Background: The incidence rate of allergic rhinitis (AR) has been increasing, which has become a global health problem. As a kind of inflammatory airway disease, allergic rhinitis has a large number of inflammatory cells and inflammatory mediators that participate. Bilirubin is an effective endogenous antioxidant and anti-inflammatory molecule. This study aims to explore the relationship between bilirubin and allergic rhinitis, and to explore the potential value of bilirubin-related metabolites in blood and urine in the assessment of AR disease.
Methods: A total of 63 allergic rhinitis (AR-S group) patients and 86 healthy controls (NC-S group) were enrolled. Venous blood was obtained for measurement of serum total IgE levels and bilirubin parameters. Patients were classified into normal IgE level group (AR2-S group) and elevated IgE level group (AR1-S group). Ten subjects were randomly selected from each group, which were AR2 group, AR1 group and NC group. Urine samples were measured with the nano UPLC-MS/MS system consisting of a Nanoflow HPLC system (EASY-nLC 1000 system from Thermo Scientific) and Orbitrap Fusion Lumos mass spectrometer (Thermo Scientific).
Results: The mean total TBIL level (12.5 vs 15.7 μmol /L, p <0.001), median total DBIL level (4.4 vs 5.3 μmol /L, p <0.001) and mean total IBIL level (8.1 vs 10.3 μmol/L, p <0.001) in AR-S group were significantly lower than those in NC-S group. The mean total TBIL level (13.1 vs 15.7 μmol /L, p = 0.007), median total DBIL level (4.74 vs 5.3 μmol /L, p = 0.022), and mean total IBIL level (8.39 vs 10.3 μmol/L, p = 0.005) in AR2-S were significantly lower than those in NC-S group. The median total TBIL level (12.0 vs 15.7 μmol /L, p < 0.001), median total DBIL level (4.09 vs 5.3 μmol /L, p < 0.001), and median total IBIL level (7.91vs 10.3 μmol/L, p <0.001) in AR1-S were significantly lower than those in NC-S group. In addition, we found that there were 15 urine differential proteins related to bilirubin metabolism in AR2 and AR1. Their relative expression levels increased or decreased successively in NC group, normal IgE level group (AR2) and increased IgE level group (AR1).
Conclusions: Compared with healthy people, the levels of bilirubin metabolites in patients with allergic rhinitis were decrease in the blood. The levels of bilirubin metabolites in urine of patients with allergic rhinitis have changed. This result suggests that bilirubin may be a new target for AR diagnosis and treatment.