Orchestrating Nitric Oxide and Carbon Monoxide Signaling Molecules for Synergistic Treatment of MRSA Infections.

The local delivery of gaseous signaling molecules (GSMs) has shown promising therapeutic potential. However, although GSMs have a subtle interplay in physiological and pathological conditions, the co-delivery of different GSMs for therapeutic purposes remains unexplored. Herein, we covalently graft a nitric oxide (NO)-releasing N-nitrosamine moiety onto the carbon monoxide (CO)-releasing 3-hydroxyflavone (3-HF) antenna, resulting in the first NO/CO-releasing donor. Under visible light irradiation, photo-mediated co-release of NO and CO reveals a superior antimicrobial effect toward Gram-positive bacteria with a combination index of 0.053. The synergy of NO and CO hyperpolarizes and permeabilizes bacterial membranes, which, however, shows negligible hemolysis and no evident toxicity toward normal mammalian cells. Moreover, the co-release of NO and CO can efficiently treat MRSA infection in a murine skin wound model, showing a better therapeutic capacity than vancomycin.

Iron oxide nanoparticles exert inhibitory effects on N-Bis(2-hydroxypropyl)nitrosamine (DHPN)-induced lung tumorigenesis in rats.

Iron oxide nanoparticles (magnetite) have been widely used in industry and medicine. However, the safety assessment of magnetite has not been fully completed. The present study was conducted to assess effects of magnetite on carcinogenic activity, using a medium-term bioassay protocol. A total of 100 male Fischer 344 rats, 6 weeks old, were randomly divided into 5 groups of 20 animals each, and given a basal diet and drinking water containing 0 or 0.1% of N-bis(2-hydroxypropyl)nitrosamine (DHPN) for 2 weeks. Two weeks later, the rats were intratracheally instilled magnetite 7 times at an interval of 4 weeks, at the doses of 0, 1.0 or 5.0 mg/kg body weight, and sacrificed at the end of the experimental period of 30 weeks. The multiplicities of macroscopic lung nodules and histopathologically diagnosed bronchiolo-alveolar hyperplasia, induced by DHPN, were both significantly decreased by the high dose of magnetite. The expression of minichromosome maintenance (MCM) protein 7 in non-tumoral alveolar epithelial cells, and the number of CD163-positive macrophages in tumor nodules were both significantly reduced by magnetite. It is suggested that magnetite exerts inhibitory effects against DHPN-induced lung tumorigenesis, by the reduction of alveolar epithelial proliferation and the M2 polarization of tumor-associated macrophages.

Dose-Related Modulatory Effects of Polymeric Black Tea Polyphenols (PBPs) on Initiation and Promotion Events in B(a)P and NNK-Induced Lung Carcinogenesis.

Our understanding of dose-related effects of polymeric black tea polyphenols (PBPs), the most abundant polyphenols in black tea, is limited. In the present study, the effect of various doses of black tea (0.75, 1.5, and 3%)-derived PBP-rich extract on biochemical parameters and lung carcinogenicity in A/J mice was investigated. Pretreatment with PBPs showed the dose-related decrease in B(a)P-induced expression and activity of CYP1A1 in the liver while CYP1A2 expression and activity in the lung. Dose-dependent significant increase in PBP-mediated over-expression and activity of GSTs (alpha in the liver while pi in the lung) were observed in polyphenol-treated groups. Significant dose-related decrease in number and intensity of BPDE-DNA adducts were observed in liver and lung. Black tea (1.5%, 3%)-derived PBPs showed dose-mediated decrease in lung tumor incidence and multiplicity which was further correlated with different molecular markers like cell proliferation and apoptosis in B(a)P and NNK model. In conclusion, dose-dependent chemopreventive effects of PBPs, both anti-initiating (induction of phase II and inhibition of carcinogen-induced phase-I enzymes leading to decrease in BPDE-DNA adducts) and anti-promoting (decreased cell proliferation and increased apoptosis lowering incidence and/or multiplicity of lung lesions), were observed in A/J mice without significant toxicity.

Phenylbutyl isoselenocyanate modulates phase I and II enzymes and inhibits 4-(methylnitrosamino)-1-(3-pyridyl)- 1-butanone-induced DNA adducts in mice.

Lung cancer remains one of the most preventable forms of cancer with about 90% of cases attributed to cigarette smoking. Over the years, the development of chemopreventive agents that could inhibit, delay, or reverse the lung carcinogenesis process has been an active field of research, however, without much attainment. Through extensive structure-activity relationship studies, we recently identified a novel agent phenylbutyl isoselenocyanate (ISC-4), designed on the basis of naturally occurring isothiocyanates well known for their lung cancer prevention properties, as a potential chemopreventive agent. In this study, we used A/J mice to evaluate the lung cancer chemopreventive potential of ISC-4. A single intragastric dose of 1.25 µmol ISC-4 resulted in a time-dependent increase of selenium levels in serum, liver, and lung, suggesting that ISC-4 is orally bioavailable, a key requirement for a chemopreventive agent. This dose also resulted in a time-dependent inhibition of microsomal cytochrome P450 (Cyp450) activity and delayed increases in phase II UDP-glucuronyl transferase (Ugt) and glutathione-S-transferase (Gst) activity. ISC-4 was able to induce mRNA expression of Cyp, Ugt, and Gst enzyme isoforms in liver, but in lung, it inhibited Cyp isoforms while inducing Ugt and Gst isoforms. In addition, ISC-4 effectively inhibited methyl-DNA adduct formation in mice fed diet supplemented with ISC-4 for two weeks and then treated with the tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. These results suggest that ISC-4 is a strong candidate for development as a chemopreventive agent.

[Investigation on relationship between flavonoid content and inhibitory ability to nitrosamine synthesis for eleven Chinese herbal medicines].

The eleven Chinese herbal medicine containing flavonoids are applied as raw materials to explore the relationship between the inhibitory ratio of nitrosamine synthesis, the scavenging ratio of nitrite and the flavonoid content in the samples. The inhibitory ratio of nitrosamine synthesis and the scavenging ratio of nitrite of the 11 herbal medicines, Vit C and rutin were determined in intro compare with Vit C and the standard ample of rutin. The results indicate that each sample exhibits certain ability to inhibitiory nitrosamine synthesis. Among these samples, Honeysuckle flower is found to be of best effects, its inhibitory ratio and scavenging ratio reaches 78.5% and 60.5%, respectively. Except kudzuvine root, the other samples with higher content of flavonoid result in a higher inhibitory or scavenging ratio, and the relative coefficient reaches a value of 0.9338 and 0.9272, respectively, displaying notable positive correlation. The concentrations of IC50 (g x L(-1)) of flavonoid extracted from honeysuckle, rutin and VC were 0.013, 0.022 and 0.187, respectively. While the inhibitory ratio of synthesis of nitrosamines reached 50%, and those were 0.042, 0.024 and 0.041, respectively. While scavenging ratio of nitrite reaches 50%. The inhibitory ratio of synthesis of nitrosamine of flavonoids extracted from honeysuckle flower is higher than that of Vit C and rutin, and the scavenging ratio of nitrite is similar to that of Vit C.

Expression of NF-kappaB parallels COX-2 expression in oral precancer and cancer: association with smokeless tobacco.

Nuclear Factor-kappaB (NF-kappaB) activation and COX-2 overexpression have been reported in head and neck cancer, but the relationship between these proteins remains to be investigated. To determine the relationship between NF-kappaB and COX-2 in Smokeless Tobacco (ST) associated oral tumorigenesis, we performed immunohistochemistry in serial sections from 107 OSCCs, 78 oral precancerous lesions (OPLs) (58 hyperplasias, 20 dysplasias) and 15 histologically normal oral tissues and correlated with clinicopathological data. Significant increase in NF-kappaB and COX-2 immunopositivity was observed from normal oral mucosa to OPLs to OSCCs (p = 0.009 and p = 0.002 respectively). Upregulation of NF-kappaB and COX-2 was observed as early as in hyperplasia [p = 0.006; OR = 6.1 and p = 0.003; OR = 7.6, respectively]. Expression of both proteins was found to be significantly associated in OPLs (p = 0.000; OR = 12.6) and OSCCs (p = 0.001; OR = 4.0). Intriguingly, khaini consumption correlated with NF-kappaB immunopositivity in OPLs (p = 0.05, OR = 3.8) and OSCCs (p = 0.01, OR = 3.4) and with COX-2 expression in OPLs (p = 0.03; OR = 4.3). In vitro experimental system of ST associated oral carcinogenesis was used to demonstrate ST (khaini) and NNK mediated activation of NF-kappaB and COX-2, supporting the clinical data. In conclusion, this study demonstrates correlation between over expression of NF-kappaB and COX-2 in early precancerous stages of development of oral cancer and sustained elevation down the tumorigenic pathway, underscoring their potential as targets for early intervention. In vitro studies demonstrated that NNK may be one of the carcinogenic components of ST (khaini) inducing activation of NF-kappaB and COX-2 in oral precancer and cancer cells, suggesting plausible role in ST-induced oral carcinogenesis.

The organoselenium compound 1,4-phenylenebis(methylene)selenocyanate inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced tumorgenesis and enhances glutathione-related antioxidant levels in A/J mouse lung.

Selenium, in the form of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) but not Se-enriched yeast (Se-yeast), was highly effective at inhibiting lung tumors induced by the tobacco specific nitrosamine (TSNA) 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice and at reducing NNK-induced DNA methylation and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in the lung. Our goal was to determine if p-XSC but not Se-yeast is effective at inducing levels of glutathione (GSH)-related antioxidants and reducing markers of GSH oxidation in the NNK-induced lung tumor model. In the first bioassay, 6-week-old mice were fed either control or experimental diets (containing 10 ppm as selenium from p-XSC or Se-yeast) and, beginning at 8 weeks of age, received NNK (3 micromol) by gavage once weekly for 8 weeks. After 18 weeks, p-XSC significantly reduced NNK-induced tumor burden by 74% (10.4 +/- 6.0 versus 2.7 +/- 1.5 tumors/mouse, P < 0.001) and tumor incidence from 96% to 68% (P < 0.01), whereas, Se-yeast had no effect. Lung GSH levels were unchanged by either NNK or Se-yeast, but were increased 70% in mice treated with both NNK and p-XSC (P < 0.01) and 41% in mice treated with p-XSC alone. In the second bioassay, the time course of effects of p-XSC was examined. As early as one week after initiation of p-XSC feeding lung and blood selenium levels were increased nearly six- and two-fold, respectively. Increases of 120% for GSH and 65% for Cys were observed in p-XSC groups compared to controls within one week after initiation of p-XSC feeding (P < 0.01). The levels of protein-bound:free GSH ratios and Cys ratios were significantly decreased in p-XSC-treated mice, regardless of NNK status, suggesting a decrease in the levels of oxidative stress. Altogether, these results indicate that p-XSC is a potent inducer of GSH and related thiol antioxidants in the lung leading to decreased levels of oxidative stress and suggest that p-XSC inhibits tumor formation, in part, by protecting against oxidative damage.

MRP8, ATP-binding cassette C11 (ABCC11), is a cyclic nucleotide efflux pump and a resistance factor for fluoropyrimidines 2',3'-dideoxycytidine and 9'-(2'-phosphonylmethoxyethyl)adenine.

MRP8 (ABCC11) is a recently identified cDNA that has been assigned to the multidrug resistance-associated protein (MRP) family of ATP-binding cassette transporters, but its functional characteristics have not been determined. Here we examine the functional properties of the protein using transfected LLC-PK1 cells. It is shown that ectopic expression of MRP8 reduces basal intracellular levels of cAMP and cGMP and enhances cellular extrusion of cyclic nucleotides in the presence or absence of stimulation with forskolin or SIN-1A. Analysis of the sensitivity of MRP8-overexpressing cells revealed that they are resistant to a range of clinically relevant nucleotide analogs, including the anticancer fluoropyrimidines 5'-fluorouracil (approximately 3-fold), 5'-fluoro-2'-deoxyuridine (approximately 5-fold), and 5'-fluoro-5'-deoxyuridine (approximately 3-fold), the anti-human immunodeficiency virus agent 2',3'-dideoxycytidine (approximately 6-fold) and the anti-hepatitis B agent 9'-(2'-phosphonylmethoxynyl)adenine (PMEA) (approximately 5-fold). By contrast, increased resistance was not observed for several natural product chemotherapeutic agents. In accord with the notion that MRP8 functions as a drug efflux pump for nucleotide analogs, MRP8-transfected cells exhibited reduced accumulation and increased efflux of radiolabeled PMEA. In addition, it is shown by the use of in vitro transport assays that MRP8 is able to confer resistance to fluoropyrimidines by mediating the MgATP-dependent transport of 5'-fluoro-2'-deoxyuridine monophosphate, the cytotoxic intracellular metabolite of this class of agents, but not of 5'-fluorouracil or 5'-fluoro-2'-deoxyuridine. We conclude that MRP8 is an amphipathic anion transporter that is able to efflux cAMP and cGMP and to function as a resistance factor for commonly employed purine and pyrimidine nucleotide analogs.

Antimutagenic effect of fruit and vegetable ethanolic extracts against N-nitrosamines evaluated by the Ames test.

The inhibitory effect of nine fruit and vegetable ethanolic extracts against the mutagenicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA), and N-nitrosopiperidine (NPIP) was evaluated by means of the Ames test. Licorice ethanolic extract was the only one that showed an inhibitory effect (ranging from moderate to strong) against mutagenicity of all N-nitrosamines tested. This ethanolic extract showed the greatest inhibition effect against NPIP (72%), NDMA (45%), and NPYR (39%). The greatest inhibition effect (51%) of the mutagenicity of NDBA was shown by kiwi ethanolic extract. Vegetable and fruit ethanolic extracts that exhibited an antimutagenic effect (at the range 50-2000 microg/plate), in decreasing order, against NDMA and NPYR were as follows: licorice > kiwi > carrot and licorice > broccoli > pineapple > kiwi, respectively. Decreasing orders against NDBA and NPIP were, respectively, kiwi > onion > licorice = garlic > green pepper > carrot and licorice > garlic > pineapple > carrot.

The effect of epigallocatechin galleate and sarcophytol A on DNA strand breakage induced by tobacco-specific nitrosamines and stimulated human phagocytes.

The tobacco-specific nitrosamines (TSNAs) are metabolites of nicotine and are major carcinogens in cigarette smoke. Chronic inflammation may promote the carcinogenic effect of these nitrosamines through the generation of oxygen radicals as evidenced by an increase in DNA strand breakage in cultured human lung cells treated with stimulated human phagocytes and TSNAs. Sarcophytol A (SaA), a simple monohydroxycembratetraene isolated from marine soft coral, and (-)-epigallocatechin galleate (EGCG), one of the main constituents of green tea, both inhibit tumor promotion. To evaluate their effect on TSNA-induced genetic damage, cultured human lung cells were pretreated with SaA or EGCG and then exposed to the TSNA 4-(N-methyl-N-n-trosamino)-1-(3-pyridyl)-1-butanone (NNK) and stimulated human phagocytes and then assayed for single-strand DNA breaks. Both SaA and EGCG provided significant protection against the induction of genetic damage in these cells and may prove useful in the chemoprevention of tobacco-induced carcinogenesis.

Inhibitory effect of retinoid on esophageal carcinogenesis in rats induced by N-nitroso-N-methylbutylamine in relation to cellular retinoic acid-binding protein.

The inhibitory effect of a synthetic retinoid, ethyl alltrans-9-(4-methoxy-2, 3, 6-trimethyl-phenyl)-3, 7-dimethyl-2, 4, 6, 8-nonatetraenoate (Tigason), on esophageal carcinogenesis in F344 rats induced by N-nitroso-N-methylbutylamine (NMBA) was evaluated. The animals were given NMBA daily in their drinking water for 21 weeks at a concentration of 15 mg per liter ad libitum starting at 8 weeks of age. One week before the beginning of NMBA treatment, the rats were divided randomly into Tigason-fed and -unfed groups. Thirty-five rats were fed a diet supplemented with Tigason at a concentration of 30 mg per kg of diet, and 80 rats were given a basal diet alone. In NMBA-treated rats, multiple papillomas were seen 11 weeks after NMBA treatment and squamous cell carcinoma developed 12 weeks after NMBA; the tumors increased in number thereafter, and the numbers of papillomas and carcinomas were the same at 17 and 21 weeks after NMBA. At 21 weeks after NMBA treatment, the number of papillomas was similar, regardless of the dietary Tigason supplement, however, the number of esophageal squamous cell carcinomas was significantly lower in the Tigason-fed rats than in -unfed animals (p < 0.025). In normal esophageal tissues, a small amount of cellular retinoic acid-binding protein (cRABP) was detected throughout the experimental period, while during carcinogenesis, the levels of cRABP increased continuously until 16 weeks after NMBA; the cRABP level was higher in papillomas than in squamous cell carcinomas. As Tigason specificially blocked the progression of papillomas to carcinomas, it may be a promising candidate chemopreventive agent in esophageal carcinogenesis.

Effect of green tea catechins on the amount of 8-hydroxydeoxyguanosine (8-OHdG) in pancreatic and hepatic DNA after a single administration of N-nitrosobis(2-oxopropyl)amine (BOP).

Effects of green tea catechins on N-nitrosobis(2-oxopropyl)amine (BOP)-induced oxidative stress in pancreas and liver were examined. Hamsters were divided into two groups: one group was given free access to a 0.1% solution of green tea catechins as drinking water (c-ham) and the other to plain tap water (w-ham) for 1 week before subcutaneous injection of BOP 20 mg/kg body weight. Zero, 1, 2, 6, 12, 24, and 48 h after BOP injection, the pancreas and liver were excised and the tissue concentration of lipid peroxides (TBA values) and the amount of 8-hydroxydeoxyguanosine (8-OHdG) in nuclear DNA were measured. The concentration of lipid peroxides and the amount of 8-OHdG in the pancreas showed similar patterns of change between c- and w-ham. Soon after BOP injection, the concentration of lipid peroxides and the amount of 8-OHdG increased with a peak at 1 and 6 h, respectively. Their peak values of c-ham were significantly depressed compared with those of w-ham. Both levels returned to steady-state levels by 24 h. In the liver, the concentration of lipid peroxides and the amount of 8-OHdG were not affected by BOP administration. These results suggest that BOP induces oxidative damages in the target organ and oral intake of green tea catechins has a protective effect on the oxidative stress.

S-allyl cysteine inhibits nitrosomorpholine formation and bioactivation.

Water extracts of garlic, deodorized garlic powder, and onions, but not leeks, were found to significantly (p < 0.05) reduce the in vitro formation of N-nitrosomorpholine (NMOR), a known liver carcinogen. Addition of increasing quantities (20, 40, and 80 mM) of S-allyl cysteine (SAC), a water-soluble compound in processed garlic, depressed NMOR formation by 16%, 27%, and 43%, respectively (p < 0.05). The ability of SAC to block NMOR formation decreased as the NaNO7 and morpholine concentrations increased. SAC and its non-allyl analog S-propyl cysteine effectively blocked NMOR formation. SAC and S-propyl cysteine were less effective than isomolar cysteine in reducing NMOR formation (p < 0.05). The oil-soluble sulfur compounds diallyl disulfide (DADS), dipropyl disulfide, and diallyl sulfide were ineffective inhibitors of NMOR generation (p > 0.05). SAC and DADS reduced the mutagenicity of NMOR in Salmonella typhimurium TA100 (p < 0.05). SAC at 70 mumol/plate reduced the number of histidine revertants per plate by 51% (p < 0.05), whereas DADS at 0.12 mumol/plate reduced mutant colony number by 76% (p < 0.05). SAC and DADS were more effective than isomolar cysteine in reducing NMOR mutagenicity (p < 0.05). The ability of sulfur compounds in garlic and onions to depress nitrosamine formation and bioactivation in these studies is consistent with epidemiologic evidence that higher intake of allium plants is associated with a reduction in the risks of some cancers.

Effects of dietary fat content on the metabolism of NNK and on DNA methylation induced by NNK.

The available data support the concept that high-fat diets increase cytochrome P-450 activities in the liver, leading to increased rates of carcinogen metabolism and, in some instances, DNA adduct formation. Therefore we investigated whether a high-fat diet can also influence DNA methylation by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the lungs of rats. Male F344 rats were fed a regular AIN-76A low-fat (5% corn oil) or AIN-76A high-fat (23.5% corn oil) diet. After three weeks on this dietary regimen, the animals were injected subcutaneously once daily for four days with NNK at 0.39 mmol/kg body wt. Groups of rats were sacrificed 4 and 24 hours after the last NNK administration; livers and lungs were excised for DNA isolation. We found that the high-fat diet significantly enhanced the formation of O6-methylguanine (O6-mGua) in the rat lung four hours (p < 0.01) after the last carcinogen administration. This may, in part, account for our previous finding in regard to the enhancing effect of the high-fat diet on NNK-induced lung carcinogenesis. There was no effect on O6-mGua or 7-mGua in the rat liver at either time point. To further elucidate the enhancing effect of the high-fat diet on DNA methylation by NNK in the lung, we determined its effect on the in vitro and in vivo metabolism of NNK. The in vitro data indicated that dietary fat has no measurable effect on liver and lung microsomal mixed-function oxidase in catalyzing the metabolic activation of NNK. The results of the metabolism study of NNK in vivo appear to be consistent with the in vitro finding, in that fat had no effect on the excretion pattern of NNK or on the distribution pattern of its urinary metabolites. It is apparent that the enhancing effect of the high-fat diet on O6-mGua in the lung of rats that was measured four hours after NNK injection requires future investigations.

Effect of N-nitrosoamines and nitrosationable pesticide tetramethylthiuram disulfide on soil microbiocenosis and potato yield: a model system.

The effect of carcinogenic N-nitrosoamines (NA), NA-producing tetramethylthiuram disulfide (TMTD) pesticide, and of various doses of nitrogen fertilizers (90, 180, and 270 kg/ha) on the forming and vital functions of microbiocenosis of light gray forest soil was studied. The quantity, nitrifying activity, and gas production of nitrifying bacteria increased under the influence of NA. The nitrosodimethylamine (NDMA) and the nitrosodibutilamine (NDBA) changed the correlation between the number of soil-inhabiting fungi and bacteria so that the former prevailed. The greatest effect was observed on the twentieth day of cultivation of the soil when high concentrations of NDMA (50 mcg/kg) and NDBA (105 mcg/kg) were used. The typical dominant species among the fungi was the phytotoxigenic Penicillium funiculosum. The nitrosationable pesticide tetramethylthiuram disulfide (TMTD) applied with nitrogen fertilizers in a dose of 180 and 270 kg/ha exerted an influence on the microbiocenosis of the soil similar to NA. The potato yield decreased and the ecology of microbiocenosis deteriorated under these conditions in a model vegetable experiment. It is suggested that the nitrosoamines and their precursors may change the balance of nitrogen, decrease the yield of plants, and deteriorate the ecological balance.

Inhibition of herpes simplex virus replication and protein synthesis by non-smoked tobacco, tobacco alkaloids and nitrosamines.

Inhibitory effects of snuff extract and the tobacco chemicals nicotine, anabasine, diethyl-N-nitrosamine (DEN), and the tobacco-specific nitrosamines (TSNA), N-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on herpes simplex virus type 1 (HSV-1) replication in vitro and on HSV-1 protein synthesis in infected cells were analysed. Snuff extract and nicotine caused a significant reduction of HSV-1 attachment to cell membranes whereas anabasine, DEN, NNN and NNK did not affect adsorption of HSV-1. Virus production assays in the presence of snuff added after virus adsorption resulted in a significantly reduced production of virus at low multiplicities of infection (MOI), but at high MOI the inhibitory effect of snuff extract was less pronounced. DEN, NNN and NNK only affected virus production at toxic concentrations. Nicotine and anabasine reduced virus production in non-toxic doses but not at the concentrations present in snuff extract. In HSV-infected cells exposed to snuff extract, the immediate early (alpha-) infected cell proteins (ICPs) 4 and 27 (as well as the early (beta-) ICPs 6 and 8) were markedly increased, whereas the late (gamma-) ICPs 5, 11 and 29 were reduced. Nicotine had a less pronounced stimulating effect on the production of alpha-proteins but no detectable effect on production of beta- or gamma-proteins. Anabasine, DEN, NNN and NNK did not affect HSV protein synthesis at non-toxic concentrations. Synthesis of thymidine kinase and DNA polymerase was significantly reduced by snuff extract. Also nicotine and anabasine affected thymidine kinase and DNA polymerase but only at toxic concentrations. The production of the cellular protein actin, which almost disappears a few hours after HSV-1 infection, remained at a significant level in HSV-infected cells exposed to snuff. Thus snuff extract blocks the replicative cycle of HSV at an early stage, which results in an increased production of alpha-proteins in the infected cells and in prolonged maintenance of cellular functions. This may be of importance for HSV-induced transformation and the development of HSV-associated tumours.

Effect of tobacco extract and N'-nitrosonornicotine on the carcinogen metabolising enzymes under different dietary vitamin B status.

Studies were carried out to evaluate the changes in the phase I and II enzymes of xenobiotic metabolism, on treatment with tobacco extract (TE) and a tobacco specific carcinogen, N'-nitrosonornicotine (NNN) in Sprague-Dawley rats maintained on vitamin B complex sufficient and deficient semi-synthetic diets. Both TE and NNN significantly increased the hepatic and pulmonary phase I enzymes in the vitamin B sufficient (SB+) and deficient (SB-) animals. However, the percent increase in enzyme activities was drastically higher in the SB- treated group as compared to those in the SB(+)-treated group. On the other hand, TE and NNN significantly depressed the liver and lung glutathione (GSH) level and glutathione S-transferase (GST) activity in the SB- animals, while the opposite effect was observed in the SB(+)-treated animals. Furthermore, both the treatments depleted the hepatic pool of vitamin A, with a concurrent increase in that of vitamin C in SB+ and SB- groups.

Lack of effect of selenium on induction of tumors of esophagus and bladder in rats by two nitrosamines.

The effect of differences in level of dietary selenium on the induction of esophageal and bladder tumors in rats by two nitrosamines was investigated. Groups of 20 female F344 rats were given a synthetic diet containing less than 0.05 ppm Se to which selenium (as sodium selenite) was added at the concentration of 0.35, 0.7, 1.4 and 2.1 ppm selenium. These four groups, plus one without added Se, were treated with 20 ml per rat per day, 5 days a week, of a solution of nitrosomethylcyclohexylamine containing 5 mg/liter. A parallel five groups were treated in the same way with a solution of nitrosomethyl-3-carboxypropylamine in drinking water containing 600 mg per liter, as drinking water. Treatment lasted 28 weeks, at which time some animals had developed tumors. A group of 20 rats fed 0, 1.4 and 2.1 ppm Se was not treated with carcinogen. Rats consuming 1.4 ppm or 2.1 ppm Se gained weight more slowly than other groups. There was no significant difference in survival between the five groups treated with each carcinogen but receiving different dietary levels of selenium. Neither was there any significant difference between groups receiving each carcinogen in the incidence of tumors of the esophagus induced by nitrosomethylcyclohexylamine or of tumors of the urinary bladder induced by nitrosomethylcarboxypropylamine. Control rats on the synthetic diets did not survive as well as untreated rats eating regular chow diet. In these conditions there was no effect of dietary selenium levels on the induction of tumors in female rats by the two carcinogenic nitrosamines we used.

Inhibition of dietary fat promoted development of (pre)neoplastic lesions in exocrine pancreas of rats and hamsters by supplemental selenium and beta-carotene.

The modulating effects of selenium and beta-carotene on the development of putative preneoplastic foci in exocrine pancreas were investigated in rats and hamsters, treated with azaserine and N-nitrosobis(2-oxopropyl)amine (BOP), respectively. The animals were fed a semipurified diet high in saturated fat (20% lard) either supplemented or not with beta-carotene or selenium. A separate group maintained on a diet low in saturated fat (5% lard) was incorporated as an extra control group. The animals were given their diets 12 days after the last treatment with carcinogen. Four months postinitiation, the pancreata were quantitatively examined for the number and size of putative (pre)neoplastic lesions. Rats as well as hamsters maintained on a low-fat diet had significantly less putative preneoplastic pancreatic lesions as compared to animals fed a diet containing 20% lard. Selenium and beta-carotene both inhibited the growth of basophilic foci in rat pancreas. In hamster pancreas, beta-carotene and selenium caused a significant decrease in the number of early ductal complexes. The number of carcinomas was decreased in the beta-carotene group and increased in the group fed a diet high in selenium.

Alteration of natural killer cell-mediated cytotoxicity in rats treated with selenium, diethylnitrosamine and ethylnitrosourea.

Weanling, female Sprague--Dawley rats were divided into 14 separate groups. Three of these groups were administered 0.5, 2.0 or 5.0 ppm selenium (Se) in the drinking water for 10 weeks. Three groups received intraperitoneal injections of 1, 5 or 10 mg/kg diethylnitrosamine (DEN) twice weekly for 10 weeks. The remaining animals received 0.150% or 0.316% ethylurea (EU) in the feed and 1 or 10 ppm nitrite as sodium nitrite in the drinking water either alone or in combination. Separate groups of rats treated with cyclophosphamide (CY) were included as positive immuno-suppressed controls. Following the 10-week chemical exposure period, splenic natural killer (NK) cell-mediated cytotoxicity was assessed by a 4-h chromium release assay using YAC-1 tumor cells as targets. The NK cell cytotoxic response was enhanced in both the low and medium dose selenium-exposed groups. In contrast, rats exposed to 0.316% EU + 10 ppm NO2 had significantly depressed NK cell activity. CY treatment also resulted in a significant reduction of splenic NK cell cytotoxicity.