The serum-and glucocorticoid-inducible kinase Sgk-1 is involved in pulmonary vascular remodeling: role in redox-sensitive regulation of tissue factor by thrombin

RS BelAiba, T Djordjevic, S Bonello, F Artunc… - Circulation …, 2006 - ahajournals.org
RS BelAiba, T Djordjevic, S Bonello, F Artunc, F Lang, J Hess, A Görlach
Circulation research, 2006ahajournals.org
The stress-responsive serum-and glucocorticoid-inducible kinase Sgk-1 is involved in
osmoregulation and cell survival and may contribute to fibrosis and hypertension. However,
the function of Sgk-1 in vascular remodeling and thrombosis, 2 major determinants of
pulmonary hypertension (PH), has not been elucidated. We investigated the role of Sgk-1 in
thrombin signaling and tissue factor (TF) expression and activity in pulmonary artery smooth
muscle cells (PASMC). Thrombin increased Sgk-1 activity and mRNA and protein …
The stress-responsive serum- and glucocorticoid-inducible kinase Sgk-1 is involved in osmoregulation and cell survival and may contribute to fibrosis and hypertension. However, the function of Sgk-1 in vascular remodeling and thrombosis, 2 major determinants of pulmonary hypertension (PH), has not been elucidated. We investigated the role of Sgk-1 in thrombin signaling and tissue factor (TF) expression and activity in pulmonary artery smooth muscle cells (PASMC). Thrombin increased Sgk-1 activity and mRNA and protein expression. H2O2 similarly induced Sgk-1 expression. Antioxidants, dominant-negative Rac, and depletion of the NADPH oxidase subunit p22phox diminished thrombin-induced Sgk-1 expression. Inhibition of p38 mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and phosphoinositide-dependent kinase-1 prevented thrombin-induced Sgk-1 expression. Thrombin or Sgk-1 overexpression enhanced TF expression and procoagulant activity, whereas TF upregulation by thrombin was diminished by kinase-deficient Sgk-1 and was not detectable in fibroblasts from mice deficient in sgk-1 (sgk1−/−). Similarly, dexamethasone treatment failed to induce TF expression and activity in lung tissue from sgk1−/− mice. Transcriptional induction of TF by Sgk-1 was mediated through nuclear factor κB. Finally, Sgk-1 and TF proteins were detected in the media of remodeled pulmonary vessels associated with PH. These data show that thrombin potently induces Sgk-1 involving NADPH oxidases, phosphatidylinositol 3-kinase, p38 mitogen-activated protein kinase, and phosphoinositide-dependent kinase-1, and that activation of nuclear factor κB by Sgk-1 mediates TF expression and activity by thrombin. Because enhanced procoagulant activity can promote pulmonary vascular remodeling, and Sgk-1 and TF were present in the media of remodeled pulmonary vessels, this pathway may play a critical role in vascular remodeling in PH.
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