Mast cell chemoattractants in allergic rhinitis

Salib, Rami Jean (2005) Mast cell chemoattractants in allergic rhinitis. University of Southampton, Doctoral Thesis.

Abstract

Epithelial mast cell accumulation is a characteristic feature of allergic rhinitis.  The mechanism for this tissue localization is undefined.  This study has evaluated the nasal expression of the known mast cell chemoattractants eotaxin, stem cell factor (SCF) and the transforming growth factor-beta (TGF-β) isoforms, TGF-β1, TGF-β2 and TGF-β3, along with their receptors CCR-3, c-kit, and TGF-βRI, -βRII, -βRIII, respectively.  The initial studies focused on immunohistochemical expression of protein in nasal biopsy specimens from rhinitic (perennial and seasonal allergic rhinitis (SAR)) and non-rhinitic subjects (healthy controls and asymptomatic out of season, seasonal rhinitis), evaluating the level of expression and tissue localization.  Based on these results, the study extended to the evaluation of nasal lavage measures of luminal protein in the same study groups for TGF-β1, TGF-β2 and eotaxin.  These measures were related to symptom reporting and lavage alpha 2-macroglobulin (α2MG), as indices of clinical disease severity and nasal airway inflammation respectively, and more specifically to intra-luminal eosinophil accumulation, as represented by cytospin differential cell count.  Subsequently, evaluation was undertaken of TGF-β1, -β2 and –β3, TGF-β RI, - β RII and – β RIII and eotaxin gene expression by real-time quantitative polymerase chain reaction (TaqMan RT-PCR) in whole biopsies, and compared to that for tumour necrosis factor-alpha (TNF-α), as a positive control, and connective tissue growth factor (CTGF), as a downstream marker of TGF-β bioactivity, in the same populations.  This study was extended to also evaluate gene expression for Smad proteins.  Finally to understand the basis for TGF-β expression in epithelial cells, a series of in vitro studies, involving evaluation of both protein release into supernatant fluid and tissue gene expression, were undertaken on RPMI 2650 cells, a nasal epithelial cell line, investigating the effects of allergens (house dust mite (HDM) and grass pollen (GP)), TNF-α and the Th2 cytokines interleukin (IL)-4 and IL-13.

Evidence was found of significantly increased epithelial immunoreactivity for TGF-β1, -β2, -βRII, and – βRIII in the perennial and seasonal allergic rhinitis compared with healthy controls.  TGF-βRI and –β RII were found to co-localise to mast cells.  There was no increase in SCF immunoreactivity within the epithelium in naturally occurring disease.  Significant correlations were found between epithelial immunoreactivity for TGF-β1, -β2, -βRI, -βRII and the number of epithelial mast cells.  These findings of enhanced epithelial TGF-β immunoreactivity in allergic rhinitis, the correlation with intra-epithelial mast cell numbers, and the co-localisation of TGF-β receptors to mast cells, suggest that the epithelial expression of TGF-β may represent an important biological process involved in either the recruitment or retention of mast cells within the epithelium in naturally occurring allergic rhinitis.

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