Inhibitory effects of galanin on evoked [Ca2+]i responses in cultured myenteric neurons

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.

High-fat diet impairs duodenal barrier function and elicits glia-dependent changes along the gut-brain axis that are required for anxiogenic and depressive-like behaviors

BACKGROUND

Mood and metabolic disorders are interrelated and may share common pathological processes. Autonomic neurons link the brain with the gastrointestinal tract and constitute a likely pathway for peripheral metabolic challenges to affect behaviors controlled by the brain. The activities of neurons along these pathways are regulated by glia, which exhibit phenotypic shifts in response to changes in their microenvironment. How glial changes might contribute to the behavioral effects of consuming a high-fat diet (HFD) is uncertain. Here, we tested the hypothesis that anxiogenic and depressive-like behaviors driven by consuming a HFD involve compromised duodenal barrier integrity and subsequent phenotypic changes to glia and neurons along the gut-brain axis.

METHODS

C57Bl/6 male mice were exposed to a standard diet or HFD for 20 weeks. Bodyweight was monitored weekly and correlated with mucosa histological damage and duodenal expression of tight junction proteins ZO-1 and occludin at 0, 6, and 20 weeks. The expression of GFAP, TLR-4, BDNF, and DCX were investigated in duodenal myenteric plexus, nodose ganglia, and dentate gyrus of the hippocampus at the same time points. Dendritic spine number was measured in cultured neurons isolated from duodenal myenteric plexuses and hippocampi at weeks 0, 6, and 20. Depressive and anxiety behaviors were also assessed by tail suspension, forced swimming, and open field tests.

RESULTS

HFD mice exhibited duodenal mucosa damage with marked infiltration of immune cells and decreased expression of ZO-1 and occludin that coincided with increasing body weight. Glial expression of GFAP and TLR4 increased in parallel in the duodenal myenteric plexuses, nodose ganglia, and hippocampus in a time-dependent manner. Glial changes were associated with a progressive decrease in BDNF, and DCX expression, fewer neuronal dendritic spines, and anxiogenic/depressive symptoms in HFD-treated mice. Fluorocitrate (FC), a glial metabolic poison, abolished these effects both in the enteric and central nervous systems and prevented behavioral alterations at week 20.

CONCLUSIONS

HFD impairs duodenal barrier integrity and produces behavioral changes consistent with depressive and anxiety phenotypes. HFD-driven changes in both peripheral and central nervous systems are glial-dependent, suggesting a potential glial role in the alteration of the gut-brain signaling that occurs during metabolic disorders and psychiatric co-morbidity.

Effect of Streptozotocin-Inducted Diabetes on the Pathophysiology of Enteric Neurons in the Small Intestine Based on the Porcine Diabetes Model

Hyperglycemia is one of the main causes of diabetes complications. Gastrointestinal (GI) disturbances are one of the most frequent complications during diabetes. The porcine digestive tract possesses physiological and pathological similarities to the human digestive tract. This also applies to the innervation of the gastrointestinal tract. In this study, the influence of experimentally-inducted hyperglycemia was examined on the expression of vesicular acetylcholine transporter (VAChT), cocaine- and amphetamine-regulated transcript (CART), galanin (GAL), vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP) in the enteric nervous system (ENS) neurons in the small intestine of the pig. During the current study, an increased number of neurons containing CART, VIP, GAL, and CGRP under streptozotocin injection were observed. The augmentation of expression included all enteric plexuses present in the small intestine. The same results were obtained in the case of VAChT; namely, chronic hyperglycemia led to an increase in the number of neurons utilizing VAChT in all investigated plexuses. The obtained results suggested that the function of neuropeptides studied in this experiment depended on their localization in the ENS structures, as well as part of the GI tract. Diabetes led to alterations in the neurochemical phenotype of small intestine enteric neurons.

Distribution and Neurochemistry of the Porcine Ileocaecal Valve Projecting Sensory Neurons in the Dorsal Root Ganglia and the Influence of Lipopolysaccharide from Different Serotypes of Salmonella spp. on the Chemical Coding of DRG Neurons in the Cell Cultures

The ileocecal valve (ICV)—a sphincter muscle between small and large intestine—plays important roles in the physiology of the gastrointestinal (GI) tract, but many aspects connected with the innervation of the ICV remain unknown. Thus, the aim of this study was to investigate the localization and neurochemical characterization of neurons located in the dorsal root ganglia and supplying the ICV of the domestic pig. The results have shown that such neurons mainly located in the dorsal root ganglia (DRG) of thoracic and lumbar neuromers show the presence of substance P (SP), calcitonin gene-related peptide (CGRP), and galanin (GAL). The second part of the experiment consisted of a study on the influence of a low dose of lipopolysaccharide (LPS) from Salmonella serotypes Enteritidis Minnesota and Typhimurium on DRG neurons. It has been shown that the LPS of these serotypes in studied doses does not change the number of DRG neurons in the cell cultures, but influences the immunoreactivity to SP and GAL. The observed changes in neurochemical characterization depend on the bacterial serotype. The results show that DRG neurons take part in the innervation of the ICV and may change their neurochemical characterization under the impact of LPS, which is probably connected with direct actions of this substance on the nervous tissue and/or its pro-inflammatory activity.

Cocaine- and amphetamine-regulated transcript (CART) peptide in the enteric nervous system of the porcine esophagus

Cocaine- and amphetamine-regulated transcript peptide (CART) is widely distributed within the central and peripheral nervous system. In the brain, CART is considered as the main anorectic peptide involved in the regulation of food intake. Contrary to the central nervous system, a lot of aspects connected with the distribution and functions of CART within the enteric nervous system (ENS) still remain unknown. The aim of the present study was to investigate, for the first time, the population of CART-like immunoreactive (CART-LI) neurons within the porcine esophagus and the denotation of their neurochemical coding. During this experiment, the distribution of CART-LI neurons and the colocalization of CART with other neuronal active substances were examined using standard double- and triple-immunofluorescence techniques in enteric plexuses of cervical, thoracic, and abdominal esophagus fragments. The obtained results showed that CART is present in a relatively high percentage of esophageal neurons (values fluctuated from 45.2±0.9% in the submucous plexus of the thoracic esophagus to 58.1±5.0% in the myenteric plexus of the same fragment of the esophagus). Moreover, CART colocalized with a wide range of other active neuronal substances, mainly with the vesicular acetylcholine transporter (VAChT, a marker of cholinergic neurons), neuronal isoform of nitric oxide synthase (nNOS, a marker of nitrergic neurons), vasoactive intestinal polypeptide (VIP) and galanin (GAL). The number of CART-positive neuronal cells and their neurochemical coding clearly depended on the fragment of esophagus studied and the type of enteric plexus. The obtained results suggest that CART may play important and multidirectional roles in the neuronal regulation of esophageal functions.

The effect of sildenafil on gastric motility and satiation in healthy controls

Sildenafil induces relaxation of smooth muscle cells by blocking PDE5. Dyspepsia is one of sildenafil's most frequently reported adverse events, suggesting its effect on gastric motility. Our aim was to study the effect of sildenafil on gastric accommodation (GA) and gastric emptying (GE) in healthy volunteers (HVs).

Methods

Sildenafil (50 mg) or placebo was randomly administered to 16 blinded HVs. After a manometry probe and an infusion catheter were positioned in the proximal stomach, the intragastric pressure (IGP) was measured before and during nutrient drink infusion (ND, 60 ml/min). HVs were asked to score their hunger, satiation and six epigastric symptoms at five-minute intervals. The experiment ended when the HVs scored maximal satiation during ND infusion at one-minute intervals. To assess GE, breath samples were collected every 15 minutes for six hours after the meal (244 kcal).

Results

ND infusion induced a drop in proximal stomach IGP, which was suppressed by sildenafil (average area under the curve for sildenafil: -33.6 ± 8.8 mmHg; placebo: -60.8 ± 11.3 mmHg, p = 0.005). Sildenafil-treated volunteers reached earlier maximal satiation compared to placebo (678 ± 70 ml vs. 836 ± 82.6 ml, p = 0.019). Finally, GE was significantly slower after sildenafil (90.6 ± 5.9 min vs. 76.6 ± 7.1 min, p = 0.04).

Conclusion

Sildenafil inhibits GA, leading to significantly decreased nutrient tolerance, and slightly delays the GE rate in humans.

Modulation of the main porcine enteric neuropeptides by a single low-dose of lipopolysaccharide (LPS) Salmonella Enteritidis

Background

The present research was conducted to investigate the influence of a low, single dose of LPS, which does not result in any clinical symptoms of intoxication on the expression of selected neuropeptides within the intestines of the domestic pig.

Methods

This experiment was conducted on immature female pigs of the Pitrain × Duroc breed (n = five per group). Seven days after the intravenous injection of 10 mL saline solution for control animals and 5 μg/kg b.w. (in 10 mL saline solution) LPS Salmonella Enteritidis for the experimental group, the excised segments of duodenum, jejunum, ileum, ileocecal valve, caecum, descending colon, transverse colon, ascending colon and rectum were prepared to extract the main enteric neuropeptides, including GAL, NPY, SOM, SP, VIP.

Results

The results of this research indicate that single low-dose LPS S. Enteritidis produced changes in the content of the selected neuropeptides of the porcine intestine. The most visible changes were observed in the transverse colon, where LPS induced the increase of GAL expression from 19.41 ± 7.121 to 92.92 ± 11.447 ng/g tissue.

Conclusion

The exact functions of the substances studied and mechanisms of responses to LPS action depend on the sections of the intestines. The mechanisms of observed changes are not fully understood, but fluctuations in neuronal active substance levels may be connected with neurodegenerative and/or pro-inflammatory activity of LPS.

Epithelial expression and function of trypsin-3 in irritable bowel syndrome

OBJECTIVES

Proteases are key mediators of pain and altered enteric neuronal signalling, although the types and sources of these important intestinal mediators are unknown. We hypothesised that intestinal epithelium is a major source of trypsin-like activity in patients with IBS and this activity signals to primary afferent and enteric nerves and induces visceral hypersensitivity.

DESIGN

Trypsin-like activity was determined in tissues from patients with IBS and in supernatants of Caco-2 cells stimulated or not. These supernatants were also applied to cultures of primary afferents. mRNA isoforms of trypsin (PRSS1, 2 and 3) were detected by reverse transcription-PCR, and trypsin-3 protein expression was studied by western blot analysis and immunohistochemistry. Electrophysiological recordings and Ca²⁺ imaging in response to trypsin-3 were performed in mouse primary afferent and in human submucosal neurons, respectively. Visceromotor response to colorectal distension was recorded in mice administered intracolonically with trypsin-3.

RESULTS

We showed that stimulated intestinal epithelial cells released trypsin-like activity specifically from the basolateral side. This activity was able to activate sensory neurons. In colons of patients with IBS, increased trypsin-like activity was associated with the epithelium. We identified that trypsin-3 was the only form of trypsin upregulated in stimulated intestinal epithelial cells and in tissues from patients with IBS. Trypsin-3 was able to signal to human submucosal enteric neurons and mouse sensory neurons, and to induce visceral hypersensitivity in vivo, all by a protease-activated receptor-2-dependent mechanism.

CONCLUSIONS

In IBS, the intestinal epithelium produces and releases the active protease trypsin-3, which is able to signal to enteric neurons and to induce visceral hypersensitivity.

The Influence of Gastric Antral Ulcerations on the Expression of Galanin and GalR1, GalR2, GalR3 Receptors in the Pylorus with Regard to Gastric Intrinsic Innervation of the Pyloric Sphincter

Gastric antrum ulcerations are common disorders occurring in humans and animals. Such localization of ulcers disturbs the gastric emptying process, which is precisely controlled by the pylorus. Galanin (Gal) and its receptors are commonly accepted to participate in the regulation of inflammatory processes and neuronal plasticity. Their role in the regulation of gastrointestinal motility is also widely described. However, there is lack of data considering antral ulcerations in relation to changes in the expression of Gal and GalR1, GalR2, GalR3 receptors in the pyloric wall tissue and galaninergic intramural innervation of the pylorus. Two groups of pigs were used in the study: healthy gilts and gilts with experimentally induced antral ulcers. By double immunocytochemistry percentages of myenteric and submucosal neurons expressing Gal-immunoreactivity were determined in the pyloric wall tissue and in the population of gastric descending neurons supplying the pyloric sphincter (labelled by retrograde Fast Blue neuronal tracer). The percentage of Gal-immunoreactive neurons increased only in the myenteric plexus of the pyloric wall (from 16.14±2.06% in control to 25.5±2.07% in experimental animals), while no significant differences in other neuronal populations were observed between animals of both groups. Real-Time PCR revealed the increased expression of mRNA encoding Gal and GalR1 receptor in the pyloric wall tissue of the experimental animals, while the expression(s) of GalR2 and GalR3 were not significantly changed. The results obtained suggest the involvement of Gal, GalR1 and galaninergic pyloric myenteric neurons in the response of pyloric wall structures to antral ulcerations.

Enteric neuromodulators and mucus discharge in a fish infected with the intestinal helminth Pomphorhynchus laevis

BACKGROUND

In vertebrates, the presence of enteric worms can induce structural changes to the alimentary canal impacting on the neuroendocrine system, altering the proper functioning of the gastrointestinal tract and affecting the occurrence and relative density of endocrine cells (ECs). This account represents the first immunohistochemistry and ultrastructure-based study which documents the intimate relationship between the intestinal mucous cells and ECs in a fish-helminth system, investigating the potential effects of enteric neuromodulators on gut mucus secretion/discharge.

METHODS

A modified dual immunohisto- and histochemical staining technique was applied on intestinal sections from both infected and uninfected fish. Sections were incubated in antisera to a range of neuromodulators (i.e. leu-enkephalin, met-enkephalin, galanin and serotonin) and the glycoconjugate histochemistry of the mucous cells was determined using a subsequent alcian blue - periodic acid Schiff staining step. Dual fluorescent staining on sections prepared for confocal laser scanning microscopy and transmission electron microscopy were also used to document the relationship between ECs and mucous cells.

RESULTS

From a total of 26 specimens of Squalius cephalus sampled from the River Paglia, 16 (i.e. 62 %) specimens were found to harbour an infection of the acanthocephalan Pomphorhynchus laevis (average intensity of infection 9.2 ± 0.8 parasites host(-1), mean ± standard error). When acanthocephalans were present, the numbers of mucous cells (most notably those containing acidic or mixed glycoconjugates) and ECs secreting leu-enkephalin, met-enkephalin, galanin, serotonin were significantly higher than those seen on sections from uninfected fish. The relationship between met-enkephalin-like or serotonin-like ECs and lectin DBA positive mucous cells was demonstrated through a dual fluorescent staining. The presence of tight connections and desmosomes between mucous and ECs in transmission electron micrographs provides further evidence of this intimate relationship.

CONCLUSIONS

The presence of P. laevis induces an increase in the number of enteric ECs that are immunoreactive to leu- and met-enkephalin, galanin, and serotonin anti-sera. The mucous cells hyperplasia and enhanced mucus secretion in the helminth-infected intestines could be elicited by the increase in the number of ECs which release these regulatory substances.

Enteroglial-derived S100B protein integrates bacteria-induced Toll-like receptor signalling in human enteric glial cells

OBJECTIVE

Enteric glial cells (EGC) have been suggested to participate in host-bacteria cross-talk, playing a protective role within the gut. The way EGC interact with microorganisms is still poorly understood. We aimed to evaluate whether: EGC participate in host-bacteria interaction; S100B and Toll-like receptor (TLR) signalling converge in a common pathway leading to nitric oxide (NO) production.

DESIGN

Primary cultures of human EGC were exposed to pathogenic (enteroinvasive Escherichia coli; EIEC) and probiotic (Lactobacillus paracasei F19) bacteria. Cell activation was assessed by evaluating the expression of cFos and major histocompatibility complex (MHC) class II molecules. TLR expression in EGC was evaluated at both baseline and after exposure to bacteria by real-time PCR, fluorescence microscopy and western blot analysis. S100B expression and NO release from EGC, following exposure to bacteria, were measured in the presence or absence of specific TLR and S100B pathway inhibitors.

RESULTS

EIEC activated EGC by inducing the expression of cFos and MHC II. EGC expressed TLR at baseline. Pathogens and probiotics differentially modulated TLR expression in EGC. Pathogens, but not probiotics, significantly induced S100B protein overexpression and NO release from EGC. Pretreatment with specific inhibitors of TLR and S100B pathways abolished bacterial-induced NO release from EGC.

CONCLUSIONS

Human EGC interact with bacteria and discriminate between pathogens and probiotics via a different TLR expression and NO production. In EGC, NO release is impaired in the presence of specific inhibitors of the TLR and S100B pathways, suggesting the presence of a novel common pathway involving both TLR stimulation and S100B protein upregulation.

Chemical coding of zinc-enriched neurons in the intramural ganglia of the porcine jejunum

Zinc ions in the synaptic vesicles of zinc-enriched neurons (ZEN) seem to have an important role in normal physiological and pathophysiological processes in target organ innervation. The factor directly responsible for the transport of zinc ions into synaptic vesicles is zinc transporter 3 (ZnT3), a member of the divalent cation zinc transporters and an excellent marker of ZEN neurons. As data concerning the existence of ZEN neurons in the small intestine is lacking, this study was designed to disclose the presence and neurochemical coding of such neurons in the porcine jejunum. Cryostat sections (10 mμ thick) of porcine jejunum were processed for routine double- and triple-immunofluorescence labeling for ZnT3 in various combinations with immunolabeling for other neurochemicals including pan-neuronal marker (PGP9.5), substance P (SP), somatostatin (SOM), vasoactive intestinal peptide (VIP), nitric oxide synthase (NOS), leu-enkephalin (LENK), vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), galanin (GAL), and calcitonin-gene related peptide (CGRP). Immunohistochemistry revealed that approximately 39%, 49%, and 45% of all PGP9.5- positive neurons in the jejunal myenteric (MP), outer submucous (OSP), and inner submucous (ISP) plexuses, respectively, were simultaneously ZnT3⁺. The majority of ZnT3⁺ neurons in all plexuses were also VAChT-positive. Both VAChT-positive and VAChT-negative ZnT3⁺ neurons co-expressed a variety of active substances with diverse patterns of co-localization depending on the plexus studied. In the MP, the largest populations among both VAChT-positive and VAChT-negative ZnT3⁺ neurons were NOS-positive cells. In the OSP and ISP, substantial subpopulations of ZnT3⁺ neurons were VAChT-positive cells co-expressing SOM and GAL, respectively. The broad-spectrum of active substances that co-localize with the ZnT3⁺ neurons in the porcine jejunum suggests that ZnT3 takes part in the regulation of various processes in the gut, both in normal physiological and during pathophysiological processes.

Neurochemical characterization of zinc transporter 3-like immunoreactive (ZnT3(+)) neurons in the intramural ganglia of the porcine duodenum

The SLC30 family of divalent cation transporters is thought to be involved in the transport of zinc in a variety of cellular pathways. Zinc transporter 3 (ZnT3) is involved in the transport of zinc into synaptic vesicles or intracellular organelles. As the presence of ZnT3 immunoreactive neurons has recently been reported in both the central and peripheral nervous systems of the rat, the present study was aimed at disclosing the presence of a zinc-enriched neuron enteric population in the porcine duodenum to establish a preliminary insight into their neurochemical coding. Double- and triple-immunofluorescence labeling of the porcine duodenum for ZnT3 with the pan-neuronal marker (PGP 9.5), substance P, somatostatin, vasoactive intestinal peptide (VIP), nitric oxide synthase (NOS), leu-enkephalin, vesicular acetylcholine transporter (VAChT), neuropeptide Y, galanin (GAL), and calcitonin gene-related peptide were performed. Immunohistochemistry revealed that approximately 35, 43, and 48 % of all PGP9.5-postive neurons in the myenteric (MP), outer submucous (OSP), and inner submucous (ISP) plexuses, respectively, of the porcine duodenum were simultaneously ZnT3⁺. In the present study, ZnT3⁺ neurons coexpressed a broad spectrum of active substances, but co-localization patterns unique to the plexus were studied. In the ISP, all ZnT3⁺ neurons were VAChT positive, and the largest populations among these cells formed ZnT3⁺/VAChT⁺/GAL⁺ and ZnT3⁺/VAChT⁺/VIP⁺ cells. In the OSP and MP, the numbers of ZnT3⁺/VAChT⁺ neurons were two times smaller, and substantial subpopulations of ZnT3⁺ neurons in both these plexuses formed ZnT3⁺/NOS⁺ cells. The large population of ZnT3⁺ neurons in the porcine duodenum and a broad spectrum of active substances which co-localize with this peptide suggest that ZnT3 takes part in the regulation of various processes in the gut both in normal physiology and during pathological processes.

Liuwei Dihuang decoction facilitates the induction of long-term potentiation (LTP) in senescence accelerated mouse/prone 8 (SAMP8) hippocampal slices by inhibiting voltage-dependent calcium channels (VDCCs) and promoting N-methyl-d-aspartate receptor (NMDA) receptors

ETHNOPHARMACOLOGICAL RELEVANCE

Liuwei Dihuang decoction (LW) is a typical traditional Chinese medicine (TCM) prescription and consists of six herbs including Rehmannia glutinosa Libosch. (family: Scrophulariaceae), Cornus officinalis Sieb. (family: Cornaceae), Dioscorea opposite Thunb. (family: Dioscoreaceae), Alisma orientale (G. Samuelsson) Juz (family: Alismataceae), Poria cocos (Schw.)Wolf (family: Polyporaceae) and Paeonia suffruticosa Andrews (family: Paeoniaceae). It has long been used clinically in treatment of many kinds of diseases with the sign of Yin insufficiency of kidney.

AIM OF THE STUDY

Our previous pharmacological studies demonstrated that LW possesses effect of ameliorating the decline of the learning and memory in senescence accelerated mouse/prone 8 (SAMP8), but the mechanism has not been well established. LW-containing serum (LWCS) is used in the current study to elucidate the possible mechanisms.

MATERIALS AND METHODS

6-month-old SAMP8 was used in this study to investigate the effect of LWCS on the induction of long-term potentiation (LTP). Primary cultured hippocampal neurons were used in this study to investigate the effects of LWCS on [Ca(2+)](i), I(Ca) and N-Methyl-d-aspartate (NMDA)-evoked currents. [Ca(2+)](i) was imaged using Fluo-3 and whole-cell patch recordings were applied to study the I(Ca) and NMDA-evoked currents.

RESULTS

We find that LWCS facilitates the induction of LTP in hippocampal slices of 6-month-old SAMP8. In primary cultured hippocampal neurons, LWCS increases intracellular [Ca(2+)](i), the I(Ca) is suppressed by LWCS, and NMDA-evoked currents are promoted.

CONCLUSION

These results indicate that LW improves the synaptic plasticity by inhibiting voltage-dependent calciumchannels (VDCCs) and promoting the function of NMDA receptors. This improvement might be one of the mechanisms contributing to cognitive improvement effect of LW.

Proinflammatory stimuli activates human-derived enteroglial cells and induces autocrine nitric oxide production

BACKGROUND

Enteric glial cells (EGCs) have been recently indicated as key regulators of intestinal inflammation in animals. Whether or not this is true and how these cells participate to inflammatory responses in humans is unknown.

METHODS

We isolated primary EGCs from human small bowel and then, we purified and characterized those using specific glial markers, such as S100B and glial fibrillary acidic protein (GFAP). To mimic an inflammatory scenario, we exposed EGCs to exogenous stimuli, such as lipopolysaccharide and interferon-gamma (LPS and IFN-γ), alone or in combination, to evaluate glial activation [measuring GFAP, S100B level together with c-fos, major histocompatibility complex (MHC) class II, inducible nitric oxide (iNOS) proteins expression and nitric oxide (NO) production] and proliferation, respectively.

KEY RESULTS

We showed that, when challenged with a combination of LPS and IFN-γ, EGCs are significantly activated, as indicated by their positivity to c-fos and MHC class II. Similarly, pro-inflammatory stimuli significantly increase the cell proliferation rate, the expression of both S100B and GFAP, and the NO production consequent to the induction of EGCs-derived iNOS protein, with the last being dependent on S100B-RAGE (receptor for advanced glycation endproducts) interaction.

CONCLUSIONS & INFERENCES

Our data provide the first evidence that human EGCs directly respond to pro-inflammatory stimuli by changing their expression profile and by proliferating. The finding that stimulated EGCs are able to produce NO points to a role of this cell population in the scenario of intestinal inflammation.

Inflammation- and axotomy-induced changes in galanin-like immunoreactive (GAL-LI) nerve structures in the porcine descending colon

This study reports on changes caused by chemically driven inflammation and axotomy in galanin-like immunoreactive (GAL-LI) nerve structures in the porcine descending colon. The distribution pattern of GAL-LI structures was studied using the immunofluorescence technique in the circular muscle layer, the myenteric (MP), outer submucous (OSP) and inner submucous plexuses (ISP), and also in the mucosal layer. Under physiological conditions GAL-LI perikarya were shown to constitute 3.68 +/- 0.32%, 7.02 +/- 0.93% and 10.99 +/- 0.71% in MP, OSP and ISP, respectively. Both colitis and axotomy caused an increase in GAL-like immunoreactivity, which was different in particular parts of the bowel segment studied. The numbers of GAL-LI perikarya increased to 14.16 +/- 0.49%, 16.78 +/- 1.09% and 37.46 +/- 1.18% during colitis and 7.92 +/- 0.72%, 10.44 +/- 0.71% and 16.20 +/- 0.96% after axotomy in MP, OSP and ISP, respectively. Both these processes caused an increase in the number of GAL-LI nerve fibres in the circular muscle and mucosal layers as well as the appearance of a population of GAL-LI cells in the mucosa.

Galanin inhibition of voltage-dependent Ca(2+) influx in rat cultured myenteric neurons is mediated by galanin receptor 1

Galanin activates three receptors, the galanin receptor 1 (GalR1), GalR2, and GalR3. In the gastrointestinal tract, GalR1 mediates the galanin inhibition of cholinergic transmission to the longitudinal muscle and reduction of peristalsis efficiency in the small intestine. Galanin has also been shown to inhibit depolarization-evoked Ca2+ increases in cultured myenteric neurons. Because GalR1 immunoreactivity is localized to cholinergic myenteric neurons, we hypothesized that this inhibitory action of galanin on myenteric neurons is mediated by GalR1. We investigated the effect of galanin 1-16, which has high affinity for GalR1 and GalR2, in the presence or absence of the selective GalR1 antagonist, RWJ-57408, and of galanin 2-11, which has high affinity for GalR2 and GalR3, on Ca2+ influx through voltage-dependent Ca2+ channels in cultured myenteric neurons. Myenteric neurons were loaded with fluo-4 and depolarized by high K+ concentration to activate voltage-dependent Ca2+ channels. Intracellular Ca2+ levels were quantified with confocal microscopy. Galanin 1-16 (0.01-1 microM) inhibited the depolarization-evoked Ca2+ increase in a dose-dependent manner with an EC(50) of 0.172 microM. The selective GalR1 antagonist, RWJ-57408 (10 microM), blocked the galanin 1-16 (1 microM)-mediated inhibition of voltage-dependent Ca2+ channel. By contrast, the GalR2/GalR3 agonist, galanin 2-11 did not affect the K+-evoked Ca2+ influx in myenteric neurons. GalR1 immunoreactivity was localized solely to myenteric neurons in culture, as previously observed in intact tissue. These findings indicate that the inhibition of depolarization-evoked Ca2+ influx in myenteric neurons in culture is mediated by GalR1 and confirm the presence of functional GalR1 in the myenteric plexus. This is consonant with the hypothesis that GalR1 mediates galanin inhibition of transmitter release from myenteric neurons.

Sensory-nerve-derived neuropeptides: possible therapeutic targets

This review examines our developing understanding of the families and activities of some of the best known sensory-nerve-derived inflammatory neuropeptides, namely substance P, calcitonin gene-related peptide and galanin. Evidence to date shows involvement of these transmitters in a wide range of systems that includes roles as inflammatory modulators. There is an increasing understanding of the mechanisms involved in the release of the peptides from sensory nerves and these are key in understanding the potential of neuropeptides in modulating inflammatory responses and may also provide novel targets for anti-inflammatory therapy. The neuropeptides released act via specific G protein coupled receptors, most of which have now been cloned. There is knowledge of selective agonists and antagonists for many subtypes within these families. The study of neuropeptides in animal models has additionally revealed pathophysiological roles that in turn have led to the development of new drugs, based on selective receptor antagonism.

Memory and learning impairment induced by dexamethasone in senescent but not young mice

In this study, the memory and learning impairment induced by dexamethasone in young mice and senescent mice were evaluated by step-down inhibitory avoidance task and passive avoidance test. Colorimetric MTT(tetrazole 3-(4,5-dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide) assay and TUNEL staining were used to investigate the influence of dexamethasone on hippocampal neuronal cell death with amyloid beta-protein. It was determined the effect of dexamethasone on intracellular calcium ([Ca(2+)](i)) with amyloid beta-protein 25-35 by fluorescence imaging with a confocal laser microscope using fluo-3 acetoxymethylester (AM) as a fluorescent dye. The effect of dexamethasone on amyloid beta-protein 25-35-induced nuclear factor kappaB (NF-kappaB) was analyzed by western blot. The results showed that twenty one days dexamethasone exposure resulted in an impairment of memory and learning in senescent but not young mice. Pretreatment of isolated hippocampal neurons with dexamethasone increased the vulnerability of the hippocampal neurons to amyloid beta-protein 25-35, enhanced [Ca(2+)](i) and down-regulated the increased level of nuclear NF-kappaB p65 proteins induced by amyloid beta-protein 25-35. These results demonstrated that glucocorticoids could potentiate the neurotoxic action of amyloid beta-protein by further increasing the level of [Ca(2+)](i) and down-regulating the level of nuclear NF-kappaB protein. Since amyloid beta-protein increases in the brain with aging, glucocorticoids potentiation of the neurotoxic action of amyloid beta-protein maybe one of the mechanisms responsible for glucocorticoids-induced memory and learning impairment in senescent but not young mice, which maybe relevance to the etiology of Alzheimer's disease.

Expression of galanin receptor messenger RNAs in different regions of the rat gastrointestinal tract

Galanin effects are mediated by three G-protein-coupled receptors: galanin receptor 1 (GalR1), GalR2 and GalR3. We quantified mRNA levels of GalR1, GalR2 and GalR3 in the rat stomach, small and large intestine using real-time RT-PCR. All three GalR mRNAs were detected throughout the gut at different levels. GalR1 and GalR2 mRNA levels were higher in the large than in the small intestine. GalR2 mRNA was most abundant in the stomach. GalR3 mRNA levels were generally quite low. The differential regional distribution of GalRs suggests that the complex effects of galanin in the gut are the result of activating multiple receptor subtypes, whose density, subtype and signaling vary along the gastrointestinal tract.