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Use of Electron Paramagnetic Resonance in Biological Samples at Ambient Temperature and 77 K

The accurate and specific detection of reactive oxygen species (ROS) in different cellular and tissue compartments is essential to the study of ...

Vanderbilt University Medical Center

Vascular superoxide (O˙2 (-)) and inflammation contribute to hypertension. The mitochondria are an important source of O˙2 (-); however, the regulation of mitochondrial O˙2 (-) and the antihypertensive potential of targeting the mitochondria remain poorly defined. Angiotensin II and inflammatory cytokines, such as interleukin 17A and tumor necrosis factor-α (TNFα) significantly contribute to hypertension. We hypothesized that angiotensin II and cytokines co-operatively induce cyclophilin D (CypD)-dependent mitochondrial O˙2 (-) production in hypertension. We tested whether CypD inhibition attenuates endothelial oxidative stress and reduces hypertension. CypD depletion in CypD(-/-) mice prevents overproduction of mitochondrial O˙2 (-) in angiotensin II-infused mice, attenuates hypertension by 20 mm Hg, and improves vascular relaxation compared with wild-type C57Bl/6J mice. Treatment of hypertensive mice with the specific CypD inhibitor Sanglifehrin A reduces blood pressure by 28 mm Hg, inhibits production of mitochondrial O˙2 (-) by 40%, and improves vascular relaxation. Angiotensin II-induced hypertension was associated with CypD redox activation by S-glutathionylation, and expression of the mitochondria-targeted H2O2 scavenger, catalase, abolished CypD S-glutathionylation, prevented stimulation mitochondrial O˙2 (-), and attenuated hypertension. The functional role of cytokine-angiotensin II interplay was confirmed by co-operative stimulation of mitochondrial O˙2 (-) by 3-fold in cultured endothelial cells and impairment of aortic relaxation incubated with combination of angiotensin II, interleukin 17A, and tumor necrosis factor-α which was prevented by CypD depletion or expression of mitochondria-targeted SOD2 and catalase. These data support a novel role of CypD in hypertension and demonstrate that targeting CypD decreases mitochondrial O˙2 (-), improves vascular relaxation, and reduces hypertension.

Mitochondrial Cyclophilin D in Vascular Oxidative Stress and Hypertension.

Clinical studies have shown that Sirt3 (Sirtuin 3) expression declines by 40% by 65 years of age paralleling the increased incidence of hypertension and metabolic conditions further inactivate Sirt3 because of increased NADH (nicotinamide adenine dinucleotide, reduced form) and acetyl-CoA levels. Sirt3 impairment reduces the activity of a key mitochondrial antioxidant enzyme, superoxide dismutase 2 (SOD2) because of hyperacetylation.

Sirt3 Impairment and SOD2 Hyperacetylation in Vascular Oxidative Stress and Hypertension.

Vascular dysfunction plays a key role in the development of arteriosclerosis, heart disease and hypertension which causes one-third of deaths worldwide. Vascular oxidative stress and metabolic disorders contribute to vascular dysfunction leading to impaired vasorelaxation, vascular hypertrophy, fibrosis and aortic stiffening. Mitochondria are critical in the regulation of metabolic and antioxidant functions; therefore, mitochondria targeted treatments could be beneficial. Recent Advances: Vascular dysfunction is crucial in hypertension pathophysiology and exhibits bidirectional relationship. Metabolic disorders and oxidative stress contribute to the pathogenesis of vascular dysfunction and hypertension which are associated with mitochondrial impairment and hyperacetylation. Mitochondrial deacetylase Sirt3 is critical in the regulation of metabolic and antioxidant functions. Clinical studies show that cardiovascular disease risk factors reduce Sirt3 level and Sirt3 declines with age, paralleling the increased incidence of cardiovascular disease and hypertension. An imbalance between mitochondrial acetylation and reduced Sirt3 activity contributes to mitochondrial dysfunction and oxidative stress. We propose that mitochondrial hyperacetylation drives vicious cycle between metabolic disorders and mitochondrial oxidative stress promoting vascular dysfunction and hypertension.

Sergey Dikalov

Department of Medicine,
Division of Clinical Pharmacology,
Department of Medicine, Division of Clinical Pharmacology

Vanderbilt University Medical Center

Use of Electron Paramagnetic Resonance in Biological Samples at Ambient Temperature and 77 K

Sergey Dikalov

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Medicine,Division of Clinical Pharmacology,Department of Medicine, Division of Clinical Pharmacology

Vanderbilt University Medical Center

Use of Electron Paramagnetic Resonance in Biological Samples at Ambient Temperature and 77 K

Department of Medicine,
Division of Clinical Pharmacology,
Department of Medicine, Division of Clinical Pharmacology