Homocysteine induces expression and secretion of monocyte chemoattractant protein-1 and interleukin-8 in human aortic endothelial cells - Implications for vascular disease

Background-Proinflammatory cytokines play key roles in atherogenesis and di sease progression. Because hyperhomo-cysteinemia is an Independent risk fac tor for cardiovascular disease, we hypothesized that homocysteine could be atherogenic by altering the expression of specific cytokines in vascular en dothelial cells. Methods and Results-Northern blot and RNase protection assays showed that D L-homocysteine induced mRNA expression of the proinflammatory cytokines mon ocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) in culture d human aortic endothelial cells (HAECs). Homocysteine had no effect on exp ression of other cytokines, namely tumor necrosis factor-a, granulocyte-mac rophage colony-stimulating factor, interleukin-1 beta, and transforming gro wth factor-p. MCP-1 mRNA expression increased 1 hour after homocysteine tre atment, reached a maximum within 2 to 4 hours, and declined to basal levels over the next 24 hours. Induction of mRNA expression for both chemokines w as observed with as little as 10 mu mol/L DL-homocysteine, and maximal expr ession was achieved with 50 mu mol/L DL-homocysteine. Homocysteine also tri ggered the release of MCP-1 and IL-8 protein from HAECs into the culture me dium. The induction was specific for homocysteine, because equimolar concen trations of L-homocystine, L-cysteine, and L-methionine had no effect on mR NA levels and protein release. Furthermore, L-homocysteine induced chemokin e expression, but D-homocysteine did not, thus demonstrating enantiomeric s pecificity. The culture medium from homocysteine-treated HAECs promoted che motaxis in human peripheral blood monocytes and U937 cells. Anti-human reco mbinant MCP-1 antibody blocked the migration. Conclusions-Pathophysiological levels of L-homocysteine alter endothelial c ell function by upregulating MCP-1 and IL-8 expression and secretion. This suggests that L-homocysteine may contribute to the initiation and progressi on of vascular disease by promoting leukocyte recruitment.