Serum- and glucocorticoid-regulated kinase 1 suppresses inflammatory responses mediated by toll like receptor 4 via nuclear factor-κB

Abstract

Objective To investigate the role of serum and glucocorticoid regulated protein kinase (SGK) 1 in the inflammatory responses mediated by toll like receptors. Methods Mice were injected with lipopolysaccharide (LPS, 1 mg/kg) 2 h after the pretreatment of EMD638683 (10 mg/kg) or phosphate buffered saline (PBS) as control. At the time points of 3 and 24 h, pro-inflammatory cytokines (interleukin[IL]-6, IL-12 and tumor necrosis factor[TNF]-α) in serum were measured using enzyme-linked immunosorbent assay (ELISA). Livers and lung were harvested at 6 h and 24 h after the injection of LPS, embedded by optimum cutting temperature (OCT) and then stained with hematoxylin and eosin (HE). Peripheral blood mononuclear cell (PBMC) were isolated and stimulated by LPS with or without the pretreatment of EMD or LY294002. Cytokines (IL-6, IL-12 and TNF-α) were measured using ELISA. IKKα/β, IΚBα and nuclear factor (NF)-κB p65 were detected by Western bolt. Data were analyzed by one way analysis of variance. Results In the model of LPS-induced endotoxin sepsis, inhibition of SGK1 induced secretion of pro-inflammatory cytokine (IL-6[t=3.007, P<0.05], IL-12[t=4.413, P<0.05]and TNF-α[t=5.403, P<0.05]), increased inflammatory cells infiltration into the liver and lung within 6 h, and induced serious multiple organ damage with collapse of alveoli and fatty degeneration of liver. After 24 h, pharmacological inhibition of SGK1 with EMD638683 increased pro-inflammatory cytokine (IL-6[t=18.540, P<0.01], IL-12[t=16.520, P<0.01]and TNF-α[t=34.880, P<0.01]) production in human PBMC upon LPS stimulation and inhibited the phosphorylation of IKKα/β/IΚBα and nuclear factor (NF)-κB p65. Conclusions SGK1 suppresses the toll like receptor 4 mediated inflammatory responses via NF-κB. Key words: SGK1; Sepsis; Toll-like receptor 4; Pro-inflammatory cytokine