MMP9 and Alzheimer disease: Similarly, in luteolin-treated groups, MMP9 levels and the MMP9/β-actin ratio were significantly increased in the AD model group versus the normal group (P < 0.01); compared with the AD model group, high-dose luteolin markedly down-regulated MMP9 protein expression and the MMP9/β-actin ratio (P < 0.05).