Adenosine_2Areceptor vasodilation of rat preglomerular microvessels is mediated by EETs that activate the cAMP/PKA pathway

Abstract

Dilation of rat preglomerular microvessels (PGMV) by activation of adenosine A2A receptors (A2AR) is coupled to epoxyeicosatrienoic acid (EET) release. We have investigated the commonality of this signal transduction pathway, i.e., sequential inhibition of G(salpha), adenylyl cyclase, PKA, and Ca2+-activated K+ (KCa) channel activity, to the vasoactive responses to A2AR activation by a selective A2A agonist, CGS-21680, compared with those of 11,12-EET. Male Sprague-Dawley rats were anesthetized, and microdissected arcuate arteries (110-130 microm) were cannulated and pressurized to 80 mmHg. Vessels were superfused with Krebs solution containing NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin and preconstricted with phenylephrine. We assessed the effect of 3-aminobenzamide (10 microM), an inhibitor of mono-ADP-ribosyltranferases, on responses to 11,12-EET (3 nM) and CGS-21680 (10 microM) and found that both were inhibited by approximately 70% (P<0.05), whereas the response to SNP (10 microM) was unaffected. Furthermore, 11,12-EET (100 nM), like cholera toxin (100 ng/ml), stimulated ADP-ribose formation in homogenates of arcuate arteries compared with control. SQ-22536 (10 microM), an inhibitor of adenylyl cyclase activity, and myristolated PKI (14-22) amide (5 microM), an inhibitor of PKA, decreased activity of 11,12-EET and CGS-21680. Incubation of 11,12-EET (3 nM-3 microM) with PGMV resulted in an increase in cAMP levels (P<0.05). The responses to both 11,12-EET and CGS-21680 were significantly reduced by superfusion of iberiotoxin (100 nM), an inhibitor of KCa channel activity. Thus in rat PGMV activation of A2AR is coupled to EET release upstream of adenylyl cyclase activation and EETs stimulate mono-ADP-ribosyltransferase, resulting in Gsalpha protein activation.

Adenosine A2 Receptor Activation Attenuates Afferent Arteriolar Autoregulation During Adenosine Receptor Saturation in Rats

“…A1 receptor activation also seems to induce vasoconstriction through inhibitory G protein-dependant activation of phospholipase C. [32][33][34] A2 receptors produce vasodilation by stimulating adenylate cyclase activity to increase cAMP generation by coupling to stimulatory G proteins and also by activating vasodilation products of arachidonic acid. 18,35 Our results demonstrate that A1 receptors are more sensitive to adenosine than A2 receptors. At the low concentrations, adenosine predominantly activates A1 receptors leading to vasoconstriction, but at the high concentration, adenosine mainly activates the A2 receptors, resulting in marked vasodilation.…”

“…17 A2 receptor-mediated vasodilation results from stimulation of Gs␣ leading to increased cAMP that is partially mediated via epoxyeicosatrienoic acid release. 18 Cytochrome P450 epoxygenase metabolites have been shown to alter vascular tone in afferent arterioles and modify the autoregulatory efficiency of the preglomerular microcirculation. 19 Adenosine has been suggested as both a mediator and a modulator of renal autoregulation.…”

Functional characterization of cytochrome P450-derived epoxyeicosatrienoic acids in adipogenesis and obesity

“…During the early differentiation of preadipocytes, inhibition of ERK and activation of the AMP-activated protein kinase (AMPK) and cAMP/protein kinase A (PKA) signaling pathways inhibit PPAR ␥ , C/EBP ␣ , and SREBP1c activation and adipocyte differentiation (39)(40)(41). Previous studies have demonstrated that promoting the effects of EETs attenuates ERK1/2 dephosphorylation in endothelial cells, activates AMPK activity in liver, and activates the cAMP/PKA pathway in the vascular system ( 12,42,43 ), suggesting that a complex interaction between CYP-derived EETs and multiple signaling pathways also likely exist in the early phase of adipogenesis. Future studies are needed to delineate the key signaling pathways that underlie the inhibitory effects of EETs on adipocyte differentiation.…”

Arachidonic acid cytochrome P450 epoxygenase pathway

“…This paracrine mechanism involves the Ga s protein, adenylyl cyclase activation, and an increase in cAMP (5). A similar pathway involving ADP-ribosylation of Ga s , an increase in cAMP, and protein kinase A activation produces EET-stimulated vasodilation of preglomerular renal microvessels (24). Likewise, a cAMP-protein kinase A mechanism mediates the EET-stimulated increase in StAR protein and steroid hormone production (25).…”