Serine protease allergen favours Th2 responses via PAR-2 and STAT-3 activation in murine model

Abstract

Background

Protease activity of Per a 10 favours Th2 responses by differential regulation of IL-12p70 and IL-23 cytokine subunits. The present study aims to elucidate the underlying mechanism of differential regulation of IL-12p70 and IL-23.

Methods

PAR-2 activation was blocked in murine model by administering SAM11 before each sensitization. CD11c⁺ p-STAT3⁺ cells were measured in lungs by flow cytometry. BMDCs were pre-treated with SAM-11 or isotype control or stattic and stimulated with Per a 10. p-STAT3 levels were measured using Western blot. Transcript levels of IL-12p35, IL12/23p40 and IL-23p19 were measured using RT PCR. Cytokine levels were analysed using ELISA.

Results

Protease activity of Per a 10 increases p-STAT3 levels in mice lungs, which gets reduced on PAR-2 blockage. Percentage of p-STAT3⁺ CD11c⁺ cells was higher in Per a 10 administered mice and gets reduced upon PAR-2 blockage. IL-12p35 and IL-12p70 levels were higher, IL-23p19 and IL-23 levels were lower in both SAM-11 treated mice and BMDCs indicating a role of PAR-2 mediated signalling. IL-4, TSLP, IL-17A, EPO activity, total cell count and specific IgE and IgG1 levels were lower in SAM-11 administered mice. Inhibiting STAT3 activation via stattic also leads to lower levels of IL-23p19, IL-23 and higher level of IL-12p35.

Conclusions

Per a 10 leads to PAR-2 activation on BMDCs resulting in downstream activation of STAT3 to regulate the balance between IL-12/IL-23 subunits causing a cytokine milieu rich in IL-23 to favour Th2 polarization.

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