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S R Tannenbaum

Publications and source records attributed to S R Tannenbaum.

At least 55 records · Page 3Linked to original sources
PubMed1997

Comparative metabolism of tamoxifen and DNA adduct formation and in vitro studies on genotoxicity.

Tamoxifen has been demonstrated to be hepatocarcinogenic in some but not all strains of the laboratory rat and is not a carcinogen in the mouse. To resolve the question of whether tamoxifen is genotoxic in humans, many laboratories have studied its interspecies metabolism and its propensity to form DNA adducts. This review of the literature concludes that tamoxifen is not genotoxic in adult women based on comparative metabolism and the absence of measurable DNA adducts in women treated with tamoxifen. In addition, tamoxifen does not appear to be mutagenic in in vitro assays.

Animals↗
PubMed1996

The chemistry of the S-nitrosoglutathione/glutathione system.

S-Nitrosothiols have generated considerable interest due to their ability to act as nitric oxide (NO) donors and due to their possible involvement in bioregulatory systems-e.g., NO transfer reactions. Elucidation of the reaction pathways involved in the modification of the thiol group by S-nitrosothiols is important for understanding the role of S-nitroso compounds in vivo. The modification of glutathione (GSH) in the presence of S-nitrosoglutathione (GSNO) was examined as a model reaction. Incubation of GSNO (1 mM) with GSH at various concentrations (1-10 mM) in phosphate buffer (pH 7.4) yielded oxidized glutathione, nitrite, nitrous oxide, and ammonia as end products. The product yields were dependent on the concentrations of GSH and oxygen. Transient signals corresponding to GSH conjugates, which increased by one mass unit when the reaction was carried out with 15N-labeled GSNO, were identified by electrospray ionization mass spectrometry. When morpholine was present in the reaction system, N-nitrosomorpholine was formed. Increasing concentrations of either phosphate or GSH led to lower yields of N-nitrosomorpholine. The inhibitory effect of phosphate may be due to reaction with the nitrosating agent, nitrous anhydride (N2O3), formed by oxidation of NO. This supports the release of NO during the reaction of GSNO with GSH. The products noted above account quantitatively for virtually all of the GSNO nitrogen consumed during the reaction, and it is now possible to construct a complete set of pathways for the complex transformations arising from GSNO + GSH.

Glutathione↗
PubMed1996

Bicarbonate inhibits N-nitrosation in oxygenated nitric oxide solutions.

N-Nitrosation in oxygenated nitric oxide (NO middle dot) solutions was previously shown to be significantly inhibited by phosphate and chloride presumably by anion scavenging of the nitrosating agent nitrous anhydride, N2O3 (Lewis, R. S., Tannenbaum, S. R., and Deen, W. M. (1995) J. Am. Chem. Soc. 117, 3933-3939). Here, bicarbonate is shown to exhibit this same inhibitory effect. Rate constants for reaction of morpholine, phosphate, and bicarbonate with N2O3 relative to N2O3 hydrolysis at pH 8.9 were determined to be (3.7 +/- 0.2) x 10(4) M-1, (4.0 +/- 0.9) x 10(2) M-1, and (9.3 +/- 1.5) x 10(2) M-1, respectively. The morpholine and phosphate rate constants at pH 8.9 are similar to those reported at pH 7.4 assuring that these results are relevant to physiological conditions. The rate constant for this previously unrecognized reaction of bicarbonate with N2O3 suggests the strong scavenging ability of bicarbonate; accordingly, bicarbonate may contribute to reducing deleterious effects of N2O3. This is biologically important due to substantial bicarbonate concentrations in vivo, approximately 30 mM. Bicarbonate was previously shown to alter peroxynitrite reactivity; however, carbon dioxide is the probable reactive species. Bicarbonate is therefore potentially important in determining the fate of two reactive species generated from nitric oxide, N2O3 and ONOO-, and may thus act as a regulator of NO middle dot-induced toxicity.

Bicarbonates↗
PubMed1996

Nitric oxide production in SJL mice bearing the RcsX lymphoma: a model for in vivo toxicological evaluation of NO.

SJL mice spontaneously develop pre-B-cell lymphoma that we hypothesized might stimulate macrophages to produce nitric oxide (NO.). Transplantation of an aggressive lymphoma (RcsX) was used to induce tumor formation. Urinary nitrate excretion was measured as an index of NO. production and was found to increase 50-fold by 13 days after tumor injection. NO. production was prevented by the addition of a nitric oxide synthase (NOS) inhibitor. The expression of inducible NOS (iNOS) in various tissues was estimated by Western blot analysis and localized by immunohistochemistry. The synthase was detected in the spleen, lymph nodes, and liver of treated but not control mice. To assess whether the iNOS-staining cells were macrophages, spleen sections from ResX-bearing animals were costained with anti-iNOS antibody and the anti-macrophage antibody moma-2. Expression of iNOS was found to be limited to a subset of the macrophage population. The concentration of gamma-interferon, a cytokine known to induce NO. production by macrophages, in the serum of tumor-bearing mice, was measured and found to be elevated 25-fold above untreated mice. The ability of ResX-activated macrophages to inhibit splenocyte growth in primary culture was estimated and macrophage-derived NO. was found to inhibit cell division 10-fold. Our findings demonstrate that ResX cells stimulate NO. production by macrophages in the spleen and lymph nodes of SJL mice, and we believe this experimental model will prove useful for study of the toxicological effects of NO. under physiological conditions.

Animals↗
PubMed1996

The role of nitric oxide (NO.) in the carcinogenic process.

The inflammatory process has long been known to be a risk factor for human cancers, particularly of the lung, bladder, colon, stomach, and female breast. Earlier hypothesis cited production of oxygen radicals, release of cytokines, and synthesis of prostaglandins and leukotrienes as biochemical modulators of the carcinogenic process. The discovery of NO. as a product of cells in the immune system has implicated this chemical in the mechanism of carcinogenesis, particularly when NO. is overproduced over a long period of time. After briefly reviewing the important chemical reactions of NO. under physiological conditions, we examine how the chemistry of its key reactants toward biologically important molecules relate to DNA damage and cytotoxicity. In these two processes, NO may play an important role in currently accepted models of multistage carcinogenesis.

Apoptosis↗
PubMed1996

NO-induced oxidative stress and glutathione metabolism in rodent and human cells.

Nitric oxide (NO.), a radical species produced by many types of cells, is known to play a critical role in both regulatory processes and cell defense, yet it may also participate in collateral reactions, leading to DNA damage and cell death in both NO-generating and neighboring cells. Glutathione has been shown to protect cells from the toxic effects of free radicals and reactive oxygen species. The goal of this study was to investigate whether differences in glutathione metabolism could account for the resistance or sensitivity to cell killing by NO.. The cytotoxic effect of NO. was examined in CHO-AA8 (Chinese Hamster Ovary) cells and TK6 (human lymphoblastoid) cells pretreated with L-buthionine SR-sulfoximine (BSO), a potent inhibitor of gamma-glutamylcysteine synthetase, and with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), an irreversible inhibitor of glutathione reductase. The consequences resulting from the depletion of glutathione levels and from the arrest of oxidoreduction allowed us to show the involvement of glutathione in protecting cells from NO. and to investigate the importance of changes in glutathione metabolism on NO-induced toxicity. In CHO-AA8 cells, we found that treatment with NO. resulted in the oxidation of reduced glutathione (GSH) to oxidized glutathione (GSSG) and to mixed glutathione disulfides (GSSR). The resulting depletion of GSH stimulated its de novo synthesis, enabling the cells to resist killing by NO.. A slight difference in GSH metabolism was observed in TK6 cells. NO. led to an increase in GSSG levels similar to that observed in CHO-AA8 cells, however, a decrease in GSH levels, no change in GSSR levels, and higher levels of toxicity were also found, suggesting that NO-treated TK6 cells are not as competent in GSH homeostasis as CHO cells. We conclude that GSH is involved in protecting cells from killing by NO. and that both de novo synthesis of GSH and GSSG reduction are important in maintaining an adequate level of protection for the cells.

Animals↗
PubMed1996

Kinetics of S-nitrosation of thiols in nitric oxide solutions.

The S-nitroso adducts of nitric oxide (NO) may serve as carriers of NO and play a role in cell signaling and/or cytotoxicity. A quantitative understanding of the kinetics of S-nitrosothiol formation in solutions containing NO and O2 is important for understanding these roles of S-nitroso compounds in vivo. Rates of S-nitrosation in aqueous solutions were investigated for three thiols: glutathione, N-acetylcysteine, and N-acetylpenicillamine. Nitrous anhydride (N2O3), an intermediate in the formation of nitrite from NO and O2, is the most likely NO donor for N-nitrosation of amines as well as for S-nitrosation of thiols, at physiological pH. This motivated the use of a competitive kinetics approach, in which the rates of thiol nitrosation were compared with that of a secondary amine, morpholine. The kinetic studies were carried out with known amounts of NO and O2 in solutions containing one thiol (400 microM) and morpholine (200-5700 microM) in 0.01 M phosphate buffer at pH 7.4 and 23 degrees C. It was found that disulfide formation, transnitrosation reactions, and decomposition of the S-nitrosothiols was expressed as k7[N2O3][RSH], where RSH represents the thiol. The rate constant for S-nitrosation relative to that for N2O3 hydrolysis (k4) was found to be k7/k4 = (4.15 +/- 0.28) x 10(4), (2.11 +/- 0.11) x 10(4), and (0.48 +/- 0.04) x 10(4) M-1 for glutathione, N-acetylcysteine, and N-acetylpenicillamine, respectively. The overall (observed) rates of nitrosothiol formation reflect the fact that [N2O3] varies [NO]2[O2] and that [N2O3] also depends on [RSH] and the concentration of phosphate. Using a detailed kinetic model to account for these effects, the present results could be reconciled with apparently dissimilar findings reported previously by others.

Acetylcysteine↗
PubMed1995

Kinetic analysis of the fate of nitric oxide synthesized by macrophages in vitro.

To investigate the fate of nitric oxide (NO) synthesized by activated macrophages, the concentrations of NO and its principal reaction products, nitrite (NO2-) and nitrate (NO3-), were measured as a function of time in suspension cultures of RAW264.7 macrophages attached to microcarrier beads. Synthesis of NO became evident 2-5 h after stimulation of the cells, and steady concentrations of NO were achieved after about 9 h. The appearance of NO in the extracellular fluid coincided with the appearance of NO2- and NO3-, which were formed thereafter at approximately equal and constant rates. Using a kinetic model based on rate constants measured previously in cell-free systems, only half of the NO2- formed could be accounted for by the reaction of NO with O2. It is known that NO reacts with superoxide (O2.) to give peroxynitrite and that NO also reacts with peroxynitrite to yield NO2-, so that the latter reaction may explain the "excess" NO2- formation. Adding superoxide dismutase to the medium markedly reduced the ratio of NO3- to NO2-, consistent with the hypothesis that NO3- in the medium results primarily from the extracellular reaction of NO with O2-.. The addition of morpholine, a model amine, resulted in formation of N-nitrosomorpholine, concurrent with the other products. Measured rates of nitrosomorpholine formation were 6-fold lower than predictions based on kinetics in simple solutions, suggesting that in the cell culture system there were additional reactions that lowered the concentration of nitrous anhydride, the principal nitrosating agent formed from NO and O2.

Cell Line↗
PubMed1995

Nitric oxide production in relation to spontaneous B-cell lymphoma and myositis in SJL mice.

SJL mice spontaneously develop B cell lymphomas (historically described as reticulum cell sarcomas) by 12 months of age and inflammatory muscle disease (myositis) by 6 months of age. Tumors originate in mesenteric lymph nodes and in Peyer's patches and resemble human germinal center lymphomas. The growth of reticulum cell sarcomas is completely dependent on cytokine production by normal T cells. The spontaneous myositis, which resembles human idiopathic myositis, is characterized by various abnormalities in skeletal muscle, including infiltration with inflammatory cells consisting primarily of macrophages. The participation of different cytokines in the pathogenesis of the lymphoma and the massive invasion of macrophages into muscle tissues led us to investigate the possible involvement of nitric oxide (NO.), which is known to be synthesized by activated macrophages under inflammatory conditions. Elevated NO. production, measured by urinary nitrate excretion, by SJL mice in comparison with BALB/c control mice was observed as early as 7 weeks of age. Both aging and degree of spontaneous myositis correlated with increased nitric oxide production. Oral administration of N-monomethyl-L-arginine, an inhibitor of nitric oxide synthase (NOS), reduced urinary nitrate excretion and also the severity of myositis. Immunohistochemical analysis revealed the presence of inducible NOS (iNOS) in cells in the spleen, lymph nodes, and skeletal muscle. The iNOS is primarily responsible for the enhanced nitric oxide production. Morphology of cells that stained positive for iNOS was similar to that of macrophages infiltrating into the affected tissues. Chronic production of elevated amounts of nitric oxide by the SJL mice, therefore, provides a useful in vivo model for future studies of cellular damage resulting from endogenously produced NO.in combination with oxygen radicals.

Amino Acid Oxidoreductases↗
PubMed1995

Lysine adducts between methyltetrahydrophthalic anhydride and collagen in guinea pig lung.

The formation of adducts between methyltetrahydrophthalic anhydride (MTHPA), an important industrial chemical and potent allergen, and collagen from guinea pig lung tissue was investigated. Collagen peptides were obtained from the lung tissue by homogenization, defatting, washing, and digestion with collagenase. In experiments in vitro, lung tissue was exposed to 8.4 mumol (50 microCi) of 14C MTHPA. The amount of adducts was 97 nmol MTHPA/g of wet tissue as determined from the bound radioactivity. In a study in vivo, four guinea pigs were injected intratracheally with 8.4 mumol of 14C MTHPA each. The amount of adducts was 0-1.2 nmol MTHPA/g of wet tissue (determined by bound radioactivity). N epsilon-methyltetrahydrophthaloyl-L-lysine (MTHPL) was synthesized and characterized by NMR, UV, and mass spectrometry (MS). A method to analyze MTHPL, after derivatization with methanol and pentafluorobenzoyl chloride, using gas chromatography-MS was developed. Analysis of Pronase-digested MTHPA-exposed lung tissue showed a concentration of 19 nmol MTHPL/g wet lung in vitro and between 0 and 0.15 nmol MTHPL/g wet lung in vivo. Thus, 20% in vitro and 12-15% in vivo of the bound radioactivity was found as adducts with lysine. These results are a first step toward studies of allergenic epitopes in proteins and methods for biological monitoring of exposure to acid anhydrides.

Animals↗
PubMed1995

Roles of nitric oxide in inducible resistance of Escherichia coli to activated murine macrophages.

Nitric oxide (NO.) is produced as a cytotoxic free radical through enzymatic oxidation of L-arginine in activated macrophages. Pure NO. gas was previously found to induce the Escherichia coli soxRS oxidative stress regulon, which is readily monitored by using a soxS'::lac fusion. The soxRS system includes antioxidant defenses, such as a superoxide dismutase and a DNA repair enzyme for oxidative damage, and protects E. coli from the cytotoxicity of NO.-generating macrophages. Previous experiments involved exposing E. coli to a bolus of NO. rather than the steadily generated gas expected of activated macrophages. We show here detectable induction of soxS transcription by NO. delivered at rates as low as 25 microM/h. Maximal induction was observed at 25 microM NO. per h under anaerobic conditions but at 125 microM/h aerobically. After incubation with murine macrophages, soxS expression was induced in the phagocytosed bacteria up to approximately 30-fold after an 8-h exposure. This in vivo induction was almost completely eliminated by the NO. synthase inhibitor NG-monomethyl-L-arginine. The inhibitor increased the survival of a delta soxRS strain but not that of wild-type E. coli after phagocytosis, which suggests that induction of the soxRS regulon by NO. can counteract most of the cytotoxic effects of NO. production by the macrophages. We show that the soxRS-regulated enzyme glucose-6-phosphate dehydrogenase is an important element of the defense against macrophages.

Animals↗
PubMed1995

Plasma arginine, citrulline, and ornithine kinetics in adults, with observations on nitric oxide synthesis.

The plasma fluxes of ornithine (Orn), arginine (Arg), and citrulline (Cit) and rate of conversion of labeled ornithine-to-citrulline (QOrn-->Cit) were estimated in six healthy adult men receiving an arginine-rich or arginine-free L-amino acid-based diet, each for 6 days. On day 7 an 8-h (3-h fast, 5-h fed) primed continuous intravenous infusion of L-[guanido-15N,15N] arginine, L-[ureido-13C]citrulline, L-[5,5,2H2]ornithine, and L-[5,5,5-2H3]leucine was conducted. Mean citrulline fluxes (mumol.kg-1.h-1) were 10.4-13.6 for the various conditions and/or diets and remained unchanged (P > 0.05). Arginine flux was lowered (P < 0.01) by 38% for fed state during arginine-free period. Ornithine fluxes for arginine-rich were (P < 0.01) reduced with the arginine-free diet. Rates of QOrn-->Cit declined by 30% (P < .05) during the fed arginine-free period. Short-term restriction in the dietary supply of arginine did not alter the rate of whole body nitric oxide synthesis. One subject showed a very high output of nitrate on arginine-free diet (6 times average for remaining subjects).

Adult↗
PubMed1995

Inhaled nitric oxide does not alter endotoxin-induced nitric oxide synthase activity during rat lung perfusion.

Nitric oxide (NO) has been demonstrated to decrease its own synthesis in tissue preparations. We tested the hypothesis that endogenous NO synthesis induced by lipopolysaccharides (LPS) would be decreased by exogenous NO during isolated lung perfusion. Rats were pretreated with either saline or LPS 48 h before lung harvest. Endogenous NO synthase activity was measured as conversion of L-[14C]-arginine to L-[14C]citrulline during 90 min of perfusion. NO (100 ppm) was added to the ventilating gas during perfusion of lungs from one group of control or LPS-treated rats. A second group of control or LPS-treated rats was exposed chronically to 100 ppm NO for the 48 h before lung harvest, in addition to receiving 100 ppm NO added to the ventilating gas during lung perfusion. We conclude that conversion of L-[14C]arginine to L-[14C]citrulline was minimal in control lungs and increased in response to LPS pretreatment. NO added to the ventilating gas for the 90 min of ex vivo perfusion did not alter the rate of L-[14C]citrulline production. In vivo exposure to 100 ppm NO for 48 h did not alter the induction of inducible NO synthase activity as measured during ex vivo lung perfusion. This indicates that inhaled NO does not exert negative-feedback inhibition on inducible NO synthase in the ex vivo rat lung.

Administration, Inhalation↗
PubMed1995

Glutathione S-transferase M1 genotype affects aminobiphenyl-hemoglobin adduct levels in white, black and Asian smokers and nonsmokers.

Cigarette smoking is the major cause of bladder cancer in men in the United States, and the arylamines contained in cigarettes smoke, including 4-amino-biphenyl (4-ABP), are believed to play an important role in the induction of bladder cancer among smokers. N-acetylation, which is catalyzed by the genetically controlled hepatic N-acetyltransferase enzyme displaying two phenotypes (slow versus rapid), is a detoxification pathway for arylamines with regard to bladder carcinogenesis. In Los Angeles, CA, non-Hispanic white (white), black, and Asian males have comparable smoking habits and yet dramatically different risks of bladder cancer (31 of 100,000 in whites, 16 of 100,000 in blacks, and 13 of 100,000 in Chinese and Japanese). Previously, we have demonstrated that the prevalence of slow acetylators (the high-risk phenotype) was highest in whites (54%), intermediate in blacks (34%), and lowest in Asians (14%). We also showed that mean 3- and 4-ABP hemoglobin adduct levels were significantly higher in cigarette smokers relative to nonsmokers, and that the level increased with increasing number of cigarettes smoke/day. Most importantly, slow acetylators consistently exhibited higher mean levels of ABP hemoglobin adducts relative to rapid acetylators, regardless of race and level of cigarette smoking. We assessed 151 residents of Los Angeles County (CA) who were either white, black, or Asian (Chinese or Japanese) and over the age of 30 years for their glutathione S-transferase M1 (GSTM1) genotype (null versus non-null), acetylator phenotype (slow versus rapid), levels of 3- and 4-ABP hemoglobin adducts, and current use of tobacco products. Whites (27%) had the highest prevalence of the highest risk profile (slow acetylator, GSTM1 null), followed by blacks (15%) and Asians (2.7%), and the difference was statistically significant (P = 0.006). Whites also had less than one-half the prevalence of the "protective" profile (rapid acetylator, GSTM1 non-null) relative to blacks and Asians (23 versus 57%; P = 0.0001). Regardless of race and level of cigarette smoking, mean levels of 3- and 4-ABP hemoglobin adducts were higher in subjects possessing the higher risk (GSTM1/acetylator profile. Mean level of 4-ABP hemoglobin adduct (adjusting for race, cigarette smoking, and acetylator phenotype) was significantly higher in subjects possessing the GSTM1-null versus GSTM1-non-null genotype (46.5 versus 36.0 pg/g Hb; P = 0.037). The comparable difference in mean levels of 3-ABP hemoglobin adduct was borderline significant (1.6 versus 1.1 pg/g Hb; P = 0.07). Thus, our results suggest that GSTM1 is involved in the detoxification of 3- and 4-ABP and may contribute to the racial variation in bladder cancer incidence among white, black, and Asian males in Los Angeles, CA.

Adult↗
PubMed1995

MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline): metabolism in humans and urinary metabolites in human populations.

The metabolism of the heterocyclic amines has been extensively studied in rodents and limited studies have been conducted in nonhuman primates. A study has been undertaken on the metabolism of 2-amino-3,8-dimethylimadazo[4,5-f]quinoxaline (MeIQx) in human subjects consuming normal cooked foods. A variety of fish and meat products has been cooked in several ways and fed to human volunteers. Urine was collected and analyzed according to methods developed for this purpose. Earlier rodent studies using radioactive MeIQx had suggested that the principal urinary excretion products included unmetabolized MeIQx, MeIQx sulfamate and MeIQx N-glucuronide. Conditions were developed for HPLC analysis of the free amine and its conjugates in human urine and for total hydrolysis of the conjugates to the free amine. Extraction and cleanup from urine were made possible by the availability of suitable monoclonal antibodies to MeIQx which could be used for immunoaffinity chromatography. For sensitive detection of the amounts present in human urine, gas chromatographymass spectrometry (GC-MS) was used in the negative chemical ionization mode. These studies have demonstrated that the distribution of metabolites in humans strongly resembles that in the rat. The sulfamate and N-glucuronide appear to be predominant human metabolites, while no evidence could be found of N-acetyl MeIQx. Subsequent to the studies just described, the methods developed were applied to urines collected in an epidemiological study on aromatic amine metabolism in Los Angeles. The study includes African American, White, and Asian people who have been phenotyped for caffeine acetylator status.

Adult↗
PubMed1994

Nitric oxide production is intensely and persistently increased in tissue by thermal injury.

NO is a major messenger molecule which regulates immunity and vascular tone, serves as a neurotransmitter and participates in wound healing. It has also been known to be increased in vivo by thermal injury. Urinary nitrate excretion and tissue levels of NO synthase activity were measured after a non-lethal thermal injury. Urinary nitrate excretion decreased by 90% 24-48 h after injury, but dramatically increased by 10-fold thereafter for 30-40 days after injury and remained elevated until the wound healed. This response was inhibited by a competitive inhibitor of NO synthase. These rates of urinary nitrate excretion suggest that NO production is dramatically affected by injury in a pattern that is distinct from that observed after lipopolysaccharide administration. On the basis of these findings, we suggest that the hyperdynamic cardiovascular and hypermetabolic responses seen to continue weeks after thermal injury could be a result of the autocrine and paracrine effects of NO generated locally within the tissues in addition to that generated by inflammatory cells.

Amino Acid Oxidoreductases↗