title: Perivascular adipose tissue-derived relaxing factors: release by peptide agonists via proteinase-activated receptor-2 (PAR2) and non-PAR2 mechanisms.
abstract: OBJECTIVE
  We hypothesized that proteinase-activated receptor-2 (PAR2)-mediated vasorelaxation in murine aorta tissue can be due in part to the release of adipocyte-derived relaxing factors (ADRFs).
  
  
  METHODS
  Aortic rings from obese TallyHo and C57Bl6 intact or PAR2-null mice either without or with perivascular adipose tissue (PVAT) were contracted with phenylephrine and relaxation responses to PAR2-selective activating peptides (PAR2-APs: SLIGRL-NH(2) and 2-furoyl-LIGRLO-NH(2) ), trypsin and to PAR2-inactive peptides (LRGILS-NH(2) , 2-furoyl-OLRGIL-NH(2) and LSIGRL-NH(2) ) were measured. Relaxation was monitored in the absence or presence of inhibitors that either alone or in combination were previously shown to inhibit ADRF-mediated responses: L-NAME (NOS), indomethacin (COX), ODQ (guanylate cyclase), catalase (H(2) O(2) ) and the K(+) channel-targeted reagents, apamin, charybdotoxin, 4-aminopyridine and glibenclamide.
  
  
  RESULTS
  Endothelium-intact PVAT-free preparations did not respond to PAR2-inactive peptides (LRGILS-NH(2) , LSIGRL-NH(2) , 2-furoyl-OLRGIL-NH(2) ), whereas active PAR2-APs (SLIGRL-NH(2) ; 2-furoyl-LIGRLO-NH(2) ) caused an L-NAME-inhibited relaxation. However, in PVAT-containing preparations treated with L-NAME/ODQ/indomethacin together, both PAR2-APs and trypsin caused relaxant responses in PAR2-intact, but not PAR2-null-derived tissues. The PAR2-induced PVAT-dependent relaxation (SLIGRL-NH(2) ) persisted in the presence of apamin plus charybdotoxin, 4-aminopyridine and glibenclamide, but was blocked by catalase, implicating a role for H(2) O(2) . Surprisingly, the PAR2-inactive peptides, LRGILS-NH(2) and 2-furoyl-OLRGIL-NH(2) (but not LSIGRL-NH(2) ), caused relaxation in PVAT-containing preparations from both PAR2-null and PAR2-intact (C57Bl, TallyHo) mice. The LRGILS-NH(2) -induced relaxation was distinct from the PAR2 response, being blocked by 4-aminopyridine, but not catalase.
  
  
  CONCLUSIONS
  Distinct ADRFs that may modulate vascular tone in pathophysiological settings can be released from murine PVAT by both PAR2-dependent and PAR2-independent mechanisms.
authors: Libin Cardiovascular Institute of Alberta, University of Calgary Faculty of Medicine, Calgary, AB, Canada.
authors: Y
authors: Y
authors: Li
authors: K
authors: K
authors: Mihara
authors: M
authors: M
authors: Saifeddine
authors: A
authors: A
authors: Krawetz
authors: D C W
authors: DC
authors: Lau
authors: H
authors: H
authors: Li
authors: H
authors: H
authors: Ding
authors: C R
authors: CR
authors: Triggle
authors: M D
authors: MD
authors: Hollenberg
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