Crosstalk Between SMPDL3b and NADPH Oxidases Mediates Radiation-Induced Damage of Renal Podocytes

Abstract

Patients undergoing radiotherapy (RT) for various tumors localized in the abdomen or pelvis often suffer from radiation nephrotoxicity as collateral damage. Renal podocytes are vulnerable targets for ionizing radiation and contribute to radiation-induced nephropathies. Our prior work previously highlighted the importance of the lipid-modifying enzyme sphingomyelinase acid phosphodiesterase like 3b (SMPDL3b) in modulating the radiation response in podocytes and glomerular endothelial cells. Hereby, we investigated the interplay between SMPDL3b and oxidative stress in mediating radiation injury in podocytes. We demonstrated that the overexpression of SMPDL3b in cultured podocytes (OE) reduced superoxide anion generation and NADPH oxidase activity compared to wild-type cells (WT) post-irradiation. Furthermore, OE podocytes showed downregulated levels of NOX1 and NOX4 after RT. On the other hand, treatment with the NOX inhibitor GKT improved WTs' survival post-RT and restored SMPDL3b to basal levels. in vivo, the administration of GKT restored glomerular morphology and decreased proteinuria in 26-weeks irradiated mice. Taken together, these results suggest a novel role for NOX-derived reactive oxygen species (ROS) upstream of SMPDL3b in modulating the response of renal podocytes to radiation.

SMPDL3b modulates radiation‐induced DNA damage response in renal podocytes

“…Our group previously demonstrated that IR‐induced loss of SMPDL3b triggers podocytes dysfunction by disrupting their cytoskeletal integrity and sphingolipid homeostasis. However, SMPDL3b overexpression conferred radioresistance by partially reversing these alterations, enhancing DSBs repair, 32 and mitigating oxidative stress by decreasing the activity and protein expression of NADPH oxidases 41 . Furthermore, we reported that SMPDL3b modulates IR‐induced damage of human glomerular endothelial cells, whereby it gets upregulated post‐IR in contrast to podocytes 38 .…”

“…However, SMPDL3b overexpression conferred radioresistance by partially reversing these alterations, enhancing DSBs repair, 32 and mitigating oxidative stress by decreasing the activity and protein expression of NADPH oxidases. 41 Furthermore, we reported that SMPDL3b modulates IR-induced damage of human glomerular endothelial cells, whereby it gets upregulated post-IR in contrast to podocytes. 38 Therefore, our work hints that SMPDL3b changes are cell-specific.…”

“…The specific expression of sphingomyelin phosphodiesterase acid‐like 3b (SMPDL3b) in podocytes modulates stress signaling 37 and cellular ceramide‐1‐phosphate (C1P) levels 38–40 . We previously reported a fundamental role for SMPDL3b in modulating IR‐induced damage of podocytes 32,41 and glomerular endothelial cells 38 . However, the molecular mechanisms by which SMPDL3b modulates podocytes injury remain unknown.…”

Cytosine–phosphate–guanine oligodeoxynucleotides alleviate radiation-induced kidney injury in cervical cancer by inhibiting DNA damage and oxidative stress through blockade of PARP1/XRCC1 axis

“…After 1 week of acclimation, mice were used as control mice or subjected to modeling as RKI mice. RKI mice were irradiated with X-rays at a dose of 14 Gy, with a dose rate of 2.35 cGy/min at the kidney site, 5 days per week for 4 weeks (180 times of rotation during each irradiation to optimize dose uniformity) [ 28 , 29 ]. After 4 weeks, a fully automated biochemical analyzer (AU5800, Beckman Coulter Inc., Chaska, MN) was used to measure serum blood urea nitrogen (BUN) and creatinine values.…”

“…In brief, the sections were stained with hematoxylin for 10 min, differentiated with 1% hydrochloric acid alcohol for 30 s, stained with eosin for 1 min, and dehydrated with gradient alcohol (concentrations of 70%, 80%, 90%, 95%, and 100%, respectively) for 1 min each. After being cleared with xylene, the sections were sealed with neutral gum, and the morphological changes were finally photographed and observed under a light microscope (BX50; Olympus Corp., Tokyo, Japan) [ 29 ].…”