Sphingomyelinase-like phosphodiesterase 3b mediates radiation-induced damage of renal podocytes.
The molecular mechanisms responsible for the development of proteinuria and glomerulosclerosis in radiation nephropathy remain largely unknown. Podocytes are increasingly recognized as key players in the pathogenesis of proteinuria in primary and secondary glomerular disorders. The lipid-modulating enzyme sphingomyelin phosphodiesterase acid-like 3B (SMPDL3b) is a key determinant of podocyte injury and a known off target of the anti-CD20 antibody rituximab (RTX). The current study investigates the role of sphingolipids in radiation-induced podocytopathy. After a single dose of radiation (8 Gy), several ceramide species were significantly elevated. In particular, C16:00, C24:00, and C24:1 ceramides were the most abundant ceramide species detected. These changes were paralleled by a time-dependent drop in SMPDL3b protein, sphingosine, and sphingosine-1-phosphate levels. Interestingly, SMPDL3b-overexpressing podocytes had higher basal levels of sphingosine-1-phosphate and maintained basal ceramide levels after irradiation. Morphologically, irradiated podocytes demonstrated loss of filopodia and remodeling of cortical actin. Furthermore, the actin binding protein ezrin relocated from the plasma membrane to the cytosol as early as 2 h after radiation. In contrast, SMPDL3b overexpressing podocytes were protected from radiation-induced cytoskeletal remodeling. Treatment with RTX before radiation exposure partially protected podocytes from SMPDL3b loss, cytoskeletal remodeling, and caspase 3 cleavage. Our results demonstrate that radiation injury induces early cytoskeletal remodeling, down-regulation of SMPDL3b, and elevation of cellular ceramide levels. Overexpression of SMPDL3b and pretreatment with RTX confer a radioprotective effect in cultured podocytes. These findings indicate a potential role for SMPDL3b and RTX in radiation-induced podocytopathy.-Ahmad, A., Mitrofanova, A., Bielawski, J., Yang, Y., Marples, B., Fornoni, A., Zeidan, Y. H. Sphingomyelinase-like phosphodiesterase 3b mediates radiation-induced damage of renal podocytes.
Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, USA.
Anis
A
Ahmad
Peggy and Harold Katz Family Drug Discovery Center, University of Miami, Miami, Florida, USA.|Department of Surgery, University of Miami, Miami, Florida, USA.|Department of Medicine, University of Miami, Miami, Florida, USA.
Alla
A
Mitrofanova
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.
Jacek
J
Bielawski
Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, USA.
Yidong
Y
Yang
Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, USA.
Brian
B
Marples
Peggy and Harold Katz Family Drug Discovery Center, University of Miami, Miami, Florida, USA.|Department of Medicine, University of Miami, Miami, Florida, USA.|Division of Nephrology, Department of Medicine, University of Miami, Miami, Florida, USA; and.
Alessia
A
Fornoni
Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, Florida, USA; yz09@aub.edu.lb.|Department of Radiation Oncology, American University of Beirut, Beirut, Lebanon.
Youssef H
YH
Zeidan
D000818:Animals; D002518:Ceramides / Q000378:metabolism; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007155:Immunologic Factors / Q000008:administration & dosage / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D050199:Podocytes / Q000378:metabolism* / Q000528:radiation effects*; D000069283:Rituximab / Q000008:administration & dosage / Q000494:pharmacology; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism*
D002518:Ceramides; D007155:Immunologic Factors; D000069283:Rituximab; C508196:SMPDL3B protein, human; D013108:Sphingomyelin Phosphodiesterase; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; C000595964:sphingomyelinase-like phosphodiesterase 3b, mouse
cancer; ceramide; lipids; radioprotection