We examined whether the nuclear localization of caspase-activated DNase (CAD) are involved in cadmium-induced apoptosis. Exposure of porcine kidney LLC-PK₁ cells to cadmium cleaved poly (ADP-ribose) polymerase (PRAP) as sufficiently as TNF-α did in the renal cells. However, nuclear localization of CAD was not seen during cadmium-induced renal apoptosis, but done during apoptosis by TNF-α. On other hands, in rat splenocytes cadmium could induce nuclear localization of CAD. Thus, our data suggest that activation of caspase is not always to allow the translocation of CAD into the nuclei for the internucleosomal cleavage of DNA, and suggest that the same apoptotic stimulus by cadmium may utilize different sets of caspase cascades or unknown death pathways which are coupled to the caspase proteolysis in different cell types.

A previous study showed that single intracisternal administration of p-nitrotoluene into neonatal rats caused hyperactivity. To evaluate the neural risk assessment of p-nitrotoluene, it is crucial to test the potential of the chemical via environmental exposure route. In this study, we tested the hypothesis that oral exposure to p-nitrotoluene would exhibit the effects observed previously with direct instillation. Oral administration of 600 μg/day p-nitrotoluene into male Wistar rat pups, 5 days to 3 weeks of age, caused significant hyperactivity at 4-5 weeks of age. Treated rats were about 1.3 times active in the nocturnal phase than the vehicle-treated control rats (p < 0.05). The long-term effects of the chemical caused a large reduction in tyrosine hydroxylase (TH) immunoreactivity in the midbrain at 7 weeks of age, at which terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling-positive cells were detected. Immunohistochemical analysis of glial fibrillary acidic protein also revealed p-nitrotoluene-induced gliosis in the substantia nigra, suggesting neurodegeneration. Furthermore, neonatal p-nitrotoluene-induced lesion decreased the gene expression levels of dopamine transporter in adult rats. Thus, we conclude that p-nitrotoluene via oral exposure route caused rat hyperactivity, concomitant with gliosis and impairment of TH immunoreactivity, most likely due to degeneration of dopaminergic neurons.

Poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) was administered at dietary levels of 0 (control), 0.3, 0.8 and 2.5% to groups of 20 male and 20 female CB6F1-Tg rasH2 (rasH2) mice for 26 weeks. As a positive control, 10 rasH2 mice of each sex received a single intraperitoneal injection of 75 mg/kg N-methyl-N-nitrosourea (MNU). There were no differences in survival between Ge-132-treated groups and the control. Loose stool, increase water intake, and dilatation of the cecum were evident in both male and female 2.5% groups; however, there were no histopathological abnormality found in the cecums of these mice. There was no significant Ge-132 treatment-related increase in the incidence of any neoplastic lesions compared to negative control. In the positive control MNU groups, malignant lymphomas and squamous cell papillomas of the forestomach frequently occurred. Thus, the experimental system employed showed clear negative results for induction of tumors due to Ge-132 administration, indicating the absence of Ge-132 carcinogenicity in mice.

Drug candidates sometimes cause a prolongation of the electrocardiogram QT-interval (QT) and torsades de pointes in humans, despite the fact that they do not cause them in non-rodent animals. Recent studies suggest that the cardiomyocytes derived from human induced-pluripotent stem cells (hiPS-CMs) are of sufficient quality to assess the cardiotoxicity of drugs in the preclinical setting. Thus, the usefulness of hiPS-CMs in correctly predicting the cardiotoxicity of drug candidates in the clinical setting, was examined using conventional drugs in the calcium transient analysis system FDSS/μCELL and the multielectrode array system MED64. The selection of the test drugs was based on previously reported studies. E-4031 and cisapride prolong the QT in humans, dogs and monkeys. Both drugs prolonged the calcium fluorescence peak width (PWD) in the FDSS/μCELL system and the field potential duration (FPD) in the MED64 system, both of which are thought to be surrogates of the QT. Diphenhydramine, famotidine and E-8010 prolong the QT in humans but not in dogs or monkeys. These drugs prolonged the PWD and FPD. On the other hand, verapamil and nifedipine prolong the QT in dogs or monkeys but not in humans. Both drugs shortened the PWD and FPD. These results suggest that the hiPS-CMs assay could correctly predict the QT effects in humans. The hiPS-CMs would be useful for predicting the effects of drug candidates on the QT of humans in preclinical in vitro studies.

Animal tests, such as the local lymph node assay (LLNA), are the gold standard for assaying skin-sensitizing potential. However, because of concerns about animal welfare, extensive research has been conducted on the use of various cell lines, such as human leukemia cells, for in vitro assays of skin-sensitizing potential, but such assays have not replaced animal tests as stand-alone assays. Because Langerhans cells—a type of dendritic cell—are the main antigen-presenting cells in the epidermis and because they play a central role in the induction of allergic skin disorders, these cells may be useful for skin-sensitizing-potential assays. Here, we investigated the utility of the murine dendritic cell line DC2.4 for in vitro assay of the skin-sensitization potential of 2,4-dinitrochlorobenzene (DNCB), 2-mercaptobenzothiazole (MBT), and α-hexyl cinnamaldehyde (HCA), which are categorized as extremely, moderately, and weakly sensitizing, respectively, on the basis of LLNA results. DC2.4 cell viability decreased dose-dependently with increasing concentration upon treatment with each of the compounds for 24 hr; the DNCB, MBT, and HCA concentrations that resulted in 75% cell viability were 6.07, 120.14, and 118.70 μg/mL, respectively. At nontoxic concentrations (concentrations less than the 75% cell viability concentrations), these compounds dose-dependently upregulated the expression of both CD86 and CD54 on the surface of DC2.4 cells. Their potency decreased in the order DNCB > MBT > HCA, which agrees with the order indicated by the LLNA. These results suggest that DC2.4 cells may be a viable replacement for human leukemia cells in in vitro assays of skin-sensitization potential.

To analyze the permeability of rat skin to silver nanoparticles, the dorsal skin of Sprague-Dawley rats was exposed to 5 nm Ag nanoparticles or silver nitrate (Ag⁺ ions) percutaneously for 24 hr after disruption of the epidermal barrier by tape stripping (TS) or acetone wiping (AC). Systemic toxicity was examined hematologically and histopathologically, and by assessing blood biochemistry. Although parakeratosis, decrease in keratohyaline granule, and thickening in the epidermis occurred following exposure to both 5 nm Ag nanoparticles and Ag⁺ ions after TS or AC, no Ag-specific changes were observed. Inductively coupled plasma mass spectrometry (ICP-MS) showed silver in the skin of rats exposed to both 5 nm Ag nanoparticles and Ag⁺ ions after TS or AC. Silver was only detected in the liver of rats exposed to Ag⁺ ions after TS, but not exposed to 5 nm Ag nanoparticles after TS or AC. No abnormal histopathological changes in the liver were observed in all rats. In the blood, silver was below detectable levels in all rats and had no adverse effects on hematology or blood biochemistry. These results indicate that silver ions released from 5 nm Ag nanoparticles can percutaneously infiltrate the body only when the skin barrier is disrupted, but does not induce any acute toxicity.

It is known that phototoxicity is related to chemical structure. We have previously reported a prediction method of chemical structure-based in silico phototoxicity for in vitro 3T3 NRU-PT assay. To improve the concordance of the method, here we added new descriptors related to another mechanism of phototoxicity. We focused on potential energy, which certainly contributes to chemical reactivity regardless of photo-irradiation. As a result, stretch-bend, a form of potential energy, was found as a new descriptor of phototoxicity. Our analysis strongly indicates that chemical reactivity is an important factor for phototoxic outcome.