Department of Internal Medicine and Cardiology, Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburgerplatz 1, 13353, Berlin, Germany.
Department of Physiology I, Eberhard-Karls University, Wilhelmstr. 56, 72076, Tübingen, Germany.
Pflugers Arch. 2019 Jun;471(6):889-899. doi: 10.1007/s00424-019-02256-5. Epub 2019 Jan 31.
The serum- and glucocorticoid-inducible kinase 1 (SGK1) is a key regulator of osteo-/chondrogenic transdifferentiation and subsequent calcification of vascular smooth muscle cells (VSMCs). The phenotypical transdifferentiation of VSMCs is associated with increased interleukin-18 (IL-18) levels and generalized inflammation. Therefore, the present study investigated the possible involvement of SGK1 in IL-18-induced vascular calcification. Experiments were performed in primary human aortic smooth muscle cells (HAoSMCs) treated with recombinant human IL-18 protein in control or high phosphate conditions and following SGK1 knockdown by siRNA or pharmacological inhibition of SGK1, PI3K, and PDK1. As a result, IL-18 treatment increased SGK1 mRNA and protein expression in HAoSMCs. IL-18 upregulated SGK1 mRNA expression in a dose-dependent manner. This effect was paralleled by upregulation of the mRNA expression of MSX2 and CBFA1, osteogenic transcription factors, and of tissue-nonspecific alkaline phosphatase (ALPL), an osteogenic enzyme, as markers of increased osteo-/chondrogenic transdifferentiation. Phosphate treatment increased SGK1 and osteogenic markers mRNA expression as well as ALPL activity and induced calcification of HAoSMCs, all effects significantly augmented by additional treatment with IL-18. Conversely, silencing of SGK1 or cotreatment with the SGK1 inhibitor EMD638683 blunted the effects of IL-18 on osteo-/chondrogenic transdifferentiation and calcification of HAoSMCs. The procalcific effects of IL-18 were similarly suppressed in the presence of PI3K or PDK1 inhibitors. In conclusion, SGK1 expression is upregulated by IL-18 in VSMCs and SGK1 participates in the intracellular signaling of IL-18-induced osteo-/chondrogenic transdifferentiation of VSMCs. Thus, SGK1 may serve as therapeutic target to limit the progression of medial vascular calcification during vascular inflammation.
血清和糖皮质激素诱导的激酶 1（SGK1）是骨/软骨细胞向分化和随后血管平滑肌细胞（VSMCs）钙化的关键调节因子。VSMCs 的表型向分化与白细胞介素-18（IL-18）水平升高和全身炎症有关。因此，本研究探讨了 SGK1 是否参与 IL-18 诱导的血管钙化。实验在原代人主动脉平滑肌细胞（HAoSMCs）中进行，用重组人 IL-18 蛋白在对照或高磷条件下处理，并通过 siRNA 或 SGK1、PI3K 和 PDK1 的药理学抑制进行 SGK1 敲低。结果，IL-18 处理增加了 HAoSMCs 中的 SGK1 mRNA 和蛋白表达。IL-18 以剂量依赖的方式上调 SGK1 mRNA 表达。这种作用伴随着骨/软骨细胞向分化增加的标志物，即 MSX2 和 CBFA1 成骨转录因子和组织非特异性碱性磷酸酶（ALPL）的 mRNA 表达上调，ALPL 是一种成骨酶。磷酸盐处理增加了 SGK1 和成骨标志物的 mRNA 表达以及 ALPL 活性，并诱导 HAoSMCs 钙化，所有这些作用都因额外用 IL-18 处理而显著增强。相反，沉默 SGK1 或与 SGK1 抑制剂 EMD638683 共同处理可削弱 IL-18 对 HAoSMCs 骨/软骨细胞向分化和钙化的作用。PI3K 或 PDK1 抑制剂的存在也抑制了 IL-18 的促钙化作用。总之，IL-18 在 VSMCs 中上调 SGK1 表达，SGK1 参与 IL-18 诱导的 VSMCs 骨/软骨细胞向分化的细胞内信号转导。因此，SGK1 可作为治疗靶点，限制血管炎症期间中膜血管钙化的进展。
