MitoQ Has Diverse Effects on H₂O₂-Induced Oxidative Stress and the NRF2 Signalling Pathway in Aortic Smooth Muscle...

Oxidative stress plays a central role in the development and progression of abdominal aortic aneurysms (AAA), as it severely impairs the function and survival of vascular smooth muscle cells (VSMCs). MitoQ (mitoquinone mesylate), a mitochondria-specific antioxidant, was shown to reverse age-related arterial stiffening and improve vascular endothelial function, among other things, by interacting with the NRF2 signalling pathway. The aim of this study was to compare how long-term treatment with low doses of MitoQ affects the NRF2 stress response in VSMCs, derived from different origins (AAA-SMC, healthy aortic SMC, and immortalized VSMC (iHAoSMC)). We found a significant reduction in NRF2 and KEAP1 levels in the aortic wall of patients with AAA, accompanied by increased 8-OHdG levels, indicating defects in the response to oxidative stress. In contrast, relative NRF2 expression in tissue extracts and VSMC-enriched areas was higher in patients with AAA than in healthy aortic tissue. In vitro, baseline NRF2 protein levels were significantly higher in AAA-SMC and in iHAoSMC than in VSMC from healthy aorta, whereas NRF2 activity did not differ between AAA-derived and healthy VSMC. AAA-derived SMC were found to be less vulnerable against toxic concentrations of MitoQ than healthy VSMC, and the cell viability was differentially affected by H₂O₂. Acute oxidative stress by H₂O₂ increased NRF2 activity in AAA-SMC and iHAoSMC, but not in healthy VSMC. Pre-treatment of the cells for 7 days with low-dose (10 nM) MitoQ resulted in significantly increased NRF2 activity in AAA-SMC and iHAoSMC, but not in healthy VSMC, which was accompanied by a significant reduction of ROS production, particularly in AAA-derived SMC. Our data demonstrate that prolonged treatment with low doses of MitoQ has a protective effect, particularly on VSMCs from AAA, without affecting healthy aortic VSMCs. Moreover, immortalized cells can be used as a model for investigating oxidative stress responses in AAA-SMC, even though they do not react in exactly the same way. Overall, our findings confirm the cytoprotective potential of MitoQ to limit oxidative stress, particularly in AAA-SMC that is clinically observed in the abdominal aneurysm wall.