Ca2+ and Inositol 1,4,5-Trisphosphate–Mediated Signaling Across the Myoendothelial Junction

BE Isakson, SI Ramos, BR Duling - Circulation research, 2007 - Am Heart Assoc
BE Isakson, SI Ramos, BR Duling
Circulation research, 2007Am Heart Assoc
Second messenger signaling between endothelial cells (ECs) and vascular smooth muscle
cells (VSMCs) is poorly understood, but intracellular Ca2+ concentrations ([Ca2+] i) in the 2
cells are coordinated, possibly through gap junctions at the myoendothelial junction. To
study heterocellular calcium signaling, we used a vascular cell coculture model composed
of monolayers of ECs and VSMCs. Stimulation of either cell type leads to an increase in
[Ca2+] i in the stimulated cell and a secondary increase in [Ca2+] i in the other cell type that …
Second messenger signaling between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) is poorly understood, but intracellular Ca2+ concentrations ([Ca2+]i) in the 2 cells are coordinated, possibly through gap junctions at the myoendothelial junction. To study heterocellular calcium signaling, we used a vascular cell coculture model composed of monolayers of ECs and VSMCs. Stimulation of either cell type leads to an increase in [Ca2+]i in the stimulated cell and a secondary increase in [Ca2+]i in the other cell type that was blocked by gap junction inhibitors. To determine which second messengers are involved, we initially depleted Ca2+ stores in the endoplasmic reticulum Ca2+ with thapsigargin in ECs or VSMCs, but this had no effect on heterocellular calcium signaling. Alternatively, we loaded ECs or VSMCs with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) to buffer changes in [Ca2+]i. BAPTA loading of ECs inhibited agonist-induced increases in intracellular calcium concentration ([Ca2+]i), in both ECs and VSMCs. In contrast, BAPTA loading of the VSMCs blunted the VSMC response but did not alter the secondary increase in EC [Ca2+]i. Xestospongin C (an inositol 1,4,5-trisphosphate receptor inhibitor) had no effect on the secondary Ca2+ response, but when xestospongin C or thapsigargin was loaded into ECs and BAPTA into VSMCs, intercellular Ca2+ signaling was completely blocked. We conclude that 1,4,5-trisphosphate and Ca2+ originating in the VSMCs induces the secondary increase in EC [Ca2+]i but stimulation of the ECs generates a Ca2+ dependent response in the VSMCs.
Am Heart Assoc