CREB Phosphorylation Research Articles

Clofarabine induces ERK/MSK/CREB activation through inhibiting CD99 on Ewing sarcoma cells.

Clofarabine, an FDA approved purine analog, is used in the treatment of relapsed or refractory acute lymphoblastic leukemia. Clofarabine acts by inhibiting DNA synthesis. We demonstrated that clofarabine may have a novel function though inhibiting CD99, a transmembrane protein highly expressed on Ewing Sarcoma (ES) cells. CD99 is a validated target in ES whose inhibition may lead to a high therapeutic index for patients. Here we present additional data to support the hypothesis that clofarabine acts on CD99 and regulates key signaling pathways in ES. Cellular thermal shift assay indicated a direct interaction between clofarabine and CD99 in ES cell lysates. Clofarabine induced ES cell death does not require clofarabine’s conversion to its active form by deoxycytidine kinase. A phosphokinase array screen with clofarabine and a CD99 blocking antibody identified alterations in signaling pathways. CD99 inhibition with clofarabine in ES cells caused rapid and sustained phosphorylation of ERK, MSK, and CREB. However, activation of this pathway did not correlate with clofarabine induced ES cell death. In summary, we demonstrated that clofarabine may activate ERK, MSK, and CREB phosphorylation through CD99 within minutes, however this paradoxical activation and subsequent ES cell death requires additional investigation.

Metabolic changes in synovial cells in early inflammation: Involvement of CREB phosphorylation in the anti-inflammatory effect of 2-deoxyglucose

The involvement of metabolic reprogramming has been suggested to contribute to the pathophysiology of rheumatoid arthritis (RA). Glycolysis is enhanced in synovial cell metabolism in RA patients. Inhibitors of glycolysis are known to have anti-inflammatory effects. But, changes in the metabolism of normal synovial membranes or synovial cells during the early stages of inflammation remains unknown. Moreover, there are still many aspects of inflammatory signaling pathways altered by glycolysis inhibitors, that remain unclear. In this study we found that, in normal, non-pathological bovine synovial cells, most of ATP synthesis was generated by mitochondrial respiration. However, during the early of stages inflammation, initiated by lipopolysaccharide (LPS) exposure, synovial cells shifted to glycolysis for ATP production. The glycolysis inhibitor 2-deoxyglucose (2DG) reversed LPS induced increases in glycolysis for ATP production and suppressed the expression of inflammatory cytokines and proteolytic enzymes. 2DG suppressed the phosphorylation of the transcription factor cAMP response element binding protein (CREB) enhanced by LPS. Treatment with a CREB inhibitor reversed the expression of LPS-stimulated inflammatory cytokines and proteolytic enzymes. This study showed that changes in metabolism occur during the early stages of inflammation of synovial cells and can be reversed by 2DG and signaling pathways associated with CREB phosphorylation.

Metso Outotec Corp, Finland

Colorectal cancer (CRC) is the most fatal gastrointestinal tumor and it is urge to explore powerful drugs for the treatment. Diosgenin (DSG) as a new steroidal had been reported exerts anti-tumor activity in multiple cancers, including CRC. However, the potential mechanism of DSG suppresses CRC remains further to be revealed. Here, we reported that DSG inhibited proliferation of CRC cells in dose- and time-dependent manner, induced apoptosis by modulating p53 and Bcl-2 family proteins expression to mediate mitochondrial apoptosis pathway, suppressed migration and invasion by reducing MMP-9 (matrix metalloproteinase) and decreased aerobic glycolysis by mediating glucose transporter (GLUT) like GLUT3 and GLUT4, and pyruvate carboxylase PC downregulation. Intriguingly, mechanistic study suggests those phenotypes involved DSG inhibited cAMP/PKA/CREB pathway in CRC cells, and result to inhibit the phosphorylation of CREB to regulate the transcription of genes above-mentioned. Finally, nude mice xenograft tumor model further indicated that DSG could be a great agent to suppress the growth of CRC cells in vivo and have no obvious side effects. Taken together, we revealed a unique mechanism that DSG suppresses CRC cells through cAMP/PKA/CREB pathway and DSG is a promising candidate drug for CRC treatment.

Polydeoxyribonucleotide Attenuates Airway Inflammation Through A2AR Signaling Pathway in PM10-Exposed Mice.

PurposeInhalation of air containing high amounts of particular matter (PM) causes various respiratory disorders including asthma, chronic obstructive pulmonary disease, and lung cancer. The changes of expression of inflammatory factors by polydeoxyribonucleotide (PDRN) administration in the PM10-exposed trachea inflammation model were evaluated.MethodsPM10 was administered to mouse trachea to induce acute inflammatory damage, and changes in inflammatory factors were observed after administration of PDRN and 3,7-dimethyl-1-propargylxanthine (DMPX) for 3 days daily. Expression of inflammatory cytokines, adenosine A2A receptor (A2AR), protein kinase A (PKA), 3΄,5΄-cyclic adenosine monophosphate responsive element binding protein (CREB) were detected by enzyme‐linked immunosorbent assay, immunofluorescence, and western blot assay.ResultsPM-exposed trachea showed increased tumor necrosis factor (TNF)-α and interleukin (IL)-1β expression, and expression of TNF-α and IL-1β was inhibited by PDRN treatment in PM-exposed mice. PM-exposed trachea showed increased nuclear factor (NF)-κB phosphorylation, and phosphorylation of nuclear factor-kappa B was inhibited by PDRN treatment in PM-exposed mice. PM-exposed trachea showed increased expression of A2AR, but PDRN treatment more enhanced A2AR expression in PM-exposed mice. PKA phosphorylation was not changed and CREP phosphorylation was decreased, however PDRN treatment increased phosphorylation of PKA and CREB in PM-exposed mice. DMPX treatment blocked all the effects of PDRN on PM-exposed mice, demonstrating that the action of PDRN occurs via A2AR.ConclusionsPDRN treatment attenuated inflammation in the trachea of the PM10-exposed mice. This improving effect of PDRN can be ascribed to the activation of A2AR through the cAMP-PKA pathway.

Levo-tetrahydropalmatine attenuates the acquisition of fentanyl-induced conditioned place preference and the changes in ERK and CREB phosphorylation expression in mice

Levo-tetrahydropalmatine (L-THP) is the main active ingredient of Corydalis and Stephania and is widely used for its sedative, analgesic, and neuroleptic effects. Though L-THP is an antagonist of dopamine receptors and has been proven to be effective in treating drug addiction, its effect on fentanyl-induced reward learning still remains unclear. This experiment was designed to investigate the effects of L-THP on fentanyl-induced rewarding behavior through conditioned place preference (CPP) in mice. Western blot assays were used to dissect the accompanying changes in the phosphorylation of extracellular signal-regulated kinase (ERK) and cAMP response element binding protein (CREB) in related brain regions, including the hippocampus (Hip), caudate putamen (CPu), prefrontal cortex (PFC), and nucleus accumbens (NAc), which may mediate the effects of L-THP on fentanyl-induced CPP. The results revealed that fentanyl could induce CPP in mice at doses of 0.025 mg/kg, 0.05 mg/kg, 0.1 mg/kg, and 0.2 mg/kg, and L-THP could attenuate the acquisition of fentany-induced CPP at a dose of 10.0 mg/kg. The levels of p-ERK and p-CREB of the saline+fentanyl group (0.05 mg/kg) increased significantly in the Hip, NAc, and PFC compared to the saline+saline group. Furthermore, L-THP (10.0 mg/kg) co-administered with fentanyl during conditioning prevented the enhanced phosphorylation of ERK and CREB in the Hip, NAc, and PFC. Our research revealed that L-THP could suppress the rewarding properties of fentanyl-induced CPP, the inhibitory effect may be related to the suppression of ERK and CREB phosphorylation in the Hip, NAc, and PFC of mice. Thus, L-THP may have therapeutic potential for fentanyl addiction.

Modulation of Cyclic AMP Levels in Fallopian Tube Cells by Natural and Environmental Estrogens.

Autocrine/paracrine factors generated in response to 17β-estradiol (E2) within the fallopian tube (FT) facilitate fertilization and early embryo development for implantation. Since cyclic AMP (cAMP) plays a key role in reproduction, regulation of its synthesis by E2 may be of biological/pathophysiological relevance. Herein, we investigated whether cAMP production in FT cells (FTCs) is regulated by E2 and environmental estrogens (EE’s; xenoestrogens and phytoestrogens). Under basal conditions, low levels of extracellular cAMP were detectable in bovine FTCs (epithelial cells and fibroblasts; 1:1 ratio). Treatment of FTCs with forskolin (AC; adenylyl cyclase activator), isoproterenol (β-adrenoceptor agonist) and IBMX (phosphodiesterase (PDE) inhibitor) dramatically (>10 fold) increased cAMP; whereas LRE1 (sAC; soluble AC inhibitor) and 2’,5’-dideoxyadenosine (DDA; transmembrane AC (tmAC)) inhibitor decreased cAMP. Comparable changes in basal and stimulated intracellular cAMP were also observed. Ro-20-1724 (PDE-IV inhibitor), but not milrinone (PDE-III inhibitor) nor mmIBMX (PDE-I inhibitor), augmented forskolin-stimulated cAMP levels, suggesting that PDE-IV dominates in FTCs. E2 increased cAMP levels and CREB phosphorylation in FTCs, and these effects were mimicked by EE’s (genistein, 4-hydroxy-2’,4’,6’-trichlorobiphenyl, 4-hydroxy-2’,4’,6’-dichlorobiphenyl). Moreover, the effects of E2 and EE were blocked by the tmAC inhibitor DDA, but not by the ERα/β antagonist ICI182780. Moreover, BAPTA-AM (intracellular-Ca2+ chelator) abrogated the effects of E2, but not genistein, on cAMP suggesting differential involvement of Ca2+. Treatment with non-permeable E2-BSA induced cAMP levels and CREB-phosphorylation; moreover, the stimulatory effects of E2 and EEs on cAMP were blocked by G15, a G protein-coupled estrogen receptor (GPER) antagonist. E2 and IBMX induced cAMP formation was inhibited by LRE1 and DDA suggesting involvement of both tmAC and sAC. Our results provide the first evidence that in FTCs, E2 and EE’s stimulate cAMP synthesis via GPER. Exposure of the FT to EE’s and PDE inhibitors may result in abnormal non-cyclic induction of cAMP levels which may induce deleterious effects on reproduction.

Protective Effects of p-Coumaric Acid Isolated from Vaccinium bracteatum Thunb. Leaf Extract on Corticosterone-Induced Neurotoxicity in SH-SY5Y Cells and Primary Rat Cortical Neurons

Corticosterone (CORT)-induced oxidative stress and neurotoxicity can cause neuronal dysfunction and mental disorders. In the present study, we investigated the effects and mechanism of the HP-20 resin fraction of the water extract of Vaccinium bracteatum leaves (NET-D1602) and its bioactive compound p-coumaric acid on neuronal cell damage in SH-SY5Y cells and primary culture of rat cortical cells. NET-D1602 and p-coumaric acid significantly improved cell viability in CORT-induced neurotoxicity in SH-SY5Y cells and primary cultures of rat cortical cells, and increased the activities of antioxidant enzymes (superoxide dismutase and catalase) against CORT-induced neurotoxicity in SH-SY5Y cells. NET-D1602 and p-coumaric acid increased the phosphorylation levels of ERK1/2 and cAMP response element-binding protein (CREB) in cortical neurons. In addition, CREB phosphorylation by NET-D1602 and p-coumaric acid was dramatically reversed by PKA, c-Raf/ERK, PI3K, and mTOR inhibitors. Lastly, we demonstrated the neuroprotective effects of NET-D1602 (3 and 10 μg/mL) and p-coumaric acid (3 and 10 μM) via increased CREB phosphorylation in CORT-induced neurotoxicity mediated via the ERK1/2, Akt, and mTOR pathways. These results suggest that p-coumaric acid is a potential neuroprotective component of NET-D1602, with the ability to protect against CORT-induced neurotoxicity by regulating ERK1/2, Akt, and mTOR-mediated CREB phosphorylation.

Mucosal acidosis elicits a unique molecular signature in epithelia and intestinal tissue mediated by GPR31-induced CREB phosphorylation

Metabolic changes associated with tissue inflammation result in significant extracellular acidosis (EA). Within mucosal tissues, intestinal epithelial cells (IEC) have evolved adaptive strategies to cope with EA through the up-regulation of SLC26A3 to promote pH homeostasis. We hypothesized that EA significantly alters IEC gene expression as an adaptive mechanism to counteract inflammation. Using an unbiased RNA sequencing approach, we defined the impact of EA on IEC gene expression to define molecular mechanisms by which IEC respond to EA. This approach identified a unique gene signature enriched in cyclic AMP response element-binding protein (CREB)-regulated gene targets. Utilizing loss- and gain-of-function approaches in cultured epithelia and murine colonoids, we demonstrate that EA elicits prominent CREB phosphorylation through cyclic AMP-independent mechanisms that requires elements of the mitogen-activated protein kinase signaling pathway. Further analysis revealed that EA signals through the G protein-coupled receptor GPR31 to promote induction of FosB, NR4A1, and DUSP1. These studies were extended to an in vivo murine model in conjunction with colonization of a pH reporter Escherichia coli strain that demonstrated significant mucosal acidification in the TNFΔARE model of murine ileitis. Herein, we observed a strong correlation between the expression of acidosis-associated genes with bacterial reporter sfGFP intensity in the distal ileum. Finally, the expression of this unique EA-associated gene signature was increased during active inflammation in patients with Crohn's disease but not in the patient control samples. These findings establish a mechanism for EA-induced signals during inflammation-associated acidosis in both murine and human ileitis.

Insights into the impact of inflammatory acidification on the mucosa

Mucosal acidification is an often-underappreciated aspect of mucosal inflammation. Like other chronic inflammatory diseases, tissue acidification has been observed in inflammatory bowel disease (IBD) patients, with reports of colonic pH as low as 4. We recently demonstrated that neutrophil (PMN) transepithelial migration rapidly acidifies the microenvironment resulting in inflammatory acidification of the mucosa. Furthermore, we identified an adaptive tissue response in IEC which buffered extracellular acidification during PMN transepithelial migration, suggesting pH homeostasis is important during acute inflammation. Very little is known in regard to the impact of extracellular acidification on the intestinal epithelial cell (IEC) function. To better understand the impact of extracellular pH on IEC cell function, we investigated the impact of extracellular acidosis on IEC gene expression. Guided by an unbiased RNAseq of T84 IEC exposed to low pH, we identified significant induction of several CREB associated genes. Based on this observation, we examined the phosphorylation of CREB under acidic conditions. Under acidic conditions, CREB is rapidly phosphorylated. We observed CREB phosphorylation within 5 minutes of exposure to acidic conditions and peaks at 30 min. Extending these studies we investigated the mechanism(s) involved in acidosis induced CREB phosphorylation. Interestingly, cAMP signaling, a common signaling pathway for CREB phosphorylation, appears to not be involved in acidosis-induced CREB phosphorylation. Under acidic conditions, there was no significant increase in cAMP levels in IEC and acidosis-induced CREB phosphorylation was still observed in T84 IEC treated with cAMP inhibitors. KEGG analysis of the RNAseq data revealed the induction of several MAPK regulatory genes, including members of the NR4A and DUSP families. Based on this observation we examined several key proteins involved in MAPK signaling, ERK1/2 and MSK1. Under acidic conditions ERK1/2 and MSK1 are rapidly phosphorylation and treatment with a MEK1/2 or MSK1 inhibitor significant attenuated CREB phosphorylation under acidic conditions. Further examination revealed CREB phosphorylation signals through the GaI-linked GPCR, GRP31. Finally, we extended our studies in vivo and examined mucosal acidification in a murine model of ileitis, TNFΔARE mice. Using a novel pH reporting E. coli strain, we identified significant mucosal acidification in the distal ileum of TNFΔARE mice when compared to WT mice. Mucosal acidification was positively correlated with the expression of several acidification associated genes; FosB, NR4A1, and CXCL1. These results identify extracellular acidification as a significant signaling mechanism during tissue inflammation. Thus, regulation of GPR31 or MSK1 may serve as new therapeutic targets to limit acidosis signaling during mucosal inflammation.

Gα s Directly Drives PDZ‐RhoGEF Signaling to Cdc42

G proteins stimulate RhoGEFs that control cell morphology through actin-cytoskeleton remodeling. Gα12 and Gα13 interact with RH-RhoGEFs (RGS-homology domain RhoGEFs), driving RhoA activation. However, whether additional Gα proteins directly regulate RH-RhoGEFs was not known. To respond this question, we first evaluated the morphological effects of constitutively active DH/PH constructs from p115RhoGEF/ARHGEF1, PDZ-RhoGEF (PRG)/ARHGEF11, and LARG/ARHGEF12. As expected, the three constructs promoted cell contraction and activated RhoA, consistent with their known specificity. Intriguingly, PRG-DH/PH also induced filopodia-like cell protrusions and directly activated Cdc42. Constitutively active Gαs (GαsQ227L) increased the ability of PRG-DH/PH or endogenous PRG to interact with and activate Cdc42. Using a chemogenetic approach, with DREADD receptors, we demonstrated that Gs-coupled receptors, but not those coupled to Gi or Gq, drive PRG activity towards Cdc42. Given that Gαs interacted with PRG DH/PH region, we looked for potential inhibitory effects of the minimal fragment from PRG (linker) that binds GαsQ227L. This construct, the PRG-linker, interfered with GαsQ227L:PRG interaction and PRG:Cdc42 affinity. Besides, it attenuated Gαs signaling by Gs-DREADDs and Gs-coupled prostaglandin receptors (assessed by phosphorylation of CREB and PKA substrates). Altogether, our results demonstrate that Gαs can recognize PRG as a novel effector directing its DH/PH catalytic module to gain affinity for Cdc42.

Differential Modulation of β2AR Mediated cAMP/PKA/CREB Signaling Cascade in Normal versus Asthmatic Airway Epithelial Cells

Nearly 25 million people in the U.S. suffer from asthma. While there is no panacea for asthma, symptomatic relief is achieved by the current therapeutic interventions, including β2-adrenergic receptor (β2AR) agonists. Chronic usage of β2AR agonists can have serious implications like airway hyper-responsiveness and receptor desensitization, and along with unknown mechanisms, can ultimately culminate into tachyphylaxis to the response. Previously, our laboratory has extensively explored the critical role of reactive oxygen species (ROS) in modulating β2AR function. To begin to assess the physiological role of the β2AR-ROS linkage in asthma, here, we assessed Isoproterenol (ISO)-induced β2AR mediated Gαs/cAMP/CREB pathway in small airway epithelial cells from asthma patients (SAEC-A) compared to those from non-diseased control patients (SAEC-N). Given the importance of β2AR mediated cAMP production and its role in airway bronchodilation, as well as tachyphylaxis that occurs upon chronic use of β2AR agonists, our results may shed light on the role of oxidants in altering β2AR responses in asthma. To assess cAMP levels, cells were analyzed using highly sensitive luciferase-based biosensor. Briefly, SAEC were transfected with GloSensorTM -22F cAMP plasmid (8μg) using Lipofectamine3000. Luminescence was measured following treated with the ISO. To assess the effects of downstream cAMP-mediated transcription, cells were stimulated with H2O, Forskolin (FSK) (10 μM) & ISO (100μM) for 20 min and lysed. Lysates were resolved using SDS-PAGE and immunoprobed for phospho-cAMP response element-binding protein (pCREB), total CREB and β-actin. Similarly, SAEC-N/A lysates were assessed for Adenylyl Cyclase (AC-5/6) and Phosphodiesterase (PDE4) by immunoblot. β2AR agonism with ISO significantly increased cAMP production in SAEC from asthma patients compared to non-diseased control. In spite of elevated cAMP production in asthmatic SAEC, both ISO and FSK were able to induce significant increase in CREB phosphorylation, leading to heightened pCREB/CREB response in SAEC-N as compared to SAEC-A. ISO-mediated increased cAMP response in asthmatic SAEC compared to non-diseased control, were linked with physiologically altered expression of key cAMP mediators, specifically, heightened basal expression of AC-5/6 and PDE4, in asthmatic SAEC compared to SAEC-N. ISO mediated increased cAMP production in asthmatic SAEC indicated altered agonist modulated β2AR downstream signaling in diseased versus non-diseased SAEC. Further, heightened basal expression of AC-5/6 in asthmatic SAEC supports the above mentioned consequence. In addition, elevated CREB phosphorylation in non-diseased SAEC suggests alterations of β2AR-mediated PKA/CREB signaling in asthma. Future results will probe the effects of elevated ROS in these signal cascades.

CRISPR/Cas9‐mediated knockout of G proteins and β‐arrestins defines their specific but interdependent roles in dopamine D1 receptor signaling

The dopamine D1 receptor (D1R) is a G protein-coupled receptor which regulates key brain functions including voluntary movement, memory, attention, and reward. Selective agonist activation of the D1R may also provide novel neurotherapeutics for neurodegenerative and neuropsychiatric disorders. The D1R canonically activates the heterotrimeric G proteins Gαs, and possibly Gαolf, which activate adenylyl cyclase (AC) to increase cAMP/PKA signaling. The D1R also engages β-arrestin proteins which may transduce β-arrestin dependent signaling by scaffolding and activating kinases. However, the distinct roles of Gαs, Gαolf versus β-arrestins 1 and 2 for D1R signaling remains largely undefined. Here we utilize CRISPR/Cas9 engineered HEK293 cells in which Gαs, Gαolf, β-arrestin1 and β-arrestin2 are stably knocked out (KO) to delineate D1R pharmacology and signaling mechanisms. Western blots confirmed a complete loss of Gαs, Gαolf, β-arrestin1 or β-arrestin2 proteins in KO cells versus parental wildtype cells. Dose responses with the D1R agonist SKF-81297 or β2AR agonist isoproterenol induced robust cAMP production in wildtype cells that was eliminated in Gαs/olf KO cells. Re-expression of Gαs or Gαolf in KO cells rescued D1R-mediated cAMP signaling similar to wildtype cells. Interestingly, the D1R had significantly higher cAMP signaling when coupling via Gαs as compared to Gαolf, while the β2AR only coupled with Gαs to stimulate cAMP signaling. Western blotting indicated Gαs/olf KO completely blocked agonist induced CREB phosphorylation by both D1R and β2AR agonists, indicating a strict dependence on Gαs/olf and cAMP/PKA signaling to activate CREB. In major contrast, β-arrestin1/2 KO significantly increased the intensity and duration of cAMP signaling and CREB phosphorylation by the β2AR. β-arrestin1/2 KO also entirely blocked agonist-induced D1R internalization and impaired D1R desensitization while Gαs/olf KO had no effect on D1R internalization. Key controls of re-expressing Gαs, Gαolf, β-arrestin1 or β-arrestin2 in KO cells completely restored signaling or internalization similar to wildtype cells, indicating CRISPR/Cas9 targeting did not result in non-specific or compensatory effects in the pathways under study. Notably, β-arrestin1/2 KO also potentiated and prolonged D1R or β2AR-induced ERK1/2 phosphorylation. D1R-induced ERK1/2 phosphorylation in β-arrestin1/2 KO cells was eliminated by the SRC inhibitor SU6656 or the MEK inhibitor U0126, suggesting that D1R signaling via a Gαs/SRC/MEK pathway is essential for ERK1/2 activation. Taken together, our studies indicate that Gαs is the dominant transducer for D1R cAMP, CREB and ERK1/2 signaling and that β-arrestins provide distinctly interdependent roles with G proteins in modulating the duration and intensity of D1R and β2AR signaling cascades. Using CRISPR/Cas9 KO model cells, future studies will examine the distinct contributions of β-arrestins 1 and 2 and Gαs/olf for D1R pharmacology, which will be useful in the development of novel D1R biased agonists.

The changes of nociception and the signal molecules expression in the dorsal root ganglia and the spinal cord after cold water swimming stress in mice.

Several studies have previously reported that exposure to stress provokes behavioral changes, including antinociception, in rodents. In the present study, we studied the effect of acute cold-water (4°C) swimming stress (CWSS) on nociception and the possible changes in several signal molecules in male ICR mice. Here, we show that 3 min of CWSS was sufficient to produce antinociception in tail-flick, hot-plate, von-Frey, writhing, and formalin-induced pain models. Significantly, CWSS strongly reduced nociceptive behavior in the first phase, but not in the second phase, of the formalin-induced pain model. We further examined some signal molecules' expressions in the dorsal root ganglia (DRG) and spinal cord to delineate the possible molecular mechanism involved in the antinociceptive effect under CWSS. CWSS reduced p-ERK, p-AMPKα1, p-AMPKα2, p-Tyk2, and p-STAT3 expression both in the spinal cord and DRG. However, the phosphorylation of mTOR was activated after CWSS in the spinal cord and DRG. Moreover, p-JNK and p-CREB activation were significantly increased by CWSS in the spinal cord, whereas CWSS alleviated JNK and CREB phosphorylation levels in DRG. Our results suggest that the antinociception induced by CWSS may be mediated by several molecules, such as ERK, JNK, CREB, AMPKα1, AMPKα2, mTOR, Tyk2, and STAT3 located in the spinal cord and DRG.

Beta 2-adrenergic receptor mediates noradrenergic action to induce cyclic adenosine monophosphate response element-binding protein phosphorylation in satellite glial cells of dorsal root ganglia to regulate visceral hypersensitivity.

Sympathoneuronal outflow into dorsal root ganglia (DRG) is suggested to be involved in sympathetically maintained chronic pain, which is mediated by norepinephrine (NE) action on DRG cells. This study combined in vitro and in vivo approaches to identify the cell types of DRG that received NE action and examined cell type-specific expression of adrenergic receptors (ARs) in DRG. Using DRG explants, we identified that NE acted on satellite glial cells (SGCs) to induce the phosphorylation of cAMP response element-binding protein (CREB). Using primarily cultured SGCs, we identified that beta (β)2-adrenergic receptor but not alpha (α)adrenergic receptor nor other βAR isoforms mediated NE-induced CREB phosphorylation and CRE-promoted luciferase transcriptional activity. Using fluorescence in situ hybridization and affinity purification of mRNA from specific cell types, we identified that β2AR was expressed by SGCs but not DRG neurons. We further examined β2AR expression and CREB phosphorylation in vivo in a model of colitis in which sympathetic nerve sprouting in DRG was observed. We found that β2AR expression and CREB phosphorylation were increased in SGCs of thoracolumbar DRG on day 7 after colitis induction. Inhibition but not augmentation of β2AR reduced colitis-induced calcitonin gene-related peptide release into the spinal cord dorsal horn and colonic pain responses to colorectal distention. Prolonged activation of β2AR in naive DRG increased calcitonin gene-related peptide expression in DRG neurons. These findings provide molecular basis of sympathetic modulation of sensory activity and chronic pain that involves β2AR-mediated signaling in SGCs of DRG.

PDGF-BB-mediated activation of CREB in vascular smooth muscle cells alters cell cycling via Rb, FoxO1 and p27kip1

Introduction & AimThe vascular response to injury leads to the secretion of several factors, including platelet-derived growth factor (PDGF-BB). PDGF-BB stimulates smooth muscle cell (SMC) conversion to the synthetic phenotype, thereby enhancing proliferation and migration, and contributing to neointimal hyperplasia. Likewise, the cAMP response element binding protein (CREB) transcription factor has been shown to mediate SMC proliferation in response to various mitogens. We therefore investigated the contribution of CREB to PDGF-BB-dependent proliferation of SMCs with the intention of identifying signaling pathways involved both up and downstream of CREB activation. Methods & ResultsTreatments were performed on vascular SMCs from a porcine coronary artery explant model. The role of CREB was examined via adenoviral expression of a dominant-negative CREB mutant (kCREB) as well as inhibition of CREB binding protein (CBP). Involvement of the p27kip1 pathway was determined using a constitutively expressing p27kip1 adenoviral vector. PDGF-BB stimulated transient CREB phosphorylation on Ser-133 via ERK1/2-, PI3-kinase- and Src-dependent pathways. Expression of kCREB decreased PDGF-BB-dependent cell proliferation. PCNA expression and Rb phosphorylation were also inhibited by kCREB. These cell cycle proteins are controlled via p27kip1 expression in response to CREB-dependent post-translational modification of FoxO1. kCREB had no effect on Cyclin D1 expression, but did prevent PDGF-BB-induced Cyclin D1 nuclear translocation. An interaction inhibitor of CBP confirmed that Cyclin D1 is downstream of PDGF-BB and CREB. ConclusionCREB phosphorylation is required for SMC proliferation in response to PDGF-BB. This phenotypic change requires CBP and is mediated by Cyclin D1 and p27kip as a result of changes in FoxO1 activity.

Release of adenosine-induced immunosuppression: Comprehensive characterization of dual A2A/A2B receptor antagonist

Immunosuppression is one of the main mechanisms facilitating tumor expansion. It may be driven by immune checkpoint protein expression, anti-inflammatory cytokine secretion or enhanced metabolic enzyme production, leading to the subsequent build-up of metabolites such as adenosine. Under physiological conditions, adenosine prevents the development of tissue damage resulting from a prolonged immune response; the same mechanism might be employed by tumor tissue to promote immunosuppression. Immune cells expressing A2A and A2B adenosine receptors present in an adenosine-rich environment have suppressed effector functions, such as cytotoxicity, proinflammatory cytokine release, antigen presentation and others, making them inert to cancer cells. This study was designed to investigate the dual antagonist potential of SEL330-639 to abolish adenosine-driven immunosuppression. SEL330-639 has slow dissociation kinetics. It inhibits cAMP production in human CD4+ cells, CD8+ cells and moDCs, which leads to diminished CREB phosphorylation and restoration of antitumor cytokine production (IL-2, TNFα, IL-12) in multiple primary human immune cells. The aforementioned results were additionally validated by gene expression analysis and functional assays in which NK cell line cytotoxicity was recovered by SEL330-639. Adenosine-driven immunosuppression is believed to preclude the effectiveness of immune checkpoint inhibitor therapies. Hence, there is an urgent need to develop new immuno-oncological strategies. Here, we comprehensively characterize SEL330-639, a novel dual A2A/A2B receptor antagonist effective in both lymphoid and myeloid cell populations with nanomolar potency. Due to its tight binding to the A2A and A2B receptors, this binding is sustained even at high adenosine concentrations mimicking the upper limit of the range of adenosine levels observed in the tumor microenvironment.

Fgf15 Neurons of the Dorsomedial Hypothalamus Control Glucagon Secretion and Hepatic Gluconeogenesis.

The counterregulatory response to hypoglycemia is an essential survival function. It is controlled by an integrated network of glucose-responsive neurons, which trigger endogenous glucose production to restore normoglycemia. The complexity of this glucoregulatory network is, however, only partly characterized. In a genetic screen of a panel of recombinant inbred mice we previously identified Fgf15, expressed in neurons of the dorsomedial hypothalamus (DMH), as a negative regulator of glucagon secretion. Here, we report on the generation of Fgf15CretdTomato mice and their use to further characterize these neurons. We show that they were glutamatergic and comprised glucose-inhibited and glucose-excited neurons. When activated by chemogenetics, Fgf15 neurons prevented the increase in vagal nerve firing and the secretion of glucagon normally triggered by insulin-induced hypoglycemia. On the other hand, they increased the activity of the sympathetic nerve in the basal state and prevented its silencing by glucose overload. Higher sympathetic tone increased hepatic Creb1 phosphorylation, Pck1 mRNA expression, and hepatic glucose production leading to glucose intolerance. Thus, Fgf15 neurons of the DMH participate in the counterregulatory response to hypoglycemia by a direct adrenergic stimulation of hepatic glucose production while suppressing vagally induced glucagon secretion. This study provides new insights into the complex neuronal network that prevents the development of hypoglycemia.

4R-cembranoid confers neuroprotection against LPS-induced hippocampal inflammation in mice

BackgroundChronic brain inflammation has been implicated in the pathogenesis of various neurodegenerative diseases and disorders. For example, overexpression of pro-inflammatory cytokines has been associated with impairments in hippocampal-dependent memory. Lipopolysaccharide (LPS) injection is a widely used model to explore the pathobiology of inflammation. LPS injection into mice causes systemic inflammation, neuronal damage, and poor memory outcomes if the inflammation is not controlled. Activation of the alpha-7 nicotinic receptor (α7) plays an anti-inflammatory role in the brain through vagal efferent nerve signaling. 4R-cembranoid (4R) is a natural compound that crosses the blood-brain barrier, induces neuronal survival, and has been shown to modulate the activity of nicotinic receptors. The purpose of this study is to determine whether 4R reduces the deleterious effects of LPS-induced neuroinflammation and whether the α7 receptor plays a role in mediating these beneficial effects.MethodsEx vivo population spike recordings were performed in C57BL/6J wild-type (WT) and alpha-7-knockout (α7KO) mouse hippocampal slices in the presence of 4R and nicotinic receptor inhibitors. For in vivo studies, WT and α7KO mice were injected with LPS for 2 h, followed by 4R or vehicle for 22 h. Analyses of IL-1β, TNF-α, STAT3, CREB, Akt1, and the long-term novel object recognition test (NORT) were performed for both genotypes. In addition, RNA sequencing and RT-qPCR analyses were carried out for 12 mRNAs related to neuroinflammation and their modification by 4R.Results4R confers neuroprotection after NMDA-induced neurotoxicity in both WT and α7KO mice. Moreover, hippocampal TNF-α and IL-1β levels were decreased with 4R treatment following LPS exposure in both strains of mice. 4R restored LPS-induced cognitive decline in NORT. There was a significant increase in the phosphorylation of STAT3, CREB, and Akt1 with 4R treatment in the WT mouse hippocampus following LPS exposure. In α7KO mice, only pAkt levels were significantly elevated in the cortex. 4R significantly upregulated mRNA levels of ORM2, GDNF, and C3 following LPS exposure. These proteins are known to play a role in modulating microglial activation, neuronal survival, and memory.ConclusionOur results indicate that 4R decreases the levels of pro-inflammatory cytokines; improves memory function; activates STAT3, Akt1, and CREB phosphorylation; and upregulates the mRNA levels of ORM2, GDNF, and C3. These effects are independent of the α7 nicotinic receptor.

Administration of isoliquiritigenin prevents nonalcoholic fatty liver disease through a novel IQGAP2-CREB-SIRT1 axis.

Isoliquiritigenin (ISO) is a flavonoid extracted from the root of licorice, which serves various biological and pharmacological functions including antiinflammatory, antioxidation, liver protection, and heart protection. However, the mechanism of its action remains elusive and the direct target proteins of ISO have not been identified so far. Through cell-based screening, we identified ISO as a potent lipid-lowering compound. ISO treatment successfully ameliorated fatty acid-induced cellular lipid accumulation and improved nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) by increasing PPARα-dependent lipid oxidation and decreasing SREBPs-dependent lipid synthesis. Both these signaling required the activation of SIRT1. Knockdown of SIRT1 resulted in the reversal of ISO beneficiary effects suggesting that the lipid-lowering activity of ISO was regulated by SIRT1 expression. To identify the direct target of ISO, limited proteolysis combined with mass spectrometry (LiP-SMap) strategy was applied and IQGAP2 was identified as the direct target for ISO in regulating lipid homeostasis. In the presence of ISO, both mRNA and protein levels of SIRT1 were increased; however, this effect was abolished by blocking IQGAP2 expression using siRNA. To explore how IQGAP2 regulated the expression level of SIRT1, proteome profiler human phospho-kinase array kit was used to reveal possible phosphorylated kinases and signaling nodes that ISO affected. We found that through phosphorylation of CREB, ISO transduced signals from IQGAP2 to upregulate SIRT1 expression. Thus, we not only demonstrated the molecular basis of ISO in regulating lipid metabolism but also exhibited for the first time a novel IQGAP2-CREB-SIRT1 axis in treating NAFLD/NASH.

Inhibition of PDE4 by apremilast attenuates skin fibrosis through directly suppressing activation of M1 and T cells.

Systemic sclerosis (SSc) is a life-threatening chronic connective tissue disease with the characteristics of skin fibrosis, vascular injury, and inflammatory infiltrations. Though inhibition of phosphodiesterase 4 (PDE4) has been turned out to be an effective strategy in suppressing inflammation through promoting the accumulation of intracellular cyclic adenosine monophosphate (cAMP), little is known about the functional modes of inhibiting PDE4 by apremilast on the process of SSc. The present research aimed to investigate the therapeutic effects and underlying mechanism of apremilast on SSc. Herein, we found that apremilast could markedly ameliorate the pathological manifestations of SSc, including skin dermal thickness, deposition of collagens, and increased expression of α-SMA. Further study demonstrated that apremilast suppressed the recruitment and activation of macrophages and T cells, along with the secretion of inflammatory cytokines, which accounted for the effects of apremilast on modulating the pro-fibrotic processes. Interestingly, apremilast could dose-dependently inhibit the activation of M1 and T cells in vitro through promoting the phosphorylation of CREB. In summary, our research suggested that inhibiting PDE4 by apremilast might provide a novel therapeutic option for clinical treatment of SSc patients.