Abstract B159: Investigating the neuroimmune interaction between nociceptive neurons and dendritic cells

Nociceptive somatosensory neurons (nociceptors) have recently been established as controllers of immune responses in the context of infections, allergic airway inflammation, and imiquimod (IMQ)-induced psoriasiform skin inflammation. In most of these models, myeloid cells including dendritic cells (DCs) were shown to be a target of the actions of nociceptors. DCs form a bridge between the innate and adaptive immune system and it is mostly through their actions that the adaptive immune system gets activated. Notably, DCs were previously found to engage in a direct physical interaction with nociceptors as well as to be affected by soluble neuropeptides produced by the latter. Conflicting results have, however, been reported with regards to the function and the requirement of neuropeptides for the nociceptor:DC interaction under in vivo settings, suggesting a degree of context-dependency, while the requirement for physical interaction of the two cell types has not been tested. Inherently, in vivo approaches are not readily amenable for dissection of the molecular underpinnings of the interaction, and involvement of other, accessory cells can be difficult to exclude. Consequently, we have established an in-vitro nociceptor:DC co-culture system, which, compared to in vivo settings, allows us to dissect nociceptor:DC interactions in a less complex, reductionist setting.Using the in vitro co-culture setup, we show that dendritic cells and nociceptors engage in tight physical interactions, as well as that nociceptors produce chemo-attractant signals, which act directly on DCs. Further, we demonstrate that nociceptors enhance production of IL-6 and IL12-p40 cytokines by dendritic cells in response to IMQ, a TLR7 agonist. Strikingly, this effect was only apparent when DCs and nociceptors were allowed direct contact, suggesting a contact or proximity-based mechanism of interaction. In addition to IMQ, we identify other pathogen-associated molecular pattern (PAMP) molecules, which elicit a cytokine response that can be enhanced in the presence of nociceptors. Next, using live cell imaging, we showed that, as described previously, treatment of nociceptors with capsaicin, a TRPV-1 channel agonist, results in calcium flux and membrane depolarization of the neuronal cells. Strikingly, similar changes can be observed in DCs interacting with the neurons, while DCs alone do not exhibit any such behavior when treated with capsaicin. To further substantiate our findings, we utilized channelrhodopsin-expressing neurons, which can be activated by blue light without any other perturbations of the system. Importantly, light-induced activation of such neurons was sufficient to drive a calcium flux in the interacting DCs.Finally, to gain an unbiased view of the effects that nociceptors have on DCs, we performed RNA sequencing of DCs after co-culture. Strikingly, we observed profound changes in gene expression across DC subsets when DCs were cultured with neurons without any further stimulation as well as when they were treated with IMQ in the co-culture.In summary, we have developed an in vitro system that allows us to investigate the interactions between nociceptors and DCs. Using this system, we have confirmed that nociceptors directly communicate with DCs, we addressed the requirement for physical interactions of the two cell types and we have begun to shed light on the molecular underpinnings of these interactions. Citation Format: Pavel Hanc, Siyi Huang, Ulrich H. von Andrian. Investigating the neuroimmune interaction between nociceptive neurons and dendritic cells [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B159.