Department of Physiology, University of Tübingen, Tübingen, Germany.
FASEB J. 2010 Jun;24(6):1989-96. doi: 10.1096/fj.09-142265. Epub 2010 Feb 2.
Dendritic cells (DCs) are antigen-presenting cells that provide a link between innate and adaptive immunity. Ca(2+)-dependent signaling plays a central regulatory role in DC responses to diverse antigens. DCs are a primary target of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], a secosteroid hormone, that, in addition to its well-established action on Ca(2+) homeostasis, possesses immunomodulatory properties. Surprisingly, nothing is known about its effects on DC cytosolic Ca(2+) activity. The present study explored whether 1,25(OH)(2)D(3) modifies the intracellular Ca(2+) concentration (Ca(2+)) in DCs. Here we show that mouse DCs expressed K(+)-independent (NCX1-3) and K(+)-dependent (NCKX1, 3, 4, and 5) Na(+)/Ca(2+) exchangers. Acute application of LPS (100 ng/ml) to DCs increased Ca(2+), an effect significantly blunted by prior incubation with 1,25(OH)(2)D(3). 1,25(OH)(2)D(3) increased the membrane abundance of the NCKX1 protein, up-regulated the K(+)- and Na(+)-dependent Ca(2+) entry and enhanced the K(+)-dependent Na(+)/Ca(2+) exchanger currents. The NCKX blocker 3',4'-dichlorobenzamyl (DBZ) reversed the inhibitory effect of 1,25(OH)(2)D(3) on the LPS-induced increase of Ca(2+). Expression of the costimulatory molecule CD86 was down-regulated by 1,25(OH)(2)D(3), an effect reversed by DBZ. In summary, 1,25(OH)(2)D(3) blunts the LPS-induced increase in Ca(2+) by stimulation of Na(+)/Ca(2+) exchanger-dependent Ca(2+) extrusion, an effect that contributes to 1,25(OH)(2)D(3)-mediated immunosuppression. The results disclose completely novel mechanisms in the regulation of DC maturation and function.
树突状细胞 (DCs) 是一种抗原呈递细胞，它们在先天免疫和适应性免疫之间提供了联系。Ca(2+) 依赖性信号在 DC 对各种抗原的反应中起着核心调节作用。DCs 是 1,25-二羟维生素 D(3) [1,25(OH)(2)D(3)]的主要靶标，1,25(OH)(2)D(3) 是一种甾体激素，除了对 Ca(2+) 稳态的明确作用外，还具有免疫调节特性。令人惊讶的是，人们对其对 DC 细胞溶质 Ca(2+) 活性的影响一无所知。本研究探讨了 1,25(OH)(2)D(3) 是否会改变 DC 细胞内 Ca(2+) 浓度 (Ca(2+))。在这里，我们表明，小鼠 DCs 表达了 K(+) 非依赖性 (NCX1-3) 和 K(+) 依赖性 (NCKX1、3、4 和 5) Na(+)/Ca(2+) 交换器。LPS(100ng/ml)急性应用于 DCs 会增加 Ca(2+)，而先用 1,25(OH)(2)D(3) 孵育则显著减弱了这种作用。1,25(OH)(2)D(3) 增加了 NCKX1 蛋白的膜丰度，上调了 K(+) 和 Na(+) 依赖性 Ca(2+) 内流，并增强了 K(+) 依赖性 Na(+)/Ca(2+) 交换器电流。NCKX 阻断剂 3'，4'-二氯苯甲酰基 (DBZ) 逆转了 1,25(OH)(2)D(3) 对 LPS 诱导的 Ca(2+)增加的抑制作用。1,25(OH)(2)D(3) 下调了共刺激分子 CD86 的表达，DBZ 逆转了这一作用。总之，1,25(OH)(2)D(3) 通过刺激 Na(+)/Ca(2+) 交换器依赖性 Ca(2+) 外排来抑制 LPS 诱导的 Ca(2+)增加，这一作用有助于 1,25(OH)(2)D(3) 介导的免疫抑制。研究结果揭示了 DC 成熟和功能调节的全新机制。
