Molecular Signaling and Dysfunction of the Human Reactive Enteric Glial Cell Phenotype: Implications for GI Infection, IBD, POI, Neurological, Motility, and GI Disorders

Clinical observations or animal studies implicate enteric glial cells in motility disorders, irritable bowel syndrome, inflammatory bowel disease, gastrointestinal (GI) infections, postoperative ileus, and slow transit constipation. Mechanisms underlying glial responses to inflammation in human GI tract are not understood. Our goal was to identify the "reactive human enteric glial cell (rhEGC) phenotype" induced by inflammation, and probe its functional relevance.

The "rhEGC phenotype" is identified by a complex cascade of pro-inflammatory pathways leading to alterations of important molecular and functional signaling pathways (Ca, purinergic, and mechanosensory) that could disrupt GI motility. Inflammation induced a "purinergic switch" from ATP to adenosine diphosphate/adenosine/uridine triphosphate signaling. Findings have implications for GI infection, inflammatory bowel disease, postoperative ileus, motility, and GI disorders.

Human enteric glial cells in culture from 15 GI-surgical specimens were used to study gene expression, Ca, and purinergic signaling by Ca/fluo-4 imaging and mechanosensitivity. A nanostring panel of 107 genes was designed as a read out of inflammation, transcription, purinergic signaling, vesicular transport protein, channel, antioxidant, and other pathways. A 24-hour treatment with lipopolysaccharide (200 μg/mL) and interferon-γ (10 μg/mL) was used to induce inflammation and study molecular signaling, flow-dependent Ca responses from 3 mL/min to 10 mL/min, adenosine triphosphate (ATP) release, and ATP responses.

Treatment induced a "rhEGC phenotype" and caused up-regulation in messenger RNA transcripts of 58% of 107 genes analyzed. Regulated genes included inflammatory genes (54%/IP10; IFN-γ; CxCl2; CCL3; CCL2; C3; s100B; IL-1β; IL-2R; TNF-α; IL-4; IL-6; IL-8; IL-10; IL-12A; IL-17A; IL-22; and IL-33), purine-genes (52%/AdoR2A; AdoR2B; P2RY1; P2RY2; P2RY6; P2RX3; P2RX7; AMPD3; ENTPD2; ENTPD3; and NADSYN1), channels (40%/Panx1; CHRNA7; TRPV1; and TRPA1), vesicular transporters (SYT1, SYT2, SNAP25, and SYP), transcription factors (relA/relB, SOCS3, STAT3, GATA_3, and FOXP3), growth factors (IGFBP5 and GMCSF), antioxidant genes (SOD2 and HMOX1), and enzymes (NOS2; TPH2; and CASP3) (P < 0.0001). Treatment disrupted Ca signaling, ATP, and mechanical/flow-dependent Ca responses in human enteric glial cells. ATP release increased 5-fold and s100B decreased 33%. Conclusions: The "rhEGC phenotype" is identified by a complex cascade of pro-inflammatory pathways leading to alterations of important molecular and functional signaling pathways (Ca, purinergic, and mechanosensory) that could disrupt GI motility. Inflammation induced a "purinergic switch" from ATP to adenosine diphosphate/adenosine/uridine triphosphate signaling. Findings have implications for GI infection, inflammatory bowel disease, postoperative ileus, motility, and GI disorders.