Effect of agmatine against cell death induced by NMDA and glutamate in neurons and PC12 cells

1. Aims: Agmatine is an endogenous guanido amine and has been shown to be neuroprotective in vitro and in vivo. The aims of this study are to investigate whether agmatine is protective against cell death induced by different agents in cultured neurons and PC12 cells. 2. Methods: Cell death in neurons, cultured from neonatal rat cortex, was induced by incubating with (a) NMDA (100 muM) for 10 min, (b) staurosporine (protein kinase inhibitor, 100 nM) for 24 h, and (c) calcimycin (calcium ionophore, 100 nM) for 24 h in the presence and absence of agmatine (1 muM to 1 mM). Cell death in PC12 cells was induced by exposure to glutamate (10 mM), staurosporine (100 nM), and calcimycin (100 nM). The activity of lactate dehydrogenase (LDH) in the medium was measured as the marker of cell death and normalized to cellular LDH activity. 3. Results: Agmatine significantly reduced the medium LDH in NMDA-treated neurons but failed to reduce the release of LDH induced by staurosporin or calcimycin. In PC12 cells, agmatine significantly reduced LDH release induced by glutamate exposure, but not by staurosporine or calcimycin. Agmatine itself neither increased LDH release nor directly inhibited the enzyme activity. 4. Conclusion: We conclude that agmatine protects against NMDA excitotoxicity in neurons and PC12 cells but not the cell death induced by protein kinase blockade or increase in cellular calcium.