The innate inflammatory pathways involved in the frequent exacerbator phenotypes of asthma and COPD are not well understood. This study aimed to investigate airway innate immune activation and systemic inflammation as predictors of exacerbations in asthma and COPD.
In this prospective cohort study, baseline airway IL-1β, serum C-reactive protein, and IL-6 were assessed in 152 participants with stable asthma (n = 63) or COPD (n = 89) and were related to exacerbations over the following 12 months. Clinical characteristics and inflammatory biomarkers were compared between the frequent (two or more exacerbations in the follow-up) and infrequent exacerbators. The frequent exacerbation phenotype and exacerbation frequency were analyzed with multivariable modeling. The relationships among airway inflammation, systemic inflammation, and future exacerbations were examined using path analysis.
Ninety-four participants experienced a total of 201 exacerbations, and 36.4% had two or more exacerbations. Serum IL-6 and sputum gene expression of IL-1β at baseline were higher in the frequent exacerbators with COPD. Significant pathways initiated by previous exacerbations were identified as occurring through activation of the IL-1β-systemic inflammatory axis leading to future exacerbations in COPD. Systemic inflammation was also associated with increased exacerbation risk in asthma.
Airway IL-1β and systemic inflammation are associated with frequent exacerbations and may mediate a vicious cycle between previous and future exacerbations in COPD. Treatment strategies aimed at attenuating these inflammatory pathways to reduce COPD exacerbations deserve further investigation.