Mechanisms of oxidant-induced chronic bronchitis

描述（由申请人提供）： 粘液高分泌、杯状细胞增生和化生以及粘膜下腺体肥大是慢性支气管炎的病理生理和组织学特征。表皮生长因子（EGF）信号传导的激活被认为是气道上皮的许多这些形态学变化的原因。香烟烟雾是人类受试者慢性支气管炎的主要原因，也已被证明至少部分地通过氧化应激和EGF信号传导诱导粘蛋白分泌和粘液细胞增生。EGF在气道中表达，刺激EGF受体（EGFR），并且如我们所示，通过组织激肽释放酶（TK）的切割由pro-EGF制成。我们还表明，TK是由粘膜下腺体分泌的透明质酸，抑制TK的活性。Hybryonan还使支气管TK固定在上皮表面，在气道表面产生一个容易获得但无活性的TK库。活性氧（ROS）可以裂解hyaturonan，从而释放活化的TK。在慢性支气管炎中，与正常受试者相比，气道中ROS和活性TK升高，可能是由于ROS持续降解透明质酸。我们推测，在这些条件下，活性TK的可用性增加是氧化应激和EGF介导的气道粘液细胞增生之间的关键环节。该提案将检验ROS介导的杯状细胞化生和粘膜下腺细胞增生通过多步级联发生的假设，该级联从透明质酸降解（起始步骤）开始，导致活化TK的持续释放（引发步骤），从而增加成熟EGF的可用性（活化步骤），进而激活EGFR（信号传导步骤）。具体目标是：1）证实并扩展我们的初步体外观察结果，即活性氧降解上皮结合的透明质酸，从而释放活性TK，进而切割pro-EGF以激活EGFR（培养物中的概念验证）; 2）评价从慢性支气管炎患者获得的气道中的透明质酸降解、TK活化和pro-EGF加工（人类疾病中的概念证明）;和3）检查TK介导的pro-EGF切割是否调节粘膜下腺细胞增殖（概念的相关性）。因此，拟议的实验将研究氧化应激和慢性支气管炎之间的新联系，并可能确定新的方法来防止甚至逆转气道粘膜的这种变化。

DESCRIPTION (provided by applicant): Mucus hypersecretion, goblet celt hyperplasia and metaplasia as well as submucosal gland hypertrophy are pathophysiological and histological hallmarks of chronic bronchitis. The activation of epidermal growth factor (EGF) signaling is believed to be responsible for many of these morphological changes of the airway epithelium. Cigarette smoke, the major cause of chronic bronchitis in human subjects, has also been demonstrated to induce mucin secretion and mucous cell hyperplasia, at least in part, via oxidative stress and EGF signaling. EGF is expressed in the airways, stimulates the EGF receptor (EGFR) and, as shown by us, is made from pro-EGF through cleavage by tissue kaltikreJn (TK). We have also shown that TK is secreted by submucosal glands together with hyaluronan, which inhibits the activity of TK. Hyaluronan also immobilizes bronchial TK at the epithelial surface, creating a pool of readily available, yet inactive TK at the airway surface. Reactive oxygen species (ROS) can cleave hyaturonan, thereby releasing activateded TK. In chronic bronchitis, ROS and active TK are elevated in the airway compared to normal subjects, possibly due to continued degradation of hyaluronan by ROS. We hypothesize that the increased availability of active TK in these conditions is a critical link between oxidative stress and EGF-mediated airway mucous cell hyperplasia. This proposal will test the hypothesis that ROS-mediated goblet cell metaplasia and submucosai gland celt hyperplasia occurs through a multi-step cascade beginning with hyaturonan degradation (initiation step) that results in sustained release of activated TK (priming step) and thereby increased availability of mature EGF (activation step) that in turn activates EGFR (signaling step). The specific aims are: 1) to confirm and extend our preliminary in vitro observations that ROS degrade epithelialbound hyaluronan and thereby release active TK that in turn cleaves pro-EGF to activate EGFR (proof of concept in culture); 2) to evaluate hyaluronan degradation, TK activation and pro-EGF processing in airways obtained from patients with chronic bronchitis (proof of concept in human disease); and 3) to examine whether TK-mediated pro-EGF cleavage regulates submucosal gland cell proliferation (relevance of concept). The proposed experiments will thus examine a new link between oxidative stress and chronic bronchitis and may identify new approaches to prevent or even reverse such changes in the airway mucosa.