Heparin induces rat aorta relaxation via integrin-dependent activation of muscarinic M3 receptors.
Previous reports have shown that heparin may promote human hypotension and vascular relaxation by elevation of NO levels through unclear mechanisms. We hypothesized that endothelial muscarinic M(3) receptor activation mediates the heparin-induced vasodilation of rat aortic rings. The experiments were carried out using unfractionated heparin extracted from bovine intestinal mucosa, which elicited an endothelium and NO-dependent relaxation of aortic segments with maximal potency and efficacy (EC(50): 100±10 μmol/L; E(max): 41±3%). Atropine and 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide inhibitors reduced the heparin-dependent relaxation, indicating that M(3) muscarinic receptor is involved in this phenomenon. However, no direct binding of heparin to muscarinic receptors was observed. More importantly, studies performed using the arginine-glycine-aspartic acid peptide and 1-(1,1-dimethylethyl)-3-(1-naphthalenyl)-1H-pyrazolo[3,4-day]pyrimidin-4-amine, an Src family inhibitor, reduced by 51% and 73% the heparin-dependent relaxation, respectively, suggesting the coupling of heparin and M(3) receptor through extracellular matrix molecules and integrin. Furthermore, unfractionated heparin induced activation of focal adhesion protein kinase, Src, and paxillin. Finally, fluorescence resonance energy transfer approach confirmed the interaction of the M(3) receptor to integrin. Taken together, these data demonstrate the participation of M(3) receptor and integrin in heparin-dependent relaxation of vascular smooth muscle. These results provide new insights into the molecular mechanism and potential pharmacological action of heparin in vascular physiology.
Paredes-Gamero
Edgar J
EJ
Departamento de Bioquímica, Universidade Federal de São Paulo, São Paulo, Brazil.
Medeiros
Valquíria P
VP
Farias
Eduardo H C
EH
Justo
Giselle Z
GZ
Trindade
Edvaldo S
ES
Andrade-Lopes
Ana L
AL
Godinho
Rosely O
RO
de Miranda
Antonio
A
Ferreira
Alice T
AT
Tersariol
Ivarne L S
IL
Nader
Helena B
HB
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D001285:Atropine / Q000494:pharmacology; D015153:Blotting, Western; D002417:Cattle; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism / Q000502:physiology; D031541:Fluorescence Resonance Energy Transfer; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D009842:Oligopeptides / Q000494:pharmacology; D051419:Paxillin / Q000378:metabolism; D011485:Protein Binding; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D043587:Receptor, Muscarinic M3 / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology
D000925:Anticoagulants; D016023:Integrins; D009842:Oligopeptides; D051419:Paxillin; D043587:Receptor, Muscarinic M3; D014665:Vasodilator Agents; D009569:Nitric Oxide; C047981:arginyl-glycyl-aspartic acid; D001285:Atropine; D006493:Heparin; D016392:Proto-Oncogene Proteins pp60(c-src); D000109:Acetylcholine