Effect of Dietary Nucleosides and Nucleotides on Murine Allergic Rhinitis

Antiallergic Effects of N,N-dicoumaroylspermidine Isolated from Lithospermum erythrorhizon on Mast Cells and Ovalbumin-Induced Allergic Rhinitis

In East Asia, the dried root of Lithospermum erythrorhizon has been utilized as an anti-inflammatory, antipyretic, detoxifying, and anti-inflammatory agent. Recently, we reported that L. erythrorhizon protects against allergic rhinitis; however, the component within L. erythrorhizon that exerts antiallergic activity remains unknown. The purpose of the current study was to isolate and characterize the antiallergic active components in an ethanolic extract of L. erythrorhizon roots. We examined the antiallergic effects of L. erythrorhizon reflux ethanol extracts in an ovalbumin (OVA)-induced allergic rhinitis mouse model, and compared the chemical compounds extracted using the hot reflux and cold extraction methods. Chromatographic separation identified two novel anthraquinones, erythrin A and B, one newly discovered compound from the Lithospermum genus, N1″,N3″-dicoumaroylspermidine, and nineteen other recognized compounds. Their chemical structures were elucidated by single (1D) and 2D analysis of nuclear magnetic resonance (NMR) spectroscopic data, as well as high resolution mass spectrometry. Among the identified compounds, N,N′-dicoumaroylspermidine strongly inhibited the release of β-hexosaminidase, as well as the production of IL-3, IL-4, and IL-13 by IgE-sensitized and BSA-stimulated RBL-2H3 cells. Using the OVA-induced allergic rhinitis mouse model, we showed that N,N′-dicoumaroylspermidine reduced the production of serum OVA-specific IgE and the number of inflammatory cells in nasal lavage fluid. N,N′-dicoumaroylspermidine isolated from L. erythrorhizon exhibits antiallergic properties, making it potentially effective for allergic rhinitis.

Roots of Lithospermum erythrorhizon Alleviated Ovalbumin-Induced Allergic Rhinitis and IgE-triggered Degranulation of RBL-2H3 Cells

Lithospermum erythrorhizon (L. erythrorhizon) root is used in traditional medicine for its anti-inflammatory, antibacterial, and antioxidant properties. However, no studies have examined its impact on allergic rhinitis (AR). Here, we explored the protective effects of L. erythrorhizon in immunoglobulin E (IgE)-stimulated RBL-2H3 cells and in an ovalbumin (OVA)-induced AR mouse model. In the latter, we examined nasal mucosal inflammation, allergen-specific cytokine production, and histological changes to the nasal mucosa. In the mouse model, oral administration of an ethanol extract of L. erythrorhizon (LE) led to a marked reduction in rubbing and sneeze frequency, a significant decrease in serum OVA-specific IgE and IgG1 levels, and a significant increase in the IgG2a/IgG1 ratio. LE also reduced expression of interleukin (IL)-4, IL-5, and IL-13 in nasal lavage fluid (NALF), and suppressed inflammatory cell infiltration and epithelial degradation in nasal tissues. In IgE-stimulated RBL-2H3 cells, LE suppressed release of degranulation markers such as β-hexosaminidase and histamine. Based on these findings, we suggest that LE may ameliorate OVA-induced AR by regulating mast cell-mediated inflammatory responses.

Dietary ribonucleotides modulate type 1 and type 2 T-helper cell responses against ovalbumin in young BALB/cJ mice

Dietary ribonucleotides have been shown to augment type 1 T-helper cell (Th1) responses to a protein antigen (Ag) in Th1-prone C57BL/6 mice, but their effects on type 2 Th (Th2)-prone mice are unknown. BALB/cJ mice have skewed Th2 responses against ovalbumin (OVA), characterized by augmented production of Th2 cytokines and immunoglobulin (Ig)G1/IgE antibodies (Ab); Th1 responses augment IgG2a Ab production, whereas Th2 responses augment IgG1/IgE Ab production. In this study, we determined the effects of dietary ribonucleotides obtained from yeast on the balance of Th1/Th2 responses against OVA in young BALB/cJ mice. Mice were fed a ribonucleotide-free (NF) or ribonucleotide-supplemented (NS) diet (4.74 g nucleotides/kg diet) and given OVA (10 microg/dose) with incomplete Freund's adjuvant (IFA) at 3 and 6 wk. We assessed T-cell responses in the regional draining lymph nodes (LN) by measuring production and expression of Th1/Th2 cytokines, interferon-gamma (IFN-gamma) and interleukin-5 (IL-5), respectively. Anti-OVA IgG subclass and IgE Ab levels were determined 3 wk after the first OVA challenge and 5 d and 2 wk after the second OVA challenge. Dietary ribonucleotides significantly augmented OVA-specific IFN-gamma production by the regional draining LN cells after the first and second OVA challenges. The NS diet increased anti-OVA IgG2a Ab levels after the first OVA challenge and both anti-OVA IgG2a and anti-OVA IgG2b after the second challenge. OVA-specific IgG1 and IgE Ab levels were lower (P < 0.05) after the second OVA challenge in mice fed the NS diet. Dietary ribonucleotides did not affect production or expression of IL-5. Our findings thus indicate that in Th2-prone BALB/c J mice, dietary ribonucleotides modulated skewed Th2 responses against OVA toward Th1 as measured by production of IFN-gamma, a Th1 cytokine, and changes in anti-OVA Ab isotype levels.