The serum level and significance of lysyl oxidase-like 2 in patients with rheumatoid arthritis-associated interstitial lung disease.

Our previous experiments found that lysyl oxidase-like 2 (LOXL2) may be a useful preclinical serological marker for pulmonary fibrosis in the mouse model. The role of LOXL2 in rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is still unclear. We investigated whether serum LOXL2 levels are associated with RA-ILD patients. The levels of serum LOXL2 were measured by enzyme-linked immunosorbent assay in 49 RA-ILD patients (21 patients with ILD disease duration < 3 months; 28 patients with ILD disease duration > 3 months), 43 RA patients without ILD and 20 normal healthy controls. We assessed the correlations between the serum LOXL2 levels and clinical variables. Serum LOXL2 levels were significantly higher in RA patients than in normal healthy controls (326.79 ± 192.56 vs. 53.27 ± 35.86 pg/ml, P < 0.01). No significant difference was present between the RA-ILD group and RA without ILD group (298.87 ± 219.85 vs. 358.60 ± 152.16 pg/ml, P = 0.13). Notably, the serum LOXL2 levels were significantly higher in patients with ILD disease duration < 3 months than in those with ILD disease duration > 3 months (462.71 ± 208.97 vs. 175.99 ± 130.55 pg/ml, P < 0.01) or without ILD (462.71 ± 208.97 vs. 358.60 ± 152.16 pg/ml, P = 0.03). The serum LOXL2 levels in RA-ILD patients significantly correlated with DAS28 (r = 0.31, P = 0.034), C-reactive protein (r = 0.41, P = 0.004), rheumatoid factor (r = 0.41, P = 0.003), forced vital capacity (r = - 0.39, P = 0.02), and diffusion capacity of the lung for carbon monoxide (r = - 0.44, P = 0.009). LOXL2 may be involved in the pathogenesis of rheumatoid arthritis-associated interstitial lung disease and might be helpful in early diagnosis of RA-ILD.