title: Mast cell activation by fibrinogen-related homologous c-terminal peptides (haptides) modulates systemic blood pressure.
abstract: BACKGROUND
  Haptides are a family of short peptides homologous to C-termini sequences of fibrinogen chains β and γ (haptides Cβ and preCγ, respectively) which were previously shown to penetrate and bind cells.
  
  
  OBJECTIVE
  This work investigates the systemic effect of the haptides with possible clinical implications.
  
  
  METHODS
  Intra-arterial monitoring in rats recorded the haptides' effects on systemic blood pressure. In parallel, their effect was also tested in vitro on isolated rat peritoneal mast cells and on human mast cells.
  
  
  RESULTS
  Intra-arterial monitoring in rats showed that intravenous administration of low haptides concentrations (35-560 μg/kg rat) caused a shocklike behavior with transient decrease in the systolic and diastolic blood pressure by up to 55% (P < .05) in a dose-dependent manner and a minor increase in their heart rate. Randomly scrambled sequences of the haptides had no such effect, suggesting a specific interaction with receptors. Intravenous administration of blockers to histamine receptors H1 and H2 before haptides administration attenuated this effect. Furthermore, in vitro incubation of human LAD2 mast cell line or isolated rat peritoneal mast cells with the haptides caused degranulation of the mast cells. We found that the haptides Cβ and preCγ activated mast cells causing histamine release, resulting in a steep decrease in blood pressure, comparable to anaphylactic shock.
  
  
  CONCLUSIONS
  In treating vascular occlusive diseases, massive fibrinolysis is induced, and haptide-containing sequences are released. We suggest that treatment with histamine receptor blockers or with mast cell stabilizing agents in such pathological conditions may overcome this effect.
authors.affiliation: Laboratory of Biotechnology and Radiobiology, Sharett Institute of Oncology, Jerusalem, Israel.
authors.forename: Maamoun
authors.initials: M
authors.lastname: Basheer
authors.forename: Herzl
authors.initials: H
authors.lastname: Schwalb
authors.forename: Maoz
authors.initials: M
authors.lastname: Nesher
authors.forename: Dan
authors.initials: D
authors.lastname: Gilon
authors.forename: Irit
authors.initials: I
authors.lastname: Shefler
authors.forename: Yoseph A
authors.initials: YA
authors.lastname: Mekori
authors.forename: Oz M
authors.initials: OM
authors.lastname: Shapira
authors.forename: Raphael
authors.initials: R
authors.lastname: Gorodetsky
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D015550:Cell Degranulation / Q000187:drug effects; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000276:immunology*; D010455:Peptides / Q000276:immunology / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000941:Antigens; D006634:Histamine H1 Antagonists; D010455:Peptides; C023456:fibrinogen-related antigen