Herbal extracts that induce type I interferons through Toll-like receptor 4 signaling

Misa Nakasuji-Togi; Sumihito Togi; Keita Saeki; Yasuhiko Kojima; Keiko Ozato

doi:10.29219/fnr.v66.5524

Herbal extracts that induce type I interferons through Toll-like receptor 4 signaling

Food Nutr Res. 2022 Jan 28:66. doi: 10.29219/fnr.v66.5524. eCollection 2022.

Authors

Misa Nakasuji-Togi^{1

2

3}, Sumihito Togi^{1

4

5}, Keita Saeki¹, Yasuhiko Kojima⁶, Keiko Ozato¹

Affiliations

¹ Division of Developmental Biology, Eunice Kennedy Institute of Child Health and Human Development, National Institutes of Health, MD, USA.
² Department of Regenerative Medicine, School of Medicine, Kanazawa Medical University, Ishikawa, Japan.
³ Center for Regenerative Medicine, Kanazawa Medical University Hospital, Ishikawa, Japan.
⁴ Division of Genomic Medicine, Department of Advanced Medicine, Medical Research Institute, Kanazawa Medical University, Ishikawa, Japan.
⁵ Center for Clinical Genomics, Kanazawa Medical University Hospital, Ishikawa, Japan.
⁶ NPO Interferon Herb Research Institute, Tokyo, Japan.

Abstract

Background: A mixture of five herbal extracts called internatural (INT), which is prepared from pumpkin seeds, purple turmeric, pearl barley, corn pistil, and cinnamon, is widely used by people in Japan and elsewhere for its immunity-enhancing effects and general health. Although anecdotal evidence indicates its efficacy, the mechanisms by which INT boosts immunity have remained unknown.

Objective: The aim of this study was to investigate whether INT induces type I interferons (IFNs) in murine bone marrow-derived macrophages (BMDMs) and by what mechanism.

Design: We measured induction of type I IFNs (IFNβ and IFNα) in BMDMs treated with INT or other Toll-like receptor ligands: bacterial lipopolysaccharides (LPS), dsRNA, poly(I:C), and CpG oligonucleotides. To investigate whether INT signals through Toll-like receptor 4 (TLR4), we tested TLR4-specific inhibitor. We also tested if INT utilizes TLR4 adaptors, toll/IL-1 receptor (TIR) domain-containing adaptor (TRIF), or myeloid differentiation factor 88 (MyD88), we examined INT induction of IFNβ in TRIF-KO and MyD88-KO BMDMs. We then investigated whether INT provides an antiviral effect upon fibroblasts either directly or indirectly using the encephalomyocarditis virus (EMCV) model.

Results: We first observed that INT, when added to BMDMs, potently induces type I IFNs (IFNβ and IFNα) within 2 h. INT induction of IFN expression was mediated by TLR4, which signaled through the TRIF/MyD88 adaptors, similar to LPS. A high-molecular-weight fraction (MW > 10,000) of INT extracts contained IFN-inducing activity. Supernatants from INT-treated BMDMs protected untreated fibroblast from EMCV infection as reduced viral titers.

Conclusions: INT induced type I IFN mRNA and proteins in BMDMs and other cell types. This induction was mediated by TLR4, which transduces signals using the TRIF/MyD88 pathway. The high-MW component of INT contained type I IFN inducing activity. The supernatants from INT-treated cells displayed antiviral activity and protected cells from EMCV infection. These findings indicate that INT is a novel natural IFN inducer that strengthens host's innate immunity.

Keywords: Toll-like receptors; herbal medicine; interferon; macrophages; pathogen resistance.