Onion Bulb Extract Inhibits Airway Inflammation in a Mouse Model of Allergic Asthma

Abstract

Asthma represents a global health challenge. The main pharmacotherapy is synthetic. Additionally, chemical and biological-based drugs are costly and have significant side effects. In contrast, the use of natural products, such as onions (Allium cepa L., Amaryllidaceae), in the treatment of airway diseases has increased worldwide because of few safety concerns and their perceived efficacy. However, their pharmacological actions remain largely uncharacterized. This research investigates whether onion bulb extract (OBE) can 1) prevent the development of the asthma phenotype (preventative treatment approach) and/or 2) reverse the established asthma phenotype (therapeutic treatment approach). Male Balb/c mice were used throughout the study. Two protocols were used: a therapeutic (21 days) and a preventative (19 days) treatment protocol. PBS and house dust mites (HDM)-challenged mice treated with vehicle or OBE (30, 60, and 100 mg/kg i.p.). Preventative (100 mg/kg i.p.), therapeutic (60 mg/kg i.p.), and OBE treatments resulted in a down-regulation of HDM-induced airway cellular influx, histopathological changes, and an increase in the expression of pro-inflammatory signaling pathways (EGFR, ERK1/2, AKT, pro-inflammatory cytokines, and serum IgE). The presented data show that OBE is an effective anti-inflammatory agent with preventative and therapeutic anti-asthma effects. These findings imply that onion or OBE may be used as an adjunct therapeutic agent for established asthma and/or to prevent the development of allergic asthma. However, further studies are needed to identify the active constituents and demonstrate proof-of-concept in humans.