Effect of vitamin E succinate on smokeless tobacco-induced production of nitric oxide by rat peritoneal macrophages and J774A.1 macrophage cells in culture

Cytotoxicity, oxidative stress, and inflammatory response of smokeless tobacco extracts and cytotoxicity of combustible cigarette whole smoke in a 3D oral organotypic buccal cell model

Oral disease is frequently associated with viral and environmental exposures and oral hygiene. The use of tobacco is a risk factor in the development of oral disease. Cytotoxicity, inflammatory response, and oxidative stress have been reported to have a role in the development of oral disease. These three endpoints were evaluated in a 3D human oral buccal model, EpiOral™, following exposure to CORESTA reference smokeless tobacco products (CRPs) and cigarette whole smoke. CRPs for Swedish style snus (CRP1), moist snuff (CRP2), and dry snuff (CRP3) were each extracted in complete artificial saliva (CAS) with a ratio of 300 mg CRP to 1 mL of CAS. Each of the CRP extracts (15-300 mg/ml) were applied to the apical side of a 3D organotypic buccal cell model for 24 or 48 h continuously, then cytotoxicity (LDH), oxidative stress (8-isoprostane), and inflammatory response (IP10, IL-1α, and IL-8) were measured. Experiments with 3R4F cigarettes were conducted by exposing the buccal tissues to whole smoke for a maximum of 2.5 h. Cytotoxicity (MTT) was measured 24 h post-exposure. Exposure of buccal tissues to whole smoke from a cigarette induced a dose-dependent cytotoxic response. In contrast, the CRP extracts elicited minimal cytotoxicity (<15%) when compared to CAS (vehicle control), but time- and dose-dependent effects on oxidative stress and inflammatory response were observed. Collectively, these data demonstrate that a 3D organotypic buccal human model may be used to assess biological mechanisms (MOAs) involved in the development of oral disease following exposure to smokeless tobacco products and may be applicable for differentiation between tobacco product categories.

Effects of vitamin E on reproductive hormones and testis structure in chronic dioxin-treated mice

The purpose of this study was to investigate the effects of vitamin E on reproductive hormones and testis structure in mice treated with 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD). Five experimental groups of a combination of TCDD and vitamin E were designed as follows: 0 ng/kg/d and 0 mg/kg/d (control group), 100 ng/kg/d and 0 mg/kg/d (Group I), 100 ng/kg/d and 20 mg/kg/d (Group II), 100 ng/kg/d and 100 mg/kg/d (Group III), and 100 ng/kg/d and 500 mg/kg/d (Group IV) respectively. Vitamin E and TCDD were given by oral gavage for 7 weeks. The results demonstrated that TCDD decreased the levels of brain gonadotropin releasing hormone (GnRH), testis luteinizing hormone (LH) and follicle stimulating hormone (FSH), serum testosterone and testis spermatozoa number, and damaged testis structure. Vitamin E at 20 mg/kg alleviated the decrease of GnRH; vitamin E at 20, 100, and 500 mg/kg antagonized the decline of LH and FSH; vitamin E at 20 and 100 mg/kg reversed the decrease of testosterone and spermatozoa number; and vitamin E at 100 mg/kg decreased the damage of the testis structure caused by TCDD. The results indicate that vitamin E antagonizes the reproductive endocrine toxicity and alleviates the changes in testicular structure caused by TCDD.

Evaluation of in vitro assays for assessing the toxicity of cigarette smoke and smokeless tobacco

BACKGROUND

In vitro toxicology studies of tobacco and tobacco smoke have been used to understand why tobacco use causes cancer and to assess the toxicologic impact of tobacco product design changes. The need for toxicology studies has been heightened given the Food and Drug Administration's newly granted authority over tobacco products for mandating tobacco product performance standards and evaluate manufacturers' health claims about modified tobacco products. The goal of this review is to critically evaluate in vitro toxicology methods related to cancer for assessing tobacco products and to identify related research gaps.

METHODS

PubMed database searches were used to identify tobacco-related in vitro toxicology studies published since 1980. Articles published before 1980 with high relevance also were identified. The data were compiled to examine (a) the goals of the study, (b) the methods for collecting test substances, (c) experimental designs, (d) toxicologic end points, and (e) relevance to cancer risk.

RESULTS

A variety of in vitro assays are available to assess tobacco smoke that address different modes of action, mostly using non-human cell models. However, smokeless tobacco products perform poorly in these assays. Although reliable as a screening tool for qualitative assessments, the available in vitro assays have been poorly validated for quantitative comparisons of different tobacco products. Assay batteries have not been developed, although they exist for nontobacco assessments. Extrapolating data from in vitro studies to human risks remains hypothetical.

CONCLUSIONS

In vitro toxicology methods are useful for screening toxicity, but better methods are needed for today's context of regulation and evaluation of health claims.

Influence of maternal nicotine exposure on neonatal rat oxidant-antioxidant system and effect of ascorbic acid supplementation

There have been a few studies that examined the oxidative stress effects of nicotine during pregnancy and lactation. We aimed to determine the adverse effects of maternal nicotine exposure during pregnancy and lactation on oxidant-antioxidant system, and to determine a protective effect of ascorbic acid (Asc). Gravid rats were assigned into four groups. In Group 1, pregnant rats received 6-mg/kg/day nicotine subcutaneously during pregnancy from 1 to 21 days of gestation and lactation (until postnatal day 21). Group 2 received nicotine and Asc for the same period. In Group 3, the rats received nicotine during lactation. Control pregnant rats (Group 4) received only saline subcutaneously. Serum malondialdehyde (MDA), myeloperoxidase (MPO), and superoxide dismutase (SOD) levels were determined at 21 days of age. Nicotine exposure decreased birth weight and pregnancy weight gain. MDA values of the rat pups exposed to nicotine in both Groups 1 and 2 were higher than those of control and Group 3. SOD and MPO values of the groups were similar. Mean birth weight and serum MDA levels of Groups 1 and 2 were similar. Nicotine exposure via placental transfer increases oxidative stress as manifested by an increase in MDA level. Asc supplementation does not prevent the adverse effects of maternal nicotine exposure.

Effect of vitamin E on reproductive function in the mice treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin*

The study was conducted to determine the effects of vitamin E on reproductive performance in mice treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The 75 female and 40 male mice were randomly assigned into five groups. The levels of both TCDD and vitamin E given by gavage were 0 and 0 (Control group), 100 and 0 (experimental group I), 100 and 20 (experimental group II), 100 and 100 (experimental group III), and 100 ng/kg/day and 500 mg/kg/day (experimental group IV), respectively. Males and females were mixed to mate at the ratio of 1:2 after 4-week experiment. The gavage treatments were continued until the end of gestation in female mice after mating. The results showed that the litter number, survival rate, and body weight at birth of offspring in experimental group I had significantly decreased, and the females’ pregnancy rate and pup sex ratio in experimental group I had the decreasing tendencies when compared with the control group. The litter number in experimental group III, survival rate in experimental group II and III, body weight at birth in experimental group III and IV exhibited significant increase compared with experimental group I. The female pregnancy rate in both experimental group III and IV recovered to 100%, but there were no significant differences when compared with experimental group I. The pups’ sex ratio had a gradually increasing tendency with increase of vitamin E level, but there was no significant difference among experimental group I–IV. The results suggest that TCDD could induce reproductive toxicity in mice, whereas vitamin E alleviated adverse effects on reproductive performance in mice caused by TCDD.

Effects of superoxide dismutase and polyclonal tumor necrosis factor-alpha antibodies on chloroacetate-induced cellular death and superoxide anion production by J774.A1 macrophages

Dichloroacetate (DCA) and trichloroacetate (TCA) are by-products that are formed during the process of water chlorination and have been previously shown to induce superoxide anion (SA) production and cellular death when added to J774.A1 macrophage cultures. In this study, the effects of superoxide dismutase (SOD) and polyclonal tumor necrosis factor-alpha (TNF-alpha) antibodies on DCA- and TCA-induced SA production and cellular death have been tested on the J774.A1 macrophage cultures. TCA and DCA were added to different cultures either alone, each at a concentration of 16 mM, or in combination with SOD (2-12 units/ml), or with TNF-alpha antibodies (10 and 25 units/ml). Cells were incubated for 48 h, after which cellular death/viability, lactate dehydrognase (LDH) leakage by the cells, and SA production by the cells were determined. While TCA and DCA caused significant cellular toxicity, indicated by reduction in cellular viability and increases in LDH leakage and SA production, SOD addition resulted in significant reduction of the effects induced by the compounds. On the other hand, addition of TNF-alpha antibodies to the DCA- and TCA-treated cultures resulted in significant reduction of DCA- but not TCA-induced cellular death and SA production by the cells. Although these results suggest a significant role for SA in DCA- and TCA-induced cellular death, they may also suggest two different mechanisms for the chloroacetate-induced SA production by the cells.

1-O-hexyl-2,3,5-trimethylhydroquinone inhibits IkappaB phosphorylation and degradation-linked inducible nitric oxide synthase expression: beyond antioxidant function

Inducible nitric oxide (NO) production in macrophages plays an important role in atherosclerosis, the protective effects of vitamin E and its derivatives perhaps being partly mediated by alteration in this parameter. We have investigated the influence of a novel synthesized vitamin E derivative, 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), on NO production in the RAW 264.7 mouse macrophage cell line. HTHQ dose-dependently inhibited lipopolysaccharide (LPS)-induced NO production through reducing LPS-triggered inducible nitric oxide synthase (iNOS) expression. The phosphorylation and subsequent degradation of IkappaB caused by LPS in RAW 264.7 cells was markedly blocked. The free radical scavenging activity of HTHQ was only 2-fold that of vitamin E, whereas its inhibition of NO production was found to be nearly 500-fold stronger. Our results indicated that HTHQ suppressed NO production in macrophages by blocking IkappaB degradation and thus inhibiting iNOS expression. The inhibitory activity of HTHQ on NO production did not parallel its free radical scavenging activity, implying a possible involvement of additional functions.

Protective effects of antioxidants against smokeless tobacco-induced oxidative stress and modulation of Bcl-2 and p53 genes in human oral keratinocytes

The oral use of chewing tobacco has greatly increased in recent years, and this usage is associated with cancers of the mouth, lip, nasal cavities, esophagus and gut. Oral cancer accounts for 3% of all cancers in U.S.A. and is the seventh most common cancer. Previous studies in our laboratory have demonstrated the protective abilities of a novel IH636 grape seed proanthocyanidin extract (GSPE) against reactive oxygen species both in vitro and in vivo models, and provided significantly better protection as compared to vitamins C, E and beta-carotene. In the recent past, we have demonstrated smokeless tobacco (STE)-induced oxidative stress, apoptotic cell death in a primary culture of normal human oral keratinocytes (NHOK), and have compared the protective abilities of vitamins C and E, singly and in combination, and GSPE in this pathobiology [Free Rad. Biol. Med., 26, 992-1000 (1999)]. In the present study, we have assessed the protective role of vitamins C and E, and GSPE against STE-induced modulation of intracellular oxidized states in NHOK cells as demonstrated by laser scanning confocal microscopy. Approximately 11%, 26%, 28% and 50% protection were observed following incubation with vitamin C, vitamin E, a combination of vitamins C plus E, and GSPE, respectively. DNA fragmentation was assessed as an index of oxidative DNA damage and similar results were observed. Furthermore, the cellular viability and functional roles of Bcl-2, p53 and c-myc genes were assessed in STE-induced oxidative stress in NHOK cells. NHOK cells were treated with STE (0-200 micrograms/ml) for 24 h and changes in the expression of Bcl-2, p53 and c-myc genes were measured by reverse transcriptase-polymerase chain reaction (RT-PCR), and the protective effect of GSPE was assessed. Approximately a 2.0-fold increase in p53 gene expression was observed following incubation of the oral keratinocytes with 100 micrograms/ml of STE, beyond which the expression of p53 decreased, confirming increased apoptotic cell death with a higher concentration of STE as reported earlier. GSPE significantly modulated STE-induced changes in p53. The expression of antiapoptotic Bcl-2 gene decreased with STE treatment and the expression of Bcl-2 gene increased significantly following preincubation with GSPE. No significant change in the expression of transcription factor c-myc gene responsible for cell cycle growth was observed following incubation with STE and/or GSPE. Thus, c-myc may not be involved in STE-induced cytotoxicity towards NHOK cells. These results suggest that antioxidant protection of STE-induced cellular injury is associated with alterations in Bcl-2 and p53 expression.

Time- and concentration-dependent production of superoxide anion, nitric oxide, DNA damage and cellular death by ricin in the J774A.1 macrophage cells

The time- and concentration-dependent effects of ricin on some biomarkers of cellular toxicity, including production of superoxide anion (O2-), nitric oxide (NO), and DNA single strand breaks (SSB), as well as cellular death, have been examined in the J774A.1 macrophage cell cultures. Various concentrations of ricin have been added to various cell cultures, and the cells were incubated for 12, 24, 36, and 48 hours. Following 12 hour incubation, ricin did not cause significant increases in any of those biomarkers. However, time- and concentration-dependent increases were observed in the induction of all the biomarkers after incubation for 24-48 hours. Approximately twofold increases in the production of O2- were observed after incubation with 1 and 10 ng/mL of ricin for 24 and 36-48 hours, respectively. The concentrations of ricin that caused approximately twofold increases in the rate of DNA-SSB are 10 and 1-10 ng/mL after 24 and 36-48 hours incubation, respectively. Approximately twofold increases in NO production were only observed after incubation of the cultures with 1-10 ng/mL of ricin for 36-48 hours. Fifty percent reductions in cellular viability were also observed with ricin concentrations of 10-100, 10, and 1-10 ng/mL, after incubation for 24, 36, and 48 hours, respectively.

Ricin-induced toxicity in the macrophage J744A.1 cells: the role of TNF-alpha and the modulation effects of TNF-alpha polyclonal antibody

Ricin is a natural toxin of the castor beans (Ricinus communus). We studied the time- and concentration-dependent effects of ricin on the release of TNF-alpha and lactate dehydrogenase (LDH), as well as the modulation of the ricin-induced effects by TNF-alpha antibody in the J774A.1 cells. When added at concentrations ranging from 0 to 1000 ng/mL, ricin caused concentration-dependent increases in the release of TNF-alpha after incubation for 12 to 24 hours. Concentration-dependent increases in the leakage of LDH were also observed after incubation of the cells with those concentrations of ricin for 24 to 48 hours. Addition of 5 units/mL of rabbit anti-mouse TNF-alpha polyclonal antibody (TNF-alpha antibody) 2 hours prior to the addition of ricin resulted in a decrease in the ricin-induced toxicity, indicated by the release of LDH by the cells. However, when added at concentrations higher than 5 units/mL, the antibody resulted in either no effect or an increase in the ricin-induced LDH leakage. These results suggest that secretion of TNF-alpha by the macrophages in response to ricin plays a significant role in the toxicity of ricin and that TNF-alpha antibody can antagonize the effects of ricin in this cell line when added at relatively low concentrations.

Smokeless tobacco, oxidative stress, apoptosis, and antioxidants in human oral keratinocytes

We have investigated the effects of a smokeless tobacco extract (STE) on lipid peroxidation, cytochrome c reduction, DNA fragmentation and apoptotic cell death in normal human oral keratinocyte cells, and assessed the protective abilities of selected antioxidants. The cells, isolated and cultured from human oral tissues, were treated with STE (0-300 microl;g/ml) for 24 h. Superoxide anion production was determined by cytochrome c reductase. Oxidative tissue damage was determined by lipid peroxidation and DNA fragmentation, whereas apoptotic cell death was assessed by flow cytometry. STE-induced fragmentation of genomic DNA was also determined by gel electrophoresis. The comparative protective abilities of vitamin C (75 microM), vitamin E (75 microM), a combination of vitamins C & E (75 microM each), and a novel grape seed proanthocyanidin (IH636) extract (GSPE) (100 microg/ml) against STE induced oxidative stress and tissue damage were also determined. Following treatment of the cells with 300 microg STE/ml 1.5-7.6-fold increases in lipid peroxidation, cytochrome c reduction and DNA fragmentation were observed. The addition of the antioxidants to cells treated with STE provided 10-54% decreases in these parameters. Approximately 9, 29, and 35% increases in apoptotic cell death were observed following treatment with 100, 200, and 300 microg STE/ml, respectively, and 51-85% decreases in apoptotic cell death were observed with the antioxidants. The results demonstrate that STE produces oxidative tissue damage and apoptosis, which can be attenuated by antioxidants including vitamin C, vitamin E, a combination of vitamins C plus E and GSPE. GSPE exhibited better protection against STE than vitamins C and E, singly and in combination.

Subchronic effects of smokeless tobacco extract (STE) on hepatic lipid peroxidation, DNA damage and excretion of urinary metabolites in rats

The oral use of moist smokeless tobacco products (snuff) is causally associated with cancer of the mouth, lip, nasal cavities, esophagus and gut. The mechanism by which smokeless tobacco constituents produce genetic and tissue damage is not known. Recent studies in our laboratories have shown that an aqueous extract of smokeless tobacco (STE) activates macrophages with the resultant production of reactive oxygen species (ROS), including nitric oxide. Furthermore, the administration of acute doses of STE (125-500 mg/kg) to rats induces dose dependent increases in mitochondrial and microsomal lipid peroxidation, enhances DNA single strand breaks, and significantly increases the urinary excretion of the lipid metabolites malondialdehyde, formaldehyde, acetaldehyde and acetone. Since the use of tobacco is a chronic process, the effects of an aqueous extract of STE in rats following low dose exposure were examined. Female Sprague-Dawley rats were treated orally with 25 mg STE/kg every other day for 105 days. The effects of subchronic treatment of STE on hepatic microsomal and mitochondrial lipid peroxidation and the incidence of hepatic nuclear DNA damage were assessed. Lipid peroxidation increased 1.4- to 3.3-fold in hepatic mitochondria and microsome with STE treatment between 0 and 105 days with respect to control animals while hepatic DNA single strand breaks increased up to 3.4-fold. Maximum increases in lipid peroxidation and DNA single strand breaks occurred between 75 and 90 days of treatment. Urinary excretion of the four lipid metabolites malondialdehyde, formaldehyde, acetaldehyde and acetone was monitored by high pressure liquid chromatography (HPLC) with maximum increases being observed between 60 and 75 days of treatment. The results clearly indicate that low dose subchronic administration of STE induces an oxidative stress resulting in tissue damaging effects which may contribute to the toxicity and carcinogenicity of STE.

Comparative in vitro oxygen radical scavenging ability of zinc methionine and selected zinc salts and antioxidants

1. The concentration-dependent scavenging abilities of zinc DL-methionine, zinc sulfate, zinc gluconate, zinc picolinate and selected free radical scavengers, including superoxide dismutase (SOD), catalase, mannitol, allopurinol and DL-methionine, were examined against biochemically generated superoxide anion, hydroxyl radical and hypochlorite radical plus hypochlorous acid, by chemiluminescence and cytochrome c reduction. 2. Zinc methionine was the most effective of the zinc compounds that were tested. Following incubations with superoxide anion, hydroxyl radical, and hypochlorite radical-generating systems, in the presence of 50 microM zinc DL-methionine approximately 38%, 47% and 28% inhibition in reactive oxygen species generation was observed, respectively, compared to control groups. 3. The protective abilities of various zinc salts, as well as selected free radical scavengers and antioxidants were also assessed on phorbol ester (TPA)-induced lactate dehydrogenase (LDH) release from cultured PC-12 cells. Preincubation showed better protection than coincubation. Approximately 45% and 50% inhibition in TPA-induced LDH leakage was observed following preincubation with 50 microM zinc DL-methionine and 50 microM vitamin E succinate, respectively. Zinc DL-methionine exhibited better protection against LDH leakage than any other zinc salt tested. 4. The results indicate that zinc DL-methionine can attenuate the biochemical consequences of oxygen free radicals, and is comparable to other well-known antioxidants and free radical scavengers in the in vitro system that was employed.

Naphthalene-induced oxidative stress in rats and the protective effects of vitamin E succinate

Quinone metabolites of naphthalene (NAP) are known to produce lipid peroxidation. However, the ability of naphthalene to induce oxidative stress in experimental animals has not been extensively investigated. Furthermore, the effects of vitamin E succinate [(+)-alpha-tocopherol acid succinate; VES] on naphthalene-induced oxidative stress and tissue damage were assessed. Female Sprague-Dawley rats were treated with a single oral dose of 1100 mg naphthalene/kg (0.50 LD50) in corn oil. Vitamin E succinate-treated rats received 100 mg VES/kg/day orally for 3 d before naphthalene treatment, and 40 mg VES/kg/d after NAP administration. Hepatic and brain tissues and urine samples were collected 0, 12, 24, 48, and 72 h after NAP treatment. Naphthalene treatment resulted in a 2.1-fold increase in lipid peroxidation in liver and brain mitochondria at the 24-h time point. Increases in hepatic and brain mitochondrial lipid peroxidation in VES plus NAP-treated rats were 39-46% less than NAP treated rats at 24 h. DNA-single strand breaks increased 3.0-fold in hepatic tissues in NAP treated rats, and increased only 1.6-fold in VES protected rats at the 24-h time point. Glutathione (GSH) decreased by 83 and 49% in hepatic and brain tissues, respectively, in NAP-treated rats at the 24-h time point, while GSH content in VES plus NAP-treated rats decreased 47 and 21% in hepatic and brain tissues, respectively, at this same time point. Microsomal membrane fluidity, a measurement of membrane damage, increased 1.9- and 1.7-fold in liver and brain tissues, respectively, in NAP-treated rats, and only 1.3- and 1.2-fold in NAP plus VES-treated rats at the 24-h time point. The urinary excretion of malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) was determined at 0-96 h after NAP administration. Between 12-24 h after NAP administration maximal excretion of the four urinary lipid metabolites was observed, with increases of 4.5-, 2.7-, 2.3-, and 2.8-fold for MDA, FA, ACT, and ACON, respectively, at the 24-h time point. VES reduced the NAP-induced excretion of these urinary metabolites by 28-49% 24 h after NAP administration. These results support the hypothesis that NAP induces oxidative stress and tissue damage, and that vitamin E succinate provides significant protection.

Chromium-induced production of reactive oxygen species, DNA single-strand breaks, nitric oxide production, and lactate dehydrogenase leakage in J774A.1 cell cultures

The involvement of oxidative stress in the toxicity of chromium (VI) and chromium (III) has been proposed. We have therefore examined the effects of these cations on the production of superoxide anion, nitric oxide (NO), and DNA single strand breaks (SSB) in J774A.1 macrophage cells in culture as well as the effects on lactate dehydrogenase (LDH) leakage and cell viability. Following a 48 hour incubation, over twofold increases in superoxide anion and NO production were observed at concentrations of approximately 0.30 and 50 microM for Cr (VI) and Cr (III), respectively. The patterns of cell viability and LDH leakage paralleled superoxide anion and NO production for Cr (VI) and Cr (III). A 50% decrease in viability was observed at approximately the concentrations that produced a twofold increase in superoxide and NO production. Concentration-dependent increases in DNA-SSB were observed after incubation with Cr (III) with maximum increases occurring at a concentration of approximately 60 microM. Cr (VI) had no effect on the incidence of DNA-SSB at any of the tested concentrations. The results indicate that Cr (VI) and Cr (III) are toxic to the J774A.1 cell line, and the toxicity may be due at least in part to an oxidative stress induced by the production of reactive oxygen species.

Protective effects of free radical scavengers and antioxidants against smokeless tobacco extract (STE)-induced oxidative stress in macrophage J774A.1 cell cultures

Previous studies have demonstrated that an aqueous smokeless tobacco extract (STE) administered in an acute oral dose to rats induces an enhanced induction of hepatic mitochondrial and microsomal lipid peroxidation, hepatic nuclear DNA single strand breaks, enhanced excretion of urinary lipid metabolites, including malondialdehyde, formaldehyde, acetaldehyde and acetone, and increased production of nitric oxide (NO) by peritoneal macrophage cells. These observations indicate that STE induces the production of oxygen free radicals. We have therefore examined the in vitro incubation of cultured J774A.1 macrophage cells with STE on the release of the enzyme lactate dehydrogenase (LDH) into the media as an indicator of cellular membrane damage and cytotoxicity. The amount of LDH released by STE was both concentration- and time-dependent. The cytotoxicity of STE to macrophage J774A.1 cells in culture was further determined from percent viability after various periods of incubation. The addition of 250 micrograms STE/ml to the cultured J774A.1 cells resulted in a 2.9-fold increase in the release of LDH. Individual coincubation with superoxide dismutase (SOD), catalase, mannitol, and allopurinol had no significant effect on the release of LDH into the culture medium, while a combination of the four free radical scavengers resulted in a 59% decrease in the STE-induced release of LDH. At 75 microM concentrations of viramine E and vitamin E succinate, approximately 28% and 41% inhibitions were observed in STE-induced LDH leakage, respectively. Taken together with previous studies, the results indicate that STE activates macrophage cells, resulting in the production of reactive oxygen species.(ABSTRACT TRUNCATED AT 250 WORDS)