Factor Cyclic AMP-responsive Element Binding Research Articles

CaMKIV/CREB/BDNF signaling pathway expression in prefrontal cortex, amygdala, hippocampus and hypothalamus in streptozotocin-induced diabetic mice with anxious-like behavior.

Individuals with diabetes mellitus (DM) tend to manifest anxiety and depression, which could be related to changes in the expression of calcium/calmodulin-dependent protein kinase IV (CaMKIV), transcription factor cyclic AMP-responsive element binding protein (CREB), phosphorylated CREB (pCREB) and brain-derived neurotrophic factor (BDNF) in different brain regions. The objective of this study was to determine whether mice with type 1 diabetes (T1DM) induced with streptozotocin show a profile of anxious-type behaviors and alterations in the expression/activity of CaMKIV, CREB, pCREB and BDNF in different regions of the brain (prefrontal cortex, amygdala, hippocampus and hypothalamus) in comparison to non-diabetic mice (NDB). Mice with 3months of chronic DM showed an anxious-like behavioral profile in two anxiety tests (Open Field and Elevated Plus Maze), when compared to NDB. There were significant differences in the expression of cell signaling proteins: diabetic mice had a lower expression of CaMKIV in the hippocampus, a greater expression of CREB in the amygdala and hypothalamus, as well as a lower pCREB/CREB in hypothalamus than NDB mice (P < 0.05). This is the first study evaluating the expression of CaMKIV in the brain of animals with DM, who presented lower expression of this protein in the hippocampus. In addition, it is the first time that CREB was evaluated in amygdala and hypothalamus of animals with DM, who presented a higher expression. Further research is necessary to determine the possible link between expression of CaMKIV and CREB, and the behavioral profile of anxiety in diabetic animals.

Adipose expression of CREB3L3 modulates body weight during obesity

We found the hepatic transcription factor Cyclic-AMP Responsive Element Binding Protein 3-like-3 (CREB3L3) to be expressed in adipose tissue, and selectively downregulated in the more metabolically protective subcutaneous adipose tissue in obese mice and humans. We sought to elucidate the specific role of this factor in adipose biology. CREB3L3 fat-specific knockout mice were fed a high-fat diet to induce obesity and metabolic dysfunction. Additionally, we injected a flip-excision adeno-associated virus directly into the subcutaneous inguinal adipose tissue of Adiponectin-Cre mice to create a depot-specific overexpression model for further assessment. Fat-specific ablation of CREB3L3 enhanced weight gain and insulin resistance following high-fat feeding, as fat-specific knockout mice expended less energy and possessed more inflammatory adipose tissue. Conversely, inguinal fat CREB3L3 overexpression deterred diet-induced obesity and ameliorated metabolic dysfunction. Together, this study highlights the relevance of CREB3L3 in obese adipose tissue and demonstrates its role as a powerful body weight modulator.

Role of Liver Growth Factor (LGF) in Parkinson's Disease: Molecular Insights and Therapeutic Opportunities.

Parkinson's disease is the most common neurodegenerative movement disorder with unclear etiology and only symptomatic treatment to date. Toward the development of novel disease-modifying agents, neurotrophic factors represent a reasonable and promising therapeutic approach. However, despite the robust preclinical evidence, clinical trials using glial-derived neurotrophic factor (GDNF) and neurturin have been unsuccessful. In this direction, the therapeutic potential of other trophic factors in PD and the elucidation of the underlying molecular mechanisms are of paramount importance. The liver growth factor (LGF) is an albumin-bilirubin complex acting as a hepatic mitogen, which also exerts regenerative effects on several extrahepatic tissues including the brain. Accumulating evidence suggests that intracerebral and peripheral administration of LGF can enhance the outgrowth of nigrostriatal dopaminergic axonal terminals; promote the survival, migration, and differentiation of neuronal stem cells; and partially protect against dopaminergic neuronal loss in the substantia nigra of PD animal models. In most studies, these effects are accompanied by improved motor behavior of the animals. Potential underlying mechanisms involve transient microglial activation, TNF-α upregulation, and activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and of the transcription factor cyclic AMP response-element binding protein (CREB), along with anti-inflammatory and antioxidant pathways. Herein, we summarize recent preclinical evidence on the potential role of LGF in PD pathogenesis, aiming to shed more light on the underlying molecular mechanisms and reveal novel therapeutic opportunities for this debilitating disease.

138-OR: Ablating Adipose CREB3l3 Preserves Metabolic Health during Obesity

During obesity, the adipose tissue becomes supersaturated with lipids, leading to inflammation, the release of free fatty acids into the bloodstream, and the development of metabolic syndrome. However, a small obese subpopulation does not develop metabolic syndrome and has been deemed to have “metabolically healthy” obesity (MHO). Our lab has created a mouse model that mimics MHO, via adipose-specific ablation of the ER-bound transcription factor cyclic-AMP Responsive Element Binding Protein 3-like-3 (CREB3L3). We have discovered that CREB3L3 is not only expressed in adipose tissue, but selectively downregulated in the “metabolically protective” subcutaneous fat in obese mice and human patients. We hypothesized that CREB3L3 downregulation could contribute to the healthier metabolic profile of subcutaneous fat during obesity, so we created a CREB3L3 fat-specific knockout (KO) mouse. CREB3L3 KO mice had enhanced diet-induced obesity following 12 weeks of high-fat diet feeding and significantly larger inguinal white adipose tissue (iWAT) and epididymal white adipose tissue (eWAT) compared to wild type controls. Unexpectedly, the KO mice do not exhibit the reduction in glucose tolerance or insulin sensitivity that would be expected with their more obese phenotype, which is likely due to the enlarged adipose tissues. The KO mice do not exhibit the expected dyslipidemia or hepatic steatosis, suggesting that the KO adipose tissue sequesters lipids away from these spaces. Additionally, the KO iWAT and eWAT have reduced inflammatory marker expression, suggesting that CREB3L3 plays a role in adipose inflammation. Indeed, we observed that obese mice overexpressing CREB3L3 via direct injection of a CREB3L3 adeno-associated virus into the iWAT and eWAT had marked upregulation of IL-1B and MCP1 in both of these tissues. Together, these data suggest that adipose ablation of CREB3L3 preserves metabolic health during obesity by allowing the adipose tissue to meet the body’s lipid storage demands via healthy expansion. Disclosure M.A. McCann: None. S. Li: None. Y. Li: None. V. Gil: None. C. LIew: None. Funding National Institutes of Health (R01DK109015)

P.2.e.003 The impact of antipsychotic drugs in depression: a role for adult neurogenesis?

Constituents extracted from the leaves of the Ginkgo biloba tree possess beneficial properties that may buffer the aging nervous system from deterioration due to oxidative stress. In the present investigation, a standardized extract of G. biloba (EGb 761) or an equal volume of the vehicle was administered (100 mg/kg/day) to senescent (20-month) C57BL/6 male mice for up to 82 consecutive days. Animals were tested twice in the Morris water maze (MWM) after 28 and 70 days of treatment. No differences were observed in acquisition or retention of performance on the water maze. Elevated-plus maze (EPM) trials were conducted prior to and subsequent to the chronic treatment regimen. Marked baseline differences in plus-maze performance were present in the first experiment. A second experiment used a matched-pairs design to minimize preexisting differences. Results supported the hypothesis that EGb 761 may serve as an antistress buffer, attenuating the increase in anxiety typically observed in animals after cold water exposure. Tissue samples from the hippocampus and cortex were analyzed by Western blot for the transcription factor cyclic-AMP response element binding (CREB) protein. EGb 761 had no significant effect on immunoreactivity to CREB from either the hippocampus or the cerebral cortex.

The disruption of CREB/BDNF/TrkB signaling. Dynamic changes induced by zinc deficiency

Background Our previous studies indicated that expression of several proteins involved in numerous aspects of plasticity in the central nervous system (CNS) is modulated by four-week dietary deprivation of trace element zinc. The levels of the phosphorylated forms of transcription factor cyclic AMP response-element binding (pCREB) protein, neurotrophin brain derived neurotrophic factor (BDNF) protein and high-affinity tropomyosine-related kinase B receptor (TrkB) protein were significantly decreased in the hippocampus of rats fed a zinc-deficient diet for four weeks. However, no changes of these proteins between rats subjected to four-week zinc restriction and the control animals were found in the prefrontal cortex. Aims Here we examined whether six-week dietary zinc deprivation induces changes in the protein levels of pCREB, BDNF and TrkB in the prefrontal cortex and hippocampus of rats. Methods Male Sprague Dowley rats (5-week-old) were fed a 50 mg Zn/kg (control group) or a 3 mg Zn/kg (zinc deficient group) diet for six weeks. The protein levels of pCREB, BDNF and TrkB were measured using western blotting. Results The levels of pCREB and BDNF proteins were significantly decreased (by 46% and 52%) in the prefrontal cortex and (by 44% and 54%) in the hippocampus of rats subjected to six-week zinc-deficient diet when compared with that of the control animals. Interestingly, at the same time point an increase (by 153%) in TrkB protein was observed in the prefrontal cortex of group fed zinc-deficient diet for six weeks compared to the control group. Conclusions The present data reports that six-week dietary zinc deprivation, unlike four-week zinc restriction, influences not only the hippocampus, but also the prefrontal cortex of rats. One can assume that CREB/ BDNF/TrkB proteins levels changes are dynamic in response to zinc deprivation and vary not only across brain regions but also in the course of time.

Roles of CREB in the regulation of FMRP by group I metabotropic glutamate receptors in cingulate cortex

BackgroundFragile X syndrome is caused by lack of fragile X mental retardation protein (FMRP) due to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the central nervous system contribute to higher brain functions including learning/memory, mental disorders and persistent pain. The transcription factor cyclic AMP-responsive element binding protein (CREB) is involved in important neuronal functions, such as synaptic plasticity and neuronal survival. Our recent study has shown that stimulation of Group I mGluRs upregulated FMRP and activated CREB in anterior cingulate cortex (ACC), a key region for brain cognitive and executive functions, suggesting that activation of Group I mGluRs may upregulate FMRP through CREB signaling pathway.ResultsIn this study, we demonstrate that CREB contributes to the regulation of FMRP by Group I mGluRs. In ACC neurons of adult mice overexpressing dominant active CREB mutant, the upregulation of FMRP by stimulating Group I mGluR is enhanced compared to wild-type mice. However, the regulation of FMRP by Group I mGluRs is not altered by overexpression of Ca2+-insensitive mutant form of downstream regulatory element antagonist modulator (DREAM), a transcriptional repressor involved in synaptic transmission and plasticity.ConclusionOur study has provided further evidence for CREB involvement in regulation of FMRP by Group I mGluRs in ACC neurons, and may help to elucidate the pathogenesis of fragile X syndrome.

Coincidence Signaling of Dopamine D1-Like and M1 Muscarinic Receptors in the Regulation of Cyclic AMP Formation and CREB Phosphorylation in Mouse Prefrontal Cortex

In the prefrontal cortex, dopamine D₁-like and M₁ muscarinic receptors are both involved in the regulation of attentional, cognitive and emotional processes but so far no information has been provided on their functional interaction. In the present study we show that in mouse medial prefrontal cortex, concomitant activation of M₁ muscarinic receptors potentiated D₁-like receptor-induced cyclic AMP formation through a mechanism involving activation of G_q/11 and the release of G protein βγ subunits. Immunohistochemical studies indicated that the adenylyl cyclase isoforms AC2 and AC4 are expressed in mouse prefrontal cortex and that they colocalize with D₁-like receptors with a greater association for AC4. In primary cultures of frontal cortex neurons, D₁-like receptor-induced Ser133 phosphorylation of the transcription factor cyclic AMP-responsive element binding protein (CREB) was potentiated by concurrent stimulation of M₁ receptors. Suppression of AC4 expression with small interfering RNA transfection reduced D₁ stimulation of cyclic AMP formation and CREB phosphorylation and abolished the M₁ potentiation, whereas knockdown of AC2 had no significant effects. These data indicate that in mouse prefrontal cortex G_q/11-coupled M₁ receptor and G_s-coupled D₁-like receptor inputs converge on AC4 with a consequent enhancement of cyclic AMP formation and signaling to the nucleus.

Dynamic O-GlcNAc modification regulates CREB-mediated gene expression and memory formation

The transcription factor CREB is a key regulator of many neuronal processes, including brain development, circadian rhythm, and long-term memory. Studies of CREB have focused on its phosphorylation, although the diversity of CREB functions in the brain suggests additional forms of regulation. Here we expand on a chemoenzymatic strategy for quantifying glycosylation stoichiometries to characterize the functional roles of CREB glycosylation in neurons. We show that CREB is dynamically O-GlcNAc-modified in response to neuronal activity and glycosylation represses CREB-dependent transcription by impairing its association with the co-activator CRTC/TORC. Blocking glycosylation of CREB altered cellular function and behavioral plasticity, enhancing both axonal and dendritic growth and long-term memory consolidation. Our findings demonstrate a new role for O-glycosylation in memory formation and provide a mechanistic understanding of how glycosylation contributes to critical neuronal functions. Moreover, we identify a previously unknown mechanism for the regulation of activity-dependent gene expression, neural development, and memory.

The transcription factor cyclic AMP–responsive element–binding protein H regulates triglyceride metabolism

Here we report that the transcription factor cyclic AMP-responsive element-binding protein H (CREB-H, encoded by CREB3L3) is required for the maintenance of normal plasma triglyceride concentrations. CREB-H-deficient mice showed hypertriglyceridemia secondary to inefficient triglyceride clearance catalyzed by lipoprotein lipase (Lpl), partly due to defective expression of the Lpl coactivators Apoc2, Apoa4 and Apoa5 (encoding apolipoproteins C2, A4 and A5, respectively) and concurrent augmentation of the Lpl inhibitor Apoc3. We identified multiple nonsynonymous mutations in CREB3L3 that produced hypomorphic or nonfunctional CREB-H protein in humans with extreme hypertriglyceridemia, implying a crucial role for CREB-H in human triglyceride metabolism.

Claudin-18 gene structure, regulation, and expression is evolutionary conserved in mammals

Claudin-18 isoform 2 (CLDN18.2) is one of the few members of the human claudin family of tight junction molecules with strict restriction to one cell lineage. The objective of the current study was to compare molecular structure and tissue distribution of this gastrocyte specific molecule in mammals. We show here that the CLDN18.2 protein sequence is highly conserved, in particular with regard to functionally relevant domains in mouse, rat, rabbit, dog, monkey and human and also in lizards. Moreover, promoter regions of orthologs are highly homologous, including the binding site of the transcription factor cyclic AMP–responsive element binding protein (CREB), which is known to regulate activation of human CLDN18.2. Employing RT-PCR and immunohistochemistry, we found that, analogous to the human gene, all orthologous CLDN18.2 transcripts and proteins are exclusively expressed in differentiated gastric cells. Gene structure, promoter elements and RNA expression pattern of the lung-tissue specific Claudin-18 isoform 1 (CLDN18.1) as well, are homologous across species. These findings exemplify phylogenetic conservation of lineage-specific members of a multigene family. Given that CLDN18.2 is a novel drug target candidate, our data is also relevant for drug development as it reveals all six investigated mammalian species as suitable models for testing safety of CLDN18.2 targeting regimen.

Persistent Cyclooxygenase-2 Inhibition Downregulates NF-κB, Resulting in Chronic Intestinal Inflammation in the Min/+ Mouse Model of Colon Tumorigenesis

Cyclooxygenase-2 (COX-2) inhibition prevents adenoma formation in humans and mouse models of colon cancer. The selective COX-2 inhibitor celecoxib reduces COX-2 and prostaglandin E(2) (PGE(2)) expression and adenomas in the intestine of Min/+ mice after treatment for several weeks, but prolonged treatment increases PGE(2) production, resulting in drug-resistant tumor formation and transforming growth factor beta (TGFbeta)-dependent intestinal fibrosis. In this study, we examined pathways that regulate COX-2 expression and suppress chronic intestinal inflammation. We show that NF-kappaB signaling was inhibited in the ileum of Min/+ mice receiving long-term treatment with celecoxib. This effect was associated with inhibition of TGFbeta-associated kinase-1 and IkappaB kinase alpha/beta activities and reduced expression of the Toll-like receptor (TLR) 2 and TLR4 that enhance colonic barrier function. Additionally, we observed reduced activities of protein kinases c-Jun NH(2)-terminal kinase 1 and protein kinase A and transcription factor cyclic AMP-responsive element binding protein, regulators of COX-2 expression, which cross-talk with NF-kappaB. In ileum subjected to long-term celecoxib treatment, we noted relatively higher expression of COX-2, vascular endothelial growth factor, and interleukin-1beta in Paneth cells, whereas NF-kappaB and COX-2 were more strongly expressed by an expanded population of stromal myofibroblasts. Our findings argue that celecoxib resistance is an acquired adaptation to changes in the crypt microenvironment that is associated with chronic intestinal inflammation and impaired acute wound-healing responsiveness.

Nucleus Accumbens CREB Activity is Necessary for Nicotine Conditioned Place Preference

The ability of nicotine to alter firing of dopamine neurons is the first step leading to nicotine reward, but activation of intracellular signaling pathways downstream of nicotinic acetylcholine receptors is likely to be critical for longer-term consequences of nicotine exposure, including conditioned reward. The transcription factor cyclic AMP-regulated binding protein (CREB) is important for new gene transcription and in its phosphorylated form (pCREB) promotes long-term changes in synaptic strength. Previous studies have implicated nucleus accumbens (NAc) CREB activity in the modulation of cocaine and morphine reward, and have shown that nicotine conditioned place preference (CPP) is associated with NAc CREB activation. It is not clear whether CPP elicits phosphorylation of CREB or if elevations in pCREB support nicotine CPP. In the current study, we investigated levels of CREB and pCREB during Pavlovian conditioning with nicotine in a novel context in the absence of chamber choice. Nicotine context conditioning resulted in elevated pCREB levels in the NAc shell but not the NAc core of mice following placement in the nicotine-paired chamber in the absence of nicotine. To test if CREB activity in the NAc shell contributes to cue-induced responses that may precipitate nicotine seeking, we used viral-mediated gene transfer of a dominant negative CREB construct in the NAc shell of C57BL/6J mice and found that disruption of CREB activation prior to training blocked nicotine place preference across a range of doses. Taken together, these studies identify the NAc shell as a brain region where CREB activity is essential for nicotine CPP.

TGFBI Deficiency Predisposes Mice to Spontaneous Tumor Development

Loss of TGFBI, a secreted protein induced by transforming growth factor-beta, has been implicated in cell proliferation, tumor progression, and angiogenesis by in vitro studies. However, in vivo antitumor functions of TGFBI as well as the underlying molecular mechanism are not well understood. To these aims, we have generated a mouse model with disruption of TGFBI genomic locus. Mice lacking TGFBI show a retarded growth and are prone to spontaneous tumors and 7,12-dimethylbenz(a)anthracene-induced skin tumors. In relation to wild-type (WT) mouse embryonic fibroblasts (MEF), TGFBI(-/-) MEFs display increased frequencies of chromosomal aberration and micronuclei formation and exhibit an enhanced proliferation and early S-phase entry. Cyclin D1 is up-regulated in TGFBI(-/-) MEFs, which correlates with aberrant activation of transcription factor cyclic AMP-responsive element binding protein (CREB) identified by chromatin immunoprecipitation and luciferase reporter assays. TGFBI reconstitution in TGFBI(-/-) cells by either retroviral infection with WT TGFBI gene or supplement with recombinant mouse TGFBI protein in the culture medium leads to the suppression of CREB activation and cyclin D1 expression, and further inhibition of cell proliferation. Cyclin D1 up-regulation was also identified in most of the tumors arising from TGFBI(-/-) mice. Our studies provide the first evidence that TGFBI functions as a tumor suppressor in vivo.

Claudin-18 Splice Variant 2 Is a Pan-Cancer Target Suitable for Therapeutic Antibody Development

Antibody-based cancer therapies have emerged as the most promising therapeutics in oncology. The purpose of this study was to discover novel targets for therapeutic antibodies in solid cancer. We combined data mining and wet-bench experiments to identify strictly gastrocyte lineage-specific cell surface molecules and to validate them as therapeutic antibody targets. We identified isoform 2 of the tight junction molecule claudin-18 (CLDN18.2) as a highly selective cell lineage marker. Its expression in normal tissues is strictly confined to differentiated epithelial cells of the gastric mucosa, but it is absent from the gastric stem cell zone. CLDN18.2 is retained on malignant transformation and is expressed in a significant proportion of primary gastric cancers and the metastases thereof. In addition to its orthotopic expression, we found frequent ectopic activation of CLDN18.2 in pancreatic, esophageal, ovarian, and lung tumors, correlating with distinct histologic subtypes. The activation of CLDN18.2 depends on the binding of the transcription factor cyclic AMP-responsive element binding protein to its unmethylated consensus site. Most importantly, we were able to raise monoclonal antibodies that bind to CLDN18.2 but not to its lung-specific splice variant and recognize the antigen on the surface of cancer cells. Its highly restricted expression pattern in normal tissues, its frequent ectopic activation in a diversity of human cancers, and the ability to specifically target this molecule at the cell surface of tumor cells qualify CLDN18.2 as a novel, highly attractive pan-cancer target for the antibody therapy of epithelial tumors.

Calcium/calmodulin kinase kinase β has a male-specific role in memory formation

The calcium/calmodulin (CaM) kinase cascade regulates gene transcription, which is required for long-term memory formation. Previous studies with Camkk2 null mutant mice have shown that in males calcium/calmodulin kinase kinase β (CaMKKβ) is required for spatial memory formation and for activation of the transcription factor cyclic AMP-responsive element binding protein (CREB) in the hippocampus by spatial training. Here we show that CaMKKβ is not required for spatial memory formation in female mice as female Camkk2 null mutants were not impaired in spatial memory formation and they had the same level of hippocampal CREB phosphorylation after spatial training as female wild-type mice. Furthermore, we show that male but not female Camkk2 null mutants were impaired in long-term potentiation (LTP) at hippocampal CA1 synapses. Finally, a transcriptional analysis of male Camkk2 null mutants led to the identification of a gene, glycosyl phosphatidyl-inositol anchor attachment protein 1 (GAA1), whose hippocampal mRNA expression was up-regulated by spatial and contextual training in male but not in female wild-type mice. Taken together, we conclude that CaMKKβ has a male-specific function in hippocampal memory formation and we have identified male-restricted transcription occurring during hippocampal memory formation.

Long-Term Memory Deficits in Pavlovian Fear Conditioning in Ca2+/Calmodulin Kinase Kinase α-Deficient Mice

Signaling by the Ca(2+)/calmodulin kinase (CaMK) cascade has been implicated in neuronal gene transcription, synaptic plasticity, and long-term memory consolidation. The CaM kinase kinase alpha (CaMKKalpha) isoform is an upstream component of the CaMK cascade whose function in different behavioral and learning and memory paradigms was analyzed by targeted gene disruption in mice. CaMKKalpha mutants exhibited normal long-term spatial memory formation and cued fear conditioning but showed deficits in context fear during both conditioning and long-term follow-up testing. They also exhibited impaired activation of the downstream kinase CaMKIV/Gr and its substrate, the transcription factor cyclic AMP-responsive element binding protein (CREB) upon fear conditioning. Unlike CaMKIV/Gr-deficient mice, the CaMKKalpha mutants exhibited normal long-term potentiation and normal levels of anxiety-like behavior. These results demonstrate a selective role for CaMKKalpha in contextual fear memory and suggest that different combinations of upstream and downstream components of the CaMK cascade may serve distinct physiological functions.

Genetic Alteration of Anxiety and Stress-Like Behavior in Mice Lacking CaMKIV

Calcium-calmodulin-dependent protein kinase IV (CaMKIV) phosphorylates the major transcription factor cyclic AMP-response element binding protein (CREB), which plays a role in emotional behavior. Here, CaMKIV knockout mice (CaMKIV-/-) were tested in a battery of stress and anxiety-related behavioral tests, to determine if CaMKIV plays a role in emotional behavior. CaMKIV-/-exhibited a decrease in anxiety-like behavior in both the elevated plus maze and dark-light emergence tests when compared to wild-type mice. Both the acoustic startle response and prepulse inhibition of startle were decreased with the deletion of CaMKIV. In addition, CaMKIV-/- mice displayed a lack of stress-induced analgesia following restraint or cold swim stress. Our results demonstrate a key role for CaMKIV in anxiety and stress-related behavior.

CREB DNA binding activation by a 50-Hz magnetic field in HL60 cells is dependent on extra- and intracellular Ca 2+ but not PKA, PKC, ERK, or p38 MAPK

To investigate the possible mechanism of gene transcription changes induced by magnetic field (MF), we examined the DNA binding behavior of the transcription factor cyclic-AMP responsive element binding protein (CREB) in HL60 cells after exposure to a 0.1 mT 50-Hz extremely low frequency (ELF) sinusoidal MF by a gel shift assay. Magnetic field induced a time-dependent activation of CREB binding. The complex formation increased shortly after MF exposure for 10 min, reaching a peak level after 1 h, and then recovered to basal level at 4 h after exposure. A novel MF-induced ATF2/ATF2 homodimer formation was observed after MF exposure for 30 min, 1, and 2 h. Furthermore, We found that the MF-induced increase of CREB DNA binding in HL60 cells was dependent on both extracellular and intracellular Ca 2+ but not PKA, PKC, ERK, or p38 MAPK by using various pathway inhibitors. These data indicate that MF exposure activates CREB DNA binding through calcium-related signal transduction pathways under our experimental conditions.

Ginkgo biloba extract : Cognitive enhancer or antistress buffer

Constituents extracted from the leaves of the Ginkgo biloba tree possess beneficial properties that may buffer the aging nervous system from deterioration due to oxidative stress. In the present investigation, a standardized extract of G. biloba (EGb 761) or an equal volume of the vehicle was administered (100 mg/kg/day) to senescent (20-month) C57BL/6 male mice for up to 82 consecutive days. Animals were tested twice in the Morris water maze (MWM) after 28 and 70 days of treatment. No differences were observed in acquisition or retention of performance on the water maze. Elevated-plus maze (EPM) trials were conducted prior to and subsequent to the chronic treatment regimen. Marked baseline differences in plus-maze performance were present in the first experiment. A second experiment used a matched-pairs design to minimize preexisting differences. Results supported the hypothesis that EGb 761 may serve as an antistress buffer, attenuating the increase in anxiety typically observed in animals after cold water exposure. Tissue samples from the hippocampus and cortex were analyzed by Western blot for the transcription factor cyclic-AMP response element binding (CREB) protein. EGb 761 had no significant effect on immunoreactivity to CREB from either the hippocampus or the cerebral cortex.