Methods Peripheral blood neutrophils isolated from asthmatic as well as healthy controls were stimulated, or not, with IL-21, IL-23, and IL-6 cytokines and levels of gene as well as protein expression of IL-17 cytokines were determined using RT-PCR and flow cytometry, respectively. In addition, to investigate the mechanism of IL-21, IL-23, and IL-6 induced IL-17 release, level of Stat3 phosphorylation in neutrophils was determined following stimulation with these cytokines.
Results IL-21, IL-23, and IL-6 induced the production of IL-17 cytokines within peripheral blood neutrophils. Interestingly, the level of induced IL-17 cytokine were significantly higher in asthmatic compared to healthy control neutrophils. Stat3 phosphorylation was required for induction of IL-17 within neutrophils suggesting that a Stat3-RORgt pathway is involved and critical for regulating IL-21, 23, and 6 induced IL-17 production from neutrophils.
Conclusion Th-17 regulatory cytokines, IL-21, IL-23, and IL-6 induce the production of pro-inflammatory cytokine IL-17 from neutrophils in a much higher levels during asthma. This environment of high IL-17 levels could stimulate neutrophils to produce highly reactive oxygen radicals that would exacerbate the airway inflammatory response during asthma via their cytotoxic and tissue-destructive activity.