Abstract-We recently showed that chronic inhibition of NO synthesis by N -nitro-L-arginine methyl ester (L-NAME) causes coronary vascular remodeling (ie, vascular fibrosis and medial thickening) in rats. To test the hypothesis that the inhibition of NO synthesis induces inflammatory changes in the heart, we characterized the inflammatory lesions that occurred during L-NAME administration and determined whether inflammation involved the induction of monocyte chemoattractant protein-1 (MCP-1) in vivo. During the first week of L-NAME administration to Wistar-Kyoto rats, we observed a marked infiltration of mononuclear leukocytes (ED1-positive macrophages) and fibroblast-like cells (␣-smooth muscle actin-positive myofibroblasts) into the coronary vessels and myocardial interstitial areas. These inflammatory changes were associated with the expression of proliferating cell nuclear antigen and MCP-1 (both mRNA and protein). The areas affected by inflammatory changes, as well as the expression of MCP-1 mRNA, declined after longer (28 days) treatment with L-NAME and were replaced by vascular and myocardial remodeling. Our results support the hypothesis that the inhibition of NO synthesis induces inflammatory changes in coronary vascular and myocardial tissues and involves MCP-1 expression. Results also suggest that the early stages of inflammatory changes are important in the development of later-stage structural changes observed in rat hearts. (Arterioscler Thromb Vasc

Abstract-We previously reported that chronic inhibition of nitric oxide (NO) synthesis with N -nitro-L-arginine methyl ester (L-NAME) induces inflammatory changes (monocyte infiltration, myofibroblast formation, and monocyte chemoattractant protein-1 [MCP-1] and transforming growth factor-␤1 [TGF-␤1] expression) in the rat heart and vessel. There is debate regarding whether TGF-␤1 exhibits proinflammatory or anti-inflammatory activities. We used the rat model to investigate the role of TGF-␤ in the pathogenesis of such inflammatory changes. We show here that infiltrating monocytes and myofibroblasts in the inflammatory lesions produced TGF-␤1 on the third day of L-NAME administration. Cotreatment with a monoclonal antibody against TGF-␤1, but not with control IgG, prevented the L-NAME-induced cardiac inflammation. The antibody also significantly inhibited the gene expression of MCP-1, P-selectin, and intercellular adhesion molecule-1. In summary, the antibody against TGF-␤1 prevented inflammatory changes in rat heart and vessel induced by chronic inhibition of NO synthesis, suggesting that increased production of TGF-␤1 is involved in the inflammatory changes in this model. Key Words: endothelium-derived factor Ⅲ growth substances Ⅲ inflammation Ⅲ adhesion molecule Ⅲ angiotensin II Ⅲ fibrosis C ardiovascular disorders such as hypertension, hypercholesterolemia, atherosclerosis, and aging are associated with endothelial dysfunction that leads to the reduced bioactivity of nitric oxide (NO). 1-7 We 8 -12 and others 13 have recently shown that chronic inhibition of NO synthesis with N -nitro-L-arginine methyl ester (L-NAME) induces marked monocyte infiltration into the coronary vessels associated with induction of monocyte chemoattractant protein-1 (MCP-1) during the first week of the treatment and causes vascular remodeling (medial thickening and fibrosis) and myocardial remodeling (fibrosis and hypertrophy) after 4 to 8 weeks of the treatment in animals.We have recently reported that early induction of transforming growth factor-␤1 (TGF-␤1) contributes to cardiac fibrosis in this model. 10 However, the role of TGF-␤1 in the pathogenesis of early inflammatory changes in this model has not been examined. There is considerable debate regarding whether TGF-␤1 exhibits proinflammatory or antiinflammatory activities (for review, see References 14 and 15). For example, it has been demonstrated that in vivo gene transfer of TGF-␤1 causes tissue inflammatory changes and subsequent fibrosis in the lung 16 and blood vessels, 17 whereas the major phenotype of the TGF-␤1 knockout mice is an early-onset inflammation in most tissues of the body. 18,19 TGF-␤1 is usually secreted from many cell types as a biologically inactive or latent form. 20 The activation mechanisms of latent TGF-␤1 complex in vivo have not been fully elucidated. Thus, demonstration of mere expression of total TGF-␤1 may not provide sufficient evidence of its function. To address direct in vivo evidence for the functional importance of TGF-␤1, a neutralizing...

Kubo-Inoue, Mayuko, Kensuke Egashira, Makoto Usui, Masao Takemoto, Kisho Ohtani, Makoto Katoh, Hiroaki Shimokawa, and Akira Takeshita. Long-term inhibition of nitric oxide synthesis increases arterial thrombogenecity in rat carotid artery. Am J Physiol Heart Circ Physiol 282: H1478-H1484, 2002. First published November 29, 2001 10.1152/ajpheart.00739.2001.-Reduced activity of endothelial nitric oxide (NO) may be involved in thrombus formation on atherosclerotic plaques, a major cause of acute coronary syndrome. However, mechanisms of such increase in arterial thrombogenecity have not been fully understood. We previously reported that long-term inhibition of NO synthesis by administration of N G -nitro-L-arginine methyl ester (L-NAME) causes hypertension and activates vascular tissue angiotensin-converting enzyme (ACE) activity. We used this model to investigate the mechanism by which long-term impairment of NO activity increases arterial thrombogenecity. We observed cyclic flow variations (CFVs), a reliable marker of platelet thrombi, after the production of stenosis of the carotid artery in rats treated with L-NAME for 4 wk. The thrombin antagonist argatroban suppressed the CFVs. The CFVs were detected in rats receiving L-NAME plus hydralazine but not in rats receiving L-NAME plus an ACE inhibitor (imidapril). Treatment with the ACE inhibitor imidapril, but not with hydralazine, prevented L-NAME-induced increases in carotid arterial ACE activity and attenuated tissue factor expression. These results suggest that long-term inhibition of endothelial NO synthesis may increase arterial thrombogenecity at least in part through angiotensin IIinduced induction of tissue factor and the resultant thrombin generation. These data provide a new insight as to how endothelial NO exhibits antithrombogenic properties of the endothelium.thrombosis; angiotensin-converting enzyme; tissue factor; thrombin OCCLUSIVE OR NONOCCLUSIVE thrombus formation on atherosclerotic plaque is believed to be of prime importance in the cause of acute coronary syndrome as well as the progression of atherosclerosis. Such thrombus formation is triggered by endothelial dysfunction, by exposure of plaque components or local mediators in the subendothelial layers to blood components after endothelial disruption (plaque rupture), or by systemic blood factors (17,25). Thus any interventions that may reduce the risk of thrombus formation might be expected to improve patient outcomes. The antithrombotic effects of nitric oxide (NO) have been studied mainly in in vitro conditions or in in vivo conditions with acute blockade of NO activity. However, the mechanisms by which long-term impairment of NO activity can increase arterial thrombogenesis are not fully understood.Atherosclerosis has been demonstrated to be associated with endothelial dysfunction, which leads to the abnormal production of NO. Endothelial NO has been shown to regulate vascular tone and to inhibit platelet aggregation, thrombus formation, leukocyte adhesion, and vascular proliferation (3,...