Intra- and extra-cellular signaling by Cardiolipin in Lung injury

细菌性肺炎引发强烈的宿主反应，导致过度炎症、氧化应激和上皮细胞损伤，最终导致ARDS。目前，治疗ARDS的治疗干预措施仍然局限于肺保护策略，因为还没有出现新的分子机制驱动的治疗干预措施。参与上皮损伤演变的具体途径仍然难以捉摸。在初步实验中，我们发现线粒体特异的磷脂，心磷脂(CL)，是一个关键的损伤信号，导致严重的上皮性肺损伤。我们观察到，在细菌感染小鼠肺上皮细胞或小鼠后，CL从线粒体膜内向外迁移，在线粒体膜上作为线粒体自噬、有丝分裂吞噬的新信号。我们还发现，细菌感染诱导细胞色素c(Cytc)介导的CL过氧化是细胞凋亡的关键步骤。因此，外化CL的过氧化作用就像一个分子开关，触发了细胞的凋亡机制。最后，我们证明CL和氧化CL(CLOX)从受损的宿主细胞释放到循环中，并作为线粒体衍生的损伤相关分子模式(DAMP-CL)，触发先天性和获得性免疫反应。我们的中心假设是，细菌感染刺激了线粒体CLS的揭开和释放，而线粒体CLS是加速有丝分裂和细胞凋亡所必需的细胞内信号；一旦释放到循环中，CLS就作为DAMP-CL诱导先天和获得性免疫反应。本研究的具体目的是确定：1.细菌诱导的肺远端上皮细胞有丝分裂中CL不对称及其崩溃的机制和信号转导作用。2.CL过氧化的分子途径及抗细菌诱导的远端肺上皮细胞凋亡的小分子调节剂的设计与应用。3.循环中CuCLox作为DAMP-CL的物种的分子同一性。基于CL是肺上皮细胞有丝分裂、细胞凋亡和先天/获得性免疫反应中独特的细胞内外信号的极具创新性的概念，我们将为肺保护药物的开发探索四类新的CL信号调节因子

Bacterial pneumonia triggers an exuberant host response with excessive inflammation, oxidative stress, and epithelial cell damage culminating in ARDS. At present, therapeutic interventions to treat ARDS remain limited to lung-protective strategies, as newer molecular mechanism-driven therapeutic interventions have not yet emerged. The specific pathways involved in the evolution of epithelial damage remain elusive. In preliminary experiments, we discovered that a mitochondria-specific phospholipid, cardiolipin (CL), is a critical damage signal that produces severe epithelial lung injury. We observed that after bacterial infection of murine lung epithelial cells or mice, CL transmigrates from the inner to the outer mitochondrial membrane where it acts as a novel signal for autophagy of mitochondria, mitophagy. We also showed that bacterial infection induces cytochrome c (cyt c)-mediated CL peroxidation as a pivotal step in apoptosis. Thus peroxidation of externalized CL acts as a molecular switch that triggers the apoptotic machinery. Finally, we demonstrate that CL and oxidized CL (Clox) are released from injured host cells into circulation and act as mitochondria-derived damage associated molecular patterns (DAMP-CL) triggering innate and adaptive immune responses. Our central hypothesis is that bacterial infection stimulates the unmasking and release of mitochondrial Cls that are indispensible intracellular signals in accelerating mitophagy and apoptosis; upon release into circulation, Cls act as DAMP-CL inducing innate and adaptive immune responses. The Specific Aims of the proposed studies are to determine the: 1. Mechanisms and signaling role of CL asymmetry and its collapse in bacterial-induced mitophagy in distal lung epithelia. 2. Molecular pathways of CL peroxidation and the design and application of small-molecule regulators that protect against bacterial¿ induced distal lung epithelial apoptosis. 3. Molecular identity of species of CUCLox as DAMP-CL in circulation. Based on the highly innovative concept that CL is a unique intra- and extra-cellular signal in mitophagy, apoptosis, and innate/adaptive immune responses in pulmonary epithelium, we will explore four new classes of regulators of CL signaling for the development of pulmonary protective drugs