Nerve growth factor activates a Ras-dependent protein kinase that stimulates c-fos transcription via phosphorylation of CREB

Intrinsic electrical activity drives small-cell lung cancer progression

Elevated or ectopic expression of neuronal receptors promotes tumour progression in many cancer types1,2; neuroendocrine (NE) transformation of adenocarcinomas has also been associated with increased aggressiveness3. Whether the defining neuronal feature, namely electrical excitability, exists in cancer cells and impacts cancer progression remains mostly unexplored. Small-cell lung cancer (SCLC) is an archetypal example of a highly aggressive NE cancer and comprises two major distinct subpopulations: NE cells and non-NE cells4,5. Here we show that NE cells, but not non-NE cells, are excitable, and their action potential firing directly promotes SCLC malignancy. However, the resultant high ATP demand leads to an unusual dependency on oxidative phosphorylation in NE cells. This finding contrasts with the properties of most cancer cells reported in the literature, which are non-excitable and rely heavily on aerobic glycolysis. Additionally, we found that non-NE cells metabolically support NE cells, a process akin to the astrocyte-neuron metabolite shuttle6. Finally, we observed drastic changes in the innervation landscape during SCLC progression, which coincided with increased intratumoural heterogeneity and elevated neuronal features in SCLC cells, suggesting an induction of a tumour-autonomous vicious cycle, driven by cancer cell-intrinsic electrical activity, which confers long-term tumorigenic capability and metastatic potential.

Small-molecule probe for IBD risk variant GPR65 I231L alters cytokine signaling networks through positive allosteric modulation

The proton-sensing heterotrimeric guanine nucleotide-binding protein-coupled receptor GPR65 is expressed in immune cells and regulates tissue homeostasis in response to decreased extracellular pH, which occurs in the context of inflammation and tumorigenesis. Genome-wide association studies linked GPR65 to several autoimmune and inflammatory diseases such as multiple sclerosis and inflammatory bowel disease (IBD). The loss-of-function GPR65 I231L IBD risk variant alters cellular metabolism, impairs protective tissue functions, and increases proinflammatory cytokine production. Hypothesizing that a small molecule designed to potentiate GPR65 at subphysiological pH could decrease inflammatory responses, we found positive allosteric modulators of GPR65 that engage and activate both human and mouse orthologs of the receptor. We observed that the chemical probe BRD5075 alters cytokine and chemokine programs in dendritic cells, establishing that immune signaling can be modulated by targeting GPR65. Our investigation offers improved chemical probes to further interrogate the biology of human GPR65 and its clinically relevant genetic variants.

BDNF- and VEGF-Responsive Stimulus to an NGF Mimic Cyclic Peptide with Copper Ionophore Capability and Ctr1/CCS-Driven Signaling

Neurotrophins are a family of growth factors that play a key role in the development and regulation of the functioning of the central nervous system. Their use as drugs is made difficult by their poor stability, cellular permeability, and side effects. Continuing our effort to use peptides that mimic the neurotrophic growth factor (NGF), the family model protein, and specifically the N-terminus of the protein, here we report on the spectroscopic characterization and resistance to hydrolysis of the 14-membered cyclic peptide reproducing the N-terminus sequence (SSSHPIFHRGEFSV (c-NGF(1-14)). Far-UV CD spectra and a computational study show that this peptide has a rigid conformation and left-handed chirality typical of polyproline II that favors its interaction with the D5 domain of the NGF receptor TrkA. c-NGF(1-14) is able to bind Cu2+ with good affinity; the resulting complexes have been characterized by potentiometric and spectroscopic measurements. Experiments on PC12 cells show that c-NGF(1-14) acts as an ionophore, influencing the degree and the localization of both the membrane transporter (Ctr1) and the copper intracellular transporter (CCS). c-NGF(1-14) induces PC12 differentiation, mimics the protein in TrkA phosphorylation, and activates the kinase cascade, inducing Erk1/2 phosphorylation. c-NGF(1-14) biological activities are enhanced when the peptide interacts with Cu2+ even with the submicromolar quantities present in the culture media as demonstrated by ICP-OES measurements. Finally, c-NGF(1-14) and Cu2+ concur to activate the cAMP response element-binding protein CREB that, in turn, induces the brain-derived neurotrophic factor (BDNF) and the vascular endothelial growth factor (VEGF) release.

Analysis of the interaction of a non-canonical twin half-site of Cyclic AMP-Response Element (CRE) with CRE-binding protein

Differential regulation of a gene having either canonical or non-canonical cyclic AMP response element (CRE) in its promoter is primarily accomplished by its interactions with CREB (cAMP-response element binding protein). The present study aims to delineate the mechanism of the CREB-CRE interactions at the Oncostatin-M (osm) promoter by in vitro and in silico approaches. The non-canonical CREosm consists of two half-CREs separated by a short intervening sequence of 9 base pairs. In this study, in vitro binding assays revealed that out of the two CRE half-sites, the right half-CRE was indispensable for binding of CREB, while the left sequence showed weaker binding ability and specificity. Genome-wide modeling and high throughput free energy calculations for the energy-minimized models containing CREB-CREosm revealed that there was no difference in the binding of CREB to the right half of CREosm site when compared to the entire CREosm. These results were in accordance with the in vitro studies, confirming the indispensable role of the right half-CREosm site in stable complex formation with the CREB protein. Additionally, conversion of the right half-CREosm site to a canonical CRE palindrome showed stronger CREB binding, irrespective of the presence or absence of the left CRE sequence. Thus, the present study establishes an interesting insight into the interaction of CREB with a CRE variant located at the far end of a TATA-less promoter of a cytokine-encoding gene, which in turn could be involved in the regulation of transcription under specific conditions.

Coupling of binding and differential subdomain folding of the intrinsically disordered transcription factor CREB

The cyclic AMP response element binding protein (CREB) contains a basic leucine zipper motif (bZIP) that forms a coiled coil structure upon dimerization and specific DNA binding. Although this state is well characterized, key features of CREB bZIP binding and folding are not well understood. We used single-molecule Förster resonance energy transfer (smFRET) to probe conformations of CREB bZIP subdomains. We found differential folding of the basic region and leucine zipper in response to different binding partners; a strong and previously unreported DNA-independent dimerization affinity; folding upon binding to nonspecific DNA; and evidence of long-range interdomain interactions in full-length CREB that modulate DNA binding. These studies provide new insights into DNA binding and dimerization and have implications for CREB function.

CD24 Expression Dampens the Basal Antiviral State in Human Neuroblastoma Cells and Enhances Permissivity to Zika Virus Infection

Zika virus (ZIKV) exhibits distinct selectivity for infection of various cells and tissues, but how host cellular factors modulate varying permissivity remains largely unknown. Previous studies showed that the neuroblastoma cell line SK-N-AS (expressing low levels of cellular protein CD24) was highly restricted for ZIKV infection, and that this restriction was relieved by ectopic expression of CD24. We tested the hypothesis that CD24 expression allowed ZIKV replication by suppression of the antiviral response. SK-N-AS cells expressing an empty vector (termed CD24-low cells) showed elevated basal levels of phosphorylated STAT1, IRF-1, IKKE, and NFκB. In response to exogenously added type I interferon (IFN-I), CD24-low cells had higher-level induction of antiviral genes and activity against two IFN-I-sensitive viruses (VSV and PIV5-P/V) compared to SK-N-AS cells with ectopic CD24 expression (termed CD24-high cells). Media-transfer experiments showed that the inherent antiviral state of CD24-low cells was not dependent on a secreted factor such as IFN-I. Transcriptomics analysis revealed that CD24 expression decreased expression of genes involved in intracellular antiviral pathways, including IFN-I, NFκB, and Ras. Our findings that CD24 expression in neuroblastoma cells represses intracellular antiviral pathways support the proposal that CD24 may represent a novel biomarker in cancer cells for susceptibility to oncolytic viruses.

SS18-SSX drives CREB activation in synovial sarcoma

Purpose

Synovial sarcoma (SySa) is a rare soft tissue tumor characterized by a reciprocal t(X;18) translocation. The chimeric SS18-SSX fusion protein represents the major driver of the disease, acting as aberrant transcriptional dysregulator. Oncogenic mechanisms whereby SS18-SSX mediates sarcomagenesis are incompletely understood, and strategies to selectively target SySa cells remain elusive. Based on results of Phospho-Kinase screening arrays, we here investigate the functional and therapeutic relevance of the transcription factor CREB in SySa tumorigenesis.

Methods

Immunohistochemistry of phosphorylated CREB and its downstream targets (Rb, Cyclin D1, PCNA, Bcl-xL and Bcl-2) was performed in a large cohort of SySa. Functional aspects of CREB activity, including SS18-SSX driven circuits involved in CREB activation, were analyzed in vitro employing five SySa cell lines and a mesenchymal stem cell model. CREB mediated transcriptional activity was modulated by RNAi-mediated knockdown and small molecule inhibitors (666-15, KG-501, NASTRp and Ro 31-8220). Anti-proliferative effects of the CREB inhibitor 666-15 were tested in SySa avian chorioallantoic membrane and murine xenograft models in vivo.

Results

We show that CREB is phosphorylated and activated in SySa, accompanied by downstream target expression. Human mesenchymal stem cells engineered to express SS18-SSX promote CREB expression and phosphorylation. Conversely, RNAi-mediated knockdown of SS18-SSX impairs CREB phosphorylation in SySa cells. Inhibition of CREB activity reduces downstream target expression, accompanied by suppression of SySa cell proliferation and induction of apoptosis invitro and in vivo.

Conclusion

In conclusion, our data underline an essential role of CREB in SySa tumorigenesis and provides evidence for molecular targeted therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13402-022-00673-w.

Cyclic AMP-dependent activation of ERK via GLP-1 receptor signalling requires the neuroendocrine cell-specific guanine nucleotide exchanger NCS-RapGEF2

Cyclic AMP activation of the Rap-Braf-MEK-ERK pathway after signalling initiated by the neuropeptide pituitary adenylate cyclase-activating peptide (PACAP), via the Gs -protein coupled receptor (Gs PCR) PAC1, occurs uniquely through the neuritogenic cAMP sensor Rap guanine nucleotide exchange factor 2 (NCS-RapGEF2) in Neuroscreen-1 (NS-1) neuroendocrine cells. We examined the expression of other Family B Gs PCRs in this cell line and assessed cAMP elevation and neuritogenesis after treatment with their cognate peptide ligands. Exposure of NS-1 cells to the VIPR1/2 agonist vasoactive intestinal polypeptide, or the GLP1R agonist exendin-4, did not induce neuritogenesis, or elevation of cAMP, presumably as a result of insufficient receptor protein expression. Vasoactive intestinal polypeptide and exendin-4 did induce neuritogenesis after transduction of human VIPR1, VIPR2 and GLP1R into NS-1 cells. Exendin-4/GLP1R-stimulated neuritogenesis was MEK-ERK-dependent (blocked by U0126), indicating its use of the cAMP→RapGEF2→ERK neuritogenic signalling pathway previously identified for PACAP/PAC1 signalling in NS-1 cells. NCS-RapGEF2 is expressed in the rodent insulinoma cell lines MIN6 and INS-1, as well as in human pancreatic islets. As in NS-1 cells, exendin-4 caused ERK phosphorylation in INS-1 cells. Reduction in RapGEF2 expression after RapGEF2-shRNA treatment reduced exendin-4-induced ERK phosphorylation. Transcriptome analysis of INS-1 cells after 1 hour of exposure to exendin-4 revealed an immediate early-gene response that was composed of both ERK-dependent and ERK-independent signalling targets. We propose that cAMP signalling initiated by glucagon-like peptide 1 (GLP-1) in pancreatic beta cells causes parallel activation of multiple cAMP effectors, including NCS-RapGEF2, Epac and protein kinase A, to separately control various facets of GLP-1 action, including insulin secretion and transcriptional modulation.

Synergistic integration of dihydro-artemisinin with γ-aminobutyric acid results in a more potential anti-depressant

Three hybrids of dihydro-artemisinin (DHA) with β-aminopropionic acid, γ-aminobutyric acid, and histamine have been designed and synthesized. The conjugate of DHA with GABA labelled as 5b was confirmed the most active candidate against both Cort- and SNP-induced PC12 cell impairments with EC₅₀ value of 8.04 ± 0.35, and 9.38 ± 0.56 μM, respectively. 5b was clearly highlighted as a good modulator on protein expression of Akt, Bcl-2, and Bax, indicating its functions against programmed cell apoptosis. 5b significantly reversed the Cort-induced excessive calcium influx and release from internal organelles. It was demonstrated the ability to express increased levels of β-tubulin III and to up-regulate phosphorylation level of cAMP response element-binding protein (CREB), leading to cell differentiation. It can penetrate blood - brain barrier (BBB) with propriate stability. Altogether, these data strongly support that 5b is a potential anti-depressant.

Slit/Robo signaling regulates Leydig cell steroidogenesis

BACKGROUND

First identified as a regulator of neuronal axon guidance, Slit/Robo signaling has since been implicated in additional physiologic and pathologic processes, such as angiogenesis, organogenesis and cancer progression. However, its roles in the regulation of testis function have been little explored.

METHODS

Immunohistochemistry and RT-qPCR analyses were performed to detect the expression of Slit/Robo signaling effectors in the adult mouse testis. To identify the roles and mechanisms of Slit/Robo signaling in the regulation of steroidogenesis, RT-qPCR, immunoblotting and hormone measurements were carried out using Leydig cells (primary cultures and the MA10 cell line) treated with exogenous SLIT ligands, and testes from Robo1-null mice.

RESULTS

Slit1, -2 and -3 and Robo1 and -2 expression was detected in the adult mouse testis, particularly in Leydig cells. In vitro treatment of Leydig cells with exogenous SLIT ligands led to a decrease in the expression of the steroidogenic genes Star, Cyp11a1, and Cyp17a1. SLIT2 treatment decreased the phosphorylation of the key steroidogenic gene regulator CREB, possibly in part by suppressing AKT activity. Furthermore, SLIT2 treatment reduced the responsiveness of MA10 cells to luteinizing hormone by decreasing the expression of Lhcgr. Consistent with these in vitro results, an increase in testicular Star mRNA levels and intra-testicular testosterone concentrations were found in Robo1-null mice. Finally, we showed that the expression of the Slit and Robo genes in Leydig cells is enhanced by testosterone treatment in vitro, by an AR-independent mechanism.

CONCLUSION

Taken together, these results suggest that Slit/Robo signaling represents a novel mechanism that regulates Leydig cell steroidogenesis. It may act in an autocrine/paracrine manner to mediate negative feedback by testosterone on its own synthesis. Video Abstract.

The use of melatonin to mitigate the adverse metabolic side effects of antipsychotics

Antipsychotic drugs are efficacious first-line treatments for many individuals diagnosed with a psychiatric illness. However, their adverse metabolic side-effect profile, which resembles the metabolic syndrome, represents a significant clinical problem that increases morbidity and limits treatment adherence. Moreover, the mechanisms involved in antipsychotic-induced adverse metabolic effects (AMEs) are unknown and mitigating strategies and interventions are limited. However, recent clinical trials show that nightly administration of exogenous melatonin may mitigate or even prevent antipsychotic-induced AMEs. This clinical evidence in combination with recent preclinical data implicate the circadian system in antipsychotic-induced AMEs and their mitigation. In this chapter, we provide an overview on the circadian system and its involvement in antipsychotic-induced AMEs, as well as the potential beneficial effect of nightly melatonin administration to mitigate them.

Eudebeiolide B Inhibits Osteoclastogenesis and Prevents Ovariectomy-Induced Bone Loss by Regulating RANKL-Induced NF-κB, c-Fos and Calcium Signaling

Eudebeiolide B is a eudesmane-type sesquiterpenoid compound isolated from Salvia plebeia R. Br., and little is known about its biological activity. In this study, we investigated the effects of eudebeiolide B on osteoblast differentiation, receptor activator nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in vitro and ovariectomy-induced bone loss in vivo. Eudebeiolide B induced the expression of alkaline phosphatase (ALP) and calcium accumulation during MC3T3-E1 osteoblast differentiation. In mouse bone marrow macrophages (BMMs), eudebeiolide B suppressed RANKL-induced osteoclast differentiation of BMMs and bone resorption. Eudebeiolide B downregulated the expression of nuclear factor of activated T-cells 1 (NFATc1) and c-fos, transcription factors induced by RANKL. Moreover, eudebeiolide B attenuated the RANKL-induced expression of osteoclastogenesis-related genes, including cathepsin K (Ctsk), matrix metalloproteinase 9 (MMP9) and dendrocyte expressed seven transmembrane protein (DC-STAMP). Regarding the molecular mechanism, eudebeiolide B inhibited the phosphorylation of Akt and NF-κB p65. In addition, it downregulated the expression of cAMP response element-binding protein (CREB), Bruton's tyrosine kinase (Btk) and phospholipase Cγ2 (PLCγ2) in RANKL-induced calcium signaling. In an ovariectomized (OVX) mouse model, intragastric injection of eudebeiolide B prevented OVX-induced bone loss, as shown by bone mineral density and contents, microarchitecture parameters and serum levels of bone turnover markers. Eudebeiolide B not only promoted osteoblast differentiation but inhibited RANKL-induced osteoclastogenesis through calcium signaling and prevented OVX-induced bone loss. Therefore, eudebeiolide B may be a new therapeutic agent for osteoclast-related diseases, including osteoporosis, rheumatoid arthritis and periodontitis.

Inward Rectifier K+ Currents Contribute to the Proarrhythmic Electrical Phenotype of Atria Overexpressing Cyclic Adenosine Monophosphate Response Element Modulator Isoform CREM-IbΔC-X

BACKGROUND Transgenic mice (TG) with heart-directed overexpresion of the isoform of the transcription factor cyclic adenosine monophosphate response element modulator (CREM), CREM-IbΔC-X, display spontaneous atrial fibrillation (AF) and action potential prolongation. The remodeling of the underlying ionic currents remains unknown. Here, we investigated the regulatory role of CREM-IbΔC-X on the expression of K⁺ channel subunits and the corresponding K⁺ currents in relation to AF onset in TG atrial myocytes. METHODS AND RESULTS ECG recordings documented the absence or presence of AF in 6-week-old (before AF onset) and 12-week-old TG (after AF onset) and wild-type littermate mice before atria removal to perform patch clamp, contractility, and biochemical experiments. In TG atrial myocytes, we found reduced repolarization reserve K⁺ currents attributed to a decrease of transiently outward current and inward rectifier K⁺ current with phenotype progression, and of acetylcholine-activated K⁺ current, age independent. The molecular determinants of these changes were lower mRNA levels of Kcnd2/3, Kcnip2, Kcnj2/4, and Kcnj3/5 and decreased protein levels of K⁺ channel interacting protein 2 (KChIP2 ), Kir2.1/3, and Kir3.1/4, respectively. After AF onset, inward rectifier K⁺ current contributed less to action potential repolarization, in line with the absence of outward current component, whereas the acetylcholine-induced action potential shortening before AF onset (6-week-old TG mice) was smaller than in wild-type and 12-week-old TG mice. Atrial force of contraction measured under combined vagal-sympathetic stimulation revealed increased sensitivity to isoprenaline irrespective of AF onset in TG. Moreover, we identified Kcnd2, Kcnd3, Kcnj3, and Kcnh2 as novel CREM-target genes. CONCLUSIONS Our study links the activation of cyclic adenosine monophosphate response element-mediated transcription to the proarrhythmogenic electrical remodeling of atrial inward rectifier K⁺ currents with a role in action potential duration, resting membrane stability, and vagal control of the electrical activity.

Optical control of ERK and AKT signaling promotes axon regeneration and functional recovery of PNS and CNS in Drosophila

Neuroregeneration is a dynamic process synergizing the functional outcomes of multiple signaling circuits. Channelrhodopsin-based optogenetics shows the feasibility of stimulating neural repair but does not pin down specific signaling cascades. Here, we utilized optogenetic systems, optoRaf and optoAKT, to delineate the contribution of the ERK and AKT signaling pathways to neuroregeneration in live Drosophila larvae. We showed that optoRaf or optoAKT activation not only enhanced axon regeneration in both regeneration-competent and -incompetent sensory neurons in the peripheral nervous system but also allowed temporal tuning and proper guidance of axon regrowth. Furthermore, optoRaf and optoAKT differ in their signaling kinetics during regeneration, showing a gated versus graded response, respectively. Importantly in the central nervous system, their activation promotes axon regrowth and functional recovery of the thermonociceptive behavior. We conclude that non-neuronal optogenetics targets damaged neurons and signaling subcircuits, providing a novel strategy in the intervention of neural damage with improved precision.

Most cells have a built-in regeneration signaling program that allows them to divide and repair. But, in the cells of the central nervous system, which are called neurons, this program is ineffective. This is why accidents and illnesses affecting the brain and spinal cord can cause permanent damage. Reactivating regeneration in neurons could help them repair, but it is not easy. Certain small molecules can switch repair signaling programs back on. Unfortunately, these molecules diffuse easily through tissues, spreading around the body and making it hard to target individual damaged cells. This both hampers research into neuronal repair and makes treatments directed at healing damage to the nervous system more likely to have side-effects. It is unclear whether reactivating regeneration signaling in individual neurons is possible.

One way to address this question is to use optogenetics. This technique uses genetic engineering to fuse proteins that are light-sensitive to proteins responsible for relaying signals in the cell. When specific wavelengths of light hit the light-sensitive proteins, the fused signaling proteins switch on, leading to the activation of any proteins they control, for example, those involved in regeneration.

Wang et al. used optogenetic tools to determine if light can help repair neurons in fruit fly larvae. First, a strong laser light was used to damage an individual neuron in a fruit fly larva that had been genetically modified so that blue light would activate the regeneration program in its neurons. Then, Wang et al. illuminated the cell with dim blue light, switching on the regeneration program. Not only did this allow the neuron to repair itself, it also allowed the light to guide its regeneration. By focusing the blue light on the damaged end of the neuron, it was possible to guide the direction of the cell's growth as it regenerated.

Regeneration programs in flies and mammals involve similar signaling proteins, but blue light does not penetrate well into mammalian tissues. This means that further research into LEDs that can be implanted may be necessary before neuronal repair experiments can be performed in mammals. In any case, the ability to focus treatment on individual neurons paves the way for future work into the regeneration of the nervous system, and the combination of light and genetics could reveal more about how repair signals work.

IL-4R alpha deficiency influences hippocampal-BDNF signaling pathway to impair reference memory

Like pro-inflammatory cytokines, the role of anti-inflammatory cytokines in both learning and memory has been investigated, revealing beneficial effects for both interleukin-4 and interleukin-13 via the common interleukin-4 receptor alpha chain complex. In this study, using the Morris water maze spatial task for cognition, we compared interleukin-4 receptor alpha- deficient mice and their ligands interleukin-4/ interleukin-13 double deficient mice, on a Balb/c background. We demonstrate that while interleukin-4/ interleukin-13 double deficient mice are significantly impaired in both learning and reference memory, interleukin-4 receptor alpha-deficiency impairs only reference memory, compared to the wild-type control mice. In order to better understand how interleukin-4 receptor alpha- deficient mice are able to learn but not remember, we investigated the BDNF/TrkB- and the ARC-signaling pathways. We show that interleukin-4 receptor alpha-deficiency disrupts activation of BDNF/TrkB- and ARC-signaling pathways during reference memory, while the pathway for spatial learning is spared.

Hotspots of Aberrant Enhancer Activity in Fibrolamellar Carcinoma Reveal Candidate Oncogenic Pathways and Therapeutic Vulnerabilities

Fibrolamellar carcinoma (FLC) is a rare, therapeutically intractable liver cancer that disproportionately affects youth. Although FLC tumors exhibit a distinct gene expression profile, the chromatin regulatory landscape and the genes most critical for tumor cell survival remain unclear. Here, we use chromatin run-on sequencing to discover ∼7,000 enhancers and 141 enhancer hotspots activated in FLC relative to nonmalignant liver. Bioinformatic analyses reveal aberrant ERK/MEK signaling and candidate master transcriptional regulators. We also define the genes most strongly associated with hotspots of FLC enhancer activity, including CA12 and SLC16A14. Treatment of FLC cell models with inhibitors of CA12 or SLC16A14 independently reduce cell viability and/or significantly enhance the effect of the MEK inhibitor cobimetinib. These findings highlight molecular targets for drug development, as well as drug combination approaches.

Follistatin is a novel therapeutic target and biomarker in FLT3/ITD acute myeloid leukemia

Internal tandem duplication of Fms-like tyrosine kinase 3 (FLT3/ITD) occurs in about 30% of acute myeloid leukemia (AML) and is associated with poor response to conventional treatment and adverse outcome. Here, we reported that human FLT3/ITD expression led to axis duplication and dorsalization in about 50% of zebrafish embryos. The morphologic phenotype was accompanied by ectopic expression of a morphogen follistatin (fst) during early embryonic development. Increase in fst expression also occurred in adult FLT3/ITD-transgenic zebrafish, Flt3/ITD knock-in mice, and human FLT3/ITD AML cells. Overexpression of human FST317 and FST344 isoforms enhanced clonogenicity and leukemia engraftment in xenotransplantation model via RET, IL2RA, and CCL5 upregulation. Specific targeting of FST by shRNA, CRISPR/Cas9, or antisense oligo inhibited leukemic growth in vitro and in vivo. Importantly, serum FST positively correlated with leukemia engraftment in FLT3/ITD AML patient-derived xenograft mice and leukemia blast percentage in primary AML patients. In FLT3/ITD AML patients treated with FLT3 inhibitor quizartinib, serum FST levels correlated with clinical response. These observations supported FST as a novel therapeutic target and biomarker in FLT3/ITD AML.

Akebia Saponin D suppresses inflammation in chondrocytes via the NRF2/HO-1/NF-κB axis and ameliorates osteoarthritis in mice

Akebia Saponin D promotes the translocation of NRF2 into nucleus, activates NRF2/HO-1 pathway and inhibits NF-κB pathway in chondrocytes, and ultimately alleviates osteoarthritis development.

Microglia CREB-Phosphorylation Mediates Amyloid-β-Induced Neuronal Toxicity

Extracellular accumulation of amyloid-β (Aβ) forming senile plaques is one of the hallmark pathologies in Alzheimer's disease (AD), while the mechanisms underlying the neuronal toxic effect of Aβ are not fully understood. Here, we found that intracerebroventricular infusion of the aged Aβ42 in mice only induces memory deficit at 24 h but not at 7 days. Interestingly, a remarkably increased CREB (cAMP response element-binding protein) Ser133-phosphorylation (pS133-CREB) with microglial activation was detected at 24 h but not at 7 days after Aβ infusion. Aβ treatment for 24 h increased pS133-CREB level in microglia of the hippocampal non-granular cell layers with remarkably decreased pS133-CREB immunoreactivity in neurons of the hippocampal granular cell layers, including CA1, CA3, and DG subsets. Inhibition of microglia activation by minocycline or CREB phosphorylation by H89, an inhibitor of protein kinase A (PKA), abolished Aβ-induced microglia CREB hyperphosphorylation with restoration of neuronal function and attenuation of inflammatory response, i.e., reduced levels of interleukin-6 (IL6) and pCREB binding of matrix metalloproteinase-9 (MMP9) DNA. Finally, treatment of the primary hippocampal neurons with Aβ-potentiated microglia media decreased neuronal GluN1 and GluA2 levels, while simultaneous inhibition of PKA restored the levels. These novel findings reveal that intracerebroventricular infusion of Aβ only induces transient memory deficit in mice and the molecular mechanisms involve a stimulated microglial CREB phosphorylation.

Roles of Cyclic AMP Response Element Binding Activation in the ERK1/2 and p38 MAPK Signalling Pathway in Central Nervous System, Cardiovascular System, Osteoclast Differentiation and Mucin and Cytokine Production

There are many downstream targets of mitogen-activated protein kinase (MAPK) signalling that are involved in neuronal development, cellular differentiation, cell migration, cancer, cardiovascular dysfunction and inflammation via their functions in promoting apoptosis and cell motility and regulating various cytokines. It has been reported that cyclic AMP response element-binding protein (CREB) is phosphorylated and activated by cyclic AMP signalling and calcium/calmodulin kinase. Recent evidence also points to CREB phosphorylation by the MAPK signalling pathway. However, the specific roles of CREB phosphorylation in MAPK signalling have not yet been reviewed in detail. Here, we describe the recent advances in the study of this MAPK-CREB signalling axis in human diseases. Overall, the crosstalk between extracellular signal-related kinase (ERK) 1/2 and p38 MAPK signalling has been shown to regulate various physiological functions, including central nervous system, cardiac fibrosis, alcoholic cardiac fibrosis, osteoclast differentiation, mucin production in the airway, vascular smooth muscle cell migration, steroidogenesis and asthmatic inflammation. In this review, we focus on ERK1/2 and/or p38 MAPK-dependent CREB activation associated with various diseases to provide insights for basic and clinical researchers.

3'-Daidzein Sulfonate Sodium Protects Against Chronic Cerebral Hypoperfusion-Mediated Cognitive Impairment and Hippocampal Damage via Activity-Regulated Cytoskeleton-Associated Protein Upregulation

The learning and memory impairment caused by chronic cerebral hypoperfusion (CCH) is permanent and seriously affects the daily life of patients and their families. The compound 3'-daidzein sulfonate sodium (DSS) protects against CCH-mediated memory impairment and hippocampal damage in a rat model. In the present study, we further investigated the underlying mechanisms of this effect in the rat two-vessel occlusion (2VO) and the oxygen and glucose deprivation (OGD) primary hippocampal neuron models. The hippocampal expression of the activity-regulated cytoskeleton associated protein (Arc) following DSS administration was detected in vivo and in vitro and behavioral testing was used to investigate the role of Arc in the DSS-mediated rescue of CCH-induced neurotoxicity. DSS increased hippocampal Arc expression both in vivo and in vitro. Arc overexpression increased and Arc knockdown decreased hippocampal neuronal densities in rat 2VO model, when compared to DSS treatment alone. Arc overexpression decreased and Arc knockdown increased apoptotic hippocampal neurons in rat 2VO and OGD primary hippocampal neuron models, when compared to DSS treatment alone. Arc overexpression enhanced and Arc knockdown inhibited the beneficial effect of DSS on 2VO-induced cognitive impairment. DSS restored the neuronal OGD-mediated phosphorylation decrease in protein kinase alpha (PKA), extracellular signal-regulated protein kinases 1/2 (ERK1/2) and cAMP response element binding protein (CREB), in vitro. PKA and ERK1/2 inhibition blocked the DSS-mediated effects on neuronal apoptosis and OGD-induced Arc downregulation. In conclusion, DSS protects against CCH-mediated cognitive impairment and hippocampal damage via Arc upregulation, which is activated by the PKA/CREB and ERK/CREB signaling pathways. Our study further confirms the potential use of DSS as an effective treatment for CCH-associated diseases.

Opioid Activity in the Locus Coeruleus Is Modulated by Chronic Neuropathic Pain

Pain affects both sensory and emotional aversive responses, often provoking depression and anxiety-related conditions when it becomes chronic. As the opioid receptors in the locus coeruleus (LC) have been implicated in pain, stress responses, and opioid drug effects, we explored the modifications to LC opioid neurotransmission in a chronic constriction injury (CCI) model of short- and long-term neuropathic pain (7 and 30 days after nerve injury). No significant changes were found after short-term CCI, yet after 30 days, CCI provoked an up-regulation of cAMP (cyclic 5'-adenosine monophosphate), pCREB (phosphorylated cAMP response element binding protein), protein kinase A, tyrosine hydroxylase, and electrical activity in the LC, as well as enhanced c-Fos expression. Acute mu opioid receptor desensitization was more intense in these animals, measured as the decline of the peak current caused by [Met5]-enkephalin and the reduction of forskolin-stimulated cAMP produced in response to DAMGO. Sustained morphine treatment did not markedly modify certain LC parameters in CCI-30d animals, such as [Met5]-enkephalin-induced potassium outward currents or burst activity and c-Fos rebound after naloxone precipitation, which may limit the development of some typical opioid drug-related adaptations. However, other phenomena were impaired by long-term CCI, including the reduction in forskolin-stimulated cAMP accumulation by DAMGO after naloxone precipitation in morphine dependent animals. Overall, this study suggests that long-term CCI leads to changes at the LC level that may contribute to the anxiodepressive phenotype that develops in these animals. Furthermore, opioid drugs produce complex adaptations in the LC in this model of chronic neuropathic pain.

Regulatory role of sphingosine kinase and sphingosine-1-phosphate receptor signaling in progenitor/stem cells

Balanced sphingolipid signaling is important for the maintenance of homeostasis. Sphingolipids were demonstrated to function as structural components, second messengers, and regulators of cell growth and survival in normal and disease-affected tissues. Particularly, sphingosine kinase 1 (SphK1) and its product sphingosine-1-phosphate (S1P) operate as mediators and facilitators of proliferation-linked signaling. Unlimited proliferation (self-renewal) within the regulated environment is a hallmark of progenitor/stem cells that was recently associated with the S1P signaling network in vasculature, nervous, muscular, and immune systems. S1P was shown to regulate progenitor-related characteristics in normal and cancer stem cells (CSCs) via G-protein coupled receptors S1Pn (n = 1 to 5). The SphK/S1P axis is crucially involved in the regulation of embryonic development of vasculature and the nervous system, hematopoietic stem cell migration, regeneration of skeletal muscle, and development of multiple sclerosis. The ratio of the S1P receptor expression, localization, and specific S1P receptor-activated downstream effectors influenced the rate of self-renewal and should be further explored as regeneration-related targets. Considering malignant transformation, it is essential to control the level of self-renewal capacity. Proliferation of the progenitor cell should be synchronized with differentiation to provide healthy lifelong function of blood, immune systems, and replacement of damaged or dead cells. The differentiation-related role of SphK/S1P remains poorly assessed. A few pioneering investigations explored pharmacological tools that target sphingolipid signaling and can potentially confine and direct self-renewal towards normal differentiation. Further investigation is required to test the role of the SphK/S1P axis in regulation of self-renewal and differentiation.

The Phosphorylation of CREB at Serine 133 Is a Key Event for Circadian Clock Timing and Entrainment in the Suprachiasmatic Nucleus

Within the suprachiasmatic nucleus (SCN)-the locus of the master circadian clock- transcriptional regulation via the CREB/CRE pathway is implicated in the functioning of the molecular clock timing process, and is a key conduit through which photic input entrains the oscillator. One event driving CRE-mediated transcription is the phosphorylation of CREB at serine 133 (Ser¹³³). Indeed, numerous reporter gene assays have shown that an alanine point mutation in Ser¹³³ reduces CREB-mediated transcription. Here, we sought to examine the contribution of Ser¹³³ phosphorylation to the functional role of CREB in SCN clock physiology in vivo. To this end, we used a CREB knock-in mouse strain, in which Ser¹³³ was mutated to alanine (S/A CREB). Under a standard 12 h light-dark cycle, S/A CREB mice exhibited a marked alteration in clock-regulated wheel running activity. Relative to WT mice, S/A CREB mice had highly fragmented bouts of locomotor activity during the night phase, elevated daytime activity, and a delayed phase angle of entrainment. Further, under free-running conditions, S/A CREB mice had a significantly longer tau than WT mice and reduced activity amplitude. In S/A CREB mice, light-evoked clock entrainment, using both Aschoff type 1 and 6 h "jet lag" paradigms, was markedly reduced relative to WT mice. S/A CREB mice exhibited attenuated transcriptional drive, as assessed by examining both clock-gated and light-evoked gene expression. Finally, SCN slice culture imaging detected a marked disruption in cellular clock phase synchrony following a phase-resetting stimulus in S/A CREB mice. Together, these data indicate that signaling through CREB phosphorylation at Ser¹³³ is critical for the functional fidelity of both SCN timing and entrainment.

A Chinese Herbal Preparation, Xiao-Er-An-Shen Decoction, Exerts Neuron Protection by Modulation of Differentiation and Antioxidant Activity in Cultured PC12 Cells

Xiao-Er-An-Shen Decoction (XEASD), a Chinese herbal formula, has been used in clinic for treating insomnia and mental excitement in children and adolescents. However, less of scientific data supports its effectiveness in clinic. Here, we aim to study the role of XEASD in regulating neuron differentiation and antioxidant activity. An HPLC-MS was used to chemically standardize herbal extract of XEASD. The standardized herbal extracts of XEASD (0.3–3.0 mg/mL) were applied onto cultured PC12 cells for 48 hours. The treatment with XEASD extract induced neurite outgrowth of PC12 cells in a dose-dependent manner, having the highest response by ~50% of differentiated cells. Application of XEASD extract dose dependently stimulated expressions of NF68, NF160, and NF200 in cultured PC12 cells. Furthermore, XEASD activated the phosphorylation of cAMP responsive element binding protein on PC12 cells, the effect of which was blocked by H89, a protein kinase A inhibitor. Moreover, XEASD showed free radical scavenging activity and stimulated the transcriptional activity of ARE. These results supported the neurobeneficial effects of XEASD in the induction of neurite outgrowth and protection against oxidative stress and could be useful for neurological diseases, in which neurotrophin deficiency and oxidation insult are involved.

Grass Carp Prolactin Gene: Structural Characterization and Signal Transduction for PACAP-induced Prolactin Promoter Activity

In this study, structural analysis of grass carp prolactin (PRL) gene was performed and the signaling mechanisms for pituitary adenylate cyclase-activating peptide (PACAP) regulation of PRL promoter activity were investigated. In αT3-1 cells, PRL promoter activity could be induced by oPACAP₃₈ which was blocked by PACAP antagonist but not the VIP antagonist. The stimulatory effect of oPACAP₃₈ was mimicked by activation of AC/cAMP and voltage-sensitive Ca²⁺ channel (VSCC) signaling, or induction of Ca²⁺ entry. In parallel, PACAP-induced PRL promoter activity was negated or inhibited by suppressing cAMP production, inhibiting PKA activity, removal of extracellular Ca²⁺, VSCC blockade, calmodulin (CaM) antagonism, and inactivation of CaM kinase II. Similar sensitivity to L-type VSCC, CaM and CaM kinase II inhibition were also observed by substituting cAMP analog for oPACAP₃₈ as the stimulant for PRL promoter activity. Moreover, PACAP-induced PRL promoter activity was also blocked by inhibition of PLC signaling, attenuation of [Ca²⁺]i immobilization via IP3 receptors, and blockade of PI3K/P₇₀^S6K pathway. The PACAP-induced PRL promoter activation may involve transactivation of the transcription factor CREB. These results suggest that PACAP can stimulate PRL promoter activation by PAC1 mediated functional coupling of the Ca²⁺/CaM/CaM kinase II cascades with the AC/cAMP/PKA pathway. Apparently, other signaling pathways, including PLC/IP3 and PI3K/P₇₀^S6K cascades, may also be involved in PACAP induction of PRL gene transcription.

AD-Related N-Terminal Truncated Tau Is Sufficient to Recapitulate In Vivo the Early Perturbations of Human Neuropathology: Implications for Immunotherapy

The NH₂tau 26-44 aa (i.e., NH₂htau) is the minimal biologically active moiety of longer 20-22-kDa NH₂-truncated form of human tau-a neurotoxic fragment mapping between 26 and 230 amino acids of full-length protein (htau40)-which is detectable in presynaptic terminals and peripheral CSF from patients suffering from AD and other non-AD neurodegenerative diseases. Nevertheless, whether its exogenous administration in healthy nontransgenic mice is able to elicit a neuropathological phenotype resembling human tauopathies has not been yet investigated. We explored the in vivo effects evoked by subchronic intracerebroventricular (i.c.v.) infusion of NH₂htau or its reverse counterpart into two lines of young (2-month-old) wild-type mice (C57BL/6 and B6SJL). Six days after its accumulation into hippocampal parenchyma, significant impairment in memory/learning performance was detected in NH₂htau-treated group in association with reduced synaptic connectivity and neuroinflammatory response. Compromised short-term plasticity in paired-pulse facilitation paradigm (PPF) was detected in the CA3/CA1 synapses from NH₂htau-impaired animals along with downregulation in calcineurin (CaN)-stimulated pCREB/c-Fos pathway(s). Importantly, these behavioral, synaptotoxic, and neuropathological effects were independent from the genetic background, occurred prior to frank neuronal loss, and were specific because no alterations were detected in the control group infused with its reverse counterpart. Finally, a 2.0-kDa peptide which biochemically and immunologically resembles the injected NH₂htau was endogenously detected in vivo, being present in hippocampal synaptosomal preparations from AD subjects. Given that the identification of the neurotoxic tau species is mandatory to develop a more effective tau-based immunological approach, our evidence can have important translational implications for cure of human tauopathies.

BCAP promotes osteoclast differentiation through regulation of the p38-dependent CREB signaling pathway

Many studies have determined that PI3K-Akt signaling pathways play important roles in osteoclast differentiation and function. In the present study, we investigated the roles of B-cell adaptor for PI3K (BCAP), which is a PI3K binding molecule, in osteoclasts. Overexpression of BCAP in osteoclast precursor cells enhanced osteoclast differentiation induced by tumor necrosis factor alpha (TNF-α) as well as receptor activator of nuclear factor-κB ligand (RANKL). Conversely, osteoclast differentiation mediated by both cytokines was attenuated when BCAP expression was downregulated using small interfering RNA. Notably, BCAP induced Akt activation only upon stimulation by RANKL, but not by TNF-α. However, BCAP activated p38-dependent cAMP response element-binding protein (CREB) phosphorylation induced by both RANKL and TNF-α. Collectively, we showed that BCAP plays an important role in osteoclast differentiation by regulating the p38-dependent CREB signaling pathway, and that BCAP might be a new therapeutic target for bone diseases.

3'-Daidzein sulfonate sodium protects against memory impairment and hippocampal damage caused by chronic cerebral hypoperfusion

3′-Daidzein sulfonate sodium (DSS) is a new synthetic water-soluble compound derived from daidzein, a soya isoflavone that plays regulatory roles in neurobiology. In this study, we hypothesized that the regulatory role of DSS in neurobiology exhibits therapeutic effects on hippocampal damage and memory impairment. To validate this hypothesis, we established rat models of chronic cerebral hypoperfusion (CCH) by the permanent occlusion of the common carotid arteries using the two-vessel occlusion method. Three weeks after modeling, rat models were intragastrically administered 0.1, 0.2, and 0.4 mg/kg DSS, once a day, for 5 successive weeks. The Morris water maze test was performed to investigate CCH-induced learning and memory deficits. TUNEL assay was used to analyze apoptosis in the hippocampal CA1, CA3 regions and dentate gyrus. Hematoxylin-eosin staining was performed to observe the morphology of neurons in the hippocampal CA1, CA3 regions and dentate gyrus. Western blot analysis was performed to investigate the phosphorylation of PKA, ERK1/2 and CREB in the hippocampal PKA/ERK1/2/CREB signaling pathway. Results showed that DSS treatment greatly improved the learning and memory deficits of rats with CCH, reduced apoptosis of neurons in the hippocampal CA1, CA3 regions and dentate gyrus, and increased the phosphorylation of PKA, ERK1/2, and CREB in the hippocampus. These findings suggest that DSS protects against CCH-induced memory impairment and hippocampal damage possibly through activating the PKA/ERK1/2/CREB signaling pathway.

A Review of Dietary Ziziphus jujuba Fruit (Jujube): Developing Health Food Supplements for Brain Protection

The fruits of Ziziphus jujuba, known as jujube or Chinese date, are being consumed all around the world because of their health benefits, as both food and herbal medicine. Traditionally, one of the main functions of jujube, as described in herbal medicine, is to benefit our brain by calming down the mind and improving quality of sleep. Here, the activities of jujubes on nervous system are summarized and discussed. Jujube possesses neuroprotective activities, including protecting neuronal cells against neurotoxin stress, stimulating neuronal differentiation, increasing expression of neurotrophic factors, and promoting memory and learning. Flavonoid, cAMP, and jujuboside could be the potential bioactive ingredients to account for the aforesaid biological activities. These findings imply that jujube is a potential candidate for development of health supplements for prevention and/or treatment of neurological diseases.

Activation of PERK Elicits Memory Impairment through Inactivation of CREB and Downregulation of PSD95 After Traumatic Brain Injury

The PKR-like ER kinase (PERK), a transmembrane protein, resides in the endoplasmic reticulum (ER). Its activation serves as a key sensor of ER stress, which has been implicated in traumatic brain injury (TBI). The loss of memory is one of the most common symptoms after TBI, but the precise role of PERK activation in memory impairment after TBI has not been well elucidated. Here, we have shown that blocking the activation of PERK using GSK2656157 prevents the loss of dendritic spines and rescues memory deficits after TBI. To elucidate the molecular mechanism, we found that activated PERK phosphorylates CAMP response element binding protein (CREB) and PSD95 directly at the S129 and T19 residues, respectively. Phosphorylation of CREB protein prevents its interaction with a coactivator, CREB-binding protein, and subsequently reduces the BDNF level after TBI. Conversely, phosphorylation of PSD95 leads to its downregulation in pericontusional cortex after TBI in male mice. Treatment with either GSK2656157 or overexpression of a kinase-dead mutant of PERK (PERK-K618A) rescues BDNF and PSD95 levels in the pericontusional cortex by reducing phosphorylation of CREB and PSD95 proteins after TBI. Similarly, administration of either GSK2656157 or overexpression of PERK-K618A in primary neurons rescues the loss of dendritic outgrowth and number of synapses after treatment with a PERK activator, tunicamycin. Therefore, our study suggests that inhibition of PERK phosphorylation could be a potential therapeutic target to restore memory deficits after TBI.SIGNIFICANCE STATEMENT Traumatic brain injury (TBI) is the leading cause of death and disability around the world and affects 1.7 million Americans each year. Here, we have shown that TBI-activated PKR-like ER kinase (PERK) is responsible for memory deficiency, which is the most common problem in TBI patients. A majority of PERK's biological activities have been attributed to its function as an eIF2α kinase. However, our study suggests that activated PERK mediates its function via increasing phosphorylation of CAMP response element binding protein (CREB) and PSD95 after TBI. Blocking PERK phosphorylation rescues spine loss and memory deficits independently of phosphorylation of eIF2α. Therefore, our study suggests that CREB and PSD95 are novel substrates of PERK, so inhibition of PERK phosphorylation using GSK2656157 would be beneficial against memory impairment after TBI.

Olanzapine-induced early cardiovascular effects are mediated by the biological clock and prevented by melatonin

Second generation antipsychotics (SGA) are associated with adverse cardiometabolic side effects contributing to premature mortality in patients. While mechanisms mediating these cardiometabolic side effects remain poorly understood, three independent studies recently demonstrated that melatonin was protective against cardiometabolic risk in SGA-treated patients. As one of the main target areas of circulating melatonin in the brain is the suprachiasmatic nucleus (SCN), we hypothesized that the SCN is involved in SGA-induced early cardiovascular effects in Wistar rats. We evaluated the acute effects of olanzapine and melatonin in the biological clock, paraventricular nucleus and autonomic nervous system using immunohistochemistry, invasive cardiovascular measurements, and Western blot. Olanzapine induced c-Fos immunoreactivity in the SCN followed by the paraventricular nucleus and dorsal motor nucleus of the vagus indicating a potent induction of parasympathetic tone. The involvement of a SCN-parasympathetic neuronal pathway after olanzapine administration was further documented using cholera toxin-B retrograde tracing and vasoactive intestinal peptide immunohistochemistry. Olanzapine-induced decrease in blood pressure and heart rate confirmed this. Melatonin abolished olanzapine-induced SCN c-Fos immunoreactivity, including the parasympathetic pathway and cardiovascular effects while brain areas associated with olanzapine beneficial effects including the striatum, ventral tegmental area, and nucleus accumbens remained activated. In the SCN, olanzapine phosphorylated the GSK-3β, a regulator of clock activity, which melatonin prevented. Bilateral lesions of the SCN prevented the effects of olanzapine on parasympathetic activity. Collectively, results demonstrate the SCN as a key region mediating the early effects of olanzapine on cardiovascular function and show melatonin has opposing and potentially protective effects warranting additional investigation.

Nerve Growth Factor Signaling from Membrane Microdomains to the Nucleus: Differential Regulation by Caveolins

Membrane microdomains or "lipid rafts" have emerged as essential functional modules of the cell, critical for the regulation of growth factor receptor-mediated responses. Herein we describe the dichotomy between caveolin-1 and caveolin-2, structural and regulatory components of microdomains, in modulating proliferation and differentiation. Caveolin-2 potentiates while caveolin-1 inhibits nerve growth factor (NGF) signaling and subsequent cell differentiation. Caveolin-2 does not appear to impair NGF receptor trafficking but elicits prolonged and stronger activation of MAPK (mitogen-activated protein kinase), Rsk2 (ribosomal protein S6 kinase 2), and CREB (cAMP response element binding protein). In contrast, caveolin-1 does not alter initiation of the NGF signaling pathway activation; rather, it acts, at least in part, by sequestering the cognate receptors, TrkA and p75NTR, at the plasma membrane, together with the phosphorylated form of the downstream effector Rsk2, which ultimately prevents CREB phosphorylation. The non-phosphorylatable caveolin-1 serine 80 mutant (S80V), no longer inhibits TrkA trafficking or subsequent CREB phosphorylation. MC192, a monoclonal antibody towards p75NTR that does not block NGF binding, prevents exit of both NGF receptors (TrkA and p75NTR) from lipid rafts. The results presented herein underline the role of caveolin and receptor signaling complex interplay in the context of neuronal development and tumorigenesis.

CREB at the Crossroads of Activity-Dependent Regulation of Nervous System Development and Function

The central nervous system is a highly plastic network of cells that constantly adjusts its functions to environmental stimuli throughout life. Transcription-dependent mechanisms modify neuronal properties to respond to external stimuli regulating numerous developmental functions, such as cell survival and differentiation, and physiological functions such as learning, memory, and circadian rhythmicity. The discovery and cloning of the cyclic adenosine monophosphate (cAMP) responsive element binding protein (CREB) constituted a big step toward deciphering the molecular mechanisms underlying neuronal plasticity. CREB was first discovered in learning and memory studies as a crucial mediator of activity-dependent changes in target gene expression that in turn impose long-lasting modifications of the structure and function of neurons. In this chapter, we review the molecular and signaling mechanisms of neural activity-dependent recruitment of CREB and its cofactors. We discuss the crosstalk between signaling pathways that imprints diverse spatiotemporal patterns of CREB activation allowing for the integration of a wide variety of stimuli.

Synergistic Neuroprotective Effects of Two Herbal Ingredients via CREB-Dependent Pathway

As two natural oligosaccharide esters, 3,6’-Disinapoyl sucrose (DISS) and tenuifolisideA (TFSA) are originating from the root of Polygala tenuifolia Willd, a traditional Chinese medicine used in treatment of mental disorders. Previous reports have shown that both of them possess in vitro neuroprotective effects by stimulating different upstream pathways related with cyclic AMP-responsive element-binding protein (CREB). In the present study, we investigated the additive neuroprotective effects of DISS and TFSA on Glu-induced damage of SY5Y cells and purposed the possible underlying mechanism. The interaction between DISS and TFSA showed a clear-cut synergistic effect as evidenced by combination index (CI). Additional evidence from biochemical (NOS activity) assays confirmed their additive inhibition on the Glu-induced NOS hyperactivation. Moreover, we showed that co-treatment of DISS and TFSA resulted in an additively up-regulated phosphorylation of CREB as well as increased expressions of CRTC1 and BDNF. Neuroprotective effects of DISS and TFSA on Glu-induced decrease in cell viability were blocked by MAPK/ERK1/2 inhibitor (U0126) and PI3-K inhibitor (LY290042). Nevertheless, the CRTC1 or BDNF expression induced by these two compounds was significantly reduced in the presence of either ERK or PI3-K inhibitor, indicating that the two oligosaccharide esters shared some common pathways in the regulation of CREB-BDNF pathway. Taken together, we, for the first time, showed that DISS and TFSA exerted the additive neuroprotective effects on CREB-BDNF signaling pathway through complementary mechanisms.

Expression of Iron Regulatory Protein 1 Is Regulated not only by HIF-1 but also pCREB under Hypoxia

The inconsistent of responses of IRP1 and HIF-1 alpha to hypoxia and the similar tendencies in the changes of IRP1 and pCREB contents led us to hypothesize that pCREB might be involved in the regulation of IRP1 under hypoxia. Here, we investigated the role of pCREB in IRP1 expression in HepG2 cells under hypoxia using quantitative PCR, western blot, immunofluorescence, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP). We demonstrated that 1) Hypoxia increased pCREB levels inside of the nucleus; 2) Putative CREs were found in the IRP1 gene; 3) Nuclear extracts of HepG2 cells treated with hypoxia could bind to CRE1 and CRE3, and 100-fold competitor of putative CREs could abolish the binding activity to varying degrees; 4) pCREB was found in the CRE1 and CRE3 DNA-protein complexes of EMSA; 5) CRE1 and CRE3 binding activity of IRP1 depended on CREB activation but not on HIF-1; 6) Increased IRP1 expression under hypoxia could be prevented by LY294002; 7) ChIP assays demonstrated that pCREB binds to IRP1 promoter; and 8) HIF-1 and/or HIF-2 siRNA had no effect on the expression of pCREB and IRP1 proteins in cells treated with hypoxia for 8 hours. Our findings evidenced for the involvement of pCREB in IRP1 expression and revealed a dominant role of PI3K/Akt pathway in CREB activation under hypoxia and also suggested that dual-regulation of IRP1 expression by HIF-1 and pCERB or other transcription factor(s) under hypoxia might be a common mechanism in most if not all of hypoxia-inducible genes.

A subchronic toxicity study of Radix Dipsaci water extract by oral administration in F344 rats

Radix Dipsaci, the dried root of Dipsacus asperoides C.Y. Cheng & T.M.Ai, has therapeutic effects on various disorders, and in particular, bone and joint disease. Despite such ethnomedicinal benefits, there is very little information regarding its in vivo toxicity or adverse effects. This study was conducted to evaluate the potential toxicity of the Radix Dipsaci water Extract (RD-wE) by using F344 rats. The RD-wE was administered orally to rats at doses of 0, 125, 250, 500, 1000, and 2000 mg/kg body weight (bw)/day for 13 weeks. During the treatment period there were no mortalities attributed to RD-wE. Moreover, no toxic effects were observed with regard to body weight, clinical pathology (hematology, clinical biochemistry, and urinalysis), and anatomic pathology (gross findings, organ weight, and microscopic examination). The changes related to the treatment were excessive salivation at the mouth and soft feces, observed in male and female rats at 1000 or 2000 mg/kg bw/day, but these were not accompanied by any microscopic correlate or other pathophysiological changes. Based on these results, the oral no-observed-adverse-effect level of the RD-wE was considered to be 2000 mg/kg bw/day in both genders, although the target organs were not determined under the current experimental conditions.

Indication of nerve growth factor binding components from herbal extracts by HerboChip: a platform for drug screening on a chip

Background

HerboChip is an array of different fractions deriving from herbal extracts. This study aimed to identify effective components from Chinese medicine (CM) that interact with nerve growth factor (NGF) as a target using HerboChip.

Methods

Fifty types of CM that are traditionally used as remedies for emotion imbalance were selected and extracted with 50 % ethanol. Biotinylated-NGF was hybridized with over 300 chips coated with different HPLC-separated fractions from CM extracts and straptavidin-Cy5 was used to identify the NGF-bound fractions.

Results

Over 300 chips were screened within a week, and 17 positive hits were identified. The interaction of the identified herbal extracts with NGF was confirmed in cultured PC12 cells. Co-application of NGF and herbal extract interfered with NGF-induced expression of neurofilaments, including NF68 and NF200 in cell cultures. Western blot analysis comparing the intensity of phosphorylated cAMP response element-binding protein (CREB) over total CREB showed NGF-induced CREB phosphorylation was modulated by the identified herbal extracts. Five CM herbs showed activating activities on the NGF response and nine CM herbs showed inhibiting activities.

Conclusion

The current result supported the applicability of HerboChip for screening NGF binding components from herbal extracts.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-016-0107-8) contains supplementary material, which is available to authorized users.

REVIEW ■ : Jun, Fos, and CREB/ATF Transcription Factors in the Brain: Control of Gene Expression under Normal and Pathophysiological Conditions

The expression and activation of transcription factors and the control of gene transcription in the nervous system is a recent and rapidly expanding field in neurosciences. This research area may provide insights concerning the information transfer that arises from postsynaptic potentials or ligand-coupling of membrane receptors and terminates in gene expression. Visualization of both de novo synthesis of inducible transcription factors (ITFs) and phosphorylation of preexisting transcription factors have been used to mark neurons, pathways, and networks excited by various stimuli. This article summarizes basics of the transcription process and the complex functions of Jun, Fos, and CREB/ATF proteins, as well as the use of ITFs as experimental instruments in neurophysiology and neurobiology. The major focus is on the alterations in ITF expression following acute or chronic pathophysiological stimuli as mirrors of alterations in neuronal programs underlying adaptation, dysfunctions, or the development of diseases affecting the nervous system. NEUROSCIENTIST 2:153-161, 1996

REVIEW ■ : Regulation of Gene Expression by Neural Signals

Regulation of gene expression by extracellular signals is a ubiquitous biological mechanism controlling cell proliferation, differentiation, homeostasis, and adaptation to the environment. This article will focus on one set of issues within the broad topic of regulated gene expression: mechanisms by which neurotransmitters and neural activity regulate genes within the mature nervous system. The regulatory actions of growth factors, cytokines, and other types of extracellular signals are complex matters deserving separate review. This article proceeds from a basic overview of transcriptional regulation to a more specific discussion of the actions of two families of transcriptional regulators, the CREB family and the AP-1 family. These families of proteins are discussed because they play a central role in the regulation of gene expression by neurotransmitters and also because they exemplify many general principles of extracellular signal-regulated gene expression. NEUROSCIENTIST 2:217-224, 1996

Treatment with Akebia Saponin D Ameliorates Aβ1–42-Induced Memory Impairment and Neurotoxicity in Rats

Amyloid-β peptide (Aβ) is known to be directly associated with the progressive neuronal death observed in Alzheimer’s disease (AD). However, effective neuroprotective approaches against Aβ neurotoxicity are still unavailable. In the present study, we investigated the protective effects of Akebia saponin D (ASD), a typical compound isolated from the rhizome of Dipsacus asper Wall, on Aβ_1–42-induced impairment of learning and memory formation and explored the probable underlying molecular mechanisms. We found that treatment with ASD (30, 90 or 270 mg/kg) significantly ameliorated impaired spatial learning and memory in intracerebroventricularly (ICV) Aβ_1–42-injected rats, as evidenced by a decrease tendency in escape latency during acquisition trials and improvement in exploratory activities in the probe trial in Morris water maze (MWM). Further study showed that ASD reversed Aβ_1–42-induced accumulation of Aβ_1–42 and Aβ_1–40 in the hippocampus through down-regulating the expression of BACE and Presenilin 2 accompanied with increased the expression of TACE, IDE and LRP-1. Taken together, our findings suggested that ASD exerted therapeutic effects on Aβ-induced cognitive deficits via amyloidogenic pathway.

Simvastatin attenuates oleic acid-induced oxidative stress through CREB-dependent induction of heme oxygenase-1 in renal proximal tubule cells

BACKGROUND

Statins elicit antioxidant effects independently of their lipid-lowering properties. Heme oxygenase-1 (HO-1) induction may be a part of these pleiotropic effects, which are insufficiently described in the kidney. We hypothesize that simvastatin (SIM) transcriptionally activates HO-1 that protects renal proximal tubule cells from lipotoxic injury.

METHODS

Impact of SIM on 100 μmol/l oleic acid (OA)-mediated reactive oxygen species (ROS) production and consequent oxidative stress (4-hydroxynonenal (HNE) content) as well as cell injury/apoptosis (lactate dehydrogenase (LDH) release, caspase-3 activation) were determined in cultured renal proximal tubule (NRK52E) cells. Effect of SIM on the HO-1 promoter and its enhancer elements (antioxidant response element (ARE), CCAAT, AP1, and cAMP response element (CRE)) was also determined in reporter luciferase assays. Dominant-negative (dnMEK, M1CREB) and pharmacologic (H89) approaches were used to inhibit activation of extracellular signal regulated kinase (ERK), CREB, and protein kinase A (PKA), respectively.

RESULTS

SIM dose-dependently activated the HO-1 promoter that was essential for protection against OA-dependent ROS production/oxidative stress and LDH release/caspase-3 activation. We found that the HO-1 promoter was induced through ERK and PKA-dependent activation of the CRE by SIM.

CONCLUSION

SIM may protect the kidney from adverse effects of circulating fatty acids by upregulating the antioxidant HO-1, aside from its well-described lipid-lowering effects.

Activation of protein kinase A in the amygdala modulates anxiety-like behaviors in social defeat exposed mice

Background

Social defeat (SD) stress induces social avoidance and anxiety-like phenotypes. Amygdala is recognized as an emotion-related brain region such as fear, aversion and anxiety. It is conceivable to hypothesize that activation of amygdala is involved in SD-dependent behavioral defects.

Results

SD model was established using C57BL/6J mice that were physically defeated by different CD-1 mice for 10 days. Stressed mice exhibited decreased social interaction level in social interaction test and significant anxiety-like behaviors in elevated plus maze and open field tests. Meanwhile, a higher phosphorylation of PKA and CREB with a mutually linear correlation, and increased Fos labeled cells in the basolateral amygdala (BLA) were observed. Activation of PKA in the BLA by 8-Br-cAMP, a PKA activitor, significantly upregulated pCREB and Fos expression. To address the role of PKA activation on SD stress-induced social avoidance and anxiety-like behaviors, 8-Br-cAMP or H-89, a PKA inhibitor, was continuously administered into the bilateral BLA by a micro-osmotic pump system during the 10-day SD period. Neither H-89 nor 8-Br-cAMP affected the social behavior. Differently, 8-Br-cAMP significantly relieved anxiety-like behaviors in both general and moderate SD protocols. H-89 per se did not have anxiogenic effect in naïve mice, but aggravated moderate SD stress-induced anxiety-like behaviors. The antidepressant clomipramine reduced SD-induced anxiety and up-regulated pPKA level in the BLA.

Conclusions

These results suggest that SD-driven PKA activation in the basolateral amygdala is actually a compensatory rather than pathogenic response in the homeostasis, and modulating amygdaloid PKA may exhibit potency in the therapy of social derived disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-015-0181-3) contains supplementary material, which is available to authorized users.

Altered ERK1/2 Signaling in the Brain of Learned Helpless Rats: Relevance in Vulnerability to Developing Stress-Induced Depression

Extracellular signal-regulated kinase 1/2- (ERK1/2-) mediated cellular signaling plays a major role in synaptic and structural plasticity. Although ERK1/2 signaling has been shown to be involved in stress and depression, whether vulnerability to develop depression is associated with abnormalities in ERK1/2 signaling is not clearly known. The present study examined ERK1/2 signaling in frontal cortex and hippocampus of rats that showed vulnerability (learned helplessness, (LH)) or resiliency (non-learned helplessness, (non-LH)) to developing stress-induced depression. In frontal cortex and hippocampus of LH rats, we found that mRNA and protein expressions of ERK1 and ERK2 were significantly reduced, which was associated with their reduced activation and phosphorylation in cytosolic and nuclear fractions, where ERK1 and ERK2 target their substrates. In addition, ERK1/2-mediated catalytic activities and phosphorylation of downstream substrates RSK1 (cytosolic and nuclear) and MSK1 (nuclear) were also lower in the frontal cortex and hippocampus of LH rats without any change in their mRNA or protein expression. None of these changes were evident in non-LH rats. Our study indicates that ERK1/2 signaling is differentially regulated in LH and non-LH rats and suggests that abnormalities in ERK1/2 signaling may be crucial in the vulnerability to developing depression.

Mesoderm-specific transcript (MEST) is a negative regulator of human adipocyte differentiation

BACKGROUND

A growing body of evidence suggests that many downstream pathologies of obesity are amplified or even initiated by molecular changes within the white adipose tissue (WAT). Such changes are the result of an excessive expansion of individual white adipocytes and could potentially be ameliorated via an increase in de novo adipocyte recruitment (adipogenesis). Mesoderm-specific transcript (MEST) is a protein with a putative yet unidentified enzymatic function and has previously been shown to correlate with adiposity and adipocyte size in mouse.

OBJECTIVES

This study analysed WAT samples and employed a cell model of adipogenesis to characterise MEST expression and function in human.

METHODS AND RESULTS

MEST mRNA and protein levels increased during adipocyte differentiation of human multipotent adipose-derived stem cells. Further, obese individuals displayed significantly higher MEST levels in WAT compared with normal-weight subjects, and MEST was significantly correlated with adipocyte volume. In striking contrast to previous mouse studies, knockdown of MEST enhanced human adipocyte differentiation, most likely via a significant promotion of peroxisome proliferator-activated receptor signalling, glycolysis and fatty acid biosynthesis pathways at early stages. Correspondingly, overexpression of MEST impaired adipogenesis. We further found that silencing of MEST fully substitutes for the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) as an inducer of adipogenesis. Accordingly, phosphorylation of the pro-adipogenic transcription factors cyclic AMP responsive element binding protein (CREB) and activating transcription factor 1 (ATF1) were highly increased on MEST knockdown.

CONCLUSIONS

Although we found a similar association between MEST and adiposity as previously described for mouse, our functional analyses suggest that MEST acts as an inhibitor of human adipogenesis, contrary to previous murine studies. We have further established a novel link between MEST and CREB/ATF1 that could be of general relevance in regulation of metabolism, in particular obesity-associated diseases.