The enteric nervous system (ENS) is an incredibly complex neural network that is extensively integrated within the neuroimmunoendocrine system through countless signalling pathways that have yet to be fully characterized. In the last decade we have discovered that many more neurotransmitters are at work in the ENS than was originally thought. This opens up new avenues of research into physiological phenomena traditionally thought to be associated only with the central nervous system, such as NMDA receptor-induced excitotoxicity, and how these may influence immune interactions. In particular, the kynurenine pathway of the tryptophan catabolism produces many neuro-active and immuno-active constituents whose effects are unknown in the ENS but are of great consequence in many neurodegenerative disorders of the CNS. Our study hypothesized that co-culture of the enteric neurons with mast cells would increase neuronal survival through kynurenic acid production in quinolinic acid (QUIN)-induced excitotoxic conditions.
This study developed a novel in vitro co-culture system of enteric neurons and glia grown from murine longitudinal muscle-myenteric plexus tissue and bone marrow-derived mast cells. In addition, a pipeline in image analysis software CellProfiler was designed and optimized in order to reduce human bias and error in subsequent immunocytochemical image analysis. Furthermore, we identified the genetic expression of subunits of the NMDA glutamate receptor in cultured enteric neurons via PCR, which suggests that these cultured neurons may be susceptible to excitotoxicity. PCR analysis of cultured mast cells seemed to indicate that our cultured mast cells do not express KAT-III, the enzyme needed to produce the neuroprotective KYNA. Overall, co-culture with mast cells seemed to decrease neuronal survival. This project developed a novel methodology for the in vivo study of mast cell-nerve interactions, and lays the groundwork for future studies in excitotoxicity in the ENS. / Thesis / Master of Science (MSc) / The enteric nervous system is a vast web of nerves and immune cells that innervates the gut and interacts with the central nervous system through the gut-brain axis. An important mediator in this system is the mast cell, a type of immune cell often involved in protective responses to venoms and allergens. Intriguingly, in normal physiological conditions these cells are in close contact with nerves in the periphery, despite their potential to release damaging constituents. While mast cells are well-known for inciting inflammation and releasing toxic granules, they can also synthesize and release potentially beneficial neuroactive compounds, such as neurotransmitters or growth factors. The aim of this study was to characterize mast cell-nerve interactions in neurotoxic conditions, to see if the proximity of mast cells to nerves might serve a neuroprotective purpose.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24938 |
| Date | January 2019 |
| Creators | Knoch, Jaime |
| Contributors | Forsythe, Paul, Medical Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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