食品中丙烯酰胺的安全问题

自瑞典科学家首次从经高温油炸或烘焙的含淀粉食物中检测出较高含量的对人体有致癌可能性的丙烯酰胺后,围绕这个问题,全球食品界人士在各方面已经做了大量深入的研究工作.综述了当前丙烯酰胺在食品中的安全性,特别是致癌性方面的研究与发展.     

The Pathology of Vinyl Chloride Exposed Mice

Outbred albino laboratory mice were exposed to 50 p.p.m. and 500 p.p.m. vinyl chloride by inhalation 6 hrs./day, 5 days/week during 52 and 26 weeks, respectively. Pathologic examination showed the presence of histologically benign alveologenic lung adenomas, haem-angiosarcomas in fat tissue as well as a few benign and malignant tumours at various sites. Only one liver haemangiosarcoma was noted. All animals exposed to 500 p.p.m. developed tumours; 71 % of the animals given 50 p.p.m. were tumour bearing. The frequency of all tumours, number of tumour foci and size of foci in both groups suggest a dose-dependent carcinogenic effect of vinyl chloride. Haemocoelia due to blood vessel rupture was a common cause of death. Telangiectasis of the liver was also observed in a few animals. The role of fat tissue as well as blood vessel involvement in the pathology of vinyl chloride is discussed.     

Lack of Hepatocarcinogenicity of Combinations of Low Doses of 2-amino-3, 8-dimethylimidazo[4,5- f ]quinoxaline and Diethylnitrosamine in Rats: Indication for the Existence of a Threshold for Genotoxic Carcinogens

The purposes of the present study were to evaluate the hepatocarcinogenicity of concurrent treatment of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and diethylnitrosamine (DEN) in rats and to determine whether no effect levels of combinations of these two different structural categories of genotoxic hepatocarcinogens exist. Two 16-week rat hepatocarcinogenesis assays were performed using a total of 790 male F344 rats. In experiment 1, we evaluated the effects of concurrent treatment of a subcarcinogenic dose of DEN on rat hepatocarcinogenesis induced by various doses of MeIQx. In experiment 2, we determined hepatocarcinogenicities of combinations of MeIQx and DEN at subcarcinogenic doses, low carcinogenic doses and high carcinogenic doses. Quantitative analyses of glutathione S-transferase placental form (GST-P)-positive foci, a preneoplastic lesion of the liver in rats, revealed that concurrent treatment with subcarcinogenic doses of DEN did not enhance MeIQx-induced rat hepatocarcinogenicity. We also found that concurrent treatment with combinations of subcarcinogenic doses of DEN and MeIQx was not hepatocarcinogenic, indicating that the combined effects of subcarcinogenic doses of DEN and MeIQx were neither additive nor synergistic. Moreover, concurrent treatment with low carcinogenic doses of these 2 carcinogens did not show additive or synergistic effects. Synergetic effects were observed only in rats coadministered high carcinogenic doses of the 2 carcinogens. These results demonstrate the existence of no effect levels of combinations of these 2 genotoxic hepatocarcinogens, and provide new evidence supporting our idea that there is a threshold, at least a practical threshold, that should be considered when evaluating the risk of genotoxic carcinogens.     

Development of a Medium-term Animal Model Using gpt Delta Rats to Evaluate Chemical Carcinogenicity and Genotoxicity

In this study, the potential for development of an animal model (GPG46) capable of rapidly detecting chemical carcinogenicity and the underlying mechanisms of action were examined in gpt delta rats using a reporter gene assay to detect mutations and a medium-term rat liver bioassay to detect tumor promotion. The tentative protocol for the GPG46 model was developed based on the results of dose-response exposure to diethylnitrosamine (DEN) and treatment with phenobarbital over time following DEN administration. Briefly, gpt delta rats were exposed to various chemicals for 4 weeks, followed by a partial hepatectomy (PH) to collect samples for an in vivo mutation assay. The mutant frequencies (MFs) of the reporter genes were examined as an indication of tumor initiation. A single intraperitoneal (ip) injection of 10 mg/kg DEN was administered to rats 18 h after the PH to initiate hepatocytes. Tumor-promoting activity was evaluated based on the development of glutathione S-transferase placental form (GST-P)-positive foci at week 10. The genotoxic carcinogens 2-acetylaminofluorene (2-AAF), 2-amino-3-methylimidazo [4,5-f] quinolone (IQ) and safrole (SF), the non-genotoxic carcinogens piperonyl butoxide (PBO) and phenytoin (PHE), the non-carcinogen acetaminophen (APAP) and the genotoxic non-hepatocarcinogen aristolochic acid (AA) were tested to validate the GPG46 model. The validation results indicate that the GPG46 model could be a powerful tool in understanding chemical carcinogenesis and provide valuable information regarding human risk hazards.     

Successful drug development despite adverse preclinical findings part 2: examples

To illustrate the process of addressing adverse preclinical findings (APFs) as outlined in the first part of this review, a number of cases with unexpected APF in toxicity studies with drug candidates is discussed in this second part. The emphasis is on risk characterization, especially regarding the mode of action (MoA), and risk evaluation regarding relevance for man. While severe APFs such as retinal toxicity may turn out to be of little human relevance, minor findings particularly in early toxicity studies, such as vasculitis, may later pose a real problem. Rodents are imperfect models for endocrine APFs, non-rodents for human cardiac effects. Liver and kidney toxicities are frequent, but they can often be monitored in man and do not necessarily result in early termination of drug candidates. Novel findings such as the unusual lesions in the gastrointestinal tract and the bones presented in this review can be difficult to explain. It will be shown that well known issues such as phospholipidosis and carcinogenicity by agonists of peroxisome proliferator-activated receptors (PPAR) need to be evaluated on a case-by-case basis. The latter is of particular interest because the new PPAR α and dual α/γ agonists resulted in a change of the safety paradigm established with the older PPAR α agonists. General toxicologists and pathologists need some understanding of the principles of genotoxicity and reproductive toxicity testing. Both types of preclinical toxicities are major APF and clinical monitoring is difficult, generally leading to permanent use restrictions.     

Lung Carcinogenic Bioassay of CuO and TiO(2) Nanoparticles with Intratracheal Instillation Using F344 Male Rats

Toxicity assessment of nanoparticles, now widespread in our environment, is an important issue. We have focused attention on the carcinogenic potential of copper oxide (CuO) and titanium dioxide (TiO(2)). In experiment 1, a sequential pilot study, the effectiveness of a carcinogenic bioassay featuring intraperitoneal injection (i.p.) of 20 mg 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or 0.1% N-bis(2-hydroxypropyl)nitrosamine (DHPN) in drinking water for 2 weeks was examined. Based on the results, DHPN, as the lung carcinogen, and evaluation at week 30 were selected as the most appropriate for our purposes in Experiment 1. In experiment 2, the carcinogenic bioassay was used to assess the carcinogenic potentials of instilled nanoparticles of CuO and TiO(2). There were no significant intergroup differences in the lung neoplastic lesions induced by DHPN, although the neoplastic lesions induced by the nanoparticles in the CuO or TiO(2) intratracheal instillation (i.t.) groups, demonstrated a tendency to increase compared with the microparticles administration. At the very least, the carcinogenic bioassay with DHPN proved useful for assessment of the modifying effects of instilled particles, and further assessment of the carcinogenic potential of nanoparticles appears warranted.     

喹口恶啉-1,4-二氧化物类抗菌促生长剂特殊毒理学研究进展

喹恶啉－1，4－二氧化物取代衍生物卡巴氧、喹乙醇，西吖氧作为抗菌促生长饲料添加剂广泛应用于猪。为了评介它们的安全性，本文从致突变、致癌性和生殖毒性三方面对它们的特殊毒理学研究作了综述。     

What Do We Know about Antimicrobial Activity of Astaxanthin and Fucoxanthin?

Astaxanthin (AST) and fucoxanthin (FUC) are natural xanthophylls, having multidirectional activity, including antioxidant, anti-inflammatory, and anticancer. Both compounds also show antimicrobial activity, which is presented in this review article. There are few papers that have presented the antimicrobial activity of AST. Obtained antimicrobial concentrations of AST (200–4000 µg/mL) are much higher than recommended by the European Food Safety Authority for consumption (2 mg daily). Therefore, we suggest that AST is unlikely to be of use in the clinical treatment of infections. Our knowledge about the antimicrobial activity of FUC is better and this compound acts against many bacteria already in low concentrations 10–250 µg/mL. Toxicological studies on animals present the safety of FUC application in doses 200 mg/kg body weight and higher. Taking available research into consideration, a clinical application of FUC as the antimicrobial substance is real and can be successful. However, this aspect requires further investigation. In this review, we also present potential mechanisms of antibacterial activity of carotenoids, to which AST and FUC belong.     

rasH2 mouse: reproducibility and stability of carcinogenicity due to a standardized production and monitoring system

The rasH2 mouse was developed as a model for carcinogenicity studies in regulatory science. Its phenotype is stable during high-volume production and over successive generations. To produce rasH2 mice, three strains of mice (C57BL/6J-TgrasH2, C57BL/6J, and BALB/cByJ) were maintained individually. Since the homozygous c-HRAS genotype is lethal, hemizygous transgenic mice were maintained by crossing with inbred C57BL/6J mice. After breeding, male B6-transgenic mice were mated with female BALB/cByJ mice to obtain transgenic mice. Pups that were rasH2-Tg (tg/wt) or rasH2-Wt (wt/wt) were confirmed by genotyping. Frozen embryos were preserved by the Central Institute for Experimental Animals (CIEA) and sent to two facilities, CLEA Japan and Taconic Biosciences, where the mice were produced. Production colonies are created in both facilities and supplied to customers worldwide. To prevent genetic drift, the colonies were renewed for up to 10 generations, and renewals were carried out four times every five years from 2005 to 2021. To ensure the uniformity and maintenance of the phenotype of rasH2 mice, the carcinogen susceptibilities were monitored in every renewal of colonies by CIEA based on a standard protocol of the short-term carcinogenicity study using the positive control compound N-methyl-N-nitrosourea (MNU). Furthermore, simple carcinogenicity monitoring targeting the forestomach, the organ most sensitive to MNU, was performed approximately once a year. Based on the optimally designed production and monitoring systems, the quality of rasH2 mice with reproducibility and stability of carcinogenicity is maintained and supplied globally.     

Survey of tumorigenic sensitivity in 6-month rasH2-Tg mice studies compared with 2-year rodent assays

The pharmacokinetic endpoint of a 25-fold increase in human exposure is one of the specified criteria for high-dose selection for 2-year carcinogenicity studies in rodents according to ICH S1C(R2). However, this criterion is not universally accepted for 6-month carcinogenicity tests in rasH2-Tg mice. To evaluate an appropriate multiple for rasH2-Tg mice, we evaluated data for 53 compounds across five categories of rasH2-Tg mouse-positive [(1) genotoxic and (2) non-genotoxic] carcinogens and rasH2-Tg mouse-negative [(3) non-genotoxic carcinogens with clear or uncertain human relevance; (4) non-genotoxic rodent-specific carcinogens; and (5) non-carcinogens], and surveyed their tumorigenic activities and high doses in rasH2-Tg mice and 2-year rodent models. Our survey indicated that area under the curve (AUC) margins (AMs) or body surface area-adjusted dose ratios (DRs) of tumorigenesis in rasH2-Tg mice to the maximum recommended human dose (MRHD) were 0.05- to 5.2-fold in 6 category (1) compounds with small differences between models and 0.2- to 47-fold in 7 category (2) including three 2-year rat study-negative compounds. Among all 53 compounds, including 40 compounds of the rasH2-Tg mouse-negative category (3), (4), and (5), no histopathologic risk factors for rodent neoplasia were induced only at doses above 50-fold AM or DR in rasH2-Tg mice except for two compounds, which induced hyperplasia and had no relationship with the tumors observed in the rasH2-Tg mouse or 2-year rodent studies. From the results of these surveys, we confirmed that exceeding a high dose level of 50-fold AM in rasH2-Tg mouse carcinogenicity studies does not appear to be of value.