ENTEROCYTE APOPTOSIS AFTER INTESTINAL RESECTION

描述（由申请人提供）：肠道适应是对大量小肠切除术（SBR）的关键代偿反应，其特征是肠细胞周转率增加，通过增殖和凋亡的升高来衡量。在本基金的上一个资助周期中，凋亡对适应程度的重要性得到了揭示，因为当细胞凋亡被积极抑制时，观察到适应性的增强。虽然SBR后细胞凋亡升高的机制目前尚不清楚，但我们已经确定这种反应是由表皮生长因子受体（EGFR）信号传导调节的，并且需要促凋亡Bcl02家族成员Bax和转录因子信号换能器和转录激活因子(STAT)-1的表达。作为这些关键观察的延伸，我们提出了EGFR信号调节Bax的表达和活性以调节切除诱导的细胞凋亡的全局假设。为了验证这一假设，我们的目标是：1)确定STAT-1在肠道适应过程中对Bax表达的调节作用。STAT-1的表达和活性将在SBR后的回肠以及诱导细胞凋亡后的细胞培养中测定。STAT-1缺乏对Bax表达和凋亡的影响将被测量，并研究Bax启动子上可能的STAT-1结合位点。2)确定p38 α丝裂原活化蛋白激酶（MAPK）在切除诱导适应过程中作为Bax活性调节剂的作用。我们将在小鼠和体外细胞凋亡模型中记录SBR后p38表达/活性和Bax激活的时空分布。条件性的、肠道特异性的p38表达缺失对Bax活性和细胞凋亡的影响将在SBR后确定。3)确定EGFR调控Bax表达和活性的机制。EGFR信号增强或中断对STAT-1和p38激活和表达的影响将被记录。在EGFR抑制的情况下，stat1或p38表达减弱对细胞凋亡和Bax活性及表达的影响将被确定。本应用程序中提出的研究将确定最相关的信号通路，以指导大规模SBR后的凋亡。彻底了解诱导细胞凋亡的确切机制是将治疗靶点从实验到临床转化的基础，目的是最大限度地刺激肠黏膜的再生，以应对大量肠道损失。公共卫生相关性：大量肠道丢失后，剩余的肠道试图重新生长以补偿。如果这种反应不完全，患者将终生接受静脉营养和所有相关并发症。本项目旨在了解粘膜细胞死亡对肠道再生过程的贡献。了解这一重要反应的确切分子调控可能会导致创新疗法，旨在改善肠道灾难性损失后的肠道再生。

DESCRIPTION (provided by applicant): Intestinal adaptation is a critical, compensatory response to massive small bowel resection (SBR) and characterized by increased enterocyte turnover as gauged by elevated rages of both proliferation and apoptosis. The significance of apoptosis to the magnitude of adaptation was revealed during the previous funding cycle of this grant as amplified adaptation was observed when apoptosis was actively inhibited. While the mechanisms(s) for elevated apoptosis after SBR is presently unknown, we have established that this response is regulated by epidermal growth factor receptor (EGFR) signaling and requires expression of the proapototic Bcl02 family member Bax and the transcription factor signal transducer and activator of transcription (STAT)-1. As an extension of these key observations, we propose the global hypothesis that EGFR signaling modulates the expression and activity of Bax to regulate resection-induced apoptosis. To test this hypothesis our aims are: 1) Determine the role for STAT-1 in the regulation of Bax expression during intestinal adaptation. STAT-1 expression and activity will be determined in the ileum after SBR as well as in cell culture following induction of apoptosis. The effect of STAT-1 deficiency on Bax expression and apoptosis will be measured and putative STAT-1 binding sites on Bax promoter will be investigated. 2) Determine the role of p38alpha mitogen-activated protein kinase (MAPK) as modulator of Bax activity during resection induced adaptation. A temporal and spatial profile of p38 expression/activity and Bax activation will be recorded after SBR in mice and complementary in vitro models of apoptosis. The effect of conditional, intestine-specific deletion of p38 expression on Bax activity and apoptosis will be determined after SBR. 3) Determine the mechanism for EGFR regulation of Bax expression and activity. The effect of enhanced or disrupted EGFR signaling on STAT-1 and p38 activation and expression will be recorded. The effect of attenuated STAT-1 or p38 expression in the context of EGFR inhibition on apoptosis and Bax activity and expression will be determined. The proposed studies in this application will identify the most relevant signaling pathway to direct apoptosis after massive SBR. A thorough understanding of the precise mechanism for induction of apoptosis is fundamental for bench-to-bedside translation of therapeutic targets intended to maximally stimulate regrowth of the intestinal mucosa in response to massive intestinal loss. PUBLIC HEALTH RELEVANCE: Following massive intestinal loss, the remaining bowel attempts to grow back to compensate. If this response is incomplete, the patient will be subjected to a lifetime of nutrition by vein and all the associated complications. This project is designed to understand the contribution of mucosal cell death to the process of intestinal regrowth. Understanding the exact molecular regulation of this important response may lead to innovative therapy intended to improve intestinal regrowth following a catastrophic loss of the intestine.