Zinc-binding protein metallothionein 3 protects vascular smooth muscle cells from ferroptosis via blocking lysosomal degradation of GPX4.

Aortic dissection (AD) is a life-threatening vascular emergency characterized by medial degeneration and vascular smooth muscle cell (VSMC) loss. Although disruption of zinc homeostasis has been reported in patients with AD, how zinc ions and their regulatory proteins influence VSMC survival and disease progression remains unknown. In this study, single-cell analyses revealed that ferroptosis and zinc-related pathways were significantly enriched in VSMCs from patients with AD, showing a strong correlation between the two processes, and zinc levels were markedly elevated in dissected aortas. Furthermore, zinc exposure promoted ferroptosis in cultured primary human aortic smooth muscle cells (HASMCs). By integrating transcriptomic data from AD tissues and VSMC ferroptosis models, metallothionein-3 (MT3), a zinc-binding protein, was identified as a candidate regulator. Functional studies demonstrated that MT3 overexpression markedly attenuated lipid peroxidation, reduced reactive oxygen species accumulation, and protected VSMCs from ferroptotic cell death, whereas MT3 knockdown increased oxidative stress and exacerbated ferroptotic injury. Mechanistically, MT3 directly interacted with glutathione peroxidase 4 (GPX4), enhanced its protein stability, without altering its transcriptional expression, and promoted glutathione synthesis, thereby activating the glutathione-GPX4 antioxidant defense pathway and mitigating oxidative injury. Notably, restoration of GPX4 effectively rescued the pro-ferroptotic effects of MT3 deficiency on HASMCs. These findings establish a previously unrecognized zinc-MT3-GPX4 axis as a critical determinant of VSMC ferroptosis in AD, linking zinc dysregulation to medial degeneration, and highlighting MT3 as a potential mechanistic candidate target to preserve vascular integrity and limit disease progression. KEY MESSAGES: Impaired zinc homeostasis is implicated in the development of aortic dissection (AD). Zinc-binding protein metallothionein 3 (MT3) mitigates lipid peroxidation and protects vascular smooth muscle cells from ferroptosis. MT3 directly interacts with glutathione peroxidase 4 (GPX4) to prevent its lysosomal degradation, thereby enhancing the glutathione-GPX4 antioxidant defense pathway. MT3 is a potential mechanistic candidate target for preserving vascular integrity and limiting AD progression.