Increased mitochondrial superoxide in the brain, but not periphery, sensitizes mice to angiotensin II-mediated hypertension (original) (raw)
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Antioxidants & Redox Signaling, 2014
Aims: Angiotensin II (AngII)-induced superoxide (O 2 -) production by the NADPH oxidases and mitochondria has been implicated in the pathogenesis of endothelial dysfunction and hypertension. In this work, we investigated the specific molecular mechanisms responsible for the stimulation of mitochondrial O 2 and its downstream targets using cultured human aortic endothelial cells and a mouse model of AngII-induced hypertension. Results: Western blot analysis showed that Nox2 and Nox4 were present in the cytoplasm but not in the mitochondria. Depletion of Nox2, but not Nox1, Nox4, or Nox5, using siRNA inhibits AngII-induced O 2 production in both mitochondria and cytoplasm. Nox2 depletion in gp91phox knockout mice inhibited AngIIinduced cellular and mitochondrial O 2 and attenuated hypertension. Inhibition of mitochondrial reverse electron transfer with malonate, malate, or rotenone attenuated AngII-induced cytoplasmic and mitochondrial O 2 production. Inhibition of the mitochondrial ATP-sensitive potassium channel (mitoK + ATP ) with 5-hydroxydecanoic acid or specific PKCe peptide antagonist (EAVSLKPT) reduced AngII-induced H 2 O 2 in isolated mitochondria and diminished cytoplasmic O 2 -. The mitoK + ATP agonist diazoxide increased mitochondrial O 2 -, cytoplasmic c-Src phosphorylation and cytoplasmic O 2 suggesting feed-forward regulation of cellular O 2 by mitochondrial reactive oxygen species (ROS). Treatment of AngII-infused mice with malate reduced blood pressure and enhanced the antihypertensive effect of mitoTEMPO. Mitochondria-targeted H 2 O 2 scavenger mitoEbselen attenuated redox-dependent c-Src and inhibited AngII-induced cellular O 2 -, diminished aortic H 2 O 2 , and reduced blood pressure in hypertensive mice. Innovation and Conclusions: These studies show that Nox2 stimulates mitochondrial ROS by activating reverse electron transfer and both mitochondrial O 2 and reverse electron transfer may represent new pharmacological targets for the treatment of hypertension. Antioxid. Redox Signal. 00, 000-000.
The extracellular superoxide dismutase (SOD3), a secretory copper-containing enzyme, regulates angiotensin II (Ang II)-induced hypertension by modulating levels of extracellular superoxide anion. The present study was designed to determine the role of the copper transporter Menkes ATPase (MNK) in Ang II-induced SOD3 activity and hypertension in vivo. Here we show that chronic Ang II infusion enhanced systolic blood pressure and vascular superoxide anion production in MNK mutant (MNK mut ) mice as compared with those in wild-type mice, which are associated with impaired acetylcholine-induced endothelium-dependent vasorelaxation in MNK mut mice. These effects in MNK mut mice are rescued by infusion of the SOD mimetic Tempol. By contrast, norepinephrine-induced hypertension, which is not associated with an increase in vascular superoxide anion production, is not affected in MNK mut mice. Mechanistically, basal and Ang II infusion-induced increase in vascular SOD3-specific activity is significantly inhibited in MNK mut mice. Coimmunoprecipitation analysis reveals that Ang II stimulation promotes association of MNK with SOD3 in cultured vascular smooth muscle cell and in mouse aortas, which may contribute to SOD3-specific activity by increasing copper delivery to SOD3 through MNK. In summary, MNK plays an important role in modulating Ang II-induced hypertension and endothelial function by regulating SOD3 activity and vascular superoxide anion production and becomes a potential therapeutic target for oxidant stress-dependent cardiovascular diseases.
Hypertension, 2010
The circumventricular organs (CVO) lack a well-formed blood-brain barrier and produce superoxide (O 2 •− ) in response to angiotensin II and other hypertensive stimuli. This increase in central O 2 •− has been implicated in regulation of blood pressure. The extracellular superoxide dismutase (SOD3) is highly expressed in cells associated with CVO, and particularly with tanycytes lining this region. To understand the role of SOD3 in the CVO in blood pressure regulation, we performed intracerebroventricular (ICV) injection an adenovirus encoding Cre-recombinase (AdCre, 5×10 8 particles/ml) in mice with loxP sites flanking the SOD3 coding region (SOD3 loxp/loxp mice). An adenovirus encoding red-fluorescent protein (AdRFP) was injected as a control. Deletion of CVO SOD3 increased baseline blood pressure modestly and markedly augmented the hypertensive response to low-dose angiotensin II (140 ng/kg/day), while ICV injection of AdRFP had minimal effects on these parameters. AdCre treated mice exhibited increased sympathetic modulation of heart rate and blood pressure variability, increased vascular superoxide production and T cell activation as characterized by increased circulating CD69+/CD3+ cells. Deletion of CVO SOD3 also markedly increased vascular T cell and leukocyte infiltration caused by angiotensin II. We conclude that SOD3 in the CVO plays a critical role in regulation of blood pressure and its loss promotes T cell activation and vascular inflammation, in part by modulating sympathetic outflow. These findings provide insight into how central signals produce vascular inflammation in response to hypertensive stimuli such as angiotensin II.
Role of the NADPH Oxidases in the Subfornical Organ in Angiotensin II-Induced Hypertension
Hypertension, 2012
Reactive oxygen species and the NADPH oxidases contribute to hypertension via mechanisms that remain undefined. Reactive oxygen species produced in the central nervous system have been proposed to promote sympathetic outflow, inflammation, and hypertension, but the contribution of the NADPH oxidases to these processes in chronic hypertension is uncertain. We therefore sought to identify how NADPH oxidases in the subfornical organ (SFO) of the brain regulate blood pressure and vascular inflammation during sustained hypertension. We produced mice with loxP sites flanking the coding region of the NADPH oxidase docking subunit p22 phox . SFO-targeted injections of an adenovirus encoding cre-recombinase markedly diminished p22 phox , Nox2, and Nox4 mRNA in the SFO, as compared with a control adenovirus encoding red-fluorescent protein injection. Increased superoxide production in the SFO by chronic angiotensin II infusion (490 ng/kg min –1 ×2 weeks) was blunted in adenovirus encoding cre...
Review Pathogenesis of Target Organ Damage in Hypertension: Role of Mitochondrial Oxidative Stress
2015
Abstract: Hypertension causes target organ damage (TOD) that involves vasculature, heart, brain and kidneys. Complex biochemical, hormonal and hemodynamic mechanisms are involved in the pathogenesis of TOD. Common to all these processes is an increased bioavailability of reactive oxygen species (ROS). Both in vitro and in vivo studies explored the role of mitochondrial oxidative stress as a mechanism involved in the pathogenesis of TOD in hypertension, especially focusing on atherosclerosis, heart disease, renal failure, cerebrovascular disease. Both dysfunction of mitochondrial proteins, such as uncoupling protein-2 (UCP2), superoxide dismutase (SOD) 2, peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), calcium channels, and the interaction between mitochondria and other sources of ROS, such as NADPH oxidase, play an important role in the development of endothelial dysfunction, cardiac hypertrophy, renal and cerebral damage in hypertension. Commonly used anti-hy...
Antioxidants & Redox Signaling, 2011
Previous studies identified NADPH oxidases (Nox) and mitochondrial electron transport chain at complex I as major cellular sources of reactive oxygen species (ROS) mediating systemic and cellular responses to intermittent hypoxia (IH). In the present study, we investigated potential interactions between Nox and the mitochondrial complex I and assessed the contribution of mitochondrial ROS in IH-evoked elevation in blood pressure. IH treatment led to stimulus-dependent activation of Nox and inhibition of complex I activity in rat pheochromocytoma (PC)12 cells. After re-oxygenation, Nox activity returned to baseline values within 3 h, whereas the complex I activity remained downregulated even after 24 h. IH-induced complex I inhibition was prevented by Nox inhibitors, Nox2 but not Nox 4 siRNA, in cell cultures and was absent in gp91 phox-=Y (Nox2 knock-out; KO) mice. Using pharmacological inhibitors, we show that ROS generated by Nox activation mobilizes Ca 2+ flux from the cytosol to mitochondria, leading to S-glutathionylation of 75-and 50-kDa proteins of the complex I and inhibition of complex I activity, which results in elevated mitochondrial ROS. Systemic administration of mito-tempol prevented the sustained but not the acute elevations of blood pressure in IH-treated rats, suggesting that mitochondrial-derived ROS contribute to sustained elevation of blood pressure. Antioxid. Redox Signal. 14, 533-542.
Redox Biology, 2014
Angiotensin II (AngII) is the main effector peptide of the renin-angiotensin system (RAS), and contributes to the pathogenesis of cardiovascular disease by exerting its effects on an array of different cell types, including central neurons. AngII intra-neuronal signaling is mediated, at least in part, by reactive oxygen species, particularly superoxide (O 2 d À). Recently, it has been discovered that mitochondria are a major subcellular source of AngII-induced O 2 d À. We have previously reported that over-expression of manganese superoxide dismutase (MnSOD), a mitochondrial matrix-localized O 2 d À scavenging enzyme, inhibits AngII intra-neuronal signaling. Interestingly, over-expression of copper/zinc superoxide dismutase (CuZnSOD), which is believed to be primarily localized to the cytoplasm, similarly inhibits AngII intra-neuronal signaling and provides protection against AngII-mediated neurogenic hypertension. Herein, we tested the hypothesis that CuZnSOD over-expression in central neurons localizes to mitochondria and inhibits AngII intra-neuronal signaling by scavenging mitochondrial O 2 d À. Using a neuronal cell culture model (CATH.a neurons), we demonstrate that both endogenous and adenovirusmediated over-expressed CuZnSOD (AdCuZnSOD) are present in mitochondria. Furthermore, we show that over-expression of CuZnSOD attenuates the AngII-mediated increase in mitochondrial O 2 d À levels and the AngII-induced inhibition of neuronal potassium current. Taken together, these data clearly show that over-expressed CuZnSOD in neurons localizes in mitochondria, scavenges AngII-induced mitochondrial O 2 d À , and inhibits AngII intra-neuronal signaling.