Marie Therese Walsh

Eosinophil Peroxidase Signals via Epidermal Growth Factor–2 to Induce Cell Proliferation

Eosinophils exert many of their inflammatory effects in allergic disorders through the degranulation and release of intracellular mediators, including a set of cationic granule proteins that include eosinophil peroxidase. Studies suggest that eosinophils are involved in remodeling. In previous studies, we showed that eosinophil granule proteins activate mitogen-activated protein kinase signaling. In this study, we investigated the receptor mediating eosinophil peroxidase-induced signaling and downstream effects. Human cholinergic neuroblastoma IMR32 and murine melanoma B16.F10 cultures, real-time polymerase chain reaction, immunoprecipitations, and Western blotting were used in the study. We showed that eosinophil peroxidase caused a sustained increase in both the expression of epidermal growth factor-2 (HER2) and its phosphorylation at tyrosine 1248, with the consequent activation of extracellular-regulated kinase 1/2. This, in turn, promoted a focal adhesion kinase-dependent egress of the cyclin-dependent kinase inhibitor p27(kip) from the nucleus to the cytoplasm. Eosinophil peroxidase induced a HER2-dependent up-regulation of cell proliferation, indicated by an up-regulation of the nuclear proliferation marker Ki67. This study identifies HER2 as a novel mediator of eosinophil peroxidase signaling. The results show that eosinophil peroxidase, at noncytotoxic levels, can drive cell-cycle progression and proliferation, and contribute to tissue remodeling and cell turnover in airway disease. Because eosinophils are a feature of many cancers, these findings also suggest a role for eosinophils in tumorigenesis.

Eosinophil peroxidase induces the expression and function of acid-sensing ion channel-3 in allergic rhinitis: in vitro evidence in cultured epithelial cells

Acid‐sensing ion channels (ASIC) are a family of acid‐activated ligand‐gated cation channels. As tissue acidosis is a feature of inflammatory conditions, such as allergic rhinitis (AR), we investigated the expression and function of these channels in AR.

Mechanism of Sphingosine 1-Phosphate- and Lysophosphatidic Acid-Induced Up-Regulation of Adhesion Molecules and Eosinophil Chemoattractant in Nerve Cells

The lysophospholipids sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) act via G-protein coupled receptors S1P1–5 and LPA1–3 respectively, and are implicated in allergy. Eosinophils accumulate at innervating cholinergic nerves in asthma and adhere to nerve cells via intercellular adhesion molecule-1 (ICAM-1). IMR-32 neuroblastoma cells were used as an in vitro cholinergic nerve cell model. The Gi coupled receptors S1P1, S1P3, LPA1, LPA2 and LPA3 were expressed on IMR-32 cells. Both S1P and LPA induced ERK phosphorylation and ERK- and Gi-dependent up-regulation of ICAM-1 expression, with differing time courses. LPA also induced ERK- and Gi-dependent up-regulation of the eosinophil chemoattractant, CCL-26. The eosinophil granule protein eosinophil peroxidase (EPO) induced ERK-dependent up-regulation of transcription of S1P1, LPA1, LPA2 and LPA3, providing the situation whereby eosinophil granule proteins may enhance S1P- and/or LPA- induced eosinophil accumulation at nerve cells in allergic conditions.