CPT1a downregulation protects against cholesterol-induced fibrosis in tubular epithelial cells by downregulating TGFβ-1 and inflammasome

Background: Dyslipidemia causes renal damage; however, the detailed molecular mechanism has not been clarified. It is known that carnitine palmitoyl transferase 1-a (CPT1a) gene encodes an enzyme involved in fatty acid oxidation and, therefore, lipid content. In the present study, we investigated whether the accumulation of lipids induced by 7-ketocholesterol (7-KC) in tubular epithelial cells produce a fibrotic and inflammatory response through CPT1a. Methods: Using an epithelial cell line, NRK-52E, we determine if intracellular accumulation of 7-KC modulates profibrotic and inflammatory events through CPT1a gene expression. In addition, the direct effects of CPT1a genetic modification has been studied. Results: Our results revealed that high levels of 7-KC induce increased expression of CPT1a, TGF-beta 1, alpha-SMA and NLRP3 that was correlated with lipid content. GW3965 treatment, which have shown to facilitate the efflux of cholesterol, eliminated the intracellular lipid droplets of 7-KC laden cells and decreased the expression of CPT1a, TGF-beta 1, alpha- SMA and NLRP3. Furthermore, CPT1a Knockdown and C75 pre-treatment increased lipid content but decreased TGF-beta 1, alpha- SMA and NLRP3. Conclusions: Our findings reveal that the profibrotic effect of 7-KC on renal epithelial cells are mediated by CPTla overexpression, which acts on TGF-beta 1, alpha-SMA and NLRP3. Thus, CPT1a downregulation protects against 7-KC-induced fibrosis in tubular epithelial cells by downregulating TGF-beta 1, alpha- SMA and NLRP3. (C) 2019 The Authors. Published by Elsevier Inc.