Targeting USP11 may alleviate radiation-induced pulmonary fibrosis by regulating endothelium tight junction

Radiation-induced pulmonary fibrosis (RIPF) is a major side effect after radiotherapy for thoracic malignancies. However, rare anti-RIPF therapeutics show definitive effects for treating this disease. Ubiquitin-specific peptidase 11 (USP11) has been reported to promote transforming growth factor β (TGFβ) signaling which plays an essential role underlying RIPF. Herein, we explored the role of USP11 on RIPF. In the present study, USP11-knockout (<i>Usp11^-/-</i>) mice were used to explore the effects of USP11 on RIPF. The lung tissue was obtained after receiving 30 Gy X-ray irradiation. The expression of USP11, TGF-β1, and a-SMA was determined by immunohistochemical and Western Blot, respectively. γ-H₂AX foci and TUNEL positive cells were detected by fluorescent technique to assess DNA damage and apoptosis. High-throughput proteomic analysis was applied to further explore the related mechanisms. The transwell co-culture method was used to investigate bystander effects in HELF cells induced by irradiated HMEC-1 cells <i>in vitro</i>. Here we found that radiation activated USP11 <i>in vivo</i> and <i>in vitro</i>. Our results showed that USP11 deficiency effectively decreased serum TGF-β1 level, suppressed α-SMA expression, and mitigated pulmonary fibrosis. In addition, fewer γ-H₂AX foci and decreased apoptotic cells were identified after irradiation in the primary cells isolated from the lungs of <i>Usp11^-/-</i> mice. High-throughput proteomics analysis results showed that 22-upregulated and 158-downregulated proteins were identified in the lung tissues of <i>Usp11^-/-</i> mice after irradiation. Furthermore, gene set enrichment analysis (GSEA) revealed that USP11 deficiency affects the tight junction signaling pathway. We verified that USP11 deficiency remarkably reinforced tight junction in the endothelial cells and alleviated TGF-β1 to inhibit fibrosis of fibroblast cells. The present study preliminarily showed that USP11-knockout mitigated RIPF via reinforcement endothelial barrier function.