Ethanol extract of Adiantum capillus-veneris L. suppresses the production of inflammatory mediators by inhibiting NF-κB activation

Ethnopharmacological relevance: Adiantum capillus-veneris L. is a wildly distributed plant species and has been extensively used in south of China as traditional folk medicine for the treatment of inflammatory diseases. Aim of the study: To investigate the anti-inflammatory effect of ethanolic extracts of Adiantum capillus-veneris L. and the involvement of NF-kappa B signaling in the regulation of inflammation. Materials and methods: The plant ethanolic extracts were initially tested against lipopolysaccharide (LPS)-induced prostaglandin E-2 (PGE(2)) production in RAW264.7 mouse macrophages, and interleukin 6 (IL-6) and tumor necrosis factor (TNF) production in human U937 monocytes. The effect of the plant extracts on the transcription factor nuclear factor kappa B (NF-kappa B) pathway was evaluated in TNF-alpha stimulated HepG2 cells by luciferase gene reporter assay and Western blotting at the transcriptional and translational levels. Subsequently, the inhibition of NF-kappa B downstream gene expression (IL-8 and ICAM-1) by the plant extracts was assessed via quantitative real time polymerase chain reaction (qPCR). Lastly, the anti-inflammatory activities of the plant extracts in vivo were evaluated by testing spleen index and NF-kappa B related protein expression in LPS-stimulated CD1 mice. Results: The plant ethanolic extracts effectively suppressed PGE(2), IL-6 and TNF release with an IC50 less than 50 mu g/ml. Moreover, luciferase expression could be specifically blocked in HepG2 cells, not in HEK293 cells, showing that the plant extracts displayed a cell-specific pattern on NF-kappa B gene transcription. The assayed biological activity also depended on the order of adding TNF-alpha and the plant extracts because the plant extracts could only block the NF-kappa B activation if added earlier but were unable to stop the signal when added after TNF-alpha. However, the plant extracts did not exert any effect on ubiquitination which regulates several steps in the NF-kappa B pathway. Additionally, the plant extracts down-regulated phosphorylation of IKK alpha/beta at S176/180, p38 at T180/Y182 and p65 at S536, but not p65 at S276. This was confirmed by their ability to selectively abrogate the induction of IL-8 transcription, whereas the ICAM-1 gene, which is not transcribed selectively by an NF-kappa B complex containing a form of p65 phosphorylated on Ser536, did not change. Finally, the plant extracts at 200 mu g/mg could normalize the LPS-induced elevation of spleen index as well as NF-kappa B and p38 activations in CD1 mice. Conclusion: The present studies presents the potential utilization of this plant extracts, as a natural resources for the development of an anti-inflammatory medicine. (c) 2013 Published by Elsevier Ireland Ltd.