|It has been demonstrated that hydrogen peroxide (H2O2) is directly associated with elevated matrix metalloproteinase-2 (MMP-2) expression in several cell lines. Electrochemically reduced water (ERW), produced near the cathode during electrolysis, and scavenges intracellular H2O2 in human fibrosarcoma HT1080 cells. RT-PCR and zymography analyses revealed that when HT1080 cells were treated with ERW, the gene expression of MMP-2 and membrane type 1 MMP and activation of MMP-2 was repressed, resulting in decreased invasion of the cells into matrigel. ERW also inhibited H2O2-induced MMP-2 upregulation. To investigate signal transduction involved in MMP-2 downregulation, mitogen-activated protein kinase (MAPK)-specific inhibitors, SB203580 (p38 MAPK inhibitor), PD98059 (MAPK/extracellular regulated kinase kinase 1 inhibitor) and c-Jun NH2-terminal kinase inhibitor II, were used to block the MAPK signal cascade. MMP-2 gene expression was only inhibited by SB203580 treatment, suggesting a pivotal role of p38 MAPK in regulation of MMP-2 gene expression. Western blot analysis showed that ERW downregulated the phosphorylation of p38 both in H2O2-treated and untreated HT1080 cells. These results indicate that the inhibitory effect of ERW on tumor invasion is due to, at least in part, its antioxidative effect.