Gastrin-releasing peptide receptor signaling in the integration of stress and memory

Dopamine release and dopamine-related gene expression in the amygdala are modulated by the gastrin-releasing peptide in opposite directions during stress-enhanced fear learning and extinction

Fear extinction leads to a decrease of originally acquired fear responses after the threat is no longer present. Fear extinction is adaptive and critical for organism's survival, but deficits in extinction may lead to exaggerated fear in animals or post-traumatic stress disorder (PTSD) in humans. Dopamine has recently emerged as essential for fear extinction and PTSD, however the neural circuits serving this dopamine function are only beginning to be investigated, and the dopamine intracellular signaling pathways are unknown. We generated gastrin-releasing peptide gene knockout (Grp-/-) mice and found that they exhibit enhanced fear memory in a stress-enhanced fear learning (SEFL) paradigm, which combines stress exposure and fear extinction, two features critical for developing PTSD. Using in vivo fiber photometry to record dopamine signals, we found that the susceptibility of Grp-/- mice to SEFL is paralleled by an increase in basolateral amygdala (BLA) dopaminergic binding during fear conditioning and early extinction. Combined optogenetics and ex vivo electrophysiology showed an increase in presynaptic ventral tegmental area (VTA)-BLA connectivity in Grp-/- mice, demonstrating a role of dysregulated input from the VTA on BLA function in the absence of the GRP. When examining gene transcription using RNA-seq and qPCR, we discovered concerted down-regulation in dopamine-related genes in the BLA of Grp-/- mice following long-term SEFL memory recall that was not observed in naïve conditions. These experiments demonstrate that the GRP regulates dopamine function in stress-enhanced fear processing and identify the Grp as the first gene known to regulate dopaminergic control of fear extinction.

Brain RFamide Neuropeptides in Stress-Related Psychopathologies

The RFamide peptide family is a group of proteins that share a common C-terminal arginine-phenylalanine-amide motif. To date, the family comprises five groups in mammals: neuropeptide FF, LPXRFamides/RFamide-related peptides, prolactin releasing peptide, QRFP, and kisspeptins. Different RFamide peptides have their own cognate receptors and are produced by different cell populations, although they all can also bind to neuropeptide FF receptors with different affinities. RFamide peptides function in the brain as neuropeptides regulating key aspects of homeostasis such as energy balance, reproduction, and cardiovascular function. Furthermore, they are involved in the organization of the stress response including modulation of pain. Considering the interaction between stress and various parameters of homeostasis, the role of RFamide peptides may be critical in the development of stress-related neuropathologies. This review will therefore focus on the role of RFamide peptides as possible key hubs in stress and stress-related psychopathologies. The neurotransmitter coexpression profile of RFamide-producing cells is also discussed, highlighting its potential functional significance. The development of novel pharmaceutical agents for the treatment of stress-related disorders is an ongoing need. Thus, the importance of RFamide research is underlined by the emergence of peptidergic and G-protein coupled receptor-based therapeutic targets in the pharmaceutical industry.

The olfactory bulb: A neuroendocrine spotlight on feeding and metabolism

Olfaction is the most ancient sense and is needed for food-seeking, danger protection, mating and survival. It is often the first sensory modality to perceive changes in the external environment, before sight, taste or sound. Odour molecules activate olfactory sensory neurons that reside on the olfactory epithelium in the nasal cavity, which transmits this odour-specific information to the olfactory bulb (OB), where it is relayed to higher brain regions involved in olfactory perception and behaviour. Besides odour processing, recent studies suggest that the OB extends its function into the regulation of food intake and energy balance. Furthermore, numerous hormone receptors associated with appetite and metabolism are expressed within the OB, suggesting a neuroendocrine role outside the hypothalamus. Olfactory cues are important to promote food preparatory behaviours and consumption, such as enhancing appetite and salivation. In addition, altered metabolism or energy state (fasting, satiety and overnutrition) can change olfactory processing and perception. Similarly, various animal models and human pathologies indicate a strong link between olfactory impairment and metabolic dysfunction. Therefore, understanding the nature of this reciprocal relationship is critical to understand how olfactory or metabolic disorders arise. This present review elaborates on the connection between olfaction, feeding behaviour and metabolism and will shed light on the neuroendocrine role of the OB as an interface between the external and internal environments. Elucidating the specific mechanisms by which olfactory signals are integrated and translated into metabolic responses holds promise for the development of targeted therapeutic strategies and interventions aimed at modulating appetite and promoting metabolic health.

GRP/GRPR signaling pathway aggravates hyperuricemia-induced renal inflammation and fibrosis via ABCG2-dependent mechanisms

The gastrin-releasing peptide receptor (GRPR) binds to ligands such as gastrin-releasing peptide (GRP) and plays a variety of biological roles. In this study, we investigated the therapeutic effect of a novel gastrin-releasing peptide receptor antagonist RH-1402 in hyperuricemia-induced kidney fibrosis and its underlying mechanisms. We conducted enzyme linked immunosorbent assay (ELISA) and immunohistochemical analyses and found that proGRP and GRPR expression levels were significantly increased in patients with hyperuricemic nephropathy (HN) and HN mice. GRPR knockdown significantly attenuated inflammatory and fibrotic responses in adenosine-treated human proximal tubule epithelial cells. GRPR knockout or GRPR conditional knockout in renal tubular epithelial cells significantly alleviated the decline in renal function and fibrosis in HN mice in vivo. RNA-seq and String database analysis revealed that GRP/GRPR promoted HN by suppressing the ABCG2/PDZK1 and increasing TGF-β/Smad3 levels by activating the NF-κB pathway. Overexpression of GRPR increased TGF-β/Smad3 levels, where as it reduced ABCG2/PDZK1 levels in adenosine-treated HK2 cells, which was reversed by the NF-κB inhibitor. Furthermore, we evaluated the therapeutic effects of the novel GRPR inhibitor RH-1402 on hyperuricaemia-induced renal injury and evaluated the inflammatory and fibrosis responses in vivo and in vitro. Pre-treatment with RH-1402 attenuated hyperuricaemia-induced renal injury, restored renal function, and suppressed renal inflammation and fibrosis. Taken together, GRPR enhances hyperuricaemia-induced tubular injury, inflammation, and renal fibrosis via ABCG2-dependent mechanisms and may serve as a promising therapeutic target for HN treatment.

Role of the GRP/GRPR System in Regulating Brain Functions

Re-examining the relationship between neuropeptide systems and neural circuits will help us to understand more intensively the critical role of neuropeptides in brain function as the neural circuits responsible for specific brain functions are gradually revealed. Gastrin-releasing peptide receptors (GRPRs) are Gαq-coupling neuropeptide receptors and widely distributed in the brain, including hippocampus, amygdala, hypothalamus, nucleus tractus solitarius (NTS), suprachiasmatic nucleus (SCN), paraventricular nucleus of the hypothalamus (PVN), preoptic area of the hypothalamus (POA), preBötzinger complex (preBötC), etc., implying the GRP/GRPR system is involved in modulating multiple brain functions. In this review, we focus on the functionality of GRPR neurons and the regulatory role of the GRP/GRPR system in memory and cognition, fear, depression and anxiety, circadian rhythms, contagious itch, gastric acid secretion, food intake, body temperature, and sighing behavior. It can be found that GRPR is usually centered on a certain brain nucleus or anatomical structure and modulates richer or more specific behaviors by connecting with additional different nuclei. In order to explain the regulatory mechanism of the GRP/GRPR system, more precise intervention methods are needed.

Major depressive disorder and chronic gastritis: A bidirectional two-sample Mendelian randomization study

OBJECTIVE

Observational studies have posited a strong correlation between chronic gastritis (CG) and major depressive disorder (MDD), but the nature of this association remains uncertain, owing to the challenges of establishing the temporal sequence. The present study sought to elucidate the elusive relationship between CG and MDD by employing a bidirectional two-sample Mendelian randomization (MR) approach.

METHODS

We extracted instrumental variants for MDD and CG from published genome-wide association study data, focusing on individuals of primarily European descent. A comprehensive suite of MR estimations and sensitivity analyses was performed to ensure the robustness of the findings. Each outcome database was analyzed separately in both directions.

RESULTS

For MDD and CG, 221 and 5 genetic variants, respectively, were selectively extracted as instrumental variants. The results suggest that MDD is causally associated with an elevated risk of CG (IVW: 23andMe, OR = 1.33; 95% CI = 1.15-1.54; p = 1.06 × 10-4); conversely, no strong evidence was found to corroborate that CG exerts a causal effect on the incidence of MDD (IVW: OR = 1.01; 95% CI = 0.95-1.07; p = 0.68).

CONCLUSIONS

These findings provide novel insights into the causal relationship between CG and MDD, which may have implications for clinical decision-making in patients with MDD and CG.

GRPR down-regulation inhibits spermatogenesis through Ca2+ mediated by PLCβ/IP3R signaling pathway in long-term formaldehyde-exposed rats

Formaldehyde (FA), which is known as an air pollutant, has been proven to induce male infertility. However, the underlying mechanism of FA-induced male infertility remains elusive. In this study, 24 male SD rats were exposed to different levels of FA (0, 0.5, 2.46, and 5 mg/m3) for eight consecutive weeks. Through HE staining and sperm smear, we observed that FA exposure resulted in spermatogenic injury and the sperm quality decreased in rats. The qRT-PCR and Western blot analysis further revealed that GRPR was down-regulated in testicular tissues of FA-exposed rats as well as primary spermatogenic cells. Meanwhile, ZDOCK uncovered an interaction between GRPR and PLCβ. In addition, the CCK8, Fluo 3-AM and Flow cytometry results showed that FA exposure suppressed the expression of GRPR, PLCβ and IP3R, consequently reducing the Ca2+ concentration in spermatogenic cells, inducing apoptosis and inhibiting proliferation of spermatogenic cells. Moreover, rescue experiments confirmed that promoting GRPR could improve intracellular Ca2+ concentration by upregulating PLCβ and IP3R, partially reducing the apoptosis and promoting the proliferation of FA-treated spermatogenic cells. These findings revealed that GRPR participates in spermatogenesis through Ca2+ mediated by the PLCβ/IP3R signaling pathway in FA-exposed rats.

Novel insight on GRP/GRPR axis in diseases

The gastrin-releasing peptide receptor (GRPR), a member of the G protein-coupled receptors (GPCRs), binds to ligands such as gastrin-releasing peptide (GRP) and plays a variety of biological roles. GRP/GRPR signalling is involved in the pathophysiological processes of many diseases, including inflammatory diseases, cardiovascular diseases, neurological diseases, and various cancers. In the immune system, the unique function of GRP/GRPR in neutrophil chemotaxis suggests that GRPR can be directly stimulated through GRP-mediated neutrophils to activate selective signalling pathways, such as PI3K, PKC, and MAPK, and participate in the occurrence and development of inflammation-related diseases. In the cardiovascular system, GRP increases intercellular adhesion molecule 1 (ICAM-1) and induces vascular cell adhesion molecule-1 (VCAM-1). GRP activates ERK1/2, MAPK, and AKT, leading to cardiovascular diseases, including myocardial infarction. Central nervous system signal transduction mediated by the GRP/GRPR axis plays a vital role in emotional responses, social interaction, and memory. The GRP/GRPR axis is elevated in various cancers, including lung, cervical, colorectal, renal cell, and head and neck squamous cell carcinomas. GRP is a mitogen in a variety of tumour cell lines. Its precursor, pro-gastrin-releasing peptide (ProGRP), may play an important role as an emerging tumour marker in early tumour diagnosis. GPCRs serve as therapeutic targets for drug development, but their function in each disease remains unclear, and their involvement in disease progression has not been well explored or summarised. This review lays out the above mentioned pathophysiological processes based on previous research conclusions. The GRP/GRPR axis may be a potential target for treating multiple diseases, and the study of this signalling axis is particularly important.

Gastrin-releasing peptide regulates fear learning under stressed conditions via activation of the amygdalostriatal transition area

The amygdala, a critical brain region responsible for emotional behavior, is crucially involved in the regulation of the effects of stress on emotional behavior. In the mammalian forebrain, gastrin-releasing peptide (GRP), a 27-amino-acid mammalian neuropeptide, which is a homolog of the 14-amino-acid amidated amphibian peptide bombesin, is highly expressed in the amygdala. The levels of GRP are markedly increased in the amygdala after acute stress; therefore, it is known as a stress-activated modulator. To determine the role of GRP in emotional behavior under stress, we conducted some behavioral and biochemical experiments with GRP-knockout (KO) mice. GRP-KO mice exhibited a longer freezing response than wild-type (WT) littermates in both contextual and auditory fear (also known as threat) conditioning tests only when they were subjected to acute restraint stress 20 min before the conditioning. To identify the critical neural circuits associated with the regulation of emotional memory by GRP, we conducted Arc/Arg3.1-reporter mapping in the amygdala with an Arc-Venus reporter transgenic mouse line. In the amygdalostriatal transition area (AST) and the lateral side of the basal nuclei, fear conditioning after restraint stress increased neuronal activity significantly in WT mice, and GRP KO was found to negate this potentiation only in the AST. These results indicate that the GRP-activated neurons in the AST are likely to suppress excessive fear expression through the regulation of downstream circuits related to fear learning following acute stress.

A neuropeptide making memories

Neuropeptides are the most diverse class of signaling molecules in the brain. Despite evidence for their involvement in several behavioral functions, the precise circuit elements and neuronal computations they control remain elusive. In this issue, Melzer et al. (2021) reveal how the neuropeptide GRP facilitates memory in the neocortex.

Deploying new generation sequencing for the study of flesh color depletion in Atlantic Salmon (Salmo salar)

BACKGROUND

The flesh pigmentation of farmed Atlantic salmon is formed by accumulation of carotenoids derived from commercial diets. In the salmon gastrointestinal system, the hindgut is considered critical in the processes of carotenoids uptake and metabolism. In Tasmania, flesh color depletion can noticeably affect farmed Atlantic salmon at different levels of severity following extremely hot summers. In this study, RNA sequencing (RNA-Seq) was performed to investigate the reduction in flesh pigmentation. Library preparation is a key step that significantly impacts the effectiveness of RNA sequencing (RNA-Seq) experiments. Besides the commonly used whole transcript RNA-Seq method, the 3' mRNA-Seq method is being applied widely, owing to its reduced cost, enabling more repeats to be sequenced at the expense of lower resolution. Therefore, the output of the Illumina TruSeq kit (whole transcript RNA-Seq) and the Lexogen QuantSeq kit (3' mRNA-Seq) was analyzed to identify genes in the Atlantic salmon hindgut that are differentially expressed (DEGs) between two flesh color phenotypes.

RESULTS

In both methods, DEGs between the two color phenotypes were associated with metal ion transport, oxidation-reduction processes, and immune responses. We also found DEGs related to lipid metabolism in the QuantSeq method. In the TruSeq method, a missense mutation was detected in DEGs in different flesh color traits. The number of DEGs found in the TruSeq libraries was much higher than the QuantSeq; however, the trend of DEGs in both library methods was similar and validated by qPCR.

CONCLUSIONS

Flesh coloration in Atlantic salmon is related to lipid metabolism in which apolipoproteins, serum albumin and fatty acid-binding protein genes are hypothesized to be linked to the absorption, transport and deposition of carotenoids. Our findings suggest that Grp could inhibit the feeding behavior of low color-banded fish, resulting in the dietary carotenoid shortage. Several SNPs in genes involving in carotenoid-binding cholesterol and oxidative stress were detected in both flesh color phenotypes. Regarding the choice of the library preparation method, the selection criteria depend on the research design and purpose. The 3' mRNA-Seq method is ideal for targeted identification of highly expressed genes, while the whole RNA-Seq method is recommended for identification of unknown genes, enabling the identification of splice variants and trait-associated SNPs, as we have found for duox2 and duoxa1.

Modulation of expression of fear by oxytocin signaling in the central amygdala: From reduction of fear to regulation of defensive behavior style

Many studies in preclinical animal models have described fear-reducing effects of the neuropeptide oxytocin in the central nucleus of the amygdala. However, recent studies have refined the role of oxytocin in the central amygdala, which may extend to the selection of an active defensive coping style in the face of immediate threat, and also fear-enhancing effects have been reported. On top of this, oxytocin enables the discrimination of unfamiliar conspecifics on the basis of their emotional state, which could allow for the selection of an appropriate coping style. This is in line with many observations that support the hypothesis that the precise outcome of oxytocin signaling in the central amygdala or other brain regions depends on the emotional or physiological state of an animal. In this review, we highlight a number of studies to exemplify the diverse effects oxytocin exerts on fear in the central amygdala of rodents. These are discussed in the context of the organization of the neural network within the central amygdala and in relation to the oxytocin-synthesizing neurons in the hypothalamus.

Embelin Improves the Spatial Memory and Hippocampal Long-Term Potentiation in a Rat Model of Chronic Cerebral Hypoperfusion

Alzheimer's disease (AD) is the second most occurring neurological disorder after stroke and is associated with cerebral hypoperfusion, possibly contributing to cognitive impairment. In the present study, neuroprotective and anti-AD effects of embelin were evaluated in chronic cerebral hypoperfusion (CCH) rat model using permanent bilateral common carotid artery occlusion (BCCAO) method. Rats were administered with embelin at doses of 0.3, 0.6 or 1.2 mg/kg (i.p) on day 14 post-surgery and tested in Morris water maze (MWM) followed by electrophysiological recordings to access cognitive abilities and synaptic plasticity. The hippocampal brain regions were extracted for gene expression and neurotransmitters analysis. Treatment with embelin at the doses of 0.3 and 0.6 mg/kg significantly reversed the spatial memory impairment induced by CCH in rats. Embelin treatment has significantly protected synaptic plasticity impairment as assessed by hippocampal long-term potentiation (LTP) test. The mechanism of this study demonstrated that embelin treatment alleviated the decreased expression of BDNF, CREB1, APP, Mapt, SOD1 and NFκB mRNA levels caused by CCH rats. Furthermore, treatment with embelin demonstrated neuromodulatory activity by its ability to restore hippocampal neurotransmitters. Overall these data suggest that embelin improve memory and synaptic plasticity impairment in CCH rats and can be a potential drug candidate for neurodegenerative disease-related cognitive disorders.

Gastrin-releasing peptide promotes the migration of vascular smooth muscle cells through upregulation of matrix metalloproteinase-2 and -9

Gastrin-releasing peptide (GRP) has been reported to be implicated in the pathogenesis of inflammatory disorders. The migration and proliferation of vascular smooth muscle cells (VSMCs) are key components of vascular inflammation that leads to the development of atherosclerosis. The present study aimed to investigate the molecular effect of GRP on VSMC proliferation and migration. We report that GRP significantly enhanced the proliferation and migration of rat VSMCs. GRP increased mRNA and protein expression of matrix metalloproteinase-2 and -9 (MMP-2/9) in VSMCs. The induction of MMP-2/9 by GRP was regulated by the activation of the signal transducer and activator of transcription-3 (STAT3). In addition, STAT3-knockdown of VSMCs by siRNA or blockade of the GRP receptor inhibited GRP-induced migration of VSMCs. Taken together, our findings indicate that GRP promotes the migration of VSMCs through upregulation of MMP-2/9 via STAT3 activation.

Gastrin-releasing peptide attenuates fear memory reconsolidation

BACKGROUND

Gastrin Releasing Peptide (GRP) may play a role in fear learning. The GRP Receptor is expressed in the basolateral amygdala and hippocampus, and central administration of GRP mediates fear learning. The effects of GRP on reconsolidation, however, have been minimally explored. Reconsolidation, the process by which formed memories are rendered labile following recall, provides a window of opportunity for pharmacological intervention. Although evidence suggests the window of opportunity to alter reactivated consolidation memory can be as long as 6 h, shorter intervals have not been extensively investigated.

METHOD

Male Sprague-Dawley rats received six 1.0 mA continuous footshocks. 24 h later, were re-exposed to the context (shock chamber). Immediately following memory retrieval rats received i.p. injection of GRP (10 nmol/kg), Flumazenil (1 mg/kg), GRP + Flumazenil (10 nmol/kg GRP with 1 mg/kg Flumazenil), or Vehicle. Other groups received GRP or Vehicle at 0, 10, 30, or 60 min post-reactivation. 24 h and 5 days later rats were assessed for fear expression upon re-exposure to the fearful stimulus.

RESULTS

GRP significantly attenuated the reconsolidation of learned fear when administered immediately (but not 10 min or longer) following recall. Some of the variability in the impact of treatments aimed at disrupting fear memories may be governed, in part, by the time-frame of the reconsolidation window. Our results indicate that the effect of immediate administration persisted for at least 5 days. Co-administration of benzodiazepine-receptor antagonist Flumazenil blocked this effect, suggesting the effect is mediated via a GABAergic mechanism.

Bombesin attenuated ischemia-induced spatial cognitive and synaptic plasticity impairment associated with oxidative damage

The dysfunction of spatial cognition is a character to various neurological disorders and therapeutic strategy. However, it is limited to known risk factors clinically so far. Gastrin releasing peptide (GRP) signaling is a neuropeptide system mediating emotional memory events. However, the effects of GRP agonist on spatial cognition and hippocampal synaptic plasticity are rarely investigated, especially in pathologic condition. This study was designed to investigate the long-term effects of GRPR agonist, bombesin, against cognitive impairment induced by chronic cerebral ischemia in rats and its possible mechanisms. Our results revealed that bombesin administration (30 μg/kg/day, for 14 continuous days) significantly protected the cognitive and synaptic plasticity impairments as assessed by the Morris water maze and long-term potentiation tests. The mechanism studies demonstrated that bombesin significantly alleviated the decreased activity of total superoxide dismutase (T-SOD), catalase (CAT) and altered the increased the content of malondialdehyde (MDA). Besides, the decreased expression of synapse plasticity-related proteins, calcium- calmodulin- dependent protein kinase II (CaMKII) and synaptophysin (SYP) in the hippocampus were increased with drug treatment. In conclusion, bombesin could protect the oxidative stress and expression of proteins, which were important for synaptic plasticity and cognitive function impairment induced by chronic cerebral ischemia. Our study is presented to provide novel insights into the effects of bombesin on spatial learning and memory, which should be further explored as a potential drug in disorders involving deficits in cognitive function.

Distribution of the pig gastrin-releasing peptide receptor and the effect of GRP on porcine Leydig cells

Gastrin-releasing peptide (GRP) is a mammalian bombesin (BN)-like peptide which plays a role in a number of important physiological functions via its receptor (gastrin-releasing peptide receptor, GRPR) in most animals. However, little is known about the gene encoding GRPR and its functions (especially reproduction) in pigs. In this study, we first cloned and analyzed the pig GRPR cDNA. Then we systematically investigated the expression levels of GRPR mRNA by relative real-time PCR (RT-PCR), and analyzed the distribution of the GRPR protein in pig tissues via immunohistochemistry (IHC). Finally, we studied the effect of GRP on testosterone secretion and GRPR (mRNA and protein) expression in Leydig cells. Results showed that the pig GRPR cDNA cloned at 1487bp, including one open reading frame (ORF) of 1155bp and encodes 384 amino acids. Significantly, compared with other species, the cDNA sequence and amino acid sequence of the pig GRPR were highly homologous and conservative. The RT-PCR results showed that: in the central nervous system (CNS) and the pituitary, GRPR mRNA was found in the cerebellum, hypophysis, spinal cord and hypothalamus; in the peripheral tissues, GRPR mRNA was mainly expressed in the pancreas, esophagus, ovary, testis, spleen, thymus, jejunum lymph node, muscle and fat. Moreover, the IHC results showed that GRPR immunoreactivity was widely distributed in the pig tissues and organs, such as the pancreas, esophagus, testis, ovary, spleen, pituitary gland and adrenal gland. In addition, we found that GRP promotes testosterone secretion, and increases GRPR mRNA and protein expression in cultured Leydig cells in vitro. These molecular and morphological data not only describe the anatomical locations of GRPR in pigs, but also provide the theoretical foundation for further research into its possible physiological functions in pigs. These results suggest that the GRP/GRPR system may play an important role in regulating the reproductive system of the boar.

Neuronal signals regulate obesity induced β-cell proliferation by FoxM1 dependent mechanism

Under insulin-resistant conditions such as obesity, pancreatic β-cells proliferate to prevent blood glucose elevations. A liver–brain–pancreas neuronal relay plays an important role in this process. Here, we show the molecular mechanism underlying this compensatory β-cell proliferation. We identify FoxM1 activation in islets from neuronal relay-stimulated mice. Blockade of this relay, including vagotomy, inhibits obesity-induced activation of the β-cell FoxM1 pathway and suppresses β-cell expansion. Inducible β-cell-specific FoxM1 deficiency also blocks compensatory β-cell proliferation. In isolated islets, carbachol and PACAP/VIP synergistically promote β-cell proliferation through a FoxM1-dependent mechanism. These findings indicate that vagal nerves that release several neurotransmitters may allow simultaneous activation of multiple pathways in β-cells selectively, thereby efficiently promoting β-cell proliferation and maintaining glucose homeostasis during obesity development. This neuronal signal-mediated mechanism holds potential for developing novel approaches to regenerating pancreatic β-cells.

Neuronal signals, in particular those transmitted via the vagal nerve, regulate both β-cell function and proliferation. Here, Yamamoto et al. show that the forkhead box M1 pathway is required for vagal signal-mediated induction of β-cell proliferation during obesity.

Psychological effects of Helicobacter pylori-associated atrophic gastritis in patients under 50 years: A cross-sectional study

BACKGROUND

While gastrointestinal function is known to be closely related to psychological status, the influence of Helicobacter pylori-associated atrophic gastritis is currently unknown. We aimed to determine whether atrophic gastritis status or H. pylori infection is associated with psychological distress or depressed mood.

MATERIALS AND METHODS

We performed a cross-sectional, observational study involving 975 Japanese individuals (503 females; mean age, 44 ± 8 years) who underwent a health checkup. Psychological distress was defined as a Kessler-6 Scale score ≥13 and depressive mood as a Center for Epidemiological Studies Depression Scale score ≥ 16. The odds ratios with 95% confidence intervals assessing the risk of psychological distress or depressive mood associated with H. pylori infection (H. pylori-specific immunoglobulin G levels >10 U/mL) and atrophic gastritis status (pepsinogen I levels < 70 μg/L and pepsinogen I/II ratio < 3) were calculated using multiple logistic analysis adjusting for several covariates.

RESULTS

Individuals with atrophic gastritis had a significantly higher risk of experiencing psychological distress, with younger females (<50 years) displaying the highest risk for psychological distress and depressive mood regardless of H. pylori infection status. Among females aged <50 years, H. pylori-seropositive participants with atrophic gastritis (HP+AG+) showed the highest risk of psychological distress (OR, 16.4; 95% CI, 3.45-94.9) and depression (OR, 2.86; 95% CI, 1.31-6.05), using HP-AG- status as the reference.

CONCLUSIONS

Our findings support the results of previous animal studies regarding the psychological response to gastritis in humans. Further studies are needed to elucidate whether H. pylori eradication provides psychological benefits.

Pharmacological Effects of Two Novel Bombesin-Like Peptides from the Skin Secretions of Chinese Piebald Odorous Frog (Odorrana schmackeri) and European Edible Frog (Pelophylax kl. esculentus) on Smooth Muscle

Bombesin-like peptides, which were identified from a diversity of amphibian skin secretions, have been demonstrated to possess several biological functions such as stimulation of smooth muscle contraction and regulation of food intake. Here, we report two novel bombesin-like peptides, bombesin-OS and bombesin-PE, which were isolated from Odorrana schmackeri and Pelophylax kl. esculentus, respectively. The mature peptides were identified and structurally confirmed by high performance Scliquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). Subsequently, the effects of these purified chemically-synthetic peptides on smooth muscle were determined in bladder, uterus, and ileum. The synthetic replications were revealed to have significant pharmacological effects on these tissues. The EC₅₀ values of bombesin-OS for bladder, uterus and ileum, were 10.8 nM, 33.64 nM, and 12.29 nM, respectively. Furthermore, compared with bombesin-OS, bombesin-PE showed similar contractile activity on ileum smooth muscle and uterus smooth muscle, but had a higher potency on bladder smooth muscle. The EC₅₀ value of bombesin-OS for bladder was around 1000-fold less than that of bombesin-PE. This suggests that bombesin-OS and bombesin-PE have unique binding properties to their receptors. The precursor of bombesin-OS was homologous with that of a bombesin-like peptide, odorranain-BLP-5, and bombesin-PE belongs to the ranatensin subfamily. We identified the structure of bombesin-OS and bombesin-PE, two homologues peptides whose actions may provide a further clue in the classification of ranid frogs, also in the provision of new drugs for human health.

Administration of a Histone Deacetylase Inhibitor into the Basolateral Amygdala Enhances Memory Consolidation, Delays Extinction, and Increases Hippocampal BDNF Levels

Gene expression related to the formation and modification of memories is regulated epigenetically by chromatin remodeling through histone acetylation. Memory formation and extinction can be enhanced by treatment with inhibitors of histone deacetylases (HDACs). The basolateral amygdala (BLA) is a brain area critically involved in regulating memory for inhibitory avoidance (IA). However, previous studies have not examined the effects of HDAC inhibition in the amygdala on memory for IA. Here we show that infusion of an HDAC inhibitor (HDACi), trichostatin A (TSA), into the BLA, enhanced consolidation of IA memory in rats when given at 1.5, 3, or 6 h posttraining, but not when the drug was infused immediately after training. In addition, intra-BLA administration of TSA immediately after retrieval delayed extinction learning. Moreover, we show that intra-BLA TSA in rats given IA training increased the levels of brain-derived neurotrophic factor in the dorsal hippocampus, but not in the BLA itself. These findings reveal novel aspects of the regulation of fear memory by epigenetic mechanisms in the amygdala.

A Placebo-Controlled Crossover Trial of Gastrin-Releasing Peptide in Childhood Autism

OBJECTIVES

The aim of this study was to evaluate the efficacy, safety, and tolerability of gastrin-releasing peptide (GRP) compared with placebo in autism spectrum disorder symptoms.

METHODOLOGY

This is a randomized, double-blind, placebo-controlled crossover trial using GRP 160 pmol/kg for 4 consecutive days in 10 children with autism. Outcomes were measured by the Aberrant Behavior Checklist (ABC) scale.

RESULTS

All participants were boys, aged between 4 and 9 years. There was a reduction in the scores of the ABC range and its subscales after use GRP and placebo. The reduction was more prominent with GRP, particularly in the subscale "hyperactivity and noncompliance," but there was no statistical difference between the results (P = 0.334). After a week of infusion, 5 children showed improvement of 25% or greater in the total score of the ABC scale with GRP use and 2 with placebo use; however, there was no statistical difference (P = 0.375). There were no adverse effects, changes in vital signs, or laboratory abnormalities associated with the use of GRP.

CONCLUSIONS

The results of this study, despite the small sample size, reinforce previous data on the safety of the GRP in short-term use. There is a need for further research with other designs and a larger sample size to evaluate the efficacy and safety of GRP in children with autism.

Neuropeptide gastrin-releasing peptide induces PI3K/reactive oxygen species-dependent migration in lung adenocarcinoma cells

Nerve fibers and neurotransmitters have increasingly been shown to have a role in tumor progression. Gastrin-releasing peptide is a neuropeptide linked to tumor aggressiveness, acting as an autocrine tumor growth factor by binding to its receptor, gastrin-releasing peptide receptor, expressed by many tumors. Although neuropeptides have been previously linked to tumor cell proliferation, more recent studies have uncovered roles for neuropeptides in chemotaxis and metastasis. Understanding the precise roles of such peptides in cancer is crucial to optimizing targeted therapy design. We have previously described that gastrin-releasing peptide acts directly as a chemotactic factor for neutrophils, dependent on PI3K, ERK, and p38. In this study, we investigated roles for gastrin-releasing peptide in lung adenocarcinoma. We asked if gastrin-releasing peptide would act as a proliferative and/or chemotactic stimulus for gastrin-releasing peptide receptor-expressing tumor cells. In A549 cells, a non-small cell lung carcinoma line, the treatment with gastrin-releasing peptide leads to activation of AKT and ERK1/2, and production of reactive oxygen species. Gastrin-releasing peptide induced migration of A549 cells, dependent on gastrin-releasing peptide receptor and PI3K, but not ERK. However, no proliferation was observed in these cells in response to gastrin-releasing peptide, and gastrin-releasing peptide did not promote resistance to treatment with a chemotherapy drug. Our results suggest that, similar to what happens in neutrophils, gastrin-releasing peptide is a migratory, rather than a proliferative, stimulus, for non-small cell lung carcinoma cells, indicating a putative role for gastrin-releasing peptide and gastrin-releasing peptide receptor in metastasis.

Gastrin-releasing peptide induces monocyte adhesion to vascular endothelium by upregulating endothelial adhesion molecules

Gastrin-releasing peptide (GRP) is a neuropeptide that plays roles in various pathophysiological conditions including inflammatory diseases in peripheral tissues; however, little is known about whether GRP can directly regulate endothelial inflammatory processes. In this study, we showed that GRP promotes the adhesion of leukocytes to human umbilical vein endothelial cells (HUVECs) and the aortic endothelium. GRP increased the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by activating nuclear factor-κB (NF-κB) in endothelial cells. In addition, GRP activated extracellular signal-regulated kinase 1/2 (ERK1/2), p38MAPK, and AKT, and the inhibition of these signaling pathways significantly reduced GRP-induced monocyte adhesion to the endothelium. Overall, our results suggested that GRP may cause endothelial dysfunction, which could be of particular relevance in the development of vascular inflammatory disorders.

Histone Modifications in a Mouse Model of Early Adversities and Panic Disorder: Role for Asic1 and Neurodevelopmental Genes

Hyperventilation following transient, CO₂-induced acidosis is ubiquitous in mammals and heritable. In humans, respiratory and emotional hypersensitivity to CO₂ marks separation anxiety and panic disorders, and is enhanced by early-life adversities. Mice exposed to the repeated cross-fostering paradigm (RCF) of interference with maternal environment show heightened separation anxiety and hyperventilation to 6% CO₂-enriched air. Gene-environment interactions affect CO₂ hypersensitivity in both humans and mice. We therefore hypothesised that epigenetic modifications and increased expression of genes involved in pH-detection could explain these relationships. Medullae oblongata of RCF- and normally-reared female outbred mice were assessed by ChIP-seq for H3Ac, H3K4me3, H3K27me3 histone modifications, and by SAGE for differential gene expression. Integration of multiple experiments by network analysis revealed an active component of 148 genes pointing to the mTOR signalling pathway and nociception. Among these genes, Asic1 showed heightened mRNA expression, coherent with RCF-mice’s respiratory hypersensitivity to CO₂ and altered nociception. Functional enrichment and mRNA transcript analyses yielded a consistent picture of enhancement for several genes affecting chemoception, neurodevelopment, and emotionality. Particularly, results with Asic1 support recent human findings with panic and CO₂ responses, and provide new perspectives on how early adversities and genes interplay to affect key components of panic and related disorders.

Histone deacetylase inhibition prevents the impairing effects of hippocampal gastrin-releasing peptide receptor antagonism on memory consolidation and extinction

Hippocampal gastrin-releasing peptide receptors (GRPR) regulate memory formation and extinction, and disturbances in GRPR signaling may contribute to cognitive impairment associated with neurodevelopmental disorders. Histone acetylation is an important epigenetic mechanism that regulates gene expression involved in memory formation, and histone deacetylase inhibitors (HDACis) rescue memory deficits in several models. The present study determined whether inhibiting histone deacetylation would prevent memory impairments produced by GRPR blockade in the hippocampus. Male Wistar rats were given an intrahippocampal infusion of saline (SAL) or the HDACi sodium butyrate (NaB) shortly before inhibitory avoidance (IA) training, followed by an infusion of either SAL or the selective GRPR antagonist RC-3095 immediately after training. In a second experiment, the infusions were administered before and after a retention test trial that served as extinction training. As expected, RC-3095 significantly impaired consolidation and extinction of IA memory. More importantly, pretraining administration of NaB, at a dose that had no effect when given alone, prevented the effects of RC-3095. In addition, the combination of NaB and RC-3095 increased hippocampal levels of the brain-derived neurotrophic factor (BDNF). These findings indicate that HDAC inhibition can protect against memory impairment caused by GRPR blockade.

A Stress-Related Peptide Bombesin Centrally Induces Frequent Urination through Brain Bombesin Receptor Types 1 and 2 in the Rat

Stress exacerbates symptoms of bladder dysfunction including overactive bladder and bladder pain syndrome, but the underlying mechanisms are unknown. Bombesin-like peptides and bombesin receptor types 1 and 2 (BB1 and BB2, respectively) in the brain have been implicated in the mediation/integration of stress responses. In this study, we examined effects of centrally administered bombesin on micturition, focusing on their dependence on 1) the sympathoadrenomedullary system (a representative mechanism activated by stress exposure) and 2) brain BB receptors in urethane-anesthetized (1.0-1.2 g/kg, i.p.) male rats. Intracerebroventricularly administered bombesin significantly shortened intercontraction intervals (ICI) at both doses (0.1 and 1 nmol/animal) without affecting maximal voiding pressure. Bombesin at 1 nmol induced significant increments of plasma noradrenaline and adrenaline levels, which were both abolished by acute bilateral adrenalectomy. On the other hand, adrenalectomy showed no effects on the bombesin-induced shortening of ICI. Much lower doses of bombesin (0.01 and 0.03 nmol/animal, i.c.v.) dose-dependently shortened ICI. Pretreatment with either a BB1 receptor antagonist (BIM-23127; d-Nal-cyclo[Cys-Tyr-d-Trp-Orn-Val-Cys]-Nal-NH2; 3 nmol/animal, i.c.v.) or a BB2 receptor antagonist (BEA; H-d-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHEt; 3 nmol/animal, i.c.v.), respectively, suppressed the BB (0.03 nmol/animal, i.c.v.)-induced shortening of ICI, whereas each antagonist by itself (1 and 3 nmol/animal, i.c.v.) had no significant effects on ICI. Bombesin (0.03 nmol/animal, i.c.v.) significantly reduced voided volume per micturition and bladder capacity without affecting postvoid residual volume or voiding efficiency. These results suggest that brain bombesin and BB receptors are involved in facilitation of the rat micturition reflex to induce bladder overactivity, which is independent of the sympathoadrenomedullary outflow modulation.

From neural to genetic substrates of panic disorder: Insights from human and mouse studies

Fear is an ancestral emotion, an intrinsic defensive response present in every organism. Although fear is an evolutionarily advantageous emotion, under certain pathologies such as panic disorder it might become exaggerated and non-adaptive. Clinical and preclinical work pinpoints that changes in cognitive processes, such as perception and interpretation of environmental stimuli that rely on brain regions responsible for high-level function, are essential for the development of fear-related disorders. This review focuses on the involvement of cognitive function to fear circuitry disorders. Moreover, we address how animal models are contributing to understand the involvement of human candidate genes to pathological fear and helping achieve progress in this field. Multidisciplinary approaches that integrate human genetic findings with state of the art genetic mouse models will allow to elucidate the mechanisms underlying pathology and to develop new strategies for therapeutic targeting.