title: ETA and ETB receptors are expressed in vascular adventitial fibroblasts.
abstract: The adventitia has been recognized to play important roles in vascular oxidative stress, remodeling, and contraction. We recently demonstrated that adventitial fibroblasts are able to express endothelin (ET)-1 in response to ANG II. However, it is unclear whether ET-1 receptors are expressed in the adventitia. We therefore investigated the expression and roles of both ET(A) and ET(B) receptors in collagen synthesis and ET-1 clearance in adventitial fibroblasts. Adventitial fibroblasts were isolated and cultured from the mouse thoracic aorta by the explant method. Cultured cells were treated with ANG II (100 nmol/l) or ET-1 (10 pM) in the presence or absence of the ANG II type 1 receptor antagonist losartan (100 μM), the ET-1 receptor antagonists BQ-123 (ET(A) receptor, 1 μM) and BQ-788 (ET(B) receptor, 1 μM), and the ET(B) receptor agonist sarafotoxin 6C (100 nM). ET-1 peptide levels were determined by ELISA, whereas ET(A), ET(B), and collagen levels were determined by Western blot analysis. ANG II increased ET-1 peptide levels in a time-dependent manner. ANG II increased ET(A) and ET(B) receptor protein levels as well as collagen in a similar fashion. ANG II-induced collagen was reduced while in the presence of BQ-123, suggesting a role for the ET(A) receptor in the regulation of the extracellular matrix. ANG II treatment in the presence of BQ-788 significantly increased ET-1 peptide levels. Conversely, the ET(B) receptor agonist sarafotoxin 6C significantly decreased ET-1 peptide levels. These data implicate a role for the ET(B) receptor in the clearance of the ET-1 peptide. In conclusion, both ET(A) and ET(B) receptors are expressed in adventitial fibroblasts, which paves the ground for the biological significance of adventitial ET-1. The ET(A) receptor subtype mediates collagen I expression, whereas the ET(B) receptor subtype may play a protective role through increasing the clearance of the ET-1 peptide.
authors.affiliation: Department of Community Health Sciences, Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Boyd
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Rätsep
authors.forename: Li Li
authors.initials: LL
authors.lastname: Ding
authors.forename: Hui Di
authors.initials: HD
authors.lastname: Wang
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D003238:Connective Tissue / Q000187:drug effects / Q000378:metabolism*; D019332:Endothelin-1 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D019808:Losartan / Q000494:pharmacology; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D044022:Receptor, Endothelin A / Q000187:drug effects / Q000378:metabolism*; D044023:Receptor, Endothelin B / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014757:Viper Venoms / Q000494:pharmacology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D024042:Collagen Type I; D019332:Endothelin-1; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D014757:Viper Venoms; C057354:sarafotoxins s6; D000804:Angiotensin II; C086539:BQ 788; D019808:Losartan; C072247:cyclo(Trp-Asp-Pro-Val-Leu)