title: Orally administered diflunisal stabilizes transthyretin against dissociation required for amyloidogenesis.
abstract: OBJECTIVE
  Rate-limiting transthyretin (TTR) tetramer dissociation and monomer misfolding enable misassembly into numerous aggregate morphologies including amyloid, a process genetically linked to and thought to cause amyloid pathology. T119M TTR trans-suppressor subunit inclusion into tetramers otherwise composed of disease-associated subunits ameliorates human amyloidosis by increasing the tetramer dissociation barrier. Diflunisal binding to the 99% unoccupied L-thyroxine binding sites in TTR also increases the tetramer dissociation barrier; hence, we investigated the feasibility of using diflunisal for the treatment of human TTR amyloidosis using healthy volunteers.
  
  
  METHODS
  Diflunisal (125, 250 or 500 mg bid) was orally administered to groups of 10 subjects for 7 days to evaluate serum diflunisal concentration, diflunisal binding stoichiometry to TTR, and the extent of diflunisal imposed TTR kinetic stabilization against urea- and acid-mediated TTR denaturation in human serum. The rates of urea-mediated tetramer dissociation and acid-mediated aggregation as a function of diflunisal concentration were also evaluated in vitro, utilizing physiologically relevant concentrations identified by the above experiments.
  
  
  RESULTS
  In the 250 mg bid group, 12 h after the 13th oral dose, the diflunisal serum concentration of 146 +/- 39 microM was sufficient to afford a TTR binding stoichiometry exceeding 0.95 +/- 0.13 ( approximately 1.75 corrected). Diflunisal binding to TTR at this dose slowed urea-mediated dissociation and acid-mediated TTR aggregation at least, threefold (p < 0.05) in serum and in vitro, consistent with kinetic stabilization of TTR.
  
  
  CONCLUSIONS
  Diflunisal-mediated kinetic stabilization of TTR should ameliorate TTR amyloidoses, provided that the nonsteroidal anti-inflammatory drug liabilities can be managed clinically.
authors.affiliation: Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Sekijima
authors.forename: Maria A
authors.initials: MA
authors.lastname: Dendle
authors.forename: Jeffery W
authors.initials: JW
authors.lastname: Kelly
mesh_terms: D000328:Adult; D000682:Amyloid / Q000378:metabolism*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D004061:Diflunisal / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011228:Prealbumin / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry; D044967:Serum
chemical_list: D000682:Amyloid; D000894:Anti-Inflammatory Agents, Non-Steroidal; D011228:Prealbumin; D011994:Recombinant Proteins; D004061:Diflunisal