Periodic Reporting for period 4 - ENTRI (Enteric-nervous-system-mediated regulation of intestinal inflammation)
Période du rapport: 2024-01-01 au 2024-06-30
The nervous system and the immune system, as the body’s primary sensory interfaces, play a crucial role in maintaining body homeostasis. The preservation of homeostasis at mucosal barriers, particularly the intestinal mucosa, is vital for preventing inflammation. The impact of chronic intestinal inflammation, as seen in conditions like inflammatory bowel disease (IBD), is not just a health concern but also has significant socioeconomic implications.
Inflammation in the intestine is triggered and maintained by the mucosal immune system, which comprises tissue-resident immune cells, including innate lymphoid cells (ILCs), which are enriched at mucosal barriers and maintain barrier homeostasis. For this purpose, immune cells interact with the surrounding cell type, including but not limited to neurons, in the tissue niche.
Enteric-associated neurons can be subdivided into the intrinsic innervation and extrinsic innervation of the intestine. The intrinsic innervation is embedded in the gut wall and called the enteric nervous system (ENS), whereas the extrinsic fibers originate from ganglia outside of the intestine. The interplay between ENS and the 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 altered in the context of IBD. In fact, there several findings suggest a close interaction between the nervous system and the immune system. However, how these two systems exchange information and coordinate responses with consequences for chronic intestinal inflammatory disorders is poorly understood, and elucidating this is the underlying topic of this proposal.
To this end, we characterized the changes occurring in the ENS during intestinal inflammation because neurons could participate in inflammation, for example, via the expression of cytokine receptors. Therefore, we focused on how enteric neurons sense and react to intestinal inflammation and what the functional consequences are. Based on our data, we propose the following conclusions. The ENS is dynamically regulated by and senses inflammation. Enteric neurons adjust their metabolism and production of inflammatory mediators accordingly and undergo iron-mediated cell death. The cell death in enteric neurons is regulated by interferon signals sensed by neurons via Ifnar1.
From the side of the immune system, we investigated group 2 innate lymphoid cells (ILC2s) as a component of the mucosal immune system and how they are regulated by the factors derived from various cell types in the tissue niche, such as neurons, stromal cells and epithelial cells. The cells in the tissue niche form functional units promoting neuro-immune interactions and type 2 immune responses. Therefore, we hypothesize that neuro-ILC units have an important role in the regulation of inflammation, immunity, and allergy at mucosal barriers.
Indeed, our data demonstrate that ILC2s have essential functions in the regulation of mucosal inflammation relevant to allergic asthma and anti-worm immunity and control the homeostasis of immune cells, such as eosinophils and B1 related to allergy.
Overall, our study exposes the ENS and the interfaces with the type 2 immune responses as an essential signaling hub for intestinal homeostasis with important consequences for mucosal immunity and human health.
Inflammation in the intestine is triggered and maintained by the mucosal immune system, which comprises tissue-resident immune cells, including innate lymphoid cells (ILCs), which are enriched at mucosal barriers and maintain barrier homeostasis. For this purpose, immune cells interact with the surrounding cell type, including but not limited to neurons, in the tissue niche.
Enteric-associated neurons can be subdivided into the intrinsic innervation and extrinsic innervation of the intestine. The intrinsic innervation is embedded in the gut wall and called the enteric nervous system (ENS), whereas the extrinsic fibers originate from ganglia outside of the intestine. The interplay between ENS and the 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 altered in the context of IBD. In fact, there several findings suggest a close interaction between the nervous system and the immune system. However, how these two systems exchange information and coordinate responses with consequences for chronic intestinal inflammatory disorders is poorly understood, and elucidating this is the underlying topic of this proposal.
To this end, we characterized the changes occurring in the ENS during intestinal inflammation because neurons could participate in inflammation, for example, via the expression of cytokine receptors. Therefore, we focused on how enteric neurons sense and react to intestinal inflammation and what the functional consequences are. Based on our data, we propose the following conclusions. The ENS is dynamically regulated by and senses inflammation. Enteric neurons adjust their metabolism and production of inflammatory mediators accordingly and undergo iron-mediated cell death. The cell death in enteric neurons is regulated by interferon signals sensed by neurons via Ifnar1.
From the side of the immune system, we investigated group 2 innate lymphoid cells (ILC2s) as a component of the mucosal immune system and how they are regulated by the factors derived from various cell types in the tissue niche, such as neurons, stromal cells and epithelial cells. The cells in the tissue niche form functional units promoting neuro-immune interactions and type 2 immune responses. Therefore, we hypothesize that neuro-ILC units have an important role in the regulation of inflammation, immunity, and allergy at mucosal barriers.
Indeed, our data demonstrate that ILC2s have essential functions in the regulation of mucosal inflammation relevant to allergic asthma and anti-worm immunity and control the homeostasis of immune cells, such as eosinophils and B1 related to allergy.
Overall, our study exposes the ENS and the interfaces with the type 2 immune responses as an essential signaling hub for intestinal homeostasis with important consequences for mucosal immunity and human health.
To assess the changes happening in ENS neurons during intestinal inflammation, we sort-purified fluorescently-labeled neuronal nuclei from ENS neurons in the context of intestinal inflammation, provoking distinct cytokine milieu, and performed bulk and single-nucleus RNA sequencing.
Enteric neurons maintain their organ-specific and function-dependent signature during. However, we detected a conserved inflammatory program triggered in neurons independent of the cytokine milieu stimulated by the inflammation. The biological processes underlying this conserved response were related to sensing, leukotriene metabolism, defense response, metabolic processes, and regulation of cell death. Indeed, we could show that during colitis, enteric neurons undergo ferroptosis, a type of iron-mediated cell death. We investigated how cell signals trigger cell death in enteric neurons. Our data show that interferon signaling is activated in enteric neurons during inflammation and is an important regulator of cell death. It may display a target for the treatment of long-term symptoms associated with neuronal loss in the gastrointestinal tract during intestinal infection of IBD.
Type 2 immune responses, including ILC2s, are regulated by signals provided by other cell types in the tissue niche. These factors include neuropeptides and alarmins, cytokines released by stromal cells, and epithelial cells to protect the mucosal barrier and drive inflammation. We investigated how alarmins and neuropeptide signals are integrated on a cellular level in ILC2s. While alarmins and neuropeptides can both directly regulate ILC2s, we could additionally show that neuropeptides can modulate alarmin secretion. The alarmin IL-33 is mainly found in a subtype of stromal cells in the intestine. Interestingly, the IL-33-expressing stromal cells were poised to interact with neurons and neuropeptides stimulation for stromal cells to regulate IL-33 expression in stromal cells and stimulation of ILC2s. Therefore, our studies reveal signaling circuits mediated by alarmins and neuropeptides that regulate crosstalk between neurons, stromal cells, and ILC2s.
Our transcriptional profiling strategy allowed us to dissect the transcriptional programs differentially regulated in ILC2s and pivotal molecular downstream regulators for mucosal immunology. Importantly, we could define the essential function of ILC2s in the context of type 2 immune responses at barrier surfaces. We found that eosinophils, B1 cells, and antibody production are dependent on ILC2 signals, namely IL-5 and upstream signals, including IL-33, in the context of allergic asthma and worm infection, and the NMU - Areg pathway in IBD.
The studies outlined were published in scientific journals and orally presented at various national and international conferences for dissemination. We also communicated Press releases and participated in outreach activities to discuss with a broader audience.
Enteric neurons maintain their organ-specific and function-dependent signature during. However, we detected a conserved inflammatory program triggered in neurons independent of the cytokine milieu stimulated by the inflammation. The biological processes underlying this conserved response were related to sensing, leukotriene metabolism, defense response, metabolic processes, and regulation of cell death. Indeed, we could show that during colitis, enteric neurons undergo ferroptosis, a type of iron-mediated cell death. We investigated how cell signals trigger cell death in enteric neurons. Our data show that interferon signaling is activated in enteric neurons during inflammation and is an important regulator of cell death. It may display a target for the treatment of long-term symptoms associated with neuronal loss in the gastrointestinal tract during intestinal infection of IBD.
Type 2 immune responses, including ILC2s, are regulated by signals provided by other cell types in the tissue niche. These factors include neuropeptides and alarmins, cytokines released by stromal cells, and epithelial cells to protect the mucosal barrier and drive inflammation. We investigated how alarmins and neuropeptide signals are integrated on a cellular level in ILC2s. While alarmins and neuropeptides can both directly regulate ILC2s, we could additionally show that neuropeptides can modulate alarmin secretion. The alarmin IL-33 is mainly found in a subtype of stromal cells in the intestine. Interestingly, the IL-33-expressing stromal cells were poised to interact with neurons and neuropeptides stimulation for stromal cells to regulate IL-33 expression in stromal cells and stimulation of ILC2s. Therefore, our studies reveal signaling circuits mediated by alarmins and neuropeptides that regulate crosstalk between neurons, stromal cells, and ILC2s.
Our transcriptional profiling strategy allowed us to dissect the transcriptional programs differentially regulated in ILC2s and pivotal molecular downstream regulators for mucosal immunology. Importantly, we could define the essential function of ILC2s in the context of type 2 immune responses at barrier surfaces. We found that eosinophils, B1 cells, and antibody production are dependent on ILC2 signals, namely IL-5 and upstream signals, including IL-33, in the context of allergic asthma and worm infection, and the NMU - Areg pathway in IBD.
The studies outlined were published in scientific journals and orally presented at various national and international conferences for dissemination. We also communicated Press releases and participated in outreach activities to discuss with a broader audience.
How enteric neurons react to intestinal inflammation was largely unknown due to limitations in purifying neurons from complex tissues for sequencing purposes. We used a genetic trick to tag neuronal nuclei for sort-purification and sequencing to overcome this limitation. This allowed us to monitor the changes in transcriptome occurring in enteric neurons during intestinal inflammation. This comprehensive study not only provides a valuable resource for the community but also enables us to investigate some of the prominent pathways in depth. In this way, we could demonstrate the importance of ferroptosis in enteric neurons and the influence of type I interferon on enteric neurons and cell death regulation.
These data have broad implications for understanding inflammation and neural adaptation of cell death, pain, and motility but could also open new avenues and perspectives regarding degeneration imposed on enteric neurons, for example, in inflammatory bowel disease.
These data have broad implications for understanding inflammation and neural adaptation of cell death, pain, and motility but could also open new avenues and perspectives regarding degeneration imposed on enteric neurons, for example, in inflammatory bowel disease.