Molecular and cellular neurosciences
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Mol. Cell. Neurosci. · Jan 2008
Activation of the nuclear factor of activated T-cells (NFAT) mediates upregulation of CCR2 chemokine receptors in dorsal root ganglion (DRG) neurons: a possible mechanism for activity-dependent transcription in DRG neurons in association with neuropathic pain.
Upregulation of CCR2 chemokine receptor expression by dorsal root ganglion (DRG) neurons is an important process in the development and maintenance of neuropathic pain. CCR2 is not expressed by DRG neurons under normal conditions but is upregulated in several animal models of neuropathic pain where its signaling is excitatory. However, the molecular mechanisms underlying neuronal upregulation of CCR2 have not been investigated. ⋯ Activation of the NFAT pathway in the DRG neuronal cell line F11 increased CCR2 promoter activity and induced CCR2 transcription. Moreover, depolarization of cultured DRG neurons induced de novo synthesis of CCR2 mRNA, which was blocked by the calcineurin inhibitors cyclosporin A and FK506. These data indicate that CCR2 is a target of the NFAT pathway and suggest that tonic excitation of DRG neurons in association with chronic pain may lead to neuronal CCR2 upregulation via activation of the NFAT pathway.
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Mol. Cell. Neurosci. · Nov 2007
Interleukin-1beta mediates proliferation and differentiation of multipotent neural precursor cells through the activation of SAPK/JNK pathway.
Neural precursor cells (NPCs) have been experimentally used to repair the damaged nervous system either by exogenous transplantation or by endogenous activation. In post-injury inflammation, an array of cytokines including interleukin-1beta (IL-1beta) are released by host as well as invading immune cells and increased markedly. In the present study, we investigated the effects of IL-1beta on the survival, proliferation, differentiation and migration of NPCs as well as underlying intracellular signaling pathways. ⋯ We also found that IL-1ra had no effect on the transmigration of NPCs in vitro. Finally, we showed that the effect of IL-1beta on NPCs proliferation and differentiation appeared to be mediated by SAPK/JNK, but not ERK, P38MAPK nor NF-kappaB pathways. These findings collectively suggest that the inflammatory environment following CNS injuries may influence the ability of NPCs to repair the damage.
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Mol. Cell. Neurosci. · Oct 2007
GDNF selectively promotes regeneration of injury-primed sensory neurons in the lesioned spinal cord.
Axonal regeneration within the CNS fails due to the growth inhibitory environment and the limited intrinsic growth capacity of injured neurons. Injury to DRG peripheral axons induces expression of growth associated genes including members of the glial-derived neurotrophic factor (GDNF) signaling pathway and "preconditions" the injured cells into an active growth state, enhancing growth of their centrally projecting axons. ⋯ Consistent with the in vitro results, the in vivo effect was seen only at low GDNF concentrations. We conclude that peripheral nerve injury upregulates GDNF signaling pathway components and that exogenous GDNF treatment selectively promotes axonal growth of injury-primed sensory neurons in a concentration-dependent fashion.
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Mol. Cell. Neurosci. · Oct 2007
The Cav3.2/alpha1H T-type Ca2+ current is a molecular determinant of excitatory effects of GABA in adult sensory neurons.
In addition to its inhibitory action, reports have shown that, in sensory neurons, GABA can be responsible for excitatory effects leading to painful behavior. The cellular mechanisms for these excitatory effects remain largely unknown. Although the high intracellular chloride concentration allows GABA(A) receptor activation to depolarize all adult sensory neurons, we show that GABA, acting through GABA(A) receptors, can generate, in vitro, action potential and intracellular Ca(2+) increase only in a subset of neurons expressing a prominent T-type Ca(2+) current. ⋯ In addition to gene inhibition, pharmacological analysis of Ca(2+) channel subunits shows the amplifying role of T-current in GABA(A) current-induced membrane depolarization and the involvement of both T-current and high voltage activated Ca(2+) current in GABA(A)-induced intracellular Ca(2+) increase. Altogether, these data establish that the Cav3.2/alpha1H, T-current is responsible for GABA-induced cell excitability and intracellular Ca(2+) increase. Our results reveal a positive cross-talk between T-channel and GABA(A) receptor in adult sensory neurons and indicate that Cav3.2/alpha1H, T-type Ca(2+) channel may be the molecular determinant for excitatory effects of GABA in peripheral somatosensory system.
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Mol. Cell. Neurosci. · Jun 2007
The sodium channel Nav1.5a is the predominant isoform expressed in adult mouse dorsal root ganglia and exhibits distinct inactivation properties from the full-length Nav1.5 channel.
Nav1.5 is the principal voltage-gated sodium channel expressed in heart, and is also expressed at lower abundance in embryonic dorsal root ganglia (DRG) with little or no expression reported postnatally. We report here the expression of Nav1.5 mRNA isoforms in adult mouse and rat DRG. ⋯ The Na+ current produced by the Nav1.5a isoform has a voltage-dependent inactivation significantly shifted to more negative potentials (by approximately 5 mV) compared to the full-length Nav1.5 when expressed in the DRG neuroblastoma cell line ND7/23. These results imply that the alternatively spliced exon 18 of Nav1.5 plays a role in channel inactivation and that Nav1.5a is likely to make a significant contribution to adult DRG neuronal function.