Astragalus Root and Elderberry Fruit Extracts Enhance the IFN-β Stimulatory Effects of Lactobacillus acidophilus in Murine-Derived Dendritic Cells

Hanne Frøkiær,Gudrun Weiss,John Flanagan,Emilie Fromentin,Louise Henningsen,Alvin Ibarra,Marc Roller,Stine Broeng Metzdorff,Roland Lang

doi:10.1371/journal.pone.0047878

Hanne Frøkiær, Gudrun Weiss + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0047878

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Abstract

Many foods and food components boost the immune system, but little data are available regarding the mechanisms by which they do. Bacterial strains have disparate effects in stimulating the immune system. Indendritic cells, the gram-negative bacteria Escherichia coli upregulates proinflammatory cytokines, whereas gram-positive Lactobacillus acidophilus induces a robust interferon (IFN)-β response. The immune-modulating effects of astragalus root and elderberry fruit extracts were examined in bone marrow-derived murine dendritic cells that were stimulated with L. acidophilus or E. coli. IFN-β and other cytokines were measured by ELISA and RT-PCR. Endocytosis of fluorescence-labeled dextran and L. acidophilus in the presence of elderberry fruit or astragalus root extract was evaluated in dendritic cells. Our results show that both extracts enhanced L. acidophilus-induced IFN-β production and slightly decreased the proinflammatory response to E. coli. The enhanced IFN-β production was associated with upregulation of toll-like receptor 3 and to a varying degree, the cytokines IL-12, IL-6, IL-1β and TNF-α. Both extracts increased endocytosis in immature dendritic cells, and only slightly influenced the viability of the cells. In conclusion, astragalus root and elderberry fruit extracts increase the IFN-β inducing activity of L. acidophilus in dendritic cells, suggesting that they may exert antiviral and immune-enhancing activity.

Highlights

Foods and food components with immune-boosting activity are constantly sought after [1]
In the present study we aimed to investigate the immunomodulatory effect of astragalus root and elderberry fruit extracts in dendritic cells that were stimulated with L. acidophilus or E. coli
IL-12 (Figure 1A, 1B), TNF-a (Figure 2A, 2B) and IL-6 (Figure 2 E, 2F) levels increased in dendritic cells to the same extent on stimulation with E. coli and L. acidophilus

Summary

Introduction

Foods and food components with immune-boosting activity are constantly sought after [1]. Certain lactobacilli induce interferon (IFN)-b and interleukin (IL) production in dendritic cells, which leads to upregulation of type 1 helper T cells (Th1) [3].IFN-b induces IL-12, TLR3 and other genes that mediate viral defense—culminating in robust stimulation of the adaptive immune system [4]. In contrast to L.acidophilus, the gram-negative Escherichia coli strain Nissle 1917 leads to IL-12 production, albeit at lower levels, it does not induce significant IFN-b production or upregulation of viral defense genes [3]. Dendritic cells are model cells that can be used to assess the immune-modulating activities of food and food components. The responses that are generated in dendritic cells, with regard to surface marker expression and cytokine production, depend on the cellular events that are induced by specific microorganisms [9]

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