SMPDL3b mediates radiation-induced human glomerular endothelial cell Injury

Abstract

Background: Radiotherapy has been a milestone in the field of oncology, though, for many tumors, the cure comes at a price. Innocent tissue bystanders get their share of the radiation, the latter leading to cell death and compromising many bodily functions. One of the major concerns in treating abdominal and spine cancers is the collateral damage that the kidneys suffer. Renal failure can be a major cause of death in such patients even when cancer subsides. Our group has been long investigating the alterations in podocyte signaling pathways in radiation-induced renal damage as well as in other podocytopathies, with particular focus on lipidomics. A major player, sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) has been identified in the chain of events leads to podocyte dysfunction upon exposure to radiation. Changes at the level of protein expression of this newly identified enzyme are linked to alterations in cellular sphingolipidomic profile and hence cellular function and survival. However, since podocytes are not the only determinants of the integrity of the glomerular filtration barrier (GFB) and kidney function, our project extends to explore other cell lines. Aims: We aimed to establish a radiation dose-response curve of a relatively new cell line, referred to as conditionally immortalized human glomerular endothelial cells. We also aimed to reveal the effect of radiation on these cells by unraveling the signaling pathway that links proteomics, namely NADPH oxidases and oxidative stress, to the alterations in the sphingolipidomic profile and the subsequent effect of this on cell survival. Similar to our previous work on human podocytes, SMPDL3b will be at the center of our focus. Materials and Methods: Human glomerular endothelial cells were be cultured as required. To establish the dose-response curve, a colony-forming unit assay will be used. The cells were irradiated at 4Gy and sent to mass spectrometry for analysis of the sphingolipid profile. The levels of expression of NOX1 and SMPDL3b post-