Epithelial Alarmins in Serum and Exhaled Breath in Patients with Idiopathic Pulmonary Fibrosis: A Prospective One-Year Follow-Up Cohort Study

Abstract

Background: Recently, epithelial alarmins have been shown to play important roles in non-allergen driven respiratory diseases like idiopathic pulmonary fibrosis (IPF). Little is known about the expression of the epithelial alarmins in IPF. Methods: This study aimed to prospectively examine interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP) levels in the serum and exhaled breath condensate (EBC) in patients with IPF before and after one-year of antifibrotic treatment. A total of 82 volunteers, including 52 patients diagnosed with IPF that qualified for antifibrotic therapy as well as 30 controls, were examined. All study participants underwent baseline peripheral blood and EBC sampling. In 35 out of 52 IPF subjects, a follow-up sampling was performed after 12 months of antifibrotic treatment. Concentrations of alarmins in the serum and EBC were evaluated by means of ELISA. Results: Baseline TSLP concentrations were significantly elevated in patients with IPF compared to controls both in the serum (p < 0.05) and EBC (p < 0.0001). Baseline IL-25 and IL-33 serum and EBC levels did not differ significantly between IPF subjects and controls. Prospective analysis of changes in the epithelial alarmin levels showed significantly decreased IL-25 and TSLP EBC concentrations after 12 months of antifibrotic treatment (p < 0.05), which was observed in the subgroup of IPF patients treated with pirfenidone, but not in those treated with nintedanib. In stable patients with IPF over a study period (absolute forced vital capacity (FVC) % of predicted decline/year ≤ 5%, n = 25), a significant decrease in the EBC levels of both IL-25 and TSLP after 12 months of antifibrotic treatment was noted (p < 0.05), whereas, in progressor IPF patients (absolute FVC % of predicted decline/year > 5%, n = 10), a significant decrease was noted in the IL-25 EBC levels only (p < 0.05). Conclusions: Elevated TSLP levels in patients with IPF and their significant decrease in the lung compartment during antifibrotic therapy in stable patients with IPF, but not in progressors, support its significant contribution to pro-fibrotic type 2 immune responses in IPF. Noted changes in the epithelial alarmins concentration in the lung compartment during pirfenidone therapy may suggest its possible interaction with epithelial alarmins pathways in IPF.

Exhaled Biomarkers in Idiopathic Pulmonary Fibrosis—A Six-Month Follow-up Study in Patients Treated with Pirfenidone

“…A six-month treatment with pirfenidone did not significantly change the EBC concentrations of IL-6, IL-8 and VEGF. This is consistent with earlier findings on other EBC cytokines [20]. There are, however, reports on antifibrotic treatment-induced changes in the cytokine profile in serum [37,38], but these did not include the cytokines investigated in the present study.…”

“…In their analysis of alarmins in serum and EBC, Majewski et al reported a weak but negative correlation between serum and EBC IL-33. Despite higher serum and EBC TSLP levels in IPF patients when compared to controls in that study, the concentrations of TSLP in these two materials did not correlate [20]. Krauss et al also did not find relationships between EBC and BALF concentrations of PGE2 and 8-isoprostane in patients with different interstitial lung diseases, including IPF [25].…”

“…Although a previous report showed that EBC analysis might modestly contribute to the diagnosis and monitoring of IPF [25], some authors demonstrated that EBC composition might discriminate between IPF patients and control subjects [20,26]. It seems that these equivocal findings may result from the complex cytokine interplay in the pathogenesis of IPF and a (still) insufficient knowledge of the specific cytokines involved.…”

“…Exhaled breath condensate (EBC) is a noninvasively collected matrix from the respiratory tract, which contains various inflammatory mediators. Majewski et al demonstrated that interleukin 25 and 33 are detectable in EBC from patients with IPF and that their concentrations show some significant correlations with lung function in these patients [20]. We hypothesized that EBC might be a promising respiratory sample to provide additional insight into the mechanisms involved in the pathogenesis of IPF and to monitor antifibrotic treatment.…”

Regulation of cellular senescence by extracellular matrix during chronic fibrotic diseases

“…However, the contribution of DAMPs and the effect of targeting this therapeutically in fibrosis is less well explored. Majewski and colleagues examined the levels of IL-25, IL-33 and thymic stromal lymphopoietin (TSLP) in patients with IPF and followed them after one year of treatment with the antifibrotic drugs nintedanib or pirfenidone [ 252 ]. The baseline levels of TSLP were elevated in IPF patients compared with controls, while IL-25 and IL-33 levels did not vary.…”