The role and biology of Fra-1 in lung injury and repair

描述（由申请人提供）：支气管上皮中毒性损伤后的异常细胞增殖和分化可导致包括肺癌在内的各种呼吸系统疾病的发展，但涉及这些过程的潜在分子机制仍然是谜。本研究的前提是AP-1转录因子家族作为环境生物传感器对各种外部毒性刺激进行感知，并调控参与细胞增殖和分化的基因。最近，我们发现AP-1家族成员fr -1 （fos相关转录因子-1）上调参与气道鳞状化生（一种肿瘤前病变）的基因表达。其他研究表明，暴露于二氧化硅和石棉后，Fra-1的表达会延长，从而导致支气管上皮细胞转化。此外，我们还在体外和体内观察到，在气道上皮细胞中，佛波酯PMA和烟草烟雾诱导了fr -1的表达。因此，我们假设，有毒物质长期诱导Fra-1表达损害了正常支气管上皮细胞的生长和分化，从而改变了肺防御和损伤修复过程，最终导致细胞转化。验证上述假设的具体目的是：1)通过体内足迹、缺失/突变和电泳迁移位移试验确定调节PMA和烟草烟雾诱导的Fra-1表达的启动子顺式作用元件和反式作用因子。2)利用药物抑制剂和各种丝裂原活化蛋白激酶的基因突变体，阐明介导PMA和烟草烟雾诱导的fra1表达的信号转导途径；3)研究Fra-1在PMA和烟草烟雾诱导的支气管上皮损伤修复和转化中的功能作用。为了实现这些目标，我们将使用两种独立但互补的方法，即利用体外细胞培养和体内转基因小鼠模型，过度表达野生型或显性负突变的Fra-1，特别是在支气管上皮细胞中。这些研究将为毒物诱导基因表达的机制提供更多的见解，并确定Fra-1在肺部生物学和毒物诱导的呼吸发病机制中的特定作用。此外，这些结果应该使我们能够识别肺特异性fr -1诱导基因，这可能提供独特的机会，将它们用作潜在的诊断标记或药物靶点，用于早期检测和预防呼吸道发病机制。

DESCRIPTION (provided by applicant): Aberrant cell proliferation and differentiation following toxic injury to bronchial epithelium can lead to the development of various respiratory diseases including lung cancer, but the underlying molecular mechanisms involved in such processes remain enigmatic. The proposed research is based on the premise that AP-1 family of transcriptional factors act as environmental biosensors to various external toxic stimuli and regulate genes involved in cell proliferation and differentiation. Recently we have shown that Fra-1 (fos-related transcription factor-1), a member AP-1 family, up regulates the gene expression involved in airway squamous metaplasia, a preneoplastic lesion. Other studies have demonstrated a protracted expression of Fra-1 in response to silica and asbestos exposure, which causes bronchial epithelial cell transformation. Furthermore, we have observed that Fra-1 expression is induced by phorbol ester PMA and tobacco smoke in airway epithelial cells both in vitro and in vivo. Therefore, we hypothesize that protracted induction of Fra-1 expression by toxicants compromises the normal bronchial epithelial cell growth and differentiation thereby altering pulmonary defense and injury-repair processes, which culminate in cellular transformation. The proposed Specific Aims to test the above hypothesis are to: 1) Define the promoter cis-acting elements and trans-acting factors that regulate PMA and tobacco smoke-inducible Fra-1 expression by in vivo footprinting, deletion/mutation and electrophoretic mobility shift assays. 2) Elucidate the signal transduction pathways that mediate PMA- and tobacco smoke-inducible fra1 expression employing pharmacological inhibitors as well as genetic mutants of various mitogen-activated protein kinases; and 3) Examine the functional role of Fra-1 in PMA- and tobacco smoke-induced bronchial epithelial injury-repair and transformation. To achieve these objectives, we will use two independent, but complementary approaches that utilize in vitro cell culture and in vivo transgenic mouse models that over express wild type or dominant negative-mutant Fra-1, specifically in bronchial epithelial cells. These studies should provide additional insight into mechanisms of toxicant-inducible gene expression and also establish the specific role for Fra-1 in lung biology and toxicant-induced respiratory pathogenesis. Also, these results should enable us to identify lung-specific Fra-1-inducible genes that might offer unique opportunity to use them as potential diagnostic markers or drug targets for early detection and prevention of respiratory pathogenesis.