Magnesium leachates suppress inflammatory phenotype of vascular smooth muscle cells by downregulating the NF-κB p50/KLF5 signaling

Background Atherosclerosis is a chronic inflammatory disease in which vascular smooth muscle cells (VSMCs) undergo phenotypic switching. Inflammatory, macrophage-like VSMCs contribute to neointimal hyperplasia and plaque instability. Biodegradable magnesium (Mg)-based stents have favorable mechanical and biological properties, but their in-situ degradation releases magnesium ions (Mg²⁺) that may modulate the vascular microenvironment and influence inflammatory VSMCs behavior, potentially affecting stent performance and therapeutic outcomes in atherosclerosis. Methods Primary rat VSMCs were induced with IL-1β, oxidized LDL, or cholesterol to generate inflammatory/macrophage-like phenotypes, then exposed to extracts from pure Mg or AZ31 stent alloys or Mg²⁺. Phenotypic markers and functions were evaluated by qRT-PCR, western blotting, immunofluorescence, ELISA, and phagocytosis assays. RNA sequencing and bioinformatic analyses identified Mg²⁺-responsive genes and pathways. Mechanisms were tested using lentiviral gene overexpression, NF-κB inhibition, and luciferase reporter assays. Results Both alloy extracts and Mg²⁺ significantly reduced adhesion molecules, proinflammatory cytokines/chemokines, and their secretion in three inflammatory VSMC models, while increasing contractile gene expression. Mg²⁺ attenuated NF-κB p50 nuclear translocation and inhibited its transcriptional activity, suppressing inflammatory gene programs. KLF5 was downregulated following the initial suppression of NF-κB by Mg²⁺. NF-κB and KLF5 reciprocally regulated each other, forming a positive feedback loop to sustain the inflammatory phenotype of VSMCs; Mg²⁺ disrupted this loop in macrophage-like VSMCs and promoted their reversion toward a contractile state. Conclusions Mg²⁺ accumulation from Mg-stent degradation restrains the NF-κB p50/KLF5 feedback circuit, inhibits inflammatory phenotypic switching of VSMCs, and limits proinflammatory activity, supporting Mg-based stents for vascular intervention and restenosis prevention. Statement of significance Inflammatory, macrophage-like phenotypic switching of vascular smooth muscle cells (VSMCs) is a key driver of neointimal hyperplasia, plaque instability, and restenosis. While biodegradable magnesium-based stents exhibit suitable mechanical properties, the biological effects of magnesium ions released during degradation remain incompletely understood. This study demonstrates that magnesium ions suppress inflammatory VSMC phenotypes by inhibiting NF-κB p50 signaling and disrupting the NF-κB/KLF5 positive feedback loop recognized to sustain inflammatory gene programs in VSMCs. By facilitating the transition of macrophage-like VSMCs toward a contractile state, magnesium ions reduce proinflammatory activity within the vascular microenvironment. These findings provide mechanistic insight into the immunomodulatory role of Mg-based stents and demonstrate their potential significance in improving vascular intervention and restenosis prevention.