Document Type

Journal Article

Department/Unit

School of Chinese Medicine

Title

Inhibition of DNA-dependent protein kinase reduced palmitate and oleate-induced lipid accumulation in HepG2 cells

Language

English

Abstract

Purpose: The aim of this study is to investigate the involvement of DNA-dependent protein kinase (DNA-PK) in palmitate and oleate-induced lipid accumulation in hepatocytes. Methods: We treated HepG2 with free fatty acids (FFA) (0.33 mM palmitate and 0.66 mM oleate) mixture to induce lipid accumulation. Cellular lipid was determined by Nile Red staining followed by flow cytometry detection as well as phase contrast and fluorescence microscope examination. Cell viability was detected by MTT assay. Apoptosis was detected by DAPI staining. Lipogenic gene expression was examined by real-time PCR at mRNA level and Western blotting at protein level. Promoter transcriptional activity was measured by dual luciferase assay. Results: FFA treatment neither affected HepG2 cells viability nor induced DNA fragmentation, while induced cellular lipid accumulation was associated by the upregulation of sterol regulatory element-binding protein-1 (SREBP1) and fatty acid synthase (FAS) at both mRNA and protein levels. Interestingly, we also found that both the protein phosphatase 2A (PP2A) protein expression and DNA-PK activity were increased in these cells. Inhibition of PP2A by okadaic acid, knockdown of DNA-PK by siRNA or inhibition of DNA-PK by specific DNA-PK inhibitors curtailed the FFA-induced upregulations of the SREBP1 mRNA expression and the nuclear active SREBP1 protein expression, and reduced FFA-induced upregulation of FAS promoter transcriptional activity and lipid accumulation. Conclusion: This is the first time suggesting that inhibition of DNA-PK reduced FFA-induced lipid accumulation in hepatocytes. This finding might help us better understand non-alcoholic steatohepatitis pathogenesis. © Springer-Verlag Berlin Heidelberg 2012.

Keywords

DNA-PK, Hepatocellular steatosis, Lipid, Oleate, Palmitate, PP2A

Publication Date

2013

Source Publication Title

European Journal of Nutrition

Volume

52

Issue

6

Start Page

1621

End Page

1630

Publisher

Springer Verlag

DOI

10.1007/s00394-012-0467-5

Link to Publisher's Edition

http://dx.doi.org/10.1007/s00394-012-0467-5

ISSN (print)

14366207

ISSN (electronic)

14366215

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