Protective effects of fangchinoline and tetrandrine on hydrogen peroxide-induced oxidative neuronal cell damage in cultured rat cerebellar granule cells

The present study was performed to examine the neuroprotective effects of fangchinoline (FAN) and tetrandrine (TET), bisbenzylisoquinoline alkaloids, which exhibit the characteristics of Ca2+ channel blockers, on H2O2-induced neurotoxicity using cultured rat cerebellar granule neurons. H2O2 produced a concentration-dependent reduction of cell viability, which was blocked by (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801), an N-methyl-D-aspartate (NMDA) receptor antagonist, verapamil, an L-type Ca2+ channel blocker, and N-G-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Pretreatment with FAN and TET over a concentration range of 0.1 to 10 muM significantly decreased the H2O2-induced neuronal cell death as assessed by a trypan blue exclusion test, a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay and the number of apoptotic nuclei. In addition, FAN and TET inhibited the H2O2-induced elevation of glutamate release into the medium, elevation of the cytosolic free Ca2+ concentration ([Ca2+](c)), and generation of reactive oxygen species (ROS). These results suggest that FAN and TET may mitigate the harmful effects of H2O2-induced neuronal cell death by interfering with the increase of [Ca2+](C), and then by inhibiting glutamate release and generation of ROS.