Nitric oxide-mediated neuronal apoptosis in rats with recurrent febrile seizures through endoplasmic reticulum stress pathway

Nitric oxide (NO), as a neurotransmitter, exerts various physiological and pathological effects on the brain. Excess NO is toxic to neurons and may cause neuronal apoptosis. However, the cascade of NO-mediated apoptosis is not fully understood. We utilized a recurrent febrile seizures (FS) rat model and found that plasma NO was increased, neuronal apoptosis was evident, the expression of glucose-regulated Protein78 (GRP78, a well-established marker of ER stress) was elevated, and caspase-12 (an ER stress-specific proapoptosis molecule) was activated in the hippocampus in a time-dependent manner after recurrent FS. Administration of sodium nitroprusside (SNP, an NO donor) enhanced neuronal apoptosis, down-regulated the expression of GRP78, and increased that of caspase-12 in FS + SNP groups compared with FS groups. In contrast, treatment with N-G-nitrol-L-arginine methyl ester (L-NAME, a competitive NO synthase inhibitor) inhibited neuronal apoptosis, up-regulated the expression of GRP78, and decreased that of caspase-12 in FS + L-NAME groups compared with FS groups. These results suggest that NO mediates neuronal apoptosis caused by recurrent FS, and that the ER stress pathway is involved in NO-mediated neuronal apoptosis. (C) 2008 Elsevier Ireland Ltd. All rights reserved.