GENETICS OF MURINE AIRWAY SODIUM ABSORPTION: ROLE IN CF

上皮离子转运被认为是囊性纤维化(CF)等疾病的重要因素，但体内离子运动的调节尚不清楚。在慢性阻塞性肺疾病中，氯离子通道CFTR的突变导致呼吸黏膜对钠的吸收增加，这一过程被认为有助于慢性阻塞性肺疾病的病理生理。如果吸收的增加确实导致了疾病，目前尚不清楚它是影响了启动细菌感染的过程，还是有助于感染的持续，或者两者兼而有之。盐转运改变的机制存在争议，但包括L)降低电解质水平导致粘膜干燥和清除性差，2)改变呼吸道衬里液体的组成，从而降低抗菌肽的杀菌活性，或3)某些其他机制。也有证据表明，钠吸收的增加可能不是病理生理学的一部分，而是CFTR缺陷引起的CF上皮细胞信号通路改变的结果。为了更好地了解体内钠转运的调节和CFTR在这一调节中的作用，本申请建议通过使用近交系小鼠3L/6J和A/J及其杂交后代、重组自交系和共体系来定位和鉴定导致鼻部跨上皮钠转运自然变异的基因。我们发现，菌株间的变异是相当可遗传的，可能是由于少数基因造成的。为了阐明钠转运m-Cf的作用，小鼠的Cf等位基因将在与不同钠吸收水平相关的近交系背景上进行同源基因处理。在这些小鼠中，将评估钠吸收对细菌介导的肺部疾病的影响，方法是通过将携带细菌的琼脂珠滴入呼吸道诱导小鼠患上慢性感染。动物清除感染的能力以及它们的炎症反应将被监测。

Epithelial ion transport is thought to be an important factor in disorders such as cystic fibrosis (CF), but the regulation of ion movement in vivo is not well understood. In CF, mutations in the chloride channel, CFTR, lead to increased sodium absorption across the respiratory mucosa, a process thought to contribute to the pathophysiology of the CF airway. If the increased absorption does contribute to the disease, it is not clear if it impacts on processes that allow bacterial infection to initiate, or if it aids in allowing the infection to persist, or both. Mechanisms implicating altered salt transport are controversial, but include l) reduced electrolyte levels leading to desiccated mucosa and poor clearance, 2) altering composition of the airway lining fluid in a way that lessens bactericidal activity of antimicrobial peptides, or 3) some other mechanism. Evidence also exists suggesting that the increased sodium absorption may not contribute to the pathophysiology, but is instead a consequence of signaling pathways altered in CF epithelia in response to the CFTR defect. To better understand the in vivo regulation of sodium transport and the role of CFTR in that regulation, this application proposes to map and identify genes contributing to natural variation in nasal transepithelial sodium transport by using inbred mouse lines C57)3L/6J and A/J and their hybrid progeny, recombinant inbred lines, and consomic lines. We have found that the inter-strain variation is quite heritable and is likely due to a small number of genes. To address the role of sodium transport m CF, murine CF alleles will be made congenic on inbred backgrounds associated with different levels of sodium absorption. The influence of sodium absorption on bacterially-mediated lung disease in these mice will be assessed using mice are induced to have a chronic infection by instilling bacteria-laden agar beads into the airway. The ability of the animals to clear the infection, as well as their inflammatory responses, will be monitored.