Determination of potential thresholds for N-ethyl-N-nitrosourea and ethyl methanesulfonate based on a multi-endpoint genotoxicity assessment platform in rats.

The main goal of the study was to investigate the genotoxic response of N-ethyl-N-nitrosourea (ENU) and ethyl methanesulfonate (EMS) at low doses in a multi-endpoint genotoxicity assessment platform in rats and to derive potential thresholds and related metrics. Male Sprague-Dawley rats were treated by daily oral gavage for 28 consecutive days with ENU (0.25 ~ 8 mg/kg bw) and EMS (5 ~ 160 mg/kg bw), both with six closely spaced dose levels. Pig-a gene mutation assay, micronucleus test, and comet assay were performed in several timepoints. Then, the dose-response relationships were analyzed for possible points of departure (PoD) using the no observed genotoxic effect level and benchmark dose (BMD) protocols with different critical effect sizes (CES, 0.05, 0.1, 0.5, and 1SD). Overall, dose-dependent increases in all investigated endpoints were found for ENU and EMS. PoDs varied across genetic endpoints, timepoints, and statistical methods, and selecting an appropriate lower 95% confidence limit of BMD needs a comprehensive consideration of the mode of action of chemicals, the characteristics of tests, and the model fitting methods. Under the experimental conditions, the PoDs of ENU and EMS were 0.0036 mg/kg bw and 1.7 mg/kg bw, respectively.

Characterization of benzo[a]pyrene and colchicine based on an in vivo repeat-dosing multi-endpoint genotoxicity quantitative assessment platform.

Two prototypical genotoxicants, benzo[a]pyrene (B[a]P) and colchicine (COL), were selected as model compounds to deduce their quantitative genotoxic dose-response relationship at low doses in a multi-endpoint genotoxicity assessment platform. Male Sprague-Dawley rats were treated with B[a]P (2.5-80 mg/kg bw/day) and COL (0.125-2 mg/kg bw/day) daily for 28 days. The parameters included were as follows: comet assay in the peripheral blood and liver, Pig-a gene mutation assay in the peripheral blood, and micronucleus test in the peripheral blood and bone marrow. A significant increase was observed in Pig-a mutant frequency in peripheral blood for B[a]P (started at 40 mg/kg bw/day on Day 14, started at 20 mg/kg bw/day on Day 28), whereas no statistical difference for COL was observed. Micronucleus frequency in reticulocytes of the peripheral blood and bone marrow increased significantly for B[a]P (80 mg/kg bw/day on Day 4, started at 20 mg/kg bw/day on Days 14 and 28 in the blood; started at 20 mg/kg bw/day on Day 28 in the bone marrow) and COL (started at 2 mg/kg bw/day on Day 14, 1 mg/kg bw/day on Day 28 in the blood; started at 1 mg/kg bw/day on Day 28 in the bone marrow). No statistical variation was found in indexes of comet assay at all time points for B[a]P and COL in the peripheral blood and liver. The dose-response relationships of Pig-a and micronucleus test data were analyzed for possible point of departures using three quantitative approaches, i.e., the benchmark dose, breakpoint dose, and no observed genotoxic effect level. The practical thresholds of the genotoxicity of B[a]P and COL estimated in this study were 0.122 and 0.0431 mg/kg bw/day, respectively, and our results also provided distinct genotoxic mode of action of the two chemicals.

General toxicity and genotoxicity of altertoxin I: A novel 28-day multiendpoint assessment in male Sprague-Dawley rats.

The mycotoxin altertoxin I (ATX-I) is one of secondary metabolites produced by Alternaria fungi and is frequently detected as food and feed contaminants. Little is known about the genotoxicity of the ATX-I. In order to evaluate potential genotoxicity and general toxicity of ATX-I, the novel 28-day multiendpoint (Pig-a assay + micronucleus [MN] test + comet assay) genotoxicity platform was applied. Male Sprague-Dawley (SD) rats were randomized to five groups (six rats per group), that is, a positive control group (N-ethyl-N-nitrosourea [ENU], 40 mg/kg.bw/d), two solvent control groups (PBS and corn oil), and two ATX-I-treated groups (low-dose group [1.10 µg/kg.bw/d] and high-dose group [5.51 µg/kg.bw/d]). Treatments were administered by oral gavage to male SD rats for 28 consecutive days. Histopathological damages in the liver, kidney, and spleen were observed, but without significant changes in hematological and serum biochemical parameters. Genotoxic endpoints indicated that ATX-I could cause DNA damage. To summarize, in a relatively low-dose range, ATX-I may not have direct genotoxicity in vivo but could induce liver, kidney, and spleen damage.

Alternariol monomethyl ether toxicity and genotoxicity in male Sprague-Dawley rats: 28-Day in vivo multi-endpoint assessment.

Alternariol monomethyl ether (AME), a typical Alternaria toxin, has often been detected in grains. We have measured the general toxicity and genotoxicity of AME with a 28-day multi-endpoint (Pig-a assay + in vivo micronucleus [MN] test + comet assay) platform. Male Sprague-Dawley rats were administered AME (1.84, 3.67, or 7.35 µg/kg body weight/day), N-Ethyl-N-nitrosourea (40 mg/kg body weight/day), or corn oil by gavage for 28 consecutive days. Another group (AME-high-dose + recovery) was maintained for a further 14 days after the end of the AME administration. Hematology and serum biochemistry results suggested that AME might compromise the immune system. The histopathology results indicated that AME can cause liver (inflammatory cell infiltration, steatosis, and edema), kidney (renal glomerular atrophy), and spleen (white pulp atrophy) damage. The genotoxicity results showed that AME can induce gene mutations, chromosome breakage, and DNA damage, but the effects were diminished after the recovery period. According to point-of-departure analysis (BMDL10), the risk to the population of exposure to AME cannot be ignored and further assessment is needed.

Genotoxicity of three mycotoxin contaminants of rice: 28-day multi-endpoint assessment in rats.

Deoxynivalenol (DON), zearalenone (ZEN), and fumonisin B1 (FB1), as the main mycotoxins contaminating rice, often coexist in food. Thus, we have measured the genotoxicity of the three rice fungal contaminants, singly and in different combinations, with a 28-day multi-endpoint (Pig-a assay + in vivo micronucleus [MN] test + comet assay) genotoxicity platform. Male Sprague-Dawley rats received the agents orally via gavage for 28 consecutive days, before performing the abovementioned tests. Results indicated that low dose of a single mycotoxin did not show significant genotoxicity. However, some of these mycotoxins in combination induced significant genotoxicity in the peripheral blood and tissues, at sacrifice. In the peripheral blood, the binary combination of DON and FB1 significantly induced MN. In the liver, ZEN might aggravate the DNA-damaging effects of DON and FB1. Therefore, the genotoxicity of sub-chronic exposure to mycotoxins in combination cannot be ignored.

Assessment of a 10-year dog deworming programme on the transmission of Echinococcus multilocularis in Tibetan communities in Sichuan Province, China.

Human alveolar echinococcosis (AE) is considered a neglected zoonotic disease by the World Health Organization (WHO). The causative pathogen, Echinococcus multilocularis, lives as an adult tapeworm in the intestinal tract of canines. AE was identified as an emerging public health issue in Tibetan communities of Shiqu County 20 years ago. On St. Lawrence Island, Alaska (USA), in the 1980s peri-domestic transmission of E. multilocularis was controlled by regular deworming of owned dogs over a 10-year period. In Tibetan communities, on the Tibetan Plateau, control of E. multilocularis transmission is challenging due to the continental setting, complex epidemiology, disease ecology, geography, and socio-cultural factors. However, a control programme based on deworming owned dogs using praziquental (PZQ) has been carried out since 2006. Assessment was conducted in townships where baseline data were available 10 years prior. Purging of dogs by oral administration of arecoline was used to measure E. multilocularis prevalence, trapping small mammals around communities was employed to assess the change in infection of pikas and voles, and analysis of human AE abdominal ultrasound-based data was used to understand the change in prevalence in the past decade. In all three evaluated townships, the E. multilocularis prevalence in owned dogs was significantly (P < 0.01) reduced from 7.23% (25/346) during 2000-2003 to 0.55% (1/181) in 2016. Human AE ultrasound-based prevalence (adjusted for age and sex) in five evaluated townships decreased significantly (P < 0.01) from 6.25% (200/3,198) during 2000-2002 to 3.67% (706/19,247) during 2015-2017. The 2016 prevalence of E. multilocularis metacestodes in small mammal intermediate hosts was not significantly different from the prevalence in 2008. The control programme was effective in reducing E. multilocularis infection in owned dogs and human AE prevalence, but did not significantly impact infection in wildlife intermediate hosts.

Disease burden of echinococcosis in Tibetan communities-A significant public health issue in an underdeveloped region of western China.

Echinococcosis is considered by the World Health Organization (WHO) to be a neglected zoonotic disease in the world. Some Tibetan communities were found to be highly endemic for echinococcosis just 20 years ago. Until recently, we were able to understand the overall disease burden of echinococcosis in Tibetan communities after prevalence data being available from nationwide investigations from 2012 to 2016. Data were abstracted from 9 publications regarding to echinococcosis prevalence between 2016-2018; from 10 data bases on echinococcosis prevalence for 151 Tibetan counties; and statistics of population, Gross Domestic Product (GDP) and health staff from 44 local statistic bureaus and government websites at provincial, prefecture and county level, and 2 books of provincial yearly statistics. These data were used to estimate the Disability Adjusted Life Years (DALYs) due to cystic echinococcosis (CE) and alveolar echinococcosis (AE). The distribution of DALYs was presented geographically and economically. The echinococcosis DALYs in the Tibetan communities were estimated to be 126,159 (95%UI 122,415-137,675) annually using the method recommended by WHO. AE DALYs were estimated to be 105,829 (95%UI 101,969-117,090), which were more than CE DALYs of 20,330 (95%UI 19,690-21,581). Echinococcosis affects people more in underdeveloped areas. There was a tendency that a higher echinococcosis DALYs were usually correlated a higher altitude. Health services are also poorly provided in terms of number of health staff of 5.05 per 1000 population in comparison with the national average of 5.8 per 1000 population. The data suggest that the echinococcosis burden in the center region of Qinghai-Tibet plateau is higher than that of other regions, and consequently more control and health services should be provided to the region.