Alveolar macrophages in scleroderma lung disease are activated by TGF-β and IL-4 but not TNF-α

Background

We reported previously that alveolar macrophages from scleroderma patients with lung inflammation are characterized by an activated gene expression profile.

Objective

The purpose of this study was to identify the molecular mediators that have activated alveolar macrophages in scleroderma lung disease, through an analysis of transcription factor activation.

Methods

Freshly isolated alveolar macrophages were negatively selected by depleting CD3⁺ cells from BAL cells of six patients with lung inflammation. Nuclear translocation of 55 transcription factors was evaluated using a protein/DNA array system (Panomics). Data were analyzed using hierarchical clustering.

Results and conclusion

Three distinct clusters of translocated transcription factors were notable. One cluster included Smad3/4 as well as other factors involved in or activated by TGF-β signaling, including CREB/p300, Fast-1, the glucocorticoid receptor element, and GAS/ISRE. A second cluster included Stat5/6 and other factors activated by IL-4 signaling, including GATA, Sp1, and early-response element. The third cluster included factors that were translocated to the nucleus in low levels in only a few samples. This cluster included NF-κB, which is critical in signaling by TNF-α and IL-1, and several other transcription factors activated by TNF-α signaling. In animal models, macrophages that are activated by TGF-β or IL-4 have been associated with the subsequent development of fibrosis. Thus, we directly demonstrate cellular activation by the profibrotic factors TGF-β and IL-4 in involved tissues from scleroderma patients.