Study on miRNA expression and regulatory network of Amygdalus mongolica oil and amygdalin in the treatment of pulmonary fibrosis

Introduction: Amygdalus mongolica (Maxim.) Ricker is a traditional Chinese medicine known for its ability to relieve cough and expectorate phlegm and is commonly used to treat dry throat, dry cough, and bronchitis. A. mongolica oil and amygdalin were the active components isolated from the seed kernel seeds of A. mongolica. The main objective of this study was to investigate the effects of A. mongolica oil and amygdalin on bleomycin-induced pulmonary fibrosis (PF) in rats by integrating pharmacodynamic, transcriptomics, and bioinformatics, to determine the changes of miRNAs in both against PF, and to explore the underlying mechanisms. Methods: A rat model of PF was induced by administering bleomycin through the trachea. The rats were randomized into several groups: a control group (CON), an untreated model group (MOD), an active control group treated with pirfenidone (PFD), and groups receiving different doses of A. mongolica oil (5 g/kg [OIL-L], 10 g/kg [OIL-M], and 15 g/kg [OIL-H]), or amygdalin (20 mg/kg [AMY-L], 40 mg/kg [AMY-M], and 80 mg/kg [AMY-H]). After 28 days, samples were collected for subsequent pharmacodynamic and transcriptomic analyses. Results: The results demonstrated that A. mongolica oil and amygdalin effectively reduced the abnormally elevated levels of IL-1β, IL-6, HA, LN and COL-IV in PF rats and alleviated bleomycin-induced pulmonary fibrotic changes. Furthermore, compared to the MOD group, the expression levels of 27 miRNAs were up-regulated and 23 miRNAs were down-regulated in the OIL 10 g/kg group. Among the up-regulated miRNAs, two novel differentially expressed miRNAs (DE-miRNAs) were identified. In the AMY 20 mg/kg group, 12 miRNAs were up-regulated and 10 were down-regulated when compared to the MOD group. These DE-miRNAs were found to be enriched in pathways such as the PI3K-Akt signalling pathway, MAPK signalling pathway, and calcium signalling pathway. The microRNAs miR-301b-3p, miR-667-5p, miR-363-3p, and miR-540-3p may be associated with both the anti-PF mechanism of A. mongolica oil and the anti-PF mechanism of amygdalin. Discussion: Numerous studies have demonstrated the significance of various pathways, including PI3K-Akt, MAPK, and calcium signalling pathways, in the mechanism of PF and the development of anti-PF medications. Meanwhile, multiple miRNAs, including miR-301b-3p, miR-667-5p, miR-363-3p, and miR-540-3p, have been found to be associated with lung disease and fibrosis. Conclusions: The present experiments confirmed the effectiveness of A. mongolica oil and amygdalin in reducing inflammation and fibrosis in bleomycin-induced PF rats, with particularly favorable outcomes observed in the A. mongolica oil 10 g/kg versus amygdalin 20 mg/kg. Meanwhile, miRNAs miR-301b-3p, miR-667-5p, miR-363-3p and miR-540-3p were found to be potentially associated with both A. mongolica oil and amygdalin anti-PF mechanisms. Based on our findings, we suggest that these miRNAs might play key roles in the anti-PF mechanism of A. mongolica. The individual miRNAs require further investigation.