Background: Idiopathic pulmonary fibrosis (IPF) is a progressive diffuse parenchymal disease with a poor prognosis. A variety of cytokines and chemokines are involved in its pathophysiology. The aim of this study was to evaluate the clinical features in IPF patients with the expression of suppressor of cytokine signaling 1 (SOCS-1), which acts as a negative regulator of cytokine signaling.
Methods: IPF patients (n = 20) and healthy controls (n = 16) were included in this study. The expression of SOCS-1 was analyzed in peripheral blood mononuclear cells (PBMC) of subjects using RT-PCR. Interleukin 4 (IL-4), transforming growth factor β1 (TGF-β1) and type I collagen expression were also analyzed in each individual using enzyme-linked immunosorbent assay (ELISA). The clinical characteristics of IPF patients were delineated. These results were analyzed by SPSS13.0 statistics software.
Results: SOCS-1 mRNA expression was significantly decreased in the PBMC of IPF patients compared with healthy controls; serum levels of IL-4 and TGF-β1 were higher in IPF patients. The patients with lower expression of SOCS-1 developed lower percentage of forced vital capacity (FVC%) and DLCO/VA. A patients' SOCS-1 mRNA level was negatively correlated with serum levels of IL-4, and negatively correlated with their high-resolution computed tomography (HRCT) scores.
Conclusions: SOCS-1 mRNA can be detected in PBMC, and it is down-regulated in IPF patients. The expression of SOCS-1 is associated with the severity of IPF patients' symptoms, so it might be the predictor of disease severity. SOCS-1 might play an important role in IPF by reducing the expression of the T helper type 2 (Th2) cell-related cytokine IL-4.