Procaterol Upregulates Peroxisome Proliferator-Activated Receptor-γ Expression in Human Eosinophils

Abstract

Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor that regulates immune reaction. We have previously demonstrated that human eosinophils express PPARγ and that stimulation with a synthetic agonist for PPARγ attenuated the factor-induced eosinophil activations. However, the modulator of PPARγ expression in eosinophils has not yet been studied. In this study, we investigated the effect of procaterol, the synthetic β₂-adrenoceptor agonist widely used as bronchodilators in asthma, on the PPARγ expression in eosinophils. Purified human peripheral blood eosinophil and the eosinophilic cell line EoL-1 were cultured with procaterol. This was followed by PPARγ measurement using flow cytometer and quantitative real-time RT-PCR. We observed that PPARγ was constitutively expressed by EoL-1 and the purified eosinophils and that the therapeutic concentration (10^–9M) of procaterol markedly enhanced PPARγ protein expression, which was reversed by the selective β₂-adrenoceptor antagonist ICI-118551. The PPARγ mRNA expression in EoL-1 and eosinophils was also induced by procaterol. These findings suggest that procaterol could modulate the eosinophil function by increasing the expression of PPARγ.