CCP1 Inhibits Pulmonary Fibrosis by Suppressing Fibrotic Progression Through the EIF4B/PI3K/AKT Pathways

Pulmonary fibrosis (PF), particularly idiopathic pulmonary fibrosis, is a chronic and fatal disease. However, the precise pathogenic mechanisms underlying this condition remain elusive. We employed LASSO regression and random forest analyses, combined with expression profiling in TGFβ1-induced MRC-5 cells and bleomycin-induced PF mouse models, to identify differentially expressed genes. These analyses revealed that cytoplasmic carboxypeptidase 1 (CCP1) was significantly downregulated in fibrotic conditions. Relevant signaling pathways were further identified through RNA sequencing (RNA-seq). Subsequent functional studies were conducted using qRT-PCR, western blot, hematoxylin and eosin (HE) staining, Masson's trichrome staining, immunohistochemistry (IHC), immunofluorescence, scratch assays, EdU assays, RNA interference, and co-immunoprecipitation (co-IP). Functional studies revealed that CCP1 knockdown promoted cell migration, proliferation, and the transformation of MRC-5 cells into a fibrotic phenotype, as evidenced by increased expression of fibrosis-associated markers (FN1, COL 1α1, and ACTA2) and dysregulated expression of apoptosis-related markers (BCL2 and BAX). Conversely, CCP1 overexpression inhibited these processes. CCP1 was discovered to inhibit the PI3K/AKT signaling pathway by binding to eukaryotic initiation factor 4B (EIF4B). Overexpression of EIF4B activated the fibrotic process and interacted with c-Myc. In vivo studies further demonstrated that CCP1 inhibited PF by suppressing EIF4B to inhibit the PI3K/AKT signaling pathway. In summary, our results demonstrate that CCP1 inhibits the development of PF by suppressing the EIF4B/PI3K/AKT axis. This study offers new perspectives into the pathogenesis of PF and underscores CCP1 as a potential therapeutic target for managing this condition.