The role of SPARC in lung fibrosis

描述（由申请人提供）：由于蒙大拿州利比市的严重健康状况，全国已经注意到石棉相关疾病（ARD）。近60年来，利比的矿工和居民都暴露在镇上附近采矿活动中被石棉污染的蛭石中。与其他人群相比，职业和环境暴露个体的ARD发病率都要高得多（ATSDR, 2003）。然而，接触石棉污染的蛭石并不局限于利比居民：这种蛭石在全国范围内的分布以及疾病发展的长潜伏期使石棉相关疾病（ARD）成为一个持续的公共卫生问题。我们之前研究了石棉暴露小鼠模型中的基因表达变化，并确定了一个候选基因，我们假设该基因在疾病进展中起作用。SPARC（酸性分泌蛋白，富含半胱氨酸）在暴露于几种石棉纤维（包括Libby角孔）的小鼠肺中可重复地增加表达。SPARC是一种基质细胞蛋白，通过对生长因子活性的假设调节，参与调节细胞外基质（ECM）与细胞的相互作用。这个项目的目标是描述SPARC在接触利比角闪洞和青橄榄石石棉作为阳性对照时的作用。在我们的研究中需要验证的假设是，SPARC的表达是石棉暴露后肺纤维化发展的重要一步。为了验证这一假设，具体目的将是：1)评估经气管内灌注石棉诱导肺纤维化后，SPARC缺失和匹配的野生型小鼠体内SPARC和TGF-¿信号级联蛋白的表达情况，并进行比较

DESCRIPTION (provided by applicant): National attention has been drawn to asbestos-related diseases (ARD) due to the serious health situation in Libby, Montana. For almost 60 years Libby miners and residents were exposed to asbestos- contaminated vermiculite from a mining operation near town. Both occupationally- and environmentally- exposed individuals have shown a much higher incidence of ARD than the rest of the population (ATSDR, 2003). However, exposure to the asbestos-contaminated vermiculite is not limited to Libby residents: distribution of this vermiculite nationwide and the long latent period for disease development make asbestos-related diseases (ARD) a continuing public health issue. We previously investigated gene expression changes in a mouse model of asbestos exposure and identified a candidate gene for study that we hypothesize plays a role in disease progression. SPARC (secreted protein acidic and rich in cysteine) demonstrates reproducibly increased expression in mouse lungs exposed to several types of asbestos fibers, including the Libby amphibole. SPARC is a matricellular protein involved in the regulation of extracellular matrix (ECM) - cell interactions through a hypothesized modulation of growth factor activity. The goal of this project is to delineate the role of SPARC in response to exposure to the Libby amphibole and crocidolite asbestos as a positive control. The hypothesis to be tested in our studies is that expression of SPARC is a significant step in the development of lung fibrosis after asbestos exposure. To test the hypothesis, the specific aims will 1) ssess the in vivo expression of SPARC and proteins in the TGF-¿ signaling cascade in SPARC-null and matched wild-type mice after induction of lung fibrosis through intratracheal asbestos instillation, and compare this with the effects of subsequent RNAi transduction to control SPARC expression in wild-type mice, and 2) establish the in vitro gene and protein expression of SPARC as well as extracellular matrix production in mouse primary lung fibroblasts and an immortalized human lung fibroblast cell line stimulated by TGF-¿ or amphiboles before and after Sparc expression inhibition by RNAi. The investigation proposed here will further determine the role of SPARC in fibrosis development after amphibole exposure, specifically targeting how inhibition of SPARC expression can regulate ECM production. Proteins involved in pathways regulated by SPARC could provide targets for potential therapies that might also be beneficial for the treatment of similar, non-asbestos caused diseases such as idiopathic pulmonary fibrosis.