The
interleukin (IL)-1 family of
cytokines is strongly associated with
systemic sclerosis (SSc) and pulmonary involvement, but the molecular mechanisms are poorly understood. The aim of this study was to assess the role of IL-1α and IL-1β in pulmonary vascular and interstitial remodelling in a mouse model of SSc.IL-1α and IL-1β were localised in lungs of SSc patients and in the
fos-related antigen-2 (Fra-2) transgenic (TG) mouse model of SSc. Lung function, haemodynamic parameters and
pulmonary inflammation were measured in Fra-2 TG mice with or without 8 weeks of treatment with the
IL-1 receptor antagonist
anakinra (25 mg·kg-1·day-1). Direct effects of
IL-1 on pulmonary arterial smooth muscle cells (PASMCs) and parenchymal fibroblasts were investigated in vitroFra-2 TG mice exhibited increased
collagen deposition in the lung, restrictive lung function and enhanced muscularisation of the vasculature with concomitant
pulmonary hypertension reminiscent of the changes in SSc patients. Immunoreactivity of IL-1α and IL-1β was increased in Fra-2 TG mice and in patients with SSc.
IL-1 stimulation reduced
collagen expression in PASMCs and parenchymal fibroblasts via distinct signalling pathways. Blocking
IL-1 signalling in Fra-2 TG worsened
pulmonary fibrosis and restriction, enhanced T-helper cell type 2 (Th2)
inflammation, and increased the number of pro-fibrotic, alternatively activated macrophages.Our data suggest that blocking
IL-1 signalling as currently investigated in several clinical studies might aggravate
pulmonary fibrosis in specific patient subsets due to Th2 skewing of immune responses and formation of alternatively activated pro-fibrogenic macrophages.