Aberrantly Expressed Galectin-9 is Involved in the Immunopathogenesis of anti-MDA5-Positive Dermatomyositis-Associated Interstitial Lung Disease
Abstract Background: Rapidly progressive interstitial lung disease (RP-ILD) has high mortality rate and poor prognosis. Galectin-9 (Gal-9) plays multiple functions in immune regulation. We investigated Gal-9 expression in patients with dermatomyositis (DM) and the impact of Gal-9 on the development of DM-ILD. Methods: Enzyme-linked immunosorbent assay and qRT-PCR were used to examine Gal-9 expression in the sera and isolated peripheral blood mononuclear cells (PBMCs) from patients with DM. Immunohistochemistry was performed to analyze the expression of Gal-9 and its ligand (T-cell immunoglobulin mucin (Tim)-3 and CD44) in lung tissues from patients who were positive for anti-melanoma differentiation-associated gene 5 (MDA5). The effect of Gal-9 on human lung fibroblasts (MRC-5) was also investigated in vitro. Results: Serum Gal-9 levels were significantly higher in patients with DM than in those with immune-mediated necrotizing myopathy and healthy controls (p < 0.001). Higher levels of serum Gal-9 were observed in anti-MDA5-positive patients with DM than in anti-MDA5-negative patients with DM (33.8 (21.9–44.7) vs 16.2 (10.0–26.9) ng/mL, p < 0.001). Among the anti-MDA5-positive patients with DM, serum Gal-9 levels were associated with ILD severity. Serum Gal-9 levels were significantly correlated with disease activity in anti-MDA5-positive patients with DM in both cross-sectional and longitudinal studies. PBMCs isolated from anti-MDA5-positive patients with DM (3.7 ± 2.3 ng/mL) produced higher levels of Gal-9 than those from patients with immune-mediated necrotizing myopathy (1.1 ± 0.3 ng/mL, p = 0.022) and healthy controls (1.4 ± 1.2 ng/mL, p = 0.045). The mRNA levels of Gal-9 were positively correlated with levels of type-I interferon-inducible genes MX1 (r = 0.659, p = 0.020) and IFIH1 (r = 0.787, p = 0.002) in PBMCs from anti-MDA5-positive patients with DM. Immunohistochemistry revealed increased Gal-9 and Tim-3 expression in the lung tissues of patients with DM and RP-ILD. In vitro stimulation with Gal-9 protein increased CCL2 mRNA expression in MRC-5 fibroblasts.Conclusions: Among anti-MDA5-positive patients with DM, Gal-9 could be a promising biomarker for monitoring disease activity, particularly for RP-ILD severity. Aberrant expression of the Gal-9/Tim-3 axis may be involved in the immunopathogenesis of DM-ILD.