The loss of sustained Ca²⁺signaling underlies suppressed endothelial nitric oxide production in preeclamptic pregnancies: implications for new therapy

Abstract

]i) and NO in umbilical vein endothelium of normal and PE subjects that is still intact and on the vessel luminal surface. This was achieved by dissection and preloading with fura 2 and DAF-2 imaging dyes, respectively, before subsequent challenge with ATP (100 M, 30 min). As a control to reveal the content of active endothelial nitric oxide synthase (eNOS) per vessel segment, results were compared with a maximal stimulus with ionomycin (5 M, 30 min). We show for the first time that normal umbilical vein endothelial cells respond to ATP with sustained bursting that parallels sustained NO output. Furthermore, in subjects with PE, a failure of sustained [Ca 2ϩ ]i bursting occurs in response to ATP and is associated with blunted NO output. In contrast, NO responses to maximal [Ca 2ϩ ]i elevation using ionomycin and the levels of eNOS protein are more similar between groups than the responses to ATP. When the endothelial cells from PE subjects are isolated and allowed to recover in culture, they regain the ability under fura 2 imaging to show multiple [Ca 2ϩ ]i bursts otherwise seen in the cells from normal subjects. Thus novel clinical therapy aimed at restoring function in vivo may be possible. calcium ion; endothelium; hypertension PREGNANCY IS ASSOCIATED WITH a need to expand maternal blood volume and increase cardiac output to allow for the increased blood flow to the uterus. Normal maternal vascular adaptation also involves enhanced vasodilation, including sustained and pronounced activation of endothelial nitric oxide synthase (eNOS) to make nitric oxide (NO). The greatest effect is seen in the uterus, but enhanced vasodilation is also seen in the systemic circulation (6,17

Vascular adaptation in pregnancy and endothelial dysfunction in preeclampsia

“…And while EDHF plays an important role in augmenting increased uterine blood flow, if not causing it in certain situations, it also seems likely changes in [Ca 2+ ] i signaling may be equally important to NO, PGI2 and EDHF function given the action of 2-APB in each case. Consistent with this, it is also relevant that we reported recently that the endothelial cells of umbilical cords from PE women at late term show defects in sustained and coordinated endothelial Ca 2+ bursting (Krupp et al 2013) and while NO output was measured and a decrease observed, we did not measure PGI2 or EDHF.…”

“…By late gestation (3 rd trimester) the vessel architecture of the uterus is essentially developed and any further increases in blood flow are now dependent on a sustained vasodilation of those existing vessels. Clinically, it is the mid to late gestation period when most cases of PE present themselves to physicians, and PE subjects are known to show reduced capacity for vasodilation (Kenny et al 2002; Krupp et al 2013; Yamamoto et al 2010). …”

Altered VEGF-stimulated Ca2+ signaling in part underlies pregnancy-adapted eNOS activity in UAEC

“…Such information suggests future endothelial-targeted therapies that protect and even improve endothelial CCE mechanisms mediated via IP3R/TRPC interaction could not only improve vasodilatory responses to G-protein coupled activators of PLC-beta but also growth factor activation of PLC-gamma. This type of global rescue of responses may be critical in applications aimed at disease states such as preeclampsia where sustained Ca2+ responses to ATP (and other agonists) have otherwise failed and associated vasodilation is lacking (Krupp, et al 2013). …”

Maternal Vascular Physiology in Preeclampsia

“…18,19 Further, agoniststimulated NO production is reduced in isolated umbilical arteries from women with preeclampsia. 20 Phosphorylation of endothelial NO synthase and changes in intracellular Ca 2+ concentrations in endothelial cells are the main determinants of NO production.…”

“…29 The reduction in PGI 2 production may be because of impaired endothelial Ca 2+ signaling as determined in intact umbilical vein endothelium from patients with preeclampsia. 19 Reactive oxygen species may also contribute to inhibition of PGI 2 production. …”