Upregulation of interleukin-19 in severe asthma: a potential saliva biomarker for asthma severity

Abstract

Interleukin (IL)-19, a designated IL-20 subfamily cytokine, has been implicated in inflammatory disorders including rheumatoid arthritis, psoriasis and, lately, asthma. Here, through the analysis of transcriptomic datasets of lung tissue of large asthma cohorts, we report that IL-19 expression is upregulated in asthma and correlates with disease severity. The gene expression of IL-19 was significantly higher in lung tissue from patients with severe and mild/moderate asthma compared to healthy controls. IL-19 protein level, however, was significantly higher in the blood and saliva of patients with severe asthma compared to mild/moderate subgroups as measured by ELISA assay. IL-19 protein level was not affected by corticosteroid treatment in plasma. Our data provide insights into the potential use of IL-19 as a saliva marker for asthma severity and a potential therapeutic target.

FIGURE 1

Gene expression of interleukin (IL)-19, IL-6 and IL-17 in bronchial biopsies from patients with asthma of different severity categories. The data are for bronchial biopsies from patients with severe asthma (n=42) and mild/moderate asthma (n=18) and healthy controls (n=13) from the U-BIOPRED Project and Australian Newcastle severe asthma cohorts (GSE147881). a) IL-19 gene expression was significantly increased in the lungs of patients with severe and mild/moderate asthma compared to healthy controls. b) IL-6 gene expression was significantly increased in the lungs of patients with severe asthma compared to healthy controls. c) There was a trend towards increased IL-17 gene expression in the lungs of patients with severe and mild/moderate asthma compared to healthy controls. d) IL-20R1 and IL-20R2 gene expression increased in the lungs of patients with severe and mild/moderate asthma compared to healthy controls. e) IL-20R1 and IL-20R2 gene expression increased in severe asthmatic bronchial fibroblasts compared to healthy bronchial fibroblasts. Treatment of these cells with 100 ng·mL⁻¹ IL-19 increased IL-20R1 and IL-20R2 gene expression levels. Fold change presented relative to healthy controls. Two-way comparison was done using two-tailed t-test. ns: nonsignificant. *: p<0.05; **: p<0.01; ***: p<0.001; ****: p<0.0001.

FIGURE 2

Gene expression of interleukin (IL)-19, IL-6 and IL-17 in bronchial brushing, blood and sputum samples from patients with asthma of different severity categories. a–c) The data are for bronchial brushing from patients with severe asthma (n=38) and mild/moderate asthma (n=50) and healthy controls (n=20) from the SARP cohorts (GSE43696). a) IL-19 gene expression is significantly increased in the bronchial brushings from patients with severe asthma compared to healthy controls, and there is a trend towards increased IL-19 expression in bronchial brushings from patients with mild/moderate asthma compared to healthy controls. b) There was a trend towards increased IL-6 gene expression in bronchial brushing from patients with severe and mild/moderate asthma compared to healthy controls. c) No distinct pattern was found in IL-17 gene expression in bronchial brushings from patients with severe and mild/moderate asthma compared to healthy controls. d–f) The data are for peripheral blood mononuclear cells (PBMCs) (GSE132006) from patients with allergic asthma (n=5) and healthy controls (n=5). d) There was a trend towards increased IL-19 gene expression in PBMCs from patients with asthma compared to healthy controls. e) No distinct pattern was found in IL-6 gene expression in PBMCs from patients with asthma compared to healthy controls. f) No distinct pattern was found in IL-17 gene expression in PBMCs from patients with asthma compared to healthy controls. g–i) The data are for sputum (GSE137268) from patients with controlled (n=21) and uncontrolled (n=21) asthma. g) IL-19 gene expression was slightly increased in the sputum of patients with uncontrolled asthma compared those with controlled asthma. h) There was a trend towards increased IL-6 expression in the sputum of patients with uncontrolled asthma compared to those with controlled asthma. i) No distinct pattern was found for IL-17 expression in the sputum of patients with uncontrolled asthma compared to those with controlled asthma. Two-way comparison was done using two-tailed t-tests (GSE43696). Limma adjusted p<0.05 (GSE132006 and GSE137268). ns: nonsignificant. *: p<0.05; **: p<0.01.

FIGURE 3

Plasma and saliva interleukin (IL)-19, IL-6 and IL-17 levels in patients with asthma of different severity categories. The data are for samples from patients with severe asthma (n=18) and mild/moderate asthma (n=12) and healthy controls (n=6). a, b) IL-19 level was significantly increased in plasma (a) and saliva (b) of patients with severe asthma compared to mild/moderate asthma; the increase in IL-19 level was more pronounced in saliva than in plasma level. c, d) There was a trend towards increased plasma IL-6 level (c) in patients with severe asthma compared to mild/moderate asthma, and a significant increase in saliva IL-6 level (d) in patients with severe asthma compared to mild/moderate asthma. e, f) No distinct pattern was found in plasma IL-17 levels (e) in patients with severe asthma compared to mild/moderate asthma, but there was a trend towards increased saliva IL-17 levels (f) in patients with severe asthma compared to mild/moderate asthma. Two-way comparison was done using two-tailed t-test. ns: nonsignificant. *: p<0.05; ****: p<0.0001.

FIGURE 4

Plasma interleukin (IL)-19 levels in asthma patients on different treatment regimens. a) Gene expression level of IL-19 in bronchial biopsies from healthy, non-smoker, non-allergic male volunteers treated with placebo or inhaled budesonide (1600 μg). The data show no difference in IL-19 expression levels between the two groups. b) Gene expression level of IL-19 in the peripheral blood mononuclear cells (PBMCs) untreated or treated with dexamethasone (500 nM) for 24 h. The data show no difference in IL-19 expression level between the treated and untreated PBMCs. c) Azithromycin and omalizumab decreases IL-19 plasma level in severe asthma. The data show that treatment with these medications significantly decreased IL-19 plasma level in patients with severe asthma. Two-way comparison was done using two-tailed t-tests. ns: nonsignificant. ****: p<0.0001.

FIGURE 5

Gene expression of interleukin (IL)-10, IL-20 and IL-24 in bronchial biopsies from patients with asthma of different severity categories. The data are from U-BIOPRED Project and Australian Newcastle severe asthma cohorts (GSE147881). a) IL-10 gene expression was significantly decreased in the lungs of patients with severe asthma compared to healthy controls. b) There was a trend towards increased lung IL-20 expression in patients with mild/moderate asthma compared to healthy controls. c) IL-24 gene expression was significantly decreased in the lungs of patients with mild/moderate asthma compared to healthy controls. Two-way comparison was done using two-tailed t-tests. ns: nonsignificant. *: p<0.05; **: p<0.01.