16K-Prolactin Inhibits Activation of Endothelial Nitric Oxide Synthase, Intracellular Calcium Mobilization, and Endothelium-Dependent Vasorelaxation

Abstract

Activation of endothelial nitric oxide synthase (eNOS) and subsequent nitric oxide production (NO) are events that mediate the effect of important angiogenic, vasopermeability, and vasorelaxation factors, including vascular endothelial growth factor (VEGF), bradykinin (BK), and acetylcholine (ACh). The N-terminal 16-kDa fragment of prolactin (16K-PRL) acts on endothelial cells to inhibit angiogenesis both in vivo and in vitro. Here, we show that 16K-PRL inhibits VEGF-induced eNOS activation in endothelial cells. Inhibition of eNOS activation may mediate the antiangiogenic properties of 16K-PRL, because the NO donor (Z)-1-[2-(2-aminoethyl)- N-(2-ammonio-ethyl)amino]diazen-1-ium-1,2-diolate (DETANONOate) prevented 16K-PRL from blocking the VEGF-induced proliferation of endothelial cells. In addition, 16K-PRL inhibited eNOS activation by BK and blocked the BK-evoked transient increase in intracellular Ca(2+) in endothelial cells. This finding suggests that 16K-PRL interferes with the mobilization of intracellular Ca(2+), thereby inhibiting the Ca(2+)-dependent activation of eNOS. Blockage of eNOS activation can lead to inhibition of vasodilation. Consistently, 16K-PRL inhibited BK-induced relaxation of coronary vessels in isolated perfused guinea pig hearts. Moreover, 16K-PRL inhibited eNOS activation induced by ACh, and this action resulted in the inhibition of both ACh-evoked relaxation of coronary vessels in isolated perfused rat hearts and ACh-induced, endothelium-dependent relaxation of rat aortic segments. In conclusion, 16K-PRL can block the Ca(2+)-mediated activation of eNOS by three different vasoactive substances, and this action results in the inhibition of both angiogenesis and vasorelaxation.

The prolactin family hormones regulate vascular tone through NO and prostacyclin production in isolated rat aortic rings

“…The administration of INDO decreased PRL-induced relaxation from 50% to 18% ( Figure 7B and 7D); moreover, the increased production of prostacyclin I 2 (PGI 2 ) by Figure 7E), suggesting that the PRL-induced vasodilatory effect is mediated by both PGI 2 and an unidentified mediator. This treatment did not affect the ACh response ( Figure 7D) in the presence of the endothelium, as was reported previously [41] ; moreover, preincubation with L-NAME did not modify the PRL-induced vasodilatory effect ( Figure 7A and 7B) or the production of NO ( Figure 7C) but did block ACh-induced NO-mediated endothelial relaxation ( Figure 7A), confirming that PRL does not interfere with NO synthesis.…”

“…The relaxation pattern was similar to the pattern of endothelium-dependent relaxation induced by ACh [36,41] . These effects were also dependent on NO production; in the case of the rings preincubated with L-NAME, the vasodilator effects were decreased to 10% for GH and 3% for PL ( Figures 2BI, 2BII, and 2D).…”

“…In the present study, we demonstrated that GH and PL induce vasodilation in an isolated rat aortic ring model in a cumulative dose-dependent manner, an effect that results from the endothelial release of NO, like the effect induced by ACh [41,49] . In contrast, PRL did not induce these effects, as the first dose of PRL induced a vasodilatory response of approximately 50% of the maximum contraction, but subsequent doses exerted a biphasic effect that consisted primarily of contraction followed by relaxation.…”

“…GH and PL induce eNOS phosphorylation at serine 1177 in rat aortic endothelial cells It is well known that vasoactive agents such as vascular endothelial growth factor (VEGF), bradykinin (BK) and ACh activate eNOS [41][42][43][44][45] via the phosphorylation of the serine 1177 residue and the subsequent production of small amounts of NO [44,46,47] . We investigated whether GH and PL stimulate eNOS via the phosphorylation of its serine 1177 residue in cultured aortic endothelial cells.…”

La prolactine et son fragment 16 kDa dans les tissus de mammifères

“…Dans la rétine, les produits de clivage de la PRL inactivent eNOS (endothelial nitric oxide synthase) par l'intermédiaire d'une inactivation de la phosphatase 2A et il a été suggéré qu'ils inhibent ainsi l'activation de la production de NO (nitric oxide) induite par le VEGF [24]. La PRL 16K pourrait exercer des effets anti-angiogénique, vasorelaxant et inhibiteur de la migration sur les cellules endothéliales [25,26].…”