title: Docosahexaenoic acid ameliorates palmitate-induced lipid accumulation and inflammation through repressing NLRC4 inflammasome activation in HepG2 cells.
abstract: BACKGROUND
  N-3 polyunsaturated fatty acids, such as docosahexaenoic acid (DHA; 22:6n-3), has clinical significance in the prevention and reversal of nonalcoholic steatohepatitis (NASH). However, the precious mechanism underlying remains unclear. The inflammasome, a multiprotein complex formed by NOD-like receptor (NLR) family members, has been recently shown to be activated in NASH and promote the cleavage of the pro-inflammatory cytokines to their maturation forms.
  
  
  METHODS
  HepG2 cells were exposed to different dose of PA for 24 h with or without the preincubation of 50 μM DHA for another 24 h and then lipid deposition was assessed with Oil red O staining and intracellular triglyceride (TG) determination. Secretory levels of inflammatory cytokines and Caspase-1 activity were determined by ELISA assays. Gene expression and protein levels were determined by quantitative RCR and western blotting, respectively.
  
  
  RESULTS
  Palmitate (PA) dose-dependently increased lipid accumulation, TG content and induced the secretion of interleukin-1β (IL-1β), IL-18, TNF-α and MCP-1 from HepG2 cells. Preincubation with DHA significantly alleviated PA-induced lipid accumulation and inflammatory agents. DHA was also found to attenuate PA-induced NOD-like receptor protein 4 (NLRC4) mRNA expression. Furthermore, PA induced caspase-1 activation in a dose-dependent manner, resulting in exacerbating of procaspase-1 and pro-IL-1β processing. Knockdown of NLRC4 partially abrogated PA-induced caspase-1 activation and IL-1β maturation and completely abolished these events in the presence of DHA.
  
  
  CONCLUSIONS
  Our findings indicate DHA attenuates PA-induced lipid accumulation and inflammation through suppressing NLRC4 inflammasome activation, caspase-1 activation and IL-1β cleavage.
authors.affiliation: Guangdong Provincial Key Laboratory of Food, Nutrition and Health, School of Public Health, Sun Yat-sen University, Guangzhou, China. lingwh@mail.sysu.edu.cn.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Luo
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.forename: Tianran
authors.initials: T
authors.lastname: Shen
authors.forename: Xilan
authors.initials: X
authors.lastname: Tang
authors.forename: Yunjun
authors.initials: Y
authors.lastname: Xiao
authors.forename: Tangbin
authors.initials: T
authors.lastname: Zou
authors.forename: Min
authors.initials: M
authors.lastname: Xia
authors.forename: Wenhua
authors.initials: W
authors.lastname: Ling