To this end we used an NF-κB inhibitor (Bay11) and the mTOR inhibitor rapamycin. TLR-triggered IL-10 production was significantly reduced after treatment with Bay11 or rapamycin alone and nearly absent after combined inhibitor usage (Fig. 5C). As expected for NF-κB inhibition, TLR2/4-induced TNF and IL-12 secretion levels were decreased under Bay11 treatment, but only TNF production remained unaffected by rapamycin, thus, confirming its selective regulation via NF-κB (Supporting Information Fig. 2D). Altogether, these findings suggested

a possible involvement of the PKB/Akt and p38 MAPK pathways in LPS-induced IL-10 regulation learn more and provided the notion that IRAK4 might serve as a differential regulator of PKB/Akt and/or p38 EPZ-6438 clinical trial MAPK signaling and could thereby determine the IL-10/IL-12 ratio. Furthermore, IL-10 secretion is partially dependent on NF-κB, but is additionally driven by the PKB/Akt/mTOR pathway in an NF-κB-independent manner.

Based on these results we subsequently focused on the PKB/Akt pathway. Analysis of mRNA expression by quantitative real time RT-PCR showed that expression of IL-10 in response to LPS stimulation is markedly reduced in the presence of rapamycin, Akt inhibitor or wortmannin (Fig. 6A). This indicated that interference with PI3K/PKB/Akt/mTOR signaling negatively regulates- IL-10 synthesis at a transcriptional level. Confirming our hypothesis, western blot analysis demonstrated increased phosphorylation of the Akt kinase on Thr308 in IRAK4-silenced monocytes PD184352 (CI-1040) stimulated with LPS (Fig. 6B). This effect was specific as this was not observed under MyD88 knockdown conditions, which, by contrast, decreased phospho-Akt levels to those measured in unstimulated cells (Fig. 6B). Thus, this experiment

highlighted the selective role of IRAK4 in the quantitative regulation of PKB/Akt activation. Also in line with these findings we detected enhanced phosphorylation of the PKB/Akt-mTOR-dependent transcription factor FoxO3a in IRAK4-silenced monocytes (Fig. 6C). As a last step we wanted to assess the functional impact of IRAK4-silencing on T-cell responses. To this end we used co-cultures of monocytes and allogenic CD8+ or CD4+ T cells. The results demonstrated that IRAK4-silenced monocytes represent weaker inducers of CD8+ as well as CD4+ T-cell proliferation than monocytes transfected with control siRNA (Fig. 7A). Notably, flow cytometric analysis of expression of monocyte activation markers, for example, CD14, CD80, CD86, PDL-1, MHCII, and ICOS-L was not affected by IRAK4 knockdown (not shown). But, suppressive monocyte function was found to be IL-10-dependent, as full T-cell stimulatory capacity was restored via neutralization of IL-10 in the co-cultures (Fig. 7B).