Phospholipase D regulates calcium oscillation frequency and nuclear factor-κB activity in histamine-stimulated human endothelial cells

Histamine stimulates [Ca²⁺]i oscillations in human aortic endothelial cells (HAEC), the frequency of which regulates the activity of nuclear factor-κB (NF-κB). This study was performed to determine whether phospholipase D (PLD) is involved in this signaling pathway. At a concentration of 1 μM, which stimulates [Ca²⁺]i oscillations in this cell type, histamine initiated a twofold increase in [³²P]phosphatidybutanol (PBt), an index of PLD activity as early as 5 min after stimulation. During established [Ca²⁺]i oscillations induced by 1 μM histamine, 0.3% n-butanol, which "functionally" redirects phosphatidic acid formed by PLD to PBt, decreased [Ca²⁺]i oscillation frequency by ∼50% and produced a similar reduction in NF-κB activity. In the presence of the inositol 1, 4, 5-trisphosphate receptor blocker xesto-spongin C, which itself decreases the frequency of histamine-stimulated [Ca²⁺]i oscillations, n-butanol produced a further decrease in oscillation frequency that was not associated with an additional reduction in NF-κB activity. This study shows that activation of PLD by histamine regulates [Ca²⁺]i oscillation frequency and NF-κB activity in HAEC.