ALXR/FPR Mediated Signaling in Severe Asthma (AMSA)-The Severe Asthma Research Program (SARP) III

Severe asthma accounts for the majority of the morbidity and mortality related to asthma. It is characterized by persistent airway inflammation despite anti-inflammatory therapy, persistent airway hyperresponsiveness, and "remodeling" of the airways that includes fibrosis. Lipoxin A4 (LXA4) and 15-epimer-LXA4 are lipid-derived mediators that have been shown to promote anti-inflammatory and pro-resolving cellular responses through their effects at ALX/FPR2 receptors. They promote resolution of inflammation, inhibit airway hyperresponsiveness, and counteract pro-fibrotic processes. Investigators at the Brigham and Women's Hospital and others have shown that the ALX effector pathway and its constituent ligands (ALX axis) is perturbed in severe asthma (SA) compared with non-severe asthma (NSA). Specifically, in SA LXA4 production is decreased and ALX/FPR2 receptor expression is reduced. Further, investigators at the Brigham and Women's Hospital have shown that low levels of lipoxins, relative to pro phlogistic leukotrienes, are associated with reduced airway function (FEV1). Considering these data and the function of the ALX axis, it appears that perturbations of constituents of this axis could identify, and perhaps underlie, several of the processes that characterize severe, progressive asthma. Further to this point, work in progress being done at the Brigham and Women's Hospital indicates that corticosteroids (CS) interactions with the ALX axis may underlie some of these perturbations. CS can decrease the production of LXA4. More importantly, while CS increase production of pro-resolving annexin A1, they also appear to promote pro-inflammatory signaling through ALX/FPR2 via upregulation of serum amyloid A (SAA). SAA is expressed in the lung and is associated with exacerbations of COPD.

Hypotheses:

Peripheral blood leukocytes and bronchoalveolar lavage fluids will be obtained from SA and NSA subjects before and after intramuscular triamcinolone at baseline to test the hypothesis that in vivo corticosteroids will reduce pro-inflammatory cellular responses and enhance LXA4-mediated anti-inflammatory responses in the majority of asthmatic subjects. There is a sub-group of individuals with severe asthma in which in vivo corticosteroids will paradoxically increase pro-inflammatory responses. Investigators will also test the hypothesis that such paradoxical signaling can be overcome by lipoxins. In addition, investigators will test the hypothesis that basal p anti-inflammatory responses are dampened in severe asthma.

Investigators at the Brigham and Women's Hospital hypothesize that a cohort of severe asthmatic subjects with impaired counter-regulatory signaling will have a specific ALX axis phenotype that will predispose them to increased inflammation, asthma exacerbations and disease progression.

Investigators will test the hypothesis that in vivo corticosteroids will not increase (and may decrease) LXA4 or 15-epi-LXA4 but will increase annexin A1 and serum amyloid A and that the levels of these compounds post-CS will differ by disease severity, remaining stable over a 3 year interval.