In Vitro Simulation of Aerobic Exercise Effects in Neutrophils in Severe Asthma: Involvement of Kinins

Severe asthma presents a sub-phenotype characterized by concomitant eosinophilia and neutrophilia. In this context, bradykinin activate both eosinophils and neutrophils. Aerobic exercise (AE) reduces eosinophilic asthma phenotype, mainly by inducing the IL-10 release, but whether AE can reduce severe neutrophilic asthma is unknown. A HDM (100ug/mouse, 3x/week, 6 weeks) model of asthma in C57Bl6 mice was used and the mice were treated with AE (5x/week, 4 weeks, beginning after 2nd week of HDM administration). Furthermore, using an in vitro model, we tested the hypothesis that IL-10 (as induced by AE) could inhibit neutrophils hyperactivation induced by HDM and bradykinin. So, freshly isolated human neutrophils (immunomagnetic separation) were first stimulated with Dermatophagoides pteronyssinuns (HDM; 100ug/mL) ± Bradykinin (40ug/mL) ± IL-10 (10ng/mL). The results demonstrated that HDM+AE group presented less neutrophils in BAL (p<0.001) and in blood (p<0.001) and increased the levels of IL-10 in BAL (p<0.001) and in plasma (p<0.001), while the expression (qRT-PCR) of B1 receptor was reduced in the lung tissue of HDM+AE group (p<0.01). In addition, HDM alone induced neutrophils activation, as denoted by increased release of IL-1beta (p<0.0001), as well as Bradykinin alone (p<0.0001), while IL-10 did not inhibit HDM activation (HDM x HDM+BK+IL-10; p<0.9217) and Bradykinin (Bradykinin x HDM+BK+IL-10; p<0.1034). However, IL-10 inhibited HDM+Bradykinin (HDM+BK x HDM+BK+IL-10; p<0.0001). We conclude that aerobic exercise inhibits severe neutrophilic asthma phenotype involving kinin signaling.