Relaxin-3/RXFP1 Axis Regulates the Phenotypic Switch of Diabetic Vascular Smooth Muscle Cells by Inhibiting H3K18la-Mediated Egfr Transcription.

BACKGROUND: The phenotypic switching of vascular smooth muscle cells (VSMCs) is a critical pathophysiological mechanism of diabetic vascular remodeling. There is increasing evidence indicating that endogenous relaxin-3 exhibits cardiovascular effects, including vasodilation, reversal of ventricular remodeling, and attenuation of myocardial fibrosis. This study investigates the role of relaxin-3 as a key regulator in the phenotypic switching of VSMCs and elucidates its underlying mechanisms. METHODS: We generated a diabetic rat model to investigate the biological roles of relaxin-3 in diabetic vascular remodeling. Metabolomic profiling characterized relaxin-3-induced metabolic changes in VSMCs under high glucose treatment. Combined chromatin immunoprecipitation sequencing and RNA sequencing data were used to further investigate the gene regulatory mechanisms of relaxin-3 in the phenotypic switching of VSMCs and target genes regulated by H3K18la (histone H3 lysine 18 lactylation). RESULTS: Relaxin-3 and its receptor RXFP1 (relaxin family peptide receptor 1) were upregulated in diabetic human and rat aortas. Silencing of relaxin-3 or RXFP1 expression inhibited VSMC contractile phenotype protein expression and promoted VSMC proliferation. Relaxin-3 treatment mitigated the phenotypic switching of VSMCs via RXFP1, preserving VSMCs' contractile phenotype. Further, relaxin-3 treatment lowered the glycolytic rate and lactate production during the phenotypic switching of VSMCs and decreased histone lactylation. Mechanistically, relaxin-3 suppressed LDHA (lactate dehydrogenase A)-mediated lactate production and H3K18la-mediated EGFR (epidermal growth factor receptor) transcription, and blocked PKM2 (pyruvate kinase M2) nuclear translocation, thereby preventing PKM2/β-catenin complex formation. CONCLUSIONS: Relaxin-3 alleviated the phenotypic switching of diabetic VSMCs through a dual mechanism: inhibiting lactate-mediated H3K18la and disrupting the intranuclear PKM2/β-catenin interaction, thereby preserving the contractile VSMC phenotype.