Puerarin alleviates depressive-like behaviors in high-fat diet-induced diabetic mice via modulating hippocampal GLP-1R/BDNF/TrkB signaling

OBJECTIVE

Depression is one of the most common complications in patients with diabetes. Our previous study demonstrated puerarin, a dietary isoflavone, improved glucose homeostasis and β-cell regeneration in high-fat diet (HFD)-induced diabetic mice. Here, we aim to evaluate the potential effect of puerarin on diabetes-induced depression.

METHODS

The co-occurrence of diabetes and depression with related biochemical alterations were confirmed in HFD mice and db/db mice, respectively using behavioral analysis, ELISA and western blotting assay. Furthermore, impacts of puerarin on depression-related symptoms and pathological changes were investigated in HFD mice.

RESULTS

The results showed that puerarin effectively alleviated the depression-like behaviors of HFD mice, down-regulated serum levels of corticosterone and IL-1β, while up-regulated the content of 5-hydroxytryptamine. Simultaneously, puerarin increased the number of hippocampal neurons in HFD mice, and suppressed the apoptosis of neurons to protect the hippocampal neuroplasticity. GLP-1R expression in hippocampus of HFD mice was enhanced by puerarin, which subsequently activated AMPK, CREB and BDNF/TrkB signaling to improve neuroplasticity. Importantly, our data indicated that puerarin had an advantage over fluoxetine or metformin in treating diabetes-induced depression.

CONCLUSION

Taken together, puerarin exerts anti-depressant-like effects on HFD diabetic mice, specifically by improving hippocampal neuroplasticity via GLP-1R/BDNF/TrkB signaling. Puerarin as a dietary supplement might be a potential candidate in intervention of diabetes with comorbid depression.

Fatty acid binding protein 5 promotes the proliferation, migration, and invasion of hepatocellular carcinoma cells by degradation of Krüppel-like factor 9 mediated by miR-889-5p via cAMP-response element binding protein

Mounting evidence has demonstrated that fatty acid binding protein 5 (FABP5) is commonly upregulated in many human malignancies. However, the mechanisms explaining the involvement of FABP5 in hepatocellular carcinoma (HCC) remain unclear. In this study, we demonstrated the involvement of FABP5 and its downstream signaling molecules in HCC progression. We first confirmed that FABP5 expression was upregulated in HCC. Additionally, FABP5 promoted HCC cells proliferation, migration, and invasion. Mechanistic investigation showed that FABP5 could improve cAMP-response element binding protein (CREB) phosphorylation. Meanwhile, CREB, as a transcription factor, upregulated the miR-889-5p expression by binding to the miR-889-5p promoter region. Consequently, miR-889-5p led to downregulation of Krüppel-like factor 9 (KLF9) by binding to the 3ʹ-UTR of the KLF9 mRNA, potentiating the PI3K/AKT signaling pathway and promoting the proliferation, migration, and invasion of HCC cells. Our findings have identified a FABP5/CREB/miR-889-5p/KLF9 axis for HCC progression, and we postulate that blocking this key signaling pathway may represent a promising strategy for HCC treatment.

cAMP-response element binding protein mediates podocyte injury in diabetic nephropathy by targeting lncRNA DLX6-AS1

BACKGROUND

Progressive proteinuria is one of the earliest clinical features of diabetic nephropathy (DN). In our previous study, lncRNA DLX6-AS1 (DLX6-AS1, Dlx6os1 in the mouse) was found to be associated with the extent of albuminuria in DN patients. Furthermore, the lack of Dlx6os1 was pivotal in switching off the inflammatory response in db/db mouse model. However, the regulatory factors responsible for elevated DLX6-AS1 in DN remains unknown.

METHODS

To identify potential regulatory factors for DLX6-AS1, JASPAR database and DNA pull down combined subsequent liquid chromatography-tandem mass spectrometry were used. Dual-luciferase reporter assay and chromatin immunoprecipitation were then performed to confirm binding sites. We also investigated the effects of the regulatory factors on DN progression in db/db mouse model and cultured human podocytes.

RESULTS

Our analyses demonstrated that cAMP-response element binding protein (CREB) was highly expressed and closely associated with DLX6-AS1 in DN. In db/db mouse and in cultured podocytes, CREB silencing significantly reduced the level of DLX6-AS1 or Dlx6os1 and attenuated renal damage. Mechanistically, CREB overexpression aggravated renal inflammation and destroyed the structure of podocytes by targeting DLX6-AS1. The damaging role of CREB in podocyte injury was also inhibited by 666-15, a selective inhibitor, in a dose-dependent manner. In vivo, the inhibition of CREB by 666-15 significantly attenuated albuminuria and ameliorated inflammatory infiltration in podocytes.

CONCLUSIONS

Our findings indicated that CREB is a key mediator of podocyte injury and acts by regulating DLX6-AS1. Thus, CREB may be an effective and potential therapeutic target for the treatment of DN.

EphB2 activates CREB-dependent expression of Annexin A1 to regulate dendritic spine morphogenesis

Dendritic spines are the postsynaptic structure to mediate signal transduction in neural circuitry, whose function and plasticity are regulated by organization of their molecular architecture and by the expression of target genes and proteins. EphB2, a member of the Eph receptor tyrosine kinase family, potentiates dendritic spine maturation through cytoskeleton reorganization and protein trafficking. However, the transcriptional mechanisms underlying prolonged activation of EphB2 signaling during dendritic spine morphogenesis are unknown. Herein, we performed transcriptional profiling by stimulating EphB2 signaling and identified differentially expressed genes implicated in pivotal roles at synapses. Notably, we characterized an F-actin binding protein, Annexin A1, whose expression was induced by EphB2 signaling; the promotor activity of its coding gene Anxa1 is regulated by the activity of CREB (cAMP-response element-binding protein). Knockdown of Annexin A1 led to a significant reduction of mature dendritic spines without an obvious deficit in the complexity of dendrites. Altogether, our findings suggest that EphB2-induced, CREB-dependent Annexin A1 expression plays a key role in regulating dendritic spine morphology.

Perfluorooctane sulfonate (PFOS) disrupts testosterone biosynthesis via CREB/CRTC2/StAR signaling pathway in Leydig cells

Perfluorooctane sulfonate (PFOS), a stable end-product of perfluorinated compounds (PFCs), is associated with male reproductive disorders, but its underlying mechanisms are still unclear. We used in vivo and in vitro models to investigate the effects of PFOS on testosterone biosynthesis and related mechanisms. First, male ICR mice were orally administered PFOS (0-10 mg/kg/bw) for 4 weeks. Bodyweight, sperm count, reproductive hormones, mRNA expression of the genes related to testosterone biosynthesis, and the protein expression of protein kinase A (PKA), p38 mitogen-activated protein kinase (MAPK), cAMP-response element binding protein (CREB), CREB regulated transcription coactivator 2 (CRTC2) and steroidogenic acute regulatory protein (StAR) were evaluated. Furthermore, mouse primary Leydig cells were used to delineate the molecular mechanisms that mediate the effects of PFOS on testosterone biosynthesis. Our results demonstrated that PFOS dose-dependently decreased sperm count, testosterone level, CRTC2/StAR expression, and damaged testicular interstitium morphology, paralleled by increase in phosphorylated PKA, CREB and p38 in testes. Additionally, similar to the in vivo results, PFOS significantly decreased testosterone secretion, CRTC2/StAR expression, interaction between CREB and CRTC2 and binding of CREB/CRTC2 to StAR promoter region, paralleled by increase in phosphorylated-p38, PKA, and CREB expression. Meanwhile, inhibition of p38 by SB203580, or inhibition of PKA by H89 can significantly alleviate the above PFOS-induced effects. As such, the present study highlights a role of the CREB/CRTC2/StAR signaling pathway in PFOS-induced suppression of testosterone biosynthesis, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

Exogenous IGF-1 alleviates depression-like behavior and hippocampal mitochondrial dysfunction in high-fat diet mice

BACKGROUND

Some evidence suggests that depression is more common in obese patients. This fact gives us a hint that obesity might be a promoter of depression, though a conclusion can not be drawn. The aim of the study was: (1) to confirm whether obesity induced by high-fat diet (HFD) promotes depression-like behaviors in mice, (2) to explore the protective role of insulin-like growth factor-1 (IGF-1) in such behavioral disorder of the animals and (3) to reveal whether mitochondrial mechanism was involved in such protective effect of the reagent.

METHODS

C57BL/6 J mice were fed with HFD to establish a model of obesity. Then, the animals were separately or simultaneously treated with PEG-IGF-1, 666-15 (CREB blocker) and SR-18292 (PGC-1α blocker). After that, depression-like behaviors were assessed using sucrose preference test and tail suspension test. In hippocampus, respiratory control ratio, ATP generation and red/green fluorescence ratio were adopted to reveal mitochondrial function. Also in hippocampus, expressions of p-CREB and PGC-1α were measured using western blotting.

RESULTS

HFD mice showed depression-like behaviors compared with control mice. Such diet also caused mitochondrial dysfunction and inhibition of CREB/PGC-1α signal pathway in hippocampus of these animals. After PEG-IGF-1 intervention, all the abnormalities mentioned above can be partly reversed. After 666-15 or SR-18292 treatment, such protective effect of PEG-IGF-1 can be attenuated, and the mice suffered from the re-deterioration of behavioral and mitochondrial abnormalities in hippocampus.

CONCLUSION

IGF-1 alleviated depression-like behaviors and mitochondrial dysfunction through the activation of CREB/PGC-1α signal pathway in HFD mice.

Exogenous IGF-1 improves cognitive function in rats with high-fat diet consumption

Insulin-like growth factor-1 (IGF-1) improves cognitive function, but its mechanism has not been elucidated. The aim of the study was to explore whether IGF-1 exerted its protective effect on cognitive function and anxiety behavior through the activation of PI3K/Akt/CREB pathway in high-fat diet rats. Neuronal cells HT22 were treated with nothing, IGF-1, IGF-1 + LY294002 or IGF-1 + 666-15. Expressions of p-PI3K, p-Akt and p-CREB were measured using Western blot analysis. Thirty C57BL/6J rats were used. After feeding with high-fat diet, normal saline, PEG-IGF-1, PEG-IGF-1 + LY294002 or PEG-IGF-1 + 666-15 was treated. Cognitive function and anxiety behavior were assessed by Morris water maze and open field test. Several inflammation and oxidative stress biomarkers were measured using recognized methods. Expressions of p-PI3K and p-CREB were also measured using Western blot analysis. After IGF-1 treatment in cells, expressions of p-PI3K, p-Akt and p-CREB were increased. Furthermore, LY294002 downregulated the expressions of these three proteins, but 666-15 only inhibited the expression of CREB in the cells. Compared with the control rats, we found abnormalities of cognitive function and anxiety behavior, inhibition of PI3K/Akt/CREB pathway and increase of oxidative stress and inflammation in high-fat diet rats. After PEG-IGF-1 treatment, the changes in high-fat diet rats were reversed. Then, we blocked the pathway and found that these blockers attenuated the protective effects of PEG-IGF-1. In conclusion, IGF-1 improved cognitive function and anxiety behavior in high-fat diet rats and inhibited inflammation and oxidative stress in hippocampus tissue through the activation of PI3K/Akt/CREB pathway.

Rapid antidepressant actions of imipramine potentiated by zinc through PKA-dependented regulation of mTOR and CREB signaling

The slow onset of traditional antidepressants has become an urgent clinical issue, researchers are constantly exploring new antidepressants with prompt action. Previous studies have found that zinc levels were decreased in serum and brain of depressed patients or animal models. Zinc treatment can improve depressive symptoms and enhance the antidepressant effects of monoamine antidepressants. However, its mechanism of action is still unclear. This present study aims to investigate whether the zinc can enhance the rapid action of traditional antidepressant imipramine and to explore the potential mechanisms of action through the rapid antidepressant targets CREB (cAMP-response element binding protein) and mTOR (mammalian target of the rapamycin). Drug treatment included intraperitoneal injection of imipramine or zinc alone and imipramine plus zinc. Zinc had a rapid enhanced antidepressive effect on the imipramine and achieved a rapid antidepressant effect similar to ketamine. Combination of zinc with imipramine rapidly enhanced the phosphorylation of mTOR Ser2448 and CREB Ser133, and increased the expression of mTOR and CREB, which were dependent on the activation of PKA. In conclusion, combination therapy with zinc and monoamine antidepressants may overcome the problem of slow-onset action of traditional antidepressants in clinical uses.

Royal Jelly Alleviates Cognitive Deficits and β-Amyloid Accumulation in APP/PS1 Mouse Model Via Activation of the cAMP/PKA/CREB/BDNF Pathway and Inhibition of Neuronal Apoptosis

Alzheimer’s disease (AD) is characterized clinically by progressive cognitive decline and pathologically by the accumulation of amyloid-β (Aβ) in the brain. Royal jelly (RJ), a secretion of honeybee hypopharyngeal and mandibular glands, has previously been shown to have anti-aging and neuromodulatory activities. In this study, we discovered that 3 months of RJ treatment substantially ameliorated behavioral deficits of APP/PS1 mice in the Morris Water Maze (MWM) test and step-down passive avoidance test. Our data also showed that RJ significantly diminished amyloid plaque pathology in APP/PS1 mice. Furthermore, RJ alleviated c-Jun N-terminal kinase (JNK) phosphorylation-induced neuronal apoptosis by suppressing oxidative stress. Importantly, hippocampal cyclic adenosine monophosphate (cAMP), p-PKA, p-CREB and BDNF levels were significantly increased in the APP/PS1 mice after RJ treatment, indicating that the cAMP/PKA/CREB/BDNF pathway might be related to the ameliorative effect of RJ on cognitive decline. Collectively, these results provide a scientific basis for using RJ as a functional food for targeting AD pathology.

Late starting treadmill exercise improves spatial leaning ability through suppressing CREP/BDNF/TrkB signaling pathway following traumatic brain injury in rats

Traumatic brain injury (TBI) causes deficit in spatial learning and memory function. Physical activity ameliorates neurological dysfunction after TBI. We investigated the effect of late starting treadmill exercise on spatial learning ability in relation with cAMP-response element binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling pathway using TBI rats. For this study, radial 8-arm maze test, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) staining, caspase-3 immunohistochemistry, and western blot for Bax, Bcl-2, BDNF, tyrosine kinase B (TrkB), CREB, and phosphorylated CREP (p-CREB) were performed. TBI was induced by an electromagnetic-controlled cortical impact. The rats in the exercise groups were scheduled to run on a treadmill for 30 min once a day for 8 weeks starting 3 weeks after TBI. TBI impaired spatial learning ability and increased caspase-3 expression in the hippocampal dentate gyrus. TBI enhanced Bax expression and suppressed Bcl-2 expression in the hip-pocampus. TBI increased BDNF and TrkB expressions, resulted in the enhancement of p-CREB/CREB ratio in the hippocampus. However, treadmill exercise improved spatial learning ability, decreased caspase-3 expression, suppressed Bax expression, and increased Bcl-2 expression. Treadmill exercise alleviated TBI-induced over-expression of BDNF and TrkB, which suppressed phosphorylation of CREB in the hippocampus. In the present study, late starting treadmill exercise improved spatial learning ability through suppressing TBI-induced activation of CREB/BDNF/TrkB signaling pathway after TBI.

Cholera toxin enhances interleukin-17A production in both CD4+ and CD8+ cells via a cAMP/protein kinase A-mediated interleukin-17A promoter activation

Cholera toxin (CT) is a bacterial component that increases intracellular cAMP levels in host cells and suppresses T-cell activation. Recently, CT was reported to induce T helper type 17-skewing dendritic cells and activate interleukin-17A (IL-17A) production in CD4⁺ T cells through a cAMP-dependent pathway. However, the underlying mechanism by which cAMP regulates IL-17A production in T cells is not completely defined. In this study, we took advantage of a small molecule protein kinase A (PKA) inhibitor (H89) and different cAMP analogues: a PKA-specific activator (N6-benzoyl-adenosine-cAMP), an exchange protein activated by cAMP-specific activator (Rp-8-chlorophenylthio-2'-O-methyl cAMP), and a PKA inhibitor (Rp-8-bromo-cAMP), to elucidate the signalling cascade of cAMP in IL-17A regulation in T cells. We found that CT induced IL-17A production and IL-17A promoter activity in activated CD4⁺ T cells through a cAMP/PKA pathway. Moreover, this regulation was via cAMP-response element binding protein (CREB) -mediated transcriptional activation by using the transfection of an IL-17A promoter-luciferase reporter construct and CREB small interfering RNA in Jurkat cells. Also, we showed that CREB bound to the CRE motif located at -183 of the IL-17A promoter in vitro. Most interestingly, not only in CD4⁺ T cells, CT also enhanced cAMP/PKA-dependent IL-17A production and CREB phosphorylation in CD8⁺ T cells. In conclusion, our data suggest that CT induces an IL-17A-dominated immune microenvironment through the cAMP/PKA/CREB signalling pathway. Our study also highlights the potentials of CT and cAMP in modulating T helper type 17 responses in vivo.

MicroRNA-365 alleviates morphine analgesic tolerance via the inactivation of the ERK/CREB signaling pathway by negatively targeting β-arrestin2

BACKGROUND

Morphine is widely used in clinical practice for a class of analgesic drugs, long-term use of morphine will cause the action of tolerance. MicroRNAs have been reported to be involved in morphine analgesic tolerance..

METHODS

Forty male SD rats were selected and randomly divided into 5 groups: the control group, morphine tolerance group, miR-365 mimic + morphine (miR-365 mimic) group, miR-365 inhibitor + morphine (miR-365 inhibitor) group and miR-365 negative control (NC) + morphine (miR-365 NC) group. After the administration of morphine at 0 d, 1 d, 3 d, 5 d and 7 d, behavioral testing was performed. A dual luciferase reporter gene assay was performed to confirm the relationship between miR-365 and β-arrestin2, RT-qPCR was used to detect miR-365, β-arrestin2, ERK and CREB mRNA expressions, western blotting was used to evaluate the protein expressions of β-arrestin2, ERK, p-ERK, CREB and p-CREB, ELISA was used to detect the contents of IL-1β, TNF-α and IL-18, while immunofluorescence staining was used to measure the GFAP expression. Intrathecal injection of mir365 significantly increased the maximal possible analgesic effect (%MPE) in morphine tolerant rats. β-arrestin2 was the target gene of miR-365.

RESULTS

The results obtained showed that when compared with the morphine tolerance group, there was an increase in miR-365 expression and a decrease in the β-arrestin2, ERK, CREB protein expressions, contents of IL-1β, TNF-α, IL-18 and GFAP expression in the miR-365 mimic group, while the miR-365 inhibitor group displayed an opposite trend.

CONCLUSIONS

The results of this experiment suggest that by targeting β-arrestin2 to reduce the contents of IL-1β, TNF-α and IL-18 and by inhibiting the activation of ERK/CREB signaling pathway, miR-365 could lower morphine analgesic tolerance.

FFPM, a PDE4 inhibitor, reverses learning and memory deficits in APP/PS1 transgenic mice via cAMP/PKA/CREB signaling and anti-inflammatory effects

Thus far, phosphodiesterase-4 (PDE4) inhibitors have not been approved for application in Alzheimer's disease (AD) in a clinical setting due to severe side effects, such as nausea and vomiting. In this study, we investigated the effect of FFPM, a novel PDE4 inhibitor, on learning and memory abilities, as well as the underlying mechanism in the APP/PS1 mouse model of AD. Pharmacokinetic studies have revealed that FFPM efficiently permeates into the brain, and reached peak values in plasma 2 h after orally dosing. A 3-week treatment with FFPM, at doses of 0.25 mg/kg and 0.5 mg/kg, significantly improved the learning and memory abilities of APP/PS1 transgenic mice in the Morris water maze and the Step-down passive avoidance task. Interestingly, we found that while rolipram (0.5 mg/kg) reduced the duration of the α2 adrenergic receptor-mediated anesthesia induced by xylazine/ketamine, FFPM (0.5 mg/kg) or the vehicle did not have an evident effect. FFPM increased the cAMP, PKA and CREB phosphorylation and BDNF levels, and reduced the NF-κB p65, iNOS, TNF-α and IL-1β levels in the hippocampi of APP/PS1 trangenic mice, as observed by ELISA and Western blot analysis. Taken together, our data demonstrated that the reversal effect of FFPM on cognitive deficits in APP/PS1 transgenic mice might be related to stimulation of the cAMP/PKA/CREB/BDNF pathway and anti-inflammatory effects. Moreover, FFPM appears to have potential as an effective PDE4 inhibitor in AD treatment with little emetic potential.

Low-level laser irradiation modulates brain-derived neurotrophic factor mRNA transcription through calcium-dependent activation of the ERK/CREB pathway

Low-level laser (LLL) irradiation has been reported to promote neuronal differentiation, but the mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) has been confirmed to be one of the most important neurotrophic factors because it is critical for the differentiation and survival of neurons during development. Thus, this study aimed to investigate the effects of LLL irradiation on Bdnf messenger RNA (mRNA) transcription and the molecular pathway involved in LLL-induced Bdnf mRNA transcription in cultured dorsal root ganglion neurons (DRGNs) using Ca²⁺ imaging, pharmacological detections, RNA interference, immunocytochemistry assay, Western blot, and qPCR analysis. We show here that LLL induced increases in the [Ca²⁺] _i level, Bdnf mRNA transcription, cAMP-response element-binding protein (CREB) phosphorylation, and extracellular signal-regulated kinase (ERK) phosphorylation, mediated by Ca²⁺ release via inositol triphosphate receptor (IP3R)-sensitive calcium (Ca²⁺) stores. Blockade of Ca²⁺ increase suppressed Bdnf mRNA transcription, CREB phosphorylation, and ERK phosphorylation. Downregulation of phosphorylated (p)-CREB reduced Bdnf mRNA transcription triggered by LLL. Furthermore, blockade of ERK using PD98059 inhibitor reduced p-CREB and Bdnf mRNA transcription induced by LLL. Taken together, these findings establish the Ca²⁺-ERK-CREB cascade as a potential signaling pathway involved in LLL-induced Bdnf mRNA transcription. To our knowledge, this is the first report of the mechanisms of Ca²⁺-dependent Bdnf mRNA transcription triggered by LLL. These findings may help further explore the complex molecular signaling networks in LLL-triggered nerve regeneration in vivo and may also provide experimental evidence for the development of LLL for clinical applications.

The effect of lead exposure on expression of SIRT1 in the rat hippocampus

Based on how the silent information regulator 2 homolog 1 (SIRT1) regulates the cyclic AMP response element binding protein (CREB), which is the molecular switch of long-term memory that maintains cognitive function, it is postulated that the impact of lead (Pb) on SIRT1 is one of the mechanisms leading to Pb-induced cognitive and learning deficits. Hence, the purpose of this study was to investigate the effect of Pb exposure on the expression of SIRT1, and the reversion effect of resveratrol, which is an activator of SIRT1. We examined the effects of maternal rat ingestion of Pb in drinking water during gestation and lactation on the expression of SIRT1 and CREB in the hippocampus of their offspring at postnatal week 3 (PNW3) and 52 (PNW52), and then reexamined these effects in offspring after intragastric administration of resveratrol for 4 weeks. Pb exposure decreased SIRT1 and CREB phosphorylation in a dose-dependent manner in the rat hippocampus at both PNW3 and 52, and resveratrol reversed those losses. These results indicated that SIRT1 might be a novel target to prevent Pb neurotoxicity.

Morris Water Maze Training in Mice Elevates Hippocampal Levels of Transcription Factors Nuclear Factor (Erythroid-derived 2)-like 2 and Nuclear Factor Kappa B p65

Research has identified several transcription factors that regulate activity-dependent plasticity and memory, with cAMP-response element binding protein (CREB) being the most well-studied. In neurons, CREB activation is influenced by the transcription factor nuclear factor kappa B (NF-κB), considered central to immunity but more recently implicated in memory. The transcription factor early growth response-2 (Egr-2), an NF-κB gene target, is also associated with learning and memory. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2), an antioxidant transcription factor linked to NF-κB in pathological conditions, has not been studied in normal memory. Given that numerous transcription factors implicated in activity-dependent plasticity demonstrate connections to NF-κB, this study simultaneously evaluated protein levels of NF-κB, CREB, Egr-2, Nrf2, and actin in hippocampi from young (1 month-old) weanling CD1 mice after training in the Morris water maze, a hippocampal-dependent spatial memory task. After a 6-day acquisition period, time to locate the hidden platform decreased in the Morris water maze. Mice spent more time in the target vs. non-target quadrants of the maze, suggestive of recall of the platform location. Western blot data revealed a decrease in NF-κB p50 protein after training relative to controls, whereas NF-κB p65, Nrf2 and actin increased. Nrf2 levels were correlated with platform crosses in nearly all tested animals. These data demonstrate that training in a spatial memory task results in alterations in and associations with particular transcription factors in the hippocampus, including upregulation of NF-κB p65 and Nrf2. Training-induced increases in actin protein levels caution against its use as a loading control in immunoblot studies examining activity-dependent plasticity, learning, and memory.

Liraglutide is neurotrophic and neuroprotective in neuronal cultures and mitigates mild traumatic brain injury in mice

Traumatic brain injury (TBI), a brain dysfunction for which there is no present effective treatment, is often caused by a concussive impact to the head and affects an estimated 1.7 million Americans annually. Our laboratory previously demonstrated that exendin-4, a long-lasting glucagon-like peptide 1 receptor (GLP-1R) agonist, has neuroprotective effects in cellular and animal models of TBI. Here, we demonstrate neurotrophic and neuroprotective effects of a different GLP-1R agonist, liraglutide, in neuronal cultures and a mouse model of mild TBI (mTBI). Liraglutide promoted dose-dependent proliferation in SH-SY5Y cells and in a GLP-1R over-expressing cell line at reduced concentrations. Pre-treatment with liraglutide rescued neuronal cells from oxidative stress- and glutamate excitotoxicity-induced cell death. Liraglutide produced neurotrophic and neuroprotective effects similar to those of exendin-4 in vitro. The cAMP/PKA/pCREB pathway appears to play an important role in this neuroprotective activity of liraglutide. Furthermore, our findings in cell culture were well-translated in a weight drop mTBI mouse model. Post-treatment with a clinically relevant dose of liraglutide for 7 days in mice ameliorated memory impairments caused by mTBI when evaluated 7 and 30 days post trauma. These data cross-validate former studies of exendin-4 and suggest that liraglutide holds therapeutic potential for the treatment of mTBI. Exendin-4, a long-lasting glucagon-like peptide 1 receptor (GLP-1R) agonist, has neuroprotective effects in cellular and animal models of traumatic brain injury (TBI). Here, we demonstrate neurotrophic and neuroprotective effects of a different GLP-1R agonist, liraglutide, in neuronal cultures and a mouse model of mild TBI (mTBI). Liraglutide promoted dose-dependent proliferation in SH-SY5Y cells and in a GLP-1R over-expressing cell line at reduced concentrations. Pretreatment with liraglutide rescued neuronal cells from oxidative stress- and glutamate excitotoxicity-induced cell death. Liraglutide produced neurotrophic and neuroprotective effects similar to those of exendin-4 in vitro, likely involving the cAMP/PKA/pCREB pathway. Our findings in cell culture were well-translated in a weight-drop mTBI mouse model. Post-treatment with a clinically relevant dose of liraglutide for 7 days in mice ameliorated memory impairments caused by mTBI.

Detection of CREB phosphorylation via Zr (IV) ion mediated signal amplification

Phosphorylation of protein plays a vital regulatory role in a variety of biological processes. We herein report a novel method to assay the level of phosphorylated cAMP-response element binding protein (CREB) via Zr(4+) mediated signal amplification using gold nanoparticle/DNA/methylene blue (GNP/DNA/MB) nanocomposites. In this method the probe DNA immobilized at a gold electrode surface can specifically and efficiently recognize the phosphorylated target protein CREB. Then Zr(4+) links the phosphorylated CREB with GNP/DNA/MB nanocomposites by coordinating the phosphate groups on both CREB and the nanocomposites. Since the nanocomposites can provide high sensitivity (limit of detection: 0.25 nM) for the detection, efficient and highly sensitive bioanalysis of the expression level of phosphorylated protein CREB in human placenta tissues has also been conducted in this work. Our method is reported which shows acceptable stability, reproducibility for assaying of the protein phosphorylation states in real biosamples under physiological and pathological conditions with great potential for clinical applications in future.

CART attenuates endoplasmic reticulum stress response induced by cerebral ischemia and reperfusion through upregulating BDNF synthesis and secretion

Cocaine and amphetamine regulated transcript (CART), a neuropeptide, has shown strong neuroprotective effects against cerebral ischemia and reperfusion (I/R) injury in vivo and in vitro. Here, we report a new effect of CART on ER stress which is induced by cerebral I/R in a rat model of middle cerebral artery occlusion (MCAO) or by oxygen and glucose deprivation (OGD) in cultured cortical neurons, as well as a new functionality of BDNF in the neuroprotection by CART against the ER stress in cerebral I/R. The results showed that CART was effective in reducing the neuronal apoptosis and expression of ER stress markers (GRP78, CHOP and cleaved caspase12), and increasing the BDNF expression in I/R injury rat cortex both in vivo and in vitro. In addition, the effects of CART on ischemia-induced neuronal apoptosis and ER stress were suppressed by tyrosine receptor kinase B (TrkB) IgG, whereas the effects of CART on BDNF transcription, synthesis and secretion were abolished by CREB siRNA. This work suggests that CART is functional in inhibiting the cerebral I/R-induced ER stress and neuronal apoptosis by facilitating the transcription, synthesis and secretion of BDNF in a CREB-dependent way.

Defective synaptic transmission and structure in the dentate gyrus and selective fear memory impairment in the Rsk2 mutant mouse model of Coffin-Lowry syndrome

The Coffin-Lowry syndrome (CLS) is a syndromic form of intellectual disability caused by loss-of-function of the RSK2 serine/threonine kinase encoded by the rsk2 gene. Rsk2 knockout mice, a murine model of CLS, exhibit spatial learning and memory impairments, yet the underlying neural mechanisms are unknown. In the current study, we examined the performance of Rsk2 knockout mice in cued, trace and contextual fear memory paradigms and identified selective deficits in the consolidation and reconsolidation of hippocampal-dependent fear memories as task difficulty and hippocampal demand increase. Electrophysiological, biochemical and electron microscopy analyses were carried out in the dentate gyrus of the hippocampus to explore potential alterations in neuronal functions and structure. In vivo and in vitro electrophysiology revealed impaired synaptic transmission, decreased network excitability and reduced AMPA and NMDA conductance in Rsk2 knockout mice. In the absence of RSK2, standard measures of short-term and long-term potentiation (LTP) were normal, however LTP-induced CREB phosphorylation and expression of the transcription factors EGR1/ZIF268 were reduced and that of the scaffolding protein SHANK3 was blocked, indicating impaired activity-dependent gene regulation. At the structural level, the density of perforated and non-perforated synapses and of multiple spine boutons was not altered, however, a clear enlargement of spine neck width and post-synaptic densities indicates altered synapse ultrastructure. These findings show that RSK2 loss-of-function is associated in the dentate gyrus with multi-level alterations that encompass modifications of glutamate receptor channel properties, synaptic transmission, plasticity-associated gene expression and spine morphology, providing novel insights into the mechanisms contributing to cognitive impairments in CLS.

Syntheses and evaluation of novel isoliquiritigenin derivatives as potential dual inhibitors for amyloid-beta aggregation and 5-lipoxygenase

A series of new isoliquiritigenin (ISL) derivatives were synthesized and evaluated as dual inhibitors for amyloid-beta (Aβ) aggregation and 5-lipoxygenase (5-LO). It was found that all these synthetic compounds inhibited Aβ (1-42) aggregation effectively with their IC₅₀ values ranged from 2.2 ± 1.5 μM to 23.8 ± 2.0 μM. These derivatives also showed inhibitory activity to 5-LO with their IC50 values ranged from 6.1 ± 0.1 μM to 35.9 ± 0.3 μM. Their structure-activity relationships (SAR) and mechanisms of inhibitions were studied. This study provided potentially important information for further development of ISL derivatives as multifunctional agents for Alzheimer's disease (AD) treatment.