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

细菌性肺炎引发宿主过度的炎症反应、氧化应激和上皮细胞损伤，最终导致ARDS。目前，治疗ARDS的干预措施仍然局限于肺保护策略，因为新的分子机制驱动的治疗干预措施尚未出现。参与上皮损伤进化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性磷脂，心磷脂（CL）是导致严重上皮性肺损伤的关键损伤信号。我们观察到，细菌感染小鼠肺上皮细胞或小鼠后，CL从线粒体膜内转移到线粒体膜外，并作为线粒体自噬（mitophagy）的新信号。我们还发现细菌感染诱导细胞色素c （cyt c）介导的CL过氧化是细胞凋亡的关键步骤。因此，外化CL的过氧化作用作为触发凋亡机制的分子开关。最后，我们证明了CL和氧化CL （Clox）从受损的宿主细胞释放到循环中，并作为线粒体源性损伤相关分子模式（DAMP-CL）触发先天和适应性免疫反应。我们的中心假设是，细菌感染刺激线粒体Cls的暴露和释放，这是加速线粒体自噬和细胞凋亡必不可少的细胞内信号；释放进入循环后，Cls作为DAMP-CL诱导先天和适应性免疫反应。拟议研究的具体目的是确定：1。远端肺上皮细菌诱导的有丝分裂中CL不对称及其崩溃的机制和信号作用。2. CL过氧化的分子途径和小分子调节因子的设计和应用，以防止细菌诱导的远端肺上皮细胞凋亡。3. 循环中CUCLox为DAMP-CL的分子特性研究。基于CL是一种独特的细胞内和细胞外信号这一高度创新的概念，我们将探索四类新的CL信号调节因子，用于开发肺保护药物

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