Effect of dexamethasone on Na+/Ca2+ exchanger in dendritic cells

Heise N, Shumilina E, Nurbaeva MK, Schmid E, Szteyn K, Yang W, Xuan NT, Wang K, Zemtsova IM, Duszenko M, Lang F. Effect of dexamethasone on Na+/Ca2+ exchanger in dendritic cells. Am J Physiol Cell Physiol 300: C1306-C1313, 2011. First published February 9, 2011; doi: 10.1152/ajpcell.00396.2010.-Ca+-dependent signaling regulates the function of dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. The activity of DCs is suppressed by glucocorticoids, potent immunosuppressive hormones. The present study explored whether the glucocorticoid dexamethasone influences the cytosolic Ca2+ concentration ([Ca2+](i)) in DCs. To this end, DCs were isolated from mouse bone marrow. According to fura-2 fluorescence, exposure of DCs to lipopolysaccharide (LPS, 100 ng/ml) increased [Ca2+](i), an effect significantly blunted by overnight incubation with 10 nM dexamethasone before LPS treatment. Dexamethasone did not affect the Ca2+ content of intracellular stores, sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2 and SERCA3 expression, ryanodine receptor (RyR)1 expression, or Ca2+ entry through store-operated Ca2+ channels. In contrast, dexamethasone increased the transcript level and the membrane protein abundance of the Na+/Ca2+ exchanger NCX3. The activity of Na+/Ca2+ exchangers was assessed by removal of extracellular Na+ in the presence of external Ca2+, a maneuver triggering the Ca2+ influx mode. Indeed, Na+ removal resulted in a rapid transient increase of [Ca2+](i) and induced an outwardly directed current as measured in whole cell patch-clamp experiments. Dexamethasone significantly augmented the increase of [Ca2+](i) and the outward current following removal of extracellular Na+. The NCX blocker KB-R7943 reversed the inhibitory effect of dexamethasone on LPS-induced increase in [Ca2+](i). Dexamethasone blunted LPS-induced stimulation of CD86 expression and TNF-alpha production, an effect significantly less pronounced in the presence of NCX blocker KB-R7943. In conclusion, our results show that glucocorticoid treatment blunts LPS-induced increase in [Ca2+](i) in DCs by increasing expression and activity of Na+/Ca2+ exchanger NCX3. The effect contributes to the inhibitory effect of the glucocorticoid on DC maturation.