Heparin Induces Rat Aorta Relaxation via Integrin-Dependent Activation of Muscarinic M ₃ Receptors

Abstract

Abstract-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 : 100Ϯ10 mol/L; E max : 41Ϯ3%). 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. (Hypertension. 2010;56:713-721.)Key Words: heparin Ⅲ muscarinic receptors Ⅲ M 3 receptor Ⅲ integrin Ⅲ smooth muscle relaxation Ⅲ aorta T he successful use of heparin in the treatment of thromboembolic diseases has been associated with numerous pharmacological actions of this complex polysaccharide. Alterations in the blood vessel and associated cells, such as platelet hyperactivity, inflammatory processes, endothelial dysfunction, and angiogenesis, lead to the development of diseases related to clot formation, which can be efficiently modulated by heparin and its derivatives. [1][2][3] Heparin is a glycosaminoglycan composed of repeating 13 4-linked ␣-D-glucosamine, mainly N-sulfated, and uronic acid, either ␤-D-glucuronic acid or ␣-L-iduronic acid; also, O-sulfation occurs at different positions of the disaccharide units. 4,5 Although heparin usually acts as an anticoagulant, 6 other biological activities have also been described, including antiviral, 7 antibacterial, 8 and antithrombotic effects. This antithrombotic action has been related, at least in part, to the increased production of a peculiar heparan sulfate proteoglycan produced by the endothelium. 9 -11 In addition, heparin modulates the function of many proteins, for example, the myosin from skeletal muscle, 12 the inositol 1,4,5-trisphosphate receptor inhibition, 13 and the activation of Na ϩ /Ca 2ϩ ...

Influence of Hemodynamic Variations on the Pharmacokinetics of Landiolol in Patients Undergoing Cardiovascular Surgery

“…31) Previous studies have described the hypotensive mechanisms of heparin as an endothelium-dependent relaxation and endothelial NO synthase activation by heparin, 15) or the participation of M3 receptor and integrin in heparin-dependent relaxation of vascular smooth muscle. 16) In this study, systemic heparinization (300 U/kg) significantly decreased MAP, CI, and HVBFI. HVBFI changed in parallel to changes in CI.…”

“…14) Previous studies have described the hypotensive mechanisms of heparin as an endothelium-dependent relaxation, or heparin-dependent relaxation, of vascular smooth muscle. 15,16) Hypotension due to decreased systemic vascular resistance may reduce hepatic blood flow, because a nearly linear correlation between systemic arterial blood pressure and hepatic arterial blood flow has been found. 17,18) In previous studies, hepatic blood flow has been measured using intraoperative transesophageal echocardiography to investigate the effect of laparoscopic cholecystectomy, 19) intraabdominally insufflated carbon dioxide, 20) and thoracic epidural anesthesia.…”

“…38,39) Recently, TEE has been reported to be effective for evaluating hepatic blood flow during the intraoperative period. [16][17][18][19][20][21] However, 3 to 27% of patients receiving TEE evaluation of hepatic blood flow are reported to present poor quality sonographic images. 20,21,25) In this study, decreased HVBFI was observed after administration of heparin with one excluded patient (5%, 1/19).…”

Muscarinic Receptors and Their Antagonists in COPD: Anti-Inflammatory and Antiremodeling Effects

“…However, activation of M 3 receptors on vascular endothelial cells also induces the synthesis of nitric oxide, which diffuses to adjacent vascular smooth muscle cells and causes vasodilatation [32]. …”

“…In rat bladder, hyaluronic acid ameliorated H 2 O 2 -induced hyperactivity, possibly via the antioxidant activity and the inhibition of purinergic and muscarinic signaling pathway [83]. In rat vascular smooth muscle cells of the aorta, M 3 receptors were involved in heparin-dependent relaxation [32]. In rabbits, acetylcholine-induced reactive oxygen species generation in myocytes and the intact heart was mediated via transactivation of EGF receptors through MMP-dependent release of heparin-binding EGF via muscarinic receptors [84].…”