Biofactors - Volume 10, issue 2-3

Article Type: Other

Citation: Biofactors, vol. 10, no. 2-3, pp. 83-83, 1999

Authors: Swindell, Eric C. | Eichele, Gregor

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 85-89, 1999

Authors: Carlberg, Carsten

Article Type: Research Article

Abstract: Vitamin A (retinol) and vitamin D are lipid soluble vitamins that are precursors of the nuclear hormones all‐trans retinoic acid (RA) and 1\alpha ,25‐dihydroxyvitamin D_{3} (VD) that bind with high affinity to their cognate nuclear receptors, referred to as retinoic acid receptor (RAR) and vitamin D receptor (VDR). Both types of nuclear receptors are structurally related and belong to the same subclass of the nuclear receptor superfamily, a large family of ligand‐inducible transcription factors. Both RAR and VDR form heterodimers preferentially with the nuclear receptor for 9‐cis RA, referred to as the retinoid X receptor (RXR), but …functional RAR‐VDR heterodimers have also been observed. Moreover, both types of nuclear receptors interact in a ligand‐dependent fashion with members of the same class of co‐activator, co‐repressor and co‐integrator proteins. These similar molecular mechanisms of action provide several possibilities for an interaction of RARs with VDR that are all based on allosteric protein–protein interactions. These interactions can result in either an additive or a transrepressive functional interference between RA and VD. The two remaining lipid soluble vitamins, vitamins E and K, are not known to interact with nuclear receptors, but their structure does not exclude this possibility. Moreover, for vitamin E modulatory effects on transcription factors, such as AP‐1, have been described. This review will discuss briefly gene regulation by the four lipid soluble vitamins. Show more

Keywords: Vitamins A, D, E and K, nuclear receptors, transcriptional regulation

Citation: Biofactors, vol. 10, no. 2-3, pp. 91-97, 1999

Authors: Vershinin, Alexander

Article Type: Research Article

Abstract: Carotenoids first emerged in archaebacteria as lipids reinforcing cell membranes. To serve this function their long molecules have extremely rigid backbone due to the linear chain of usually 10 to 11 conjugated C= C bonds in trans‐configuration – the length corresponding the thickness of hydrophobic zone of membrane which they penetrate as “molecular rivets”. Carotenoids retain their membrane‐reinforcing function in some fungi and animals. The general structure of carotenoid molecule, originally having evolved for mechanical functions in membranes, possess a number of other properties that were later used for independent functions. The most striking fact is that these …properties proved to fit some new functions to perfection. – The polyene chain of 9–11 double bonds absorbs light precisely in the gap of chlorophyll absorption – function as accessory light‐harvesting pigments in all plants; – Unique arrangement of electronic levels owing to the by polyene chain structure makes carotenoids the only natural compounds capable of excitation energy transfer both (i) from carotenoid excited state to chlorophyll in the light‐harvesting complex and (ii) from triplet chlorophyll or singlet oxygen to carotenoid in photosynthetic reaction centers – protection of RC from photodamage. The linear system of conjugated C= C bonds provides high reducing potential of carotenoid molecules making them potent antioxidants in lipid formations. Still, there is a lack of evidence of the chemical antioxidant function of carotenoids, especially in higher organisms; most data demonstrate an antioxidant ability rather than a function. Carotenoids have many other independent biological functions, including: specific coloration patterns in plants and animals, screening from excessive light and spectral filtering, defense of egg proteins from proteases in some invertebrates; the direct carotenoid derivative – retinal – acts as visual pigment in all animals and as chromophore in bacteriorhodopsin photosynthesis, retinoic acid in animals and abscisic acid in plants serve as hormones. All these functions utilize various properties (mechanical, electronic, stereospecific) of a single structure evolved in bacteria for a single membrane‐reinforcing function, thus demonstrating an example of pure evolutionary preadaptation. One of the practical conclusions that can be reached by reviewing uniquely diverse properties and functions of carotenoids is that, when considering possible mechanisms of their effects in organisms (e.g., anticarcinogenic action), all their functional traits should be taken into account. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 99-104, 1999

Authors: Siems, Werner G. | Sommerburg, Olaf | van Kuijk, Frederik J.G.M.

Article Type: Research Article

Abstract: Major carotenoids of human plasma and tissues were exposed to radical‐initiated autoxidation conditions. The consumption of lutein and zeaxanthin, the only carotenoids in the retina, and lycopene and \beta ‐carotene, the most effective quenchers of singlet oxygen in plasma, were compared. Under all conditions of free radical‐initiated autoxidation of carotenoids which were investigated, the breakdown of lycopene and \beta ‐carotene was much faster than that of lutein and zeaxanthin. Under the influence of UV light in presence of Rose Bengal, by far the highest breakdown rate was found for \beta ‐carotene, followed by lycopene. Bleaching of …carotenoid mixtures mediated by NaOCl, addition of azo‐bis‐isobutyronitril (AIBN), and the photoirradiation of carotenoid mixtures by natural sunlight lead to the following sequence of breakdown rates: lycopene > \beta ‐carotene > zeaxanthin > lutein. The slow degradation of the xanthophylls zeaxanthin and lutein may be suggested to explain the majority of zeaxanthin and lutein in the retina of man and other species. In correspondence to that, the rapid degradation of \beta ‐carotene and lycopene under the influence of natural sunlight and UV light is postulated to be the reason for the almost lack of those two carotenoids in the human retina. Nevertheless, a final proof of that theory is lacking. Show more

Keywords: Carotenoids, lutein, zeaxanthin, lycopene, \beta‐carotene, retina, UV light, photoirradiation

Citation: Biofactors, vol. 10, no. 2-3, pp. 105-113, 1999

Authors: Traber, Maret G.

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 115-120, 1999

Authors: Sommerburg, O. | Sostmann, K. | Grune, T. | Ehrich, J.H.H.

Article Type: Research Article

Abstract: Background: MDA, a major product of LPO, was shown to be increased in plasma of patients with end‐stage renal failure (ESRF) undergoing hemodialysis (HD). Elevated oxidative stress in ESRF patients is a result of multiple pathogenetic factors. HD treatment has been shown to be one important cause of accelerated radical generation. The aim of our study was to examine whether treatment with a dialysis membrane which has alpha‐tocopherol hydrophobically bonded to its surface (Excebrane by Terumo, Japan) can decrease oxidative stress due to HD. Methods: 10 ESRF patients undergoing HD three times weekly were examined. First, analysis was done …when patients were still dialysed with the membranes used before the study. Thereafter, samples were taken when patients were dialysed first time with the Excebrane membrane, and six weeks after Excebrane treatment. Samples were collected always before and after HD session. A method with HPLC‐separation and flourimetric detection was used to measure plasma concentration of MDA. Results: After HD with the regularly used membranes MDA was found significantly increased (before HD 1.92 [1.81–2.02] \mu M (median and interquartile ranges) vs. after HD 2.26 [2.02–2.60] \mu M, p<{} 0.05) suggesting that MDA was produced during HD. The first time Excebrane was used MDA was decreased significantly (before HD 2.04 [1.95–2.88] \mu M vs. after HD 1.35 [1.19–1.92] \mu M, p<{} 0.05). After six weeks of Excebrane treatment, plasma MDA did not change significantly during HD (before HD 2.01 [1.69–2.62] \mu M vs. after HD 1.95 [1.42–2.20] \mu M). Conclusion: Oxidative stress due to HD might be significantly decreased by the Excebrane membrane. However, after six weeks of treatment with Excebrane no effect was seen on the initial plasma concentration of MDA compared to the time before. Show more

Keywords: Hemodialysis, vitamin E, end‐stage renal failure, antioxidants, radicals, oxidative stress

Citation: Biofactors, vol. 10, no. 2-3, pp. 121-124, 1999

Authors: Lotito, Silvina B. | Fraga, César G.

Article Type: Research Article

Abstract: We evaluated the antioxidant effect of (+ )‐catechin (CTCH), in the presence of physiological antioxidant levels of ascorbic acid (AA), \alpha ‐tocopherol (AT) and beta‐carotene (BC), in human plasma oxidised with AAPH. Following a five‐hour incubation, the formation of lipid oxidation products (TBARS) was almost doubled, and the concentrations of lipid soluble antioxidants were 10 to 30% from the initial levels. In these conditions, AA was consumed within the first hour of incubation. The addition of CTCH prevented AT and BC depletion and TBARS formation, but had no effect on AA consumption. When the kinetics of oxidation were …analysed CTCH oxidation preceded lipid soluble antioxidant depletion, but no consumption of CTCH was associated to AA oxidation. Considering that CTCH could contribute to the antioxidant activity of red wine, we first characterised both the antioxidant capacity and CTCH content of several wines. The wines with highest content of CTCH and antioxidant activity were also the most effective in preventing AAPH‐mediated oxidation of plasma vitamin E. Results support the idea that CTCH could have a role as a physiological antioxidant in human plasma, and that CTCH of wine could contribute to the antioxidant status of human plasma. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 125-130, 1999

Authors: Kishi, Takeo | Takahashi, Takayuki | Usui, Akinori | Okamoto, Tadashi

Article Type: Research Article

Abstract: Ubiquinone (UQ) reductase responsible for reduction of non‐mitochondrial UQ was investigated in rats toward demonstrating an antioxidant role of UQ. In the liver, most of cellular UQ‐10 reductase activity was attributable to a novel NADPH‐UQ reductase in cytosol. The enzyme was not inhibited by dicumarol and rotenone, and had a K_\mathrm{m} of 19 \mu M for NADPH and 307 \mu M for NADH at the optimum pH 7.4. The enzyme was purified 300‐fold to apparent homogeneity from the liver cytosol by an affinity chromatographic method. The purified enzyme reduced UQ‐10 in lecithin liposomes, and protected the …liposomes from lipid peroxidation. Furthermore, supplementation of rats with UQ‐10 was observed to increase the enzyme level in their livers without affecting levels of other antioxidant factors. The observations suggested that cytosolic NADPH‐UQ reductase is responsible for cellular UQ redox cycle as an endogenous antioxidant. Show more

Keywords: Ubiquinone, quinone reductases, NADPH dehydrogenases, antioxidants, rats

Citation: Biofactors, vol. 10, no. 2-3, pp. 131-138, 1999

Authors: Sakamoto, Wataru | Nishihira, Jun | Fujie, Katsutoshi | Iizuka, Tadashi | Handa, Hiroshi | Ozaki, Mitsuru | Yukawa, Susumu

Article Type: Research Article

Abstract: Macrophage migration inhibitory factor (MIF), a putative cytokine involved in inflammatory and immune responses, was identified in rat peritoneal macrophages by Western blot analysis and its secretion into culture medium by enzyme‐linked immunosorbent assay. To clarify the possibility of vitamin E as an immune modulator, we investigated the effect of vitamin E on MIF production in macrophages in response to calcium ionophore A23187 and lipopolysaccharide (LPS). Intraperitoneal injections of vitamin E (5 mg per rat) for 6 successive days resulted in a significant increase of \alpha ‐tocopherol content in peritoneal macrophages. \alpha ‐Tocopherol content of macrophages in vitamin …E‐treated rats was 478.3 \pm 90.7 ng/10^{6} cells, whereas in control rats it was 1.5 \pm 0.5 ng/10^{6} cells. For the control macrophages, total MIF content of the medium (2.5 \times 10^{6} cells/18 ml) without stimulation was 40.7 \pm 3.6 ng after 14 h culture, whereas stimulation with calcium ionophore A23187 (400 nM) and LPS (5.0 \mu g/ml) induced the elevation of MIF content to 65.9 \pm 7.5 ng and 74.3 \pm 10.4 ng, respectively (p<{} 0.05, n={} 3). On the other hand, vitamin E‐enriched macrophages without stimulation showed less MIF content (14.0 \pm 4.2 ng) than the control (p<{} 0.05, n={} 3). Similarly, the increase of MIF of vitamin E‐treated macrophages was significantly suppressed after stimulation with calcium ionophore A23187 or LPS, compared with the control macrophages (p<{} 0.01, n={} 3). From analysis of intracellular MIF content by Western blot, we found no alteration of intracellular MIF content of vitamin E‐macrophages, in contrast to the decreased content of control stimulated‐macrophages, showing that vitamin E suppressed MIF secretion into the culture medium. Taken together, these results indicate that vitamin E may contribute to the regulation of inflammatory and immune responses through regulation of MIF secretion, possibly by modulating macrophage‐membrane architecture. Show more

Keywords: Vitamin E, macrophages, macrophage migration inhibitory factor (MIF), lipopolysaccharide (LPS), calcium ionophore A23187

Citation: Biofactors, vol. 10, no. 2-3, pp. 139-143, 1999

Authors: Goossens, Vera | De Vos, Kurt | Vercammen, Dominique | Steemans, Margino | Vancompernolle, Katia | Fiers, Walter | Vandenabeele, Peter | Grooten, Johan

Article Type: Research Article

Abstract: TNF is produced during inflammation and induces, among other activities, cell death in sensitive tumour cells. We previously reported an increased generation of ROS in TNF‐treated L929 fibrosarcoma cells prior to cell death. These ROS are of mitochondrial origin and participate in the cell death process. Presently, we focus on the identification of parameters that control ROS production and subsequent cytotoxicity. From the cytotoxic properties and susceptibility to scavenging of TNF‐induced ROS as compared to pro‐oxidant‐induced ROS we conclude that TNF‐mediated ROS generation and their lethal action are confined to the inner mitochondrial membrane. Oxidative substrates, electron‐transport inhibitors, glutathione and …thiol‐reactive agents but also caspase inhibitors modulate TNF‐induced ROS production and imply the existence of a negative regulator of ROS production. Inactivation of this regulator by a TNF‐induced reduction of NAD(P)H levels and/or formation of intraprotein disulfides would be responsible for ROS generation. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 145-156, 1999

Authors: Mohamed, Abdel Khalek | Bierhaus, Angelika | Schiekofer, Stephan | Tritschler, Hans | Ziegler, Reinhard | Nawroth, Peter P.

Article Type: Research Article

Abstract: A common endpoint of hyperglycemia dependent cellular changes is the generation of reactive oxygen intermediates (ROIs) and the presence of elevated oxidative stress. Therefore, oxidative stress is supposed to play an important role in the development of late diabetic complications. Formation of advanced glycation end products (AGE’s) due to elevated nonenzymatic glycation of proteins, lipids and nucleic acids is accompanied by oxidative, radical‐generating reactions and thus represents a major source for oxygen free radicals under hyperglycemic conditions. Once formed, AGE’s can influence cellular function by binding to several binding sites including the receptor for AGE’s, RAGE. Binding of AGE’s (and …other ligands) to RAGE results in generation of intracellular oxidative stress and subsequent activation of the redox‐sensitive transcription factor NF‐\kappa B in vitro and in vivo. Consistently, activation of NF‐\kappa B in diabetic patients correlates with the quality of glycemic control and can be reduced by treatment with the antioxidant \alpha ‐lipoic acid. The development of techiques allowing for a tissue culture independent measurement of NF‐\kappa B activation in patients with diabetes mellitus gives insights into the molecular mechanisms linking diabetes mellitus and hyperglycemia with formation of advanced glycated endproducts and generation of oxidative stress finally resulting in oxidative stress mediated cellular activation. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 157-167, 1999

Authors: Jacob, S. | Rett, K. | Henriksen, E.J. | Häring, H.‐U.

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 169-174, 1999

Authors: Böl, Gaby‐Fleur | Tewes, Frank | Brigelius‐Flohé, Regina

Article Type: Research Article

Abstract: Stimulation of the Interleukin‐1 receptor type I (IL‐1‐RI) with IL‐1 activates an associated serine/threonine kinase, IRAK, which phosphorylates downstream targets, resulting in NF\kappa B activation. The signaling cascade is accompanied by oxidative processes and contains putative targets for redox regulation. Preincubation of the murine T cell line EL‐4 and the human umbilical cord vein endothelial cell line ECV 304 with thiol modifying compounds like diamide, menadione or phenylarsine oxide inhibited the IL‐1‐induced phosphorylation of an endogenous substrate with a molecular mass of 60 kD. In the endothelial cell line, a second target of about 85 kD was phosphorylated after …IL‐1 stimulation, which was also inhibited by thiol modification. These data suggest that IL‐1 signal transduction depends on free thiols which might be targets for redox regulation not only in lymphocytes, but also in endothelial cells. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 175-178, 1999

Authors: Blanco, B. | Ferrández, M.D. | Correa, R. | Del Rio, M. | Guaza, C. | Hernanz, A. | De la Fuente, M.

Article Type: Research Article

Abstract: The administration of the thiol compounds, N‐acetylcysteine (NAC) and in particular thioproline (thiazolidine‐4‐carboxylic acid) at 0.1% w/w concentration in the diet, improves lymphocyte functions in old female Swiss mice, as has been shown in our previous studies. In the present work, adult mice from two different strains, namely BALB/c (an inbred strain) and OF1‐Swiss (noninbred strain), were fed a diet supplemented with the above dose of each thiol compound jointly for five weeks. At 28 weeks of age, peritoneal cell suspensions were obtained and different steps of the phagocytic process, the most representative activity of macrophages, as well as interleukin‐1\beta …(IL‐1\beta ) production, were studied. Thus, adherence to substrate, mobility directed to a chemoattractant gradient (chemotaxis), ingestion of inert particles and superoxide anion production were analysed. The results show that diet supplementation with NAC plus thioproline increased all macrophage functions studied with the exception of superoxide anion production, which was decreased. These effects were more evident in macrophages from Swiss mice, whereas in BALB/c mice the stimulation of phagocytosis and IL‐1\beta production was lower and no differences were seen after treatment in adherence and superoxide anion production. These data suggest that immune function can be improved in adult mice by administration of the above thiol compounds, especially in the noninbred strain of OF1‐Swiss mice. Show more

Keywords: Thioproline, N‐acetylcysteine, macrophages, phagocytic function, interleukin‐1\beta

Citation: Biofactors, vol. 10, no. 2-3, pp. 179-185, 1999

Authors: Molina‐Holgado, F. | Hernanz, A. | de la Fuente, M. | Guaza, C.

Article Type: Research Article

Abstract: The pathological mechanisms that cause central nervous system (CNS) dysfunction in most neurological diseases are not well established. Theiler’s murine encephalomyelitis virus (TMEV) is known to interact with cells of the CNS and its intracerebral inoculation to susceptible mice strains causes neurological disorders resembling multiple sclerosis (MS). In this study, we reported that primary astrocyte cultures from SJL/J susceptible mice when infected with TMEV released important amounts of nitrites (NO_{2}^{-} ) to the culture medium, as measured in the supernatants 24 hours after infection. In addition, we observed an increment in the production of tumour necrosis factor alpha (TNF‐\alpha …) by susceptible SJL/J strain derived astrocytes infected with TMEV. The treatment with the thiolic antioxidant N‐acetyl‐cysteine partially suppressed the virus‐stimulated production of nitric oxide and TNF‐\alpha, in a dose response fashion. These results indicate that during viral infection astrocytes are an important cellular source of nitric oxide and TNF‐\alpha , substances which play important roles during CNS inflammatory events. The effects of the antioxidant N‐acetyl‐cysteine, modulating the production of the above compounds by TMEV‐infected astrocytes may be a significant factor in preventing CNS demyelination. Show more

Keywords: N‐acetyl‐cysteine, nitric oxide, tumour necrosis factor‐\alpha, Theiler’s virus, astrocyte cultures

Citation: Biofactors, vol. 10, no. 2-3, pp. 187-193, 1999

Authors: Correa, R. | Blanco, B. | Del Río, M. | Víctor, V. | Guayerbas, N. | Medina, S. | De la Fuente, M.

Article Type: Research Article

Abstract: A previous study has shown that diet supplementation with thioproline (thiazolidine‐4‐carboxylic acid, TCA), an intracellular sulfhydril antioxidant and free radical scavenger, stimulates lymphocyte functions in old mice. In the present work, the effect of thioproline ingestion on the phagocytic functions of peritoneal macrophages, namely adherence, chemotaxis, phagocytosis and superoxide anion production was studied in adult female OF1‐Swiss mice, that were fed thioproline (0.1% w/w) for five weeks, starting this ingestion at the age of 22 \pm 2 weeks. Mice were divided into a fast and a slow group based on their exploratory activity, which was assessed by their …performance in a T‐shaped maze. Slow mice showed a worse phagocytic activity with respect to fast animals. After thioproline treatment, a stimulation of all the functions studied as well as a neutralization of the superoxide radical were observed. The effect of this antioxidant was stronger in the slow than in the fast group. Thus, a diet supplemented with thioproline may enhance the immune functions, especially when they are depressed. Show more

Keywords: Thioproline, macrophages, phagocytic function, ageing

Citation: Biofactors, vol. 10, no. 2-3, pp. 195-200, 1999

Authors: Duine, Johannis A.

Article Type: Research Article

Abstract: Glutathione is not a universal coenzyme for formaldehyde oxidation. MySH (mycothiol, 1‐O‐(2' ‐[N‐acetyl‐L‐cysteinyl]amido‐2' ‐deoxy‐\propto ‐D‐glucopyranosyl)‐D‐myo‐inositol) is GSH’s counterpart as coenzyme in formaldehyde dehydrogenase from certain Gram‐positive bacteria. However, formaldehyde dissimilation and detoxification not only proceed via thiol‐dependent but also via thiol‐independent dehydrogenases. The distinct structures and enzymatic properties of MySH‐dependent and GSH‐dependent formaldehyde dehydrogenases could provide clues for development of selective drugs against pathogenic Mycobacteria. It is to be expected that other new types of thiol‐dependent formaldehyde dehydrogenases will be discovered in the future. Indications exist that the product of thiol‐dependent formaldehyde oxidation, the thiol formate ester, …is not only hydrolytically converted into thiol and formate but can also be oxidatively converted in some cases by a molybdoprotein aldehyde dehydrogenase into the corresponding carbonate ester, decomposing spontaneously into CO_{2} and the thiol. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 201-206, 1999

Authors: Rhee, Sue Goo | Kang, Sang Won | Netto, Luis E. | Seo, Min Seok | Stadtman, Earl R.

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 207-209, 1999

Authors: Sherman, David R. | Mdluli, Khisimuzi | Hickey, Mark J. | Barry, III, Clifton E. | Stover, C. Kendall

Article Type: Research Article

Abstract: The Mycobacterium tuberculosis AhpC is similar to a family of bacterial and eukaryotic antioxidant proteins with alkylhydroperoxidase (Ahp) and thioredoxin‐dependent peroxidase (TPx) activities. AhpC expression is associated with resistance to the front‐line antitubercular drug isoniazid in the naturally resistant organisms E. coli and M. smegmatis. We identified several isoniazid‐resistant M. tuberculosis isolates with ahpC promoter mutations resulting in AhpC overexpression. These strains were more resistant to cumene hydroperoxide than were wild‐type strains. However, these strains were unchanged in their sensitivity to isoniazid, refuting a role for AhpC in detoxification of this drug. All the isoniazid‐resistant, AhpC‐overexpressing strains were also deficient …in activity of the mycobacterial catalase‐peroxidase KatG. KatG, the only known catalase in M. tuberculosis, is required for activation of isoniazid. We propose that compensatory ahpC promoter mutations are selected from KatG‐deficient, isoniazid‐resistant M. tuberculosis during infections, to mitigate the added burden imposed by organic peroxides on these strains. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 211-217, 1999

Authors: Arnér, Elias S.J.

Article Type: Research Article

Abstract: Mammalian thioredoxin reductase catalyzes NADPH dependent reduction of a wide variety of substrates and plays a central role in redox regulation and antioxidant defence. Recently the enzyme was discovered to be a selenoprotein with a catalytically active penultimate selenocysteine residue. Dinitrohalobenzenes irreversibly inhibit the enzyme with a concomitant induction of an NADPH oxidase activity, producing superoxide. A model explaining the reactivity of dinitrohalobenzenes with thioredoxin reductase is presented, involving dinitrophenyl‐derivatization of both the selenocysteine residue and its neighboring cysteine residue, reduction by NADPH of the enzyme‐bound flavin in dinitrophenyl‐alkylated enzyme (dnp‐TrxR), followed by two consecutive one‐electron transfers from the flavin …to nitro groups of the dnp‐moieties in dnp‐TrxR, forming nitro anion radicals. The nitro radicals react with oxygen to form superoxide, again generating dnp‐TrxR with an oxidized flavin, which may then follow another cycle of NADPH‐dependent superoxide production. Dinitrohalobenzene compounds are well known for their immunostimulatory properties. Here it is proposed that the inflammatory components of this immunostimulation can be mediated by interaction with the thioredoxin system, via effects on cell function by superoxide production, oxidative stress and increased extracellular levels of thioredoxin. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 219-226, 1999

Authors: Ebert‐Dümig, Regina | Schütze, Norbert | Jakob, Franz

Article Type: Research Article

Keywords: Thioredoxin reductase, vitamin D3, monocyte

Citation: Biofactors, vol. 10, no. 2-3, pp. 227-235, 1999

Authors: Lacourciere, Gerard M.

Article Type: Research Article

Abstract: Selenophosphate synthetase, the product of the selD gene, produces the highly active selenium donor, monoselenophosphate, from selenide and ATP. Positional isotope exchange experiments have shown hydrolysis of ATP occurs by way of a phosphoryl‐enzyme intermediate. Although, mutagenesis studies have demonstrated Cys^{17} in the Escherichia coli enzyme is essential for catalytic activity the nucleophile in catalysis has not been identified. Recently, selenophosphate synthetase enzymes have been identified from other organisms. The human enzyme which contains a threonine residue corresponding to Cys^{17} in the E. coli enzyme, has been overexpressed in E. coli. The purified enzyme shows no …detectable activity in the in vitro selenophosphate synthetase assay. In contrast, when the human enzyme is expressed to complement a selD mutation in E. coli, in the presence of ^{75} Se, incorporation of ^{75} Se into bacterial selenoproteins is observed. The inactive purified human enzyme together with the very low determined specific activity of the E. coli enzyme (83 nmol/min/mg) suggest an essential component for the formation of selenophosphate has not been identified. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 237-244, 1999

Authors: Wingler, Kirstin | Brigelius‐Flohé, Regina

Article Type: Research Article

Abstract: The gastrointestinal glutathione peroxidase (GI‐GPx) is the fourth member of the GPx family. In rodents, it is exclusively expressed in the gastrointestinal tract, in humans also in liver. It has, therefore, been discussed to function as a primary barrier against the absorption of ingested hydroperoxides. A vital function of GI‐GPx can be deduced from the unusual stability of its mRNA under selenium‐limiting conditions, the presence of low amounts of GI‐GPx protein in selenium deficiency where cGPx is absent, and the fast reappearance of the GI‐GPx protein upon refeeding of cultured cells with selenium compared to the slower reappearance of cGPx …protein. Furthermore, the Secis efficiency of GI‐GPx is low when compared to cGPx and PHGPx. It is, however, almost independent of the selenium status of the cells tested. All these characteristics rank GI‐GPx high in the hierarchy of selenoproteins and point to a role of GI‐GPx which might be more crucial than that of cGPx, at least in the gastrointestinal system. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 245-249, 1999

Authors: Maiorino, Matilde | Flohé, Leopold | Roveri, Antonella | Steinert, Peter | Wissing, Josef B. | Ursini, Fulvio

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 251-256, 1999

Authors: Soda, Kenji | Oikawa, Tadao | Esaki, Nobuyoshi

Article Type: Research Article

Abstract: Various vitamin B_6 enzymes play important roles in mammalian and microbial metabolism of selenium amino acids. Selenocysteine is synthesized from selenohomocysteine by catalysis of cystathionine \beta ‐synthase and cystathionine \gamma ‐lyase, which both require pyridoxal phosphate. Selenocysteine \beta ‐lyase, a new B_6 ‐enzyme, exclusively catalyzes \beta ‐elimination of selenocysteine, and occurs in mammalian systems and bacteria. Methionine \gamma ‐lyase, cysteine desulfurase, cysteine sulfinate desulfinase, and D‐selenocystine \alpha ,\beta ‐lyase, which are B_6 ‐enzymes, act on cysteine, cysteine sulfinate, D‐cystine, and their derivatives, and their …selenium counterparts indiscriminately. Their reaction mechanisms are comparatively described. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 257-262, 1999

Authors: Andreesen, Jan R. | Wagner, Matthias | Sonntag, Denise | Kohlstock, Martin | Harms, Claudia | Gursinsky, Torsten | Jäge, Jana | Parther, Tina | Kabisch, Ute | Gräntzdörffer, Andrea | Pich, Andreas | Söhling, Brigitte

Article Type: Research Article

Abstract: Electron transfer reactions for the reduction of glycine in Eubacterium acidaminophilum involve many selenocysteine (U)‐ and thiol‐containing proteins, as shown by biochemical and molecular analysis. These include an unusual thioredoxin system (‐CXXC‐), protein A (‐CXXU‐) and the substrate‐specific protein B of glycine reductase (‐UXXCXXC‐). Most probably a selenoether is formed at protein B by splitting the C‐N‐bond after binding of the substrate. The carboxymethyl group is then transferred to the selenocysteine of protein A containing a conserved motif. The latter protein acts as a carbon and electron donor by giving rise to a protein C‐bound acetyl‐thioester and a mixed selenide‐sulfide …bond at protein A that will be reduced by the thioredoxin system. The dithiothreitol‐dependent D‐proline reductase of Clostridium sticklandii exhibits many similarities to protein B of glycine reductase including the motif containing selenocysteine. In both cases proprotein processing at a cysteine residue gives rise to a blocked N‐terminus, most probably a pyruvoyl group. Formate dehydrogenase and some other proteins from E. acidaminophilum contain selenocysteine, e.g., a 22 kDa protein showing an extensive homology to peroxiredoxins involved in the detoxification of peroxides. Show more

Keywords: Selenocysteine, Gram‐positive bacteria, anaerobic reductase systems, peroxiredoxins, proprotein processing

Citation: Biofactors, vol. 10, no. 2-3, pp. 263-270, 1999

Authors: Bernal, Juan

Article Type: Research Article

Abstract: The development of the brain is critically dependent on an adequate supply of iodine. Iodine is an integral part of thyroid hormone, which acts on brain development by regulating the expression of target genes. The active thyroid hormone, T3, is generated in part in the thyroid gland, but about 80% of T3 in brain is formed locally from T4 deiodination mainly by the action of a specific iodothyronine deiodinase. This enzyme is highly expressed in astrocytes, which take up T4 from the blood and deliver T3 for neuronal use. In the target cells T3 binds to nuclear receptors which are …transcription factors. The T3 receptors are expressed in the brain before fetal thyroid gland function and may be activated by maternal thyroid hormone during midgestation. Although a group of thyroid hormone target genes has been identified in recent years, many basic questions of thyroid hormone action in the brain remain to be elucidated. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 271-276, 1999

Authors: Nilsson, Mikael

Article Type: Research Article

Abstract: Thyroid hormone is an essential regulator of developmental growth and metabolism in vertebrates. Iodine is a necessary constituent of thyroid hormone. Due to the scarcity and uneven distribution of iodine on the Earth’s crust, the structure of the thyroid gland is adjusted to collect and store this element in order to secure a continuous supply of thyroid hormone throughout life. Still, disease resulting from hypothyroidism due to iodine deficiency is a global health problem, illustrating the great biological significance that iodine saving mechanisms have evolved. Iodide is accumulated together with prohormone (thyroglobulin) in the lumen of the thyroid follicles. The …rate‐limiting step of this transport is the sodium/iodide symporter located in the basolateral plasma membrane of the thyroid follicular cells. Iodide is also transferred across the apical plasma membrane into the lumen where hormonogenesis takes place. In this review, recent progress in the understanding of transepithelial iodide transport in the thyroid is summarized. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 277-285, 1999

Authors: Baumgartner, E. Regula | Suormala, Terttu

Article Type: Research Article

Citation: Biofactors, vol. 10, no. 2-3, pp. 287-290, 1999

Authors: Molloy, Anne M. | Mills, James L. | Kirke, Peadar N. | Weir, Donald G. | Scott, John M.

Article Type: Research Article

Abstract: Periconceptional folic acid supplementation prevents approximately 70% of neural tube defects (NTDs). While most women carrying affected fetuses do not have deficient blood folate levels, the risk of having an NTD affected child is inversely correlated with pregnancy red cell folate levels. Current research is focused on the discovery of genetic abnormalities in folate related enzymes which might explain the role of folate in NTD prevention. The first candidate gene to emerge was the C677T variant of 5,10‐methylenetetrahydrofolate reductase. Normal subjects who are homozygous for the mutation (TT) have red cell folate status some 20% lower than expected. It is …now established that the prevalence of the TT genotype is significantly higher among spina bifida cases and their parents. Nevertheless, our studies show that the variant does not account for the reduced blood folate levels in many NTD affected mothers. We conclude that low maternal folate status may in itself be the most important risk factor for NTDs and that food fortification may be the only population strategy of benefit in the effort to eliminate NTDs. Show more

Keywords: Folate status, methylenetetrahydrofolate reductase, neural tube defects, thermolabile MTHFR, red cell folates, pregnancy

Citation: Biofactors, vol. 10, no. 2-3, pp. 291-294, 1999

Authors: Itokawa, Y. | Hashizume, N. | Asano, M. | Igarashi, O. | Mino, M. | Ihara, H. | Ishiwata, Y. | Kadowaki, H. | Kubota, N. | Okazaki, M. | Sueki, K. | Ishida, Y. | Gorin, M. | Sato, T. | Sayama, Y. | Shimomura, K. | Takano, H. | Nakamura, T. | Hanawa, M. | Niimura, H. | Morio, T. | Chibata, I. | Okuda, K.

Article Type: Research Article

Abstract: Standard reference ranges for all laboratory test values are mandatory. This study was designed to establish a reference range for blood vitamin B_{1} levels, since the normal range has not been determined in the Japanese population. We founded the Japan Committee for Vitamin Laboratory Standards, which was incorporated with the Vitamin Society of Japan and the Japanese Society of Nutrition and Food Science. We standardized whole blood vitamin B_{1} levels using three HPLC techniques (post‐column reverse‐phase HPLC, pre‐column reverse‐phase HPLC, and precolumn GP‐HPLC). The reference range was obtained in 54 volunteers administered a 1,800 kcal diet …with 2 mg of vitamin B_{1} (1.74 mg measured) daily to avoid marginal vitamin B_{1} deficiency in the population. The range for each assay was 26–47, 28–51, and 28–56 ng/ml, respectively. Our data suggest that 26–28 ng/ml is the lower limit of normal for whole blood vitamin B_{1} , but further studies in a larger population are needed in order to obtain more definitive results. Show more

Citation: Biofactors, vol. 10, no. 2-3, pp. 295-299, 1999

Authors: Horiuchi, Masahisa | Kobayashi, Keiko | Masuda, Mina | Terazono, Hiroki | Saheki, Takeyori

Article Type: Research Article

Abstract: We isolated a mouse homologue cDNA of pyruvate dehydrogenase (PDH) kinase 4 (PDK4) with differential mRNA display as an up‐regulated gene in the hypertrophied ventricles of juvenile visceral steatosis (JVS) mice with systemic carnitine deficiency. The PDK4 mRNA level was 5 times higher in JVS mice than in control mice under fed conditions. After 24 h starvation, this level increased to 20 times in JVS and 7 times in control, compared with the control fed level. On the other hand, carnitine administration reduced the high level of PDK4 mRNA in JVS mice to the control fed level. In control mice, …the change in PDK4 mRNA was inversely correlated with the change in PDH activity. In JVS mice, however, the PDK4 mRNA level was not always correlated with the active‐form PDH level. Show more

Keywords: Carnitine deficiency, cardiac hypertrophy, differential display, juvenile visceral steatosis mouse, pyruvate dehydrogenase kinase

Citation: Biofactors, vol. 10, no. 2-3, pp. 301-309, 1999