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Papers by farhad amiri

Research paper thumbnail of Resistance arteries of Ang II-infused osteopetrotic mice show reduced impairment of endothelial function, oxidative stress, and vascular remodeling: Role of inflammation and mCSF in hypertension

American Journal of Hypertension, 2005

Vascular damage induced by angiotensin (Ang) II may be partially mediated by vascular inflammatio... more Vascular damage induced by angiotensin (Ang) II may be partially mediated by vascular inflammation and reactive oxygen species. Atherogenesis is inhibited in homozygous osteopetrotic (op/op) mice lacking macrophage colony-stimulating factor (mCSF). No data are currently available on the interaction between mCSF deficiency and hypertension. We investigated the effects of Ang II on function and structure, NAD(P)H oxidase activity and vascular inflammation in resistance mesenteric arteries from op/op mice. Adult op/op, heterozygous (op/ϩ), and wild type (ϩ/ϩ) mice were infused with Ang II (1000 ng/kg/min, sc) or vehicle for 14 days. Blood pressure (BP) was measured by radio-telemetry. Vascular structure and fnction were assessed in mesenteric resistance arteries mounted on a pressurized myograph. NADPH oxidase activity was evaluated by lucigenin chemiluminescence and macrophage infiltration was assessed with confocal microscopy.Ang II elevated SBP (mmHg) only in ϩ/ϩ and op/ϩ (168Ϯ9 and 177Ϯ2, PϽ0.01 vs. controls), but not in op/op mice (151Ϯ7 vs. control, 143Ϯ4). Mesenteric arteries from Ang II-treated opϩ/ϩ and op/ϩ mice exhibited reduced Ach-mediated-relaxation (maximal relaxation respectively 64% and 67% vs. 84% and 93% in controls, PϽ0.05), which was unaffected by L-NAME. Op/op mice infused with Ang II showed significantly less endothelial dysfunction as measured by Ach-induced relaxation (87% vs. 96% in controls), which were further impaired by pre-incubation with L-NAME. Arteries from Ang II-infused ϩ/ϩ and op/ϩ mice showed increased media:lumen ratio (PϽ0.01) and media thickness (PϽ0.01), neither of which were different in op/op mice compared with untreated counterparts. Media cross sectional area was increased (PϽ0.05) by Ang II only in ϩ/ϩ mice. NADPH oxidase activity and macrophage infiltration were increased by Ang II infusion in opϩ/ϩ (PϽ0.05) but unchanged in op/ϩ and op/op mice compared to controls. These findings indicate that mCSF-deficient mice were more resistant to endothelial dysfunction, vascular remodeling and oxidative stress induced by Ang II, suggesting a critical role of proinflammatory mediators in vascular injury associated with Ang II-induced hypertension.

Research paper thumbnail of PPAR Activator Effects on Ang II-Induced Vascular Oxidative Stress and Inflammation

Docosahexaenoic acid (DHA), a peroxisome proliferator-activated receptor- (PPAR) activator, reduc... more Docosahexaenoic acid (DHA), a peroxisome proliferator-activated receptor- (PPAR) activator, reduces blood pressure (BP) in some hypertensive models by unclear mechanisms. We tested the hypothesis that DHA would prevent BP elevation and improve vascular dysfunction in angiotensin (Ang) II-infused rats by modulating of NADPH oxidase activity and inflammation in vascular wall. Sprague-Dawley rats received Ang II (120 ng/kg per minute SC)

Research paper thumbnail of Peroxisome proliferator activated receptors, inflammation, the vasculature and the heart

Inflammation and Cardiac Diseases, 2003

Over the last dozen years since the discovery of the family of transcription factor termed peroxi... more Over the last dozen years since the discovery of the family of transcription factor termed peroxisome proliferator activated receptors (PPAR) [1], an impressive number of studies have investigated the characteristics, ligands and functional roles as well as molecular mechanisms of PPARs. Although PPARs were formerly believed to regulate genes involved only in lipid and glucose metabolism, a large number of more recent studies have explored the role of PPARs in cell growth, cell migration as well as in inflammation. The function of PPARs in inflammation was first demonstrated by Devchand et al. [2] who showed that pro-inflammatory eicosanoid leukotriene B4 binds to PPARa and induces transcription of genes involved in wand (3-oxidation. In this chapter, we briefly summarize the role of PPARs in inflammation generally, and discuss in greater detail the role of PPARs in the heart. We will discuss molecular, biochemical, physiological and pharmacological roles of PPARa and PPARy in the regulation of cardiac hypertrophy, inflammation and cardiac function, and introduce novel concepts relating to PPARs as transcription factors in the regulation of the expression of inflammatory response genes as mechanisms that participate in the pathophysiology of cardiac disease.

Research paper thumbnail of PPARα activator fenofibrate inhibits myocardial inflammation and fibrosis in angiotensin II-infused rats

Journal of Molecular and Cellular Cardiology, 2004

Background.-Peroxisome proliferator-activated receptor (PPAR)a is highly expressed in the heart. ... more Background.-Peroxisome proliferator-activated receptor (PPAR)a is highly expressed in the heart. PPARa may play a role in cardiac hypertrophy, but effects on cardiac function, inflammation, and fibrosis are unknown. We tested the hypothesis that the PPARa activator fenofibrate prevents myocardial inflammation and fibrosis in angiotensin (Ang) II-infused rats. Methods and results.-Sprague Dawley rats received Ang II (120 ng/kg/min subcutaneously), fenofibrate (100 mg/kg/d p.o.), or Ang II + fenofibrate. After 7 d, systolic blood pressure (mmHg) was elevated (P < 0.01) in Ang II-infused rats (173 ± 4) vs. controls (115 ± 2) and reduced by fenofibrate (137 ± 5). Electrophoretic mobility shift assay demonstrated that Ang II upregulated cardiac nuclear factor kappa B activity by 50%. Ang II significantly increased cardiac expression of vascular-cell adhesion molecule-1, platelet endothelial cell adhesion molecule, and intercellular adhesion molecule-1. Increases in expression of these inflammatory mediators were normalized by fenofibrate. Ang II-induced expression of transforming growth factor-b1, collagen deposition, and macrophage infiltration were partially prevented by fenofibrate. Conclusions.-The PPARa activator fenofibrate prevented development of hypertension, and improved myocardial inflammation and collagen deposition in Ang II-infused rats. The hypolipidemic drug fenofibrate may be useful in prevention and treatment of myocardial disease associated with hypertension and hyperlipidemia.

Research paper thumbnail of Angiotensin II and endothelin-1 regulate MAP kinases through different redox-dependent mechanisms in human vascular smooth muscle cells

Journal of Hypertension, 2004

Objective The role of reactive oxygen species (ROS) in mitogen-activated protein kinase (MAPK) si... more Objective The role of reactive oxygen species (ROS) in mitogen-activated protein kinase (MAPK) signaling by angiotensin (Ang) II and endothelin-1 (ET-1) in human vascular smooth muscle cells (VSMC) was investigated. Design VSMCs were derived from resistance arteries from healthy subjects. MAPK activity was assessed using phospho-specific antibodies. ROS generation was measured by CMH2DCFDA fluorescence and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity by lucigenin chemiluminescence. Results Ang II and ET-1 increased MAPK phosphorylation (P < 0.01). Pre-treatment with Tiron and Tempol, •O 2 2 scavengers, attenuated agonist-stimulated phosphorylation of p38MAPK, c-Jun N-terminal kinases (JNK) and ERK5, but not of ERK1/2 (extracellular signalregulated kinases). Apocynin and diphenylene iodinium (DPI), NAD(P)H oxidase inhibitors, decreased Ang IIinduced responses 60-70%. ET-1-mediated MAPK phosphorylation was unaffected by apocynin but was reduced (> 50%) by thenoyltrifluoroacetone (TIFT) and carboxyl cyanide-m-chlorophenylhydrazone (CCCP), mitochondrial inhibitors. Allopurinol and N ø-nitro-Larginine methyl ester (L-NAME), xanthine oxidase and nitric oxide synthase (NOS) inhibitors, respectively, did not influence MAPK activation. Intracellular ROS generation, was increased by Ang II and ET-1 (P < 0.01). DPI inhibited Ang II-but not ET-1-mediated ROS production. Expression of p22phox and p47phox and activation of NAD(P)H oxidase were increased by Ang II but not by ET-1. CCCP and TIFT significantly attenuated ET-1-mediated ROS formation (P < 0.05), without influencing Ang II effects. Conclusions Ang II activates p38MAPK, JNK and ERK5 primarily through NAD(P)H oxidase-generated ROS. ET-1 stimulates these kinases via redox-sensitive processes that involve mitochondrial-derived ROS. These data suggest that redox-dependent activation of MAPKs by Ang II and ET-1 occur through distinct ROS-generating systems that could contribute to differential signaling by these agonists in VSMCs.

Research paper thumbnail of Deleterious combined effects of salt-loading and endothelial cell restricted endothelin-1 overexpression on blood pressure and vascular function in mice

Journal of Hypertension, 2010

Background We previously showed that young transgenic mice overexpressing preproendothelin-1 spec... more Background We previously showed that young transgenic mice overexpressing preproendothelin-1 specifically in endothelial cells had hypertrophic remodeling, endothelial dysfunction, increased vascular NADPH oxidase activity, and inflammation in mesenteric small arteries without blood pressure (BP) elevation compared to nontransgenic wild-type littermates. To assess the consequences of salt-loading and the role of endothelin receptors, we investigated the effects of these on vascular structure, function, and oxidative stress in mesenteric arteries in salt-loaded transgenic mice treated with endothelin receptor antagonists. Methods Ten-month-old male transgenic and wild-type littermates were salt-loaded (4% NaCl) and treated with endothelin subtype A receptor antagonist (ET A RA, ABT-627, 5 mg/kg per day), endothelin subtype B receptor antagonist (ET B RA; A-192621, 30 mg/kg per day), or ET A /BRA (bosentan, 100 mg/kg per day) for 4 weeks. BP was measured by radiotelemetry, vascular reactivity of mesenteric small arteries was studied on a pressurized myograph, and vascular NADPH oxidase activity was studied by lucigenin chemiluminescence. Results TransgenicRsalt mice had significantly increased BP compared with wild-typeRsalt mice, which was prevented by ET A RA and dual ET A/B RA but further increased by ET B antagonism. Increased small artery media/lumen ratio of transgenicRsalt mice was significantly decreased only by dual ET A/B RA (P < 0.01), whereas no differences were found in media cross-sectional area. Impaired maximal relaxation of small arteries to acetylcholine was significantly prevented with ET A RA and ET A/B RA (P < 0.05). N v-nitro-L-arginine methyl ester-induced reduction of acetylcholine maximal relaxation was partially prevented by ET A RA, completely prevented by dual, and partially restored by vitamin C preincubation following dual ET A/B RA. The blunted endothelin-1 contractile response of small arteries found in transgenicRsalt mice was partially restored by ET A RA and completely prevented by dual ET A/B R antagonism. The vasoconstrictor response to endothelin-1 was not altered in the presence or absence of ET B RA. Increased vascular NADPH oxidase activity of transgenicRsalt mice was further increased by ET B RA but returned to levels seen in wild-typeRsalt mice under either ET A RA and ET A/B RA. Conclusion TransgenicRsalt mice with endothelin-1 overexpression have structural alterations of mesenteric resistance vessels, endothelial dysfunction due to reduced nitric oxide bioavailability, a reduced responsiveness to endothelin-1, and enhanced vascular NADPH oxidase activity. ET B RA further exacerbated these effects, whereas ET A RA significantly improved but did not normalize them in chronically salt-loaded transgenic mice with endothelial cell human endothelin-1 overexpression. Salt and endothelin-1 overexpression have deleterious additive effects on vascular remodeling mediated by ET A R and ET B R. ET B R probably located in the endothelium, however, also exerts beneficial effects on endothelial function in this experimental paradigm. The present study provides the first in-vivo demonstration that endothelin-1 overexpression when associated with high-salt intake results in enhanced endothelial dysfunction and vascular remodeling of resistance vessels, and contributes to elevated BP, via ET A R and ET B R.

Research paper thumbnail of Dual angiotensin-converting enzyme/neutral endopeptidase inhibition on cardiac and renal fibrosis and inflammation in DOCA-salt hypertensive rats

Journal of Hypertension, 2005

Microvascular remodeling contributes to increased cardiovascular risk in hypertension. The dual a... more Microvascular remodeling contributes to increased cardiovascular risk in hypertension. The dual angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) inhibitor omapatrilat improves small artery remodeling in hypertension. The aim of the present study was to compare effects of omapatrilat to the ACE inhibitor fosinopril and the AT 1 antagonist irbesartan on the coronary microvasculature in spontaneously hypertensive rats (SHR). Tenweek-old SHR were treated for 10 weeks with omapatrilat (20 or 40 mg/kg/d), irbesartan (50 mg/kg/d), or fosinopril (20 mg/kg/d). Arterioles and capillaries were identified in the myocardium by immunolabeling. After 10 weeks, systolic blood pressure (BP) was significantly reduced in treated versus untreated SHR (P Ͻ .01). Myocardial arteriolar density/mm 2 was higher (P Ͻ .05) in untreated SHR versus Wistar-Kyoto (WKY), and was reduced by omapatrilat (at both high and low doses) and by fosinopril (P Ͻ .01). Irbesartan decreased only subepicardial arteriolar density (P Ͻ .05). Myocardial capillary density/mm 2 was decreased in untreated SHR versus WKY (P Ͻ .01), associated with increase in cardiomyocyte cross-sectional area and cardiomyocyte-to-capillary ratio, and a decrease in myocyte density. Omapatrilat (at both high and low doses) resulted in increased capillary density, decreased myocyte hypertrophy and cardiomyocyte to capillary ratio, and increased myocyte density (P Ͻ .01). Fosinopril and irbesartan reduced myocyte hypertrophy of SHR, but had no effect on capillary density. Dual ACE/NEP inhibition was more effective than ACE inhibition or AT 1 antagonism in improving microvascular and cardiomyocyte remodeling in the hypertensive heart. This suggests a role for NEP inhibition added to blockade of the renin-angiotensin system that may explain the greater efficacy of omapatrilat.

Research paper thumbnail of Characterization of a New Murine Transgenic Model of Endothelial Cell Human ENDOTHELIN-1 OVEREXPRESSION.4

Journal of Hypertension, 2004

Research paper thumbnail of Effects of PPAR-γ Knock-down and Hyperglycemia on Insulin Signaling in Vascular Smooth Muscle Cells From Hypertensive Rats

Journal of Cardiovascular Pharmacology, 2007

Peroxisome proliferator-activated receptor (PPAR)-gamma, a target in the treatment of diabetes, i... more Peroxisome proliferator-activated receptor (PPAR)-gamma, a target in the treatment of diabetes, improves insulin sensitivity and exerts cardiovascular protective effects by mechanisms that are not completely elucidated. To investigate underlying molecular mechanisms responsible for PPAR-gamma-associated vascular insulin signaling in hypertension, we tested whether PPAR-gamma downregulation in vascular smooth muscle cells (VSMC) from WKY and SHRSP rats would decrease insulin signaling and glucose uptake and whether this response would be worsened by hyperglycemia to a greater extent in VSMC of hypertensive origin. Passaged mesenteric artery VSMC grown in euglycemic (5.5 mmol/L) or hyperglycemic media (25.0 mmol/L) were treated with PPAR-gamma-siRNA (5 nmol/L), PPAR-gamma antagonist (GW-9662, 10 micromol/L), or PPAR-gamma activator (rosiglitazone, 10 micromol/L) in the presence or absence of insulin (100 nmol/L). Immunoblotting revealed that hyperglycemia and PPAR-gamma inhibition significantly (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) decreased insulin-stimulated insulin receptor (IR)-beta, Akt, and glycogen synthase kinase (GSK)-3beta phosphorylation, whereas phosphotyrosine phosphatase (PTP)-1B expression was increased in VSMC from both strains. These effects were more pronounced in SHRSP under hyperglycemia. Rosiglitazone tended to increase insulin-mediated IR-beta, Akt, and GSK-3beta phosphorylation in VSMC from both strains, whereas insulin-induced PTP-1B expression was reduced by hyperglycemia. Insulin-stimulated GLUT-4 expression and glucose transport were attenuated by hyperglycemia in both VSMC. These data suggest that PPAR-gamma inhibition results in decreased insulin signaling, particularly in SHR, in an IR-beta phosphorylation-dependent manner.

Research paper thumbnail of Spironolactone Improves Angiotensin-Induced Vascular Changes and Oxidative Stress

Hypertension, 2002

Angiotensin II plays an important role in vascular remodeling. We investigated the role of aldost... more Angiotensin II plays an important role in vascular remodeling. We investigated the role of aldosterone, which is stimulated by angiotensin II, as a mediator of angiotensin II–induced vascular structural and functional alterations. Sprague-Dawley rats (n=8 to 12/group) received angiotensin II (120 ng/kg per minute, subcutaneously) for 14 days ± spironolactone or hydralazine (25 mg/kg per day). An additional group received aldosterone (750 ng/h, subcutaneously) ± spironolactone. Systolic blood pressure was increased by angiotensin II ( P <0.001) and reduced by spironolactone and hydralazine ( P <0.001). Aldosterone-induced increase of blood pressure was reduced by spironolactone ( P <0.05). In mesenteric small arteries studied on a pressurized myograph, media/lumen ratio was increased ( P <0.001) and acetylcholine-mediated relaxation was impaired in angiotensin II–infused rats ( P <0.001); both were partially improved by spironolactone ( P <0.05) but not by hydralazi...

Research paper thumbnail of Countervailing vascular effects of rosiglitazone in high cardiovascular risk mice: role of oxidative stress and PRMT-1

Clinical Science, 2010

In the present study, we tested the hypothesis that the PPARγ (peroxisome-proliferator-activated ... more In the present study, we tested the hypothesis that the PPARγ (peroxisome-proliferator-activated receptor γ) activator rosiglitazone improves vascular structure and function in aged hyperhomocysteinaemic MTHFR (methylene tetrahydrofolate reductase) gene heterozygous knockout (mthfr+/−) mice fed a HCD (high-cholesterol diet), a model of high cardiovascular risk. One-year-old mthfr+/− mice were fed or not HCD (6 mg·kg−1 of body weight·day−1) and treated or not with rosiglitazone (20 mg·kg−1 of body weight·day−1) for 90 days and compared with wild-type mice. Endothelium-dependent relaxation of carotid arteries was significantly impaired (−40%) only in rosiglitazone-treated HCD-fed mthfr+/− mice. Carotid M/L (media-to-lumen ratio) and CSA (cross-sectional area) were increased (2-fold) in mthfr+/− mice fed or not HCD compared with wild-type mice (P<0.05). Rosiglitazone reduced M/L and CSA only in mthfr+/− mice fed a normal diet. Superoxide production was increased in mthfr+/− mice fed...

Research paper thumbnail of Role of aldosterone in angiotensin II-induced cardiac and aortic inflammation, fibrosis, and hypertrophy

Canadian Journal of Physiology and Pharmacology, 2005

Activation of the renin–angiotensin–aldosterone system is associated with increased extracellular... more Activation of the renin–angiotensin–aldosterone system is associated with increased extracellular matrix and inflammatory markers in the cardiovascular system. We evaluated the effects of aldosterone antagonism on cardiovascular structure, collagen deposition, and expression of inflammatory markers in 2-week angiotensin (Ang) II-infused rats (120 ng·kg–1·min–1, s.c.) ± spironolactone or hydralazine (25 mg·kg–1·d–1). Aortic and cardiac collagen density was evaluated with Sirius red staining. NFκB and AP-1 were measured by a electrophoretic mobility shift assay, and ED-1 (macrophage marker) and vascular cell adhesion molecule-1 (VCAM-1) were measured by immunohistochemistry. Ang II increased blood pressure (176 ± 2 mmHg vs. 115 ± 1 mmHg in controls, p < 0.01), which was attenuated by spironolactone (147 ± 4 mmHg, p < 0.01) and prevented by hydralazine (124 ± 2 mmHg, p < 0.01). Ang II enhanced left ventricular interstitial collagen type I/III deposition (4.1% ± 0.1% vs. 3.1% ±...

Research paper thumbnail of Long-term effects of the PPARγ activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

Canadian Journal of Physiology and Pharmacology, 2004

We investigated the long-term effects of the thiazolidinedione PPARγ activator pioglitazone on ca... more We investigated the long-term effects of the thiazolidinedione PPARγ activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of malignant of hypertension. Six-week-old SHRSP were treated with pioglitazone (10 mg/kg per day p.o.) for 20 weeks. The rise in systolic blood pressure (SBP) in SHRSP was only transiently and slightly attenuated by pioglitazone (P < 0.05). On one hand, cardiac hypertrophy was little affected by the pioglitazone treatment, and there was only a reduction of subepicardial interstitial fibrosis. On the other hand, left ventricular NFκB and AP-1 binding activities, the expression of TNFα, and the adhesion of molecule PECAM were significantly decreased by pioglitazone treatment. Expression of the pro-apoptotic proteins p53 and bax was significantly increased by pioglitazone. Thus, pioglitazone-attenuated cardiac inflammation in SHRSP had little effect on BP or cardiac hypertrophy. PPARγ activation may play...

Research paper thumbnail of Effect of Hyperhomocystinemia and Hypertension on Endothelial Function in Methylenetetrahydrofolate Reductase–Deficient Mice

Arteriosclerosis, Thrombosis, and Vascular Biology, 2003

Objective— We evaluated the effect of hyperhomocystinemia and angiotensin (Ang) II on vascular fu... more Objective— We evaluated the effect of hyperhomocystinemia and angiotensin (Ang) II on vascular function and structure in methylenetetrahydrofolate reductase knockout mice ( Mthfr +/− ). Methods and Results— Mthfr +/− and controls ( Mthfr +/+ ) received Ang II (400 ng/kg per min SC) or saline (14 days). Blood pressure, similar in Mthfr +/− and Mthfr +/+ , was increased by Ang II. Acetylcholine- and bradykinin-induced relaxations were impaired in mesenteric resistance arteries (pressurized myograph) in Mthfr +/− and in Ang II–infused Mthfr +/+ mice and additionally blunted in Ang II–infused Mthfr +/− mice. The inhibition by L-NAME on acetylcholine was reduced in Mthfr +/− and in Ang II– Mthfr +/+ and absent in Ang II– Mthfr +/− mice. In these groups, vitamin C improved the response to acetylcholine and restored the inhibition by L-NAME. The media to lumen ratio of small arteries, similar in Mthfr +/− and Mthfr +/+ , was increased by Ang II. Vascular NADPH oxidase activity, similar in ...

Research paper thumbnail of Reduced Vascular Remodeling, Endothelial Dysfunction, and Oxidative Stress in Resistance Arteries of Angiotensin II–Infused Macrophage Colony-Stimulating Factor–Deficient Mice

Arteriosclerosis, Thrombosis, and Vascular Biology, 2005

Objective—Angiotensin (Ang) II-induced vascular damage may be partially mediated by reactive oxyg... more Objective—Angiotensin (Ang) II-induced vascular damage may be partially mediated by reactive oxygen species generation and inflammation. Homozygous osteopetrotic mice (Op/Op), deficient in macrophage colony-stimulating factor (m-CSF), exhibit reduced inflammation. We therefore investigated Ang II effects on vascular structure, function, and oxidant stress generation in this model.Methods and Results—Adult Op/Op, heterozygous (Op/+), and wild type (+/+) mice underwent 14-day Ang II (1000 ng/kg per minute) or saline infusion. Blood pressure (BP) was assessed by radiotelemetry, mesenteric resistance artery vascular reactivity was studied on a pressurized myograph, and vascular superoxide and NAD(P)H oxidase activity by lucigenin chemiluminescence. Ang II increased BP in Op/+ and +/+ mice but not in Op/Op. Ang II-treated Op/+ and +/+ mice showed reduced acetylcholine-mediated relaxation (maximal relaxation, respectively, 64% and 67% versus 84% and 93% in respective controls;P<0.05), ...

Research paper thumbnail of Resistance artery remodeling in deoxycorticosterone acetate-salt hypertension is dependent on vascular inflammation: evidence from m-CSF-deficient mice

American Journal of Physiology-Heart and Circulatory Physiology, 2006

Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-depende... more Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-dependent component. ET-1-induced vascular damage may be mediated in part by oxidative stress and vascular inflammation. Homozygous osteopetrotic ( Op/Op) mice, deficient in macrophage colony-stimulating factor (m-CSF), exhibit reduced inflammation. We investigated in osteopetrotic ( Op/Op) mice the effects of DOCA-salt hypertension on vascular structure, function, and oxidative stress, the latter as manifested by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase activity. Mice were implanted with DOCA (200 mg/mouse, under 5% isofluorane anesthesia) and given saline for 14 days. Systolic blood pressure (mmHg) was significantly increased (146 ± 2 and 138 ± 1; P < 0.001 vs. basal 115 ± 3 and 115 ± 3, respectively) by DOCA-salt in wild-type (+/+) and heterozygous ( Op/+) mice, but not in Op/Op mice (130 ± 1 vs. basal 125 ± 3). Norepinephrine contractile response was signific...

Research paper thumbnail of PPAR-γ inhibits ANG II-induced cell growth via SHIP2 and 4E-BP1

American Journal of Physiology-Heart and Circulatory Physiology, 2005

The present study evaluated the effects of peroxisome proliferator-activated receptor (PPAR)-γ ac... more The present study evaluated the effects of peroxisome proliferator-activated receptor (PPAR)-γ activators on ANG II-induced signaling pathways and cell growth. Vascular smooth muscle cells (VSMC) derived from rat mesenteric arteries were treated with ANG II, with/without the AT1 receptor blocker valsartan or the AT2 receptor blocker PD-123319, after pretreatment for 24 h with the PPAR-γ activators 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) or rosiglitazone. Both 15d-PGJ2 and rosiglitazone decreased ANG II-induced DNA synthesis. Rosiglitazone treatment increased nuclear PPAR-γ expression and activity in VSMC. However, rosiglitazone did not alter expression of PPAR-α/β, ERK 1/2, Akt, or ANG II receptors. 15d-PGJ2 and rosiglitazone decreased ERK 1/2 and Akt peak activity, both of which were induced by ANG II via the AT1 receptor. Rosiglitazone inhibited ANG II-enhanced phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), as well as Src homology (SH) 2-contain...

Research paper thumbnail of Angiotensin II activation of the JAK/STAT pathway in mesangial cells is altered by high glucose

Kidney International, 2002

Angiotensin II activation of the JAK/STAT pathway in mesanthe onset and progression of diabetic c... more Angiotensin II activation of the JAK/STAT pathway in mesanthe onset and progression of diabetic complications [1]. gial cells is altered by high glucose. Several hypotheses such as hyperosmolarity, glycation Background. Both high glucose (HG) and angiotensin II end products, oxidant formation, abnormality of sorbi-(Ang II) causes glomerular mesangial cell (GMC) growth and tol and myoinositol metabolism, and protein kinase C increased synthesis of matrix proteins like collagen IV contrib-(PKC) activation through de novo synthesis of diacyluting to diabetic nephropathy. We have recently found that exposure of vascular smooth muscle cells to HG augments glycerol (DAG) have been proposed to explain the varithe Ang II activation of the growth promoting JAK/STAT ous pathophysiological changes induced by high glucose pathway. We hypothesized that Ang II activation of the JAK/ (HG) [2-4]. These changes, which affect many cell types STAT pathway is altered by HG in GMC, and that this pathway such as vascular smooth muscle cells (VSMC) and glomight be linked to the Ang II-induced growth and overproducmerular mesangial cells (GMC), include increases in contion of collagen IV in GMC in HG conditions. Methods. GMC were cultured under normal glucose (NG; tractility, cellular proliferation, permeability, and extra-5.5 mmol/L) and HG (25 mmol/L) for 48 hours and stimulated cellular matrix (ECM) and cytokine production [5]. with Ang II (0.1 mol/L) for various times. GMC lysate was Moreover, the beneficial therapeutical effects of angiothen immunoprecipitated and/or immunoblotted with SHP-1, tensin-converting enzyme (ACE) inhibitors and angio-SHP-2 and phosphospecific JAK2 and STAT antibodies. The tensin II (Ang II) type 1 receptor (AT 1) antagonists in HG and Ang II induced growth and collagen IV synthesis the treatment of diabetic nephropathy [6, 7] suggest that studies were performed in GMC transfected with JAK2 antisense or JAK2 sense. GMC growth was monitored via [ 3 H]the renin-angiotensin system (RAS) plays an important thymidine incorporation, and collagen IV synthesis via ELISA. role in the renal complications seen in diabetic patients Results. We found that Ang II-induced JAK2, STAT1, with insulin-dependent (type I) diabetes mellitus (DM), STAT3, STAT5A/B and SHP-2 phosphorylations were ensuch as above-normal increases in glomerular filtration hanced by HG, whereas that of SHP-1 was reduced. Ang IIrate [8, 9]. induced growth and collagen IV synthesis also were increased under HG conditions. Transfection of GMC with JAK2 anti-It has long been established that GMC have microfilsense oligonucleotides blocked the Ang II-induced growth and aments that contract in response to Ang II mediated collagen IV synthesis in both NG and HG conditions. by specific Ang II receptor subtypes [10], indicating a Conclusion. These results provide evidence that activation plausible role of GMC in the regulation of glomerular of the JAK/STAT pathway by HG or/and Ang II may be of size, blood flow, and filtration via contraction [11]. The importance in the increased GMC cell growth and collagen IV effects of Ang II are exerted through high affinity memsynthesis that is seen in diabetic nephropathy. brane-bound receptors, namely AT 1 and Ang II type 2 (AT 2) receptors [12]. Most of the known effects of Ang II have been attributed to AT 1 , which has a high affinity The results of the Diabetes Control and Complications for the selective antagonist losartan. On the other hand, Trial have shown that strict glycemic control can prevent AT 2 has a high affinity for the selective antagonist PD 123319. Both Ang II receptor types have been localized in humans and rats but their distribution is not uniform

Research paper thumbnail of Hyperglycemia Enhances Angiotensin II-induced Janus-activated Kinase/STAT Signaling in Vascular Smooth Muscle Cells

Journal of Biological Chemistry, 1999

Research paper thumbnail of Angiotensin II blockade prevents hyperglycemia-induced activation of JAK and STAT proteins in diabetic rat kidney glomeruli

American Journal of Physiology-Renal Physiology, 2004

Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibito... more Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibitors or ANG II-receptor antagonists slows progression of nephropathy in diabetes, indicating ANG II plays an important role in its development. We previously reported that hyperglycemia augments both ANG II-induced growth and activation of Janus kinase (JAK)2 and signal transducers and activators of transcription (STAT) proteins in cultured rat mesangial cells. Furthermore, we demonstrated that the tyrosine kinase enzyme JAK2 plays a key role in both ANG II- and hyperglycemia-induced growth in these cells. We hypothesized that the ACE inhibitor captopril and the ANG II-receptor antagonist candesartan would hinder hyperglycemic-induced activation of JAK and STAT proteins in rat glomeruli, demonstrating that ANG II plays an important role in the activation of these proteins in vivo. Adult male Sprague-Dawley rats were given either streptozotocin (STZ; 60 mg/kg iv) or vehicle, and glomeruli w...

Research paper thumbnail of Resistance arteries of Ang II-infused osteopetrotic mice show reduced impairment of endothelial function, oxidative stress, and vascular remodeling: Role of inflammation and mCSF in hypertension

American Journal of Hypertension, 2005

Vascular damage induced by angiotensin (Ang) II may be partially mediated by vascular inflammatio... more Vascular damage induced by angiotensin (Ang) II may be partially mediated by vascular inflammation and reactive oxygen species. Atherogenesis is inhibited in homozygous osteopetrotic (op/op) mice lacking macrophage colony-stimulating factor (mCSF). No data are currently available on the interaction between mCSF deficiency and hypertension. We investigated the effects of Ang II on function and structure, NAD(P)H oxidase activity and vascular inflammation in resistance mesenteric arteries from op/op mice. Adult op/op, heterozygous (op/ϩ), and wild type (ϩ/ϩ) mice were infused with Ang II (1000 ng/kg/min, sc) or vehicle for 14 days. Blood pressure (BP) was measured by radio-telemetry. Vascular structure and fnction were assessed in mesenteric resistance arteries mounted on a pressurized myograph. NADPH oxidase activity was evaluated by lucigenin chemiluminescence and macrophage infiltration was assessed with confocal microscopy.Ang II elevated SBP (mmHg) only in ϩ/ϩ and op/ϩ (168Ϯ9 and 177Ϯ2, PϽ0.01 vs. controls), but not in op/op mice (151Ϯ7 vs. control, 143Ϯ4). Mesenteric arteries from Ang II-treated opϩ/ϩ and op/ϩ mice exhibited reduced Ach-mediated-relaxation (maximal relaxation respectively 64% and 67% vs. 84% and 93% in controls, PϽ0.05), which was unaffected by L-NAME. Op/op mice infused with Ang II showed significantly less endothelial dysfunction as measured by Ach-induced relaxation (87% vs. 96% in controls), which were further impaired by pre-incubation with L-NAME. Arteries from Ang II-infused ϩ/ϩ and op/ϩ mice showed increased media:lumen ratio (PϽ0.01) and media thickness (PϽ0.01), neither of which were different in op/op mice compared with untreated counterparts. Media cross sectional area was increased (PϽ0.05) by Ang II only in ϩ/ϩ mice. NADPH oxidase activity and macrophage infiltration were increased by Ang II infusion in opϩ/ϩ (PϽ0.05) but unchanged in op/ϩ and op/op mice compared to controls. These findings indicate that mCSF-deficient mice were more resistant to endothelial dysfunction, vascular remodeling and oxidative stress induced by Ang II, suggesting a critical role of proinflammatory mediators in vascular injury associated with Ang II-induced hypertension.

Research paper thumbnail of PPAR Activator Effects on Ang II-Induced Vascular Oxidative Stress and Inflammation

Docosahexaenoic acid (DHA), a peroxisome proliferator-activated receptor- (PPAR) activator, reduc... more Docosahexaenoic acid (DHA), a peroxisome proliferator-activated receptor- (PPAR) activator, reduces blood pressure (BP) in some hypertensive models by unclear mechanisms. We tested the hypothesis that DHA would prevent BP elevation and improve vascular dysfunction in angiotensin (Ang) II-infused rats by modulating of NADPH oxidase activity and inflammation in vascular wall. Sprague-Dawley rats received Ang II (120 ng/kg per minute SC)

Research paper thumbnail of Peroxisome proliferator activated receptors, inflammation, the vasculature and the heart

Inflammation and Cardiac Diseases, 2003

Over the last dozen years since the discovery of the family of transcription factor termed peroxi... more Over the last dozen years since the discovery of the family of transcription factor termed peroxisome proliferator activated receptors (PPAR) [1], an impressive number of studies have investigated the characteristics, ligands and functional roles as well as molecular mechanisms of PPARs. Although PPARs were formerly believed to regulate genes involved only in lipid and glucose metabolism, a large number of more recent studies have explored the role of PPARs in cell growth, cell migration as well as in inflammation. The function of PPARs in inflammation was first demonstrated by Devchand et al. [2] who showed that pro-inflammatory eicosanoid leukotriene B4 binds to PPARa and induces transcription of genes involved in wand (3-oxidation. In this chapter, we briefly summarize the role of PPARs in inflammation generally, and discuss in greater detail the role of PPARs in the heart. We will discuss molecular, biochemical, physiological and pharmacological roles of PPARa and PPARy in the regulation of cardiac hypertrophy, inflammation and cardiac function, and introduce novel concepts relating to PPARs as transcription factors in the regulation of the expression of inflammatory response genes as mechanisms that participate in the pathophysiology of cardiac disease.

Research paper thumbnail of PPARα activator fenofibrate inhibits myocardial inflammation and fibrosis in angiotensin II-infused rats

Journal of Molecular and Cellular Cardiology, 2004

Background.-Peroxisome proliferator-activated receptor (PPAR)a is highly expressed in the heart. ... more Background.-Peroxisome proliferator-activated receptor (PPAR)a is highly expressed in the heart. PPARa may play a role in cardiac hypertrophy, but effects on cardiac function, inflammation, and fibrosis are unknown. We tested the hypothesis that the PPARa activator fenofibrate prevents myocardial inflammation and fibrosis in angiotensin (Ang) II-infused rats. Methods and results.-Sprague Dawley rats received Ang II (120 ng/kg/min subcutaneously), fenofibrate (100 mg/kg/d p.o.), or Ang II + fenofibrate. After 7 d, systolic blood pressure (mmHg) was elevated (P < 0.01) in Ang II-infused rats (173 ± 4) vs. controls (115 ± 2) and reduced by fenofibrate (137 ± 5). Electrophoretic mobility shift assay demonstrated that Ang II upregulated cardiac nuclear factor kappa B activity by 50%. Ang II significantly increased cardiac expression of vascular-cell adhesion molecule-1, platelet endothelial cell adhesion molecule, and intercellular adhesion molecule-1. Increases in expression of these inflammatory mediators were normalized by fenofibrate. Ang II-induced expression of transforming growth factor-b1, collagen deposition, and macrophage infiltration were partially prevented by fenofibrate. Conclusions.-The PPARa activator fenofibrate prevented development of hypertension, and improved myocardial inflammation and collagen deposition in Ang II-infused rats. The hypolipidemic drug fenofibrate may be useful in prevention and treatment of myocardial disease associated with hypertension and hyperlipidemia.

Research paper thumbnail of Angiotensin II and endothelin-1 regulate MAP kinases through different redox-dependent mechanisms in human vascular smooth muscle cells

Journal of Hypertension, 2004

Objective The role of reactive oxygen species (ROS) in mitogen-activated protein kinase (MAPK) si... more Objective The role of reactive oxygen species (ROS) in mitogen-activated protein kinase (MAPK) signaling by angiotensin (Ang) II and endothelin-1 (ET-1) in human vascular smooth muscle cells (VSMC) was investigated. Design VSMCs were derived from resistance arteries from healthy subjects. MAPK activity was assessed using phospho-specific antibodies. ROS generation was measured by CMH2DCFDA fluorescence and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity by lucigenin chemiluminescence. Results Ang II and ET-1 increased MAPK phosphorylation (P < 0.01). Pre-treatment with Tiron and Tempol, •O 2 2 scavengers, attenuated agonist-stimulated phosphorylation of p38MAPK, c-Jun N-terminal kinases (JNK) and ERK5, but not of ERK1/2 (extracellular signalregulated kinases). Apocynin and diphenylene iodinium (DPI), NAD(P)H oxidase inhibitors, decreased Ang IIinduced responses 60-70%. ET-1-mediated MAPK phosphorylation was unaffected by apocynin but was reduced (> 50%) by thenoyltrifluoroacetone (TIFT) and carboxyl cyanide-m-chlorophenylhydrazone (CCCP), mitochondrial inhibitors. Allopurinol and N ø-nitro-Larginine methyl ester (L-NAME), xanthine oxidase and nitric oxide synthase (NOS) inhibitors, respectively, did not influence MAPK activation. Intracellular ROS generation, was increased by Ang II and ET-1 (P < 0.01). DPI inhibited Ang II-but not ET-1-mediated ROS production. Expression of p22phox and p47phox and activation of NAD(P)H oxidase were increased by Ang II but not by ET-1. CCCP and TIFT significantly attenuated ET-1-mediated ROS formation (P < 0.05), without influencing Ang II effects. Conclusions Ang II activates p38MAPK, JNK and ERK5 primarily through NAD(P)H oxidase-generated ROS. ET-1 stimulates these kinases via redox-sensitive processes that involve mitochondrial-derived ROS. These data suggest that redox-dependent activation of MAPKs by Ang II and ET-1 occur through distinct ROS-generating systems that could contribute to differential signaling by these agonists in VSMCs.

Research paper thumbnail of Deleterious combined effects of salt-loading and endothelial cell restricted endothelin-1 overexpression on blood pressure and vascular function in mice

Journal of Hypertension, 2010

Background We previously showed that young transgenic mice overexpressing preproendothelin-1 spec... more Background We previously showed that young transgenic mice overexpressing preproendothelin-1 specifically in endothelial cells had hypertrophic remodeling, endothelial dysfunction, increased vascular NADPH oxidase activity, and inflammation in mesenteric small arteries without blood pressure (BP) elevation compared to nontransgenic wild-type littermates. To assess the consequences of salt-loading and the role of endothelin receptors, we investigated the effects of these on vascular structure, function, and oxidative stress in mesenteric arteries in salt-loaded transgenic mice treated with endothelin receptor antagonists. Methods Ten-month-old male transgenic and wild-type littermates were salt-loaded (4% NaCl) and treated with endothelin subtype A receptor antagonist (ET A RA, ABT-627, 5 mg/kg per day), endothelin subtype B receptor antagonist (ET B RA; A-192621, 30 mg/kg per day), or ET A /BRA (bosentan, 100 mg/kg per day) for 4 weeks. BP was measured by radiotelemetry, vascular reactivity of mesenteric small arteries was studied on a pressurized myograph, and vascular NADPH oxidase activity was studied by lucigenin chemiluminescence. Results TransgenicRsalt mice had significantly increased BP compared with wild-typeRsalt mice, which was prevented by ET A RA and dual ET A/B RA but further increased by ET B antagonism. Increased small artery media/lumen ratio of transgenicRsalt mice was significantly decreased only by dual ET A/B RA (P < 0.01), whereas no differences were found in media cross-sectional area. Impaired maximal relaxation of small arteries to acetylcholine was significantly prevented with ET A RA and ET A/B RA (P < 0.05). N v-nitro-L-arginine methyl ester-induced reduction of acetylcholine maximal relaxation was partially prevented by ET A RA, completely prevented by dual, and partially restored by vitamin C preincubation following dual ET A/B RA. The blunted endothelin-1 contractile response of small arteries found in transgenicRsalt mice was partially restored by ET A RA and completely prevented by dual ET A/B R antagonism. The vasoconstrictor response to endothelin-1 was not altered in the presence or absence of ET B RA. Increased vascular NADPH oxidase activity of transgenicRsalt mice was further increased by ET B RA but returned to levels seen in wild-typeRsalt mice under either ET A RA and ET A/B RA. Conclusion TransgenicRsalt mice with endothelin-1 overexpression have structural alterations of mesenteric resistance vessels, endothelial dysfunction due to reduced nitric oxide bioavailability, a reduced responsiveness to endothelin-1, and enhanced vascular NADPH oxidase activity. ET B RA further exacerbated these effects, whereas ET A RA significantly improved but did not normalize them in chronically salt-loaded transgenic mice with endothelial cell human endothelin-1 overexpression. Salt and endothelin-1 overexpression have deleterious additive effects on vascular remodeling mediated by ET A R and ET B R. ET B R probably located in the endothelium, however, also exerts beneficial effects on endothelial function in this experimental paradigm. The present study provides the first in-vivo demonstration that endothelin-1 overexpression when associated with high-salt intake results in enhanced endothelial dysfunction and vascular remodeling of resistance vessels, and contributes to elevated BP, via ET A R and ET B R.

Research paper thumbnail of Dual angiotensin-converting enzyme/neutral endopeptidase inhibition on cardiac and renal fibrosis and inflammation in DOCA-salt hypertensive rats

Journal of Hypertension, 2005

Microvascular remodeling contributes to increased cardiovascular risk in hypertension. The dual a... more Microvascular remodeling contributes to increased cardiovascular risk in hypertension. The dual angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) inhibitor omapatrilat improves small artery remodeling in hypertension. The aim of the present study was to compare effects of omapatrilat to the ACE inhibitor fosinopril and the AT 1 antagonist irbesartan on the coronary microvasculature in spontaneously hypertensive rats (SHR). Tenweek-old SHR were treated for 10 weeks with omapatrilat (20 or 40 mg/kg/d), irbesartan (50 mg/kg/d), or fosinopril (20 mg/kg/d). Arterioles and capillaries were identified in the myocardium by immunolabeling. After 10 weeks, systolic blood pressure (BP) was significantly reduced in treated versus untreated SHR (P Ͻ .01). Myocardial arteriolar density/mm 2 was higher (P Ͻ .05) in untreated SHR versus Wistar-Kyoto (WKY), and was reduced by omapatrilat (at both high and low doses) and by fosinopril (P Ͻ .01). Irbesartan decreased only subepicardial arteriolar density (P Ͻ .05). Myocardial capillary density/mm 2 was decreased in untreated SHR versus WKY (P Ͻ .01), associated with increase in cardiomyocyte cross-sectional area and cardiomyocyte-to-capillary ratio, and a decrease in myocyte density. Omapatrilat (at both high and low doses) resulted in increased capillary density, decreased myocyte hypertrophy and cardiomyocyte to capillary ratio, and increased myocyte density (P Ͻ .01). Fosinopril and irbesartan reduced myocyte hypertrophy of SHR, but had no effect on capillary density. Dual ACE/NEP inhibition was more effective than ACE inhibition or AT 1 antagonism in improving microvascular and cardiomyocyte remodeling in the hypertensive heart. This suggests a role for NEP inhibition added to blockade of the renin-angiotensin system that may explain the greater efficacy of omapatrilat.

Research paper thumbnail of Characterization of a New Murine Transgenic Model of Endothelial Cell Human ENDOTHELIN-1 OVEREXPRESSION.4

Journal of Hypertension, 2004

Research paper thumbnail of Effects of PPAR-γ Knock-down and Hyperglycemia on Insulin Signaling in Vascular Smooth Muscle Cells From Hypertensive Rats

Journal of Cardiovascular Pharmacology, 2007

Peroxisome proliferator-activated receptor (PPAR)-gamma, a target in the treatment of diabetes, i... more Peroxisome proliferator-activated receptor (PPAR)-gamma, a target in the treatment of diabetes, improves insulin sensitivity and exerts cardiovascular protective effects by mechanisms that are not completely elucidated. To investigate underlying molecular mechanisms responsible for PPAR-gamma-associated vascular insulin signaling in hypertension, we tested whether PPAR-gamma downregulation in vascular smooth muscle cells (VSMC) from WKY and SHRSP rats would decrease insulin signaling and glucose uptake and whether this response would be worsened by hyperglycemia to a greater extent in VSMC of hypertensive origin. Passaged mesenteric artery VSMC grown in euglycemic (5.5 mmol/L) or hyperglycemic media (25.0 mmol/L) were treated with PPAR-gamma-siRNA (5 nmol/L), PPAR-gamma antagonist (GW-9662, 10 micromol/L), or PPAR-gamma activator (rosiglitazone, 10 micromol/L) in the presence or absence of insulin (100 nmol/L). Immunoblotting revealed that hyperglycemia and PPAR-gamma inhibition significantly (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) decreased insulin-stimulated insulin receptor (IR)-beta, Akt, and glycogen synthase kinase (GSK)-3beta phosphorylation, whereas phosphotyrosine phosphatase (PTP)-1B expression was increased in VSMC from both strains. These effects were more pronounced in SHRSP under hyperglycemia. Rosiglitazone tended to increase insulin-mediated IR-beta, Akt, and GSK-3beta phosphorylation in VSMC from both strains, whereas insulin-induced PTP-1B expression was reduced by hyperglycemia. Insulin-stimulated GLUT-4 expression and glucose transport were attenuated by hyperglycemia in both VSMC. These data suggest that PPAR-gamma inhibition results in decreased insulin signaling, particularly in SHR, in an IR-beta phosphorylation-dependent manner.

Research paper thumbnail of Spironolactone Improves Angiotensin-Induced Vascular Changes and Oxidative Stress

Hypertension, 2002

Angiotensin II plays an important role in vascular remodeling. We investigated the role of aldost... more Angiotensin II plays an important role in vascular remodeling. We investigated the role of aldosterone, which is stimulated by angiotensin II, as a mediator of angiotensin II–induced vascular structural and functional alterations. Sprague-Dawley rats (n=8 to 12/group) received angiotensin II (120 ng/kg per minute, subcutaneously) for 14 days ± spironolactone or hydralazine (25 mg/kg per day). An additional group received aldosterone (750 ng/h, subcutaneously) ± spironolactone. Systolic blood pressure was increased by angiotensin II ( P <0.001) and reduced by spironolactone and hydralazine ( P <0.001). Aldosterone-induced increase of blood pressure was reduced by spironolactone ( P <0.05). In mesenteric small arteries studied on a pressurized myograph, media/lumen ratio was increased ( P <0.001) and acetylcholine-mediated relaxation was impaired in angiotensin II–infused rats ( P <0.001); both were partially improved by spironolactone ( P <0.05) but not by hydralazi...

Research paper thumbnail of Countervailing vascular effects of rosiglitazone in high cardiovascular risk mice: role of oxidative stress and PRMT-1

Clinical Science, 2010

In the present study, we tested the hypothesis that the PPARγ (peroxisome-proliferator-activated ... more In the present study, we tested the hypothesis that the PPARγ (peroxisome-proliferator-activated receptor γ) activator rosiglitazone improves vascular structure and function in aged hyperhomocysteinaemic MTHFR (methylene tetrahydrofolate reductase) gene heterozygous knockout (mthfr+/−) mice fed a HCD (high-cholesterol diet), a model of high cardiovascular risk. One-year-old mthfr+/− mice were fed or not HCD (6 mg·kg−1 of body weight·day−1) and treated or not with rosiglitazone (20 mg·kg−1 of body weight·day−1) for 90 days and compared with wild-type mice. Endothelium-dependent relaxation of carotid arteries was significantly impaired (−40%) only in rosiglitazone-treated HCD-fed mthfr+/− mice. Carotid M/L (media-to-lumen ratio) and CSA (cross-sectional area) were increased (2-fold) in mthfr+/− mice fed or not HCD compared with wild-type mice (P<0.05). Rosiglitazone reduced M/L and CSA only in mthfr+/− mice fed a normal diet. Superoxide production was increased in mthfr+/− mice fed...

Research paper thumbnail of Role of aldosterone in angiotensin II-induced cardiac and aortic inflammation, fibrosis, and hypertrophy

Canadian Journal of Physiology and Pharmacology, 2005

Activation of the renin–angiotensin–aldosterone system is associated with increased extracellular... more Activation of the renin–angiotensin–aldosterone system is associated with increased extracellular matrix and inflammatory markers in the cardiovascular system. We evaluated the effects of aldosterone antagonism on cardiovascular structure, collagen deposition, and expression of inflammatory markers in 2-week angiotensin (Ang) II-infused rats (120 ng·kg–1·min–1, s.c.) ± spironolactone or hydralazine (25 mg·kg–1·d–1). Aortic and cardiac collagen density was evaluated with Sirius red staining. NFκB and AP-1 were measured by a electrophoretic mobility shift assay, and ED-1 (macrophage marker) and vascular cell adhesion molecule-1 (VCAM-1) were measured by immunohistochemistry. Ang II increased blood pressure (176 ± 2 mmHg vs. 115 ± 1 mmHg in controls, p < 0.01), which was attenuated by spironolactone (147 ± 4 mmHg, p < 0.01) and prevented by hydralazine (124 ± 2 mmHg, p < 0.01). Ang II enhanced left ventricular interstitial collagen type I/III deposition (4.1% ± 0.1% vs. 3.1% ±...

Research paper thumbnail of Long-term effects of the PPARγ activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

Canadian Journal of Physiology and Pharmacology, 2004

We investigated the long-term effects of the thiazolidinedione PPARγ activator pioglitazone on ca... more We investigated the long-term effects of the thiazolidinedione PPARγ activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of malignant of hypertension. Six-week-old SHRSP were treated with pioglitazone (10 mg/kg per day p.o.) for 20 weeks. The rise in systolic blood pressure (SBP) in SHRSP was only transiently and slightly attenuated by pioglitazone (P < 0.05). On one hand, cardiac hypertrophy was little affected by the pioglitazone treatment, and there was only a reduction of subepicardial interstitial fibrosis. On the other hand, left ventricular NFκB and AP-1 binding activities, the expression of TNFα, and the adhesion of molecule PECAM were significantly decreased by pioglitazone treatment. Expression of the pro-apoptotic proteins p53 and bax was significantly increased by pioglitazone. Thus, pioglitazone-attenuated cardiac inflammation in SHRSP had little effect on BP or cardiac hypertrophy. PPARγ activation may play...

Research paper thumbnail of Effect of Hyperhomocystinemia and Hypertension on Endothelial Function in Methylenetetrahydrofolate Reductase–Deficient Mice

Arteriosclerosis, Thrombosis, and Vascular Biology, 2003

Objective— We evaluated the effect of hyperhomocystinemia and angiotensin (Ang) II on vascular fu... more Objective— We evaluated the effect of hyperhomocystinemia and angiotensin (Ang) II on vascular function and structure in methylenetetrahydrofolate reductase knockout mice ( Mthfr +/− ). Methods and Results— Mthfr +/− and controls ( Mthfr +/+ ) received Ang II (400 ng/kg per min SC) or saline (14 days). Blood pressure, similar in Mthfr +/− and Mthfr +/+ , was increased by Ang II. Acetylcholine- and bradykinin-induced relaxations were impaired in mesenteric resistance arteries (pressurized myograph) in Mthfr +/− and in Ang II–infused Mthfr +/+ mice and additionally blunted in Ang II–infused Mthfr +/− mice. The inhibition by L-NAME on acetylcholine was reduced in Mthfr +/− and in Ang II– Mthfr +/+ and absent in Ang II– Mthfr +/− mice. In these groups, vitamin C improved the response to acetylcholine and restored the inhibition by L-NAME. The media to lumen ratio of small arteries, similar in Mthfr +/− and Mthfr +/+ , was increased by Ang II. Vascular NADPH oxidase activity, similar in ...

Research paper thumbnail of Reduced Vascular Remodeling, Endothelial Dysfunction, and Oxidative Stress in Resistance Arteries of Angiotensin II–Infused Macrophage Colony-Stimulating Factor–Deficient Mice

Arteriosclerosis, Thrombosis, and Vascular Biology, 2005

Objective—Angiotensin (Ang) II-induced vascular damage may be partially mediated by reactive oxyg... more Objective—Angiotensin (Ang) II-induced vascular damage may be partially mediated by reactive oxygen species generation and inflammation. Homozygous osteopetrotic mice (Op/Op), deficient in macrophage colony-stimulating factor (m-CSF), exhibit reduced inflammation. We therefore investigated Ang II effects on vascular structure, function, and oxidant stress generation in this model.Methods and Results—Adult Op/Op, heterozygous (Op/+), and wild type (+/+) mice underwent 14-day Ang II (1000 ng/kg per minute) or saline infusion. Blood pressure (BP) was assessed by radiotelemetry, mesenteric resistance artery vascular reactivity was studied on a pressurized myograph, and vascular superoxide and NAD(P)H oxidase activity by lucigenin chemiluminescence. Ang II increased BP in Op/+ and +/+ mice but not in Op/Op. Ang II-treated Op/+ and +/+ mice showed reduced acetylcholine-mediated relaxation (maximal relaxation, respectively, 64% and 67% versus 84% and 93% in respective controls;P<0.05), ...

Research paper thumbnail of Resistance artery remodeling in deoxycorticosterone acetate-salt hypertension is dependent on vascular inflammation: evidence from m-CSF-deficient mice

American Journal of Physiology-Heart and Circulatory Physiology, 2006

Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-depende... more Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-dependent component. ET-1-induced vascular damage may be mediated in part by oxidative stress and vascular inflammation. Homozygous osteopetrotic ( Op/Op) mice, deficient in macrophage colony-stimulating factor (m-CSF), exhibit reduced inflammation. We investigated in osteopetrotic ( Op/Op) mice the effects of DOCA-salt hypertension on vascular structure, function, and oxidative stress, the latter as manifested by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase activity. Mice were implanted with DOCA (200 mg/mouse, under 5% isofluorane anesthesia) and given saline for 14 days. Systolic blood pressure (mmHg) was significantly increased (146 ± 2 and 138 ± 1; P < 0.001 vs. basal 115 ± 3 and 115 ± 3, respectively) by DOCA-salt in wild-type (+/+) and heterozygous ( Op/+) mice, but not in Op/Op mice (130 ± 1 vs. basal 125 ± 3). Norepinephrine contractile response was signific...

Research paper thumbnail of PPAR-γ inhibits ANG II-induced cell growth via SHIP2 and 4E-BP1

American Journal of Physiology-Heart and Circulatory Physiology, 2005

The present study evaluated the effects of peroxisome proliferator-activated receptor (PPAR)-γ ac... more The present study evaluated the effects of peroxisome proliferator-activated receptor (PPAR)-γ activators on ANG II-induced signaling pathways and cell growth. Vascular smooth muscle cells (VSMC) derived from rat mesenteric arteries were treated with ANG II, with/without the AT1 receptor blocker valsartan or the AT2 receptor blocker PD-123319, after pretreatment for 24 h with the PPAR-γ activators 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) or rosiglitazone. Both 15d-PGJ2 and rosiglitazone decreased ANG II-induced DNA synthesis. Rosiglitazone treatment increased nuclear PPAR-γ expression and activity in VSMC. However, rosiglitazone did not alter expression of PPAR-α/β, ERK 1/2, Akt, or ANG II receptors. 15d-PGJ2 and rosiglitazone decreased ERK 1/2 and Akt peak activity, both of which were induced by ANG II via the AT1 receptor. Rosiglitazone inhibited ANG II-enhanced phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), as well as Src homology (SH) 2-contain...

Research paper thumbnail of Angiotensin II activation of the JAK/STAT pathway in mesangial cells is altered by high glucose

Kidney International, 2002

Angiotensin II activation of the JAK/STAT pathway in mesanthe onset and progression of diabetic c... more Angiotensin II activation of the JAK/STAT pathway in mesanthe onset and progression of diabetic complications [1]. gial cells is altered by high glucose. Several hypotheses such as hyperosmolarity, glycation Background. Both high glucose (HG) and angiotensin II end products, oxidant formation, abnormality of sorbi-(Ang II) causes glomerular mesangial cell (GMC) growth and tol and myoinositol metabolism, and protein kinase C increased synthesis of matrix proteins like collagen IV contrib-(PKC) activation through de novo synthesis of diacyluting to diabetic nephropathy. We have recently found that exposure of vascular smooth muscle cells to HG augments glycerol (DAG) have been proposed to explain the varithe Ang II activation of the growth promoting JAK/STAT ous pathophysiological changes induced by high glucose pathway. We hypothesized that Ang II activation of the JAK/ (HG) [2-4]. These changes, which affect many cell types STAT pathway is altered by HG in GMC, and that this pathway such as vascular smooth muscle cells (VSMC) and glomight be linked to the Ang II-induced growth and overproducmerular mesangial cells (GMC), include increases in contion of collagen IV in GMC in HG conditions. Methods. GMC were cultured under normal glucose (NG; tractility, cellular proliferation, permeability, and extra-5.5 mmol/L) and HG (25 mmol/L) for 48 hours and stimulated cellular matrix (ECM) and cytokine production [5]. with Ang II (0.1 mol/L) for various times. GMC lysate was Moreover, the beneficial therapeutical effects of angiothen immunoprecipitated and/or immunoblotted with SHP-1, tensin-converting enzyme (ACE) inhibitors and angio-SHP-2 and phosphospecific JAK2 and STAT antibodies. The tensin II (Ang II) type 1 receptor (AT 1) antagonists in HG and Ang II induced growth and collagen IV synthesis the treatment of diabetic nephropathy [6, 7] suggest that studies were performed in GMC transfected with JAK2 antisense or JAK2 sense. GMC growth was monitored via [ 3 H]the renin-angiotensin system (RAS) plays an important thymidine incorporation, and collagen IV synthesis via ELISA. role in the renal complications seen in diabetic patients Results. We found that Ang II-induced JAK2, STAT1, with insulin-dependent (type I) diabetes mellitus (DM), STAT3, STAT5A/B and SHP-2 phosphorylations were ensuch as above-normal increases in glomerular filtration hanced by HG, whereas that of SHP-1 was reduced. Ang IIrate [8, 9]. induced growth and collagen IV synthesis also were increased under HG conditions. Transfection of GMC with JAK2 anti-It has long been established that GMC have microfilsense oligonucleotides blocked the Ang II-induced growth and aments that contract in response to Ang II mediated collagen IV synthesis in both NG and HG conditions. by specific Ang II receptor subtypes [10], indicating a Conclusion. These results provide evidence that activation plausible role of GMC in the regulation of glomerular of the JAK/STAT pathway by HG or/and Ang II may be of size, blood flow, and filtration via contraction [11]. The importance in the increased GMC cell growth and collagen IV effects of Ang II are exerted through high affinity memsynthesis that is seen in diabetic nephropathy. brane-bound receptors, namely AT 1 and Ang II type 2 (AT 2) receptors [12]. Most of the known effects of Ang II have been attributed to AT 1 , which has a high affinity The results of the Diabetes Control and Complications for the selective antagonist losartan. On the other hand, Trial have shown that strict glycemic control can prevent AT 2 has a high affinity for the selective antagonist PD 123319. Both Ang II receptor types have been localized in humans and rats but their distribution is not uniform

Research paper thumbnail of Hyperglycemia Enhances Angiotensin II-induced Janus-activated Kinase/STAT Signaling in Vascular Smooth Muscle Cells

Journal of Biological Chemistry, 1999

Research paper thumbnail of Angiotensin II blockade prevents hyperglycemia-induced activation of JAK and STAT proteins in diabetic rat kidney glomeruli

American Journal of Physiology-Renal Physiology, 2004

Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibito... more Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibitors or ANG II-receptor antagonists slows progression of nephropathy in diabetes, indicating ANG II plays an important role in its development. We previously reported that hyperglycemia augments both ANG II-induced growth and activation of Janus kinase (JAK)2 and signal transducers and activators of transcription (STAT) proteins in cultured rat mesangial cells. Furthermore, we demonstrated that the tyrosine kinase enzyme JAK2 plays a key role in both ANG II- and hyperglycemia-induced growth in these cells. We hypothesized that the ACE inhibitor captopril and the ANG II-receptor antagonist candesartan would hinder hyperglycemic-induced activation of JAK and STAT proteins in rat glomeruli, demonstrating that ANG II plays an important role in the activation of these proteins in vivo. Adult male Sprague-Dawley rats were given either streptozotocin (STZ; 60 mg/kg iv) or vehicle, and glomeruli w...