B. D. Bauman1, A. Louiselle1, E. Zheng1, J. Meng1, S. Roy1, B. Segura1 1University Of Minnesota,Minneapolis, MN, USA
Introduction:
The opioid epidemic is a growing concern for American physicians. The increased use of prescription opioids has been linked to a growing number of complications. Side effects from opioid use include nausea, vomiting, and constipation. Emerging evidence suggests that morphine use may be associated with sepsis although the mechanism is undefined. Enteric glial cells (EGCs) are the most numerous cell population in the enteric nervous system and contribute to the maintenance of intestinal barrier function through the production of a variety of trophic factors including Glial Derived Neurotrophic Factor (GDNF). We sought to determine the effect of morphine on enteric glia and hypothesized that morphine contributes to EGC dysfunction and increased gut permeability.
Methods:
We tested our hypothesis using in-vitro methodology including QPCR, cell co-culture in a transwell system, cell staining and microscopy, and electronic cell-impendence sensing (ECIS). Rat Intestinal Epithelial Cell (IEC-6) and EGC lines were purchased from ATCC. We measured permeability in the transwell system with 4kD FITC-Dextran and 70kD Rhodamine-Dextran. Further, production of the tight junction protein, ZO-1, was monitored as a measure of epithelial barrier integrity. Statistical significance was determined using a student t-test.
Results:
Morphine receptor antibody staining was positive on EGCs. GDNF RNA expression within EGCs was decreased by morphine treatment. FITC-dextran permeability was decreased in the co-culture model of unstimulated EGCs while the barrier protective effect of EGC co-culture was lost when EGCs were treated with morphine for 72 hours. In the ECIS model, barrier integrity was diminished when IEC-6 cells were exposed to culture media from morphine-treated EGCs (EGC-CM), while barrier integrity was maintained with standard EGC-CM. ZO-1 production was decreased in morphine treated IEC-6 cells yet maintained in the presence of treatment with EGC-CM.
Conclusion:
EGCs contain receptors for Morphine. Morphine stimulated EGCs have diminished capability to preserve intestinal barrier function, apparently through decreased production of GDNF, although other trophic factors may be involved. IEC6 cells have decreased ZO-1 expression in the presence of Morphine. IEC6 ZO-1 production is restored in the presence of EGC conditioned media stimulation. Further studies are warranted to delineate the role of enteric glial cell function in opioid signaling and sepsis.