Page 55 - ebook

Novel function of SGK1 in shear stress induced endothelial inflammation

Ye-eun Jang, San-guk Yun *

1 Biological sciences, Inje University, Gimhae-si 50834, Korea

SGK1 (serum and glucocorticoid inducible kinase) is reported to promote cell

survival by its anti-oxidation activity in endothelial cells. Additionally, it is also

implicated in inflammatory signaling via PI3K, MR (mineralocorticoid receptor)

and NF-kB-dependent pathway. Here, we found that SGK1 is transcriptionally

induced by oscillatory shear stress and mediates pro-inflammatory response in

endothelial cells. Several candidate receptors responsible for SGK-1 induction

have been tested and ALK-1(Activin A Receptor Like Type 1) knockdown

completely abrogated flow-induced SGK-1 induction and NF-kB-dependent

inflammatory activation. These results suggest a novel flow-induced endothelial

inflammation pathway and therapeutic targets for vascular inflammatory diseases

such as atherosclerosis.

(A) (B)
(A) (B)

Figure.3 Under oscillatory shear stress, ALK1 KD and SGK1 KD decrease monocyte adhesion.

(A)Thp-1 adhesion assay of control and SGK1 KD and ALk1 KD. (B) Quantification of adherent monocytes. (n=3)

(*p<0.05) (**p<0.005)

Figure.1 Under oscillatory shear stress, SGK1 regulates the inflammatory response.

(A) VCAM-1, SGK1, YAP, NF-kB protein levels determined by Western blots. Under OS for 16hr, it was confirmed that

protein expression of SGK1 was significantly increased, and phosphorylation of p-p65 and protein expression level of total - Cell culture of bovine aortic endothelial cells(BAECs)

YAP were significantly decreased in SGK1 knockdown. (B) Quantification of Western blot results. (n=3) (*p<0.05)

(**p<0.005) - siRNA(SGK1) knockdown -Western blot analysis

- Monocyte adhesion - qPCR analysis - Shear stress

(A) (B)

Endothelial cells in our body induce an inflammatory response in blood vessels

when subjected to oscillatory shear stress that resists blood flow in blood vessels

with laminar flow. In addition, increased monocyte adhesion in this environment is

essential for the onset and exacerbation of atherosclerosis, a lipid-induced

inflammatory disease, of monocytes and their progeny macrophages.

We demonstrated that monocyte adhesion in ECs was significantly reduced upon
(C)

knockdown of SGK1 and ALk1. Furthermore, it was also confirmed that the

expression of SGK1 was induced by ALk1, and as the expression of YAP and

phosphorylation of NF-kB increased, the expression of VCAM-1 was increased.

It is already known that VCAM-1 (vascular cell adhesion molecule-1) is induced by

YAP and NF-kB.

In addition, it was confirmed that phosphorylation of p-p65, a subunit of NF-kB,

was completely abolished in SGK1 knockdown, but was not completely abolished

in ALK1 knockdown. Based on these results, we thought that the expression of

SGK1 is regulated by ALk1, but the activity of SGK1 will further increase through

some subsequent pathway, and this requires additional research.

Figure.2 Under oscillatory shear stress, ALK1 regulates SGK1 expression and NF-kB

phosphorylation.

(A) Knockdown confirmation through the mRNA levels of AT-1, ALK1, and MR. (B) NF-kB, SGK1 protein levels are In conclusion, we demonstrated that ALK1 activated by oscillatory shear stress

determined by Western blot. Under OS for 16hr, ALK1 KD significantly reduced the expression of SGK1 and decreased

phosphorylation of p-p65. (C) Quantification of Western blot results. (n=3) (*p<0.05) induces the vascular inflammatory response by inducing the expression of SGK1 to

increase monocyte adhesion.