Piperine inhibits eosinophil infiltration and airway hyperresponsiveness by suppressing T cell activity and Th2 cytokine production in the ovalbumin-induced asthma model

Objectives This study aimed to investigate the effect of piperine on airway hyper-responsiveness, pulmonary eosinophilic infiltration, various immune cell phenotypes, Th2 cytokine production, immunoglobulin E and histamine production in a murine model of asthma. Methods Asthma was induced in Balb/c mice by ovalbumin sensitization and inhalation. Piperine (4.5 and 2.25 mg/kg) was orally administered 5 times a week for 8 weeks. At 1 day after the last ovalbumin exposure, airway hyperresponsiveness was determined and samples of bronchoalveolar lavage fluid, lung cells and serum were collected for further analysis. Key findings Piperine-treated groups had suppressed eosinophil infiltration, allergic airway inflammation and airway hyperresponsiveness, and these occurred by suppression of the production of interleukin-4, interleukin-5, immunoglobulin E and histamine. Moreover, polymerase chain reaction products for thymus and activation regulated chemokine from lung cell RNA preparations were decreased in the piperine-treated group compared with control groups, although transforming growth factor-β products were increased in the piperine-treated group. Conclusions The results suggest that the therapeutic mechanism by which piperine effectively treats asthma is based on a reduction of Th2 cytokines (interleukin-4, interleukin-5), eosinophil infiltration, and by marked reduction of thymus and activation regulated chemokine, eotaxin-2 and interleukin-13 mRNA expression (especially transcription of nuclear factor-β dependent genes) in lung tissue, as well as reduced interleukin-4, interleukin-5 and eotaxin levels in bronchoalveolar lavage fluid, and histamine and ovalbumin-specific immunoglobulin E production in serum.