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Background: Doxorubicin (DOXO) chemotherapy increases risk for cardiovascular disease in part by inducing endothelial dysfunction in conduit arteries. However, the mechanisms mediating DOXO-associated endothelial dysfunction in (intact) arteries and treatment strategies are not established. Objectives: We tested the hypothesis that DOXO impairs endothelial function in conduit arteries via excessive mitochondrial reactive oxygen species (ROS) and that these effects could be prevented by treatment with a mitochondrial-targeted antioxidant (MitoQ). Methods: Endothelial function (endothelium-dependent dilation [EDD] to acetylcholine) and vascular mitochondrial ROS were assessed 4 weeks following administration (10 mg/kg intraperitoneal injection) of DOXO. A separate cohort of mice received chronic (4 weeks) oral supplementation with MitoQ (drinking water) for 4 weeks following DOXO. Results: EDD in isolated pressurized carotid arteries was 55% lower 4 weeks following DOXO (peak EDD, DOXO: 42 ± 7% vs. sham: 94 ± 3%; p = 0.006). Vascular mitochondrial ROS was 52% higher and manganese (mitochondrial) superoxide dismutase was 70% lower after DOXO versus sham (p = 0.0008). Endothelial function was rescued by administration of the mitochondrial-targeted antioxidant, MitoQ, to the perfusate. Exposure to plasma from DOXO-treated mice increased mitochondrial ROS in cultured endothelial cells. Analyses of plasma showed differences in oxidative stress-related metabolites and a marked reduction in vascular endothelial growth factor A in DOXO mice, and restoring vascular endothelial growth factor A to sham levels normalized mitochondrial ROS in endothelial cells incubated with plasma from DOXO mice. Oral MitoQ supplementation following DOXO prevented the reduction in EDD (97 ± 1%; p = 0.002 vs. DOXO alone) by ameliorating mitochondrial ROS suppression of EDD. Conclusions: DOXO-induced endothelial dysfunction in conduit arteries is mediated by excessive mitochondrial ROS and ameliorated by mitochondrial-specific antioxidant treatment. Mitochondrial ROS is a viable therapeutic target for mitigating arterial dysfunction with DOXO.

Nitroxide small molecule agents are in development as preventative or therapeutic pharmaceutical drugs for age-related macular degeneration and cardiovascular disease, which are two major diseases of aging. These aging diseases are associated with patient genetics, smoking, diet, oxidative stress and chronic inflammation. Nitroxide drugs preventing aging-, smoking-, high sugar or high fat diet-, or radiation- and other environmental-induced pathophysiological conditions in aging disease are reviewed. Tempol (TP), Tempol Hydroxylamine (TP-H), and TP-H prodrug (OT-551) are evaluated in (1) nonsmokers versus smokers with cutaneous microvascular dysfunction, rapidly reversed by cutaneous TP; (2) elderly cancer patients at risk for radiation-induced skin burns or hair loss, prevented by topical TP; and (3) elderly smoker or nonsmoker Age-related Macular Degeneration (AMD) patients at risk for vision loss, prevented by daily eye drops of OT-551. The human data indicates safety and efficacy for these nitroxide drugs. Both TP and TP-H topically penetrate and function in skin or mucosa, protecting and treating radiation burns and hair loss or smoking-induced cutaneous vascular dysfunction. TP and TP-H do not penetrate the cornea, while OT-551 does effectively penetrate and travels to the back of the eye, preserving visual acuity and reducing low luminance deficit and night vision loss in dry AMD smokers and non-smoker patients. Topical, oral or injectable drug formulations are discussed.

Age-related increases in aortic stiffness, assessed by pulse wave velocity (PWV), predict cardiovascular (CV)-related mortality, but the upstream drivers are incompletely understood. Purpose: To determine if higher circulating levels of the gut microbiome-derived metabolite trimethylamine-N-oxide (TMAO) contribute to age-related aortic stiffening. Methods and Results: Plasma TMAO concentrations were higher in healthy middle-aged-to-older (45–79 y; N = 83) vs. young (18–27 y; N = 14) humans (6.3 ± 0.6 vs. 1.8 ± 0.3 μM; p < 0.01) and positively related to carotid-femoral (c-f) PWV (r2 = 0.15, p < 0.0001). To determine the role of TMAO in established age-related aortic stiffness, we supplemented old mice (27 mo; N = 12–16/group) with 1% 3,3-dimethyl-1-butanol (DMB; suppresses microbiota-dependent TMAO production) in drinking water for 8–10 weeks vs. normal drinking water (control). Relative to young mice (3 mo; N = 23), old mice had higher aortic (a) PWV (412 ± 17 vs. 349 ± 11 cm/s; p < 0.01), but DMB had no effect on aPWV (p = 0.58 vs. control) despite suppressing plasma TMAO (control: 8.7 ± 6.3 vs. DMB: 4.3 ± 1.2 µM, p = 0.07) to young levels (3.8 ± 2.6 µM). Next, to determine if TMAO contributes to the development of aortic stiffening, we initiated DMB at mid-life (18 mo; i.e., before the onset of stiffening; N = 8–21/age/treatment). aPWV was similar between young and 18 month-old mice (363 ± 5 cm/s; p = 0.58), but increased progressively with age in control mice (24 mo: 401 ± 13 cm/s, p = 0.03 vs. young; 27 mo: 442 ± 10 cm/s, p < 0.001 vs. young), whereas age-related increases in PWV were considerably attenuated by DMB (24 mo: 359 ± 9 cm/s; 27 mo: 388 ± 10 cm/s, both p < 0.01 vs. control). Conclusions: Age-related increases in TMAO contribute to the development of aortic stiffness. TMAO-targeted interventions initiated in mid-life may prevent/delay age-related aortic stiffening and reduce CV risk. Funding: HL134887-02S1, AG060884, HL140875, AG000279.