The injurious effects of hypercapnia on the alveolar epithelium

描述（由申请人提供）：在使用“允许性高碳酸血症”策略通气的呼吸衰竭患者中观察到高pCO2水平。我们和其他研究者最近报道了二氧化碳分压水平升高会对肺泡上皮产生有害影响。具体来说，我们已经报道了高碳酸血症通过抑制肺泡上皮Na、k - atp酶和损害肺泡液清除而导致肺泡上皮短期和长期功能障碍。因此，本应用的重点是确定在高碳酸血症条件下导致肺泡Na、k - atp酶下调和肺泡液清除受损的具体机制/信号通路。我们建议通过四个相关的目的来研究高碳酸血症对肺泡上皮的影响：在与特定目的1相关的实验中，我们将确定可溶性腺苷酸环化酶是否参与高碳酸血症诱导的肺泡上皮Na，K- atp酶下调；在与特定Aim #2相关的实验中，我们将确定高碳酸血症诱导的JNK激活是否导致lim结构域蛋白7 （LMO7）磷酸化和Na， k - atp酶内吞；在与特异性Aim # 3相关的研究中，我们将确定Na， k - atp酶泛素化是否导致其下调，并提出鉴定特异性E2和E3泛素连接酶；在与特定Aim # 4相关的研究中，我们将确定高碳酸血症是否会进一步损害轻度呼吸机诱导的肺损伤（VILI）模型的损伤，以及sAC、JNK、LMO7和泛素化途径的下调是否会逆转高碳酸血症对啮齿动物肺泡液清除的有害影响。在第一轮拨款中，我们已完成大部分建议的研究，并就目前的每项具体目标进行初步实验，以支持这项拨款建议的可行性。本实验将提供高碳酸血症对肺泡上皮影响的新信息，揭示肺泡上皮功能障碍的机制，对急性肺损伤患者的认识和治疗具有重要意义。

DESCRIPTION (provided by applicant): High pCO2 levels are observed in patients with respiratory failure ventilated with the "permissive hypercapnia" strategy. We and other investigators have recently reported that elevated pCO2 levels can have deleterious effects on the alveolar epithelium. Specifically, we have reported that hypercapnia leads to short and long term dysfunction of the alveolar epithelium by inhibiting the alveolar epithelial Na,K-ATPase and impairing alveolar fluid clearance. Therefore, the focus of this application is to determine the specific mechanisms/signaling pathways that lead to alveolar Na,K-ATPase downregulation and impairment in alveolar fluid clearance during hypercapnic conditions. We propose to study the effects of hypercapnia on the alveolar epithelium via four interrelated aims: in experiments pertaining to specific Aim # 1, we will determine whether the soluble adenylyl cyclase participates in the hypercapnia-induced Na,K- ATPase downregulation in the alveolar epithelium; in experiments pertaining to specific Aim #2, we will determine whether hypercapnia-induced JNK activation leads to LIM-domain only protein 7 (LMO7) phosphorylation and Na,K-ATPase endocytosis; in studies pertaining to specific Aim # 3, we will determine whether Na,K-ATPase ubiquitination leads to its downregulation and propose to identify the specific E2 and E3 ubiquitin ligase; and in studies pertaining to specific Aim # 4, we will determine whether hypercapnia further impairs injury in a model of mild ventilator-induced lung injury (VILI) and whether the downregulation of of sAC, JNK, LMO7 and ubiquitination pathway will reverse the deleterious effects of hypercapnia on alveolar fluid clearance in rodents. In the first cycle of this grant, we have completed most of the proposed research and conducted preliminary experiments for each of the current specific aims which support the feasibility of this grant proposal. The proposed experiments will generate novel information on the effects of hypercapnia on the alveolar epithelium and shed light on the mechanisms leading to alveolar epithelial dysfuntion which is of significance to the understanding and treatment of patients with acute lung injury.