Asthmatics with High Serum Amyloid A have Pro-inflammatory HDL: Implications for Augmented Systemic and Airway Inflammation.

RATIONALE:Serum amyloid A (SAA) is bound to high-density lipoproteins (HDL) in blood. Although SAA is increased in the blood of asthmatics, it is not known whether this modifies asthma severity. OBJECTIVE:To define the clinical characteristics of asthmatics with high SAA levels and assess whether HDL from SAA-high asthmatics is pro-inflammatory. METHODS:SAA levels in serum from asthmatic and non-asthmatic subjects were quantified by ELISA. HDL isolated from asthmatics with high SAA levels were used to stimulate human monocytes and were intravenously administered to BALB/c mice. RESULTS:A SAA level > 108.8 μg/ml was defined as the threshold to identify 11% of an asthmatic cohort (n = 146) as being SAA-high. SAA-high asthmatics were characterized by increased serum C-reactive protein, IL-6, and TNF-α; older age; and an increased prevalence of obesity and severe asthma. HDL isolated from SAA-high asthmatics (SAA-high HDL) had an increased content of SAA as compared to HDL from SAA-low asthmatics and induced the secretion of IL-6, IL-1β and TNF-α from human monocytes via a FPR2/ATP/P2X7R axis. Intravenous administration to mice of SAA-high HDL, but not normal HDL, induced systemic inflammation and amplified allergen-induced neutrophilic airway inflammation and goblet cell metaplasia. CONCLUSION:SAA-high asthmatics are characterized by systemic inflammation, older age, and an increased prevalence of obesity and severe asthma. HDL from SAA-high asthmatics is pro-inflammatory and, when intravenously administered to mice, induces systemic inflammation, and amplifies allergen-induced neutrophilic airway inflammation. This suggests that systemic inflammation induced by SAA-high HDL may augment disease severity in asthma.