The present study was designed to test the hypothesis that estrogen receptors (ER) in the blood vessel wall play a role in the modulation of the release of endothelium-derived nitric oxide (EDNO). Both basal and stimulated release of EDNO were determined in aortic rings isolated from female and male wild-type and male homozygous estrogen receptor knock-out (ERKO) mice.125 I-17 ␤ -estradiol binding in aortic tissue showed significantly more high affinity cytosolicnuclear-binding sites in male compared with female wildtype mice. Estrogen receptor transcripts were present in the aorta of male wild-type mice, but they were absent in male ERKO animals. Basal release of EDNO (determined by endothelium-dependent contraction caused by N G -nitro-Larginine) was significantly higher in aorta of wild-type male mice compared with wild-type female mice, and significantly lower in the aorta of male ERKO compared with male wild-type mice. Acetylcholine-induced endotheliumdependent relaxation was similar in all groups studied. No difference was observed in the activity of calcium-dependent nitric oxide synthase in homogenates of lungs and brain taken from male wild-type and ERKO mice. These studies show a significant association between the number of estrogen receptors and basal release of EDNO in the aorta of mice, and suggest that decreased vascular estrogen receptor number may represent a novel risk factor for cardiovascular diseases.

Abstract-We have previously demonstrated that urokinase-type plasminogen activator (uPA) is highly expressed in the aneurysmal segment of the abdominal aorta (AAA) in apolipoprotein E-deficient (apoE Ϫ/Ϫ ) mice treated with angiotensin II (Ang II). In the present study, we tested the hypothesis that uPA is essential for AAA formation in this model. An osmotic minipump containing Ang II (1.44 mg/kg per day) was implanted subcutaneously into 7-to 11-month-old male mice for 1 month. Ang II induced AAA in 9 (90%) of 10 hyperlipidemic mice deficient in apoE (apoE Ϫ/Ϫ /uPA ϩ/ϩ mice) but in only 2 (22%) of 9 mice deficient in both apoE and uPA (apoE Ϫ/Ϫ /uPA Ϫ/Ϫ mice) (PϽ0.05). Although the expansion of the suprarenal aorta was significantly less in apoE Ϫ/Ϫ /uPA Ϫ/Ϫ mice than in apoE Ϫ/Ϫ /uPA ϩ/ϩ mice, the aortic diameters of the aorta immediately above or below the suprarenal aorta were similar between the 2 groups. Ang II induced AAA in 7 (39%) of 18 strain-matched wild-type C57 black/6J control mice. The incidence was significantly higher in atherosclerotic apoE-deficient (apoE Ϫ/Ϫ ) mice, in which 8 (100%) of 8 mice developed AAA. Only 1 (4%) of 27 uPA Ϫ/Ϫ mice developed AAA after Ang II treatment. We conclude the following: (1) uPA plays an essential role in Ang II-induced AAA in mice with or without preexisting hyperlipidemia and atherosclerosis; (2) uPA deficiency does not affect the diameter of the nonaneurysmal portion of the aorta; and (3)

Urokinase-type plasminogen activator (uPA) is increased in human abdominal aortic aneurysm (AAA).Chronic infusion of angiotensin II (Ang II) results in AAA in apolipoprotein E-deficient mice. We tested the hypothesis that Ang II infusion results in an elevation of uPA expression contributing to aneurysm formation. Ang II or vehicle was infused by osmotic pumps into apoE-KO mice. All mice treated with Ang II developed a localized expansion of the suprarenal aorta (75% increase in outer diameter), accompanied by an elevation of blood pressure (22 mmHg), compared to the vehicle-treated group. Histological examination of the dilated aortic segment revealed similarities to human AAA including focal elastin fragmentation, macrophage infiltration, and intravascular hemorrhage. Ang II treatment resulted in a 13-fold increase in the expression of uPA mRNA in the AAA segment in contrast to a twofold increase in the atherosclerotic aortic arch. Increased uPA protein was detected in the abdominal aorta as early as 10 days after Ang II infusion before significant aorta expansion. Thus, Ang II infusion results in macrophage infiltration, increased uPA activity, and aneurysm formation in the abdominal aorta of apoE-KO mice. These data are consistent with a causal role for uPA in the pathogenesis of AAA. Abdominal aortic aneurysm (AAA) is a chronic degenerative disease characterized by segmental weakening and dilation of the vascular wall. Recent estimates indicate that the prevalence of AAA is 4 to 9% in adults older than 65 years of age and is known to be associated with atherosclerosis, aging, hypertension, and cigarette smoking. Continued tissue remodeling results in silent expansion of the AAA with an increased risk of spontaneous rupture. Currently the only available treatments for AAAs are surgical resection and replacement or, more recently, insertion of an endovascular stent. The etiology of AAA is unclear. The extracellular matrix plays an essential role in maintaining the integrity of the vascular wall. Elastin and collagen fibers are the major components of this extracellular matrix. Both plasmin and matrix metalloproteinases (MMPs) are capable of degrading extracellular matrix, including collagen, elastin, and fibrin. Urokinase-type plasminogen activator (uPA) hydrolyzes plasminogen to form plasmin, which in turn activates MMPs. The in vivo activity of uPA is also regulated by local concentrations of its major inhibitor, PAI-1. Biochemical studies have demonstrated increased proteolytic activity in the aortic wall of AAA. Schneiderman and colleagues 1 showed that uPA mRNA as well as the tissue-type plasminogen activator (tPA), co-localized with infiltrating macrophages, is significantly increased in human AAA. Increased activities of MMP-2, -3, -9, and -12 in AAA have also been reported. [2][3][4][5] Atherosclerotic aortic lesions from high-cholesterol diet-fed apoE-KO mice show fragmentation of the elastic lamellae and rupture of the media resulting in pseudomicroaneurysm formation. These pathological changes are ...

The human BTG1 protein is thought to be a potential tumour suppressor because its overexpression inhibits NIH 3T3 cell proliferation. However, little is known about how BTG1 exerts its anti-proliferative activity. In this study, we used the yeast 'two-hybrid' system to screen for interacting protein partners and identified human carbon catabolite repressor protein (CCR4)-associative factor 1 (hCAF-1), a homologue of mouse CAF-1 (mCAF-1) and Saccharomyces cerevisiae yCAF-1/POP2. In vitro the hCAF-1/BTG1 complex formation was dependent on the phosphorylation of a putative p34cdc2 kinase site on BTG1 (Ser-159). In yeast, the Ala-159 mutant did not interact with hCAF-1. In addition, phosphorylation of Ser-159 in vitro showed specificity for the cell cycle kinases p34CDK2/cyclin E and p34CDK2/cyclin A, but not for p34CDK4/cyclin D1 or p34cdc2/cyclin B. Cell synchrony experiments with primary cultures of rat aortic smooth-muscle cells (RSMCs) demonstrated that message and protein levels of rat CAF-1 (rCAF-1) were up-regulated under conditions of cell contact, as previously reported for BTG1 [Wilcox, Scott, Subramanian, Ross, Adams-Burton, Stoltenborg and Corjay (1995) Circulation 92, I34-I35]. Western blot and immunohistochemical analysis showed that rCAF-1 localizes to the nucleus of contact-inhibited RSMCs, where it was physically associated with BTG1, as determined by co-immunoprecipitation with anti-hCAF-1 antisera. Overexpression of hCAF-1 in NIH 3T3 and osteosarcoma (U-2-OS) cells was itself anti-proliferative with colony formation reduced by 67% and 90% respectively. Taken together, these results indicate that formation of the hCAF-1/BTG1 complex is driven by phosphorylation at BTG1 (Ser-159) and implicates this complex in the signalling events of cell division that lead to changes in cellular proliferation associated with cell-cell contact.