Sustainably released nanoparticle-based rhynchophylline limits pulmonary fibrosis by inhibiting the TEK-PI3K/AKT signaling pathway

BACKGROUND: Pulmonary fibrosis (PF) is a rapidly progressing and irreversible disease, and the currently available types of clinical drugs are limited and inefficient. In our previous study, we observed that Rhynchophylline (Rhy) hindered tendon adhesion and stimulated the healing of injured tendon structures. Considering the similar mechanisms between adhesion formation and PF, we explored the roles of Rhy in PF. METHODS: The cytotoxicity of Rhy was tested by a Cell Counting Kit-8 (CCK-8) assay. The degree of PF was evaluated by Western blot (WB), Masson and hematoxylin-eosin (HE) staining, and hydroxyproline quantification. The Rhy-loaded nanoparticles were prepared through an emulsification sonication technique and characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The release of the Rhy-loaded nanoparticles was tested using the absorbance value of the supernatant. Transcriptome sequencing was performed to determine the downstream target and pathway of Rhy, which was then verified by WB. RESULTS: In vitro, Rhy decreased Transforming Growth Factor Beta 1 (TGF-β1)-induced abnormal overexpression of fibronectin (FN), collagen I (Col I), α-smooth muscle actin (α-SMA) in a dose-dependent manner in human lung fibroblast (HFL1) cells. In vivo, we confirmed (through Masson staining) that the intraperitoneal injection of Rhy reduced collagen deposition and the fibrotic area in a dose-dependent manner. Our results indicated that the Rhy-loaded nanoparticles intratracheal spray intuitively narrowed collagen deposition, shrank collagen deposition and the fibrotic area (Masson and HE staining), and reduced the expression of fibrosis-related markers (WB). Meanwhile, the lung index value and hydroxyproline content were markedly lower than the bleomycin (BLM)-treated group. By transcriptional sequencing analysis, we identified Receptor Tyrosine Kinase (TEK)-Phosphatidylinositol 3-Kinase/Protein Kinase B (PI3K/AKT) as the downstream target and pathway of Rhy. It was also observed that Rhy could reverse the TGF-β1-induced TEK and phosphorylated AKT (p-AKT) elevated expression. CONCLUSIONS: Our findings indicate that Rhy constrained PF progression by inhibiting TEK-PI3K/AKT signaling pathway. Hence, this sustainable release system of Rhy is a highly effective therapy to limit PF and should be developed.