Anti-allergic effect of Cyclopia (honeybush) extracts via anti-degranulation activity in a murine allergy model for inhaled antigen

Abstract

The anti-allergic effects of extracts prepared from two species of honeybush, Cyclopia genistoides and Cyclopia subternata, were demonstrated in vivo in a murine allergy model for inhaled antigen induced with ovalbumin (OVA) inhalation to mimic pollen allergy. Intake of the extracts increased the production of OVA-specific immunoglobulin (Ig) E (IgE), IgG1, and IgG2a antibodies in serum and significantly suppressed anaphylactic reaction-induced body temperature decline. Moreover, the extracts significantly inhibited antigen-antibody-induced degranulation in RBL-2H3 cells. They also inhibited body temperature decline when the allergic mice were given them after antigen sensitization, indicating that anti-degranulation activity is the major mechanism underlying the anti-allergic effect of Cyclopia extracts. Despite their qualitative and quantitative differences in phenolic composition, the two extracts exhibited similar effects, suggesting that several active compounds might be involved in the activity. Therefore, oral administration of either Cyclopia extract potentially exerts a systemic anti-allergic effect, supporting the increased consumption of honeybush tea for general wellness and improved quality of life.

Keywords: Cyclopia; IgE; RBL-2H3 cell; anti-allergic activity; degranulation; honeybush; respiratory allergy model.

Fig. 1.

Effects of C. genistoides and C. subternata extracts on antigen challenge-induced body surface temperature decline in a murine allergy model for inhaled antigen. (a) Schematic diagram of the animal model protocol. DO11.10 mice inhaled an atomized ovalbumin (OVA)-containing solution for 6 weeks and concomitantly consumed the honeybush extracts (1 mg/mL) as drinking fluid throughout the experimental period. Four days after the last OVA inhalation, the OVA solution was injected into the abdominal cavity of each mouse, and the change in body surface temperature of the mouse’s abdomen was measured. The experiment was performed with five animals per group. (b) The results of the anaphylactic reaction were evaluated based on the decrease in body temperature. The results are expressed as the mean ± standard deviation. *Significant differences from the control group are indicated by p<0.05. The results are representative of two independent experiments.

Fig. 2.

Effects of C. genistoides and C. subternata extracts on ovalbumin (OVA)-specific antibody production in a murine allergy model for inhaled antigen. The DO11.10 mice were treated as described in Fig. 1. Briefly until the anaphylactic test, OVA-specific (a) IgE, (b) IgG1, and (c) IgG2a serum titers were measured for every week. The experiment was performed with five animals per group. The results are expressed as the mean ± standard deviation. *Significant differences from the control group are indicated by p<0.05. The results are representative of two independent experiments.

Fig. 3.

Inhibition of antigen-induced degranulation of RBL-2H3 cells by C. genistoides and C. subternata extracts. RBL-2H3 cells were stimulated by an anti-dinitrophenylhydrazine (DNP)–IgE antibody and DNP–HSA in the presence of the (a) C. subternata and (b) C. genistoides extracts. The degranulation rate was calculated by measuring β-hexosaminidase release from the cells. The experiment was performed using five wells per group. The results are expressed as the mean ± standard deviation. *Significant differences from the control group are indicated by p<0.05. The results are representative of three independent experiments.

Fig. 4.

Effects of C. genistoides and C. subternata extracts on antigen challenge-induced body surface temperature decline followed by extract treatment in a murine allergy model for inhaled antigen. (a) Schematic diagram of the animal model protocol. The DO11.10 mice inhaled an atomized ovalbumin (OVA)-containing solution for 4 weeks instead of 6 weeks, and after the last inhalation, the mice were treated with the extracts for 3 days. The mice were subsequently subjected to the anaphylactic test described in Fig. 1, and the changes in body surface temperature were measured. The experiment was performed with five animals per group. (b) The results of the anaphylactic reaction were evaluated based on the decrease in body temperature. The results are expressed as the mean ± standard deviation. *Significant differences from the control group are indicated by p<0.05. The results are representative of two independent experiments.

Fig. 5.

Differences in body surface temperature suppression levels between Figs. 1b and 4b. The area bounded by the horizontal axis and the line of each mouse in Figs. 1b and 4b was calculated, and the area ratios for the C. genistoides and C. subternata groups relative to the control group were calculated. The results were shown as mean of each group ± standard deviation.