The ganglioside GM3 protects against abdominal aortic aneurysm by suppressing ferroptosis in vascular smooth muscle cells
Background: Abdominal aortic aneurysm (AAA) is a potentially life-threatening condition, but approved medical therapies to prevent AAA progression and rupture are currently lacking. Sphingolipids metabolism disorders are associated with the occurrence and development of AAA. It has been discovered that ganglioside GM3, a sialic acid-containing type of glycosphingolipid, plays a protective role in atherosclerosis which is an important risk factor for AAA, but the potential contribution of GM3 to AAA development has not been investigated.  Methods: We performed a metabolomics study to evaluated GM3 level in plasma of human AAA patients. We profiled GM3 synthase (ST3GAL5) expression in the mouse model of aneurysm and human AAA tissues through western blotting and immunofluorescence staining. RNA sequencing, proteomic analysis, affinity purification and mass spectrometry, surface plasmon resonance (SPR) analysis, and functional studies were used to dissect the molecular mechanism of GM3-regulating ferroptosis. We conditionally deleted and overexpressed St3gal5 in smooth muscle cells (SMCs) in vivo to investigate its role in AAA.  Results: We found significantly reduced plasma levels of the GM3 in human AAA patients. GM3 content and ST3GAL5 expression were all decreased in abdominal aortic VSMCs in AAA patients and mouse model. RNA-sequencing analysis showed that ST3GAL5 silencing in human aortic SMCs (HASMCs) induced ferroptosis. Importantly, we showed that GM3 interacted directly with the extracellular domain of transferrin receptor 1 (TFR1), a cell membrane protein critical for cellular iron uptake, disrupted its interaction with holo-transferrin. SMC-specific St3gal5 knockout exacerbated iron accumulation at lesion sites and significantly promoted AAA development, while GM3 supplementation suppressed lipid peroxidation, reduced iron deposition in aortic VSMCs and markedly decreased AAA incidence.  Conclusions: Together, these results suggest that GM3 dysregulation promotes ferroptosis of VSMCs in AAA. Furthermore, GM3 may constitute a new therapeutic target for the treatment of AAA. Overall design: To understand how GM3 affected cellular processes in VSMCs, we conducted RNA sequencing (RNA-seq) in human aortic smooth muscle cells (HASMCs) transfected with ST3GAL5 siRNA (siST3GAL5) or control siRNA (siNC).