Palmitic Acid Induces Extracellular Vesicle Release in Human Renal Proximal Tubule Epithelial Cells

Abstract

Lipotoxicity, an accumulation of intracellular lipid metabolites, has been proposed as an important pathogenic mechanism leading to kidney dysfunction in the context of metabolic disease. Palmitate, a predominant lipid derivative, can cause lipoapoptosis and the release of inflammatory extracellular vesicles (EVs) in hepatocytes. This study was aimed to investigate whether free fatty acid palmitate could increase EV release in renal tubular epithelial cells. A human proximal tubule epithelial cell line, HK‐2, was incubated with 1% bovine serum albumin (BSA), BSA‐conjugated palmitic acid (PA, 250 μM), BSA‐conjugated oleic acid (OA, 250 μM), or diluent (control) for 24 hours. The released EVs were isolated by ultracentrifugation, then characterized and quantified by immunoblot and nanoparticle‐tracking analysis (NTA). To examine the uptake of EVs by tubular cells, isolated EVs were further labelled and applied to HK‐2 cells. According to the NTA, the size distribution of HK‐2‐derived EVs was 30–200 nm with a similar mode size in all four groups. Interestingly, incubation of HK‐2 cells with 1%BSA alone significantly increased the release of EVs compared to the vehicle control. Moreover, BSA‐induced EV release was further increased by approximately two‐fold in the presence of PA, whereas EV production was not significantly changed by the addition of OA. PA (250 μM)‐enhanced EV release in HK‐2 is independent of cell apoptosis since apoptosis‐related proteins were not different between BSA and BSA‐PA groups. Both confocal microscopy and flow cytometry analyses confirmed that labeled lipid‐induced EVs were taken up by HK‐2 cells. Collectively, our results indicate that saturated fatty acid palmitate stimulates EV release from HK‐2 cells. Lipid‐induced EVs may serve as an untapped source to evaluate novel signaling pathways contributing to nephropathy progression.Support or Funding InformationNIH Diabetes and Digestive Kidney Disease Grant Number: R25DK1136559MSM Interdisciplinary Sleep/Clinical Cardiovascular Research Training Program (T32)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.