Magnolol Inhibits iNOS, p38 Kinase, and NF-κB/Rel in Murine Macrophages

  • Li Mei Hong (Department of Pharmacology, Chosun University College of Medicine) ;
  • Chang In-Youp (Department of Anatomy, Chosun University College of Medicine) ;
  • Youn Ho-Jin (Department of Pharmacology, Chosun University College of Medicine) ;
  • Jang Dae-Sik (Korea Institute of Oriental Medicine) ;
  • Kim Jin-Sook (Korea Institute of Oriental Medicine) ;
  • Jeon Young-Jin (Department of Pharmacology, Chosun University College of Medicine)
  • Published : 2006.09.30

Abstract

We demonstrate that magnolol, a hydroxylated biphenyl compound isolated from Magnolia officinalis, inhibits LPS-induced expression of iNOS gene in RAW 264.7 cells(murine macrophage cell line). Treatment of RAW 264.7 cells with magnolol inhibited LPS-stimulated nitric oxide production in a dose-related manner. RT-PCR analysis showed that the decrease of NO was due to the inhibition of iNOS gene expression. Western immunoblot analysis of phosphorylate p38 kinase showed magnolol significantly inhibited the phosphorylation of p38 kinase which is important in the regulation of iNOS gene expression. The specific p38 inhibiter SB203580 abrogated the LPS-induced NO generation and iNOS expression, whereas the selective MEK-1 inhibitor PD98059 did not affect the NO induction. Immunostaining of p65 and reporter gene assay showed that magnolol inhibited NF-${\kappa}/Rel$ nuclear translocation and transcriptional activation, respectively. Collectively, this series of experiments indicates that magnolol inhibits iNOS gene expression by blocking NF-k/Rel and p38 kinase signaling. Due to the critical role that NO release plays in mediating inflammatory responses, the inhibitory effects of magnolol or iNOS suggest that magnolol may represent a useful anti-inflammatory agent.

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