The Experts below are selected from a list of 1518 Experts worldwide ranked by ideXlab platform
James E. Klaunig - One of the best experts on this subject based on the ideXlab platform.
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Kupffer cells participate in 2-butoxyethanol-induced liver Hemangiosarcomas.
Toxicology, 2010Co-Authors: Lisa M. Kamendulis, Stacy M Corthals, James E. KlaunigAbstract:2-Butoxyethanol increases Hemangiosarcomas selectively in male mouse liver after chronic inhalation through mechanisms that have not fully been elucidated. Hemolysis, a primary toxic effect associated with 2-butoxyethanol exposure in rodents, increased hemosiderin (iron) deposition in Kupffer cells in the liver. These findings, along with the induction of hepatic neoplastic lesions, led to our hypothesis that the induction Hemangiosarcomas by 2-butoxyethanol is due to the activation of Kupffer cells, subsequent to hemolysis, that results in the induction of DNA synthesis in target cells (endothelial cells); allowing for the selective proliferation of preneoplastic target cells and/or the promotion of new initiated cells. The present studies were conducted to determine whether Kupffer cells contributed to 2-butoxyethanol-induced endothelial DNA synthesis in the liver, thereby determining whether a linkage exists between these events. Male B6C3F1 mice were treated with 450 and 900 mg/kg 2-butoxyethanol (via daily gavage; 5x/week) for 7 days in the presence or absence of Kupffer cell depletion (via clodronate-encapsulated liposomes). 2-Butoxyethanol (450 and 900 mg/kg/day) increased the number of F4/80 stained cells (Kupffer cells) compared to controls (approximately 1.3- and approximately 1.6-fold over control, respectively). Clodronate liposome treatment reduced the number of Kupffer cells by >90%, as assessed by F4/80 immunohistochemistry. Increased hemolysis, measured by increases in relative spleen weights and decreased hematocrit was confirmed in 2-butoxyethanol treated mice. The percentage of iron-stained endothelial cells increased by approximately 11-fold over control, and endothelial cell DNA synthesis increased approximately 1.7-fold over control in 2-butoxyethanol exposed mice. Importantly, Kupffer cell depletion reduced 2-butoxyethanol-induced iron staining and hepatic endothelial cell DNA synthesis. These studies provide evidence supporting the hypothesis that the Kupffer cell modulates 2-butoxyethanol-induced endothelial cell DNA synthesis, and therefore may contribute to Hemangiosarcoma induction by 2-butoxyethanol.
Lisa M. Kamendulis - One of the best experts on this subject based on the ideXlab platform.
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Kupffer cells participate in 2-butoxyethanol-induced liver Hemangiosarcomas.
Toxicology, 2010Co-Authors: Lisa M. Kamendulis, Stacy M Corthals, James E. KlaunigAbstract:2-Butoxyethanol increases Hemangiosarcomas selectively in male mouse liver after chronic inhalation through mechanisms that have not fully been elucidated. Hemolysis, a primary toxic effect associated with 2-butoxyethanol exposure in rodents, increased hemosiderin (iron) deposition in Kupffer cells in the liver. These findings, along with the induction of hepatic neoplastic lesions, led to our hypothesis that the induction Hemangiosarcomas by 2-butoxyethanol is due to the activation of Kupffer cells, subsequent to hemolysis, that results in the induction of DNA synthesis in target cells (endothelial cells); allowing for the selective proliferation of preneoplastic target cells and/or the promotion of new initiated cells. The present studies were conducted to determine whether Kupffer cells contributed to 2-butoxyethanol-induced endothelial DNA synthesis in the liver, thereby determining whether a linkage exists between these events. Male B6C3F1 mice were treated with 450 and 900 mg/kg 2-butoxyethanol (via daily gavage; 5x/week) for 7 days in the presence or absence of Kupffer cell depletion (via clodronate-encapsulated liposomes). 2-Butoxyethanol (450 and 900 mg/kg/day) increased the number of F4/80 stained cells (Kupffer cells) compared to controls (approximately 1.3- and approximately 1.6-fold over control, respectively). Clodronate liposome treatment reduced the number of Kupffer cells by >90%, as assessed by F4/80 immunohistochemistry. Increased hemolysis, measured by increases in relative spleen weights and decreased hematocrit was confirmed in 2-butoxyethanol treated mice. The percentage of iron-stained endothelial cells increased by approximately 11-fold over control, and endothelial cell DNA synthesis increased approximately 1.7-fold over control in 2-butoxyethanol exposed mice. Importantly, Kupffer cell depletion reduced 2-butoxyethanol-induced iron staining and hepatic endothelial cell DNA synthesis. These studies provide evidence supporting the hypothesis that the Kupffer cell modulates 2-butoxyethanol-induced endothelial cell DNA synthesis, and therefore may contribute to Hemangiosarcoma induction by 2-butoxyethanol.
Felix A De La Iglesia - One of the best experts on this subject based on the ideXlab platform.
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spontaneous and thiazolidinedione induced b6c3f1 mouse Hemangiosarcomas exhibit low ras oncogene mutation frequencies
Toxicology and Applied Pharmacology, 1999Co-Authors: Steven K Duddy, Suzanne Gorospe, Michael R Bleavins, Felix A De La IglesiaAbstract:Hemangiosarcomasare uncommon malignant endothelial cell tumors in humans and experimental animal species. The mechanisms giving rise to these tumors are poorly understood even though the histotypes are comparable between humans and rodents. Activating mutations in cellular ras protooncogenes have been detected in sporadic and chemically induced human and rodent Hemangiosarcomas. Ras activation significantly modulates tumor angiogenesis, suggesting that mutations in ras genes might be causally related to vascular tumorigenesis. To more clearly define the role of ras in experimental vascular tumorigenesis, mutations in the Ki- and Ha-ras genes were characterized in 63 Hemangiosarcomas that arose unexpectedly in control and treated B6C3F1 mice during a two-year carcinogenicity study of the thiazolidinedione troglitazone. DNA was extracted from paraffin sections of mouse Hemangiosarcomas, control liver, or positive control hepatocellular carcinomas with defined mutations in the Ki- or Ha-ras genes. Exons 1 and 2 of the Ki- and Ha-ras genes were independently amplified using primer extension preamplification/locus-specific heminested PCR, and PCR amplicons were directly sequenced to identify mutations in codons 12, 13, or 61. Activating mutations were detected in 3 of 63 Hemangiosarcomas: a single G-->A transition in the second position of Ki-ras codon 13 in a tumor from a treated animal and two G-->T transversions in the second position of Ha-ras codon 13, one in a single tumor from a control animal and one in a tumor from a treated animal. These mutations are consistent with endogenous mutagenesis arising from oxidative DNA damage. The low frequency of mutation (<5%) indicates that ras mutations did not contribute significantly to Hemangiosarcoma development and suggests that mutational ras activation may not be a necessary step in vascular tumorigenesis in mice.
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p53 is not inactivated in b6c3f1 mouse vascular tumors arising spontaneously or associated with long term administration of the thiazolidinedione troglitazone
Toxicology and Applied Pharmacology, 1999Co-Authors: Steven K Duddy, Suzanne Gorospe, Michael R Bleavins, R F Parker, A W Gough, P E Rowse, L A Dethloff, Felix A De La IglesiaAbstract:Hemangiomas and Hemangiosarcomas are uncommon in rodents and humans and, as such, the mechanisms giving rise to these tumors are poorly understood. Inactivating mutations in the p53 gene have been detected in sporadic and chemically induced human and rodent Hemangiosarcomas. Additionally, experimental ablation of p53 function in mice by targeted gene disruption increases the incidence of both spontaneous and carcinogen-induced vascular tumors. These findings implicate p53 disruption in vascular tumor development. In this study, we characterized p53 inactivation immunocytochemically and by gene sequencing in a large number of vascular tumors that developed in B6C3F1 mice during a long-term (2-year) study of the thiazolidinedione troglitazone. For comparative purposes, a murine Hemangiosarcoma induced by polyoma middle-T antigen, which transforms endothelial cells via a p53-independent mechanism, five spontaneous human Hemangiosarcoma specimens, and species-specific positive control tissues were also evaluated by immunocytochemistry for p53 inactivation. While 20% of the human Hemangiosarcomas and all positive control tissues expressed significant levels of nuclear p53, indicating functional inactivation of the protein, none of the 161 mouse vascular tumors studied expressed detectable p53 protein. The absence of inactivating mutations was confirmed in eight of the histologically most malignant mouse Hemangiosarcomas by sequencing exons 5 to 8 of the p53 gene. These results demonstrate that p53 inactivation did not play a role in development of the vascular tumors seen in the long-term study of troglitazone, and they indicate that loss of p53 function is not essential for vascular tumor development in mice.
Jon C Cook - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Expression Profiles of Hematopoietic Stem Cell, Endothelial Cell, and Myeloid Cell Antigens in Spontaneous and Chemically Induced Hemangiosarcomas and Hemangiomas in Mice
2016Co-Authors: Satoko Kakiuchi-kiyota, Jon C Cook, Torrie A. Crabbs, Lora L. Arnold, Karen L. Pennington, David E. Malarkey, M. CohenAbstract:It is unclear whether the process of spontaneous and chemically induced Hemangiosarcoma and hemangioma formation in mice involves the transformation of differentiated endothelial cells (ECs) or recruitment of multipotential bone marrow–derived hematopoietic stem cells or endothelial progenitor cells (EPCs), which show some degree of endothelial differentiation. In the present study, immunohistochemical staining for hematopoie-tic stem cell markers (CD45 and CD34), EC markers (vascular endothelial growth factor receptor 2 [VEGFR2], CD31, and factor VIII–related antigen), and a myeloid lineage marker (CD14) was employed to better define the origin of Hemangiosarcomas and hemangiomas in mice. Staining was negative for CD45, factor VIII–related antigen, and CD14 and positive for CD34, VEGFR2, and CD31, indicating that mouse Hemangiosarcomas and hemangiomas are composed of cells derived from EPCs expressing CD34, VEGFR2, and CD31 but not factor VIII–related antigen. The lack of CD45 expression suggests that mouse vascular tumors may arise from EPCs that are at a stage later than hematopoietic stem cells. Since factor VIII–related antigen expression is known to occur later than CD31 expression in EPCs, our observations may indicate that these tumor cells are arrested at a stage prior to complete differentiation. In addition, myeloid lineage cells do not appear to contribute to Hemangiosarcoma and heman-gioma formation in mice
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the role of hypoxia in 2 butoxyethanol induced Hemangiosarcoma
Toxicological Sciences, 2010Co-Authors: Daphna Laifenfeld, Annalyn Gilchrist, David A Drubin, Milena Jorge, Sean Eddy, Brian P Frushour, Bill Ladd, Leslie A Obert, Mark Gosink, Jon C CookAbstract:To understand the molecular mechanisms underlying compound-induced Hemangiosarcomas in mice, and therefore, their human relevance, a systems biology approach was undertaken using transcriptomics and Causal Network Modeling from mice treated with 2-butoxyethanol (2-BE). 2-BE is a hemolytic agent that induces Hemangiosarcomas in mice. We hypothesized that the hemolysis induced by 2-BE would result in local tissue hypoxia, a well-documented trigger for endothelial cell proliferation leading to Hemangiosarcoma. Gene expression data from bone marrow (BM), liver, and spleen of mice exposed to a single dose (4 h) or seven daily doses of 2-BE were used to develop a mechanistic model of Hemangiosarcoma. The resulting mechanistic model confirms previous work proposing that 2-BE induces macrophage activation and inflammation in the liver. In addition, the model supports local tissue hypoxia in the liver and spleen, coupled with increased erythropoeitin signaling and erythropoiesis in the spleen and BM, and suppression of mechanisms that contribute to genomic stability, events that could be contributing factors to Hemangiosarcoma formation. Finally, an immunohistochemistry method (Hypoxyprobe) demonstrated that tissue hypoxia was present in the spleen and BM. Together, the results of this study identify molecular mechanisms that initiate Hemangiosarcoma, a key step in understanding safety concerns that can impact drug decision processes, and identified hypoxia as a possible contributing factor for 2-BE–induced Hemangiosarcoma in mice.
Daphna Laifenfeld - One of the best experts on this subject based on the ideXlab platform.
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the role of hypoxia in 2 butoxyethanol induced Hemangiosarcoma
Toxicological Sciences, 2010Co-Authors: Daphna Laifenfeld, Annalyn Gilchrist, David A Drubin, Milena Jorge, Sean Eddy, Brian P Frushour, Bill Ladd, Leslie A Obert, Mark Gosink, Jon C CookAbstract:To understand the molecular mechanisms underlying compound-induced Hemangiosarcomas in mice, and therefore, their human relevance, a systems biology approach was undertaken using transcriptomics and Causal Network Modeling from mice treated with 2-butoxyethanol (2-BE). 2-BE is a hemolytic agent that induces Hemangiosarcomas in mice. We hypothesized that the hemolysis induced by 2-BE would result in local tissue hypoxia, a well-documented trigger for endothelial cell proliferation leading to Hemangiosarcoma. Gene expression data from bone marrow (BM), liver, and spleen of mice exposed to a single dose (4 h) or seven daily doses of 2-BE were used to develop a mechanistic model of Hemangiosarcoma. The resulting mechanistic model confirms previous work proposing that 2-BE induces macrophage activation and inflammation in the liver. In addition, the model supports local tissue hypoxia in the liver and spleen, coupled with increased erythropoeitin signaling and erythropoiesis in the spleen and BM, and suppression of mechanisms that contribute to genomic stability, events that could be contributing factors to Hemangiosarcoma formation. Finally, an immunohistochemistry method (Hypoxyprobe) demonstrated that tissue hypoxia was present in the spleen and BM. Together, the results of this study identify molecular mechanisms that initiate Hemangiosarcoma, a key step in understanding safety concerns that can impact drug decision processes, and identified hypoxia as a possible contributing factor for 2-BE–induced Hemangiosarcoma in mice.