High doses of sodium phenobarbital (NaPB), a constitutive androstane receptor (CAR) activator, have been shown to produce hepatocellular tumors in rodents by a mitogenic mode of action (MOA) involving CAR activation. The effect of 1-week dietary treatment with NaPB on liver weight and histopathology, hepatic CYP2B enzyme activity and CYP2B/3A mRNA expression, replicative DNA synthesis and selected genes related to cell proliferation, and functional transcriptomic and metabolomic analyses was studied in male CD-1 mice, Wistar Hannover (WH) rats, and chimeric mice with human hepatocytes. The treatment of chimeric mice with 1000-1500-ppm NaPB resulted in plasma levels around 3-5-fold higher than those observed in human subjects given therapeutic doses of NaPB. NaPB produced dose-dependent increases in hepatic CYP2B activity and CYP2B/3A mRNA levels in all animal models. Integrated functional metabolomic and transcriptomic analyses demonstrated that the responses to NaPB in the human liver were clearly different from those in rodents. Although NaPB produced a dose-dependent increase in hepatocyte replicative DNA synthesis in CD-1 mice and WH rats, no increase in replicative DNA synthesis was observed in human hepatocyte-originated areas of chimeric mice. In addition, treatment with NaPB had no effect on Ki-67, PCNA, GADD45?, and MDM2 mRNA expression in chimeric mice, whereas significant increases were observed in CD-1 mice and/or WH rats. However, increases in hepatocyte replicative DNA synthesis were observed in chimeric mice both in vivo and in vitro after treatment epidermal growth factor. Thus, although NaPB could activate CAR in both rodent and human hepatocytes, NaPB did not increase replicative DNA synthesis in human hepatocytes of chimeric mice, whereas it was mitogenic to rat and mouse hepatocytes. As human hepatocytes are refractory to the mitogenic effects of NaPB, the MOA for NaPB-induced rodent liver tumor formation is thus not relevant for humans.
S-53482 and S-23121 are N-phenylimide herbicides and produced embryolethality, teratogenicity (mainly ventricular septal defects and wavy ribs), and growth retardation in rats in conventional oral developmental toxicity studies. Our objective in this study was to investigate whether the compounds induce developmental toxicity via the dermal route, which is more relevant to occupational exposure, hence better addressing human health risks.
Skin sensitization resulting in allergic contact dermatitis is a common occupational health issue. In this study, the effect of mixing two skin sensitizers on the skin sensitization response was investigated. Skin sensitizers are generally classified into T helper type 1 (Th1) or T helper type 2 (Th2), depending on the induced cytokine profile. Dinitrochlorobenzene (DNCB) and oxazolone (Oxa) are Th1 skin sensitizers and phthalic anhydride (PA) and toluene diisocyanate (TDI) are Th2 skin sensitizers. We investigated the effect on skin sensitization response to mixtures of three pairs of these sensitizers: DNCB and Oxa, DNCB and PA, and PA and TDI, using guinea pig maximization test and mouse ear swelling test. In guinea pigs sensitized with the mixture of DNCB and Oxa or PA and TDI, there were changes of skin sensitization response to DNCB and Oxa, and that to PA. On the other hand, there was no mixture effect in guinea pigs sensitized with the mixture of DNCB and PA. The skin sensitization responses were decreased in mice sensitized with the mixtures of DNCB and Oxa or PA and TDI, whereas the mixture effect was not observed in mice sensitized with the mixture of DNCB and PA. The present findings revealed that mixture effect on the skin sensitization response was observed after simultaneous exposure to two skin sensitizers, and the effect was determined by combinations of mixed skin sensitizers.
S-53482 is an N-phenylimide herbicide and shows a remarkable species difference in developmental toxicity between rats and rabbits. The herbicide produced embryolethality, teratogenicity (mainly ventricular septal defects and wavy ribs), and growth retardation in rats, but not in rabbits. Our objective in this study was to investigate differences in developmental toxicity among N-phenylimide compounds structurally similar to S-53482 to better characterize the developmental effects of S-53482 on rat and rabbit embryos as part of research investigation to elucidate a mechanism of rat developmental toxicity produced by S-53482. This paper is part of a series of studies to be published serially.
We have established rat models of pancreatic ductal adenocarcinoma (PDAC) in which expression of a human H-ras(G12V) or K-ras(G12V) oncogene regulated by the Cre/lox system drives pancreatic carcinogenesis. Pancreatic ductal adenocarcinoma which develops in H-ras(G12V) and K-ras(G12V) transgenic rats is cytogenetically and histopathologically similar to human PDAC. The present study was designed to determine the feasibility of using the commercially available H-ras(G12V) transgenic rat to find diagnostic protein biomarkers for human pancreatic cancer.
Pancreatic ductal adenocarcinoma (PDAC) is one of the most debilitating malignancies in humans, and one of the reasons for this is the inability to diagnose this disease early in its development. To search for biomarkers that can be used for early diagnosis of PDAC, we established a rat model of human PDAC in which expression of a human K-ras(G12V) oncogene and induction of PDAC are regulated by the Cre/lox system. In the present study, transgenic rats bearing PDAC and control transgenic rats with normal pancreatic tissues were used for metabolomic analysis of serum and pancreatic tissue by non-targeted and targeted gas chromatography-mass spectrometry and transcriptomic analysis of pancreatic tissue by microarray. Comparison of the metabolic profiles of the serum and pancreatic tissue of PDAC-bearing and control rats identified palmitoleic acid as a metabolite, which was significantly decreased in the serum of PDAC-bearing animals. Transcriptomic analysis indicated that several transcripts involved in anaerobic glycolysis and nucleotide degradation were increased and transcripts involved in the trichloroacetic acid cycle were decreased. Other transcripts that were changed in PDAC-bearing rats were adenosine triphosphate citrate lyase (decreased: fatty acid biosynthesis), fatty acid synthase (increased: fatty acid biosynthesis) and arachidonate 5-lipoxygenase activating protein (increased: arachidonic acid metabolism). Overall, our results suggest that the decreased serum levels of palmitoleic acid in rats with PDAC was likely due to its decrease in pancreatic tissue and that palmitoleic acid should be investigated in human samples to assess its diagnostic significance as a serum biomarker for human PDAC.
Polycystic ovary syndrome (PCOS) is a common lifestyle-related endocrinopathy in women of reproductive age and is associated with several mental health problems. We examined the genotypic distributions of IRS-1 Gly972Arg and CYP11B2 -344T/C, which were previously described as influencing PCOS, and assayed the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-?), in a set of female patients with borderline personality disorder (BPD) with comorbid major depressive disorder (MDD) (n = 50) and age-matched control subjects (n = 100), to investigate the predisposition for BPD with MDD. The results showed that the patients were more frequently IRS-1 972Arg variant allele carriers (P = 0.013; OR 6.68; 95% CI = 1.30-34.43) and homozygous for the CYP11B2 -344C variant allele (P = 0.022; OR = 3.32; 95% CI = 1.18-9.35) than the control subjects. The IL-6 level was significantly higher in the patients than in the controls (P < 0.0001). There was no significant difference in the serum TNF-? level between patients with BPD with MDD and the healthy comparison group (P = 0.5273). In conclusion, the predisposition for BPD with MDD is associated with that for PCOS, in the female Japanese population. An elevated serum IL-6 level is considered to be a possible biomarker of BPD with MDD.
To evaluate the effects of a variety of chemical, biological and physiological stimuli on erythropoiesis, in vitro assays using erythroid progenitor cells from humans or laboratory animals are well-known methods. On the other hand, little has been reported on in vitro assays using mature erythroblasts such as polychromatic erythroblasts. In the present study, we established a convenient method for enrichment of polychromatic erythroblasts from rat bone marrow and confirmed their development in vitro. To establish a method for the enrichment of polychromatic erythroblasts, bone marrow cells from 3- and 10-week-old rats were separated by discontinuous density gradient centrifugation using Percoll. As a result, polychromatic erythroblasts were most highly enriched in the bone marrow fraction from 3-week old rats at the density interface between 1.040 and 1.058 g/ml. The enriched polychromatic erythroblasts were then cultured in growth medium supplemented with 20% fetal bovine serum in the presence or absence of erythropoietin for 48 hr. During the culture period, cell proliferation and maturation to orthochromatic erythroblasts were observed, and intracellular heme contents were also increased. In particular, the culture in the presence of erythropoietin revealed higher proliferation of erythroid cells, and therefore might be more appropriate for in vitro experiments on the effects of various stimuli on late-stage erythropoiesis.
To address the functional roles of genetic polymorphisms of brain-derived neurotrophic factor (BDNF) in Alzheimers disease (AD) from a neuropsychological aspect, we used a cross-sectional study design to investigate the association between novel single nucleotide polymorphisms (SNPs) of the BDNF gene (Val66Met (G196A) and C270T) and the Frontal Assessment Battery (FAB) score, which reflects executive function as a non-memory cognitive impairment.
Teratomas commonly occur in the testis and ovary, whereas in the uterus they are rare. The authors report findings for a mass detected in the uterus of a 26-week-old mouse in a colony of C57BL/6 bred in their laboratory. The mass was located in the endometrium and protruded into the lumen. Histopathologically, it consisted of abnormal diploblastic or triploblastic tissues. Bone with a growth plate and myeloid cells, as well as cartilage, was mainly observed. It also included melanocytes, exocrine gland-like cells, striated muscle, and neuron-like cells. While these tissues were accompanied by extensive necrosis, all of them were well differentiated and lacked features of malignancy, such as invasion and metastasis. This mouse had experienced parturition, but fetal tissue was not observed in the lesion. Therefore, the lesion was diagnosed as a benign teratoma, which was spontaneously developed in the uterus.
This study was conducted to evaluate the effects of procymidone (PCM) on development of male rabbit fetal external genitalia. PCM was administered once daily by gavage at dose levels of 0 (control) and 125mg/kg/day to pregnant rabbits from gestation day 6 through 28 and fetal external genitalia was observed in detail. This treatment period covered the critical stage of sexual differentiation of fetal external genitalia in rabbits. In the maternal animals, food consumption was reduced in the PCM group. There were no effects of PCM on maternal caesarean sectioning data or fetal external observations. In fetal external genitalia observations, there were no significant differences between the control and PCM treatment group in any of the following parameters: ano-genital distance (AGD), phallus boundary-genital distance, diameter of preputial lamella, ventral gap of preputial lamella, or ventral gap to diameter ration of preputial lamella, though severe feminization such as decreasing of AGD and hypospadias in male rat offspring at the dose level of 125 mg/kg of PCM were reported. These results suggest that PCM has no effect on fetal external genitalia development in male rabbit fetuses, and species difference of developmental effects of PCM on sexual differentiation exists.
The aim of the present study was to develop a quantitative evaluation method for detecting antiandrogenic activity of chemicals in rabbits that are regularly used for developmental toxicity studies. Kbl: New Zealand White rabbits (n = 8-9) were injected intramuscularly with an antiandrogen, cyproterone acetate (CA; 10 mg/kg body weight [BW]/day), on gestation days (GD) 13-24. On GD 29, live fetuses were obtained by cesarean section and sexed by examination of the internal genitalia. The external genitalia were evaluated in cross-section measurements of the phallus by both diameter and width of the ventral gap of the preputial lamella with a micrometer under a stereoscopic microscope. The diameters of the preputial lamella were 1015 +/- 83.5, 856 +/- 64.0, and 865 +/- 72.6 microm in control males, control females, and CA-treated males, respectively. The ventral gaps of the preputial lamella were 26 +/- 8.2, 437 +/- 72.3, and 318 +/- 59.4 microm in the control males, control females, and CA-treated males, respectively. There were statistically significant differences in both parameters between control males and control females or CA-treated males. The lower fetal BW in CA-treated males did not disturb the detection of the feminization of the ventral gap of the preputial lamella; however, the diameter of the preputial lamella might be influenced by fetal BW because no difference in the relative diameter of the preputial lamella was found between control males and CA-treated males. These results demonstrated that this approach could detect the antiandrogen activity of CA quantitatively by feminization of male external genitalia in rabbit fetuses.
PCM-CH2OH [N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1,2-dicarboximide] and PA-CH2OH [2-carboxyl-N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1-carboxamide] are metabolites of the fungicide procymidone [N-(3,5-dichlorophenyl)-1,2-dimethylcyclopropane-1,2-dicarboximide] in rat. The distribution and metabolism of PCM-CH2OH and PA-CH2OH were here clarified by analyzing plasma and tissues (liver, kidney, heart, lung, spleen and ovary) of female rats after single subcutaneous administration of [phenyl-14C]PCM-CH2OH and [phenyl-14C]PA-CH2OH at 62.5 mg/kg, respectively. In both rats dosed with PCM-CH2OH and PA-CH2OH, the radioactivity was similarly distributed into plasma and tissues, and PA-CH2OH was detected as the main metabolite in plasma, whereas PCM-CH2OH predominated in tissues except for kidney at 1 h after administration of PA-CH2OH. Furthermore, the cyclization ratio [PCM-CH2OH/(PCM-CH2OH+PA-CH2OH)] increased in tissues of PA-CH2OH dosed rats with passage of time. Both procymidone and PCM-CH2OH have convertible conformations (closed and open ring forms), so influence of pH conditions to their conversion was examined. Both compounds demonstrated closed rings under acidic conditions, and open rings under alkaline conditions. Generally, intracellar pH is kept at approximately neutral, and extracellular pH is kept at 0.6-0.7 units higher in all the animal species, so that our in vitro results supported in vivo findings.
High doses of Metofluthrin (MTF) have been shown to produce liver tumours in rats by a mode of action (MOA) involving activation of the constitutive androstane receptor leading to liver hypertrophy, induction of cytochrome P450 (CYP) forms and increased cell proliferation. The aim of this study was to compare the effects of MTF with those of the known rodent liver tumour promoter phenobarbital (PB) on the induction CYP2B forms and replicative DNA synthesis in cultured rat and human hepatocytes. Treatment with 50 microM MTF and 50 microM PB for 72 h increased CYP2B1 mRNA levels in male Wistar rat hepatocytes and CYP2B6 mRNA levels in human hepatocytes. Replicative DNA synthesis was determined by incorporation of 5-bromo-2-deoxyuridine over the last 24 h of a 48 h treatment period. Treatment with 10-1000 microM MTF and 100-500 microM PB resulted in significant increases in replicative DNA synthesis in rat hepatocytes. While replicative DNA synthesis was increased in human hepatocytes treated with 5-50 ng/ml epidermal growth factor or 5-100 ng/ml hepatocyte growth factor, treatment with MTF and PB had no effect. These results demonstrate that while both MTF and PB induce CYP2B forms in both species, MTF and PB only induced replicative DNA synthesis in rat and not in human hepatocytes. These results provide further evidence that the MOA for MTF-induced rat liver tumour formation is similar to that of PB and some other non-genotoxic CYP2B form inducers and that the key event of increased cell proliferation would not occur in human liver.
To verify whether anti-androgens cause transgenerational effects on spermatogenesis and DNA methylation in rats, gravid Crl:CD(SD) female rats (4 or 5/group, gestational day (GD) 0=day sperm detected) were intraperitoneally treated with anti-androgenic compounds, such as vinclozolin (100 mg/kg/day), procymidone (100 mg/kg/day), or flutamide (10 mg/kg/day), from GD 8 to GD 15. Testes were collected from F1 male pups at postnatal day (PND) 6 for DNA methylation analysis of the region (210 bp including 7 CpG sites) within the lysophospholipase gene by bisulfite DNA sequencing method. F0 and F1 males underwent the sperm analysis (count, motility and morphology), followed by DNA methylation analysis of the sperm. Remaining F1 males were cohabited with untreated-females to obtain F2 male pups for subsequent DNA methylation analysis of the testes at PND 6. These analyses showed no effects on spermatogenesis and fertility in F1 males of any treatment group. DNA methylation status in testes (F1 and F2 pups at PND 6) or sperms (F1 males at 13 weeks old) of the treatment groups were comparable to the control at all observation points, although DNA methylation rates in testes were slightly lower than those in sperm. In F0 males, no abnormalities in the spermatogenesis, fertility and DNA methylation status of sperm were observed. No transgenerational abnormalities of spermatogenesis and DNA methylation status caused by anti-androgenic compounds were observed.
Two-year treatment with high doses of Metofluthrin produced hepatocellular tumors in both sexes of Wistar rats. To understand the mode of action (MOA) by which the tumors are produced, a series of studies examined the effects of Metofluthrin on hepatic microsomal cytochrome P450 (CYP) content, hepatocellular proliferation, hepatic gap junctional intercellular communication (GJIC), oxidative stress and apoptosis was conducted after one or two weeks of treatment. The global gene expression profile indicated that most genes with upregulated expression with Metofluthrin were metabolic enzymes that were also upregulated with phenobarbital. Metofluthrin induced CYP2B and increased liver weights associated with centrilobular hepatocyte hypertrophy (increased smooth endoplasmic reticulum [SER]), and induction of increased hepatocellular DNA replication. CYP2B1 mRNA induction by Metofluthrin was not observed in CAR knockdown rat hepatocytes using the RNA interference technique, demonstrating that Metofluthrin induces CYP2B1 through CAR activation. Metofluthrin also suppressed hepatic GJIC and induced oxidative stress and increased antioxidant enzymes, but showed no alteration in apoptosis. The above parameters related to the key events in Metofluthrin-induced liver tumors were observed at or below tumorigenic dose levels. All of these effects were reversible upon cessation of treatment. Metofluthrin did not cause cytotoxicity or peroxisome proliferation. Thus, it is highly likely that the MOA for Metofluthrin-induced liver tumors in rats is through CYP induction and increased hepatocyte proliferation, similar to that seen for phenobarbital. Based on analysis with the International Life Sciences Institute/Risk Science Institute MOA framework, it is reasonable to conclude that Metofluthrin will not have any hepatocarcinogenic activity in humans, at least at expected levels of exposure.
Novel biomarkers for pancreatic ductal adenocarcinoma (PDAC) are urgently needed because of its poor prognosis. We have previously established an animal model for human PDAC using transgenic rats in which expression of a human K-ras(G12V) oncogene is regulated by the Cre/lox system. Using this model, we searched for candidate circulating microRNAs (miRNAs) for use as novel clinical diagnostic biomarkers for PDAC.
Apoptosis controls erythroid homeostasis by balancing survival and death of erythroid cells. The mitochondrial pathway of apoptosis involves regulation of apoptotic events caused by the Bcl-2 family proteins, including the anti-apoptotic and pro-apoptotic members. However, little has been reported on the role of the anti-apoptotic Bcl-2 family members in rat late-stage erythroblasts that are no longer erythropoietin (EPO)-dependent. In the present study, to investigate this we analyzed changes in apoptosis-related factors that occurred in vitro. EPO stimulation resulted in reduced apoptotic cell death of the late-stage erythroblasts accompanied by decreased caspase-3 and caspase-9 activities, which is indicative of the induction of apoptosis through the mitochondrial pathway. Analysis of mRNA expression of the Bcl-2 family proteins demonstrated that EPO stimulation up-regulated the Bcl-xL mRNA, resulting in decreases in the mRNA ratios of Bak, Bax, and Bad to Bcl-xL. Also, the mRNA ratios of Bak and Noxa to Mcl-1 were decreased, mainly due to up-regulation of Mcl-1 mRNA. These results showed a close association between reduced apoptotic cell death and increased mRNA levels of Bcl-xL and Mcl-1 in the presence of EPO. Thus, the present study suggests that Bcl-xL may be an important anti-apoptotic factor of rat late-stage erythroblasts as has been reported in murine erythroblasts. Moreover, the results also indicate the possibility that Mcl-1 may act on the rat late-stage erythroblasts as an anti-apoptotic factor.
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