Loss of biliverdin reductase‐A (BVRA) promotes lipid accumulation and lipotoxicity in mouse proximal tubule cells

Abstract

Obesity and increased lipid availability have been implicated in the development and progression of chronic kidney disease. The proximal tubule cells of the kidney are the major site of lipid accumulation in the kidney, and thus are a major target for the toxic effect of excessive lipid accumulation –lipotoxicity. The aim of the current study was to test the hypothesis that the loss of biliverdin reductase‐A (BVRA) increases the susceptibility of mouse proximal tubule cells to excess lipid accumulation and lipotoxicity. We used CRISPR‐Cas9 technology to generate a BVRA knock out (BVRA‐KO) cell line from wildtype (WT) immortalized mouse MCT proximal tubule cells. We exposed the cells for 24 hrs to 400 μM Palmitic acid (PA) and then measured lipid accumulation and markers of lipotoxicity. Lipid accumulation was 83% (p=0.0033) and 54% higher (p=0.0002) in BVRA‐KO versus WT cells at baseline and following PA treatment respectively. This suggests that both de novo lipogenesis and fatty acid uptake were higher in BVRA‐KO versus WT cells. CD36, which play a major role in fatty acid uptake, was upregulated 7.8 folds in BVRA‐KO vs. WT cells (p=0.002). In addition, NGAL1 expression, Annexin‐v FITC staining, and LDH release were all significantly higher in BVRA‐KO cells vs. WT cells, demonstrating that BVRA‐KO cells are more sensitive to PA‐induced lipotoxicity than WT cells. Phosphorylation of AKT and BAD, which play important roles in cell survival and inhibition of apoptosis, were significantly reduced by PA, only in BVRA‐KO cells (52% and 39% reduction; p=0.0019 and 0.0061 respectively). These data demonstrate the protective role of BVRA in proximal tubule cells against saturated fatty acid‐induced lipotoxicity and suggest that activating BVRA may play a protective role in obesity‐induced kidney injury.Support or Funding InformationThis work was supported by grants from the National Heart, Lung and Blood Institute K01HL‐125445 (T.D.H.), PO1HL‐051971 (D.E.S.), HL088421 (J.E.H.), and 1T32HL105324 (S.O.A) and the National Institute of General Medical Sciences P20GM‐104357 (J.E.H.).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.