γ‐H2AX formation in the urinary bladder of rats treated with two norharman derivatives obtained from o‐toluidine and aniline

Aminomethylphenylnorharman (AMPNH) and aminophenylnorharman (APNH) are mutagenic norharman derivatives obtained from o‐toluidine and aniline, respectively. APNH is carcinogenic to the urinary bladder of rats and present in urine samples of healthy volunteers, indicating that norharman derivatives may be associated with cancer development in the urinary bladder of humans. To evaluate the possible role of AMPNH and APNH in bladder carcinogenesis, we examined the formation of γ‐H2AX, a DNA damage response marker, in the urinary bladder of rats. Seven‐week‐old male F344 rats were treated with 400 ppm AMPNH or 40 ppm APNH in the diet for 4 weeks. Animals were killed at the end of administration or after 2 weeks of recovery, and immunohistochemistry for γ‐H2AX and Ki67, a cell proliferation marker, was performed. At week 4, γ‐H2AX formation in bladder epithelial cells was significantly increased by APNH treatment as compared with that in controls. AMPNH also induced upregulation of γ‐H2AX formation, although there was no statistical significance. After the recovery period, γ‐H2AX‐positive cells were reduced but remained significantly higher in AMPNH and APNH groups than in the control group. Ki67‐positive cells were significantly increased by AMPNH and APNH at week 4 and reduced to the same level as the control after 2 weeks of recovery. Expression of KRT14, a bladder stem cell marker, was also increased in the basal layer by the two norharman derivatives. Thus, AMPNH and APNH showed in vivo genotoxicity in the bladder epithelium of rats, and APNH may be a potent causative agent of bladder carcinogenesis.     

Dose dependency of γ-H2AX formation in the rat urinary bladder treated with genotoxic and nongenotoxic bladder carcinogens

We previously reported that immunostaining for γ-H2AX, a biomarker of DNA damage, in the rat urinary bladder is useful for early detection of bladder carcinogens in 28-day toxicity studies. Here, we aimed to examine the dose dependency of γ-H2AX formation in the urinary bladder of rats. Male F344 rats (aged 6 weeks) were orally administered N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN; 0%, 0.0001%, 0.001%, 0.01%, 0.02%, or 0.05% in drinking water), a genotoxic bladder carcinogen, and melamine (0%, 0.3%, 1.0%, or 3.0% in the diet), a nongenotoxic bladder carcinogen, for 2 days or 4 weeks. Immunohistochemical analysis showed that γ-H2AX- and Ki67-positive epithelial cells in the bladder urothelium were significantly increased, with a clear dose dependency, in both BBN- and melamine-treated groups. Additionally, γ-H2AX formation was detected from the lower-dose group, without increased Ki67 expression or histopathologic findings. The ratios of γ-H2AX-positive cells at week 4 in both BBN- and melamine-treated groups were higher than those on day 2, indicating the time-dependent increase in γ-H2AX formation. Immunofluorescence double-staining revealed that γ-H2AX single-positive cells without Ki67 expression were often found in the urothelium of BBN-treated rats, whereas most γ-H2AX-positive cells were Ki67-positive in the melamine group. Our results demonstrated that γ-H2AX formation in the urinary bladder increased in a clear dose-dependent manner and that γ-H2AX immunostaining has the potential to detect bladder carcinogens after a 2-day administration. Furthermore, the association of genotoxic mechanisms in bladder carcinogenesis could be determined by analyzing the colocalization of γ-H2AX and Ki67 in the urothelium.     

Toxic effects of 4‐methylthio‐3‐butenyl isothiocyanate (Raphasatin) in the rat urinary bladder without genotoxicity

We recently reported that 4‐methylthio‐3‐butenyl isothiocyanate (MTBITC) exerts chemopreventive effects on the rat esophageal carcinogenesis model at a low dose of 80 ppm in a diet. In contrast, some isothiocyanates (ITCs) have been reported to cause toxic effects, promotion activity, and/or carcinogenic potential in the urinary bladder of rats. In the present study, we investigated whether MTBITC had toxic effects in the urinary bladder similar to other ITCs, such as phenethyl ITC (PEITC). First, to examine the early toxicity of MTBITC, rats were fed a diet supplemented with 100, 300 or 1000 ppm MTBITC for 14 days. Treatment with 1000 ppm MTBITC caused increased organ weights and histopathological changes in the urinary bladder, producing lesions similar to those of 1000 ppm PEITC. In contrast, rats treated with 100 or 300 ppm MTBITC showed no signs of toxicity. Additionally, we performed in vivo genotoxicity studies to clarify whether MTBITC may exhibit a carcinogenic potential through a genotoxic mechanism in rats. Rats were treated with MTBITC for 3 days at doses of 10, 30 or 90 mg kg⁻¹ body weight by gavage, and comet assays in the urinary bladder and micronucleus assays in the bone marrow were performed. No genotoxic changes were observed after treatment with MTBITC at all doses. Overall, these results suggested that the effects of MTBITC in the rat urinary bladder are less than those of PEITC, but that MTBITC could have toxic effects through a nongenotoxic mechanism in the urinary bladder of rats at high doses. Copyright © 2016 John Wiley & Sons, Ltd.     

Integrated approach to testing and assessment for predicting rodent genotoxic carcinogenicity

We investigated the performance of an integrated approach to testing and assessment (IATA), designed to cover different genotoxic mechanisms causing cancer and to replicate measured carcinogenicity data included in a new consolidated database. Genotoxic carcinogenicity was predicted based on positive results from at least two genotoxicity tests: one in vitro and one in vivo (which were associated with mutagenicity categories according to the Globally Harmonized System classification). Substances belonging to double positives mutagenicity categories were assigned to be genotoxic carcinogens. In turn, substances that were positive only in a single mutagenicity test were assigned to be mutagens. Chemicals not classified by the selected genotoxicity endpoints were assigned to be negative genotoxic carcinogens and subsequently evaluated for their capability to elicit non‐genotoxic carcinogenicity. However, non‐genotoxic carcinogenicity mechanisms were not currently included in the developed IATA. The IATA is docked to the OECD Toolbox and uses measured data for different genotoxicity endpoints when available. Alternatively, the system automatically provides predictions by SAR genotoxicity models using the OASIS Tissue Metabolism Simulator platform. When the developed IATA was tested against the consolidated database, its performance was found to be high, with sensitivity of 74% and specificity of 83%, when measured carcinogenicity data were used along with predictions falling within the models' applicability domains. Performance of the IATA would be slightly changed to a sensitivity of 80% and specificity of 72% when the evaluation by non‐genotoxic carcinogenicity mechanisms was taken into account. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐ 3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate‐1‐14C

γ‐Cyhalothrin ( 1a ), (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate, is a single‐isomer, synthetic pyrethroid insecticide marketed by Pytech Chemicals GmbH, a joint venture between Dow AgroSciences and Cheminova A/S. As a part of the registration process there was a need to incorporate a carbon‐14 label into the cyclopropyl ring of this molecule. A high yielding radiochemical synthesis of γ‐cyhalothrin was developed from readily available carbon‐14 labeled N‐t‐Boc protected glycine. This seven step synthesis, followed by a preparative normal phase HPLC separation of diastereomers, provided 21.8 mCi of γ‐cyhalothrin‐1‐¹⁴C ( 1b ) with >98% radiochemical purity. Copyright © 2007 John Wiley & Sons, Ltd.     

Metabolic Fate of N-n-Butyl-N-(4-hydroxybutyl)-nitrosamine and its Analogues: Selective Induction of Urinary Bladder Tumours in the Rat

1. The metabolic fates of N-n-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and N, N-di-n-butylnitrosamine (DBN) were investigated in the rat and other animal species, to elucidate a possible relationship between metabolism and organotropic carcinogencity to the urinary bladder of these N-nitrosamines.

2. The principal urinary metabolite of BBN as well as of DBN in the rat was N-n-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), which was demonstrated to be the active form of these compounds as bladder carcinogen. The species difference in response to BBN or DBN is discussed on the basis of the urinary excretion rate of BCPN.

3. Metabolism in vivo and carcinogenicity of a number of BBN analogues were investigated in the rat and a general scheme for biotransformation of N-alkyl-N-(hydroxyalkyl)nitrosamines is given.

4. A possible correlation of structure and metabolism with organotropic carcinogenicity of BBN analogues is discussed, with special reference to selective induction of bladder tumours.

5. A clear demonstration of overlapping carcinogenic and mutagenic activities is presented for BBN, DBN and related compounds.     

Increased expression of miR‐34a in mouse spleen one day after exposure to N‐ethyl‐N‐nitrosourea

MicroRNAs (miRNAs) are a class of single‐stranded small RNA molecules (~22 nucleotides) that are not translated into proteins and function as regulators of gene expression. Many miRNAs are involved in carcinogenesis. One of them, miR‐34a, is associated with various p53‐initiated biological processes and may act as a tumor suppressor miRNA. Its expression is generally down‐regulated in tumor tissues and up‐regulated in tissues exposed to carcinogens chronically or subchronically. However, the response of this miRNA to acute exposure of a genotoxic carcinogen is little known. In this study, miR‐34a expression was evaluated in spleen tissues of mice treated with a dose of 120 mg kg^?1 body weight N‐ethyl‐N‐nitrosourea (ENU), a potent mutagenic carcinogen. Real‐time PCR analysis showed that the ENU exposure resulted in a 5.5‐fold increase of miR‐34a expression over the control one day after the treatment. The result suggests that miR‐34a expression responds sensitively to genotoxic insults within a short period after exposure of the mutagen, and therefore, this gene has the potential to be used as an indicator for genotoxin exposure.     

Synthesis of (±) [5‐3H] N′‐nitrosoanatabine,a tobacco‐specific nitrosamine

Tobacco‐specific N′‐nitrosamines (TSNA) are a unique class of systemic organ‐specific carcinogens. The TSNA are formed by N‐nitrosation of nicotine and of the minor tobacco alkaloids after harvesting of tobacco and during smoking. The N‐nitrosation of anatabine leads to N′‐nitrosoanatabine (NAT; 1‐nitroso‐1,2,3,4‐tetrahydro‐2,3'‐bipyridyl) which requires in‐depth assays in laboratory animals other than the rat. Furthermore, delineation of its tissue distribution and metabolism is needed for structure:activity comparisons with other TSNA and for the assessment of potential human risk from this TSNA. We have, therefore, synthesized (±)[5‐³H]NAT. 5‐Bromo‐3‐pyridine‐carboxaldehyde was condensed with ethyl carbamate prior to Diels–Alder reaction with 1,4‐butadiene to give the racemic anatabine ring system. Hydrolysis, followed by reduction with LiAlT₄ and nitrosation, led to (±)[5‐³H]NAT (60% yield, specific activity 266 mCi/mmol, radiochemical purity of >99%). Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of enantiopure non‐natural α‐amino acids using tert‐butyl (2S)‐2‐[bis‐(tert‐butoxycarbonyl)amino]‐5‐oxopentanoate as key‐intermediate:the first synthesis of(S)‐2‐amino‐oleic acid

Abstract: A general method for the synthesis of enantiopure non‐natural α‐amino acids is described. The key intermediate tert‐butyl (2S)‐2‐[bis(tert‐butoxycarbonyl)amino]‐5‐oxopentanoate was obtained from l ‐glutamic acid after suitable protection and selective reduction of the γ‐methyl ester group by DIBALH. Wittig reaction of this chiral aldehyde with various ylides led to a variety of δ,ε‐unsaturated α‐amino acids. This methodology was applied to the synthesis of (S)‐2‐amino‐oleic acid.     

Synthesis and radiolabelling of Re(CO)3‐β‐elemene derivatives as potential therapeutic radiopharmaceuticals

β‐Elemene, (1S, 2S, 4R)‐(?)‐(1‐methy‐1‐vinyl‐2,4‐diisopropenyl cyclohexane) is an anticancer agent from the Traditional Chinese Herb Medicinal. Three novel Re(CO)₃‐β‐elemene derivatives including their radioactive conjugates containing N,N,N tridentate ligands and tricarbonyl rhenium (complex 12, 13, 14) were synthesized. Their structures were characterized by infrared (IR), ¹H‐NMR and HRMS. Good radioactive yield (above 90%) and radioactive chemical purity with Re‐188 (above 95%) were obtained for all of the three derivatives (complex 15, 16, 17). The antiproliferative activity of non‐radioactive β‐elemene‐Re(CO)₃ derivatives on Lewis lung cancer cells and HeLa cell lines were evaluated by WST‐1 methods. The result shows substantial decrease in IC₅₀ values compared with the parent compound β‐elemene. The synthesis and radiosynthesis of β‐elemene tricarbonyl rhenium conjugates provide the possibility to find a new kind of potential radiopharmaceuticals on β‐elemene. Copyright © 2009 John Wiley & Sons, Ltd.     

4-Aminobiphenyl and DNA Reactivity: Case Study Within the Context of the 2006 IPCS Human Relevance Framework for Analysis of a Cancer Mode of Action for Humans

The IPCS Human Relevance Framework was evaluated for a DNA-reactive (genotoxic) carcinogen, 4-aminobiphenyl, based on a wealth of data in animals and humans. The mode of action involves metabolic activation by N-hydroxylation, followed by N-esterification leading to the formation of a reactive electrophile, which binds covalently to DNA, principally to deoxyguanosine, leading to an increased rate of DNA mutations and ultimately to the development of cancer. In humans and dogs, the urinary bladder urothelium is the target organ, whereas in mice it is the bladder and liver; in other species, other tissues can be involved. Differences in organ specificity are thought to be due to differences in metabolic activation versus inactivation. Based on qualitative and quantitative considerations, the mode of action is possible in humans. Other biological processes, such as toxicity and regenerative proliferation, can significantly influence the dose response of 4-aminobiphenyl-induced tumors. Based on the IPCS Human Relevance Framework, 4-aminobiphenyl would be predicted to be a carcinogen in humans, and this is corroborated by extensive epidemiologic evidence. The IPCA Human Relevance Framework is useful in evaluating DNA-reactive carcinogens.     

The labeling of unsaturated γ‐hydroxybutyric acid by heavy isotopes of hydrogen: iridium complex‐mediated H/D exchange by C─H bond activation vs reduction by boro‐deuterides/tritides

3‐Hydroxycyclopent‐1‐ene‐1‐carboxylic acid (HOCPCA ( 1 )) is a potent ligand for high‐affinity γ‐hydroxybutyric acid binding sites in the central nervous system. Various approaches to the introduction of a hydrogen label onto the HOCPCA skeleton are reported. The outcomes of the feasible C─H activation of olefin carbon (C‐2) by iridium catalyst are compared with the reduction of the carbonyl group (C‐3) by freshly prepared borodeuterides. The most efficient iridium catalysts proved to be Kerr bulky phosphine N‐heterocyclic species providing outstanding deuterium enrichment (up to 91%) in a short period of time. The highest deuterium enrichment (>99%) was achieved through the reduction of ketone precursor 2 by lithium trimethoxyborodeuteride. Hence, analogical conditions were used for the tritiation experiment. [³H]‐HOCPCA selectively labeled on the position C‐3 was synthetized with radiochemical purity >99%, an isolated yield of 637 mCi and specific activity = 28.9 Ci/mmol.     

Synthesis and Antimicrobial Activity of 4‐Chloro‐3‐Nitrophenylthiourea Derivatives Targeting Bacterial Type II Topoisomerases

A series of novel 4‐chloro‐3‐nitrophenylthiourea derivatives were synthesized and evaluated for their antimicrobial, antibiofilm and tuberculostatic activities. Most of compounds exhibited high antibacterial activity against both standard and hospital strains (MIC values 0.5–2 μg/mL), as compared to Ciprofloxacin. Derivatives with 3,4‐dichlorophenyl ( 11 ) and 3‐chloro‐4‐methylphenyl ( 13 ) substituents were the most promising towards Gram‐positive pathogens. Both of them exhibited antibiofilm potency and effectively inhibited the formation of biofilms of methicillin‐resistant and standard strains of Staphylococcus epidermidis. Two N‐alkylthioureas ( 20, 21 ) showed twofold to fourfold increase in in vitro potency against isolates of Mycobacterium tuberculosis, as compared to Isoniazid. An action of 7, 10 , 11, 13, 20 and 21 against activity of topoisomerases isolated from Staphylococcus aureus was studied. Synthesized compounds were found as non‐genotoxic.     

Oxidative DNA damage and in vivo mutagenicity caused by reactive oxygen species generated in the livers of p53‐proficient or ‐deficient gpt delta mice treated with non‐genotoxic hepatocarcinogens

Oxidative stress is thought to participate in chemical carcinogenesis and may trigger gene mutations. To accurately assess the carcinogenesis risk posed to humans by chemical exposure, it is important to understand the pathways by which reactive oxygen species (ROS) are generated and the effects of the resulting oxidative stress. In the present study, p53‐proficient and ‐deficient gpt delta mice were given pentachlorophenol (PCP), phenobarbital (PhB) or piperonyl butoxide (PBO), which are classified as non‐genotoxic hepatocarcinogens in rodents, at the respective carcinogenic doses for 13 weeks. Exposure to PCP or PBO, but not PhB, invoked significant increases in liver DNA 8‐hydroxydeoxyguanosine (8‐OHdG) levels. Treatment with PCP significantly increased mRNA levels of the gene encoding NAD(P):quinone oxidoreductase 1 (NQO1) in the liver, suggesting that redox cycling of the PCP metabolite tetrachlorohydroquinone gave rise to ROS. Exposure to PhB or PBO significantly elevated CYP 2B10 mRNA levels while NQO1 levels were also significantly increased in PBO‐treated mice. Therefore, in addition to involvement of the CYP catalytic pathway in the ROS‐generated system of PBO, catechol derivatives produced from the opening of the PBO functional group methylenedioxy ring probably resulted in ROS generation. However, PCP, PBO and PhB failed to increase gpt and red/gam gene mutations in the liver independently of p53. Overall, the action of oxidative stress by ROS derived from the metabolism of these carcinogens might be limited to cancer‐promoting activity, which supports the previous classification of these carcinogens as non‐genotoxic. Copyright © 2012 John Wiley & Sons, Ltd.     

Endocrine disrupting chemicals, 4‐nonylphenol,bisphenol A and butyl benzyl phthalate,impair metabolism of estradiol in male and female rats as assessed by levels of 15α‐hydroxyestrogens and catechol estrogens in urine

Bisphenol A (BPA), 4‐nonylphenol (NP) and butyl benzyl phthalate (BBP), termed endocrine‐disrupting chemicals, are known to mimic estrogen activity. The effects of these chemicals on 17β‐estradiol (E₂) metabolism in vivo in rats were examined. Male and female rats were given NP (250 mg kg^–1 day^–1), BPA (250 μg kg^–1 day^–1) or BBP (500 mg kg^–1 day^–1) by gavage for 14 days, followed by a single intraperitoneal injection of E₂ (5 mg kg^–1) on the final day. The urinary excretion over 72 hours of 2‐hydroxyestrone 1‐N‐acetylcysteine thioether, 2‐hydroxyestrone 4‐N‐acetylcysteine thioether, 4‐hydroxyestrone 2‐N‐acetylcysteine thioether, 2‐hydroxy‐17β‐estradiol (2‐OHE₂), 2‐hydroxyestrone (2‐OHE₁), 4‐hydroxy‐17β‐estradiol, 4‐hydroxyestrone, 15α‐hydroxyestriol (E₄), 15α‐hydroxy‐17β‐estradiol and 15α‐hydroxyestrone was measured. Increases in urinary excretion of 2‐OHE₁ and decreases in E₄ were observed in males treated with NP or BBP. Decreases in urinary excretion of 2‐OHE₂ and E₄ were observed in males treated with BPA. Decreases in urinary excretion of 2‐OHE₁ and 2‐OHE₂ were observed in females treated with BBP. Normalized liver and weights were increased in both sexes treated with NP or BBP. Histologic observations revealed marked changes in the distal tubules and collecting ducts in the kidneys of rats exposed to NP and BBP, and hypertrophy in the hepatocytes of the centrilobular zone of the liver. No BPA‐related effects on organ weight and on liver or kidney histopathology were found. These results suggest that the 14 day oral dosing of NP and BBP disrupted E₂ metabolism, resulting from marked morphological and functional alterations in the liver and kidneys. In addition, BPA could induce metabolic and endocrine disruption.     

Synthesis of [guanido‐13C]‐γ‐hydroxyarginine

This report describes an efficient method of synthesizing [guanido‐¹³C]‐γ‐hydroxyarginine HCl salt. Iodolactonization of N‐Boc‐protected allylglycine mainly provided the cis iodo compound 2. This was converted to an amine through azide 4. The amine 5 was reacted with N‐Boc‐protected [¹³C]thiourea to afford N‐Boc‐protected [¹³C]guanidine 6, which underwent base catalyzed ring opening. Removal of the N‐Boc group afforded [guanido‐¹³C]‐γ‐hydroxyarginine HCl salt 7 giving a 30% overall yield of the final product from N‐Boc protected allylglycine 1 in five steps. Copyright © 2008 John Wiley & Sons, Ltd.     

4β‐Hydroxywithanolide E selectively induces oxidative DNA damage for selective killing of oral cancer cells

Reactive oxygen species (ROS) induction had been previously reported in 4β‐hydroxywithanolide (4βHWE)‐induced selective killing of oral cancer cells, but the mechanism involving ROS and the DNA damage effect remain unclear. This study explores the role of ROS and oxidative DNA damage of 4βHWE in the selective killing of oral cancer cells. Changes in cell viability, morphology, ROS, DNA double strand break (DSB) signaling (γH2AX foci in immunofluorescence and DSB signaling in western blotting), and oxidative DNA damage (8‐oxo‐2′deoxyguanosine [8‐oxodG]) were detected in 4βHWE‐treated oral cancer (Ca9‐22) and/or normal (HGF‐1) cells. 4βHWE decreased cell viability, changed cell morphology and induced ROS generation in oral cancer cells rather than oral normal cells, which were recovered by a free radical scavenger N‐acetylcysteine (NAC). For immunofluorescence, 4βHWE also accumulated more of the DSB marker, γH2AX foci, in oral cancer cells than in oral normal cells. For western blotting, DSB signaling proteins such as γH2AX and MRN complex (MRE11, RAD50, and NBS1) were overexpressed in 4βHWE‐treated oral cancer cells in different concentrations and treatment time. In the formamidopyrimidine‐DNA glycolyase (Fpg)‐based comet assay and 8‐oxodG‐based flow cytometry, the 8‐oxodG expressions were higher in 4βHWE‐treated oral cancer cells than in oral normal cells. All the 4βHWE‐induced DSB and oxidative DNA damage to oral cancer cells were recovered by NAC pretreatment. Taken together, the 4βHWE selectively induced DSB and oxidative DNA damage for the ROS‐mediated selective killing of oral cancer cells.     

DNA Adduct Levels and Intestinal Lesions in Congenic Rapid and Slow Acetylator Syrian Hamsters Administered the Food Mutagens 2‐Amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) or 2‐Amino‐3‐methylimidazo[4,5‐f]quinoline (IQ

Epidemiological studies indicate that rapid acetylators with a high intake of well‐done red meat have an increased risk of colorectal cancer. Arylamine N‐acetyltransferase enzymes (E.C. 2.3.1.5) activate carcinogenic heterocyclic amines found in the crust of fried meat via O‐acetylation of their N‐hydroxylamines to reactive intermediates that bind covalently to DNA and produce mutations. Syrian hamsters as well as humans express two N‐acetyltransferase isozymes (NAT1 and NAT2) which differ in substrate specificity and genetic control. Nucleic acid substitutions in the NAT2 gene segregate individuals into rapid, intermediate and slow acetylator phenotypes. In the present paper, we examined the role of the polymorphic NAT2 acetylator genotype in carcinogenesis induced by the food mutagens 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) or 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ) by comparing Syrian hamster lines congenic at the NAT2 locus. No differences were found between rapid and slow acetylator congenic hamsters in levels of intestinal PhIP‐DNA adducts. In contrast to previous studies in rats, no carcinogen‐related induction of the preneoplastic lesions aberrant crypt foci or tumors was found in the intestines of rapid and slow acetylator congenic Syrian hamsters administered PhIP or IQ.     

Facile synthesis of Nα‐protected‐l‐α,γ‐diaminobutyric acids mediated by polymer‐supported hypervalent iodine reagent in water

Abstract: Hofmann rearrangement of N^α‐Boc‐l ‐Gln‐OH mediated by a polymer‐supported hypervalent iodine reagent poly[(4‐diacetoxyiodo)styrene] (PSDIB) in water afforded N^α‐Boc‐l ‐α,γ‐diaminobutyric acid (Boc‐Dab‐OH, 1 ) in 87% yield. N^α‐Z‐derivative (Z‐Dab‐OH, 2 ) was prepared with PSDIB in 83% yield. Since the reaction of N^α‐Fmoc‐Gln‐OH by this procedure did not proceed because of the insolubility of Fmoc‐Gln‐OH in aqueous media, we synthesized Fmoc‐Dab(Boc)‐OH ( 5 ) from 2 in 54% yield. Polymyxin B heptapeptide (PMBH) which contains four Dab residues was successfully synthesized in a solution‐phase synthesis.     

Effects of inhibition of hepatic sulfotransferase activity on renal genotoxicity induced by lucidin‐3‐O‐primeveroside

Sulfotransferase 1A (SULT1A) expression is lower in the liver of humans than that of rodents. Therefore, species differences should be taken into consideration when assessing the risk of rodent hepatocarcinogens metabolically activated by SULT1A in humans. Although some renal carcinogens require SULT1A‐mediated activation, it is unclear how SULT1A activity in the liver affects renal carcinogens. To explore the effects of SULT1A activity in the liver on genotoxicity induced by SULT1A‐activated renal carcinogens, B6C3F₁ mice or gpt delta mice of the same strain background were given lucidin‐3‐O‐primeveroside (LuP), a hepatic and renal carcinogen of rodents, for 4 or 13 weeks, respectively, and pentachlorophenol (PCP) as a liver‐specific SULT inhibitor, was given from 1 week before LuP treatment to the end of the experiment. A 4 week exposure of LuP induced lucidin‐specific DNA adduct formation. The suppression of Sult1a expression was observed only in the liver but not in the kidneys of PCP‐treated mice, but co‐administration of PCP suppressed LuP‐induced DNA adduct formation in both organs. Thirteen‐week exposure of LuP increased mutation frequencies and cotreatment with PCP suppressed these increases in both organs. Given that intact levels of SULT activity in the liver were much higher than in the kidneys of rodents, SULT1A may predominantly activate LuP in the liver, consequently leading to genotoxicity not only in the liver but also in the kidney. Thus, species differences should be considered in human risk assessment of renal carcinogens activated by SULT1A as in the case of the corresponding liver carcinogens.