Immunometabolic Profiling of Enteric Glial Cells in Response to Acute and Chronic Pro-Inflammatory Cytokine Exposure: Implications for Early Pathogenic Insights into Parkinson's Disease

Abstract

Parkinson’s disease (PD) is a widespread neurodegenerative disorder characterised by the presence of α-syn aggregates, which have been associated with the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Recent studies have shown that the intestinal environment's state can modulate the central nervous system (CNS) activity via the microbiota-gut-brain axis. Gut microbes can modulate immune and inflammatory events in the gut and trigger neuroinflammation and subsequent neurodegeneration. The enteric nervous system (ENS) is a complex network of enteric neurons and glia that can interact with the gut immune system and microbiome. Enteric glial cells (EGCs) are peripheral neuroglia associated with processes of enteric neurons in the gastrointestinal tract. EGCs can be activated and respond to proinflammatory stimuli, amplifying the inflammatory response. Studying the metabolism of EGCs in response to a long inflammation may provide new insights into the pathophysiology of neurodegenerative disorders. In this study, hESC-derived ENS cells, based on the protocol of Gogolou et al., will be used to investigate the immuno-metabolic effects of (i) acetate on the inflammation induced by pro-inflammatory stimuli, either LPS or a cytokine mix (TNF-α & IL-1β), and of (ii) chronic exposure to pro-inflammatory stimuli. LPS stimulation failed to induce inflammation in our system due to the absence of the TLR4 receptor on the cell surface of EGCs. Acetate failed to suppress inflammation following exposure to a pro-inflammatory cytokine mix. Following chronic pro-inflammatory cytokine exposure, levels of IL-6 in the first 48h were increased and steadily decreased throughout the experiment. Levels of IL-8 follow a similar trend to IL-6 release, however, the decrease is not as significant as with IL-6. Preliminary results show the presence of p129syn in the soma of the neurons following chronic exposure to pro-inflammatory cytokines. Glucose uptake is increased in cytokine-treated cells on day 2, suggesting a significant impact on metabolic processes by promoting a metabolic shift towards glycolysis. Intracellular metabolism indicates that long-term exposure to pro-inflammatory cytokines induced a major change in the EGCs' metabolic phenotype. Pathway analysis shows that after 14 days, between controls and cytokine-treated cells, multiple metabolic pathways are significantly altered. These preliminary observations of the effects of chronic pro-inflammatory cytokine exposure could be used to develop potential therapeutic targets for gut inflammation and to understand early PD pathogenesis and progression.