title: ER Stress via CHOP Pathway is Involved in FK506-Induced Apoptosis in Rat Fibroblasts.
abstract: OBJECTIVE
  Hypertrophic scars (HS) formation results from reduced apoptosis and increased proliferation of fibroblasts. Therefore, apoptosis of fibroblasts is a key target for the development of novel therapeutic strategies for HS. Previous reports demonstrated that FK506 could attenuate scar formation in vivo and FK506 could also induce endoplasmic reticulum stress (ER stress). However, the effects of FK506 on ER stress-mediated apoptosis in fibroblasts remain unclear.
  
  
  METHODS
  Rat skin fibroblasts were used in the study. Cell viability was examined using cell counting Kit-8. Apoptosis was detected by Annexin V/Propidium Iodide Double Staining. Gene silencing was performed using Small Interfering RNAs (siRNAs) or via lentiviral infection. The expression of apoptosis-related proteins was determined via Western blot. Interaction between proteins was explored by co-immunoprecipitation.
  
  
  RESULTS
  FK506 significantly reduced cell viability and induced apoptosis in fibroblasts. Interestingly, ER stress was also activated after FK506 treatment. We further demonstrated that FK506-induced apoptosis was mediated by ER stress via activating CHOP, evidenced by decreased apoptosis after inhibition of ER stress using TUDCA or silencing expression of CHOP. Furthermore, Co-immunoprecipitation results indicated that treatment of FK506 induced disassociation of FKBP12.6 from RyR2 and its translocation from ER membrane to cytosol, consequently promoting ER stress-mediated apoptosis.
  
  
  CONCLUSIONS
  FK506-induced fibroblasts apoptosis was mediated by ER stress via CHOP signaling pathway.
authors: Department of Orthopedics, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors: Jian
authors: J
authors: Tang
authors: Yingbin
authors: Y
authors: Ge
authors: Lei
authors: L
authors: Yang
authors: Xinyu
authors: X
authors: Xu
authors: Tao
authors: T
authors: Sui
authors: Dawei
authors: D
authors: Ge
authors: Jun
authors: J
authors: Que
authors: Xiaojian
authors: X
authors: Cao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D065095:Calcineurin Inhibitors / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016559:Tacrolimus / Q000494:pharmacology*; D022021:Tacrolimus Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D065095:Calcineurin Inhibitors; C497251:Ddit3 protein, rat; D034741:RNA, Small Interfering; C000612605:RyR2 protein, rat; D019837:Ryanodine Receptor Calcium Release Channel; D051742:Transcription Factor CHOP; D022021:Tacrolimus Binding Proteins; C403484:tacrolimus binding protein 1B; D016559:Tacrolimus