RTP-801 in Cigarette Smoke-Emphysema

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DESCRIPTION (provided by applicant): Our work over the past 10 years has uncovered that the disruption of alveolar structural and molecular maintenance program by cigarette smoke contributes to the pathogenesis of emphysema. The present application is centered on the concept that environmental stresses, such as caused by cigarette smoke (CS) and pollutants activate "rheostat" molecules that govern harmful alveolar septal cell responses involving oxidative stress, apoptosis, and alveolar inflammation. In line with this overall paradigm, we propose mechanistic studies targeting the cellular stress response gene RTP801, which was discovered in a screening of genes upregulated by hypoxia inducible factor-1a (HIF-a) and shown to induce oxidative stress and apoptosis. RTP801 inactivates mTORC1 (for mammalian target for rapamycin complex 1), which controls a central cell signaling pathway that acts as a physiological molecular sensor of environmental stresses. mTORC therefore integrates growth factor signaling, cell growth, and survival adaptation to adverse environmental conditions. We hypothesize that oxidative stress caused by CS activates RTP801 expression, which suppresses mTOR signaling in alveolar cells, leading to alveolar cell inflammation and apoptosis. Upregulation of RTP801 causes oxidative stress-triggered release of dynein-light chain molecule 8 (LC8) from I?B and NF-?B-activation. Our preliminary data demonstrate that RTP801 knockout mice are protected against lung inflammation, apoptosis, and emphysema caused by cigarette smoke. Specific Aim 1 will demonstrate that the stress response gene RTP801 is required for cigarette smoke- induced emphysema in mice. Specific Aim 2 will demonstrate that RTP801-induced lung inflammation and apoptosis by cigarette smoke are mediated by suppression of its downstream target mTOR. Specific Aim3 will demonstrate that RTP801 suppression of mTOR signaling causes oxidative stress-dependent displacement of the dynein-light chain molecule 8 (LC8) from I?B, leading to activation of NF-?B. These aims rely on a translational and comprehensive approach that includes knockout and transgenic mice, in vivo and in vitro manipulation of RTP801/mTOR/AKT gene expression and signaling with adenoassociated virus or adenovirus gene transduction, and siRNA or short hairpin RNA, complementary pharmacological interventions aimed at mTOR and oxidative stress, and detailed morphometric and cellular assessments of alveolar injury. Our proposal advances the concept that CS-mediated lung injury in emphysema is controlled by alveolar septal cells, as the result of the interaction of oxidative stress and molecular switches involved in cell stress responses. This interaction mediated by RTP801 may constitute a critical modulator of innate and acquired immunity and of cellular protection by growth factors, which are central to the pathogenesis of emphysema. PUBLIC HEALTH RELEVANCE: Chronic obstructive pulmonary diseases (COPD) are the 4th leading cause of mortality and morbidity, with worldwide impact. Emphysema is part of COPD and compromises about 20-60% of patients with the disease. In emphysema, the lung literally disappears, leaving behind large holes, a profound inability to breath air into and out of the lungs, and decrease in the ability of the lungs to get oxygen. Our concept is that environmental stresses, such as those cause by cigarette smoke, cause the activation of cellular responses that are originally designed to protect the host. One of these sensor molecules is RTP801. The activation of RTP801 by cigarette smoke activates inflammation and causes lung cell death. Our proposal is to prove that RTP801 is involved in emphysema caused by cigarette smoke, and the potential mechanisms involved in this process. Our studies have relevance to lung diseases, and also to other manifestations of disease caused by cigarette smoke, such as weigh loss due to muscle damage and cardiovascular disease.