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PubMed1982

Oxidation of NAD(P)H in a Reconstituted Spinach Chloroplast Preparation Using Ascorbate and Hydrogen Peroxide.

The conversion of fructose-1,6-bisphosphate to glycerate-3-phosphate (PGA) was studied in a reconstituted spinach (Spinacia oleracea L.) chloroplast preparation to determine whether a chloroplast-localized NAB(P)H-oxidizing system (Kow, Smyth, Gibbs 1982 Plant Physiol 69: 72-76 with substrates of ascorbate, NAD(P)H, and H(2)O(2) could serve as a coupling enzyme in the recycling of NAD(P)H. The rate of PGA formation was monitored as an indicator of NAD(P) generation. With NAD as a cofactor, ascorbate enhanced PGA formation, and an additional increase resulted upon addition of glucose-glucose oxidase, a H(2)O(2)-generating enzyme. This increase in PGA formation due to H(2)O(2) was eliminated by the addition of catalase. With NADP and ferredoxin as cofactors, the recycling of NADP apparently was catalyzed both by ferredoxin-NADP reductase coupled to O(2) and by the NAD(P)H-oxidizing system.It was concluded that the oxidation of NAD(P)H by a system using ascorbate and H(2)O(2) can serve as a means of recycling NAD(P)H but that another reaction involving ascorbate and NAD(P)H may also function in the spinach chloroplast.

Journal Article↗
PubMed1989

Purification and Characterization of NAD Malic Enzyme from Leaves of Eleusine coracana and Panicum dichotomiflorum.

NAD malic enzyme (EC 1.1.1.39), which is involved in C(4) photosynthesis, was purified to electrophoretic homogeneity from leaves of Eleusine coracana and to near homogeneity from leaves of Panicum dichotomiflorum. The enzyme from each C(4) species was found to have only one type of subunit by SDS polyacrylamide gel electrophoresis. The M(r) of subunits of the enzme from E. coracana and P. dichotommiflorum was 63 and 61 kilodaltons, respectively. The native Mr of the enzyme from each species was determined by gel filtration to be about 500 kilodaltons, indicating that the NAD malic enzyme from C(4) species is an octamer of identical subunits. The purified NAD malic enzyme from each C(4) species showed similar kinetic properties with respect to concentrations of malate and NAD; each had a requirement for Mn(2+) and activation by fructose- 1,6-bisphosphate (FBP) or CoA. A cooperativity with respect to Mn(2+) was apparent with both enzymes. The activator (FBP) did not change the Hill value but greatly decreased K(0.5) (the concentration giving half-maximal activity) for Mn(2+). The enzyme from E. coracana showed a very low level of activity when NADP was used as substrate, but this activity was also stimulated by FBP. Significant differences between the enzymes from E. coracana and P. dichotomiflorum were observed in their responses to the activators and their immunochemical properties. The enzyme from E. coracana was largely dependent on the activators FBP or CoA, regardless of concentration of Mn(2+). In contrast, the enzyme from P. dichotomiflorum showed significant activity in the absence of the activator, especially at high concentrations of Mn(2+). Both immunodiffusion and immunoprecipitation, using antiserum raised against the purified NAD malic enzyme from E. coracana, revealed partial antigenic differences between the enzymes from E. coracana and P. dichotomiflorum. The activity of the NAD malic enzyme from Amaranthus edulis, a typical NAD malic enzyme type C(4) dicot, was not inhibited by the antiserum raised against the NAD malic enzyme from E. coracana.

Journal Article↗
PubMed2006

NAD(P)H oxidase modulates angiogenesis and the development of portosystemic collaterals and splanchnic hyperaemia in portal hypertensive rats.

BACKGROUND: Recent studies have shown the presence of vascular endothelial growth factor (VEGF)-dependent splanchnic angiogenesis in experimental models of portal hypertension, and the role of such neovascularisation on the development of both portosystemic collaterals and hyperdynamic splanchnic circulation. However, the mechanisms modulating angiogenesis in portal hypertension are unknown. Experimental evidence indicates that NAD(P)H oxidase is required for VEGF-induced angiogenesis. Interestingly, we have recently shown that splanchnic NAD(P)H oxidase activity is significantly increased in portal hypertensive rats. Therefore, it could be possible that activated NAD(P)H oxidases modulate angiogenesis in portal hypertension. AIM: To determine the effects of chronic NAD(P)H oxidase inhibition on angiogenesis and splanchnic haemodynamics in portal hypertensive rats. METHODS: Partial portal vein-ligated and sham-operated rats were treated with the NAD(P)H oxidase inhibitor apocynin, or with vehicle for 5 days. Then, the expression of angiogenesis markers (western blotting), the formation of portosystemic collaterals (radioactive microspheres) and the production of superoxide anion (lucigenin-enhanced chemiluminescence) were determined. Mean arterial pressure, portal pressure, and superior mesenteric arterial blood flow and resistance were also measured. RESULTS: In portal hypertensive rats, NAD(P)H oxidase blockade significantly decreased portosystemic collateral formation, and superior mesenteric arterial flow. It also reduced the splanchnic expression of VEGF, VEGF receptor-2 and CD31, and attenuated the increased production of superoxide, compared with vehicle. CONCLUSIONS: NAD(P)H oxidase plays an important role in experimental portal hypertension, modulating splanchnic angiogenesis, the formation of portosystemic collaterals and the development of splanchnic hyperdynamic circulation. These results suggest that NAD(P)H oxidase may represent a new target in the treatment of portal hypertension.

Acetophenones↗
PubMed1993

Effects of afterload and heart rate on NAD(P)H redox state in the isolated rabbit heart.

NAD(P)H redox state was monitored using surface fluorescence in isolated, normothermic, working rabbit hearts under conditions of limited substrate (glucose alone) and abundant substrate (glucose + lactate). To alter work, afterload was varied between 75 and 150 cmH2O or heart rate was increased in steps until no further increase in myocardial oxygen consumption (MVO2) occurred. Alterations in afterload did not cause a significant change in NAD(P)H fluorescence. Progressive increases in heart rate did not alter NAD(P)H emission until MVO2 began to decline (approximately 300 beats/min), ventricular performance decompensated, and there was evidence of ischemia, at which time NAD(P)H fluorescence increased. Although the addition of 3 mM lactate to the perfusate resulted in a rapid increase in NAD(P)H fluorescence, NAD(P)H fluorescence still did not respond to altered workload. The results suggest that NAD(P)H redox state is not the primary stimulus for increased myocardial respiration secondary to tachycardia or afterload. However, despite increased rates of cardiac work, NAD(P)H was maintained at a relatively stable level, suggesting that reducing equivalent supply to the electron transport chain increases in parallel with increased MVO2.

Animals↗
PubMed2004

Systemic regulation of vascular NAD(P)H oxidase activity and nox isoform expression in human arteries and veins.

OBJECTIVE: Impaired endothelial function, characterized by nitric oxide scavenging by increased superoxide production, is a hallmark of vascular disease states. However, molecular mechanisms regulating superoxide production in human blood vessels remain poorly defined. METHODS AND RESULTS: We compared endothelial function, vascular superoxide production, and the expression of NAD(P)H oxidase subunits in arteries and veins from patients undergoing coronary bypass surgery (n=86). Superoxide release was similar in arteries and veins. Inhibitor studies revealed that the NAD(P)H oxidase system was a quantitatively and proportionately greater source of superoxide in veins, whereas xanthine oxidase also contributed significantly to superoxide production in arteries. Moreover, NAD(P)H oxidase molecular composition differed in veins and arteries; veins expressed more nox2 and p22phox, whereas the relative expression of nox4 was greater in arteries. However, there were strong correlations between p22phox and nox4 expression and between superoxide production, NAD(P)H oxidase activity, and endothelial function in arteries and veins from the same patient. CONCLUSIONS: In individuals with coronary artery disease, changes in vascular superoxide production, endothelial function, and NAD(P)H oxidase activity and expression are related in veins and arteries. These findings highlight the importance of systemic effects on the molecular regulation of the NAD(P)H oxidases in human vascular disease. Endothelial dysfunction is characterized by increased superoxide production. NAD(P)H oxidase activity and endothelial function are correlated in veins and arteries in coronary artery disease, suggesting regulation by systemic factors. The expression of the NAD(P)H oxidase subunits p22phox and nox4, although different in veins and arteries, are also correlated.

Acetylcholine↗
PubMed2006

Mycophenolate acid inhibits endothelial NAD(P)H oxidase activity and superoxide formation by a Rac1-dependent mechanism.

Endothelial dysfunction precedes hypertension and atherosclerosis and predicts cardiac allograft vasculopathy and death in heart transplant recipients. Endothelial overproduction of reactive oxygen species, such as superoxide anions produced by NAD(P)H oxidase, induces endothelial dysfunction. Because immunosuppressive drugs have been associated with increased reactive oxygen species production and endothelial dysfunction, we sought to elucidate the underlying mechanisms. Reactive oxygen species, release of superoxide anions, and NAD(P)H oxidase activity were studied in human umbilical vein endothelial cells and in polymorphonuclear neutrophils. Gp91ds-tat was used to specifically block NAD(P)H oxidase. Transcriptional activation of different subunits of NAD(P)H oxidase was assessed by real-time RT-PCR. Rac1 subunit translocation and activation were studied by membrane fractionation and pull-down assays. Calcineurin inhibitors significantly increased endothelial superoxide anions production because of NAD(P)H oxidase, whereas mycophenolate acid (MPA) blocked it. MPA also attenuated the respiratory burst induced by neutrophil NAD(P)H oxidase. Because transcriptional activation of NAD(P)H oxidase was not affected, but addition of guanosine restored endothelial superoxide anions formation after MPA treatment, we speculate that the inhibitory effect of MPA was mediated by depletion of cellular guanosine triphosphate content. This prevented activation of Rac1 and, thus, of endothelial NAD(P)H oxidase. Because all heart transplant recipients are at risk for cardiac allograft vasculopathy development, these differential effects of immunosuppressants on endothelial oxidative stress should be considered in the choice of immunosuppressive drugs.

Calcineurin Inhibitors↗
PubMed2001

Induction of NAD(P)H oxidase by oxidized low-density lipoprotein in human endothelial cells: antioxidative potential of hydroxymethylglutaryl coenzyme A reductase inhibitor therapy.

BACKGROUND: Elevated oxidative stress and superoxide anion formation in vascular cells could promote conversion of LDL to atherogenic oxidized LDL (oxLDL), contributing to endothelial dysfunction and atherosclerosis. As a major source of vascular superoxide anion formation, an endothelial NAD(P)H oxidase, similar to the leukocyte enzyme, has been identified. METHODS AND RESULTS: To elucidate functional differences between NAD(P)H oxidases of endothelial cells and leukocytes, DNA sequences of endothelial NAD(P)H oxidase subunits were determined. Gp91phox cDNA sequence showed no difference between the 2 cell types. Endothelial p67phox cDNA sequence revealed 2 known polymorphisms, which do not affect NAD(P)H oxidase function. Next, we analyzed relative mRNA expression of NAD(P)H subunits in human umbilical vein endothelial cells (HUVECs) and leukocytes using a common cRNA standard in competitive reverse transcription-polymerase chain reaction. NAD(P)H oxidase subunits p22phox and p47phox are expressed at a similar level in both cell types, whereas p67phox (2.5%) and gp91phox (1.1%) are expressed at a much lower level in endothelial cells than in leukocytes. Differences of gp91phox expression in leukocytes and HUVECs correlate with differences in superoxide release. Gp91phox mRNA and endothelial superoxide anion formation are induced in response to oxLDL in HUVECs. Furthermore, a lower gp91phox mRNA expression was found in internal mammary artery biopsy samples of patients with coronary artery disease treated with HMG-CoA reductase inhibitors before coronary bypass surgery. CONCLUSIONS: We conclude that oxLDL induces proatherosclerotic NAD(P)H oxidase expression and superoxide anion formation in human endothelial cells and an antioxidative potential of HMG-CoA reductase inhibition via reduction of vascular NAD(P)H oxidase expression.

Antioxidants↗
PubMed2004

Contribution of vascular NAD(P)H oxidase to endothelial dysfunction in heart failure and the therapeutic effects of HMG-CoA reductase inhibitor.

BACKGROUND: The vascular NAD(P)H oxidase-derived superoxide anion (O(2)-) plays a crucial role in the pathological progression of hypertension and atherosclerosis, and HMG-CoA reductase inhibitors (statins) have vascular antioxidant effects. However, it is unclear whether the vascular NAD(P)H oxidase is involved in the endothelial dysfunction of congestive heart failure (CHF) and whether HMG-CoA reductase inhibitors (statins) exert their vasoprotective effects in CHF. The present study examined both the involvement of vascular NAD(P)H oxidase in endothelial dysfunction in dogs with tachycardia-induced CHF and the therapeutic effect of a statin (pitavastatin). METHODS AND RESULTS: Femoral blood flow (FBF) responses to acetylcholine was significantly impaired in the CHF group, but were improved by pitavastatin. Vascular O(2)- production, NAD(P)H oxidase activity and Nox4 and p47phox expression were significantly elevated in CHF compared with the normal group. The elevated O(2)-production in the CHF group was suppressed by the NAD(P)H oxidase inhibitor, apocynin, to the normal level. In contrast, neither the gene expression nor the activity of endothelial nitric oxide synthase (eNOS) differed significantly between the normal and CHF groups. However, pitavastatin significantly suppressed O(2)- production, NAD(P)H oxidase activity and Nox4 and p47phox expression and increased eNOS expression and activity compared with the CHF group. CONCLUSIONS: The activated vascular NAD(P)H oxidase contributes to endothelial dysfunction in CHF, which was partly improved by pitavastatin via its inhibition of NAD(P)H oxidase.

Acetylcholine↗
PubMed1984

A Ca2+, Calmodulin-dependent NAD kinase from corn is located in the outer mitochondrial membrane.

NAD kinase activity from dark grown corn coleoptiles is shown to be almost totally dependent on Ca2+ and calmodulin. Nearly all of the enzyme activity is found in a particulate fraction. Upon differential and density gradient centrifugation the NAD kinase activity co-migrates with the mitochondrial cytochrome c oxidase whereas marker activities for nuclei, etioplasts, endoplasmic reticulum, and microbodies could well be separated, indicating that the NAD kinase is associated with mitochondria. This NAD kinase, associated with intact mitochondria, can be activated by exogenously added Ca2+ and calmodulin. In order to investigate the submitochondrial localization of the NAD kinase, the organelles were ruptured by osmotic treatment and sonication and the submitochondrial fractions were separated by density gradient centrifugation. The NAD kinase activity exhibits the same density pattern as the antimycin A-insensitive NADH-dependent cytochrome c reductase, a marker enzyme of the outer mitochondrial membrane. Marker enzymes for the mitochondrial matrix and the inner mitochondrial membrane reveal different density profiles. These results indicate that the Ca2+, calmodulin-dependent NAD kinase from coleoptiles of dark grown corn seedlings is located at the outer mitochondrial membrane. The physiological relevance of the location and the Ca2+, calmodulin-dependence of the NAD kinase will be discussed.

Calcium↗
PubMed1982

Influence of DL-ethionine on the NAD content and on the activity of the poly(ADPR)synthetase in the rat liver.

1. Ethionine, an analogue of methionine, is known to cause a number of serious changes. In this study, its influence on the NAD + NADH2 content and on the activity of the poly(ADPR)synthetase in rat liver has been investigated. 2. DL-Ethionine decreases the content of NAD + NADH2 in adrenalectomized, but not in normal animals. 3. After injection of nicotinamide the NAD + NADH2 content in the liver of adrenalectomized rats is much higher than in that of normal ones. 4. DL-Ethionine diminishes the NAD synthesis caused by nicotinamide in adrenalectomized animals and increases it in normal ones. DL-Tryptophan induces only a slight NAD synthesis, which is reduced in adrenalectomized animals by thionine. 5. 1-Methylnicotinamide slightly decreases the NAD concentration in normal animals, but increases it considerably in adrenalectomized ones. DL-ethionine reduces the NAD + NADH content in adrenalectomized animals in the presence of 1-methylnicotinamide. 6. The activity of poly(ADPR)synthetase of in-vitro tested nuclei is slightly increased after treatment with DL-ethionine.

Adrenalectomy↗
PubMed1987

Binding of NAD+ by cholera toxin.

1. The Km for NAD+ of cholera toxin working as an NAD+ glycohydrolase is 4 mM, and this is increased to about 50 mM in the presence of low-Mr ADP-ribose acceptors. Only molecules having both the adenine and nicotinamide moieties of NAD+ with minor alterations in the nicotinamide ring can be competitive inhibitors of this reaction. 2. This high Km for NAD+ is also reflected in the dissociation constant, Kd, which was determined by a variety of methods. 3. Results from equilibrium dialysis were subject to high error, but showed one binding site and a Kd of about 3 mM. 4. The A1 peptide of the toxin is digested by trypsin, and this digestion is completely prevented by concentrations of NAD+ above 50 mM. Measurement (by densitometric scanning of polyacrylamide-gel electrophoretograms) of the rate of tryptic digestion at different concentrations of NAD+ allowed a more accurate determination of Kd = 4.0 +/- 0.4 mM. Some analogues of NAD+ that are competitive inhibitors of the glycohydrolase reaction also prevented digestion.

Adenosine Diphosphate↗
PubMed1999

Ligand-induced internalization of CD38 results in intracellular Ca2+ mobilization: role of NAD+ transport across cell membranes.

CD38, a transmembrane glycoprotein widely expressed in vertebrate cells, is a bifunctional ectoenzyme catalyzing the synthesis and hydrolysis of cyclic ADP-ribose (cADPR). cADPR is a universal second messenger that releases calcium from intracellular stores. Since cADPR is generated by CD38 at the outer surface of many cells, where it acts intracellularly, increasing attention is paid to addressing this topological paradox. Recently, we demonstrated that CD38 is a catalytically active, unidirectional transmembrane transporter of cADPR, which then reaches its receptor-operated intracellular calcium stores. Moreover, CD38 was reported to undergo a selective and extensive internalization through non clathrin-coated endocytotic vesicles upon incubating CD38(+) cells with either NAD+ or thiol compounds: these endocytotic vesicles can convert cytosolic NAD into cADPR despite an asymmetric unfavorable orientation that makes the active site of CD38 intravesicular. Here we demonstrate that the cADPR-generating activity of the endocytotic vesicles results in remarkable and sustained increases of intracellular free calcium concentration in different cells exposed to either NAD+, or GSH, or N-acetylcysteine. This effect of CD38-internalizing ligands on intracellular calcium levels was found to involve a two-step mechanism: 1) influx of cytosolic NAD+ into the endocytotic vesicles, mediated by a hitherto unrecognized dinucleotide transport system that is saturable, bidirectional, inhibitable by 8-N3-NAD+, and characterized by poor dinucleotide specificity, low affinity, and high efficiency; 2) intravesicular CD38-catalyzed conversion of NAD+ to cADPR, followed by outpumping of the cyclic nucleotide into the cytosol and subsequent release of calcium from thapsigargin-sensitive stores. This unknown intracellular trafficking of NAD+ and cADPR based on two distinctive and specific transmembrane carriers for either nucleotide can affect the intracellular calcium homeostasis in CD38(+) cells.

3T3 Cells↗
PubMed2004

Acute ammonia intoxication induces an NMDA receptor-mediated increase in poly(ADP-ribose) polymerase level and NAD metabolism in nuclei of rat brain cells.

Acute ammonia toxicity is mediated by excessive activation of NMDA receptors. Activation of NMDA receptors leads to activation of poly(ADP-ribose) polymerase (PARP) which mediates NMDA excitotoxicity. PARP is activated following DNA damage and may lead to cell death via NAD+ and ATP depletion. The aim of the present work was to assess whether acute ammonia intoxication in vivo leads to increased PARP in brain cells nuclei and to altered NAD+ and superoxide metabolism and the contribution of NMDA receptors to these alterations. Acute ammonia intoxication increases PARP content twofold in brain cells nuclei.NAD+ content decreased by 55% in rats injected with ammonia. This was not due to decreased NAD+ synthetase nor increased NAD+ hydrolase activities and would be due to increased NAD+ consumption by PARP. Superoxide radical formation increased by 75% in nuclei of brains of rats injected with ammonia, that also induced protein nitrotyrosylation and DNA damage. Blocking NMDA receptors prevented ammonia-induced PARP, superoxide and nitrotyrosylation increase, DNA damage and NAD+ decrease. These results show that acute ammonia intoxication in vivo leads to activation of NMDA receptors, leading to increased superoxide formation and PARP content and depletion of NAD+ in brain cells nuclei that contribute to ammonia toxicity.

Amide Synthases↗
PubMed1976

NAD glycohydrolase activity in hearts with acute experimental infarction.

Myocardial ischemia was produced in dogs by occluding the descending coronary artery. NAD decreased in the ischemic tissue taken 2 h after the arterial ligature, and an equivalent amount of nicotinamide was detected instead. A further breakdown occurred when fragments of ischemic and nonischemic tissue were incubated at 37 degrees C. In contrast, NAD concentration remained unchanged for as long as 60 min in incubated fragments from normal heart. When normal tissue was homogenized, an immediate hydrolysis of NAD was observed with the formation of stoichiometric amounts of nicotinamide. An excess of nicotinamide completely inhibited the NAD degradation. The NAD glycohydrolase activity assayed in vitro was similar in normal, ischemic, and nonischemic cardiac homogenates. The conclusions are that the NAD loss in the ischemic heart is due to the tissue NAD glycohydrolase activity and that the cell disorganization provoked by the occlusion of the coronary artery seems to facilitate the reaction between the substrate and the enzyme.

Animals↗
PubMed1993

Submitochondrial localization of the NAD+ glycohydrolase. Implications for the role of pyridine nucleotide hydrolysis in mitochondrial calcium fluxes.

The submitochondrial location of the NAD+ glycohydrolase (NADase) and its role in mitochondrial ADP-ribosyl transfer reactions were investigated in isolated rat liver mitochondria. The NADase catalyzes the hydrolysis of NAD+ to ADP-ribose and nicotinamide. Hydrolysis of intramitochondrial NAD+ has been suggested to be the first step in a nonenzymatic mono(ADP-ribosylation) by free ADP-ribose of an inner membrane-associated acceptor peptide and that this protein is involved in regulating calcium efflux from mitochondria during exposure to oxidants. The results of the present study indicate that mitochondrial NADase activity lies outside the matrix space, however. This was determined by assessing the rates of hydrolysis of externally added NAD+ by intact mitochondria and comparing these rates with those obtained when the mitochondria were permeabilized with detergent. No significant difference was observed in the rate of NAD+ hydrolysis when detergent was added indicating that NAD+ hydrolysis by mitochondria does not necessitate its access to the matrix space. The submitochondrial location of the NADase was investigated further by digitonin titration of isolated mitochondria. Digitonin titration of the mitochondria released NADase activity with the outer membrane marker, monoamine oxidase. The digitonin titration data also suggest that the outer membrane is the exclusive location of the NADase. The incorporation of radioactive label derived from [3H]NAD+ into submitochondrial particles proceeds at comparable rates in the absence or presence of NADase activity, indicating that the production of free ADP-ribose is not necessary for intramitochondrial ADP-ribosyl transfer reactions. Thus the conclusions of this study suggest that due to the submitochondrial location of the NADase, it does not participate in intramitochondrial pyridine nucleotide hydrolysis or nonenzymatic mono(ADP-ribosylation) during oxidative stress in mitochondria.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

[NAD-metabolizing capacity of Saccharomyces cerevisiae mutants].

The activity of the key enzymes of the salvage synthesis and degradation of NAD (nicotinic acid mononucleotide pyrophosphorylase and NAD glycohydrolase) was studied in Saccharomyces cerevisiae mutants selected earlier as potential producers of NAD. An enhanced NAD-producing ability of the mutants was shown to be related to their reduced NAD-degrading activity: thus, NAD glycohydrolase in mutants 110, 118, and 206 was inactive in all growth phases regardless of the level of NAD biosynthesis.

Mutation↗
PubMed2000

Automated assay for nicotinamide adenine dinucleotide (NAD+).

Sulfur mustard (HD), a vesicating chemical warfare compound, has been shown to deplete the nicotinamide adenine dinucleotide (NAD+) content in several cell systems and tissues. This NAD+ depletion has been proposed as an indicator of HD exposure and can be used to evaluate potential antivesicant compounds. To examine NAD+ levels, an automated method based on the alcohol dehydrogenase cycling assay of Jacobson and Jacobson and utilizing a Cobas FARA clinical analyzer has been developed. Automation of this assay led to smaller sample volumes and more efficient use of personnel and resources. The usefulness of this automated method was tested by evaluating the protection, if any, by the topical application of vitamin D or betamethasone against HD-induced NAD+ depletion in skin punches from the hairless guinea pig. The results showed that the samples exposed to HD exhibited significant decreases in NAD+ levels when compared with controls. However, neither vitamin D nor betamethasone demonstrated protection against HD-induced NAD+ depletion. In fact, betamethasone exacerbated the NAD+ depletion when compared with the HD exposed group. This assay appears to be useful for testing potential antivesicant compounds using both in vivo and in vitro exposure systems.

Animals↗
PubMed2003

Reconstructing eukaryotic NAD metabolism.

In addition to its well-known role as a coenzyme in oxidation-reduction reactions, the distinct role of NAD as a precursor for molecules involved in cell regulation has been clearly established. The involvement of NAD in these regulatory processes is based on its ability to function as a donor of ADP-ribose; NAD synthesis is therefore required to avoid depletion of the intracellular pool. The rising interest in the biosynthetic routes leading to NAD formation and the highly conserved nature of the enzymes involved prompted us to reconstruct the NAD biosynthetic routes operating in distinct eukaryotic organisms. The evidence obtained from biochemical and computational analysis provides a good example of how complex metabolic pathways may evolve. In particular, it is proposed that the development of several NAD biosynthetic routes during evolution has led to partial functional redundancy, allowing a given pathway to freely acquire novel functions unrelated to NAD biosynthesis.

Adenosine Diphosphate Ribose↗