Enhancing effects of Scutellaria baicalensis and some of its constituents on TGF-β1 gene expression in RAW 264.7 murine macrophage cell line

Transforming growth factor beta 1 (TGF-beta 1) has been implicated as an inhibitor of cell proliferation and a potent inducer of apoptosis. Scutellaria baicalensis Georgi (SbG) has been widely used in Asia and recent investigations have shown that SbG has anticancer, antiviral, and anti-inflammatory effects. The aim of this study is to investigate the modulatory effect of SbG on TGF-beta 1 gene expression. By using RAW 264.7 cell line as an in vitro model, the effects of SbG on TGF-beta 1 gene expression were evaluated by ELISA, reverse-transcription polymerase chain reaction (RTPCR) and quantitative PCR. Many inhibitors such as mitogen-activated protein kinase (MAPK) inhibitor (PD98059), p38-MAPK inhibitor (SB203580), NF-kappa B inhibitor (aspirin) and protein kinase C inhibitor (H7) were used to determine the possible signal transduction pathways. The results showed that crude extracts of SbG as well as its pure compounds, baicalin, baicalein and chrysin up-regulated TGF-beta 1 gene expression on RAW 264.7 cells in a concentration-dependent manner. However, the flavonoid of SbG, wogonin, did not up-regulate TGF-beta 1 expression on gene and protein levels on RAW264.7 cells. The facts that aspirin and H7 but not PD98059 and SB203580 blocked the enhancing effect suggested that NF-kappa B and PKC might be involved in baicalin-enhanced TGF-beta 1 gene expression. We conclude that SbG up-regulates TGF-beta 1 gene expression on RAW264.7 cells through NF-kappa B and PKC pathways and this might provide evidence to explain the therapeutic effect and potential adverse effects on the clinical use of Scutellaria baicalensis Georgi.