Modulation of radiation‐induced damage of human glomerular endothelial cells by SMPDL3B

Abstract

The intracellular molecular pathways involved in radiation‐induced nephropathy are still poorly understood. Glomerular endothelial cells are key components of the structure and function of the glomerular filtration barrier but little is known about the mechanisms implicated in their injury and repair. The current study establishes the response of immortalized human glomerular endothelial cells (GEnC) to ionizing radiation (IR). We investigated the role of sphingolipids and the lipid‐modifying enzyme sphingomyelin phosphodiesterase acid‐like 3b (SMPDL3b) in radiation‐induced GEnC damage. After delivering a single dose of radiation, long and very‐long‐chain ceramide species, and the expression levels of SMPDL3b were elevated. In contrast, levels of ceramide‐1‐phosphate (C1P) dropped in a time‐dependent manner although mRNA and protein levels of ceramide kinase (CERK) remained stable. Treatment with C1P or knocking down SMPDL3b partially restored cell survival and conferred radioprotection. We also report a novel role for the NADPH oxidase enzymes (NOXs), namely NOX1, and NOX‐derived reactive oxygen species (ROS) in radiation‐induced GEnC damage. Subjecting cultured endothelial cells to radiation was associated with increased NOX activity and superoxide anion generation. Silencing NOX1 using NOX1‐specific siRNA mitigated radiation‐induced oxidative stress and cellular injury. In addition, we report a novel connection between NOX and SMPDL3b. Treatment with the NOX inhibitor, GKT, decreased radiation‐induced cellular injury and restored SMPDL3b basal levels of expression. Our findings indicate the importance of SMPDL3b as a potential therapeutic target in radiation‐induced kidney damage.

Role of Sphingolipid Signaling in Glomerular Diseases: Focus on DKD and FSGS

“…Pretreatment with rituximab mitigated radiation-induced cytoskeletal changes and increased expression levels of SMPDL3b [ 101 ]. In contrast, a single dose of radiation applied to human immortalized glomerular endothelial cells results in increased levels of SMPDL3b and decreased levels of C1P [ 102 ], while treatment with exogenous C1P or genetic knocking down of SMPDL3b partially protects glomerular endothelial cells. Notably, inhibition of NOX1 seems sufficient to restore normal expression of SMPDL3b and to reduce radiation-induced damage of glomerular endothelial cells.…”

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

“…Glomerular endothelial cells (GenC), are key players in the onset and progression of numerous kidney diseases including radiation injury. Radiation-induced oxidative stress in glomerular endothelial cells has been examined by another study from our group ( 42 ). Irradiated GenC showed increased NOX activity and superoxide anion generation.…”

A Rheostat of Ceramide and Sphingosine-1-Phosphate as a Determinant of Oxidative Stress-Mediated Kidney Injury

“…Table 1 summarizes the localization of enzymes that regulate ceramide formation and SphKs in the kidney [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. Regarding subcellular localization of enzymes, sphingomyelin synthase (SMS)1/2 is predominantly in the Golgi and to a small extent in the plasma membrane [ 20 ].…”