Evidence for a contribution of store-operated Ca 2+ channels to NO-mediated endothelium-dependent relaxation of guinea-pig aorta in response to a Ca 2+ ionophore, A23187

Abstract

A23187 (6S-[6alpha,8beta,9beta,11alpha]-5-(methylamino) -2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl]-1,7- dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazolecarboxylic acid, calcimycin), an antibiotic Ca2+ ionophore, produces an endothelium-dependent vascular relaxation. In the present study, pharmacological features were functionally characterized of endothelium-dependent relaxant response of guinea-pig aorta to A23187, especially focusing on the possible Ca2+ source and Ca2+ mobilization mechanisms in endothelial cells responsible for the vasorelaxant response to the Ca2+ ionophore. A23187-induced endothelium-dependent relaxation was suppressed profoundly by N(G)-nitro-L-arginine (L-NNA; 3 x 10(-4) M) or calmidazolium (3 x 10(-5) M), suggesting that nitric oxide (NO) produced by the enhanced activation of Ca2+/calmodulin-dependent endothelial NO synthase (eNOS) is largely responsible for the relaxant response of this artery to A23187. In the Ca2+-free solution without EGTA, NO-mediated endothelium-dependent relaxation induced by A23187 was almost abolished, which suggests that Ca2+ entry from extracellular space into endothelial cells plays the key role in the A23187-induced functional vasorelaxation. On the other hand, SK&F96365 (1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole; 5 x 10(-5) M) and Ni2+ (3 x 10(-4) M), both of which inhibit capacitative Ca2+ influx through store-operated Ca2+ channels (SOCCs), attenuated significantly NO-mediated endothelium-dependent relaxation by A23187. Furthermore, A23187-induced endothelium-dependent relaxation was suppressed more strongly than endothelium-independent relaxation induced by SIN-1 (3-morpholino-sydnonimine), an NO donor, when aortic preparation was preconstricted with high KCl instead of agonistic stimulation (prostaglandin F2alpha). These findings suggest that NO-mediated endothelium-dependent relaxant response of guinea-pig aorta to A23187 is preceded by the increase in endothelial cytosolic free Ca2+ concentration ([Ca2+]cyt) due to the enhanced Ca2+ influx from extracellular space. In the enhanced Ca2+ entry leading to the stimulation of eNOS and NO-mediated functional relaxant response of guinea-pig aorta to A23187, activation of SOCCs but not the Ca2+ entry through plasma membrane Ca2+-specific routes made by A23187 seems to play the predominant role. It is most likely that A23187 acts primarily at the Ca2+ store sites in endothelial cells, which subsequently depletes stored Ca2+ to activate SOCCs via unidentified mechanisms.

Recombinant interleukin-1ß dilates steelhead trout coronary microvessels: effect of temperature and role of the endothelium, nitric oxide and prostaglandins

“…However: (1) a number of authors show that fish vascular beds are dilated by NO, and thus, provide evidence for an endothelial NO system in this taxa (Mustafa et al, 1997;Nilsson and Söderström, 1997;Mustafa and Agnisola, 1998); (2) several studies (Fritsche et al, 2000;McNeill and Perry, 2006;Wang et al, 2007;Amelio et al, 2008) have identified eNOS immunoreactivity in various fish tissues, including the vascular endothelium, when using heterologous mammalian eNOS antibodies (Olson and Donald, 2009;Imbrogno et al, 2014); and (3) Andreakis et al (2011) suggest that a neuronal NOS (nNOS) isoform with an 'endotheliallike' consensus may cover some functional features typical of the eNOS isoform. As has previously been reported for mammals (Taniguchi et al, 1999;Oliveira et al, 2009), we showed that NO is involved in A23187-mediated vasodilation of isolated trout coronary arterioles (Fig. 4A), and that this effect was completely dependent on the presence of an intact endothelium.…”

Differences in eNOS Activity Because of Subcellular Localization Are Dictated by Phosphorylation State Rather than the Local Calcium Environment

“…It has long been known that intracellular Ca 2ϩ is an absolute requirement for eNOS activation (38). Furthermore, it is now widely accepted that when sustained NO production is triggered by a number of Ca 2ϩ -elevating agents such as the IP 3 generating agonist histamine, the SERCA inhibitor thapsigargin, or the Ca 2ϩ ionophore A-23187, the major source of this Ca 2ϩ is the influx of extracellular Ca 2ϩ via CCE (22,39,40). The localization of WTeNOS in plasma membrane caveolae, sites where CCE channels have also been proposed to reside (41), raised the tempting hypothesis that the decreased NO production by G2AeNOS upon stimulation of CCE was simply a result of the construct experiencing lower localized [Ca 2ϩ ] than the WTeNOS because of greater spatial separation from Ca 2ϩ influx channels.…”

Estrogen Induces the Akt-dependent Activation of Endothelial Nitric-oxide Synthase in Vascular Endothelial Cells

“…BecauseA23187induceseNOSactivationandproducesendothelium-dependent vascular relaxation, Ca 2ϩ entry from the extracellular space into endothelial cells also plays a key role (19,59). Ca 2ϩ /calmodulin-dependent protein kinase kinase can activate and phosphorylate Akt (74).…”

“…A23187 induces eNOS activation and produces endothelium-dependent vascular relaxation (19,59). Thus, eNOS activity is largely regulated by Ca 2ϩ mobilization.…”