Jehad H. Edwan

Flt-3 Ligand Reverses Late Allergic Response and Airway Hyper-Responsiveness in a Mouse Model of Allergic Inflammation

Flt3 ligand (Flt3-L) is a growth factor for dendritic cells and induces type 1 T cell responses. We recently reported that Flt3-L prevented OVA-induced allergic airway inflammation and suppressed late allergic response and airway hyper-responsiveness (AHR). In the present study we examined whether Flt3-L reversed allergic airway inflammation in an established model of asthma. BALB/c mice were sensitized and challenged with OVA, and AHR to methacholine was established. Then mice with AHR were randomized and treated with PBS or 6 μg of Flt3-L i.p. for 10 days. Pulmonary functions and AHR to methacholine were examined after rechallenge with OVA. Treatment with Flt3-L of presensitized mice significantly suppressed (p < 0.001) the late allergic response, AHR, bronchoalveolar lavage fluid total cellularity, absolute eosinophil counts, and inflammation in the lung tissue. There was a significant decrease in proinflammatory cytokines (TNF-α, IL-4, and IL-5) in bronchoalveolar lavage fluid, with a significant increase in serum IL-12 and a decrease in serum IL-5 levels. There was no significant effect of Flt3-L treatment on serum IL-4 and serum total IgE levels. Sensitization with OVA significantly increased CD11b+CD11c+ cells in the lung, and this phenomenon was not significantly affected by Flt3-L treatment. These data suggest that Flt3-L can reverse allergic airway inflammation and associated changes in pulmonary functions in murine asthma model.

Flt3-L Increases CD4+CD25+Foxp3+ICOS+ Cells in the Lungs of Cockroach-Sensitized and -Challenged Mice

We previously reported in an ovalbumin-induced model of allergic asthma that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c(high)CD8 alpha(high)CD11b(low) dendritic cells in the lung. In this study, we investigated the effect of Flt3-L in a clinically relevant aeroallergen-induced asthma on the phenotypic expression of lung T cells. Balb/c mice were sensitized and challenged with cockroach antigen (CRA), and AHR to methacholine was established. These mice received three intraperitoneal injections of anti-CD25 antibody (PC61; 250 microg) and Flt3-L (3 microg) daily for 10 days. Cytokines and Ig levels in the serum were measured and differential bronchoalveolar lavage fluid (BALF) cell counts were examined. Flt3-L reversed AHR to methacholine to the control level. Flt3-L significantly decreased levels of BALF IL-5, IFN-gamma, eosinophilia and substantially increased IL-10 and the number of CD4(+)CD25(+) Forkhead winged helix transcription factor box P3 (Foxp3(+)) IL-10(+) T cells in the lung. Administration of PC61 antibody blocked the effect of Flt3-L and substantially increased AHR, eosinophilia, and BALF IL-5 and IFN-gamma levels, and decreased BALF IL-10 levels and the number of CD4(+)CD25(+)Foxp3(+)IL-10(+) T cells. Flt3-L significantly decreased CD62-L, but increased inducible costimulatory molecule and Foxp3 mRNA expression in the CD4(+)CD25(+) T cells isolated from lungs of Flt3-L-treated, CRA-sensitized mice compared to CRA-sensitized mice without Flt3-L treatment and PBS control group. Flt3-L significantly inhibited the effect of CRA sensitization and challenge to increase GATA3 expression in lung CD4(+)CD25(+) T cells. Collectively, these data suggest that the therapeutic effect of Flt3-L is mediated by increased density of naturally occurring CD4(+)CD25(+)Foxp3(+)IL-10(+)ICOS(+) T-regulatory cells in the lung. Flt3-L could be a therapeutic strategy for the management and prevention of allergic asthma.

Flt3-ligand plasmid prevents the development of pathophysiological features of chronic asthma in a mouse model

Airway inflammation and remodeling are primary characteristics of long-standing asthma. A balance between the TH1/TH2 cytokines regulates the accumulation and activation of inflammatory cells, including mast cells and eosinophils. Recently, we demonstrated that pUMVC3-hFLex, an active plasmid, mammalian expression vector for the secretion of Flt3-L, reversed established airway hyperresponsiveness (AHR) in a murine model of acute allergic airway inflammation. The present experiments were undertaken to examine the effect of pUMVC3-hFLex in a chronic model of allergic airway inflammation that was established in Balb/c mice by sensitization and challenge with ovalbumin (OVA). pUMVC3-hFLex or the control plasmid, pUMVC3, were administered by injection into the muscle interior tibialis. Treatment with pUMVC3-hFLex completely reversed established AHR (p<0.05), and this effect continued even after several exposures to the allergen (p<0.05). pUMVC3-hFLex treatment prevented the development of goblet cell hyperplasia and subepithelial fibrosis, and significantly reduced serum levels of IL-4 and IL-5, and increased serum IL-10 levels (p<0.05) with no effect on serum IL-13. Serum IgE or serum total and anti-OVA IgG1 and IgG2a levels did not change. Total BALF cellularity and BALF IL-5 levels were reduced (p<0.05), but there was no significant effect on BALF IL-10 and IL-13. These results suggest that pUMVC3-hFLex treatment can prevent the development of airway remodeling and maintain airway protection in chronic experimental asthma model, and might provide a novel approach for treating chronic asthma.