Ethoxyquin mediates lung fibrosis and cellular immunity in BLM-CIA mice by inhibiting HSP90.

BACKGROUND

Patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) are characterized by severe pulmonary fibrosis and immune dysregulation. Heat shock protein 90 (HSP90) is involved in the progression of pulmonary fibrosis and the immune response.

OBJECTIVES

This study aimed to explore whether HSP90 regulates the development of RA-ILD and its underlying mechanism.

MATERIAL AND METHODS

In vivo, collagen-induced arthritis (CIA)-mice were treated with bleomycin (BLM) to establish an arthritic mouse model of pulmonary fibrosis. In vitro, human lung fibroblast 1 (HLF1) was exposed to transforming growth factor beta 1 (TGF-β1) to simulate an RA-ILD model. The RA-ILD models were treated with the HSP90 inhibitor ethoxyquin (EQ) to explore the potential mechanism of HSP90 in RA-ILD. Histopathological analysis was performed, and pulmonary fibrosis was evaluated. The differentiation of M1/M2 macrophages and Th1/Th17/Treg cells was assessed. The role of the TGF-β/Smad2/3 pathway in EQ-mediated RA-ILD progression was also explored.

RESULTS

HSP90α and HSP90β were upregulated in the RA-ILD models. Ethoxyquin mitigated arthritis in BLM-CIA mice, and reduced the expression of alpha-smooth muscle actin (α-SMA), collagen I (Col-1) and fibronectin (FN), as well as hydroxyproline content, thereby relieving pulmonary fibrosis. In addition, EQ increased M1 macrophages and inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNF-α) levels; conversely, EQ decreased M2 macrophages and vascular endothelial growth factor (VEGF)-A and TGF-β1 contents. It also decreased Th17 (interleukin (IL)-17) while increasing Th1 (interferon gamma (IFN-γ)) and Treg (Foxp3), and restricted the expression of transforming growth factor beta type receptor I and II (TGF-βRI and TGF-βRII) and the phosphorylation of Smad2 and Smad3.

CONCLUSIONS

This study revealed that EQ regulated pulmonary fibrosis and cellular immunity by inhibiting HSP90, appearing to act through the TGF-β/Smad2/3 pathway. These findings suggest that EQ holds potential as a therapeutic agent for treating RA-ILD.