Rotte Anand, Pasham Venkanna, Eichenmüller Melanie, Yang Wenting, Bhandaru Madhuri, Lang Florian
Department of Physiology, University of Tübingen, Tübingen, Germany.
Cell Physiol Biochem. 2011;28(2):305-14. doi: 10.1159/000331746. Epub 2011 Aug 16.
Glucocorticoids regulate the function of dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. Glucocorticoids influence the function of other cell types by modulating the activity of the Na(+)/H(+)exchanger (NHE), a carrier involved in the regulation of cytosolic pH and cell volume. The present study explored whether dexamethasone influences Na(+)/H(+) exchanger activity in DCs. The DCs were isolated from mouse bone marrow, cell volume was estimated from forward scatter in FACS analysis, cytosolic pH (pH(i)) utilizing BCECF fluorescence and Na(+)/H(+) exchanger activity from the Na(+) dependent realkalinization after an ammonium pulse. Treatment with the glucocorticoid dexamethasone (100 nM; 1, 4, 16 and 24h) significantly decreased pH(i) (≥4 h) and gradually increased Na(+)/H(+) exchanger activity (=16 h). The stimulation of Na(+)/H(+) exchanger activity by dexamethasone was virtually abrogated by glucocorticoid receptor blocker mefiprestone (1 μM) and NHE3 inhibitor dimethyl amiloride (5 μM), but not prevented by NHE1 inhibitor cariporide (10 μM). Dexamethasone treatment significantly increased SGK1 mRNA levels. Stimulation of Na(+)/H(+) exchanger activity by dexamethasone was blunted in DCs lacking SGK1. Dexamethasone treatment did not significantly alter ROS formation but significantly decreased the forward scatter. Exposure of DCs to lipopolysacharide (LPS, 1 μg/ml) led to a transient increase followed by a decline of Na(+)/H(+) exchanger activity and to enhanced forward scatter as well as ROS formation, all effects significantly blunted in the presence of dexamethasone (100 nM). In conclusion, glucocorticoid treatment decreased pH(i) and cell volume, effects paralleled by upregulation of Na(+)/H(+) exchanger activity in DCs. Moreover, glucocorticoids blunted the stimulation of Na(+)/H(+) exchanger activity, cell swelling and ROS formation following LPS treatment.
糖皮质激素调节树突状细胞（DCs）的功能，DCs是连接固有免疫和适应性免疫的抗原呈递细胞。糖皮质激素通过调节Na(+)/H(+)交换体（NHE）的活性来影响其他细胞类型的功能，NHE是一种参与调节胞质pH值和细胞体积的载体。本研究探讨了地塞米松是否会影响DCs中Na(+)/H(+)交换体的活性。DCs从小鼠骨髓中分离得到，细胞体积通过流式细胞术分析中的前向散射来估计，利用BCECF荧光测定胞质pH值（pH(i)），并通过铵脉冲后Na(+)依赖性再碱化来测定Na(+)/H(+)交换体的活性。用糖皮质激素地塞米松（100 nM；1、4、16和24小时）处理显著降低了pH(i)（≥4小时），并逐渐增加了Na(+)/H(+)交换体的活性（=16小时）。地塞米松对Na(+)/H(+)交换体活性的刺激几乎被糖皮质激素受体阻滞剂米非司酮（1 μM）和NHE3抑制剂二甲基氨氯吡脒（5 μM）消除，但未被NHE1抑制剂卡立泊来德（10 μM）阻止。地塞米松处理显著增加了SGK1 mRNA水平。在缺乏SGK1的DCs中，地塞米松对Na(+)/H(+)交换体活性的刺激减弱。地塞米松处理未显著改变活性氧的形成，但显著降低了前向散射。将DCs暴露于脂多糖（LPS，1 μg/ml）导致Na(+)/H(+)交换体活性短暂增加，随后下降，并导致前向散射增强以及活性氧形成，在地塞米松（100 nM）存在的情况下，所有这些效应均显著减弱。总之，糖皮质激素处理降低了pH(i)和细胞体积，同时DCs中Na(+)/H(+)交换体活性上调。此外，糖皮质激素减弱了LPS处理后对Na(+)/H(+)交换体活性、细胞肿胀和活性氧形成的刺激。
