title: Toll-like receptor 7/8 agonist resiquimod induces late preconditioning in neonatal cardiac myocytes.
abstract: OBJECTIVE
  To investigate whether R-848 (resiquimod, toll-like receptor 7/8 agonist) can induce late preconditioning in neonatal cardiac myocytes.
  
  
  METHODS
  The protective effects of R-848 on neonatal myocytes against anoxia-reoxygenation-induced injury were tested, and intracellular reactive oxygen species (ROS) were determined. The protein synthesis inhibitor cyclohexamide (CH) and the ROS scavenger N-acetylcysteine (NAC) were used in this model to test if new protein synthesis and oxidative stress were necessary for their cardioprotective effects. The activation of nuclear factor kappa B (NFκB) and hypoxia inducible factor 1 (HIF1) was investigated by electrophoretic mobility shift assays (EMSA), and inducible nitric oxide synthase (iNOS) was assessed by immunoblotting. After iNOS was down-regulated by small interfering RNA (siRNA) transfection, the cardioprotective effect was reassessed.
  
  
  RESULTS
  ROS were triggered soon after R-848 (0.01-1.0 μg/L) administration, however, the cardioprotective effect of which was induced 24 h later. This protection was abolished by CH or NAC pretreatment. NFκB and HIF1 activation and iNOS up-regulation were involved in this protective mechanism. The cardioprotective effect was also attenuated after iNOS was knocked down.
  
  
  CONCLUSIONS
  R-848 provided a cardioprotective effect through a late preconditioning mechanism via a ROS/NFκB-HIF1/iNOS-dependent pathway.
authors.affiliation: Department of Cardiovascular Surgery, RenJi Hospital of Shanghai Jiaotong University, Shanghai 200127, China.
authors.forename: Yong-yi
authors.initials: YY
authors.lastname: Wang
authors.forename: Sha
authors.initials: S
authors.lastname: Liu
authors.forename: Feng
authors.initials: F
authors.lastname: Lian
authors.forename: Wen-gang
authors.initials: WG
authors.lastname: Yang
authors.forename: Song
authors.initials: S
authors.lastname: Xue
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D015687:Cell Hypoxia; D004305:Dose-Response Relationship, Drug; D055785:Gene Knockdown Techniques; D051793:Hypoxia-Inducible Factor 1 / Q000378:metabolism; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects; D010100:Oxygen / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D051199:Toll-Like Receptor 7 / Q000819:agonists; D051200:Toll-Like Receptor 8 / Q000819:agonists
chemical_list: D002316:Cardiotonic Agents; D051793:Hypoxia-Inducible Factor 1; D007093:Imidazoles; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; D052247:Nitric Oxide Synthase Type II; D010100:Oxygen; C402365:resiquimod