3,4-Dihydroxybenzoic acid from Smilacis chinae rhizome protects amyloid β protein (25–35)-induced neurotoxicity in cultured rat cortical neurons

The neuroprotective effect of 3,4-dihydroxybenzoic acid (3,4-DHBA) isolated from Smilacis chinae rhizome against Aβ (25–35)-induced neurotoxicity on cultured rat cortical neurons was found in this study. The protective effect of 3,4-DHBA against Aβ (25–35)-induced neuronal cell death was investigated by measuring cell viability via a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay and Hoechst 33342 staining. 3,4-DHBA (1 and 10 μM) concentration-dependently inhibited 10 μM Aβ (25–35)-induced neuronal apoptotic death. 3,4-DHBA (1 and 10 μM) inhibited 10 μM Aβ (25–35)-induced elevation of cytosolic Ca2+ concentration ([Ca2+]c), which was measured by a fluorescent dye, Fluo-4 AM. 3,4-DHBA also inhibited glutamate release into medium, reactive oxygen species (ROS) generation, and caspase-3 activation, which were induced by 10 μM Aβ (25–35). These results suggest that 3,4-DHBA prevents Aβ (25–35)-induced neuronal cell damage by interfering with the increase of [Ca2+]c, and then by inhibiting glutamate release, generation of ROS and caspase-3 activity.