Differential fibronectin expression in activated C6 glial cells treated with ethanol

Protective Effects of Alpha-Lipoic Acid on Glutamate-Induced Cytotoxicity in C6 Glioma Cells

Glutamate-mediated cytotoxicity has been implicated in the pathogenesis of neurological diseases, including Parkinson's disease, Alzheimer's disease, and stroke. In this study, we investigated the protective effects of alpha-lipoic acid (ALA), a naturally occurring thiol antioxidant, on glutamate-induced cytotoxicity in cultured C6 astroglial cells. Exposure to high-dose glutamate (10 mM) caused oxidative stress and mitochondrial dysfunction through the elevation of reactive oxygen species, depletion of glutathione, and loss of the mitochondrial membrane potential (ΔΨ_m). Pretreatment with ALA (200 µM), however, significantly inhibited the glutamate-induced oxidative stress and mitochondrial dysfunction. ALA pretreatment dose-dependently suppressed glutamate-induced apoptotic events including altered nuclear morphology and activation of caspase-3. In addition, ALA significantly attenuated glutamate-induced endoplasmic reticulum (ER) stress markers; namely, glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), protein kinase regulated by RNA (PKR)-like ER-associated kinase (PERK), eukaryotic translation initiation factor 2 alpha (eIF2α), inositol-requiring enzyme 1 (IRE1), CCAAT/enhancer binding protein homologous protein (CHOP), and caspase-12. We confirmed that CHOP and caspase-12 are key mediators of glutamate-induced ER stress. Furthermore, exposure of the cells to a caspase-12-specific inhibitor and CHOP small interfering RNAs (siRNAs) led to restoration of the ΔΨ_m that was damaged by glutamate treatment. These results suggest that ALA can effectively suppress oxidative stress, mitochondrial dysfunction, and ER stress in astroglial cells.

Effects of Ethanol on Brain Extracellular Matrix: Implications for Alcohol Use Disorder

The brain extracellular matrix (ECM) occupies the space between cells and is involved in cell-matrix and cell-cell adhesion. However, in addition to providing structural support to brain tissue, the ECM activates cell signaling and controls synaptic transmission. The expression and activity of brain ECM components are regulated by alcohol exposure. This review will discuss what is currently known about the effects of alcohol on the activity and expression of brain ECM components. An interpretation of how these changes might promote alcohol use disorder (AUD) will be also provided. Ethanol (EtOH) exposure decreases levels of structural proteins involved in the interstitial matrix and basement membrane, with a concomitant increase in proteolytic enzymes that degrade these components. In contrast, EtOH exposure generally increases perineuronal net components. Because the ECM has been shown to regulate both synaptic plasticity and behavioral responses to drugs of abuse, regulation of the brain ECM by alcohol may be relevant to the development of alcoholism. Although investigation of the function of brain ECM in alcohol abuse is still in early stages, a greater understanding of the interplay between ECM and alcohol might lead to novel therapeutic strategies for treating AUD.

Protective effect of anthocyanidins against sodium dithionite-induced hypoxia injury in C6 glial cells

The present study investigated the neuroprotective effect of anthocyanidins, including cyanidin, delphinidin, malvidin, pelargonidin, and peonidin, against hypoxia in C6 glial cells. The cells were first incubated with a medium containing anthocynidin in normoxia condition and then with a medium containing sodium dithionite (Na2S2O4) in an anaerobic incubator for the hypoxia treatment. Methylthiazole tetrazolium test and evaluation of antioxidant enzyme activities and glutathione concentration were performed on the treated cells. At least 74% of the C6 cells preincubated with 25 mg/L of any of the five anthocyanidins in serum-free Dulbecco's modified Eagle's medium at 37 °C for 24 h survived the hypoxia treatment as compared with a survival rate between 47 and 59% for the control that was preincubated without an anthocyanidin. The cells preincubated with any of the five anthocyanidins showed higher catalase activity and glutathione concentration after the hypoxia treatment as compared with the corresponding samples without the preincubation with anthocyanidin. The cells preincubated with malvidin, pelargonidin, or peonidin also showed higher superoxide dismutase activities. The results of this study justify further research for the development of anthocyanidins into neuroprotective food ingredients against hypoxia injury.

Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

Evidence from in vivo and epidemiological studies suggests that organophosphorus insecticides (OPs) are developmental neurotoxicants, but possible underlying mechanisms are still unclear. Astrocytes are increasingly recognized for their active role in normal neuronal development. This study sought to investigate whether the widely-used OP diazinon (DZ), and its oxygen metabolite diazoxon (DZO), would affect glial-neuronal interactions as a potential mechanism of developmental neurotoxicity. Specifically, we investigated the effects of DZ and DZO on the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons. The results show that both DZ and DZO adversely affect astrocyte function, resulting in inhibited neurite outgrowth in hippocampal neurons. This effect appears to be mediated by oxidative stress, as indicated by OP-induced increased reactive oxygen species production in astrocytes and prevention of neurite outgrowth inhibition by antioxidants. The concentrations of OPs were devoid of cytotoxicity, and cause limited acetylcholinesterase inhibition in astrocytes (18 and 25% for DZ and DZO, respectively). Among astrocytic neuritogenic factors, the most important one is the extracellular matrix protein fibronectin. DZ and DZO decreased levels of fibronectin in astrocytes, and this effect was also attenuated by antioxidants. Underscoring the importance of fibronectin in this context, adding exogenous fibronectin to the co-culture system successfully prevented inhibition of neurite outgrowth caused by DZ and DZO. These results indicate that DZ and DZO increase oxidative stress in astrocytes, and this in turn modulates astrocytic fibronectin, leading to impaired neurite outgrowth in hippocampal neurons.

Neurotrophic factor expression in expandable cell populations from brain samples in living patients with Parkinson's disease

Cell-based therapies offer promise for patients with Parkinson's disease (PD); however, durable and effective transplantation substrates need to be defined. This study characterized the feasibility and growth properties of primary cultures established from small-volume brain biopsies taken during deep brain stimulation (DBS) surgery in patients with PD. The lineage and expression of neurotrophic factors with known beneficial actions in PD-affected brain circuitry were also evaluated. Nineteen patients with PD undergoing DBS surgery consented to brain biopsies prior to electrode implantation. Cultures from these samples exhibited exponential and plateau phases of growth and were readily expanded throughout multiple passages. There was robust expression of progenitor markers and the unexpected colocalization of neural and mesenchymal proteins. The oligodendrocyte transcription factor, Olig1, and the myelin-specific sphingolipid, galactocerebroside, were coexpressed with each of glial-derived neurotrophic factor, brain-derived neurotrophic factor, and cerebral dopamine neurotrophic factor. Fluorescence-activated cell sorting demonstrated homogeneous expression of both nestin and Olig1 throughout the expanded cultures. Cells remained viable after a year in cryostorage. These findings confirm the feasibility of small brain biopsies as an expandable source of autologous cell substrate in living patients and demonstrate the complex phenotype of these cells, with implications for therapeutic application in PD and other neurological diseases.

Implications of central immune signaling caused by drugs of abuse: mechanisms, mediators and new therapeutic approaches for prediction and treatment of drug dependence

In the past two decades a trickle of manuscripts examining the non-neuronal central nervous system immune consequences of the drugs of abuse has now swollen to a significant body of work. Initially, these studies reported associative evidence of central nervous system proinflammation resulting from exposure to the drugs of abuse demonstrating key implications for neurotoxicity and disease progression associated with, for example, HIV infection. However, more recently this drug-induced activation of central immune signaling is now understood to contribute substantially to the pharmacodynamic actions of the drugs of abuse, by enhancing the engagement of classical mesolimbic dopamine reward pathways and withdrawal centers. This review will highlight the key in vivo animal, human, biological and molecular evidence of these central immune signaling actions of opioids, alcohol, cocaine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA). Excitingly, this new appreciation of central immune signaling activity of drugs of abuse provides novel therapeutic interventions and opportunities to identify 'at risk' individuals through the use of immunogenetics. Discussion will also cover the evidence of modulation of this signaling by existing clinical and pre-clinical drug candidates, and novel pharmacological targets. Finally, following examination of the breadth of central immune signaling actions of the drugs of abuse highlighted here, the current known common immune signaling components will be outlined and their impact on established addiction neurocircuitry discussed, thereby synthesizing a common neuroimmune hypothesis of addiction.

Manganese inhibits the ability of astrocytes to promote neuronal differentiation

Manganese (Mn) is a known neurotoxicant and developmental neurotoxicant. As Mn has been shown to accumulate in astrocytes, we sought to investigate whether Mn would alter astrocyte-neuronal interactions, specifically the ability of astrocytes to promote differentiation of neurons. We found that exposure of rat cortical astrocytes to Mn (50-500 microM) impaired their ability to promote axonal and neurite outgrowth in hippocampal neurons. This effect of Mn appeared to be mediated by oxidative stress, as it was reversed by antioxidants (melatonin and PBN) and by increasing glutathione levels, while it was potentiated by glutathione depletion in astrocytes. As the extracellular matrix protein fibronectin plays an important role in astrocyte-mediated neuronal neurite outgrowth, we also investigated the effect of Mn on fibronectin. Mn caused a concentration-dependent decrease of fibronectin protein and mRNA in astrocytes lysate and of fibronectin protein in astrocyte medium; these effects were also antagonized by antioxidants. Exposure of astrocytes to two oxidants, H2O2 and DMNQ, similarly impaired their neuritogenic action, and led to a decreased expression of fibronectin. Mn had no inhibitory effect on neurite outgrowth when applied directly onto hippocampal neurons, where it actually caused a small increase in neuritogenesis. These results indicate that Mn, by targeting astrocytes, affects their ability to promote neuronal differentiation by a mechanism which is likely to involve oxidative stress.

Candidate genes, pathways and mechanisms for alcoholism: an expanded convergent functional genomics approach

We describe a comprehensive translational approach for identifying candidate genes for alcoholism. The approach relies on the cross-matching of animal model brain gene expression data with human genetic linkage data, as well as human tissue data and biological roles data, an approach termed convergent functional genomics. An analysis of three animal model paradigms, based on inbred alcohol-preferring (iP) and alcohol-non-preferring (iNP) rats, and their response to treatments with alcohol, was used. A comprehensive analysis of microarray gene expression data from five key brain regions (frontal cortex, amygdala, caudate-putamen, nucleus accumbens and hippocampus) was carried out. The Bayesian-like integration of multiple independent lines of evidence, each by itself lacking sufficient discriminatory power, led to the identification of high probability candidate genes, pathways and mechanisms for alcoholism. These data reveal that alcohol has pleiotropic effects on multiple systems, which may explain the diverse neuropsychiatric and medical pathology in alcoholism. Some of the pathways identified suggest avenues for pharmacotherapy of alcoholism with existing agents, such as angiotensin-converting enzyme (ACE) inhibitors. Experiments we carried out in alcohol-preferring rats with an ACE inhibitor show a marked modulation of alcohol intake. Other pathways are new potential targets for drug development. The emergent overall picture is that physical and physiological robustness may permit alcohol-preferring individuals to withstand the aversive effects of alcohol. In conjunction with a higher reactivity to its rewarding effects, they may able to ingest enough of this nonspecific drug for a strong hedonic and addictive effect to occur.

Ethanol-Inhibited [3H]Thymidine Incorporation via Protein Kinase C-p44/42 Mitogen-Activated Protein Kinase/Phospholipase A2Signal Pathway in Renal Proximal Tubule Cells

BACKGROUND

Ethanol exposure leads to changes of cell proliferation in a variety of cell types. However, how ethanol affects the proliferation of renal proximal tubule cells is not known.

METHODS

To examine the effect of ethanol on cell proliferation and its related signaling pathway, [H]thymidine incorporation, release of [H]arachidonic acid (AA), and Western blotting of protein kinase C (PKC)/mitogen-activated protein kinase (MAPK) were performed in primary cultured rabbit renal proximal tubule cells.

RESULTS

Ethanol inhibited [H]thymidine incorporation in a time- and dose-dependent manner. An inhibitory effect of ethanol on [H]thymidine incorporation was predominantly observed after 12 hr of treatment with 100 mM ethanol. Ethanol increased AA release and prostaglandin E2 production. In addition, ethanol-induced inhibition of [H]thymidine incorporation was blocked by phospholipase A2 inhibitors and was significantly blocked by PKC inhibitors. Indeed, ethanol induced a PKC translocation from the cytosolic to the membrane fraction. In addition, ethanol-induced inhibition of [H]thymidine incorporation was blocked by PD 98059 (a p44/42 MAPK inhibitor), but not by SB 203580 (a p38 MAPK inhibitor), and ethanol increased the phosphorylation of p44/42 MAPK. Results of phosphorylated p44/42 MAPK by ethanol were consistent with those of [H]thymidine incorporation and [H]AA-release experiments.

CONCLUSIONS

Ethanol inhibited [H]thymidine incorporation via PKC, p44/42 MAPK, and phospholipase A2 signaling pathways in primary cultured renal proximal tubule cells.

Lipopolysaccharide plus 12-o-tetradecanoylphorbol 13-acetate induction of migration and invasion of glioma cells in vitro and in vivo: Differential inhibitory effects of flavonoids

In an earlier study, we reported that nitric oxide is involved in lipopolysaccharide plus 12-o-tetradecanoylphorbol 13-acetate-induced malignant transformation via increases in metalloproteinase 9 enzyme activity and inducible nitric oxide synthase gene expression in rat glioma C6 cells, however the mechanism has remained undefined. Lipopolysaccharide plus 12-o-tetradecanoylphorbol 13-acetate, but not lipopolysaccharide or 12-o-tetradecanoylphorbol 13-acetate alone, induced transformation in glioma C6 cells (but not in human glioblastoma cells GBM-8401 cells) without affecting their viability. An increase in inducible nitric oxide synthase protein expression, nitric oxide production, and metalloproteinase 9 enzyme activity is identified lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate-treated C6 cells, however lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate and 12-o-tetradecanoylphorbol 13-acetate (but not lipopolysaccharide) addition shows the similar inductive pattern on metalloproteinase 9 enzyme activity without affecting inducible nitric oxide synthase protein expression and nitric oxide production in GBM-8401 cells. Treatment of C6 cells with lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate increases the expression of phosphorylated extracellular regulated protein kinases and Jun N-terminal kinases, but not p38, proteins, and an addition of the extracellular regulated protein kinases inhibitor PD98059 or Jun N-terminal kinases inhibitors SP600125, but not the p38 inhibitor SB203580, significantly blocked lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate-induced inducible nitric oxide synthase protein expression and metalloproteinase 9 enzyme activity accompanied by blocking morphological transformation in C6 cells. Among 19 structurally related flavonoids, kaempferol and wogonin exhibit significant inhibitory effects on lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate-induced morphological transformation and colony formation, and attenuation of inducible nitric oxide synthase, phosphorylated extracellular regulated protein kinases protein expression, and metalloproteinase 9 enzyme activity was observed. 2'-OH flavone at a dose of 100 microM inhibition of lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate-induced events via apoptosis induction is identified. Furthermore, lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate, but not lipopolysaccharide or 12-o-tetradecanoylphorbol 13-acetate, induces tumoral invasion and migration in vitro and in vivo, and those are blocked by kaempferol and wogonin addition. These data suggest that combination of lipopolysaccharide and 12-o-tetradecanoylphorbol 13-acetate promotes tumoral progression via activating metalloproteinase 9 enzyme activity and inducible nitric oxide synthase gene expression, which is located downstream of mitogen-activated protein kinases activation, in rat glioma cells C6. Kaempferol and wogonin exhibit effective inhibitory effects on lipopolysaccharide/12-o-tetradecanoylphorbol 13-acetate-induced events, and thus possess the potential for further development.

Differential effects of ethanol on glial signal transduction initiated by lipopolysaccharide and interferon-gamma

Although the pathogenic effects of alcohol abuse on brain are well established, its specific effects on the intracellular signal transduction pathways of glial cells in the central nervous system (CNS) are poorly understood. In this study, we evaluated how ethanol affects the glial signal transduction associated with inflammatory activation. Lipopolysaccharide (LPS), gangliosides, and interferon (IFN)-gamma induced the inflammatory activation of glia, which was differentially influenced by ethanol: 1) ethanol inhibited LPS- or gangliosides-induced, but not IFNgamma-induced, glial activation as demonstrated by the production of nitric oxide and the expression of inflammatory genes such as interleukin-1beta, tumor necrosis factor-alpha, IP-10, and CD86; 2) nuclear factor (NF)-kappaB or JAK/STAT1 pathway was necessary for LPS- or IFNgamma-induced glial activation, respectively; 3) ethanol inhibited LPS-induced NF-kappaB activation; and 4) ethanol did not significantly affect IFNgamma-induced STAT1/IRF-1 activation. Based on these results, ethanol seems to inhibit selectively some parts of the glial signal transduction pathways that are associated with inflammatory activation, which may lead to the deregulation of CNS inflammatory responses.

Corpus callosal microstructural integrity influences interhemispheric processing: a diffusion tensor imaging study

Normal aging and chronic alcoholism result in disruption of brain white matter microstructure that does not typically cause complete lesions but may underlie degradation of functions requiring interhemispheric information transfer. We examined whether the microstructural integrity of the corpus callosum assessed with diffusion tensor imaging (DTI) would relate to interhemispheric processing speed. DTI yields estimates of fractional anisotropy (FA), a measure of orientation and intravoxel coherence of water diffusion usually in white matter fibers, and diffusivity (<D>), a measure of the amount of intracellular and extracellular fluid diffusion. We tested the hypothesis that FA and <D> would be correlated with (i) the crossed-uncrossed difference (CUD), testing visuomotor interhemispheric transfer; and (ii) the redundant targets effect (RTE), testing parallel processing of visual information presented to each cerebral hemisphere. FA was lower and <D> higher in alcoholics than in controls. In controls but not alcoholics, large CUDs correlated with low FA and high <D> in total corpus callosum and regionally in the genu and splenium. In alcoholics but not controls, small RTEs, elicited with equiluminant stimuli, correlated with low FA in genu and splenium and high <D> in the callosal body. The results provide in vivo evidence for disruption of corpus callosum microstructure in normal aging and alcoholism that has functional ramifications for efficiency in interhemispheric processing.

Alcohol and gene expression in the central nervous system

AIMS

To describe recent research focusing on the analysis of gene and protein expression relevant to understanding ethanol consumption, dependence and effects, in order to identify common themes.

METHODS

A selective literature search was used to collate the relevant data.

RESULTS

Over 160 genes have been individually assessed before or after ethanol administration, as well as in genetically selected lines. Techniques for studying gene expression include northern blots, differential display, real time reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization. More recently, high throughput functional genomic technology, such as DNA microarrays, has been used to examine gene expression. Recent gene expression analyses have dramatically increased the number of candidate genes (nine array papers have illuminated 600 novel gene transcripts that may contribute to alcohol abuse and alcoholism).

CONCLUSIONS

Although functional genomic experiments (transcriptome analysis) have failed to identify a single alcoholism gene, they have illuminated important pathways and gene products that may contribute to the risk of alcohol abuse and alcoholism.

Ethanol selectively modulates inflammatory activation signaling of brain microglia

In spite of well-known deleterious effects of alcohol on the nervous system in general, its specific effect on the brain immune system remains poorly understood. In order to better understand the effect of alcohol consumption on the innate immunity and inflammatory responses in the central nervous system (CNS), we sought to determine how ethanol influences inflammatory activation of microglia that function as the resident immune defense system of the brain. After treatment of BV-2 mouse microglial cells or rat primary microglia cultures with various stimuli, nitric oxide (NO) production was measured as an indicator of microglial activation. Pretreatment of the cells with ethanol (10-100 mM) for 1 h resulted in a significant decrease in lipopolysaccharide (LPS)-induced, but not interferon-gamma (IFNgamma)-induced, NO production, indicating that ethanol specifically inhibits LPS-induced inflammatory activation of microglia. This was further supported by the ethanol inhibition of LPS-induced IL-1beta expression. In addition, ethanol pretreatment selectively regulated LPS-induced NF-kappaB signaling pathway without affecting IFNgamma-induced signal transducer and activator of transcription 1 (STAT1) phosphorylation, interferon regulatory factor-1 (IRF-1) induction or IFNgamma-inducible IP-10 expression. The modulation of LPS-induced NF-kappaB by ethanol was due to the inhibition of coactivator p300. Altogether, these results suggest that acute ethanol exposure may selectively modulate signal transduction pathways associated with inflammatory activation of microglia, which may lead to derangement of CNS immune and inflammatory responses.

Dual mechanisms for ethanol-induced inhibition of monocyte chemotactic protein-3 mRNA expression in activated glial cells

The differential display of mRNA technique was used to screen the expressed genes in control and 50 mM chronic ethanol-treated rat C6 glial cells, with and without activation by lipopolysaccharide (LPS) combined with phorbol 12-myristate 13-acetate (PMA). One differentially expressed transcript was identified as that corresponding to the chemokine monocyte chemotactic protein (MCP)-3. MCP-3 is a broadly active chemokine that functions in chemoattraction and activation of monocytes, T lymphocytes, eosinophils, basophils, natural killer cells, and dendritic cells. Steady-state MCP-3 mRNA levels were elevated 6-fold after 24-h stimulation of control cells but less than 3-fold after stimulation of 9-day chronic ethanol-exposed cells. One- and 5-day exposures to 50 mM ethanol were not effective at reducing steady-state MCP-3 mRNA levels in stimulated cells, whereas 1-day exposure to >150 mM ethanol was effective. Stimulation with tumor necrosis factor-alpha elevated MCP-3 mRNA in C6 glial cells to a lesser extent than with LPS plus PMA, but the effects of ethanol were consistent. To gain insight into possible mechanisms for ethanol-induced reductions in steady-state MCP-3 mRNA, additional studies examined nuclear MCP-3 RNA levels and MCP-3 mRNA degradation. MCP-3 RNA content was greatly reduced in isolated nuclei from acute and chronic ethanol-exposed cells, suggesting transcriptional inhibition. On the other hand, acute ethanol exposure enhanced degradation of preexisting MCP-3 mRNA, indicating message destabilization. Thus, the results are consistent with a dual mechanism for ethanol-induced reductions in steady-state MCP-3 mRNA levels.

Expression profiling identifies strain-specific changes associated with ethanol withdrawal in mice

Mice that exhibit characteristics of physical dependence following ethanol exposure serve as useful models of alcoholism in humans. The DBA/2J and C57BL/6J inbred strains differ in their behavioral response to ethanol withdrawal. Alterations in gene expression are believed to underlie neuroadaptation to ethanol dependence and tolerance. Therefore, the differences in ethanol withdrawal severity observed between the DBA/2J and C57BL/6J strains may be related to differential regulation of gene expression. We have used cDNA microarrays to determine the gene expression profile in the hippocampus of DBA/2J and C57BL/6J mice during withdrawal after chronic and acute ethanol exposure. Of the 7634 genes surveyed, approximately 2% were consistently differentially expressed by at least 1.4-fold in DBA/2J mice during chronic ethanol withdrawal. Less than 1% of the genes showed altered expression in C57BL/6J mice under the same conditions, or in DBA/2J mice during acute ethanol withdrawal. Strain- and treatment-specific patterns of altered expression were observed for multiple genes associated with the Janus kinase/signal transducers and activators of transcription and the mitogen activated protein kinase pathways. Genes associated with both pathways are regulated in DBA/2J mice during chronic ethanol withdrawal, and to a lesser extent during acute ethanol withdrawal. Only those genes associated with the mitogen-activated protein kinase (MAPK) pathway exhibited changes in expression in C57BL/6J mice during ethanol withdrawal. Furthermore, genes associated with retinoic acid-mediated signaling show differential expression exclusively in C57BL/6J mice. These findings represent significant differences in cellular adaptation to ethanol between the DBA/2J and C57BL/6J strains.