title: Thrombospondin-1 supports blood pressure by limiting eNOS activation and endothelial-dependent vasorelaxation.
abstract: OBJECTIVE
  Thrombospondin-1 (TSP1), via its necessary receptor CD47, inhibits nitric oxide (NO)-stimulated soluble guanylate cyclase activation in vascular smooth muscle cells, and TSP1-null mice have increased shear-dependent blood flow compared with wild-type mice. Yet, the endothelial basement membrane should in theory function as a barrier to diffusion of soluble TSP1 into the arterial smooth muscle cell layer. These findings suggested that endothelial-dependent differences in blood flow in TSP1-null mice may be the result of direct modulation of endothelial NO synthase (eNOS) activation by circulating TSP1. Here we tested the hypothesis that TSP1 inhibits eNOS activation and endothelial-dependent arterial relaxation.
  
  
  RESULTS
  Acetylcholine (ACh)-stimulated activation of eNOS and agonist-driven calcium transients in endothelial cells were inhibited by TSP1. TSP1 also inhibited eNOS phosphorylation at serine(1177). TSP1 treatment of the endothelium of wild-type and TSP1-null but not CD47-null arteries inhibited ACh-stimulated relaxation. TSP1-null vessels demonstrated greater endothelial-dependent vasorelaxation compared with the wild type. Conversely, TSP1-null arteries demonstrated less vasoconstriction to phenylephrine compared with the wild type, which was corrected upon inhibition of eNOS. In TSP1-null mice, intravenous TSP1 blocked ACh-stimulated decreases in blood pressure, and both intravenous TSP1 and a CD47 agonist antibody acutely elevated blood pressure in mice.
  
  
  CONCLUSIONS
  TSP1, via CD47, inhibits eNOS activation and endothelial-dependent arterial relaxation and limits ACh-driven decreases in blood pressure. Conversely, intravenous TSP1 and a CD47 antibody increase blood pressure. These findings suggest that circulating TSP1, by limiting endogenous NO production, functions as a pressor agent supporting blood pressure.
authors.affiliation: Vascular Medicine Institute of University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Bauer
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Miller
authors.forename: Russell W
authors.initials: RW
authors.lastname: Bandle
authors.forename: Gabor
authors.initials: G
authors.lastname: Csanyi
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Pagano
authors.forename: Philip M
authors.initials: PM
authors.lastname: Bauer
authors.forename: Jurgen
authors.initials: J
authors.lastname: Schnermann
authors.forename: David D
authors.initials: DD
authors.lastname: Roberts
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Isenberg
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D051928:CD47 Antigen / Q000276:immunology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D051379:Mice; D023421:Models, Animal; D052250:Nitric Oxide Synthase Type III / Q000187:drug effects / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D019700:Thrombospondin 1 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000906:Antibodies; D051928:CD47 Antigen; D019700:Thrombospondin 1; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010656:Phenylephrine; D052250:Nitric Oxide Synthase Type III; D000109:Acetylcholine