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G Witz

Publications and source records attributed to G Witz.

At least 55 records · Page 3Linked to original sources
PubMed1989

Biological interactions of alpha,beta-unsaturated aldehydes.

This article describes the chemical nature of alpha,beta-unsaturated aldehydes and some of their toxicological effects based on their ability to function as direct-acting alkylating agents. Selected compounds discussed include alpha,beta-unsaturated aldehydic environmental pollutants, metabolites of xenobiotics and natural products, and lipid peroxidation--and DNA oxidation products derived from cellular constituents. Briefly reviewed are sources and mechanisms of formation of the aldehydes, their reactivity with respect to glutathione and amino-groups, their toxicity based on interaction with sulfhydryl and amino targets in cells, and modulation of their toxicity by metabolism.

Aldehydes↗
PubMed1989

Arachidonic acid potentiates superoxide anion radical production by murine peritoneal macrophages stimulated with tumor promoters.

The role of arachidonic acid (AA) metabolism in the stimulation of oxygen radical production by murine peritoneal macrophages treated with tumor promoters was assessed. In vivo administration of the phospholipase A2 inhibitor dibromacetophenone, the anti-inflammatory steroid fluocinolone acetonide or the lipoxygenase inhibitor nordihydroguiaretic acid just prior to i.p. injection of phorbol-12-myristate-13-acetate (PMA, 100 ng) into unmanipulated CD-1 female mice resulted in a dose-dependent decrease in the number of peritoneal exudate cells (PEC) producing superoxide anion radical (O2) as assessed by the reduction of nitroblue tetrazolium, i.e. the formation of formazan-positive PEC. The cycloxygenase inhibitor indomethacin had no effect on the number of formazan-positive PEC caused by PMA treatment. The ability of PMA, phorbol-12,13-dibutyrate mezerein, phorbol-12,13-diacetate and 4-O-Me-PMA to stimulate the production of oxygen radicals by murine peritoneal macrophages correlated with their ability to stimulate the release of [3H]AA equivalents from the macrophages. The calcium ionophore A23187 which stimulated significant [3H]AA equivalent release did not stimulate superoxide anion radical production by the macrophages. PMA administered i.p. to SENCAR mice increased the number of formazan-positive PEC 4-to 5-fold compared with similarly treated C57BL/6 mice. PMA also stimulated the release of twice the amount of [3H]AA equivalents from peritoneal macrophages from SENCAR mice compared with that released by macrophages from C57BL/6 mice. The addition of low concentrations of AA (1-10 microM) in vitro to casein-elicited murine peritoneal macrophages treated with low concentrations of PMA (1 ng/ml) resulted in a 2-fold potentiation of the amount of superoxide anion radical produced compared with PMA treatment alone as assessed by the reduction of cytochrome c. These results demonstrate that AA and/or a lipoxygenase product can potentiate the production of oxygen radicals by murine peritoneal macrophages treated with tumor promoters.

Animals↗
PubMed1989

Tumor promoters differ in their ability to stimulate superoxide anion radical production by murine peritoneal exudate cells following in vivo administration.

The production of superoxide anion radicals by murine peritoneal exudate cells (PECs) following intraperitoneal (i.p.) injection of mouse skin tumor promoters was assessed in vitro by the reduction of nitroblue tetrazolium (NBT). Phorbol-12-myristate-13-acetate (PMA) or mezerein when administered i.p. to CD-1 female mice at a dose of 0.1 microgram caused an inflammatory response in the peritoneal cavity. PMA (0.1 microgram) also caused an increase in the number of PEC reducing NBT, i.e. formazan-positive PECs (20% positive cells) as compared to vehicle control from 15 min through 2 h following i.p. administration to unmanipulated mice. In the same system, dose-response studies demonstrated that 4-O-methyl-phorbol myristate acetate (4-O-Me-PMA) and mezerein were approximately 50 times less active than PMA, while phorbol dibutyrate (PDB), phorbol diacetate (PDA), phorbol and the calcium ionophore A23187 did not cause an increase in the number of formazan-positive PECs at the doses used. When the same compounds (0.1 microgram) were administered to mice which had been pretreated i.p. with thioglycollate 6 days prior to the experiment, PMA, PDB, 4-O-Me-PMA, mezerein and A23187 all caused an increase in the number of formazan-positive PECs 2 h after treatment. The PEC which reduced NBT in response to tumor promoters were predominantly adherent and esterase positive cells, suggesting they were macrophages. These results indicate that in vivo administration of tumor promoters results in the production of superoxide anion radicals by murine peritoneal macrophages and that the physiological state of the macrophages is important in the response to tumor promoters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The role of free radicals in tumor promotion.

A role has been suggested for free radicals and active states of oxygen in tumor promotion. There are a number of lines of support for this hypothesis, but no definitive evidence. The hypothesis has proven of value in leading to the development of models pertinent to understanding the mechanism of action of tumor promoters.

Animals↗
PubMed1989

Metabolism and toxicity of trans,trans-muconaldehyde, an open-ring microsomal metabolite of benzene.

We have previously hypothesized that ring-opened metabolites may play an important role in benzene toxicity. In this paper we review recent work related to this hypothesis. trans,trans-Muconaldehyde (TTM), a six-carbon diene dialdehyde, was shown by our laboratory to be a microsomal metabolite of benzene. This compound is a ring-opened metabolite of benzene that is hematotoxic in mice. The toxicity of TTM may stem in part from its ability to act as a direct-acting alkylating agent involving interaction with cellular sulfhydryls and/or amino groups. On the other hand, metabolism to the diacid trans,trans-muconic acid (MA), a known urinary metabolite of benzene, may represent detoxification since this results in loss of electrophilicity of the compound. Preliminary results indicate that TTM can be metabolized to MA in vitro and in vivo. The interaction of TTM in vitro with macrophages and neutrophils, key cells in the bone marrow, results in cell membrane changes, including loss of activity in the plasma membrane-bound NADPH-dependent oxidase and decreases in membrane lipid fluidity. Deoxyguanosine also was found to react with TTM, forming several different products. These findings may be due to TTM acting directly as an alkylating agent.

Aldehydes↗
PubMed1989

Chromatographic and spectrophotometric characterization of adducts formed during the reaction of trans,trans-muconaldehyde with 14C-deoxyguanosine 5'-phosphate.

Mice liver microsomes oxidatively open the benzene ring to form trans,trans-muconaldehyde, a hematotoxic unsaturated aldehyde. In the present studies, 4.5 mumole trans,trans-muconaldehyde was reacted with 14C-2'deoxyguanosine 5'-phosphate in phosphate buffer. Products were separated by high performance liquid chromatography (HPLC). Absorbance was monitored using a diode array detector, and aliquots of the HPLC eluant were collected for UV spectrophotometric analysis and scintillation counting. Under these conditions, deoxyguanosine 5'-phosphate eluted at 12.5 min and muconaldehyde at 22.0 min. The HPLC and radioactivity profiles of the muconaldehyde/deoxyguanosine reaction mixture indicated the presence of multiple adducts. Three adducts were detected eluting at 36, 39, and 42 min, which represented approximately 2.5, 2.5, and 1% of the radioactivity, respectively. These adducts had similar UV spectra with absorption maxima between 334 and 347 nm. Another product of the reaction mixture, eluting at 19.0 min and accounting for 10% of the radioactivity, was also observed. This compound had absorption maxima at 348 and 372 nm. These results suggest that trans,trans-muconaldehyde can react with deoxyguanosine monophosphate in vitro under physiological conditions to form stable adducts. Studies are being conducted to determine the structure of these adducts and whether these adducts are formed by the reaction of DNA with muconaldehyde or metabolically activated benzene.

Aldehydes↗
PubMed1989

Studies on the mechanism of benzene toxicity.

Using the 59Fe uptake method of Lee et al. it was shown that erythropoiesis in female mice was inhibited following IP administration of benzene, hydroquinone, p-benzoquinone, and muconaldehyde. Toluene protected against the effects of benzene. Coadministration of phenol plus either hydroquinone or catechol resulted in greatly increased toxicity. The combination of metabolites most effective in reducing iron uptake was hydroquinone plus muconaldehyde. We have also shown that treating animals with benzene leads to the formation of adducts of bone marrow DNA as measured by the 32P-postlabeling technique.

Aldehydes↗
PubMed1988

The development of contact hypersensitivity in mouse skin is suppressed by tumor promoters.

The ability of tumor promoters to suppress the development of contact hypersensitivity (CHS) was assessed by the mouse ear swelling assay. Application of the complete or second stage tumor promoters phorbol-12-myristate-13-acetate (PMA, 2 micrograms), croton oil (1%), benzoyl peroxide (20 mg), mezerein (2 micrograms), or phorbol-12-retinoate-13-acetate (PRA, 2 micrograms) to the abdominal surface of CF-1 female mice for 1 week (three treatments) prior to the sensitization of the same location with 0.5% 1-chloro-2,4-dinitrobenzene (DNCB) resulted in a 50% suppression (p less than 0.05) of the CHS response to DNCB. The first stage tumor promoters 4-O-Me-PMA (80 micrograms), calcium ionophore A23187 (80 micrograms), hydrogen peroxide (15%) and the non-promoting analogs phorbol-12,13-diacetate (PDA, 20 micrograms), phorbol (80 micrograms) or acetone did not suppress the response. The suppression of the development of CHS caused by PMA was dependent on the promoter being applied at the site of induction and was inhibited by application of the phospholipase A2 inhibitor dibromoacetophenone (100 micrograms), the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 100 micrograms), or the antiinflammatory steroid fluocinolone acetonide (2 micrograms). Application of PMA or mezerein 24 h prior to challenge with DNCB, to the ears of mice previously sensitized with DNCB resulted in a significant enhancement of the ear swelling response by 60% and 110%, respectively, compared with controls. The results demonstrate that tumor promoters suppress the development of CHS, and suggest the possibility that second stage promotion may involve suppression of the development of a tumor specific immune response.

Animals↗
PubMed1988

Inhalation of ozone produces a decrease in superoxide anion radical production in mouse alveolar macrophages.

The potentiation of fatal bacterial pneumonia in mice by prior inhalation of ozone occurs at levels of this oxidant pollutant that are frequently present in ambient air. A likely mechanism for this effect is an ozone-induced inhibition in the ability of pulmonary alveolar macrophages (PAM) to produce superoxide anion radical (O2-) demonstrated in the present study. A 25% decrease in PAM O2- production, as measured by nitroblue tetrazolium reduction, occurred after exposure of Swiss-Webster mice to 0.11 ppm ozone for 3 h (p less than 0.05). After 1 ppm there was almost complete inhibition of O2- release. In contrast, the rat, which is highly resistant to the potentiation of bacterial infections by ozone, was less sensitive to inhibition of PAM O2- production, as measured by cytochrome c reduction (mouse IC50, 0.41 ppm; rat IC50, 3.0 ppm ozone for 3 h). The observed decrement in mouse PAM O2- production was not associated with any change in phagocytic ability, as measured by both latex bead ingestion and 51Cr-labeled sheep red blood cell ingestion. This decrease in O2- production in the presence of normal phagocytic activity is analogous to certain of the findings in the neutrophils of children with chronic granulomatous disease. A decrease in rat PAM membrane cytochrome b558 levels was observed after ozone exposure of 3 ppm for 3 h, preliminarily suggesting that the mechanism by which ozone interferes with PAM O2- production may be through interaction with this heme-containing electron carrier.

Administration, Inhalation↗
PubMed1987

Inhibition of microsomal cytochrome c reductase activity by a series of alpha, beta-unsaturated aldehydes.

alpha, beta-Unsaturated aldehydes are reactive and cytotoxic compounds which occur in the environment and are also formed in vivo. Many of these aldehydes have been reported to inhibit hepatic cytochrome P-450. Our laboratory has shown that trans,trans-muconaldehyde (a possible metabolite of benzene) as well as acrolein and crotonaldehyde, when added to hepatic microsomes, decreased cytochrome P-450 (measured spectrophotometrically). Additional studies showed that several alpha, beta-unsaturated aldehydes also inhibited hepatic microsomal NADPH-cytochrome c reductase. Acrolein, crotonaldehyde and trans,trans-muconaldehyde all decreased NADPH-cytochrome c reductase activity in vitro. Concentrations of 0.5, 1.0 and 1.5 mM acrolein decreased activity to 60, 26 and 11% of control respectively. Similar concentrations of trans,trans-muconaldehyde inhibited NADPH-cytochrome c reductase. Crotonaldehyde was a less effective inhibitor of this enzyme. Propionaldehyde, a saturated aldehyde, had no effect on NADPH-cytochrome c reductase activity. Time course experiments with acrolein over a period of 5-45 min suggest that the loss of NADPH-cytochrome c reductase activity is non-linear. The addition of reduced glutathione protected against the inhibition of reductase activity by acrolein. Formation of these aldehydes and their subsequent inhibition of these enzymes may have important consequences in xenobiotic metabolism.

Acrolein↗
PubMed1987

Inhibition by reactive aldehydes of superoxide anion radical production from stimulated polymorphonuclear leukocytes and pulmonary alveolar macrophages. Effects on cellular sulfhydryl groups and NADPH oxidase activity.

Alpha,beta-unsaturated aldehydes such as acrolein (ACR) and crotonaldehyde (CRO) have been shown previously in our laboratory to inhibit the production of superoxide anion radical (O2-) by stimulated phagocytic cells in vitro in a dose-related manner. Based on the known reactivity of these compounds towards cellular sulfhydryls (SH), the present studies were aimed at investigating cellular SH status in relation to O2- production. Plasma membrane surface SH groups were measured using carboxypyridinedisulfide and monitoring the resultant formation of mixed disulfides through assay of thione released into the supernatant fraction. Intracellular non-protein sulfhydryls were measured using 5,5'-dithiobis-2-nitrobenzoic acid. In both human polymorphonuclear leukocytes (PMN) and rat pulmonary alveolar macrophages (PAM) there was a dose-related decrease in surface SH and soluble SH after ACR and CRO treatment. Propionaldehyde, a three-carbon saturated aldehyde, was without effect. The decrease in surface SH was greater than the decrease in soluble SH. In addition, in PMN and PAM preincubated with 5-40 microM ACR, there was a dose-related inhibition in the rate of O2- production with no effect on the lag time as measured by cytochrome c reduction. In stimulated PMN, there was a dose-related decrease in the rate after addition of 5-40 microM ACR. These data suggest that changes in SH status by reactive aldehydes can modulate the activity of the plasma membrane NADPH oxidase responsible for O2- production.

Aldehydes↗
PubMed1987

Mutagenicity and toxicity studies of several alpha,beta-unsaturated aldehydes in the Salmonella typhimurium mutagenicity assay.

alpha,beta-Unsaturated aldehydes are reactive compounds which are ubiquitous in the environment. This class of compounds has been tested for mutagenicity in Salmonella typhimurium by a number of groups who have obtained differing results. The present studies were undertaken to test the mutagenicity and toxicity of two novel alpha, beta-unsaturated aldehydes, specifically trans, trans-muconaldehyde and trans-4-hydroxynonenal, and to re-examine the mutagenicity of crotonaldehyde. Trans, trans-muconaldehyde is a newly found microsomal metabolite of benzene, and trans-4-hydroxynonenal is a toxic aldehyde formed endogenously during lipid peroxidation. Compounds were tested in S. typhimurium strain TA 100 using a 30-min liquid preincubation procedure. The present mutagenicity studies indicate that these alpha, beta-unsaturated aldehydes at first appear to be mutagenic, although only at concentrations which decrease survival counts, and result in a disappearance of the bacterial lawn. The colonies observed on mutagenicity test plates are not mutants but rather pin point survivors.

Aldehydes↗
PubMed1987

Formation of reactive metabolites from benzene.

Rat liver mitoplasts were incubated first with [3H]dGTP, to form DNA labeled in G, and then with [14C]benzene. The DNA was isolated and upon isopycnic density gradient centrifugation in CsCl yielded a single fraction of DNA labeled with both [3H] and [14C]. These data are consistent with the covalent binding of one or more metabolites of benzene to DNA. The DNA was enzymatically hydrolyzed to deoxynucleosides and chromatographed to reveal at least seven deoxyguanosine adducts. Further studies with labeled deoxyadenine revealed one adduct on deoxyadenine. [3H]Deoxyguanosine was reacted with [14C]hydroquinone or benzoquinone. The product was characterized using uv, fluorescence, mass and NMR spectroscopy. A proposed structure is described.

Animals↗
PubMed1987

Alteration of erythrocyte membrane fluidity by heavy metal cations.

Fluorescence polarization measurements were carried out on erythrocyte ghosts treated with heavy metal cations. Membranes labelled with the fluorescent lipid probe all-trans 1,6-diphenyl-1,3, 5-hexatriene (DPH) had increased DPH polarization (P) values, consistent with increased membrane lipid viscosity, when treated with 10(-3)-10(-2) M of the chloride salts of cadmium, zinc or lead for 1 hour at 37 degrees C, but not with calcium. Using cadmium as a prototype heavy metal, additional studies showed that exposure of ghosts to cadmium also increased the native protein fluorescence polarization. These increases in P values were observed at temperatures ranging from 15-40 degrees C. These data suggest that interaction of cadmium and other heavy metals with cellular membranes may alter membrane lipid and possibly membrane protein fluidity, which may contribute to abnormal cellular function.

Cadmium↗
PubMed1986

High-performance liquid chromatography analysis of the thiobarbituric acid adducts of malonaldehyde and trans,trans-muconaldehyde.

A reversed-phase HPLC method is described for the separation and analysis of the thiobarbituric acid (TBA) adducts of the reactive aldehydes muconaldehyde (MUC) and malonaldehyde (MDA). The TBA adduct of malonaldehyde was synthesized, purified, and its structure elucidated, for use as standard in quantitative HPLC studies. A detection limit of 1 X 10(-14) mol was achieved for the MUC:TBA and MDA:TBA adducts using the double monochromator fluorometric detector, 7 X 10(-13) mol was the detection limit using a variable wavelength uv-visible detector. Direct on-line identification of the eluting aldehyde:TBA adducts was achieved by the use of a diode-array uv-visible detector. The chromatographic behavior of the adducts under different mobile phase conditions was also examined. This HPLC methodology was used for the identification of muconaldehyde as a product of benzene oxidation in a hydroxyl radical generating system.

Aldehydes↗