Smooth Muscle Endothelin B Receptors Regulate Blood Pressure but Not Vascular Function or Neointimal Remodeling.

Eileen Miller,Rebecca Moorhouse,Rhoda E Kuc,Patrick W.F Hadoke,Neeraj Dhaun,David J Webb,Alicja Czopek,Raphael F.P Castellan,Robert A Kimmitt,Yuri V Kotelevtsev,Karolina M Duthie,Anthony P Davenport,Elisabeth E Fransen Van De Putte,Nicholas S Kirkby,Sibylle Christen

doi:10.1161/hypertensionaha.115.07031

Abstract

The role of smooth muscle endothelinB (ETB) receptors in regulating vascular function, blood pressure (BP), and neointimal remodeling has not been established. Selective knockout mice were generated to address the hypothesis that loss of smooth muscle ETB receptors would reduce BP, alter vascular contractility, and inhibit neointimal remodeling. ETB receptors were selectively deleted from smooth muscle by crossing floxed ETB mice with those expressing cre-recombinase controlled by the transgelin promoter. Functional consequences of ETB deletion were assessed using myography. BP was measured by telemetry, and neointimal lesion formation induced by femoral artery injury. Lesion size and composition (day 28) were analyzed using optical projection tomography, histology, and immunohistochemistry. Selective deletion of ETB was confirmed by genotyping, autoradiography, polymerase chain reaction, and immunohistochemistry. ETB-mediated contraction was reduced in trachea, but abolished from mesenteric veins, of knockout mice. Induction of ETB-mediated contraction in mesenteric arteries was also abolished in these mice. Femoral artery function was unaltered, and baseline BP modestly elevated in smooth muscle ETB knockout compared with controls (+4.2±0.2 mm Hg; P<0.0001), but salt-induced and ETB blockade-mediated hypertension were unaltered. Circulating endothelin-1 was not altered in knockout mice. ETB-mediated contraction was not induced in femoral arteries by incubation in culture medium or lesion formation, and lesion size was not altered in smooth muscle ETB knockout mice. In the absence of other pathology, ETB receptors in vascular smooth muscle make a small but significant contribution to ETB-dependent regulation of BP. These ETB receptors have no effect on vascular contraction or neointimal remodeling.

Highlights

(day 28) were analyzed using optical projection tomography, histology, and immunohistochemistry
Regulation of arterial function, blood pressure (BP), and arterial lesion formation by ETB receptors is likely to be more complex because they are expressed in endothelial cell (EC), vascular smooth muscle cells (VSMCs), and the kidney where they mediate physiologically antagonistic responses
smooth muscle cells (SMCs) isolated from the aorta of SMETB KO mice expressed the cre, delta, and flox bands, whereas controls did not express the cre and the delta bands (Figure 1B)

Summary

Introduction

(day 28) were analyzed using optical projection tomography, histology, and immunohistochemistry. ETB-mediated contraction was not induced in femoral arteries by incubation in culture medium or lesion formation, and lesion size was not altered in smooth muscle ETB knockout mice. A present on vascular smooth muscle cells (VSMCs), predominantly mediating contraction[3] and regulating blood pressure (BP).[4] They influence mitogenesis,[5] generation of reactive oxygen species, and adhesion molecule expression.[6,7] ET A receptors on leucocytes mediate cytokine release and cellular chemotaxis.[8] Many of these processes contribute to vascular remodeling, and ET-1 clearly drives arterial lesion formation (including neointimal proliferation after injury).[7] This can be inhibited by selective ET antagonism.[9,10]. ECETB receptors mediate production of vasodilator, antiproliferative, and anti-inflammatory molecules (eg, nitric oxide [NO])[11,12]; clearance of ET-1 from the circulation[13,14]; and regrowth of damaged

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Discussion

Conclusion