Gut Susceptibility to Viral Invasion: Contributing Roles of Diet, Microbiota and Enteric Nervous System to Mucosal Barrier Preservation.

The gastrointestinal lumen is a rich source of eukaryotic and prokaryotic viruses which, together with bacteria, fungi and other microorganisms comprise the gut microbiota. Pathogenic viruses inhabiting this niche have the potential to induce local as well as systemic complications; among them, the viral ability to disrupt the mucosal barrier is one mechanism associated with the promotion of diarrhea and tissue invasion. This review gathers recent evidence showing the contributing effects of diet, gut microbiota and the enteric nervous system to either support or impair the mucosal barrier in the context of viral attack.

Eosinophil-associated microinflammation in the gastroduodenal tract contributes to gastric hypersensitivity in a rat model of early-life adversity.

Gastric hypersensitivity is a major pathophysiological feature of functional dyspepsia (FD). Recent clinical studies have shown that a large number of patients with FD present with gastroduodenal microinflammation, which may be involved in the pathophysiology of FD. However, no animal model reflecting this clinical characteristic has been established. The underlying mechanism between microinflammation and FD remains unknown. In this study, using a maternal separation (MS)-induced FD model, we aimed to reproduce the gastroduodenal microinflammation and reveal the interaction between gastroduodenal microinflammation and gastric hypersensitivity. The MS model was established by separating newborn Sprague-Dawley rats for 2 h a day from postnatal day 1 to day 10. At 7-8 wk of age, electromyography was used to determine the visceromotor response to gastric distention (GD) and immunohistochemistry was performed to detect distension-associated neuronal activation as well as immunohistological changes. Our results demonstrated that MS-induced FD rats underwent gastric hypersensitivity with GD at 60 and 80 mmHg, which are related to increased p-ERK1/2 expression in the dorsal horn of T9-T10 spinal cords. Eosinophils, but not mast cells, were significantly increased in the gastroduodenal tract, and the coexpression rate of CD11b and major basic protein significantly increased in MS rats. Treatment with dexamethasone reversed gastric hypersensitivity in MS-induced FD rats by inhibiting eosinophil infiltration. These findings indicated that neonatal MS stress induces eosinophil-associated gastroduodenal microinflammation and gastric hypersensitivity in adulthood in rats. Microinflammation contributes to gastric hypersensitivity; therefore, anti-inflammatory therapy may be effective in treating patients with FD with gastroduodenal microinflammation.NEW & NOTEWORTHY We showed for the first time that neonatal MS stress-induced FD rats undergo gastroduodenal eosinophil-associated microinflammation in adulthood. Suppression of microinflammation attenuated gastric hypersensitivity in MS rats. These findings established a functional link between microinflammation and gastric hypersensitivity, which may provide a potential clue for the clinical treatment of FD.

Hydrogen sulfide in the nucleus tractus solitarii regulates gastric acid secretion in rats.

Hydrogen sulfide (H2S) is a neuromodulator in the central nervous system. The physiological function of H2S in the nucleus tractus solitarii (NTS) has rarely been reported. This research aimed to explore the role of H2S in regulating gastric functions. Wistar rats were randomly assigned to sodium hydrosulfide (NaHS; 4 and 8 nmol) groups, physiological saline (PS) group, capsazepine (10 pmol) + NaHS (4 nmol) group, L703606 (4 nmol) + NaHS (4 nmol) group, and pyrrolidine dithiocarbamate (4 nmol) + NaHS (4 nmol) group. The pH values of gastric acid were measured using a pH meter pre- and post-injection. It was found that the microinjetion of NaHS (4 and 8 nmol), an exogenous H2S donor, into the NTS (n = 6) remarkably decreased the pH values of gastric juice. The inductive effect of NaHS on gastric juice production could be suppressed by capsazepine (a transient receptor potential vanilloid 1 antagonist), L703606 (a NK1 receptor antagonist) and pyrrolidine dithiocarbamate (a nuclear fator-κB inhibitor). However, the same amount of PS did not induce any significant change in the pH value of gastric acid (P > 0.05). The findings of this study revealed that NaHS within the NTS remarkably promoted gastric acid secretion via the activation of TRPV1 channels and nuclear factor-κB-dependent mechanism in rats.

High fat diet induced obesity alters endocannabinoid and ghrelin mediated regulation of components of the endocannabinoid system in nodose ganglia.

BACKGROUND: Ghrelin and anandamide (AEA) can regulate the sensitivity of gastric vagal afferents to stretch, an effect mediated via the transient receptor potential vanilloid 1 (TPRV1) channel. High fat diet (HFD)-induced obesity alters the modulatory effects of ghrelin and AEA on gastric vagal afferent sensitivity. This may be a result of altered gastric levels of these hormones and subsequent changes in the expression of their receptors. Therefore, the current study aimed to determine the effects of ghrelin and AEA on vagal afferent cell body mRNA content of cannabinoid 1 receptor (CB1), ghrelin receptor (GHSR), TRPV1, and the enzyme responsible for the breakdown of AEA, fatty acid amide hydrolase (FAAH). METHODS: Mice were fed a standard laboratory diet (SLD) or HFD for 12wks. Nodose ganglia were removed and cultured for 14 h in the absence or presence of ghrelin or methAEA (mAEA; stable analogue of AEA). Relative mRNA content of CB1, GHSR, TRPV1, and FAAH were measured. RESULTS: In nodose cells from SLD-mice, mAEA increased TRPV1 and FAAH mRNA content, and decreased CB1 and GHSR mRNA content. Ghrelin decreased TRPV1, CB1, and GHSR mRNA content. In nodose cells from HFD-mice, mAEA had no effect on TRPV1 mRNA content, and increased CB1, GHSR, and FAAH mRNA content. Ghrelin decreased TRPV1 mRNA content and increased CB1 and GHSR mRNA content. CONCLUSIONS: AEA and ghrelin modulate receptors and breakdown enzymes involved in the mAEA-vagal afferent satiety signalling pathways. This was disrupted in HFD-mice, which may contribute to the altered vagal afferent signalling in obesity.

Proton Pump Inhibitors Prevent Gastric Antral Ulcers Induced by NSAIDs via Activation of Capsaicin-Sensitive Afferent Nerves in Mice.

BACKGROUND/AIMS: We examined the effects of proton pump inhibitors (PPIs) on gastric antral ulcers induced by non-steroidal anti-inflammatory drugs in re-fed mice and the role of capsaicin-sensitive afferent nerves (CSANs) in the protective effects of PPIs on the antral mucosa. METHODS: Male mice were administered indomethacin after 2 h of re-feeding of diet after a 24-h fast, and gastric lesions were examined 24 h after indomethacin dosing. The effects of PPIs (lansoprazole and omeprazole), histamine H2-receptor antagonists (H2-RAs, famotidine, ranitidine), capsaicin and misoprostol on the formation of antral ulcers induced by indomethacin were examined. Functional ablation of CSANs was caused by pretreatment of mice with a high dose of capsaicin. RESULTS: Indomethacin produced lesions selectively in the gastric antrum in re-fed conditions. Formation of antral ulcers was not affected by H2-RAs, but inhibited by PPIs, capsaicin and misoprostol. The anti-ulcer effect of lansoprazole was 30 times stronger than that of omeprazole. Antral ulcers induced by indomethacin were markedly aggravated in mice with ablated CSANs. The effects of PPIs and capsaicin on ulcer formation were inhibited by ablation of CSANs, pretreatment with a capsaicin receptor antagonist (capsazepine/ruthenium red) and an inhibitor of nitric oxide synthesis (L-NAME). However, the inhibitory effect of misoprostol was not prevented by the ablation of CSANs or drugs. CONCLUSIONS: The results suggested that CSANs play an important role in protection of the antral mucosa and that both lansoprazole and omeprazole are capable of preventing NSAID-induced antral ulcers by activating CSANs.

The ventral peptidergic system of the adult ascidian Ciona robusta (Ciona intestinalis Type A) insights from a transgenic animal model.

Ascidians are the sister group of vertebrates and occupy a critical position in explorations of the evolution of the endocrine and nervous systems of chordates. Here, we describe the complete ventral peptidergic system in adult transgenic Ciona robusta (Ciona intestinalis Type A) which expresses the Kaede reporter gene driven by the prohormone convertase 2 (PC2) gene promoter. Numerous PC2 promoter-driven fluorescent (Kaede-positive) non-neural cells were distributed in the blood sinus located at the anterior end of the pharynx, suggesting the acquisition of a peptidergic circulatory system in Ciona. Kaede-positive ciliated columnar cells, rounded cells, and tall ciliated cells were observed in the alimentary organs, including the endostyle, pharynx, esophagus, stomach, and intestine, suggesting that digestive functions are regulated by multiple peptidergic systems. In the heart, Kaede-positive neurons were located in the ring-shaped plexus at both ends of the myocardium. Nerve fiber-like tracts ran along the raphe and appeared to be connected with the plexuses. Such unique structures suggest a role for the peptidergic system in cardiac function. Collectively, the present anatomic analysis revealed the major framework of the ventral peptidergic system of adult Ciona, which could facilitate investigations of peptidergic regulation of the pharynx, endostyle, alimentary tissues, and heart.

Stress-induced modulation of vagal afferents.

Vagally dependent gastric functions, including motility, tone, compliance, and emptying rate, play an important role in the regulation of food intake and satiation. Vagal afferent fibers relay sensory information from the stomach, including meal-related information, centrally and initiate co-ordinated autonomic efferent responses that regulate upper gastrointestinal responses. The purpose of this mini-review is to highlight several recent studies which have uncovered the remarkable degree of neuroplasticity within gastric mechanosensitive vagal afferents and the recent study by Li et al, in this issue of Neurogastroenterology and Motility, who show that the mechanosensitivity of gastric vagal afferents is dysregulated in a murine model of chronic stress. The authors demonstrate that both gastric mucosal and tension afferents are hypersensitive following chronic stress, and responses to mucosal stroking and muscle stretch are enhanced significantly. As gastric distension and volumetric signaling is important in satiety signaling and meal termination, this may provide a mechanistic basis for the gastric hypersensitivity associated with stress-associated clinical problems such as functional dyspepsia.

Disruption of the light cycle ablates diurnal rhythms in gastric vagal afferent mechanosensitivity.

BACKGROUND: Gastric vagal afferents (GVAs) respond to mechanical stimulation, initiating satiety. These afferents exhibit diurnal fluctuations in mechanosensitivity, facilitating food intake during the dark phase in rodents. In humans, desynchrony of diurnal rhythms (eg, shift work) is associated with a higher risk of obesity. To test the hypothesis that shift work disrupts satiety signaling, the effect of a rotating light cycles on diurnal rhythms in GVA mechanosensitivity in lean and high-fat diet (HDF)-induced obese mice was determined. METHODS: Male C57BL/6 mice were fed standard laboratory diet (SLD) or HFD for 12 weeks. After 4 weeks, mice were randomly allocated to a normal light (NL; 12 hour light: 12 hour dark; lights on at zeitgeber time [ZT] 0) or rotating light (RL; 3-day NL cycle, 4-day reversed light cycle [lights on: ZT12] repeated) cycle for 8 weeks. At week 12, eight mice from each group were housed in metabolic cages. After 12 weeks, ex vivo GVA recordings were taken at 3 hour intervals starting at ZT0. KEY RESULTS: SLD-RL and HFD-RL gained more weight compared to SLD-NL and HFD-NL mice, respectively. Gonadal fat pad mass was higher in SLD-RL compared to SLD-NL mice. In SLD-NL mice, tension and mucosal receptor mechanosensitivity exhibited diurnal rhythms with a peak at ZT9. These rhythms were lost in SLD-RL, HFD-NL, and HFD-RL mice and associated with dampened diurnal rhythms in food intake. CONCLUSIONS & INFERENCES: GVA diurnal rhythms are susceptible to disturbances in the light cycle and/or the obese state. This may underpin the observed changes in feeding behavior.

Distributions and relationships of chemically defined enteroendocrine cells in the rat gastric mucosa.

This paper provides quantitative data on the distributions of enteroendocrine cells (EEC), defined by the hormones they contain, patterns of colocalisation between hormones and EEC relations to nerve fibres in the rat gastric mucosa. The rat stomach has three mucosal types: non-glandular stratified squamous epithelium of the fundus and esophageal groove, a region of oxyntic glands in the corpus, and pyloric glands of the antrum and pylorus. Ghrelin and histamine were both contained in closed cells, not contacting the lumen, and were most numerous in the corpus. Gastrin cells were confined to the antrum, and 5-hydroxytryptamine (5-HT) and somatostatin cells were more frequent in the antrum than the corpus. Most somatostatin cells had basal processes that in the antrum commonly contacted gastrin cells. Peptide YY (PYY) cells were rare and mainly in the antrum. The only numerous colocalisations were 5-HT and histamine, PYY and gastrin and gastrin and histamine in the antrum, but each of these populations was small. Peptide-containing nerve fibres were found in the mucosa. One of the most common types was vasoactive intestinal peptide (VIP) fibres. High-resolution analysis showed that ghrelin cells were closely and selectively approached by VIP fibres. In contrast, gastrin cells were not selectively innervated by VIP or CGRP fibres. The study indicates that there are distinct populations of gastric EEC and selective innervation of ghrelin cells. It also shows that, in contrast to EEC of the small intestine, the majority of EEC within the stomach contained only a single hormone.

Effect of TRPV1 on Activity of Isoforms of Constitutive Nitric Oxide Synthase during Regulation of Bicarbonate Secretion in the Stomach.

Application of mild irritants (1 M NaCl; pH 2.0) on the gastric mucosa potentiates the protective secretion of bicarbonates by epithelial cells. This response is mainly mediated by capsaicin-sensitive afferent nerve endings located in the submucosa. It was shown that activation of vanilloid type 1 receptors (TRPV1) induced by exogenous acidification of GM is not sufficient to potentiate the production of HCO3, including production depending on neuronal NO synthase. However, the effect of exogenous acid on TRPV1 leads to activation of endothelial NO synthase that restrict the gastric secretion of [Formula: see text].

[Gastrointestinal Spice Sensors and Their Functions].

Capsaicin is a constituent of chili pepper, and induces the burning sensation on the tongue. The site of action for capsaicin has been discovered as transient receptor potential vanilloid receptor subtype 1 (TRPV1) that resides on the membranes of pain- and heat-sensing primary afferent nerves. The immunohistochemical study on the stomach revealed that nerve fibers expressing TRPV1 exist along gastric glands in the mucosa, around blood vessels in the submucosa, in the myenteric plexus, and in the smooth muscle layers. High numbers of TRPV1-immunoreactive axons were observed in the rectum and distal colon. Therefore, capsaicin stimulates TRPV1 not only on the tongue but also in the gut. In this review, the mechanism of gastrointestinal mucosal defense enhanced by capsaicin was summarized. TRPV1 plays a protective role in gastrointestinal mucosal defensive mechanism. Hypersensitivity of afferent fibers occurs during gastrointestinal inflammation. Abnormalities of primary afferent nerve fibers are strongly associated with the visceral hypersensitive state in inflammatory bowel disease (IBD). The alteration of TRPV1 channels in mucosa contributes to the visceral hypersensitivity in colitis model mice. TRPV1-expressing neurons in the gut are thought to be extrinsic sensory afferent neurons that operate to maintain gastrointestinal functions under physiological and inflammatory states.

Impaired Gastric Myoelectrical Reactivity in Children and Adolescents with Obesity Compared to Normal-Weight Controls.

Obesity often has its onset in childhood and can be accompanied by various comorbidities such as functional gastrointestinal disorders and altered gastric myoelectrical activity (GMA). This study investigates whether obesity in childhood and adolescence is already associated with altered GMA, and whether an inpatient weight loss program affects GMA. Sixty children with obesity (OBE) and 27 normal-weight children (NW) (12.9 ± 1.7 years; 51% female) were compared for their GMA at rest, after a stress test, and after a drink-to-full water load test. A continuous electrogastrogram (EGG) was recorded and analyzed with respect to gastric slow waves and tachygastric activity. OBE were examined upon admission (T1) and before discharge (T2) following an inpatient weight loss program; NW served as control group. Compared to NW, children with obesity showed flattened GMA as indicated by lower tachygastric reactivity after stress and water load test at T1. Data of OBE did not differ between T1 and T2. EGG parameters were associated neither with sex, age, and BMI nor with subjective stress and food intake. Children with obesity show impaired gastric myoelectrical reactivity in response to a stress and water load test compared to normal-weight controls, which does not change during an inpatient weight loss program.

Galaninergic intramural nerve and tissue reaction to antral ulcerations.

BACKGROUND: Well-developed galaninergic gastric intramural nerve system is known to regulate multiple stomach functions in physiological and pathological conditions. Stomach ulcer, a disorder commonly occurring in humans and animals, is accompanied by inflammatory reaction. Inflammation can cause intramural neurons to change their neurochemical profile. Galanin and its receptors are involved in inflammation of many organs, however, their direct participation in stomach reaction to ulcer is not known. Therefore, the aim of the study was to investigate adaptive changes in the chemical coding of galaninergic intramural neurons and mRNA expression encoding Gal, GalR1, GalR2, GalR3 receptors in the region of the porcine stomach directly adjacent to the ulcer location. METHODS: The experiment was performed on 24 pigs, divided into control and experimental groups. In 12 experimental animals, stomach antrum ulcers were experimentally induced by submucosal injection of acetic acid solution. Stomach wall directly adjacent to the ulcer was examined by: (1) double immunohistochemistry-to verify the changes in the number of galaninergic neurons (submucosal, myenteric) and fibers; (2) real-time PCR to verify changes in mRNA expression encoding galanin, GalR1, GalR2, GalR3 receptors. KEY RESULTS: In the experimental animals, the number of Gal-immunoreactive submucosal perikarya was increased, while the number of galaninergic myenteric neurons and fibers (in all the stomach wall layers) remained unchanged. The expression of mRNA encoding all galanin receptors was increased. CONCLUSIONS & INTERFERENCES: The results obtained unveiled the participation of galanin and galanin receptors in the stomach tissue response to antral ulcerations.

The Impact of T-2 Toxin on Vasoactive Intestinal Polypeptide-Like Immunoreactive (VIP-LI) Nerve Structures in the Wall of the Porcine Stomach and Duodenum.

T-2 toxin is a secondary metabolite of some Fusarium species. It is well-known that this substance can harmfully impact living organisms. Among others, thanks to the ability of crossing the blood-brain barrier, T-2 toxin can affect the central nervous system. Mycotoxins mostly get into the organism through the digestive tract; therefore, first of all they have to break the intestinal barrier, wherein the important component is the enteric nervous system (ENS). However, knowledge about the impact of T-2 toxin on the ENS is rather scant. As a result of the influence of various physiological and pathological agents, ENS can undergo adaptive and reparative processes which manifest as changes in the immunoreactivity of perikaryons for neuronal active substances. So, the aim of the present investigation was to study how low doses of T-2 toxin affect vasoactive intestinal polypeptide-like immunoreactive (VIP-LI) nervous structures in the ENS of the porcine stomach and duodenum. Obtained results have shown that T-2 toxin causes an percentage increase of VIP-LI nerve cells and nerve fibers in every enteric plexus in both fragments of gastrointestinal tract studied. This shows that even low doses of T-2 toxin can have an influence on living organisms.

Transient Receptor Potential Ankyrin 1 and Substance P Mediate the Development of Gastric Mucosal Lesions in a Water Immersion Restraint Stress Rat Model.

BACKGROUND: Activation of substance P (SP) contributes to the development and maintenance of gastric lesions, but the mechanisms underlying the release of SP and SP-mediated damage to the gastric mucosa remain unknown. Transient receptor potential ankyrin 1 (TRPA1) is expressed in SP-positive neurons in the dorsal root ganglion (DRG) and stomach of rats. We hypothesized that water immersion restraint stress (WIRS) may activate and sensitize TRPA1 in DRG neurons, subsequently inducing the release of SP from DRG and stomach cells, causing the development of acute gastric mucosal lesions (AGML). METHODS: Changes in TRPA1 and SP expression in T8-11 DRG sensory neurons and the stomach in an AGML rat model were determined by reverse transcription polymerase chain reaction, western blotting and immunohistochemistry. The SP levels of serum and gastric mucosa were measured by using an enzyme-linked immunosorbent assay (ELISA). Gastric lesions were evaluated by histopathological changes. The TRPA1 antagonist HC-030031 and TRPA1 agonists allyl isothiocyanate were used to verify effect of TRPA1 and SP on AGML. RESULTS: SP and TRPA1 in the DRG and stomach were upregulated, and the serum and gastric mucosa levels of SP were increased after WIRS, which are closely associated with AGML. The release of SP was suppressed and AGML were alleviated following a selective TRPA1 antagonist HC-030031. TRPA1 agonists AITC increased release of SP and led to moderate gastric lesions. We confirmed that WIRS induced the release of SP in the DRG, stomach, serum and gastric mucosa, and in a TRPA1-dependent manner. CONCLUSIONS: Upregulated SP and TRPA1 in the DRG and stomach and increased serum and gastric mucosa SP levels may contribute to stress-induced AGML. TRPA1 is a potential drug target to reduce stress-induced AGML development in patients with acute critical illnesses. This study may contribute to the discovery of drugs for AGML treatment.

Luminal chemosensing in the gastroduodenal mucosa.

PURPOSE OF REVIEW: We report recently published knowledge regarding gut chemosensory mechanisms focusing on nutrient-sensing G protein-coupled receptors (GPCRs) expressed on gut enteroendocrine cells (EECs), tuft cells, and in afferent nerves in the gastroduodenal mucosa and submucosa. RECENT FINDINGS: Gene profiling of EECs and tuft cells have revealed expression of a variety of nutrient-sensing GPCRs. The density of EEC and tuft cells is altered by luminal environmental changes that may occur following bypass surgery or in the presence of mucosal inflammation. Some EECs and tuft cells are directly linked to sensory nerves in the subepithelial space. Vagal afferent neurons that innervate the intestinal villi express nutrient receptors, contributing to the regulation of duodenal anion secretion in response to luminal nutrients. Nutrients are also absorbed via specific epithelial transporters. SUMMARY: Gastric and duodenal epithelial cells are continually exposed to submolar concentrations of nutrients that activate GPCRs expressed on EECs, tuft cells, and submucosal afferent nerves and are also absorbed through specific transporters, regulating epithelial cell proliferation, gastrointestinal physiological function, and metabolism. The chemical coding and distribution of EECs and tuft cells are keys to the development of GPCR-targeted therapies.

Of nerves and stomach cancer.

Blocking a feed-forward cholinergic loop between gastric neurons and the mucosal epithelium may inhibit proliferation in tumor-associated stem cells.

Nerve Growth Factor Promotes Gastric Tumorigenesis through Aberrant Cholinergic Signaling.

Within the gastrointestinal stem cell niche, nerves help to regulate both normal and neoplastic stem cell dynamics. Here, we reveal the mechanisms underlying the cancer-nerve partnership. We find that Dclk1+ tuft cells and nerves are the main sources of acetylcholine (ACh) within the gastric mucosa. Cholinergic stimulation of the gastric epithelium induced nerve growth factor (NGF) expression, and in turn NGF overexpression within gastric epithelium expanded enteric nerves and promoted carcinogenesis. Ablation of Dclk1+ cells or blockade of NGF/Trk signaling inhibited epithelial proliferation and tumorigenesis in an ACh muscarinic receptor-3 (M3R)-dependent manner, in part through suppression of yes-associated protein (YAP) function. This feedforward ACh-NGF axis activates the gastric cancer niche and offers a compelling target for tumor treatment and prevention.

Role of sensory afferent nerves, lipid peroxidation and antioxidative enzymes in the carbon monoxide-induced gastroprotection against stress ulcerogenesis.

Carbon monoxide (CO) is a physiological gaseous mediator recently implicated in the mechanism of gastric mucosal defense due to its vasodilatory and antioxidative properties. Small quantities of endogenous CO are produced during heme degradation by heme oxygenase (HO-1), however, the involvement of the capsaicin-sensitive afferent neurons releasing calcitonin gene related peptide (CGRP) and anti-oxidative factors and mechanisms in the CO-induced gastroprotection against stress ulcerogenesis has been little studied. We investigated the possible role of CO released from the CO donor, tricarbonyldichlororuthenium (II) dimer (CORM-2) in the protection against water immersion and restraint stress (WRS)-induced lesions in rats with intact sensory nerves and those with capsaicin denervation and the accompanying changes in malondialdehyde (MDA) content considered as an index of lipid peroxidation, the activity of GSH and SOD-2 and gastric mucosal expression of antioxidative enzymes glutathione peroxidase (GPx) and SOD-2. Wistar rats with intact sensory nerves or those with capsaicin administered in total dose of 125 mg/kg s.c. within 3 days (capsaicin denervation) were pretreated either with 1) vehicle (saline) or 2) CORM-2 (0.1 - 0 mg/kg i.g.) with or without exogenous CGRP (10 µg/kg i.p.) and 30 min later exposed to 3.5 h of WRS. At the termination of WRS, the number of gastric lesions was counted and gastric blood flow (GBF) was assessed by H2-gas clearance technique. The mucosal content of MDA and reduced glutathione (GSH) and the activity of SOD-2 were determined and the expression of GPx-1 and SOD-2 mRNA in the gastric mucosa was analyzed by real-time PCR. The exposure of rats to 3.5 h of WRS resulted in numerous hemorrhagic gastric lesions and significantly decreased the GBF, raised MDA content and significantly decreased the mucosal SOD and GSH contents compared with intact gastric mucosa and these changes were exacerbated in rats with capsaicin denervation. Pretreatment with CORM-2 (1 mg/kg i.g.) which in our previous studies significantly reduced the ethanol and aspirin-induced gastric damage, significantly decreased the number of WRS-induced gastric lesions while raising the GBF and significantly increasing the activity of SOD and GSH (P < 0.05). The pretreatment with CORM-2 significantly decreased MDA content as compared with vehicle-pretreated rats exposed to WRS (P < 0.05). The reduction of WRS damage and the accompanying increase in the GBF as well as the significant decrease in MDA content and the increase in GSH content and SOD activity induced by CORM-2 (1 µg/kg i.g.) were all significantly altered in rats with capsaicin denervation (P < 0.05). The concurrent treatment of CORM-2 with exogenous CGRP in rats with or without sensory nerves tended to decrease the number of WRS lesions as compared with CORM-2 alone pretreated animals and significantly increased the GBF over the values measured in gastric mucosa of CORM-2 alone pretreated rats with or without capsaicin denervation. Such combined administration of CORM-2 and CGRP in rats with capsaicin denervation significantly inhibited an increase in MDA and 4-HNE content and evoked a significant increase in the GSH concentration (P < 0.05) remaining without significant effect on the increase in SOD activity observed with CORM-2 alone. The gastric mucosal expression of SOD-2- and GPx-1 mRNA was significantly increased as compared with those in intact gastric mucosa (P < 0.05). The pretreatment with CORM-2 applied with or without CGRP failed to significantly alter the mRNA expression for SOD-2 and GPx in the gastric mucosa of rats exposed to WRS. Both, the expression of SOD-2- and GPx-1 mRNA was significantly increased in capsaicin denervated rats exposed to WRS rats (P < 0.05) and this effect was abolished by the pretreatment with CORM-2. The expression of SOD-2 tended to decrease, though insignificantly, in rats pretreated with the combination of CORM-2 and CGRP as compared with that detected in CORM-2 alone in rats with capsaicin denervation. In contrast, the mRNA expression of GPx-1 was significantly decreased in gastric mucosa of capsaicin-denervated rats treated with the combination of CORM-2 and CGRP as compared with CORM-2 alone pretreated animals. We conclude that 1) CORM-2 releasing CO exerts gastroprotective activity against stress ulcerogenesis and this effect depends upon an increase in the gastric microcirculation and the vasodilatory activity of this gaseous mediator, and 2) the sensory nerve endings releasing CGRP can contribute, at least in part, to the CO-induced gastric hyperemia, the attenuation of gastric mucosal lipid peroxidation and prevention of oxidative stress as indicated by the CORM-2-induced normalization of the antioxidative enzyme expression enhanced in gastric mucosa of capsaicin-denervated rats.

Neurochemical Plasticity of the Coeliac-Superior Mesenteric Ganglion Complex Neurons Projecting to the Prepyloric Area of the Porcine Stomach following Hyperacidity.

This study was designed to determine neurochemical properties of the coeliac-superior mesenteric ganglion (CSMG) neurons supplying the prepyloric area of the porcine stomach in physiological state and following experimentally induced hyperacidity. To localize sympathetic neurons innervating the studied area of stomach, the neuronal retrograde tracer Fast Blue (FB) was applied to control animals and hydrochloric acid infusion (HCl) groups. After 23 days, animals of the HCl group were reintroduced into a state of general anesthesia and intragastrically given 5 mL/kg of body weight of 0.25 M aqueous solution of hydrochloric acid. On the 28th day, all animals were sacrificed. The CSMG complexes were then collected and processed for double-labeling immunofluorescence. In the control animals, FB-positive perikarya displayed immunoreactivity to tyrosine hydroxylase (TH), dopamine ß-hydroxylase (DßH), neuropeptide Y (NPY), and galanin (GAL). Experimentally induced gastric hyperacidity changed the neurochemical phenotype of the studied neurons. An upregulated expression of GAL and NPY and the de novo synthesis of neuronal nitric oxide synthase (nNOS) and leu5-enkephalin (LENK) as well as downregulated expression of TH and DßH in the stomach-projecting neurons were observed. These findings enrich existing knowledge about the participation of these active substances in adaptive mechanism(s) of the sympathetic neurons during pathological processes within the gastrointestinal tract.