Pregnancy induced reprogramming of endothelial function in response to ATP: Evidence for post receptor Ca2+ signaling plasticity

Abstract

Studies of uterine artery endothelial cells in primary culture (UAEC) have shown that ATP stimulates eNOS activation in cells obtained during late pregnancy (P-UAEC) to a greater extent that in cells obtained in the nonpregnant state (NP-UAEC). While ATP-stimulated intracellular free Ca2+ ([Ca2+]i) in the initial peak is similar, P-UAEC show a greater sustained phase that underlies a greater and more prolonged eNOS activation in uterine artery endothelium. While P2X and P2Y receptors are both present in UAEC, a number of studies suggest P2Y2 mediates the Ca2+ and eNOS responses to ATP. After the initial [Ca2+]i peak, the sustained phase is a form of Capacitative Ca2+ Entry (CCE) which is dependent on extracellular Ca2+ and fully blocked (along with the initial peak) by blockers of IP3 generation (U73122) or IP3 action (2-APB). One form of channel associated with CCE in an IP3 dependent fashion is the transient receptor potential cation channels (TRPC) family, and particularly TRPC3 and 6. While TRPC3 and 6, and many other proteins involved in the responses (P2Y2, Gq, IP3R1/2/3 and PLC beta3) are all expressed in UAEC, none are expressed at different levels in NP-vs. P-UAEC. Nonetheless, immunoprecipitation studies still show that functional association of TRPC3 with IP3R2 in response to ATP in P-UAEC far exceeds that observed in NP-UAEC. We have found that the pregnancy enhanced sustained [Ca2+]i response requires a pregnancy enhanced cell-cell communication via connexin 43 (CX43) Gap junctions. We have also found that the prolonged [Ca2+]i response observed in UAEC is buffered by the mitochondria in a manner further enhanced by pregnancy. We conclude that pregnancy adaptation of UAEC function involves reprogramming at multiple levels of cell signaling to prolong [Ca2+]i responses and cell-cell synchronization, thereby greatly enhancing eNOS activation. © Springer Science+Business Media B.V. 2010.