Serine protease allergen favours Th2 responses via PAR‐2 and STAT3 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. This study aimed 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 SAM 11 before each sensitization. CD 11c + p‐ STAT 3 + cells were measured in lungs by flow cytometry. BMDC s were pretreated with SAM 11 or isotype control or stattic and stimulated with Per a 10. p‐ STAT 3 levels were measured using Western blot. Transcript levels of IL ‐12p35, IL ‐12/23p40 and IL ‐23p19 were measured using RT ‐ PCR . Cytokine levels were analysed using ELISA . Results Protease activity of Per a 10 increased p‐ STAT 3 levels in mouse lungs, which was reduced upon PAR ‐2 blockage. Percentage of p‐ STAT 3 + CD 11c + cells was higher in Per a 10‐administered mice and was reduced upon PAR ‐2 blockage. IL ‐12p35 and IL ‐12p70 levels were higher, and IL ‐23p19 and IL ‐23 levels were lower in both SAM 11‐treated mice and BMDC s 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 STAT 3 activation via stattic also leads to lower levels of IL ‐23p19 and IL ‐23 and higher levels of IL ‐12p35. Conclusions Per a 10 leads to PAR ‐2 activation on BMDC s resulting in downstream activation of STAT 3 to regulate the balance between IL ‐12/ IL ‐23 subunits causing a cytokine milieu rich in IL ‐23 to favour Th2 polarization.