Neuroprotective activities of catalpol against CaMKII-dependent apoptosis induced by LPS in PC12 cells

Background and Purpose Neurodegenerative diseases present progressive neurological disorder induced by cell death or apoptosis. Catalpol, an iridoid glucoside isolated from the root of Rehmannia glutinosa Libosch, is present in a wide range of plant families. Although catalpol is an effective anti-apoptotic agent in LPS-induced neurodegeneration, the underlying mechanism has not been established. Here we have identified some of the mechanisms involved the prevention by catalpol of apoptosis induced by LPS in an experimental model of neurodegeneration in vitro. Experimental Approach Apoptosis was induced by adding LPS (80 ng center dot mL(-1)) to pheochromocytoma (PC12) cells, pretreated with catalpol for 12h. We measured intracellular reactive oxygen species (ROS), apoptosis and intracellular calcium concentration ([Ca2+](i)) by flow cytometry or laser confocal scanning microscopy. We also analysed the protein expression of Bcl-2, Bax and Ca2+-calmodulin-dependent protein kinase II (CaMKII)-dependent apoptosis signal-regulating kinase-1 (ASK-1)/JNK/p38 signalling pathway in PC12 cells by Western blot. Key Results Catalpol stimulated expression of Bcl-2 and inhibited the expression of Bax. Catalpol also attenuated the increase in Ca2+ concentration induced by LPS in PC12 cells and down-regulated CaMK phosphorylation. The CaMKII-dependent ASK-1/JNK/p38 signalling cascade was blocked by catalpol. All these changes were accompanied by a decrease of apoptosis induced by LPS in PC12 cells. Conclusions and Implications The data presented here provide new mechanistic insights into the links between the CaMKII-dependent ASK-1/JNK/p38 signalling pathway and the protective effect of catalpol on apoptosis induced by LPS in PC12 cells.