Discovery of a Synergistic Inhibitor of cAMP-Response Element Binding Protein (CREB)-Mediated Gene Transcription with -

BDNF-TrkB signaling orchestrates the buildup process of local sleep

Sleep debt accumulates during wakefulness, leading to increased slow wave activity (SWA) during sleep, an encephalographic marker for sleep need. The use-dependent demands of prior wakefulness increase sleep SWA locally. However, the circuitry and molecular identity of this "local sleep" remain unclear. Using pharmacology and optogenetic perturbations together with transcriptomics, we find that cortical brain-derived neurotrophic factor (BDNF) regulates SWA via the activation of tyrosine kinase B (TrkB) receptor and cAMP-response element-binding protein (CREB). We map BDNF/TrkB-induced sleep SWA to layer 5 (L5) pyramidal neurons of the cortex, independent of neuronal firing per se. Using mathematical modeling, we here propose a model of how BDNF's effects on synaptic strength can increase SWA in ways not achieved through increased firing alone. Proteomic analysis further reveals that TrkB activation enriches ubiquitin and proteasome subunits. Together, our study reveals that local SWA control is mediated by BDNF-TrkB-CREB signaling in L5 excitatory cortical neurons.

Mechanisms contributing to inhibition of retinal ganglion cell death by cell permeable peptain-1 under glaucomatous stress

This study assesses the neuroprotective potential of CPP-P1, a conjugate of an anti-apoptotic peptain-1 (P1) and a cell-penetrating peptide (CPP) in in vitro, in vivo, and ex vivo glaucoma models. Primary retinal ganglion cells (RGCs) were subjected to either neurotrophic factor (NF) deprivation for 48 h or endothelin-3 (ET-3) treatment for 24 h and received either CPP-P1 or vehicle. RGC survival was analyzed using a Live/Dead assay. Axotomized human retinal explants were treated with CPP-P1 or vehicle for seven days, stained with RGC marker RBPMS, and RGC survival was analyzed. Brown Norway (BN) rats with elevated intraocular pressure (IOP) received weekly intravitreal injections of CPP-P1 or vehicle for six weeks. RGC function was evaluated using a pattern electroretinogram (PERG). RGC and axonal damage were also assessed. RGCs from ocular hypertensive rats treated with CPP-P1 or vehicle for seven days were isolated for transcriptomic analysis. RGCs subjected to 48 h of NF deprivation were used for qPCR target confirmation. NF deprivation led to a significant loss of RGCs, which was markedly reduced by CPP-P1 treatment. CPP-P1 also decreased ET-3-mediated RGC death. In ex vivo human retinal explants, CPP-P1 decreased RGC loss. IOP elevation resulted in significant RGC loss in mid-peripheral and peripheral retinas compared to that in naive rats, which was significantly reduced by CPP-P1 treatment. PERG amplitude decline in IOP-elevated rats was mitigated by CPP-P1 treatment. Following IOP elevation in BN rats, the transcriptomic analysis showed over 6,000 differentially expressed genes in the CPP-P1 group compared to the vehicle-treated group. Upregulated pathways included CREB signaling and synaptogenesis. A significant increase in Creb1 mRNA and elevated phosphorylated Creb were observed in CPP-P1-treated RGCs. Our study showed that CPP-P1 is neuroprotective through CREB signaling enhancement in several settings that mimic glaucomatous conditions. The findings from this study are significant as they address the pressing need for the development of efficacious therapeutic strategies to maintain RGC viability and functionality associated with glaucoma.

Endoplasmic reticulum stress impedes regulated secretion by governing key exocytotic and granulogenic molecular switches

Dense core vesicles (DCVs) and synaptic vesicles are specialised secretory vesicles in neurons and neuroendocrine cells, and abnormal release of their cargo is associated with various pathophysiologies. Endoplasmic reticulum (ER) stress and inter-organellar communication are also associated with disease biology. To investigate the functional status of regulated exocytosis arising from the crosstalk of a stressed ER and DCVs, ER stress was modelled in PC12 neuroendocrine cells using thapsigargin. DCV exocytosis was severely compromised in ER-stressed PC12 cells and was reversed to varying magnitudes by ER stress attenuators. Experiments with tunicamycin, an independent ER stressor, yielded similar results. Concurrently, ER stress also caused impaired DCV exocytosis in insulin-secreting INS-1 cells. Molecular analysis revealed blunted SNAP25 expression, potentially attributed to augmented levels of ATF4, an inhibitor of CREB that binds to the CREB-binding site. The effects of loss of function of ATF4 in ER-stressed cells substantiated this attribution. Our studies revealed severe defects in DCV exocytosis in ER-stressed cells for the first time, mediated by reduced levels of key exocytotic and granulogenic switches regulated via the eIF2α (EIF2A)-ATF4 axis.

Naringin Mediates Adult Hippocampal Neurogenesis for Antidepression via Activating CREB Signaling

The brain-derived neurotrophic factor/tropomyosin receptor kinase B/cAMP response element-binding protein (BDNF/TrkB/CREB) signaling pathway is a critical therapeutic target for inducing adult hippocampal neurogenesis and antidepressant therapy. In this study, we tested the hypothesis that naringin, a natural medicinal compound, could promote adult hippocampal neurogenesis and improve depression-like behaviors via regulating the BDNF/TrkB/CREB signaling pathway. We first investigated the effects of naringin on promoting adult hippocampal neurogenesis in both normal and chronic corticosterone (CORT)-induced depressive mice. Under physiological condition, naringin treatment enhanced the proliferation of neural stem/progenitor cells (NSPCs) and accelerated neuronal differentiation. In CORT-induced depression mouse model, naringin treatment promoted neuronal differentiation and maturation of NSPCs for hippocampal neurogenesis. Forced swim test, tail suspension test, and open field test confirmed the antidepressant and anxiolytic effects of naringin. Co-treatment of temozolomide (TMZ), a neurogenic inhibitor, abolished these antidepressant and anxiolytic effects. Meanwhile, naringin treatment increased phosphorylation of cAMP response element binding protein (CREB) but had no effect on the expression of brain-derived neurotrophic factor and phosphorylation of TrkB in the hippocampus of CORT-induced depressive mice. Co-treatment of CREB inhibitor 666-15, rather than TrkB inhibitor Cyc-B, abolished the neurogenesis-promoting and antidepressant effects of naringin. Taken together, naringin has antidepressant and anxiolytic effects, and the underlying mechanisms could be attributed to enhance hippocampal neurogenesis via activating CREB signaling.

Alveolar macrophage-derived progranulin mediated pro-inflammatory Il-6 expression via regulating Creb1 in silicosis model

Progranulin (PGRN) is a secreted factor involved in inflammatory diseases. However, the function of PGRN in silica-induced lung inflammation has not been elucidated. In this study, we demonstrated that PGRN in serum and lung tissues was markedly increased in silicosis mouse model. And immunohistochemistry results showed that PGRN was mainly expressed in alveolar macrophages, which was further confirmed in silica-treated alvelar macrophages cell line (MH-S) in vitro. PGRN promoted pro-inflammatory cytokines transcription such as interleukin (Il)-6, tumor necrosis factor-α (Tnf-α) and Il-1β in MH-S cells, and the increasing of Il-6 was most obvious. Knockdown of PGRN blocked the silica-induced elevation of intracellular Il-6 in MH-S cells. Furthermore, we also found that PGRN could increase the phosphorylation of Cyclic AMP-responsive element-binding protein 1 (Creb1), a transcriptional regulator of Il-6. Inhibition of p-Creb1 by the phosphorylation inhibitor of Creb1 (666-15) decreased PGRN-induced intracellular Il-6 production in MH-S cells. In conclusion, PGRN was highly increased in silicosis mouse model and upregulated inflammatory cytokines expression. These findings suggested that PGRN might be a key mediator in silica-induced inflammation and provided a new clue for the diagnosis and drug therapy of silicosis.

Design, Synthesis and Biological Evaluation of Prodrugs of 666-15 as Inhibitors of CREB-Mediated Gene Transcription

cAMP-response element binding protein (CREB) is a transcription factor involved in multiple cancers. Chemical inhibitors of CREB represent potential anticancer agents. We previously identified 666-15 as a potent CREB inhibitor. While 666-15 showed efficacious anticancer activity in vivo through intraperitoneal (IP) injection, its oral bioavailability is limited. To increase its oral bioavailability, we describe synthesis and evaluation of prodrugs based on 666-15. The amino acid esters were attempted, but they were not stable for detailed characterization. The corresponding sulfate and phosphates were prepared. The sulfate of 666-15 was too stable to release 666-15 while the phosphates were converted into 666-15 with half-lives of ∼2 h. Phosphate 3 was also a potent CREB inhibitor with anti-breast cancer activity. Furthermore, compound 3 showed much improved oral bioavailability at 38%. These studies support that 3 can be used as an oral CREB inhibitor while IP administration of 666-15 is preferred for in vivo applications.

The transcribed ultraconserved element uc.51 promotes the proliferation and metastasis of breast cancer by stabilizing NONO

Long noncoding RNAs have recently emerged as significant contributors to cancers, including breast cancer (BC). One class of long noncoding RNAs called transcribed ultraconserved regions (T-UCRs) is highly conserved in many species and closely related to diverse physiological and pathological processes. However, the function of T-UCRs in BC remains largely unclear. In this study, we identified uc.51, a T-UCR that is overexpressed in both BC tissues and cell lines and is correlated with larger tumor size. Loss- and gain-of-function assays were performed in vitro and demonstrated that uc.51 promotes the proliferation, migration, and invasion of BC cells. Mechanistically, non-POU domain-containing octamer-binding protein (NONO) was found to physically interact with uc.51 by RNA pulldown followed by mass spectrometry. This interaction was further verified by RNA immunoprecipitation. Moreover, uc.51 positively regulated the expression of NONO, maintained its stability through the ubiquitin-proteasome system, and activated the phosphorylation of CREB. Rescue experiments demonstrated that NONO overexpression compensated for the attenuated influence on BC progression resulting from downregulation of uc.51, indicating that NONO functions downstream of uc.51. In vivo functional experiments also revealed a positive correlation between uc.51 expression and tumor size. Ki-67 and NONO levels in the lv-uc.51-shRNA group were decreased compared with those in the lv-con-shRNA group, according to the immunohistochemical staining results, and a decreased incidence of distant metastasis was observed in the lv-uc.51-shRNA group in the xenograft model. Collectively, our results reveal a substantial role for the uc.51-NONO axis in BC progression and indicate that the uc.51-NONO axis has potential to be a therapeutic target for BC.

Azadirachtin downregulates the expression of the CREB gene and protein in the brain and directly or indirectly affects the cognitive behavior of the Spodoptera litura fourth-instar larvae

BACKGROUND

Azadirachtin has the potential to be used for pest control. Nevertheless, few studies have investigated the effects of azadirachtin on the cognitive behavior of pests. In this study, expression of the cAMP response element-binding protein (CREB) and its gene were studied via a series of experiments in Spodoptera litura larvae treated with azadirachtin.

RESULTS

RNA-Seq analysis of S. litura larvae treated with azadirachtin was undertaken. According to Kyoto Encyclopedia of Genes and Genomes analysis, the top 20 enriched pathways included neuroactive ligand-receptor interaction pathways, with seven significantly differentially expressed genes including CREB. Quantitative real time polymerase chain reaction (qRT-PCR) results indicated that the CREB gene was expressed during all developmental stages of S. litura, but relative expression of the CREB gene was significantly downregulated after treatment with azadirachtin. Grayscale statistical analysis also showed that expression levels of protein kinase A (PKA), extracellular signal-regulated kinase (ERK) and CREB proteins were significantly downregulated after treatment with azadirachtin. Moreover, RNA interference results showed that the effect of azadirachtin on the cognitive behavior of S. litura was consistent with that seen after interfering with CREB. In addition, larval selectivity to addictive odor sources was reduced, and the initial reaction time was increased.

CONCLUSIONS

This study clarified that azadirachtin can affect the cognitive behavior of S. litura and treatment with azadirachtin resulted in a downregulation of gene and protein expression of CREB and its pathway proteins. © 2020 Society of Chemical Industry.

Characterization of the G protein-coupled receptor kinase 6 promoter reveals a functional CREB binding site

Background

G protein-coupled receptor kinase 6 (GRK6) is part of the G protein-coupled receptor kinase family, whose members act as key regulators of seven-transmembrane receptor signalling. GRK6 seems to play a role in regulation of inflammatory processes, but mechanisms of transcriptional regulation of GRK6 expression in inflammatory cell lines have not been characterized. Protein kinase C (PKC) signalling is also involved in inflammatory regulation and an impact of PKC activation on GRK6 protein expression was described previously. Thus, the aim of this study was to 1) characterize the GRK6 promoter, and 2) investigate a potential influence of PKC on GRK6 expression.

Methods

Five deletion constructs of the GRK6 promoter were cloned. After transient transfection into a human T cell line, promoter activity was assessed using luciferase reporter gene assays. Putative transcription factor binding sites were identified, mutated, and binding was investigated using electrophoretic mobility shift assays (EMSA). Following stimulation with a PKC activator, GRK6 expression on mRNA and protein levels was assessed by reverse transcriptase qPCR and Western blots.

Results

Investigation of the GRK6 promoter revealed a putative cAMP responsive element (CRE), whose mutation led to decreased promoter activity (p = 0.0006). Functionality of the CRE binding protein (CREB) binding site was verified in EMSA blots. Stimulation with a PKC activator resulted in decreased GRK6 promoter activity (p = 0.0027), mRNA (p = 0.04) and protein expression.

Conclusion

We characterized the human GRK6 promoter and identified promoter activity to be influenced by a CREB binding site. PKC might be one determinant contributing to altered GRK6 expression.

Leite L, da S. Tavares-Henriques M, Lopes LAF, Oliveira LGR, Silva-Filho SE, da Silveira APS, Cuman RKN, de S. Silva-Comar FM, Comar JF, do A. Brasileiro L, dos Santos JN, de Freitas WR, Leão KV, da Silva JG, Klein RC, Klein MHF, da S. Ramos BH, Fernandes CKC, de L. Ribas DG, Oesterreich SA. Modulation of the Serotonergic Receptosome in the Treatment of Anxiety and Depression: A Narrative Review of the Experimental Evidence

Serotonin (5-HT) receptors are found throughout central and peripheral nervous systems, mainly in brain regions involved in the neurobiology of anxiety and depression. 5-HT receptors are currently promising targets for discovering new drugs for treating disorders ranging from migraine to neuropsychiatric upsets, such as anxiety and depression. It is well described in the current literature that the brain expresses seven types of 5-HT receptors comprising eighteen distinct subtypes. In this article, we comprehensively reviewed 5-HT1-7 receptors. Of the eighteen 5-HT receptors known today, thirteen are G protein-coupled receptors (GPCRs) and represent targets for approximately 40% of drugs used in humans. Signaling pathways related to these receptors play a crucial role in neurodevelopment and can be modulated to develop effective therapies to treat anxiety and depression. This review presents the experimental evidence of the modulation of the “serotonergic receptosome” in the treatment of anxiety and depression, as well as demonstrating state-of-the-art research related to phytochemicals and these disorders. In addition, detailed aspects of the pharmacological mechanism of action of all currently known 5-HT receptor families were reviewed. From this review, it will be possible to direct the rational design of drugs towards new therapies that involve signaling via 5-HT receptors.

What turns CREB on? And off? And why does it matter?

Altered expression and function of the transcription factor cyclic AMP response-binding protein (CREB) has been identified to play an important role in cancer and is associated with the overall survival and therapy response of tumor patients. This review focuses on the expression and activation of CREB under physiologic conditions and in tumors of distinct origin as well as the underlying mechanisms of CREB regulation by diverse stimuli and inhibitors. In addition, the clinical relevance of CREB is summarized, including its use as a prognostic and/or predictive marker as well as a therapeutic target.

Mechanistic insights into the activation of ester prodrugs of 666-15

cAMP-response element binding protein (CREB) is an oncogenic transcription factor implicated in many different types of cancer. We previously reported the discovery of 666-15 as a potent inhibitor of CREB-mediated gene transcription. In an effort to improve the aqueous solubility of 666-15, amino ester prodrugs 1 and 4 were designed and synthesized. Detailed chemical and biological studies of 1 and 4 revealed that a small portion of the prodrugs were converted into 666-15 through intermediate 3 instead of a long-range O,N-acyl transfer reaction that was initially proposed. These results provide unique insights into the activation of these ester prodrugs.

New horizons from novel therapies in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a relatively rare, but highly lethal cancer of the pleural mesothelial cells. Its pathoge-nesis is integrally linked to asbestos exposure. In spite of recent developments providing a more detailed understanding of the pathogenesis, the outcomes continue to be poor. To date, trimodality therapy involving surgery coupled with chemotherapy and/or radiotherapy remains the standard of therapy. The development of resistance of the tumor cells to radiation and several che-motherapeutic agents poses even greater challenges in the management of this cancer. Ionizing radiation damages cancer cell DNA and aids in therapeutic response, but it also activates cell survival signaling pathways that helps the tumor cells to overcome radiation-induced cytotoxicity. A careful evaluation of the biology involved in mesothelioma with an emphasis on the workings of pro-survival signaling pathways might offer some guidance for treatment options. This review focuses on the existing treatment options for MPM, novel treatment approaches based on recent studies combining the use of inhibitors which target different pro-survival pathways, and radiotherapy to optimize treatment.