Targeting ERK1/2 attenuates neutrophil extracellular traps-mediated pro-inflammatory and pro-fibrotic effects in myositis-associated interstitial lung disease

OBJECTIVE: This study aimed to investigate the mechanism and therapeutic potential of targeting the extracellular signal-regulated kinase 1/2 (ERK1/2) signalling pathway in myositis-associated interstitial lung disease, focusing on its role in neutrophil extracellular traps (NETs)-mediated pro-inflammatory and pro-fibrotic processes. METHODS: Lung tissue samples were collected from patients with idiopathic inflammatory myopathy-associated ILD (IIM-ILD) and from mice with experimental autoimmune myositis (EAM) and a myositis-associated interstitial lung disease model (MAILD). Multiple experimental techniques, including immunohistochemistry, western blotting, immunofluorescence and transcriptome sequencing were employed to analyse ERK1/2 activation, NETs infiltration and the expression of epithelial-mesenchymal transition (EMT)-related markers. The ERK1/2 inhibitor U0126 was applied both in vivo and in vitro for interventional validation. RESULTS: The ERK1/2 signalling pathway was activated in the lung tissues of IIM-ILD patients and in the EAM and MAILD mouse models. Substantial NETs infiltration was observed in the lung tissues of EAM and MAILD mice. NETs induced EMT and the release of pro-inflammatory factors by activating ERK1/2. Inhibiting NETs formation attenuated ERK1/2 phosphorylation and the downstream fibrotic process. Administration of the ERK1/2 inhibitor U0126 not only effectively alleviated NETs-induced EMT and inflammatory responses but also significantly reduced pulmonary inflammation infiltration and NETs formation in the MAILD model. CONCLUSION: NETs-mediated pro-inflammatory and pro-fibrotic processes contribute to the progression of myositis-associated interstitial lung disease by activating the ERK1/2 signalling pathway. Targeting ERK1/2 effectively inhibits this pathogenic cascade, providing a novel strategy for clinical treatment.