Enhancement of CREB ^Serine-133 phosphorylation through nitric oxide-mediated signaling induced by bacterial lipopolysaccharide in vascular smooth muscle cells from rats

Nitric oxide (NO) induced by bacterial lipopolysaccharide (LPS) plays a critical role in various patho-physiological implications, such as atherosclerosis, vasculitis and septic shock. In addition, cAMP-responsive element binding protein (CREB), an important transcription factor for cell differentiation, has been shown to be involved in atherosclerogenesis in VSMCs. Here we investigated the possibility whether LPS-induced NO signaling led to phosphorylation of cAMP-responsive element binding protein on Serine-133 (CREB ^Ser-133 ) in cultured vascular smooth muscle cells (VSMCs) from rats. Addition of LPS (1-10 μg/ml) for 48 hours increased not only the production NO, but also the phosphorylation of CREB ^Ser-133 . The use of NOS inhibitor (100-500 μM L-NAME) blocked the magnitudes of both LPS-induced NO production and CREB ^Ser-133 phosphorylation. In addition, either a guanylyl cyclase (GC) inhibitor (30 μM ODQ) or a cGMP-dependent protein kinase (PKG) inhibitor (20 μM (Rp)-8-pCPT-cGMPs) significantly attenuated the magnitudes of LPS-induced CREB ^Ser-133 phosphorylation, suggesting the involvement of NO-GC-PKG signaling. Thus, the present study suggests that NO-mediated signaling activated by bacterial LPS, at least in part, enhance CREB ^Ser-133 phosphorylation in cultured VSMCs. The findings here may provide not only signaling pathway involved in VSMC differentiation during inflammatory response, but also new insight into possible therapeutic intervention.