In vitro co-culture approach reveals multi-modal control of dendritic cell functions by nociceptors

Abstract

Abstract Nociceptors – sensory neurons that respond to noxious stimuli by eliciting the sensation of pain or itch – are increasingly beginning to be appreciated as controllers of the immune response. Notably, dendritic cells (DCs) – myeloid cells of the immune system – were previously found to be impacted by nociceptors, however, while some functional outcomes of the interaction have been described, our mechanistic understanding of the underlying molecular communication network is rudimentary at best and a bigger picture pertaining the modalities and outcomes of the interaction is missing entirely. Consequently, here, we have established a novel in vitro co-culture system for DCs and nociceptors, which allowed us to explore in detail the modalities and outcomes of their communication. We show that DCs and nociceptors engage in a tight physical interaction and that nociceptors have the ability to attract DCs by production of the chemokine CCL2. Additionally, nociceptors enhance pro-inflammatory cytokine production by activated DCs in a contact-dependent, neuropeptide-independent manner, and nociceptive activity induces membrane depolarization and calcium flux in the interacting DCs. Next, using RNA sequencing, we identified genes that are controlled by nociceptors in steady-state DCs in the absence of immune stimulation, and uncovered a nociceptor-induced program of enhanced sentinel function, characterized by an increased expression of pro-IL1b but no overt immune activation of DCs both in vitro and in vivo. Finally, we identified the CGRP family of neuropeptides as nociceptor-derived signals mediating this effect.