GENETICS OF MURINE AIRWAY SODIUM ABSORPTION: ROLE IN CF

上皮细胞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还不清楚。在CF中，氯离子通道CFTR的突变导致整个呼吸道粘膜的钠吸收增加，这一过程被认为有助于CF气道的病理生理学。如果增加的吸收确实有助于疾病，则尚不清楚它是否影响允许细菌感染开始的过程，或者它是否有助于允许感染持续，或者两者兼而有之。涉及改变的盐转运的机制是有争议的，但包括1）降低的电解质水平导致干燥的粘膜和差的清除，2）以降低抗微生物肽的杀菌活性的方式改变气道衬里流体的组成，或3）一些其他机制。还存在证据表明，增加的钠吸收可能不会导致病理生理学，而是CF上皮细胞中响应于CFTR缺陷而改变的信号传导途径的结果。为了更好地理解钠转运的体内调节和CFTR在该调节中的作用，本申请提出通过使用近交小鼠系C57）3L/6 J和A/J及其杂交后代、重组近交系和同源系来定位和鉴定有助于鼻经上皮钠转运中的天然变异的基因。我们已经发现，菌株间的变异是相当遗传的，可能是由于少数基因。为了解决钠转运在CF中的作用，将在与不同水平的钠吸收相关的近交背景上使鼠CF等位基因同源。将通过向气道滴注载菌琼脂珠诱导小鼠慢性感染，评估钠吸收对这些小鼠中细菌介导的肺病的影响。将监测动物清除感染的能力以及它们的炎症反应。

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.