title: Glucose 6-phosphate dehydrogenase knockdown enhances IL-8 expression in HepG2 cells via oxidative stress and NF-κB signaling pathway.
abstract: BACKGROUND
  This study was designed to investigate the effect of glucose 6-phosphate dehydrogenase (G6PD) deficiency on pro-inflammatory cytokine secretion using a palmitate-induced inflammation HepG2 in vitro model. The modulation of cellular pro-inflammatory cytokine expression under G6PD deficiency during chronic hepatic inflammation has never been investigated before.
  
  
  METHODS
  The culture medium of untreated and palmitate-treated G6PD-scramble (Sc) and G6PD-knockdown (Gi) HepG2 cells were subjected to cytokine array analysis, followed by validation with ELISA and qRT-PCR of the target cytokine. The mechanism of altered cytokine secretion in palmitate-treated Sc and Gi HepG2 cells was examined in the presence of anti-oxidative enzyme (glutathione peroxidase, GPX), anti-inflammatory agent (curcumin), NF-κB inhibitor (BAY11-7085) and specific SiRNA against NF-κB subunit p65.
  
  
  RESULTS
  Cytokine array analysis indicated that IL-8 is most significantly increased in G6PD-knockdown HepG2 cells. The up-regulation of IL-8 caused by G6PD deficiency in HepG2 cells was confirmed in other G6PD-deficient cells by qRT-PCR. The partial reduction of G6PD deficiency-derived IL-8 due to GPX and NF-κB blockers indicated that G6PD deficiency up-regulates pro-inflammatory cytokine IL-8 through oxidative stress and NF-κB pathway.
  
  
  CONCLUSIONS
  G6PD deficiency predisposes cells to enhanced production of pro-inflammatory cytokine IL-8. Mechanistically, G6PD deficiency up-regulates IL-8 through oxidative stress and NF-κB pathway. The palmitate-induced inflammation in G6PD-deficient HepG2 cells could serve as an in vitro model to study the role of altered redox homeostasis in chronic hepatic inflammation.
authors.affiliation: Healthy Aging Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.|Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Hung-Chi
authors.initials: HC
authors.lastname: Yang
authors.affiliation: Healthy Aging Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.|Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.|Department of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Mei-Ling
authors.initials: ML
authors.lastname: Cheng
authors.affiliation: Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Yi-Syuan
authors.initials: YS
authors.lastname: Hua
authors.affiliation: Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Wu
authors.affiliation: Molecular Medicine Research Center, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Hsin-Ru
authors.initials: HR
authors.lastname: Lin
authors.affiliation: Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Hui-Ya
authors.initials: HY
authors.lastname: Liu
authors.affiliation: Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Hung-Yao
authors.initials: HY
authors.lastname: Ho
authors.affiliation: Healthy Aging Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.|Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan 333 Taiwan.|Department of Clinical Pathology, Chang Gung Memorial Hospital, Kwei-Shan, Tao-Yuan 333 Taiwan.
authors.forename: Daniel Tsun-Yee
authors.initials: DT
authors.lastname: Chiu
keywords: Antioxidant; G6PD deficiency; IL-8; NF-κB; Oxidative stress; Palmitate; Pro-inflammatory cytokine