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Sansores-España LD, Melgar-Rodríguez S, Olivares-Sagredo K, Cafferata EA, Martínez-Aguilar VM, Vernal R, Paula-Lima AC, Díaz-Zúñiga J. Oral-Gut-Brain Axis in Experimental Models of Periodontitis: Associating Gut Dysbiosis With Neurodegenerative Diseases. FRONTIERS IN AGING 2021; 2:781582. [PMID: 35822001 PMCID: PMC9261337 DOI: 10.3389/fragi.2021.781582] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/08/2021] [Indexed: 12/12/2022]
Abstract
Periodontitis is considered a non-communicable chronic disease caused by a dysbiotic microbiota, which generates a low-grade systemic inflammation that chronically damages the organism. Several studies have associated periodontitis with other chronic non-communicable diseases, such as cardiovascular or neurodegenerative diseases. Besides, the oral bacteria considered a keystone pathogen, Porphyromonas gingivalis, has been detected in the hippocampus and brain cortex. Likewise, gut microbiota dysbiosis triggers a low-grade systemic inflammation, which also favors the risk for both cardiovascular and neurodegenerative diseases. Recently, the existence of an axis of Oral-Gut communication has been proposed, whose possible involvement in the development of neurodegenerative diseases has not been uncovered yet. The present review aims to compile evidence that the dysbiosis of the oral microbiota triggers changes in the gut microbiota, which creates a higher predisposition for the development of neuroinflammatory or neurodegenerative diseases.The Oral-Gut-Brain axis could be defined based on anatomical communications, where the mouth and the intestine are in constant communication. The oral-brain axis is mainly established from the trigeminal nerve and the gut-brain axis from the vagus nerve. The oral-gut communication is defined from an anatomical relation and the constant swallowing of oral bacteria. The gut-brain communication is more complex and due to bacteria-cells, immune and nervous system interactions. Thus, the gut-brain and oral-brain axis are in a bi-directional relationship. Through the qualitative analysis of the selected papers, we conclude that experimental periodontitis could produce both neurodegenerative pathologies and intestinal dysbiosis, and that periodontitis is likely to induce both conditions simultaneously. The severity of the neurodegenerative disease could depend, at least in part, on the effects of periodontitis in the gut microbiota, which could strengthen the immune response and create an injurious inflammatory and dysbiotic cycle. Thus, dementias would have their onset in dysbiotic phenomena that affect the oral cavity or the intestine. The selected studies allow us to speculate that oral-gut-brain communication exists, and bacteria probably get to the brain via trigeminal and vagus nerves.
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Affiliation(s)
- Luis Daniel Sansores-España
- Periodontal Biology Laboratory, Faculty of Dentistry, University of Chile, Santiago, Chile
- Faculty of Dentistry, Autonomous University of Yucatán, Mérida, México
| | | | | | - Emilio A. Cafferata
- Department of Periodontology, School of Dentistry, Universidad Científica Del Sur, Lima, Perú
| | | | - Rolando Vernal
- Periodontal Biology Laboratory, Faculty of Dentistry, University of Chile, Santiago, Chile
| | - Andrea Cristina Paula-Lima
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
| | - Jaime Díaz-Zúñiga
- Periodontal Biology Laboratory, Faculty of Dentistry, University of Chile, Santiago, Chile
- Department of Medicine, Faculty of Medicine, University of Atacama, Copiapó, Chile
- *Correspondence: Jaime Díaz-Zúñiga, ,
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Nagu P, Parashar A, Behl T, Mehta V. Gut Microbiota Composition and Epigenetic Molecular Changes Connected to the Pathogenesis of Alzheimer's Disease. J Mol Neurosci 2021; 71:1436-1455. [PMID: 33829390 DOI: 10.1007/s12031-021-01829-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 03/11/2021] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder, and its pathogenesis is not fully known. Although there are several hypotheses, such as neuroinflammation, tau hyperphosphorylation, amyloid-β plaques, neurofibrillary tangles, and oxidative stress, none of them completely explain the origin and progression of AD. Emerging evidence suggests that gut microbiota and epigenetics can directly influence the pathogenesis of AD via their effects on multiple pathways, including neuroinflammation, oxidative stress, and amyloid protein. Various gut microbes such as Actinobacteria, Bacteroidetes, E. coli, Firmicutes, Proteobacteria, Tenericutes, and Verrucomicrobia are known to play a crucial role in the pathogenesis of AD. These microbes and their metabolites modulate various physiological processes that contribute to AD pathogenesis, such as neuroinflammation and other inflammatory processes, amyloid deposition, cytokine storm syndrome, altered BDNF and NMDA signaling, impairing neurodevelopmental processes. Likewise, epigenetic markers associated with AD mainly include histone modifications and DNA methylation, which are under the direct control of a variety of enzymes, such as acetylases and methylases. The activity of these enzymes is dependent upon the metabolites generated by the host's gut microbiome, suggesting the significance of epigenetics in AD pathogenesis. It is interesting to know that both gut microbiota and epigenetics are dynamic processes and show a high degree of variation according to diet, stressors, and environmental factors. The bidirectional relation between the gut microbiota and epigenetics suggests that they might work in synchrony to modulate AD representation, its pathogenesis, and progression. They both also provide numerous targets for early diagnostic biomarkers and for the development of AD therapeutics. This review discusses the gut microbiota and epigenetics connection in the pathogenesis of AD and aims to highlight vast opportunities for diagnosis and therapeutics of AD.
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Affiliation(s)
- Priyanka Nagu
- Department of Pharmaceutics, Govt. College of Pharmacy, Rohru, Himachal Pradesh, India.,Department of Pharmacy, Shri Jagdishprasad Jhabarmal Tibrewala University, Jhunjhunu, Rajasthan, India
| | - Arun Parashar
- Faculty of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, Himachal Pradesh, India
| | - Tapan Behl
- Chitkara College of Pharmacy, Chitkara University, Punjab, India
| | - Vineet Mehta
- Department of Pharmacology, Govt. College of Pharmacy, Rohru, Himachal Pradesh, India.
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Birsen İ, İzgüt-Uysal VN, Soylu H, Üstünel İ. The effect of apelin-13 on gastric ischemia/reperfusion injury: the roles of sensory nerves and vagus nerve. Can J Physiol Pharmacol 2019; 98:282-295. [PMID: 31821012 DOI: 10.1139/cjpp-2019-0502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Apelin is a peptide that plays a role in physiological processes such as angiogenesis, apoptosis, and proliferation. The aim of this study was to investigate the role of capsaicin-sensitive afferent neurons and vagus in the effect of apelin against ischemia/reperfusion (I/R) injury. The experimental groups were (1) control, (2) I/R, (3) apelin + I/R, (4) vagotomy + I/R, (5) vagotomy + apelin + I/R, (6) capsaicin + I/R, (7) capsaicin + apelin + I/R, (8) lorglumide + I/R, and (9) lorglumide + apelin + I/R. To test the potential gastroprotective effect of apelin-13, apelin-13 (2 mg/kg i.v.) was administered just before both ischemia and reperfusion. A vagotomy was performed 1 week before I/R in the vagotomized groups; capsaicin (125 mg/kg s.c.) was administrated 2 weeks before I/R in the capsaicin-treated groups and lorglumide (5 mg/kg i.p.) was administered 30 min before I/R in the lorglumide-treated groups. After I/R, a variety parameters in gastric tissue were analyzed. cfos expression was determined in brainstem samples. In the I/R group, the lesion index, myeloperoxidase activity, lipid peroxidation, nitric oxide, and tumor necrosis factor-α increased, and mucosal blood flow, prostaglandin-E2, and calcitonin gene related peptide decreased. Apelin prevented the damaging effects of I/R and increased cfos expression in brainstem areas. Vagotomy, capsaicin, and lorglumide largely eliminated the gastroprotective effects of apelin-13. This study showed that sensory nerves and the vagus play regulatory roles in apelin-induced gastroprotection. Cholecystokinin may play a role in the effect of apelin through sensory neurons.
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Affiliation(s)
- İlknur Birsen
- Department of Physiology, Faculty of Medicine, Biruni University, 34096 İstanbul, Turkey
| | - V Nimet İzgüt-Uysal
- Department of Physiology, Faculty of Medicine, Akdeniz University, 07070 Antalya, Turkey
| | - Hakan Soylu
- Department of Histology and Embryology, Faculty of Medicine, Düzce University, 81620 Düzce, Turkey
| | - İsmail Üstünel
- Department of Histology and Embryology, Faculty of Medicine, Akdeniz University, 07070 Antalya, Turkey
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Mulders RJ, de Git KCG, Schéle E, Dickson SL, Sanz Y, Adan RAH. Microbiota in obesity: interactions with enteroendocrine, immune and central nervous systems. Obes Rev 2018; 19:435-451. [PMID: 29363272 DOI: 10.1111/obr.12661] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 11/27/2017] [Accepted: 11/27/2017] [Indexed: 02/06/2023]
Abstract
Western diets, with high consumption of simple sugars and saturated fats, contribute to the rise in the prevalence of obesity. It now seems clear that high-fat diets cause obesity, at least in part, by modifying the composition and function of the microorganisms that colonize in the gastrointestinal tract, the microbiota. The exact pathways by which intestinal microbiota contribute to obesity remain largely unknown. High-fat diet-induced alterations in intestinal microbiota have been suggested to increase energy extraction, intestinal permeability and systemic inflammation while decreasing the capability to generate obesity-suppressing short-chain fatty acids. Moreover, by increasing systemic inflammation, microglial activation and affecting vagal nerve activity, 'obese microbiota' indirectly influence hypothalamic gene expression and promote overeating. Because the potential of intestinal microbiota to induce obesity has been recognized, multiple ways to modify its composition and function are being investigated to provide novel preventive and therapeutic strategies against diet-induced obesity.
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Affiliation(s)
- R J Mulders
- Master's Programme Science and Business Management, Utrecht University, Utrecht, The Netherlands
| | - K C G de Git
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - E Schéle
- Institute for Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - S L Dickson
- Institute for Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Y Sanz
- Microbial Ecology, Nutrition and Health Research Group, Institute of Agrochemistry and Food Technology, National Research Council (IATA-CSIC), Valencia, Spain
| | - R A H Adan
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
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Holzer P, Farzi A, Hassan AM, Zenz G, Jačan A, Reichmann F. Visceral Inflammation and Immune Activation Stress the Brain. Front Immunol 2017; 8:1613. [PMID: 29213271 PMCID: PMC5702648 DOI: 10.3389/fimmu.2017.01613] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 11/07/2017] [Indexed: 12/20/2022] Open
Abstract
Stress refers to a dynamic process in which the homeostasis of an organism is challenged, the outcome depending on the type, severity, and duration of stressors involved, the stress responses triggered, and the stress resilience of the organism. Importantly, the relationship between stress and the immune system is bidirectional, as not only stressors have an impact on immune function, but alterations in immune function themselves can elicit stress responses. Such bidirectional interactions have been prominently identified to occur in the gastrointestinal tract in which there is a close cross-talk between the gut microbiota and the local immune system, governed by the permeability of the intestinal mucosa. External stressors disturb the homeostasis between microbiota and gut, these disturbances being signaled to the brain via multiple communication pathways constituting the gut-brain axis, ultimately eliciting stress responses and perturbations of brain function. In view of these relationships, the present article sets out to highlight some of the interactions between peripheral immune activation, especially in the visceral system, and brain function, behavior, and stress coping. These issues are exemplified by the way through which the intestinal microbiota as well as microbe-associated molecular patterns including lipopolysaccharide communicate with the immune system and brain, and the mechanisms whereby overt inflammation in the GI tract impacts on emotional-affective behavior, pain sensitivity, and stress coping. The interactions between the peripheral immune system and the brain take place along the gut-brain axis, the major communication pathways of which comprise microbial metabolites, gut hormones, immune mediators, and sensory neurons. Through these signaling systems, several transmitter and neuropeptide systems within the brain are altered under conditions of peripheral immune stress, enabling adaptive processes related to stress coping and resilience to take place. These aspects of the impact of immune stress on molecular and behavioral processes in the brain have a bearing on several disturbances of mental health and highlight novel opportunities of therapeutic intervention.
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Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria
| | - Aitak Farzi
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Ahmed M Hassan
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Geraldine Zenz
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Angela Jačan
- CBmed GmbH-Center for Biomarker Research in Medicine, Graz, Austria
| | - Florian Reichmann
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
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Oświęcimska J, Szymlak A, Roczniak W, Girczys-Połedniok K, Kwiecień J. New insights into the pathogenesis and treatment of irritable bowel syndrome. Adv Med Sci 2017; 62:17-30. [PMID: 28135659 DOI: 10.1016/j.advms.2016.11.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 10/16/2016] [Accepted: 11/12/2016] [Indexed: 02/08/2023]
Abstract
Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders (FGID), characterized by abdominal pain and a change in stool form that cannot be explained by structural abnormalities. Its prevalence ranges from 9 to 23% of the worldwide population. The pathophysiology of IBS is diverse and not well understood. Biopsychosocial concept assumes that the disease is a product of psychosocial factors and altered at multiple levels of gut physiology interactions. Some aetiological factors have been identified, yet. One of the most important is the disruption of brain-gut mutual communication that leads to visceral hypersensitivity. Also genetic and epigenetic factors are involved. Chronic stress may predispose to IBS as well as exacerbate its symptoms. Both quantitative and qualitative disorders of the gut microbiota are observed. There is also a relationship between the IBS symptoms and the intake of a specific type of food products. In the diarrhoea type of IBS the role of previous gastrointestinal infection is demonstrated. Recent studies have suggested that visceral hypersensitivity in patients with IBS may be secondary to the activation of the immune cells and low-grade inflammation. Clinical symptoms of IBS include abdominal pain and change in bowel habits as well as somatic and psychiatric comorbidities. IBS is diagnosed on the basis of Rome Diagnostic Criteria. Recently, their newest version (Rome IV) has been presented. The aim of this review is to summarize the past decade progress in IBS diagnosis, main pathophysiological aspects and therapeutic management strategy.
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Affiliation(s)
- Joanna Oświęcimska
- Chair and Department of Paediatrics, School of Medicine with Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, Poland.
| | - Agnieszka Szymlak
- Department of Paediatric Endocrinology, Prof. Stanisław Szyszko Independent Public University Hospital No 1 in Zabrze, Medical University of Silesia in Katowice, Poland
| | - Wojciech Roczniak
- Institute of Medicine, Jan Grodek State Vocational School in Sanok, Poland
| | - Katarzyna Girczys-Połedniok
- Chair and Department of Psychiatry, School of Medicine with Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, Poland
| | - Jarosław Kwiecień
- Chair and Department of Paediatrics, School of Medicine with Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, Poland
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Yarandi SS, Peterson DA, Treisman GJ, Moran TH, Pasricha PJ. Modulatory Effects of Gut Microbiota on the Central Nervous System: How Gut Could Play a Role in Neuropsychiatric Health and Diseases. J Neurogastroenterol Motil 2016; 22:201-12. [PMID: 27032544 PMCID: PMC4819858 DOI: 10.5056/jnm15146] [Citation(s) in RCA: 157] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 01/12/2016] [Accepted: 01/27/2016] [Indexed: 12/11/2022] Open
Abstract
Gut microbiome is an integral part of the Gut-Brain axis. It is becoming increasingly recognized that the presence of a healthy and diverse gut microbiota is important to normal cognitive and emotional processing. It was known that altered emotional state and chronic stress can change the composition of gut microbiome, but it is becoming more evident that interaction between gut microbiome and central nervous system is bidirectional. Alteration in the composition of the gut microbiome can potentially lead to increased intestinal permeability and impair the function of the intestinal barrier. Subsequently, neuro-active compounds and metabolites can gain access to the areas within the central nervous system that regulate cognition and emotional responses. Deregulated inflammatory response, promoted by harmful microbiota, can activate the vagal system and impact neuropsychological functions. Some bacteria can produce peptides or short chain fatty acids that can affect gene expression and inflammation within the central nervous system. In this review, we summarize the evidence supporting the role of gut microbiota in modulating neuropsychological functions of the central nervous system and exploring the potential underlying mechanisms.
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Affiliation(s)
- Shadi S Yarandi
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
| | - Daniel A Peterson
- Division of Immunology, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Glen J Treisman
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Timothy H Moran
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Pankaj J Pasricha
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
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Herrity AN, Rau KK, Petruska JC, Stirling DP, Hubscher CH. Identification of bladder and colon afferents in the nodose ganglia of male rats. J Comp Neurol 2014; 522:3667-82. [PMID: 24845615 DOI: 10.1002/cne.23629] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/19/2014] [Accepted: 05/19/2014] [Indexed: 12/14/2022]
Abstract
The sensory neurons innervating the urinary bladder and distal colon project to similar regions of the central nervous system and often are affected simultaneously by various diseases and disorders, including spinal cord injury. Anatomical and physiological commonalities between the two organs involve the participation of shared spinally derived pathways, allowing mechanisms of communication between the bladder and colon. Prior electrophysiological data from our laboratory suggest that the bladder also may receive sensory innervation from a nonspinal source through the vagus nerve, which innervates the distal colon as well. The present study therefore aimed to determine whether anatomical evidence exists for vagal innervation of the male rat urinary bladder and to assess whether those vagal afferents also innervate the colon. Additionally, the relative contribution to bladder and colon sensory innervation of spinal and vagal sources was determined. By using lipophilic tracers, neurons that innervated the bladder and colon in both the nodose ganglia (NG) and L6/S1 and L1/L2 dorsal root ganglia (DRG) were quantified. Some single vagal and spinal neurons provided dual innervation to both organs. The proportions of NG afferents labeled from the bladder did not differ from spinal afferents labeled from the bladder when considering the collective population of total neurons from either group. Our results demonstrate evidence for vagal innervation of the bladder and colon and suggest that dichotomizing vagal afferents may provide a neural mechanism for cross-talk between the organs.
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Affiliation(s)
- April N Herrity
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky, 40202; Kentucky Spinal Cord Injury Research Center University of Louisville, Louisville, Kentucky, 40202
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Duca FA, Sakar Y, Lepage P, Devime F, Langelier B, Doré J, Covasa M. Replication of obesity and associated signaling pathways through transfer of microbiota from obese-prone rats. Diabetes 2014; 63:1624-36. [PMID: 24430437 DOI: 10.2337/db13-1526] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Aberrations in gut microbiota are associated with metabolic disorders, including obesity. However, whether shifts in the microbiota profile during obesity are a characteristic of the phenotype or a consequence of obesogenic feeding remains elusive. Therefore, we aimed to determine differences in the gut microbiota of obese-prone (OP) and obese-resistant (OR) rats and examined the contribution of this microbiota to the behavioral and metabolic characteristics during obesity. We found that OP rats display a gut microbiota distinct from OR rats fed the same high-fat diet, with a higher Firmicutes-to-Bacteroidetes ratio and significant genera differences. Transfer of OP but not OR microbiota to germ-free (GF) mice replicated the characteristics of the OP phenotype, including reduced intestinal and hypothalamic satiation signaling, hyperphagia, increased weight gain and adiposity, and enhanced lipogenesis and adipogenesis. Furthermore, increased gut permeability through conventionalization resulted in inflammation by proinflammatory nuclear factor (NF)-κB/inhibitor of NF-κB kinase subunit signaling in adipose tissue, liver, and hypothalamus. OP donor and GF recipient animals harbored specific species from Oscillibacter and Clostridium clusters XIVa and IV that were completely absent from OR animals. In conclusion, susceptibility to obesity is characterized by an unfavorable microbiome predisposing the host to peripheral and central inflammation and promoting weight gain and adiposity during obesogenic feeding.
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Affiliation(s)
- Frank A Duca
- UMR1913-Microbiologie de l'Alimentation au Service de la Santé, l'Institut National de la Recherche Agronomique, Jouy-en-Josas, France
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Neuropeptides and the microbiota-gut-brain axis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 817:195-219. [PMID: 24997035 DOI: 10.1007/978-1-4939-0897-4_9] [Citation(s) in RCA: 269] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neuropeptides are important mediators both within the nervous system and between neurons and other cell types. Neuropeptides such as substance P, calcitonin gene-related peptide and neuropeptide Y (NPY), vasoactive intestinal polypeptide, somatostatin and corticotropin-releasing factor are also likely to play a role in the bidirectional gut-brain communication. In this capacity they may influence the activity of the gastrointestinal microbiota and its interaction with the gut-brain axis. Current efforts in elucidating the implication of neuropeptides in the microbiota-gut-brain axis address four information carriers from the gut to the brain (vagal and spinal afferent neurons; immune mediators such as cytokines; gut hormones; gut microbiota-derived signalling molecules) and four information carriers from the central nervous system to the gut (sympathetic efferent neurons; parasympathetic efferent neurons; neuroendocrine factors involving the adrenal medulla; neuroendocrine factors involving the adrenal cortex). Apart from operating as neurotransmitters, many biologically active peptides also function as gut hormones. Given that neuropeptides and gut hormones target the same cell membrane receptors (typically G protein-coupled receptors), the two messenger roles often converge in the same or similar biological implications. This is exemplified by NPY and peptide YY (PYY), two members of the PP-fold peptide family. While PYY is almost exclusively expressed by enteroendocrine cells, NPY is found at all levels of the gut-brain and brain-gut axis. The function of PYY-releasing enteroendocrine cells is directly influenced by short chain fatty acids generated by the intestinal microbiota from indigestible fibre, while NPY may control the impact of the gut microbiota on inflammatory processes, pain, brain function and behaviour. Although the impact of neuropeptides on the interaction between the gut microbiota and brain awaits to be analysed, biologically active peptides are likely to emerge as neural and endocrine messengers in orchestrating the microbiota-gut-brain axis in health and disease.
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Holzer P, Reichmann F, Farzi A. Neuropeptide Y, peptide YY and pancreatic polypeptide in the gut-brain axis. Neuropeptides 2012; 46:261-74. [PMID: 22979996 PMCID: PMC3516703 DOI: 10.1016/j.npep.2012.08.005] [Citation(s) in RCA: 325] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 08/04/2012] [Accepted: 08/09/2012] [Indexed: 02/06/2023]
Abstract
The gut-brain axis refers to the bidirectional communication between the gut and the brain. Four information carriers (vagal and spinal afferent neurons, immune mediators such as cytokines, gut hormones and gut microbiota-derived signalling molecules) transmit information from the gut to the brain, while autonomic neurons and neuroendocrine factors carry outputs from the brain to the gut. The members of the neuropeptide Y (NPY) family of biologically active peptides, NPY, peptide YY (PYY) and pancreatic polypeptide (PP), are expressed by cell systems at distinct levels of the gut-brain axis. PYY and PP are exclusively expressed by endocrine cells of the digestive system, whereas NPY is found at all levels of the gut-brain and brain-gut axis. The major systems expressing NPY comprise enteric neurons, primary afferent neurons, several neuronal pathways throughout the brain and sympathetic neurons. In the digestive tract, NPY and PYY inhibit gastrointestinal motility and electrolyte secretion and in this way modify the input to the brain. PYY is also influenced by the intestinal microbiota, and NPY exerts, via stimulation of Y1 receptors, a proinflammatory action. Furthermore, the NPY system protects against distinct behavioural disturbances caused by peripheral immune challenge, ameliorating the acute sickness response and preventing long-term depression. At the level of the afferent system, NPY inhibits nociceptive input from the periphery to the spinal cord and brainstem. In the brain, NPY and its receptors (Y1, Y2, Y4, Y5) play important roles in regulating food intake, energy homeostasis, anxiety, mood and stress resilience. In addition, PP and PYY signal to the brain to attenuate food intake, anxiety and depression-related behaviour. These findings underscore the important role of the NPY-Y receptor system at several levels of the gut-brain axis in which NPY, PYY and PP operate both as neural and endocrine messengers.
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Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
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Increase in gastric acid-induced afferent input to the brainstem in mice with gastritis. Neuroscience 2007; 145:1108-19. [PMID: 17303342 DOI: 10.1016/j.neuroscience.2006.12.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Revised: 11/25/2006] [Accepted: 12/12/2006] [Indexed: 01/17/2023]
Abstract
Acid challenge of the gastric mucosa is signaled to the brainstem. This study examined whether mild gastritis due to dextrane sulfate sodium (DSS) or iodoacetamide (IAA) enhances gastric acid-evoked input to the brainstem and whether this effect is related to gastric myeloperoxidase activity, gastric histology, gastric volume retention or cyclooxygenase stimulation. The stomach of conscious mice was challenged with NaCl (0.15 M) or HCl (0.15 and 0.25 M) administered via gastric gavage. Two hours later, activation of neurons in the nucleus tractus solitarii (NTS) was visualized by c-Fos immunocytochemistry. Gastritis was induced by DSS (molecular weight 8000; 5%) or IAA (0.1%) added to the drinking water for 7 days. Relative to NaCl, intragastric HCl increased the number of c-Fos protein-expressing cells in the NTS. Pretreatment with DSS or IAA for 1 week did not alter the c-Fos response to NaCl but significantly enhanced the response to HCl by 54 and 74%, respectively. Either pretreatment elevated gastric myeloperoxidase activity and induced histological injury of the mucosal surface. In addition, DSS caused dilation of the gastric glands and damage to the parietal cells. HCl-induced gastric volume retention was not altered by IAA but attenuated by DSS pretreatment. Indomethacin (5 mg/kg) failed to significantly alter HCl-evoked expression of c-Fos in the NTS of control, DSS-pretreated and IAA-pretreated mice. We conclude that the gastritis-evoked increase in the gastric acid-evoked c-Fos expression in the NTS is related to disruption of the gastric mucosal barrier, mucosal inflammation, mucosal acid influx and enhanced activation of the afferent stomach-NTS axis.
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Neuhuber WL, Raab M, Berthoud HR, Wörl J. Innervation of the mammalian esophagus. ADVANCES IN ANATOMY EMBRYOLOGY AND CELL BIOLOGY 2006. [PMID: 16573241 DOI: 10.1007/978-3-540-32948-0_1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Understanding the innervation of the esophagus is a prerequisite for successful treatment of a variety of disorders, e.g., dysphagia, achalasia, gastroesophageal reflux disease (GERD) and non-cardiac chest pain. Although, at first glance, functions of the esophagus are relatively simple, their neuronal control is considerably complex. Vagal motor neurons of the nucleus ambiguus and preganglionic neurons of the dorsal motor nucleus innervate striated and smooth muscle, respectively. Myenteric neurons represent the interface between the dorsal motor nucleus and smooth muscle but they are also involved in striated muscle innervation. Intraganglionic laminar endings (IGLEs) represent mechanosensory vagal afferent terminals. They also establish intricate connections with enteric neurons. Afferent information is implemented by the swallowing central pattern generator in the brainstem, which generates and coordinates deglutitive activity in both striated and smooth esophageal muscle and orchestrates esophageal sphincters as well as gastric adaptive relaxation. Disturbed excitation/inhibition balance in the lower esophageal sphincter results in motility disorders, e.g., achalasia and GERD. Loss of mechanosensory afferents disrupts adaptation of deglutitive motor programs to bolus variables, eventually leading to megaesophagus. Both spinal and vagal afferents appear to contribute to painful sensations, e.g., non-cardiac chest pain. Extrinsic and intrinsic neurons may be involved in intramural reflexes using acetylcholine, nitric oxide, substance P, CGRP and glutamate as main transmitters. In addition, other molecules, e.g., ATP, GABA and probably also inflammatory cytokines, may modulate these neuronal functions.
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Holzer P. Efferent-like roles of afferent neurons in the gut: Blood flow regulation and tissue protection. Auton Neurosci 2006; 125:70-5. [PMID: 16542883 PMCID: PMC4363547 DOI: 10.1016/j.autneu.2006.01.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2006] [Revised: 01/14/2006] [Accepted: 01/14/2006] [Indexed: 10/24/2022]
Abstract
The maintenance of gastrointestinal mucosal integrity depends on the rapid alarm of protective mechanisms in the face of pending injury. To this end, the gastric mucosa is innervated by intrinsic sensory neurons and two populations of extrinsic sensory neurons: vagal and spinal afferents. Extrinsic afferent neurons constitute an emergency system that is called into operation when the gastrointestinal mucosa is endangered by noxious chemicals. The function of these chemoceptive afferents can selectively be manipulated and explored with the use of capsaicin which acts via a cation channel termed TRPV1. Many of the homeostatic actions of spinal afferents are brought about by transmitter release from their peripheral endings. When stimulated by noxious chemicals, these afferents enhance gastrointestinal blood flow and activate hyperaemia-dependent and hyperaemia-independent mechanisms of protection and repair. In the rodent foregut these local regulatory roles of sensory neurons are mediated by calcitonin gene-related peptide and nitric oxide. The pathophysiological potential of the neural emergency system is best portrayed by the gastric hyperaemic response to acid back-diffusion, which is governed by spinal afferent nerve fibres. This mechanism limits damage to the surface of the mucosa and creates favourable conditions for rapid restitution and healing of the wounded mucosa. Other extrinsic afferent neurons, particularly in the vagus nerve, subserve gastrointestinal homeostasis by signalling noxious events in the foregut to the central nervous system and eliciting autonomic, emotional-affective and neuroendocrine reactions. Under conditions of inflammation and injury, chemoceptive afferents are sensitized to peripheral stimuli and in this functional state contribute to the hyperalgesia associated with functional dyspepsia and irritable bowel syndrome. Thus, if GI pain is to be treated by sensory neuron-directed drugs it needs to be considered that these drugs do not inhibit nociception at the expense of GI mucosal vulnerability.
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Affiliation(s)
- Peter Holzer
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
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