ATP release during apoptosis and its relevance to apoptotic cell clearance

描述（由申请人提供）：人体每天有数以十亿计的细胞发生凋亡并被有效清除，防止炎症性疾病的发生。在系统性红斑狼疮和动脉粥样硬化等疾病状态中，凋亡细胞清除的缺陷已被发现，并与自身免疫的发展有关。凋亡细胞的清除取决于吞噬细胞定位和吞噬死亡细胞的能力。这两个过程分别由凋亡细胞产生的“找我”和“吃我”信号介导。我的初步研究表明，在细胞凋亡过程中，ATP在细胞外介质中积累，可以作为“找我”信号。目前尚不清楚细胞外ATP是如何在细胞凋亡过程中积累的，也不清楚这如何影响凋亡细胞的有效清除。在本提案中，我计划确定ATP在凋亡细胞的细胞外介质中积累的机制，以及ATP在有效清除凋亡细胞中的作用。在Aim 1中，我们将利用细胞系研究pannexin 1半通道在细胞凋亡过程中ATP释放中的作用，以及pannexin 1在细胞凋亡过程中的调节机制。我们还将研究外ATP酶活性在细胞凋亡期间细胞外ATP积累中的作用，作为ATP积累的一个可能的促进因素。在目的2中，我们将重点关注ATP如何影响凋亡细胞的清除。具体来说，我们将通过检测吞噬蛋白表达和吞噬能力来研究凋亡细胞上清液中的核苷酸如何影响吞噬细胞吞噬凋亡细胞的能力。我们还旨在探讨凋亡细胞上清液中的核苷酸如何作用于血管内皮细胞，以增加单核细胞向受影响区域的浸润。细胞在正常和病理过程中都会死亡，并被其他细胞有效地吸收。死亡细胞的清除对于预防炎症非常重要，炎症在包括动脉粥样硬化和自身免疫性疾病在内的许多疾病过程中起着重要作用。了解死亡细胞如何促进自身的清除是一个具有广泛意义的重要问题。

DESCRIPTION (provided by applicant): Every day, billions of cells undergo apoptosis in the human body and are efficiently cleared, preventing the onset of inflammatory disease. Defects in the clearance of apoptotic cells have been identified in disease states, such as systemic lupus erythematosus and atherosclerosis, and have been implicated in the development of autoimmunity. The clearance of apoptotic cells depends on the ability of a phagocyte to locate and engulf the dying cell. These two processes are mediated by the so called "find-me" and "eat-me" signals, respectively, that are produced by apoptotic cells. My preliminary studies suggest that ATP accumulates in the extracellular medium during apoptosis, and can act as a "find-me" signal. It is unknown how extracellular ATP accumulates during apoptosis, or how this may influence the efficient clearance of apoptotic cells. In this proposal, I plan to determine the mechanism by which ATP accumulates in the extracellular medium of apoptotic cells, and the role that this plays in the efficient clearance of apoptotic cells. In Aim 1, we will use cell lines to examine the role of pannexin 1 hemichannels in the release of ATP during apoptosis, and the mechanism of pannexin 1 regulation during apoptosis. We will also examine the role of ecto-ATPase activity in the accumulation of extracellular ATP during apoptosis, as a possible contributory factor in the accumulation of ATP. In Aim 2, we will focus on how ATP may influence apoptotic cell clearance. Specifically, we will investigate how nucleotides in the apoptotic cell supernatants affect the ability of phagocytes to engulf apoptotic cells, by examining engulfment protein expression and phagocytic ability. We also aim to explore how nucleotides in the apoptotic cell supernatants may act on vascular endothelial cells to increase monocyte diapedesis to the affected area. Cells die during both normal and pathological processes, and are taken up efficiently by other cells. The clearance of dying cells is important for preventing inflammation, which is implicated as playing an important role in many disease processes including atherosclerosis and autoimmune disease. Understanding how dying cells promote their own clearance is an important issue with widespread implications.