Perivascular adipose tissue-derived relaxing factors: release by peptide agonists via proteinase-activated receptor-2 (PAR2) and non-PAR2 mechanisms

Abstract

BACKGROUND AND PURPOSEWe 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). EXPERIMENTAL APPROACHAortic 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-NH2 and 2-furoyl-LIGRLO-NH2), trypsin and to PAR2-inactive peptides (LRGILS-NH2, 2-furoyl-OLRGIL-NH2 and LSIGRL-NH2) 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 (H2O2) and the K + channel-targeted reagents, apamin, charybdotoxin, 4-aminopyridine and glibenclamide. KEY RESULTSEndothelium-intact PVAT-free preparations did not respond to PAR2-inactive peptides (LRGILS-NH2, LSIGRL-NH2, 2-furoyl-OLRGIL-NH2), whereas active PAR2-APs (SLIGRL-NH2; 2-furoyl-LIGRLO-NH2) 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-NH2) persisted in the presence of apamin plus charybdotoxin, 4-aminopyridine and glibenclamide, but was blocked by catalase, implicating a role for H2O2. Surprisingly, the PAR2-inactive peptides, LRGILS-NH2 and 2-furoyl-OLRGIL-NH2 (but not LSIGRL-NH2), caused relaxation in PVAT-containing preparations from both PAR2-null and PAR2-intact (C57Bl, TallyHo) mice. The LRGILS-NH2-induced relaxation was distinct from the PAR2 response, being blocked by 4-aminopyridine, but not catalase. CONCLUSIONSDistinct ADRFs that may modulate vascular tone in pathophysiological settings can be released from murine PVAT by both PAR2-dependent and PAR2-independent mechanisms.

Soluble dipeptidyl peptidase-4 induces microvascular endothelial dysfunction through proteinase-activated receptor-2 and thromboxane A2 release

“…The activation of vascular PAR2 has been described to evoke vasorelaxation [25], as well as vasoconstriction [26]. The activation of PAR2 has further been associated with a rapid cellular release of a series of agonists triggering the immediate autocrine or paracrine transactivation of other non-PAR G protein-coupled receptors, including prostanoid receptors [23].…”

Mentors And The Butterfly Effect: Triggers For Discovering Signalling by Proteinases via Proteinase-Activated Receptors (PARs) And More

“…As a consequence, in a given setting, the actions of proteinases or PAR-agonists may be due both to PAR-activated and PARindependent mechanisms, as we have found for adipocytetriggered vascular regulation [38] and as we observed for the regulation of intestinal transport [58]. To sort out the PAR from non-PAR targets of either PAR-activating peptides or enzymes, it is essential, as outlined above, to use a peptide structure-activity approach for the PAR-APs and to employ PAR-null cells, isolated tissues or intact mice as enzyme and PAR2-AP targets [38]. If PARs are the targets, which are the activating enzymes?…”

“…As outlined above and illustrated in Figure 2, mechanisms other than those involving the PARs can account for proteinase-triggered signals; and the PARactivating peptides can stimulate PAR-independent signalling via other targets, as we [37,38] and others have found [39]. As a consequence, in a given setting, the actions of proteinases or PAR-agonists may be due both to PAR-activated and PARindependent mechanisms, as we have found for adipocytetriggered vascular regulation [38] and as we observed for the regulation of intestinal transport [58]. To sort out the PAR from non-PAR targets of either PAR-activating peptides or enzymes, it is essential, as outlined above, to use a peptide structure-activity approach for the PAR-APs and to employ PAR-null cells, isolated tissues or intact mice as enzyme and PAR2-AP targets [38].…”

“…us, even though some of the PAR-activating peptides can have o -target e ects [37][38][39], the use of PAR-AP structure-activity information in the context of studies with PAR null mice can validate a role for PARs 1, 2 and 4 in any given system [40][41][42].…”

Whole genome sequence analysis of the TALLYHO/Jng mouse

“…In addition to genetic analysis, the TH mouse has been used in the development of therapeutic agents for obesity and type 2 diabetes [12, 13] and has also served as a model system for many diabetes and obesity related abnormalities, including decreased exercise capacity [14], impaired wound healing [15–17], periodontitis [18], tissue susceptibility to hypoxia [19, 20], bone loss [21, 22], circadian disruption [23], and vasculature abnormalities [24–26]. …”