IP-10 is a potential biomarker of cystic fibrosis acute pulmonary exacerbations

Abstract

Background: Cystic fibrosis (CF) is characterized by acute pulmonary exacerbations (APE). The CF nasal airway exhibits a similar ion transport defect as the lung, and colonization, infection, and inflammation within the nasal passages are common among CF patients. Nasal lavage fluid (NLF) is a minimally invasive means to collect upper airway samples.

Methods: We collected NLF at the onset and resolution of CF APE and compared a 27-plex cytokine profile to stable CF outpatients and normal controls. We also tested IP-10 levels in the bronchoalveolar lavage fluid (BALF) of CF patients. Well-differentiated murine sinonasal monolayers were exposed to bacterial stimulus, and IP-10 levels were measured to test epithelial secretion.

Results: Subjects hospitalized for APE had elevated IP-10 (2582 pg/mL [95% CL of mean: 818,8165], N=13) which significantly decreased (647 pg/mL [357,1174], P<0.05, N =13) following antimicrobial therapy. Stable CF outpatients exhibited intermediately elevated levels (680 pg/mL [281,1644], N=13) that were less than CF inpatients upon admission (P=0.056) but not significantly different than normal controls (342 pg/mL [110,1061]; P=0.3, N=10). IP-10 was significantly increased in CF BALF (2673 pg/mL [1306,5458], N=10) compared to healthy post-lung transplant patients (8.4 pg/mL [0.03,2172], N=5, P<0.001). IP-10 levels from well-differentiated CF murine nasal epithelial monolayers exposed to Pseudomonas PAO-1 bacteria-free prep or LPS (100 nM) apically for 24 hours were significantly elevated (1159 ± 147, P<0.001 for PAO-1; 1373 ± 191, P<0.001 for LPS vs. 305 ± 68 for vehicle controls). Human sino-nasal epithelial cells derived from CF patients had a similar response to LPS (34% increase, P<0.05, N=6).

Conclusions: IP-10 is elevated in the nasal lavage of CF patients with APE and responds to antimicrobial therapy. IP-10 is induced by airway epithelia following stimulation with bacterial pathogens in a murine model. Additional research regarding IP-10 as a potential biomarker is warranted.

Figure 1. IP-10 levels in nasal lavage fluid.

A. IP-10 levels in the nasal lavage of CF inpatients hospitalized for APE (N=13) compared to normal (Non-CF) healthy subjects (N=10) and stable CF outpatients (N=13) B. Levels of IP-10 observed in subjects hospitalized and treated for APE (*P<0.05, N=13). C. FEV₁ % predicted before and after treatment for APE in the APE Cohort.

Figure 2. IP-10 levels in bronchoalveolar lavage fluid (BALF).

IP-10 levels in the BALF from CF patients (N=10) compared to post-lung transplant controls (N=5) and non-CF lung disease controls (N=20).

Figure 3. IP-10 levels in the serosal compartment of well-differentiated murine airway epithelial monolayers.

IP-10 levels in the basolateral compartment of well-differentiated nasal airway epithelial monolayers derived from CFTR (-/-) and CFTR (+/+) mice exposed to PAO-1 (bacteria-free prep from 20 hour log-phase growth) or sterile LPS (100 nM) apically for 24 hours. No statistically significant difference was observed between CF and WT IP-10 levels at each respective condition. **P<0.005, ***P<0.0001 vs. PBS control; N=10-13 monolayers per treatment.

Figure 4. IP-10 levels in the serosal compartment of well differentiated human airway epithelial monolayers.

IP-10 levels in the basolateral compartment of well-differentiated nasal epithelial monolayers derived from human subjects with and without CF undergoing routine sinus surgery were exposed to sterile LPS (100nM) apically for 24 hours. *P<0.05, ***P<0.0001; N=6 monolayers per treatment. All data are normalized to baseline (vehicle control) condition to control for variance between donors and cell lots.