Shikonins, phytocompounds from Lithospermum erythrorhizon, inhibit the transcriptional activation of human tumor necrosis factor alpha promoter in vivo.
Tumor necrosis factor alpha (TNF-alpha) contributes to the pathogenesis of both acute and chronic inflammatory diseases and has been a target for the development of new anti-inflammatory drugs. Shikonins, the naphthoquinone pigments present in the root tissues of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae), have been reported to exert anti-inflammatory effects both in vitro and in vivo. In this study, we evaluated the effects of shikonin and its derivatives on the transcriptional activation of human TNF-alpha promoter in a gene gun-transfected mouse skin system by using a luciferase reporter gene assay. The crude plant extract of L. erythrorhizon as well as derived individual compounds shikonin, isobutyryl shikonin, acetyl shikonin, dimethylacryl shikonin and isovaleryl shikonin showed significant dose-dependent inhibition of TNF-alpha promoter activation. Among the tested compounds, shikonin and isobutyryl shikonin exhibited the highest inhibition of TNF-alpha promoter activation and also showed significant suppression of transgenic human TNF-alpha mRNA expression and protein production. We demonstrated that shikonin-inhibitory response was retained in the core TNF-alpha promoter region containing the TATA box and a 48-bp downstream sequence relative to the transcription start site. Further our results indicated that shikonin suppressed the basal transcription and activator-regulated transcription of TNF-alpha by inhibiting the binding of transcription factor IID protein complex (TATA box-binding protein) to TATA box. These in vivo results suggest that shikonins inhibit the transcriptional activation of the human TNF-alpha promoter through interference with the basal transcription machinery. Thus, shikonins may have clinical potential as anti-inflammatory therapeutics.
Staniforth
Vanisree
V
Institute of BioAgricultural Sciences, Academia Sinica, Taipei 11529, Taiwan, Republic of China.
Wang
Sheng-Yang
SY
Shyur
Lie-Fen
LF
Yang
Ning-Sun
NS
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001623:Betamethasone / Q000737:chemistry; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D018014:Gene Transfer Techniques; D006801:Humans; D006854:Hydrocortisone / Q000737:chemistry; D007249:Inflammation; D029684:Lithospermum / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008956:Models, Chemical; D016328:NF-kappa B / Q000378:metabolism; D009285:Naphthoquinones / Q000737:chemistry / Q000494:pharmacology*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000378:metabolism; D013997:Time Factors; D051996:Transcription Factor RelA; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D019076:Transgenes; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D016328:NF-kappa B; D009285:Naphthoquinones; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; C016101:shikonin; D001623:Betamethasone; D008156:Luciferases; D006854:Hydrocortisone