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.

Hippocampus-associated cognitive impairments are a common, highly conserved symptom of both schizophrenia (SCZ) and bipolar disorder (BPD). Although the hippocampus is likely an impacted region in SCZ/BPD patients, the molecular and cellular underpinnings of these impairments are difficult to identify. An emerging class of mouse models for these psychiatric diseases display similar cognitive impairments to those observed in human patients. The hippocampi of these mice possess a conserved pathophysiological alteration; we term the ‘immature dentate gyrus' (iDG), characterized by increased numbers of calretinin-positive immature neuronal progenitors, a dearth of calbindin-positive mature neurons and (often) constitutively increased neurogenesis. Although these models provide a link between cellular dysfunction and behavioral alteration, limited translational validity exists linking the iDG to human pathophysiology. In this study, we report the initial identification of an iDG-like phenotype in the hippocampi of human SCZ/BPD patients. These findings suggest a new motif for the etiology of these diseases and link an emerging class of mouse models to the human disease condition.

An increasing body of evidence suggests that alterations in neurogenesis and oxidative stress are associated with a wide variety of CNS diseases, including Alzheimer’s disease, schizophrenia and Parkinson’s disease, as well as routine loss of function accompanying aging. Interestingly, the association between neurogenesis and the production of reactive oxidative species (ROS) remains largely unexamined. The adult CNS harbors two regions of persistent lifelong neurogenesis: the subventricular zone and the dentate gyrus (DG). These regions contain populations of quiescent neural stem cells (NSCs) that generate mature progeny via rapidly-dividing progenitor cells. We hypothesized that the energetic demands of highly proliferative progenitors generates localized oxidative stress that contributes to ROS-mediated damage within the neuropoietic microenvironment. In vivo examination of germinal niches in adult rodents revealed increases in oxidized DNA and lipid markers, particularly in the subgranular zone (SGZ) of the dentate gyrus. To further pinpoint the cell types responsible for oxidative stress, we employed an in vitro cell culture model allowing for the synchronous terminal differentiation of primary hippocampal NSCs. Inducing differentiation in primary NSCs resulted in an immediate increase in total mitochondria number and overall ROS production, suggesting oxidative stress is generated during a transient window of elevated neurogenesis accompanying normal neurogenesis. To confirm these findings in vivo, we identified a set of oxidation-responsive genes, which respond to antioxidant administration and are significantly elevated in genetic- and exercise-induced model of hyperactive hippocampal neurogenesis. While no direct evidence exists coupling neurogenesis-associated stress to CNS disease, our data suggest that oxidative stress is produced as a result of routine adult neurogenesis.

Hibernation results in dramatic changes in body temperature and metabolism; however, the central nervous system remains active during deep torpor. By cloning c-fos cDNA from the 13-lined ground squirrel (Spermophilus tridecemlineatus) and using squirrel c-fos mRNA probe for in situ hybridization histochemistry, we systematically analyzed and identified specific brain regions that were activated during six different phases of the hibernation bout. During entrance into torpor, we detected activation of the ventrolateral subdivision of the medial preoptic area ('thermoregulatory center'), and the reticular thalamic nucleus, which is known to inhibit the somatomotor cortex. During torpor, c-fos expression in the cortex was suppressed while the reticular thalamic nucleus remained uniformly active. Throughout torpor the suprachiasmatic nucleus ('biological clock') showed increasing activity, likely participating in phase-change regulation of the hibernation bout. Interestingly, during torpor very strong c-fos activation was seen in the epithelial cells of the choroid plexus and in tanycytes at the third ventricle, both peaking near the beginning of arousal. In arousal, activity of the suprachiasmatic and reticular thalamic nuclei and choroid epithelial cells diminished, while ependymal cells in the lateral and fourth ventricles showed stronger activity. Increasing body temperature during arousal was driven by the activation of neurons in the medial part of the preoptic area. In interbout awake animals, we demonstrated the activation of hypothalamic neurons located in the arcuate nucleus and the dorsolateral hypothalamus, areas involved in food intake. Our observations indicate that the hibernation bout is closely regulated and orchestrated by specific regions of the central nervous system. J. Comp. Neurol. 505:443-458, 2007. (c) 2007 Wiley-Liss, Inc.

As a model of the reperfusion injury found in stroke, we have exposed neurons to hypoxia followed by reoxygenation. Neurons treated with hypoxia/reoxygenation (H/R) respond by activating nuclear factor-B (NF B), releasing cytochrome c from their mitochondria, and ultimately dying. Further supporting an apoptotic mechanism, expression of the antiapoptotic Bcl-2 and Bcl-x proteins was increased following H/R. In this model, adenoviral-mediated transduction of I B expression inhibited NF B activation and significantly accelerated cytochrome c release and caspase-dependent neuronal death. At the same time, expression of mutated I B prevented the increased expression of endogenous Bcl-2 and Bcl-x. In the presence of mutated I B, singular overexpression of only Bcl-2 by adenoviral-mediated transduction significantly inhibited cytochrome c release, caspase-3-like activation, and cell death in response to H/R. These findings suggest a pathway where NF B activation induces overexpression of Bcl-2 and Bcl-x, which function to prevent apoptotic cell death following H/R treatments. Key Words: Hypoxia/reoxygenation -Nuclear factor-B-Cytochrome c-Bcl-2-Bcl-xNeurons. J. Neurochem. 75, 683-693 (2000).Cerebral ischemia followed by reperfusion usually results in delayed neuronal death. Although the precise mechanism leading to the cell death that results from ischemia and reperfusion is not known, a number of studies suggest that neuronal death following reperfusion injury involves apoptosis. Following an ischemia/reperfusion event, dying neurons display histological and biochemical markers characteristic of apoptosis (MacManus et al., 1993;Kihara et al., 1994;Li et al., 1995). Of the apoptosis-related proteins found to be induced, expression of the Bcl-2 and Bcl-xL proteins that normally serve to suppress apoptosis is enhanced in neurons that survive ischemia (Chen et al., 1997). As a proapoptotic member of the Bcl-2 family, Bax protein expression is increased in those neurons that degenerate in ischemic brain (Isenmann et al., 1998). As a mediator and marker of apoptosis in various cell types, caspase-3 is also activated following transient cerebral ischemia (Chen et al., 1998). Taken together, these observations suggest that certain patterns of gene induction play a role in determining the fate of neuronal survival in the ischemic brain.Nuclear factor-B (NF B) is a ubiquitous transcription factor that is activated in response to inflammation and/or oxidative stress like that caused by hypoxia/ reoxygenation (H/R) (Siebenlist et al., 1994;Baldwin, 1996). Activation of NF B can inhibit, but is also reported to promote, apoptosis in a cell type-and stimulusdependent manner (Sonenshein, 1997). In neuronal cells, activation of NF B protected hippocampal neurons against apoptosis induced by oxidative stress (Mattson et al., 1997) or hypoxia (Tamatani et al., 1999). In contrast, recent reports suggest that NF B activation induces apoptosis in cerebellar neurons exposed to glutamate (Grilli et al., 1996). NF B was also found...