Role of calcitonin gene-related peptide and nitric oxide in the gastroprotective effect of capsaicin in the rat

ELP1, the Gene Mutated in Familial Dysautonomia, Is Required for Normal Enteric Nervous System Development and Maintenance and for Gut Epithelium Homeostasis

Familial dysautonomia (FD) is a rare sensory and autonomic neuropathy that results from a mutation in the ELP1 gene. Virtually all patients report gastrointestinal (GI) dysfunction and we have recently shown that FD patients have a dysbiotic gut microbiome and altered metabolome. These findings were recapitulated in an FD mouse model and moreover, the FD mice had reduced intestinal motility, as did patients. To understand the cellular basis for impaired GI function in FD, the enteric nervous system (ENS; both female and male mice) from FD mouse models was analyzed during embryonic development and adulthood. We show here that not only is Elp1 required for the normal formation of the ENS, but it is also required in adulthood for the regulation of both neuronal and non-neuronal cells and for target innervation in both the mucosa and in intestinal smooth muscle. In particular, CGRP innervation was significantly reduced as was the number of dopaminergic neurons. Examination of an FD patient's gastric biopsy also revealed reduced and disoriented axons in the mucosa. Finally, using an FD mouse model in which Elp1 was deleted exclusively from neurons, we found significant changes to the colon epithelium including reduced E-cadherin expression, perturbed mucus layer organization, and infiltration of bacteria into the mucosa. The fact that deletion of Elp1 exclusively in neurons is sufficient to alter the intestinal epithelium and perturb the intestinal epithelial barrier highlights a critical role for neurons in regulating GI epithelium homeostasis.

Electrical neuromodulation therapy for inflammatory bowel disease

Inflammatory bowel disease (IBD) is an inflammatory disease of the gastrointestinal (GI) tract. It has financial and quality of life impact on patients. Although there has been a significant advancement in treatments, a considerable number of patients do not respond to it or have severe side effects. Therapeutic approaches such as electrical neuromodulation are being investigated to provide alternate options. Although bioelectric neuromodulation technology has evolved significantly in the last decade, sacral nerve stimulation (SNS) for fecal incontinence remains the only neuromodulation protocol commonly utilized use for GI disease. For IBD treatment, several electrical neuromodulation techniques have been studied, such as vagus NS, SNS, and tibial NS. Several animal and clinical experiments were conducted to study the effectiveness, with encouraging results. The precise underlying mechanisms of action for electrical neuromodulation are unclear, but this modality appears to be promising. Randomized control trials are required to investigate the efficacy of intrinsic processes. In this review, we will discuss the electrical modulation therapy for the IBD and the data pertaining to it.

Neuronal regulation of the gut immune system and neuromodulation for treating inflammatory bowel disease

The gut immune system in the healthy intestine is anti-inflammatory, but can move to a pro-inflammatory state when the gut is challenged by pathogens or in disease. The nervous system influences the level of inflammation through enteric neurons and extrinsic neural connections, particularly vagal and sympathetic innervation of the gastrointestinal tract, each of which exerts anti-inflammatory effects. Within the enteric nervous system (ENS), three neuron types that influence gut immune cells have been identified, intrinsic primary afferent neurons (IPANs), vasoactive intestinal peptide (VIP) neurons that project to the mucosa, and cholinergic neurons that influence macrophages in the external muscle layers. The enteric neuropeptides, calcitonin gene-related peptide (CGRP), tachykinins, and neuromedin U (NMU), which are contained in IPANs, and VIP produced by the mucosa innervating neurons, all influence immune cells, notably innate lymphoid cells (ILCs). ILC2 are stimulated by VIP to release IL-22, which promotes microbial defense and tissue repair. Enteric neurons are innervated by the vagus, and, in the large intestine, by the pelvic nerves. Vagal nerve stimulation reduces gut inflammation, which may be both by stimulation of efferent (motor) pathways to the ENS, and stimulation of afferent pathways that connect to integrating centers in the CNS. Efferent pathways from the CNS have their anti-inflammatory effects through either or both vagal efferent neurons and sympathetic pathways. The final neurons in sympathetic pathways reduce gut inflammation by the action of noradrenaline on β2 adrenergic receptors expressed by immune cells. Activation of neural anti-inflammatory pathways is an attractive option to treat inflammatory bowel disease that is refractory to other treatments. Further investigation of the ways in which enteric reflexes, vagal pathways and sympathetic pathways integrate their effects to modulate the gut immune system and gut inflammation is needed to optimize neuromodulation therapy.

Effect of Chemically-Induced Diabetes Mellitus on Phenotypic Variability of the Enteric Neurons in the Descending Colon in the Pig

Gastrointestinal neuropathy in diabetes is one of numerous diseases resulting in abnormal functioning of the gastrointestinal tract (GIT), and it may affect any section of the GIT, including the descending colon. In the gastrointestinal system, the neurons are arranged in an interconnecting network defined as the enteric nervous system (ENS) which includes the myenteric plexus and the submucosal plexuses: inner and outer. Regular functioning of the ENS is determined by normal synthesis of the neurotransmitters and neuromodulators. This paper demonstrates the effect of hyperglycaemia on the number of enteric neurons which are immunoreactive to: neural isoform of nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), galanin (GAL), calcitonin generelated peptide (CGRP) and cocaine amphetamine-regulated transcript (CART) in the porcine descending colon. It was demonstrated that there was a statistically significant increase in the number of neurons within the myenteric plexus immunoreactive to all investigated substances. In the outer submucosal plexus, the CART-positive neurons were the only ones not to change, whereas no changes were recorded for nNOS or CART in the inner submucosal plexus. This study is the first study to discuss quantitative changes in the neurons immunoreactive to nNOS, VIP, GAL, CGRP and CART in the descending colon in diabetic pigs.

Bioelectronics in the brain-gut axis: focus on inflammatory bowel disease (IBD)

Accumulating evidence shows that intestinal homeostasis is mediated by cross-talk between the nervous system, enteric neurons and immune cells, together forming specialized neuroimmune units at distinct anatomical locations within the gut. In this review, we will particularly discuss how the intrinsic and extrinsic neuronal circuitry regulates macrophage function and phenotype in the gut during homeostasis and aberrant inflammation, such as observed in inflammatory bowel disease (IBD). Furthermore, we will provide an overview of basic and translational IBD research using these neuronal circuits as a novel therapeutic tool. Finally, we will highlight the different challenges ahead to make bioelectronic neuromodulation a standard treatment for intestinal immune-mediated diseases.

Afferent renal innervation in anti-Thy1.1 nephritis in rats

Afferent renal nerves exhibit a dual function controlling central sympathetic outflow via afferent electrical activity and influencing intrarenal immunological processes by releasing peptides such as calcitonin gene-related peptide (CGRP). We tested the hypothesis that increased afferent and efferent renal nerve activity occur with augmented release of CGRP in anti-Thy1.1 nephritis, in which enhanced CGRP release exacerbates inflammation. Nephritis was induced in Sprague-Dawley rats by intravenous injection of OX-7 antibody (1.75 mg/kg), and animals were investigated neurophysiologically, electrophysiologically, and pathomorphologically 6 days later. Nephritic rats exhibited proteinuria (169.3 ± 10.2 mg/24 h) with increased efferent renal nerve activity (14.7 ± 0.9 bursts/s vs. control 11.5 ± 0.9 bursts/s, n = 11, P < 0.05). However, afferent renal nerve activity (in spikes/s) decreased in nephritis (8.0 ± 1.8 Hz vs. control 27.4 ± 4.1 Hz, n = 11, P < 0.05). In patch-clamp recordings, neurons with renal afferents from nephritic rats showed a lower frequency of high activity following electrical stimulation (43.4% vs. 66.4% in controls, P < 0.05). In vitro assays showed that renal tissue from nephritic rats exhibited increased CGRP release via spontaneous (14 ± 3 pg/mL vs. 6.8 ± 2.8 pg/ml in controls, n = 7, P < 0.05) and stimulated mechanisms. In nephritic animals, marked infiltration of macrophages in the interstitium (26 ± 4 cells/mm²) and glomeruli (3.7 ± 0.6 cells/glomerular cross-section) occurred. Pretreatment with the CGRP receptor antagonist CGRP_8-37 reduced proteinuria, infiltration, and proliferation. In nephritic rats, it can be speculated that afferent renal nerves lose their ability to properly control efferent sympathetic nerve activity while influencing renal inflammation through increased CGRP release.

Mycotoxins and the Enteric Nervous System

Mycotoxins are secondary metabolites produced by various fungal species. They are commonly found in a wide range of agricultural products. Mycotoxins contained in food enter living organisms and may have harmful effects on many internal organs and systems. The gastrointestinal tract, which first comes into contact with mycotoxins present in food, is particularly vulnerable to the harmful effects of these toxins. One of the lesser-known aspects of the impact of mycotoxins on the gastrointestinal tract is the influence of these substances on gastrointestinal innervation. Therefore, the present study is the first review of current knowledge concerning the influence of mycotoxins on the enteric nervous system, which plays an important role, not only in almost all regulatory processes within the gastrointestinal tract, but also in adaptive and protective reactions in response to pathological and toxic factors in food.

Potential Antiulcer Agents From Plants: A Comprehensive Review

Background:

Peptic ulcer is a deep gastrointestinal erosion disorder that involves the entire mucosal thickness and can even penetrate the muscular mucosa. Nowadays, several plants and compounds derived from it have been screened for their antiulcer activity. In the last few years, there has been an exponential growth in the field of herbal medicine. This field has gained popularity in both developing and developed countries because of their natural origin and less side effects.

Objective:

This review aims to provide a comprehensive summary of currently available knowledge of medicinal plants and phytoconstituents reported for their anti-ulcer properties.

Methods:

The worldwide accepted database like SCOPUS, PUBMED, SCIELO, NISCAIR, ScienceDirect, Springerlink, Web of Science, Wiley, SciFinder and Google Scholar were used to retrieve available published literature.

Results:

A comprehensive review of the present paper is an attempt to list the plants with antiulcer activity. The review narrates the dire need to explore potential chemical moieties that exert an antiulcer effect, from unexploited traditional plants. Furthermore, the present study reveals the intense requirement to exploit the exact mechanism through which either the plant extracts or their active constituents exhibit their antiulcer properties.

Conclusion:

This article is the compilation of the plants and its constituents reported for the treatment of peptic ulcers. The Comprehensive data will surely attract the number of investigators to initiate further research that might lead to the drugs for the treatment of ulcers. As sufficient scientific data is not available on plants, most of the herbals cannot be recommended for the treatment of diseases. This can be achieved by research on pure chemical structures derived from plants or to prepare new lead compounds with proven beneficial preclinical in vitro and in vivo effects. However, a lot remains to be done in further investigations for the better status of medicinal plants.

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

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

Bioelectric neuromodulation for gastrointestinal disorders: effectiveness and mechanisms

The gastrointestinal tract has extensive, surgically accessible nerve connections with the central nervous system. This provides the opportunity to exploit rapidly advancing methods of nerve stimulation to treat gastrointestinal disorders. Bioelectric neuromodulation technology has considerably advanced in the past decade, but sacral nerve stimulation for faecal incontinence currently remains the only neuromodulation protocol in general use for a gastrointestinal disorder. Treatment of other conditions, such as IBD, obesity, nausea and gastroparesis, has had variable success. That nerves modulate inflammation in the intestine is well established, but the anti-inflammatory effects of vagal nerve stimulation have only recently been discovered, and positive effects of this approach were seen in only some patients with Crohn's disease in a single trial. Pulses of high-frequency current applied to the vagus nerve have been used to block signalling from the stomach to the brain to reduce appetite with variable outcomes. Bioelectric neuromodulation has also been investigated for postoperative ileus, gastroparesis symptoms and constipation in animal models and some clinical trials. The clinical success of this bioelectric neuromodulation therapy might be enhanced through better knowledge of the targeted nerve pathways and their physiological and pathophysiological roles, optimizing stimulation protocols and determining which patients benefit most from this therapy.

Changes in VIP-, SP- and CGRP- like immunoreactivity in intramural neurons within the pig stomach following supplementation with low and high doses of acrylamide

Acrylamide is one of the food toxins to which the human body is exposed. Although researchers' interest in acrylamide has been growing in recent years, the knowledge of its effect on the gastrointestinal tract, especially on intramural neurons which form the enteric nervous system is scarce. The aim of this experiment was to determine the influence of acrylamide, administered at doses equivalent to the human tolerable daily intake (TDI, 0.5 μg/kg b.w./day) and ten times higher than the TDI (5 μg/kg b.w./day), on the distribution of vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene related peptide (CGRP) in intramural neurons of the domestic pig stomach. Using double immunofluorescent labelling we revealed that the ENS neurons underwent adaptive changes in response to the supplementation of acrylamide, which manifested themselves as increased expression of VIP, SP and CGRP, both in intramural neurons and by an increase in the nerve density in submucous and muscular layers in the porcine stomach. These substances take part in defensive reactions of neurons and transmission of sensory reactions may play an important role in protecting the stomach against the harmful effect of acrylamide. Moreover, it has been shown that acrylamide induces a significant response of ENS neurons even in TDI dose, which suggests that it is not neutral to the body. These findings may be the basis for further toxicological studies addressing the question if currently permitted minimal content of acrylamide in the food does jeopardize the health of human consumers?

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.

The Influence of Inflammation and Nerve Damage on the Neurochemical Characterization of Calcitonin Gene-Related Peptide-Like Immunoreactive (CGRP-LI) Neurons in the Enteric Nervous System of the Porcine Descending Colon

The enteric nervous system (ENS), localized in the wall of the gastrointestinal tract, regulates the functions of the intestine using a wide range of neuronally-active substances. One of them is the calcitonin gene-related peptide (CGRP), whose participation in pathological states in the large intestine remains unclear. Therefore, the aim of this study was to investigate the influence of inflammation and nerve damage using a double immunofluorescence technique to neurochemically characterize CGRP-positive enteric nervous structures in the porcine descending colon. Both pathological factors caused an increase in the percentage of CGRP-positive enteric neurons, and these changes were the most visible in the myenteric plexus after nerve damage. Moreover, both pathological states change the degree of co-localization of CGRP with other neurochemical factors, including substance P, the neuronal isoform of nitric oxide synthase, galanin, cocaine- and amphetamine-regulated transcript peptide and vesicular acetylcholine transporter. The character and severity of these changes depended on the pathological factor and the type of enteric plexus. The obtained results show that CGRP-positive enteric neurons are varied in terms of neurochemical characterization and take part in adaptive processes in the descending colon during inflammation and after nerve damage.

The Influence of Low Doses of Zearalenone and T-2 Toxin on Calcitonin Gene Related Peptide-Like Immunoreactive (CGRP-LI) Neurons in the ENS of the Porcine Descending Colon

The enteric nervous system (ENS) can undergo adaptive and reparative changes in response to physiological and pathological stimuli. These manifest primarily as alterations in the levels of active substances expressed by the enteric neuron. While it is known that mycotoxins can affect the function of the central and peripheral nervous systems, knowledge about their influence on the ENS is limited. Therefore, the aim of the present study was to investigate the influence of low doses of zearalenone (ZEN) and T-2 toxin on calcitonin gene related peptide-like immunoreactive (CGRP-LI) neurons in the ENS of the porcine descending colon using a double immunofluorescence technique. Both mycotoxins led to an increase in the percentage of CGRP-LI neurons in all types of enteric plexuses and changed the degree of co-localization of CGRP with other neuronal active substances, such as substance P, galanin, nitric oxide synthase, and cocaine- and amphetamine-regulated transcript peptide. The obtained results demonstrate that even low doses of ZEN and T-2 can affect living organisms and cause changes in the neurochemical profile of enteric neurons.

Differential gene expression in the oxyntic and pyloric mucosa of the young pig

The stomach is often considered a single compartment, although morphological differences among specific areas are well known. Oxyntic mucosa (OXY) and pyloric mucosa (PYL, in other species called antral mucosa) are primarily equipped for acid secretion and gastrin production, respectively, while it is not yet clear how the remainder of genes expressed differs in these areas. Here, the differential gene expression between OXY and PYL mucosa was assessed in seven starter pigs. Total RNA expression was analyzed by whole genome Affymetrix Porcine Gene 1.1_ST array strips. Exploratory functional analysis of gene expression values was done by Gene Set Enrichment Analysis, comparing OXY and PYL. Normalized enrichment scores (NESs) were calculated for each gene (statistical significance defined when False Discovery Rate % <25 and P-values of NES<0.05). Expression values were selected for a set of 44 genes and the effect of point of gastric sample was tested by analysis of variance with the procedure for repeated measures. In OXY, HYDROGEN ION TRANSMEMBRANE TRANSPORTER ACTIVITY gene set was the most enriched set compared to PYL, including the two genes for H⁺/K⁺-ATPase. Pathways related to mitochondrial activity and feeding behavior were also enriched (primarily cholecystokinin receptors and ghrelin). Aquaporin 4 was the top-ranking gene. In PYL, two gene sets were enriched compared with OXY: LYMPHOCYTE ACTIVATION and LIPID RAFT, a gene set involved in cholesterol-rich microdomains of the plasma membrane. The single most differentially expressed genes were gastrin and secretoglobin 1A, member 1, presumably located in the epithelial line, to inactivate inflammatory mediators. Several genes related to mucosal integrity, immune response, detoxification and epithelium renewal were also enriched in PYL (P<0.05). The data indicate that there is significant differential gene expression between OXY of the young pig and PYL and further functional studies are needed to confirm their physiological importance.

Extrinsic primary afferent neurons projecting to the pylorus in the domestic pig--localization and neurochemical characteristics

The pig, as an omnivorous animal, seems to be especially valuable species in "gastrointestinal" experiments. The importance of the pylorus in the proper functioning of the digestive tract is widely accepted. Although it is commonly known that sensory innervation plays an important role in the regulation of gastric activity and gastrointestinal tissue resistance, there is complete lack of data on the extrinsic afferents projecting to the swine pylorus. The present experiment has been designed to discover the precise localization and neurochemical properties of the primary sensory neurons projecting to the porcine pylorus. Combined retrograde tracing technique and double immunocytochemistry were applied in five piglets. An additional RT-PCR reaction was used to confirm the presence of all investigated neurotransmitters in the studied ganglia. Traced neurons were localized within the bilateral nodose ganglia of the vagus and bilateral dorsal root ganglia spreading from Th4 to L1. Fast Blue-positive afferents expressed immunoreactivity to substance P, calcitonin gene-related peptide, neuronal isoform of nitric oxide synthase, and galanin. In the vagal and spinal ganglia, the percentages of traced neurons immunoreactive to these substances were 54.8, 10.7, 49.6, 7.4 % and 22.2, 75.5, 95.2 %, respectively, and the solitary perikarya were Gal immunoreactive. The presence of all substances studied in the ganglion tissue was confirmed by RT-PCR technique.

The protective effects of lafutidine for bortezomib induced peripheral neuropathy

Peripheral neuropathy (PN) caused by bortezomib is an important complication of multiple myeloma. Subcutaneous injection of bortezomib reduced PN, but 24% of cases were grade 2 PN and 6% of cases were grade 3 PN. PN higher than grade 2 was not resolved by subcutaneous injection. PN higher than grade 3 has serious dose limiting toxicity and is the cause of discontinuing bortezomib treatment. Lafutidine is an H2-blocker with gastroprotective activity and is thought to function by increasing mucosal blood flow via capsaicin sensitive neurons. The same activity of lafutidine is considered to improve glossodynia and taxane induced PN. We hypothesized that lafutidine prevents or improves PN that is caused by bortezomib. In the current study, bortezomib was administered in the usual manner (intravenous administration of bortezomib 1.3 mg/m², twice a week for 2 weeks, followed by 1 week without treatment) for up to four cycles to compare our data with other studies. Lafutidine was administered orally at a dose of 10 mg twice daily. In our eight evaluated cases, the total occurrence of PN was four out of eight patients (50%). There were only grade 1 PN (4 out of 8) cases, and no cases higher than grade 2. We conclude that (1) the total occurrence of PN was not improved, (2) there was no PN after the first course, (3) there were only grade 1 cases and there were no cases higher than grade 2, and (4) no cases discontinued bortezomib treatment because of PN. This is the first report showing that lafutidine is useful for the amelioration of bortezomib induced PN.

Cost Effectiveness Associated with Helicobacter pylori Screening and Eradication in Patients Taking Nonsteroidal Anti-Inflammatory Drugs and/or Aspirin

BACKGROUND/AIMS

This study was performed to investigate the cost effectiveness of Helicobacter pylori screening/eradication in South Korean patients treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and/or aspirin.

METHODS

A decision Markov model was used to estimate the effectiveness and economic impact of an H. pylori screening/eradication strategy compared to a no-screening strategy among patients who were included in the model at the age of 40 years. Utility weights were applied to four of the health status groups to reflect quality-adjusted life years (QALY). The costs of screening, H. pylori eradication, and managing peptic ulcer and ulcer complications were obtained from South Korea-specific data.

RESULTS

The total costs per patient were US $2,454 for the H. pylori screening/eradication and US $3,182 for the no-screening strategy. The QALYs for the two strategies were 16.05 and 15.73, respectively. The results were robust for the analyses of all different cohort groups who entered the model at the age of 30, 50, or 60 years and for NSAIDs-naïve patients. Through the probabilistic sensitivity analysis, the robustness of our study's results was also determined.

CONCLUSIONS

The H. pylori screening/eradication strategy was found to be less expensive and more effective compared to the no-screening strategy among South Korean patients taking NSAIDs and/or aspirin.

Calcitonin gene-related peptide is a promising marker in ulcerative colitis

BACKGROUND

Assessment of the severity and extent of disease activity continues to present challenges for physicians in the treatment of ulcerative colitis. Standard markers that can objectively reflect disease activity are useful for physicians to both evaluate the course of ulcerative colitis and monitor the effectiveness of therapy for any given patient.

AIMS

We hypothesize that calcitonin gene-related peptide (CGRP) can reflect the activity and severity of ulcerative colitis and be used as a marker to assess the effectiveness of various therapies.

METHODS

We examined the expression levels of CGRP by reverse transcription polymerase chain reaction (RT-PCR) and semi-quantitative immunohistochemisty in mucosal biopsies from 38 patients with UC and 18 controls. Levels of CGRP mRNA and protein expression were compared between patients and controls with the clinical activity index (CAI) and the endoscopic activity index (EAI) for various levels of UC severity.

RESULTS

Our results showed that the levels of CGRP mRNA and protein expression were significantly reduced in UC patients compared to controls. This effect was more pronounced in patients with more severe cases of UC. There is a statistically significant negative correlation between levels of CGRP mRNA expression and CAI/EAI scores. A statistically significant negative correlation was also found between levels of CGRP protein expression and CAI/EAI scores. Overall, high CAI and EAI scores were accompanied by low CGRP mRNA and protein expression levels.

CONCLUSION

Levels of CGRP protein and mRNA expression in the colonic mucosa of patients are closely associated with UC severity and corroborate traditional indices used to assess the disease.

Pharmacokinetic and ulcerogenic studies of naproxen prodrugs designed for specific brain delivery

Naproxen (Nap) is an NSAID used as a neuroprotective agent to treat several neurodegenerative diseases. The observed limited brain bioavailability of the drug prompted the design of several chemical delivery systems. We report the synthesis and preliminary in vitro and in vivo investigations of Nap prodrugs with dihydropyridine (I) and ascorbic acid (II) through an ester spacer to target specific brain delivery of Nap. The purpose of this study was to determine the brain bioavailability of Nap after oral administration of the prodrugs in rats. The results showed moderate oral bioavailability of prodrugs (AUC = 53-94 h · μg/mL) in rats compared with parent Nap (AUC = 155 h · μg/mL) at equimolar doses. Contrarily, there was a twofold increase in Nap levels in the brain with the prodrugs compared to parent Nap. The enhanced brain bioavailability may be attributed to the specific carrier system in addition to the reduced percentage of plasma protein binding of Nap. Plasma protein binding of the tested prodrugs was investigated in vitro using equilibrium dialysis. The percentage of plasma free fraction of prodrugs (9-15%) was significantly greater than that of Nap (about 5%) when tested at 20 μM, illustrating more available prodrug to cross the blood brain barrier. A significant decrease in gastric ulcerogenicity of the prodrugs compared with parent Nap was also noted. In conclusion, oral dihydropyridine and ascorbate prodrugs for brain site-specific delivery of Nap may be promising candidates for safe, chronic use of NSAIDs for the treatment of neurodegenerative diseases.

Selective gene expression by rat gastric corpus epithelium

The gastrointestinal (GI) tract is divided into several segments that have distinct functional properties, largely absorptive. The gastric corpus is the only segment thought of as largely secretory. Microarray hybridization of the gastric corpus mucosal epithelial cells was used to compare gene expression with other segments of the columnar GI tract followed by statistical data subtraction to identify genes selectively expressed by the rat gastric corpus mucosa. This provides a means of identifying less obvious specific functions of the corpus in addition to its secretion-related genes. For example, important properties found by this GI tract comparative transcriptome reflect the energy demand of acid secretion, a role in lipid metabolism, the large variety of resident neuroendocrine cells, responses to damaging agents and transcription factors defining differentiation of its epithelium. In terms of overlap of gastric corpus genes with the rest of the GI tract, the distal small bowel appears to express many of the gastric corpus genes in contrast to proximal small and large bowel. This differential map of gene expression by the gastric corpus epithelium will allow a more detailed description of major properties of the gastric corpus and may lead to the discovery of gastric corpus cell differentiation genes and those mis-regulated in gastric carcinomas.

Gastroprotective action of Cochinchina momordica seed extract is mediated by activation of CGRP and inhibition of cPLA(2)/5-LOX pathway

Cochinchina momordica seed extract (SKMS10), which is composed of the major compounds momordica saponins, has been evaluated for its gastroprotective effects in rat models of acute gastric mucosal damage. Ethanol and water immersion restraint stress (WRS) induced gastric damage, including hemorrhages and edema, was significantly attenuated by pretreatment with SK-MS10. In addition, SK-MS10 reduced increases of mucosal myeloperoxidase (MPO), IL-1β, and TNFα levels and the expression of cPLA(2), and 5-LOX induced by ethanol or WRS. SK-MS10 also increased hexosamine, adherent mucus, and the expression of MUC5AC. Furthermore, SK-MS10 enhanced the mucosal expression of the CGRP gene and its serum levels.N(G)-methyl L-arginine (L-NMMA) or capsaicin desensitization reversed the SK-MS10-induced gastroprotection effect. These results suggest that SK-MS10 is a gastroprotective agent against acute gastric mucosal damage by suppressing proinflammatory cytokines, downregulating cPLA(2), 5-LOX, and increasing the synthesis of mucus. Furthermore, CGRP-NO pathway was found to play an important role in these gastroprotective effects of SK-MS10.

CGRP function-blocking antibodies inhibit neurogenic vasodilatation without affecting heart rate or arterial blood pressure in the rat

BACKGROUND AND PURPOSE

Calcitonin gene-related peptide (CGRP) receptor antagonists effectively abort migraine headache and inhibit neurogenic vasodilatation in humans as well as rat models. Monoclonal antibodies typically have long half-lives, and we investigated whether or not function-blocking CGRP antibodies would inhibit neurogenic vasodilatation with a long duration of action and therefore be a possible approach to preventive therapy of migraine. During chronic treatment with anti-CGRP antibodies, we measured cardiovascular function, which might be a safety concern of CGRP inhibition.

EXPERIMENTAL APPROACH

We used two rat blood flow models that measure electrically stimulated vasodilatation in the skin or in the middle meningeal artery (MMA). These vasomotor responses are largely dependent on the neurogenic release of CGRP from sensory afferents. To assess cardiovascular function during chronic systemic anti-CGRP antibody treatment, we measured heart rate and blood pressure in conscious rats.

KEY RESULTS

Treatment with anti-CGRP antibodies inhibited skin vasodilatation or the increase in MMA diameter to a similar magnitude as treatment with CGRP receptor antagonists. Although CGRP antibody treatment had a slower onset of action than the CGRP receptor antagonists, the inhibition was still evident 1 week after dosing. Chronic treatment with anti-CGRP antibodies had no detectable effects on heart rate or blood pressure.

CONCLUSIONS AND IMPLICATIONS

We showed for the first time that anti-CGRP antibodies exert a long lasting inhibition of neurogenic vasodilatation in two different rat models of arterial blood flow. We have provided strong preclinical evidence that anti-CGRP antibody may be a suitable drug candidate for the preventive treatment of migraine.

Capsaicin-induced increase of intestinal cefazolin absorption in rats

The effect of capsaicin on intestinal cefazolin absorption was examined by means of an in situ closed loop method in rats to clarify whether the vanilloid receptor (TRPV1) is involved in drug absorption driven by passive diffusion. In control experiments with 1 mg/mL cefazolin, the amount of cefazolin absorbed from the closed loop was 15.3+/-1.5 microg/cm in the rat jejunum. The absorption amount was increased to 22.8+/-0.9 and 23.4+/-2.4 microg/cm when capsaicin was applied with cefazolin at concentrations of 10 and 400 microM, respectively. The enhancing effect of capsaicin on cefazolin absorption was suppressed when ruthenium red, a non-selective inhibitor of transient receptor potential (TRP) cation channels, was intravenously infused into the rat during the experiment. Cefazolin accumulation in the intestinal tissue was not altered in the presence of capsaicin. Collectively, the mechanism accounting for the capsaicin-induced increase in the intestinal cefazolin absorption is probably that capsaicin associating with TRPV1 increases the intrinsic permeability of cefazolin in intestine.

Effects of Capsaicin on Intestinal Cephalexin Absorption in Rats

The effects of capsaicin on intestinal cephalexin absorption were investigated by means of in situ single pass perfusion in rats to clarify whether this pungent compound present in spice is a potential factor altering the intestinal drug absorption processes. Under the control condition, cephalexin was absorbed at a rate of 1.16+/-0.08 and 0.90+/-0.06 nmol/min/cm in the jejunum and ileum, respectively. The intestinal cephalexin absorption rate was decreased when capsaicin was dissolved in the perfusate at a concentration of 400 microM, being 0.54+/-0.07 and 0.46+/-0.10 nmol/min/cm in the jejunum and ileum, respectively. The inhibitive effect of capsaicin on intestinal cephalexin absorption was diminished when ruthenium red, a non-selective inhibitor of the transient receptor potential (TRP) cation channels, was intravenously infused into the rat during the experiment. Moreover, when we evaluated the paracellular permeability of cephalexin by utilizing a competitive inhibitor, glycylsarcosine, it was demonstrated that glycylsarcosine-insensitive intestinal cephalexin absorption in the jejunum was increased by 4.5 times in the presence of 400 microM capsaicin. These findings indicate that capsaicin affects both transcellular and paracellular pathways of intestinal cephalexin absorption by interacting with the TRP cation channels in intestinal tissues, in which capsaicin seems to change the transport activity of H+/peptide co-transporter 1 (PEPT1), and to a lesser degree, it seems to alter the paracellular permeability of the intestinal epithelia.

Capsaicin and gastric ulcers

In recent years, infection of the stomach with the organism Helicobacter Pylori has been found to be the main cause of gastric ulcers, one of the common ailments afflicting humans. Excessive acid secretion in the stomach, reduction in gastric mucosal blood flow, constant intake of non-steroid anti-inflammatory drugs (NSAIDS), ethanol, smoking, stress etc. are also considered responsible for ulcer formation. The prevalent notion among sections of population in this country and perhaps in others is that "red pepper" popularly known as "Chilli," a common spice consumed in excessive amounts leads to "gastric ulcers" in view of its irritant and likely acid secreting nature. Persons with ulcers are advised either to limit or avoid its use. However, investigations carried out in recent years have revealed that chilli or its active principle "capsaicin" is not the cause for ulcer formation but a "benefactor." Capsaicin does not stimulate but inhibits acid secretion, stimulates alkali, mucus secretions and particularly gastric mucosal blood flow which help in prevention and healing of ulcers. Capsaicin acts by stimulating afferent neurons in the stomach and signals for protection against injury causing agents. Epidemiologic surveys in Singapore have shown that gastric ulcers are three times more common in the "Chinese" than among Malaysians and Indians who are in the habit of consuming more chillis. Ulcers are common among people who are in the habit of taking NSAIDS and are infected with the organism "Helicobacter Pylori," responsible for excessive acid secretion and erosion of the mucosal layer. Eradication of the bacteria by antibiotic treatment and avoiding the NSAIDS eliminates ulcers and restores normal acid secretion.

Protective effect of proteinase-activated receptor 2 activation on motility impairment and tissue damage induced by intestinal ischemia/reperfusion in rodents

We hypothesized that proteinase-activated receptor-2 (PAR(2)) modulates intestinal injuries induced by ischemia/reperfusion. Ischemia (1 hour) plus reperfusion (6 hours) significantly delayed gastrointestinal transit (GIT) compared with sham operation. Intraduodenal injection of PAR(2)-activating peptide SLIGRL-NH(2) significantly accelerated transit in ischemia/reperfusion but not in sham-operated rats. GIT was significantly delayed in ischemia/reperfusion and sham-operated PAR(2)(-/-) mice compared with PAR(2)(+/+). SLIGRL-NH(2) significantly accelerated transit in ischemia/reperfusion in PAR(2)(+/+) but not in PAR(2)(-/-) mice. Prevention of mast cell degranulation with cromolyn, ablation of visceral afferents with capsaicin, and antagonism of calcitonin gene-related peptide (CGRP) and neurokinin-1 receptors with CGRP(8-37) and RP67580, respectively, abolished the SLIGRL-NH(2)-induced stimulatory effect on transit in ischemia/reperfusion. Tissue damage was significantly reduced by SLIGRL-NH(2); this effect was not observed in cromolyn-, capsaicin-, or RP67580-treated rats but was detected following CGRP(8-37). Intestinal PAR(2) mRNA levels were not affected by SLIGRL-NH(2) in ischemia/reperfusion. We propose that PAR(2) modulates GIT and tissue damage in intestinal ischemia/reperfusion by a mechanism dependent on mast cells and visceral afferents. PAR(2) effect on transit might be mediated by CGRP and substance P, whereas the effect on tissue damage appears to involve substance P but not CGRP. PAR(2) might be a signaling system in the neuroimmune communication in intestinal ischemia/reperfusion.

Nitric oxide synthase activity in rat gastric mucosa contributes to mucin synthesis elicited by calcitonin gene-related peptide

The majority of research for the calcitonin gene-related peptide (CGRP) in the stomach has been devoted to the submucosal blood flow, and only slight attention has been paid to its involvement in the gastric epithelial function. In this study, we examined the age-related change in the CGRP-containing nerves and its effects on the mucus metabolism. We compared the immunoreactivity for CGRP in the gastric mucosa of 7-week-old rats (young) to that of 52-week-old animals (middle-aged). The effects of CGRP on the mucin biosynthesis were compared using the stomachs from both young and middle-aged rats. The nitric oxide synthase (NOS) activity was measured in the surface and deep mucosa of the gastric corpus. The density of the CGRP nerve fibers was reduced in both the lamina propria and submucosa of the middle-aged rats compared to the young rats. CGRP stimulated the mucin biosynthesis in the cultured corpus mucosa from the 7-week-old rats, but not from the 52-week-old rats. The total NOS activity of the surface layer in the corpus mucosa was markedly reduced in the middle-aged rats compared to the young rats. These findings demonstrate the age-dependent reduction in the CGRP-induced mucin biosynthesis, as well as in the density of the CGRP fibers in the rat stomach. The decreased NOS activity in the surface layer of the oxyntic mucosa in the aged rats may also be a principal cause for the lack of regulation of the mucin biosynthesis by CGRP.

Mechanisms underlying capsaicin-stimulated secretion in the stomach: comparison with mucosal acidification

The effects of capsaicin and mucosal acidification on gastric HCO3(-) secretion were compared in wild-type and prostacyclin (PGI2) IP receptor or prostaglandin E receptor EP1 or EP3 knockout C57BL/6 mice as well as rats. Under urethane anesthesia, the stomach was mounted on an ex vivo chamber, perfused with saline, and the secretion of HCO3(-) was measured at pH 7.0 using the pH-stat method. Capsaicin or 200 mM HCl was applied to the chamber for 10 min. Capsaicin increased the secretion of HCO3(-) in rats and wild-type mice, the response at 0.3 mg/ml being equivalent to that induced by acidification. This effect of capsaicin in rats was abolished by ablation of capsaicin-sensitive afferent neurons and attenuated by indomethacin, N(G)-nitro-L-arginine methylester (L-NAME), and capsazepine [transient receptor potential vanilloid type 1 (TRPV1) antagonist] but not FR172357 [3-bromo-8-[2,6-dichloro-3-[N[(E)-4-(N,N-dimethylcarbamoyl) cinnamidoacetyl]-N-methylamino]benzyloxy]-2-metylimidazo[1,2-a]pyridine; bradykinin B2 antagonist] or the EP1 antagonist. The acid-induced HCO3(-) secretion was attenuated by indomethacin, L-NAME, the EP1 antagonist, and sensory deafferentation, but not affected by capsazepine or FR172357. Prostaglandin E2 (PGE2), NOR-3 [(+/-)-(E)-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexeneamine] (NO donor), and bradykinin stimulated the secretion of HCO3(-), and the effect of bradykinin was blocked by indomethacin and L-NAME as well as FR172357. The stimulatory effect of capsaicin disappeared in IP (-/-) mice, whereas that of acidification disappeared in EP1 (-/-) mice. Intragastric application of capsaicin increased mucosal PGI2 but not PGE2 levels in the rat stomach. These results suggested that both capsaicin and acid increase gastric HCO3(-) secretion via a common pathway, involving PG and NO as well as capsaicin-sensitive afferent neurons, yet their responses differ concerning TRPV1 or prostanoid receptor dependence.

Gastric HCO3− secretion induced by mucosal acidification: Different mechanisms depending on acid concentration

We compared the HCO3- secretory responses induced by mucosal acidification at different HCl concentrations (100 and 200 mM HCl) in the rat stomach. Under urethane anesthesia, the stomach was mounted on an ex vivo chamber and perfused with saline under inhibition of acid secretion by omeprazole (60 mg/kg, i.p.). TheHCO3- secretion was measured at pH 7.0 using a pH-stat method and by adding 2 mM HCl. The acidification was performed by exposure of the mucosa to 100 mMor 200 mM HCl for 10 min. The secretion of HCO3- was increased by acidification of the mucosa at both 100 and 200 mM of HCl, and the maximal HCO3- response was 1.5-times greater at the latter concentration. The HCO3- responses induced by 100 and 200 mM HCl were both totally inhibited by prior administration of indomethacin, an inhibitor of prostaglandin (PG) production. The HCO3- stimulatory effect of 200 mM HCl was also significantly attenuated by pre-treatment with N(G)-nitro L-arginine methyl ester (L-NAME), the inhibitor of nitric oxide (NO) synthase, as well as chemical ablation of capsaicin-sensitive afferent neurons, whereas that of 100 mM HCl was affected by neither of these treatments. We conclude that the mucosal acidification stimulates gastric HCO3- secretion in different mechanisms, depending on the concentration of acid; the response caused by 100 mM HCl is mediated only by PGs, while that caused by 200 mM HCl is mediated by both capsaicin-sensitive afferent neurons and NO, in addition to PGs.

Bombesin-induced gastroprotection

Bombesin is an endogenous gut peptide that is prominent in the stomach. In addition to its effects on modulating acid and gut peptide secretion, recent evidence indicates that bombesin is a potent gastroprotective agent. This review article examines the ability of bombesin to prevent gastric injury. Its protective actions appear to be mediated primarily via the release of endogenous gastrin, as gastroprotection is negated by blockade of gastrin receptors. Bombesin-induced gastroprotection and gastrin release are modified by somatostatin. Immunoneutralization of endogenous somatostatin increases the ability of bombesin to prevent gastric injury by increasing gastrin release. In mechanistic studies, ablation of capsaicin-sensitive afferent neurons abolishes bombesin-induced gastroprotection while cyclo-oxygenase inhibition partially reverses this effect. Nitric oxide synthase inhibition also negates bombesin-induced gastroprotection as well as the ability of bombesin to increase gastric mucosal blood flow. Taken together, the available evidence indicates that bombesin causes release of endogenous gastrin that activates sensory neurons located in the gastric mucosa. Activation of sensory neurons causes increased production of nitric oxide through activation of constitutive nitric oxide synthase, which leads to a resultant increase in gastric mucosal blood flow and renders the stomach less susceptible to damage from luminal irritants.

Cetraxate raises levels of calcitonin gene-related peptide and substance P in human plasma

Cetraxate hydrochloride (cetraxate), an anti-ulcer drug, produces a dose-related increase in mucosal blood flow. Recently, it was found that capsaicin-sensitive afferent nerves play an important role in gastric mucosal defence. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP) and substance P in the stomach. We studied the effect of cetraxate on human plasma CGRP and substance P in healthy subjects. Cetraxate (800 mg) or placebo were orally administered to five healthy males. Blood samples were taken before, and at 20, 40, 60, 90, 120, 180 and 240 min after administration, followed by the extracting procedure, and submitted to a highly sensitive enzyme immunoassay system for CGRP and substance P. Single administration of cetraxate caused significant increases in plasma CGRP concentration at 60-120 min compared with placebo. Cetraxate significantly increased plasma substance P levels at 40-90 min compared with placebo. In this study, we hypothesized that cetraxate might indirectly stimulate capsaicin-sensitive afferent nerves and increase mucosal blood flow, and that this may be a key mechanism underlying its gastroprotective action.

Interaction of cyclooxygenase isoenzymes, nitric oxide, and afferent neurons in gastric mucosal defense in rats

The cyclooxygenase (COX)-2 inhibitors 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU) (0.02-2 mg/kg) and N-[2-(cyclohexyloxy)-4-nitrofenyl]-methanesulfonamide (NS-398) (0.01-1 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (0.05-5 mg/kg), and dexamethasone (1 mg/kg) were studied in rats challenged with intragastric acid (300 mM HCl). All compounds induced severe gastric damage when rats were treated concurrently with the inhibitor of constitutive and inducible nitric-oxide (NO) synthase N(G)-monomethyl-L-arginine methyl ester (L-NAME) (3 or 40 mg/kg). DFU and NS-398 caused significantly less damage in rats receiving the selective inhibitor of inducible NO synthase N-(3-(aminomethyl)benzyl)acetamidine (1400W) (0.3 mg/kg). The COX-1 inhibitor SC-560 induced moderate damage in the acid-challenged stomach even without suppression of NO, but damage was aggravated by L-NAME. The COX-3 inhibitor phenacetin (400 mg/kg) did not injure the gastric mucosa despite suppression of NO. Furthermore, DFU, NS-398, SC-560, and dexamethasone caused severe injury in the acid-challenged stomach of rats pretreated with capsaicin to ablate afferent neurons. The mucosal damage induced by the COX-1 inhibitor, the COX-2 inhibitors, and dexamethasone in L-NAME- or capsaicin-treated rats was reversed by coadministration of 16,16-dimethyl-prostaglandin E2 (2 x 8 ng/kg). Gross mucosal damage was paralleled by histology. Our results support the concept that endogenous NO, prostaglandins, and afferent neurons act in concert in the regulation of gastric mucosal integrity. The prostaglandins necessary for mucosal defense in the face of NO suppression, and afferent nerve ablation can be derived either from COX-1 or COX-2. The data do not propose a protective role for a phenacetin-sensitive COX-3. Our findings suggest that not only COX-1 but also COX-2 has important functions in the maintenance of gastric integrity.

Effect of Sho-hange-ka-bukuryo-to on Gastrointestinal Peptide Concentrations in the Plasma of Healthy Human Subjects

Sho-hange-ka-bukuryou-to, a traditional Chinese herbal (Kampo) medicine, has been used to treat hyperemesis of pregnancy, nausea and vomiting. Most traditional herbal medicines are prepared from several herbs. For example, Sho-hange-ka-bukuryo-to is prepared from three herbs: Pinelliae Tuber, Zingiberis Rhizoma and Hoelen. Thus, to determine the precise mechanism of the pharmacological effects of Chinese herbal medicines is too difficult. So we have elucidated the effect of some Chinese herbal medicines by examining the change of the plasma levels of brain-gut peptides. In this study, we investigated the effects of Sho-hange-ka-bukuryo-to on the plasma levels of gut-regulated peptides (gastrin, somatostatin, motilin and vasoactive intestinal peptide (VIP)) and gastrointestinal mucosa regulatory neuropeptides (calcitonin gene-related peptide (CGRP) and substance P) in healthy human subjects. A single oral administration of Sho-hange-ka-bukuryo-to caused significant increases in plasma somatostatin-, CGRP- and substance P-immunoreactive substance (IS) levels, compared with a placebo group. Transient elevation of gastrin-IS levels in the placebo group was inhibited by the administration of Sho-hange-ka-bukuryo-to, but the medicine showed no effects on plasma motilin- or VIP-IS levels. In conclusion, these results might indicate that the pharmacological action of Sho-hange-ka-bukuryo-to is closely related to changes in gastrin-, somatostatin-, CGRP- and substance P-IS levels in human plasma.

Comparison of the effects of hange-shashin-to and rikkunshi-to on human plasma calcitonin gene-related peptide and substance P levels

Regarding the gastroprotective function as a neural emergency system, sensory afferent neurons in the gastrointestinal mucosa regulate neuropeptide (calcitonin gene-related peptide (CGRP), substance P, etc.) levels, and those peptides play various physiological roles. To determine whether the pharmacological effects of Hange-shashin-to and Rikkunshi-to on the gastrointestine are due to changes in gastrointestinal mucosa regulatory peptides levels, we investigated the levels of CGRP-like immunoreactive substances (IS) and substance P-IS in plasma from healthy subjects. A single oral administration of Hange-shashin-to caused significant increases in CGRP-IS (40-60 min) and substance P-IS (60-180 min) levels in the plasma compared with the levels induced by a placebo. Rikkunshi-to and a 5.0 g Pinelliae tuber extract had no significant effect on CGRP-IS and substance P-IS levels. Extract of a 2.5 g Zingiberis rhizoma significantly caused increases in CGRP-IS at 40 min and in substance P-IS at 60 min. These results, in comparison with Kampo medicines, might indicate that the pharmacological actions of Hange-shashin-to closely are related to changes in CGRP-IS and substance P-IS levels, while Zingiberis rhizoma partially might participate in those effects of Hange-shashin-to.

Somatostatin-induced gastric protection against ethanol: involvement of nitric oxide and effects on gastric mucosal blood flow

BACKGROUND/AIMS

The mechanisms of somatostatin-mediated gastroprotection are not fully understood. Aims of this study were to determine in the rat the role of nitric oxide (NO) in somatostatin-induced effects on gastric mucosal protection and blood flow (GMBF) in the absence and in the presence of intraluminal ethanol.

METHODS

Ethanol (70% v/v)-induced gastric mucosal injury after orogastric dosing was quantitated at 30 min and GMBF determined in an ex vivo gastric chamber preparation.

RESULTS

Somatostatin (4 microg/kg; i.p.) protection against ethanol-induced ulceration was prevented by the NO inhibitor L-NNA and restored by L-arginine, but not D-arginine. Somatostatin (1-8 microg/kg; i.p.) did not effect basal GMBF. The gastroprotective dose of somatostatin (4 microg/kg; i.p.) prevented the decrease in GMBF caused by ethanol. L-NNA reversed this vascular effect of somatostatin.

CONCLUSION

Somatostatin-induced gastroprotection and restoration of GMBF during ethanol exposure involve mechanisms which are dependent on NO generation.

Localization of calcitonin gene-related peptide receptors in rat gastric mucosa

The location of calcitonin gene-related peptide (CGRP) receptors in the rat stomach has not been elucidated. It was recently reported that the CGRP receptor is formed when a calcitonin-receptor-like receptor (CRLR) and receptor activity modifying protein (RAMP) 1 are co-expressed on the cell membrane. The aim of this study was to determine the location and the role of CGRP receptors in the rat gastric mucosa. Gene expressions of CRLR and RAMP1 were investigated by Northern blot analysis, reverse transcription-polymerase chain reaction (RT-PCR), and in situ hybridization. Immunohistochemical stainings for CGRP, somatostatin, gastrin, and chromogranin A were performed. Gastric endocrine cells were collected by counterflow-elutriation and their responses to CGRP were studied. CRLR and RAMP1 mRNA was expressed mainly in small gastric epithelial cells in the pyloric glands. The mRNA expression had a similar distribution to that of D cells. In cultured gastric endocrine cells, CGRP enhanced somatostatin production, while it inhibited the secretion of histamine and gastrin. Our results suggest that CGRP receptors are expressed in D cells in the rat gastric mucosa and control production and secretion of somatostatin.

Sensitizing effects of lafutidine on CGRP-containing afferent nerves in the rat stomach

1. Capsaicin sensitive afferent nerves play an important role in gastric mucosal defensive mechanisms. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP), which seems to be the predominant neurotransmitter of spinal afferents in the rat stomach, exerting many pharmacological effects by a direct mechanism or indirectly through second messengers such as nitric oxide (NO). 2. Lafutidine is a new type of anti-ulcer drug, possessing both an antisecretory effect, exerted via histamine H(2) receptor blockade, and gastroprotective activities. Studies with certain antagonists or chemical deafferentation techniques suggest the gastroprotective actions of lafutidine to be mediated by capsaicin sensitive afferent nerves, but this is an assumption based on indirect techniques. In order to explain the direct relation of lafutidine to afferent nerves, we conducted the following studies. 3. We determined CGRP and NO release from rat stomach and specific [(3)H]-resiniferatoxin (RTX) binding to gastric vanilloid receptor subtype 1 (VR1), which binds capsaicin, using EIA, a microdialysis system and a radioreceptor assay, respectively. 4. Lafutidine enhanced both CGRP and NO release from the rat stomach induced by a submaximal dose of capsaicin, but had no effect on specific [(3)H]-RTX and capsaicin binding to VR1. 5. In conclusion, our findings demonstrate that lafutidine modulates the activity of capsaicin sensitive afferent nerves in the rat stomach, which may be a key mechanism involved in its gastroprotective action.

Effects of vanilloid receptor agonists and antagonists on gastric antral ulcers in rats

Defunctionalization of capsaicin-sensitive afferent nerves by pretreatment with a neurotoxic dose of capsaicin aggravates gastric ulcers in rats. In the present study, we investigated the roles of vanilloid receptors in gastric antral ulcers, using vanilloid receptor agonists and antagonists. Gastric antral ulcers were induced by a combination of diethyldithiocarbamate and 1 N HCl in refed rats. The administration of ruthenium red (1.5 mg/kg, s.c., twice daily) aggravated gastric antral ulcers (ulcer index: control, 33.7+/-13.7 mm(2); ruthenium red, 99.9+/-11.0 mm(2)). A similar result was observed in rats pretreated with a neurotoxic dose of capsaicin. On the other hand, capsaicin (1-10 mg/kg, p.o., twice daily) inhibited antral ulcer formation (ulcer index: control, 99.2+/-20.6 mm(2); capsaicin 10 mg/kg, 37.0+/-11.7 mm(2)). A similar effect was obtained in rats treated with the novel antiulcer drug, lafutidine (3-10 mg/kg, p.o., twice daily), which has gastroprotective activity mediated by capsaicin-sensitive afferent nerves. The antiulcer effects of capsaicin and lafutidine were abolished by ruthenium red and by pretreatment with a neurotoxic dose of capsaicin. These results suggest that vanilloid receptors play a gastroprotective role in gastric antral ulcers. In addition, treatment with ruthenium red may be an alternative tool for defunctionalization of capsaicin-sensitive afferent nerves.

Protective effect of amtolmetin guacyl versus placebo diclofenac and misoprostol in healthy volunteers evaluated as gastric electrical activity in alcohol-induced stomach damage

Amtolmetin guacyl (AMG) is a nonsteroidal antiinflammatory drug (NSAID) of high therapeutic activity and free of damaging effects on the gastrointestinal tract. Since acute ulcer and nausea have been found to be associated with gastric dysrhythmias, cutaneous electrogastrography and ultrasonographic study of the gastric emptying time were performed simultaneously in 24 healthy volunteers before and for 180 min after a liquid meal with 0.5 g/kg body weight of alcohol in double-blind, placebo-controlled, crossover studies. Before the recording session, each subject had taken placebo, AMG, a standard NSAID, or a gastric protective drug for four days. Alcohol administration increased the tachygastria percentage while diclofenac, AMG, and misoprostol alone did not induce gastrointestinal symptoms and gastric dysrhythmias. As regards alcohol-induced gastric dysrhythmia, placebo and diclofenac showed a clear increase in tachygastria while AMG and misoprostol did not. AMG is able to induce a normalization of gastric dysrhythmia induced by alcohol administration probably due to its peculiar mechanism of action, which involves capsaicin and CGRP pathways.

Transient prevention of ethanol-induced gastric lesion by capsaicin due to release of endogenous calcitonin gene-related peptide in rats

Pre-exposure of the rat gastric mucosa to capsaicin reduced the mucosal lesion by 50% ethanol to 1/4. Treatment with an antagonist of calcitonin gene-related peptide (CGRP), CGRP (8-37), nullified the effect of capsaicin. During constant perfusion of the gastric lumen with physiological saline + pepstatin, the CGRP level was not increased by 50% ethanol, but it showed a peak (802.5 +/- 145.7 pg/2 min) after 1.6 mM capsaicin. Four minutes after capsaicin, the CGRP level was kept at a high level and the gastric lesion was markedly reduced by re-exposure of the mucosa to 50% ethanol. At 20-30 min after capsaicin, the CGRP levels returned to the resting level and the reddened area by 50% ethanol was not reduced. It was concluded that capsaicin transiently prevented the mucosal lesion through CGRP release.

Sensory pathways and cyclooxygenase regulate mucus gel thickness in rat duodenum

We previously showed that the duodenal hyperemic response to acid occurs through activation of capsaicin-sensitive afferent nerves with subsequent release of vasodilatory substances such as calcitonin gene-related peptide (CGRP) and nitric oxide. We then tested the hypothesis that similar factors regulate duodenal mucus gel thickness. Gel thickness was optically measured using in vivo microscopy in anesthetized rats. Duodenal mucosae were superfused with pH 7.0 buffer with vanilloid receptor agonist capsaicin, bradykinin, or PGE(2) injection or were challenged with pH 2.2 solution, with or without the vanilloid antagonist capsazepine, human CGRP-(8-37), N(G)-nitro-L-arginine methyl ester, and indomethacin. Other rats underwent sensory ablation with high-dose capsaicin pretreatment. Acid, bradykinin, capsaicin, and PGE(2) all quickly thickened the gel. Antagonism of vanilloid and CGRP receptors, inhibition of nitric oxide synthase, and sensory deafferentation delayed gel thickening, suggesting that the capsaicin pathway mediated the initial burst of mucus secretion that thickened the gel. Indomethacin abolished gel thickening due to acid, bradykinin, and capsaicin. Inhibition of gel thickening by indomethacin in response to multiple agonists suggests that cyclooxygenase activity is essential for duodenal gel thickness regulation. Duodenal afferent neural pathways play an important role in the modulation of cyclooxygenase-mediated physiological control of gel thickness.

Recent advances in gastrointestinal pathophysiology: role of heat shock proteins in mucosal defense and ulcer healing

The defense mechanism of the gastrointestinal mucosa against aggressive factors, such as hydrochloric acid, bile acid and non-steroidal anti-inflammatory drugs, mainly consists of functional, humoral and neuronal factors. Mucus-alkaline secretion, mucosal microcirculation, and motility act as functional factors, while prostaglandins and nitric oxide act as humoral factors, and capsaicin sensitive sensory neurons act as neuronal factors. All the above factors are known to contribute to mucosal protection. In recent years, heat shock proteins (HSPs), to include HSP70, have been implicated to be an additional factor utilized for the defense mechanisms of the gastrointestinal mucosa at the intracellular level. The expression of HSP70 and HSP47 markedly changes during the development and healing of chronic gastric ulcers in rats. It was revealed that HSC70 (a constitutive form of HSP70) is coprecipitated with cyclooxygenase-1 and the neuronal form of nitric oxide synthase after treatment with a mild irritant (20% ethanol). A positive relationship between enhanced interaction of HSC70 with either cyclooxygenase-1 or nitric oxide synthase and mucosal protection against a strong irritant (100% ethanol) was observed. It was concluded that HSPs might contribute to mucosal defense mechanisms and ulcer healing, most probably through protecting key enzymes related to cytoprotection.

Adaptive cytoprotection mediated by prostaglandin I(2) is attributable to sensitization of CRGP-containing sensory nerves

BACKGROUND & AIMS

The phenomenon by which the gastric mucosa is protected in response to mild irritants has been called adaptive cytoprotection, a mechanism believed to be related to production of endogenous prostaglandins (PGs). We tested whether PGs generated by mild irritant prevent injury through the release of calcitonin gene-related peptide (CGRP) from the sensory nerves using prostanoid receptor-knockout mice.

METHODS

The stomach was doubly cannulated and perfused with 1 mol/L NaCl or 50% ethanol. CGRP levels in the perfusate were determined by enzyme immunoassay, and the injured area was estimated at the end of perfusion.

RESULTS

Preperfusion with mildly hypertonic saline (1 mol/L NaCl) increased generation of gastric PGE(2) and PGI(2) and reduced ethanol-induced mucosal damage. Exposure of ethanol after 1 mol/L NaCl increased intragastric CGRP levels from 166 +/- 27 to 713 +/- 55 pg/2 min (n = 4, P < 0.05), and the protective action of 1 mol/L NaCl was inhibited by indomethacin treatment. CGRP antagonist blocked 1 mol/L NaCl-induced protective effect. Intragastric perfusion of 50% ethanol after administration of PGI(2), but not of PGE(2), increased CGRP levels. Application of 1 mol/L NaCl to IP receptor-knockout mice (IP(-/-)) did not elicit the protective effects seen in the wild-type on ethanol-induced gastric mucosal lesions. Protective effect of 1 mol/L NaCl was observed in EP3 receptor-knockout mice (EP3(-/-)). CGRP level during ethanol perfusion was not increased in IP(-/-) but was increased in EP3(-/-) and wild-type counterparts after preperfusion of 1 mol/L NaCl.

CONCLUSIONS

These results indicate that the endogenous PGI(2) generated by 1 mol/L NaCl may have a protective role in gastric mucosal injury through enhancement of CGRP release from gastric mucosa. This mechanism may explain the adaptive cytoprotection observed after treatment with mild irritants.

The plant kingdom as a source of anti-ulcer remedies

Phytogenic agents have traditionally been used by herbalists and indigenous healers for the prevention and treatment of peptic ulcer. This article reviews the anti-acid/anti-peptic, gastro-protective and/or anti-ulcer properties of the most commonly employed herbal medicines and their identified active constituents. Botanical compounds with anti-ulcer activity include flavonoids (i.e. quercetin, naringin, silymarin, anthocyanosides, sophoradin derivatives) saponins (i.e. from Panax japonicus and Kochia scoparia), tannins (i.e. from Linderae umbellatae), gums and mucilages (i.e. gum guar and myrrh). Among herbal drugs, liquorice, aloe gel and capsicum (chilli) have been used extensively and their clinical efficacy documented. Also, ethnomedical systems employ several plant extracts for the treatment of peptic ulcer. Despite progress in conventional chemistry and pharmacology in producing effective drugs, the plant kingdom might provide a useful source of new anti-ulcer compounds for development as pharmaceutical entities or, alternatively, as simple dietary adjuncts to existing therapies.

Nitric oxide synthase inhibition negates bombesin-induced gastroprotection

BACKGROUND

Bombesin prevents gastric injury primarily by the release of endogenous gastrin. Gastroprotection by exogenous gastrin is negated by nitric oxide synthase inhibition, which implicates a role for nitric oxide as a protective mediator. Because both endothelial and inducible isoforms of this enzyme can play a role in mucosal defense, this study was done to examine the contrasting effects of 2 nitric oxide synthase inhibitors on bombesin-induced gastroprotection.

METHODS

Rats were given subcutaneous saline or bombesin (10-100 microg/kg) 30 minutes before they received a 1-mL orogastric bolus of acidified ethanol (150 mmol/L of hydrochloric acid/50% ethanol) and rats were killed 5 minutes later for assessment of macroscopic injury (mm(2)). Gastric mucosal blood flow was measured by laser Doppler. Endothelial, neural, and inducible nitric oxide synthase were assessed by using Western immunoblot.

RESULTS

Bombesin decreased gastric mucosal damage, and dose-dependently increased blood flow when compared with saline-treated rats. Endothelial but not neural or inducible nitric oxide synthase immunoreactivity was increased by bombesin. In additional studies, intraperitoneal administration of N(G)-nitro-l-arginine methyl ester (l-NAME, 5-10 mg/kg), a nonselective nitric oxide synthase inhibitor, negated bombesin-induced gastroprotection and hyperemia, whereas the selective inducible inhibitor aminoguanidine (45 mg/kg) did not. Subcutaneous (SC) l-arginine (300 mg/kg), but not d-arginine, abolished the effects of l-NAME.

CONCLUSIONS

Taken together, these data suggest that nitric oxide produced by the endothelial isoform of nitric oxide synthase plays an important role in mediating the gastroprotective and hyperemic actions associated with bombesin.

L-Arginine protects and exacerbates ethanol-induced rat gastric mucosal injury

BACKGROUND AND AIMS

We have previously demonstrated that 60% ethanol (EtOH) increases macromolecular leakage and induces focal lesion formation in areas of permanent flow stasis within gastric mucosal vessels. Nitric oxide (NO) may prevent lesion formation by inhibiting leakage. This study used fluorescent in vivo microscopy to investigate (i) whether L-arginine (NO precursor) prevented EtOH induced injury and (ii) the mechanisms of protection.

METHODS

Experiments were carried out on anaesthetized rats (hypnorm/diazepam) receiving either intra-arterial fluorescein isothiocyanate-bovine serum albumin (0.2 mL/100 g), a marker for quantitating leakage, or Acridine red (0.1 mL/100 g) which labels leukocytes. Animals then received 100, 300 or 500 mg/kg L-arginine (i.a.) followed by 60% EtOH or distilled water, topically applied to the gastric mucosa (n = 6 for each group). Vessel diameter, macromolecular leakage of labelled albumin from post capillary venules (PCV) and capillaries and leukocyte activity were quantitated using image analysis.

RESULTS

L-Arginine (100 mg/kg) did not increase vessel diameter or prevent EtOH-induced lesion formation and leakage. Both 300 mg/kg and 500 mg/kg alone induced significant and sustained increases in PCV diameter after 15 (P< 0.01) and 5 min (P< 0.001), respectively. Lesion formation was only prevented by 300 mg/kg L-arginine, whereas 500 mg/kg exacerbated haemorrhagic lesion formation over the entire exposed mucosa. Neither 300 mg/kg nor 500 mg/kg L-arginine prevented leakage following EtOH. No leukocyte activity was observed following EtOH with or without L-arginine pretreatment.

CONCLUSION

L-Arginine (300 mg/kg) prevented lesion formation. The mechanism of protection probably involved the increased blood flow in the dilated PCV and not the inhibition of leakage. The combined effects of EtOH and the possible high NO levels exacerbate gastric mucosal damage despite the increases observed in vessel diameter.

CGRP modulates mucin synthesis in surface mucus cells of rat gastric oxyntic mucosa

We examined the effects of the calcitonin gene-related peptide (CGRP), including the possible participation of nitric oxide (NO), on mucin biosynthesis in the surface epithelium and remaining deep mucosa as well as the entire mucosa and compared the distribution of CGRP and NO synthase (NOS) using a combination of double immunofluorescence labeling and multiple dye filter. Pieces of tissue obtained from the corpus and antrum were incubated in a medium containing [(3)H]glucosamine and CGRP, with or without the NOS inhibitor. CGRP dose-dependently enhanced [(3)H]glucosamine incorporation into the corpus mucin but had no effect on antral mucin biosynthesis. The CGRP receptor antagonist, CGRP-(8-37), prevented the increase in (3)H-labeled corpus mucin. This stimulation of corpus mucin synthesis disappeared after removal of the surface mucus cell layer. CGRP activated the mucin biosynthesis in the surface mucus cells. In the full-thickness corpus mucosa, CGRP-induced activation was completely blocked by the NOS inhibitor. CGRP-immunoreactive fibers were intertwined within the surface mucus cell layer with type I NOS immunoreactivity. These results show that CGRP-stimulated mucin biosynthesis mediated by NO is limited to surface mucus cells of the rat gastric oxyntic mucosa.