TLR2-EGR1 signaling axis modulates TGFβ1-induced differentiation of fibroblasts into myofibroblasts in pulmonary fibrosis.

Pulmonary fibrosis is a progressive lung condition characterized by the excessive activation of myofibroblasts. Transforming growth factor beta 1 (TGFβ1) plays a crucial role in the differentiation of fibroblasts into myofibroblasts. In addition, toll-like receptor 2 (TLR2), known for its role in immune responses, contributes to pulmonary fibrosis by promoting myofibroblast differentiation. However, the interplay between TGFβ1 and TLR2 signaling pathways in myofibroblast differentiation has remained elusive. In the present study, we investigated the involvement of TLR2 in TGFβ1-induced fibroblast differentiation into myofibroblasts using IMR-90 human pulmonary fibroblasts as a model cell line. We found that TLR2 activation induced myofibroblast differentiation by enhancing the expression of early growth response 1 (EGR1) via the mitogen-activated protein kinase (MAPK) signaling pathway. Elevated EGR1 levels were detected in the lung tissues of a bleomycin (BLM)-induced mouse model of pulmonary fibrosis. Moreover, the administration of tomaralimab, an antagonistic anti-TLR2 antibody, reduced the EGR1 expression and collagen deposition. Altogether, targeting the TLR2-EGR1 pathway could be a promising therapeutic approach for pulmonary fibrosis by blocking TGFβ1-induced myofibroblast differentiation.