title: High Uric Acid Activates the ROS-AMPK Pathway, Impairs CD68 Expression and Inhibits OxLDL-Induced Foam-Cell Formation in a Human Monocytic Cell Line, THP-1.
abstract: OBJECTIVE
  Hyperuricemia is part of the metabolic-syndrome cluster of abdominal obesity, impaired glucose tolerance, insulin resistance, dyslipidemia, and hypertension. Monocytes/macrophages are critical in the development of metabolic syndrome, including gout, obesity and atherosclerosis. However, how high uric acid (HUA) exposure affects monocyte/macrophage function remains unclear. In this study, we investigated the molecular mechanism of HUA exposure in monocytes/macrophages and its impact on oxidized low-density lipoprotein (oxLDL)-induced foam-cell formation in a human monocytic cell line, THP-1.
  
  
  METHODS
  We primed THP-1 cells with phorbol-12-myristate-13-acetate (PMA) for differentiation, then exposed cells to HUA and detected the production of reactive oxygen species (ROS) and analyzed the level of phospho-AMPKα. THP-1 cells were pre-incubated with Compound C, an AMPK inhibitor, or N-acetyl-L-cysteine (NAC), a ROS scavenger, or HUA before PMA, to assess CD68 expression and phospho-AMPKα level. PMA-primed THP-1 cells were pre-treated with oxLDL before Compound C and HUA treatment. Western blot analysis was used to examine the levels of phospho-AMPKα, CD68, ABCG1, ABCA1, cyclooxygenase-2 (COX-2) and NF-κB (p65). Flow cytometry was used to assess ROS production and CD68 expression in live cells. Oil-red O staining was used to observe oxLDL uptake in cells.
  
  
  RESULTS
  HUA treatment increased ROS production in PMA-primed THP-1 cells; NAC blocked HUA-induced oxidative stress. HUA treatment time-dependently increased phospho-AMPKα level in PMA-primed THP-1 cells. The HUA-induced oxidative stress increased phospho-AMPKα levels, which was blocked by NAC. HUA treatment impaired CD68 expression during cell differentiation by activating the AMPK pathway, which was reversed by Compound C treatment. Finally, HUA treatment inhibited oxLDL uptake in the formation of foam cells in THP-1 cells, which was blocked by Compound C treatment. HUA treatment significantly increased the expression of ABCG1 and reversed the oxLDL-reduced ABCG1 expression but did not affect the expression of ABCA1, NF-κB (p65) or COX-2.
  
  
  CONCLUSIONS
  HUA exposure activated the ROS-AMPK pathway, impaired CD68 expression, and inhibited oxLDL-induced foam-cell formation in a human monocytic cell line, THP-1.
authors.affiliation: Department of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Chaohuan
authors.initials: C
authors.lastname: Luo
authors.forename: Xueke
authors.initials: X
authors.lastname: Lian
authors.forename: Liangli
authors.initials: L
authors.lastname: Hong
authors.forename: Jingfang
authors.initials: J
authors.lastname: Zou
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.forename: Yuzhang
authors.initials: Y
authors.lastname: Zhu
authors.forename: Tianliang
authors.initials: T
authors.lastname: Huang
authors.forename: Yongneng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yaqiu
authors.initials: Y
authors.lastname: Hu
authors.forename: Huier
authors.initials: H
authors.lastname: Yuan
authors.forename: Tengfei
authors.initials: T
authors.lastname: Wen
authors.forename: Wanling
authors.initials: W
authors.lastname: Zhuang
authors.forename: Bozhi
authors.initials: B
authors.lastname: Cai
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Jiexiong
authors.initials: J
authors.lastname: Huang
authors.forename: Jidong
authors.initials: J
authors.lastname: Cheng
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1 / Q000378:metabolism; D000111:Acetylcysteine / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000378:metabolism; D005487:Foam Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008954:Models, Biological; D009000:Monocytes / Q000166:cytology*; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D051996:Transcription Factor RelA / Q000378:metabolism; D014527:Uric Acid / Q000494:pharmacology*; D000097382:CD68 Molecule
chemical_list: D055372:AMP-Activated Protein Kinases; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D000111:Acetylcysteine; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D051546:Cyclooxygenase 2; D008077:Lipoproteins, LDL; D017382:Reactive Oxygen Species; D013755:Tetradecanoylphorbol Acetate; D051996:Transcription Factor RelA; D014527:Uric Acid; C419353:ABCG1 protein, human; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C099252:oxidized low density lipoprotein