Critical Role for T Cells in Sephadex-Induced Airway Inflammation: Pharmacological and Immunological Characterization and Molecular Biomarker Identification

Abstract

Intratracheal instillation of Sephadex particles is a convenient model for assessing the impact of potential anti-inflammatory compounds on lung eosinophilia thought to be a key feature in asthma pathophysiology. However, the underlying cellular and molecular mechanisms involved are poorly understood. We have studied the time course of Sephadex-induced lung eosinophilia, changes in pulmonary T cell numbers, and gene and protein expression as well as the immunological and pharmacological modulation of these inflammatory indices in the Sprague Dawley rat. Sephadex increased T cell numbers (including CD4+ T cells) and evoked a pulmonary eosinophilia that was associated with an increase in gene/protein expression of the Th2-type cytokines IL-4, IL-5, and IL-13 and eotaxin in lung tissue. Sephadex instillation also induced airway hyperreactivity to acetylcholine and bradykinin. A neutralizing Ab (R73) against the αβ-TCR caused 54% depletion of total (CD2+) pulmonary T cells accompanied by a significant inhibition of IL-4, IL-13 and eotaxin gene expression together with suppression (65% inhibition) of eosinophils in lung tissue 24 h after Sephadex treatment. Sephadex-induced eosinophilia and Th2 cytokine gene and/or protein expression were sensitive to cyclosporin A and budesonide, compounds that inhibit T cell function, suggesting a pivotal role for T cells in orchestrating Sephadex-induced inflammation in this model.

Production of Granulomatous Inflammation in Lungs of Rat Pups and Adults by Sephadex Beads

“…These studies show the role played by eotaxin in eosinophil recruitment in the lung tissue. After Sephadex bead injection, both eotaxin and eosinophils increased in a dose-related manner in the BALF from adults, which was consistent with previous results (15,30,37). In contrast, no treatment-related changes in eotaxin were observed in our pup model.…”

“…This is not consistent with a previous study (30) that showed that gene or protein expression of IFN-␥ was not increased after Sephadex bead treatment even in the adult rat lung. Unfortunately, there is no clear explanation for this difference.…”

“…Blocking antibodies to eotaxin suppressed eosinophilic infiltration in the BALF from rats that were treated with Sephadex beads (15). In addition, the time course of eotaxin expression after Sephadex bead administration was related to the appearance of eosinophilic infiltration in the rat lungs (30,37). These studies show the role played by eotaxin in eosinophil recruitment in the lung tissue.…”

“…However, RANTES in the BALF was significantly increased in pups but not in adults. Previous study (30) also showed that Sephadex bead treatment had no effect on gene or protein expression of RANTES in lungs. These studies indicate that RANTES does not contribute to lung eosinophilic infiltration in the Sephadex-treated adult rat model.…”

Preclinical Profile of Ciclesonide, a Novel Corticosteroid for the Treatment of Asthma

“…24 h after Sephadex administration; body weight was recorded followed by the removal of the heart and lungs en bloc. Next, the lungs were excised, and determination of wet lung weights along with correction for 100 g of initial body weight was performed as previously described (Belvisi et al, 2000;Haddad et al, 2002).…”