Abstract-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 (nϭ8 to 12/group) received angiotensin II (120 ng/kg per minute, subcutaneously) for 14 days Ϯ spironolactone or hydralazine (25 mg/kg per day). An additional group received aldosterone (750 ng/h, subcutaneously) Ϯ spironolactone. Systolic blood pressure was increased by angiotensin II (PϽ0.001) and reduced by spironolactone and hydralazine (PϽ0.001). Aldosterone-induced increase of blood pressure was reduced by spironolactone (PϽ0.05).In mesenteric small arteries studied on a pressurized myograph, media/lumen ratio was increased (PϽ0.001) and acetylcholine-mediated relaxation was impaired in angiotensin II-infused rats (PϽ0.001); both were partially improved by spironolactone (PϽ0.05) but not by hydralazine. Aldosterone-induced increase of media/lumen ratio (PϽ0.001) and impaired response to acetylcholine (PϽ0.001) were normalized by spironolactone. Response to sodium nitroprusside was similar in all groups. Aortic NADPH oxidase activity was increased (PϽ0.01) by angiotensin II and reduced by spironolactone and hydralazine. Aldosterone also increased (PϽ0.05) activation of NADPH oxidase, an effect abolished by spironolactone. Plasma thiobarbituric acid-reactive substances (a marker of oxidative stress), higher in angiotensin II and aldosterone rats (PϽ0.001), were normalized by spironolactone. In conclusion, spironolactone, which inhibited aldosterone actions, partially corrected structural and functional angiotensin II-induced abnormalities. These effects were associated with reduced vascular NADPH oxidase activity and decreased plasma markers of oxidative stress. Our findings suggest that aldosterone may mediate some of angiotensin II-induced vascular effects in hypertension, in part via increased oxidative stress.

Background-Pioglitazone and rosiglitazone, thiazolidinedione peroxisome proliferator-activated receptor-␥ (PPAR␥) activators, reduce blood pressure (BP) in some hypertensive models by unclear mechanisms. We tested the hypothesis that pioglitazone or rosiglitazone would prevent BP elevation and vascular dysfunction in angiotensin (Ang) II-infused rats by direct vascular effects. Methods and Results-Sprague-Dawley rats received Ang II (120 ng · kg Ϫ1 · min Ϫ1 SC) with or without pioglitazone (10 mg · kg Ϫ1 · d

Background-Endothelin (ET)-1 is a potent vasoconstrictor that contributes to vascular remodeling in hypertension and other cardiovascular diseases. Endogenous ET-1 is produced predominantly by vascular endothelial cells. To directly test the role of endothelium-derived ET-1 in cardiovascular pathophysiology, we specifically targeted expression of the human preproET-1 gene to the endothelium by using the Tie-2 promoter in C57BL/6 mice. Methods and Results-Ten-week-old male C57BL/6 transgenic (TG) and nontransgenic (wild type; WT) littermates were studied. TG mice exhibited 3-fold higher vascular tissue ET-1 mRNA and 7-fold higher ET-1 plasma levels than did WT mice but no significant elevation in blood pressure. Despite the absence of significant blood pressure elevation, TG mice exhibited marked hypertrophic remodeling and oxidant excess-dependent endothelial dysfunction of resistance vessels, altered ET-1 and ET-3 vascular responses, and significant increases in ET B expression compared with WT littermates. Moreover, TG mice generated significantly higher oxidative stress, possibly through increased activity and expression of vascular NAD(P)H oxidase than did their WT counterparts. Conclusions-In this new murine model of endothelium-restricted human preproET-1 overexpression, ET-1 caused structural remodeling and endothelial dysfunction of resistance vessels, consistent with a direct nonhemodynamic effect of ET-1 on the vasculature, at least in part through the activation of vascular NAD(P)H oxidase.

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/ϩ), and wild type (ϩ/ϩ) 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/ϩ and ϩ/ϩ mice but not in Op/Op. Ang II-treated Op/ϩ and ϩ/ϩ mice showed reduced acetylcholine-mediated relaxation (maximal relaxation, respectively, 64% and 67% versus 84% and 93% in respective controls; PϽ0.05), which was unaffected by L-NAME. Ang II-infused Op/Op mice arteries showed significantly less endothelial dysfunction than vehicle-infused counterparts (maximal relaxation 87% versus 96% in shams). Resistance arteries from Ang II-infused ϩ/ϩ and Op/ϩ mice had significantly increased media-tolumen ratio and media thickness, neither of which was altered in Op/Op mice compared with untreated littermates. Vascular media cross-sectional area, NAD(P)H oxidase activity and expression, and vascular cell adhesion molecule (VCAM)-1 expression were significantly increased by Ang II only in ϩ/ϩ mice (PϽ0.05). Key Words: hypertension Ⅲ macrophages Ⅲ reactive oxygen species I nflammation plays an important pathophysiological role in the development and progression of atherosclerosis, hypertension, and other conditions associated with vascular damage. 1 Macrophage colony-stimulating factor (m-CSF) functions as a chemotactic factor for monocytes, regulates effector functions of mature monocytes and macrophages, and modulates inflammatory responses by stimulating the production of other cytokines, adhesion molecules, and growth factors. 2,3 Macrophages have the ability to secrete various cytokines, including tumor necrosis factor (TNF)-␣ that can ultimately influence vascular inflammation. 4 Mice deficient in m-CSF, the result of a spontaneously occurring osteopetrotic mutation within the m-CSF gene, possess macrophage deficiency, monocytopenia, and defective bone formation. [5][6][7] Recently, it was demonstrated that m-CSF-deficient mice fed an atherogenic diet or crossed into a hypercholesterolemic apolipoprotein E-null background have significant reduction in atherosclerotic lesions. 8,9 However, whether reduced macrophage number as a result of the osteopetrotic mutation confers microvascular protection in hypertension remains to be determined. These mice may represent a good model to better understand mechanisms leading to vascular injury mediated by oxidative stress and inflammation in hypertension associated with the activation of the renin-angio...

The NAD(P)H oxidase inhibitor apocynin reduced blood pressure elevation and prevented structural alterations, endothelial dysfunction, and collagen deposition in the media of small arteries in Ang II-infused mice. Although hydralazine also decreased blood pressure, it had no effects on vascular collagen content. Our findings suggest that NAD(P)H oxidase activity plays an important role in vascular functional and structural changes and in the composition of the vascular wall in Ang II-dependent hypertension.

Abstract-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) with or without DHA (2.5 mL of oil containing 40% DHA/d PO) for 7 days. Systolic BP (mm Hg), elevated in Ang II-infused rats (172Ϯ3) versus controls (108Ϯ2, PϽ0.01), was reduced by DHA (112Ϯ4). In mesenteric small arteries studied in a pressurized myograph, media/lumen ratio was increased (PϽ0.05) and acetylcholine-induced relaxation impaired in Ang II-infused rats (PϽ0.05); both were normalized by DHA. In blood vessels of Ang II-infused rats, NADPH oxidase activity measured by chemiluminescence and expression of adhesion molecules intercellular adhesion molecule and vascular cell adhesion molecule-1 were significantly increased. These changes were abrogated by DHA. PPAR␣ activator DHA attenuated the development of hypertension, corrected structural abnormalities, and improved endothelial dysfunction induced by Ang II. These effects are associated with decreased oxidative stress and inflammation in the vascular wall.

High glucose (HG) causes glomerular mesangial cell (GMC) growth, production of transforming growth factor (TGF)-␤, and increased synthesis of matrix proteins such as fibronectin, contributing to diabetic nephropathy. We recently found that exposure of cells to HG also activates the growth-promoting enzyme janus kinase 2 (JAK2) and its latent signal transducers and activators of transcription (STAT) transcription factors (STAT1, STAT3, and STAT5). Our purpose was to determine the effect that inhibition of JAK2 and these STAT transcription factors has on the HG-induced increase in TGF-␤ and fibronectin synthesis in GMC. Exposure of GMC to 25 mmol/l glucose caused the activation of JAK2, STAT1, STAT3, and STAT5 plus an increase in TGF-␤ and fibronectin synthesis, as compared with 5.5 mmol/l glucose. This HG-induced increase in synthesis of TGF-␤ and fibronectin was prevented by concomitant incubation with AG-490, a specific JAK2 inhibitor. The HG-induced JAK2, STAT1, and STAT3 tyrosine phosphorylations in GMC were also abolished by AG-490. Preincubation of GMC cultured in 25 mmol/l glucose with a specific JAK2 or STAT1 antisense oligonucleotide also prevented both TGF-␤ and fibronectin synthesis. These results provide direct evidence for linkages between JAK2, STAT1, and the glucose-induced overproduction of TGF-␤ and fibronectin in GMC.

These results provide evidence that activation of the JAK/STAT pathway by HG or/and Ang II may be of importance in the increased GMC cell growth and collagen IV synthesis that is seen in diabetic nephropathy.