SGK1 induces vascular smooth muscle cell calcification through NF-κB signaling
Jakob Voelkl, … , Florian Lang, Ioana Alesutan
Jakob Voelkl, … , Florian Lang, Ioana Alesutan
Published June 11, 2018
Citation Information: J Clin Invest. 2018;128(7):3024-3040. https://doi.org/10.1172/JCI96477.
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Research Article Cell biology Vascular biology

SGK1 induces vascular smooth muscle cell calcification through NF-κB signaling

Abstract

Medial vascular calcification, associated with enhanced mortality in chronic kidney disease (CKD), is fostered by osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Here, we describe that serum- and glucocorticoid-inducible kinase 1 (SGK1) was upregulated in VSMCs under calcifying conditions. In primary human aortic VSMCs, overexpression of constitutively active SGK1S422D, but not inactive SGK1K127N, upregulated osteo-/chondrogenic marker expression and activity, effects pointing to increased osteo-/chondrogenic transdifferentiation. SGK1S422D induced nuclear translocation and increased transcriptional activity of NF-κB. Silencing or pharmacological inhibition of IKK abrogated the osteoinductive effects of SGK1S422D. Genetic deficiency, silencing, and pharmacological inhibition of SGK1 dissipated phosphate-induced calcification and osteo-/chondrogenic transdifferentiation of VSMCs. Aortic calcification, stiffness, and osteo-/chondrogenic transdifferentiation in mice following cholecalciferol overload were strongly reduced by genetic knockout or pharmacological inhibition of Sgk1 by EMD638683. Similarly, Sgk1 deficiency blunted vascular calcification in apolipoprotein E–deficient mice after subtotal nephrectomy. Treatment of human aortic smooth muscle cells with serum from uremic patients induced osteo-/chondrogenic transdifferentiation, effects ameliorated by EMD638683. These observations identified SGK1 as a key regulator of vascular calcification. SGK1 promoted vascular calcification, at least partly, via NF-κB activation. Inhibition of SGK1 may, thus, reduce the burden of vascular calcification in CKD.

Authors

Jakob Voelkl, Trang T.D. Luong, Rashad Tuffaha, Katharina Musculus, Tilman Auer, Xiaoming Lian, Christoph Daniel, Daniel Zickler, Beate Boehme, Michael Sacherer, Bernhard Metzler, Dietmar Kuhl, Maik Gollasch, Kerstin Amann, Dominik N. Müller, Burkert Pieske, Florian Lang, Ioana Alesutan

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Figure 1

SGK1 expression in VSMCs.

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SGK1 expression in VSMCs. (A) Scatter dot plots and arithmetic means ± S...
(A) Scatter dot plots and arithmetic means ± SEM (n = 6 per group; arbitrary units [AU]) of SGK1 relative mRNA expression in primary HAoSMCs following treatment with control (CTR) or aldosterone (Aldo), dexamethasone (Dex), β-glycerophosphate (Pi), glucose, recombinant human TGF-β1 protein, or recombinant human BMP-2 protein. (B) Representative original Western blots and scatter dot plots and arithmetic means ± SEM (n = 4 per group; AU) of normalized SGK1/GAPDH protein ratio in HAoSMCs following treatment with triggers of osteo-chondrogenic transdifferentiation. *P < 0.05, **P < 0.01, ***P < 0.001 statistically significant vs. control-treated HAoSMCs (1-way ANOVA with Tukey-Honestly Significant Difference [HSD] [A] and with Games-Howell post hoc test [B]). (C and D) Scatter dot plots and arithmetic means ± SEM (AU) of Sgk1 relative mRNA expression in aortic tissue from kl/kl mice and WT mice (C, n = 7 per group) and DBA mice without (CTR) or with subtotal nephrectomy (Nx) (D, n = 7–8 per group). (E and F) Scatter dot plots and arithmetic means ± SEM (AU) of SGK1 (E) and MSX2 (F) relative mRNA expression in coronary artery tissue from patients with maintained (CTR, n = 10) and impaired (IRF, n = 9) renal function. **P < 0.01 statistically significant vs. WT mice, control-treated mice, or CTR patients, respectively (unpaired 2-tailed t test for C–F). (G) Correlation of SGK1 and MSX2 relative mRNA expression (AU) in coronary artery tissue from CTR and IRF patients. P represents the 2-tailed probability value of the Pearson correlation. (H) Representative original histological images (n = 5 per group) showing SGK1 expression as well as ectopic calcification by von Kossa staining (calcification, gray to black) in coronary artery sections from control patients and dialysis patients. Scale bars: 100 μm.