Peroxisome proliferator-activated receptor-gamma (PPAR gamma) is a nuclear receptor that regulates immune reaction. We have previously demonstrated that human eosinophils express PPAR gamma and that stimulation with a synthetic agonist for PPAR gamma attenuated the factor-induced eosinophil activations. However, the modulator of PPAR gamma expression in eosinophils has not yet been studied. In this study, we investigated the effect of procaterol, the synthetic beta(2)-adrenoceptor agonist widely used as bronchodilators in asthma, on the PPAR gamma expression in eosinophils. Purified human peripheral blood eosinophil and the eosinophilic cell line EoL-1 were cultured with procaterol. This was followed by PPAR gamma measurement using flow cytometer and quantitative real-time RT-PCR. We observed that PPAR gamma was constitutively expressed by EoL-1 and the purified eosinophils and that the therapeutic concentration (10(-9) M) of procaterol markedly en-hanced PPAR-gamma protein expression, which was reversed by the selective beta(2)-adrenoceptor antagonist ICI-118551. The PPAR-gamma 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 PPAR gamma. Copyright (c) 2006 S. Karger AG, Basel.