Periodic Reporting for period 3 - ENTRI (Enteric-nervous-system-mediated regulation of intestinal inflammation)
Période du rapport: 2022-07-01 au 2023-12-31
Unlike most organs, the intestine has its own nervous system, the enteric nervous system (ENS). The ENS is part of the autonomous nervous system, which acts largely out of voluntary control. The primary function of the ENS is to orchestrate the contraction of the longitudinal and circular muscles of the intestine for mixing and caudal transport of food in the gastrointestinal tract, called peristalsis. However, it is becoming increasingly clear that the ENS has a function beyond peristalsis in integrating multiple sensory signals and coordinating the response with the immune system to maintain homeostasis in the intestine. In order to perform this immunoregulatory function, the ENS is both a receiver of signals, but also a regulator of effector response.
Intestinal inflammation is the disturbance of intestinal homeostasis, which can become detrimental during chronic inflammation, such as in inflammatory bowel disease (IBD), with a critical socioeconomic impact. Inflammation in the intestine is mainly mediated by resident immune cells, called the mucosal immune system. The mucosal immune system includes populations of innate lymphocytes called innate lymphoid cells, which are enriched at mucosal barriers and which have been linked to the maintenance of intestinal homeostasis.
In homeostasis but even more in the context of inflammation, the ENS communicates with the mucosal immune system. The interplay between ENS and immune system influences chronic inflammation, for example, in IBD, and hallmarks of this disease such as pain, cramping, and diarrhea could be explained by ENS functions. We could recently show that the ENS is expanded in the context of IBD. However, the functional significance of the ENS for chronic intestinal inflammatory disorders remains poorly understood.
How these two systems communicate is not well investigated because of limitations in measuring gene expression in the ENS and limitations in genetic inferring with components of the immune system. Therefore, we aim to describe the changes occurring in the ENS in intestinal inflammation because neurons have the ability to react to inflammatory signals, for instance, via the expression of cytokine receptors. Further, we investigate how the innate lymphoid cells, which react to many neuropeptides produced in the ENS, contribute to intestinal homeostasis and immunity with important implications for human health. We believe that the ENS is an essential signaling hub for intestinal homeostasis. Therefore, we aim to reveal key signaling pathways of the bidirectional crosstalk with immune cells on a molecular level.
Intestinal inflammation is the disturbance of intestinal homeostasis, which can become detrimental during chronic inflammation, such as in inflammatory bowel disease (IBD), with a critical socioeconomic impact. Inflammation in the intestine is mainly mediated by resident immune cells, called the mucosal immune system. The mucosal immune system includes populations of innate lymphocytes called innate lymphoid cells, which are enriched at mucosal barriers and which have been linked to the maintenance of intestinal homeostasis.
In homeostasis but even more in the context of inflammation, the ENS communicates with the mucosal immune system. The interplay between ENS and immune system influences chronic inflammation, for example, in IBD, and hallmarks of this disease such as pain, cramping, and diarrhea could be explained by ENS functions. We could recently show that the ENS is expanded in the context of IBD. However, the functional significance of the ENS for chronic intestinal inflammatory disorders remains poorly understood.
How these two systems communicate is not well investigated because of limitations in measuring gene expression in the ENS and limitations in genetic inferring with components of the immune system. Therefore, we aim to describe the changes occurring in the ENS in intestinal inflammation because neurons have the ability to react to inflammatory signals, for instance, via the expression of cytokine receptors. Further, we investigate how the innate lymphoid cells, which react to many neuropeptides produced in the ENS, contribute to intestinal homeostasis and immunity with important implications for human health. We believe that the ENS is an essential signaling hub for intestinal homeostasis. Therefore, we aim to reveal key signaling pathways of the bidirectional crosstalk with immune cells on a molecular level.
1. Expansion of ENS and Neuromedin U+ neurons during inflammation
The reaction of the ENS to inflammatory stimuli and its consequence are remain elusive. Therefore, we aim to describe and characterize changes occurring in the ENS during acute and chronic intestinal inflammation. Indeed, we could measure a robust and dynamic expansion of enteric neurons and glial cells in inflammatory bowel disease, arguing that the ENS reacts to the cytokine environment. The findings could potentially explain some of the symptoms observed in IBD patients, such as pain and diarrhea. We chose an open-end approach to investigate the transcriptional changes during intestinal inflammation in the ENS using sort-purification of fluorescent nuclei and next-generation sequencing. The neuropeptide Neuromedin U, which mediates activation of ILC2, was induced in various inflammatory settings and characterized one out of two subsets of sensory neurons in the ENS. At the moment, we perform in silico analysis of the data obtained from the sequencing experiments to dissect molecular pathways regulated in the ENS during inflammation.
2. Sensing of neuropeptides and alarmins by immune cells
Immune cells, particularly a group of innate lymphocytes called group 2 innate lymphoid cells (ILC2), carry receptors for neuronal-derived factors, such as neuropeptides. In addition, ILC2s react to alarmins, cytokines such as IL-25 IL-33 and TSLP, which are secreted in tissues upon infection, inflammation or cell death. We aim to better characterize the biological effect mediated by various neuropeptide- and alarmin-sensing pathways in ILC2. We could identify candidate genes regulated in ILC2 by individual alarmin or neuropeptides using transcriptional profiling and immunophenotyping. Using bioinformatical analysis, we could delineate proinflammatory or homeostatic pathways triggered in ILC2s that could be potentially harnessed for therapy.
3. Non-redundant functions of ILC2s in mucosal immunity
How important ILC2s are in concert with other immune cells for mucosal immunity is one of the outstanding questions in the field today. Our research has exposed the critical function ILC2s fulfill for mucosal inflammation and immunity. Using different models, we could clearly demonstrate the non-redundant role of ILC2 for mucosal immunity. Our data indicate a dysregulated myeloid immune response in the absence of ILC2. In particular, our work identified eosinophilic granulocytes as a critical downstream receiver of ILC2, a pathway we will further investigate. Furthermore, the non-redundant functions of ILC2s were not only limited to the myeloid compartment, but also resulted in a disturbed response of the intestinal epithelium during infection, including defective goblet and tuft cell hyperplasia. Further, our data include immunoregulatory functions for type 3 immune response. In total, we could identify ILC2s as an essential player in mucosal immunology.
The reaction of the ENS to inflammatory stimuli and its consequence are remain elusive. Therefore, we aim to describe and characterize changes occurring in the ENS during acute and chronic intestinal inflammation. Indeed, we could measure a robust and dynamic expansion of enteric neurons and glial cells in inflammatory bowel disease, arguing that the ENS reacts to the cytokine environment. The findings could potentially explain some of the symptoms observed in IBD patients, such as pain and diarrhea. We chose an open-end approach to investigate the transcriptional changes during intestinal inflammation in the ENS using sort-purification of fluorescent nuclei and next-generation sequencing. The neuropeptide Neuromedin U, which mediates activation of ILC2, was induced in various inflammatory settings and characterized one out of two subsets of sensory neurons in the ENS. At the moment, we perform in silico analysis of the data obtained from the sequencing experiments to dissect molecular pathways regulated in the ENS during inflammation.
2. Sensing of neuropeptides and alarmins by immune cells
Immune cells, particularly a group of innate lymphocytes called group 2 innate lymphoid cells (ILC2), carry receptors for neuronal-derived factors, such as neuropeptides. In addition, ILC2s react to alarmins, cytokines such as IL-25 IL-33 and TSLP, which are secreted in tissues upon infection, inflammation or cell death. We aim to better characterize the biological effect mediated by various neuropeptide- and alarmin-sensing pathways in ILC2. We could identify candidate genes regulated in ILC2 by individual alarmin or neuropeptides using transcriptional profiling and immunophenotyping. Using bioinformatical analysis, we could delineate proinflammatory or homeostatic pathways triggered in ILC2s that could be potentially harnessed for therapy.
3. Non-redundant functions of ILC2s in mucosal immunity
How important ILC2s are in concert with other immune cells for mucosal immunity is one of the outstanding questions in the field today. Our research has exposed the critical function ILC2s fulfill for mucosal inflammation and immunity. Using different models, we could clearly demonstrate the non-redundant role of ILC2 for mucosal immunity. Our data indicate a dysregulated myeloid immune response in the absence of ILC2. In particular, our work identified eosinophilic granulocytes as a critical downstream receiver of ILC2, a pathway we will further investigate. Furthermore, the non-redundant functions of ILC2s were not only limited to the myeloid compartment, but also resulted in a disturbed response of the intestinal epithelium during infection, including defective goblet and tuft cell hyperplasia. Further, our data include immunoregulatory functions for type 3 immune response. In total, we could identify ILC2s as an essential player in mucosal immunology.
The response of the ENS to inflammation is almost a black box, despite the importance for human health. We now have the technical possibilities to investigate the ENS in inflammatory settings using nuclei sequencing. In addition to the data obtained, we will employ single nuclei sequencing to extend this our analysis to subsets of enteric sensory neurons, interneurons, excitatory and inhibitory secreto-motor neurons. The extrinsic innervation of the intestine will also be explored. The anticipated results will provide a comprehensive map of the ENS in inflammatory settings and carry tremendous potential for prevention and therapy in the future.
The work carried out in this proposal will further provide an unprecedented breakdown of ILC2 function in type 2 immune response and the consequences for mucosal immunology. Combined with next-generation sequencing technologies, we are in a position to dissect immunoregulatory pathways controlled by ILC2 in immune and non-immune cells. In addition, we will further complement our analysis of cell-intrinsic activation pathways in ILC2 by defining epigenetic changes associated with ILC2 activation. Both datasets in combination will uncover critical signaling hubs that shape ILC2 biology with immense potential for future research.
The work carried out in this proposal will further provide an unprecedented breakdown of ILC2 function in type 2 immune response and the consequences for mucosal immunology. Combined with next-generation sequencing technologies, we are in a position to dissect immunoregulatory pathways controlled by ILC2 in immune and non-immune cells. In addition, we will further complement our analysis of cell-intrinsic activation pathways in ILC2 by defining epigenetic changes associated with ILC2 activation. Both datasets in combination will uncover critical signaling hubs that shape ILC2 biology with immense potential for future research.