Cyclovirobuxinum D suppresses lipopolysaccharide-induced inflammatory responses in murine macrophages in vitro by blocking JAK-STAT signaling pathway

Aim: Cyclovirobuxinum D (CVB-D), an alkaloid isolated from the Chinese medicinal plant Buxus microphylla, has been found to be effective to treat cardiac insufficiency, arrhythmias and coronary heart disease: In the present study, we investigated the effects of CVB-D on the inflammatory responses in lipopolysaccharide (LPS)-stimulated murine macrophages in vitro and the underlying mechanisms. Methods: Murine macrophage cell line RAW264.7 cells were incubated in the presence of LPS (0.1 mu g/mL) for 24 h. The cell viability was measured using MU assay. The release of NO and cytokines were detected using the Griess test and ELISA, respectively. The mRNA and protein levels were determined using RT-PCR and Western blot, respectively. Reporter gene assays were used to analyze the transcriptional activity of NF-kappa B. Results: Treatment of RAW264.7 cells with CVB-D (25-300 mu mol/L) did not affect the cell viability. Pretreatment with CVB-D (50, 100 and 200 mu mol/L) concentration-dependently decreased NO release and iNOS expression in LPS-treated RAW264.7 cells (its IC50 value in inhibition of NO production was 144 mu mol/L). CVB-D also concentration-dependently inhibited the secretion and mRNA expression of IL-1 beta and IL-6 in LPS-treated RAW264.7 cells. Furthermore, CVB-D remarkably inhibited the phosphorylation of STAT1 and STAT3, as well as JAK2 in LPS-treated RAW264.7 cells, but did not affect the activation of NF-kappa B and MAPKs pathways. Pretreatment with the JAK2 specific inhibitor AG490 (30 mu mol/L) produced similar effects on NO release and iNOS expression in LPS-treated RAW264.7 cells. Conclusion: CVB-D exerts anti-inflammatory effects in LPS-stimulated murine macrophages in vitro at least in part by blocking the JAK-STAT signaling pathway. The anti-inflammatory actions of CVB-D may contribute to its cardioprotection.