Effects of acrylamide on protein degradation pathways in human liver-derived cells and the efficacy of N-acetylcysteine and curcumin

Abstract

Acrylamide is a harmful chemical, and its metabolism occurs mainly in the liver. Acrylamide can form adducts on proteins. Protein homeostasis is vital for metabolic and secretory functions of the liver. No study has investigated the effect of acrylamide on the ubiquitin-proteasome system (UPS). Also, the effect of acrylamide on autophagy and its regulation is not fully known. We aimed to investigate the effects of acrylamide on the UPS, autophagy, mammalian target of rapamycin (mTOR), and heat shock protein 70 (HSP70) in HepG2 cells as well as to examine the effects of N-acetylcysteine and curcumin on these parameters in acrylamide-treated cells. HepG2 cells were initially treated with variable concentrations of acrylamide (0.01–0.1–1–10 mM) for 24 hours. Then, HepG2 cells were treated with 5 mM N-acetylcysteine and 6.79 µM curcumin in the presence of 10 mM acrylamide for 24 hours. Cell viability was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Ubiquitinated protein, mTOR, microtubule-associated proteins 1 A/1B light chain 3B-II (LC3B-II), and HSP70 levels were measured by immunoblotting. Acrylamide at 10 mM concentration, without any significant change at lower concentrations, caused an increase in ubiquitinated protein, LC3B-II, and HSP70 levels and a decrease in mTOR phosphorylation. Furthermore, 5 mM N-acetylcysteine caused a decrease in ubiquitinated protein and HSP70 levels; however, 6.79 µM curcumin did not affect 10 mM in acrylamide-treated cells. Our study showed that acrylamide at high concentration inhibits UPS and mTOR, activates autophagy, and increases HSP70 levels in HepG2 cells, and N-acetylcysteine reduces UPS inhibition and HSP70 levels in acrylamide-treated cells.

Keywords:

• Acrylamide
• liver
• HepG2 cell line
• ubiquitin-proteasome system
• autophagy
• mammalian target of rapamycin
• heat shock protein 70
• N-acetylcysteine
• curcumin

Acknowledgements

Scientific Research Appropriation of Trakya University (Turkey) supported this study under grant number: TÜBAP 2018/265 as a part of the M.Sc. thesis of Abdullah Yahya Salih Al-Hajm. The authors thank the Technology Research and Development Center of Trakya University (TÜTAGEM) for providing the ECL detection system for immunoblotting and liquid nitrogen for the storage of cells.

Disclosure statement

The authors report no conflict of interest.

Additional information

Funding

This study was supported by Scientific Research Appropriation of Trakya University - Turkey under grant number [TÜBAP 2018/265].