Little is known of the regulation of interleukin-23 secretion in dendritic cells (DC) despite its importance for human Th17 responses. Here we show for first time that the Ataxia Telangiectasia Mutated (ATM) pathway, involved in DNA-damage-sensing, acts as an IL-23 repressor. Inhibition of ATM with the highly-selective antagonist, KU55933, markedly increased IL-23 secretion human monocyte-derived DC (moDC) and freshly isolated myeloid DC (myDC). In contrast, inhibiting the closely related mammalian target of rapamycin (mTOR) had no effect on IL-23. Priming naïve CD4+ T-cells with ATM-inhibited DC increased Th17 responses over and above those obtained with mature DC. Whilst ATM-blockade increased the abundance of p19, p35 and p40 mRNA, IL-12p70 secretion was unaffected. In order to further examine a role for ATM in IL-23 regulation we exposed DC to low doses of ionizing radiation. Exposure of DC to X-rays resulted in ATM phosphorylation and a corresponding depression of IL-23. Importantly, ATM-inhibition with KU55933 prevented radiation-induced ATM phosphorylation and abrogated the capacity of X-rays to suppress IL-23. To explore how ATM repressed IL-23 we examined a role for ER-stress responses by measuring generation of the spliced form of X-box protein-1 (XBP1s), a key ER-stress transcription factor. Inhibition of ATM increased the abundance of XBP1s mRNA and this was followed 3hr later by increased peak p19 transcription and IL-23 release. In summary, ATM-activation or inhibition respectively inhibited or augmented IL-23 release. This novel role of the ATM pathway represents a new therapeutic target in autoimmunity and vaccine development.
Summary Interleukin‐23 (IL‐23) is important for T helper type 17 (Th17) responses and strategies to regulate IL‐23 in human dendritic cells (DC) are limited. This study describes a novel means to control IL‐23 secretion by conditioning DC with a phosphatidyl inositol 3‐kinase inhibitor Wortmannin (WM). Treatment of monocyte‐derived DC with WM increased Toll‐like receptor (TLR) ‐dependent IL‐23 secretion 10‐fold and IL‐12p70 twofold, but IL‐27 was unaffected. The effect of WM was restricted to TLR3/4 pathways, did not occur through TLR2, TLR7/8 or Dectin‐1, and was characterized by increased p19, p35 and p40 transcription. These responses were not solely dependent on phosphatidyl inositol 3‐kinase as the alternative inhibitor LY294002 did not modulate IL‐23 production. The normal patterns of activation of mitogen‐activated protein kinase pathways were unaffected by WM‐conditioning but IL‐23 secretion required p38, ERK and JNK pathways. Importantly, this effect was manifest in populations of blood DC. Conditioning freshly isolated myeloid DC with WM before TLR3 or TLR4 triggering resulted in high levels of IL‐23 secretion and an absence of IL‐12p70. These WM‐conditioned myeloid DC were highly effective at priming Th17 responses from naive CD4+ T cells. Our findings provide a novel means to generate IL‐23‐rich environments and Th17 responses and suggest as yet unidentified regulatory factors, identification of which will provide new approaches to control IL‐23‐dependent immunity in infectious disease, autoimmunity and malignancy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.