Decreased Expression of Membrane IL-5 Receptor α on Human Eosinophils: II. IL-5 Down-Modulates Its Receptor Via a Proteinase-Mediated Process

Reversal of eosinophilic inflammation has been an elusive therapeutic goal in the management of asthma pathogenesis. In this regard, GM-CSF is a primary candidate cytokine regulating eosinophil activation and survival in the lung; however, its molecular mechanism of propagation and maintenance of stimulated eosinophil activation is not well understood. In this study, we elucidate those late interactions occurring between the GM-CSF receptor and activated eosinophil signaling molecules. Using coimmunoprecipitation with GM-CSF-stimulated eosinophils, we have identified that the GM-CSF receptor β-chain (GMRβ) interacted with ICAM-1 and Shp2 phosphatase, as well as Slp76 and ADAP adaptor proteins. Separate experiments using affinity binding with a tyrosine-phosphorylated peptide containing an ITIM (ICAM-1 residues 480–488) showed binding to Shp2 phosphatase and GMRβ. However, the interaction of GMRβ with the phosphorylated ICAM-1-derived peptide was observed only with stimulated eosinophil lysates, suggesting that the interaction of GMRβ with ICAM-1 required phosphorylated Shp2 and/or phosphorylated GMRβ. Importantly, we found that inhibition of ICAM-1 in activated eosinophils blocked GM-CSF-induced expression of c-fos, c-myc, IL-8, and TNF-α. Moreover, inhibition of ICAM-1 expression with either antisense oligonucleotide or an ICAM-1-blocking Ab effectively inhibited ERK activation and eosinophil survival. We concluded that the interaction between ICAM-1 and the GM-CSF receptor was essential for GM-CSF-induced eosinophil activation and survival. Taken together, these results provide novel mechanistic insights defining the interaction between ICAM-1 and the GM-CSF receptor and highlight the importance of targeting ICAM-1 and GM-CSF/IL-5/IL-3 receptor systems as a therapeutic strategy to counter eosinophilia in asthma.

Section: Discussionsupporting

confidence: 61%

Section: Blockade Of Icam-1 Expression Inhibits Prolongation Of Eosinmentioning

confidence: 99%

Cross-Talk between ICAM-1 and GM-CSF Receptor Signaling Modulates Eosinophil Survival and Activation

Pazdrak

Young

Stafford

et al. 2008

“…Recently, it has been demonstrated that IL-5 can down-modulate its receptor, thereby limiting IL-5-dependent inflammatory conditions. Moreover, this down-modulation could be partially reversed through MMP inhibitors, BB-94 and GM6001, suggesting contribution from an MMPdependent pathway (28).…”

Section: Discussionmentioning

confidence: 94%

Matrix Metalloproteinase-9 Deficiency Results in Enhanced Allergen-Induced Airway Inflammation

McMillan

Kearley

Campbell

et al. 2004

167

133

Matrix metalloproteinases (MMPs) are a large family of endopeptidases that proteolytically degrade extracellular matrix. Many different cells produce MMP-9, and levels have been shown to be up-regulated in patients with allergic asthma. The aim of this study was to investigate the in vivo role of MMP-9 during allergen-induced airway inflammation. Acute allergic pulmonary eosinophilia was established in MMP-9 knockout (KO) and wild-type (WT) control mice by sensitization and challenge with OVA. Cell recruitment was significantly increased in both bronchoalveolar lavage (BAL) and lung tissue compartments in MMP-9 KO mice compared with WT mice. This heightened cell recruitment was primarily due to increased eosinophils and Th2 cells in the BAL and lung tissue of MMP-9 KO mice in comparison with WT controls. Moreover, levels of the Th2 cytokines, IL-4 and IL-13, and the chemokines eotaxin/CCL11 and macrophage-derived chemokine/CCL22 were substantially increased in MMP-9 KO mice compared with WT after OVA challenge. Resolution of eosinophilia was similar between MMP-9 KO and WT mice, but Th2 cells persisted in BAL and lungs of MMP-9 KO mice for longer than in WT mice. Our results indicate that MMP-9 is critically involved in the recruitment of eosinophils and Th2 cells to the lung following allergen challenge, and suggest that MMP-9 plays a role in the development of Th2 responses to allergen.

“…Thus, the levels of IL-5 in the epithelial lining fluid of these subjects (all of whom were dual responders) are estimated to be ϳ10 -100 ng/ml. Treatment of blood eosinophils in vitro with IL-5 at concentrations in this range is known to saturate the IL-5 receptor (63-68) and lead to ␣ M ␤ 2 up-regulation and activation and induction of adhesion to ICAM-1 and other substrates (36,60,61), priming and enhanced response to chemoattractants (69), enhanced viability (70), degranulation and granule protein release (30), IL-5 receptor ␣ down-regulation (71), and enhanced expression of certain genes (72). In contrast, median concentrations of the other IL-5 family cytokines before dilution are estimated to be ϳ1-3 ng/ml.…”

Section: Discussionmentioning

confidence: 99%

Up-Regulation and Activation of Eosinophil Integrins in Blood and Airway after Segmental Lung Antigen Challenge

Johansson¹,

Kelly

Busse

et al. 2008

Self Cite

117

We hypothesized that there are clinically relevant differences in eosinophil integrin expression and activation in patients with asthma. To evaluate this, surface densities and activation states of integrins on eosinophils in blood and bronchoalveolar lavage (BAL) of 19 asthmatic subjects were studied before and 48 h after segmental Ag challenge. At 48 h, there was increased expression of αD and the N29 epitope of activated β1 integrins on blood eosinophils and of αM, β2, and the mAb24 epitope of activated β2 integrins on airway eosinophils. Changes correlated with the late-phase fall in forced expiratory volume in 1 s (FEV1) after whole-lung inhalation of the Ag that was subsequently used in segmental challenge and were greater in subjects defined as dual responders. Increased surface densities of αM and β2 and activation of β2 on airway eosinophils correlated with the concentration of IL-5 in BAL fluid. Activation of β1 and β2 on airway eosinophils correlated with eosinophil percentage in BAL. Thus, eosinophils respond to an allergic stimulus by activation of integrins in a sequence that likely promotes eosinophilic inflammation of the airway. Before challenge, β1 and β2 integrins of circulating eosinophils are in low-activation conformations and αDβ2 surface expression is low. After Ag challenge, circulating eosinophils adopt a phenotype with activated β1 integrins and up-regulated αDβ2, changes that are predicted to facilitate eosinophil arrest on VCAM-1 in bronchial vessels. Finally, eosinophils present in IL-5-rich airway fluid have a hyperadhesive phenotype associated with increased surface expression of αMβ2 and activation of β2 integrins.