Growth Factors /Inflammatory Mediators /Target-organ Tox

生长因子/炎症介质/靶器官毒素

• 批准号: 6837521
• 负责人: Dori R Germolec
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6837521
• 关键词: apoptosis; arsenic; carcinogenesis; cell proliferation; cytokine; environment related neoplasm /cancer; environmental exposure; environmental toxicology; enzyme activity; fibroblasts; gene expression; gene mutation; genetically modified animals; glutathione; growth factor; human tissue; inflammation; keratinocyte; laboratory mouse; metal poisoning; microarray technology; oxidative stress; prostaglandin endoperoxide synthase; skin hypersensitivity; skin neoplasms; tissue /cell culture

The main focus of this project is to investigate the complex cytokine regulatory network involved in arsenic-induced dermatotoxicity. Pathway mapping studies using normal human epidermal keratinocytes (NHEK) indicated that short-term, non-toxic arsenic-exposure results in the modulation of multiple genes from several classes (e.g., oxidative stress, glutathione metabolism, heat shock/stress response, cell proliferation and DNA damage). Array studies further revealed that the expression of cyclooxygenase-2 (COX-2), a gene that plays a prominent role in skin cancer, is highly induced in a dose-dependent manner following arsenic exposure. Subsequent studies indicate that arsenic also elevates the level of COX-2 protein in NHEK. These events appear to be dependent on signaling via mitogen- and stress-related kinases; the activities of which are modulated by arsenic. The induction of COX-2 by arsenic also correlated with increased prostaglandin levels, an end product of COX-2 activty, in culture media and increased DNA synthesis. We have determined that the induction of COX-2 following arsenic exposure is, in part, dependent on activation of specific MAP kinase (MAPK) signaling pathways, in particular the ERK or p42/44 MAPK. Our studies indicate that the induction of COX-2 is independent of p38 MAPK phosphorylation. This pattern is similar to that observed with growth factors specific for keratinocytes, such as Fibroblast Growth Factor-7, but contrasts with that of Epidermal Growth Factor, which activates both p38 and p42/44. Interestingly, compounds that inhibit either the p38 and p42/44 pathway can attenuate elevation of COX-2. COX-2 inhibitors suppress biological processes in keratinocytes that we associate with the neoplastic process, including cell proliferation and TGF alpha secretion. We are currently investigating alterations in growth and inflammatory mediators following arsenic exposure in dermal fibroblasts. Similar to NHEK, these cells have been shown to be sensitive to low-dose arsenic exposure. However, they exhibit a number of cell-specific responses not observed in NHEK and will allow us to more accurately model the interactions between the two cell types that occur in human skin. In addition, we are collaborating with Drs. Miroslav Styblo and Luz Maria Del Razo to evaluate the utility of Transforming Growth Factor alpha as a biomarker for arsenic exposure. In collaboration with Dr. Michael Waalkes laboratory, we are currently conducting microarray studies in tissues from in vivo studies conducted using the Tg.AC mouse to determine if similar alterations in genes associated with oxidative stress, metabolism, heat shock/stress response, cell proliferation and DNA damage occur. Tissues from these studies have also been provided to a number of collaborators and are being used to develop models of tissue distribution of arsenic, effects on signaling pathways in the brain and the effects on enzymes associated with oxidative stress. Additional in vivo studies are examining the efficacy of Celecoxib, a COX-2 inhibitor, in modulating papillomagenesis in Tg.AC mice following arsenic exposure. Studies on the effects of arsenic exposure on dermal sensitization in Balb/c mice were completed during this period. Exposure to arsenic via the drinking water attenuated chemical-induced contact dermatitis during both the induction and elicitation phases of the immune response. Mechanistic studies suggest that this suppression is likely due to cytokine-induced alterations in the migration of Langerhans cells from the skin to the draining lymph node and subsequent effects on antigen presentation and cell proliferation. During this reporting period we have also completed studies on the role of Tumor Necrosis Factor alpha in TCDD-induced induction of apoptosis. As an offshoot of these studies, in collaboration with Dr. Nigel Walker, we are comparing species- and gender-specific gene expression in rodents following TCDD exposure to elucidate the genetic mechanisms that may underlie differential susceptibility to TCDD-induced hepatocarcinogenesis. TSC-22, a Transforming Growth Factor beta inducible transcription factor that can induce apoptosis was suppressed in the rat, but was not altered by either chronic or acute TCDD exposure in the mouse.

本项目的主要重点是研究砷诱导的皮肤毒性中复杂的细胞因子调控网络。使用正常人表皮角质形成细胞（NHEK）的通路作图研究表明，短期、无毒的砷暴露导致来自几类（例如，氧化应激、谷胱甘肽代谢、热休克/应激反应、细胞增殖和DNA损伤）。阵列研究进一步揭示，环氧合酶-2（考克斯-2），一种在皮肤癌中起重要作用的基因，在砷暴露后以剂量依赖的方式被高度诱导。随后的研究表明，砷还提高了NHEK中考克斯-2蛋白的水平。这些事件似乎是依赖于信号通过有丝分裂原和应力相关的激酶，其活动是由砷调制。砷对考克斯-2的诱导作用还与培养基中前列腺素水平的增加和DNA合成的增加有关，前列腺素是考克斯-2活性的终产物。我们已经确定砷暴露后考克斯-2的诱导部分依赖于特异性MAP激酶（MAPK）信号通路的激活，特别是ERK或p42/44 MAPK。我们的研究表明考克斯-2的诱导不依赖于p38 MAPK磷酸化。这种模式与角质形成细胞特异性生长因子如成纤维细胞生长因子-7所观察到的模式相似，但与激活p38和p42/44的表皮生长因子形成对比。有趣的是，抑制p38和p42/44通路的化合物可以减弱考克斯-2的升高。考克斯-2抑制剂抑制角质形成细胞中与肿瘤过程相关的生物学过程，包括细胞增殖和TGF α分泌。我们目前正在研究砷暴露后皮肤成纤维细胞生长和炎症介质的变化。与NHEK类似，这些细胞已被证明对低剂量砷暴露敏感。然而，它们表现出许多在NHEK中未观察到的细胞特异性反应，这将使我们能够更准确地模拟人类皮肤中两种细胞类型之间的相互作用。此外，我们正在与Miroslav Styblo和Luz Maria Del Razo博士合作，评估转化生长因子α作为砷暴露生物标志物的效用。 与Michael Waalkes博士实验室合作，我们目前正在使用Tg.AC小鼠进行的体内研究中进行组织微阵列研究，以确定与氧化应激，代谢，热休克/应激反应，细胞增殖和DNA损伤相关的基因是否发生类似的变化。来自这些研究的组织也被提供给一些合作者，并被用于开发砷的组织分布模型，对大脑中信号通路的影响以及对与氧化应激相关的酶的影响。其他的体内研究正在检查塞来昔布（一种考克斯-2抑制剂）在砷暴露后调节Tg.AC小鼠乳头状瘤发生方面的疗效。在此期间完成了砷暴露对Balb/c小鼠皮肤致敏作用的研究。暴露于砷通过饮用水衰减化学诱导的接触性皮炎在诱导和激发阶段的免疫反应。机制研究表明，这种抑制可能是由于苦参碱诱导的朗格汉斯细胞从皮肤迁移到引流淋巴结的改变以及随后对抗原呈递和细胞增殖的影响。 在本报告所述期间，我们还完成了关于肿瘤坏死因子α在TCDD诱导的细胞凋亡中的作用的研究。作为这些研究的一个分支，我们与奈杰尔步行者博士合作，比较了啮齿动物在接触TCDD后的物种和性别特异性基因表达，以阐明可能导致TCDD诱导肝癌发生的不同易感性的遗传机制。TSC-22是一种可诱导细胞凋亡的转化生长因子β诱导型转录因子，在大鼠中受到抑制，但在小鼠中，无论是慢性还是急性TCDD暴露都没有改变。