IL‐33‐activated murine mast cells control the dichotomy between RORγt⁺ and Helios⁺T_regs via the MK2/3‐mediated IL‐6 production in vitro

Abstract

In mast cells, IL-33 typically induces the activation of NF-κB, which results in the production of cytokines such as IL-6 and IL-2. Here, we demonstrate that the IL-33-induced IL-6 production in murine mast cells and the formation of RORγt + T regs essentially depends on the MAPKAPs, MK2, and MK3 (MK2/3) downstream of MyD88. In contrast to this, the IL-33-induced and MyD88-dependent IL-2 production in mast cells contributes to the maintenance of Helios + T regs . Thereby, the IL-33-induced IL-2 response and, thus, the maintenance of Helios + T regs are limited by an IL-6-mediated autocrine negative feedback stimulation acting on mast cells. Collectively, we present MK2/3 in IL-33-activated mast cells as a signaling node, which controls the dichotomy between RORγt + T reg and Helios + T reg in vitro. Keywords: IL-33 r IL-6 r Mast cells r T regs r MK2/3 Additional supporting information may be found online in the Supporting Information section at the end of the article. C 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Deutsche Forschungsgemeinschaft (DFG DR 1113/1-1 to S.D.) and by the Interdisziplinäres Zentrum für klinische Forschung, Jena (IZKF-MSP1 medical scientist program to N.A.).

IL‐3 is essential for ICOS‐L stabilization on mast cells, and sustains the IL‐33‐induced RORγt+ Treg generation via enhanced IL‐6 induction

“…Interestingly, the addition of IL‐2 recovered the maintenance of RORγt − Helios + T regs in the presence of IL‐3 and IL‐33 (Figure 4A,B). This suggested that the reduction in RORγt − Helios + T regs resulted from a deficiency of IL‐2 in the culture, which is normally produced by IL‐33‐stimulated BMMCs 21 . In contrast to conditions with SCF costimulation, 21 IL‐3 strongly reduced the IL‐33‐induced production of IL‐2 by mast cells (Figure 4C).…”

“…We recently showed that IL‐33‐stimulated BMMCs induce RORγt + T regs from RORγt − T regs 21 . We analysed Tregs in the cocultures with mast cells as represented by the gating strategy shown in Figure B.…”

“…A maintenance factor for Helios + T regs is IL‐2 21 . To investigate whether the reduction of RORγt − Helios + T regs can be rescued by the addition of IL‐2, we added IL‐2 to the coculture of IL‐3‐IL‐33‐stimulated BMMCs and T regs .…”

“…One stable subpopulation of FoxP3 + T regs is characterized by the expression of the transcription factor RORγt 20 and can predominantly be found in gut‐associated lymphoid tissues (GALT) or on mucosal surface 20 . Recently, we found that IL‐33‐activated mast cells control the dichotomy between RORγt + and HELIOS + T regs via the production of IL‐6 21 . Growth factors such as IL‐3 and SCF modulate IL‐33‐induced cytokine responses in mast cells 1,12,22,23 …”

The IL-33-induced p38-/JNK1/2-TNFα axis is antagonized by activation of β-adrenergic-receptors in dendritic cells

“…(2020) 10:8152 | https://doi.org/10.1038/s41598-020-65072-3 www.nature.com/scientificreports www.nature.com/scientificreports/ the p38-MK2/3 signaling module and JNK1/2. Similar to mast cells 12,31,36 the p38-MK2/3 signaling module limits the activation of JNK1/2 and thus the proliferation of BMDCs by feedback inhibition ( Supplementary Fig. 3A).…”