Chronic alcohol consumption affects gastrointestinal motility and reduces the proportion of neuronal NOS-immunoreactive myenteric neurons in the murine jejunum

The Oxidative Stress and Nervous Distress Connection in Gastrointestinal Disorders

Oxidative stress is increasingly recognized as a central player in a range of gastrointestinal (GI) disorders, as well as complications stemming from therapeutic interventions. This article presents an overview of the mechanisms of oxidative stress in GI conditions and highlights a link between oxidative insult and disruption to the enteric nervous system (ENS), which controls GI functions. The dysfunction of the ENS is characteristic of a spectrum of disorders, including neurointestinal diseases and conditions such as inflammatory bowel disease (IBD), diabetic gastroparesis, and chemotherapy-induced GI side effects. Neurons in the ENS, while essential for normal gut function, appear particularly vulnerable to oxidative damage. Mechanistically, oxidative stress in enteric neurons can result from intrinsic nitrosative injury, mitochondrial dysfunction, or inflammation-related pathways. Although antioxidant-based therapies have shown limited efficacy, recognizing the multifaceted role of oxidative stress in GI diseases offers a promising avenue for future interventions. This comprehensive review summarizes the literature to date implicating oxidative stress as a critical player in the pathophysiology of GI disorders, with a focus on its role in ENS injury and dysfunction, and highlights opportunities for the development of targeted therapeutics for these diseases.

The Impact of Malnutrition on the Hospital and Infectious Outcomes of Patients Admitted With Alcoholic Hepatitis: 2011 to 2017 Analysis of US Hospitals

GOALS

We specifically evaluate the effect of malnutrition on the infection risks of patients admitted with alcoholic hepatitis using a national registry of hospitalized patients in the United States.

BACKGROUND

Malnutrition is a common manifestation of alcoholic hepatitis that affects patient outcomes.

STUDY

2011 to 2017 National Inpatient Sample was used to isolated patients with alcoholic hepatitis, stratified using malnutrition (protein-calorie malnutrition, sarcopenia, and weight loss/cachexia) and matched using age, gender, and race with 1:1 nearest neighbor matching method. Endpoints included mortality and infectious endpoints.

RESULTS

After matching, there were 10,520 with malnutrition and 10,520 malnutrition-absent controls. Mortality was higher in the malnutrition cohort [5.02 vs. 2.29%, P<0.001, odds ratio (OR): 2.25, 95% confidence interval (CI): 1.93-2.63], as were sepsis (14.2 vs. 5.46, P<0.001, OR: 2.87, 95% CI: 2.60-3.18), pneumonia (10.9 vs. 4.63%, P<0.001, OR: 2.51, 95% CI: 2.25-2.81), urinary tract infection (14.8 vs. 9.01%, P<0.001, OR: 1.76, 95% CI: 1.61-1.91), cellulitis (3.17 vs. 2.18%, P<0.001, OR: 1.47, 95% CI: 1.24-1.74), cholangitis (0.52 vs. 0.20%, P<0.001, OR: 2.63, 95% CI: 1.59-4.35), and Clostridium difficile infection (1.67 vs. 0.91%, P<0.001, OR: 1.85, 95% CI: 1.44-2.37). In multivariate models, malnutrition was associated with mortality [P<0.001, adjusted odds ratio (aOR): 1.61, 95% CI: 1.37-1.90] and infectious endpoints: sepsis (P<0.001, aOR: 2.42, 95% CI: 2.18-2.69), pneumonia (P<0.001, aOR: 2.19, 95% CI: 1.96-2.46), urinary tract infection (P<0.001, aOR: 1.68, 95% CI: 1.53-1.84), cellulitis (P<0.001, aOR: 1.46, 95% CI: 1.22-1.74), cholangitis (P=0.002, aOR: 2.27, 95% CI: 1.36-3.80), and C. difficile infection (P<0.001, aOR: 1.89, 95% CI: 1.46-2.44).

CONCLUSION

This study shows the presence of malnutrition is an independent risk factor of mortality and local/systemic infections in patients admitted with alcoholic hepatitis.

Alcohol and gastric motility: pathophysiological and therapeutic implications

Alcohol has been associated with alterations in gastric motility. The literature identifies that various factors play a role in alcohol's effect on gastric emptying including differences in alcohol concentration, osmolarity, caloric content, amino acids as well as different processing techniques (fermentation vs distillation). Additionally, chronic alcohol consumption has been shown to alter the myenteric nitrergic system resulting in impaired gastrointestinal motor function, and it also has an inhibitory effect on the release of several neurotransmitters that play a key role in gastrointestinal motility, including acetylcholine. Whether social or limited intake of alcohol could have a therapeutic role has not been apparent. Serendipitously, we have identified a therapeutic role for alcohol with a meal in the entity of dumping syndrome (DS) where there is postprandial rapid emptying of voluminous and hyperosmolar gastric contents into the small bowel. In the clinical setting of DS attributed to impaired vagal nerve function, there was normalization of gastric emptying and resolution of accompanying symptoms when drinking a glass of wine before and during meals. We propose that alcohol's anticholinergic effect was augmented in the setting of vagal nerve denervation resulting in slowing of gastric emptying and in alleviation of symptoms of early DS. This review article provides an in-depth analysis of the published literature on alcohol and gastric motility focusing on the accumulated knowledge that may have clinical application and relevance.

Prevalence and sociodemographic determinants of dyspepsia in the general population of Rwanda

Introduction

Dyspepsia accounts for a significant burden of worldwide disease, but there is a relative paucity of data from the sub-Saharan African setting. We undertook to describe the burden, risk factors and severity of dyspepsia across Rwanda.

Methods

We performed a population-based clustered cross-sectional survey between November 2015 and January 2016, nationwide in Rwanda, using the Short Form Leeds Dyspepsia Questionnaire to describe the presence and severity of dyspepsia, and the Short Form Nepean Dyspepsia Index to describe the concomitant quality of life effects. Univariate and multivariate logistic regression models were constructed to correlate measured sociodemographic factors with dyspepsia.

Results

The prevalence of clinically significant dyspepsia in the general Rwandan population was 14.2% (283/2000). The univariate factors that significantly predicted severity were gender, profession, socioeconomic status, and non-steroidal anti-inflammatory drug, aspirin and alcohol use, with gender, current smoking, aspirin use both in the past and currently, and alcohol use in the past remaining significant on multivariate modelling. Dyspeptics had a significantly lower gastrointestinal-related quality of life, though the sociodemographic factors measured did not modify the observed quality of life.

Conclusion

Dyspepsia is prevalent in the Rwandan setting and is associated with a significant burden on quality of life. More work is required to determine the pathological entities involved, and the optimal approach to mitigating this burden.

The intestinal regionalization of acute norovirus infection is regulated by the microbiota via bile acid-mediated priming of type III interferon

Evidence has accumulated to demonstrate that the intestinal microbiota enhances mammalian enteric virus infections1. For example, we and others previously reported that commensal bacteria stimulate acute and persistent murine norovirus infections2-4. However, in apparent contradiction of these results, the virulence of murine norovirus infection was unaffected by antibiotic treatment. This prompted us to perform a detailed investigation of murine norovirus infection in microbially deplete mice, revealing a more complex picture in which commensal bacteria inhibit viral infection of the proximal small intestine while simultaneously stimulating the infection of distal regions of the gut. Thus, commensal bacteria can regulate viral regionalization along the intestinal tract. We further show that the mechanism underlying bacteria-dependent inhibition of norovirus infection in the proximal gut involves bile acid priming of type III interferon. Finally, the regional effects of the microbiota on norovirus infection may result from distinct regional expression profiles of key bile acid receptors that regulate the type III interferon response. Overall, these findings reveal that the biotransformation of host metabolites by the intestinal microbiota directly and regionally impacts infection by a pathogenic enteric virus.

The Dietary Management of Patients with Irritable Bowel Syndrome: A Narrative Review of the Existing and Emerging Evidence

Even though irritable bowel syndrome (IBS) has been known for more than 150 years, it still remains one of the research challenges of the 21st century. According to the current diagnostic Rome IV criteria, IBS is characterized by abdominal pain associated with defecation and/or a change in bowel habit, in the absence of detectable organic causes. Symptoms interfere with the daily life of patients, reduce health-related quality of life and lower the work productivity. Despite the high prevalence of approximately 10%, its pathophysiology is only partly understood and seems multifactorial. However, many patients report symptoms to be meal-related and certain ingested foods may generate an exaggerated gastrointestinal response. Patients tend to avoid and even exclude certain food products to relieve their symptoms, which could affect nutritional quality. We performed a narrative paper review of the existing and emerging evidence regarding dietary management of IBS patients, with the aim to enhance our understanding of how to move towards an individualized dietary approach for IBS patients in the near future.

Diet in Irritable Bowel Syndrome (IBS): Interaction with Gut Microbiota and Gut Hormones

Diet plays an important role not only in the pathophysiology of irritable bowel syndrome (IBS), but also as a tool that improves symptoms and quality of life. The effects of diet seem to be a result of an interaction with the gut bacteria and the gut endocrine cells. The density of gut endocrine cells is low in IBS patients, and it is believed that this abnormality is the direct cause of the symptoms seen in IBS patients. The low density of gut endocrine cells is probably caused by a low number of stem cells and low differentiation progeny toward endocrine cells. A low fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diet and fecal microbiota transplantation (FMT) restore the gut endocrine cells to the level of healthy subjects. It has been suggested that our diet acts as a prebiotic that favors the growth of a certain types of bacteria. Diet also acts as a substrate for gut bacteria fermentation, which results in several by-products. These by-products might act on the stem cells in such a way that the gut stem cells decrease, and consequently, endocrine cell numbers decrease. Changing to a low-FODMAP diet or changing the gut bacteria through FMT improves IBS symptoms and restores the density of endocrine cells.

Nitrergic Enteric Neurons in Health and Disease-Focus on Animal Models

Nitrergic enteric neurons are key players of the descending inhibitory reflex of intestinal peristalsis, therefore loss or damage of these neurons can contribute to developing gastrointestinal motility disturbances suffered by patients worldwide. There is accumulating evidence that the vulnerability of nitrergic enteric neurons to neuropathy is strictly region-specific and that the two main enteric plexuses display different nitrergic neuronal damage. Alterations both in the proportion of the nitrergic subpopulation and in the total number of enteric neurons suggest that modification of the neurochemical character or neuronal death occurs in the investigated gut segments. This review aims to summarize the gastrointestinal region and/or plexus-dependent pathological changes in the number of nitric oxide synthase (NOS)-containing neurons, the NO release and the cellular and subcellular expression of different NOS isoforms. Additionally, some of the underlying mechanisms associated with the nitrergic pathway in the background of different diseases, e.g., type 1 diabetes, chronic alcoholism, intestinal inflammation or ischaemia, will be discussed.

When fasted is not empty: a retrospective cohort study of gastric content in fasted surgical patients†

Background

Perioperative aspiration leads to significant morbidity and mortality. Point-of-care gastric ultrasound is an emerging tool to assess gastric content at the bedside.

Methods

We performed a retrospective cohort study of baseline gastric content on fasted elective surgical patients. The primary outcome was the incidence of full stomach (solid content or >1.5 ml kg−1 of clear fluid). Secondary outcomes included: gastric volume distribution (entire cohort, each antral grade); the association between gastric fullness, fasting intervals, and co-morbidities; anaesthetic management changes and incidence of aspiration.

Results

We identified 538 patients. Thirty-two patients (6.2%) presented with a full stomach. Nine of these (1.7%) had solid content and 23 (4.5%) had clear fluid >1.5 ml kg−1. An empty stomach was documented in 480 (89.8%) patients. The examination was inconclusive in the remaining 20 patients (5.0%). As expected, increasing antral grade was correlated with larger antral cross-sectional area and higher gastric volume (P<0.001). Of the 32 patients with a full stomach, only six had a documented risk factor for prolonged gastric emptying. The anaesthetic management was changed in all nine patients with solid content. No aspiration was reported.

Conclusions

This retrospective cohort study suggests that a small proportion of elective surgical patients may present with a full stomach despite the recommended duration of fasting. Further research is needed to establish the clinical implications of these findings in the elective setting. At present, the clinical role of gastric ultrasound continues to be for the evaluation of gastric contents to guide management when the risk of aspiration is uncertain or unknown.

FGF 21 deficiency slows gastric emptying and reduces initial blood alcohol concentration in mice exposed to acute alcohol in fasting state

Excess alcohol consumption can lead to alcoholic liver disease. Fibroblast growth factor 21 (FGF21) is a metabolic regulator with multiple physiologic functions. Previous study demonstrated that FGF21 deficiency exacerbated alcohol-induced liver injury and exogenous FGF21 administration protected liver from chronic alcohol-induced injury. In this study, we aimed to explore the role of FGF21 in alcohol metabolism in mice. FGF21 knockout (KO) mice and the wild type(WT) control mice were divided into two groups and fasted for 24 h followed by a bonus of alcohol treatment at a dose of 5 g/kg body weight via gavage. Serum alcohol concentration was measured after gavage at 0.5, 2, 3, 4 and 6 h, respectively. At the end, gastric and liver tissues were collected. Serum alcohol concentration of KO mice was significantly lower than that of WT at 0.5 h after alcohol expose. There were no significant differences in alcohol dehydrogenase (ADH) activity and aldehyde dehydrogenase 2 (ALDH2) activity in gastric and liver tissues between WT and the KO mice. However, gastric emptying time of KO mice was much longer than that of WT mice. In addition, the intestinal permeability and serum GLP-1 level of KO mice were significantly higher than that of WT mice. These results suggest that FGF21 deficiency slow gastric emptying rate and indirectly influence initial alcohol metabolism in mice exposed to acute alcohol. Our findings provide additional information for understanding the gastrointestinal mechanism of alcoholic liver disease and other alcohol use disorders.

Gastric electrical stimulation improves enteric neuronal survival

Research and clinical experience with vagotomy have confirmed that damage to the central nervous system severely affects physiological movement in the gastrointestinal system. The aim of this study was to investigate the effects of synchronized dual-pulse gastric electrical stimulation (SGES) on the apoptosis of enteric neurons and the possible pathways involved in these effects in vagotomized rats. For this purpose, Male Sprague-Dawley (SD) rats were randomized into a control group, an early subdiaphragmatic vagotomized group (ESDV group), an early subdiaphragmatic vagotomized group with short-term SGES (ESDV + SSGES group), a terminal subdiaphragmatic vagotomized group (TSDV group) and a terminal subdiaphragmatic vagotomized group with long-term SGES (TSDV + LSGES group). The expression levels of connexin 43 (Cx43), glial cell line-derived neurotrophic factor (GDNF), p-Akt, pan-Akt and PGP9.5 were assessed by RT-qPCR, western blot analysis and immunofluorescence staining. Apoptosis was determined by terminal-deoxynucleoitidyl transferase-mediated nick-end labeling (TUNEL) assay. We found that Cx43 expression was decreased in the ESDV and TSDV groups, but was significantly upregulated in the SSGES and LSGES groups. In addition, the GDNF and PGP9.5 expression levels were significantly decreased in the ESDV group compared with the control and TSDV groups and were upregulated in both the SSGES and LSGES groups. The LSGES group exhibited a clear increase in p-Akt expression compared with the TSDV group. Fewer TUNEL-positive cells were observed in the SSGES and LSGES groups than in the ESDV and TSDV groups. More TUNEL-positive cells were found in the stomach of rats subjected to subdiaphragmatic vagotomy. On the whole, our data indicate that SGES improved enteric neuronal survival, possibly through GDNF and the phosphatidylinositol 3-kinase (PI3K)/Akt pathways.

Binge Drinking of Ethanol during Adolescence Induces Oxidative Damage and Morphological Changes in Salivary Glands of Female Rats

This study investigates morphological and biochemistry effects of binge ethanol consumption in parotid (PG) and submandibular (SG) salivary glands of rats from adolescence to adulthood. Female Wistar rats (n = 26) received ethanol at 3 g/kg/day (20% w/v) for 3 consecutive days/week from the 35th until the 62nd day of life. Animals were treated in two periods: 1 week (G1) and 4 weeks (G2), with a control (treated with distilled water) and an ethanol group to each period. In morphological analysis, morphometric and immunohistochemistry evaluation for smooth muscle actin (αSMA), cytokeratin-18 (CK-18), and vimentin (VIM) were made. Biochemical changes were analyzed by concentration of nitrites and levels of malondialdehyde (MDA). The difference between groups in each analysis was evaluated by Mann-Whitney U test or Student's t-test (p ≤ 0.05). PG showed, at one week of ethanol exposure, lower CK-18 and α-SMA expression, as well as MDA levels. After four weeks, lower CK-18 and higher MDA levels were observed in PG exposed to ethanol, in comparison to control group. SG showed lower α-SMA expression after 1 and 4 weeks of ethanol exposure as well as higher MDA levels after 1 week. Ethanol binge consumption during adolescence promotes tissue and biochemical changes with only one-week binge in acinar and myoepithelial PG cells.

British Dietetic Association systematic review and evidence-based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update)

BACKGROUND

The first British Dietetic Association (BDA) guidelines for the dietary management of irritable bowel syndrome (IBS) in adults were published in 2012. Subsequently, there has been a wealth of new research. The aim of this work was to systematically review the evidence for the role of diet in the management of IBS and to update the guidelines.

METHODS

Twelve questions relating to diet and IBS were defined based on review of the previous guideline questions, current evidence and clinical practice. Chosen topics were on healthy eating and lifestyle (alcohol, caffeine, spicy food, elimination diets, fat and fluid intakes and dietary habits), milk and dairy, dietary fibre, fermentable carbohydrates, gluten, probiotics and elimination diets/food hypersensitivity. Data sources were CINAHL, Cochrane Register of Controlled Trials, Embase, Medline, Scopus and Web of Science up to October 2015. Studies were assessed independently in duplicate using risk of bias tools specific to each included study based on inclusion and exclusion criteria for each question. National Health and Medical Research Council grading evidence levels were used to develop evidence statements and recommendations, in accordance with Practice-based Evidence in Nutrition Global protocol used by the BDA.

RESULTS

Eighty-six studies were critically appraised to generate 46 evidence statements, 15 clinical recommendations and four research recommendations. The IBS dietary algorithm was simplified to first-line (healthy eating, provided by any healthcare professional) and second-line [low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) to be provided by dietitian] dietary advice.

CONCLUSIONS

These guidelines provide updated comprehensive evidence-based details to achieve the successful dietary management of IBS in adults.

Gut region-dependent alterations of nitrergic myenteric neurons after chronic alcohol consumption

Chronic alcohol abuse damages nearly every organ in the body. The harmful effects of ethanol on the brain, the liver and the pancreas are well documented. Although chronic alcohol consumption causes serious impairments also in the gastrointestinal tract like altered motility, mucosal damage, impaired absorption of nutrients and inflammation, the effects of chronically consumed ethanol on the enteric nervous system are less detailed. While the nitrergic myenteric neurons play an essential role in the regulation of gastrointestinal peristalsis, it was hypothesised, that these neurons are the first targets of consumed ethanol or its metabolites generated in the different gastrointestinal segments. To reinforce this hypothesis the effects of ethanol on the gastrointestinal tract was investigated in different rodent models with quantitative immunohistochemistry, in vivo and in vitro motility measurements, western blot analysis, evaluation of nitric oxide synthase enzyme activity and bio-imaging of nitric oxide synthesis. These results suggest that chronic alcohol consumption did not result significant neural loss, but primarily impaired the nitrergic pathways in gut region-dependent way leading to disturbed gastrointestinal motility. The gut segment-specific differences in the effects of chronic alcohol consumption highlight the significance the ethanol-induced neuronal microenvironment involving oxidative stress and intestinal microbiota.

Relationship between patterns of alcohol consumption and gastrointestinal symptoms among patients with irritable bowel syndrome

OBJECTIVES

Heavy alcohol intake may exacerbate gastrointestinal (GI) symptoms in adults with irritable bowel syndrome (IBS); however, the role of alcohol in IBS is unclear. We investigated prospective associations between daily patterns of alcohol intake and next day's GI symptoms using daily diaries.

METHODS

In an observational study of women aged 18-48 years with IBS and healthy controls, participants recorded daily GI symptoms, alcohol intake, caffeine intake, and cigarette smoking for ≈ 1 month. GI symptoms included abdominal pain, abdominal bloating, intestinal gas, diarrhea, constipation, nausea, stomach pain, heartburn, and indigestion. Binge drinking was defined as 4+ alcohol-containing drinks/day.

RESULTS

Patterns of alcohol intake did not differ between IBS patients and controls. Although patterns of drinking were associated with GI symptoms among women with IBS, this was not the case with the healthy controls. The strongest associations for IBS patients were between binge drinking and the next day's GI symptoms (e.g., diarrhea, P=0.006; nausea, P=0.01; stomach pain, P=0.009; and indigestion, P=0.004), whereas moderate and light drinking either were not associated or weakly associated with GI symptoms. Associations between alcohol intake and GI symptoms were stronger for women with IBS-diarrhea than for IBS-constipation or IBS-mixed. Effects of binge drinking on GI symptoms were strongest when comparing between individuals (rather than within individuals).

CONCLUSIONS

Our findings indicate that IBS symptoms differ according to the pattern of alcohol intake among IBS patients, suggesting that the pattern of drinking may in part explain the inconsistent findings between alcohol and IBS symptoms.

Characterisation of cocaine- and amphetamine- regulated transcript-like immunoreactive (CART-LI) enteric neurons in the porcine small intestine

The aim of this study was to investigate the distribution and the number of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) neurons and the co-localisation of CART with substance P (SP), somatostatin (SOM), nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) within the enteric nervous system (ENS) in the porcine small intestine. Accordingly, the myenteric plexus (MP), outer submucous plexus (OSP) and inner submucous plexus (ISP) of the small intestine (duodenum, jejunum and ileum) were studied by double-labelling immunofluorescence technique. CART-LI neurons were observed in all gut fragments and all types of intramural plexuses studied and amounted from 0.2 ± 0.1% in the ISP of ileum to 22.4 ± 2.4% in the MP of this segment. The co-localisation of CART and NOS or/and VIP was observed depending on the segment of the gut and the complexity of the intramural plexus. On the other hand, during this study the co-localisation of CART and SOM or/and SP was not observed. The present study, for the first time, presents a detailed description of the CART distribution pattern and co-localisation with other neuromodulators within the ENS of the porcine small intestine.

Diabetes-related alterations in the enteric nervous system and its microenvironment

Gastric intestinal symptoms common among diabetic patients are often caused by intestinal motility abnormalities related to enteric neuropathy. It has recently been demonstrated that the nitrergic subpopulation of myenteric neurons are especially susceptible to the development of diabetic neuropathy. Additionally, different susceptibility of nitrergic neurons located in different intestinal segments to diabetic damage and their different levels of responsiveness to insulin treatment have been revealed. These findings indicate the importance of the neuronal microenvironment in the pathogenesis of diabetic nitrergic neuropathy. The main focus of this review therefore was to summarize recent advances related to the diabetes-related selective nitrergic neuropathy and associated motility disturbances. Special attention was given to the findings on capillary endothelium and enteric glial cells. Growing evidence indicates that capillary endothelium adjacent to the myenteric ganglia and enteric glial cells surrounding them are determinative in establishing the ganglionic microenvironment. Additionally, recent advances in the development of new strategies to improve glycemic control in type 1 and type 2 diabetes mellitus are also considered in this review. Finally, looking to the future, the recent and promising results of metagenomics for the characterization of the gut microbiome in health and disease such as diabetes are highlighted.

Chronic alcohol consumption induces an overproduction of NO by nNOS- and iNOS-expressing myenteric neurons in the murine small intestine

BACKGROUND

There are indications that alterations in the nitric oxide (NO) system of relaxation mediate gastrointestinal motor disturbances induced by chronic alcohol consumption (CAC). As CAC is known to inhibit the motility of the mouse small intestine, we investigated in this model if CAC affects basal NO synthesis by myenteric neurons and which NOS isoforms are involved.

METHODS

The instantaneous NO synthesis of individual neurons was optically measured in whole-mount preparations loaded with the NO synthesis indicator DAF-FM, and the expression of nNOS, iNOS and eNOS was determined by immunohistochemistry.

KEY RESULTS

The DAF-FM recordings showed that CAC induced an increase in neuronal NO synthesis (absolute fluorescence: control 34±12; CAC 140±56; mean±SD; P<0.0004). Neurons of control mice expressed the nNOS (29±3% of total) and iNOS (28±1%) isoforms. eNOS expression was observed in <0.5% of the neurons. Chronic alcohol consumption caused an increase in the proportion of iNOS-expressing neurons (to 33±5%; P<0.01) and a decrease in nNOS-expressing neurons (to 22±3%; P<0.0001), without altering the proportion of NO-producing neurons (control 55±13%; CAC 56± 11%; P=0.82).

CONCLUSIONS & INFERENCES

Chronic alcohol consumption induces a marked increase in NO synthesis by jejunal myenteric neurons, accompanied by an up-regulation of iNOS-expressing neurons and a downregulation of nNOS neurons. We conclude that the overproduction of NO may be a direct cause of gastrointestinal motility disturbances.

Nitric oxide in enteric nervous system mediated the inhibitory effect of vasopressin on the contraction of circular muscle strips from colon in male rats

BACKGROUND

Arginine vasopressin (AVP) is widely used in the treatment of critical diseases with hypotension, but the reports about its effect on gastrointestinal motility are controversial. The purpose of this study was to characterize the role of AVP in the regulation of colonic motility and the underlying mechanism.

METHODS

The contraction of the circular muscle strips (CM) of colon in male rats was monitored by a polygraph. The expressions of cytoplasmic inducible nitric oxide synthase (iNOS), I-κB, and the nuclear P65 in proximal colon were measured by Western blot. The V(1) receptors (V(1) Rs) and iNOS were localized by immunohistochemistry. The content of nitric oxide (NO) in the colon was measured by Griess reagent at the absorbance of 560 nm.

KEY RESULTS

Arginine vasopressin (10(-10) -10(-6) mol L(-1)) caused a concentration-dependent inhibition on CM contraction. Pretreatment with one of the following chemicals, including V-1880 (10(-7) mol L(-1)), TTX (10(-5) mol L(-1)), L-NAME (10(-4) mol L(-1)), NPLA (10(-7) mol L(-1)), SMT (10(-3) mol L(-1)), and PDTC (10(-3) mol L(-1)), attenuated the inhibitory effect of AVP on CM contraction. Arginine vasopressin increased the expression of iNOS and the content of NO in proximal colon. These effects were attenuated by pretreatment with PDTC (10(-3) mol L(-1)). Following AVP administration, the amount of cytoplasmic I-κB decreased, but that of nuclear P65 increased. Double immunofluorescence labeling revealed that V(1) Rs and iNOS were co-localized on the cells of myenteric plexus in proximal colon.

CONCLUSIONS & INFERENCES

Arginine vasopressin inhibited the contraction of CM in proximal colon. This effect was mediated by NO produced from NF-κB-iNOS pathway and neuronal NOS activation in myenteric plexus.