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Role of endothelial Nox2 NADPH oxidase in angiotensin II-induced hypertension and vasomotor dysfunction.

Murdoch CE, Alom-Ruiz SP, Wang M, Zhang M, Walker S, Yu B, Brewer A, Shah AM - Basic Res. Cardiol. (2011)

Bottom Line: Basal NADPH oxidase activity, endothelial function and blood pressure were unaltered in Tg compared to wild-type littermates.Angiotensin II caused a greater increase in ROS production in Tg compared to wild-type aorta and attenuated acetylcholine-induced vasorelaxation.Both low and high dose chronic angiotensin II infusion increased telemetric ambulatory blood pressure more in Tg compared to wild-type, but with different patterns of BP change and aortic remodeling depending upon the dose of angiotensin II dose.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Division, King's College London British Heart Foundation Centre, London, UK.

ABSTRACT
NADPH oxidase (Nox)-derived reactive oxygen species (ROS) are known to be involved in angiotensin II-induced hypertension and endothelial dysfunction. Several Nox isoforms are expressed in the vessel wall, among which Nox2 is especially abundant in the endothelium. Endothelial Nox2 levels rise during hypertension but little is known about the cell-specific role of endothelial Nox2 in vivo. To address this question, we generated transgenic mice with endothelial-specific overexpression of Nox2 (Tg) and studied the effects on endothelial function and blood pressure. Tg had an about twofold increase in endothelial Nox2 levels which was accompanied by an increase in p22phox levels but no change in levels of other Nox isoforms or endothelial nitric oxide synthase (eNOS). Basal NADPH oxidase activity, endothelial function and blood pressure were unaltered in Tg compared to wild-type littermates. Angiotensin II caused a greater increase in ROS production in Tg compared to wild-type aorta and attenuated acetylcholine-induced vasorelaxation. Both low and high dose chronic angiotensin II infusion increased telemetric ambulatory blood pressure more in Tg compared to wild-type, but with different patterns of BP change and aortic remodeling depending upon the dose of angiotensin II dose. These results indicate that an increase in endothelial Nox2 levels contributes to angiotensin II-induced endothelial dysfunction, vascular remodeling and hypertension.

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Changes in NADPH oxidase activity, subunits and antioxidants. a NADPH oxidase activity in WT and Tg aortic homogenates under basal conditions (left) and after angiotensin II (AngII 0.1 μM, 30 min) stimulation (right). n > 10; P < 0.05. b Nitrotyrosine levels in aorta from Wt and Tg mice treated with saline or angiotensin II infusion. Representative blots and mean data from three experiments (*P < 0.05). c mRNA expression of p22phox, p47phox, p67phox, Nox4 and eNOS in aorta. N = 6, P = NS. d Protein expression of p22phox in aorta. Representative blots at top and mean data from three experiments at bottom. *P < 0.05. e mRNA expression of SOD isoforms and catalase in aorta. n > 6, *P < 0.05. f SOD activity by NBT zymography in aortic homogenates. N = 6, P = NS
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Fig3: Changes in NADPH oxidase activity, subunits and antioxidants. a NADPH oxidase activity in WT and Tg aortic homogenates under basal conditions (left) and after angiotensin II (AngII 0.1 μM, 30 min) stimulation (right). n > 10; P < 0.05. b Nitrotyrosine levels in aorta from Wt and Tg mice treated with saline or angiotensin II infusion. Representative blots and mean data from three experiments (*P < 0.05). c mRNA expression of p22phox, p47phox, p67phox, Nox4 and eNOS in aorta. N = 6, P = NS. d Protein expression of p22phox in aorta. Representative blots at top and mean data from three experiments at bottom. *P < 0.05. e mRNA expression of SOD isoforms and catalase in aorta. n > 6, *P < 0.05. f SOD activity by NBT zymography in aortic homogenates. N = 6, P = NS

Mentions: The effect of Nox2 overexpression on NADPH oxidase activity was investigated in aortic homogenates. NADPH-dependent superoxide production was similar in Tg compared to wild-type littermates (Fig. 3a). However, after acute exposure of aortae to angiotensin II (0.1 μM, 30 min), there was a significantly greater increase in NADPH oxidase activity in Tg compared to wild-type (85% cf. 34%; Fig. 3a). Diphenyleneiodonium (DPI, 10 μM), tiron (10 mM) and apocynin (10 μM) inhibited the chemiluminescence signal in all experiments, whereas l-NAME (100 μM), rotenone (2 μM) and allopurinol (100 μM) had no effect (Online Resource 2), indicating that NADPH oxidase was the likely source. To also assess in vivo activation of Nox2, we studied aortic tissue from mice that were infused with saline or angiotensin II (1.1 mg/kg/day for 2 weeks). Aortic nitrotyrosine levels were quantified as a readout of increased NO/ROS interaction resulting from increased superoxide generation. Angiotensin II infusion increased nitrotyrosine levels in both groups of mice but the levels were significantly higher in the Tg group (Fig. 3b). These data are consistent with the knowledge that Nox2 oxidase is normally quiescent and requires agonist activation so that an increase in expression level per se will not increase oxidase activity [1].Fig. 3


Role of endothelial Nox2 NADPH oxidase in angiotensin II-induced hypertension and vasomotor dysfunction.

Murdoch CE, Alom-Ruiz SP, Wang M, Zhang M, Walker S, Yu B, Brewer A, Shah AM - Basic Res. Cardiol. (2011)

Changes in NADPH oxidase activity, subunits and antioxidants. a NADPH oxidase activity in WT and Tg aortic homogenates under basal conditions (left) and after angiotensin II (AngII 0.1 μM, 30 min) stimulation (right). n > 10; P < 0.05. b Nitrotyrosine levels in aorta from Wt and Tg mice treated with saline or angiotensin II infusion. Representative blots and mean data from three experiments (*P < 0.05). c mRNA expression of p22phox, p47phox, p67phox, Nox4 and eNOS in aorta. N = 6, P = NS. d Protein expression of p22phox in aorta. Representative blots at top and mean data from three experiments at bottom. *P < 0.05. e mRNA expression of SOD isoforms and catalase in aorta. n > 6, *P < 0.05. f SOD activity by NBT zymography in aortic homogenates. N = 6, P = NS
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Fig3: Changes in NADPH oxidase activity, subunits and antioxidants. a NADPH oxidase activity in WT and Tg aortic homogenates under basal conditions (left) and after angiotensin II (AngII 0.1 μM, 30 min) stimulation (right). n > 10; P < 0.05. b Nitrotyrosine levels in aorta from Wt and Tg mice treated with saline or angiotensin II infusion. Representative blots and mean data from three experiments (*P < 0.05). c mRNA expression of p22phox, p47phox, p67phox, Nox4 and eNOS in aorta. N = 6, P = NS. d Protein expression of p22phox in aorta. Representative blots at top and mean data from three experiments at bottom. *P < 0.05. e mRNA expression of SOD isoforms and catalase in aorta. n > 6, *P < 0.05. f SOD activity by NBT zymography in aortic homogenates. N = 6, P = NS
Mentions: The effect of Nox2 overexpression on NADPH oxidase activity was investigated in aortic homogenates. NADPH-dependent superoxide production was similar in Tg compared to wild-type littermates (Fig. 3a). However, after acute exposure of aortae to angiotensin II (0.1 μM, 30 min), there was a significantly greater increase in NADPH oxidase activity in Tg compared to wild-type (85% cf. 34%; Fig. 3a). Diphenyleneiodonium (DPI, 10 μM), tiron (10 mM) and apocynin (10 μM) inhibited the chemiluminescence signal in all experiments, whereas l-NAME (100 μM), rotenone (2 μM) and allopurinol (100 μM) had no effect (Online Resource 2), indicating that NADPH oxidase was the likely source. To also assess in vivo activation of Nox2, we studied aortic tissue from mice that were infused with saline or angiotensin II (1.1 mg/kg/day for 2 weeks). Aortic nitrotyrosine levels were quantified as a readout of increased NO/ROS interaction resulting from increased superoxide generation. Angiotensin II infusion increased nitrotyrosine levels in both groups of mice but the levels were significantly higher in the Tg group (Fig. 3b). These data are consistent with the knowledge that Nox2 oxidase is normally quiescent and requires agonist activation so that an increase in expression level per se will not increase oxidase activity [1].Fig. 3

Bottom Line: Basal NADPH oxidase activity, endothelial function and blood pressure were unaltered in Tg compared to wild-type littermates.Angiotensin II caused a greater increase in ROS production in Tg compared to wild-type aorta and attenuated acetylcholine-induced vasorelaxation.Both low and high dose chronic angiotensin II infusion increased telemetric ambulatory blood pressure more in Tg compared to wild-type, but with different patterns of BP change and aortic remodeling depending upon the dose of angiotensin II dose.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Division, King's College London British Heart Foundation Centre, London, UK.

ABSTRACT
NADPH oxidase (Nox)-derived reactive oxygen species (ROS) are known to be involved in angiotensin II-induced hypertension and endothelial dysfunction. Several Nox isoforms are expressed in the vessel wall, among which Nox2 is especially abundant in the endothelium. Endothelial Nox2 levels rise during hypertension but little is known about the cell-specific role of endothelial Nox2 in vivo. To address this question, we generated transgenic mice with endothelial-specific overexpression of Nox2 (Tg) and studied the effects on endothelial function and blood pressure. Tg had an about twofold increase in endothelial Nox2 levels which was accompanied by an increase in p22phox levels but no change in levels of other Nox isoforms or endothelial nitric oxide synthase (eNOS). Basal NADPH oxidase activity, endothelial function and blood pressure were unaltered in Tg compared to wild-type littermates. Angiotensin II caused a greater increase in ROS production in Tg compared to wild-type aorta and attenuated acetylcholine-induced vasorelaxation. Both low and high dose chronic angiotensin II infusion increased telemetric ambulatory blood pressure more in Tg compared to wild-type, but with different patterns of BP change and aortic remodeling depending upon the dose of angiotensin II dose. These results indicate that an increase in endothelial Nox2 levels contributes to angiotensin II-induced endothelial dysfunction, vascular remodeling and hypertension.

Show MeSH
Related in: MedlinePlus