Galanin diminishes cortical spreading depolarization across rodents - A candidate for treatment?

Galanin (Gal) is a neuropeptide with the potential to ameliorate cortical spreading depolarization (CSD), an electrophysiological phenomenon occurring after brain injury or in migraine aura. Gal is expressed in all cortical neurons both in rat and in mouse cortices. Here we investigated whether the effect of Gal on CSD previously described in the rat is conserved in the mouse cortex. In rats, the topical application of Gal to the cortex for 1 h did not induce any change in CSD amplitudes, propagation velocity, or threshold of elicitation. Rather, topical application of Gal for 3 h was necessary to obtain a significant decrease in these CSD parameters and to develop a remarkable increase in the KCl threshold to elicit a CSD in rat cortex. In contrast, the topical application of Gal on cortical surface for 1 h in mice was sufficient to significantly attenuate CSD amplitudes and increase threshold. A thinner cortex, a faster diffusion or different affinity/expression of receptors for Gal are possible reasons to explain this difference in the time course between rats and mice. Our data are relevant to postulate Gal as a potential target for inhibition of CSD under pathological situations such as stroke or ischemia. SIGNIFICANCE STATEMENT: The neuropeptide Galanin (Gal) is expressed in all neurons throughout the cerebral cortex, both in rats and mice, and is able to reduce or even inhibit Cortical Spreading Depolarization, thus, Gal has the potential to control neuronal excitability that may identify Gal as a target in drug development against CSD.

Glyphosate-induced changes in the expression of galanin and GALR1, GALR2 and GALR3 receptors in the porcine small intestine wall

Glyphosate is the active ingredient of glyphosate-based herbicides and the most commonly used pesticide in the world. The goal of the present study was to verify whether low doses of glyphosate (equivalent to the environmental exposure) evoke changes in galanin expression in intramural neurons in the small intestine in pigs and to quantitatively determine changes in the level of galanin receptor encoding mRNA (GALR1, GALR2, GALR3) in the small intestine wall. The experiment was conducted on 15 sexually immature gilts divided into three study groups: control (C)-animals receiving empty gelatin capsules; experimental 1 (G1)-animals receiving a low dose of glyphosate (0.05 mg/kg b.w./day); experimental 2 (G2)-animals receiving a higher dose of glyphosate (0.5 mg/kg b.w./day) orally in gelatine capsules for 28 days. Glyphosate ingestion led to an increase in the number of GAL-like immunoreactive intramural neurons in the porcine small intestine. The results of RT-PCR showed a significant increase in the expression of mRNA, which encodes the GAL-receptors in the ileum, a decreased expression in the duodenum and no significant changes in the jejunum. Additionally, intoxication with glyphosate increased the expression of SOD2-encoding mRNA in the duodenum and decreased it in the jejunum and ileum, but it did not affect SOD1 expression. The results suggest that it may be a consequence of the cytotoxic and/or neurotoxic properties of glyphosate and/or its ability to induce oxidative stress.

Long-term enhancements in antidepressant efficacy and neurogenesis: Effects of intranasal co-administration of neuropeptide Y 1 receptor (NPY1R) and galanin receptor 2 (GALR2) agonists in the ventral hippocampus

This study evaluates the sustained antidepressant-like effects and neurogenic potential of a 3-day intranasal co-administration regimen of galanin receptor 2 (GALR2) agonist M1145 and neuropeptide Y Y1 receptor (NPY1R) agonist [Leu31, Pro34]NPY in the ventral hippocampus of adult rats, with outcomes analyzed 3 weeks post-treatment. Utilizing the forced swimming test (FST), we found that this co-administration significantly enhances antidepressant-like behaviors, an effect neutralized by the GALR2 antagonist M871, highlighting the synergistic potential of these neuropeptides in modulating mood-related behaviors. In situ proximity ligation assay (PLA) indicated a significant increase in GALR2/NPYY1R heteroreceptor complexes in the ventral hippocampal dentate gyrus, suggesting a molecular basis for the behavioral outcomes observed. Moreover, proliferating cell nuclear antigen (PCNA) immunolabeling revealed increased cell proliferation in the subgranular zone of the dentate gyrus, specifically in neuroblasts as evidenced by co-labeling with doublecortin (DCX), without affecting quiescent neural progenitors or astrocytes. The study also noted a significant uptick in the number of DCX-positive cells and alterations in dendritic morphology in the ventral hippocampus, indicative of enhanced neuronal differentiation and maturation. These morphological changes highlight the potential of these agonists to facilitate the functional integration of new neurons into existing neural circuits. By demonstrating the long-lasting effects of a brief, 3-day intranasal administration of GALR2 and NPY1R agonists, our findings contribute significantly to the understanding of neuropeptide-mediated neuroplasticity and herald novel therapeutic strategies for the treatment of depression and related mood disorders, emphasizing the therapeutic promise of targeting neurogenesis and neuronal maturation processes.

Transient expression of the neuropeptide galanin modulates peripheral‑to‑central connectivity in the somatosensory thalamus during whisker development in mice

The significance of transient neuropeptide expression during postnatal brain development is unknown. Here, we show that galanin expression in the ventrobasal thalamus of infant mice coincides with whisker map development and modulates subcortical circuit wiring. Time-resolved neuroanatomy and single-nucleus RNA-seq identified complementary galanin (Gal) and galanin receptor 1 (Galr1) expression in the ventrobasal thalamus and the principal sensory nucleus of the trigeminal nerve (Pr5), respectively. Somatodendritic galanin release from the ventrobasal thalamus was time-locked to the first postnatal week, when Gal1R+ Pr5 afferents form glutamatergic (Slc17a6+) synapses for the topographical whisker map to emerge. RNAi-mediated silencing of galanin expression disrupted glutamatergic synaptogenesis, which manifested as impaired whisker-dependent exploratory behaviors in infant mice, with behavioral abnormalities enduring into adulthood. Pharmacological probing of receptor selectivity in vivo corroborated that target recognition and synaptogenesis in the thalamus, at least in part, are reliant on agonist-induced Gal1R activation in inbound excitatory axons. Overall, we suggest a neuropeptide-dependent developmental mechanism to contribute to the topographical specification of a fundamental sensory neurocircuit in mice.

Cortical spreading depolarization is a potential target for rat brain excitability modulation by Galanin

The inhibitory neuropeptide Galanin (Gal) has been shown to mediate anticonvulsion and neuroprotection. Here we investigated whether Gal affects cortical spreading depolarization (CSD). CSD is considered the pathophysiological neuronal mechanism of migraine aura, and a neuronal mechanism aggravating brain damage upon afflictions of the brain. Immunohistochemistry localized Gal and the Gal receptors 1-3 (GalR1-3) in native rat cortex and evaluated microglial morphology after exposure to Gal. In anesthetized rats, Gal was applied alone and together with the GalR antagonists M40, M871, or SNAP 37889 locally to the exposed cortex. The spontaneous electrocorticogram and CSDs evoked by remote KCl pressure microinjection were measured. In rat cortex, Gal was present in all neurons of all cortical layers, but not in astrocytes, microglia and vessels. GalR2 and GalR3 were expressed throughout all neurons, whereas GalR1 was preponderantly located at neurons in layers IV and V, but only in about half of the neurons. In susceptible rats, topical application of Gal on cortex decreased CSD amplitude, slowed CSD propagation velocity, and increased the threshold for KCl to ignite CSD. In some rats, washout of previously applied Gal induced periods of epileptiform patterns in the electrocorticogram. Blockade of GalR2 by M871 robustly prevented all Gal effects on CSD, whereas blockade of GalR1 or GalR3 was less effective. Although microglia did not express GalRs, topical application of Gal changed microglial morphology indicating microglial activation. This effect of Gal on microglia was prevented by blocking neuronal GalR2. In conclusion, Gal has the potential to ameliorate CSD thus reducing pathophysiological neuronal events caused by or associated with CSD.

The parenting hub of the hypothalamus is a focus of imprinted gene action

Imprinted genes are subject to germline epigenetic modification resulting in parental-specific allelic silencing. Although genomic imprinting is thought to be important for maternal behaviour, this idea is based on serendipitous findings from a small number of imprinted genes. Here, we undertook an unbiased systems biology approach, taking advantage of the recent delineation of specific neuronal populations responsible for controlling parental care, to test whether imprinted genes significantly converge to regulate parenting behaviour. Using single-cell RNA sequencing datasets, we identified a specific enrichment of imprinted gene expression in a recognised "parenting hub", the galanin-expressing neurons of the preoptic area. We tested the validity of linking enriched expression in these neurons to function by focusing on MAGE family member L2 (Magel2), an imprinted gene not previously linked to parenting behaviour. We confirmed expression of Magel2 in the preoptic area galanin expressing neurons. We then examined the parenting behaviour of Magel2-null(+/p) mice. Magel2-null mothers, fathers and virgin females demonstrated deficits in pup retrieval, nest building and pup-directed motivation, identifying a central role for this gene in parenting. Finally, we show that Magel2-null mothers and fathers have a significant reduction in POA galanin expressing cells, which in turn contributes to a reduced c-Fos response in the POA upon exposure to pups. Our findings identify a novel imprinted gene that impacts parenting behaviour and, moreover, demonstrates the utility of using single-cell RNA sequencing data to predict gene function from expression and in doing so here, have identified a purposeful role for genomic imprinting in mediating parental behaviour.

Galanin System in the Human Bile Duct and Perihilar Cholangiocarcinoma

BACKGROUND

Perihilar cholangiocarcinoma (pCCA) is characterised by poor outcomes. Early diagnosis is essential for patient survival. The peptide galanin (GAL) and its receptors GAL1-3 are expressed in various tumours. Detailed characterisation of the GAL system in pCCA is lacking. Our study sought to characterise GAL and GAL1-3 receptor (GAL1-3-R) expression in the healthy human bile duct, in cholestasis and pCCA.

METHODS

Immunohistochemical staining was performed in healthy controls (n = 5) and in the peritumoural tissues (with and without cholestasis) (n = 20) and tumour tissues of pCCA patients (n = 33) using validated antibodies. The score values of GAL and GAL1-3-R expression were calculated and statistically evaluated.

RESULTS

GAL and GAL1-R were expressed in various bile duct cell types. GAL2-R was only slightly but still expressed in almost all the examined tissues, and GAL3-R specifically in cholangiocytes and capillaries. In a small pCCA patient cohort (n = 18), high GAL expression correlated with good survival, whereas high GAL3-R correlated with poor survival.

CONCLUSIONS

Our in-depth characterisation of the GAL system in the healthy human biliary duct and pCCA in a small patient cohort revealed that GAL and GAL3-R expression in tumour cells of pCCA patients could potentially represent suitable biomarkers for survival.

Structure and Function of Neuronal Circuits Linking Ventrolateral Preoptic Nucleus and Lateral Hypothalamic Area

To understand how sleep-wakefulness cycles are regulated, it is essential to disentangle structural and functional relationships between the preoptic area (POA) and lateral hypothalamic area (LHA), since these regions play important yet opposing roles in the sleep-wakefulness regulation. GABA- and galanin (GAL)-producing neurons in the ventrolateral preoptic nucleus (VLPO) of the POA (VLPOGABA and VLPOGAL neurons) are responsible for the maintenance of sleep, while the LHA contains orexin-producing neurons (orexin neurons) that are crucial for maintenance of wakefulness. Through the use of rabies virus-mediated neural tracing combined with in situ hybridization (ISH) in male and female orexin-iCre mice, we revealed that the vesicular GABA transporter (Vgat, Slc32a1)- and galanin (Gal)-expressing neurons in the VLPO directly synapse with orexin neurons in the LHA. A majority (56.3 ± 8.1%) of all VLPO input neurons connecting to orexin neurons were double-positive for Vgat and Gal Using projection-specific rabies virus-mediated tracing in male and female Vgat-ires-Cre and Gal-Cre mice, we discovered that VLPOGABA and VLPOGAL neurons that send projections to the LHA received innervations from similarly distributed input neurons in many brain regions, with the POA and LHA being among the main upstream areas. Additionally, we found that acute optogenetic excitation of axons of VLPOGABA neurons, but not VLPOGAL neurons, in the LHA of male Vgat-ires-Cre mice induced wakefulness. This study deciphers the connectivity between the VLPO and LHA, provides a large-scale map of upstream neuronal populations of VLPO→LHA neurons, and reveals a previously uncovered function of the VLPOGABA→LHA pathway in the regulation of sleep and wakefulness.SIGNIFICANCE STATEMENT We identified neurons in the ventrolateral preoptic nucleus (VLPO) that are positive for vesicular GABA transporter (Vgat) and/or galanin (Gal) and serve as presynaptic partners of orexin-producing neurons in the lateral hypothalamic area (LHA). We depicted monosynaptic input neurons of GABA- and galanin-producing neurons in the VLPO that send projections to the LHA throughout the entire brain. Their input neurons largely overlap, suggesting that they comprise a common neuronal population. However, acute excitatory optogenetic manipulation of the VLPOGABA→LHA pathway, but not the VLPOGAL→LHA pathway, evoked wakefulness. This study shows the connectivity of major components of the sleep/wake circuitry in the hypothalamus and unveils a previously unrecognized function of the VLPOGABA→LHA pathway in sleep-wakefulness regulation. Furthermore, we suggest the existence of subpopulations of VLPOGABA neurons that innervate LHA.

Galanin expression varies with parental care and social status in a wild cooperatively breeding fish

As many busy parents will attest, caring for young often comes at the expense of having time to feed and care for oneself. Galanin is a neuropeptide that regulates food intake and modulates parental care; however, the relative importance of galanin in the regulation of feeding versus caring by parents has never been evaluated before under naturalistic settings. Here, we assessed how expression of the galanin system varied in two brain regions, the hypothalamus (which regulates feeding) and the preoptic area (which modulates social behaviours including care) in a wild cichlid fish, Neolamprologus pulcher. Females with young had higher hypothalamic expression of galanin receptor 1a, and the highest expression of galanin and galanin receptor 1a was observed in females that foraged the least. However, expression of five other feeding-related neuropeptides did not change while females were caring for young suggesting that changes in the hypothalamic galanin system may not have been directly related to changes in food intake. The preoptic galanin system was unaffected by the presence of young, but preoptic galanin expression was higher in dominant females (which are aggressive, regularly reproduce and care for young) compared to subordinate females (which are submissive, rarely reproduce but often help care for young). Additionally, preoptic galanin expression was higher in fish that performed more territory defense. Overall, our results indicate that galanin has brain-region-specific roles in modulating both parental care and social status in wild animals.

The distribution and chemical coding of urinary bladder trigone-projecting neurons in testicular and aorticorenal ganglia in male pigs

Combined retrograde tracing and double-labelling immunofluorescence were used to investigate the distribution and chemical coding of neurons in testicular (TG) and aorticoerenal (ARG) ganglia supplying the urinary bladder trigone (UBT) in juvenile male pigs (n=4, 12 kg. of body weight). Retrograde fluorescent tracer Fast Blue (FB) was injected into the wall of the bladder trigone under pentobarbital anesthesia. After three weeks all the pigs were deeply anesthetized and transcardially perfused with 4% buffered paraformaldehyde. TG and ARG, were collected and processed for double-labelling immunofluorescence. The expression of tyrosine hydroxylase (TH) or dopamine beta-hydroxylase (DBH), neuropeptide Y (NPY), somatostatin (SOM), galanin (GAL), nitric oxide synthase (NOS) and vesicular acetylcholine transporter (VAChT) were investigated. The cryostat sections were examined with a Zeiss LSM 710 confocal microscope equipped with adequate filter blocks. The TG and ARG were found to contain many FB-positive neurons projecting to the UBT (UBT-PN). The UBT-PN were distributed in both TG and ARG. The majority of them were found in the right ganglia, mostly in TG. Immunohistochemistry disclosed that the vast majority of UBT-PN were noradrenergic (TH- and/or DBH-positive). Many noradrenergic neurons contained also immunoreactivity to NPY, SOM or GAL. Most of the UBT-PN were supplied with VAChT-, or NOS- IR (immunoreactive) varicose nerve fibres. This study has revealed a relatively large population of differently coded prevertebral neurons projecting to the porcine urinary bladder. As judged from their neurochemical organization these nerve cells constitute an important element of the complex neuro-endocrine system involved in the regulation of the porcine urogenital organ function.

Structure of the human galanin receptor 2 bound to galanin and Gq reveals the basis of ligand specificity and how binding affects the G-protein interface

Galanin is a neuropeptide expressed in the central and peripheral nervous systems, where it regulates various processes including neuroendocrine release, cognition, and nerve regeneration. Three G-protein coupled receptors (GPCRs) for galanin have been discovered, which is the focus of efforts to treat diseases including Alzheimer’s disease, anxiety, and addiction. To understand the basis of the ligand preferences of the receptors and to assist structure-based drug design, we used cryo-electron microscopy (cryo-EM) to solve the molecular structure of GALR2 bound to galanin and a cognate heterotrimeric G-protein, providing a molecular view of the neuropeptide binding site. Mutant proteins were assayed to help reveal the basis of ligand specificity, and structural comparison between the activated GALR2 and inactive hβ2AR was used to relate galanin binding to the movements of transmembrane (TM) helices and the G-protein interface.

Spexin modulates molecular thermogenic profile of adipose tissue and thermoregulatory behaviors in female C57BL/6 mice

Thermoregulation is the physiological process by which an animal regulates body temperature in response to its environment. It is known that galanin, a neuropeptide widely distributed throughout the central nervous system and secreted by the gut, plays a role in thermoregulatory behaviors and metabolism. We tested the ability of the novel neuropeptide spexin, which shares sequence homology to galanin, to regulate these functions in female mice. Supraphysiological levels of spexin in C57BL/6 mice did not lead to weight loss after 50 days of treatment. Behavioral analysis of long-term spexin treatment showed it decreased anxiety and increased thermoregulatory nest building, which was not observed when mice were housed at thermoneutral temperatures. Treatment also disrupted the thermogenic profile of brown and white adipose tissue, decreasing mRNA expression of Ucp1 in BAT and immunodetection of β3-adrenergic receptors in gWAT. Our results reveal novel functions for spexin as a modulator of thermoregulatory behaviors and adipose tissue metabolism.

Hypothalamic Galanin-producing neurons regulate stress in zebrafish through a peptidergic, self-inhibitory loop

Animals possess neuronal circuits inducing stress to avoid or cope with threats present in their surroundings, for instance, by promoting behaviors, such as avoidance and escape. However, mechanisms must exist to tightly control responses to stressors, since overactivation of stress circuits is deleterious for the wellbeing of an organism. The underlying neuronal dynamics responsible for controlling behavioral responses to stress have remained unclear. Here, we describe a neuronal circuit in the hypothalamus of zebrafish larvae that inhibits stress-related behaviors and prevents excessive activation of the neuroendocrine pathway hypothalamic-pituitary-interrenal axis. Central components of this circuit are neurons secreting the neuropeptide Galanin, as ablation of these neurons led to abnormally high levels of stress. Surprisingly, we found that Galanin has a self-inhibitory action on Galanin-producing neurons. Our results suggest that hypothalamic Galanin-producing neurons play an important role in fine-tuning stress responses by preventing potentially harmful overactivation of stress-regulating circuits.

Galanin family peptides: Molecular structure, expression and roles in the neuroendocrine axis and in the spinal cord

Galanin is a neurohormone as well as a neurotransmitter and plays versatile physiological roles for the neuroendocrine axis, such as regulating food intake, insulin level and somatostatin release. It is expressed in the central nervous system, including hypothalamus, pituitary, and the spinal cord, and colocalises with other neuronal peptides within neurons. Structural analyses reveal that the human galanin precursor is 104 amino acid (aa) residues in length, consisting of a mature galanin peptide (aa 33-62), and galanin message-associated peptide (GMAP; aa 63-104) at the C-terminus. GMAP appears to exhibit distinctive biological effects on anti-fungal activity and the spinal flexor reflex. Galanin-like peptide (GALP) has a similar structure to galanin and acts as a hypothalamic neuropeptide to mediate metabolism and reproduction, food intake, and body weight. Alarin, a differentially spliced variant of GALP, is specifically involved in vasoactive effect in the skin and ganglionic differentiation in neuroblastic tumors. Dysregulation of galanin, GALP and alarin has been implicated in various neuroendocrine conditions such as nociception, Alzheimer's disease, seizures, eating disorders, alcoholism, diabetes, and spinal cord conditions. Further delineation of the common and distinctive effects and mechanisms of various types of galanin family proteins could facilitate the design of therapeutic approaches for neuroendocrine diseases and spinal cord injury.

Spexin and Galanin in Metabolic Functions and Social Behaviors With a Focus on Non-Mammalian Vertebrates

Spexin (SPX) and galanin (GAL) are two neuropeptides that are phylogenetically related and have descended from a common ancestral gene. Considerable attention has been given to these two multifunctional neuropeptides because they share GAL receptors 1,2, and 3. Since GAL and SPX-synthesizing neurons have been detected in several brain areas, therefore, it can be speculated that SPX and GAL are involved in various neurophysiological functions. Several studies have shown the functions of these two neuropeptides in energy regulation, reproduction, and response to stress. SPX acts as a satiety factor to suppress food intake, while GAL has the opposite effect as an orexigenic factor. There is evidence that SPX acts as an inhibitor of reproductive functions by suppressing gonadotropin release, while GAL modulates the activity of gonadotropin-releasing hormone (GnRH) neurons in the brain and gonadotropic cells in the pituitary. SPX and GAL are responsive to stress. Furthermore, SPX can act as an anxiolytic factor, while GAL exerts anti-depressant and pro-depressive effects depending on the receptor it binds. This review describes evidence supporting the central roles of SPX and GAL neuropeptides in energy balance, reproduction, stress, and social behaviors, with a particular focus on non-mammalian vertebrate systems.

The evolving roles of alarin in physiological and disease conditions, and its future potential clinical implications

Alarin is a member of the galanin family of neuropeptides that is widely expressed in the central nervous system and peripheral tissues in humans and rodents. It was initially isolated fifteen years ago in ganglionic cells of human neuroblastoma. Subsequently, it was demonstrated to be broadly distributed in the blood vessels, skin, eyes, peripheral and central nervous systems, thymus, gastrointestinal tract, and endocrine organs of different species. Alarin is a 25 amino acid neuropeptide derived from the alternative splicing of the GALP gene, missing exon 3. It is found to be involved in several physiological functions that include feeding behavior, energy homeostasis, glucose homeostasis, body temperature, and reproduction. It has also vasoactive, anti-inflammatory, anti-edema, and antimicrobial activities. However, the physiological effects of alarin have not been fully elucidated and the receptors that mediate these effects are not currently known. Unearthing the novel biological effects of alarin and its unidentified receptors will therefore be a task in future biomedical research. In addition, alarin is involved in various disease conditions, such as metabolic syndrome, obesity, insulin resistance, type 2 diabetes, diabetic retinopathy, hypertension, cardiac fibrosis, polycystic ovarian syndrome, and depression. Thus, alarin may serve as a promising tool for future pharmacological treatment and diagnosis. But further research is awaited to confirm whether alarin has a protective or pathological role in these diseases. This article provides a comprehensive review on the evolving implications of alarin in a variety of physiological and disease conditions, and its future perspectives.

Effect of NSAIDs Supplementation on the PACAP-, SP- and GAL-Immunoreactive Neurons in the Porcine Jejunum

Side effects associated with nonsteroidal anti-inflammatory drugs (NSAIDs) treatment are a serious limitation of their use in anti-inflammatory therapy. The negative effects of taking NSAIDs include abdominal pain, indigestion nausea as well as serious complications such as bleeding and perforation. The enteric nervous system is involved in regulation of gastrointestinal functions through the release of neurotransmitters. The present study was designed to determine, for the first time, the changes in pituitary adenylate cyclase-activating polypeptide (PACAP), substance P (SP) and galanin (GAL) expression in porcine jejunum after long-term treatment with aspirin, indomethacin and naproxen. The study was performed on 16 immature pigs. The animals were randomly divided into four experimental groups: control, aspirin, indomethacin and naproxen. Control animals were given empty gelatin capsules, while animals in the test groups received selected NSAIDs for 28 days. Next, animals from each group were euthanized. Frozen sections were prepared from collected jejunum and subjected to double immunofluorescence staining. NSAIDs supplementation caused a significant increase in the population of PACAP-, SP- and GAL-containing enteric neurons in the porcine jejunum. Our results suggest the participation of the selected neurotransmitters in regulatory processes of the gastrointestinal function and may indicate the direct toxic effect of NSAIDs on the ENS neurons.

The Role of Galanin in Cerebellar Granule Cell Migration in the Early Postnatal Mouse during Normal Development and after Injury

Galanin, one of the most inducible neuropeptides, is widely present in developing brains, and its expression is altered by pathologic events (e.g., epilepsy, ischemia, and axotomy). The roles of galanin in brain development under both normal and pathologic conditions have been hypothesized, but the question of how galanin is involved in fetal and early postnatal brain development remains largely unanswered. In this study, using granule cell migration in the cerebellum of early postnatal mice (both sexes) as a model system, we examined the role of galanin in neuronal cell migration during normal development and after brain injury. Here we show that, during normal development, endogenous galanin participates in accelerating granule cell migration via altering the Ca2+ and cAMP signaling pathways. Upon brain injury induced by the application of cold insults, galanin levels decrease at the lesion sites, but increase in the surroundings of lesion sites. Granule cells exhibit the following corresponding changes in migration: (1) slowing down migration at the lesion sites; and (2) accelerating migration in the surroundings of lesion sites. Experimental manipulations of galanin signaling reduce the lesion site-specific changes in granule cell migration, indicating that galanin plays a role in such deficits in neuronal cell migration. The present study suggests that manipulating galanin signaling may be a potential therapeutic target for acutely injured brains during development.SIGNIFICANCE STATEMENT Deficits in neuronal cell migration caused by brain injury result in abnormal development of cortical layers, but the underlying mechanisms remain to be determined. Here, we report that on brain injury, endogenous levels of galanin, a neuropeptide, are altered in a lesion site-specific manner, decreasing at the lesion sites but increasing in the surroundings of lesion sites. The changes in galanin levels positively correlate with the migration rate of immature neurons. Manipulations of galanin signaling ameliorate the effects of injury on neuronal migration and cortical layer development. These results shed a light on galanin as a potential therapeutic target for acutely injured brains during development.

The Role of Galanin during Bacterial Infection in Larval Zebrafish

Galanin is a peptide that is conserved among different species and plays various roles in an organism, although its entire role is not completely understood. For many years, galanin has been linked mainly with the neurotransmission in the nervous system; however, recent reports underline its role in immunity. Zebrafish (Danio rerio) is an intensively developing animal model to study infectious diseases. In this study, we used larval zebrafish to determine the role of galanin in bacterial infection. We showed that knockout of galanin in zebrafish leads to a higher bacterial burden and mortality during Mycobacterium marinum and Staphylococcus aureus infection, whereas administration of a galanin analogue, NAX 5055, improves the ability of fish to control the infection caused by both pathogens. Moreover, the transcriptomics data revealed that a lower number of genes were regulated in response to mycobacterial infection in gal−/− mutants compared with their gal+/+ wild-type counterparts. We also found that galanin deficiency led to significant changes in immune-related pathways, mostly connected with cytokine and chemokine functions. The results show that galanin acts not only as a neurotransmitter but is also involved in immune response to bacterial infections, demonstrating the complexity of the neuroendocrine system and its possible connection with immunity.

Neuropeptides of the human magnocellular hypothalamus

Hypothalamic magnocellular nuclei with their large secretory neurons are unique and phylogenetically conserved brain structures involved in the continual regulation of important homeostatic and autonomous functions in vertebrate species. Both canonical and newly identified neuropeptides have a broad spectrum of physiological activity at the hypothalamic neuronal circuit level located within the supraoptic (SON) and paraventricular (PVN) nuclei. Magnocellular neurons express a variety of receptors for neuropeptides and neurotransmitters and therefore receive numerous excitatory and inhibitory inputs from important subcortical neural areas such as limbic and brainstem populations. These unique cells are also densely innervated by axons from other hypothalamic nuclei. The vast majority of neurochemical maps pertain to animal models, mainly the rodent hypothalamus, however accumulating preliminary anatomical structural studies have revealed the presence and distribution of several neuropeptides in the human magnocellular nuclei. This review presents a novel and comprehensive evidence based evaluation of neuropeptide expression in the human SON and PVN. Collectively this review aims to cast a new, medically oriented light on hypothalamic neuroanatomy and contribute to a better understanding of the mechanisms responsible for neuropeptide-related physiology and the nature of possible neuroendocrinal interactions between local regulatory pathways.

Ferulic acid, a phytochemical with transient anorexigenic effects in birds

Ferulic acid (FA) is a phenolic acid found within the plant cell wall that has physiological benefits as an antioxidant. Although metabolic benefits of FA supplementation are described, lacking are reports of effects on appetite regulation. Thus, our objective was to determine if FA affects food or water intake, using chicks as a model. At 4 days post-hatch, broiler chicks were intraperitoneally injected with 0 (vehicle), 12.5, 25, or 50 mg/kg of FA. Chicks treated with 50 mg/kg of FA consumed 70% less food than controls at 30 min post-injection, and the effect dissipated thereafter. Water intake was not affected at any time. In a behavior analysis, FA-treated chicks defecated fewer times than vehicle-injected chicks, while other behaviors were not affected. There was an increase in c-Fos immunoreactivity within the hypothalamic arcuate nucleus (ARC) of FA-treated chicks, and no differences were detected in other nuclei. mRNA abundance was measured in the whole hypothalamus and the ARC. There was decreased hypothalamic galanin, ghrelin, melanocortin receptor 3, and pro-opiomelanocortin (POMC) mRNA in FA-treated chicks. Within the ARC, there was an increase in c-Fos mRNA and a decrease in POMC mRNA in response to FA. It is likely that the mechanism responsible for mediating FA's transient effects on food intake originates within the ARC, possibly involving POMC. A greater understanding of the short-term, mild appetite-suppressive effects of FA may have applications to treating eating disorders and modulating food intake in animal models of obesity.

Galanin and neuropeptide Y interactions elicit antidepressant activity linked to neuronal precursor cells of the dentate gyrus in the ventral hippocampus

A need for new antidepressants is necessary since traditional antidepressants have several flaws. Neuropeptide Y(NPY) Y1 receptor (NPYY1R) and galanin (GAL) receptor 2 (GALR2) interact in several regions of the limbic system, including the hippocampus. The current study assesses the antidepressant effects induced by GALR2 and NPYY1R coactivation, together with the evaluation of cell proliferation through 5-Bromo-2'-deoxyuridine expression within the dentate gyrus of the ventral hippocampus (vDG). We employed in situ proximity ligation assay to manifest GALR2/NPYY1R heteroreceptor complexes. Additionally, the expression pattern of GALR2 and the activation of the extracellular-regulated kinases (ERK) pathway after GALR2 and NPYY1R costimulation in cell cultures were examined. GALR2 and NPYY1R coactivation resulted in sustained antidepressant behaviors in the FST after 24 h, linked to increased cell proliferation in the vDG. Moreover, an increased density of GALR2/NPYY1R heteroreceptor complexes was observed in vDG, on doublecortin-expressing neuroblasts. Recruitment of the GALR2 expression to the plasma membrane was observed upon the coactivation of GALR2 and NPYY1R in cell cultures, presumably associated to the enhanced effects on the activation of ERK pathway. GALR2 may promote the GALR2/NPYY1R heteroreceptor complexes formation in the ventral hippocampus. It may induce a transformation of cell proliferation toward a neuronal lineage by enhancement of ERK pathway. Thus, it may give the mechanism for the antidepressant behavior observed. These results may provide the basis for the development of heterobivalent agonist pharmacophores, targeting GALR2/NPYY1R heteromers, especially in the neuronal precursor cells of the dentate gyrus in the ventral hippocampus for the novel treatment of depression.

The intermediate nucleus in humans: Cytoarchitecture, chemoarchitecture, and relation to sleep, sex, and Alzheimer disease

The intermediate nucleus of Brockhaus (INH), also known as the interstitial nucleus of the anterior hypothalamus-1 of Allen and Gorski (INAH-1), the sexually dimorphic nucleus of Swaab and colleagues (SDN), and the ventrolateral preoptic nucleus of Saper and colleagues (VLPO), is a cluster of largely galanin-expressing neurons in the lateral preoptic area, at the level of the crossing of the anterior commissure and dorsal to the supraoptic nucleus. The number of Nissl-stained neurons in the INH has been reported to be larger in men than women and to decrease with aging, although these findings have been controversial, in part because of differences in patient populations and methods used to assess the nucleus. However, recent studies have confirmed that the number of galanin-immunoreactive INH neurons is larger in men than women and decreases with age and have reported further loss with Alzheimer disease. The galanin-immunoreactive VLPO neurons have been thought to drive sleep behavior in many species, and their numbers in older humans correlate with the amount of consolidated sleep they experience. Sleep differences between men and women, during aging, and with Alzheimer disease may also depend upon the integrity of this nucleus.

Effects of trigeminal nerve injury on the expression of galanin and its receptors in the rat trigeminal ganglion

In the spinal nervous system, the expression of galanin (GAL) and galanin receptors (GALRs) that play important roles in the transmission and modulation of nociceptive information can be affected by nerve injury. However, in the trigeminal nervous system, the effects of trigeminal nerve injury on the expression of GAL are controversy in the previous studies. Besides, little is known about the effects of trigeminal nerve injury on the expression of GALRs. In the present study, the effects of trigeminal nerve injury on the expression of GAL and GALRs in the rat trigeminal ganglion (TG) were investigated by using quantitative real-time reverse transcription-polymerase chain reaction and immunohistochemistry. To identify the nerve-injured and nerve-uninjured TG neurons, activating transcription factor 3 (ATF3, the nerve-injured neuron marker) was stained by immunofluorescence. The levels of GAL mRNA in the rostral half and caudal half of the TG dramatically increased after transection of infraorbital nerve (ION) and inferior alveolar nerve (IAN), respectively. Immunohistochemical labeling of GAL and ATF3 revealed that GAL level was elevated in both injured and adjacent uninjured small and medium-sized TG neurons after ION/IAN transection. In addition, the levels of GAL₂R-like immunoreactivity were reduced in both injured and adjacent uninjured TG neurons after ION/IAN transection, while levels of GAL₁R and GAL₃R-like immunoreactivity remained unchanged. Furthermore, the number of small to medium-sized TG neurons co-expressing GAL- and GAL₁R/GAL₂R/GAL₃R-like immunoreactivity was significantly increased after ION/IAN transection. In line with previous studies in other spinal neuron systems, these results suggest that GAL and GALRs play functional roles in orofacial neuropathic pain and trigeminal nerve regeneration after trigeminal nerve injury.

Inferior vagal ganglion galaninergic response to gastric ulcers

Galanin is a neuropeptide widely expressed in central and peripheral nerves and is known to be engaged in neuronal responses to pathological changes. Stomach ulcerations are one of the most common gastrointestinal disorders. Impaired stomach function in peptic ulcer disease suggests changes in autonomic nerve reflexes controlled by the inferior vagal ganglion, resulting in stomach dysfunction. In this paper, changes in the galaninergic response of inferior vagal neurons to gastric ulceration in a pig model of the disease were analyzed based on the authors' previous studies. The study was performed on 24 animals (12 control and 12 experimental). Gastric ulcers were induced by submucosal injections of 40% acetic acid solution into stomach submucosa and bilateral inferior vagal ganglia were collected one week afterwards. The number of galanin-immunoreactive perikarya in each ganglion was counted to determine fold-changes between both groups of animals and Q-PCR was applied to verify the changes in relative expression level of mRNA encoding both galanin and its receptor subtypes: GalR1, GalR2, GalR3. The results revealed a 2.72-fold increase in the number of galanin-immunoreactive perikarya compared with the controls. Q-PCR revealed that all studied genes were expressed in examined ganglia in both groups of animals. Statistical analysis revealed a 4.63-fold increase in galanin and a 1.45-fold increase in GalR3 mRNA as compared with the controls. No differences were observed between the groups for GalR1 or GalR2. The current study confirmed changes in the galaninergic inferior vagal ganglion response to stomach ulcerations and demonstrated, for the first time, the expression of mRNA encoding all galanin receptor subtypes in the porcine inferior vagal ganglia.

Galanin neuron activation in feeding, parental care, and infanticide in a mouthbrooding African cichlid fish

Galanin is a conserved neuropeptide involved in parental care and feeding. While galanin is known to mediate parental care and infanticide in rodents, its role in parental care and feeding behaviors in other taxa, particularly fishes, remains poorly understood. Mouthbrooding is an extreme form of parental care common in fishes in which caregivers carry offspring in their buccal cavity for the duration of development, resulting in obligatory starvation. In the cichlid fish Astatotilapia burtoni, females brood their young for ~2 wks and perform maternal care after release by collecting them into their mouth when threatened. However, females will cannibalize their brood after ~5 days. To examine the role of gal in feeding and maternal care, we collected mouthbrooding, fed, and starved females, as well as those displaying post-release maternal care and infanticide behaviors. Activation of gal neurons in the preoptic area (POA) was associated with parental care, providing the first link between gal and offspring-promoting behaviors in fishes. In contrast, activation of gal neurons in the lateral tuberal nucleus (NLT), the Arcuate homolog, was associated with feeding and infanticide. Overall, these data suggest gal is functionally conserved across vertebrate taxa with POA gal neurons promoting maternal care and Arc/NLT gal neurons promoting feeding.

RNA-seq analysis of galaninergic neurons from ventrolateral preoptic nucleus identifies expression changes between sleep and wake

BACKGROUND

Previous studies show that galanin neurons in ventrolateral preoptic nucleus (VLPO-Gal) are essential for sleep regulation. Here, we explored the transcriptional regulation of the VLPO-Gal neurons in sleep by comparing their transcriptional responses between sleeping mice and those kept awake, sacrificed at the same diurnal time.

RESULTS

RNA-sequencing (RNA-seq) analysis was performed on eGFP(+) galanin neurons isolated using laser captured microdissection (LCM) from VLPO. Expression of Gal was assessed in our LCM eGFP(+) neurons via real time qPCR and showed marked enrichment when compared to LCM eGFP(-) cells and to bulk VLPO samples. Gene set enrichment analysis utilizing data from a recent single-cell RNA-seq study of the preoptic area demonstrated that our VLPO-Gal samples were highly enriched with galanin-expressing inhibitory neurons, but not galanin-expressing excitatory neurons. A total of 263 genes were differentially expressed between sleep and wake in VLPO-Gal neurons. When comparing differentially expressed genes in VLPO-Gal neurons to differentially expressed genes in a wake-active neuronal region (the medial prefrontal cortex), evidence indicates that both systemic and cell-specific mechanisms contribute to the transcriptional regulation in VLPO-Gal neurons. In both wake-active and sleep-active neurons, ER stress pathways are activated by wake and cold-inducible RNA-binding proteins are activated by sleep. In contrast, expression of DNA repair genes is increased in VLPO-Gal during wakefulness, but increased in wake-active cells during sleep.

CONCLUSION

Our study identified transcriptomic responses of the galanin neurons in the ventrolateral preoptic nucleus during sleep and sleep deprivation. Data indicate that VLPO contains mainly sleep-active inhibitory galaninergic neurons. The VLPO galanin neurons show responses to sleep and wake similar to wake-active regions, indicating these responses, such as ER stress and cold-inducible RNA-binding proteins, are systemic affecting all neuronal populations. Region-specific differences in sleep/wake responses were also identified, in particular DNA repair. Our study expands knowledge about the transcriptional response of a distinct group of neurons essential for sleep.

Coordinated Targeting of Galanin Receptors on Cholangiocytes and Hepatic Stellate Cells Ameliorates Liver Fibrosis in Multidrug Resistance Protein 2 Knockout Mice

Galanin (Gal) is a peptide with a role in neuroendocrine regulation of the liver. In this study, we assessed the role of Gal and its receptors, Gal receptor 1 (GalR1) and Gal receptor 2 (GalR2), in cholangiocyte proliferation and liver fibrosis in multidrug resistance protein 2 knockout (Mdr2KO) mice as a model of chronic hepatic cholestasis. The distribution of Gal, GalR1, and GalR2 in specific liver cell types was assessed by laser-capture microdissection and confocal microscopy. Galanin immunoreactivity was detected in cholangiocytes, hepatic stellate cells (HSCs), and hepatocytes. Cholangiocytes expressed GalR1, whereas HSCs and hepatocytes expressed GalR2. Strategies were used to either stimulate or block GalR1 and GalR2 in FVB/N (wild-type) and Mdr2KO mice and measure biliary hyperplasia and hepatic fibrosis by quantitative PCR and immunostaining of specific markers. Galanin treatment increased cholangiocyte proliferation and fibrogenesis in both FVB/N and Mdr2KO mice. Suppression of GalR1, GalR2, or both receptors in Mdr2KO mice resulted in reduced bile duct mass and hepatic fibrosis. In vitro knockdown of GalR1 in cholangiocytes reduced α-smooth muscle actin expression in LX-2 cells treated with cholangiocyte-conditioned media. A GalR2 antagonist inhibited HSC activation when Gal was administered directly to LX-2 cells, but not via cholangiocyte-conditioned media. These data demonstrate that Gal contributes not only to cholangiocyte proliferation but also to liver fibrogenesis via the coordinate activation of GalR1 in cholangiocytes and GalR2 in HSCs.

Galanin System in Human Glioma and Pituitary Adenoma

Expression of neuropeptides and their corresponding receptors has been demonstrated in different cancer types, where they can play a role in tumor cell growth, invasion, and migration. Human galanin (GAL) is a 30-amino-acid regulatory neuropeptide which acts through three G protein-coupled receptors, GAL₁-R, GAL₂-R, and GAL₃-R that differ in their signal transduction pathways. GAL and galanin receptors (GALRs) are expressed by different tumors, and direct involvement of GAL in tumorigenesis has been shown. Despite its strong expression in the central nervous system (CNS), the role of GAL in CNS tumors has not been extensively studied. To date, GAL peptide expression, GAL receptor binding and mRNA expression have been reported in glioma, meningioma, and pituitary adenoma. However, data on the cellular distribution of GALRs are sparse. The aim of the present study was to examine the expression of GAL and GALRs in different brain tumors by immunohistochemistry. Anterior pituitary gland (n = 7), pituitary adenoma (n = 9) and glioma of different WHO grades I-IV (n = 55) were analyzed for the expression of GAL and the three GALRs with antibodies recently extensively validated for specificity. While high focal GAL immunoreactivity was detected in up to 40% of cells in the anterior pituitary gland samples, only one pituitary adenoma showed focal GAL expression, at a low level. In the anterior pituitary, GAL₁-R and GAL₃-R protein expression was observed in up to 15% of cells, whereas receptor expression was not detected in pituitary adenoma. In glioma, diffuse and focal GAL staining was noticed in the majority of cases. GAL₁-R was observed in eight out of nine glioma subtypes. GAL₂-R immunoreactivity was not detected in glioma and pituitary adenoma, while GAL₃-R expression was significantly associated to high-grade glioma (WHO grade IV). Most interestingly, expression of GAL and GALRs was observed in tumor-infiltrating immune cells, including neutrophils and glioma-associated macrophages/microglia. The presence of GALRs on tumor-associated immune cells, especially macrophages, indicates that GAL signaling contributes to homeostasis of the tumor microenvironment. Thus, our data indicate that GAL signaling in tumor-supportive myeloid cells could be a novel therapeutic target.

The impact of low and high doses of acrylamide on the intramural neurons of the porcine ileum

The present study was designed to assess the influence of acrylamide supplementation, in tolerable daily intake (TDI) dose and a dose ten times higher than TDI, on the neurochemical phenotype of the ENS neurons and synthesis of proinflammatory cytokines in the wall of the porcine ileum. The study was performed on 15 juvenile female Danish Landrace pigs, divided into three groups: C group- animals receiving empty gelatine capsules, LD group- animals receiving capsules with the TDI dose (0.5 μg/kg b.w./day) of acrylamide and HD group- animals receiving acrylamide in a dose ten times higher than the TDI (5 μg/kg b.w./day) in a morning meal for 28 days. It was established that supplementation of acrylamide led to an increase in substance P (SP)-, calcitonin gene-related peptide (CGRP)-, galanin (GAL)- and vesicular acetylcholine transporter (VAChT)-like immunoreactive (LI) neurons as well as a decrease in neuronal nitric oxide synthase (nNOS) -like immunoreactivity in all types of ileum intramural plexuses. Moreover, using ELISA method, an increase in the level of proinflammatory cytokines (IL-1β, IL-6 and TNF- α) was noted in the ileum wall. The results suggest that SP, CGRP, GAL, nNOS and VACHT participate in the regulation of inflammatory conditions induced by acrylamide supplementation.

Alterations in Galanin-Like Immunoreactivity in the Enteric Nervous System of the Porcine Stomach Following Acrylamide Supplementation

In recent years, a significant increase in the consumption of products containing large amounts of acrylamide (e.g., chips, fries, coffee), especially among young people has been noted. The present study was created to establish the impact of acrylamide supplementation, in tolerable daily intake (TDI) dose and a dose ten times higher than TDI, on the population of galanin-like immunoreactive (GAL-LI) stomach neurons in pigs. Additionally, in the present study, the possible functional co-operation of GAL with other neuroactive substances and their role in acrylamide intoxication was investigated. Using double-labelling immunohistochemistry, alterations in the expression of GAL were examined in the porcine stomach enteric neurons after low and high doses of acrylamide supplementation. Generally, upregulation in GAL-LI immunoreactivity in both myenteric and submucous plexuses was noted in all stomach fragments studied. Additionally, the proportion of GAL-expressing cell bodies simultaneously immunoreactive to vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS) and cocaine- and amphetamine- regulated transcript peptide (CART) also increased. The results suggest neurotrophic or/and neuroprotective properties of GAL and possible co-operation of GAL with VIP, nNOS, CART in the recovery processes in the stomach enteric nervous system (ENS) neurons following acrylamide intoxication.

[Nutritional status alters the mRNA expressions of galanin and its receptors in taste buds of rats]

The nutritional and metabolic status alters the peripheral taste perception and food intake by participating in the modulation of taste information integration. The taste receptors and neuropeptides in the taste buds are the important targets of this modulation process. To explore the effects of nutritional status on the expressions of galanin and its receptors in the taste buds, we compared the mRNA levels of galanin and its specific receptor GalR2 in the taste buds among the high-fat diet induced obese rats (HF), chronically restricted diet rats (CR) and control rats. The high-fat diet, half of chow diet, and normal chow diet were given to HF, CR and control groups for 6 weeks, respectively. The body weight and some metabolic indexes, including blood glucose, triglyceride and cholesterol levels were detected. The mRNA expressions of galanin and its receptors in taste buds were determined using real-time PCR. Results showed that compared with control rats, the body weights, levels of blood glucose and triglyceride were significantly elevated in HF rats; while the mRNA expressions of galanin and GalR2 were dramatically decreased. However, galanin mRNA expression in CR rats was increased to 2.3 times of that in control group. Considering the results obtained from our previous studies, we conclude that the behavioral changes in tasting choice of HF rats may be related to the expressions of galanin and GalR2 in the taste buds. The changes of galanin and GalR2 in taste buds are involved in the peripheral mechanism of nutritional status regulating taste perception and feeding behavior in rats.

Hyperglycaemia-Induced Downregulation in Expression of nNOS Intramural Neurons of the Small Intestine in the Pig

Diabetic autonomic peripheral neuropathy (PN) involves a broad spectrum of organs. One of them is the gastrointestinal (GI) tract. The molecular mechanisms underlying the pathogenesis of digestive complications are not yet fully understood. Digestion is controlled by the central nervous system (CNS) and the enteric nervous system (ENS) within the wall of the GI tract. Enteric neurons exert regulatory effects due to the many biologically active substances secreted and released by enteric nervous system (ENS) structures. These include nitric oxide (NO), produced by the neural nitric oxide synthase enzyme (nNOS). It is a very important inhibitory factor, necessary for smooth muscle relaxation. Moreover, it was noted that nitrergic innervation can undergo adaptive changes during pathological processes. Additionally, nitrergic neurons function may be regulated through the synthesis of other active neuropeptides. Therefore, in the present study, using the immunofluorescence technique, we first examined the influence of hyperglycemia on the NOS- containing neurons in the porcine small intestine and secondly the co-localization of nNOS with vasoactive intestinal polypeptide (VIP), galanin (GAL) and substance P (SP) in all plexuses studied. Following chronic hyperglycaemia, we observed a reduction in the number of the NOS-positive neurons in all intestinal segments studied, as well as an increased in investigated substances in nNOS positive neurons. This observation confirmed that diabetic hyperglycaemia can cause changes in the neurochemical characteristics of enteric neurons, which can lead to numerous disturbances in gastrointestinal tract functions. Moreover, can be the basis of an elaboration of these peptides analogues utilized as therapeutic agents in the treatment of GI complications.

Biomarker Discovery for Immunotherapy of Pituitary Adenomas: Enhanced Robustness and Prediction Ability by Modern Computational Tools

Pituitary adenoma (PA) is prevalent in the general population. Due to its severe complications and aggressive infiltration into the surrounding brain structure, the effective management of PA is required. Till now, no drug has been approved for treating non-functional PA, and the removal of cancerous cells from the pituitary is still under experimental investigation. Due to its superior specificity and safety profile, immunotherapy stands as one of the most promising strategies for dealing with PA refractory to the standard treatment, and various studies have been carried out to discover immune-related gene markers as target candidates. However, the lists of gene markers identified among different studies are reported to be highly inconsistent because of the greatly limited number of samples analyzed in each study. It is thus essential to substantially enlarge the sample size and comprehensively assess the robustness of the identified immune-related gene markers. Herein, a novel strategy of direct data integration (DDI) was proposed to combine available PA microarray datasets, which significantly enlarged the sample size. First, the robustness of the gene markers identified by DDI strategy was found to be substantially enhanced compared with that of previous studies. Then, the DDI of all reported PA-related microarray datasets were conducted to achieve a comprehensive identification of PA gene markers, and 66 immune-related genes were discovered as target candidates for PA immunotherapy. Finally, based on the analysis of human protein⁻protein interaction network, some promising target candidates (GAL, LMO4, STAT3, PD-L1, TGFB and TGFBR3) were proposed for PA immunotherapy. The strategy proposed together with the immune-related markers identified in this study provided a useful guidance for the development of novel immunotherapy for PA.

Thalamic integration of social stimuli regulating parental behavior and the oxytocin system

Critically important components of the maternal neural circuit in the preoptic area robustly activated by suckling were recently identified. In turn, suckling also contributes to hormonal adaptations to motherhood, which includes oxytocin release and consequent milk ejection. Other reproductive or social stimuli can also trigger the release of oxytocin centrally, influencing parental or social behaviors. However, the neuronal pathways that transfer suckling and other somatosensory stimuli to the preoptic area and oxytocin neurons have been poorly characterized. Recently, a relay center of suckling was determined and characterized in the posterior intralaminar complex of the thalamus (PIL). Its neurons containing tuberoinfundibular peptide 39 project to both the preoptic area and oxytocin neurons in the hypothalamus. The present review argues that the PIL is a major relay nucleus conveying somatosensory information supporting maternal behavior and oxytocin release in mothers, and may be involved more generally in social cue evoked oxytocin release, too.

Spexin as a neuroendocrine signal with emerging functions

Spexin (SPX), a novel peptide coevolved with the galanin/kisspeptin family, was first identified by bioinformatics prior to its protein purification/functional studies. Its mature peptide is highly conserved among different vertebrate classes. Based on the studies in mammals and fish models, SPX was found to be widely distributed at tissue level, secreted into systemic circulation, identified at notable levels in central nervous system and peripheral tissues, and has been confirmed/implicated in multiple functions in different tissues/organs, suggesting that SPX may serve as a neuroe​ndocrine signal with pleotropic functions. In this article, different isoforms of SPX and their binding with their cognate receptors GalR2 and GalR3, the biological functions of SPX reported in mammals including GI tract movement, energy balance and weight loss, fatty acid uptake, glucose homeostasis, nociception and cardiovascular/renal functions, as well as the recent findings in fish models regarding the role of SPX in reproduction and feeding control will be reviewed with interesting questions for future investigations.

Neuropeptides and lymphocyte populations in the porcine ileum and ileocecal lymph nodes during postnatal life

The maturation-related changes in the concentrations of galanin (Gal), vasoactive intestinal polypeptide (VIP), substance P (SP) and somatostatin (Som), as well as in subpopulations of lymphocytes expressing antigens CD2 (lymphocytes T), CD4 (T helper), CD8 (T cytotoxic), CD21 (B lymphocytes), CD5-/CD8+ (NK cells) and TCRgamma/delta (gut mucosal/intraepitelial cells) were studied in the ileal Peyer's patches and ileo-cecal lymph nodes in female pigs aged 3 days, 2 weeks, 4 weeks and 4 months. As regards neuropeptide concentrations statistically significant changes in the ileum and lymph nodes were found only in case of Gal and VIP. The concentrations of neuropeptides were significantly higher only in new-born animals. As regards the changes in subpopulations of lymphocytes, statistically significant changes were noticed only in 4-months old animals and were dealing only with CD2+ and TCRgamma/delta cells in the ileum as well as CD4+, CD8+, CD21+ and TCRgamma/delta in lymph nodes. The highest number of CD8+, CD21+ and TCRgamma/delta lymphocytes occurred in 4-months old animals.

Neuronal hypothalamic regulation of body metabolism and bone density is galanin dependent

In the brain, the ventral hypothalamus (VHT) regulates energy and bone metabolism. Whether this regulation uses the same or different neuronal circuits is unknown. Alteration of AP1 signaling in the VHT increases energy expenditure, glucose utilization, and bone density, yet the specific neurons responsible for each or all of these phenotypes are not identified. Using neuron-specific, genetically targeted AP1 alterations as a tool in adult mice, we found that agouti-related peptide-expressing (AgRP-expressing) or proopiomelanocortin-expressing (POMC-expressing) neurons, predominantly present in the arcuate nucleus (ARC) within the VHT, stimulate whole-body energy expenditure, glucose utilization, and bone formation and density, although their effects on bone resorption differed. In contrast, AP1 alterations in steroidogenic factor 1-expressing (SF1-expressing) neurons, present in the ventromedial hypothalamus (VMH), increase energy but decrease bone density, suggesting that these effects are independent. Altered AP1 signaling also increased the level of the neuromediator galanin in the hypothalamus. Global galanin deletion (VHT galanin silencing using shRNA) or pharmacological galanin receptor blockade counteracted the observed effects on energy and bone. Thus, AP1 antagonism reveals that AgRP- and POMC-expressing neurons can stimulate body metabolism and increase bone density, with galanin acting as a central downstream effector. The results obtained with SF1-expressing neurons, however, indicate that bone homeostasis is not always dictated by the global energy status, and vice versa.

The Influence of High and Low Doses of Bisphenol A (BPA) on the Enteric Nervous System of the Porcine Ileum

Bisphenol A, used in the production of plastic, is able to leach from containers into food and cause multidirectional adverse effects in living organisms, including neurodegeneration and metabolic disorders. Knowledge of the impact of BPA on enteric neurons is practically non-existent. The destination of this study was to investigate the influence of BPA at a specific dose (0.05 mg/kg body weight/day) and at a dose ten times higher (0.5 mg/kg body weight/day), given for 28 days, on the porcine ileum. The influence of BPA on enteric neuron immunoreactive to selected neuronal active substances, including substance P (SP), vasoactive intestinal polypeptide (VIP), galanin (GAL), vesicular acetylcholine transporter (VAChT—used here as a marker of cholinergic neurons), and cocaine- and amphetamine-regulated transcript peptide (CART), was studied by the double immunofluorescence method. Both doses of BPA affected the neurochemical characterization of the enteric neurons. The observed changes depended on the type of enteric plexus but were generally characterized by an increase in the number of cells immunoreactive to the particular substances. More visible fluctuations were observed after treatment with higher doses of BPA. The results confirm that even low doses of BPA may influence the neurochemical characterization of the enteric neurons and are not neutral for living organisms.

Involvement of galanin and galanin receptor 1 in nociceptive modulation in the central nucleus of amygdala in normal and neuropathic rats

The present study was performed to explore the role of galanin and galanin receptor 1 (GalR 1) in nociceptive modulation in the central nucleus of amygdala (CeA) in normal rats and rats with neuropathy, and the involvement of GalR 1 and PKC was also investigated. The hindpaw withdrawal latencies (HWLs) to thermal and mechanical stimulations were increased in a dose-dependent manner after intra-CeA injection of galanin in both normal rats and rats with neuropathy. The increased HWLs were significantly attenuated by intra-CeA injection of galanin receptor antagonist M40, indicating an involvement of galanin receptor in nociceptive modulation in CeA. Furthermore, intra-CeA administration of the GalR 1 agonist M 617 induced increases in HWLs in normal rats, suggesting that GalR 1 may be involved in galanin-induce antinociception in CeA. Additionally, intra-CeA injection of the PKC inhibitor inhibited galanin-induced antinociception, showing an involvement of PKC in galanin-induced antinociception in CeA of normal rats. Moreover, there was a significant increase in GalR1 content in CeA in rats with neuropathy than that in normal rats. These results illustrated that galanin induced antinociception in CeA in normal rats and rats with neuropathy, and there is an up-regulation of GalR1 expression in rats with neuropathy.

Changes in expression of inhibitory substances in the intramural neurons of the stomach following streptozotocin- induced diabetes in the pig

AIM

Influence of chronic hyperglycemia on chemical coding of enteric neurons in stomach using pig as a model for human diabetic complications.

METHODS

Ten pigs were divided into two groups: diabetic (D group, n = 5) and control (C group, n = 5). Pigs constituting the experimental group were given streptozotocin (150 mg/kg). Animals were euthanized six weeks after the induction of diabetes. The samples of stomach were collected from animals of both groups. The cryostat sections were processed for double immunofluorescence staining using primary antisera directed towards pan-neuronal marker (Hu C/D) proteins and/or neuronal isoform of nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP) and galanin (GAL).

RESULTS

In the control group in the myenteric ganglia (MG) of the corpus we have noted 22.28% ± 1.19% of nNOS positive neurons, while in diabetic group we have found 40.74% ± 2.22% of nNOS immunoreactive perikarya (increase by 82.85 %). In turn in the pylorus we have observed 15.91% ± 0.58% nNOS containing neurons in control animals and 35.38% ± 1.54% in the diabetes group (increase by 122.37%). In the MG of the antrum and submucosal ganglion (SG) in the corpus hyperglycemia did not cause statistically significant changes. With regard to VIP-positive cell bodies in the antrum MG in the control animals we have noted 18.38 ± 1.39% and 40.74% ± 1.77% in the experimental group (increase by 121.65%). While in the corpus we have observed 23.20% ± 0.23% in the control and 30.93% ± 0.86% in the diabetes group (increase by 33.31%). In turn in the pylorus VIP positive cells bodies constituted 23.64% ± 1.56% in the control group and 31.20% ± 1.10% in the experimental group (increase by 31.97%). In the submucosal ganglion in the corpus we have noted 43.61% ± 1.06% in the control animals and 37.00% ± 1.77% in the experimental group (decrease by 15.15%). Expression of GAL-positive perikarya showed statistically significant changes only in the MG of the antrum and pylorus. In the antrum GAL positive perykarya constituted 26.53% ± 1.52% in the control and 36.67% ± 1.02% in the experimental animals (increase by 38.22%). While in the pylorus GAL positive neurons in the control group constituted 16.32% ± 0.92% and 17.99% ± 0.38% in the experimental animals (increase by 10.23%).

CONCLUSION

Our results support the hypothesis that in the course of diabetes, long term episodes of high glucose serum level may influence the chemical phenotyping of enteric neurons.

Distribution of the neuro-regulatory peptide galanin in the human eye

Galanin (GAL) is a neuro-regulatory peptide involved in many physiological and pathophysiological processes. While data of GAL origin/distribution in the human eye are rather fragmentary and since recently the presence of GAL-receptors in the normal human eye has been reported, we here systematically search for sources of ocular GAL in the human eye. Human eyes (n=14) were prepared for single- and double-immunohistochemistry of GAL and neurofilaments (NF). Cross- and flat-mount sections were achieved; confocal laser-scanning microscopy was used for documentation. In the anterior eye, GAL-immunoreactivity (GAL-IR) was detected in basal layers of corneal epithelium, endothelium, and in nerve fibers and keratinocytes of the corneal stroma. In the conjunctiva, GAL-IR was seen throughout all epithelial cell layers. In the iris, sphincter and dilator muscle and endothelium of iris vessels displayed GAL-IR. It was also detected in stromal cells containing melanin granules, while these were absent in others. In the ciliary body, ciliary muscle and pigmented as well as non-pigmented ciliary epithelium displayed GAL-IR. In the retina, GAL-IR was detected in cells associated with the ganglion cell layer, and in endothelial cells of retinal blood vessels. In the choroid, nerve fibers of the choroidal stroma as well as fibers forming boutons and surrounding choroidal blood vessels displayed GAL-IR. Further, the majority of intrinsic choroidal neurons were GAL-positive, as revealed by co-localization-experiments with NF, while a minority displayed NF- or GAL-IR only. GAL-IR was also detected in choroidal melanocytes, as identified by the presence of intracellular melanin-granules, as well as in cells lacking melanin-granules, most likely representing macrophages. GAL-IR was detected in numerous cells and tissues throughout the anterior and posterior eye and might therefore be an important regulatory peptide for many aspects of ocular control. Upcoming studies in diseased tissue will help to clarify the role of GAL in ocular homeostasis.

The neuropeptides Galanin and Galanin(1-15) in depression-like behaviours

Galanin is a 29 amino acid neuropeptide widely distributed in neurons within the central nervous system. Galanin exerts its biological activities through three different G protein-receptors and participates in a number of functions, including mood regulation. Not only Galanin but also Galanin N-terminal fragments like Galanin(1-15) are active at the central level. In this work, we review the latest findings in studies on Galanin and Galanin(1-15) in depression-related behaviours. Our focus is on animal models for depression, and we pay some attention to research data obtained in human studies. Since Serotonin (5-HT), especially through 5-HT1A, and Galanin receptors interact at both pre-and postsynaptic level, the development of drugs targeting potential GAL₁-GAL₂-5-HT1A heteroreceptor complexes linked to the raphe-hippocampal 5-HT neurons may represent new treatment strategies in depression.

The neuropeptide galanin modulates natural killer cell function

Natural killer (NK) cells are part of the innate immune system and combat pathogens and tumors by secreting pro-inflammatory cytokines like interferon gamma (IFN-γ) and by their cytotoxic action. Galanin is a neuropeptide also expressed in peripheral tissue where it impacts several physiological functions, including inflammation. The effects of galanin are mediated via three receptors, GAL_1-3. Since other neuropeptides have been shown to regulate NK cell activity, we investigated the potential of galanin to modulate human NK cell function. NK cells were isolated from human peripheral blood mononuclear cells. mRNA expression was analyzed by qRT-PCR. The dynamic mass redistribution of NK cells upon regulatory peptide stimulation was determined by label-free biochip technology. IFN-γ producing NK cells were identified by flow cytometry analysis and IFN-γ secretion was measured by ELISA. NK cell cytotoxicity was analyzed by flow cytometry via CD107a mobilization. NK cells were found to express the receptor GAL₂ but not GAL₁, GAL₃ or galanin. Galanin per se did not affect the dynamic mass redistribution of NK cells, but significantly enhanced the response of NK cells to IL-18. Galanin significantly modulated the IFN-γ production of the CD56^bright NK cell population upon IL-12 and IL-18 stimulation. Furthermore, galanin significantly modulated the IL-12 and IL-18 stimulated IFN-γ secretion. NK cell cytotoxicity was not modulated by galanin treatment. Galanin can be classified as an immunomodulatory peptide as it is able to sensitize NK cells toward specific cytokines.

Acute central effects of alarin on the regulation on energy homeostasis

Hypothalamic neuropeptides influence the main components of energy balance: metabolic rate, food intake, body weight as well as body temperature, by exerting either an overall anabolic or catabolic effect. The contribution of alarin, the most recently discovered member of the galanin peptide family to the regulation of energy metabolism has been suggested. Our aim was to analyze the complex thermoregulatory and food intake-related effects of alarin in rats. Adult male Wistar rats received different doses of alarin (0.3; 1; 3 and 15μg corresponding approximately to 0.1, 0.33, 1, and 5 nmol, respectively) intracerebroventricularly. Regarding thermoregulatory analysis, oxygen consumption (indicating metabolic rate), core temperature and heat loss (assessed by tail skin temperature) were recorded in an Oxymax indirect calorimeter system complemented with thermocouples and Benchtop thermometer. In order to investigate potential prostaglandin-mediated mechanisms of the hyperthermic effect of alarin, effects of intraperitoneally applied non-selective (indomethacin, 2mg/kg) or selective cyclooxygenase inhibitor (COX-2 inhibitor meloxicam, 1; 2mg/kg) were tested. Effects of alarin on daytime and nighttime spontaneous food intake, as well as, 24-h fasting-induced re-feeding were recorded in an automated FeedScale system. Alarin increased oxygen consumption with simultaneous suppression of heat loss leading to a slow coordinated rise in core temperature. Both applied COX-inhibitors suppressed this action. Alarin failed to induce daytime food intake, but suppressed spontaneous nighttime and also fasting-induced re-feeding food intake. Alarin appears to elicit a slow anorexigenic and prostaglandin-mediated, fever-like hyperthermic response in rats. Such a combination would characterize a catabolic mediator. The potential involvement of alarin in sickness behavior may be assumed.

Regulatory element-based prediction identifies new susceptibility regulatory variants for osteoporosis

Despite genome-wide association studies (GWASs) have identified many susceptibility genes for osteoporosis, it still leaves a large part of missing heritability to be discovered. Integrating regulatory information and GWASs could offer new insights into the biological link between the susceptibility SNPs and osteoporosis. We generated five machine learning classifiers with osteoporosis-associated variants and regulatory features data. We gained the optimal classifier and predicted genome-wide SNPs to discover susceptibility regulatory variants. We further utilized Genetic Factors for Osteoporosis Consortium (GEFOS) and three in-house GWASs samples to validate the associations for predicted positive SNPs. The random forest classifier performed best among all machine learning methods with the F1 score of 0.8871. Using the optimized model, we predicted 37,584 candidate SNPs for osteoporosis. According to the meta-analysis results, a list of regulatory variants was significantly associated with osteoporosis after multiple testing corrections and contributed to the expression of known osteoporosis-associated protein-coding genes. In summary, combining GWASs and regulatory elements through machine learning could provide additional information for understanding the mechanism of osteoporosis. The regulatory variants we predicted will provide novel targets for etiology research and treatment of osteoporosis.

Maternally involved galanin neurons in the preoptic area of the rat

Recent selective stimulation and ablation of galanin neurons in the preoptic area of the hypothalamus established their critical role in control of maternal behaviors. Here, we identified a group of galanin neurons in the anterior commissural nucleus (ACN), and a distinct group in the medial preoptic area (MPA). Galanin neurons in ACN but not the MPA co-expressed oxytocin. We used immunodetection of phosphorylated STAT5 (pSTAT5), involved in prolactin receptor signal transduction, to evaluate the effects of suckling-induced prolactin release and found that 76 % of galanin cells in ACN, but only 12 % in MPA were prolactin responsive. Nerve terminals containing tuberoinfundibular peptide 39 (TIP39), a neuropeptide that mediates effects of suckling on maternal motivation, were abundant around galanin neurons in both preoptic regions. In the ACN and MPA, 89 and 82 % of galanin neurons received close somatic appositions, with an average of 2.9 and 2.6 per cell, respectively. We observed perisomatic innervation of galanin neurons using correlated light and electron microscopy. The connection was excitatory based on the glutamate content of TIP39 terminals demonstrated by post-embedding immunogold electron microscopy. Injection of the anterograde tracer biotinylated dextran amine into the TIP39-expressing posterior intralaminar complex of the thalamus (PIL) demonstrated that preoptic TIP39 fibers originate in the PIL, which is activated by suckling. Thus, galanin neurons in the preoptic area of mother rats are innervated by an excitatory neuronal pathway that conveys suckling-related information. In turn, they can be topographically and neurochemically divided into two distinct cell groups, of which only one is affected by prolactin.

Distribution and chemical coding of sensory neurons innervating the skin of the porcine hindlimb

The aim of the present study was to establish the origin and chemical phenotyping of neurons involved in skin innervation of the porcine hind leg. The dorsal root ganglia (DRGs) of the lumbar (L₄-L₆) and sacral (S₁-S₃) spinal nerves were visualized using the fluorescent tracer Fast Blue (FB). The morphometric analysis of FB-positive (FB+)neurons showed that in the L₄, L₅, S₁ and S₂ DRGs, the small-sized perikarya constituted the major population, whereas in the L₆ and S₃ DRGs the medium-sized cells made up the major population. In all these ganglia, large-sized FB+ perikarya constituted only a small percentage of all FB+ neurons. Immunohistochemistry revealed that small- and medium-sized FB+ perikarya contained sensory markers such as: substance P (SP), calcitonin gene related peptide (CGRP) and galanin (GAL); as well as various other factors such as somatostatin (SOM), calbindin-D28k (CB), pituitary adenylate cyclase-activating polypeptide (PACAP) and neuronal nitric oxide synthase (nNOS). Meanwhile large-sized FB+ perikarya usually expressed SP, CGRP or PACAP. In the lumbar DRGs, some large cells also contained SOM and CB. Double-labeling immunohistochemistry showed that SP-positive neurons co-expressed CGRP, GAL or PACAP; while PACAP-positive cells co-expressed GAL or nNOS. Neurons stained for SOM were also immunoreactive for CB or GAL, while neurons stained for nNOS were also immunoreactive for GAL. In conclusion, the present data has indicated that the distribution and chemical phenotyping of the porcine skin-projecting neurons are different within DRGs of the lumbar (forming a femoral nerve) and sacral (forming a sciatic nerve) spinal nerves.

Spinal neuropeptide expression and neuropathic behavior in the acute and chronic phases after spinal cord injury: Effects of progesterone administration

Patients with spinal cord injury (SCI) develop chronic pain that severely compromises their quality of life. We have previously reported that progesterone (PG), a neuroprotective steroid, could offer a promising therapeutic strategy for neuropathic pain. In the present study, we explored temporal changes in the expression of the neuropeptides galanin and tyrosine (NPY) and their receptors (GalR1 and GalR2; Y1R and Y2R, respectively) in the injured spinal cord and evaluated the impact of PG administration on both neuropeptide systems and neuropathic behavior. Male rats were subjected to spinal cord hemisection at T13 level, received daily subcutaneous injections of PG or vehicle, and were evaluated for signs of mechanical and thermal allodynia. Real time PCR was used to determine relative mRNA levels of neuropeptides and receptors, both in the acute (1day) and chronic (28days) phases after injury. A significant increase in Y1R and Y2R expression, as well as a significant downregulation in GalR2 mRNA levels, was observed 1day after SCI. Interestingly, PG early treatment prevented Y1R upregulation and resulted in lower NPY, Y2R and GalR1 mRNA levels. In the chronic phase, injured rats showed well-established mechanical and cold allodynia and significant increases in galanin, NPY, GalR1 and Y1R mRNAs, while maintaining reduced GalR2 expression. Animals receiving PG treatment showed basal expression levels of galanin, NPY, GalR1 and Y1R, and reduced Y2R mRNA levels. Also, and in line with previously published observations, PG-treated animals did not develop mechanical allodynia and showed reduced sensitivity to cold stimulation. Altogether, we show that SCI leads to considerable changes in the spinal expression of galanin, NPY and their associated receptors, and that early and sustained PG administration prevents them. Moreover, our data suggest the participation of galaninergic and NPYergic systems in the plastic changes associated with SCI-induced neuropathic pain, and further supports the therapeutic potential of PG- or neuropeptide-based therapies to prevent and/or treat chronic pain after central injuries.

The Effect of Stress on the Galaninergic System in the Rat Adenohypophysis: mRNA Expression and Immunohistochemistry of Galanin Receptors

The neuropeptide galanin is a widely distributed neurotransmitter/neuromodulator that regulates a variety of physiological processes and also participates in the regulation of stress responses. The effect of stress is dependent on the activity of the hypothalamic-adenohypophyseal-adrenal axis. Although the adenohypophysis is a crucial part of this axis, galanin peptides and their receptors have not yet been identified in this part of the pituitary after activation of the stress response. Since there are many controversies about the occurrence of individual galanin receptor subtypes in the adenohypophysis under basal conditions, we decided to verify their presence immunohistochemically, and we clearly demonstrated that the adenohypophysis expresses neuropeptides galanin, galanin-like peptide, and subtypes of galanin receptors GalR1, GalR2 and GalR3. The specificity of the reactions was confirmed by Western blots for galanin receptors. Using real-time qPCR we also demonstrated the presence of three GalR subtypes, with the highest expression of GalR2. In addition, we tested the effect of stress. We found that acute stress did not induce any changes in the GalR2 expression, but increased expression of GalR1 and decreased that of GalR3. We confirmed the involvement of the galanin system in the stress regulation in the adenohypophysis.