Characterization of cytochrome P450 2E1 activity by the [14C]nitrosodimethylamine breath test

The objective of this study was to measure the rate of demethylation of nitrosodimethylamine in vivo in the rat and determine its value to assess CYP2E1 activity in intact animals. Nitrosodimethylamine labeled with 14C on both methyl groups was administered to rats and exhaled 14CO2 was collected during 2-3 h. The nitrosodimethylamine breath test was increased by inducers of CYP2E1, such as ethanol (+139%) and 4-methylpyrazole (+115%), and decreased by the inhibitor diallyl sulfide (-53%). In addition, the nitrosodimethylamine breath test was not changed significantly by inducers specific for other cytochrome P450 such as beta-naphthoflavone, dexamethasone, and phenobarbital. The specificity of the induction by 4-methylpyrazole and of the inhibition by diallyl sulfide for CYP2E1 was determined using the [14C]caffeine (CYP1A2), [14C]aminopyrine (CYP2C11), and [14C]erythromycin (CYP3A2) breath tests. 4-Methylpyrazole treatment caused a small increase of the caffeine (+33%) and aminopyrine (+9%) breath tests and no change of the erythromycin breath test. Diallyl sulfide treatment led to a small decrease of the caffeine breath test (-33%) and of the aminopyrine breath test (-13%) but a 23% increase of the erythromycin breath test. It is concluded that the [14C]nitrosodimethylamine breath test is useful to assess CYP2E1 activity in vivo in the rat.     

Diallyl sulfide--a flavour component from garlic (Allium sativum) attenuates lipid peroxidation in mice infected with Trichinella spiralis.

We investigated the antioxidant capacity of diallyl sulfide (DAS) in the course of experimental trichinellosis in C3H mice. For this purpose, the mice were orally infected with either Trichinella spiralis larvae (300 larvae/mouse) or treated per os with normal saline (control), and 12 hrs later, they were treated per os with DAS (200 mg/kg b.w) daily for 5 or 20 days. On day 5 and 35 of the post-infection period (5 and 35 dpi), thiobarbituric-acid reactive substances (TBARS) in the small intestinal mucosa and diaphragm samples and the total antioxidant status (TAS) of blood were determined. Trichinella spiralis increased TBARS and decreased TAS in the intestinal phase of invasion. However, in the muscular phase mice, neither TBARS nor TAS was found to be different from those of the control. Diallyl sulfide has been shown to decrease TBARS and the agent did not have any effect(s) on the total antioxidant status of blood in Trichinella-infected mice. The results suggest that diallyl sulfide may be an effective antioxidant candidate and may therefore play a significant role in the defense against lipid peroxidation in trichinellosis.     

N′-Isopropylnornicotine in Burley Tobacco (Nicotiana tabacum)

Allyl sulfides such as diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), typical flavor components of Allium vegetables, have been shown to inhibit benzo[a]pyrene (B[a]P)-induced carcinogenesis in animal models. As a possible mechanism of this inhibition, the effect of these volatile substances on cytochrome P450 (CYP)1 (CYP1A1, 1A2 and 1B1)-mediated bioactivation of B[a]P was investigated using a human hepatoma cell model (HepG2). DADS and DATS inhibited the B[a]P-induced ethoxyresorufin O-deethylase (EROD) activity, a marker enzyme for CYP1, by 30-90% and 70-95% at 100-1,000 μM concentration, respectively. The cell viability, an indicator of the capacity to inhibit B[a]P bioactivation, was increased by treatments of 100-1,000 μM DADS and 10-100 μM DATS. Immunoblot results indicated that the B[a]P inducible CYP1A2 protein was suppressed by 100-1,000 μM of DADS and 10-100 μM of DATS, but CYP1A1 and 1B1 were not detectable in any microsomes. Analysis of B[a]P metabolites revealed that the level of 7,8-diol formed was significantly reduced in the DADS and DATS treated microsomes as compared to the control. The level of 9,10-diol and 4,5-diol formed was also lowered by the allyl sulfide treatments. These results suggest that the protective mechanism of allyl sulfides on B[a]P-induced carcinogenesis is possibly related with the modulation of CYP1-mediated bioactivation of B[a]P.     

Diallyl sulfide content and antimicrobial activity against food-borne pathogenic bacteria of chives (Allium schoenoprasum)

Chives, a member of the Alliaceae family, have been used in food and medicine in Thailand for a long time. Diallyl sulfides (diallyl monosulfide, dially disulfide, diallyl trisulfide, and diallyl tetrasulfide) are believed to be responsible for the antimicrobial activity of plants in this family. In this study, chive oil was examined for its diallyl sulfide content and its antimicrobial activity against some strains of food-borne pathogenic bacteria. Chive oil had a very low concentration of diallyl monosulfide in comparison with the other diallyl sulfides. They inhibited all pathogenic bacteria used in this study with a different degree of inhibition. Chive oil was also shown to be able to inhibit Escherichia coli O157:H7 in a food model. This study is the first report describing not only the diallyl disulfide content of chive oil, but also its antimicrobial activity against food-borne pathogens in both a test tube and food model.     

Structure-activity relationships of organosulfur compounds as inhibitors of cytochrome P450 1-mediated activation of benzo[a]pyrene in a human cell model

Twelve naturally-occurring organosulfur compounds were investigated as inhibitors of cytochrome P450 1 (CYP450 1)-mediated activation of benzo[a]pyrene (B[a]P) in human hepatoma (HepG2) cells. Inhibition depended on the presence of a diallyl group and the number of S atoms. Diallyl trisulfide (DATS), with a diallyl group and three S atoms, had the highest activity with an IC₅₀ of 0.4 mM, and 1.5-fold higher potency than diallyl disulfide (DADS) containing a diallyl group and two S atoms. Organosulfur compounds containing an alkyl group were less effective, or even ineffective, inhibitors of both CYP450 1 and B[a]P-induced cytotoxicity than DADS and DATS. Alliin and S-allyl cysteine containing the S-cysteinyl group had no inhibition.     

Modulation of cytochrome P4501-mediated bioactivation of benzo[a]pyrene by volatile allyl sulfides in human hepatoma cells.

Allyl sulfides such as diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), typical flavor components of Allium vegetables, have been shown to inhibit benzo[a]pyrene (B[a]P)-induced carcinogenesis in animal models. As a possible mechanism of this inhibition, the effect of these volatile substances on cytochrome P450 (CYP)1 (CYP1A1, 1A2 and 1B1)-mediated bioactivation of B[a]P was investigated using a human hepatoma cell model (HepG2). DADS and DATS inhibited the B[a]P-induced ethoxyresorufin O-deethylase (EROD) activity, a marker enzyme for CYP1, by 30-90% and 70-95% at 100-1,000 microM concentration, respectively. The cell viability, an indicator of the capacity to inhibit B[a]P bioactivation, was increased by treatments of 100-1,000 microM DADS and 10-100 microM DATS. Immunoblot results indicated that the B[a]P inducible CYP1A2 protein was suppressed by 100-1,000 microM of DADS and 10-100 microM of DATS, but CYP1A1 and 1B1 were not detectable in any microsomes. Analysis of B[a]P metabolites revealed that the level of 7,8-diol formed was significantly reduced in the DADS and DATS treated microsomes as compared to the control. The level of 9,10-diol and 4,5-diol formed was also lowered by the allyl sulfide treatments. These results suggest that the protective mechanism of allyl sulfides on B[a]P-induced carcinogenesis is possibly related with the modulation of CYP1-mediated bioactivation of B[a]P.     

Effects of dietary chemopreventive phytochemicals on P-glycoprotein function

The effects of dietary phytochemicals on P-glycoprotein function were investigated using human multidrug-resistant carcinoma KB-C2 cells and the fluorescent P-glycoprotein substrates daunorubicin and rhodamine 123. The effects of natural chemopreventive compounds, capsaicin found in chilli peppers, curcumin in turmeric, [6]-gingerol in ginger, resveratrol in grapes, sulforaphane in broccoli, 6-methylsulfinyl hexyl isothiocyanate (6-HITC) in Japanese horseradish wasabi, indole-3-carbinol (I3C) in cabbage, and diallyl sulfide and diallyl trisulfide in garlic, were examined. The accumulation of daunorubicin in KB-C2 cells increased in the presence of capsaicin, curcumin, [6]-gingerol, and resveratrol in a concentration-dependent manner. The accumulation of rhodamine 123 in KB-C2 cells was also increased, and the efflux of rhodamine 123 from KB-C2 cells was decreased by these phytochemicals. Sulforaphane, 6-HITC, I3C, and diallyl sulfide and diallyl trisulfide had no effect. These results suggest that dietary phytochemicals, such as capsaicin, curcumin, [6]-gingerol, and resveratrol, have inhibitory effects on P-glycoprotein and potencies to cause drug-food interactions.     

Induction of chromosome damage by benzo[a]pyrene, 2-aminofluorene and cyclophosphamide in the root cells of Vicia faba

The induction of sister-chromatid exchanges (SCEs) and chromosome aberrations (CAs) by benzo[a]pyrene (BP), 2-aminofluorene (2-AF) and cyclophosphamide (CP) in the root cells of Vicia faba was examined. BP and 2-AF induced CAs, but not SCEs. CP induced both SCEs and CAs.     

Chromosome aberrations in metaphase II-oocytes. Stage sensitivity in the mouse oogenesis to amethopterin and cyclophosphamide

The stage sensitivity in oogenesis of C₃H mice was investigated by transplacental treatment of embryonic oogonia and oocytes at meiotic prophase I. After birth the stages of early and late dictyotene as well as the preovulatory and ovulatory phases were treated. Chromosome analysis was performed in unfertilized metaphase II-oocytes after induced ovulation [pregnant mare's serum (PMS) and human chorionic gonadotrophin (HCG)]. As test compounds both the folic acid antagonist amethopterin (M) and the alkylating agent cyclophosphamide (C) were used.Embryonic oogonia as well as the preovulatory phase of oogenesis proved to be most sensitive for the induction of chromosomal aberrations. The investigation with graded doses during the preovulatory stage demonstrated the dose-dependent frequency of the induced types of chromosomal abnormalities.The high sensitivity of these stages where chromosome segregation takes place, e.g. oogonia, preovulatory stage, seems to be related to an additional induction of aneuploidies.     

Inhibition of the benzo[<Emphasis Type="Italic">a</Emphasis>]pyrene-induced toxicity by allyl sulfides in human epidermal keratinocytes

Diallyl sulfide (DAS) and diallyl disulfide (DADS) at 25 g ml^–1decreased the benzo[a]pyrene (B[a]P)-induced colony growth inhibition of human epidermal keratinocytes. DAS and DADS decreased B[a]P-DNA and B[a]P-protein adducts by 65% and 49–55%, respectively. The B[a]P-induced ethoxyresorufin O-deethylase activity, a marker enzyme for cytochrome P450 1, was decreased from 3 to 1.7–1.9 nmol min^–1 mg^–1 microsomal protein by DAS and DADS treatments. The activity of glutathione S-transferase, a detoxifying enzyme for B[a]P, but was decreased by DADS, but was unaffected by DAS.     

Liver subcellular fractions from rats treated by organosulfur compounds from Allium modulate mutagen activation

The effects of in vivo administration of naturally occurring organosulfur compounds (OSCs) from Allium species were studied on the activation of several mutagens. Male SPF Wistar rats were given p.o. one of either diallyl sulfide (DAS), diallyl disulfide (DADS), dipropyl sulfide (DPS) or dipropyl disulfide (DPDS) during 4 consecutive days and the ability of hepatic S9 and microsomes from treated rats to activate benzo[a]pyrene (BaP), cyclophosphamide (CP), dimethylnitrosamine (DMN), N-nitrosopiperidine (N-PiP) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was determined in the Ames test. Administration of DAS, DPS and DPDS resulted in a significant increase of the activation of BaP, CP, N-PiP and PhIP mediated by S9 and microsomes while DADS treatment only increased the mutagenicity of PhIP. In contrast, S9 from DADS-treated rats significantly inhibited the mutagenicity of N-PiP and BaP. DAS, DADS and DPS strongly inhibited DMN mutagenicity while DPDS enhanced it. To understand the mechanisms underlying these effects, the modifications of the activities of specific isozymes of CYP involved in the activation of these mutagens were studied. DAS, DPS and DPDS strongly enhanced pentoxyresorufin O-dealkylase (PROD) activity related to CYP2B and slightly increased ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase (MROD) activities related to CYP1A family. DADS exerted the same effects than other OSCs but to a lesser extent. p-Nitrophenol hydroxylase (PNPH) activity related to CYP2E1 was inhibited by DAS and DADS, whereas DPDS significantly increased this activity. Hence, the effects of OSCs on the mutagenicity of several genotoxic compounds are mediated by modification (enhancement or inhibition) of specific CYP involved in their activation.     

Biosynthesis and urinary excretion of methyl sulfonium derivatives of the sulfur mustard analog, 2-chloroethyl ethyl sulfide, and other thioethers

Thioether methyltransferase was previously shown to catalyze the S-adenosylmethionine-dependent methylation of dimethyl selenide, dimethyl telluride, and various thioethers to produce the corresponding methyl onium ions. In this paper we show that the following thioethers are also substrates for this enzyme in vitro: 2-hydroxyethyl ethyl sulfide, 2-chloroethyl ethyl sulfide, thiodiglycol, t-butyl sulfide, and isopropyl sulfide. To demonstrate thioether methylation in vivo, mice were injected with [methyl-3H]methionine plus different thioethers, and extracts of lungs, livers, kidneys, and urine were analyzed by high-performance liquid chromatography for the presence of [3H]methyl sulfonium ions. The following thioethers were tested, and all were found to be methylated in vivo: dimethyl sulfide, diethyl sulfide, methyl n-propyl sulfide, tetrahydrothiophene, 2-(methylthio)ethylamine, 2-hydroxyethyl ethyl sulfide, and 2-chloroethyl ethyl sulfide. This supports our hypothesis that the physiological role of thioether methyltransferase is to methylate seleno-, telluro-, and thioethers to more water-soluble onium ions suitable for urinary excretion. Conversion of the mustard gas analog, 2-chloroethyl ethyl sulfide, to the methyl sulfonium derivative represents a newly discovered mechanism for biochemical detoxification of sulfur mustards, as this conversion blocks formation of the reactive episulfonium ion that is the ultimate alkylating agent for this class of compounds.     

Control of murine hair follicle regression (catagen) by TGF-beta1 in vivo.

The regression phase of the hair cycle (catagen) is an apoptosis-driven process accompanied by terminal differentiation, proteolysis, and matrix remodeling. As an inhibitor of keratinocyte proliferation and inductor of keratinocyte apoptosis, transforming growth factor beta1 (TGF-beta1) has been proposed to play an important role in catagen regulation. This is suggested, for example, by maximal expression of TGF-beta1 and its receptors during late anagen and the onset of catagen of the hair cycle. We examined the potential involvement of TGF-beta1 in catagen control. We compared the first spontaneous entry of hair follicles into catagen between TGF-beta1 null mice and age-matched wild-type littermates, and assessed the effects of TGF-beta1 injection on murine anagen hair follicles in vivo. At day 18 p.p., hair follicles in TGF-beta1 -/- mice were still in early catagen, whereas hair follicles of +/+ littermates had already entered the subsequent resting phase (telogen). TGF-beta1-/- mice displayed more Ki-67-positive cells and fewer apoptotic cells than comparable catagen follicles from +/+ mice. In contrast, injection of TGF-beta1 into the back skin of mice induced premature catagen development. In addition, the number of proliferating follicle keratinocytes was reduced and the number of TUNEL + cells was increased in the TGF-beta1-treated mice compared to controls. Double visualization of TGF-beta type II receptor (TGFRII) and TUNEL reactivity revealed colocalization of apoptotic nuclei and TGFRII in catagen follicles. These data strongly support that TGF-beta1 ranks among the elusive endogenous regulators of catagen induction in vivo, possibly via the inhibition of keratinocyte proliferation and induction of apoptosis. Thus, TGF-betaRII agonists and antagonists may provide useful therapeutic tools for human hair growth disorders based on premature or retarded catagen development (effluvium, alopecia, hirsutism).     

Garlic extract diallyl sulfide (DAS) activates nuclear receptor CAR to induce the Sult1e1 gene in mouse liver

Constituent chemicals in garlic extract are known to induce phase I and phase II enzymes in rodent livers. Here we have utilized Car(+/+) and Car(-/-) mice to demonstrate that the nuclear xenobiotic receptor CAR regulated the induction of the estrogen sulfotransferase Sult1e1 gene by diallyl sulfide (DAS) treatment in mouse liver. DAS treatment caused CAR accumulation in the nucleus, resulting in a remarkable increase of SULT1E1 mRNA (3,200 fold) and protein in the livers of Car(+/+) females but not of Car(-/-) female mice. DAS also induced other CAR-regulated genes such as Cyp2b10, Cyp3a11 and Gadd45β. Compared with the rapid increase of these mRNA levels, which began as early as 6 hours after DAS treatment, the levels of SULT1E1 mRNA began increasing after 24 hours. This slow response to DAS suggested that CAR required an additional factor to activate the Sult1e1 gene or that this activation was indirect. Despite the remarkable induction of SULT1E1, there was no decrease in the serum levels of endogenous E2 or increase of estrone sulfate while the clearance of exogenously administrated E2 was accelerated in DAS treated mice.     

Metabolism of the Fungicide S-n-Butyl S′-p-tert-Butylbenzyl N-3-Pyridyldithiocarbonimidate (S-1358) in Rats

S-1358 was rapidly absorbed, metabolized and readily excreted via urine and feces from orally dosed rats. Excretion of radioactivity was almost complete within 4 days. The radioactivity was distributed mainly in stomach, intestines, liver and kidneys. It seems that S-1358 and its metabolites do not persist in organs and tissues following a single oral dosing.

Major urinary metabolites of the benzyl-labeled S-1358 were p-(1,1-dimethyl-2-hydroxyethyl)benzyl methyl sulfide [B], p-(1,1-dimethyl-2-hydroxyethyl)benzyl methyl sulfone [A], p-(1-methyl-1-carboxylethyl)benzyl methyl sulfide [D], p-(1-methyl-1-carboxylethyl)benzyl methyl sulfone [C] and their glucuronide conjugates. Fecal metabolites were S-n-butyl S′-(1, 1-dimethyl-2-hydroxyethyl)benzyl N-3-pyridyldithiocarbonimidate [MR], A, B, C and D. These metabolites were also found in the bile. The pyridine-labeled S-1358 gave rise to 2-(3′-pyridylimino)-4-carboxylthiazolidine [HM] and 3-aminopyridine [AP] in the urine, and MR and AP in the feces. Intact S-1358 was a major component of the fecal radioactivity.     

A sensitive method for quantitation of beta-lyase metabolites of sulfur mustard as 1,1'-sulfonylbis[2-(methylthio)ethane] (SBMTE) in human urine by isotope dilution liquid chromatography-positive ion-electrospray-tandem mass spectrometry

A method for measurement of an important biological marker, 1,1'-sulfonylbis[2-(methylthio)ethane] (SBMTE) of sulfur mustard agent HD [bis-(2-chloroethyl)sulfide] in human urine, to quantify HD exposure, is presented. It employs TiCl3 reduction of beta-lyase metabolites to SBMTE, and automated solid-phase extraction sample preparation, followed by isotope dilution liquid chromatography-positive ion-electrospray ionization-tandem mass spectrometry with 7.5 min/sample cycle time, to achieve SBMTE quantitation of up to 200 samples/24h a day. Percent relative standard deviations over the calibration range varied from 12.0% at 0.1 ng/mL to 0.9% at 100 ng/mL, and the limit of detection from a 0.5 mL sample was below the lowest level calibration standard of 0.1 ng/mL.     

NF-kappaB transmits Eda A1/EdaR signalling to activate Shh and cyclin D1 expression, and controls post-initiation hair placode down growth

A novel function of NF-kappaB in the development of most ectodermal appendages, including two types of murine pelage hair follicles, was detected in a mouse model with suppressed NF-kappaB activity (c(IkappaBalphaDeltaN)). However, the developmental processes regulated by NF-kappaB in hair follicles has remained unknown. Furthermore, the similarity between the phenotypes of c(IkappaBADeltaN) mice and mice deficient in Eda A1 (tabby) or its receptor EdaR (downless) raised the issue of whether in vivo NF-kappaB regulates or is regulated by these novel TNF family members. We now demonstrate that epidermal NF-kappaB activity is first observed in placodes of primary guard hair follicles at day E14.5, and that in vivo NF-kappaB signalling is activated downstream of Eda A1 and EdaR. Importantly, ectopic signals which activate NF-kappaB can also stimulate guard hair placode formation, suggesting a crucial role for NF-kappaB in placode development. In downless and c(IkappaBalphaDeltaN) mice, placodes start to develop, but rapidly abort in the absence of EdaR/NF-kappaB signalling. We show that NF-kappaB activation is essential for induction of Shh and cyclin D1 expression and subsequent placode down growth. However, cyclin D1 induction appears to be indirectly regulated by NF-kappaB, probably via Shh and Wnt. The strongly decreased number of hair follicles observed in c(IkappaBalphaDeltaN) mice compared with tabby mice, indicates that additional signals, such as TROY, must regulate NF-kappaB activity in specific hair follicle subtypes.     

Nuclear damage of colon epithelial cells by the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is modulated by dietary lipids

Intestinal damage in C57BL/6J female mice was quantified by measuring the frequency of nuclear aberrations in colonic crypts. The animals were maintained on the following diets: standard (5% lipids, 5% cellulose); low- and high-cellulose (0-20% cellulose); high lipids (20% maize oil or 20% olive oil). All groups of animals were treated by gavage either with saline or 250 mg/kg of the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). After 24 h their colons were removed and stained and the nuclear aberrations scored under the microscope. The administration of IQ markedly increased the number of colon aberrations in all of the treated animals. Variations in dietary fiber did not modify the colon-damaging activity of this compound. Maize oil slightly increased the colon-damaging activity, whereas significant protection was observed in the animals on a high-lipid olive-oil diet. These results show that composition of the diet may vary the genotoxic effect of this dietary carcinogen.