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Effect of ascorbic acid supplementation on nitric oxide metabolites and systolic blood pressure in rats exposed to lead
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Abstracts / Toxicology Letters 180S (2008) S32–S246
M14 Oncogenic signals of HER2/neu in transformed cells induced by anti-benzo[a]pyrene-7,8-diol-9,10-epoxide Yiguo Jiang 1,∗ , Juan Fu 2 , Anne Greenlee 3 , Yuelan Shen 1 , Xuemin Chen 2 1
Institute for Chemical Carcinogenesis, State Key Laboratory of Respiratory Diseases, Guangzhou Medical College, Guangzhou, China, 2 Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, 3 Eastern Oregon University and Center for Research on Occupational and Environmental Toxicology, La Grande, OR, United States Anti-benzo[a]pyrene-7, 8-diol-9, 10-epoxide (anti-BPDE) is a metabolite of benzo[a]pyrene (B[a]P) and acts as a potent mutagen in mammalian systems; however, molecular mechanisms related to anti-BPDE-induced carcinogenesis are poorly understood. Here, we used malignant human bronchial epithelial cells (16HBE-T) transformed by exposure to anti-BPDE to help characterize possible molecular mechanisms of carcinogenesis. We hypothesized that malignant cells would show altered expression of the HER2/neu oncogene and that RNA interference could be used to identify changes in expression of downstream oncogenes c-myc and cyclin D1. Our findings suggest that HER2/neu, c-Myc and cyclin D1 oncogenes were overexpressed at both mRNA (4.0-, 2.6- and 1.7fold) and protein (1.5-, 2.1- and1.6-fold) levels in the 16HBE-T, compared with those in vehicle-treated control cells. The expression of c-Myc and cyclin D1 were significantly down-regulated (60%) after inhibition of HER2/neu using two different small interference RNAs in the 16HBE-T. Down regulation of HER2/neu in HBE-T-neu cells significantly increased the proportion of cells in G0/G1 phase (67.1% ± 2.1%) and decreased the proportion in S phase (17.3% ± 4.1%). In comparison to 16HBE-T, the cell line established by infecting 16HBE-T with retrovirus carrying shRNA targeting HER2/neu exhibited significantly lower viability over 7 days of culture. Together, these findings suggest that HER2/neu may alter the expression of regulatory genes controlling cell proliferation, cell division and apoptosis in human bronchial epithelial cells following anti-BPDE transformation. The results may help explain epithelial cell transformation following exposure to anti-BPDE and implicate HER2/neu oncogenic signaling in anti-BPDE-induced carcinogenesis. doi:10.1016/j.toxlet.2008.06.659 M15 Effect of ascorbic acid supplementation on nitric oxide metabolites and systolic blood pressure in rats exposed to lead Ali Khoshbaten 1,∗ , Alireza Asgari 2 , Ali Norooz zadeh 3 , Mohammad Amani 3 1
Chemical Injuries Research Center, Tehran, Islamic Republic of Iran, Exercise and Fitness Research Center, Tehran, Islamic Republic of Iran, 3 Department of Physiology and Biophysics, Tehran, Islamic Republic of Iran 2
Introduction: Extended exposure to low levels of lead causes high blood pressure in human and laboratory animals. The mechanism is not completely recognized, but it is relatively implicated with generation of free radicals, oxidant agents such as ROS and decrease of available nitric oxide (NO). In this study, the effect of ascorbic acid as an antioxidant on nitric oxide metabolites and systolic blood pressure in rats exposed to low levels of lead was investigated.
Materials and methods: The adult male Wistar rats weighing 200–250 g were divided into four groups: control, lead acetate (receiving 100 ppm lead acetate in drinking water), lead acetate plus ascorbic acid (receiving 100 ppm lead acetate and 1 g/l ascorbic acid in drinking water) and ascorbic acid (receiving 1 g/l ascorbic acid in drinking water) groups. The animals were anaesthetized with ketamin/xylazine (50 and 7 mg/kg, respectively, ip) and systolic blood pressure was then measured from the tail of the animals by sphygmomanometer. Nitric oxide levels in serum were measured indirectly by evaluation of its stable metabolites (total nitrite and nitrate (NOx )) using spectrophotometric method of Griess reaction. Results: After 8 and 12 weeks, systolic blood pressure in lead acetate group was significantly elevated. Ascorbic acid supplementation prevents the systolic blood pressure rise in lead acetate plus ascorbic acid group. The serum NOx levels in lead acetate group significantly decreased in relation with the control group, but this reduction was not significantly different between lead acetate plus ascorbic acid group and the control group. Conclusion: Results of this study suggest that ascorbic acid as an antioxidant prevents the lead induced hypertension. This effect can be medicated by inhibition of NOx oxidation and thereby increasing available NO. doi:10.1016/j.toxlet.2008.06.660 M16 Neophobia in rats and mice is an extremely sensitive endpoint of TCDD toxicity Sanna Lensu 1,∗ , Raimo Pohjanvirta 3 , Jouko Viluksela 2 , Jouni T. Tuomisto 2
Tuomisto 2 , Matti
1 University of Kuopio, Department of Pharmacology and Toxicology, Kuopio, Finland, 2 National Public Health Institute, Toxicology Laboratory, Kuopio, Finland, 3 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
Dioxins are lipid-soluble environmental contaminants. In humans they concentrate in fat having thus often long elimination half-lives. Dioxins cause a wide variety of effects, mediated almost solely via intracellular aryl hydrocarbon receptor (AhR). In dioxin responses there is a large interspecies and interstrain variability. Another unique feature is exceptionally delayed mortality and practically total lack of immediate external signs of toxicity. Death ensues 2–5 weeks afterwards, preceded by wasting and weight loss of the exposed laboratory animals. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is the most potent congener of dioxins. To further define its toxic effects, we studied consummatory behaviours in different rat strains and lines as well as in AhR-knockout and C57BL/6J mice. These strains/lines vary in both their AhR structure/expression and sensitivity to TCDD. In our studies, adult animals were exposed to different doses with variable follow-up times. Our aim was to elucidate the role of AhR in behavioural responses and clarify in more detail some aspects of TCDD-induced alterations in feeding and drinking. In support of our previous findings, we discovered that TCDDtreated rats refused to eat a novel food item even if it was highly pleasurable such as chocolate. This avoidance of unfamiliar food or drink occurred regardless of strain or sex. Novelty avoidance appeared within hours after exposure, and persisted for about a week. Neophobia seems to be an extremely sensitive endpoint occurring at a very low dose level (30 ng/kg) and after shorter
Abstracts / Toxicology Letters 180S (2008) S32–S246
M14 Oncogenic signals of HER2/neu in transformed cells induced by anti-benzo[a]pyrene-7,8-diol-9,10-epoxide Yiguo Jiang 1,∗ , Juan Fu 2 , Anne Greenlee 3 , Yuelan Shen 1 , Xuemin Chen 2 1
Institute for Chemical Carcinogenesis, State Key Laboratory of Respiratory Diseases, Guangzhou Medical College, Guangzhou, China, 2 Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, 3 Eastern Oregon University and Center for Research on Occupational and Environmental Toxicology, La Grande, OR, United States Anti-benzo[a]pyrene-7, 8-diol-9, 10-epoxide (anti-BPDE) is a metabolite of benzo[a]pyrene (B[a]P) and acts as a potent mutagen in mammalian systems; however, molecular mechanisms related to anti-BPDE-induced carcinogenesis are poorly understood. Here, we used malignant human bronchial epithelial cells (16HBE-T) transformed by exposure to anti-BPDE to help characterize possible molecular mechanisms of carcinogenesis. We hypothesized that malignant cells would show altered expression of the HER2/neu oncogene and that RNA interference could be used to identify changes in expression of downstream oncogenes c-myc and cyclin D1. Our findings suggest that HER2/neu, c-Myc and cyclin D1 oncogenes were overexpressed at both mRNA (4.0-, 2.6- and 1.7fold) and protein (1.5-, 2.1- and1.6-fold) levels in the 16HBE-T, compared with those in vehicle-treated control cells. The expression of c-Myc and cyclin D1 were significantly down-regulated (60%) after inhibition of HER2/neu using two different small interference RNAs in the 16HBE-T. Down regulation of HER2/neu in HBE-T-neu cells significantly increased the proportion of cells in G0/G1 phase (67.1% ± 2.1%) and decreased the proportion in S phase (17.3% ± 4.1%). In comparison to 16HBE-T, the cell line established by infecting 16HBE-T with retrovirus carrying shRNA targeting HER2/neu exhibited significantly lower viability over 7 days of culture. Together, these findings suggest that HER2/neu may alter the expression of regulatory genes controlling cell proliferation, cell division and apoptosis in human bronchial epithelial cells following anti-BPDE transformation. The results may help explain epithelial cell transformation following exposure to anti-BPDE and implicate HER2/neu oncogenic signaling in anti-BPDE-induced carcinogenesis. doi:10.1016/j.toxlet.2008.06.659 M15 Effect of ascorbic acid supplementation on nitric oxide metabolites and systolic blood pressure in rats exposed to lead Ali Khoshbaten 1,∗ , Alireza Asgari 2 , Ali Norooz zadeh 3 , Mohammad Amani 3 1
Chemical Injuries Research Center, Tehran, Islamic Republic of Iran, Exercise and Fitness Research Center, Tehran, Islamic Republic of Iran, 3 Department of Physiology and Biophysics, Tehran, Islamic Republic of Iran 2
Introduction: Extended exposure to low levels of lead causes high blood pressure in human and laboratory animals. The mechanism is not completely recognized, but it is relatively implicated with generation of free radicals, oxidant agents such as ROS and decrease of available nitric oxide (NO). In this study, the effect of ascorbic acid as an antioxidant on nitric oxide metabolites and systolic blood pressure in rats exposed to low levels of lead was investigated.
Materials and methods: The adult male Wistar rats weighing 200–250 g were divided into four groups: control, lead acetate (receiving 100 ppm lead acetate in drinking water), lead acetate plus ascorbic acid (receiving 100 ppm lead acetate and 1 g/l ascorbic acid in drinking water) and ascorbic acid (receiving 1 g/l ascorbic acid in drinking water) groups. The animals were anaesthetized with ketamin/xylazine (50 and 7 mg/kg, respectively, ip) and systolic blood pressure was then measured from the tail of the animals by sphygmomanometer. Nitric oxide levels in serum were measured indirectly by evaluation of its stable metabolites (total nitrite and nitrate (NOx )) using spectrophotometric method of Griess reaction. Results: After 8 and 12 weeks, systolic blood pressure in lead acetate group was significantly elevated. Ascorbic acid supplementation prevents the systolic blood pressure rise in lead acetate plus ascorbic acid group. The serum NOx levels in lead acetate group significantly decreased in relation with the control group, but this reduction was not significantly different between lead acetate plus ascorbic acid group and the control group. Conclusion: Results of this study suggest that ascorbic acid as an antioxidant prevents the lead induced hypertension. This effect can be medicated by inhibition of NOx oxidation and thereby increasing available NO. doi:10.1016/j.toxlet.2008.06.660 M16 Neophobia in rats and mice is an extremely sensitive endpoint of TCDD toxicity Sanna Lensu 1,∗ , Raimo Pohjanvirta 3 , Jouko Viluksela 2 , Jouni T. Tuomisto 2
Tuomisto 2 , Matti
1 University of Kuopio, Department of Pharmacology and Toxicology, Kuopio, Finland, 2 National Public Health Institute, Toxicology Laboratory, Kuopio, Finland, 3 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
Dioxins are lipid-soluble environmental contaminants. In humans they concentrate in fat having thus often long elimination half-lives. Dioxins cause a wide variety of effects, mediated almost solely via intracellular aryl hydrocarbon receptor (AhR). In dioxin responses there is a large interspecies and interstrain variability. Another unique feature is exceptionally delayed mortality and practically total lack of immediate external signs of toxicity. Death ensues 2–5 weeks afterwards, preceded by wasting and weight loss of the exposed laboratory animals. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is the most potent congener of dioxins. To further define its toxic effects, we studied consummatory behaviours in different rat strains and lines as well as in AhR-knockout and C57BL/6J mice. These strains/lines vary in both their AhR structure/expression and sensitivity to TCDD. In our studies, adult animals were exposed to different doses with variable follow-up times. Our aim was to elucidate the role of AhR in behavioural responses and clarify in more detail some aspects of TCDD-induced alterations in feeding and drinking. In support of our previous findings, we discovered that TCDDtreated rats refused to eat a novel food item even if it was highly pleasurable such as chocolate. This avoidance of unfamiliar food or drink occurred regardless of strain or sex. Novelty avoidance appeared within hours after exposure, and persisted for about a week. Neophobia seems to be an extremely sensitive endpoint occurring at a very low dose level (30 ng/kg) and after shorter