Microarray analysis supports a role for ccaat/enhancer-binding protein-beta in brain injury

NRSF regulates age-dependently cognitive ability and its conditional knockout in APP/PS1 mice moderately alters AD-like pathology

NRSF/REST (neuron-restrictive silencer element, also known as repressor element 1-silencing transcription factor), plays a key role in neuronal homeostasis as a transcriptional repressor of neuronal genes. NRSF/REST relates to cognitive preservation and longevity of humans, but its specific functions in age-dependent and Alzheimer's disease (AD)-related memory deficits remain unclear. Here, we show that conditional NRSF/REST knockout either in the dorsal telencephalon or specially in neurons induced an age-dependently diminished retrieval performance in spatial or fear conditioning memory tasks and altered hippocampal synaptic transmission and activity-dependent synaptic plasticity. The NRSF/REST deficient mice were also characterized by an increase of activated glial cells, complement C3 protein and the transcription factor C/EBPβ in the cortex and hippocampus. Reduction of NRSF/REST by conditional depletion upregulated the activation of astrocytes in APP/PS1 mice, and increased the C3-positive glial cells, but did not alter the Aβ loads and memory retrieval performances of 6- and 12-month-old APP/PS1 mice. Simultaneously, overexpression of NRSF/REST improved cognitive abilities of aged wild type, but not in AD mice. These findings demonstrated that NRSF/REST is essential for the preservation of memory performance and activity-dependent synaptic plasticity during aging and takes potential roles in the onset of age-related memory impairments. However, while altering the glial activation, NRSF/REST deficiency does not interfere with the Aβ deposits and the electrophysiological and cognitive AD-like pathologies.

C/EBPβ Regulates TFAM Expression, Mitochondrial Function and Autophagy in Cellular Models of Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder that results from the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Since there are only symptomatic treatments available, new cellular and molecular targets involved in the onset and progression of this disease are needed to develop effective treatments. CCAAT/Enhancer Binding Protein β (C/EBPβ) transcription factor levels are altered in patients with a variety of neurodegenerative diseases, suggesting that it may be a good therapeutic target for the treatment of PD. A list of genes involved in PD that can be regulated by C/EBPβ was generated by the combination of genetic and in silico data, the mitochondrial transcription factor A (TFAM) being among them. In this paper, we observed that C/EBPβ overexpression increased TFAM promoter activity. However, downregulation of C/EBPβ in different PD/neuroinflammation cellular models produced an increase in TFAM levels, together with other mitochondrial markers. This led us to propose an accumulation of non-functional mitochondria possibly due to the alteration of their autophagic degradation in the absence of C/EBPβ. Then, we concluded that C/EBPβ is not only involved in harmful processes occurring in PD, such as inflammation, but is also implicated in mitochondrial function and autophagy in PD-like conditions.

Regulation of the p75 neurotrophin receptor attenuates neuroinflammation and stimulates hippocampal neurogenesis in experimental Streptococcus pneumoniae meningitis

Background

Streptococcus pneumoniae meningitis is a destructive central nervous system (CNS) infection with acute and long-term neurological disorders. Previous studies suggest that p75NTR signaling influences cell survival, apoptosis, and proliferation in brain-injured conditions. However, the role of p75NTR signaling in regulating pneumococcal meningitis (PM)-induced neuroinflammation and altered neurogenesis remains largely to be elucidated.

Methods

p75NTR signaling activation in the pathological process of PM was assessed. During acute PM, a small-molecule p75NTR modulator LM11A-31 or vehicle was intranasally administered for 3 days prior to S. pneumoniae exposure. At 24 h post-infection, clinical severity, histopathology, astrocytes/microglia activation, neuronal apoptosis and necrosis, inflammation-related transcription factors and proinflammatory cytokines/mediators were evaluated. Additionally, p75NTR was knocked down by the adenovirus-mediated short-hairpin RNA (shRNA) to ascertain the role of p75NTR in PM. During long-term PM, the intranasal administration of LM11A-31 or vehicle was continued for 7 days after successfully establishing the PM model. Dynamic changes in inflammation and hippocampal neurogenesis were assessed.

Results

Our results revealed that both 24 h (acute) and 7, 14, 28 day (long-term) groups of infected rats showed increased p75NTR expression in the brain. During acute PM, modulation of p75NTR through pretreatment of PM model with LM11A-31 significantly alleviated S. pneumoniae-induced clinical severity, histopathological injury and the activation of astrocytes and microglia. LM11A-31 pretreatment also significantly ameliorated neuronal apoptosis and necrosis. Moreover, we found that blocking p75NTR with LM11A-31 decreased the expression of inflammation-related transcription factors (NF-κBp65, C/EBPβ) and proinflammatory cytokines/mediators (IL-1β, TNF-α, IL-6 and iNOS). Furthermore, p75NTR knockdown induced significant changes in histopathology and inflammation-related transcription factors expression. Importantly, long-term LM11A-31 treatment accelerated the resolution of PM-induced inflammation and significantly improved hippocampal neurogenesis.

Conclusion

Our findings suggest that the p75NTR signaling plays an essential role in the pathogenesis of PM. Targeting p75NTR has beneficial effects on PM rats by alleviating neuroinflammation and promoting hippocampal neurogenesis. Thus, the p75NTR signaling may be a potential therapeutic target to improve the outcome of PM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02294-w.

δ-secretase in neurodegenerative diseases: mechanisms, regulators and therapeutic opportunities

Mammalian asparagine endopeptidase (AEP) is a cysteine protease that cleaves its protein substrates on the C-terminal side of asparagine residues. Converging lines of evidence indicate that AEP may be involved in the pathogenesis of several neurological diseases, including Alzheimer's disease, Parkinson's disease, and frontotemporal dementia. AEP is activated in the aging brain, cleaves amyloid precursor protein (APP) and promotes the production of amyloid-β (Aβ). We renamed AEP to δ-secretase to emphasize its role in APP fragmentation and Aβ production. AEP also cleaves other substrates, such as tau, α-synuclein, SET, and TAR DNA-binding protein 43, generating neurotoxic fragments and disturbing their physiological functions. The activity of δ-secretase is tightly regulated at both the transcriptional and posttranslational levels. Here, we review the recent advances in the role of δ-secretase in neurodegenerative diseases, with a focus on its biochemical properties and the transcriptional and posttranslational regulation of its activity, and discuss the clinical implications of δ-secretase as a diagnostic biomarker and therapeutic target for neurodegenerative diseases.

Interactions of Aromatase and Seladin-1: A Neurosteroidogenic and Gender Perspective

Aromatase and seladin-1 are enzymes that have major roles in estrogen synthesis and are important in both brain physiology and pathology. Aromatase is the key enzyme that catalyzes estrogen biosynthesis from androgen precursors and regulates the brain’s neurosteroidogenic activity. Seladin-1 is the enzyme that catalyzes the last step in the biosynthesis of cholesterol, the precursor of all hormones, from desmosterol. Studies indicated that seladin-1 is a downstream mediator of the neuroprotective activity of estrogen. Recently, we also showed that there is an interaction between aromatase and seladin-1 in the brain. Therefore, the expression of local brain aromatase and seladin-1 is important, as they produce neuroactive steroids in the brain for the protection of neuronal damage. Increasing steroid biosynthesis specifically in the central nervous system (CNS) without affecting peripheral hormone levels may be possible by manipulating brain-specific promoters of steroidogenic enzymes. This review emphasizes that local estrogen, rather than plasma estrogen, may be responsible for estrogens’ protective effects in the brain. Therefore, the roles of aromatase and seladin-1 and their interactions in neurodegenerative events such as Alzheimer’s disease (AD), ischemia/reperfusion injury (stroke), and epilepsy are also discussed in this review.

Molecular cloning, characterisation, and expression patterns of pigeon CCAAT/enhancer binding protein-α and -β genes

1. CCAAT/enhancer binding proteins (C/EBPs), as a family of transcription factors, consists of six functionally and structurally related proteins which share a conserved basic leucine zipper (bZIP) DNA-binding domain. The aim of this study was to clone the full-length coding sequences (CDS) of C/EBP-α and -β genes, and determine the abundance of these two genes in various tissues of white king pigeon (C. livia). 2. The complete cDNA sequences of C/EBP-α and -β genes were cloned from pigeons by using PCR combined with rapid amplification of cDNA ends (RACE). The sequences were bioinformatically analysed, and the tissue distribution determined by quantitative real-time RT-PCR (qRT-PCR). 3. The results showed that the full-length cDNA sequences of pigeon C/EBP-α and -β genes were 2,807bp and 1,778bp, respectively. The open reading frames of C/EBP-α (978 bp) and -β (987bp) encoded 325 amino acids and 328 amino acids, respectively. The pigeon C/EBP-α and C/EBP-β proteins were predicted to have a conserved basic leucine zipper (bZIP) domain, which is a common structure feature of the C/EBP family. Multiple sequence alignments indicated that pigeon C/EBP-α and -β shared more than 90% amino-acid identity with their corresponding homologues in other avian species. Phylogenetic analysis revealed that these two proteins were highly conserved across different species and evolutionary processes. QRT-PCR results indicated that the pigeon C/EBP-α and -β mRNA transcripts were expressed in all investigated organs. The mRNA expression levels of pigeon C/EBP-α in descending order, were in spleen, heart, liver, lung, kidney and muscle. The pigeon C/EBP-β gene had the most abundant expression in lung, followed by the kidney, with minimal expression detected in muscle. 4. This study investigated the full-length cDNA sequences, genetic characteristics and tissue distribution of pigeon C/EBP-α and -β genes and found that they may have functions in various tissues of pigeon. This provides a foundation for further study for regulatory mechanisms of these two genes in birds.

Spatiotemporal activation of the C/EBPβ/δ-secretase axis regulates the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) neuropathological hallmarks include senile plaques with aggregated amyloid beta as a major component, neurofibrillary tangles (NFT) containing truncated and hyperphosphorylated Tau, extensive neuronal loss, and chronic neuroinflammation. However, the key molecular mechanism that dominates the pathogenesis of AD remains elusive for AD. Here we show that the C/EBPβ/δ-secretase axis is activated in an age-dependent manner in different brain regions of the 3×Tg AD mouse model, elevating δ-secretase-truncated APP and Tau proteolytic truncates and promoting senile plaques and NFT formation in the brain, associated with gradual neuronal loss and chronic neuroinflammation. Depletion of inflammatory cytokine-regulated transcription factor C/EBPβ from 3×Tg mice represses APP, Tau, and δ-secretase expression, which subsequently inhibits APP and Tau cleavage, leading to mitigation of AD pathologies. Knockout of δ-secretase from 3×Tg mice strongly blunts AD pathogenesis. Consequently, inactivation of the C/EBPβ/δ-secretase axis ameliorates cognitive dysfunctions in 3×Tg mice by blocking APP and Tau expression and their pathological fragmentation. Thus, our findings support the notion that C/EBPβ/δ-secretase axis plays a crucial role in AD pathogenesis.

C/EBPβ regulates delta-secretase expression and mediates pathogenesis in mouse models of Alzheimer's disease

Delta-secretase cleaves both APP and Tau to mediate the formation of amyloid plaques and neurofibrillary tangle in Alzheimer’s disease (AD). However, how aging contributes to an increase in delta-secretase expression and AD pathologies remains unclear. Here we show that a CCAAT-enhancer-binding protein (C/EBPβ), an inflammation-regulated transcription factor, acts as a key age-dependent effector elevating both delta-secretase (AEP) and inflammatory cytokines expression in mediating pathogenesis in AD mouse models. We find that C/EBPβ regulates delta-secretase transcription and protein levels in an age-dependent manner. Overexpression of C/EBPβ in young 3xTg mice increases delta-secretase and accelerates the pathological features including cognitive dysfunctions, which is abolished by inactive AEP C189S. Conversely, depletion of C/EBPβ from old 3xTg or 5XFAD mice diminishes delta-secretase and reduces AD pathologies, leading to amelioration of cognitive impairment in these AD mouse models. Thus, our findings support that C/EBPβ plays a pivotal role in AD pathogenesis via increasing delta-secretase expression.

Delta-secretase cleaves both APP and Tau, and contributes to Alzheimer’s disease-like pathology. Here the authors show that C/EBPβ, a regulator of inflammation, also regulates transcription of delta-secretase in an age-dependent manner and contributes to Alzheimer’s disease-like pathology in mouse models.

CCAAT/Enhancer binding protein β silencing mitigates glial activation and neurodegeneration in a rat model of Parkinson's disease

The CCAAT/Enhancer binding protein β (C/EBPβ) is a transcription factor involved in numerous physiological as well as pathological conditions in the brain. However, little is known regarding its possible role in neurodegenerative disorders. We have previously shown that C/EBPβ regulates the expression of genes involved in inflammatory processes and brain injury. Here, we have analyzed the effects of C/EBPβ interference in dopaminergic cell death and glial activation in the 6-hydroxydopamine model of Parkinson's disease. Our results showed that lentivirus-mediated C/EBPβ deprivation conferred marked in vitro and in vivo neuroprotection of dopaminergic cells concomitant with a significant attenuation of the level of the inflammatory response and glial activation. Additionally, C/EBPβ interference diminished the induction of α-synuclein in the substantia nigra pars compacta of animals injected with 6-hydroxydopamine. Taking together, these results reveal an essential function for C/EBPβ in the pathways leading to inflammatory-mediated brain damage and suggest novel roles for C/EBPβ in neurodegenerative diseases, specifically in Parkinson's disease, opening the door for new therapeutic interventions.

CCAAT enhancer binding protein β has a crucial role in regulating breast cancer cell growth via activating the TGF-β-Smad3 signaling pathway

The aim of the present study was to examine the effect of CCAAT enhancer binding protein β (C/EBPβ) on human breast cancer cells. The plasmids pCDH-C/EBPβ and pLKO.1-shC/EBPβ were constructed and were infected into MDA-MB-468 cells, to provide C/EBPβ overexpressing and C/EBPβ knockdown cells, respectively. Cell viability, cell cycle and apoptosis were observed by MTT assay and flow cytometry analysis. Protein expression levels of C/EBPβ, TGF-β1, P-Smad3 and Smad3 were detected by western blotting. MTT assay showed that the absorbance of MDA-MB-468 cells in the pCDH-C/EBPβ group was increased, whereas that in the pLKO.1-shC/EBPβ group was decreased, compared with the respective control at 48 and 72 h. Flow cytometric analysis indicated that the percentage of cells in the G2 phase was significantly increased in the pCDH-C/EBPβ group (P<0.05) and decreased in the pLKO.1-shC/EBPβ group compared with the respective control group. The proportion of apoptotic cells was decreased in the pCDH-C/EBPβ group and increased in the pLKO.1-shC/EBPβ group compared with the controls. The scratch-wound assay revealed that MDA-MB-468 cells depleted of C/EBPβ exhibited reduced motility compared with the control cells. Moreover, western blotting demonstrated that pCDH-C/EBPβ increased transforming growth factor (TGF)β1 and P-Smad3 protein expression and decreased Smad3 protein expression, whereas pLKO.1-shC/EBPβ decreased TGFβ1 and P-Smad3 protein expression and increased Smad3 protein expression levels. The present study demonstrated that C/EBPβ has a crucial role in regulating breast cancer cell growth through activating TGF-β-Smad3 signaling. These findings suggest that C/EBPβ may be a potential therapeutic target for breast cancer; however, in vivo studies are required to confirm this.

Complement component 3 (C3) expression in the hippocampus after excitotoxic injury: role of C/EBPβ

Background

The CCAAT/enhancer-binding protein β (C/EBPβ) is a transcription factor implicated in the control of proliferation, differentiation, and inflammatory processes mainly in adipose tissue and liver; although more recent results have revealed an important role for this transcription factor in the brain. Previous studies from our laboratory indicated that CCAAT/enhancer-binding protein β is implicated in inflammatory process and brain injury, since mice lacking this gene were less susceptible to kainic acid-induced injury. More recently, we have shown that the complement component 3 gene (C3) is a downstream target of CCAAT/enhancer-binding protein β and it could be a mediator of the proinflammatory effects of this transcription factor in neural cells.

Methods

Adult male Wistar rats (8–12 weeks old) were used throughout the study. C/EBPβ^+/+ and C/EBPβ^–/– mice were generated from heterozygous breeding pairs. Animals were injected or not with kainic acid, brains removed, and brain slices containing the hippocampus analyzed for the expression of both CCAAT/enhancer-binding protein β and C3.

Results

In the present work, we have further extended these studies and show that CCAAT/enhancer-binding protein β and C3 co-express in the CA1 and CA3 regions of the hippocampus after an excitotoxic injury. Studies using CCAAT/enhancer-binding protein β knockout mice demonstrate a marked reduction in C3 expression after kainic acid injection in these animals, suggesting that indeed this protein is regulated by C/EBPβ in the hippocampus in vivo.

Conclusions

Altogether these results suggest that CCAAT/enhancer-binding protein β could regulate brain disorders, in which excitotoxic and inflammatory processes are involved, at least in part through the direct regulation of C3.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0742-0) contains supplementary material, which is available to authorized users.

Identification of a 5-Methylcytosine Site that may Regulate C/EBPβ Binding and Determine Tissue-Specific Expression of the BPI Gene in Piglets

Bactericidal/permeability-increasing protein (BPI) plays an important role in innate immune defense in mammals. A previous study showed that BPI gene expression correlates to gram-negative bacteria resistance. However, this gene showed tissue-specific expression in piglets and strongly expressed only in the digestive tract. To investigate the mechanisms governing the tissue-specificity, bisulfite sequencing PCR and next generation sequencing were used for high accuracy methylation quantitation of CpG islands of BPI gene upstream in 11 different tissues from weaned Yorkshire piglets. Additionally, qPCR was used to examine mRNA levels of BPI gene as well as transcription factor. We additionally analyzed transcriptional regulation by studying key 5-methylcytosine sites and transcription factors. Results showed that BPI mRNA levels significantly correlated with the overall methylation as well as methylation at mC-15 which was non-CpG site, no significant correlation could be found between the BPI and transcription factor mRNA levels, EMSA test showed that C/EBPβ could interact with BPI wild-type promoter DNA, but not methylated DNA. So we confirmed that methylation of mC-15 residue could inhibit the ability of C/EBPβ binding to the BPI promoter and affect the expression, and this mechanism probably plays a role in the tissue specificity of BPI gene expression in weaned piglets.

CCAAT/enhancer binding protein β induces motility and invasion of glioblastoma cells through transcriptional regulation of the calcium binding protein S100A4

We have previously shown that decreased expression of CCAAT/enhancer binding protein β (C/EBPβ) inhibits the growth of glioblastoma cells and diminishes their transformation capacity and migration. In agreement with this, we showed that C/EBPβ depletion decreases the mRNA levels of different genes involved in metastasis and invasion. Among these, we found S100 calcium binding protein A4 (S100A4) to be almost undetectable in glioblastoma cells deficient in C/EBPβ. Here, we have evaluated the possible role of S100A4 in the observed effects of C/EBPβ in glioblastoma cells and the mechanism through which S100A4 levels are controlled by C/EBPβ. Our results show that C/EBPβ suppression significantly reduced the levels of S100A4 in murine GL261 and human T98G glioblastoma cells. By employing an S100A4-promoter reporter, we observed a significant induction in the transcriptional activation of the S100A4 gene by C/EBPβ. Furthermore, overexpression of S100A4 in C/EBPβ-depleted glioblastoma cells reverses the enhanced migration and motility induced by this transcription factor. Our data also point to a role of S100A4 in glioblastoma cell invasion and suggest that the C/EBPβ gene controls the invasive potential of GL261 and T98G cells through direct regulation of S100A4. Finally, this study indicates a role of C/EBPβ on the maintenance of the stem cell population present in GL261 glioblastoma cells.

Redox modulation of adipocyte differentiation: hypothesis of "Redox Chain" and novel insights into intervention of adipogenesis and obesity

In view of the global prevalence of obesity and obesity-associated disorders, it is important to clearly understand how adipose tissue forms. Accumulating data from various laboratories implicate that redox status is closely associated with energy metabolism. Thus, biochemical regulation of the redox system may be an attractive alternative for the treatment of obesity-related disorders. In this work, we will review the current data detailing the role of the redox system in adipocyte differentiation, as well as identifying areas for further research. The redox system affects adipogenic differentiation in an extensive way. We propose that there is a complex and interactive "redox chain," consisting of a "ROS-generating enzyme chain," "combined antioxidant chain," and "transcription factor chain," which contributes to fine-tune the regulation of ROS level and subsequent biological consequences. The roles of the redox system in adipocyte differentiation are paradoxical. The redox system exerts a "tridimensional" mechanism in the regulation of adipocyte differentiation, including transcriptional, epigenetic, and posttranslational modulations. We suggest that redoxomic techniques should be extensively applied to understand the biological effects of redox alterations in a more integrated way. A stable and standardized "redox index" is urgently needed for the evaluation of the general redox status. Therefore, more effort should be made to establish and maintain a general redox balance rather than to conduct simple prooxidant or antioxidant interventions, which have comprehensive implications.

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ are transcription factors of the basic-leucine zipper class which share phylogenetic, structural and functional features. In this review we first describe in depth their basic molecular biology which includes fascinating aspects such as the regulated use of alternative initiation codons in the C/EBPβ mRNA. The physical interactions with multiple transcription factors which greatly opens the number of potentially regulated genes or the presence of at least five different types of post-translational modifications are also remarkable molecular mechanisms that modulate C/EBPβ and C/EBPδ function. In the second part, we review the present knowledge on the localization, expression changes and physiological roles of C/EBPβ and C/EBPδ in neurons, astrocytes and microglia. We conclude that C/EBPβ and C/EBPδ share two unique features related to their role in the CNS: whereas in neurons they participate in memory formation and synaptic plasticity, in glial cells they regulate the pro-inflammatory program. Because of their role in neuroinflammation, C/EBPβ and C/EBPδ in microglia are potential targets for treatment of neurodegenerative disorders. Any strategy to reduce C/EBPβ and C/EBPδ activity in neuroinflammation needs to take into account its potential side-effects in neurons. Therefore, cell-specific treatments will be required for the successful application of this strategy.

CCAAT/enhancer binding protein β directly regulates the expression of the complement component 3 gene in neural cells: implications for the pro-inflammatory effects of this transcription factor

Background

The CCAAT/enhancer-binding protein β (C/EBPβ) is a transcription factor, which was first identified as a regulator of differentiation and inflammatory processes mainly in adipose tissue and liver; however, its function in the brain was largely unknown for many years. Previous studies from our laboratory indicated that C/EBPβ is implicated in inflammatory process and brain injury, since mice lacking this gene were less susceptible to kainic acid-induced injury.

Methods

We first performed cDNA microarrays analysis using hippocampal RNA isolated from C/EBPβ^+/+ and C/EBPβ^−/− mice. Immunocytochemical and immunohistochemical studies were done to evaluate C/EBPβ and C3 levels. Transient transfection experiments were made to analyze transcriptional regulation of C3 by C/EBPβ. To knockdown C/EBPβ and C3 expression, mouse astrocytes were infected with lentiviral particles expressing an shRNA specific for C/EBPβ or an siRNA specific for C3.

Results

Among the genes displaying significant changes in expression was complement component 3 (C3), which showed a dramatic decrease in mRNA content in the hippocampus of C/EBPβ^−/− mice. C3 is the central component of the complement and is implicated in different brain disorders. In this work we have found that C/EBPβ regulates C3 levels in rodents glial in vitro and in the rat Substantia nigra pars compacta (SNpc) in vivo following an inflammatory insult. Analysis of the mouse C3 promoter showed that it is directly regulated by C/EBPβ through a C/EBPβ consensus site located at position −616/-599 of the gene. In addition, we show that depletion of C/EBPβ by a specific shRNA results in a significant decrease in the levels of C3 together with a reduction in the increased levels of pro-inflammatory agents elicited by lipopolysaccharide treatment.

Conclusions

Altogether, these results indicate that C3 is a downstream target of C/EBPβ, and it could be a mediator of the pro-inflammatory effects of this transcription factor in neural cells.

The transcription factor CCAAT enhancer-binding protein β protects rat cerebellar granule neurons from apoptosis through its transcription-activating isoforms

CCAAT enhancer-binding protein β is a transcription factor that is involved in many brain processes, although its role in neuronal survival/death remains unclear. By using primary cultures of rat cerebellar granule neurons, we have shown here that CCAAT enhancer-binding protein β is present as all of its isoforms: the transcriptional activators liver activator proteins 1 and 2, and the transcriptional inhibitor liver inhibitory protein. We have also shown that liver activator protein 1 undergoes post-translational modifications, such as phosphorylation and sumoylation. These isoforms have different subcellular localizations, liver activator protein 2 being found in the cytosolic fraction only, liver inhibitory protein in the nucleus only, and liver activator protein 1 in both fractions. Through neuronal apoptosis induction by shifting mature cerebellar granule neurons to low-potassium medium, we have demonstrated that nuclear liver activator protein 1 expression decreases and its phosphorylation disappears, whereas liver inhibitory protein levels increase in the nuclear fraction, suggesting a pro-survival role for liver activator protein transcriptional activation and a pro-apoptotic role for liver inhibitory protein transcriptional inhibition. To confirm this, we transfected cerebellar granule neurons with plasmids expressing liver activator protein 1, liver activator protein 2, or liver inhibitory protein respectively, and observed that both liver activator proteins, which increase CCAAT-dependent transcription, but not liver inhibitory protein, counteracted apoptosis, thus demonstrating the pro-survival role of liver activator proteins. These data significantly improve our current understanding of the role of CCAAT enhancer-binding protein β in neuronal survival/apoptosis.

Phycocyanobilin promotes PC12 cell survival and modulates immune and inflammatory genes and oxidative stress markers in acute cerebral hypoperfusion in rats

Since the inflammatory response and oxidative stress are involved in the stroke cascade, we evaluated here the effects of Phycocyanobilin (PCB, the C-Phycocyanin linked tetrapyrrole) on PC12 cell survival, the gene expression and the oxidative status of hypoperfused rat brain. After the permanent bilateral common carotid arteries occlusion (BCCAo), the animals were treated with saline or PCB, taking samples 24h post-surgery. Global gene expression was analyzed with GeneChip Rat Gene ST 1.1 from Affymetrix; the expression of particular genes was assessed by the Fast SYBR Green RT-PCR Master Mix and Bioplex methods; and redox markers (MDA, PP, CAT, SOD) were evaluated spectrophotometrically. The PCB treatment prevented the H2O2 and glutamate induced PC12 cell injury assessed by the MTT assay, and modulated 190 genes (93 up- and 97 down-regulated) associated to several immunological and inflammatory processes in BCCAo rats. Furthermore, PCB positively modulated 19 genes mostly related to a detrimental pro-inflammatory environment and counteracted the oxidative imbalance in the treated BCCAo animals. Our results support the view of an effective influence of PCB on major inflammatory mediators in acute cerebral hypoperfusion. These results suggest that PCB has a potential to be a treatment for ischemic stroke for which further studies are needed.

Effects of experimental diabetes on C/EBP proteins in rat hippocampus, sciatic nerve and ganglia

Neurodegeneration is one of the most important complications of diabetes mellitus (DM). The exact mechanisms underlying neurodegeneration related to diabetic complications such as cognitive deficits and peripheral neuropathy are not clarified yet. Due to the fact that CCAAT/enhancer binding proteins (C/EBPs) have roles in cognitive functions, memory, synaptic plasticity, inflammation, lipid storage, and response to neurotrophic factors, it is possible to suggest that these transcription factors could have roles in neurodegeneration. Hence, in this study, the effects of experimental diabetes on C/EBPs in the hippocampus, sciatic nerve, and ganglia tissues were examined. After experimentally induced diabetes, immunoreactivity of related proteins was measured by western blotting. C/EBPα immunoreactivity in the hippocampus was not altered at 4-weeks but significantly decreased at 12-weeks of diabetes. C/EBPβ immunoreactivity was not altered at 4-weeks whereas significantly increased at 12-weeks of diabetes. In the ganglion, C/EBPα immunoreactivity was significantly decreased in diabetes, but C/EBPβ immunoreactivity was not affected. In the sciatic nerve, C/EBPα and β immunoreactivities were significantly decreased in diabetic rats. Furthermore, insulin therapy prevented diabetes-induced alterations in C/EBPα and β immunoreactivities. This study indicated, for the first time, that DM altered the immunoreactivity of C/EBPs in the nervous system. C/EBPs might be one of the important molecular targets which are responsible for neurodegeneration seen in diabetes.

A multidimensional approach to an in-depth proteomics analysis of transcriptional regulators in neuroblastoma cells

The dynamic regulation of transcriptional events is fundamental to many aspects of neuronal cell functions. However, proteomics methods have not been routinely used in global neuroproteomics analyses of transcriptional regulators because they are much less abundant than the "house-keeping" proteins in cells and tissues. Recent improvements in both biochemical preparations of nuclear proteins and detection sensitivities of proteomics technologies have made the global analysis of nuclear transcriptional regulators possible. We report here an optimised neuroproteomic method for the analysis of transcriptional regulators in the nuclear extracts of SHSY-5Y neuroblastoma cells by combining an improved nuclear protein extraction procedure with multidimensional peptide separation approaches. We found that rigorous removal of cytoplasmic proteins and solubilisation of DNA-associated proteins improved the number of nuclear proteins identified. Furthermore, we discovered that multidimensional peptide separations by either strong cation exchange (SCX) chromatography or electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) analysis detected more than 1800 nuclear proteins, which constitutes one of the largest datasets of nuclear proteins reported for a neuronal cell. Thus, in-depth analysis of transcriptional regulators for studying neurological diseases are increasingly feasible.

C/EBPβ regulates multiple IL-1β-induced human astrocyte inflammatory genes

Background

CCAAT enhancer-binding protein (C/EBP)β regulates gene expression in multiple organ systems and cell types, including astrocytes in the central nervous system (CNS). Inflammatory stimuli, interleukin (IL)-1β, tumor necrosis factor-α, human immunodeficiency virus (HIV)-1 and lipopolysaccharide induce astrocyte C/EBPβ expression. C/EBPβ is detectable in brains of Alzheimer’s disease (AD), Parkinson’s disease (PD) and HIV-1-associated dementia (HAD) patients, yet little is known about how C/EBPβ contributes to astrocyte gene regulation during neuroinflammation.

Methods

The expression of 92 human inflammation genes was compared between IL-1β-treated primary human astrocytes and astrocytes transfected with C/EBPβ-specific small interfering (si)RNA prior to IL-1β treatment for 12 h. Transcripts altered by > two-fold compared to control were subjected to one-way analysis of variance and Newman-Keuls post-test for multiple comparisons. Expression of two genes, cyclooxygenase-2 (COX-2) and bradykinin receptor B2 (BDKRB2) was further confirmed in additional human astrocyte donors. Astrocytes were treated with mitogen-activated protein kinase-selective inhibitors, then with IL-1β for 12 or 24 h followed by COX-2 and BDKRB2, expression analyses.

Results

IL-1β altered expression of 29 of 92 human inflammation genes by at least two-fold in primary human astrocytes in 12 h. C/EBPβ knockdown affected expression of 17 out of 29 IL-1β-regulated genes by > 25%. Two genes relevant to neuroinflammation, COX-2 and BDKRB2, were robustly decreased and increased, respectively, in response to C/EBPβ knockdown, and expression was confirmed in two additional donors. COX-2 and BDKRB2 mRNA remained altered in siRNA-transfected astrocytes at 12, 24 or 72 h. Inhibiting p38 kinase (p38K) activation blocked IL-1β-induced astrocyte COX-2 mRNA and protein expression, but not IL-1β-induced astrocyte BDKRB2 expression. Inhibiting extracellular-regulated kinase (ERK)1/2 activation blocked IL-1β-induced BDKRB2 mRNA expression while increasing COX-2 expression.

Conclusion

These data support an essential role for IL-1β in the CNS and identify new C/EBPβ functions in astrocytes. Additionally, this work suggests p38K and ERK1/2 pathways may regulate gene expression in a complementary manner to fine tune the IL-1β-mediated astrocyte inflammatory response. Delineating a role for C/EBPβ and other involved transcription factors in human astrocyte inflammatory response may lead to effective therapies for AD, PD, HAD and other neurological disorders.

CCAAT/enhancer binding protein-δ expression by dendritic cells regulates CNS autoimmune inflammatory disease

CCAAT enhancer binding protein-delta (C/EBPδ) is a transcription factor that regulates inflammatory processes mediating bystander neuronal injury and CNS autoimmune inflammatory disease. The mechanism of the involvement of C/EBPδ in these processes remains to be determined. Here, we examined the cellular source(s) and mechanisms by which C/EBPδ may be involved in an animal model of multiple sclerosis. Mice deficient in C/EBPδ expression exhibited less severe clinical disease than wild-type littermates in response to induction of experimental autoimmune encephalomyelitis (EAE) by vaccination with a myelin oligodendrocyte glycoprotein (MOG) fragment. This reduction in EAE severity was associated with a significant alteration in the complement of major CNS T-helper (Th) cell subtypes throughout disease, manifest as reduced ratios of Th17 cells to regulatory T-cells (Tregs). Studies in bone marrow chimeric mice indicated that C/EBPδ expression by peripherally derived immune cells mediates C/EBPδ involvement in EAE. Follow up in vitro and in vivo examination of dendritic cell (DC) mediated Th-cell development suggests that C/EBPδ suppresses DC expression of interleukin-10 (IL-10), favoring Th17 over Treg development. In vitro and in vivo blockade of IL-10 signaling attenuated the effect of reduced C/EBPδ expression by DCs on Th17:Treg ratios. These findings identify C/EBPδ as an important DC transcription factor in CNS autoimmune inflammatory disease by virtue of its capacity to alter the Th17:Treg balance in an IL-10 dependent fashion.

Identification of the role of C/EBP in neurite regeneration following microarray analysis of a L. stagnalis CNS injury model

Background

Neuronal regeneration in the adult mammalian central nervous system (CNS) is severely compromised due to the presence of extrinsic inhibitory signals and a reduced intrinsic regenerative capacity. In contrast, the CNS of adult Lymnaea stagnalis (L. stagnalis), a freshwater pond snail, is capable of spontaneous regeneration following neuronal injury. Thus, L. stagnalis has served as an animal model to study the cellular mechanisms underlying neuronal regeneration. However, the usage of this model has been limited due to insufficient molecular tools. We have recently conducted a partial neuronal transcriptome sequencing project and reported over 10,000 EST sequences which allowed us to develop and perform a large-scale high throughput microarray analysis.

Results

To identify genes that are involved in the robust regenerative capacity observed in L. stagnalis, we designed the first gene chip covering ~15, 000 L. stagnalis CNS EST sequences. We conducted microarray analysis to compare the gene expression profiles of sham-operated (control) and crush-operated (regenerative model) central ganglia of adult L. stagnalis. The expression levels of 348 genes were found to be significantly altered (p < 0.05) following nerve injury. From this pool, 67 sequences showed a greater than 2-fold change: 42 of which were up-regulated and 25 down-regulated. Our qPCR analysis confirmed that CCAAT enhancer binding protein (C/EBP) was up-regulated following nerve injury in a time-dependent manner. In order to test the role of C/EBP in regeneration, C/EBP siRNA was applied following axotomy of cultured Lymnaea PeA neurons. Knockdown of C/EBP following axotomy prevented extension of the distal, proximal and intact neurites. In vivo knockdown of C/EBP postponed recovery of locomotory activity following nerve crush. Taken together, our data suggest both somatic and local effects of C/EBP are involved in neuronal regeneration.

Conclusions

This is the first high-throughput microarray study in L. stagnalis, a model of axonal regeneration following CNS injury. We reported that 348 genes were regulated following central nerve injury in adult L. stagnalis and provided the first evidence for the involvement of local C/EBP in neuronal regeneration. Our study demonstrates the usefulness of the large-scale gene profiling approach in this invertebrate model to study the molecular mechanisms underlying the intrinsic regenerative capacity of adult CNS neurons.

Role of C/EBPβ transcription factor in adult hippocampal neurogenesis

BACKGROUND

The dentate gyrus of the hippocampus is one of the regions in which neurogenesis takes place in the adult brain. We have previously demonstrated that CCAAT/enhancer binding protein β (C/EBPβ) is expressed in the granular layer of the dentate gyrus of the adult mouse hippocampus. Taking into account the important role of C/EBPβ in the consolidation of long term memory, the fact that newborn neurons in the hippocampus contribute to learning and memory processes, and the role of this transcription factor, previously demonstrated by our group, in regulating neuronal differentiation, we speculated that this transcription factor could regulate stem/progenitor cells in this region of the brain.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we show, using C/EBPβ knockout mice, that C/EBPβ expression is observed in the subset of newborn cells that proliferate in the hippocampus of the adult brain. Mice lacking C/EBPβ present reduced survival of newborn cells in the hippocampus, a decrease in the number of these cells that differentiate into neurons and a diminished number of cells that are proliferating in the subgranular zone of the dentate gyrus. These results were further confirmed in vitro. Neurosphere cultures from adult mice deficient in C/EBPβ present less proliferation and neuronal differentiation than neurospheres derived from wild type mice.

CONCLUSIONS/SIGNIFICANCE

In summary, using in vivo and in vitro strategies, we have identified C/EBPβ as a key player in the proliferation and survival of the new neurons produced in the adult mouse hippocampus. Our results support a novel role of C/EBPβ in the processes of adult hippocampal neurogenesis, providing new insights into the mechanisms that control neurogenesis in this region of the brain.

CCAAT/enhancer binding protein β expression is increased in the brain during HIV-1-infection and contributes to regulation of astrocyte tissue inhibitor of metalloproteinase-1

Human immunodeficiency virus (HIV)-1-associated neurocognitive disorders (HAND) associated with infection and activation of mononuclear phagocytes (MP) in the brain, occur late in disease. Infected/activated MP initiate neuroinflammation activating glial cells and ultimately disrupting neuronal function. Astrocytes secrete tissue inhibitor of metalloproteinase (TIMP)-1 in response to neural injury. Altered TIMP-1 levels are implicated in several CNS diseases. CCAAT enhancer-binding protein β (C/EBPβ), a transcription factor, is expressed in rodent brains in response to neuroinflammation, implicating it in Alzheimer's, Parkinson's, and HAND. Here, we report that C/EBPβ mRNA levels are elevated and its isoforms differentially expressed in total brain tissue lysates of HIV-1-infected and HIV-1 encephalitis patients. In vitro, HAND-relevant stimuli additively induce C/EBPβ nuclear expression in human astrocytes through 7 days of treatment. Over-expression of C/EBPβ increases TIMP-1 promoter activity, mRNA, and protein levels in human astrocytes activated with interleukin-1β. Knockdown of C/EBPβ with siRNA decreases TIMP-1 mRNA and protein levels. These data suggest that C/EBPβ isoforms are involved in complex regulation of astrocyte TIMP-1 production during HIV-1 infection; however, further studies are required to completely understand their role during disease progression.

Spatiotemporal nuclear factor interleukin-6 expression in the rat brain during lipopolysaccharide-induced fever is linked to sustained hypothalamic inflammatory target gene induction

Rats injected with lipopolysaccharide (LPS) show brain-controlled sickness symptoms, including fever. In these animals, early genomic activation of brain cells was previously monitored by immunohistochemical detection of transcription factors such as nuclear factor (NF)-κB or signal transducer and activator of transcription (STAT)3 and was linked to the initiation or maintenance of the febrile response. To investigate whether NF-IL6 might be another important transcription factor implicated in this kind of immune-to-brain signaling, rats were injected with LPS (100 μg/kg, intraperitoneally) or phosphate-buffered saline, and brains were analyzed by immunohistochemistry, real-time PCR, or Western blot 4, 6, 8, and 10 hours later. Moderate to strong LPS-induced nuclear NF-IL6 immunoreactivity (IR) occurred in a time-dependent manner within circumventricular organs, namely, the vascular organ of the lamina terminalis, the subfornical organ, the area postrema, and the median eminence, brain structures with a leaky blood-brain barrier. Furthermore, nuclear NF-IL6-IR was observed in the pituitary gland, the choroid plexus, and the meninges as well as blood vessels throughout the entire brain. Endothelial, microglial, and ependymal cells, astrocytes, perivascular macrophages, and neurons exhibited LPS-induced nuclear NF-IL6-IR; mRNA levels of NF-IL6, responsive inflammatory genes, and NF-IL6 protein levels were significantly elevated. As opposed to observations on STAT3 or NFκB, the percentage of NF-IL6-reactive cells increased in parallel to late phases of the febrile response. In conclusion, these results suggest a potential role for NF-IL6 in the maintenance or possibly the termination of LPS-induced fever. Moreover, we propose NF-IL6 to be a delayed brain cell activation marker.

Phosphodiesterase 7 inhibition preserves dopaminergic neurons in cellular and rodent models of Parkinson disease

Background

Phosphodiesterase 7 plays a major role in down-regulation of protein kinase A activity by hydrolyzing cAMP in many cell types. This cyclic nucleotide plays a key role in signal transduction in a wide variety of cellular responses. In the brain, cAMP has been implicated in learning, memory processes and other brain functions.

Methodology/Principal Findings

Here we show a novel function of phosphodiesterase 7 inhibition on nigrostriatal dopaminergic neuronal death. We found that S14, a heterocyclic small molecule inhibitor of phosphodiesterase 7, conferred significant neuronal protection against different insults both in the human dopaminergic cell line SH-SY5Y and in primary rat mesencephalic cultures. S14 treatment also reduced microglial activation, protected dopaminergic neurons and improved motor function in the lipopolysaccharide rat model of Parkinson disease. Finally, S14 neuroprotective effects were reversed by blocking the cAMP signaling pathways that operate through cAMP-dependent protein kinase A.

Conclusions/Significance

Our findings demonstrate that phosphodiesterase 7 inhibition can protect dopaminergic neurons against different insults, and they provide support for the therapeutic potential of phosphodiesterase 7 inhibitors in the treatment of neurodegenerative disorders, particularly Parkinson disease.

Microarray evidences the role of pathologic adipose tissue in insulin resistance and their clinical implications

Clustering of insulin resistance and dysmetabolism with obesity is attributed to pathologic adipose tissue. The morphologic hallmarks of this pathology are adipocye hypertrophy and heightened inflammation. However, it's underlying molecular mechanisms remains unknown. Study of gene function in metabolically active tissues like adipose tissue, skeletal muscle and liver is a promising strategy. Microarray is a powerful technique of assessment of gene function by measuring transcription of large number of genes in an array. This technique has several potential applications in understanding pathologic adipose tissue. They are: (1) transcriptomic differences between various depots of adipose tissue, adipose tissue from obese versus lean individuals, high insulin resistant versus low insulin resistance, brown versus white adipose tissue, (2) transcriptomic profiles of various stages of adipogenesis, (3) effect of diet, cytokines, adipokines, hormones, environmental toxins and drugs on transcriptomic profiles, (4) influence of adipokines on transcriptomic profiles in skeletal muscle, hepatocyte, adipose tissue etc., and (5) genetics of gene expression. The microarray evidences of molecular basis of obesity and insulin resistance are presented here. Despite the limitations, microarray has potential clinical applications in finding new molecular targets for treatment of insulin resistance and classification of adipose tissue based on future risk of insulin resistance syndrome.

Decreased CCAAT/enhancer binding protein β expression inhibits the growth of glioblastoma cells

C/EBPβ is a leucine-zipper transcription factor implicated in the control of metabolism, development, cell differentiation, and proliferation. However, it remains unclear its role in tumor development. Here, we show that down-regulation of C/EBPβ by RNA interference inhibits proliferation in the GL261 murine glioblastoma cell line, induces an arrest of the cell cycle at the G0/G1 boundary, and diminishes their transformation capacity and migration. In addition, we show that C/EBPβ regulates the expression of several DNA damage response- and invasion-related genes. Lastly, C/EBPβ depletion significantly retards tumor onset and prolongs survival in a murine orthotopic brain tumor model. Immunohistochemical analysis revealed a significant diminution of proliferating cell nuclear antigen (PCNA) labeling in tumors derived from C/EBPβ-depleted GL261 cells compared with that in controls. These results show, for the first time, the dependence of glioma cells on C/EBPβ and suggest a potential role of this transcription factor in glioma development.

Megestrol acetate inhibits the expression of cytoplasmic aromatase through nuclear C/EBPβ in reperfusion injury-induced ischemic rat hippocampus

Global ischemia after cardiac arrest, intraoperative hypoxia/hypotension, and hemorrhagic shock causes brain injury resulting in severe neurological and neurobehavioral deficits. Neurodegeneration can be prevented by local aromatase expression, and estrogen synthesis can be neuroprotective in ischemia/reperfusion. Therefore, aromatase, the enzyme that transforms androgens to estrogens, may be a potential target for the study of reperfusion injury after brain ischemia. We investigated the expression of aromatase and C/EBPβ using western blotting in rat hippocampus after transient global ischemia plus hypotension. Immunohistochemical analysis was performed for aromatase. After 10min of ischemia, aromatase and C/EBPβ expression in cytosolic extracts were observed after 10min and 24h of reperfusion. The expression of both proteins was similar in control and damaged tissues. Immunoblot analysis demonstrated that the highest aromatase expression appeared in damaged hippocampi after 1week and was gradually reduced after 2-10weeks. C/EBPβ expression increased at 1week in nuclear extracts of damaged hippocampi. The aromatase inhibitor megestrol acetate (20mg/kg/day) suppressed aromatase and nuclear C/EBPβ levels in ischemic hippocampi. Our findings indicate that ischemia as well as chronic neurodegenerative processes leads to an increase in cytoplasmic aromatase and nuclear C/EBPβ. Thus, it is possible to hypothesize an interaction between this enzyme gene and transcription factor.

Inhibition of glioblastoma growth by the thiadiazolidinone compound TDZD-8

BACKGROUND

Thiadiazolidinones (TDZD) are small heterocyclic compounds first described as non-ATP competitive inhibitors of glycogen synthase kinase 3β (GSK-3β). In this study, we analyzed the effects of 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), on murine GL261 cells growth in vitro and on the growth of established intracerebral murine gliomas in vivo.

METHODOLOGY/PRINCIPAL FINDINGS

Our data show that TDZD-8 decreased proliferation and induced apoptosis of GL261 glioblastoma cells in vitro, delayed tumor growth in vivo, and augmented animal survival. These effects were associated with an early activation of extracellular signal-regulated kinase (ERK) pathway and increased expression of EGR-1 and p21 genes. Also, we observed a sustained activation of the ERK pathway, a concomitant phosphorylation and activation of ribosomal S6 kinase (p90RSK) and an inactivation of GSK-3β by phosphorylation at Ser 9. Finally, treatment of glioblastoma stem cells with TDZD-8 resulted in an inhibition of proliferation and self-renewal of these cells.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that TDZD-8 uses a novel mechanism to target glioblastoma cells, and that malignant progenitor population could be a target of this compound.

Age-dependent response of CCAAT/enhancer binding proteins following traumatic brain injury in mice

Exacerbated inflammatory responses have been reported following traumatic injury to the aged brain. The present study was designed to investigate the involvement of the transcription factors belonging to the CCAAT/enhancer binding protein (C/EBP) family that regulate expression of many of the pro-inflammatory genes which show increased expression following injury to the aged brain. Controlled cortical impact injury was induced in adult (5-6 months) and aged (22-24 months) C57/BL6 mice. C/EBP mRNA and protein expression were analyzed in injured cortex at 1, 3, and 7 days post-injury. Expression of C/EBPalpha was reduced relative to baseline at day 1 in both adult and aged mice, whereas, it increased at days 3 and 7 post-injury. No significant differences were observed between adult and aged brain. Upregulation of C/EBPbeta was observed 1 day following injury in both the adult and aged brain, but there were no major age-related differences in mRNA levels. However, there was higher C/EBPbeta protein in the aged brain. C/EBPdelta expression increased beginning 1 day post-injury in both adult and aged brain. In this case, the increase in C/EBPdelta expression was higher in the aged brain than in the adult at all time points studied. Expression of CCAAT/enhancer binding protein homologous protein (CHOP), a transcription factor involved in ER stress and protein unfolding responses, was also up-regulated in response to injury, but CHOP levels were significantly lower in the aged than the adult brain. Based on these results, we conclude that differential expression of C/EBP beta, delta and CHOP might contribute to the hyper-inflammatory response and poor prognosis following traumatic brain injury in the elderly patients. In addition elevated C/EBPdelta levels following TBI in the aged brain may play a role in the link between TBI and Alzheimer's disease.

Computational design and application of endogenous promoters for transcriptionally targeted gene therapy for rheumatoid arthritis

The promoter regions of genes that are differentially regulated in the synovial membrane during the course of rheumatoid arthritis (RA) represent attractive candidates for application in transcriptionally targeted gene therapy. In this study, we applied an unbiased computational approach to define proximal-promoters from a gene expression profiling study of murine experimental arthritis. Synovium expression profiles from progressing stages of collagen-induced arthritis (CIA) were classified into six distinct groups using k-means clustering. Using an algorithm based on local over-representation and comparative genomics, we identified putatively functional transcription factor-binding sites (TFBS) in TATA-dependent proximal-promoters. Applying a filter based on spacing between TATA box and transcription start site (TSS) combined with the presence of over-represented nuclear factor kappaB (NFkappaB), AP-1, or CCAAT/enhancer-binding protein beta (C/EBPbeta) sites, 382 candidate murine and human promoters were reduced to 66, corresponding to 45 genes. In vitro, 9 out of 10 computationally defined promoter regions conferred cytokine-inducible expression in murine cells and human synovial fibroblasts. Under these conditions, the serum amyloid A3 (Saa3) promoter showed the strongest transcriptional induction and strength. We applied this promoter for driving therapeutically efficacious levels of the interleukin-1 receptor antagonist (Il1rn) in a disease-regulated fashion. These results demonstrate the value of bioinformatics for guiding the selection of endogenous promoters for transcriptionally targeted gene therapy.

Nuclear calcium signaling controls expression of a large gene pool: identification of a gene program for acquired neuroprotection induced by synaptic activity

Synaptic activity can boost neuroprotection through a mechanism that requires synapse-to-nucleus communication and calcium signals in the cell nucleus. Here we show that in hippocampal neurons nuclear calcium is one of the most potent signals in neuronal gene expression. The induction or repression of 185 neuronal activity-regulated genes is dependent upon nuclear calcium signaling. The nuclear calcium-regulated gene pool contains a genomic program that mediates synaptic activity-induced, acquired neuroprotection. The core set of neuroprotective genes consists of 9 principal components, termed Activity-regulated Inhibitor of Death (AID) genes, and includes Atf3, Btg2, GADD45β, GADD45γ, Inhibin β-A, Interferon activated gene 202B, Npas4, Nr4a1, and Serpinb2, which strongly promote survival of cultured hippocampal neurons. Several AID genes provide neuroprotection through a common process that renders mitochondria more resistant to cellular stress and toxic insults. Stereotaxic delivery of AID gene-expressing recombinant adeno-associated viruses to the hippocampus confers protection in vivo against seizure-induced brain damage. Thus, treatments that enhance nuclear calcium signaling or supplement AID genes represent novel therapies to combat neurodegenerative conditions and neuronal cell loss caused by synaptic dysfunction, which may be accompanied by a deregulation of calcium signal initiation and/or propagation to the cell nucleus.

The dialogue between the synapse and the nucleus plays an important role in the physiology of neurons because it links brief changes in the membrane potential to the transcriptional regulation of genes critical for neuronal survival and long-term memory. The propagation of activity-induced calcium signals to the cell nucleus represents a major route for synapse-to-nucleus communication. Here we identified nuclear calcium-regulated genes that are responsible for a neuroprotective shield that neurons build up upon synaptic activity. We found that among the 185 genes controlled by nuclear calcium signaling, a set of 9 genes had strong survival promoting activity both in cell culture and in an animal model of neurodegeneration. The mechanism through which several genes prevent cell death involves the strengthening of mitochondria against cellular stress and toxic insults. The discovery of an activity-induced neuroprotective gene program suggest that impairments of synaptic activity and synapse-to-nucleus signaling, for example due to expression of Alzheimer's disease protein or in aging, may comprise the cells' own neuroprotective system eventually leading to cell death. Thus, malfunctioning of nuclear calcium signaling could be a key etiological factor common to many neuropathological conditions, providing a simple and unifying concept to explain disease- and aging-related cell loss.

CCAAT/enhancer binding protein beta deficiency provides cerebral protection following excitotoxic injury

The CCAAT/enhancer-binding protein beta (C/EBPbeta, also known as CEBPB) was first identified as a regulator of differentiation and inflammatory processes in adipose tissue and liver. Although C/EBPbeta was initially implicated in synaptic plasticity, its function in the brain remains largely unknown. We have previously shown that C/EBPbeta regulates the expression of genes involved in inflammatory processes and brain injury. Here, we have demonstrated that the expression of C/EBPbeta is notably increased in the hippocampus in a murine model of excitotoxicity. Mice lacking C/EBPbeta showed a reduced inflammatory response after kainic acid injection, and exhibited a dramatic reduction in pyramidal cell loss in the CA1 and CA3 subfields of the hippocampus. These data reveal an essential function for C/EBPbeta in the pathways leading to excitotoxicity-mediated damage and suggest that inhibitors of this transcription factor should be evaluated as possible neuroprotective therapeutic agents.

Loss of Fyn tyrosine kinase on the C57BL/6 genetic background causes hydrocephalus with defects in oligodendrocyte development

The supportive functions of oligodendrocytes are required for the survival and development of axons, ensuring the organization of highly specialized neuronal networks in brain. Although the molecules that regulate oligodendrocyte differentiation in vitro have been identified, their roles in vivo are largely uncertain. Here we report that fyn deficiency on the C57BL/6 genetic background resulted in premature death, showing severe hydrocephalus with neonatal onset. One week after birth, fyn-deficient mice showed enlarged lateral ventricles with thinner cerebral cortices and degenerating axons in the corpus callosum. In addition, before the onset of myelination, the number of oligodendrocytes was reduced and their morphogenesis was impaired in the cerebral cortex. These results demonstrate that Fyn is essential for normal brain development and suggest that defects in oligodendrocyte development cause degeneration of cortical axons and subsequent hydrocephalus in fyn-deficient mice.

Loss of c/EBP-beta activity promotes the adaptive to apoptotic switch in hypoxic cortical neurons

Understanding the mechanisms governing the switch between hypoxia-induced adaptive and pathological transcription may reveal novel therapeutic targets for stroke. Using an in vitro hypoxia model that temporally separates these divergent responses, we found apoptotic signaling was preceded by a decline in c/EBP-beta activity and was associated with markers of ER-stress including transient eIF2alpha phosphorylation, and the delayed induction of the bZIP proteins ATF4 and CHOP-10. Pretreatment with the eIF2alpha phosphatase inhibitor salubrinal blocked the activation of caspase-3, indicating that ER-related stress responses are integral to this transition. Delivery of either full-length, or a transcriptionally inactive form of c/EBP-beta protected cultures from hypoxic challenge, in part by inducing levels of the anti-apoptotic protein Bcl-2. These data indicate that the pathologic response in cortical neurons induced by hypoxia involves both the loss of c/EBP-beta-mediated survival signals and activation of pro-death pathways originating from the endoplasmic reticulum.

Gene expression profiling in a mouse model of infantile neuronal ceroid lipofuscinosis reveals upregulation of immediate early genes and mediators of the inflammatory response

BACKGROUND

The infantile form of neuronal ceroid lipofuscinosis (also known as infantile Batten disease) is caused by hereditary deficiency of a lysosomal enzyme, palmitoyl-protein thioesterase-1 (PPT1), and is characterized by severe cortical degeneration with blindness and cognitive and motor dysfunction. The PPT1-deficient knockout mouse recapitulates the key features of the disorder, including seizures and death by 7-9 months of age. In the current study, we compared gene expression profiles of whole brain from PPT1 knockout and normal mice at 3, 5 and 8 months of age to identify temporal changes in molecular pathways implicated in disease pathogenesis.

RESULTS

A total of 267 genes were significantly (approximately 2-fold) up- or downregulated over the course of the disease. Immediate early genes (Arc, Cyr61, c-fos, jun-b, btg2, NR4A1) were among the first genes upregulated during the presymptomatic period whereas immune response genes dominated at later time points. Chemokine ligands and protease inhibitors were among the most transcriptionally responsive genes. Neuronal survival factors (IGF-1 and CNTF) and a negative regulator of neuronal apoptosis (DAP kinase-1) were upregulated late in the course of the disease. Few genes were downregulated; these included the alpha2 subunit of the GABA-A receptor, a component of cortical and hippocampal neurons, and Hes5, a transcription factor important in neuronal differentiation.

CONCLUSION

A molecular description of gene expression changes occurring in the brain throughout the course of neuronal ceroid lipofuscinosis suggests distinct phases of disease progression, provides clues to potential markers of disease activity, and points to new targets for therapy.

Acute endotoxemia is associated with upregulation of lipocalin 24p3/Lcn2 in lung and liver

Acute endotoxemia is associated with production of acute phase proteins which regulate inflammatory responses to tissue injury. Consistent with DNA microarray experiments, we found that acute endotoxemia, induced by administration of lipopolysaccharide (LPS) to mice (1 mg/kg) or rats (5 mg/kg), resulted in increased expression of the hepatic acute phase protein, lipocalin 24p3, which was evident within 4 h and persisted for 24-48 h. Increases in 24p3 expression were also observed in the lung after LPS administration, as well as in isolated liver and lung macrophages, and Type II alveolar epithelial cells. The actions of LPS are dependent, in part, on Toll-like receptor (TLR) proteins. Macrophages from C3H/HeJ mice, which possess a nonfunctional TLR-4, expressed low levels of 24p3 mRNA when compared to cells from control C3H/OuJ mice. Whereas LPS administration increased 24p3 expression in lung and liver macrophages from control C3H/OuJ mice, minimal effects were observed in TLR-4 mutant mice demonstrating that TLR-4 is important in regulating 24p3 expression during acute endotoxemia. Promoters for genes encoding lipocalin proteins including 24p3 contain consensus sequences for transcription factors including NF-kappaB, and C/EBP. Acute endotoxemia resulted in NF-kappaB nuclear binding activity in both alveolar macrophages and Type II cells. In contrast, C/EBP activation was evident only in Type II cells, suggesting differential effects of LPS on these cell types. These data suggest that the acute phase response to acute endotoxemia involves induction of 24p3 in both the lung and liver. This protein may be important in restoring tissue homeostasis following LPS-induced injury.

Xanthine oxidoreductase is a regulator of adipogenesis and PPARgamma activity

In an effort to identify novel candidate regulators of adipogenesis, gene profiling of differentiating 3T3-L1 preadipocytes was analyzed using a novel algorithm. We report here the characterization of xanthine oxidoreductase (XOR) as a novel regulator of adipogenesis. XOR lies downstream of C/EBPbeta and upstream of PPARgamma, in the cascade of factors that control adipogenesis, and it regulates PPARgamma activity. In vitro, knockdown of XOR inhibits adipogenesis and PPARgamma activity while constitutive overexpression increases activity of the PPARgamma receptor in both adipocytes and preadipocytes. In vivo, XOR -/- mice demonstrate 50% reduction in adipose mass versus wild-type littermates while obese ob/ob mice exhibit increased concentrations of XOR mRNA and urate in the adipose tissue. We propose that XOR is a novel regulator of adipogenesis and of PPARgamma activity and essential for the regulation of fat accretion. Our results identify XOR as a potential therapeutic target for metabolic abnormalities beyond hyperuricemia.

Peroxisome proliferator-activated receptor-γ agonists induce neuroprotection following transient focal ischemia in normotensive, normoglycemic as well as hypertensive and type-2 diabetic rodents

Thiazolidinediones (TZDs) are synthetic agonists of the ligand-activated transcription factor peroxisome proliferator-activated receptor-gamma (PPARgamma). TZDs are known to curtail inflammation associated with peripheral organ ischemia. As inflammation precipitates the neuronal death after stroke, we tested the efficacy of TZDs in preventing brain damage following transient middle cerebral artery occlusion (MCAO) in adult rodents. As hypertension and diabetes complicate the stroke outcome, we also evaluated the efficacy of TZDs in hypertensive rats and type-2 diabetic mice subjected to transient MCAO. Pre-treatment as well as post-treatment with TZDs rosiglitazone and pioglitazone significantly decreased the infarct volume and neurological deficits in normotensive, normoglycemic, hypertensive and hyperglycemic rodents. Rosiglitazone neuroprotection was not enhanced by retinoic acid x receptor agonist 9-cis-retinoic acid, but was prevented by PPARgamma antagonist GW9662. Rosiglitazone significantly decreased the post-ischemic intercellular adhesion molecule-1 expression and extravasation of macrophages and neutrophils into brain. Rosiglitazone treatment curtailed the post-ischemic expression of the pro-inflammatory genes interleukin-1beta, interleukin-6, macrophage inflammatory protein-1alpha, monocyte chemoattractant protein-1, cyclooxygenase-2, inducible nitric oxide synthase, early growth response-1, CCAAT/enhancer binding protein-beta and nuclear factor-kappa B, and increased the expression of the anti-oxidant enzymes catalase and copper/zinc-superoxide dismutase. Rosiglitazone also increased the expression of the anti-inflammatory gene suppressor of cytokine signaling-3 and prevented the phosphorylation of the transcription factor signal transducer and activator of transcription-3 after focal ischemia. Thus, PPARgamma activation with TZDs might be a potent therapeutic option for preventing inflammation and neuronal damage after stroke with promise in diabetic and hypertensive subjects.

Identification and characterization of novel activity-dependent transcription factors in rat cortical neurons

Using gene chip analyses, we have identified novel neuronal activity-dependent genes. Application of 25 mM KCl to mature (14-day culture) rat cortical neurons resulted in more than 1.5-fold induction of 19 genes and reduction of 42 genes among 1200 neural genes. Changes in the overall gene expression profiles appeared to be related to the reduction of excitability and induction of cellular survival signals. Among the genes identified, three transcriptional modulators [encoding Cbp/p300-interacting transactivator with ED-rich tail 2 (CITED2), CCAAT/enhancer binding protein beta (C/EBPbeta) and neuronal orphan receptor-1, (NOR1)] were newly identified as activity-dependent transcription factors, and two of these (CITED2 and NOR1) were found to be influenced by electroconvulsive shock (ECS). NOR1 was induced in specific brain regions by behavioral activation, such as exposure to a novel environment. Because the brain regions that exhibited the induction of these newly identified neuronal activity-dependent transcriptional modulators were distinct from those showing the induction of previously identified activity-dependent genes such as c-fos, these genes might be useful markers for mapping neuronal activity in vivo.

Effects of brief cutaneous JP-8 jet fuel exposures on time course of gene expression in the epidermis

The jet fuel jet propulsion fuel 8 (JP-8) has been shown to cause an inflammatory response in the skin, which is characterized histologically by erythema, edema, and hyperplasia. Studies in laboratory animal skin and cultured keratinocytes have identified a variety of changes in protein levels related to inflammation, oxidative damage, apoptosis, and cellular growth. Most of these studies have focused on prolonged exposures and subsequent effects. In an attempt to understand the earliest responses of the skin to JP-8, we have investigated changes in gene expression in the epidermis for up to 8 h after a 1-h cutaneous exposure in rats. After exposure, we separated the epidermis from the rest of the skin with a cryotome and isolated total mRNA. Gene expression was studied with microarray techniques, and changes from sham treatments were analyzed and characterized. We found consistent twofold increases in gene expression of 27 transcripts at 1, 4, and 8 h after the beginning of the 1-h exposure that were related primarily to structural proteins, cell signaling, inflammatory mediators, growth factors, and enzymes. Analysis of pathways changed showed that several signaling pathways were increased at 1 h and that the most significant changes at 8 h were in metabolic pathways, many of which were downregulated. These results confirm and expand many of the previous molecular studies with JP-8. Based on the 1-h changes in gene expression, we hypothesize that the trigger of the JP-8-induced, epidermal stress response is a physical disruption of osmotic, oxidative, and membrane stability which activates gene expression in the signaling pathways and results in the inflammatory, apoptotic, and growth responses that have been previously identified.

Toll-like receptors differentially regulate CC and CXC chemokines in skeletal muscle via NF-kappaB and calcineurin

Immunologically active molecules such as cytokines and chemokines have been implicated in skeletal muscle weakness during sepsis as well as recovery from muscle injury. In sepsis, Toll-like receptors (TLRs) act as key sentinel molecules of the innate immune system. Here we determined skeletal muscle cell responses of two prototypical CC and CXC chemokine genes (monocyte chemoattractant protein 1 [MCP-1] and KC, respectively), to stimulation with specific TLR ligands. In addition, we examined whether NF-kappaB and calcineurin signaling are involved in these responses. Differentiated myotubes and intact whole muscles expressed TLR2, TLR4, TLR5, and TLR9. Stimulation with ligands for TLR2 (peptidoglycan) or TLR4 (LPS) elicited robust and equivalent levels of MCP-1 and KC mRNA expression, whereas stimulation of TLR5 (by flagellin) required gamma interferon priming to induce similar effects. Although both TLR2 and TLR4 ligands activated the NF-kappaB pathway, NF-kappaB reporter activity was approximately 20-fold greater after TLR4 stimulation than after TLR2 stimulation. Inhibitory effects of NF-kappaB blockade on TLR-mediated chemokine gene expression, by either pharmacological (pyrrolidine dithiocarbamate) or molecular (IKKbeta dominant-negative transfection) methods, were also more pronounced during TLR4 stimulation. In contrast, inhibitory effects on TLR-mediated chemokine expression of calcineurin blockade (by FK506) were greater for TLR2 than for TLR4 stimulation. MCP-1 and KC mRNA levels also demonstrated differential responses to NF-kappaB and calcineurin blockade during stimulation with specific TLR ligands. We conclude that skeletal muscle cells differentially utilize the NF-kappaB and calcineurin pathways in a TLR-specific manner to enable complex regulation of CC and CXC chemokine gene expression.

Decreased brain damage and curtailed inflammation in transcription factor CCAAT/enhancer binding protein beta knockout mice following transient focal cerebral ischemia

CCAAT/enhancer binding protein beta (C/EBPbeta) is a leucine-zipper transcription factor that regulates cell growth and differentiation in mammals. Expression of many pro-inflammatory genes including the cytokine interleukin-6 is known to be controlled by C/EBPbeta. We report that focal cerebral ischemia induced by transient middle cerebral artery occlusion (MCAO) significantly increases C/EBPbeta gene expression in mouse brain at between 6 and 72 h of reperfusion. To understand the functional significance of C/EBPbeta in postischemic inflammation and brain damage, we induced transient MCAO in cohorts of adult C/EBPbeta null mice and their wild-type littermates. At 3 days of reperfusion following transient MCAO, C/EBPbeta null mice showed significantly smaller infarcts, reduced neurological deficits, decreased terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells, decreased intercellular adhesion molecule 1 (ICAM1) immunopositive vessels, decreased extravasated neutrophils and fewer activated microglia/macrophages, compared with their wild-type littermates. Furthermore, GeneChip analysis showed that postischemic induction of many transcripts known to promote inflammation and neuronal damage was less pronounced in the brains of C/EBPbeta-/- mice compared with C/EBPbeta+/+ mice. These results suggest a significant role for C/EBPbeta in postischemic inflammation and brain damage.

Separation of human adipocytes by size: hypertrophic fat cells display distinct gene expression

Enlarged adipocytes are associated with insulin resistance and are an independent predictor of type 2 diabetes. To understand the molecular link between these diseases and adipocyte hypertrophy, we developed a technique to separate human adipocytes from an adipose tissue sample into populations of small cells (mean 57.6+/-3.54 microm) and large cells (mean 100.1+/-3.94 microm). Microarray analysis of the cell populations separated from adipose tissue from three subjects identified 14 genes, of which five immune-related, with more than fourfold higher expression in large cells than small cells. Two of these genes were serum amyloid A (SAA) and transmembrane 4 L six family member 1 (TM4SF1). Real-time RT-PCR analysis of SAA and TM4SF1 expression in adipocytes from seven subjects revealed 19-fold and 22-fold higher expression in the large cells, respectively, and a correlation between adipocyte size and both SAA and TM4SF1 expression. The results were verified using immunohistochemistry. In comparison with 17 other human tissues and cell types by microarray, large adipocytes displayed by far the highest SAA and TM4SF1 expression. Thus, we have identified genes with markedly higher expression in large, compared with small, human adipocytes. These genes may link hypertrophic obesity to insulin resistance/type 2 diabetes.

Stress Activation of Mammary Epithelial Cell Xanthine Oxidoreductase Is Mediated by p38 MAPK and CCAAT/Enhancer-binding Protein-β

Xanthine oxidoreductase (XOR) catalyzes the formation of uric acid from xanthine and hypoxanthine and is recognized as a source of reactive oxygen and nitrogen species. Unexpectedly, XOR was found to play an essential role in milk secretion in the differentiating mammary gland, where it is an integral component of the milk fat globule. XOR gene expression in both mammary glands and differentiating mammary epithelial cells in culture is regulated by the lactogenic hormones prolactin and cortisol. Expression in mammary epithelial cells is also regulated by inflammatory cytokines and induced by cycloheximide. Cycloheximide was found to stimulate XOR gene expression in differentiating HC11 mouse mammary epithelial cells. Activation of XOR gene expression by both cycloheximide and inflammatory cytokines suggested that XOR may be regulated by stress-activated protein kinases, the MAPKs. We demonstrate here that XOR was induced in HC11 cells by low dose cycloheximide and that expression was blocked by inhibitors of p38 MAPK. Accumulation of phospho-p38 was stimulated by low dose cycloheximide. Low dose cycloheximide stress promoted phosphorylation and nuclear accumulation of the CCAAT/enhancer-binding protein-beta (C/EBPbeta) transcription factor, which was blocked by inhibition of p38. Furthermore, C/EBPbeta was found to activate the mouse XOR promoter, and XOR promoter-C/EBPbeta protein complexes were induced by low dose cycloheximide stress. These data demonstrate, for the first time, that mouse mammary epithelial cell XOR is regulated by p38 MAPK. They identify an essential function of the C/EBPbeta transcription factor in mouse XOR expression and suggest a potential role for p38 MAPK activation of C/EBPbeta in mammary epithelial cells.

Mitogen-inducible gene 6 is an endogenous inhibitor of HGF/Met-induced cell migration and neurite growth

Hepatocyte growth factor (HGF)/Met signaling controls cell migration, growth and differentiation in several embryonic organs and is implicated in human cancer. The physiologic mechanisms that attenuate Met signaling are not well understood. Here we report a mechanism by which mitogen-inducible gene 6 (Mig6; also called Gene 33 and receptor-associated late transducer) negatively regulates HGF/Met-induced cell migration. The effect is observed by Mig6 overexpression and is reversed by Mig6 small interfering RNA knock-down experiments; this indicates that endogenous Mig6 is part of a mechanism that inhibits Met signaling. Mig6 functions in cells of hepatic origin and in neurons, which suggests a role for Mig6 in different cell lineages. Mechanistically, Mig6 requires an intact Cdc42/Rac interactive binding site to exert its inhibitory action, which suggests that Mig6 acts, at least in part, distally from Met, possibly by inhibiting Rho-like GTPases. Because Mig6 also is induced by HGF stimulation, our results suggest that Mig6 is part of a negative feedback loop that attenuates Met functions in different contexts and cell types.