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Shikonin Selectively Inhibits Splicing of Tumor Necrosis Factor‐alpha pre‐mRNA
Author(s) -
Yang NingSun,
Chiu ShaoChih
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a931
Subject(s) - messenger rna , rna splicing , gene expression , tumor necrosis factor alpha , protein kinase r , microbiology and biotechnology , biology , alternative splicing , rna , protein kinase a , chemistry , gene , phosphorylation , biochemistry , immunology , cyclin dependent kinase 2
We previously identified shikonin as a potent suppressor of TNF‐α gene expression, which interferes with the binding of basal transcription machinery to the TATA box. Here, we report that shikonin can selectively inhibit the expression of TNF‐α at the RNA splicing level. Treatment of LPS‐stimulated primary monocytes and THP‐1 cells with shikonin resulted in a blockage of TNF‐α pre‐mRNA splicing process, with the accumulation of pre‐mRNA at the expense of functional mRNA. This effect occurred under non‐cytotoxic dosages of shikonin and was highly specific, because neither a housekeeping gene nor another inflammatory cytokine gene, IL‐8, was affected under the same treatment. Shikonin was then observed to increase protein expression of IL‐8 whilst decreasing expression of TNF‐α proteins in THP‐1 cells. In comparison with known TNF‐α inhibitors, shikonin was shown to specifically inhibit the phosphorylation of dsRNA‐activated protein kinase (PKR) in THP‐1 cells. Altogether, our findings suggest that the PKR signaling pathway may serve as a primary target for inhibition by shikonin, and that the differential modulation of TNF‐α and IL‐8 protein expression can help define the anti‐inflammatory mechanism of shikonin. These findings reveal that pre‐mRNA splicing may provide a target system for future clinical applications.