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Mechanisms of suppression of inducible nitric oxide synthase (iNOS) expression in RAW 264.7 cells by andrographolide
Author(s) -
Chiou WenFei,
Chen ChiehFu,
Lin JinJung
Publication year - 2000
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703191
Subject(s) - andrographolide , nitric oxide synthase , andrographis paniculata , nitric oxide , protein biosynthesis , lipopolysaccharide , chemistry , biochemistry , microbiology and biotechnology , biology , enzyme , immunology , medicine , alternative medicine , organic chemistry , pathology
Andrographolide, an active component found in leaves of Andrographis paniculata , has been reported to exhibit nitric oxide (NO) inhibitory property in endotoxin‐stimulated macrophages, however, the detailed mechanisms remain unclear. In the present study we investigated the effect of andrographolide on the expression of inducible NO synthase (iNOS) mRNA, protein, and enzyme activity in RAW 264.7 macrophages stimulated with lipopolysaccharide (LPS) plus interferon‐γ (IFN‐γ). RAW 264.7 cells stimulated with LPS/IFN‐γ activated NO production; in this condition andrographolide (1–100 μ M ) inhibited NO production in a dose‐dependent manner with an IC 50 value of 17.4±1.1 μ M . Andrographolide also reduces the expression of iNOS protein level but without a significant effect on iNOS mRNA. The reduction of iNOS activity is thought to be caused by decreased expression of iNOS protein. In a protein stability assay, andrographolide moderately but significantly reduced the amount of iNOS protein as suggested by accelerating degradation. Furthermore, andrographolide also inhibited total protein de novo synthesis as demonstrated by [ 35 S]‐methionine incorporation. As a whole, these data suggest that andrographolide inhibits NO synthesis in RAW 264.7 cells by reducing the expression of iNOS protein and the reduction could occur through two additional mechanisms: prevention of the de novo protein synthesis and decreasing the protein stability via a post‐transcriptional mechanism. It is also possible that inhibition of iNOS protein expression and NO production under immune stimulation and/or bacteria infection may explain, in part, the beneficial effects of andrographolide as an anti‐inflammatory agent.British Journal of Pharmacology (2000) 129 , 1553–1560; doi: 10.1038/sj.bjp.0703191