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18β-Glycyrrhetinic Acid Delivered Orally Induces Isolated Lymphoid Follicle Maturation at the Intestinal Mucosa and Attenuates Rotavirus Shedding

Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, United States of America.
PLoS ONE (Impact Factor: 3.53). 11/2012; 7(11):e49491. DOI: 10.1371/journal.pone.0049491
Source: PubMed

ABSTRACT Glycyrrhizin, an abundant bioactive component of the medicinal licorice root is rapidly metabolized by gut commensal bacteria into 18β-glycyrrhetinic acid (GRA). Either or both of these compounds have been shown to have antiviral, anti-hepatotoxic, anti-ulcerative, anti-tumor, anti-allergenic and anti-inflammatory activity in vitro or in vivo. In this study, the ability of GRA to modulate immune responses at the small intestinal mucosa when delivered orally was investigated. Analysis of cytokine transcription in duodenal and ileal tissue in response to GRA treatment revealed a pattern of chemokine and chemokine receptor gene expression predictive of B cell recruitment to the gut. Consistent with this finding, GRA induced increases in CD19(+) B cells in the lamina propria and B220(+) B cell aggregates framed by CD11c(+) dendritic cells in structures resembling isolated lymphoid follicles (ILF). Using a mouse model of rotavirus infection, GRA reduced the duration of viral antigen shedding, and endpoint serum antibody titers were higher in GRA-treated animals. Together the data suggest GRA delivered orally augments lymphocyte recruitment to the intestinal mucosa and induces maturation of B cell-rich ILF independently of ectopic antigenic stimulus. These results provide further support a role for dietary ligands in modulation of dynamic intestinal lymphoid tissue.

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    ABSTRACT: ETHNOPHARMACOLOGICAL RELEVANCE: Licorice has been extensively used in traditional medicines for treatment of many diseases, including inflammations and immunological disorders. Recent studies have shown that the anti-inflammatory and immunomodulation activities of licorice have been attributed to its active component, glycyrretinic acid (GA). GA consists of two isoforms, 18α- and 18β-. However, its mechanism remains poorly understood. AIM OF THE STUDY: We compared the effects of two isoforms on Kv1.3 channels in Jurkat T cells and further characterized the inhibition of Kv1.3 channels by 18β-GA in CHO cells. In addition we examined the effects of 18β-GA on Kv1.3 gene expression, Ca(2+) influx, proliferation, as well as IL-2 production in Jurkat T cells. MATERIALS AND METHODS: Whole-cell patch-clamp technique was applied to record Kv1.3 currents in Jurkat T or CHO cells. Real-time PCR and Western blotting were used to detect gene expression. Fluo-4, CCK-8 kit and ELISA kit were used to measure Ca(2+) influx, proliferation, and IL-2 secretion in Jurkat T cells, respectively. RESULTS: Superfusion of 18β-GA (10-100µM) blocked Kv1.3 currents in Jurkat T cells, while 18α-GA at the same concentration had no effects. The 18β-GA induced inhibition followed a voltage- and concentration-dependent manner with an IC50 of 23.9±1.5µM at +40mV in CHO cells. Furthermore, 18β-GA significantly inhibited Kv1.3 gene expression. In addition, paralleling Kv1.3 inhibition, 18β- GA also inhibited Ca(2+) influx, proliferation as well as IL-2 production in Jurkat T cells. CONCLUSION: 18β-GA blocks Kv1.3 channels, which probably involves its anti-inflammatory and immunomodulation effects.
    Journal of ethnopharmacology 05/2013; DOI:10.1016/j.jep.2013.05.022 · 2.32 Impact Factor
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    ABSTRACT: 18β-glycyrrhetinic acid (GRA) is a pharmacologically active component of licorice root with documented immunomodulatory properties. We reported that GRA administered orally to mice induces B cell recruitment to isolated lymphoid follicles (ILF) in the small intestine and shortens the duration of rotavirus antigen shedding. ILF are dynamic lymphoid tissues in the gut acquired post-natally upon colonization with commensal bacteria and mature through B cell recruitment to the follicles, resulting in up-regulation of IgA synthesis in response to changes in the composition of microbiota. In this study, we investigated potential mechanisms by which GRA induces ILF maturation in the ileum and the colon using mice depleted of enteric bacteria and a select group of mice genetically deficient in pattern recognition receptors. The data show GRA was unable to induce ILF maturation in ileums of mice devoid of commensal bacteria, MyD88-/- or NOD2-/- mice, but differentially induced ILF in colons. Increased expression of chemokine and chemokine receptor genes that modulate B and T cell recruitment to the mucosa were in part dependent on NOD2, TLR, and signaling adaptor protein MyD88. Together the results suggest GRA induces ILF through cooperative signals provided by bacterial ligands under normal conditions to induce B cell recruitment to ILF to the gut, but that the relative contribution of these signals differ between ileum and colon.
    PLoS ONE 07/2014; 9(7):e100878. DOI:10.1371/journal.pone.0100878 · 3.53 Impact Factor
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