Our previous study demonstrated that
homocysteine (Hcy) mediated the expression and secretion of MCP-1 and
IL-8 in human monocytes. In the present study, we investigated whether the responsiveness of isolated monocytes to
lipopolysaccharide (LPS)-induced
chemokine secretion was enhanced in patients with
hyperhomocysteinemia (HHcy), and if so, whether this enhanced response could be inhibited by
folic acid treatment. We studied 38 control subjects and 40 patients with HHcy. The results showed that MCP-1 secretion from isolated monocytes in response to low-dose LPS in patients with HHcy was significantly higher than that in controls. After patients with HHcy underwent low-dose
folic acid treatment (0.8 mg/d) for 6 months, plasma Hcy levels were decreased and the hyper-responsiveness of MCP-1 and
IL-8 secreted by isolated monocytes was significantly reversed. Furthermore,
folic acid treatment at high concentrations (5 microM) significantly reduced the elevated levels of
reactive oxygen species,
NADPH oxidase activity and
chemokines in response to Hcy in cultured human monocytes. HHcy may contribute to
atherogenesis through enhancing the responsiveness of monocytes to inflammatory stimuli and promoting leukocyte recruitment into
atherosclerotic plaque. In addition to lowering the plasma levels of Hcy, low-dose
folic acid treatment exerts beneficial effects on patients with HHcy by inhibiting pro-inflammatory responses such as
chemokine secretion from human monocytes.