Adaptive changes of the gastrointestinal neuromuscolar function in a mouse model of Catechol-O-Methyl trasferase genetic reduction: implication in the pathogenesis of Irritable Bowel syndrome.

Enteric neuronal circuitries display a considerable ability to adapt to a changing microenvironment, which comprises several cellular "players", including neurons, enteric glial cells, smooth muscle cells, interstitial cells of Cajal, immune cells and commensal bacteria (Giaroni et al., 1999). In particular, gut microbiota seems to be directly involved in modulating the development and function of enteric nervous system (ENS), supporting the concept that changes in commensal microbiome composition, induced by infections or antibiotics, can perturb ENS integrity and activity. Neuronal circuitries in the ENS are known to communicate with the Central Nervous System (CNS) via vagal and sympathetic extrinsic pathways: the so called brain-gut axis. Current cutting-edge research suggests that the enteric microbiota, by modifying enteric neuronal circuitries, may communicate with the brain, thus influencing cognitive and behavioural functions. However, early life perturbations of gut microbiota can potentially influence neurodevelopment leading to functional bowel disorders later in life (Ianiro et al., 2016). There is increasing evidence showing that an altered microbiota composition may be related to functional or psychiatric disorders such as irritable bowel syndrome (Bonfrate et al., 2013; Kennedy et al., 2014) and autism (Finegold, 2011; Mayer et al., 2014). Irritable bowel syndrome (IBS) comprises a heterogeneous group of functional lower gastrointestinal tract disorders characterized by abdominal pain or discomfort associated with altered bowel habits and disordered defecation that may be exacerbated by emotional stress. This gut disorder cannot be explained by specific pathophysiologic mechanisms, since it is not associated with any structural finding or biological marker (Mach, 2004). However, the symptoms of IBS are related to combinations of several known physiological determinants such as abnormal motor reactivity, enhanced visceral hypersensitivity, altered mucosal immune and inflammatory functions (which includes changes in bacterial flora), and altered brain-ENS regulation, which is influenced by psychosocial and socio-cultural factors (Drossman, 2006; Ohman and Simren, 2010; Simren et al., 2013). Recently, the association between gut functional disorders, such as IBS, and catechol-O-methyl-transferase (COMT), an enzyme protein which regulates catecholamines levels in mammalian brain (Lundstrom et al., 1995; Mannisto and Kaakkola, 1999) has been proposed. In this perspective, IBS can be described as a disorder of the gut\u2013brain axis (Moloney et al., 2016). The aim of the study was to determine whether a genetic-driven defective COMT activity may affect the structural and functional integrity of murine ENS. Data obtained in the COMTtransgenic mouse model have been compared to those obtained in the gastrointestinal tract of antibiotic treated-mice in order to deplete the microbiota. Data showed that the partial deletion of COMT determined anomalies in the ENS architecture, with a marked increase in protein and mRNA expression of the glial marker S100\u3b2. Excitatory cholinergic transmission and inhibitory nitrergic neurotransmission, mainly through iNOS increased expression, led to impaired gut neuromuscular contractility. In addition, an increase of GluN1 glutamatergic subunit expression, affecting visceral hypersensitivity with critical effects on gut function, was also observed. The massive antibiotic treatment determined the same alterations in ENS structure and function observed in the COMT transgenic model. Interestingly, COMT partial genetic deletion induced changes in gut microbioma composition and some commensal intestinal microbial strains underwent drastic changes. In particular, in COMT+/- mice a significant increase of Firmicutes DNA in the ileum and colon and a significant decrease of Bacterioidetes DNA in the ileum were observed with respect to control animals, suggesting that host may affect gut microbial flora arrangement. These data confirmed the importance of studying the interplay between host and microbiota, reflecting alterations in motor and sensitive parameters which resemble some features of functional gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS). In conclusion, this study showed that both COMT genetic deletion as well as dysbiosis may be critical factors involved in the pathogenesis of functional gut disorders, such as IBS

Adaptive changes of the gastrointestinal neuromuscolar function in a mouse model of Catechol-O-Methyl trasferase genetic reduction: implication in the pathogenesis of Irritable Bowel syndrome.

Enteric neuronal circuitries display a considerable ability to adapt to a changing microenvironment, which comprises several cellular "players", including neurons, enteric glial cells, smooth muscle cells, interstitial cells of Cajal, immune cells and commensal bacteria (Giaroni et al., 1999). In particular, gut microbiota seems to be directly involved in modulating the development and function of enteric nervous system (ENS), supporting the concept that changes in commensal microbiome composition, induced by infections or antibiotics, can perturb ENS integrity and activity. Neuronal circuitries in the ENS are known to communicate with the Central Nervous System (CNS) via vagal and sympathetic extrinsic pathways: the so called brain-gut axis. Current cutting-edge research suggests that the enteric microbiota, by modifying enteric neuronal circuitries, may communicate with the brain, thus influencing cognitive and behavioural functions. However, early life perturbations of gut microbiota can potentially influence neurodevelopment leading to functional bowel disorders later in life (Ianiro et al., 2016). There is increasing evidence showing that an altered microbiota composition may be related to functional or psychiatric disorders such as irritable bowel syndrome (Bonfrate et al., 2013; Kennedy et al., 2014) and autism (Finegold, 2011; Mayer et al., 2014). Irritable bowel syndrome (IBS) comprises a heterogeneous group of functional lower gastrointestinal tract disorders characterized by abdominal pain or discomfort associated with altered bowel habits and disordered defecation that may be exacerbated by emotional stress. This gut disorder cannot be explained by specific pathophysiologic mechanisms, since it is not associated with any structural finding or biological marker (Mach, 2004). However, the symptoms of IBS are related to combinations of several known physiological determinants such as abnormal motor reactivity, enhanced visceral hypersensitivity, altered mucosal immune and inflammatory functions (which includes changes in bacterial flora), and altered brain-ENS regulation, which is influenced by psychosocial and socio-cultural factors (Drossman, 2006; Ohman and Simren, 2010; Simren et al., 2013). Recently, the association between gut functional disorders, such as IBS, and catechol-O-methyl-transferase (COMT), an enzyme protein which regulates catecholamines levels in mammalian brain (Lundstrom et al., 1995; Mannisto and Kaakkola, 1999) has been proposed. In this perspective, IBS can be described as a disorder of the gut–brain axis (Moloney et al., 2016). The aim of the study was to determine whether a genetic-driven defective COMT activity may affect the structural and functional integrity of murine ENS. Data obtained in the COMTtransgenic mouse model have been compared to those obtained in the gastrointestinal tract of antibiotic treated-mice in order to deplete the microbiota. Data showed that the partial deletion of COMT determined anomalies in the ENS architecture, with a marked increase in protein and mRNA expression of the glial marker S100β. Excitatory cholinergic transmission and inhibitory nitrergic neurotransmission, mainly through iNOS increased expression, led to impaired gut neuromuscular contractility. In addition, an increase of GluN1 glutamatergic subunit expression, affecting visceral hypersensitivity with critical effects on gut function, was also observed. The massive antibiotic treatment determined the same alterations in ENS structure and function observed in the COMT transgenic model. Interestingly, COMT partial genetic deletion induced changes in gut microbioma composition and some commensal intestinal microbial strains underwent drastic changes. In particular, in COMT+/- mice a significant increase of Firmicutes DNA in the ileum and colon and a significant decrease of Bacterioidetes DNA in the ileum were observed with respect to control animals, suggesting that host may affect gut microbial flora arrangement. These data confirmed the importance of studying the interplay between host and microbiota, reflecting alterations in motor and sensitive parameters which resemble some features of functional gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS). In conclusion, this study showed that both COMT genetic deletion as well as dysbiosis may be critical factors involved in the pathogenesis of functional gut disorders, such as IBS

Adaptive changes of the gastrointestinal neuromuscolar function in a mouse model of Catechol-O-Methyl trasferase genetic reduction: implication in the pathogenesis of Irritable Bowel syndrome.

Enteric neuronal circuitries display a considerable ability to adapt to a changing microenvironment, which comprises several cellular "players", including neurons, enteric glial cells, smooth muscle cells, interstitial cells of Cajal, immune cells and commensal bacteria (Giaroni et al., 1999). In particular, gut microbiota seems to be directly involved in modulating the development and function of enteric nervous system (ENS), supporting the concept that changes in commensal microbiome composition, induced by infections or antibiotics, can perturb ENS integrity and activity. Neuronal circuitries in the ENS are known to communicate with the Central Nervous System (CNS) via vagal and sympathetic extrinsic pathways: the so called brain-gut axis. Current cutting-edge research suggests that the enteric microbiota, by modifying enteric neuronal circuitries, may communicate with the brain, thus influencing cognitive and behavioural functions. However, early life perturbations of gut microbiota can potentially influence neurodevelopment leading to functional bowel disorders later in life (Ianiro et al., 2016). There is increasing evidence showing that an altered microbiota composition may be related to functional or psychiatric disorders such as irritable bowel syndrome (Bonfrate et al., 2013; Kennedy et al., 2014) and autism (Finegold, 2011; Mayer et al., 2014). Irritable bowel syndrome (IBS) comprises a heterogeneous group of functional lower gastrointestinal tract disorders characterized by abdominal pain or discomfort associated with altered bowel habits and disordered defecation that may be exacerbated by emotional stress. This gut disorder cannot be explained by specific pathophysiologic mechanisms, since it is not associated with any structural finding or biological marker (Mach, 2004). However, the symptoms of IBS are related to combinations of several known physiological determinants such as abnormal motor reactivity, enhanced visceral hypersensitivity, altered mucosal immune and inflammatory functions (which includes changes in bacterial flora), and altered brain-ENS regulation, which is influenced by psychosocial and socio-cultural factors (Drossman, 2006; Ohman and Simren, 2010; Simren et al., 2013). Recently, the association between gut functional disorders, such as IBS, and catechol-O-methyl-transferase (COMT), an enzyme protein which regulates catecholamines levels in mammalian brain (Lundstrom et al., 1995; Mannisto and Kaakkola, 1999) has been proposed. In this perspective, IBS can be described as a disorder of the gut–brain axis (Moloney et al., 2016). The aim of the study was to determine whether a genetic-driven defective COMT activity may affect the structural and functional integrity of murine ENS. Data obtained in the COMTtransgenic mouse model have been compared to those obtained in the gastrointestinal tract of antibiotic treated-mice in order to deplete the microbiota. Data showed that the partial deletion of COMT determined anomalies in the ENS architecture, with a marked increase in protein and mRNA expression of the glial marker S100β. Excitatory cholinergic transmission and inhibitory nitrergic neurotransmission, mainly through iNOS increased expression, led to impaired gut neuromuscular contractility. In addition, an increase of GluN1 glutamatergic subunit expression, affecting visceral hypersensitivity with critical effects on gut function, was also observed. The massive antibiotic treatment determined the same alterations in ENS structure and function observed in the COMT transgenic model. Interestingly, COMT partial genetic deletion induced changes in gut microbioma composition and some commensal intestinal microbial strains underwent drastic changes. In particular, in COMT+/- mice a significant increase of Firmicutes DNA in the ileum and colon and a significant decrease of Bacterioidetes DNA in the ileum were observed with respect to control animals, suggesting that host may affect gut microbial flora arrangement. These data confirmed the importance of studying the interplay between host and microbiota, reflecting alterations in motor and sensitive parameters which resemble some features of functional gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS). In conclusion, this study showed that both COMT genetic deletion as well as dysbiosis may be critical factors involved in the pathogenesis of functional gut disorders, such as IBS

Role of glutamatergic neurotransmission in the enteric nervous system and brain-gut axis in health and disease

Several studies have been carried out in the last 30 years in the attempt to clarify the possible role of glutamate as a neurotransmitter/neuromodulator in the gastrointestinal tract. Such effort has provided immunohistochemical, biomolecular and functional data suggesting that the entire glutamatergic neurotransmitter machinery is present in the complex circuitries of the enteric nervous system (ENS), which participates to the local coordination of gastrointestinal functions. Glutamate is also involved in the regulation of the brain-gut axis, a bi-directional connection pathway between the central nervous system (CNS) and the gut. The neurotransmitter contributes to convey information, via afferent fibers, from the gut to the brain, and to send appropriate signals, via efferent fibers, from the brain to control gut secretion and motility. In analogy with the CNS, an increasing number of studies suggest that dysregulation of the enteric glutamatergic neurotransmitter machinery may lead to gastrointestinal dysfunctions. On the whole, this research field has opened the possibility to find new potential targets for development of drugs for the treatment of gastrointestinal diseases. The present review analyzes the more recent literature on enteric glutamatergic neurotransmission both in physiological and pathological conditions, such as gastroesophageal reflux, gastric acid hypersecretory diseases, inflammatory bowel disease, irritable bowel syndrome and intestinal ischemia/reperfusion injury

Antagonism of ionotropic glutamate receptors attenuates chemical ischemia-induced injury in rat primary cultured myenteric ganglia.

Alterations of the enteric glutamatergic transmission may underlay changes in the function of myenteric neurons following intestinal ischemia and reperfusion (I/R) contributing to impairment of gastrointestinal motility occurring in these pathological conditions. The aim of the present study was to evaluate whether glutamate receptors of the NMDA and AMPA/kainate type are involved in myenteric neuron cell damage induced by I/R. Primary cultured rat myenteric ganglia were exposed to sodium azide and glucose deprivation (in vitro chemical ischemia). After 6 days of culture, immunoreactivity for NMDA, AMPA and kainate receptors subunits, GluN(1) and GluA(1-3), GluK(1-3) respectively, was found in myenteric neurons. In myenteric cultured ganglia, in normal metabolic conditions, -AP5, an NMDA antagonist, decreased myenteric neuron number and viability, determined by calcein AM/ethidium homodimer-1 assay, and increased reactive oxygen species (ROS) levels, measured with hydroxyphenyl fluorescein. CNQX, an AMPA/kainate antagonist exerted an opposite action on the same parameters. The total number and viability of myenteric neurons significantly decreased after I/R. In these conditions, the number of neurons staining for GluN1 and GluA(1-3) subunits remained unchanged, while, the number of GluK(1-3)-immunopositive neurons increased. After I/R, -AP5 and CNQX, concentration-dependently increased myenteric neuron number and significantly increased the number of living neurons. Both -AP5 and CNQX (100-500 µM) decreased I/R-induced increase of ROS levels in myenteric ganglia. On the whole, the present data provide evidence that, under normal metabolic conditions, the enteric glutamatergic system exerts a dualistic effect on cultured myenteric ganglia, either by improving or reducing neuron survival via NMDA or AMPA/kainate receptor activation, respectively. However, blockade of both receptor pathways may exert a protective role on myenteric neurons following and I/R damage. The neuroprotective effect may depend, at least in part, on the ability of both receptors to increase intraneuronal ROS production

nELAV mRNA-binding protein, HuC/D alteration in adolescent mice small intestine after antibiotic treatment-induced dysbiosis

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Effect of -AP5 and CNQX on myenteric neuron viability measured by calcein AM permeability after I/R damage.

<p>Bars indicate the percentage variation of live cells on the total cell count in the absence and presence of -AP5 and CNQX in normal metabolic conditions (empty bars), after chemical ischemia (backslash) and after reperfusion (slash). Drug treatments are reported at the bottom of each graph. Each point represents the mean of 3 experiments. Vertical bars indicate S.E.M. <i>P</i><0.01 and <i>P</i><0.001 with respect to normal metabolic conditions without drug treatment, by one way ANOVA followed by Tukey's post hoc test.</p