Simvastatin suppresses LPS-Induced akt phosphorylation in the human monocyte cell line THP-1

Background. Activation of the small GTPase, Rac, requires post-translational modification by isoprenylation. Statins interfere with this process by blocking the synthesis of isoprenoid intermediates. The protein kinase Akt is a multifunctional regulator of cell behavior that has been linked to Rac activation. We have shown that lipopolysaccharide (LPS) stimulation leads to Rac activation in THP-1 cells. Therefore, we hypothesized that LPS stimulation would also activate Akt, a downstream effector of Rac, and that this may be blocked by statin pretreatment. Materials and methods. THP-1 cells were maintained in 1% fetal calf serum with or without 20 mum simvastatin for 24 h, followed by LPS stimulation for increasing time. Cytoskeletal changes were observed using Alexa-Phalloidin. Akt was immunoprecipitated from total cell lysate. Activated Akt was detected by immunoblotting with a phospho-Akt; antibody and was quantified by image densitometry. Results. LPS stimulation of THP-1 cells results in membrane ruffling and cell polarization. Furthermore, LPS increased Akt activation in THP-1 cells when compared with the nonstimulated controls. Akt phosphorylation. peaked after 15 min of LPS stimulation and was suppressed by pretreatment with simvastatin. Conclusions. These data demonstrate that LPS stimulation leads to increased Akt phosphorylation, which can be suppressed with simvastatin pretreatment. This suggests one possible mechanism through which simvastatin could modulate LPS-induced signaling events in monocytes to improve the host response to Gram-negative infections. (C) 2004 Elsevier Inc. All rights reserved.