Endothelial Nrf2-KO Attenuates Endothelial Function and Skeletal Muscle Antioxidant Capacity

Introduction: Endothelial dysfunction is considered a key contributor to vascular pathologies. It is well-accepted that excessive reactive oxygen species and oxidative damage likely contribute to endothelial dysfunction. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is considered the master regulator of endogenous antioxidant responses. Therefore, Nrf2 may be a potential therapeutic target to protect against endothelial dysfunction. However, the roles of endothelial cell (EC)-specific Nrf2 on endothelial function are not known. The major objective of this study was to evaluate the impacts of EC Nrf2 deletion on endothelial-mediated vasodilation, which we hypothesized would be attenuated with EC Nrf2 deletion. Methods: Femoral-to-popliteal artery segments were harvested from 6-mo old C57BL/6 mice (WT, n = 6) and EC-specific Nrf2-knockout mice (Tie2-Cre-Nrf2 floxed-KO, n = 6) using both sexes (3 male and 3 female/group). Vasodilation was assessed in response to flow (30 uL·min -1 ), acetylcholine (ACh, 10 -7 -10 -3 M) with and without NΩ-Nitro-L-arginine methyl ester (L-NAME), and sodium nitroprusside (SNP, 10 -9 -10 -4 M) using videomicroscopy. Glutathione peroxidase 1 (GPX1) and catalase (CAT) skeletal muscle protein expression was assessed by immunoblotting and normalized to total protein. Results: Endothelium-dependent vasodilation was lower in Nrf2-KO compared to WT induced by flow (WT: 34.8 ± 2.9%, Nrf2-KO: 20.7 ± 3.7%, P < 0.01) and ACh (10 -3 M, WT: 68.3 ± 8.2%, Nrf2-KO: 44.5 ± 7.1%, P < 0.01). L-NAME incubation attenuated endothelium-dependent vasodilation in WT mice in response to flow (12.8 ± 4.5%, P < 0.01) and ACh (10 -3 M, 19.1 ± 4.4%, P < 0.01) but did not change in Nrf2-KO in response to flow (15.6 ± 6.8%, P = 0.28) or ACh (10 -3 M, 37.7 ± 7.0%, P = 0.16). Endothelium-independent vasodilation was not different (SNP 10 -4 M, WT: 92.7 ± 3.6%, Nrf2-KO: 81.9 ± 10.2%, P = 0.16). In addition, GPX1 was lower in Nrf2-KO mice (WT: 0.47 ± 0.06, Nrf2-KO: 0.001 ± 0.003, P < 0.01), but CAT was not different (WT: 0.16 ± 0.04, Nrf2-KO: 0.37 ± 0.21, P = 0.08). Conclusions: EC Nrf2 may play a key role in endothelial-mediated vasodilatory function. The nitric oxide synthase inhibitor L-NAME attenuated endothelial-mediated vasodilation in WT but not in EC Nrf2-KO. EC Nrf2 may play a role in skeletal muscle antioxidant homeostasis, which suggests potential systemic implications of EC Nrf2 deletion. These results suggest that the EC antioxidant defense system is linked to endothelial dysfunction and changes in the skeletal muscle redox environment, likely through nitric oxide- and oxidative stress-related mechanisms. NIH (R01 AG034995, R01 AG049868, P01HL62222) NIH National Institute of General Medical Sciences, which funds the Great Plains IDeA-CTR Network (U54GM115458) 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.