Angiotensin II, ATP and high extracellular potassium induced intracellular calcium responses in primary rat brain endothelial cell cultures

Abstract

The meninges shield the nervous system from diverse, rather harmful stimuli and pathogens from the periphery. This tissue is composed of brain endothelial cells (BECs) that express diverse ion channels and chemical‐transmitter receptors also expressed by neurons and glial cells to communicate with each other. However, information about the effects of ATP and angiotensin II on BECs is scarce, despite their essential roles in blood physiology. This work investigated in vitro if BECs from the meninges from rat forebrain respond to ATP, angiotensin II and high extracellular potassium, with intracellular calcium mobilizations and its second messenger‐associated pathways. We found that in primary BEC cultures, both ATP and angiotensin II produced intracellular calcium responses linked to the activation of inositol trisphosphate receptors and ryanodine receptors, which led to calcium release from intracellular stores. We also used RT‐PCR to explore what potassium channel subunits are expressed by primary BEC cultures and freshly isolated meningeal tissue, and which might be linked to the observed effects. We found that BECs mainly expressed the inward rectifier potassium channel subunits Kir1.1, Kir3.3, Kir 4.1 and Kir6.2. This study contributes to the understanding of the functions elicited by ATP and angiotensin II in BECs from rat meninges. SIGNIFICANCE OF THE STUDY Brain endothelial cells (BECs) express diverse ion channels and membrane receptors, which they might use to communicate with neurons and glia. This work investigated in vitro, if BECs from the rat forebrain respond to angiotensin II and ATP with intracellular calcium mobilizations. We found that these cells did respond to said substances with intracellular calcium mobilizations linked to inositol trisphosphate and ryanodine receptor activation, which led to calcium release from intracellular stores. These findings are important because they might uncover routes of active communication between brain cells and endothelial cells.

Reactive Oxygen Species and Endothelial Ca2+ Signaling: Brothers in Arms or Partners in Crime?

“…Furthermore, InsP 3 R channel activity in vascular endothelial cells may also be modulated by mitochondria, which may establish close contacts with ER cisternae (known as mitochondria-associated ER membranes or MAMs) [ 117 ] and inhibit InsP 3 -induced Ca 2+ release in endothelial cells in a H 2 O 2 -dependent manner [ 118 ]. Ryanodine receptors (RyRs) provide as an alternative pathway to release intraluminal Ca 2+ either through the process of Ca 2+ -induced Ca 2+ release (CICR) [ 119 , 120 ] or upon binding of the Ca 2+ -releasing second messenger, cyclic ADP ribose (cADPr) [ 121 ]. As reviewed elsewhere [ 26 , 106 ], endothelial RyRs are not as widely distributed as InsP 3 Rs across peripheral vasculature and are absent in circulating ECFCs [ 122 ].…”