Effects of stingless bee propolis on experimental asthma

Abstract

Bee products have been used empirically for centuries, especially for the treatment of respiratory diseases. The present study evaluated the effect of treatment with a propolis hydroalcoholic extract (PHE) produced by Scaptotrigona aff. postica stingless bee in a murine asthma model. BALB/c mice were immunized twice with ovalbumin (OVA) subcutaneously. After 14 days, they were intranasally challenged with OVA. Groups P50 and P200 received PHE by gavage at doses of 50 and 200 mg/kg, respectively. The DEXA group was treated with intraperitoneal injection of dexamethasone. The OVA group received only water. The mice were treated daily for two weeks and then they were immunized a second time with intranasal OVA. The treatment with PHE decreased the cell number in the bronchoalveolar fluid (BAL). Histological analysis showed reduced peribronchovascular inflammation after treatment with PHE especially the infiltration of polymorphonuclear cells. In addition, the concentration of interferon- γ (IFN- γ ) in the serum was decreased. These results were similar to those obtained with dexamethasone. Treatment with S. aff postica propolis reduced the pathology associated with murine asthma due an inhibition of inflammatory cells migration to the alveolar space and the systemic progression of the allergic inflammation.

Figure 1

Effect of treatment with Scaptotrigona aff. postica PHE on the number of cells present in the BAL of mice immunised and challenged with OVA. Mice in groups P50 and P200 were treated orally with PHE (50 or 200 mg/kg/animal) for 14 consecutive days. The DEXA group was treated i.p. with DEXA (1 mg/kg/animal) for 14 consecutive days. The OVA group received only oral saline solution. Total (a) and differential (b) cell counts of BAL were performed 24 hours after the last challenge. *P < 0.05 compared with the OVA group.

Figure 2

Lung histopathological sections of BALB/c mice stained with haematoxylin/eosin. Mice were immunised on days 0 and 7 with sc. injections of 4 μg OVA/1.6 mg alum. On days 14 and 21, the mice were challenged by in. with 10 μg OVA. The experiments were conducted 24 hours after the last challenge. Two magnifications were given (400 and 100x) to the clean control (a), OVA-immunised (b), DEXA-treated (c), and PHE-treated groups at 50 mg/kg (d) or 200 mg/kg (e). Arrows indicate areas of inflammation.

Figure 3

Effect of S. aff postica PHE treatment on circulating serum IFN-γ of mice immunised and challenged with OVA. The mice in groups P50 and P200 were treated orally with PHE (50 or 200 mg/kg/animal) for 14 consecutive days. The DEXA group was treated i.p. with DEXA (1 mg/kg/animal) for 14 consecutive days. The OVA group received only oral saline solution. The experiments were performed 24 hours after the last challenge.  *P ≤ 0.05 compared to the OVA group.

Figure 4

Effect of S. aff postica PHE treatment on cellular influx to the peritoneal cavity and lymphoid organs of mice immunised and challenged with OVA correspond to bone marrow (a), lymph node (b), and spleen cells (c), respectively. The cells of the peritoneal cavity were harvested and counted to assess cell migration (d). The experiments were performed 24 hours after the last challenge.*P ≤ 0.05 compared to the OVA group.