To date, there has been no well-established local lymph node assay (LLNA) that includes an elicitation phase. Therefore, we developed a modified local lymph node assay with an elicitation phase (LLNA:DAE) to discriminate true skin sensitizers from chemicals that gave borderline positive results and previously reported this assay. To develop the LLNA:DAE method as a useful stand-alone testing method, we investigated the complete procedure for the LLNA:DAE method using hexyl cinnamic aldehyde (HCA), isoeugenol, and 2,4-dinitrochlorobenzene (DNCB) as test compounds. We defined the LLNA:DAE procedure as follows: in the dose-finding test, four concentrations of chemical applied to dorsum of the right ear on days 1, 2, and 3 and dorsum of both ears on day 10. Ear thickness and skin irritation score were measured on days 1, 3, 5, 10, and 12. Local lymph nodes were excised and weighed on day 12. The test dose for the primary LLNA:DAE study was selected as the dose that gave the highest left ear lymph node weight in the dose-finding study, or the lowest dose that produced a left ear lymph node of over 4 mg. This procedure was validated using nine different chemicals. Furthermore, qualitative relationship was observed between the degree of elicitation response in the left ear lymph node and the skin sensitizing potency of 32 chemicals tested in this study and the previous study. These results indicated that LLNA:DAE method was as first LLNA method that was able to evaluate the skin sensitizing potential and potency in elicitation response.
Cadmium is a widely used heavy metal in industry and affects the male reproductive system of animals, including humans, as a result of occupational and environmental exposures. However, the molecular mechanism underlying its effect on steroidogenesis in gonads remains unclear. In this study, we demonstrated that exposure of K28 mouse testicular Leydig tumor cells to cadmium led to a significant increase in the mRNA level, promoter activity and protein level of the steroidogenic acute regulatory protein (StAR), an essential factor for steroid biosynthesis. It has been well documented that StAR gene transcription is regulated by multiple transcription factors, including cAMP-responsive element binding protein (CREB) family members and SF-1. Cadmium treatment caused an increase in CREB phosphorylation but did not alter the CREB protein level in the nucleus. EMSA studies revealed that cadmium-induced phosphorylated CREB formed specific complexes with the proximal region of the StAR gene promoter. Furthermore, co-transfection with a CREB expression plasmid significantly increased cadmium-induced StAR promoter activity. However, the nuclear level and the affinity of SF-1 protein for the StAR proximal promoter were dramatically decreased upon exposure to cadmium. Taken together, these results suggest that cadmium up-regulates StAR gene expression through phosphorylated CREB rather than through SF-1 in mouse testicular Leydig cells.
Use of laboratory animals for systemic toxicity testing is subject to strong ethical and regulatory constraints, but few alternatives are yet available. One possible approach to predict systemic toxicity of chemicals in the absence of experimental data is quantitative structure-activity relationship (QSAR) analysis. Here, we present QSAR models for prediction of maximum “no observed effect level” (NOEL) for repeated-dose, developmental and reproductive toxicities. NOEL values of 421 chemicals for repeated-dose toxicity, 315 for reproductive toxicity, and 156 for developmental toxicity were collected from Japan Existing Chemical Data Base (JECDB). Descriptors to predict toxicity were selected based on molecular orbital (MO) calculations, and QSAR models employing multiple independent descriptors as the input layer of an artificial neural network (ANN) were constructed to predict NOEL values. Robustness of the models was indicated by the root-mean-square (RMS) errors after 10-fold cross-validation (0.529 for repeated-dose, 0.508 for reproductive, and 0.558 for developmental toxicity). Evaluation of the models in terms of the percentages of predicted NOELs falling within factors of 2, 5 and 10 of the in-vivo-determined NOELs suggested that the model is applicable to both general chemicals and the subset of chemicals listed in International Nomenclature of Cosmetic Ingredients (INCI). Our results indicate that ANN models using in silico parameters have useful predictive performance, and should contribute to integrated risk assessment of systemic toxicity using a weight-of-evidence approach. Availability of predicted NOELs will allow calculation of the margin of safety, as recommended by the Scientific Committee on Consumer Safety (SCCS).
The effects of the peroxisome proliferator, dehydroepiandrosterone sulfate (DHEAS), and the typical cytochrome P450 (CYP) inducers phenobarbital (PB) and 3-methylcholanthrene (3-MC) on fatty liver were examined in rats. Treating rats with orotic acid caused marked accumulation of lipid droplets in the liver. This effect of orotic acid was almost eradicated by co-treatment with DHEAS and PB. While DHEAS or PB alone also alleviated fatty liver, treatment with 3-MC caused little effect on a reduction in lipid droplets. Histopathological examinations revealed numerous peroxisomes in the liver of rats treated with DHEAS. In addition, a significant increase in the expression on hepatic CYPs was observed in rats the fatty liver of which was attenuated. Regarding other enzymes associated with hepatic fatty acid oxidation, the expression levels of sirtuin 1, sirtuin 6, and carnitine palmitoyltransferase 1 were also upregulated most markedly by treatment with DHEAS alone. Thus, the attenuation in fatty liver observed in the present study is likely due to peroxisome proliferation and the induction of fatty acid-metabolizing enzymes by DHEAS and typical CYP inducers.
The sensitizing potential of chemicals is usually identified and characterized using in vivo methods such as the murine local lymph node assay (LLNA). Due to regulatory constraints and ethical concerns, alternatives to animal testing are needed to predict the skin sensitization potential of chemicals. For this purpose, an integrated evaluation system employing multiple in vitro and in silico parameters that reflect different aspects of the sensitization process seems promising. We previously reported that LLNA thresholds could be well predicted by using an artificial neural network (ANN) model, designated iSENS ver. 2 (integrating in vitro sensitization tests version 2), to analyze data obtained from in vitro tests focused on different aspects of skin sensitization. Here, we examined whether LLNA thresholds could be predicted by ANN using in silico-calculated descriptors of the three-dimensional structures of chemicals. We obtained a good correlation between predicted LLNA thresholds and reported values. Furthermore, combining the results of the in vitro (iSENS ver. 2) and in silico models reduced the number of chemicals for which the potency category was under-estimated. In conclusion, the ANN model using in silico parameters was shown to be have useful predictive performance. Further, our results indicate that the combination of this model with a predictive model using in vitro data represents a promising approach for integrated risk assessment of skin sensitization potential of chemicals.
Hyperhomocysteinemia (HHC) has been reported to be one of risk factors for cardiovascular disease. We investigated the effects of HHC on blood pressure regulation and its association with damage to the thoracic aorta and imbalance of redox in plasma in rats. Rats were fed a methionine enriched diet (Met diet) or a methionine and cholesterol (Met+Chol diet) enriched diet for 16 weeks to create a subchronic HHC model, in which the plasma concentration of homocysteine was about 7 times higher than that of control rats. The increase in systolic blood pressure (Δ-SBP) from sympathetic stimulation by L-epinephrine was 2- to 3-fold larger in HHC model in rats than that in control rats after several weeks of the treatment. These findings suggest that HHC deteriorates vaso-regulatory function, which could bring on an increased risk of cardiovascular events in humans. In addition, some of the elastic lamellae in the aorta were disrupted in the HHC group. However, the content of cross-linkages which give elasticity and mechanical strength in the lamellae, was not significantly different between HHC and control rats. Also plasma concentrations of thiobarbituric acid reactive substance and glutathione as indicators for redox balance in plasma were not different. In conclusion, the deterioration of vaso-regulation in HHC model in rats might be caused by the damage to elastic lamellae in the aorta, and not by oxidative stresses.
Bongkrekic acid (BKA), an antibiotic isolated from Pseudomonas cocovenans, is an inhibitory molecule of adenine nucleotide translocase. Since this translocase is a core component of the mitochondrial permeability transition pore (MPTP) formed by apoptotic stimuli, BKA has been used as a tool to abrogate apoptosis. However, the other biochemical properties of BKA have not yet been resolved. Although the definition of a fatty acid is a carboxylic acid (-COOH) with a long hydrocarbon chain (tail), when focused on the chemical structure of BKA, the molecule was revealed to be a branched unsaturated tricarboxylic acid that resembled the structure of polyunsaturated fatty acids (PUFAs). Peroxisome proliferator-activated receptors (PPARs) consist of a subfamily of three isoforms: α, β, and γ, the ligands of which include PUFAs. Using completely synthesized BKA together with simplified BKA derivatives (purity: > 98%), we herein demonstrated the utility of BKA as a selective activator of the human PPARγ isoform, which may not be associated with the anti-apoptotic nature of BKA. We also discussed the possible usefulness of BKA.
Propolis, a natural product derived from plants by honeybees, is a mixture of several hundred chemicals, including flavonoids, coumaric acids, and caffeic acids, some of which show estrogen-like activity. In this study, the estrogenic activity of crude ethanolic extract of Brazilian propolis was determined using several in vitro and in vivo assays. Propolis was found to bind to human estrogen receptors (ERs). Furthermore, propolis induced the expression of estrogen-responsive genes in ER-positive MCF-7 and Ishikawa cells. These in vitro assays suggest that propolis exerts estrogenic activity; therefore, in vivo experiments were conducted using ovariectomized rats. Oral administration of propolis (55 or 550 mg/kg/day for 3 days) significantly increased uterine wet weight and luminal epithelium thickness in comparison with the corresponding values in the corn oil-treated control group. Moreover, propolis induced ductal cell proliferation in the mammary glands. These effects were completely inhibited by full ER antagonist ICI 182,780, confirming that the effects of propolis are mediated by the ER. Our data show that oral intake of propolis induces estrogenic activity in ER-expressing organs in vivo and suggest that Brazilian propolis is a useful dietary source of phytoestrogens and a promising treatment for postmenopausal symptoms.
The effect of nanoparticles in the environment on our health is a cause of concern. The greatest concern with respect to the biological effect of nanoparticles is that they remain in the body and invade tissues, overcoming the protective mechanisms of the body. It is generally believed that nanoparticles invading a living body move into the blood and are carried by the bloodstream to all organs. However, some studies have shown that the inhaled nanoparticles directly translocate to the central nervous system by nerve uptake. Here quantification of the amount of migration of nanoparticles to organs in short time spans (1, 3, and 6 hr) was attempted by animal experiments. Furthermore, the possibility of migration of nanoparticles through the nerves that project around the alveolus, including the nodose ganglion and dorsal root ganglion (DRG), was investigated. Gold (Au) nanoparticles (15 nm) were administered to mice by intratracheal instillation and tail vein injection. After tail vein injection, most nanoparticles were distributed in the liver. After intratracheal instillation, approximately 80% of detected nanoparticles remained in the lungs at 1 hr and were believed to be translocated to digestive organs, including the stomach and intestine, at 3 and 6 hr. With respect to quantification in ganglia, the levels in most samples were lower than the limit of quantification of inductively coupled plasma mass spectrometry (ICP-MS). However, Au nanoparticles were detected in DRG in only some samples of intratracheal instillation. Therefore, this suggests the possibility of translocation of nanoparticles to DRG via nerves.
The embryonic stem cell test (EST) is a promising alternative method for evaluating embryotoxicity of test chemicals by measuring cytotoxicity and differentiation toxicity using mouse ES cells. Differentiation toxicity is analyzed by microscopically counting the beating of embryonic bodies after 10 days of culture. However, improvements are necessary to reduce the laborious manipulations involved and the time required to obtain results. We have previously reported the successful stable transfection of ES cells (ES-D3) with the heart and neural crest derivatives expressed transcript 1 (Hand1) gene and the establishment of a 96-well multi-plate-based new EST with luciferase reporter assay 6 days after treatment with test chemicals. Now, we propose an even more rapid and easier EST, named Hand1-Luc EST. We established another cell line to monitor the Hand1 gene expression via a luciferase reporter gene. By mRNA analysis and luciferase assay, we examined in detail the luciferase activity during cell differentiation, which allowed us to reduce the time of measurement from day 6 to day 5 (120 hr). Furthermore, the protocol was improved, with, among others, the measurement of cytotoxicity and differentiation toxicity taking place in the same 96-well round bottom plate instead of two different plates. With the positive control, 5-fluorouracil (5-FU), and 9 test chemicals, data with high reproducibility and very low variation (CV < 50%) in the relevant endpoints were obtained. This study shows that the Hand1-Luc EST could provide an accurate and sensitive short-term test for prediction of embryotoxicants by measuring cytotoxicity and differentiation toxicity from the same sample.
Steadily increased use of silver nanoparticles (Ag-NPs), has increased the amount of its exposure to humans and animals. Current scarce knowledge about the influences of prenatal exposure to Ag-NPs on postnatal outcomes, motivated us to investigate whether being exposed to it during pregnancy has any effects on neurobehavioral development of the adult offspring. Thirty virgin female NMRI mice were mated and treated subcutaneously once every three days from gestation day 3 until delivery, by 0, 0.2 and 2 mg/kg of bodyweight (BW) of Ag-NPs. Behavioral functions of adult offspring including spatial memory, passive avoidance learning, stress, anxiety-like behaviors and locomotor activities were assessed by commonly used neurobehavioral paradigms and the results were compared according to treatment and sex. Prenatal exposure to Ag-NPs significantly impaired their cognitive behavior in the Morris water maze. Although no evidence was observed indicating more anxiety-like behaviors in the treated offspring in the elevated plus maze, the number of defecations and leanings in the open field assay and number of passages in the light-dark box were greater in groups prenatally treated by Ag-NPs. Most of the impairments were more apparent in the offspring which had been prenatally exposed to high doses of Ag-NPs, particularly female ones. The present study indicated that the exposure of pregnant animals to Ag-NPs may lead to various neurobehavioral disorders in their offspring. Thus, more attention should be paid to avoid exposure to Ag-NPs, especially from pregnant females.
An in silico method for predicting percutaneous absorption of cosmetic ingredients was developed by using artificial neural network (ANN) analysis to predict the human skin permeability coefficient (log Kp), taking account of the physicochemical properties of the vehicle, and the apparent diffusion coefficient (log D). Molecular weight and octanol-water partition coefficient (log P) of chemicals, and log P of the vehicles, were used as molecular descriptors for predicting log Kp and log D of 359 samples, for which literature values of either or both of log Kp and log D were available. Adaptivity of the ANN model was evaluated in comparison with a multiple linear regression model (MLR) by calculating the root-mean-square (RMS) errors. Accuracy and robustness were confirmed by 10-fold cross-validation. The predictive RMS errors of the ANN model were smaller than those of the MLR model (log Kp; 0.675 vs 0.887, log D; 0.553 vs 0.658), indicating superior performance. The predictive RMS errors for log Kp and log D with the ANN model after 10-fold cross-validation analysis were 0.723 and 0.606, respectively. Moreover, we estimated the cumulative amounts of chemicals permeated into the skin during 24 hr (Q24hr) from the values of log Kp and log D by applying Fick’s law of diffusion. Our results suggest that this newly established ANN analysis method, taking account of the property of the vehicle, could contribute to non-animal risk assessment of cosmetic ingredients by providing a tool for calculating Q24hr, which is required for evaluating the margin of safety.
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