LAUSR

Age-related vascular endothelial dysfunction, characterized by reduced nitric oxide (NO) bioavailability, is mediated in part by excess production of mitochondrial reactive oxygen species (mtROS). Excess mtROS also oxidizes circulating lipids (i.e., low-density lipoprotein [LDL]) to promote endothelial dysfunction with aging. We recently showed that 6-weeks of treatment with the mitochondria-targeted antioxidant MitoQ (MQ) (20 mg/day) improved endothelial function in vivo in older adults. The improvements in endothelial function with MQ were mediated by reduced mtROS and associated with lower plasma levels of oxidized LDL (oxLDL). However, the complete mechanisms by which MQ improves endothelial function, and if MQ-related decreases in oxLDL are mechanistically involved, remain unknown. PURPOSE. To determine if chronic MQ supplementation-mediated changes in the circulating milieu contribute to improvements in endothelial cell (EC) function and the mechanistic role of reductions in oxLDL. METHODS. Plasma samples were obtained 24 h after the last dose from 19 older adults (mean±SEM: 67±1 yrs; 11 women) who completed our crossover design pilot trial to assess the efficacy of 6-weeks of MQ vs. placebo (PLA) treatment for improving endothelial function. Using an ex vivo model of endothelial function, acetylcholine (Ach)-stimulated NO bioavailability (DAR-4M-AM) was quantified in human aortic ECs (HAECs) following exposure to plasma collected after each phase of the study (MQ and PLA). The role of mtROS production (MitoSOX) in plasma-mediated changes in HAEC function was also assessed. To elucidate the role of lower oxLDL with MQ treatment on HAEC function, physiological levels of oxLDL were ‘added back’ to plasma collected from subjects after MQ treatment at a concentration corresponding to the average reduction after MQ (14 ng/mL). To determine if lower oxLDL with MQ treatment improves HAEC function through a reduction in binding to the oxLDL receptor LOX-1, HAECs were subjected to LOX-1 blocking antibodies prior to plasma exposure under the 3 experimental conditions (PLA; MQ; MQ + oxLDL [‘add back’]) in a subset of subjects (N=9; 67±1 yrs; 5 women). RESULTS. Ach-stimulated NO bioavailability was higher (PLA: 1.0±0.05; MQ: 1.24±0.08; P=0.0002) and mtROS was lower (PLA: 1.0±0.09; MQ: 0.76±0.08; P=0.003) in HAECs exposed to plasma collected from subjects after MQ treatment compared to PLA. Normalizing oxLDL (‘add back’) abolished the effects of MitoQ treatment. LOX-1 blockade modulated Ach-stimulated NO and mtROS production to levels comparable to (P>0.98) or lower than (P<0.047) MQ in all 3 groups, respectively. CONCLUSIONS. Chronic MQ supplementation in older adults alters circulating factors by decreasing plasma oxLDL to reduce oxLDL-LOX-1 signaling-mediated mtROS production and improve EC function. These findings extend insight into the mechanisms by which mitochondria-targeted antioxidant treatment improves endothelial function with aging. 1R21AG049451-01A1 (DRS); 5T32DK007135-46 (KOM); K01DK115524-01A1 (MJR) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.