Previous studies have demonstrated a relationship between hyperhomocysteinemia and endothelial dysfunction, reduced bioavailability of nitric oxide, elastinolysis and, vascular muscle cell proliferation. In vivo decreased nitric oxide production is associated with increased matrix metalloproteinase (MMP) activity and formation of nitrotyrosine. To test the hypothesis that homocysteine neutralizes vascular endothelial nitric oxide, activates metalloproteinase, causes elastinolysis and vascular hypertrophy, we isolated aortas from normotensive Wistar rats and cultured them in medium containing homocysteine, and calf serum for 14 days. Homocysteine-mediated impairment of endothelial-dependent vasodilatation was reversed by co-incubation of homocysteine with nicotinamide (an inhibitor of peroxinitrite and nitrotyrosine), suggesting a role of homocysteine in redox-mediating endothelial dysfunction and nitrotyrosine formation. The Western blot analysis, using anti-nitrotyrosine antibody, on aortic tissue homogeneates demonstrated decreased nitrotyrosine in hyperhomocysteinemic vessels treated with nicotinamide. Zymographic analysis revealed increased elastinolytic gelatinase A and B (MMP-2, -9) in homocysteine treated vessels and the treatment with nicotinamide decreases the homocysteine-induced MMP activation. Morphometric analyses revealed significant medial hypertrophic thickening (1.4 +/- 0.2-fold of control, P = 0.03) and elastin disruption in homocysteine-treated vessels as compared to control. To determine whether homocysteine causes endothelial cell injury, cross-sections of aortas were analyzed for caspase activity by incubating with Ac-YVAD-AMC (substrate for apoptotic enzyme, caspase). The endothelium of homocysteine treated vessels, and endothelial cells treated with homocysteine, showed marked labeling for caspase. The length-tension relationship of homocysteine treated aortas was shifted to the left as compared to untreated aortas, indicating reduced vascular elastic compliance in homocysteine-treated vessels. Co-incubation of homocysteine and inhibitors of MMP, tissue inhibitor of metalloproteinase-4 (TIMP-4), and caspase, YVAD-CHO, improved vascular function. The results suggest that alteration in vascular elastin/collagen ratio and activation of MMP-2 are associated with decreased NO production in hyperhomocysteinemia.

Background and Purpose The association between left atrial (LA) size, ischemic stroke, and death has not been well established in African Americans despite their disproportionately higher rates of stroke and cardiovascular mortality compared to non-Hispanic whites. Methods For the analysis, participants in the Jackson cohort of the Atherosclerosis Risk in Communities Study were followed from the date of the echocardiogram in cycle three to the date of the first ischemic stroke event (or death) or to December 31, 2004 if no ischemic stroke event (or death) was detected. Results There were 1886 participants in the study population (mean age 58.9 years, 65% women). Participants in the top quintile of LA diameter indexed to height (LA diameter/height; 2.57 to 3.55 cm/m) were more likely women, hypertensive, diabetic, and obese compared to those not in the top quintile. Over a median follow-up of 9.8 years for ischemic stroke and 9.9 years for all-cause mortality, there were 106 strokes and 242 deaths. In a multivariable model adjusting for traditional clinical risk factors, the top quintile of LA diameter/height was significantly related to ischemic stroke (HR 1.7; 95% CI: 1.1, 2.7) and all-cause mortality (HR 2.0; 95% CI: 1.5, 2.7). After further adjustment for left ventricular (LV) hypertrophy and low LV ejection fraction, the top quintile remained significantly related to all-cause mortality (HR 1.8; 95% CI: 1.3, 2.5). Conclusions In this population-based cohort of African Americans, LA size was a predictor of all-cause mortality after adjusting for traditional cardiovascular risk factors, LV hypertrophy, and low LV ejection fraction.

. Apoptosis in the left ventricle of chronic volume overload causes endocardial endothelial dysfunction in rats. Am J Physiol Heart Circ Physiol 282: H1197-H1205, 2002. First published November 29, 2001 10.1152/ajpheart.00483.2001.-The hypothesis is that chronic increases in left ventricular (LV) load induce oxidative stress and latent matrix metalloproteinase (MMP) is activated, allowing the heart to dilate in the absence of endothelial nitric oxide (NO) and thereby reduce filling pressure. To create volume overload, an arteriovenous (A-V) fistula was placed in male Sprague-Dawley rats. To decrease oxidative stress and apoptosis, 0.08 mg/ml nicotinamide (Nic) was administered in drinking water 2 days before surgery. The rats were divided into the following groups: 1) A-V fistula, 2) A-V fistula ϩ Nic, 3) sham operated, 4) sham ϩ Nic, and 5) control (unoperated); n ϭ 6 rats/group. After 4 wk, hemodynamic parameters were measured in anesthetized rats. The heart was removed and weighed, and LV tissue homogeneates were prepared. A-V fistula caused an increase in heart weight, lung weight, and end-diastolic pressure compared with the sham group. The levels of malondialdehyde (MDA; a marker of oxidative stress) was 6.60 Ϯ 0.23 ng/mg protein and NO was 6.87 Ϯ 1.21 nmol/l in the LV of A-V fistula rats by spectrophometry. Nic treatment increased NO to 13.88 Ϯ 2.5 nmol/l and decreased MDA to 3.54 Ϯ 0.34 ng/mg protein (P ϭ 0.005). Zymographic levels of MMP-2 were increased, as were protein levels of nitrotyrosine and collagen fragments by Western blot analysis. The inhibition of oxidative stress by Nic decreased nitrotyrosine content and MMP activity. The levels of tissue inhibitor of metalloproteinase-4 mRNA were decreased in A-V fistula rats and increased in A-V fistula rats treated with Nic by Northern blot analysis. TdT-mediated dUTP nick-end labeling-positive cells were increased in A-V fistula rats and decreased in fistula rats treated with Nic. Acetylcholine and nitroprusside responses in cardiac rings prepared from the above groups of rats suggest impaired endothelial-dependent cardiac relaxation. Treatment with Nic improves cardiac relaxation. The results suggest that an increase in the oxidative stress and generation of nitrotyrosine are, in part, responsible for the activation of metalloproteinase and decreased endocardial endothelial function in chronic LV volume overload. nitric oxide; malondialdehyde; collagen degradation; tissue inhibitor of metalloproteinase; arteriovenous fistula; nicotinamide; NADH oxidase; nitrotyrosine; TUNEL; cardiac ring; acetylcholine; nitroprusside; stretch; contraction; relaxation; heart failure THE EXTRACELLULAR MATRIX (ECM), particularly type I fibrillar collagen surrounding the cardiomyocytes, helps the cardiac muscle to synchronize contraction and relaxation during systole and diastole, respectively (22,53,62). To compensate for the increase in workload and to reduce the wall stress, the cardiac muscle undergoes hypertrophy. This leads to remodeling of the ECM (54). Remodelin...

2001.-To test the hypothesis that homocysteine induces constrictive vascular remodeling by inactivating peroxisome proliferator-activated receptor (PPAR), aortic endothelial cells (ECs) and smooth muscle cells (SMCs) were isolated. Collagen gels were prepared, and ECs or SMCs (10 5 ) or SMCs ϩ ECs (10 4 ) were incorporated into the gels. To characterize PPAR, agonists of PPAR-␣ [ciprofibrate (CF)] and PPAR-␥ [15-deoxy-12,14-prostaglandin J 2 (PGJ2)] were used. To determine the role of disintegrin metalloproteinase (DMP), cardiac inhibitor of metalloproteinase (CIMP) was used in collagen gels. Gel diameter at 0 h was 14.1 Ϯ 0.2 mm and was unchanged up to 24 h as measured by a digital micrometer. SMCs reduce gel diameter to 10.5 Ϯ 0.4 mm at 24 h. Addition of homocysteine to SMCs reduces further the gel diameter to 8.0 Ϯ 0.2 mm, suggesting that SMCs induce contraction and that the contraction is further enhanced by homocysteine. Addition of ECs and SMCs reduces gel diameter to 12.0 Ϯ 0.3 mm, suggesting that ECs play a role in collagen contraction. Only PGJ 2, not CF, inhibits SMC contraction. However, both PGJ 2 and CF inhibit contraction of ECs and SMCs ϩ ECs. Addition of anti-DMP blocks SMC-as well as homocysteine-mediated contraction. However, CIMP inhibits only homocysteine-mediated contraction. The results suggest that homocysteine may enhance vascular constrictive remodeling by inactivating PPAR-␣ and -␥ in ECs and PPAR-␥ in SMCs. aorta; arteriosclerosis; hypertension; peroxisome proliferator-activated receptor; fibrate; prostaglandin; endothelial cell; smooth muscle cell ARTERIAL WALL REMODELING is one of the most important factors regulating lumen diameter after acute and/or chronic vascular injury (7,28,29,44). Smooth muscle cells (SMCs) remodel the existing and new extracellular matrix (ECM). In response to ECM degradation, SMCs alter phenotype (43). The consequences of remodeling may lead to alterations in arterial wall geometry and lumen diameter (7,28,29,44). Although the extracellular environment strongly influences cell behavior, it is unclear whether the changes in matrix composition affect connective tissue shrinkage. Hyperhomocysteinemia is associated with hypertension (39) and increases vascular intimal-medial thickness (26,34). Homocysteine causes arteriosclerosis (19,36,40), endothelial cell desquamation (38), thromboresistance (22), SMC proliferation (41, 45), collagen synthesis (23, 45), oxidation of low-density lipoprotein (12), increased monocyte adhesion to the vessel wall (20), platelet aggregation (6), coagulation (34), blood rheology (8, 25), and activation of plasminogen and metalloproteinase (18, 47), the two neutral proteinases associated with remodeling. Previous studies from our laboratory have identified a redox-sensitive homocysteine receptor in SMC. This receptor regulates collagen expression (45). Primarily, there are two nuclear transcription factor (NF) receptors that control the redox state of the cell. NF-B is induced by homocysteine (3, 49). Peroxisome proliferator-activat...