Aryl hydrocarbon receptor activation affects nitrergic neuronal survival and delays intestinal motility in mice

Despite progress describing the effects of persistent organic pollutants (POPs) on the central nervous system, the effect of POPs on enteric nervous system (ENS) function remains underexplored. We studied the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a POP, and a potent aryl hydrocarbon receptor (AHR) ligand, on the ENS and intestinal motility in mice. C57Bl/6J mice treated with TCDD (2.4 µg/kg body weight) for 8 weeks (once per week) exhibited significant delay in intestinal motility as shown by reduced stool frequency, prolonged intestinal transit time, and a persistence of dye in the jejunum compared to control mice with maximal dye retention in the ileum. TCDD significantly increased Cyp1a1 expression, an AHR target gene, and reduced the total number of neurons and affected nitrergic neurons in cells isolated from WT mice, but not Ahr-/- mice. In immortalized fetal enteric neuronal cells, TCDD-induced nuclear translocation of AHR as well as increased Cyp1a1 expression. AHR activation did not affect neuronal proliferation. However, AHR activation resulted in enteric neuronal toxicity, specifically, nitrergic neurons. Our results demonstrate that TCDD adversely affects nitrergic neurons and thereby contributes to delayed intestinal motility. These findings suggest that AHR signaling in the ENS may play a role in modulating TCDD-induced gastrointestinal pathophysiology.