Agomelatine alleviates hypoxia-induced pulmonary arterial hypertension by activating mitophagy via the SIRT1/FoxO1/ULK1 signaling pathway

Human Melatonin Receptor type 1/2 (MTR1/MTR2) are widely distributed throughout the body and play essential roles in regulating cardiovascular physiology. However, the therapeutic potential of agomelatine (AGM), a melatonin analog and nonselective MTR1/MTR2 agonist, in pulmonary arterial hypertension (PAH) remains unclear. The present investigation was designed to evaluate the ameliorative potential of AGM on pulmonary vascular remodeling in a SU5416/hypoxia (SuHx)-induced PAH rat model, and to elucidate the concomitant mechanistic pathways. Our experimental data demonstrated that AGM treatment significantly diminished right ventricular systolic pressure, mitigated right ventricular hypertrophy, and attenuated medial wall thickening of pulmonary arteries. Notably, immunofluorescence staining further revealed predominant localization of MTRs within the smooth muscle layer of pulmonary arteriole. In vitro, AGM significantly suppressed hypoxia-evoked proliferative and migratory responses in human pulmonary artery smooth muscle cells (PASMCs). Mechanistically, AGM enhanced mitochondrial Reactive Oxygen Species generation and facilitated mitophagic flux, as corroborated by upregulated LC3-II protein expression, diminished p62 abundance, and increased mitochondrial-lysosomal colocalization. Transcriptomic analysis identified unc-51 like Autophagy activating kinase 1 (ULK1) as a pivotal mediator of AGM-induced Mitophagy. Genetic silencing of ULK1 abrogated the cytoprotective efficacy of AGM against hypoxia-evoked PASMC dysfunction. Further investigation revealed that AGM upregulated Sirtuin 1 (SIRT1) expression, leading to forkhead box protein 1(FOXO1) deacetylation. In contrast, inhibition of SIRT1 resulted in increased FOXO1 acetylation, which subsequently downregulated ULK1 expression and impaired Mitophagy. Collectively, these findings establish that AGM exerts therapeutic effects in PAH by enhancing ULK1-dependent Mitophagy through modulation of the SIRT1/FOXO1 signaling axis, underscoring its potential as a novel therapeutic candidate for PAH.

Melatonin analog; Mitophagy; Pulmonary arterial hypertension; Pulmonary arterial smooth muscle cells; Unc-51 like autophagy activating kinase 1.