The Ataxia Telangiectasia Mutated Kinase Pathway Regulates IL-23 Expression by Human Dendritic Cells

Abstract

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.

Neutrophil oxidative burst activates ATM to regulate cytokine production and apoptosis

“…In human dendritic cells ATM was shown to be a negative regulator of IL-23 production. 38 Furthermore, pharmacologic induction of the DNA damage response reduces levels of proinflammatory cytokines and increases survival in septic mice. 39 This protective effect was shown to be partly mediated by ATM activation, although the researchers conclude that this is a lung-specific mechanism not mediated by blood cells.…”

Immuno-silent polymer capsules encapsulating nanoparticles for bioimaging applications

“…In agreement with previous reports DC generated from CD14+ve monocytes in the presence of GM-CSF and IL-4 showed loss of CD14 expression, high HLA-DR and were positive for CD80, CD40, CD86 while CD83 expression was negative. 22,23 Upon activation with LPS/IFN-γ for 24 h DC demonstrated typical signs of maturation by increase in HLA-DR, CD80, CD40, CD86 and gain of CD83 (Figure S2a,b). [30][31][32][33][34] Resting DC and MO are very sensitive to a wide range of signals that indicate the presence of potential pathogens or damaged tissues.…”

“…Monocyte derived DCs were generated as previously described. 22,23 Briefly, positively selected CD14+ monocytes were cultured in DC medium (RPMI, 10%FBS, 1% sodium pyruvate) containing rhGM-CSF and rhIL-4 (both 1000 U/mL). Additional complete medium with cytokines was added on day 3-4.…”

The TAM family as a therapeutic target in combination with radiation therapy

“…Broadly speaking, fully differentiated myeloid cells are relatively radio-resistant; however, radiation therapy can suppress the ability of ex vivo cultured dendritic cells to stimulate T-cell responses [19,20]. Moreover, regulation of DNA damage response pathways in irradiated DC can alter the pattern of cytokine secretion of stimulated DC [21], potentially resulting in altered T-cell response profiles stimulated by these DC. Little is known about the relative effects of radiation on the distinct DC subtypes in vivo, but recent studies suggest that multiple DC subtypes are negatively affected.…”