Anti-allergic activity of glycyrrhizic acid on IgE-mediated allergic reaction by regulation of allergy-related immune cells

Abstract

Glycyrrhizic acid (GA), the major bioactive triterpene glycoside of glycyrrhiza, has been shown to possess a wide range of pharmacological properties, including anti-inflammatory and anti-viral properties. However, few studies have examined the anti-allergic activity and exact mechanism of action of GA. In the present work, the anti-allergic activity and possible mechanisms of action of GA on an immunoglobulin (Ig) E-mediated allergic reaction has been studied using three models of allergic reaction in vivo and in vitro. Active systemic allergic reaction in Balb/c mice showed that GA can suppress the increased level of IL-4 to restore the immune balance of T_H1/T_H2 cells in a dose-dependent manner. Additionally, GA attenuated significantly the B cells producing allergen-specific IgE and IgG₁ partly because of the low levels of T_H2 cytokines. Both passive cutaneous anaphylaxis in vivo and an RBL-2H3 cell-based immunological assay in vitro indicated that GA acted as a "mast cell stabilizer", as it inhibited mast cell degranulation and decreased vascular permeability by inhibiting the expression of Orai1, STIM1 and TRPC1, which blocked extracellular Ca²⁺ influxes. The current study suggests that GA may serve as an effective anti-allergic agent derived from food for the prevention and treatment of IgE-mediated allergic reaction.

Figure 1

GA attenuated clinical allergic symptoms and the variation of rectal temperature in Balb/c mice. ^* P < 0.05 as compared to the sensitization group (n = 5). (A) Schematic drawing representing the Balb/c mice active system food anaphylaxis protocols and doses used in this work. (B) Allergic symptom score and (C) The variation of rectal temperature (°C).

Figure 2

GA worked on T_H cells to modulate the T_H1/T_H2 subsets balance. ^* P < 0.05 as compared to the sensitization group (n = 5). (A) Concentration of IL-4 and (B) IFN-γ in spleen cells. (C) The ratio of IFN-γ and IL-4.

Figure 3

GA inhibited the production of OVA-specific IgE and IgG₁ from B cells. ^* P < 0.05 as compared to the sensitization group (n = 5). The level of OVA-specific (A) IgE and (B) IgG₁ in serum.

Figure 4

GA attenuated the vascular permeability by stabilizing mast cells. ^* P < 0.05 as compared to the saline control group (n = 5). (A) Schematic drawing representing the Balb/c mice passive cutaneous anaphylaxis protocols and doses used in this work. (B) Qualitative and (C) quantitative detection of the vascular permeability after Evan’s Blue Dye/DNP-HSA administration.

Figure 5

GA inhibited the degranulation of RBL-2H3 cells. ^* P < 0.05 as compared to the control group (n = 3). (A) WST-8 cell viability (%) assay for GA at various concentration (100, 500, 1000, 2000 μg/mL). (B) β-hexosaminidase release (%) of RBL-2H3 cells after GA treatment.

Figure 6

GA blocked the exCa²⁺ influx to stabilize RBL-2H3 through reducing calcium channel proteins expression. ^* P < 0.05, significantly different from control and ^# P < 0.05, significantly different from sensitization control without GA treatment (n = 3). (A) Effect of GA on [Ca²⁺]_i. (B) The mRNA relative expression of Orai1, STIM1, TRPC1 and IP3R. (C) The protein expression of calcium channel proteins.

Figure 7

The mechanism of anti-allergic effect of GA on the IgE-mediated allergic reaction.