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P068 The combination of JAK1 and TPL2 or IRAK4 inhibitors is more effective than single agents in reducing TLR-mediated cytokine responses in human monocyte populations

Hornsby, E.(1);Yadon, A.N.(2);Clarke, A.(2);Grant, E.(3);Lindsay, J.O.(1);Stagg, A.J.(1);

(1)Queen Mary University of London, Blizard Institute, London, United Kingdom;(2)Gilead Sciences- Inc., 199 East Blaine Street, Seattle, United States;(3)Gilead Sciences- Inc., 333 Lakeside Dr., Foster City, United States

Background

Dysregulated Toll-like receptor (TLR)-mediated responses in intestinal monocyte-derived cells contribute to pathology in inflammatory bowel disease (IBD). JAK inhibitors regulate the production of inflammatory mediators and are an emerging therapy in IBD.  Recent data suggest that combination therapies may be more effective than single agents, and therapies targeting aspects of TLR signalling pathways are being developed. We assessed the impact of inhibitors of IRAK4, TPL2 and JAK1 (IRAK4i, TPL2i and JAK1i, respectively) either alone or in combination on TLR-mediated cytokine responses and associated signalling pathways in classical (CD14+CD16-), intermediate (CD14+CD16+) and non-classical (CD14lowCD16+) human blood monocyte subsets.

Methods

Peripheral Blood Mononuclear Cells (PBMCs) or CD14+ monocytes from healthy volunteers were pre-incubated with TPL2i, IRAK4i or JAK1i individually or with JAK1i in combination with TPL2i or IRAK4i for 1 hour at 37°C.  Cells were then stimulated at 37°C with agonists of TLR4 (E.coli lipopolysaccharide; LPS) or TLR2 (Pam3CYSK4).  Intra-cellular staining and flow cytometry were used to measure phosphorylation of signalling molecules (NF-kappaB p65, p38 MAPK and ERK) or cytokines (TNF-alpha and IL-1-beta) in the three monocyte subsets after stimulation for 15 minutes or 3 hours respectively.

Results

Pre-incubation of PBMCs or CD14+ monocytes with IRAK4i, TPL2i or JAK1i individually led to a significant dose-dependent reduction in TLR-stimulated cytokine production (the frequency of TNF-alpha+ cells and the per cell level of IL-1-beta) within the classical, intermediate and non-classical monocyte subsets. The combination of JAK1i with IRAK4i or TPL2i had an additive effect. TPL2i reduced LPS-stimulated ERK phosphorylation, but p65 and p38 phosphorylation in response to LPS was not affected by any of the inhibitors.

Conclusion

Small molecule inhibitors of TPL2, IRAK4 and JAK1 dampen TLR4- and TLR2- mediated inflammatory responses in human monocyte subsets, by affecting pathways independent of p65 or p38.  This is due to a cell intrinsic effect on CD14+ monocytes. TPL2 inhibition may in part act to dampen cytokine production in monocytes through the reduction of ERK phosphorylation. Combining JAK1i with IRAK4i or TPL2i may be more effective in reducing inflammatory responses than single agents. Further work is required to elucidate the mechanisms by which IRAK4i and JAK1i dampen TLR-mediated inflammation in monocyte subsets. 

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