Fundamental Toxicological Sciences

2015 - Vol. 2 No. 2

2015 - Vol. 2

Toxicomics Report
DNA microarray analysis of genes in highly metastatic 4T1E/M3 murine breast cancer cells following exposure to cannabidiolic acid Vol.2, No.2, p.89-94
Shuso Takeda , Hiroyuki Okazaki , Eriko Kohro-Ikeda , Kazutaka Yoshida , Miki Tokuyasu , Yukimi Takemoto , Ramu Mizunoe , Sawa Tanaka , Tomoko Okada , Hironori Aramaki
Released: June 01, 2015
Abstract Full Text PDF[524K]

We previously identified cannabidiolic acid (CBDA), a major component of the fibertype cannabis plant, as an inhibitor of MDA-MB-231 human breast cancer cell migration in vitro (Takeda et al., 2012). Although MDA-MB-231 is a widely used human breast cancer cell line in in vitro and in vivo studies, these cells have to be injected into nude mice (immunodeficient animals) in in vivo trials. Thus, we established the murine breast cancer cell line, 4T1E/M3, which is highly metastatic to bone in BALB/c mice (Takahashi et al., 2008, 2009; Sakai et al., 2012); this murine syngeneic tumor model may be useful for identifying molecular targets for therapeutic interventions. Prior to in vivo experiments using the murine tumor model, we herein performed DNA microarray analyses of 4T1E/M3 cells, treated with CBDA for 48 hr at a sub-toxic concentration (25 μM), in order to comprehensively analyze the effects of CBDA on the genes involved in the bone metastasis of breast cancers. The results obtained revealed that the expression of matrix metalloproteinase-9 (MMP-9), transforming growth factor-β (TGF-β) inducible gene H3 (BIGH3), and parathyroid hormone-related protein (PTHrP) was markedly down-regulated by 0.11-fold, 0.22-fold, and 0.15-fold, respectively; these molecules were mutually involved in the bone metastasis of breast cancer cells.

Original Article
Measurement of oral bacterial counts in dogs by dielectrophoretic impedance Vol.2, No.2, p.83-87
Soraaki Takahashi , Motoi Kuratani , Maho Tanaka , Tetsuro Ito , Nobuyuki Kanemaki , Mitsuyuki Shirai , Ryota Nomura , Kazuhiko Nakano , Fumitoshi Asai
Released: May 27, 2015
Abstract Full Text PDF[221K]

The purpose of this study was to determine the suitability for measurement of oral bacterial counts (OBC) in dogs using a new device that operates on the principle of dielectrophoretic impedance. Using this device, bacterial counts were successfully measured in swabs collected from the mouths of 5 non-anesthetized beagles. We tried to take samplings from 6 sites in each dog’s mouth and stable counts obtained at an interval of 2 weeks showed no significant difference in any of the 6 sites over time. However, since the counts showed significant differences depending upon the number of times the swab was rubbed on the sampling site, and the time from feeding affects oral bacterial counts, special attention is needed on these 2 issues. The new device allows rapid measurement of oral bacterial counts in dogs under appropriate conditions. The simplicity of this method may make it useful in studies on agents affecting OBC in dogs.

Motor activities of newborns prenatally exposed to low-dose bisphenol A in diverse mouse strains Vol.2, No.2, p.79-82
Nao Kagawa , Munekazu Komada , Tetsuji Nagao
Released: May 27, 2015
Abstract Full Text PDF[238K]

Studies on the low-dose effects of xenoestrogens have yielded conflicting results that may have resulted from differences in estrogen sensitivity between the mouse strains used. We developed a mouse newborn behavioral testing method for evaluating the risk of neurotoxicity of environmental chemicals, by means of determining a newborn’s motor activity through applying the tare function of an analytical balance. Motor activities including crawling, pivoting, and tremors of C57BL/6J and ICR mouse newborns exposed to bisphenol A (BPA) at 200 μg/kg/day on embryonic days 6 through 18 were evaluated for 5 min on postnatal day 1 by the testing method. Motor activities of mature male offspring exposed prenatally to BPA were also evaluated in wheel cage and open field tests. Maternal BPA oral dosing increased the motor activity in newborns of both strains and mature offspring of the C57BL/6J strain. The findings indicate that both mouse strains provide adequate models for the newborn neurobehavioral study of prenatal exposure to environmentally relevant levels of estrogen-mimicking chemicals.

Original Article
Effect of prenatal methylmercury exposure on neurobehavioral development in male mice: comparison between methylmercury in fish and methylmercury chloride added to diets Vol.2, No.2, p.67-78
Miyuki Iwai-Shimada , Michiaki Yamashita , Naoyuki Kurokawa , Kunihiko Nakai , Mitsuharu Ishida , Akira Naganuma , Hiroshi Satoh
Released: April 03, 2015
Abstract Full Text PDF[481K]

While the primary source of human MeHg exposure is the consumption of fish contaminated with MeHg, it is unknown whether the toxicity of MeHg in fish is equivalent to that of MeHg chloride (MeHgCl) experimentally added to the diet. We investigated developmental and behavioral effects of MeHg derived from fish and MeHgCl added to various diets during the prenatal period in mice from GD 0 to GD 17. From 7 to 9 female C57BL/6NCr mice were assigned to each of the following exposure groups: Control (CL), CL+MeHgCl (CL+MeHg, 1.6 mgHg/kg), low MeHg tuna (LT, 0.2 mgHg/kg), LT+MeHgCl (LT+MeHg, 1.6 mgHg/kg), and high MeHg tuna (HT, 1.6 mgHg/kg). In pups, body weight was depressed and elevated by MeHg exposure in the CL+MeHg and the LT, respectively, compared with other three groups. In neurodevelopmental test, the righting reflex of 4 groups other than CL showed the facilitated developments compared to the CL. The cliff avoidance of the HT developed slower than in the CL+MeHg, LT and LT+MeHg. In water maze test, the swimming speed of the HT decreased in comparison with the CL in males but not females. The latency until falling from a rotating rod of the LT+MeHg was significantly shorter than that of the LT in males but not females. Our results are suggesting the possibility that the toxicological profiles of MeHg derived from fish and reagent MeHg are somewhat different. Our findings also provide evidence that males are more susceptible than females to prenatal MeHg exposure.

Comparative cytotoxicity of triphenylstibane and fluorine-substituted triarylpnictogens in cultured vascular endothelial cells Vol.2, No.2, p.61-66
Masaki Murakami , Tomoya Fujie , Mio Matsumura , Eiko Yoshida , Chika Yamamoto , Yasuyuki Fujiwara , Shuji Yasuike , Toshiyuki Kaji
Released: March 28, 2015
Abstract Full Text PDF[1M]

The toxicity of organic-inorganic hybrid molecules appears to depend on the toxicity of the organic structure, the metals, and their interaction. However, very little is known about the structureactivity relationship of these molecules. In the present study, we investigated the cytotoxicity of triphenylstibane (Sb25) and its fluorine-substituted derivatives the triarylstibanes, using a culture system of bovine aortic endothelial cells. The results showed that the cytotoxicity of tris(4-fluorophenyl)stibane (Sb33) and tris(3,4,5-trifluorophenyl)stibane (Sb49) was higher than that of Sb25, suggesting that introduction of fluorine atoms into the benzene rings may potentiate the cytotoxicity of Sb25 in vascular endothelial cells. However, interestingly, tris(pentafluorophenyl)stibane (Sb35) was nontoxic. The pnictogen analogues tris(pentafluorophenyl)arsane (As35) and tris(pentafluorophenyl)phosphane (P35) showed a higher cytotoxicity than that of Sb35. In addition, the potentiation was much stronger with P35 than it was with As35. The intracellular accumulation of Sb35 was very low while the accumulation of As35 was higher than that of Sb25. These results collectively suggest that the hydrophobicity and metal of the organometallic compounds do not necessarily predict their cytotoxicity and intracellular accumulation in vascular endothelial cells.

Original Article
Metabolic fate of excessive glucose in fibroblast cells in a diabetic setting Vol.2, No.2, p.55-60
Yuka Kohda , Kazuma Iwatate , Takao Tanaka , Hitoshi Matsumura
Released: February 20, 2015
Abstract Full Text PDF[327K]

Glucose is important for energy; however, excessive daily intake of sugar may act as a toxin inducing the body to become overweight or obese. High blood glucose level reduces secretion of insulin, and glucose toxicity worsens insulin resistance. We investigated the metabolic fate of excess glucose by changing glucose levels in MRC-5 fibroblasts. Uptake of glucose into fibroblasts, the first stage of glucose metabolism, was measured. Treatment of fibroblasts under diabetic conditions led to rapid glucose incorporation. Glucose was absorbed into the cell almost constantly and reached excessive levels, and its metabolism was assessed by 14CO2 output from [U-14C] D-glucose, the glucose metabolism end product. When fibroblasts were cultured in the presence of high glucose levels, CO2 production decreased significantly in comparison with normal glucose conditions. Glucose metabolism in the diabetic setting was not accompanied by an increase in glucose uptake. Diabetic patients exercise tight glycemic control to avert disorders from such glucose toxicity. Pyruvate dehydrogenase (PDH) activity is reduced in diabetes; therefore, we investigated the influence of thiamine on PDH activity and intracellular glucose concentration in fibroblast cells exposed to diabetic conditions. Thiamine reversed high glucose-induced PDH inhibition and prevented glucose accumulation. These results, taken together with those of our previous report, suggest that thiamine partially plays a role in modifying the metabolic fate of glucose and reducing glucose toxicity.