Elsevier

Journal of Functional Foods

Volume 37, October 2017, Pages 618-623
Journal of Functional Foods

Luteolin exerted less inhibitory effect on macrophage activation induced by Astragalus polysaccharide than by lipopolysaccharide

https://doi.org/10.1016/j.jff.2017.08.023Get rights and content

Highlights

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    Luteolin reduced NO level and iNOS gene level in RAP or LPS induced RAW264.7 cells.

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    Luteolin reduced cytokines level in LPS induced RAW264.7 cells.

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    Luteolin did not reduce cytokines level obviously in RAP induced RAW264.7 cells.

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    Luteolin inhibited NF-κB p65 and Akt activation in RAP induced RAW264.7 cells.

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    Luteolin did not inhibit MAPKs and IRF3 activation in RAP induced RAW264.7 cells.

Abstract

As a kind of food supplementary, polysaccharide-rich tonic herbs become more and more popular. However, little is known regarding the interaction between known active molecules with these polysaccharides. This study aims to investigate effects of luteolin on RAW264.7 cells induced by Astragalus polysaccharide RAP in comparison with lipopolysaccharide (LPS). The results showed that luteolin suppressed inflammatory meditors in LPS-induced RAW264.7 cells. While in the RAP-induced RAW264.7 cells, luteolin only decreased the NO production and iNOS gene expression, but only inhibit IL-6 at high concentration, and was ineffective in term of TNF-α. The results of western blot analysis suggested that luteolin only inhibited the phosphorylation of NF-κB p65 and Akt, but not MAPKs and IRF3 in RAP-induced RAW264.7 cells. Taken together, lutelion exerted less inhibitory effect on macrophage induced by RAP than by LPS. This study demonstrated the luteolin-containing foods may not strongly interfere the immunoregulation effect of polysaccharide RAP.

Section snippets

Induction

Flavonoids are a group of natural phenolic compounds having anti-inflammatory properties (Gerritsen et al., 1995, Kim et al., 1999, Wadsworth and Koop, 1999). Luteolin (3′,4′,5,7-tetrahydroxyflavone), as one of the well-studied flavonoid examples, is widely found in vegetables, fruits, and nuts, such as celery, broccoli, carrots, peppers, onion leaves, apple skins, peanuts and chrysanthemum flowers (Pandurangan & Esa, 2014). Accumulated evidences show that luteolin has multiple biological

Materials

LPS and griess reagent (modified) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Mouse TNF-alpha ELISA kit and IL-6 ELISA kit were purchased from eBioscience (San Diego, CA, USA). The antibody phos-P65, P65, phos-IRF3, IRF3, phos-AKT, AKT, phos–P38, P38, phos–JNK, JNK, GAPDH (Cell Signaling, Danvers, MA, USA) and phos–ERK, ERK (Santa Cruz Biotechnologies, Santa Cruz, CA), HRP-linked anti-mouse and anti-rabbit antibody were obtained from Santa Cruz. SYBR Select Master Mix for RT-PCR

Effect of luteolin on production of NO, TNF-α and IL-6 in RAP- and LPS-induced RAW264.7 cells

Stimulating the cells with RAP and LPS induced an increase in NO production from the basal level. The result showed luteolin could reduce the NO production in RAW264.7 cells induced by LPS, it is consistent with the previous reported. It also showed luteolin could inhibit production of NO at high concentration in RAW264.7 cells induced by RAP respectively (P < 0.05) (Fig. 1). The production of TNF-α and IL-6 in RAW264.7 cells was tested by ELISA assay. After LPS or RAP stimulated for 24 h, the

Discussion

This study presents an interesting finding regarding the difference between RAP and LPS. Although luteolin reduced NO production and iNOS gene expression in RAW264.7 cells induced by both RAP and LPS, and there is no significant difference in TNF-α and IL-6 production and gene expression between RAP and LPS alone treatment groups, luteolin did not inhibit the cytokines production and related gene expression in RAP-induced RAW264.7 cells. These results suggested that RAP, even exhibited some

Acknowledgments

This study was supported by HKSAR Innovation and Technology Fund (ITF), Tier 3, ITS/311/09, General Research Fund (12100615, 22100014), Health Medical Research Fund (11122531, 14150521), National Natural Sciences Foundation in China (81473341), and Hong Kong Baptist University (RC-start up grant, MPCF-001-2014/2015, RC-IRMS/14-15/06, FRG1/16-17/032 and FRG2/16-17/002).

Conflict of interest

The authors declare no conflict of interest.

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