(PQ12) Targeting SMPDL3b to Prevent Radiation-Induced Nephrotoxicity

项目总结 放射性肾病(RN)不像化疗引起的肾毒性那么常见，但仍是一种 癌症放射治疗后严重的晚期并发症。RN是不可逆转的，临床上没有有效的方法 存在预防RN或改善辐射相关的肾损伤的治疗方法。足细胞丢失，肾小管萎缩 内皮损伤与RN有关，但RN的分子调控机制尚不清楚。 我们发现鞘磷脂-磷酸二酯酶-类酸性-3b(SMPDL3b)是一种重要的 单次剂量(SD)放射治疗(RT)后肾足细胞辐射损伤调节因子的研究辐射损伤 SMPDL3b表达减少触发Ezrin的细胞重新定位和改变的形态变化 足细胞功能。用利妥昔单抗治疗，我们证明它能结合SMPDL3b并保护 C57BL/6小鼠足细胞形态，SD RT诱导的RN减少，而我们新开发的条件性RN没有 足细胞特异性SMPDL3b基因敲除小鼠。基于这些数据，我们假设鞘脂类在 在辐射诱导的足细胞病变中的作用，这支配着RN。 目的：探讨SMPDL3b在分次小剂量肾损伤中的作用机制。 放射治疗(F-RT)联合顺铂(CDDP)，因为这代表了许多实体的标准护理 癌症。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，以及 潜在的化疗引起的肾毒性。我们将通过以下三个具体实例来验证我们的假设 旨在使用体内和体外相结合的方法： 目的1：确定SMPDL3b是否调节RT相关肾损伤和功能的严重程度和潜伏期 临床相关的F-RT、CDDP和同步F-RT CDDP后的RN。这一目标还将探讨 SMPDL3b在组织耐受RT再治疗损伤中的作用，使用C57BL/6小鼠和我们独特的SMPDL3b基因敲除 SMPDL3b诱导的小鼠模型。 目的2：探讨SMPDL3b在足细胞中的表达对RT介导的足细胞的影响机制 肾小球内皮细胞(GEC)损伤。我们假设SMPDL3b影响RT诱导的 足细胞Ezrin的区域化及其通过改变内皮素-1和END1受体影响血管内皮细胞 A型(Ednra)串音。RT后GEC存活的研究将通过共培养缺乏足细胞的GEC来进行 或表达SMPDL3b。 目的3：确定靶向鞘脂是否可以预防RN。我们将调查SMPDL3b或S1P的保护 将避免C57BL/6小鼠在F-RT、CDDP和F-RT CDDP后的长期功能性肾损伤。机制 将使用我们独特的SMPDL3b基因敲除和SMPDL3b诱导的小鼠模型进行确认。 这些研究的发现将具有重要意义，因为它们提供了分子靶向的可能性 放射治疗和联合损伤后对RN和放射性相关肾损伤的缓解。

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.