Correlation research of low density granulocytes with interstitial lung disease in dermatomyositis

Abstract

Objective This study aims to test the hypothesis that low density granulocytes (LDGs) is involved in the pathogenesis of DM associated-Interstitial lung disease (ILD). Methods Forty eight DM patients (28 with ILD) and 19 age- and sex-matched healthy Chinese volunteers were recruited to this study. LDGs percentage in peripheral blood mononuclear cells (PBMCs) was tested by flow cytometry. Neutrophil-related genes (LL-37, MPO and MMP-8) expressions in PBMCs were tested by quantitative RT-PCR. Myositis disease activity assessment visual analogue scales (MYOACT) was used to assess the disease activity. Percen-tages of LDGs were compared in patients with ILD and without by using unpaired t test with Welch's correc-tion, the correlations between LDGs and clinical parameters were further analyzed by linear correlation analysis. The expressions of neutrophil-related mRNA and proteins in PBMCs were compared by using Mann-Whitney U test. Results LDGs percentage in PBMCs was 7.1-fold higher in DM patients than healthy controls [(9.1±11.5)% vs (1.3±0.7)%, t=4.664, P<0.01]. LDGs percentage in PBMCs was 2.7-fold higher in DM patients with ILD than DM patients without ILD [(12.3±14.1)% vs (4.5±2.6)%, t=2.835, P=0.008 3]. The mRNA expression level of LL-37, MPO and MMP-8 and LL-37 protein levels in the DM group were significantly higher than those in the control group. LDGs percentage positively correlated with MYOACT lung disease activity scores (r=0.439, P=0.010). Conclusion Percentage of LDGs in PBMCs is significantly increased in DM patients with ILD and positively correlated with MYOACT lung disease activity scores, suggesting that abnormall increasing of LDGs is a potential contributor to the pathogenesis of DM-associated ILD. Key words: Dermatomyositis; Lung disease, interstitial; Neutrophil extracellular traps; Low density granulocytes