Ahmad Anis, Mallela Shamroop Kumar, Ansari Saba, Alnukhali Mohammed, Ali Misha, Merscher Sandra, Pollack Alan, Zeidan Youssef H, Fornoni Alessia, Marples Brian
Department of Radiation Oncology, University of Miami, Sylvester Comprehensive Cancer Center/ Miller School of Medicine.
Peggy and Harold Katz Family Drug Discovery Center and Katz Family Division of Nephrology and Hypertension, Department of Medicine, University of Miami, Miami, Florida.
Int J Radiat Oncol Biol Phys. 2025 Apr 1;121(5):1271-1281. doi: 10.1016/j.ijrobp.2024.11.105. Epub 2024 Dec 10.
Radiation nephropathy (RN) can be a significant late complication after radiation therapy (RT) for abdominal and paraspinal tumors. The mechanisms for the development of RN are thought to involve disruption of podocyte function, leading to podocyte cell death and, finally, impaired renal function. This study investigated the mechanistic role of sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) in regulating podocyte injury and renal function after irradiation. The aim of the study was to investigate the potential linkage between (1) RT-induced renal dysfunction and podocyte SMPDL3b expression and (2) RT-induced podocyte injury and expansion of the glomerular basement membrane (GBM).
SMPDL3b wild-type, siSMPDL3b, and SMPDL3b-overexpressing podocytes were irradiated in cell culture, and cell death was assessed. SMPDL3b wild-type and podocyte-specific SMPDL3b knockout mice were treated with focal bilateral kidney X-irradiation (14 Gy, or 6 × 5 Gy), and podocyte apoptosis, renal function parameters, glomerular filtration rate, glomerular histology, and GBM ultrastructural changes via transmission electron microscopy were assessed.
Following RT treatment, a notable decrease in SMPDL3b expression was observed, accompanied by heightened levels of DNA damage, cytoskeletal alterations, and apoptotic events in cultured podocytes. SMPDL3b overexpression notably prevented DNA damage and apoptosis in cultured podocytes. Additionally, in vivo, RT exposure led to a significant decline in SMPDL3b expression, podocyte count, and renal function while concomitantly elevating GBM thickness, mesangial expansion, and renal fibrosis at the 20-week post-RT. Furthermore, in vivo, rituximab pretreatment before RT prevented SMPDL3b downregulation, podocyte loss, mesangial expansion, GBM expansion, and renal fibrosis and ultimately enhanced renal function post-RT.
Our findings collectively suggest a novel function for SMPDL3b in orchestrating the DNA damage response triggered by radiation. This study proposes that SMPDL3b exerts a regulatory influence on the repair of double-strand breaks within podocytes, consequently averting podocyte loss, GBM expansion, and the onset of RN.
放射性肾病（RN）可能是腹部和脊柱旁肿瘤放疗（RT）后一种严重的晚期并发症。RN发生的机制被认为涉及足细胞功能破坏，导致足细胞死亡，最终损害肾功能。本研究调查了酸性鞘磷脂磷酸二酯酶样3b（SMPDL3b）在调节辐射后足细胞损伤和肾功能中的机制作用。该研究的目的是调查（1）放疗诱导的肾功能障碍与足细胞SMPDL3b表达之间以及（2）放疗诱导的足细胞损伤与肾小球基底膜（GBM）扩张之间的潜在联系。
在细胞培养中对SMPDL3b野生型、siSMPDL3b和过表达SMPDL3b的足细胞进行照射，并评估细胞死亡情况。对SMPDL3b野生型和足细胞特异性SMPDL3b基因敲除小鼠进行双侧肾脏局部X线照射（14 Gy，或6×5 Gy），并评估足细胞凋亡、肾功能参数、肾小球滤过率、肾小球组织学以及通过透射电子显微镜观察GBM超微结构变化。
放疗后，观察到SMPDL3b表达显著降低，同时培养的足细胞中DNA损伤水平升高、细胞骨架改变和凋亡事件增加。SMPDL3b过表达显著预防了培养的足细胞中的DNA损伤和凋亡。此外，在体内，放疗导致SMPDL3b表达、足细胞计数和肾功能显著下降，同时在放疗后20周时GBM厚度、系膜扩张和肾纤维化增加。此外，在体内，放疗前用利妥昔单抗预处理可预防SMPDL3b下调、足细胞丢失、系膜扩张、GBM扩张和肾纤维化，并最终增强放疗后的肾功能。
我们的研究结果共同表明SMPDL3b在协调辐射引发的DNA损伤反应中具有新功能。本研究提出SMPDL3b对足细胞内双链断裂的修复发挥调节作用，从而避免足细胞丢失、GBM扩张和RN的发生。
