Mouse enteric neurons control intestinal plasmacytoid dendritic cell function via serotonin-HTR7 signaling [scRNA-seq]

Serotonergic neurons have multiple roles, including regulating mood and behavior1,2, yet it remains unclear which of these phenotypes are caused by serotonin produced by the central versus the peripheral nervous system. Neuronal serotonin is produced by the enzyme tryptophan hydroxylase 2 (Tph2). Mice that lack Tph2 exhibit decreased gut motility4 and several behavioral disorders, including decreased anxiety-like behavior and increased aggression5. To clarify the specific role of peripheral serotonergic circuits, here we engineered mice with intact Tph2 in central neurons but lacking Tph2 in peripheral neurons (Tph2fl/fl; Hand2-Cre). We discovered that PSN contribute to gut motility and are important in the control of anxiety-like behavior but do not contribute to impulsive aggression. Thus, central and peripheral serotonergic neurons have different roles in behavioral regulation. Intriguingly, animals lacking peripheral neuronal Tph2 had deficiencies in enteric immune cells, including reduced abundance of dendritic cells (DC) and IgA+ B cells in the small intestine and elevated susceptibility to oral Salmonella infection. Mechanistic studies suggest that serotonin produced by PSN promotes activation of DC through the 5-HT7 receptor, thereby facilitating DC-mediated differentiation of IgA+ B cells. Our findings highlight the importance of serotonin produced by peripheral neurons for control of behavior and gut defense and suggest that these circuits could be valuable targets for therapeutics.