Sodium-coupled neutral amino acid transporter SNAT2 – a regulatory hub of alveolar homeostasis and its critical role in acute lung injury/ARDS

钠偶联中性氨基酸转运蛋白 SNAT2 是肺泡稳态的调节中心及其在急性肺损伤/ARDS 中的关键作用

• 批准号: 441105380
• 负责人: Professor Dr. Wolfgang Kübler
• 金额: --
• 依托单位: Institut für Physiologie (CCM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/441105380?language=en
• 关键词: Sodium; coupled; neutral; amino; acid

Acute respiratory distress syndrome (ARDS), the most frequent cause of mortality in critical care medicine, is characterized by hyperinflammation, epithelial apoptosis, and a loss of alveolar-capillary barrier function with consecutive formation of a proteinaceous lung edema that ultimately results in respiratory failure. Despite numerous clinical trials, effective pharmacological treatments to improve overall survival in ARDS patients are still lacking. This unmet medical need stresses the necessity for a better understanding of the pathomechanisms underlying ARDS and the regulation of alveolar homeostasis and repair. In our project proposal, we postulate a key role for Na+-coupled neutral amino acid transporter SNAT2 in lung edema formation and alveolar epithelial apoptosis in ARDS. So far SNAT2 has not been implicated in any pulmonary pathologies. Yet, as SNAT2 mediates cellular uptake of neutral amino acids in cotransport with Na+, it may impact both Na+-driven alveolar fluid clearance (AFC) and amino acid-regulated cell signaling. In preliminary proof-of-concept data we show i) that SNAT2 expression is downregulated in response to inflammatory stimuli characteristic for ARDS, ii) that loss of SNAT2 inhibits AFC thus promoting edema formation, and iii) that SNAT2 loss aggravates ER-stress, ROS formation, and autophagy-mediated apoptosis through intracellular amino acid deprivation. SNAT2 may thus evolve as a novel master regulator of alveolar homeostasis, with SNAT2 loss promoting the classic hallmarks of ARDS.In the proposed work, we will first consolidate the relevance of SNAT2 in AFC and edema resolution in situ in isolated perfused mouse lungs, in vivo in a murine model of acute lung injury, and in vitro in a pulmonary epithelial cell culture system. Next, we will analyze SNAT2 regulation in the intact and injured alveolar epithelium. To this end, we will focus on changes in SNAT2 expression and function in response to inflammatory stimuli, bacterial toxins, or infection with live bacteria both in vitro and in situ, and dissect underlying regulatory mechanisms. Lastly, we will probe in depth for the regulatory role of SNAT2 on epithelial injury and repair processes. Specifically, we propose that in response to injury expression of ER stress markers, apoptotic and autophagic proteins, and ROS production will be increased in cells lacking functional SNAT2.We anticipate the results of our research to generate fundamental new knowledge, in that they will critically propel our understanding of dysregulated alveolar fluid transport and edema formation and generate important insights into the role of amino acids and their co-transporters in pro- and anti-apoptotic signaling pathways pertinent to alveolar epithelial injury. Our findings are expected to provide significant translational benefits by identifying SNAT2 as a potential target to improve edema resolution and maintain or restore epithelial barrier function in ARDS patients.

急性呼吸窘迫综合征（ARDS）是重症监护医学中最常见的死亡原因，其特征在于炎症过度、上皮细胞凋亡和肺泡-毛细血管屏障功能丧失，并连续形成蛋白性肺水肿，最终导致呼吸衰竭。尽管有大量的临床试验，但仍然缺乏有效的药物治疗来提高ARDS患者的总生存率。这种未满足的医学需求强调了更好地理解ARDS的病理机制以及肺泡内稳态和修复的调节的必要性。在我们的项目提案中，我们假设钠偶联中性氨基酸转运蛋白SNAT 2在ARDS肺水肿形成和肺泡上皮细胞凋亡中起关键作用。到目前为止，SNAT 2尚未涉及任何肺部病理。然而，由于SNAT 2介导细胞摄取中性氨基酸与Na+共转运，它可能会影响Na+驱动的肺泡液清除率（AFC）和氨基酸调节的细胞信号传导。在初步的概念验证数据中，我们显示i）SNAT 2表达响应于ARDS特征性的炎性刺激而下调，ii）SNAT 2的缺失抑制AFC，从而促进水肿形成，以及iii）SNAT 2缺失通过细胞内氨基酸剥夺加剧ER应激、ROS形成和自噬介导的细胞凋亡。因此，SNAT 2可能会演变为一种新的主调节器的肺泡内稳态，与SNAT 2损失促进ARDS.In建议的工作的经典标志，我们将首先巩固的相关性SNAT 2在AFC和水肿分辨率原位在离体灌注小鼠肺，在体内的小鼠模型的急性肺损伤，并在体外的肺上皮细胞培养系统。接下来，我们将分析SNAT 2在完整和受损肺泡上皮中的调节。为此，我们将专注于SNAT 2表达和功能的变化，以响应炎症刺激，细菌毒素，或感染活细菌在体外和原位，并剖析潜在的调控机制。最后，我们将深入探讨SNAT 2对上皮损伤和修复过程的调节作用。具体来说，我们提出，在缺乏功能性SNAT 2的细胞中，ER应激标志物、凋亡和自噬蛋白以及ROS产生的损伤表达将增加。我们预计我们的研究结果将产生基础性的新知识，因为它们将极大地推动我们对肺泡液体转运失调和水肿形成的理解，并产生对氨基酸及其与肺泡上皮损伤相关的促凋亡和抗凋亡信号通路中的共转运蛋白。我们的研究结果预计将提供显着的翻译的好处，确定SNAT 2作为一个潜在的目标，以改善水肿的解决和维持或恢复上皮屏障功能的ARDS患者。