The participation of galanin in pain processing at the spinal level

Gene expression in the dorsal root ganglion and the cerebrospinal fluid metabolome in polyneuropathy and opioid tolerance in rats

First-line pharmacotherapy for peripheral neuropathic pain (NP) of diverse pathophysiology consists of antidepressants and gabapentinoids, but only a minority achieve sufficient analgesia with these drugs. Opioids are considered third-line analgesics in NP due to potential severe and unpredictable adverse effects in long-term use. Also, opioid tolerance and NP may have shared mechanisms, raising further concerns about opioid use in NP. We set out to further elucidate possible shared and separate mechanisms after chronic morphine treatment and oxaliplatin-induced and diabetic polyneuropathies, and to identify potential diagnostic markers and therapeutic targets. We analysed thermal nociceptive behaviour, the transcriptome of dorsal root ganglia (DRG) and the metabolome of cerebrospinal fluid (CSF) in these three conditions, in rats. Several genes were differentially expressed, most following oxaliplatin and least after chronic morphine treatment, compared with saline-treated rats. A few genes were differentially expressed in the DRGs in all three models (e.g. Csf3r and Fkbp5). Some, e.g. Alox15 and Slc12a5, were differentially expressed in both diabetic and oxaliplatin models. Other differentially expressed genes were associated with nociception, inflammation, and glial cells. The CSF metabolome was most significantly affected in the diabetic rats. Interestingly, we saw changes in nicotinamide metabolism, which has been associated with opioid addiction and withdrawal, in the CSF of morphine-tolerant rats. Our results offer new hypotheses for the pathophysiology and treatment of NP and opioid tolerance. In particular, the role of nicotinamide metabolism in opioid addiction deserves further study.

Exploration on pharmacological mechanisms of YZP against neuropathic pain via inhibiting spinal inflammation and the rationality of its compatibility

ETHNOPHARMACOLOGICAL RELEVANCE

Yuanhu Zhitong Prescription (YZP) is a well-known traditional Chinese medicine (TCM) formula for neuropathic pain (NP) therapy with a satisfying clinical efficacy. However, the underlying pharmacological mechanism and its compatibility principle remain unclear.

AIM OF THE STUDY

This study aims to investigate the analgesic and compatibility mechanisms of YZP on neuropathic pain (NP) at the gene and biological process levels.

MATERIALS AND METHODS

The chronic constriction injury (CCI) rats were intragastrically administrated with extracts of YZP, YH and BZ separately, and then mechanical hypersensitivity were measured to evaluate the analgesic effects between YH and BZ before and after compatibility. Then, RNA-seq and bioinformatics analyses were performed to elucidate the potential mechanisms underlying YZP's analgesia and compatibility. Finally, the expression levels and significant differences of key genes were analyzed.

RESULTS

Behaviorally, both YZP and YH effectively alleviated mechanical allodynia in CCI rats, with YZP being superior to YH. In contrast, we did not observe an analgesic effect of BZ. Genetically, YZP, YH, and BZ reversed the expression levels of 52, 34, and 42 aberrant genes in the spinal cord of CCI rats, respectively. Mechanically, YZP was revealed to alleviate NP mainly by modulating the inflammatory response and neuropeptide signaling pathway, which are the dominant effective processes of YH. Interestingly, the effective targets of YZP were especially enriched in leukocyte activation and cytokine-mediated signaling pathways. Moreover, BZ was found to exert an adjunctive effect in enhancing the analgesic effect of YH by promoting skeletal muscle tissue regeneration and modulating calcium ion transport.

CONCLUSIONS

YH, as the monarch drug, plays a dominant role in the analgesic effect of YZP that effectively relieves NP by inhibiting the spinal inflammation and neuropeptide signaling pathway. BZ, as the minister drug, not only synergistically enhances analgesic processes of YH but also helps to alleviate the accompanying symptoms of NP. Consequently, YZP exerted a more potent analgesic effect than YH and BZ alone. In conclusion, our findings offer new insights into understanding the pharmacological mechanism and compatibility principle of YZP, which may support its clinical application in NP therapy.

Agonists of galanin subtype 2 receptor may prevent pancreatic cancer and agonists of angiotensin II type 2 receptor may prevent colorectal cancer

Pancreatic ductal adenocarcinoma (PDAC) remains a dreadful disease with poor prognosis. While the prognosis of colorectal carcinoma (CRC) is better than that of PDAC, it still is the second-leading cause of cancer deaths worldwide. Recently, a (methyl)lanthionine-stabilized, highly receptor-specific agonist of galanin subtype 2 (GAL2) receptor inhibited the growth of GAL2 receptor-expressing patient-derived xenografts (PDX) of pancreatic cancer. Furthermore, a lanthionine-constrained agonist of angiotensin II type 2 (AT2) receptor inhibited PDX of colorectal cancer in mice. Stimulation of GAL2 receptor may modulate immune surveillance and inhibits PDAC via cell cycle inhibition and apoptosis. Consistent with GAL2 receptor-mediated tumor inhibition, for PDAC, survival is much higher for patients with high GAL2 receptor expression. Importantly, a (methyl)lanthionine-stabilized GAL2 receptor-specific agonist enhances expression of GAL2 receptor, not only in PDAC-PDX but also in healthy tissue indicating therapeutic and preventive potentials for GAL2 receptor agonists. AT2 receptor is interacting with four tumor suppressor proteins, Src homology phosphatase 1, Src homology phosphatase 2, Promyelocytic Leukemia Zinc Finger protein and Microtuble-Associated Scaffold Protein1, the latter also known as Angiotensin-II type 2 receptor-Interacting Protein. Pathways linked to these tumor suppressor proteins may enhance immune surveillance, prevent carcinogenesis, counter proliferation and stimulate apoptosis. Taken together, current data are prompting the hypothesis of a prophylactic treatment option with stable, specific and safe agonists of GAL2 receptor and AT2 receptor to prevent the emergence of pancreatic and colorectal cancer in individuals at risk.

Class A and C GPCR Dimers in Neurodegenerative Diseases

Neurodegenerative diseases affect over 30 million people worldwide with an ascending trend. Most individuals suffering from these irreversible brain damages belong to the elderly population, with onset between 50 and 60 years. Although the pathophysiology of such diseases is partially known, it remains unclear upon which point a disease turns degenerative. Moreover, current therapeutics can treat some of the symptoms but often have severe side effects and become less effective in long-term treatment. For many neurodegenerative diseases, the involvement of G proteincoupled receptors (GPCRs), which are key players of neuronal transmission and plasticity, has become clearer and holds great promise in elucidating their biological mechanism. With this review, we introduce and summarize class A and class C GPCRs, known to form heterodimers or oligomers to increase their signalling repertoire. Additionally, the examples discussed here were shown to display relevant alterations in brain signalling and had already been associated with the pathophysiology of certain neurodegenerative diseases. Lastly, we classified the heterodimers into two categories of crosstalk, positive or negative, for which there is known evidence.

Characterization of spexin (SPX) in chickens: molecular cloning, functional analysis, tissue expression and its involvement in appetite regulation

Spexin (SPX) is a conservative tetradecapeptide which has been proven to participate in multiple physiological processes, including anxiety, feed intake, and energy metabolism in fish and mammals. However, whether SPX exists and functions in birds remain largely unknown. Using chicken (c-) as a model, the full-length cDNA encoding cSPX precursor was cloned, and it was predicted to generate a mature peptide with 14 amino acids conserved across vertebrates. The pGL4-SRE-luciferase reporter system-based functional analysis demonstrated that cSPX was effective in activating chicken galanin type Ⅱ receptor (cGALR2), cGALR2-like receptor (cGALR2L) and galanin type Ⅲ receptor (cGALR3), thus to stimulate intracellular MAPK/ERK signaling pathway. Quantitative real-time PCR revealed that SPX was widely expressed in chicken tissues, especially abundant in the central nervous system, pituitary, testes, and pancreas. Interestingly, it was noted that chicken hypothalamic SPX mRNA could be up-regulated by 24-h and 36-h fasting, heralding its latent capacity in appetite regulation. In accordance with this speculation, peripheral injection of cSPX was proved to be functional in reducing feed intake of 3-wk-old chicks. Furthermore, we found that cSPX could reduce the expression of AgRP and MCH, with a concurrent rise in CART1 mRNA level in the hypothalamic of chicks. Collectively, our findings not only provide the evidences that SPX can act as a satiety factor by orchestrating the expression of key feeding regulators in the chicken hypothalamus but also help to facilitate a better understanding of its functional evolution across vertebrates.

Gq Signaling in Autophagy Control: Between Chemical and Mechanical Cues

All processes in human physiology relies on homeostatic mechanisms which require the activation of specific control circuits to adapt the changes imposed by external stimuli. One of the critical modulators of homeostatic balance is autophagy, a catabolic process that is responsible of the destruction of long-lived proteins and organelles through a lysosome degradative pathway. Identification of the mechanism underlying autophagic flux is considered of great importance as both protective and detrimental functions are linked with deregulated autophagy. At the mechanistic and regulatory levels, autophagy is activated in response to diverse stress conditions (food deprivation, hyperthermia and hypoxia), even a novel perspective highlight the potential role of physical forces in autophagy modulation. To understand the crosstalk between all these controlling mechanisms could give us new clues about the specific contribution of autophagy in a wide range of diseases including vascular disorders, inflammation and cancer. Of note, any homeostatic control critically depends in at least two additional and poorly studied interdependent components: a receptor and its downstream effectors. Addressing the selective receptors involved in autophagy regulation is an open question and represents a new area of research in this field. G-protein coupled receptors (GPCRs) represent one of the largest and druggable targets membrane receptor protein superfamily. By exerting their action through G proteins, GPCRs play fundamental roles in the control of cellular homeostasis. Novel studies have shown Gαq, a subunit of heterotrimeric G proteins, as a core modulator of mTORC1 and autophagy, suggesting a fundamental contribution of Gαq-coupled GPCRs mechanisms in the control of this homeostatic feedback loop. To address how GPCR-G proteins machinery integrates the response to different stresses including oxidative conditions and mechanical stimuli, could provide deeper insight into new signaling pathways and open potential and novel therapeutic strategies in the modulation of different pathological conditions.

Galanin analogs prevent mortality from seizure-induced respiratory arrest in mice

Objective

Sudden Unexpected Death in Epilepsy (SUDEP) accounts for 20% of mortality in those with recurrent seizures. While risk factors, monitoring systems, and standard practices are in place, the pathophysiology of SUDEP is still not well understood. Better knowledge of SUDEP and its potential mechanisms of action is crucial to reducing risk in this patient population and developing potential treatment options. Clinical studies and animal models of SUDEP suggest that diminished post-ictal respiratory control may be the dominant mechanism contributing to mortality. Recently, it was demonstrated that the depletion of the neuropeptide galanin in the amygdala occurs in human SUDEP. The amygdala plays a key role in the central integration of respiratory signaling; the depletion of galanin may represent a critical change that predisposes individuals to SUDEP.

Materials and methods

To evaluate the impact of enhancing galaninergic signaling to potentially protect against SUDEP, we studied seizure-induced respiratory arrest (S-IRA) following central (intracerebroventricular, intra-amygdala) and systemic (intraperitoneal, subcutaneous) administration of galanin analogs. Seizure naïve and seizure experienced (fully kindled) mice were tested.

Results

Central and systemically administered galanin analogs protect against S-IRA in naïve C57Bl/6J mice. Differential efficacy between receptor subtype-selective analogs varied based on the route of administration. Sub-chronic systemic administration at doses that reduced 6 Hz seizures also protected against S-IRA. Acute treatment benefits also extended to fully kindled mice experiencing tonic extension.

Significance

These data demonstrate that galanin analogs may be protective against post-ictal respiratory collapse.

Peroxisome Metabolism Contributes to PIEZO2-Mediated Mechanical Allodynia

Mutations in the peroxisomal half-transporter ABCD1 cause X-linked adrenoleukodystrophy, resulting in elevated very long-chain fatty acids (VLCFA), progressive neurodegeneration and an associated pain syndrome that is poorly understood. In the nervous system of mice, we found ABCD1 expression to be highest in dorsal root ganglia (DRG), with satellite glial cells (SGCs) displaying higher expression than neurons. We subsequently examined sensory behavior and DRG pathophysiology in mice deficient in ABCD1 compared to wild-type mice. Beginning at 8 months of age, Abcd1-/y mice developed persistent mechanical allodynia. DRG had a greater number of IB4-positive nociceptive neurons expressing PIEZO2, the mechanosensitive ion channel. Blocking PIEZO2 partially rescued the mechanical allodynia. Beyond affecting neurons, ABCD1 deficiency impacted SGCs, as demonstrated by high levels of VLCFA, increased glial fibrillary acidic protein (GFAP), as well as genes disrupting neuron-SGC connectivity. These findings suggest that lack of the peroxisomal half-transporter ABCD1 leads to PIEZO2-mediated mechanical allodynia as well as SGC dysfunction. Given the known supportive role of SGCs to neurons, this elucidates a novel mechanism underlying pain in X-linked adrenoleukodystrophy.

Immortalized Bone Mesenchymal Stromal Cells With Inducible Galanin Expression Produce Controllable Pain Relief in Neuropathic Rats

Management of chronic pain is one of the most difficult problems in modern practice. Grafted human telomerase reverse transcriptase–immortalized bone marrow mesenchymal stromal cells (hTERT-BMSCs) with inducible galanin (GAL) expression have been considered to be a potentially safe and controllable approach for the alleviation of chronic pain. Therefore, in this study, we aimed to assess the feasibility of hTERT-BMSCs/Tet-on/GAL cells secreting GAL under the transcriptional control of doxycycline (Dox) for controllable pain relief. After transplanted into the subarachnoid space of neuropathic rats induced by spared nerve injury of sciatic nerve, their analgesic actions were investigated by behavioral tests. The results showed that the pain-related behaviors, mechanical allodynia, and thermal hyperalgesia were significantly alleviated during 1 to 7 weeks after grafts of hTERT-BMSCs/Tet-on/GAL cells without motor incoordination. Importantly, these effects could be reversed by GAL receptor antagonist M35 and regulated by Dox induction as compared with control. Moreover, the GAL level in cerebrospinal fluid and spinal GAL receptor 1 (GalR1) expression were correlated with Dox administration, but not GAL receptor 2 (GalR2). Meanwhile, spinal protein kinase Mζ (PKMζ) expression was also inhibited significantly. Taken together, these data suggest that inducible release of GAL from transplanted cells was able to produce controllable pain relief in neuropathic rats via inhibiting the PKMζ activation and activating its GalR1 rather than GalR2. This provides a promising step toward a novel stem cell–based strategy for pain therapy.

Spexin Promotes the Proliferation and Differentiation of C2C12 Cells In Vitro—The Effect of Exercise on SPX and SPX Receptor Expression in Skeletal Muscle In Vivo

SPX (spexin) and its receptors GalR2 and GalR3 (galanin receptor subtype 2 and galanin receptor subtype 3) play an important role in the regulation of lipid and carbohydrate metabolism in human and animal fat tissue. However, little is still known about the role of this peptide in the metabolism of muscle. The aim of this study was to determine the impact of SPX on the metabolism, proliferation and differentiation of the skeletal muscle cell line C2C12. Moreover, we determined the effect of exercise on the SPX transduction pathway in mice skeletal muscle. We found that increased SPX, acting via GalR2 and GalR3 receptors, and ERK1/2 phosphorylation stimulated the proliferation of C2C12 cells (p < 0.01). We also noted that SPX stimulated the differentiation of C2C12 by increasing mRNA and protein levels of differentiation markers Myh, myogenin and MyoD (p < 0.01). SPX consequently promoted myoblast fusion into the myotubule (p < 0.01). Moreover, we found that, in the first stage (after 2 days) of myocyte differentiation, GalR2 and GalR3 were involved, whereas in the last stage (day six), the effect of SPX was mediated by the GalR3 isoform. We also noted that exercise stimulated SPX and GalR2 expression in mice skeletal muscle as well as an increase in SPX concentration in blood serum. These new insights may contribute to a better understanding of the role of SPX in the metabolism of skeletal muscle.

Increased Serum Neuropeptide Galanin Level Is a Predictor of Cognitive Dysfunction in Patients with Hip Fracture

Background

Hip fracture is a common occurrence in elderly populations and is frequently followed by various levels of cognitive dysfunction, leading to adverse functional outcomes. Risk stratification of hip fracture patients to identify high-risk subsets can enable improved strategies to mitigate cognitive complications. The neuropeptide galanin has multiple neurological functions, and altered levels are documented in dementia-type and depression disorders. The present study investigated the association of serum neuropeptide galanin levels in hip fracture patients with the occurrence of cognitive dysfunction during the first week of admission.

Methods

276 hip fracture patients without preexisting delirium, cognitive impairment, or severe mental disorders were included in a cross-sectional study. Serum galanin levels were assessed by ELISA on the second day of admission. Routine clinical and laboratory variables were documented. MoCA was performed within 1 week, and those with a score < 26 were categorized with “cognitive decline.” Inferential statistics including multiple linear regression analysis were applied to determine the association of serum galanin level and cognitive status.

Results

141 patients were categorized with “cognitive decline,” and 135 patients were categorized as “cognitively normal.” Serum galanin was highly significantly increased in the “cognitive decline” group (34.2 ± 4.8, pg/ml) compared to the “cognitively normal” group (28.9 ± 3.7, pg/ml) and showed significant negative correlation with MoCA scores (r = −0.229, p = 0.016). Regression analysis showed serum galanin as the sole significant independent predictor of lower MoCA scores (β = 0.231, p = 0.035) while age, gender, blood pressure, cholesterol, and blood glucose levels had no significant association.

Conclusion

Higher serum galanin predicted the development of cognitive dysfunction and worse MoCA scores in a cohort of hip fracture patients without preexisting cognitive impairment or delirium at admission, thus warranting large-scale studies investigating galanin as a candidate biomarker to identify hip fracture patients at risk of cognitive decline.

The Influence of an Adrenergic Antagonist Guanethidine (GUA) on the Distribution Pattern and Chemical Coding of Dorsal Root Ganglia (DRG) Neurons Supplying the Porcine Urinary Bladder

Although guanethidine (GUA) was used in the past as a drug to suppress hyperactivity of the sympathetic nerve fibers, there are no available data concerning the possible action of this substance on the sensory component of the peripheral nervous system supplying the urinary bladder. Thus, the present study was aimed at disclosing the influence of intravesically instilled GUA on the distribution, relative frequency, and chemical coding of dorsal root ganglion neurons associated with the porcine urinary bladder. The investigated sensory neurons were visualized with a retrograde tracing method using Fast Blue (FB), while their chemical profile was disclosed with single-labeling immunohistochemistry using antibodies against substance P (SP), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase activating polypeptide (PACAP), galanin (GAL), neuronal nitric oxide synthase (nNOS), somatostatin (SOM), and calbindin (CB). After GUA treatment, a slight decrease in the number of FB⁺ neurons containing SP was observed when compared with untreated animals (34.6 ± 6.5% vs. 45.6 ± 1.3%), while the number of retrogradely traced cells immunolabeled for GAL, nNOS, and CB distinctly increased (12.3 ± 1.0% vs. 7.4 ± 0.6%, 11.9 ± 0.6% vs. 5.4 ± 0.5% and 8.6 ± 0.5% vs. 2.7 ± 0.4%, respectively). However, administration of GUA did not change the number of FB⁺ neurons containing CGRP, PACAP, or SOM. The present study provides evidence that GUA significantly modifies the sensory innervation of the porcine urinary bladder wall and thus may be considered a potential tool for studying the plasticity of this subdivision of the bladder innervation.

UVB irradiation induces contralateral changes in galanin, substance P and c-fos immunoreactivity in rat dorsal root ganglia, dorsal horn and lateral spinal nucleus

The selection of control group is crucial, as the use of an inadequate group may strongly affect the results. In this study we examine the effect on contralateral tissue protein levels, in a model of unilateral UVB irradiation, as the contralateral side is commonly used as a control. Previous studies have shown that UVB irradiation increases immunoreactivity for inflammatory regulated neuropeptides. Unilateral UVB irradiation of rat hind paw was performed and corresponding contralateral spinal cord and dorsal root ganglia (DRG) were collected 2-96 h after and investigated for changes in galanin, substance P and c-fos immunoreactivity. Control tissue was collected from naïve rats. Measurement of skin blood flow from contralateral heel hind paws (Doppler), revealed no change compared to naïve rats. However, UVB irradiation caused a significant reduction in the contralateral proportion of galanin immunopositive DRG neurons, at all-time points, as well as an increase in the contralateral spinal cord dorsal horn, around the central canal and in the lateral spinal nucleus (2-48 h). The contralateral proportion of SP positive DRG neurons and dorsal horn immunoreactivity was unchanged, whereas the lateral spinal nucleus area showed increased immunoreactivity (48 h). UVB irradiation also induced a slight contralateral upregulation of c-fos in the dorsal horn/central canal area (24 and 48 h). In summary, unilateral UVB irradiation induced contralateral changes in inflammatory/nociceptive neuropeptides in spinal cord and afferent pathways involved in pain signaling already within 24 h, a time point when also ipsilateral neurochemical/physiological changes have been reported for rats and humans.

Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain-Gut Axis

Coffee is one of the most popular beverages consumed worldwide. Roasted coffee is a complex mixture of thousands of bioactive compounds, and some of them have numerous potential health-promoting properties that have been extensively studied in the cardiovascular and central nervous systems, with relatively much less attention given to other body systems, such as the gastrointestinal tract and its particular connection with the brain, known as the brain–gut axis. This narrative review provides an overview of the effect of coffee brew; its by-products; and its components on the gastrointestinal mucosa (mainly involved in permeability, secretion, and proliferation), the neural and non-neural components of the gut wall responsible for its motor function, and the brain–gut axis. Despite in vitro, in vivo, and epidemiological studies having shown that coffee may exert multiple effects on the digestive tract, including antioxidant, anti-inflammatory, and antiproliferative effects on the mucosa, and pro-motility effects on the external muscle layers, much is still surprisingly unknown. Further studies are needed to understand the mechanisms of action of certain health-promoting properties of coffee on the gastrointestinal tract and to transfer this knowledge to the industry to develop functional foods to improve the gastrointestinal and brain–gut axis health.

The Role of Corticotropin-Releasing Hormone at Peripheral Nociceptors: Implications for Pain Modulation

Peripheral nociceptors and their synaptic partners utilize neuropeptides for signal transmission. Such communication tunes the excitatory and inhibitory function of nociceptor-based circuits, eventually contributing to pain modulation. Corticotropin-releasing hormone (CRH) is the initiator hormone for the conventional hypothalamic-pituitary-adrenal axis, preparing our body for stress insults. Although knowledge of the expression and functional profiles of CRH and its receptors and the outcomes of their interactions has been actively accumulating for many brain regions, those for nociceptors are still under gradual investigation. Currently, based on the evidence of their expressions in nociceptors and their neighboring components, several hypotheses for possible pain modulations are emerging. Here we overview the historical attention to CRH and its receptors on the peripheral nociception and the recent increases in information regarding their roles in tuning pain signals. We also briefly contemplate the possibility that the stress-response paradigm can be locally intrapolated into intercellular communication that is driven by nociceptor neurons. Such endeavors may contribute to a more precise view of local peptidergic mechanisms of peripheral pain modulation.

Beneficial effects of galanin system on diabetic peripheral neuropathic pain and its complications

Diabetic peripheral neuropathic pain (DPNP) is a distal spontaneous pain, caused by lesion of sensory neurons and accompanied by depression and anxiety frequently, which reduce life quality of patients and increase society expenditure. To date, antidepressants, serotonin-noradrenaline reuptake inhibitors and anticonvulsants are addressed as first-line therapy to DPNP, alone or jointly. It is urgently necessary to develop novel agents to treat DPNP and its complications. Evidences indicate that neuropeptide galanin can regulate multiple physiologic and pathophysiological processes. Pain, depression and anxiety may upregulate galanin expression. In return, galanin can modulate depression, anxiety, pain threshold and pain behaviors. This article provides a new insight into regulative effects of galanin and its subtype receptors on antidepressant, antianxiety and against DPNP. Through activating GALR1, galanin reinforces depression-like and anxiogenic-like behaviors, but exerts antinociceptive roles. While via activating GALR2, galanin is referred to as anti-depressive and anti-anxiotropic compounds, and at low and high concentration facilitates and inhibits nociceptor activity, respectively. The mechanism of the galanin roles is relative to increase in K⁺ currents and decrease in Ca²⁺ currents, as well as neurotrophic and neuroprotective roles. These data are helpful to develop novel drugs to treat DPNP and its complications.

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.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

An assembly of galanin-galanin receptor signaling network

The galanin receptor family of proteins is present throughout the central nervous system and endocrine system. It comprises of three subtypes-GalR1, GalR2, and GalR3; all of which are G-protein-coupled receptors. Galanin predominantly acts as an inhibitory, hyper-polarizing neuromodulator, which has several physiological as well as pathological functions. Galanin has a role in mediating food intake, memory, sexual behavior, nociception and is also associated with diseases such as Alzheimer's disease, epilepsy, diabetes mellitus, and chronic pain. However, the understanding of signaling mechanisms of the galanin family of neuropeptides is limited and an organized pathway map is not yet available. Therefore, a detailed literature mining of the publicly available articles pertaining to the galanin receptor was followed by manual curation of the reactions and their integration into a map. This resulted in the cataloging of molecular reactions involving 64 molecules into five categories such as molecular association, activation/inhibition, catalysis, transport, and gene regulation. For enabling easy access of biomedical researchers, the galanin-galanin receptor signaling pathway data was uploaded to WikiPathways ( https://www.wikipathways.org/index.php/Pathway:WP4970 ), a freely available database of biological pathways.

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.

A preliminary study on DRGs and spinal cord of a galanin receptor 2-EGFP transgenic mouse

The neuropeptide galanin functions via three G-protein coupled receptors, Gal_1-3-R. Both Gal₁-R and ₂-R are involved in pain signaling at the spinal level. Here a Gal₂-R-EGFP transgenic (TG) mouse was generated and studied in pain tests and by characterizing Gal₂-R expression in both sensory ganglia and spinal cord. After peripheral spared nerve injury, mechanical allodynia developed and was ipsilaterally similar between wild type (WT) and TG mice. A Gal₂-R-EGFP-positive signal was primarily observed in small and medium-sized dorsal root ganglion (DRG) neurons and in spinal interneurons and processes. No significant difference in size distribution of DRG neuronal profiles was found between TG and WT mice. Both percentage and fluorescence intensity of Gal₂-R-EGFP-positive neuronal profiles were overall significantly upregulated in ipsilateral DRGs as compared to contralateral DRGs. There was an ipsilateral reduction in substance P-positive and calcitonin gene-related peptide (CGRP)-positive neuronal profiles, and this reduction was more pronounced in TG as compared to WT mice. Moreover, Gal₂-R-EGFP partly co-localized with three pain-related neuropeptides, CGRP, neuropeptide Y and galanin, both in intact and injured DRGs, and with galanin also in local neurons in the superficial dorsal horn. Taken together, the present results provide novel information on the localization and phenotype of DRG and spinal neurons expressing the second galanin receptor, Gal₂-R, and on phenotypic changes following peripheral nerve injury. Gal2-R may also be involved in autoreceptor signaling.

Transcriptomics Analysis of Porcine Caudal Dorsal Root Ganglia in Tail Amputated Pigs Shows Long-Term Effects on Many Pain-Associated Genes

Tail amputation by tail docking or as an extreme consequence of tail biting in commercial pig production potentially has serious implications for animal welfare. Tail amputation causes peripheral nerve injury that might be associated with lasting chronic pain. The aim of this study was to investigate the short- and long-term effects of tail amputation in pigs on caudal DRG gene expression at different stages of development, particularly in relation to genes associated with nociception and pain. Microarrays were used to analyse whole DRG transcriptomes from tail amputated and sham-treated pigs 1, 8, and 16 weeks following tail treatment at either 3 or 63 days of age (8 pigs/treatment/age/time after treatment; n = 96). Tail amputation induced marked changes in gene expression (up and down) compared to sham-treated intact controls for all treatment ages and time points after tail treatment. Sustained changes in gene expression in tail amputated pigs were still evident 4 months after tail injury. Gene correlation network analysis revealed two co-expression clusters associated with amputation: Cluster A (759 down-regulated) and Cluster B (273 up-regulated) genes. Gene ontology (GO) enrichment analysis identified 124 genes in Cluster A and 61 genes in Cluster B associated with both “inflammatory pain” and “neuropathic pain.” In Cluster A, gene family members of ion channels e.g., voltage-gated potassium channels (VGPC) and receptors e.g., GABA receptors, were significantly down-regulated compared to shams, both of which are linked to increased peripheral nerve excitability after axotomy. Up-regulated gene families in Cluster B were linked to transcriptional regulation, inflammation, tissue remodeling, and regulatory neuropeptide activity. These findings, demonstrate that tail amputation causes sustained transcriptomic expression changes in caudal DRG cells involved in inflammatory and neuropathic pain pathways.

Cellular Mechanisms for Antinociception Produced by Oxytocin and Orexins in the Rat Spinal Lamina II-Comparison with Those of Other Endogenous Pain Modulators

Much evidence indicates that hypothalamus-derived neuropeptides, oxytocin, orexins A and B, inhibit nociceptive transmission in the rat spinal dorsal horn. In order to unveil cellular mechanisms for this antinociception, the effects of the neuropeptides on synaptic transmission were examined in spinal lamina II neurons that play a crucial role in antinociception produced by various analgesics by using the whole-cell patch-clamp technique and adult rat spinal cord slices. Oxytocin had no effect on glutamatergic excitatory transmission while producing a membrane depolarization, γ-aminobutyric acid (GABA)-ergic and glycinergic spontaneous inhibitory transmission enhancement. On the other hand, orexins A and B produced a membrane depolarization and/or a presynaptic spontaneous excitatory transmission enhancement. Like oxytocin, orexin A enhanced both GABAergic and glycinergic transmission, whereas orexin B facilitated glycinergic but not GABAergic transmission. These inhibitory transmission enhancements were due to action potential production. Oxytocin, orexins A and B activities were mediated by oxytocin, orexin-1 and orexin-2 receptors, respectively. This review article will mention cellular mechanisms for antinociception produced by oxytocin, orexins A and B, and discuss similarity and difference in antinociceptive mechanisms among the hypothalamic neuropeptides and other endogenous pain modulators (opioids, nociceptin, adenosine, adenosine 5’-triphosphate (ATP), noradrenaline, serotonin, dopamine, somatostatin, cannabinoids, galanin, substance P, bradykinin, neuropeptide Y and acetylcholine) exhibiting a change in membrane potential, excitatory or inhibitory transmission in the spinal lamina II neurons.

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.

Subclinical lipopolysaccharide from Salmonella Enteritidis induces neuropeptide dysregulation in the spinal cord and the dorsal root ganglia

Background

Despite increasing evidence that lipopolysaccharide (LPS) affects the biological active substances of dorsal root ganglia (DRG) we have limited knowledge of the influence of a single low dose of LPS, which does not result in any clinical symptoms of disease (subclinical LPS) on neuropeptides connected with the sensory pathway. Accordingly, in this work, we investigated the influence of subclinical LPS from Salmonella Enteritidis on selected neuropeptides: substance P (SP), galanin (GAL), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and somatostatin (SOM) in the cervical, thoracic, lumbar and sacral regions of the DRG and spinal cord.

Methods

This study was performed on immature female pigs of the Pietrain × Duroc breed. Seven days after the intravenous injection of saline solution for control animals (n = 5) and 5 μg/kg b.w. LPS from S. Enteritidis for the experimental group (n = 5), the DRG and the spinal cord were collected to extract the neuropeptides using solid-phase extraction technology.

Results

Our results demonstrated that subclinical LPS in DRG was able to change the levels of all studied neuropeptides except SOM, whereas in the spinal cord it down-regulated all studied neuropeptides in the sacral spinal cord, maintaining the concentration of all studied neuropeptides in other regions similar to that observed in the control animals. The significant differences in the intensity and character of observed changes between particular regions of the DRG suggest that the exact functions of the studied neuropeptides and mechanisms of responses to subclinical LPS action depend on specific characteristics and functions of each examination region of DRG.

Conclusions

The mechanisms of observed changes are not fully understood and require further study of the molecular interactions between subclinical LPS from S. Enteritidis and neuronal and non-neuronal cells of DRG and spinal cord. The peripheral and central pain pathways must be analysed with the aspect of unknown long-term consequences of the influence of subclinical LPS from S. Enteritidis on neuropeptides in the spinal cord and the dorsal root ganglia.

The histology, physiology, neurochemistry and circuitry of the substantia gelatinosa Rolandi (lamina II) in mammalian spinal cord

The substantia gelatinosa Rolandi (SGR) was first described about two centuries ago. In the following decades an enormous amount of information has permitted us to understand - at least in part - its role in the initial processing of pain and itch. Here, I will first provide a comprehensive picture of the histology, physiology, and neurochemistry of the normal SGR. Then, I will analytically discuss the SGR circuits that have been directly demonstrated or deductively envisaged in the course of the intensive research on this area of the spinal cord, with particular emphasis on the pathways connecting the primary afferent fibers and the intrinsic neurons. The perspective existence of neurochemically-defined sets of primary afferent neurons giving rise to these circuits will be also discussed, with the proposition that a cross-talk between different subsets of peptidergic fibers may be the structural and functional substrate of additional gating mechanisms in SGR. Finally, I highlight the role played by slow acting high molecular weight modulators in these gating mechanisms.

Synergistic effect of spexin and progesterone on pain sensitivity attenuation in ovariectomized rats

Spexin is a central modulator of nociception. The aim of the present study was to investigate the effect of intra-hippocampal CA3 (IHCA3) injection of spexin and spexin-progesterone co-administration on pain sensitivity in ovariectomized rat. Thirty-five adult female rats were divided into five groups. Sham: the animals received injection of 0.5 μL ACSF by IHCA3. Experiments 1 and 2: the animals received injection of 0.5 μL of spexin bilaterally (10 and 30 nmol/rat respectively). Experiments 3 and 4: the animals received injection of 0.5 μL of spexin bilaterally (10 and 30 nmol/rat respectively) + subcutaneous (s.c.) injection of progesterone (5 mg/kg). Ovariectomy was performed in all groups to eliminate the effects of cyclic changes in the female rats. The formalin test (formalin 2.5%) was performed following the administration of spexin and progesterone. Results showed that bilateral injection of spexin in IHCA3 at both concentrations a significant (P < .05) decrease in the pain sensitivity in the two phases of formalin test. Similarly, the bilateral injection of spexin in IHCA3 at both concentrations following the s.c. injection of progesterone significantly (P < .05) decreases pain sensitivity in two phases of the formalin test. This pain attenuation due to the co-administration of spexin and progesterone was more potent than spexin-induced analgesia. According to the present results, spexin has a modulatory effect on pain sensitivity, which becomes more pronounced by progesterone administration.

Origins and Neurochemical Characteristics of Porcine Intervertebral Disc Sympathetic Innervation: a Preliminary Report

Intervertebral disc diseases (IVDDs) form a group of a vertebral column disorders affecting a large number of people worldwide. It is estimated that approximately 30% of individuals at the age of 35 and approximately 90% of individuals at the age of 60 and above will have some form of disc-affecting pathological changes leading to disc herniation, prolapse and degeneration as well as discogenic pain. Here, we aimed to establish the origins and neurochemical characteristics of porcine intervertebral disc sympathetic innervation involved in pain signalling in IVDD patients. Pigs were given an injection of the Ominipaque contrast agent and Fast Blue (FB) retrograde tracer into the L₄-L₅ intervertebral disc and euthanized at 2, 1, and 3 months post injection. Following euthanasia, bilateral sympathetic chain ganglia (SChG) Th₁₃ to C₁ were collected. The presence, distribution and neurochemical characteristics of retrogradely labelled SChG neurons were examined. The majority (88.8%) of all FB+ cells were found in the L₃-L₅ SChG. Most FB+ neurons stained for dopamine beta hydroxylase (DBH); one-third to one-quarter stained for somatostatin (SOM), neuropeptide Y (NPY) or leu-enkephalin (LENK); and only a few stained for galanin (GAL). Compared with the control, the greatest decline in neurochemical immunostaining was observed 2 weeks post injection, and the lowest decline was noticed 1 month post injection. Our study, for the first time, provides insight into the complex patterns of intervertebral disc sympathetic innervation and suggests that the best time for neurochemical balance restoration therapy would be 1 month post-injury, when the neuronal concentration of all studied substances is close to the initial physiological level, thus providing favourable conditions for successful recovery.

The galanin and galanin receptor subtypes, its regulatory role in the biological and pathological functions

The multitalented neuropeptide galanin was first discovered 30 years ago but initially no biologic activity was found. Further research studies discovered the presence of galanin in the brain and some peripheral tissues, and galanin was identified as a modulator of neurotransmission in the central and peripheral nervous system. Over the last decade there were performed very intensive studies of the neuronal actions and also of nonneuronal actions of galanin. Other galanin family peptides have been described, namely galanin, galanin-like peptide, galanin-message associated peptide and alarin. The effect of these peptides is mediated through three galanin receptors subtypes, GalR1, GalR2 and GalR3 belonging to G protein coupled receptors, and signaling via multiple transduction pathways, including inhibition of cyclic AMP/protein kinase A (GalR1, GalR3) and stimulation of phospholipase C (GalR2). This also explains why one specific molecule of galanin can be responsible for different roles in different tissues. The present review summarizes the information currently available on the relationship between the galaninergic system and known pathological states. The research of novel galanin receptor specific agonists and antagonists is also very promising for its future role in pharmacological treatment. The galaninergic system is important target for current and future biomedical research.

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.

UVB irradiation induces rapid changes in galanin, substance P and c-fos immunoreactivity in rat dorsal root ganglia and spinal cord

Recent studies have shown that UVB irradiation induces primary and secondary hyperalgesia in rats and humans peaking about 24h after UVB exposure. In the present study we investigated the changes in galanin, substance P and c-fos immunoreactivity in rat DRG and spinal cord at the L5 level 2-96h after UVB irradiation. UVB irradiation of the heel area in rats almost increased the skin blood flow two-fold 24h after irradiation as measured by laser Doppler technique. UVB irradiation induced a significant reduction of the proportion of galanin positive DRG neurons for all time points, except at 12h. In the spinal cord, UVB irradiation induced increased immunoreactivity for galanin in the dorsal horn, the area around the central canal and interestingly also in the lateral spinal nucleus 12-96h after exposure. For substance P the proportion of substance P positive neurons was unchanged but UVB irradiation induced increased substance P immunoreactivity in the dorsal part of the spinal cord 48h after irradiation. UVB irradiation also induced c-fos immunoreactivity in the dorsal horn and the area around the central canal 24 and 48h after exposure. This translational model of UVB irradiation will induce rapid changes of neuropeptides implicated in nociceptive signaling in areas known to be of importance for nociception in a time frame, about 24h after exposure, where also neurophysiological alteration have been described in humans and rats.

Transcriptomic and behavioural characterisation of a mouse model of burn pain identify the cholecystokinin 2 receptor as an analgesic target

Burn injury is a cause of significant mortality and morbidity worldwide and is frequently associated with severe and long-lasting pain that remains difficult to manage throughout recovery. We characterised a mouse model of burn-induced pain using pharmacological and transcriptomic approaches. Mechanical allodynia elicited by burn injury was partially reversed by meloxicam (5 mg/kg), gabapentin (100 mg/kg) and oxycodone (3 and 10 mg/kg), while thermal allodynia and gait abnormalities were only significantly improved by amitriptyline (3 mg/kg) and oxycodone (10 mg/kg). The need for relatively high opioid doses to elicit analgesia suggested a degree of opioid resistance, similar to that shown clinically in burn patients. We thus assessed the gene expression changes in dorsal root ganglion neurons and pathophysiological mechanisms underpinning burn injury-induced pain using a transcriptomic approach. Burn injury was associated with significantly increased expression of genes associated with axon guidance, neuropeptide signalling, behavioural defence response and extracellular signalling, confirming a mixed neuropathic and inflammatory aetiology. Notably, among the pain-related genes that were upregulated post-injury was the cholecystokinin 2 receptor (Cckbr), a G protein-coupled receptor known as a pain target involved in reducing opioid effectiveness. Indeed, the clinically used cholecystokinin receptor antagonist proglumide (30 mg/kg) was effective at reversing mechanical allodynia, with additional analgesia evident in combination with low-dose oxycodone (1 mg/kg), including significant reversal of thermal allodynia. These findings highlight the complex pathophysiological mechanisms underpinning burn injury-induced pain and suggest that cholecystokinin-2 receptor antagonists may be useful clinically as adjuvants to decrease opioid requirements and improve analgesic management.

NPR-9, a Galanin-Like G-Protein Coupled Receptor, and GLR-1 Regulate Interneuronal Circuitry Underlying Multisensory Integration of Environmental Cues in Caenorhabditis elegans

C. elegans inhabit environments that require detection of diverse stimuli to modulate locomotion in order to avoid unfavourable conditions. In a mammalian context, a failure to appropriately integrate environmental signals can lead to Parkinson’s, Alzheimer’s, and epilepsy. Provided that the circuitry underlying mammalian sensory integration can be prohibitively complex, we analyzed nematode behavioral responses in differing environmental contexts to evaluate the regulation of context dependent circuit reconfiguration and sensorimotor control. Our work has added to the complexity of a known parallel circuit, mediated by interneurons AVA and AIB, that integrates sensory cues and is responsible for the initiation of backwards locomotion. Our analysis of the galanin-like G-protein coupled receptor NPR-9 in C. elegans revealed that upregulation of galanin signaling impedes the integration of sensory evoked neuronal signals. Although the expression pattern of npr-9 is limited to AIB, upregulation of the receptor appears to impede AIB and AVA circuits to broadly prevent backwards locomotion, i.e. reversals, suggesting that these two pathways functionally interact. Galanin signaling similarly plays a broadly inhibitory role in mammalian models. Moreover, our identification of a mutant, which rarely initiates backwards movement, allowed us to interrogate locomotory mechanisms underlying chemotaxis. In support of the pirouette model of chemotaxis, organisms that did not exhibit reversal behavior were unable to navigate towards an attractant peak. We also assessed ionotropic glutamate receptor GLR-1 cell-specifically within AIB and determined that GLR-1 fine-tunes AIB activity to modify locomotion following reversal events. Our research highlights that signal integration underlying the initiation and fine-tuning of backwards locomotion is AIB and NPR-9 dependent, and has demonstrated the suitability of C. elegans for analysis of multisensory integration and sensorimotor control.

Multiple environmental cues are sensed by an organism in order to coordinate behavioral responses. Consequently, organisms must be able to simultaneously detect and integrate multiple external stimuli in order to appropriately modify their behavior. Identifying the unique circuits mediating the response to individual stimuli and points of overlap is essential to understanding how multiple signals can be integrated for a coordinated behavioral response. In order to analyze individual circuits, we have used the model organism C. elegans. We have identified that a C. elegans neuropeptide receptor (NPR-9) and a glutamate receptor (GLR-1) function in a single interneuron to play a broad regulatory role in multiple neural circuits. Our research has identified that interneuron AIB is involved in the integration of signals from numerous sensory neurons. Moreover, regulation of AIB via a neuropeptide receptor (NPR-9) and a glutamate receptor (GLR-1) coordinates AIB activity in the context of multisensory integration. Long-range chemotaxis behavior, in which an organism alters locomotory patterns based on odorant sensation, is also regulated by NPR-9. Our analysis indicates that reversals, and thus the pirouette model, are sufficient for chemotaxis.

Lack of Galanin 3 Receptor Aggravates Murine Autoimmune Arthritis

Neurogenic inflammation mediated by peptidergic sensory nerves has a crucial impact on the pathogenesis of various joint diseases. Galanin is a regulatory sensory neuropeptide, which has been shown to attenuate neurogenic inflammation, modulate neutrophil activation, and be involved in the development of adjuvant arthritis, but our current understanding about its targets and physiological importance is incomplete. Among the receptors of galanin (GAL₁–₃), GAL₃ has been found to be the most abundantly expressed in the vasculature and on the surface of some immune cells. However, since there are minimal in vivo data on the role of GAL₃ in joint diseases, we analyzed its involvement in different inflammatory mechanisms of the K/BxN serum transfer-model of autoimmune arthritis employing GAL₃ gene-deficient mice. After arthritis induction, GAL₃ knockouts demonstrated increased clinical disease severity and earlier hindlimb edema than wild types. Vascular hyperpermeability determined by in vivo fluorescence imaging was also elevated compared to the wild-type controls. However, neutrophil accumulation detected by in vivo luminescence imaging or arthritic mechanical hyperalgesia was not altered by the lack of the GAL₃ receptor. Our findings suggest that GAL₃ has anti-inflammatory properties in joints by inhibiting vascular hyperpermeability and consequent edema formation.

Botulinum toxin type A induces changes in the chemical coding of substance P-immunoreactive dorsal root ganglia sensory neurons supplying the porcine urinary bladder

Botulinum toxin (BTX) is a potent neurotoxin which blocks acetylcholine release from nerve terminals, and therefore leads to cessation of somatic motor and/or parasympathetic transmission. Recently it has been found that BTX also interferes with sensory transmission, thus, the present study was aimed at investigating the neurochemical characterization of substance P-immunoreactive (SP-IR) bladder-projecting sensory neurons (BPSN) after the toxin treatment. Investigated neurons were visualized with retrograde tracing method and their chemical profile was disclosed with double-labelling immunohistochemistry using antibodies against SP, calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase activating polypeptide (PACAP), neuronal nitric oxide synthase (nNOS), galanin (GAL), calbindin (CB), and somatostatin (SOM). In the control group (n = 6), 45% of the total population of BPSN were SP-IR. Nearly half of these neurons co-expressed PACAP or CGRP (45% and 35%, respectively), while co-localization of SP with GAL, nNOS, SOM or CB was found less frequently (3.7%, 1.8%, 1.2%, and 0.7%, respectively). In BTX-treated pigs (n = 6), toxin-injections caused a decrease in the number of SP-IR cells containing CGRP, SOM or CB (16.2%, 0.5%, and 0%, respectively) and a distinct increase in these nerve cells immunopositive to GAL (27.2%). The present study demonstrates that BTX significantly modifies the chemical phenotypes of SP-IR BPSN.

Antinociceptive effects induced by intra-lateral habenula complex injection of the galanin receptor 1 agonist M617 in rats

The present study was performed to explore the antinociceptive effects of the galanin receptor 1 agonist M617 in lateral habenula complex in rats. Intra-lateral habenula injection of 0.1, 0.5, 1 or 2 nmol of galanin induced dose-dependent increases in hindpaw withdrawal latencies (HWLs) to noxious thermal and mechanical stimulations in rats. Furthermore, intra-lateral habenula injection of 0.1, 0.5, 1 or 2 nmol of the galanin receptor 1 agonist M617 also induced dose-dependent increases in HWLs to noxious thermal and mechanical stimulations in rats. Interestingly, there were no significant differences between the antinociceptive effects induced by intra-lateral habenula injection of 2 nmol of M617 and 2 nmol of galanin. The results indicate that galanin receptor 1 may be involved in the galanin-induced antinociceptive effects in the lateral habenula.

Physiology, signaling, and pharmacology of galanin peptides and receptors: three decades of emerging diversity

Galanin was first identified 30 years ago as a "classic neuropeptide," with actions primarily as a modulator of neurotransmission in the brain and peripheral nervous system. Other structurally-related peptides-galanin-like peptide and alarin-with diverse biologic actions in brain and other tissues have since been identified, although, unlike galanin, their cognate receptors are currently unknown. Over the last two decades, in addition to many neuronal actions, a number of nonneuronal actions of galanin and other galanin family peptides have been described. These include actions associated with neural stem cells, nonneuronal cells in the brain such as glia, endocrine functions, effects on metabolism, energy homeostasis, and paracrine effects in bone. Substantial new data also indicate an emerging role for galanin in innate immunity, inflammation, and cancer. Galanin has been shown to regulate its numerous physiologic and pathophysiological processes through interactions with three G protein-coupled receptors, GAL1, GAL2, and GAL3, and signaling via multiple transduction pathways, including inhibition of cAMP/PKA (GAL1, GAL3) and stimulation of phospholipase C (GAL2). In this review, we emphasize the importance of novel galanin receptor-specific agonists and antagonists. Also, other approaches, including new transgenic mouse lines (such as a recently characterized GAL3 knockout mouse) represent, in combination with viral-based techniques, critical tools required to better evaluate galanin system physiology. These in turn will help identify potential targets of the galanin/galanin-receptor systems in a diverse range of human diseases, including pain, mood disorders, epilepsy, neurodegenerative conditions, diabetes, and cancer.

Novel therapeutic uses and formulations of botulinum neurotoxins: a patent review (2012 - 2014)

INTRODUCTION

Botulinum neurotoxins (BoNTs) are among the most toxic of known biological molecules and function as acetylcholine release inhibitors and neuromuscular blocking agents. Paradoxically, these properties also make them valuable therapeutic agents for the treatment of movement disorders, urological conditions and hypersecretory disorders. Greater understanding of their molecular mechanism of action and advances in protein engineering has led to significant efforts to improve and expand their function with a view towards broadening their therapeutic potential.

AREAS COVERED

Searches of Espacenet and Google Patent have revealed a number of patents related to BoNTs. This review will focus on novel therapeutic uses and formulations disclosed during 2012 - 2014. The seven patents discussed will include nanoformulations of FDA-approved BoNTs, additional BoNT subtypes and novel BoNT variants and chimeras created through protein engineering. Supporting patents and related publications are also briefly discussed.

EXPERT OPINION

The clinical and commercial success of BoNTs has prompted investigation into novel BoNTs or BoNT-mediated chimeras with promising in vitro results. Distinct strategies including the use of nanoformulations and targeted delivery have been implemented to identify new indication and improved functionality. Greater understanding of their systemic exposure, efficacy and safety profiles will be required for further development.

Involvements of galanin and its receptors in antinociception in nucleus accumbens of rats with inflammatory pain

This study tested the hypothesis that antinociceptive effects of galanin and its receptors in nucleus accumbens (NAc) of rats with inflammatory pain provoked by subcutaneous injection of 0.1 ml of 2% carrageenin into the sole of the rat's left hindpaw. The hindpaw withdrawal latencies (HWLs) in response to thermal and mechanical stimulation significantly decreased in bilateral hindpaws at 3 and 4 hour after a subcutaneous injection of carrageenin. However intra-NAc injection of 2 and 3 nmol, but not 1 nmol of galanin markedly induced an increase in the HWLs in a dose-dependent way. Western blot also showed, that the expression of galanin receptor 1 (GalR1) and galanin receptor 2 (GalR2) were significantly upregulated in NAc at 3 hour after a subcutaneous injection of carrageenin. In addition, the rats were intra-NAc injected galanin, 5 min later following by intra-NAc injection of galanin receptor antagonist galantide, the galanin-induce antinociceptive effects were suppressed by galantide. The results demonstrated that galanin and its receptors might be involved in antinociception in the NAc of rats with inflammatory pain.

A role of supraspinal galanin in behavioural hyperalgesia in the rat

INTRODUCTION

In chronic pain disorders, galanin (GAL) is able to either facilitate or inhibit nociception in the spinal cord but the contribution of supraspinal galanin to pain signalling is mostly unknown. The dorsomedial nucleus of the hypothalamus (DMH) is rich in galanin receptors (GALR) and is involved in behavioural hyperalgesia. In this study, we evaluated the contribution of supraspinal GAL to behavioural hyperalgesia in experimental monoarthritis.

METHODS

In Wistar-Han males with a four week kaolin/carrageenan-induced monoarthritis (ARTH), paw-withdrawal latency (PWL) was assessed before and after DMH administration of exogenous GAL, a non-specific GALR antagonist (M40), a specific GALR1 agonist (M617) and a specific GALR2 antagonist (M871). Additionally, the analysis of c-Fos expression after GAL injection in the DMH was used to investigate the potential involvement of brainstem pain control centres. Finally, electrophysiological recordings were performed to evaluate whether pronociceptive On- or antinociceptive Off-like cells in the rostral ventromedial medulla (RVM) relay the effect of GAL.

RESULTS

Exogenous GAL in the DMH decreased PWL in ARTH and SHAM animals, an effect that was mimicked by a GALR1 agonist (M617). In SHAM animals, an unselective GALR antagonist (M40) increased PWL, while a GALR2 antagonist (M871) decreased PWL. M40 or M871 failed to influence PWL in ARTH animals. Exogenous GAL increased c-Fos expression in the RVM and dorsal raphe nucleus (DRN), with effects being more prominent in SHAM than ARTH animals. Exogenous GAL failed to influence activity of RVM On- or Off-like cells of SHAM and ARTH animals.

CONCLUSIONS

Overall, exogenous GAL in the DMH had a pronociceptive effect that is mediated by GALR1 in healthy and arthritic animals and is associated with alterations of c-Fos expression in RVM and DRN that are serotonergic brainstem nuclei known to be involved in the regulation of pain.

Galanin promotes neuronal differentiation from neural progenitor cells in vitro and contributes to the generation of new olfactory neurons in the adult mouse brain

Galanin is a pleiotropic neuropeptide widely expressed in the nervous system. It plays a role in many diverse physiological functions - including nociception, cognition and metabolism regulation - and acts as neurotrophic/neuroprotective factor for several neuronal populations. In this article we sought to determine the role of galanin on neural stem cell function and its contribution to the plasticity of the nervous system. Here we show that galanin and its receptors are expressed in neural progenitor cells (NPCs) isolated from the developing striatum. Stimulation with galanin results in upregulation of Bcl-Xl, Bcl-2, Mash-1 and Olig-2 that are part of well known pro-survival/pro-neuronal signalling pathways. Accordingly, treatment with galanin increases the number of neurons upon differentiation from these progenitors. We then show that these effects are recapitulated in NPCs isolated from the adult subventricular zone (SVZ), where galanin increases the total number of neurons and the number of newly-generated neurons upon differentiation in vitro. The significance of these findings is highlighted in the adult brain where loss of galanin leads to a marked decrease in the rate of adult SVZ neurogenesis and a reduction in the number of newly generated cells in the olfactory bulb. Interestingly, Gal-KO mice display normal performances in simple tasks of olfactory detection and discrimination, which points to the existence of a certain degree of redundancy in SVZ neurogenesis. Our findings establish the role of galanin as a modulator of neural stem cell function and support the importance of galanin for brain plasticity and repair.

Development of a high-throughput screening-compatible cell-based functional assay to identify small molecule probes of the galanin 3 receptor (GalR3)

The galanin 3 receptor (GalR3) belongs to the large G protein-coupled receptor (GPCR) family of proteins. GalR3 and two other closely related receptors, GalR1 and GalR2, together with their endogenous ligand galanin, are involved in a variety of physiological and pathophysiological processes. GalR3 in particular has been strongly implicated in addiction and mood-related disorders such as anxiety and depression. It has been the target of many drug discovery programs within the pharmaceutical industry, but despite the significant resources and effort devoted to discovery of galanin receptor subtype selective small molecule modulators, there have been very few reports for the discovery of such molecules. GalR3 has proven difficult to enable in cell-based functional assays due to its apparent poor cell surface expression in recombinant systems. Here, we describe the generation of a modified GalR3 that facilitates its cell surface expression while maintaining wild-type receptor pharmacology. The modified GalR3 has been used to develop a high-throughput screening-compatible, cell-based, cAMP biosensor assay to detect selective small molecule modulators of GalR3. The performance of the assay has been validated by challenging it against a test library of small molecules with known pharmacological activities (LOPAC; Sigma Aldrich). This approach will enable identification of GalR3 selective modulators (chemical probes) that will facilitate dissection of the biological role(s) that GalR3 plays in normal physiological processes as well as in disease states.

Inhibitory role of the spinal galanin system in the control of micturition

OBJECTIVE

To investigate the effect of intrathecal galanin on the micturition reflex in rats.

METHODS

Continuous cystometrograms (0.04 mL/min infusion rate) were performed in female Sprague-Dawley rats (225-248 g) under urethane anesthesia. After stable micturition cycles were established, galanin was administered intrathecally to evaluate changes in bladder activity. Then, to examine the involvement of opioid systems in the galanin effects, galanin was administered intrathecally when the first bladder contraction was observed after intrathecal administration of naloxone, an opioid receptor antagonist.

RESULTS

Intrathecal administration of galanin (1-10 μg) increased intercontraction intervals in a dose-dependent fashion. Intrathecal administration of galanin (1-10 μg) also increased pressure threshold in a dose-dependent fashion. These inhibitory effects of galanin (10 μg) were partially antagonized by intrathecal administration of naloxone (10 μg).

CONCLUSION

These results indicate that in urethane-anesthetized rats, galanin delays the onset of micturition through activation of the opioid mechanism, suggesting the inhibitory role of galanin system in the control of the micturition reflex.

GalR3 activation promotes adult neural stem cell survival in response to a diabetic milieu

Type 2 diabetes impairs adult neurogenesis which could play a role in the CNS complications of this serious disease. The goal of this study was to determine the potential role of galanin in protecting adult neural stem cells (NSCs) from glucolipotoxicity and to analyze whether apoptosis and the unfolded protein response were involved in the galanin-mediated effect. We also studied the regulation of galanin and its receptor subtypes under diabetes in NSCs in vitro and in the subventricular zone (SVZ) in vivo. The viability of mouse SVZ-derived NSCs and the involvement of apoptosis (Bcl-2, cleaved caspase-3) and unfolded protein response [C/EBP homologous protein (CHOP) Glucose-regulated protein 78/immunoglobulin heavy-chain binding protein (GRP78/BiP), spliced X-box binding protein 1 (XBP1), c-Jun N-terminal kinases (JNK) phosphorylation] were assessed in the presence of glucolipotoxic conditions after 24 h. The effect of diabetes on the regulation of galanin and its receptor subtypes was assessed on NSCs in vitro and in SVZ tissues isolated from normal and type 2 diabetes ob/ob mice. We show increased NSC viability following galanin receptor (GalR)3 activation. This protective effect correlated with decreased apoptosis and CHOP levels. We also report how galanin and its receptors are regulated by diabetes in vitro and in vivo. This study shows GalR3-mediated neuroprotection, supporting a potential future therapeutic development, based on GalR3 activation, for the treatment of brain disorders.

Galanin gene expression and effects of its knock-down on the development of the nervous system in larval zebrafish

Despite the known importance of galanin in the nervous system of vertebrates, the galanin gene structure and expression and the consequences of galanin deficiency in developing zebrafish are unknown. We cloned the galanin gene and analyzed its expression by using in situ hybridization, PCR, and immunocytochemistry throughout the early development of zebrafish until the end of the first week of life. The single zebrafish galanin gene encoded for a single amidated galanin peptide and a galanin message-associated peptide. Two forms resulting from alternative processing were identified. Galanin mRNA was maternally expressed and found in developing fish throughout early development. In situ hybridization showed the first positive neurons in three groups in the brain at 28 hours postfertilization. At 2 days postfertilization, three prosencephalic neuron groups were seen in the preoptic area and in rostral and caudal periventricular hypothalamus. In addition, two other groups of weakly stained neurons were visible, one in the midbrain and another in the hindbrain. Translation inhibition of galanin mRNA with morpholino oligonucleotides caused complete disappearance of galanin immunoreactivity in the brain until 7 dpf and did not induce known cascades of nonspecific pathways or morphological abnormalities. A minor disturbance of sensory ganglia was found. Galanin knockdown did not alter the expression of tyrosine hydroxylases 1 and 2, choline acetyltransferase, histidine decarboxylase, or orexin mRNA. The results suggest that galanin does not regulate the development of these key markers of specific neurons, although galanin-expressing fibers were in a close spatial proximity to several neurons of these neuronal populations.

Tetrodotoxin induced changes in the chemical coding of dorsal root ganglion neurons supplying the porcine urinary bladder

Tetrodotoxin (TTX) mode of action is based on a blocking of fast sodium channels in nerve cell membrane what, in turn, abolishes the propagation of the action potential along the nerve fibers. TTX is currently used in experimental therapies focused on neoplastic or neurogenic pain, however, as for now there is no data concerning the influence of TTX on dorsal root ganglion (DRG) sensory neurons function. Thus, the present study was aimed at characterization of neurochemical coding of porcine sensory bladder-projecting cells after bladder instillation with TTX. Retrograde tracer Fast Blue (FB) was injected into the urinary bladder wall of six juvenile female pigs and three weeks later bladder instillation with TTX (12 microg per animal) was carried out in all animals. A week later, DRGs of interest were harvested from all animals and the neurochemical characterization of FB+ neurons was performed using routine double-immunofluorescence labeling technique on 10-microm-thick cryostat sections. In TTX-treated animals the number of FB+ cells containing galanin (GAL), nitric oxide synthase (NOS), somatostatin (SOM) and calbindin (CB) was 2.5%, 2%, 0.25% and 0.2%, respectively and that of pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive (IR) cells was 43%. These data when compared with previous reports, demonstrated that TTX profoundly changed the chemical coding of porcine bladder-projecting sensory neurons thus implicating that it may be used in case of hypoactivity of afferent part of reflex arc responsible for transmission of sensory information from the urinary bladder.

Antinociceptive effects induced by injection of the galanin receptor 1 agonist M617 into central nucleus of amygdala in rats

The present study was performed to explore the antinociceptive effects of M617, a selective galanin receptor 1 agonist, in the central nucleus of amygdala (CeA) of rats. Intra-CeA injection of 0.1 nmol, 0.5 nmol and 1 nmol of M617 induced dose-dependent increases in hindpaw withdrawal latencies (HWLs) to noxious thermal and mechanical stimulations in rats. Furthermore, rats received intra-CeA administration of M617 and galanin. The HWL to noxious thermal and mechanical stimulations increased markedly, and there were no significant differences in HWLs of rats received intra-CeA administration of M617 and galanin. The results demonstrated that intra-CeA injection of M617 induced significant antinociceptive effects in CeA of rats, indicating that galanin receptor 1 may be involved in M617-induced antinociception in the CeA of rats.