Predatory Odor Exposure as a Potential Paradigm for Studying Emotional Modulation of Memory Consolidation-The Role of the Noradrenergic Transmission in the Basolateral Amygdala.

The pivotal role of the basolateral amygdala (BLA) in the emotional modulation of hippocampal plasticity and memory consolidation is well-established. Specifically, multiple studies have demonstrated that the activation of the noradrenergic (NA) system within the BLA governs these modulatory effects. However, most current evidence has been obtained by direct infusion of synthetic NA or beta-adrenergic agonists. In the present study, we aimed to investigate the effect of endogenous NA release in the BLA, induced by a natural aversive stimulus (coyote urine), on memory consolidation for a low-arousing, hippocampal-dependent task. Our experiments combined a weak object location task (OLT) version with subsequent mild predator odor exposure (POE). To investigate the role of endogenous NA in the BLA in memory modulation, a subset of the animals (Wistar rats) was treated with the non-selective beta-blocker propranolol at the end of the behavioral procedures. Hippocampal tissue was collected 90 min after drug infusion or after the OLT test, which was performed 24 h later. We used the obtained samples to estimate the levels of phosphorylated CREB (pCREB) and activity-regulated cytoskeleton-associated protein (Arc)-two molecular markers of experience-dependent changes in neuronal activity. The result suggests that POE has the potential to become a valuable behavioral paradigm for studying the interaction between BLA and the hippocampus in memory prioritization and selectivity.

Extracts of Sideritis scardica and Clinopodium vulgare Alleviate Cognitive Impairments in Scopolamine-Induced Rat Dementia.

Sideritis scardica Griseb. and Clinopodium vulgare L., belonging to the Lamiaceae family, are rich in terpenoids and phenolics and exhibit various pharmacological effects, including antioxidant, anti-inflammatory and anti-cancer activities. While the memory-enhancing impacts of S. scardica are well documented, the cognitive benefits of C. vulgare remain unexplored. This study assessed the potential effect of C. vulgare on learning and memory in healthy and scopolamine (Sco)-induced memory-impaired male Wistar rats, comparing it with the effects of S. scardica. Over a 21-day period, rats orally received extracts of cultivated S. scardica (200 mg/kg) and C. vulgare (100 mg/kg), either individually or in combination, with administration starting 10 days before and continuing 11 days simultaneously with Sco injection at a dose of 2 mg/kg intraperitoneally. The results showed that both extracts effectively mitigated Sco-induced memory impairment. Their combination significantly improved recognition memory and maintained monoaminergic function. S. scardica excelled in preserving spatial working memory, while C. vulgare exhibited comparable retention of recognition memory, robust antioxidant activity and acetylcholinesterase inhibitory activity. The extracts alleviated Sco-induced downregulation of p-CREB/BDNF signaling, suggesting neuroprotective mechanisms. The extract combination positively affected most of the Sco-induced impairments, underscoring the potential for further investigation of these extracts for therapeutic development.

Electroacupuncture attenuates ketamine-induced neuronal injury in the locus coeruleus of rats through modulation of the CAMK II/CREB pathway.

BACKGROUND: Ketamine, despite its efficacy in treating depression, raises concerns regarding safety due to potential abuse, cognitive impairment, and bladder toxicity. Ketamine can affect the locus coeruleus (LC) norepinephrine and attention networks. This study explored the protective effects of electroacupuncture (EA) on the LC of rats exposed to repeated administration of ketamine while investigating the potential role of the Calcium CaM-dependent protein kinase II (CAMK II)/ cAMP response element binding protein (CREB) pathway in mediating EA's impact on ketamine-induced neuronal injury in LC. METHODS: Rats were repeatedly injected intraperitoneally with ketamine hydrochloride (50 mg/kg) once daily for seven days. Subsequently, EA was performed at the acupoints "Zusanli" (ST36) and "Sanyinjiao" (SP-6) once daily following ketamine administration. The Morris water maze test was employed to assess behavioral changes in the rats. Neuronal injury was examined using Nissl staining, and the expression of CAMK II, CREB, and phospho-CREB (p-CREB) was evaluated through immunohistochemistry and western blotting. RESULTS: EA mitigated the cognitive and exploratory impairments and attenuated neuronal injury in the LC induced by repeated administration of ketamine. The expression of CAMK II and p-CREB proteins in the LC increased following 7 days of ketamine administration. However, EA treatment led to a downregulation of CAMK II and p-CREB expression. CONCLUSION: Repeated administration of ketamine in male rats can lead to neuronal injury and neurobehavioral dysfunction. However, EA was found to ameliorate neurodegeneration in the LC and enhance neurobehavioral symptoms. This therapeutic effect of EA may be attributed to its modulation of the CAMKII/CREB pathway, thereby mitigating the aforementioned adverse effects.

Maternal neglect alters reward-anticipatory behavior, social status stability, and reward circuit activation in adult male rats.

Introduction: Adverse early life experiences affect neuronal growth and maturation of reward circuits that modify behavior under reward predicting conditions. Previous studies demonstrate that rats undergoing denial of expected reward in the form of maternal contact (DER-animal model of maternal neglect) during early post-natal life developed anhedonia, aggressive play-fight behaviors and aberrant prefrontal cortex structure and neurochemistry. Although many studies revealed social deficiency following early-life stress most reports focus on individual animal tasks. Thus, attention needs to be given on the social effects during group tasks in animals afflicted by early life adversity. Methods: To investigate the potential impact of the DER experience on the manifestation of behavioral responses induced by natural rewards, we evaluated: 1) naïve adult male sexual preference and performance, and 2) anticipatory behavior during a group 2-phase food anticipation learning task composed of a context-dependent and a cue-dependent learning period. Results: DER rats efficiently spent time in the vicinity of and initiated sexual intercourse with receptive females suggesting an intact sexual reward motivation and consummation. Interestingly, during the context-dependent phase of food anticipation training DER rats displayed a modified exploratory activity and lower overall reward-context association. Moreover, during the cue-dependent phase DER rats displayed a mild deficit in context-reward association while increased cue-dependent locomotion. Additionally, DER rats displayed unstable food access priority following food presentation. These abnormal behaviours were accompanied by overactivation of the ventral prefrontal cortex and nucleus accumbens, as assessed by pCREB levels. Conclusions/discussion: Collectively, these data show that the neonatal DER experience resulted in adulthood in altered activation of the reward circuitry, interfered with the normal formation of context-reward associations, and disrupted normal reward access hierarchy formation. These findings provide additional evidence to the deleterious effects of early life adversity on reward system, social hierarchy formation, and brain function.

Chaperone-mediated autophagy (CMA) alleviates cognitive impairment by reducing neuronal death in sepsis-associated encephalopathy (SAE).

Sepsis-associated encephalopathy (SAE) is a common and severe complication of sepsis, which causes long-term neurological deficits, such as cognitive impairment. Despite extensive research, there is still lack of specific treatments for SAE. Chaperone-mediated autophagy (CMA), a selective type of autophagy, has been reported to be related to cognitive dysfunctions in many neurodegenerative diseases. The aim of this study was to investigate the alteration of CMA activity in the hippocampus of SAE mice and explore the neuroprotective effect of enhanced CMA. Cecal ligation and puncture (CLP) was conducted to induce SAE. In the contextual fear conditioning test, the ratio of freezing time of CLP mice significantly decreased compared with that of the mice in the Sham group, indicating cognitive impairment in SAE mice. The expression of lysosome-associated membrane protein type 2A (Lamp2a) and chaperone heat shock cognate 71 kDa protein (Hsc70), positive markers for CMA activity, decreased in hippocampal neurons of SAE mice. Although overexpression of Lamp2a in neurons via adeno-associated virus injection in the hippocampus had little effect on the mortality of septic mice, this intervention significantly alleviated the memory impairments in contextual fear conditioning test, Y-maze test and novel objective recognition test, and attenuated the neural death observed in SAE mice. We further demonstrated that the overexpression of Lamp2a in the hippocampus increased the expression of phosphorylated cyclic-AMP response element binding protein (p-CREB), brain-derived neurotrophic factor (BDNF) and B-cell lymphoma-2 (Bcl-2), and suppressed the expression of cleaved caspase-3. Taken together, our study results suggested that the upregulation of CMA activity ameliorated cognitive impairments and neuron loss in SAE mice partially through the p-CREB-BDNF/Bcl-2 signaling pathways, providing a potential therapeutic target for SAE.

Ghrelin/GHS-R1A antagonism in memory test and its effects on central molecular signaling involved in addiction in rats.

Central ghrelin signaling seems to play important role in addiction as well as memory processing. Antagonism of the growth hormone secretagogue receptor (GHS-R1A) has been recently proposed as a promising tool for the unsatisfactory drug addiction therapy. However, molecular aspects of GHS-R1A involvement in specific brain regions remain unclear. The present study demonstrated for the first time that acute as well as subchronic (4 days) administration of the experimental GHS-R1A antagonist JMV2959 in usual intraperitoneal doses including 3 mg/kg, had no influence on memory functions tested in the Morris Water Maze in rats as well as no significant effects on the molecular markers linked with memory processing in selected brain areas in rats, specifically on the ß-actin, c-Fos, two forms of the calcium/calmodulin-dependent protein kinase II (CaMKII, p-CaMKII) and the cAMP-response element binding protein (CREB, p-CREB), within the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), dorsal striatum, and hippocampus (HIPP). Furthermore, following the methamphetamine intravenous self-administration in rats, the 3 mg/kg JMV2959 pretreatment significantly reduced or prevented the methamphetamine-induced significant decrease of hippocampal ß-actin and c-Fos as well as it prevented the significant decrease of CREB in the NAC and mPFC. These results imply, that the GHS-R1A antagonist/JMV2959 might reduce/prevent some of the memory-linked molecular changes elicited by methamphetamine addiction within brain structures associated with memory (HIPP), reward (NAc), and motivation (mPFC), which may contribute to the previously observed significant JMV2959-induced reduction of the methamphetamine self-administration and drug-seeking behavior in the same animals. Further research is necessary to corroborate these results.

Endogenous but not sensory-driven activity controls migration, morphogenesis and survival of adult-born juxtaglomerular neurons in the mouse olfactory bulb.

The development and survival of adult-born neurons are believed to be driven by sensory signaling. Here, in vivo analyses of motility, morphology and Ca2+ signaling, as well as transcriptome analyses of adult-born juxtaglomerular cells with reduced endogenous excitability (via cell-specific overexpression of either Kv1.2 or Kir2.1 K+ channels), revealed a pronounced impairment of migration, morphogenesis, survival, and functional integration of these cells into the mouse olfactory bulb, accompanied by a reduction in cytosolic Ca2+ fluctuations, phosphorylation of CREB and pCREB-mediated gene expression. Moreover, K+ channel overexpression strongly downregulated genes involved in neuronal migration, differentiation, and morphogenesis and upregulated apoptosis-related genes, thus locking adult-born cells in an immature and vulnerable state. Surprisingly, cells deprived of sensory-driven activity developed normally. Together, the data reveal signaling pathways connecting the endogenous intermittent neuronal activity/Ca2+ fluctuations as well as enhanced Kv1.2/Kir2.1 K+ channel function to migration, maturation, and survival of adult-born neurons.

Stress Induces Prolonged Pain Recovery After Surgery: Involvement of Glucocorticoid-Related Pathway.

BACKGROUND: Increasing evidence suggests that chronic stress increases pain sensitivity and exacerbates existing pain. However, whether and how chronic unpredictable stress (CUS) affects surgical pain is unclear. METHODS: A postsurgical pain model was performed by longitudinal incision from 0.3 cm of the proximal edge of the heel toward the toes. The skin was sutured, and the wound site was covered. Sham surgery groups underwent the same procedure without an incision. The short-term CUS procedure was conducted by exposure of mice to 2 different stressors each day for 7 days. The behavior tests were conducted between 9:00 am and 4:00 pm. Mice were killed on day 19, and the mouse bilateral L4/5 dorsal root ganglia, spinal cord, anterior cingulate and insular cortex, and amygdala were collected for immunoblot analyses. RESULTS: Presurgical exposure of mice to CUS every day for 1-7 days showed significant depression-like behavior as evidenced by reduced sucrose preference in the sucrose consumption test and prolonged immobility time in the forced swimming task. This short-term CUS procedure did not affect the basal nociceptive response to mechanical and cold stimuli in the Von Frey and acetone-induced allodynia tests, but it delayed pain recovery after surgery, as indicated by the prolonged hypersensitivity in mechanical and cold stimuli by 12 days. The subsequent studies demonstrated that this CUS caused an increase in adrenal gland index. The abnormalities in pain recovery and adrenal gland index after surgery were reversed by a glucocorticoid receptor (GR) antagonist RU38486. Moreover, the prolonged pain recovery after surgery induced by CUS seemed to involve an increase in GR expression and decreases in cyclic adenosine monophosphate, phosphorylated cAMP response element binding protein, and brain-derived neurotrophic factor levels in emotion-related brain regions, such as anterior cingulate and insular cortex, amygdala, dorsal horn, and dorsal root ganglion. CONCLUSIONS: This finding indicates that stress-induced GR change may result in dysfunction of GR-related neuroprotective pathway.

Sex-Dependent Effect of Chronic Piromelatine Treatment on Prenatal Stress-Induced Memory Deficits in Rats.

Prenatal stress impairs cognitive function in rats, while Piromelatine treatment corrects memory decline in male rats with chronic mild stress. In the present study, we aimed to evaluate the effect of chronic treatment with the melatonin analogue Piromelatine on the associative and spatial hippocampus-dependent memory of male and female offspring with a history of prenatal stress (PNS). We report that male and female young adult offspring with PNS treated with a vehicle had reduced memory responses in an object recognition test (ORT). However, the cognitive performance in the radial arm maze test (RAM) was worsened only in the male offspring. The 32-day treatment with Piromelatine (20 mg/kg, i.p.) of male and female offspring with PNS attenuated the impaired responses in the ORT task. Furthermore, the melatonin analogue corrected the disturbed spatial memory in the male offspring. While the ratio of phosphorylated and nonphosphorylated adenosine monophosphate response element binding protein (pCREB/CREB) was reduced in the two sexes with PNS and treated with a vehicle, the melatonin analogue elevated the ratio of these signaling molecules in the hippocampus of the male rats only. Our results suggest that Piromelatine exerts a beneficial effect on PNS-induced spatial memory impairment in a sex-dependent manner that might be mediated via the pCREB/CREB pathway.

Proton-Pump Inhibitors Suppress T Cell Response by Shifting Intracellular Zinc Distribution.

Proton-pump inhibitors (PPI), e.g., omeprazole or pantoprazole, are the most widely used drugs for various gastrointestinal diseases. However, more and more side effects, especially an increased risk of infections, have been reported in recent years. The underlying mechanism has still not yet been fully uncovered. Hence, in this study, we analyzed the T cell response after treatment with pantoprazole in vitro. Pantoprazole preincubation reduced the production and secretion of interferon (IFN)-γ and interleukin (IL)-2 after the T cells were activated with phytohemagglutinin (PHA)-L or toxic shock syndrome toxin-1 (TSST-1). Moreover, a lower zinc concentration in the cytoplasm and a higher concentration in the lysosomes were observed in the pantoprazole-treated group compared to the untreated group. We also tested the expression of the zinc transporter Zrt- and Irt-like protein (Zip)8, which is located in the lysosomal membrane and plays a key role in regulating intracellular zinc distribution after T cell activation. Pantoprazole reduced the expression of Zip8. Furthermore, we measured the expression of cAMP-responsive element modulator (CREM) α, which directly suppresses the expression of IL-2, and the expression of the phosphorylated cAMP response element-binding protein (pCREB), which can promote the expression of IFN-γ. The expression of CREMα was dramatically increased, and different isoforms appeared, whereas the expression of pCREB was downregulated after the T cells were treated with pantoprazole. In conclusion, pantoprazole downregulates IFN-γ and IL-2 expression by regulating the expression of Zip8 and pCREB or CREMα, respectively.

Heat shock factor HSF1 regulates BDNF gene promoters upon acute stress in the hippocampus, together with pCREB.

Heat shock factor 1 (HSF1) is a master stress-responsive transcriptional factor, protecting cells from death. However, its gene regulation in vivo in the brain in response to neuronal stimuli remains elusive. Here, we investigated its direct regulation of the brain-derived neurotrophic factor (BDNF) gene (Bdnf) in response to acute neuronal stress stimuli in the brain. The results of immunohistochemistry and chromatin immunoprecipitation quantitative PCR (ChIP-qPCR) showed that administration of kainic acid (a glutamate receptor agonist inducing excitotoxity) to young adult mice induced HSF1 nuclear translocation and its binding to multiple Bdnf promoters in the hippocampus. Footshock, a physical stressor used for learning, also induced HSF1 binding to selected Bdnf promoters I and IV. This is, to our knowledge, the first demonstration of HSF1 gene regulation in response to neuronal stimuli in the hippocampus in vivo. HSF1 binding sites (HSEs) in Bdnf promoters I and IV were also detected when immunoprecipitated by an antibody of phosphorylated (p)CREB (cAMP-responsive element-binding protein), suggesting their possible interplay in acute stress-induced Bdnf transcription. Interestingly, their promoter binding patterns differed by KA and footshock, suggesting that HSF1 and pCREB orchestrate to render fine-tuned promoter control depending on the types of stress. Further, HSF1 overexpression increased Bdnf promoter activity in a luciferase assay, while virus infection of constitutively active-form HSF1 increased levels of BDNF mRNA and protein in vitro in primary cultured neurons. These results indicated that HSF1 activation of Bdnf promoter was sufficient to induce BDNF expression. Taken together, these results suggest that HSF1 promoter-specific control of Bdnf gene regulation plays an important role in neuronal protection and plasticity in the hippocampus in response to acute stress, possibly interplaying with pCREB.

A mink (Neovison vison) model of self-injury: Effects of CBP-CREB axis on neuronal damage and behavior.

Objective: Self-injurious behavior (SIB) is a clinically challenging problem in the general population and several clinical disorders. However, the precise molecular mechanism of SIB is still not clear. In this paper, the systematic investigation of the genesis and development of SIB is conducted based on behavioral and pathophysiology studies in mink (Neovison vison) models. Method: The night-vision video was used to observe the mink behavior, and the duration was a month. HE stain was performed to characterize the pathology change in the brain of a mink. IHC assay was performed to conduct the protein level detection of Iba-1, p-CREB, CBP, and p300 in the brain tissues. Elisa assay was used to examine the levels of NfL and NfH in serum and CSF of mink. The qRT-PCR assay was used to detect the expression of Bcl-2, NOR1, FoxO4, c-FOS, CBP, and p300 in brain tissues. Western blot was used to detect the protein levels of p-CREB, CBP, and p300 in brain tissues. We also used Evans Blue as a tracer to detect whether the blood-brain barrier was impaired in the brain of mink. Result: The behavioral test, histopathological and molecular biology experiments were combined in this paper, and the results showed that CBP was related to SIB. Mechanism analysis showed that the dysregulation of CBP in brain-activated CREB signaling will result in nerve damage of the brain and SIB symptoms in minks. More importantly, the CBP-CREB interaction inhibitor might help relieve SIB and nerve damage in brain tissues. Conclusion: Our results illustrate that the induction of CBP and the activation of CREB are novel mechanisms in the genesis of SIB. This finding indicates that the CBP-CREB axis is critical for SIB and demonstrates the efficacy of the CBP-CREB interaction inhibitor in treating these behaviors.

Conditioned-medium of stem cells from human exfoliated deciduous teeth prevent apoptosis of neural progenitors.

Purpose: This study aimed to evaluate the neuroprotective ability of the conditioned medium of stem cells from human exfoliated deciduous teeth (CM-SHED) to prevent glutamate-induced apoptosis of neural progenitors. Materials and methods: Neural progenitors were isolated from two-day-old rat brains, and the conditioned medium was obtained from a mesenchymal stem cell SHED. Four groups were examined: neural progenitor cells cultured in neurobasal medium with (N + ) and without (N-) glutamate and glycine, and neural progenitor cells cultured in CM-SHED with (K + ) and without (K-) glutamate and glycine. Results: The expression of GABA A1 receptor (GABAAR1) messenger RNA (mRNA) in neural progenitor measured by real-time quantitative PCR. GABA contents were measured by enzyme-linked immunosorbent assay, whereas the apoptosis markers caspase-3 and 7-aminoactinomycin D were analysed with a Muse® cell analyzer. The viability of neural progenitor cells in the K + group (78.05 %) was higher than the control group N- (73.22 %) and lower in the N + group (68.90 %) than in the control group. The K + group showed the highest GABA content, which significantly differed from that in the other groups, whereas the lowest content was observed in the N + group. The expression level of GABAAR1 mRNA in the K + group was the highest compared to that in the other groups. CM-SHED potently protected the neural progenitors from apoptosis. Conclusions: CM-SHED may effectively prevent glutamate-induced apoptosis of neural progenitors.

Regulation of CRE-Dependent Transcriptional Activity in a Mouse Suprachiasmatic Nucleus Cell Line.

We evaluated the signalling framework of immortalized cells from the hypothalamic suprachiasmatic nucleus (SCN) of the mouse. We selected a vasoactive intestinal peptide (VIP)-positive sub-clone of immortalized mouse SCN-cells stably expressing a cAMP-regulated-element (CRE)-luciferase construct named SCNCRE. We characterized these cells in terms of their status as neuronal cells, as well as for important components of the cAMP-dependent signal transduction pathway and compared them to SCN ex vivo. SCNCRE cells were treated with agents that modulate different intracellular signalling pathways to investigate their potency and timing for transcriptional CRE-dependent signalling. Several activating pathways modulate SCN neuronal signalling via the cAMP-regulated-element (CRE: TGACGCTA) and phosphorylation of transcription factors such as cAMP-regulated-element-binding protein (CREB). CRE-luciferase activity induced by different cAMP-signalling pathway-modulating agents displayed a variety of substance-specific dose and time-dependent profiles and interactions relevant to the regulation of SCN physiology. Moreover, the induction of the protein kinase C (PKC) pathway by phorbol ester application modulates the CRE-dependent signalling pathway as well. In conclusion, the cAMP/PKA- and the PKC-regulated pathways individually and in combination modulate the final CRE-dependent transcriptional output.

Echinochrome A Inhibits Melanogenesis in B16F10 Cells by Downregulating CREB Signaling.

Excessive increase in melanin pigment in the skin can be caused by a variety of environmental factors, including UV radiation, and can result in spots, freckles, and skin cancer. Therefore, it is important to develop functional whitening cosmetic reagents that regulate melanogenesis. In this study, we investigated the effects of echinochrome A (Ech A) on melanogenesis in the B16F10 murine melanoma cell line. We triggered B16F10 cells using α-MSH under Ech A treatment to observe melanin synthesis and analyze expression changes in melanogenesis-related enzymes (tyrosinase, tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2)) at the mRNA and protein levels. Furthermore, we measured expression changes in the microphthalmia-associated transcription factor (MITF), CREB, and pCREB proteins. Melanin synthesis in the cells stimulated by α-MSH was significantly reduced by Ech A. The expression of the tyrosinase, TYRP1, and TYRP2 mRNA and proteins was significantly decreased by Ech A, as was that of the MITF, CREB, and pCREB proteins. These results show that Ech A suppresses melanin synthesis by regulating melanogenesis-related enzymes through the CREB signaling pathway and suggest the potential of Ech A as a functional agent to prevent pigmentation and promote skin whitening.

Retrieval of olfactory fear memory alters cell proliferation and expression of pCREB and pMAPK in the corticomedial amygdala and piriform cortex.

The brain forms robust associations between odors and emotionally salient memories, making odors especially effective at triggering fearful or traumatic memories. Using Pavlovian olfactory fear conditioning (OFC), a variant of the traditional tone-shock paradigm, this study explored the changes involved in its processing. We assessed the expression of neuronal plasticity markers phosphorylated cyclic adenosine monophosphate response element binding protein (pCREB) and phosphorylated mitogen-activated protein kinase (pMAPK) 24 h and 14 days following OFC, in newborn neurons (EdU+) and in brain regions associated with olfactory memory processing; the olfactory bulb, piriform cortex, amygdale, and hippocampus. Here, we show that all proliferating neurons in the dentate gyrus of the hippocampus and glomerular layer of the olfactory bulb were colocalized with pCREB at 24 h and 14 days post-conditioning, and the number of proliferating neurons at both time points were statistically similar. This suggests the occurrence of long-term potentiation within the neurons of this pathway. Finally, OFC significantly increased the density of pCREB- and pMAPK-positive immunoreactive neurons in the medial and cortical subnuclei of the amygdala and the posterior piriform cortex, suggesting their key involvement in its processing. Together, our investigation identifies changes in neuroplasticity within critical neural circuits responsible for olfactory fear memory.

NX210c Peptide Promotes Glutamatergic Receptor-Mediated Synaptic Transmission and Signaling in the Mouse Central Nervous System.

NX210c is a disease-modifying dodecapeptide derived from the subcommissural organ-spondin that is under preclinical and clinical development for the treatment of neurological disorders. Here, using whole-cell patch-clamp recordings, we demonstrate that NX210c increased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)- and GluN2A-containing N-methyl-D-aspartate receptor (GluN2A-NMDAR)-mediated excitatory postsynaptic currents in the brain. Accordingly, using extracellular field excitatory postsynaptic potential recordings, an enhancement of synaptic transmission was shown in the presence of NX210c in two different neuronal circuits. Furthermore, the modulation of synaptic transmission and GluN2A-NMDAR-driven signaling by NX210c restored memory in mice chronically treated with the NMDAR antagonist phencyclidine. Overall, by promoting glutamatergic receptor-related neurotransmission and signaling, NX210c represents an innovative therapeutic opportunity for patients suffering from CNS disorders, injuries, and states with crippling synaptic dysfunctions.

Muscarinic Acetylcholine Receptors-Mediated Activation of PKC Restores the Hippocampal Immediate Early Gene Expression and CREB Phosphorylation in Scopolamine-Induced Amnesic Mice.

Amnesia is the inability to store new information and recall old memories. After the postulation of cholinergic hypothesis of geriatric memory dysfunction, the cholinergic signaling became a popular target to understand the underlying molecular mechanism of amnesia and its recovery. Scopolamine is a non-selective cholinergic receptor antagonist and induces amnesia through downregulation of synaptic plasticity genes including immediate early genes (IEGs). Scopolamine-induced amnesic mouse model is widely used to study the memory impairment that mimics the pathophysiology of aging, neurodegenerative, and neuropsychiatric disorders. However, a detailed understanding of cholinergic signaling-mediated regulation of plasticity-related gene expression remains elusive. Therefore, we have investigated the role of muscarinic acetylcholine receptors (mAChRs) and their downstream mediator protein kinase C (PKC) in the regulation of IEGs expression in amnesic mice hippocampus. Pilocarpine, a mAChRs agonist, was used to activate the cholinergic signaling in scopolamine-induced amnesia. Further, a PKC activator bryostatin 1 was used to understand the sole involvement of PKC as a downstream mediator of mAChRs-mediated signaling. Pilocarpine treatment significantly restored the scopolamine-induced impaired recognition memory and downregulated hippocampal IEGs expression and phosphorylation of ERK1/2 (extracellular signal-regulated kinase 1/2) and CREB (cAMP response element-binding protein). On the other hand, the bryostatin 1-mediated activation of PKC in scopolamine-induced amnesia selectively restored the hippocampal IEGs expression, recognition memory, and phosphorylation of ERK1/2 and CREB. Taken together, our findings suggest that mAChRs and their downstream mediator PKC regulate the hippocampal IEGs expression and ERK1/2-mediated CREB phosphorylation in scopolamine-induced amnesic mice.

Gestational exposure to fluoride impairs cognition in C57 BL/6 J male offspring mice via the p-Creb1-BDNF-TrkB signaling pathway.

Fluoride exposure has a detrimental effect on neurodevelopment, while the underlying processes remain unknown. The goal of this study was to investigate how fluoride impacts synaptogenesis, with a focus on the phosphorylation of Creb1 (p-Creb1)-brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) pathway. We generated a sodium fluoride (NaF) model using C57 BL/6 J mice exposed to 100 mg/L NaF from gestation day 1 (GD1) to GD20. It was identified that NaF treatment impaired the learning and memory abilities of the male offspring, reduced dendritic spine density, lowered postsynaptic density protein-95 (PSD95) and synaptophysin (SYN) expression in the male offspring's hippocampus, indicating that synaptic dysfunction may contribute to the cognitive impairment in the NaF model. In addition, in vivo experiment demonstrated that the protein abundance of BDNF and the ratio of p-Creb1 to Creb1 were increased in the hippocampus of NaF offspring, while the level of TrkB was reduced. Similarly, PC12 cells treated with NaF also showed increased expression of BDNF and decreased levels of TrkB. Notably, fluoride treatment increased p-Creb1 in vitro, while inhibiting p-Creb1 by 66615 significantly alleviated the effects of NaF exposure, indicating that p-Creb1 exerts a regulatory function in the BDNF-TrkB pathway. Altogether, these results demonstrated prenatal fluoride exposure triggered neurotoxicity in the male offspring hippocampus was linked to synaptogenesis damage caused by activating p-Creb1, which disrupted the BDNF-TrkB pathway.

Anxiety and Gene Expression Enhancement in Mice Exposed to Glyphosate-Based Herbicide.

Growing evidence demonstrates that serotonin (5-HT) depletion increases activity in the amygdala and medial prefrontal cortex (mPFC), ultimately leading to anxiety behavior. Previously, we showed that glyphosate-based herbicides (GBHs) increased anxiety levels and reduced the number of serotoninergic fibers within the mPFCs and amygdalas of exposed mice. However, the impact of this 5-HT depletion following GBH exposure on neuronal activity in these structures is still unknown. In this study, we investigated the effects of GBH on immediate early gene (IEG) activation within the mPFCs and amygdalas of treated mice from juvenile age to adulthood and its subsequent effects on anxiety levels. Mice were treated for subchronic (6 weeks) and chronic (12 weeks) periods with 250 or 500 mg/kg/day of GBH and subjected to behavioral testing using the open field and elevated plus maze paradigms. Then, we analyzed the expression levels of c-Fos and pCREB and established the molecular proxies of neuronal activation within the mPFC and the amygdala. Our data revealed that repeated exposure to GBH triggers anxiogenic behavior in exposed mice. Confocal microscopy investigations into the prelimbic/infralimbic regions of the mPFC and in basolateral/central nuclei of the amygdala disclosed that the behavioral alterations are paralleled by a robust increase in the density and labelling intensity of c-Fos- and pCREB-positive cells. Taken together, these data show that mice exposed to GBH display the hyperactivation of the mPFC-amygdala areas, suggesting that this is a potential mechanism underlying the anxiety-like phenotype.