Background: The biologic effects of endothelin-1 (ET-1) are not limited to its vasoconstricting activity. A new and highly interesting role of the endothelin axis is its involvement in immune functions. As ET-1 is highly increased during gut inflammation, the aim of this study was to see if the endothelin axis influences enteric glia cell (EGC) functions, and through them, the immune response, during gut inflammation.
Material/methods: Cultured EGCs were treated with interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNFalpha), IL-4, interferon-gamma, and ET-1. Secretion of ET-1 was detected by ELISA. Cultured EGCs were labeled with anti-glial fibrillary acidic protein (GFAP), endothelin-A (ETA), and endothelin-B (ETB), antibodies. The expression of ETA and ETB receptors was evaluated using reverse transcription PCR. Glial fibrillary acidic protein expression was determined by Western blot.
Results: ET-1 secretion of EGCs could be stimulated by IL-1 beta and TNFalpha in a time and dose-dependent manner, whereas IL-4 and interferon-gamma showed no effect on ET-1 production. Cultured EGCs expressed ETA and ETB-receptors. Endothelin B mRNA expression was increased after incubation with IL-1 beta. Incubation of cells with IL-1 beta, TNFalpha, and ET-1 led to a significant increase of GFAP in EGCs.
Conclusions: Enteric glia cells express functional ETA and ETB receptors and produce huge amounts of ET-1 during gut inflammation, which increase GFAP expression in EGCs. These ET-1/ET receptors autocrine or paracrine loops might provide a new means to modulate EGC function, such as change in gut motility, cytokine production, and regulating gut homeostasis.