Glucagon-like peptides 1 and 2 and vasoactive intestinal peptide are neuroprotective on cultured and mast cell co-cultured rat myenteric neurons

<p>Abstract</p> <p>Background</p> <p>Neuropathy is believed to be a common feature of functional and inflammatory intestinal diseases. Vasoactive intestinal peptide (VIP) is an acknowledged neuroprotective agent in peripheral, including enteric, and central neurons. The proglucagon-like hormones glucagon-like peptide 1 and 2 (GLP1 and GLP2) belong to the secretin/glucagon/VIP superfamily of peptides and GLP1 and GLP2 receptors are expressed in enteric neurons. Possible neuroprotective effects of these peptides were investigated in the present study.</p> <p>Methods</p> <p>GLP1, GLP2 and VIP were added to cultured myenteric neurons from rat small intestine or to co-cultures of myenteric neurons and rat peritoneal mast cells. Receptor selectivity was tested by the simultaneous presence of a GLP1 receptor antagonist (exendin (9-39) amide) or a VIP receptor antagonist (hybrid of neurotensin 6-11 and VIP 7-28). Neuronal survival was examined using immunocytochemistry and cell counting.</p> <p>Results</p> <p>GLP1, GLP2 and VIP significantly and concentration-dependently enhanced neuronal survival. In addition the peptides efficiently counteracted mast cell-induced neuronal cell death in a concentration-dependent manner. Exendin(9-39)amide reversed GLP1-induced neuroprotection while GLP2- and VIP-induced enhanced neuronal survival were unaffected. The VIP receptor antagonist reversed GLP1- and VIP-induced neuroprotection while the GLP2-induced effect on neuronal survival was unaffected.</p> <p>Conclusions</p> <p>By activating separate receptors VIP, GLP1 and GLP2 elicit neuroprotective effects on rat myenteric neurons cultured with or without mast cells. This implies a powerful therapeutic potential of these peptides in enteric neuropathies with a broad spectrum of applications from autoimmunity to functional disorders.</p

Expression and distribution of GnRH, LH, and FSH and their receptors in gastrointestinal tract of man and rat.

Gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) regulate the reproductive axis. Their analogs have been found to influence gastrointestinal activity and enteric neuronal survival. The aims of the study were to investigate expression and cellular distribution of GnRH, LH, and FSH and their receptors in human and rat gastrointestinal tract

Buserelin treatment to rats causes enteric neurodegeneration with moderate effects on CRF-immunoreactive neurons and Enterobacteriaceae in colon, and in acetylcholine-mediated permeability in ileum

The gonadotropin-releasing hormone (GnRH) analog buserelin causes enteric neuronal loss. Acute stress or injection of corticotropin-releasing factor (CRF) affects motility, secretion, and barrier function of the gastrointestinal tract. The aim of the study was to characterize the CRF immunoreactivity in enteric neurons after buserelin treatment, and to evaluate possible effects of enteric neuropathy on gut microbiota, intestinal permeability, and stress response behavior

Characterization of gastric mucosa biopsies reveals alterations in Huntington's Disease

Weight loss is an important complication of Huntington's disease (HD), however the mechanism for weight loss in HD is not entirely understood. Mutant huntingtin is expressed in the gastrointestinal (GI) tract and, in HD mice, mutant huntingtin inclusions are found within the enteric nervous system along the GI tract. A reduction of neuropeptides, decreased mucosal thickness and villus length, as well as gut motility impairment, have also been shown in HD mice. We therefore set out to study gastric mucosa of patients with HD, looking for abnormalities of mucosal cells using immunohistochemistry. In order to investigate possible histological differences related to gastric acid production, we evaluated the cell density of acid producing parietal cells, as well as gastrin producing cells (the endocrine cell controlling parietal cell function). In addition, we looked at chief cells and somatostatin-containing cells. In gastric mucosa from HD subjects, compared to control subject biopsies, a reduced expression of gastrin (a marker of G cells) was found. This is in line with previous HD mouse studies showing reduction of GI tract neuropeptides

Neuroimmune Interactions of Enteric Neurons and Mast Cells: Friends or Foes?

Psychological distress or physical strain lead to reduced blood flow in the intestine since other organs are prioritised. One aim of this thesis was to investigate how ischemia followed by reperfusion affects the large intestine and the enteric nervous system (ENS). To do so an experimental ischemia/reperfusion (I/R) model was set up using rat large intestine. In order to study how the ENS reacts to various mediators of stress, primary cultures of myenteric neurons from rat small and large intestine were used to study neuronal survival. The intestinal segments exposed to I/R were structurally well preserved, however, local areas containing numerous mast cells were detected in the muscle layers, the serosa and in and around the myenteric ganglia 4-20 weeks post ischemia. Myenteric ganglionic formations within such mast cell rich areas virtually lacked neurons. Myenteric neurons co-cultured with mast cells showed a markedly reduced neuronal survival. The increased neuronal cell death was largely due to mast cell degranulation. Identified mast cell mediators involved were proteinases acting via proteinase activated receptor 2 (PAR2), prostaglandin D2 (PGD2) and interleukin 6 (IL-6). Immunocytochemical examination of rat small and large intestine, revealed frequent co-localization of corticotropin releasing peptide (CRF), known to induce psychological stress reactions in mammals, and vasoactive intestinal peptide (VIP) in enteric neurons. CRF did not affect the survival of myenteric neurons in culture, but was found to counteract the VIP-induced neuroprotective effect. We also showed that the mast cell-induced increase in cell death of cultured myenteric neurons was not executed via CRF signaling pathways. In conclusion: I/R in rat large intestine attracted mast cells to invade the muscle layers and myenteric ganglia. In mast cell-infiltrated areas, ganglionic formations lacked myenteric neurons. Mast cells reduced neuronal survival when cultured together with myenteric neurons from rat small intestine. The mechanisms behind is through PAR2 activation and release of PGD2 and IL-6. Presence of CRF counteracted VIP-induced neuroprotection in cultured myenteric neurons

Vasoactive intestinal peptide rescues cultured rat myenteric neurons from lipopolysaccharide induced cell death

The role of the enteric nervous system in intestinal inflammation is not fully understood and the plethora of cellular activities concurrently ongoing in vivo renders intelligible studies difficult. In order to explore possible effects of bacterial lipopolysaccharide (LPS) on enteric neurons we utilised cultured myenteric neurons from rat small intestine. Exposure to LPS caused markedly reduced neuronal survival and increased neuronal expression of vasoactive intestinal peptide (VIP), while the expression of Toll-like receptor 4 (TLR4) was unchanged. TLR4 was expressed in approximately 35% of all myenteric neurons irrespective of if they were cultured in the presence or absence of LPS. In neurons cultured in medium, without LPS, 50% of all TLR4-immunoreactive neurons contained also VIP. Addition of LPS to the neuronal cultures markedly increased the proportion of TLR4-immunoreactive neurons also expressing VIP, while the proportion of TLR4 neurons devoid of VIP decreased. Simultaneous addition of LPS and VIP to the neuronal cultures resulted in a neuronal survival comparable to controls. CONCLUSIONS: LPS recognition by myenteric neurons is mediated via TLR4 and causes neuronal cell death. Presence of VIP rescues the neurons from LPS-induced neurodegeneration

Mast cells reduce survival of myenteric neurons in culture.

Mast cell-nerve interactions play a key role in intestinal inflammation and irritable bowel disease. Loss of enteric neurons has been reported in inflammatory conditions but the contribution of mast cells in this event is unknown. To study neuronal survival and plasticity of myenteric neurons in contact with mast cells a co-culture system using myenteric neurons from rat small intestine and peritoneal mast cells was set up. Dissociated myenteric neurons were cultured for 4 days before addition of mast cells isolated by peritoneal lavage. Neuronal survival and expression of vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) were studied by immunocytochemistry and neuronal cell counting. Myenteric neurons cultured without mast cells were used to study the rate of neuronal survival after the addition of various mast cell mediators, proteinase-activated receptor(2) (PAR(2)) agonist, VIP or corticosteroid. A striking mast cell-induced neuronal cell death was found after co-culturing. It was counteracted by the addition of mast cell stabiliser doxantrazole, protease inhibitors, PAR(2) antagonist FSLLRY-amide, corticosteroid or VIP. In myenteric neurons cultured without mast cells the PAR(2) agonist SLIGRL-amide, prostaglandin D(2) and interleukin (IL) 6 reduced neuronal survival while histamine, serotonin, heparin, IL1beta and tumour necrosis factor alpha had no effect; corticosteroid and VIP enhanced neuronal survival. The relative numbers of VIP-, but not NOS-expressing myenteric neurons increased after co-culturing. Mast cell-induced neuronal cell death is suggested to be mediated via PAR(2) activation, IL6 and prostaglandin D(2). Corticosteroid and VIP are neuroprotective and able to prevent cell death of myenteric neurons in co-culture

Infiltration of Mast Cells in Rat Colon Is a Consequence of Ischemia/Reperfusion.

Intestinal ischemia as well as mastocytosis occur in patients with inflammatory bowel disease and irritable bowel syndrome. Our aim was to clarify how ischemia with reperfusion (I/R) affects the structure, enteric neurons, and immune cells in the colon. Rats were subjected to colon ischemia for 1 h and reperfused for 1 day up to 20 weeks; sham-operated rats were used as controls. No structural remodeling of the intestinal segment was detected after I/R. The number and distribution of eosinophils were not affected by I/R. Local areas containing numerous mast cells were detected in the muscle layers, the serosa, and in and around the myenteric ganglia 4-20 weeks post ischemia. It was notable that myenteric ganglionic formations within mast-cell-rich areas virtually lacked neurons. Mast cells were rarely found in controls. In conclusion, I/R of the colon attracts mast cells, and death of myenteric neurons occurs in such locations