REGULATION OF TRANSCRIPTIONAL COMPETENCE BY CHROMIUM

六价铬（Cr(VI)）是ATSDR/EPA优先清单中排名前20的化合物之一，因为它促进间质性肺纤维化，诱发哮喘，并被认为是一种可能的人类肺癌物质。尽管有流行病学证据表明吸入Cr（VI）后职业性和环境性肺部疾病，但很少有研究确定Cr（VI）暴露肺部病理变化的细胞和分子基础。总体目标：本研究的总体目标是明确非细胞毒性浓度Cr（VI）改变气道和肺泡上皮细胞中诱导细胞因子和促纤维化基因表达的分子信号机制。我们最近定义了一种新的途径，通过该途径，Cr（VI）通过促进必需共激活物creb结合蛋白（CBP）向c-Jun的募集来抑制转录因子NF-kappaB的转录能力。我们假设Cr（VI）诱导的共激活因子募集的改变改变了诱导基因的表达谱，并增强了fas诱导的细胞凋亡。Cr（VI）的这些作用有利于肺纤维化的发展。具体目标：该资助的目标1将使用培养的人肺细胞来确定调节Cr（VI）诱导的CBP募集到特定转录因子（例如c-Jun）的细胞信号通路。Aim 2将使用这些模型来证明对CBP的竞争是Cr（VI）诱导NF-kappaB转激活丧失的速率限制步骤。cbp依赖性转录因子能力的转换对FAS诱导的细胞凋亡和基因表达的影响将被研究。最后，Aim将使用正常和独特的转基因小鼠模型来检测Cr（VI）诱导的转录因子活性调控以及体内诱导的促凋亡和促纤维化表型变化。意义：这些研究将确定暴露于Cr（VI）后诱导基因表达改变和气道和肺泡上皮细胞凋亡易感性增加的基本表观遗传学机制。气道的细胞凋亡现在被认为是肺纤维化的一个潜在的非炎症机制。因此，这些研究将把细胞培养中的观察结果转化为体内暴露模型，从而大大提高对Cr（VI）如何促进肺部疾病的基本认识。

Hexavalent chromium (Cr(VI)) is in the top 20 compounds of the ATSDR/EPA priority list since it promotes interstitial lung fibrosis, induces asthma, and is recognized as a probable human lung carcinogen. Despite the epidemiological evidence for both occupationally and environmentally-derived pulmonary disease following inhalation of Cr(VI), there are few studies that define the cellular and molecular basis for pathologic changes in the Cr(VI)-exposed lung. Overall Objective: The overall objective of the proposed studies is to define the molecular signaling mechanisms through which non-cytotoxic concentrations of Cr(VI) alter inducible cytokine and profibrotic gene expression in airway and alveolar epithelial cells. We have recently defined a novel pathway through which Cr(VI) inhibits the transcriptional competence of the transcription factor NF-kappaB by promoting recruitment of the essential co-activator CREB-binding protein (CBP) to c-Jun. We hypothesize that Cr(VI)-induced alteration of co-activator recruitment changes the profile of inducible gene expression and potentiates Fas-induced apoptosis. These effects of Cr(VI) favor development of pulmonary fibrosis. Specific Objectives: Aim 1 of the grant will use human lung cells in culture to define cellular signaling pathways that regulate Cr(VI)-induced recruitment of CBP to specific transcription factors (e.g. c-Jun). Aim 2 will use these models to demonstrate that competition for CBP is the rate limiting step in Cr(VI)- induced loss of NF-kappaB transactivation. The consequence of a switch in CBP-dependent transcription factor competence on FAS- induced apoptosis and gene expression will be examined. The final Aim will use normal and unique transgenic mouse models to examine Cr(VI)-induced regulation of transcription factor activity and of inducible pro-apoptotic and pro-fibrotic phenotypic changes in vivo. Significance: The studies will define fundamental epigenetic mechanisms for altered inducible gene expression and increased susceptibility of airway and alveolar epithelial cells to apoptosis following exposure to Cr(VI). Apoptosis of the airway is now recognized as an underlying non-inflammatory mechanism for lung fibrosis. Thus, these studies will translate observations in cell culture into in vivo models of exposure to greatly improve the basic understanding of how Cr(VI) promotes pulmonary diseases.