The fungal analog zymosan induces IL-23 and low amounts of IL-12 p70. This study addresses the molecular mechanisms underlying this cytokine pattern in human monocyte-derived dendritic cells. The transcriptional regulation of il23a, one of the chains of IL-23, depended on the activation of c-Rel and histone H3 phosphorylation, as judged from the association of c-Rel with the il23a promoter and the correlation between IL-23 production and S10-histone H3 phosphorylation. Consistent with its reduced ability to produce IL-12 p70, zymosan induced a transient occupancy of the il12a promoter by c-Rel, blocked the production of IL-12 p70 and the transcription of il12a induced by other stimuli, and triggered the expression and nuclear translocation of the transcriptional repressors of the Notch family hairy and enhancer of split (Hes)-1, Hes5, hairy/enhancer-of-split related with YRPW motif protein (Hey)-1, and TLE (transducin-like enhancer of split). Zymosan also induced the interaction of Hes1 and TLE with histone H3 phosphorylated on S10 and deacetylated on K14. Inhibition of class III histone deacetylases increased the production of IL-12 p70 and partially blunted the inhibitory effect of zymosan on the production of IL-12 p70 elicited by LPS and IFN-γ. These results indicate that the selective induction of IL-23 byβ-glucans is explained by the activation of c-Rel associated with S10-histone H3 phosphorylation in the il23a promoter mediated by mitogen- and stress-activated kinase (MSK) and/or protein kinase A, and inhibition of il12a transcription by a mechanism involving activation of several corepressors with ability to bind TLE and to promote histone deacetylation.

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Peer reviewed