The role of hedgehog signalling in the biology of eosinophils

Abstract

Eosinophils are central to T-helper 2 (Th2) immune responses and allergy and asthma pathogenesis. Their degranulation in response to allergen is a cause of airway hypersensitivity and remodelling in allergic airway disease. Previous work showed active Hedgehog/Gli Signalling via Sonic Hedgehog (SHH) in the lungs of asthmatic murine models. Murine eosinophils can transduce SHH signals, however functional effects of SHH signalling on eosinophils remain unclear. The aim of this project is to elucidate these effects. Therefore, the HL60 myeloid cell line was differentiated into a human eosinophilic population (HL60-eos) via Sodium Butyrate treatment. HL60-eos cells were cultured in the presence or absence of (1) recombinant SHH ligand or (2) GANT61, a Gli antagonist and therefore Hh signalling inhibitor. Cellular phenotype and genotype were studied via qPCR, ELISA, Flow Cytometry, and cytochemical staining. We found that culture with SHH upregulates EPX and TGF-β expression in HL60-eos cells. EPX encodes Eosinophil Peroxidase, a constituent of eosinophilic granules and responsible for cell damage during degranulation. TGF-β1 encodes the cytokine TGF-β, important for lymphocyte regulation, eosinophil chemotaxis, fibrosis, and wound healing. Further investigation is needed to characterise the eosinophilic response to SHH/GANT61 when immunostimulated, as they would be in vivo during an immune response.