Enteric glia adopt an activated pro-inflammatory state in response to human and bacterial amyloids

Abstract

Mounting evidence suggests a role for the microbiome-gut-brain axis in amyloid-associated neurodegeneration, but the pathogenic changes induced by amyloids in the gastro-intestinal tract remain elusive. To scrutinize the early response to amyloids of human and bacterial origin, we challenged primary murine myenteric networks with A{beta}1-42 (vs a scrambled version of A{beta}1-42) and curli (vs culture medium), respectively, and performed shotgun RNA sequencing. Both amyloid types induced a transcriptional signature of DNA damage and cell cycle dysregulation. Using in vitro neurosphere-derived cultures and in vivo amyloid injections we found that enteric glia and smooth muscle cells were the most responsive cell types, showing increased proliferation, {gamma}H2AX burden and SOD2 levels after amyloid challenge. Consistent with this activated state, we identified a pro-inflammatory hub in the transcriptional profile of amyloid-stimulated myenteric networks. Enteric glia were the principal source of the associated cytokines, and in vivo, this was accompanied by an influx of immune cells. Together, these results shed new light on the intrinsic vulnerability of ENS cells to both amyloid species and position enteric glial cell activation as an early driver of neurodegenerative disease progression. Significance statementThe increasing socio-economic impact of Alzheimers disease (AD), long sub-clinical disease progression window, and failure of drug candidates demand mechanistic insight into the early stages of disease development. Epidemiological associations and experimental studies in rodents suggest that the gut may be vulnerable to amyloids and mediate their transfer to the brain. However, whether and how amyloids induce local pathology in the gastro-intestinal wall is not known. We identified a pathogenic program that becomes activated in the gastro-intestinal tract after exposure to amyloid {beta} and curli (the main bacterial amyloid), and show that enteric glia are responsible for creating an amyloid-induced pro-inflammatory environment. This insight of an early response in a distant, more accessible organ than the brain, may have important implications for both disease diagnosis and therapy.