(PQ12) Targeting SMPDL3b to Prevent Radiation-Induced Nephrotoxicity

项目摘要 放射性肾病（RN）比化疗引起的肾毒性少见，但仍代表着放射性肾病。 癌症放射治疗后的严重晚期并发症。RN是不可逆的，没有有效的临床 存在预防RN或改善辐射相关的肾损伤的治疗。足细胞丢失，肾小管萎缩 和内皮损伤与RN有关，但控制RN的分子机制尚不清楚。 我们发现，鞘磷脂磷酸二酯酶-酸样-3b（SMPDL 3b）是一种重要的 单剂量（SD）放疗（RT）后肾足细胞辐射损伤的调节因子。辐射损伤 SMPDL 3b表达减少，触发ezrin的细胞重新定位和形态学改变， 足细胞功能利妥昔单抗治疗，我们证明它结合SMPDL 3b， 足细胞形态，减少SD RT诱导的RN在C57 BL/6小鼠，但不是在我们新开发的条件 足细胞特异性SMPDL 3b敲除小鼠。基于这些数据，我们假设鞘脂在 在控制RN的辐射诱导足细胞病中的作用。 目的是研究SMPDL 3b在分次小剂量肾损伤中的作用机制。 放疗（F-RT）与顺铂（CDDP）并行，因为这代表了许多实体瘤的标准治疗。 癌的我们的长期目标是发现一种基于分子的RN保护或缓解策略， 潜在的化疗诱导的肾毒性。我们将用以下三个具体的例子来检验我们的假设。 目的是使用体内-体外联合方法： 目的1：确定SMPDL 3b是否调节RT相关肾损伤的严重性和潜伏期以及功能性肾损伤。 临床相关F-RT、CDDP和同时F-RT+CDDP后的RN。这一目标还将探讨 使用C57 BL/6小鼠和我们独特的SMPDL 3b敲除， 和SMPDL 3b诱导型小鼠模型。 目的2：探讨足细胞表达SMPDL 3b影响RT介导的足细胞的机制 和肾小球内皮细胞（GEC）损伤。我们假设SMPDL 3b影响RT诱导的 足细胞Ezrin的区室化，并通过改变内皮素-1（EDN 1）和END 1受体影响GECs A型（EDNRA）串扰。RT后GEC存活将通过将GEC与缺乏足细胞的足细胞共培养来研究。 或表达SMPDL 3b。 目的3：确定靶向鞘脂是否可预防RN。我们将调查SMPDL 3b或S1 P的保护是否 将避免F-RT、CDDP和F-RT+CDDP后C57 BL/6小鼠的长期功能性肾损伤。机制 将使用我们独特的SMPDL 3b敲除和SMPDL 3b诱导型小鼠模型进行确认。 这些研究的结果将是重要的，因为它们提供了分子靶向的潜力。 缓解RT和联合治疗损伤后的RN和放射相关肾损伤。

PROJECT SUMMARY Radiation nephropathy (RN) is less common than chemotherapy-induced nephrotoxicity but still represents a serious late complication after radiation therapies for cancer. RN is irreversible and no effective clinical treatments exist to prevent RN or ameliorate radiation-associated kidney injury. Podocyte loss, tubular atrophy and endothelial damage have been linked with RN, but the molecular mechanisms governing RN are not known. We discovered that the enzyme sphingomyelin-phosphodiesterase-acid-like-3b (SMPDL3b) is an important regulator of radiation damage in renal podocytes after single dose (SD) radiotherapy (RT). Radiation damage reduced SMPDL3b expression triggering the cellular relocation of ezrin and a morphological change that altered podocyte functionality. Treatment with rituximab, which we demonstrated to bind SMPDL3b and to protect podocyte morphology, reduced SD RT induced RN in C57BL/6 mice but not in our newly-developed conditional podocyte-specific SMPDL3b knock-out mice. Based on these data we hypothesize that sphingolipids play a vital role in radiation-induced podocytopathy which governs RN. The objective is to investigate the mechanistic role of SMPDL3b in renal injury after fractionated low-dose radiotherapy (F-RT) with concurrent cisplatin (CDDP) as this represents a standard of care for many solid cancers. Our long-term goal is to discover a molecular-based protective or mitigating strategy for RN, and potentially chemotherapy-induced nephrotoxicity. We will test our hypothesis with the following three specific aims using a combined in vivo-in vitro approach: Aim 1: To determine if SMPDL3b regulates severity and latency of RT-associated kidney injury and functional RN after clinically-relevant F-RT, CDDP and concurrent F-RT+CDDP. This aim will also explore the role of SMPDL3b in tissue tolerance for RT retreatment injury, using C57BL/6 mice and our unique SMPDL3b-knockout and SMPDL3b-inducible mouse models. Aim 2: To determine the mechanism by which podocyte expression of SMPDL3b affects RT-mediated podocyte and glomerular endothelial cell (GEC) injury. We hypothesize that SMPDL3b affects RT induced compartmentalization of podocyte ezrin and affects GECs via altered endothelin-1 (EDN1) and END1 receptor type A (EDNRA) cross talk. GEC survival after RT will be studied by co-culturing GECs with podocytes lacking or expressing SMPDL3b. Aim 3: To determine if targeting sphingolipids prevents RN. We will investigate if protection of SMPDL3b or S1P will avert long-term functional renal injury in C57BL/6 mice after F-RT, CDDP and F-RT+CDDP. Mechanisms will be confirmed using our unique SMPDL3b-knockout and SMPDL3b-inducible mouse models. The findings from these studies will be significant because they offer the potential for molecular-targeted mitigation for RN, and radiation-associated kidney injury, after RT and combined modality injury.