rats, depending upon the stage of circadian rhythm, but is inhibitory to intake in fasted animals. We postulate that the effects are mediated directly or indirectly through the disinhibition of central appetite-regulating somatostatinergic pathways but, since cysteamine also inhibits dopamine-beta-hydroxylase, an effect on depletion of appetite-regulating central catecholamines cannot be excluded.

Animals↗
PubMed2004

Inhibition of pyruvate kinase activity by cystine in brain cortex of rats.

Cystinosis is a metabolic disturb associated with excessive lysosomal cystine accumulation secondary to defective cystine efflux. Patients affected by this disease develop a variable degree of symptoms depending of the involved tissues. Accumulation of cystine in the brain may lead to severe neurological symptoms. However, the mechanisms by which cystine is neurotoxic are not fully understood. Considering that pyruvate kinase (PK) is a thiolic enzyme crucial for the glycolytic pathway, and disulfides like cystine may alter thiolic enzymes by thiol/disulfide exchange, the main objective of the present study was to investigate the effect of cystine on PK activity in the brain cortex of developing Wistar rats. We also performed kinetic studies and investigated the effects of GSH, a biologically occurring thiol groups protector, and cysteamine (CysN), the drug used for cystinosis treatment, on the enzyme activity. We observed that cystine inhibited the enzyme activity by two different mechanisms, one through the competition with ADP and phosphoenolpyruvate (PEP), and the other non-competitively, probably through oxidation of the thiol groups of PK. We also observed that GSH and cysteamine fully prevented and reversed the inhibition caused by cystine. Considering that cysteamine is used in patients with cystinosis because it causes parenkimal organ cystine depletion, the present data provides a possible new beneficial effect for the use of this drug.

Animals↗
PubMed2005

Adsorption of Pb and Cd by amine-modified zeolite.

Natural zeolites, known for their excellent sorption properties towards metal cations, are widely used for the purification of wastewaters. The selectivity of clinoptilolite, a common zeolite mineral, for Pb is known to be particularly high, whereas its selectivity for Cd is often lower. Extraordinarily high sorption capacities for soft metal cations were observed in the case of thiol-functionalized silica gels and clays. In order to enhance the zeolites' sorption capacity for Cd, we treated natural heteroionic and Na-clinoptilolite in aqueous suspensions with cysteamine and propylamine solutions and investigated the sorption of Cd and Pb to amine-modified zeolite by a series of batch experiments. Stability constants for amine sorption on all zeolite samples at room temperature and 50 degrees C were obtained. Partial dimerization of cysteamine explains the enhanced sorption of this compound. In contrast, amine treatment did not enhance the adsorption capacity or selectivity of the clinoptilolite towards Cd and Pb. Instead, the amounts of adsorbed heavy metals decreased stoichometrically with increasing sorption of cysteamine and propylamine. This reduction can be explained by the blockage of channels by amine molecules and revealed that the modification of zeolites with mercaptoamines does not enhance the sorption capacity of zeolite for Cd and Pb.

Adsorption↗
PubMed2000

The importance of having high glutathione (GSH) level after bovine in vitro maturation on embryo development effect of beta-mercaptoethanol, cysteine and cystine.

Supplementation of IVM medium with cysteamine, beta-mercaptoethanol, cysteine and cystine induced bovine oocyte glutathione (GSH) synthesis, but only the effect of cysteamine on the developmental competence of these oocytes was tested. During IVM of sheep oocytes, cysteamine but not beta-mercaptoethanol increased embryo development. However, it is not known how long the high intracellular oocyte GSH levels obtained after IVM with thiol compounds, can be maintained. Thus, the present study was carried out to evaluate the effects of supplementing maturation medium with 100 microM beta-mercaptoethanol, 0.6 mM cysteine and 0.6 mM cystine on 1) intracellular GSH level after IVM, 2) after IVF, 3) in 6 to 8-cell embryos and 4) on embryo development. In oocytes after IVM and in presumptive zygotes after IVF, intracellular GSH levels were significantly higher in the treated groups (P < 0.05). While, GSH content in 6 to 8-cell embryos was similar among treatment groups (P > 0.05). Differences in cleavage rates and the percentage of embryos that developed to morula and blastocyst stages were significantly higher (P < 0.05) for treated oocytes than for those matured in the control medium. We conclude from the results that the high intracellular GSH levels after induction of GSH synthesis in bovine IVM by thiol compounds remain during IVF and are still present at the beginning of IVC, improving developmental rates. Moreover, the results indicate that this metabolic pathway is an important component of the cytoplasmic maturation process that affects the subsequent steps of in vitro embryo production.

Animals↗
PubMedDate not supplied

Gene expression and gene therapy in experimental duodenal ulceration.

Gastroduodenal ulceration is still poorly understood and changes in gene expression may provide new mechanistic insights. Previously, we demonstrated that angiogenic growth factors are potent ulcer healing agents, and the synthesis of bFGF, PDGF and VEGF is enhanced early in duodenal ulcer healing. The initial molecular event in duodenal ulceration seems to be the organ-specific early release of ET-1 in the pre-ulcerogenic stages after the administration of duodenal ulcerogen cysteamine in rats. We also briefly review here data from literature indicating a central role of ET-1 in gastroduodenal ulceration. After studying the involvement of immediate early genes (e.g. egr-1, Sp1) in ulcer development, we now investigated expression of other genes in the duodenal mucosa in the early stages of chemically induced duodenal ulceration in rats. Following a brief review of principles of gene expression and gene therapy, we review our preliminary gene expression studies, involving monitoring about 1200 genes which revealed about 160 signals and prominent changes in about 30 genes in the early stages of experimental duodenal ulceration. Cysteamine enhanced ET-B receptor gene expression in 30 min, while transcription factors (MAX, STAT 3) showed increased expression in 12 h. We recently also initiated gene therapy studies to enhance the local synthesis of PDGF and VEGF to accelerate duodenal ulcer healing, using a single dose of naked DNA (ND) or adenoviral (AV) vectors of VEGF and PDGF in rats with cysteamine-induced duodenal ulcers. Gene therapy with ND or AV of VEGF or PDGF significantly accelerated chronic duodenal ulcer healing, and increased levels of VEGF and PDGF were detected by Western blotting and ELISA in duodenal mucosa after both VEGF and PDGF gene therapy. Thus, gene expression studies provide new insights into the molecular mechanisms of duodenal ulceration and VEGF or PDGF gene therapy seems to be a new option to achieve a rapid ulcer healing.

Animals↗
PubMed2004

Immunomodulatory activity of a new family of antioxidants obtained from grape polyphenols.

We examined the potential antioxidant activity and the immunopharmacological activity of new epicatechin conjugates obtained by depolymerization of grape polymeric flavanols in the presence of cysteamine or cysteine and with or without gallate. The compounds studied were (-)-epicatechin (1), cysteinyl-epicatechin (2), cysteamine-epicatechin (3), (-)-epicatechin gallate (4), cysteinyl-epicatechin gallate (5), and cysteamine-epicatechin gallate (6) When incubated with an erythrocyte suspension, flavanols protected the erythrocyte membrane from hemolysis induced by 2,2'-azobis(2-amidinopropane) dihydrochloride, an azo free-radical initiator. All the epicatechin derivatives tested were more efficient as antioxidant than epicatechin. The most potent antioxidant was compound 6. The compounds were tested for their capacity to modulate IL-1beta and IL-6, which are the main cytokine factors influencing the acute phase of the inflammatory response. (-)-Epicatechin and its related compounds inhibited the production of IL-1beta and IL-6 in whole blood incubated in the presence of Escherichia coli lipopolysaccharide. The most efficient inhibitor of cytokine formation was compound 3.

Antioxidants↗
PubMed2005

Efficient preparation of catechin thio conjugates by one step extraction/depolymerization of pine (Pinus pinaster) bark procyanidins.

The skin penetrating antioxidant cysteamine derivative of (-)-epicatechin as well as other thio conjugates were efficiently obtained with high yields from pine (Pinus pinaster) bark by simultaneous one pot extraction and depolymerization using water and cysteamine hydrochloride. The influence of the concentration of bark, acid, and cysteamine, as well as the reaction time on the total conversion, was studied. The total conversion into the epicatechin and catechin conjugates was as high as 47 g/kg pine bark with 1666 g cysteamine/kg bark and 28 g/kg with 166 g cysteamine/kg bark. A fast cleanup step by absorption/desorption on XAD-16 greatly facilitated further purification of the active major component. At a pilot scale, 4beta-(2-aminoethylthio)epicatechin (1) (conversion 263 g, purity 35% by reversed phase high-performance liquid chromatography/weight) was obtained from 17 kg of pine bark after simultaneous extraction/depolymerization followed by cleanup with the polymeric resin in approximately 10 h. The results show that pine (P. pinaster) bark is a suitable source of flavanols for the preparation of active thio derivatives. Conditions are given for the fast and efficient preparation of the conjugates.

Catechin↗
PubMed1997

Zinc ejection as a new rationale for the use of cystamine and related disulfide-containing antiviral agents in the treatment of AIDS.

The highly conserved and mutationally intolerant retroviral zinc finger motif of the HIV-1 nucleocapsid protein (NC) is an attractive target for drug therapy due to its participation in multiple stages of the viral replication cycle. A literature search identified cystamine, thiamine disulfide, and disulfiram as compounds that have been shown to inhibit HIV-1 replication by poorly defined mechanisms and that have electrophilic functional groups that might react with the metal-coordinating sulfur atoms of the retroviral zinc fingers and cause zinc ejection. 1H NMR studies reveal that these compounds readily eject zinc from synthetic peptides with sequences corresponding to the HIV-1 NC zinc fingers, as well as from the intact HIV-1 NC protein. In contrast, the reduced forms of disulfiram and cystamine, diethyl dithiocarbamate and cysteamine, respectively, were found to be ineffective at zinc ejection, although cysteamine formed a transient complex with the zinc fingers. Studies with HIV-1-infected human T-cells and monocyte/macrophage cultures revealed that cystamine and cysteamine possess significant antiviral properties at nontoxic concentrations, which warrant their consideration as therapeutically useful anti-HIV agents.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Thiol oxidase activity of copper, zinc superoxide dismutase.

The ability of copper,zinc superoxide dismutase (Cu,Zn-SOD) to catalyze autoxidation of cysteine and other thiols was investigated by measuring thiol loss and oxygen consumption. The reaction occurred equally well with the bovine and human enzymes and produced hydrogen peroxide and the corresponding disulfide. It did not occur with manganese SOD and is not, therefore, due to the dismutase activity of the enzyme. Cysteine and cysteamine were highly reactive: the K(m) for cysteine was 1.4 mm and V(max) (with 40 microg/ml SOD) 35 microm/min; the equivalent values for cysteamine (with 20 microg/ml SOD) were 1.4 mm and 36 microm/min. With 1 mm thiol and 40 microg/ml SOD, rates of oxidation of other thiols (microm/min) were as follows: GSH, 1.0; dithiothreitol, 2.1; dihydrolipoic acid, 1.7; homocysteine, 1.6; cys-gly, 1.4; penicillamine, 0.6; and N-acetylcysteine, 0.1. SOD-mediated oxidation of cysteine, in the absence of chelating agents, proceeded only after a variable lag phase. The lag was decreased but not eliminated with Chelex-treated reagents and is attributed to interference by submicromolar concentrations of iron and possibly other transition metal ions. SOD-catalyzed oxidation of the other thiols was variably affected by adventitious metal ions and chelating agents. Reactions were all performed in the presence of desferrioxamine to obviate these effects. SOD-catalyzed oxidation of GSH and homocysteine was enhanced by cysteine through a thiol-disulfide exchange mechanism. This study characterizes a novel pro-oxidant thiol oxidase activity of Cu,Zn-SOD. It is a potential source of reactive oxidants and may contribute to the cytotoxicity of reactive thiols such as cysteine and cysteamine.

Animals↗
PubMed2005

A novel small molecule CFTR inhibitor attenuates HCO3- secretion and duodenal ulcer formation in rats.

The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) plays a crucial role in mediating duodenal bicarbonate (HCO(3)(-)) secretion (DBS). Although impaired DBS is observed in CF mutant mice and in CF patients, which would predict increased ulcer susceptibility, duodenal injury is rarely observed in CF patients and is reduced in CF mutant mice. To explain this apparent paradox, we hypothesized that CFTR dysfunction increases cellular [HCO(3)(-)] and buffering power. To further test this hypothesis, we examined the effect of a novel, potent, and highly selective CFTR inhibitor, CFTR(inh)-172, on DBS and duodenal ulceration in rats. DBS was measured in situ using a standard loop perfusion model with a pH stat under isoflurane anesthesia. Duodenal ulcers were induced in rats by cysteamine with or without CFTR(inh)-172 pretreatment 1 h before cysteamine. Superfusion of CFTR(inh)-172 (0.1-10 microM) over the duodenal mucosa had no effect on basal DBS but at 10 microM inhibited acid-induced DBS, suggesting that its effect was limited to CFTR activation. Acid-induced DBS was abolished at 1 and 3 h and was reduced 24 h after treatment with CFTR(inh)-172, although basal DBS was increased at 24 h. CFTR(inh)-172 treatment had no effect on gastric acid or HCO(3)(-) secretion. Duodenal ulcers were observed 24 h after cysteamine treatment but were reduced in CFTR(inh)-172-pretreated rats. CFTR(inh)-172 acutely produces CFTR dysfunction in rodents for up to 24 h. CFTR inhibition reduces acid-induced DBS but also prevents duodenal ulcer formation, supporting our hypothesis that intracellular HCO(3)(-) may be an important protective mechanism for duodenal epithelial cells.

Animals↗
PubMed1989

Utilization of mercaptoethylgluconamide for depleting human cystinotic fibroblasts of their accumulated lysosomal cystine.

Human cystinotic fibroblasts were completely depleted of their accumulated intracellular free cystine within a 2-h time interval when exposed to culture medium containing between 1 and 5 mM mercaptoethylgluconamide. This cystine-depleting action of mercaptoethylgluconamide was observed with three different human cystinotic fibroblast cell lines and with all three cell lines, 2 mM mercaptoethylgluconamide was as effective as 1 mM cysteamine in depleting cells of their intracellular free cystine. Cell viability was excellent for cystinotic fibroblasts exposed to 2 mM mercaptoethylgluconamide for up to 6 days in duration. Mercaptoethylgluconamide (2 mM) was sufficiently stable under cell culture conditions such that a single addition of mercaptoethylgluconamide maintained cystine depletion in human cystinotic fibroblasts for at least a 4-day period. In contrast to cysteamine, 2 mM mercaptoethylgluconamide was not capable of depleting the cystine content of isolated cystinotic lysosomes, implying that cellular integrity is necessary to achieve cystine depletion by mercaptoethylgluconamide. The efficient cystine-depleting action of mercaptoethylgluconamide coupled with its lack of offensive odor encourage further investigation of this agent to possibly complement or supplant the use of cysteamine in the treatment of nephropathic cystinosis.

Cells, Cultured↗
PubMed1992

Effects of sulfhydryl-related compounds on indomethacin-induced gastric lesions in rats: role of endogenous sulfhydryls in the pathogenesis.

The role of mucosal sulfhydryl (SH) in the pathogenesis of indomethacin-induced gastric lesions was investigated in rats. Indomethacin (25 mg/kg, s.c.) caused high-amplitude gastric contractions, resulting in linear hemorrhagic lesions in the corpus mucosa within 4 hr, but did not induce any changes in the mucosal SH levels. These lesions were prevented significantly by prior s.c. administration of cysteamine, glutathione (GSH) or diethylmaleate (DEM), irrespective of whether the mucosal SH was increased by the former two agents or reduced by the latter. N-Ethylmaleimide (NEM) tended to worsen such lesions without any effect on the mucosal SH contents. Gastric hypermotility caused by indomethacin was inhibited significantly by DEM, cysteamine and GSH, while acid secretion was reduced by DEM and NEM. Both cysteamine and GSH prevented the indomethacin-induced linear lesions even in the stomach perfused with 150 mM HCl, whereas in the animals treated with DEM, nonlinear damage was induced exclusively in the antrum by indomethacin in the presence of acid. We conclude that the mucosal SH has no relation to the ulcerogenicity of indomethacin in the gastric corpus mucosa.

Animals↗
PubMed1991

Activation of rabbit liver high affinity cAMP (type IV) phosphodiesterase by a vanadyl-glutathione complex. Characterization of the role of the sulfhydryl.

Activation of rabbit liver microsomal high affinity cAMP phosphodiesterase (Type IV PDE) by vanadyl-glutathione complexes was studied as a possible model of insulin stimulation of the enzyme in a cell-free system. The effect of VO.2GSH activation of PDE was a 21-fold decrease in the IC50 value for cGMP inhibition and a 2.6-fold increase in the Vmax of the higher affinity cAMP catalytic site. Cyclic AMP and cGMP substrate affinities and cGMP hydrolysis were unaffected by VO.2GSH activation. Selective Type IV PDE inhibitors and cGMP analogs indicated that VO.2GSH complexes activated the cGMP-inhibitable form of the Type IV PDE activities which co-localized in hepatic microsomes. The Type IV PDE activating complex appears to consist minimally of vanadyl ion and 2 oxidized electron donor compounds. The components of the electron donor required to achieve an enzyme activation complex are: 1) a free -SH group as the electron donor for vanadate reduction and 2) a minimum structure of cysteamine (NH2-CH2-CH2-SH). Maximal activation of the enzyme required near 2:1 molar ratios of either glutathione or cysteamine mixed with sodium orthovanadate. Active vanadyl-cysteamine complexes were isolated by reverse- phase high performance liquid chromatography. Tungsten, niobium, and tantalum, but not manganese, chromium, or molybdenum, substituted for vanadium to form enzyme-activating complexes with glutathione. VO.RSH complex activation occurred rapidly upon addition to microsomes and was reversible. We conclude from these studies that VO.RSH complexes and insulin activate the same form of Type IV PDE in rabbit liver microsomes; our findings are discussed with respect to the involvement of a possible electron transfer enzyme oxidation in the activation mechanism.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

DNA strand cleavage in vitro by 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]-indole, a direct-acting mutagen formed in the metabolism of carcinogenic 3-amino-1-methyl-5H-pyrido[4,3-b]indole.

3-Hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2) is a direct-acting mutagenic compound derived by metabolic activation from 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), a strongly mutagenic carcinogen. The action of N-OH-Trp-P-2 on DNA in vitro was investigated. N-OH-Trp-P-2 inactivated Bacillus subtilis transforming DNA and produced single-strand cuts in a supercoiled circular DNA (phi X174RFI) under neutral conditions. When mouse FM3A cells in culture were treated with a noncytotoxic dose of N-OH-Trp-P-2 and then the cellular DNA was examined by the alkaline elution technique, chain cleavages of the DNA were observed. Cysteamine inhibited the spontaneous degradation of N-OH-Trp-P-2 and enhanced the covalent binding of [3H]N-OH-Trp-P-2 to DNA. This finding offered an explanation for the previously observed enhancement of Trp-P-2 mutagenicity by cysteamine. In contrast cysteamine inhibited the N-OH-Trp-P-2-mediated inactivation of B. subtilis DNA as well as the strand cleavage in phi X174RFI DNA. The cleavage in phi X174RFI DNA was also inhibited by catalase. These observations indicate that the mutagenicity and DNA-cleaving activity of N-OH-Trp-P-2 are distinct from each other, that the inactivation of transforming DNA was caused mainly by strand cleavage, and that the DNA cleavage was probably caused by active oxygen radicals produced in the oxidative degradation of N-OH-Trp-P-2.

Animals↗