Enteric glial cells: cellular and molecular analysis of an emerging player in intestinal health and disease

Enteric glia have the unique feature of responding to surrounding cues and acquiring specific states, including a reactive phenotype named “gliosis”. Several studies reported that the EGC phenotype is altered in chronic inflammatory conditions, such as Crohn's disease and ulcerative colitis. However, while the role of EGCs has been well described in inflammatory bowel diseases (IBDs), their involvement in celiac disease (CD) has been poorly investigated so far. CD is a chronic T-cell-mediated enteropathy triggered by the consumption of gluten in genetically susceptible individuals. Once thought to primarily afflict children and provoke gastrointestinal symptoms, CD is now considered a systemic disorder with a broad range of clinical presentations that span all age groups. Taking into account all common features shared by IBDs and CD and the evidence that EGCs are protagonists in several gut physiological and pathological processes, it is likely that enteric glia might be involved in CD pathogenesis as well. Considering the lack of available established EGC lines and the technical difficulties related to EGCs’ extraction from sample tissue, the first step of this work was the generation of the first immortalized hEGC line (referred to as hEGC-ClK clone) through a validated lentiviral transgene protocol. Hence, hEGC-ClK cell line was finely characterized and used as an experimental model of hEGCs to test the effects of gluten-derived gliadin and gluten-derived cytotoxic peptide p31-43. Our results showed that gliadin was able to induce oxidative stress in hEGCs, followed by mitochondrial damage, and finally resulting in caspase-mediated apoptotic cell death. On the other hand, p31-43 exerted milder cytotoxic effects on hEGCs, triggering gliosis and activation of the Nrf2/Keap1-mediated antioxidant defence system. Furthermore, the molecular results were validated by proteomic analysis and compared with the effects observed in primary murine EGCs. These data highlighted the important but not sufficient contribution of p31-43 in gliadin cytotoxicity toward hEGCs, suggesting the possible involvement of other gliadin-derived peptides. Altogether, our results might suggest a possible involvement of EGCs in CD pathogenesis, identifying enteric glia as a potential novel therapeutic target for the treatment of CD patients.