title: High mobility group box 1 is a novel substrate of dipeptidyl peptidase-IV.
abstract: OBJECTIVE
  High mobility group box 1 (HMGB1) is a cytokine with a key role in tissue regeneration and angiogenesis. Previous studies have shown that topical application of HMGB1 to skin wounds of mouse models of diabetes enhanced vessel density and accelerated wound healing, suggesting that diabetes may affect endogenous HMGB1 functions. Dipeptidyl peptidase IV (DPP-IV/CD26) is a protease whose activity is increased in diabetes and whose inhibition improves glucose tolerance. Since HMGB1 contains potential DPP-IV cleavage sites, we determined whether HMGB1 may be a substrate for DPP-IV and whether DPP-IV-mediated cleavage may alter the biological activity of HMGB1.
  
  
  METHODS
  Reversed phase HPLC, mass spectrometry and western blot analyses were performed to analyse and identify HMGB1 peptides generated following DPP-IV digestion. HMGB1 angiogenic functions in the presence of DPP-IV were evaluated in vitro and in vivo. HMGB1 protein was detected in the serum of type 2 diabetic patients before and after treatment with DPP-IV inhibitors.
  
  
  RESULTS
  DPP-IV cleaved HMGB1 at its N-terminal region and affected its angiogenic functions. Specifically, DPP-IV inhibited HMGB1-induced endothelial cell migration and capillary-like structure formation, as well as HMGB1-mediated vascular network formation in Matrigel implants in mice. We had previously found that HMGB1 promoted endothelial cell migration through activation of extracellular regulated kinase signalling pathway. Here we showed that such an effect was abolished in the presence of DPP-IV. Finally, the N-terminal truncated form of HMGB1 was detected in the serum of type 2 diabetic patients, in whom DPP-IV inhibitors enhanced the levels of full-length HMGB1.
  
  
  CONCLUSIONS
  DPP-IV cleaves HMGB1 and, via this mechanism, inhibits HMGB1 angiogenic activity. Treatment with DPP-IV inhibitors may enhance HMGB1 activity in diabetic patients, thereby improving angiogenesis in this condition.
authors.affiliation: Laboratorio di Patologia Vascolare, Istituto Dermopatico dell'Immacolata, Istituto di Ricovero e Cura a Carattere Scientifico, Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Marchetti
authors.forename: A
authors.initials: A
authors.lastname: Di Carlo
authors.forename: F
authors.initials: F
authors.lastname: Facchiano
authors.forename: C
authors.initials: C
authors.lastname: Senatore
authors.forename: R
authors.initials: R
authors.lastname: De Cristofaro
authors.forename: A
authors.initials: A
authors.lastname: Luzi
authors.forename: M
authors.initials: M
authors.lastname: Federici
authors.forename: M
authors.initials: M
authors.lastname: Romani
authors.forename: M
authors.initials: M
authors.lastname: Napolitano
authors.forename: M C
authors.initials: MC
authors.lastname: Capogrossi
authors.forename: A
authors.initials: A
authors.lastname: Germani
mesh_terms: D043925:Angiogenesis Inducing Agents / Q000097:blood / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D054443:Cell Migration Assays; D002465:Cell Movement; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054873:Dipeptidyl-Peptidase IV Inhibitors / Q000494:pharmacology; D000939:Epitopes; D005260:Female; D024243:HMGB1 Protein / Q000097:blood / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D058990:Molecular Targeted Therapy; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D043925:Angiogenesis Inducing Agents; D054873:Dipeptidyl-Peptidase IV Inhibitors; D000939:Epitopes; D024243:HMGB1 Protein; D009842:Oligopeptides; D010446:Peptide Fragments; D011994:Recombinant Proteins; C041445:diprotin A; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4