Emerging data indicate that tumor necrosis factor (TNF) exerts a neuroprotective effect in response to brain injury. Here we examined the mechanism of TNF in preventing neuronal death in primary hippocampal neurons. TNF protected neurons against hypoxia-or nitric oxide-induced injury, with an increase in the antiapoptotic proteins Bcl-2 and Bcl-x as determined by Western blot and reverse transcriptase-polymerase chain reaction analysis. Treatment of neurons with an antisense oligonucleotide to bcl-2 mRNA or that to bcl-x mRNA blocked the up-regulation of Bcl-2 or Bcl-x expression, respectively, and partially inhibited the neuroprotective effect induced by TNF. Moreover, adenovirus-mediated overexpression of Bcl-2 significantly inhibited hypoxia-or nitric oxide-induced neuronal death. To examine the possible involvement of a transcription factor, NFB, in the regulation of Bcl-2 and Bcl-x expression in TNF-treated neurons, an adenoviral vector capable of expressing a mutated form of IB was used to infect neurons prior to TNF treatment. Expression of the mutant NFB completely inhibited NFB DNA binding activity and inhibited both TNF-induced up-regulation of Bcl-2 and Bcl-x expression and neuroprotective effect. These findings indicate that induction of Bcl-2 and Bcl-x expression through NFB activation is involved in the neuroprotective action of TNF against hypoxia-or nitric oxide-induced injury.

Glial cells express a variety of neurotransmitter receptors. Notably, Bergmann glial cells in the cerebellum have Ca2+-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) assembled without the GluR2 subunit. To elucidate the role of these Ca2+-permeable AMPARs, we converted them into Ca2+-impermeable receptors by adenoviral-mediated delivery of the GluR2 gene. This conversion retracted the glial processes ensheathing synapses on Purkinje cell dendritic spines and retarded the removal of synaptically released glutamate. Furthermore, it caused multiple innervation of Purkinje cells by the climbing fibers. Thus, the glial Ca2+-permeable AMPARs are indispensable for proper structural and functional relations between Bergmann glia and glutamatergic synapses.

Glioblastoma multiforme is the most undifferentiated type of brain tumor, and its prognosis is extremely poor. Glioblastoma cells exhibit highly migratory and invasive behavior, which makes surgical intervention unsuccessful. Here, we showed that glioblastoma cells express Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors assembled from the GluR1 and/or GluR4 subunits, and that their conversion to Ca(2+)-impermeable receptors by adenovirus-mediated transfer of the GluR2 cDNA inhibited cell locomotion and induced apoptosis. In contrast, overexpression of Ca(2+)-permeable AMPA receptors facilitated migration and proliferation of the tumor cells. These findings indicate that Ca(2+)-permeable AMPA receptors have crucial roles in growth of glioblastoma. Blockage of these Ca(2+)-permeable receptors may be a useful therapeutic strategy for the prevention of glioblastoma invasion.

Platelet-activating factor (PAF), a unique phospholipid mediator, possesses potent proinflammatory, smooth-muscle contractile and hypotensive activities, and appears to be crucial in the pathogenesis of bronchial asthma and in the lethality of endotoxin and anaphylactic shock. Despite this, little is known of the molecular properties of the PAF receptor and related signal transduction systems. Although several lines of evidence suggest that activation of the PAF receptor stimulates phospholipase C and subsequent inositol trisphosphate formation through G protein(s), the PAF receptor and calcium channel are reported to show a close relation. As a first approach to cloning lipid autacoid receptors, we have isolated complementary DNA for the PAF receptors. Our strategy involved gene expression in Xenopus laevis oocytes and electrophysiological detection of PAF-induced responses. Sequence analysis indicates that the receptor belongs to the superfamily of G protein-coupled receptors.