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Kidney Week

Abstract: SA-PO150

Role of SMPDL3b in Radiation-Induced Nephropathy

Session Information

  • AKI: Mechanisms - III
    November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Ahmad, Anis, Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, United States
  • Mallela, Shamroop Kumar, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, Miami, Florida, United States
  • Afaghani, Jumana, Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, United States
  • Ansari, Saba, Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, United States
  • Ali, Misha, Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, United States
  • Merscher, Sandra M., Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, Miami, Florida, United States
  • Zeidan, Youssef, American University of Beirut (AUB) School of Medicine, Beirut, Lebanon
  • Fornoni, Alessia, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, Miami, Florida, United States
  • Marples, Brian, Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, United States

Group or Team Name

  • Dept of Radiation Oncology, University of Miami, Miller School of Medicine.
Background

The kidneys are radiosensitive and dose-limiting organs for radiotherapy (RT) targeting abdominal and paraspinal tumors. Excessive radiation doses to the kidneys lead to radiation nephropathy (RN). In this study, we investigated a novel role for the lipid-modifying enzyme, sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b), in regulating the response of renal podocytes to radiation injury.

Methods

Podocytes were irradiated with either 4Gy or 8Gy and Ezrin, and apoptosis, DNA damage, and survival were quantified at different time points post-RT. For in vivo studies, 10–14 weeks old C57BL/6 received bilateral kidney irradiation of 14Gy or 6x5Gy with or without rituximab (50 mg/kg; IP, 1h before RT). 20 weeks post RT, glomerular filtration rate (GFR) was measured by transdermal monitors. Urine and serum samples were analyzed to quantify urinary albumin-to-creatinine ratio (ACR), serum BUN, and creatinine levels. Kidney cortex sections were stained with H & E, Periodic Acid-Schiff, Picrosirius red, and Masson’s trichrome staining. Ultrastructural Changes in the glomerular filtration barrier were quantified by transmission electron microscopy.

Results

Podocyte survival decreased in a dose-dependent manner post-RT. SMPDL3b overexpression prevented RT-induced DNA damage and apoptosis in cultured podocytes. 24 h post-RT, Podocyte DNA damage and apoptosis increased significantly more in podocyte-specific knockout (pSMPDL3b-KO) mouse kidney cortex than in SMPDL3b wild-type mice (p 0.0166 and p = 0.0302, respectively). Fibrosis, glomerular basement membrane (GBM), and foot process width, mesangial expansion score, BUN, creatinine ACR increased significantly more in pSMPDL3B-KO mice than in SMPDL3b wild-type mice (p <0.05). GFR decreased significantly in SMPDL3B wild type and pSMPDL3B-KO mice 20 weeks post-RT (p <0.05). Rituximab treatment to SMPDL3b wild-type mice prevented SMPDL3b downregulation, podocyte loss, reduced fibrosis, mesangial expansion score, GBM thickness, and foot process width and significantly improved renal function (BUN, Creatinine, and ACR) post-RT (p <0.05).

Conclusion

Rituximab treatment restored SMPDL3b basal expression levels and decreased radiation-induced podocyte injury and albuminuria. Our findings suggest SMPDL3b as a potential therapeutic target in radiation-induced renal damage.

Funding

  • Other NIH Support