title: Autophagy induction and CHOP under-expression promotes survival of fibroblasts from rheumatoid arthritis patients under endoplasmic reticulum stress.
abstract: BACKGROUND
  Synovial fibroblasts from rheumatoid arthritis show resistance to apoptotic stimuli, indicating they may be difficult to treat. To clearly understand these mechanisms of resistance, rheumatoid and osteoarthritis synovial fibroblasts (RASF and OASF) were exposed to endoplasmic reticulum (ER) stress such as thapsigargin, Ca2+-ATPase inhibitor.
  
  
  METHODS
  Fibroblasts were assessed microscopically for cell viability by trypan blue exclusion and for autophagic cells by LC-3II formation. Caspase-3 activity was measured as aminomethyl-coumarin (AMC) liberated from AC-DEVD-AMC. Immunoblotting was performed to compare protein expression in OASF and RASF.
  
  
  RESULTS
  ER stress caused cell death in OASF but not in RASF. Thapsigargin, a Ca2+-ATPase inhibitor, did not change the expression of GRP78, an ER chaperone in OASF and RASF, but induced another ER stress protein, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) differently, showing high levels in OASF and low levels in RASF. Thapsigargin increased the autophagy response in RASF, with autophagosome formation, beclin expression, and LC3-II conversion. Transfection with beclin siRNA inhibited autophagy and increased the susceptibility to ER stress-induced cell death. On the other hand, CHOP siRNA increased autophagy and improved cell survival, especially in RASF, indicating that CHOP is involved in regulation of autophagy and cell death, but that low expression of CHOP protects RASF from apoptosis.
  
  
  CONCLUSIONS
  Autophagy induction and CHOP under-expression increases cell resistance against ER stress-induced cell death in fibroblasts from rheumatoid arthritis patients.
authors.affiliation: Department of Rheumatology, Medical School, the Catholic University of Korea, Seoul, Republic of Korea, 150-713. yjs@catholic.ac.kr
authors.forename: Yong-Joo
authors.initials: YJ
authors.lastname: Shin
authors.forename: Song-Hee
authors.initials: SH
authors.lastname: Han
authors.forename: Do-Sung
authors.initials: DS
authors.lastname: Kim
authors.forename: Geum-Hwa
authors.initials: GH
authors.lastname: Lee
authors.forename: Wan-Hee
authors.initials: WH
authors.lastname: Yoo
authors.forename: Yong-Mo
authors.initials: YM
authors.lastname: Kang
authors.forename: Je-Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Yong Chul
authors.initials: YC
authors.lastname: Lee
authors.forename: Seoung Ju
authors.initials: SJ
authors.lastname: Park
authors.forename: Seul-Ki
authors.initials: SK
authors.lastname: Jeong
authors.forename: Hyung-Tae
authors.initials: HT
authors.lastname: Kim
authors.forename: Soo-Wan
authors.initials: SW
authors.lastname: Chae
authors.forename: Hyun-Ja
authors.initials: HJ
authors.lastname: Jeong
authors.forename: Hyung-Ryong
authors.initials: HR
authors.lastname: Kim
authors.forename: Han-Jung
authors.initials: HJ
authors.lastname: Chae
mesh_terms: D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000633:toxicity; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D010003:Osteoarthritis / Q000378:metabolism; D034741:RNA, Small Interfering; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism; D019284:Thapsigargin / Q000633:toxicity; D051742:Transcription Factor CHOP / Q000096:biosynthesis* / Q000187:drug effects; D014162:Transfection
chemical_list: C497249:DDIT3 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C000717247:HSPA5 protein, human; D034741:RNA, Small Interfering; D051742:Transcription Factor CHOP; D019284:Thapsigargin; D053148:Caspase 3