Glycyrrhizin improves the pathogenesis of psoriasis partially through IL-17A and the SIRT1-STAT3 axis.

BACKGROUND: The anti-inflammatory effect of glycyrrhizin has been widely recognized, while the specific mechanism of glycyrrhizin in psoriasis remains poorly understood. RESULTS: In the imiquimod-induced mouse model of psoriasis (IMD), we found that glycyrrhizin can substantially improve the adverse symptoms in mice. The hematoxylin-eosin staining results showed that glycyrrhizin can also improve the pathological state of skin cells in IMD mice. Using enzyme-linked immunosorbent assay (ELISA), we found that glycyrrhizin substantially inhibited the expression of IL-17A and IFN-γ in the serum of IMD mice. In order to simulate the effect of IL-17A on keratinocytes in psoriasis, we treated HaCaT cells with 100 ng/mL IL-17A (IL-17A-HaCaT cells) for 48 h. Then, using cell-counting kit-8 (CCK-8) and ELISA assays, we found that glycyrrhizin inhibited the proliferation of IL-17A-HaCaT cells and reversed the promotion of IL-6, CCL20, and TNF-α induced by IL-17A. Further, western blotting (WB) results indicated that glycyrrhizin promoted the expression of SIRT1 and inhibited the expression of STAT3 and phosphorylated STAT3 (p-STAT3). By treating IL-17A-HaCaT cells with EX-527 (a potent and selective inhibitor of SIRT1), combined with CCK-8 and WB experiments, we initially found that EX-527 inhibited the proliferation of IL-17A-HaCaT cells and promoted the expression of STAT3, p-STAT3, and acetylated STAT3 (a-STAT3). However, when glycyrrhizin was added at the same time, the proliferation of IL-17A-HaCaT cells increased, and the expression of STAT3, p-STAT3, and a-STAT3 reduced. We then knocked down the expression of SIRT1 via small interfering RNA in IL-17A-HaCaT cells, and the results were consistent with those of EX-527. CONCLUSIONS: Together, these results indicated that glycyrrhizin improved psoriasis by inhibiting the expression of IL-17A and IFN-γ in vivo and suppressed the proliferation of IL-17A-HaCaT cells and the expression of STAT3, p-STAT3, and a-STAT3 by upregulating SIRT1 in vitro.

The Effect of Flavored E-cigarettes on Murine Allergic Airways Disease.

Flavored e-cigarettes are preferred by the majority of users yet their potential toxicity is unknown. Therefore our aim was to determine the effect of selected flavored e-cigarettes, with or without nicotine, on allergic airways disease in mice. Balb/c mice were challenged with PBS or house dust mite (HDM) (Days 0, 7, 14-18) and exposed to room air or e-cigarette aerosol for 30 min twice daily, 6 days/week from Days 0-18 (n = 8-12/group). Mice were exposed to Room Air, vehicle control (50%VG/%50PG), Black Licorice, Kola, Banana Pudding or Cinnacide without or with 12 mg/mL nicotine. Mice were assessed at 72 hours after the final HDM challenge. Compared to mice challenged with HDM and exposed to Room Air, nicotine-free Cinnacide reduced airway inflammation (p = 0.045) and increased peripheral airway hyperresponsiveness (p = 0.02), nicotine-free Banana Pudding increased soluble lung collagen (p = 0.049), with a trend towards increased airway inflammation with nicotine-free Black Licorice exposure (p = 0.089). In contrast, all e-cigarettes containing nicotine suppressed airway inflammation (p < 0.001 for all) but did not alter airway hyperresponsiveness or airway remodeling. Flavored e-cigarettes without nicotine had significant but heterogeneous effects on features of allergic airways disease. This suggests that some flavored e-cigarettes may alter asthma pathophysiology even when used without nicotine.

Adjuvant activity of multimolecular complexes based on Glycyrrhiza glabra saponins, lipids, and influenza virus glycoproteins.

Numerous studies have shown that immunostimulatory complexes containing Quil-A saponin and various antigens are effective in stimulating the immune response and can be used as vaccine preparations for animals and humans. However, Quil-A saponin possesses toxicity and haemolytic activity. In the present work, a saponin-containing preparation named "Glabilox" was isolated from the roots of a Glycyrrhiza glabra L. plant by high-performance liquid chromatography (HPLC). The results showed that Glabilox has no toxicity or haemolytic activity and can form stable immunostimulatory complexes. Subcutaneous immunization of mice with an immunostimulating complex containing Glabilox and H7N1 influenza virus antigens stimulated high levels of humoral and cellular immunity. Vaccination of chickens with the same immunostimulating complex protected 100% of the animals after experimental infection with a homologous virus. Comparative studies showed that the immunogenic and protective activity of immunostimulatory complexes containing Quil-A and immunostimulatory complexes containing Glabilox are comparable to each other. The results of these studies indicated that Glycyrrhiza glabra saponins show great promise as safe and effective adjuvants.

Licochalcone A activates Keap1-Nrf2 signaling to suppress arthritis via phosphorylation of p62 at serine 349.

Licochalcone A (LCA) is derived from glycyrrhizae radix with antimicrobial, antitumor and anti-inflammatory activities. However, the anti-arthritic function of LCA and underlying mechanism has not been yet explored. The current study investigated the anti-arthritic effect of LCA and elucidated the underlying mechanism. The results showed that LCA significantly suppressed arthritis via the activation of SQSTM1 (p62)/nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling in the collagen-induced arthritis (CIA) model of DBA mice. In coincided with the results, this anti-arthritic effect of LCA was remarkably diminished in the collagen antibody-induced arthritis (CAIA) model of Nrf2-/- mice. These findings indicate that p62/Nrf2 signaling is a crucial pathway for the induction and treatment of arthritis. To further validate the effect of LCA on the arthritis, rheumatoid arthritis synovial fibroblasts (RASFs) isolated from the synovium of RA patients were employed in the study. In coincided with in vivo results, LCA inhibited the cell proliferation and arrested the cell cycle, induced apoptosis, suppressed pro-inflammatory cytokine secretion and increased expression of antioxidant enzymes via the activation of Keap1-Nrf2 signaling by enhancing p62 phosphorylation and expression, Nrf2 accumulation and Nrf2 nucleus translocation. Findings in the current study provide evidence that p62-Keap1-Nrf2 axis is a pivotal signaling pathway in development of arthritis and therapeutic efficacy of drugs, and LCA activates of Keap1-Nrf2 signaling to suppress arthritis by phosphorylation of p62 at Ser349. Collectively, LCA is valuable to be further investigated as a lead compound for application in anti-arthritis, and interference with the interaction between Nrf2 and Keap1 by phosphorylation of p62 may be a promising strategy for the discovery of anti-arthritic agents.

Glycyrrhetinic acid prevents acetaminophen-induced acute liver injury via the inhibition of CYP2E1 expression and HMGB1-TLR4 signal activation in mice.

Acetaminophen (APAP) is a widely used antipyretic and analgesic drug, which is safe and effective at the therapeutic dose. Unfortunately, excessive dosage of APAP could cause severe liver injury due to lack of effective therapy. Successful therapeutic strategies are urgently requested in clinic. Glycyrrhetinic acid (GA), derived from a traditional medicine licorice, has been shown to exert anti-inflammatory and antioxidant actions. In this study, the effect and the underlying mechanism of GA on APAP-induced hepatotoxicity were explored. Our results showed that pretreatment with GA significantly reduced serum ALT and AST activities, alleviated hepatic pathological damages with hepatocellular apoptosis, down-regulated expression of CYP2E1 mRNA and protein, increased GSH levels, and reduced reactive oxygen species (ROS) productions in the liver of APAP-exposed mice. Furthermore, GA obviously inhibited APAP-induced HMGB1-TLR4 signal activation, as evaluated by reduced hepatic HMGB1 release, p-IRAK1, p-MAPK and p-IκB expression as well as the productions of TNF-α and IL-1ß. In addition, GA attenuated hepatic neutrophils recruitment and macrophages infiltration caused by APAP. These findings reflected that GA could alleviate APAP-induced hepatotoxicity, the possible mechanism is associated with down-regulation of CYP2E1 expression and deactivation of HMGB1-TLR4 signal pathway.

Glycyrrhizin ameliorates experimental colitis through attenuating interleukin-17-producing T cell responses via regulating antigen-presenting cells.

Glycyrrhizin, a component of Chinese medicine licorice root, has the ability to inhibit the functions of high-mobility group box 1 (HMGB1). While glycyrrhizin is known to have anti-inflammatory activities, the underlying mechanisms by which glycyrrhizin inhibits inflammation during the development of trinitrobenzenesulfonic acid (TNBS)-induced experimental colitis are not well understood. This study systemically examined the regulatory effects of glycyrrhizin on inflammatory response in TNBS-induced murine colitis and explored the potential mechanisms involved in this process. We reported that glycyrrhizin treatment ameliorated colitis and decreased the production of inflammatory mediators HMGB1, IFN-γ, IL-6, TNF-α, and IL-17. In addition, glycyrrhizin regulated responses of dendritic cells (DCs) and macrophages during the development of colitis. Furthermore, administration of glycyrrhizin suppressed the proliferation of Th17 cells in colitis. Moreover, the ability of DCs and macrophages to induce the differentiation of Th17 cells was enhanced in presence of HMGB1, which was inhibited by glycyrrhizin. These results demonstrated that glycyrrhizin alleviated colitis by inhibiting the promotive effect of HMGB1 on DC/macrophage-mediated Th17 proliferation. In conclusion, HMGB1 plays an important role in the development of colitis. As an inhibitor of HMGB1, glycyrrhizin might be a novel therapy for colitis.

Isoliquiritigenin ameliorates dextran sulfate sodium-induced colitis through the inhibition of MAPK pathway.

Isoliquiritigenin (isoLQ), a chalcone found in licorice, has shown a variety of biological activity including anti-inflammatory and antioxidative effects, and the distribution of isoLQ in gastrointestinal tract was higher than any other tissues. Thus, we evaluated whether or not isoLQ attenuated the dextran sulfate sodium (DSS)-induced colitis by observing the physiological changes (body weight loss, diarrhea, bleeding stool, overall disease activity index (DAI) scores, colon length), histopathological analysis and myeloperoxidase (MPO) activities of esophagus and colon. Also, the MAPK pathways including phosphorylation of ERK1/2, p38, and AKT, and the activation of NK-κB were evaluated in colon tissue. Interestingly, the reduction of body weight and colon length, increase of diarrhea, bloody stool, DAI scores and MPO activity, and histologic disturbances in DSS-induced colitis were recovered by isoLQ treatment. Also, isoLQ treatment suppressed the phosphorylation of ERK1/2 and p38, and the activation of NK-κB compared to those in DSS-induced colitis mice. In addition, the distributions of isoLQ in colon were relatively higher in DSS-induced colitis models. All of these results suggested that isoLQ has potential activity to ameliorate the DSS-induced colitis through the inhibition of MAPK pathway.

Licochalcones suppress degranulation by decreasing the intracellular Ca2+ level and tyrosine phosphorylation of ERK in RBL-2H3 cells.

Mast cells play a key role in allergic inflammation by releasing various mediators, such as histamine, serotonin, leukotrienes and cytokines. A signaling cascade of events activated by stimulation with antigens contributes to the regulation of mast cell degranulation. While various anti-inflammatory and anti-allergic drugs have been developed that inhibit degranulation of mast cells, the inhibitory mechanism has been poorly understood. Licochalcone A (Lico A) is a retrochalcone isolated from the root of Xinjiang liquorice and has been reported to exhibit various biological activities such as anti-inflammatory activity. We examined the effects of Lico A and related chalcones on degranulation in a rat basophilic leukemia cell line, RBL-2H3. Whereas Lico A and licochalcone C (Lico C) exhibited inhibitory activity with cytotoxicity, licochalcone D (Lico D) significantly inhibited the degranulation in RBL-2H3 cells with low cytotoxicity. Moreover, Lico D significantly inhibited the Ca2+ influx and phosphorylation of extracellular signal regulated kinase (ERK) and MEK. These results suggest that Lico D inhibits mast cell degranulation via the inhibition of both extracellular Ca2+ influx and activation of the MEK-ERK pathway.

Glycyrrhizin, the main active compound in liquorice, attenuates pro-inflammatory responses by interfering with membrane-dependent receptor signalling.

The triterpene glycoside glycyrrhizin is the main active compound in liquorice. It is used as a herbal medicine owing to its anticancer, antiviral and anti-inflammatory properties. Its mode of action, however, remains widely unknown. In the present study, we aimed to elucidate the molecular mechanism of glycyrrhizin in attenuating inflammatory responses in macrophages. Using microarray analysis, we found that glycyrrhizin caused a broad block in the induction of pro-inflammatory mediators induced by the TLR (Toll-like receptor) 9 agonist CpG-DNA in RAW 264.7 cells. Furthermore, we found that glycyrrhizin also strongly attenuated inflammatory responses induced by TLR3 and TLR4 ligands. The inhibition was accompanied by decreased activation not only of the NF-kappaB (nuclear factor kappaB) pathway but also of the parallel MAPK (mitogen-activated protein kinase) signalling cascade upon stimulation with TLR9 and TLR4 agonists. Further analysis of upstream events revealed that glycyrrhizin treatment decreased cellular attachment and/or uptake of CpG-DNA and strongly impaired TLR4 internalization. Moreover, we found that the anti-inflammatory effects were specific for membrane-dependent receptor-mediated stimuli, as glycyrrhizin was ineffective in blocking Tnfa (tumour necrosis factor alpha gene) induction upon stimulation with PMA, a receptor- and membrane-independent stimulus. These observations suggest that the broad anti-inflammatory activity of glycyrrhizin is mediated by the interaction with the lipid bilayer, thereby attenuating receptor-mediated signalling.