Endogenous sphingosine-1-phosphate as a radioprotector of intestinal tissues

描述（由申请人提供）：神经酰胺和鞘氨醇-1-磷酸（S1P）是生物活性脂质，通过激活特定的信号通路来调节细胞存活。神经酰胺在辐射作用下在细胞内积累，激活细胞凋亡途径。抑制神经酰胺合成可防止辐射损伤。相反，神经酰胺代谢物S1 P在应激反应中促进细胞存活，对血管生成至关重要。S1 P可拮抗神经酰胺和辐射诱导的凋亡通路。重要的是，S1P可以防止辐射诱导的小鼠细胞凋亡和不育。因此，虽然神经酰胺会导致放射性肠炎，但其向S1P的转化提供了一种内部微调信号，限制了辐射反应的强度。我们的初步研究表明，S1P是一种有效的肠道放射保护剂，在致死剂量的辐射后促进细胞、组织和动物的存活。然而，S1P很难实现。因此，我们设计了一种替代方法来提高细胞内S1P水平并实现辐射防护。S1P由S1P裂解酶（SPL）分解代谢。SPL在肠绒毛和结肠隐窝中高度表达，维持低S1 - P水平，促进细胞更新。体外和体内DNA损伤和辐射均可诱导SPL表达，SPL表达促进辐射诱导的细胞凋亡，而抑制SPL可减弱DNA损伤后的细胞凋亡。四羟基丁基咪唑（tetrahydroxybutyl -咪唑，THI）是焦糖食用色素的一种小分子成分，最近被发现是一种SPL抑制剂。我们发现，口服THI可降低小鼠结肠和肠道组织中SPL活性并提高S1P水平。基于这些发现和观察到的放射防护效果的S1 P在老鼠身上,我们假设这提供了一个安全的手段实现辐射防护在肠道和其他组织迅速抑制SPL活动和提高细胞内和循环水平的内生radioprotectant, S1 P .应对这种可能性,我们提出了三个集成的具体目标:1)定义所需的动力学和剂量要求THI提高组织和循环S1 P水平;2)评价THI作为辐射诱发肠道病理保护者的暴露前后疗效；3)评估给药THI是否能延长辐射暴露后的生存时间。THI是一种理想的候选辐射防护剂，因为它易于输送，相关毒性最小，具有快速产品开发和多器官辐射防护的潜力。

DESCRIPTION (provided by applicant): Ceramide and sphingosine-1-phosphate (S1P) are bioactive lipids that regulate cell survival through activation of specific signaling pathways. Ceramide accumulates in cells in response to radiation and activates apoptosis pathways. Inhibiting ceramide synthesis protects against radiation injury. In contrast, the ceramide metabolite S1 P promotes cell survival in response to stress and is essential for angiogenesis. S1 P antagonizes apoptotic pathways including those induced by ceramide and radiation. Importantly, S1P prevents radiation-induced apoptosis and sterility in mice. Thus, while ceramide contributes to radiation enteritis, its conversion to S1P provides an internal fine-tuning signal that limits the intensity of radiation responses. Our preliminary studies indicate that S1P is a potent radioprotectant of the gut, promoting cell, tissue and animal survival after lethal doses of radiation. However, S1P is difficult to deliver. Thus, we have devised an alternative approach to raise intracellular levels of S1P and achieve radioprotection. S1P is catabolized by the enzyme S1 P lyase (SPL). SPL is highly expressed in intestinal villi and colonic crypts, where it maintains low S1 P levels, promoting cell turnover. SPL expression is induced by DNA damage and radiation in vitro and in vivo, and SPL expression promotes radiation-induced apoptosis, whereas SPL inhibition attenuates apoptosis after DNA damage. Tetrahydroxybutyl-imidazole (THI), a small molecule constituent of caramel food coloring, was recently found to be an SPL inhibitor. We show that oral administration of THI to mice reduces SPL activity and elevates S1P levels in colonic and intestinal tissues. Based on these findings and the observed radioprotective effect of S1 P in mice, we hypothesize that THI provides a safe means of achieving radioprotection in the gut and other tissues by rapidly inhibiting SPL activity and elevating intracellular and circulating levels of the endogenous radioprotectant, S1 P. To address this possibility, we have proposed three integrated specific aims: 1) To define the kinetics and dose requirements needed for THI to raise tissue and circulating S1 P levels; 2) To evaluate the pre- and post-expo-sure efficacy of THI as a protector of radiation-induced intestinal pathology; 3) To assess whether THI administration can prolong survival after radiation exposure. THI is an ideal candidate radioprotective agent due to its ease of delivery, minimal associated toxicity profile, and potential for rapid product development and multi-organ radioprotection.