The overexpression of peroxiredoxin-4 affects the progression of idiopathic pulmonary fibrosis

BACKGROUND: Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is life-threatening. Several serum biomarkers, such as Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D), are clinically used for evaluating AE-IPF, but these biomarkers are not adequate for establishing an early and accurate diagnosis of AE-IPF. Recently, the protective roles of the members of the peroxiredoxin (PRDX) family have been reported in IPF; however, the role of PRDX4 in AE-IPF is unclear. METHODS: Serum levels of PRDX4 protein, KL-6, SP-D and lactate dehydrogenase (LDH) in 51 patients with stable IPF (S-IPF), 38 patients with AE-IPF and 15 healthy volunteers were retrospectively assessed using enzyme-linked immunosorbent assay. Moreover, as an animal model of pulmonary fibrosis, wild-type (WT) and PRDX4-transgenic (Tg) mice were intratracheally administered with bleomycin (BLM, 2 mg/kg), and fibrotic and inflammatory changes in lungs were evaluated 3 weeks after the intratracheal administration. RESULTS: Serum levels of PRDX4 protein, KL-6, SP-D and LDH in patients with S-IPF and AE-IPF were significantly higher than those in healthy volunteers, and those in AE-IPF patients were the highest among the three groups. Using receiver operating characteristic curves, area under the curve values of serum PRDX4 protein, KL-6, SP-D, and LDH for detecting AE-IPF were 0.873, 0.698, 0.675, and 0.906, respectively. BLM-treated Tg mice demonstrated aggravated histopathological findings and poor prognosis compared with BLM-treated WT mice. Moreover, PRDX4 expression was observed in alveolar macrophages and lung epithelial cells of BLM-treated Tg mice. CONCLUSIONS: PRDX4 is associated with the aggravation of inflammatory changes and fibrosis in the pathogenesis of IPF, and serum PRDX4 may be useful in clinical practice of IPF patients.