Synergistic Treatment Approach for Pulmonary Fibrosis: Prednisone and Cyclophosphamide Regulation of Circular RNA MORF4L1 and MicroRNA-29a-3p Targeting BRD4

This study aimed to explore the effect of prednisone (PDN) combined with cyclophosphamide (CTX) on bleomycin-induced pulmonary fibrosis (PF) in rats via circular RNA mortality factor 4 like 1 (MORF4L1)/microRNA (miR)-29a-3p/Bromodomain protein 4 (BRD4) axis. A rat model of PF was induced by bleomycin and treated with PDN combined with CTX, and the lentiviral vectors that interfered with MORF4L1, miR-29a-3p, or BRD4 expression were injected into the tail vein at the same time. The mRNA expressions of MORF4L1, miR-29a-3p, BRD4, and fibrosis- associated proteins including fibronectin, connective tissue growth factor, and collagen I were detected by real-time quantitative polymerase chain reaction. The expression level of BRD4 protein in rat lungs was detected by Western blot analysis. Lung pathology of rats was observed by hematoxylin and eosin and Masson's trichrome staining. Apoptosis was observed by terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The targeting relationship between miR-29a-3p and MORF4L1 or BRD4 was verified by the bioinformatics website and dual luciferase reporter experiment. Bleomycin-induced PF enhanced MORF4L1 and BRD4 expression, inhibited miR-29a-3p expression, injured lung tissue, increased mRNA expression of fibrosis-related markers, and induced apoptosis in the lung tissue of rats. PDN combined with CTX had a therapeutic effect on PF in rats, which was further promoted by down-regulating MORF4L1 or up-regulating miR-29a-3p. After down-regulating miR-29a-3p or up-regulating BRD4, the effect of down-regulating MORF4L1 was reversed. MORF4L1 could bind to miR-29a-3p to target BRD4. In short, PDN combined with CTX can effectively improve PF through downregulating MORF4L1 to enhance miR-29a-3p-targeted regulation of BRD4.