Journal of neurochemistry
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Journal of neurochemistry · Jun 2010
Neurochemical properties of enkephalinergic neurons in lumbar spinal dorsal horn revealed by preproenkephalin-green fluorescent protein transgenic mice.
Enkephalin (ENK) has been implicated in nociceptive transmission in the spinal cord while its functional role is not clear because of difficulties in ideally visualizing ENKergic neurons. We thus developed preproenkephalin-green fluorescent protein transgenic mice to better identify ENKergic neurons. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) together with immunohistochemistry and in situ hybridization were first employed to confirm the successful transgenic manipulation and its application in showing spinal ENKergic neurons. ⋯ GABA was found to exist in 42.9 +/- 2.8% of ENKergic neurons that were mainly located in lamina I-III. The proportions of parvalbumin-, calretinin-, calbindin- and neuronal nitric oxide synthase-positive cells among the ENKergic neurons were 5.2 +/- 0.7%, 42.6 +/- 2.3%, 25.8 +/- 2.2% and 11.1 +/- 1.6%, respectively. Compared with previously findings obtained with ENK antibody labeling, this line of newly generated mice can be a reliable tool for the study of specific spinal ENKergic neuronal population.
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Journal of neurochemistry · May 2010
Insulin inhibits Abeta fibrillogenesis through a decrease of the GM1 ganglioside-rich microdomain in neuronal membranes.
Type 2 diabetes is a risk factor for late-onset Alzheimer's disease. However, the underlying mechanisms remain unknown. To investigate whether insulin is associated with the assembly of amyloid beta-protein from the cell surface, we treated nerve growth factor (NGF)-treated rat pheochromocytoma 12 (PC12) cells with insulin, which is related to the development of diabetes. ⋯ In addition, insulin failed to induce formation of fibrils from soluble amyloid beta-protein or to accelerate GM1-induced fibril formation. Furthermore, assembly of amyloid beta-protein in cultures of NGF-treated PC12 cells was significantly decreased by insulin. These results suggest that insulin inhibits amyloid beta-protein assembly by decreasing GM1 expression in detergent-resistant membrane microdomains of neuronal membranes.
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Journal of neurochemistry · May 2010
The hematopoietic factor granulocyte-colony stimulating factor improves outcome in experimental spinal cord injury.
Granulocyte-colony stimulating factor (G-CSF) is a potent hematopoietic factor that drives differentiation of neutrophilic granulocytes. We have recently shown that G-CSF also acts as a neuronal growth factor, protects neurons in vitro and in vivo, and has regenerative potential in various neurological disease models. Spinal cord injury (SCI) following trauma or secondary to skeletal instability is a terrible condition with no effective therapies available at present. ⋯ Mice treated systemically with G-CSF as well as transgenic mice over-expressing G-CSF in the CNS exhibit a strong improvement in functional outcome as measured by the BBB score and gridwalk analysis. We show that G-CSF improves outcome after experimental SCI by counteracting apoptosis, and enhancing connectivity in the injured spinal cord. We conclude that G-CSF constitutes a promising and feasible new therapy option for SCI.
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Journal of neurochemistry · Apr 2010
Ca(2+)-dependent reduction of glutamate aspartate transporter GLAST expression in astrocytes by P2X(7) receptor-mediated phosphoinositide 3-kinase signaling.
Astrocytes are responsible for clearance of extracellular glutamate, primarily through glial-specific glutamate transporter-1 and the Na(+)-dependent glutamate/aspartate transporter (GLAST). After traumatic injury to the CNS, such as spinal cord injury, persistent release of ATP from damaged neurons and activated glial cells occurs, inducing detrimental and/or beneficial effects via activation of ionotropic (P2XR) and metabotropic purinergic receptors. In this study, we show a decrease in GLAST mRNA in the lesion center and caudal portions at 24 h post-spinal cord injury. ⋯ Furthermore, deletion of the GLAST promoter and RNA decay assays showed that P2X(7)R signaling triggered post-transcriptional regulation of GLAST expression via the phosphoinositide 3-kinase cascade. The signaling pathway participating in the P2X(7)R effect on GLAST mRNA expression was identified as a Ca(2+)-dependent phosphoinositide 3-kinase-phospholipase Cgamma involving the inositol 1,4,5-trisphosphate receptor, calcium/calmodulin-dependent kinase II, and protein kinase C. We conclude that P2X(7)R activation by sustained release of ATP in the injured CNS may decrease GLAST mRNA stability via Ca(2+)-dependent signaling, suggesting that inhibition of P2X(7)R may allow for recovery of astrocytic GLAST function and protect neurons from glutamate-induced excitotoxicity.
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Journal of neurochemistry · Apr 2010
Evidence that pregabalin reduces neuropathic pain by inhibiting the spinal release of glutamate.
Pregabalin is an anti-convulsant that successfully treats many neuropathic pain syndromes, although the mechanism of its anti-hyperalgesic action remains elusive. This study aims to help delineate pregabalin's anti-hyperalgesic mechanisms. We assessed the effectiveness of pregabalin at decreasing mechanical and cold hypersensitivity induced in a rat model of neuropathic pain. ⋯ We also present the first evidence that pregabalin reduces the formalin-induced release of glutamate in SCDH. Furthermore, i.t. pregabalin reduces the enhanced noxious stimulus-induced spinal release of glutamate seen in neuropathic rats. These data suggest that pregabalin reduces neuropathic pain symptoms by inhibiting the release of glutamate in the SCDH.