David G Harrison

Publications of David G Harrison

• Endothelium-specific Sepiapterin Reductase Deficiency in DOCA-salt Hypertension.

  Authors: Ji-Youn Youn, Ting Wang, John Blair, Karine M Laude, Jeong-Ho Oak, Louise A McCann, David G Harrison, Hua Linda Cai

  American journal of physiology. Heart and circulatory physiology. 03/2012;

  The endothelial nitric oxide synthase (eNOS) requires tetrahydrobiopterin (H4B) as a cofactor, and in its absence, produces superoxide (O2(⋅-)) rather than nitric oxide (NO·), a condition referred toThe endothelial nitric oxide synthase (eNOS) requires tetrahydrobiopterin (H4B) as a cofactor, and in its absence, produces superoxide (O2(⋅-)) rather than nitric oxide (NO·), a condition referred to as eNOS uncoupling. DOCA-salt induced hypertension is associated with H4B oxidation and uncoupling of eNOS. The present study investigated whether administration of sepiapterin or H4B recouples eNOS in DOCA-salt hypertension. Bioavailable NO(⋅) detected by electron spin resonance was markedly reduced in aortas of DOCA-salt hypertensive mice. Pre-incubation with sepiapterin (10 μmol/L for 30 min) failed to improve NO· bioavailability in hypertensive aortas while it augmented NO(⋅) production from control vessels, implicating a hypertension-associated deficiency in sepiapterin reductase (SPR), the rate-limiting enzyme for sepiapterin conversion to H4B. Indeed, a decreased SPR expression was observed in aortic endothelial cells, but not in endothelium-denuded aortic remains, implicating an endothelium-specific SPR deficiency. Administration of hypertensive aortas with H4B (10 μmol/L, 30 min) partially restored vascular NO(⋅) production. Combined administration of H4B and the NADPH oxidase inhibitor apocynin (100 μmol/L, 30 min) fully restored NO⋅ bioavailability while reducing O2(⋅-) production. In angiotensin II (Ang II)-induced hypertension however, aortic endothelial SPR expression was not affected. In summary, administration of sepiapterin is not effective in recoupling eNOS in DOCA-salt hypertension, due to an endothelium-specific loss in SPR, whereas co-administration of H4B and apocynin is highly efficient in recoupling eNOS. This is consistent with our previous observations that in Ang II hypertension, endothelial deficiency in dihydrofolate reductase is alternatively responsible for uncoupling of eNOS. Taken together; these data indicate that strategies specifically targeting at different H4B metabolic enzymes might be necessary in restoring eNOS function in different types of hypertension.

• T Lymphocytes and Vascular Inflammation Contribute to Stress-Dependent Hypertension.

  Authors: Paul J Marvar, Antony Vinh, Salim Thabet, Heinrich E Lob, Duke Geem, Kerry J Ressler, David G Harrison

  Biological psychiatry. 02/2012;

  BACKGROUND: Psychological stress is a significant risk factor for hypertension and also directly affects the immune system. We have previously reported that T lymphocytes are essential forBACKGROUND: Psychological stress is a significant risk factor for hypertension and also directly affects the immune system. We have previously reported that T lymphocytes are essential for development of hypertension and that the central nervous system contributes to peripheral T-lymphocyte activation and vascular inflammation in this disease; however, the role of T-cell activation in stress-related hypertension remains unclear. METHODS: Wild-type and T-cell-deficient (RAG-1(-/-)) mice were subjected to daily episodes of stress and blood pressure was measured. Circulating T-cell activation markers and vascular infiltration of immune cells were analyzed, as were stress hormone levels and gene expression changes in the brain. The effects angiotensin II infusion in the presence of chronic stress was also studied. RESULTS: Repeated daily stress contributed to acute elevations in blood pressure that were associated with increased activation of circulating T cells and increased vascular infiltration of T cells. Repeated stress increased blood pressure in wild-type but not RAG-1(-/-) mice. Adoptive transfer of T cells to RAG-1(-/-) mice restored blood pressure elevation in response to stress. Stress-related hypertension and vascular infiltration of T cells was markedly enhanced by angiotensin II. Moreover, angiotensin II-infused mice exposed to chronic stress exhibited greater blood pressure reactivity to an episode of acute stress. CONCLUSIONS: These data demonstrate that stress-dependent hypertension triggers an inflammatory response that raises blood pressure at baseline and augments the hypertension caused by angiotensin II. These data provide insight as to how psychological stress contributes to hypertension.

• Vascular inflammatory cells in hypertension.

  Authors: David G Harrison, Paul J Marvar, Jens M Titze

  Frontiers in physiology. 01/2012; 3:128.

  Hypertension is a common disorder with uncertain etiology. In the last several years, it has become evident that components of both the innate and adaptive immune system play an essential role inHypertension is a common disorder with uncertain etiology. In the last several years, it has become evident that components of both the innate and adaptive immune system play an essential role in hypertension. Macrophages and T cells accumulate in the perivascular fat, the heart and the kidney of hypertensive patients, and in animals with experimental hypertension. Various immunosuppressive agents lower blood pressure and prevent end-organ damage. Mice lacking lymphocytes are protected against hypertension, and adoptive transfer of T cells, but not B cells in the animals restores their blood pressure response to stimuli such as angiotensin II or high salt. Recent studies have shown that mice lacking macrophages have blunted hypertension in response to angiotensin II and that genetic deletion of macrophages markedly reduces experimental hypertension. Dendritic cells have also been implicated in this disease. Many hypertensive stimuli have triggering effects on the central nervous system and signals arising from the circumventricular organ seem to promote inflammation. Studies have suggested that central signals activate macrophages and T cells, which home to the kidney and vasculature and release cytokines, including IL-6 and IL-17, which in turn cause renal and vascular dysfunction and lead to blood pressure elevation. These recent discoveries provide a new understanding of hypertension and provide novel therapeutic opportunities for treatment of this serious disease.

• Role of vascular extracellular superoxide dismutase in hypertension.

  Authors: Heinrich E Lob, Antony Vinh, Li Li, Yelena Blinder, Stefan Offermanns, David G Harrison

  Hypertension. 08/2011; 58(2):232-9.

  Previous studies indicate that superoxide is important in the modulation of blood pressure but have not specifically identified the cell types or organs involved. We created mice with loxP sitesPrevious studies indicate that superoxide is important in the modulation of blood pressure but have not specifically identified the cell types or organs involved. We created mice with loxP sites flanking the extracellular superoxide dismutase (SOD3) gene. These mice were crossed with mice expressing inducible Cre-recombinase driven by the smooth muscle myosin heavy chain promoter allowing tissue-specific deletion of SOD3. Deletion of SOD3 increased vascular superoxide and reduced vascular NO levels as detected by electron spin resonance. Despite these changes in NO and superoxide, we did not observe increases in vascular inflammation caused by angiotensin II. Moreover, deletion of vascular SOD3 did not augment hypertension in response to angiotensin II. In additional studies, we also deleted SOD3 from the circumventricular organs by intracerebroventricular injection of an adenovirus encoding Cre-recombinase. Although this raised blood pressure and augmented the hypertension caused by angiotensin II, these responses were not further increased by vascular deletion of SOD3. These data suggest that the extracellular superoxide dismutase in vascular smooth muscle is not involved in the genesis of angiotensin II-induced hypertension and further emphasize the role of central SOD3 in the modulation of blood pressure.

• Role of interleukin 17 in inflammation, atherosclerosis, and vascular function in apolipoprotein e-deficient mice.

  Authors: Meena S Madhur, Samuel A Funt, Li Li, Antony Vinh, Wei Chen, Heinrich E Lob, Yoichiro Iwakura, Yelena Blinder, Ayaz Rahman, Arshed A Quyyumi, David G Harrison

  Arteriosclerosis, thrombosis, and vascular biology. 07/2011; 31(7):1565-72.

  Interleukin 17A (IL17A) is involved in many inflammatory processes, but its role in atherosclerosis remains controversial. We examined the role of IL17A in mouse and humanInterleukin 17A (IL17A) is involved in many inflammatory processes, but its role in atherosclerosis remains controversial. We examined the role of IL17A in mouse and human atherosclerosis. Atherosclerosis was induced in apolipoprotein E (ApoE)(-/-) and IL17A/ApoE(-/-) mice using high-fat feeding, angiotensin II infusion, or partial carotid ligation. In ApoE(-/-) mice, 3 months of high-fat diet induced interferon-γ production by splenic lymphocytes, and this was abrogated in IL17A/ApoE(-/-) mice. IL17A/ApoE(-/-) mice had reduced aortic superoxide production, increased aortic nitric oxide levels, decreased aortic leukocyte and dendritic cell infiltration, and reduced weight gain after a high-fat diet compared with ApoE(-/-) mice. Despite these favorable effects, IL17A deficiency did not affect aortic plaque burden after a high-fat diet or angiotensin II infusion. In a partial carotid ligation model, IL17A deficiency did not affect percentage of stenosis but reduced outward remodeling. In this model, neutralization of the related isoform, IL17F, in IL17A/ApoE(-/-) mice did not alter atherosclerosis. Finally, there was no correlation between IL17A levels and carotid intima-media thickness in humans. IL17 contributes to vascular and systemic inflammation in experimental atherosclerosis but does not alter plaque burden. The changes in plaque composition caused by IL17 might modulate plaque stability.

• Tetrahydrobiopterin deficiency and nitric oxide synthase uncoupling contribute to atherosclerosis induced by disturbed flow.

  Authors: Li Li, Wei Chen, Amir Rezvan, Hanjoong Jo, David G Harrison

  Arteriosclerosis, thrombosis, and vascular biology. 07/2011; 31(7):1547-54.

  Tetrahydrobiopterin (BH(4)) is a critical cofactor for nitric oxide (NO) synthesis by NO synthase (NOS). Recently, we demonstrated that disturbed flow produced by partial carotid ligation decreasesTetrahydrobiopterin (BH(4)) is a critical cofactor for nitric oxide (NO) synthesis by NO synthase (NOS). Recently, we demonstrated that disturbed flow produced by partial carotid ligation decreases BH(4) levels in vivo. We therefore aimed to determine whether atherosclerosis induced by disturbed flow is due to BH(4) deficiency and NOS uncoupling and whether increasing BH(4) would prevent endothelial dysfunction, plaque inflammation, and atherosclerosis. We produced a region of disturbed flow in apolipoprotein E(-/-) mice using partial carotid ligation and fed these animals a high-fat diet. This caused endothelial NOS uncoupling as characterized by increased vascular superoxide production, altered vascular reactivity, and a change in endothelial NOS migration on low-temperature gel. These perturbations were accompanied by severe atherosclerosis, infiltration of T cells and macrophages, and an increase in cytokine production. Treatment with BH(4) recoupled NOS, decreased superoxide production, improved endothelium-dependent vasodilatation, and virtually eliminated atherosclerosis. BH(4) treatment also markedly reduced vascular inflammation and improved the cytokine milieu induced by disturbed flow. Our results highlight a key role of BH(4) deficiency and NOS uncoupling in atherosclerosis induced by disturbed flow and provide insight into the effect of modulating vascular BH(4) levels on atherosclerosis and inflammation at these sites of the circulation.

• Localization of culprit lesions in coronary arteries of patients with ST-segment elevation myocardial infarctions: relation to bifurcations and curvatures.

  Authors: Michael C McDaniel, Erin M Galbraith, Ahmad M Jeroudi, Omar R Kashlan, Parham Eshtehardi, Jin Suo, Saurabh Dhawan, Michele Voeltz, Chandan Devireddy, John Oshinski, David G Harrison, Don P Giddens, Habib Samady

  American heart journal. 03/2011; 161(3):508-15.

  Although culprit lesions in ST-segment elevation myocardial infarction (STEMI) cluster in the proximal coronary arteries, their relationship to bifurcations and curvatures, where blood flow isAlthough culprit lesions in ST-segment elevation myocardial infarction (STEMI) cluster in the proximal coronary arteries, their relationship to bifurcations and curvatures, where blood flow is disturbed, is unknown. We hypothesized that (a) culprit lesions localize to disturbed flow distal to bifurcations and curvatures and (b) the distribution of culprit lesions in the left (LCA) and right coronary arteries (RCA) and resulting infarct size are related to the location of bifurcations and curvatures. Emory University's contribution to the National Cardiovascular Data Registry was queried for STEMIs. Using quantitative coronary angiography, the distances from the vessel ostium, major bifurcations, and major curvatures to the culprit lesion were measured in 385 patients. Culprit lesions were located within 20 mm of a bifurcation in 79% of patients and closer to the bifurcation in the LCA compared with the RCA (7.4 ± 7.3 vs 17.7 ± 14.8 mm, P < .0001). Of RCA culprit lesions, 45% were located within 20 mm of a major curvature. Compared with those in the RCA, culprit lesions in the LCA were located more proximally (24.4 ± 16.5 vs 44.7 ± 28.8 mm, P = .0003) and were associated with larger myocardial infarctions as assessed by peak creatine kinase-MB (208 ± 222 vs 140 ± 153 ng/dL, P = .001) and troponin I (59 ± 62 vs 40 ± 35 ng/dL, P = .0006) and with higher in-hospital mortality (5.2% vs 1.1%, P = .04). In patients with STEMI, culprit lesions are frequently located immediately distal to bifurcations and in proximity to major curvatures where disturbed flow is known to occur. This supports the role of wall shear stress in the pathogenesis of STEMI.

• Inflammation, immunity, and hypertension.

  Authors: David G Harrison, Tomasz J Guzik, Heinrich E Lob, Meena S Madhur, Paul J Marvar, Salim R Thabet, Antony Vinh, Cornelia M Weyand

  Hypertension. 02/2011; 57(2):132-40.

• Role of increased guanosine triphosphate cyclohydrolase-1 expression and tetrahydrobiopterin levels upon T cell activation.

  Authors: Wei Chen, Li Li, Torben Brod, Omar Saeed, Salim Thabet, Thomas Jansen, Sergey Dikalov, Cornelia Weyand, Jorg Goronzy, David G Harrison

  The Journal of biological chemistry. 02/2011; 286(16):13846-51.

  Tetrahydrobiopterin (BH(4)) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O(2)(·-)) rather than NO. The rate-limiting enzyme forTetrahydrobiopterin (BH(4)) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O(2)(·-)) rather than NO. The rate-limiting enzyme for BH(4) production is guanosine triphosphate cyclohydrolase-1 (GTPCH-1). Because endogenously produced NO affects T cell function, we sought to determine whether antigen stimulation affected T cell GTPCH-1 expression and ultimately BH(4) levels. Resting T cells had minimal expression of inducible NOS (NOS2), endothelial NOS (NOS3), and GTPCH-1 protein and nearly undetectable levels of BH(4). Anti-CD3 stimulation of T cells robustly stimulated the coordinated expression of NOS2, NOS3, and GTPCH-1 and markedly increased both GTPCH-1 activity and T cell BH(4) levels. The newly expressed GTPCH-1 was phosphorylated on serine 72 and pharmacological inhibition of casein kinase II reduced GTPCH-1 phosphorylation and blunted the increase in T cell BH(4). Inhibition of GTPCH-1 with diaminohydroxypyrimidine (1 mmol/liter) prevented T cell BH(4) accumulation, reduced NO production, and increased T cell O(2)(·-) production, due to both NOS2 and NOS3 uncoupling. GTPCH-1 inhibition also promoted TH(2) polarization in memory CD4 cells. Ovalbumin immunization of mice transgenic for an ovalbumin receptor (OT-II mice) confirmed a marked increase in T cell BH(4) in vivo. These studies identify a previously unidentified consequence of T cell activation, promoting BH(4) levels, NO production, and modulating T cell cytokine production.

• Inhibition and genetic ablation of the B7/CD28 T-cell costimulation axis prevents experimental hypertension.

  Authors: Antony Vinh, Wei Chen, Yelena Blinder, Daiana Weiss, W Robert Taylor, Jörg J Goronzy, Cornelia M Weyand, David G Harrison, Tomasz J Guzik

  Circulation. 12/2010; 122(24):2529-37.

  The pathogenesis of hypertension remains poorly understood, and treatment is often unsuccessful. Recent evidence suggests that the adaptive immune response plays an important role in this disease.The pathogenesis of hypertension remains poorly understood, and treatment is often unsuccessful. Recent evidence suggests that the adaptive immune response plays an important role in this disease. Various hypertensive stimuli cause T-cell activation and infiltration into target organs such as the vessel and the kidney, which promotes vascular dysfunction and blood pressure elevation. Classically, T-cell activation requires T-cell receptor ligation and costimulation. The latter often involves interaction between B7 ligands (CD80 and CD86) on antigen-presenting cells with the T-cell coreceptor CD28. This study was therefore performed to examine the role of this pathway in hypertension. Angiotensin II-induced hypertension increased the presence of activated (CD86(+)) dendritic cells in secondary lymphatic tissues. Blockade of B7-dependent costimulation with CTLA4-Ig reduced both angiotensin II- and deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Activation of circulating T cells, T-cell cytokine production, and vascular T-cell accumulation caused by these hypertensive stimuli were abrogated by CTLA4-Ig. Furthermore, in mice lacking B7 ligands, angiotensin II caused minimal blood pressure elevation and vascular inflammation, and these effects were restored by transplantation with wild-type bone marrow. T-cell costimulation via B7 ligands is essential for development of experimental hypertension, and inhibition of this process could have therapeutic benefit in the treatment of this disease.

• The central nervous system and inflammation in hypertension.

  Authors: Paul J Marvar, Heinrich Lob, Antony Vinh, Faresa Zarreen, David G Harrison

  Current opinion in pharmacology. 12/2010; 11(2):156-61.

  In recent years a major research effort has focused on the role of inflammation, and in particular adaptive immunity, in the genesis of hypertension. Hypertension stimulates the accumulation ofIn recent years a major research effort has focused on the role of inflammation, and in particular adaptive immunity, in the genesis of hypertension. Hypertension stimulates the accumulation of inflammatory cells including macrophages and T lymphocytes in peripheral tissues important in blood pressure control, such as the kidney and vasculature. Angiotensin II modulates blood pressure via actions on the central nervous system (CNS) and the adaptive immune system. Recent work suggests that the central actions of angiotensin II via the circumventricular organs lead to activation of circulating T-cells and vascular inflammation. The neuro-immune system plays an essential role in the pathogenesis of hypertension and further understanding of this relationship could lead to the development of new treatment strategies.

• Upregulation of Nox1 in vascular smooth muscle leads to impaired endothelium-dependent relaxation via eNOS uncoupling.

  Authors: Anna E Dikalova, María Carolina Góngora, David G Harrison, J David Lambeth, Sergey Dikalov, Kathy K Griendling

  American journal of physiology. Heart and circulatory physiology. 09/2010; 299(3):H673-9.

  Recent work has made it clear that oxidant systems interact. To investigate potential cross talk between NADPH oxidase (Nox) 1 upregulation in vascular smooth muscle and endothelial function,Recent work has made it clear that oxidant systems interact. To investigate potential cross talk between NADPH oxidase (Nox) 1 upregulation in vascular smooth muscle and endothelial function, transgenic mice overexpressing Nox1 in smooth muscle cells (Tg(SMCnox1)) were subjected to angiotensin II (ANG II)-induced hypertension. As expected, NADPH-dependent superoxide generation was increased in aortas from Nox1-overexpressing mice. Infusion of ANG II (0.7 mg x kg(-1) x day(-1)) for 2 wk potentiated NADPH-dependent superoxide generation and hydrogen peroxide production compared with similarly treated negative littermate controls. Endothelium-dependent relaxation was impaired in transgenic mice, and bioavailable nitric oxide was markedly decreased. To test the hypothesis that eNOS uncoupling might contribute to endothelial dysfunction, the diet was supplemented with tetrahydrobiopterin (BH(4)). BH(4) decreased aortic superoxide production, partially restored bioavailable nitric oxide in aortas of ANG II-treated Tg(SMCnox1) mice, and significantly improved endothelium-dependent relaxation in these mice. Western blot analysis revealed less dimeric eNOS in Tg(SMCnox1) mice compared with the wild-type mice; however, total eNOS was equivalent. Pretreatment of mouse aortas with the eNOS inhibitor N(G)-nitro-L-arginine methyl ester decreased ANG II-induced superoxide production in Tg(SMCnox1) mice compared with wild-type mice, indicating that uncoupled eNOS is also a significant source of increased superoxide in transgenic mice. Thus overexpression of Nox1 in vascular smooth muscle leading to enhanced production of reactive oxygen species in response to ANG II causes eNOS uncoupling and a decrease in nitric oxide bioavailability, resulting in impaired vasorelaxation.

• Protective role of extracellular superoxide dismutase in renal ischemia/reperfusion injury.

  Authors: Markus P Schneider, Jennifer C Sullivan, Paul F Wach, Erika I Boesen, Tatsuo Yamamoto, Tohru Fukai, David G Harrison, David M Pollock, Jennifer S Pollock

  Kidney international. 08/2010; 78(4):374-81.

  Extracellular superoxide dismutase (SOD3) is highly expressed in renal tissues and a critical regulator of vascular function. We hypothesized that deletion of SOD3 would attenuate recovery of renalExtracellular superoxide dismutase (SOD3) is highly expressed in renal tissues and a critical regulator of vascular function. We hypothesized that deletion of SOD3 would attenuate recovery of renal blood flow (RBF) and increase oxidative stress and injury following renal ischemia/reperfusion (I/R). To test this, we evaluated SOD expression and activity, basal superoxide production, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in kidneys from male and female wild-type (WT) and SOD3-knockout mice. RBF, measured using an ultrasonic flow probe, and histological indices of oxidative stress and injury were assessed after 1 h of ischemia. Following ischemia, RBF was attenuated in kidneys from male, but not female, knockout mice compared with their WT counterparts. Total SOD activity was significantly reduced in male knockout compared with WT male mice but was similar in female mice of both genotypes, suggesting upregulated SOD1 activity. Basal superoxide production and NADPH oxidase activity were unrelated to the differences in RBF. After 24 h, kidneys from both genders of knockout mice were found to have more oxidative stress (3-nitrotyrosine immunohistochemistry) and renal cast formation than those from WT mice. Thus, our study found a key role for SOD3 in regulating renal I/R injury.

• Central and peripheral mechanisms of T-lymphocyte activation and vascular inflammation produced by angiotensin II-induced hypertension.

  Authors: Paul J Marvar, Salim R Thabet, Tomasz J Guzik, Heinrich E Lob, Louise A McCann, Connie Weyand, Frank J Gordon, David G Harrison

  Circulation research. 07/2010; 107(2):263-70.

  We have previously found that T lymphocytes are essential for development of angiotensin II-induced hypertension; however, the mechanisms responsible for T-cell activation in hypertension remainWe have previously found that T lymphocytes are essential for development of angiotensin II-induced hypertension; however, the mechanisms responsible for T-cell activation in hypertension remain undefined. We sought to study the roles of the CNS and pressure elevation in T-cell activation and vascular inflammation caused by angiotensin II. To prevent the central actions of angiotensin II, we created anteroventral third cerebral ventricle (AV3V) lesions in mice. The elevation in blood pressure in response to angiotensin II was virtually eliminated by AV3V lesions, as was activation of circulating T cells and the vascular infiltration of leukocytes. In contrast, AV3V lesioning did not prevent the hypertension and T-cell activation caused by the peripheral acting agonist norepinephrine. To determine whether T-cell activation and vascular inflammation are attributable to central influences or are mediated by blood pressure elevation, we administered hydralazine (250 mg/L) in the drinking water. Hydralazine prevented the hypertension and abrogated the increase in circulating activated T cells and vascular infiltration of leukocytes caused by angiotensin II. We conclude that the central and pressor effects of angiotensin II are critical for T-cell activation and development of vascular inflammation. These findings also support a feed-forward mechanism in which modest degrees of blood pressure elevation lead to T-cell activation, which in turn promotes inflammation and further raises blood pressure, leading to severe hypertension.

• Therapeutic targeting of mitochondrial superoxide in hypertension.

  Authors: Anna E Dikalova, Alfiya T Bikineyeva, Klaudia Budzyn, Rafal R Nazarewicz, Louise McCann, William Lewis, David G Harrison, Sergey I Dikalov

  Circulation research. 05/2010; 107(1):106-16.

  Superoxide (O2(-) ) has been implicated in the pathogenesis of many human diseases including hypertension; however, commonly used antioxidants have proven ineffective in clinical trials. It isSuperoxide (O2(-) ) has been implicated in the pathogenesis of many human diseases including hypertension; however, commonly used antioxidants have proven ineffective in clinical trials. It is possible that these agents are not adequately delivered to the subcellular sites of superoxide production. Because the mitochondria are important sources of reactive oxygen species, we postulated that mitochondrial targeting of superoxide scavenging would have therapeutic benefit. In this study, we found that the hormone angiotensin (Ang II) increased endothelial mitochondrial superoxide production. Treatment with the mitochondria-targeted antioxidant mitoTEMPO decreased mitochondrial O2(-), inhibited the total cellular O2(-), reduced cellular NADPH oxidase activity, and restored the level of bioavailable NO. These effects were mimicked by overexpressing the mitochondrial MnSOD (SOD2), whereas SOD2 depletion with small interfering RNA increased both basal and Ang II-stimulated cellular O2(-). Treatment of mice in vivo with mitoTEMPO attenuated hypertension when given at the onset of Ang II infusion and decreased blood pressure by 30 mm Hg following establishment of both Ang II-induced and DOCA salt hypertension, whereas a similar dose of nontargeted TEMPOL was not effective. In vivo, mitoTEMPO decreased vascular O2(-), increased vascular NO production and improved endothelial-dependent relaxation. Interestingly, transgenic mice overexpressing mitochondrial SOD2 demonstrated attenuated Ang II-induced hypertension and vascular oxidative stress similar to mice treated with mitoTEMPO. These studies show that mitochondrial O2(-) is important for the development of hypertension and that antioxidant strategies specifically targeting this organelle could have therapeutic benefit in this and possibly other diseases.

• NO solution for a radical problem: a TAL story.

  Authors: Maria Carolina Gongora, David G Harrison

  American journal of physiology. Renal physiology. 04/2010; 298(4):F883-4.

• Uncoupled cardiac nitric oxide synthase mediates diastolic dysfunction.

  Authors: Gad A Silberman, Tai-Hwang M Fan, Hong Liu, Zhe Jiao, Hong D Xiao, Joshua D Lovelock, Beth M Boulden, Julian Widder, Scott Fredd, Kenneth E Bernstein, Beata M Wolska, Sergey Dikalov, David G Harrison, Samuel C Dudley

  Circulation. 02/2010; 121(4):519-28.

  Heart failure with preserved ejection fraction is 1 consequence of hypertension and is caused by impaired cardiac diastolic relaxation. Nitric oxide (NO) is a known modulator of cardiac relaxation.Heart failure with preserved ejection fraction is 1 consequence of hypertension and is caused by impaired cardiac diastolic relaxation. Nitric oxide (NO) is a known modulator of cardiac relaxation. Hypertension can lead to a reduction in vascular NO, in part because NO synthase (NOS) becomes uncoupled when oxidative depletion of its cofactor tetrahydrobiopterin (BH(4)) occurs. Similar events may occur in the heart that lead to uncoupled NOS and diastolic dysfunction. In a hypertensive mouse model, diastolic dysfunction was accompanied by cardiac oxidation, a reduction in cardiac BH(4), and uncoupled NOS. Compared with sham-operated animals, male mice with unilateral nephrectomy, with subcutaneous implantation of a controlled-release deoxycorticosterone acetate pellet, and given 1% saline to drink were mildly hypertensive and had diastolic dysfunction in the absence of systolic dysfunction or cardiac hypertrophy. The hypertensive mouse hearts showed increased oxidized biopterins, NOS-dependent superoxide production, reduced NO production, and dephosphorylated phospholamban. Feeding hypertensive mice BH(4) (5 mg/d), but not treating with hydralazine or tetrahydroneopterin, improved cardiac BH(4) stores, phosphorylated phospholamban levels, and diastolic dysfunction. Isolated cardiomyocyte experiments revealed impaired relaxation that was normalized with short-term BH(4) treatment. Targeted cardiac overexpression of angiotensin-converting enzyme also resulted in cardiac oxidation, NOS uncoupling, and diastolic dysfunction in the absence of hypertension. Cardiac oxidation, independently of vascular changes, can lead to uncoupled cardiac NOS and diastolic dysfunction. BH(4) may represent a possible treatment for diastolic dysfunction.

• Role of the adaptive immune system in hypertension.

  Authors: David G Harrison, Antony Vinh, Heinrich Lob, Meena S Madhur

  Current opinion in pharmacology. 02/2010; 10(2):203-7.

  Recent studies have shown that both innate and adaptive immunity contribute to hypertension. Inflammatory cells, including macrophages and T cells accumulate in the vessel wall, particularly in theRecent studies have shown that both innate and adaptive immunity contribute to hypertension. Inflammatory cells, including macrophages and T cells accumulate in the vessel wall, particularly in the perivascular fat, and in the kidney of hypertensive animals. Mice lacking lymphocytes are resistant to the development of hypertension, and adoptive transfer of T cells restores hypertensive responses to angiotensin II and DOCA-salt challenge. Immune modulating agents have variable, but often-beneficial effects in ameliorating end-organ damage and blood pressure elevation in experimental hypertension. The mechanisms by which hypertension stimulates an immune response remain unclear, but might involve the formation of neoantigens that activate adaptive immunity. Identification of these neoantigens and understanding how they form might prove useful in the prevention and treatment of this widespread and devastating disease.

• Interleukin 17 promotes angiotensin II-induced hypertension and vascular dysfunction.

  Authors: Meena S Madhur, Heinrich E Lob, Louise A McCann, Yoichiro Iwakura, Yelena Blinder, Tomasz J Guzik, David G Harrison

  Hypertension. 02/2010; 55(2):500-7.

  We have shown previously that T cells are required for the full development of angiotensin II-induced hypertension. However, the specific subsets of T cells that are important in this process areWe have shown previously that T cells are required for the full development of angiotensin II-induced hypertension. However, the specific subsets of T cells that are important in this process are unknown. T helper 17 cells represent a novel subset that produces the proinflammatory cytokine interleukin 17 (IL-17). We found that angiotensin II infusion increased IL-17 production from T cells and IL-17 protein in the aortic media. To determine the effect of IL-17 on blood pressure and vascular function, we studied IL-17(-/-) mice. The initial hypertensive response to angiotensin II infusion was similar in IL-17(-/-) and C57BL/6J mice. However, hypertension was not sustained in IL-17(-/-) mice, reaching levels 30-mm Hg lower than in wild-type mice by 4 weeks of angiotensin II infusion. Vessels from IL-17(-/-) mice displayed preserved vascular function, decreased superoxide production, and reduced T-cell infiltration in response to angiotensin II. Gene array analysis of cultured human aortic smooth muscle cells revealed that IL-17, in conjunction with tumor necrosis factor-alpha, modulated expression of >30 genes, including a number of inflammatory cytokines/chemokines. Examination of IL-17 in diabetic humans showed that serum levels of this cytokine were significantly increased in those with hypertension compared with normotensive subjects. We conclude that IL-17 is critical for the maintenance of angiotensin II-induced hypertension and vascular dysfunction and might be a therapeutic target for this widespread disease.

• A model of disturbed flow-induced atherosclerosis in mouse carotid artery by partial ligation and a simple method of RNA isolation from carotid endothelium.

  Authors: Douglas Nam, Chih-Wen Ni, Amir Rezvan, Jin Suo, Klaudia Budzyn, Alexander Llanos, David G Harrison, Don P Giddens, Hanjoong Jo

  Journal of visualized experiments : JoVE. 01/2010;

  Despite the well-known close association, direct evidence linking disturbed flow to atherogenesis has been lacking. We have recently used a modified version of carotid partial ligation methods toDespite the well-known close association, direct evidence linking disturbed flow to atherogenesis has been lacking. We have recently used a modified version of carotid partial ligation methods to show that it acutely induces low and oscillatory flow conditions, two key characteristics of disturbed flow, in the mouse common carotid artery. Using this model, we have provided direct evidence that disturbed flow indeed leads to rapid and robust atherosclerosis development in Apolipoprotein E knockout mouse. We also developed a method of endothelial RNA preparation with high purity from the mouse carotid intima. Using this mouse model and method, we found that partial ligation causes endothelial dysfunction in a week, followed by robust and rapid atheroma formation in two weeks in a hyperlipidemic mouse model along with features of complex lesion formation such as intraplaque neovascularization by four weeks. This rapid in vivo model and the endothelial RNA preparation method could be used to determine molecular mechanisms underlying flow-dependent regulation of vascular biology and diseases. Also, it could be used to test various therapeutic interventions targeting endothelial dysfunction and atherosclerosis in considerably reduced study duration.