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.

Anti- and Proinflammatory Effects of 15-Deoxy-Δ^12,14-Prostaglandin J₂(15d-PGJ₂) on Human Eosinophil Functions

“…One explanation for this PPARγ up-regulation is the reflection of an inflammatory response, which is consistent with the findings of previous studies [30, 31]. However, the PPARγ expression in eosinophils was unaltered on stimulation with IL-5, which is a major eosinophil-activating cytokine that is produced abundantly at allergic inflammatory sites [26]; further, it showed no correlation with the activation marker CD25 or eosinophilic cationic proteins in serum [32]. Recent studies in our laboratory indicated that de novo synthesis of PPARγ was induced in human eosinophils by culturing them along with drugs such as β-adrenoceptor agonist or theophylline at therapeutic concentrations [26, 33].…”

“…To date, three mammalian PPAR subtypes that are encoded by separate genes have been identified – α, β (also termed δ), and γ. PPARγ is expressed by human hemopoietic cells such as monocytes, macrophages, dendritic cells, lymphocytes, and mast cells [25]. Human peripheral blood eosinophils constitutively expressed PPARγ [25, 26] that is predominantly located in the cytosol [27]. It has been shown that PPARγ undergoes nuclear translocation upon ligand activation [28].…”

“…However, the PPARγ expression in eosinophils was unaltered on stimulation with IL-5, which is a major eosinophil-activating cytokine that is produced abundantly at allergic inflammatory sites [26]; further, it showed no correlation with the activation marker CD25 or eosinophilic cationic proteins in serum [32]. Recent studies in our laboratory indicated that de novo synthesis of PPARγ was induced in human eosinophils by culturing them along with drugs such as β-adrenoceptor agonist or theophylline at therapeutic concentrations [26, 33]. Therefore, an alternative explanation is that these drugs might augment PPARγ expression in asthmatic subjects.…”

Regulation of Peroxisome Proliferator-Activated Receptor-γ Expression in Human Eosinophils by Estradiol

“…Although the influence of estradiol on cell function was previously assigned exclusively to genomic reaction, it is known that estradiol activates the membrane form of ER and can rapidly induce intracellular cyclic AMP (cAMP) elevation [24]. Recently, we found that the bronchodilators theophylline and procaterol upregulated PPARγ mRNA and protein expression in eosinophils [15, 16]. Because the functions of these drugs are mediated through cAMP signaling, elevated cAMP in eosinophils might play a role in augmentation of PPARγ expression.…”

“…Flow cytometry was used for studying the protein expression of PPARγ as previously described [15, 16]. Purified eosinophils were washed twice with PBS and then permeabilized with FIX & PERM (Caltag Lab., San Francisco, Calif., USA).…”