Mevastatin ameliorates sphingosine 1-phosphate-induced COX-2/PGE2-dependent cell migration via FoxO1 and CREB phosphorylation and translocation

Background and Purpose Sphingosine 1-phosphate (S1P), an important inflammatory mediator, has been shown to regulate COX-2 production and promote various cellular responses such as cell migration. Mevastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA), effectively inhibits inflammatory responses. However, the mechanisms underlying S1P-evoked COX-2-dependent cell migration, which is modulated by mevastatin in human tracheal smooth muscle cells (HTSMCs) remain unclear. Experimental Approach The expression of COX-2 was determined by Western blotting, real time-PCR and promoter analyses. The signalling molecules were investigated by pretreatment with respective pharmacological inhibitors or transfection with siRNAs. The interaction between COX-2 promoter and transcription factors was determined by chromatin immunoprecipitation assay. Finally, the effect of mevastatin on HTSMC migration and leukocyte counts in BAL fluid and COX-2 expression induced by S1P was determined by a cell migration assay, cell counting and Western blot. Key Results S1P stimulated mTOR activation through the Nox2/ROS and PI3K/Akt pathways, which can further stimulate FoxO1 phosphorylation and translocation to the cytosol. We also found that S1P induced CREB activation and translocation via an mTOR-independent signalling pathway. Finally, we showed that pretreatment with mevastatin markedly reduced S1P-induced cell migration and COX-2/PGE₂ production via a PPARγ-dependent signalling pathway. Conclusions and Implications Mevastatin attenuates the S1P-induced increased expression of COX-2 and cell migration via the regulation of FoxO1 and CREB phosphorylation and translocation by PPARγ in HTSMCs. Mevastatin could be beneficial for prevention of airway inflammation in the future.