Lactobacillus reuteri enhances excitability of colonic AH neurons by inhibiting calcium-dependent potassium channel opening

The microbiome is essential for normal gut intrinsic primary afferent neuron excitability in the mouse

BACKGROUND

The role of intestinal microbiota in the development and function of host physiology is of high interest, especially with respect to the nervous system. While strong evidence has accrued that intestinal bacteria alter host nervous system function, mechanisms by which this occurs have remained elusive. For this reason, we have carried out experiments examining the electrophysiological properties of neurons in the myenteric plexus of the enteric nervous system (ENS) in germ-free (GF) mice compared with specific pathogen-free (SPF) control mice and adult germ-free mice that have been conventionalized (CONV-GF) with intestinal bacteria.

METHODS

Segments of jejunum from 8 to 12 week old GF, SPF, and CONV-GF mice were dissected to expose the myenteric plexus. Intracellular recordings in current-clamp mode were made by impaling cells with sharp microelectrodes. Action potential (AP) shapes, firing thresholds, the number of APs fired at 2× threshold, and passive membrane characteristics were measured.

KEY RESULTS

In GF mice, excitability was decreased in myenteric afterhyperpolarization (AH) neurons as measured by a lower resting membrane potential and by the number of APs generated at 2× threshold. The post AP slow afterhyperpolarization (sAHP) was prolonged for GF compared with SPF and CONV-GF animals. Passive membrane characteristics were also altered in GF mice by a decrease in input resistance.

CONCLUSIONS & INFERENCES

Here, we report the novel finding that commensal intestinal microbiota are necessary for normal excitability of gut sensory neurons and thus provide a potential mechanism for the transfer of information between the microbiota and nervous system.

Lactobacillus reuteri DSM 17938 for the management of infantile colic in breastfed infants: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To determine whether administration of Lactobacillus reuteri (L reuteri) DSM 17938 is beneficial in breastfed infants with infantile colic.

STUDY DESIGN

Eighty infants aged <5 months with infantile colic (defined as crying episodes lasting 3 or more hours per day and occurring at least 3 days per week within 7 days prior to enrollment), who were exclusively or predominantly (>50%) breastfed were randomly assigned to receive L reuteri DSM 17938 (10(8) colony-forming units) (n = 40) or an identically appearing and tasting placebo (n = 40), both orally, in 5 drops, 1 time daily, for 21 days. The primary outcome measures were the treatment success, defined as the percentage of children achieving a reduction in the daily average crying time ≥ 50%, and the duration of crying (minutes per day) at 7, 14, 21, and 28 days after randomization.

RESULTS

The rate of responders to treatment was significantly higher in the probiotic group compared with the placebo group at day 7 (P = .026), at day 14 (relative risk (RR) 4.3, 95% CI 2.3-8.7), at day 21 (RR 2.7, 95% CI 1.85-4.1), and at day 28 (RR 2.5, 95% CI 1.8-3.75). In addition, throughout the study period, the median crying time was significantly reduced in the probiotic group compared with the control group.

CONCLUSION

Exclusively or predominantly breastfed infants with infantile colic benefit from the administration of L reuteri DSM 17938 compared with placebo.

Psychoactive bacteria Lactobacillus rhamnosus (JB-1) elicits rapid frequency facilitation in vagal afferents

Mounting evidence supports the influence of the gut microbiome on the local enteric nervous system and its effects on brain chemistry and relevant behavior. Vagal afferents are involved in some of these effects. We previously showed that ingestion of the probiotic bacterium Lactobacillus rhamnosus (JB-1) caused extensive neurochemical changes in the brain and behavior that were abrogated by prior vagotomy. Because information can be transmitted to the brain via primary afferents encoded as neuronal spike trains, our goal was to record those induced by JB-1 in vagal afferents in the mesenteric nerve bundle and thus determine the nature of the signals sent to the brain. Male Swiss Webster mice jejunal segments were cannulated ex vivo, and serosal and luminal compartments were perfused separately. Bacteria were added intraluminally. We found no evidence for translocation of labeled bacteria across the epithelium during the experiment. We recorded extracellular multi- and single-unit neuronal activity with glass suction pipettes. Within minutes of application, JB-1 increased the constitutive single- and multiunit firing rate of the mesenteric nerve bundle, but Lactobacillus salivarius (a negative control) or media alone were ineffective. JB-1 significantly augmented multiunit discharge responses to an intraluminal distension pressure of 31 hPa. Prior subdiaphragmatic vagotomy abolished all of the JB-1-evoked effects. This detailed exploration of the neuronal spike firing that encodes behavioral signaling to the brain may be useful to identify effective psychoactive bacteria and thereby offer an alternative new perspective in the field of psychiatry and comorbid conditions.

Voices from within: gut microbes and the CNS

Recent advances in research have greatly increased our understanding of the importance of the gut microbiota. Bacterial colonization of the intestine is critical to the normal development of many aspects of physiology such as the immune and endocrine systems. It is emerging that the influence of the gut microbiota also extends to modulation of host neural development. Furthermore, the overall balance in composition of the microbiota, together with the influence of pivotal species that induce specific responses, can modulate adult neural function, peripherally and centrally. Effects of commensal gut bacteria in adult animals include protection from the central effects of infection and inflammation as well as modulation of normal behavioral responses. There is now robust evidence that gut bacteria influence the enteric nervous system, an effect that may contribute to afferent signaling to the brain. The vagus nerve has also emerged as an important means of communicating signals from gut bacteria to the CNS. Further understanding of the mechanisms underlying microbiome-gut-brain communication will provide us with new insight into the symbiotic relationship between gut microbiota and their mammalian hosts and help us identify the potential for microbial-based therapeutic strategies to aid in the treatment of mood disorders.

Communication between gastrointestinal bacteria and the nervous system

In the past few years, intestinal microbiota has emerged as a novel target for the treatment of gut-brain axis alterations. These include functional gastrointestinal disorders, such as irritable bowel syndrome (IBS), which can be comorbid with stress-related psychiatric conditions. Thus, modulation of the microbiota (e.g. with the use of probiotics) could be proposed as a novel strategy not only for the treatment of IBS but also as an adjuvant for psychiatric treatment of anxiety and depression.

The interplay between the intestinal microbiota and the brain

The intestinal microbiota consists of a vast bacterial community that resides primarily in the lower gut and lives in a symbiotic relationship with the host. A bidirectional neurohumoral communication system, known as the gut-brain axis, integrates the host gut and brain activities. Here, we describe the recent advances in our understanding of how the intestinal microbiota communicates with the brain via this axis to influence brain development and behaviour. We also review how this extended communication system might influence a broad spectrum of diseases, including irritable bowel syndrome, psychiatric disorders and demyelinating conditions such as multiple sclerosis.

Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour

Recent years have witnessed the rise of the gut microbiota as a major topic of research interest in biology. Studies are revealing how variations and changes in the composition of the gut microbiota influence normal physiology and contribute to diseases ranging from inflammation to obesity. Accumulating data now indicate that the gut microbiota also communicates with the CNS--possibly through neural, endocrine and immune pathways--and thereby influences brain function and behaviour. Studies in germ-free animals and in animals exposed to pathogenic bacterial infections, probiotic bacteria or antibiotic drugs suggest a role for the gut microbiota in the regulation of anxiety, mood, cognition and pain. Thus, the emerging concept of a microbiota-gut-brain axis suggests that modulation of the gut microbiota may be a tractable strategy for developing novel therapeutics for complex CNS disorders.

Probiotics to improve outcomes of colic in the community: protocol for the Baby Biotics randomised controlled trial

BACKGROUND

Infant colic, characterised by excessive crying/fussing for no apparent cause, affects up to 20% of infants under three months of age and is a great burden to families, health professionals and the health system. One promising approach to improving its management is the use of oral probiotics. The Baby Biotics trial aims to determine whether the probiotic Lactobacillus reuteri DSM 17938 is effective in reducing crying in infants less than three months old (<13.0 weeks) with infant colic when compared to placebo.

METHODS/DESIGN

DESIGN

Double-blind, placebo-controlled randomised trial in Melbourne, Australia.

PARTICIPANTS

160 breast and formula fed infants less than three months old who present either to clinical or community services and meet Wessel's criteria of crying and/or fussing.

INTERVENTION

Oral once-daily Lactobacillus reuteri (1x108 cfu) versus placebo for one month.

PRIMARY OUTCOME

Infant crying/fussing time per 24 hours at one month.

SECONDARY OUTCOMES

i) number of episodes of infant crying/fussing per 24 hours and ii) infant sleep duration per 24 hours (at 7, 14, 21, 28 days and 6 months); iii) maternal mental health scores, iv) family functioning scores, v) parent quality adjusted life years scores, and vi) intervention cost-effectiveness (at one and six months); and vii) infant faecal microbiota diversity, viii) infant faecal calprotectin levels and ix) Eschericia coli load (at one month only).

ANALYSIS

Primary and secondary outcomes for the intervention versus control groups will be compared with t tests and non-parametric tests for continuous data and chi squared tests for dichotomous data. Regression models will be used to adjust for potential confounding factors. Intention-to-treat analysis will be applied.

DISCUSSION

An effective, practical and acceptable intervention for infant colic would represent a major clinical advance. Because our trial includes breast and formula-fed babies, our results should generalise to most babies with colic. If cost-effective, the intervention's simplicity is such that it could be widely taken up as a new standard of care in the primary and secondary care sectors.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN95287767.

Systemic effects of ingested Lactobacillus rhamnosus: inhibition of mast cell membrane potassium (IKCa) current and degranulation

Exposure of the intestine to certain strains lactobacillus can have systemic immune effects that include the attenuation of allergic responses. Despite the central role of mast cells in allergic disease little is known about the effect of lactobacilli on the function of these cells. To address this we assessed changes in rat mast cell activation following oral treatment with a strain of Lactobacillus known to attenuate allergic responses in animal models. Sprague Dawley rats were fed with L. rhamnosus JB-1 (1×10(9)) or vehicle control for 9 days. Mediator release from peritoneal mast cells (RPMC) was determined in response to a range of stimuli. Passive cutaneous anaphylaxis (PCA) was used to assess mast cell responses in vivo. The Ca(2+) activated K(+) channel (KCa3.1) current, identified as critical to mast cell degranulation, was monitored by whole cell patch-clamp. L. rhamnosus JB-1 treatment lead to significant inhibition of mast cell mediator release in response to a range of stimuli including IgE mediated activation. Furthermore, the PCA response was significantly reduced in treated rats. Patch-clamp studies revealed that RPMC from treated animals were much less responsive to the KCa3.1 opener, DCEBIO. These studies demonstrate that Ingestion of L. rhamnosus JB-1 leads to mast cell stabilization in rats and identify KCa3.1 as an immunomodulatory target for certain lactobacilli. Thus the systemic effects of certain candidate probiotics may include mast cell stabilization and such actions could contribute to the beneficial effect of these organisms in allergic and other inflammatory disorders.

Gut microbial communities modulating brain development and function

Mammalian brain development is initiated in utero and internal and external environmental signals can affect this process all the way until adulthood. Recent observations suggest that one such external cue is the indigenous microbiota which has been shown to affect developmental programming of the brain. This may have consequences for brain maturation and function that impact on cognitive functions later in life. This review discusses these recent findings from a developmental perspective.

Intestinal microbiota, pathophysiology and translation to probiotic use in patients with irritable bowel syndrome

Probiotic agents have received growing attention in recent years as an alternative therapeutic tool in the management of irritable bowel syndrome. In this article, we will discuss the rationale that support this indication, including the role of intestinal microbiota in gastrointestinal function in both human and animal models, potential links between an impaired microbiota imbalance and the psycho-immunopathophysiology of irritable bowel syndrome, and the results of the available clinical trials to date.

The human microbiome and its potential importance to pediatrics

The human body is home to more than 1 trillion microbes, with the gastrointestinal tract alone harboring a diverse array of commensal microbes that are believed to contribute to host nutrition, developmental regulation of intestinal angiogenesis, protection from pathogens, and development of the immune response. Recent advances in genome sequencing technologies and metagenomic analysis are providing a broader understanding of these resident microbes and highlighting differences between healthy and disease states. The aim of this review is to provide a detailed summary of current pediatric microbiome studies in the literature, in addition to highlighting recent findings and advancements in studies of the adult microbiome. This review also seeks to elucidate the development of, and factors that could lead to changes in, the composition and function of the human microbiome.

Microbes and the gut-brain axis

BACKGROUND

The 'gut-brain' or 'brain-gut axis', depending on whether we emphasize bottom-up or top-bottom pathways, is a bi-directional communication system, comprised of neural pathways, such as the enteric nervous system (ENS), vagus, sympathetic and spinal nerves, and humoral pathways, which include cytokines, hormones, and neuropeptides as signaling molecules. Recent evidence, mainly arising from animal models, supports a role of microbes as signaling components in the gut-brain axis.

AIMS

The purpose of this review is to summarize our current knowledge regarding the role of microbes, including commensals, probiotics and gastrointestinal pathogens, in bottom-up pathways of communication in the gut-brain axis. Although this has clear implications for psychiatric co-morbidity in functional and inflammatory conditions of the gut, the focus of this review will be to discuss the current evidence for a role of bacteria (commensals, probiotics, and pathogens) as key modulators of gut-brain communication.

RESULTS & CONCLUSIONS

The strongest evidence for a role of microbes as signaling components in the gut-brain axis currently arises from animal studies and indicate that mechanisms of communication are likely to be multiple. There is need for the concepts generated in animal models to be translated to the human in the future.

Time to include the gut microbiota in the hygienic standardisation of laboratory rodents

The gut microbiota (GM) composition and its impact on animal experiments has become currently dramatically relevant in our days: (1) recent progress in metagenomic technologies, (2) the availability of large scale quantitative analyses to characterize even subtle phenotypes, (3) the limited diversity of laboratory rodent GM due to strict barriers at laboratory animal vendors, and (4) the availability of up to 300.000 different transgenic mouse strains from different sources displaying a huge variety in their GM composition. In this review the GM is described as a variable in animal experiments which need to be reduced for scientific as well as ethical reasons, and strategies how to implement this in routine diagnostic procedures are proposed. We conclude that we have both enough information available to state that the GM has an essential impact on animal models, as well as the methods available to start dealing with these impacts.

The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut-brain communication

BACKGROUND

The probiotic Bifidobacterium longum NCC3001 normalizes anxiety-like behavior and hippocampal brain derived neurotrophic factor (BDNF) in mice with infectious colitis. Using a model of chemical colitis we test whether the anxiolytic effect of B. longum involves vagal integrity, and changes in neural cell function. Methods  Mice received dextran sodium sulfate (DSS, 3%) in drinking water during three 1-week cycles. Bifidobacterium longum or placebo were gavaged daily during the last cycle. Some mice underwent subdiaphragmatic vagotomy. Behavior was assessed by step-down test, inflammation by myeloperoxidase (MPO) activity and histology. BDNF mRNA was measured in neuroblastoma SH-SY5Y cells after incubation with sera from B. longum- or placebo-treated mice. The effect of B. longum on myenteric neuron excitability was measured using intracellular microelectrodes.

KEY RESULTS

Chronic colitis was associated with anxiety-like behavior, which was absent in previously vagotomized mice. B. longum normalized behavior but had no effect on MPO activity or histological scores. Its anxiolytic effect was absent in mice with established anxiety that were vagotomized before the third DSS cycle. B. longum metabolites did not affect BDNF mRNA expression in SH-SY5Y cells but decreased excitability of enteric neurons.

CONCLUSIONS & INFERENCES

In this colitis model, anxiety-like behavior is vagally mediated. The anxiolytic effect of B. longum requires vagal integrity but does not involve gut immuno-modulation or production of BDNF by neuronal cells. As B. longum decreases excitability of enteric neurons, it may signal to the central nervous system by activating vagal pathways at the level of the enteric nervous system.

Gut microbiota and sirtuins in obesity-related inflammation and bowel dysfunction

Obesity is a chronic disease characterized by persistent low-grade inflammation with alterations in gut motility. Motor abnormalities suggest that obesity has effects on the enteric nervous system (ENS), which controls virtually all gut functions. Recent studies have revealed that the gut microbiota can affect obesity and increase inflammatory tone by modulating mucosal barrier function. Furthermore, the observation that inflammatory conditions influence the excitability of enteric neurons may add to the gut dysfunction in obesity. In this article, we discuss recent advances in understanding the role of gut microbiota and inflammation in the pathogenesis of obesity and obesity-related gastrointestinal dysfunction. The potential contribution of sirtuins in protecting or regulating the circuitry of the ENS under inflamed states is also considered.

The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut-brain communication

BACKGROUND

The probiotic Bifidobacterium longum NCC3001 normalizes anxiety-like behavior and hippocampal brain derived neurotrophic factor (BDNF) in mice with infectious colitis. Using a model of chemical colitis we test whether the anxiolytic effect of B. longum involves vagal integrity, and changes in neural cell function. Methods  Mice received dextran sodium sulfate (DSS, 3%) in drinking water during three 1-week cycles. Bifidobacterium longum or placebo were gavaged daily during the last cycle. Some mice underwent subdiaphragmatic vagotomy. Behavior was assessed by step-down test, inflammation by myeloperoxidase (MPO) activity and histology. BDNF mRNA was measured in neuroblastoma SH-SY5Y cells after incubation with sera from B. longum- or placebo-treated mice. The effect of B. longum on myenteric neuron excitability was measured using intracellular microelectrodes.

KEY RESULTS

Chronic colitis was associated with anxiety-like behavior, which was absent in previously vagotomized mice. B. longum normalized behavior but had no effect on MPO activity or histological scores. Its anxiolytic effect was absent in mice with established anxiety that were vagotomized before the third DSS cycle. B. longum metabolites did not affect BDNF mRNA expression in SH-SY5Y cells but decreased excitability of enteric neurons.

CONCLUSIONS & INFERENCES

In this colitis model, anxiety-like behavior is vagally mediated. The anxiolytic effect of B. longum requires vagal integrity but does not involve gut immuno-modulation or production of BDNF by neuronal cells. As B. longum decreases excitability of enteric neurons, it may signal to the central nervous system by activating vagal pathways at the level of the enteric nervous system.

Probiotic Lactobacillus reuteri alleviates the response to gastric distension in rats

Probiotic lactic acid bacteria have been reported to alleviate symptoms in patients with irritable bowel syndrome. However, they have not been tested for use in functional gastric disease. We therefore investigated if strains previously shown to protect from response to colorectal distension (CRD) in rats also modulate response to gastric distension (GD). Healthy, male Sprague-Dawley rats were treated with viable, heat-killed, gamma-irradiated Lactobacillus reuteri or viable Lactobacillus plantarum wild type (WT), L. plantarum Dlt¯mutant, conditioned medium or medium control (9 d), and subjected to GD under anesthesia using an i.g. Teflon catheter. Effects were measured by heart rate (HR) changes during noxious distension (60 mm Hg) compared to baseline HR values. We also investigated the localization of viable, green fluorescent protein-transfected bacteria in the stomach mucosa. Viable L. reuteri decreased the bradycardia induced by noxious GD compared to placebo controls (P < 0.001). Heat-killed or gamma-irradiated L. reuteri and conditioned medium did not have a protective effect in GD. Viable L. plantarum WT and Dlt¯mutant, previously shown to be effective antinociceptive agents in CRD, showed no protective effect in GD. All viable bacteria were associated with the pars glandularis of the rat stomach. Thus, we conclude that the antinociceptive mechanisms of action of probiotic bacteria differ between the stomach and the colon. Symptom alleviation cannot be attributed to the localization of the bacteria in the stomach. Information derived from effects of CRD cannot be extrapolated to effects in the stomach, which are likely to be strain and organ specific.

Irritable bowel syndrome, gut microbiota and probiotics

Irritable bowel syndrome (IBS) is a complex disorder characterized by abdominal symptoms including chronic abdominal pain or discomfort and altered bowel habits. The etiology of IBS is multifactorial, as abnormal gut motility, visceral hypersensitivity, disturbed neural function of the brain-gut axis and an abnormal autonomic nervous system are all implicated in disease progression. Based on recent experimental and clinical studies, it has been suggested that additional etiological factors including low-grade inflammation, altered gut microbiota and alteration in the gut immune system play important roles in the pathogenesis of IBS. Therefore, therapeutic restoration of altered intestinal microbiota may be an ideal treatment for IBS. Probiotics are live organisms that are believed to cause no harm and result in health benefits for the host. Clinical efficacy of probiotics has been shown in the treatment or prevention of some gastrointestinal inflammation-associated disorders including traveler's diarrhea, antibiotics-associated diarrhea, pouchitis of the restorative ileal pouch and necrotizing enterocolitis. The molecular mechanisms, as cause of IBS pathogenesis, affected by altered gut microbiota and gut inflammation-immunity are reviewed. The effect of probiotics on the gut inflammation-immune systems and the results from clinical trials of probiotics for the treatment of IBS are also summarized.

Effects of intestinal microbiota on anxiety-like behavior

The acquisition of intestinal microbiota in the immediate postnatal period has a defining impact on the development and function of many immune and metabolic systems integral to health and well-being. Recent research has shown that the presence of gut microbiota regulates the set point for hypothalamic-pituitary-adrenal (HPA) axis activity.1 Accordingly, we sought to investigate if there were other changes of brain function such as behavioral alterations in germ free (GF) mice, and if so, to compare these to behavior of mice with normal gut microbiota. Our recent paper showed reduced anxietylike behavior in the elevated plus maze (EPM) in adult GF mice when compared to conventionally reared specific pathogen-free (SPF) mice.2 Here, we present data collected when we next colonized the adult GF mice with SPF feces thereby introducing normal gut microbiota, and then reassessed anxiety-like behavior. Interestingly, the anxiolytic behavioral phenotype observed in GF mice persisted after colonization with SPF intestinal microbiota. These data show that gut-brain interactions are important to CNS development of stress systems and that a critical window may exist after which reconstitution of microbiota and the immune system does not normalize the behavioral phenotype.

The relationship between inflammation-induced neuronal excitability and disrupted motor activity in the guinea pig distal colon

BACKGROUND

Colitis is associated with increased excitability of afterhyperpolarization neurons (AH neurons) and facilitated synaptic transmission in the myenteric plexus. These changes are accompanied by disrupted propulsive motility, particularly in ulcerated regions. This study examined the relationship between myenteric AH neuronal hyperexcitability and disrupted propulsive motility.

METHODS

The voltage-activated Na(+) channel opener veratridine, the intermediate conductance Ca(2+) -activated K(+) channel inhibitor TRAM-34 and the 5-HT(4) receptor agonist tegaserod were used to evaluate the effects of neuronal hyperexcitability and synaptic facilitation on propulsive motility in normal guinea pig distal colon. Because trinitrobenzene sulfonic acid (TNBS)-colitis-induced hyperexcitability of myenteric afferent neurons involves increases in hyperpolarization-activated, cyclic nucleotide-gated (HCN) channel activity, the HCN channel inhibitors Cs(+) and ZD7288 were used to suppress AH neuronal activity in TNBS-colitis.

KEY RESULTS

In non-inflamed preparations, veratridine halted propulsive motility (P<0.001). The rate of propulsive motor activity was significantly reduced following addition of TRAM-34 and tegaserod (P<0.001). In TNBS-inflamed preparations, in which motility was temporarily halted or obstructed at sites of ulceration, both Cs(+) and ZD7288 normalized motility through the inflamed regions. Immunohistochemistry studies demonstrated that the proportion of AH neurons in the myenteric plexus was unchanged in ulcerated regions, but there was a 10% reduction in total number of neurons per ganglion.

CONCLUSIONS AND INFERENCES

These findings support the concept that inflammation-induced neuroplasticity in myenteric neurons, involving changes in ion channel activity that lead to enhanced AH neuronal excitability, can contribute to impaired propulsive colonic motility.

Advances in understanding the relationship between irritable bowel syndrome and intestinal bacteria

Irritable bowel syndrome (IBS) is a multifactorial functional disorder of unknown cause and pathophysiology. Commensal bacteria in the digestive tract and host co-exist in a mutually beneficial relationship. If this relationship is interrupted, various types of diseases will be caused. In recent years, the development of microecology has led to a better understanding of the relationship between intestinal bacterial flora and IBS. Many studies have suggested a close relationship between intestinal bacteria and IBS. In this article, we will review the role of alterations in intestinal bacterial flora in the pathogenesis of IBS.

Lactobacillus reuteri accelerates gastric emptying and improves regurgitation in infants

BACKGROUND

Young infants are frequently affected by uncomplicated regurgitation that may persist despite dietetic and conservative interventions. On this basis, we studied the putative effects of probiotics on the frequency of regurgitation and gastric emptying time in infants with functional gastroesophageal reflux (GER).

PATIENTS AND METHODS

Forty-two infants with regurgitation were randomized to assume Lactobacillus reuteri DSM 17938 at a dose of 1 × 10(8) CFU per day and placebo for 30 days. The episodes of regurgitation were recorded by the parents each day. Gastric emptying time was recorded using real-time ultrasound at baseline and at the end of the study. Twenty-one infants without regurgitation were enroled to compare anthropometric and physiological parameters before the intervention diet.

RESULTS

Thirty-four infants completed the study (19 infants receiving probiotics and 15 placebo).At baseline, the whole group of infants was similar to the control group as regards anthropometric and physiological data. The median fasting antral area was significantly reduced, (P = 0·01) the delta in gastric emptying rate was significantly increased (P = 0·01) and the median episodes per day of regurgitation was reduced (, P < 0·001) in the probiotic group compared to the placebo group. In the whole group, the frequency of regurgitation and the basal antral area showed a positive correlation (r = 0·53, P = 0·004).

CONCLUSIONS

In infants with functional GER, L. reuteri DSM 17938 reduce gastric distension and accelerate gastric emptying. In addition, this probiotic strain seems to diminish the frequency of regurgitation.

Reduced anxiety-like behavior and central neurochemical change in germ-free mice

BACKGROUND

There is increasing interest in the gut-brain axis and the role intestinal microbiota may play in communication between these two systems. Acquisition of intestinal microbiota in the immediate postnatal period has a defining impact on the development and function of the gastrointestinal, immune, neuroendocrine and metabolic systems. For example, the presence of gut microbiota regulates the set point for hypothalamic-pituitary-adrenal (HPA) axis activity.

METHODS

We investigated basal behavior of adult germ-free (GF), Swiss Webster female mice in the elevated plus maze (EPM) and compared this to conventionally reared specific pathogen free (SPF) mice. Additionally, we measured brain mRNA expression of genes implicated in anxiety and stress-reactivity.

KEY RESULTS

Germ-free mice, compared to SPF mice, exhibited basal behavior in the EPM that can be interpreted as anxiolytic. Altered GF behavior was accompanied by a decrease in the N-methyl-D-aspartate receptor subunit NR2B mRNA expression in the central amygdala, increased brain-derived neurotrophic factor expression and decreased serotonin receptor 1A (5HT1A) expression in the dentate granule layer of the hippocampus.

CONCLUSIONS & INFERENCES

We conclude that the presence or absence of conventional intestinal microbiota influences the development of behavior, and is accompanied by neurochemical changes in the brain.

New treatments for infant colic

PURPOSE OF REVIEW

Infantile colic is a common problem within the first 3 months of life and causes considerable distress for parents and paediatricians. Despite 40 years of research, its pathogenesis is incompletely understood and treatment remains an open issue. This review will describe recent studies that have examined different kinds of interventions.

RECENT FINDINGS

Important advances in understanding the aetiopathogenesis of infantile colic have been recently proposed and opened new perspectives in its management.The composition of intestinal microbiota, specially an inadequate amount of lactobacilli and an increased concentration of coliforms, might influence the pathogenesis of infantile colic. The benefit of supplementation with Lactobacillus reuteri has been recently reported and experimental data showed the effect of probiotics may be related to the influence on gut motility and pain perception.

SUMMARY

Infantile colic is a clinical entity with a wide range of clinical presentations and outcome. Firstly, paediatricians have to exclude other underlying diseases with a medical examination and prevent feeding disorders. Then, considering the favourable clinical course of the disturbance, well tolerated strategies should be adopted. The findings highlighted in this review may promote the implementation of new researches and treatments to reduce abdominal pain related to infantile colic.

Lactobacillus reuteri DSM 17938 in infantile colic: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To test the efficacy of Lactobacillus reuteri on infantile colic and to evaluate its relationship to the gut microbiota.

STUDY DESIGN

Fifty exclusively breastfed colicky infants, diagnosed according to modified Wessel's criteria, were randomly assigned to receive either L reuteri DSM 17 938 (10(8) colony-forming units) or placebo daily for 21 days. Parental questionnaires monitored daily crying time and adverse effects. Stool samples were collected for microbiologic analysis.

RESULTS

Forty-six infants (L reuteri group: 25; placebo group: 21) completed the trial. Daily crying times in minutes/day (median [interquartile range]) were 370 (120) vs 300 (150) (P=.127) on day 0 and 35.0 (85) vs 90.0 (148) (P=.022) on day 21, in the L reuteri and placebo groups, respectively. Responders (50% reduction in crying time from baseline) were significantly higher in the L reuteri group versus placebo group on days 7 (20 vs 8; P=.006), 14 (24 vs 13; P=.007), and 21 (24 vs 15; P=.036). During the study, there was a significant increase in fecal lactobacilli (P=.002) and a reduction in fecal Escherichia coli and ammonia in the L reuteri group only (P=.001). There were no differences in weight gain, stooling frequency, or incidence of constipation or regurgitation between groups, and no adverse events related to the supplementation were observed.

CONCLUSION

L. reuteri DSM 17 938 at a dose of 10(8) colony-forming units per day in early breastfed infants improved symptoms of infantile colic and was well tolerated and safe. Gut microbiota changes induced by the probiotic could be involved in the observed clinical improvement.

The probiotic Bifidobacterium infantis 35624 displays visceral antinociceptive effects in the rat

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by recurrent abdominal pain and altering bowel habit with a high percentage of patients displaying comorbid anxiety. Growing clinical and preclinical evidence suggests that probiotic agents may restore the altered brain-gut communication in IBS. In this study, we evaluated the efficacy of repeated treatment with three different probiotics in reducing visceral pain in visceral normosensitive (Sprague-Dawley [SD]) and visceral hypersensitive (Wistar-Kyoto [WKY]) rat strains.

METHODS

Following 14 days oral gavage of Lactobacillus salivarius UCC118, Bifidobacterium infantis 35624, or Bifidobacterium breve UCC2003 both SD and WKY rats were exposed to a novel stress, the open field arena and their behavior was recorded. Subsequently, the effects of probiotics on visceral nociceptive responses were analyzed by recording pain behaviors during colorectal distension (CRD).

KEY RESULTS

It was found that there was a difference in the open field behavior between strains but none of the probiotic treatment altered behavior within each strain. Interestingly, the probiotic B. infantis 35624 but not others tested significantly reduced CRD-induced visceral pain behaviors in both rat strains. It significantly increased the threshold pressure of the first pain behavior and also reduced the total number pain behaviors during CRD.

CONCLUSIONS & INFERENCES

These data confirm that probiotics such as B. infantis 35624 are effective in reducing visceral pain and may be effective in treating certain symptoms of IBS.

Immunomodulation by commensal and probiotic bacteria

Over the past decade there has been an increasing awareness of the role played by commensal bacteria in modulating mucosal immune responses and as a consequence there is now great interest in the therapeutic potential of probiotics and other bacteria based strategies for a range of immune disorders. Here we review current understanding of the mechanisms underlying the immunomodulatory actions of commensal and probiotic bacteria and probiotic organisms. We discuss prominent cell types involved in transducing signals from these bacteria, including epithelial cells, dendritic cells and T regulatory cells. We also draw attention to emerging data indicating interplay between the gut microbiota, enteric neurons and the immune system. There is a focus on the specific aspects of bacteria-host interactions that may influence the ability of a specific organism to confer potentially beneficial changes in immune responses. It is clear that there is still much to learn regarding the determinants of the diverse immune responses elicited by different bacterial strains by building on our current knowledge in these areas it may be possible to design clinically effective, bacteria based strategies to maintain and promote health.

Effects of protein deprivation and re-feeding on P2X2 receptors in enteric neurons

AIM

To investigate the effects of malnutrition and re-feeding on the P2X(2) receptor, nitric oxide synthase (NOS), calretinin, calbindin and choline acetyltransferase (ChAT) in neurons of the rat ileum.

METHODS

We analyzed the co-localization, numbers and sizes of P2X(2)-expressing neurons in relation to NOS-immunoreactive (IR), calbindin-IR, ChAT-IR, and calretinin-IR neurons of the myenteric and submucosal plexus. The experimental groups consisted of: (1) rats maintained on normal feed throughout pregnancy until 42 d post-parturition (N); (2) rats deprived of protein throughout pregnancy and 42 d post-parturition (D); and (3) rats undernourished for 21 d post-parturition and then given a protein diet from days 22 to 42 (DR). The myenteric and submucosal plexuses were evaluated by double labeling by immunohistochemical methods for P2X(2) receptor, NOS, ChAT, calbindin and calretinin.

RESULTS

We found similar P2X(2) receptor immunoreactivity in the cytoplasm and surface membranes of myenteric and submucosal neurons from the N, D and DR groups. Double labeling of the myenteric plexus demonstrated that approximately 100% of NOS-IR, calbindin-IR, calretinin-IR and ChAT-IR neurons in all groups also expressed the P2X(2) receptor. In the submucosal plexus, the calretinin-IR, ChAT-IR and calbindin-IR neurons were nearly all immunoreactive for the P2X(2) receptor. In the myenteric plexus, there was a 19% increase in numbers per cm(2) for P2X(2) receptor-IR neurons, 64% for NOS-IR, 84% for calretinin-IR and 26% for ChAT-IR neurons in the D group. The spatial density of calbindin-IR neurons, however, did not differ among the three groups. The submucosal neuronal density increased for calbindin-IR, calretinin-IR and ChAT-IR neurons. The average size of neurons in the myenteric plexus neurons in the D group was less than that in the controls and, in the re-fed rats; there was a 34% reduction in size only for the calretinin-IR neurons.

CONCLUSION

This work demonstrates that expression of the P2X(2) receptor is present in inhibitory, intrinsic primary afferent, cholinergic secretomotor and vasomotor neurons. Undernutrition affected P2X(2) receptor expression in the submucosal plexus, and neuronal and size. These changes were rescued in the re-fed rats.

Luminal administration ex vivo of a live Lactobacillus species moderates mouse jejunal motility within minutes

Gut commensals modulate host immune, endocrine, and metabolic functions. They also affect peripheral and central neural reflexes and function. We have previously shown that daily ingestion of Lactobacillus reuteri (LR) for 9 d inhibits the pseudoaffective cardiac response and spinal single-fiber discharge evoked by visceral distension, and decreases intestinal motility and myenteric AH cell slow afterhyperpolarization (sAHP) by inhibiting a Ca-activated K (IK(Ca)) channel. We tested whether luminal LR could acutely decrease motility in an ex vivo perfusion model of naive Balb/c jejunum. Live LR dose dependently decreased motor complex pressure wave amplitudes with 9- to 16-min onset latency and an IC(50) of 5 × 10(7) cells/ml Krebs. Heat-killed LR or another live commensal, Lactobacillus salivarius, were without effect. The IK(Ca) channel blocker TRAM-34, but neither the opener (DCEBIO) nor the hyperpolarization-activated cationic channel inhibitor ZD7288 (5 μM) (or TTX 1 μM), mimicked the LR effect on motility acutely ex vivo. We provide evidence for a rapid, strain-specific, dose-dependent action of a live Lactobacillus on small intestinal motility reflexes that recapitulates the long-term effects of LR ingestion. These observations may be useful as a first step to unraveling the pathways involved in bacteria to the nervous system communication.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: psycho-neuroimmunology and the intestinal microbiota: clinical observations and basic mechanisms

This is a rapidly emerging field. The application of knowledge regarding the relationship between neural and immune systems in order to gain a better understanding of human conditions has been slow. In this discussion we describe how the brain and microbiota interact, and try to bring this into a context that is clinically relevant. We begin by describing established facts pertaining to the gut-brain axis and the role of gut bacteria. We then focus upon emerging data that will contribute to the generation of a new conceptual framework about the microbiota-gut-brain axis. In the final section we anticipate future directions of this field.

Lactobacillus reuteri ingestion and IK(Ca) channel blockade have similar effects on rat colon motility and myenteric neurones

BACKGROUND

We have previously shown that ingestion of Lactobacillus reuteri may modulate colonic enteric neuron activity but with unknown effects on colon motility. The aim of the present report was to elucidate the neuronal mechanisms of action of the probiotic by comparing the effects on motility of L. reuteri ingestion with blockade of a specific ionic current in enteric neurons.

METHODS

We have used intraluminal pressure recordings from ex vivo rat colon segments and whole cell patch clamp recordings from neurons of rat longitudinal muscle myenteric plexus preparations to investigate the effects of L. reuteri and TRAM-34 on colon motility and neurophysiology. The effects of daily feeding of 10(9) L. reuteri bacteria or acute application of TRAM-34 on threshold fluid filling pressure or pulse pressure was measured.

KEY RESULTS

Lactobacillus reuteri increased intraluminal fluid filling pressure thresholds for evoking pressure pulses by 51% from 0.47 +/- 0.17 hPa; the probiotic also decreased the pulse pressure amplitudes, but not frequency, by 18% from 3.91 +/- 0.52 hPa. The intermediate conductance calcium-dependent potassium (IK(Ca)) channel blocker TRAM-34 (3 micromol L(-1)) increased filling threshold pressure by 43% from 0.52 +/- 0.22 hPa and reduced pulse pressure amplitude by 40% from 2.63 +/- 1.11 hPa; contraction frequency was unaltered. TRAM-34 (3 micromol L(-1)) reduced membrane polarization, leak conductance and the slow afterhyperpolarization current in 16/16 myenteric rat colon AH cells but 19/19 S cells were unaffected.

CONCLUSIONS & INFERENCES

The present results are consistent with L. reuteri enhancing tonic inhibition of colon contractile activity by acting via the IK(Ca) channel current in AH cells.

Mood and gut feelings

Evidence is accumulating to suggest that gut microbes (microbiota) may be involved in neural development and function, both peripherally in the enteric nervous system and centrally in the brain. There is an increasing and intense current interest in the role that gut bacteria play in maintaining the health of the host. Altogether the mass of intestinal bacteria represents a virtual inner organ with 100 times the total genetic material contained in all the cells in the human body. Surprisingly, the characterization of this extraordinarily diverse population is only just beginning, since some 60% of these microbes have never been cultured. Commensal organisms live in a state of harmonious symbiosis with each other and their host, however, a disordered balance amongst gut microbes is now thought to be an associated or even causal factor for chronic medical conditions as varied as obesity and inflammatory bowel diseases. While evidence is still limited in psychiatric illnesses, there are rapidly coalescing clusters of evidence which point to the possibility that variations in the composition of gut microbes may be associated with changes in the normal functioning of the nervous system. This review focuses on these data and suggests that the concept should be explored further to increase our understanding of mood disorders, and possibly even uncover missing links to a number of co-morbid medical diseases.

The putative role of the intestinal microbiota in the irritable bowel syndrome

The irritable bowel syndrome (IBS) is a chronic abdominal symptom complex that is heterogeneous in terms of its clinical presentation and underlying pathophysiology and pathogenesis. It is now established that enteric infection can trigger the syndrome in at least a subset of patients. In addition, there is growing evidence of low grade inflammation and immune activation in the distal bowel of some IBS patients. These observations now prompt the question as to what maintains gut dysfunction in these patients. The intestinal microbiota influences a broad array of host organs that include the gut and the brain, and is an important determinant of normal function in these systems. Disruption of the delicate balance between the host and its intestinal microbiota (termed dysbiosis) results in changes in the mucosal immune system that range from overt inflammation as seen in Crohn's Disease, to low grade inflammation without tissue injury, as seen in a subset of IBS patients. Under experimental conditions, disruption of the microbiota also produces changes in gut sensory-motor function and immune activity. Thus, dysbiosis induced by infection, dietary change or drugs such as antibiotics could produce low grade inflammation and chronic gut dysfunction, reminiscent of that seen in IBS. Fluctuations in gut physiology destabilize the habitat of commensal bacteria and provide a basis for chronic dysbiosis. Recent observations in animal models that changes in gut flora influence behavior provide a basis for a novel unifying hypothesis that accommodates both gut dysfunction and behavioral changes that characterize many IBS patients. This hypothesis states that dysbiosis exists in at least a subset of IBS patients, as a result of infection, dietary change or drugs and contributes to gut inflammatory and functional change in addition to psychiatric co-morbidity.

Lactobacillus reuteri ingestion prevents hyperexcitability of colonic DRG neurons induced by noxious stimuli

Lactobacillus species ingestion can decrease autonomic responses and spinal fiber discharge to nociceptive colorectal distension (CRD), even in the absence of inflammation. The present study aimed to determine whether dorsal root ganglion (DRG) somas could be a locus where the antinociceptive probiotic may have an effect. Healthy rats were fed with Lactobacillus reuteri or vehicle control for 9 days whereupon they were anesthetized, and intermittent distal colonic CRD at 80 mmHg distension was either performed for 1 h or not. The animals were immediately euthanized and patch-clamp recordings taken after isolation and overnight culture from those DRG that projected to the distal colon. CRD decreased the threshold for action potential generation and increased the number of spikes discharged during a standard depolarizing test stimulus, and this effect was blocked by prior probiotic ingestion. The increase in excitability was paralleled by an increase in DRG capacitance, which was not altered by Lactobacillus reuteri ingestion. CRD did not increase tissue weight or myeloperoxidase activity. We suggest that the effects of CRD may have been caused by activity-dependent neurotransmission between DRG somas. CRD evoked increases in action potential upstroke speed, which suggests that it may also have led to augmentation of sodium channel conductances. Probiotic ingestion may have interfered with this hypothetical mechanism since it blocked the effect of CRD on the action potential.