Bromelain limits airway inflammation in an ovalbumin-induced murine model of established asthma

Allergic asthma continues to increase despite new pharmacological advances for both acute treatment and chronic-disease management. Asthma is a multifactorial disease process with genetic, allergic, infectious, environmental, and dietary origins. Researchers are investigating the benefits of lifestyle changes and alternative asthma treatments, including the ability of bromelain to inhibit inflammation. Bromelain is a commonly used, proteolytically active pineapple extract.

The present study intended to determine the ability of bromelain to reduce the inflammation of preexisting asthma via an ovalbumin (OVA)-induced murine model of allergic airway disease (AAD).

The research team designed a study examining the effects of bromelain in a control group of mice that received phosphate buffered saline (PBS) only and in an intervention group that received bromelain in PBS. Setting The study took place in the Department of Immunology at the University of Connecticut's School of Medicine, Farmington. Intervention The research team sensitized female C57BL/6J mice with intraperitoneal OVA/alum and then challenged them with OVA aerosolization for 10 consecutive days. On day 4, the team began administering daily doses of PBS to the control group (n = 10) and bromelain (6mg/kg) in PBS to the bromelain (intervention) group (n = 10).

The primary measures included bronchoalveolar lavage (BAL) cellular differential, cellular phenotype via flow cytometry, and lung histology. Additional outcomes included testing for serum cytokines and immunoglobulin.

Bromelain treatment of AAD mice (bromelain group) resulted in significant anti-inflammatory activity as indicated by reduced BAL total leukocytes (P < .05), eosinophils (P < .05), and cellular infiltrates via lung pathology (P < .005), as compared to the control group. In addition, bromelain significantly reduced BAL CD4+ and CD8+ T cells without affecting cell numbers in the spleen or hilar lymph node. The study found decreased interleukins IL-4, IL-12, IL-17, as well as IFN-α in the serum of bromelain-treated animals.

The results suggest that bromelain has a therapeutic effect in established AAD, which may translate into an effective adjunctive therapy in patients with similar conditions, such as allergic asthma, who have chosen to initiate treatment after the onset of symptoms.