Homocysteine Upregulates Vascular Cell Adhesion Molecule-1 Expression in Cultured Human Aortic Endothelial Cells and Enhances Monocyte Adhesion

Abstract

Abstract-Elevated plasma homocysteine is an independent risk factor for atherosclerosis. We hypothesized that homocysteine enhances monocyte/human aortic endothelial cell (HAEC) interactions, a pivotal early event in atherogenesis, by upregulating endothelial adhesion molecules. After incubation of cultured HAECs with reduced DL-homocysteine for up to 24 hours, adhesion of human monocytes to homocysteine-stimulated HAECs was significantly upregulated in a time-and dose-dependent fashion. Pretreatment of HAECs with 100 mol/L homocysteine caused a 4.5-fold increase in the adhesion of normal human monocytes (PϽ0.001). Similarly, adhesion of monocytic U937 cells was maximally elevated by 3.5-fold at 100 mol/L homocysteine (PϽ0.001). In support of our hypothesis, vascular cell adhesion molecule (VCAM)-1 mRNA expression increased 5-fold in HAECs after 3 hours of treatment with 100 mol/L homocysteine, as assessed by quantitative reverse transcription-polymerase chain reaction. Neutralizing antibody studies confirmed the involvement of VCAM-1 in mediating monocyte adhesion to homocysteine-stimulated HAECs. Coincubation of HAECs with homocysteine and tumor necrosis factor-␣ synergistically elevated monocyte adhesion as well as VCAM-1 protein expression, with the latter evaluated by flow cytometry. Preincubation of HAECs with cyclooxygenase inhibitors completely abrogated homocysteine-induced monocyte adhesion, whereas scavenging reactive oxygen species and the elevation of NO caused partial inhibition only. These data support the notion that the proinflammatory effects of homocysteine may have important implications in atherogenesis. Key Words: human aortic endothelial cells Ⅲ homocysteine Ⅲ monocyte adhesion Ⅲ vascular cell adhesion molecule-1 Ⅲ cyclooxygenase H omocysteine (Hcy) is a sulfhydryl amino acid metabolite of dietary methionine. Elevated plasma Hcy is an independent cardiovascular risk factor that is associated with accelerated atherosclerosis and increased cerebrovascular/ischemic heart disease. 1 Without intervention, nearly 50% of the patients with congenital hyperhomocystinuria (ie, total plasma Hcy [tHcy] levels Ͼ200 mol/L versus 7 to 14 mol/L in normal individuals) will experience a major cardiovascular event by the age of 30 years. 2 However, more frequently seen in the general population are modestly elevated tHcy levels, which are nonetheless strong predictors of existent and future development of vascular pathologies. 3 Elevated Hcy appears to contribute to cardiovascular disease, in part, by inducing endothelial cell (EC) dysfunction. In vivo, moderately elevated tHcy causes EC damage, 4 exacerbates hypertension-related atherosclerosis, 4 and impairs flowmediated arterial dilation. 5 In vitro, Hcy-thiolactone is cytotoxic to ECs, 6 and the free reduced thiol (HcyH) alters the endothelial expression of bioactive molecules, such as NO, interleukin (IL)-8, and tissue factor. 7,8 Additionally, HcyH increases leukocyte adhesion to cultured human umbilical vein ECs, 9 and elevated tHcy induces adhesion m...

Microarray analysis of homocysteine‐responsive genes in cardiac neural crest cells in vitro

“…Our research group and others have shown that hyperhomocysteinemia has a significant impact upon a variety of cellular functions that are important in early development, including mitosis (Dalton et al, 1997;Fritzer-Szekeres et al, 1998), apoptosis (Boot et al, 2003;Sachdev, 2005), differentiation (Rosenquist et al, 1996;Boot et al, 2003), migration (Brauer and Rosenquist, 2002;Boot et al, 2006), and directional outgrowth (Latacha and Rosenquist, 2005). In adult cells, elevated homocysteine has been shown to have an adverse effect upon functions that also are important during development, but may not yet have been fully explored in embryos; these functions include cell adhesion (Silverman et al, 2002) and contractility (Bonaventura et al, 2004).…”

Homocysteine-Induced Endothelin-1 Release Is Dependent on Hyperglycaemia and Reactive Oxygen Species Production in Bovine Aortic Endothelial Cells

“…This is most likely due to Hcy causing endothelial dysfunction [2, 3], which is important in the initiation of atherogenesis. Previous studies have shown that Hcy causes an increased expression of adhesion molecules [2] and increased release of MCP-1 and IL-8 from endothelial cells [3]. These studies, however, were all done in conditions of normoglycaemia.…”

Homocysteine Enhances Endothelial Apoptosis via Upregulation of Fas-Mediated Pathways

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