S-Adenosylhomocysteine Promotes the Invasion of C6 Glioma Cells via Increased Secretion of Matrix Metalloproteinase-2 in Murine Microglial BV2 Cells

Abstract

S-Adenosylhomocysteine (SAH) is a risk factor for many diseases, including tumor progression and neurodegenerative disease. In this study, we examined the hypothesis that SAH may indirectly enhance the invasion of C6 glioma cells by induction of matrix metalloproteinase-2 (MMP-2) secreted from the murine microglia BV2 cells. We obtained conditioned medium (CM) by incubating BV2 cells with SAH (1-50nM) for 24 h. We found that the SAH-containing CM (SAH-BV2-CM) strongly enhanced the invasiveness of C6 glioma cells and that this effect increased with increasing concentrations of SAH in the SAH-BV2-CM. The effect of CM could be attributed to its MMP-2 activity, as a result of increased protein and messenger RNA expression of MMP-2 in BV2 cells induced by SAH. In BV2 cells treated with SAH, the binding abilities of nuclear factor-kappa B (NF-kappaB) and stimulatory protein-1 (Sp1) to the MMP-2 promoter were increased, whereas the level of NF-kappaB inhibitor was decreased. In addition, SAH significantly increased the phosphorylation of extracellular signal-regulated kinase (ERK) and phosphatidylinositol-3-kinase/serine/threonine protein kinase (or protein kinase B) (PI3K/Akt) proteins but did not affect that of c-Jun NH2-terminal kinase or p38. Pretreatment of BV2 cells with an inhibitor specific for ERK (U0126) markedly abated the expression of ERK and MMP-2. Furthermore, SAH significantly and dose dependently decreased tissue inhibitor of metalloproteinase-2 (TIMP-2) in BV2 cells. Thus, SAH may induce the invasiveness of C6 glioma cells by decreased TIMP-2 expression and increased MMP-2 expression in BV2 cells. The latter effect is likely mediated through the ERK and PI3K/Akt pathways, with increased binding activities of NF-kappaB and Sp1 to the MMP-2 gene promoter.