The active metabolite of spleen tyrosine kinase inhibitor fostamatinib abrogates the CD4⁺ T cell-priming capacity of dendritic cells.

Abstract

OBJECTIVES:

Spleen tyrosine kinase (SYK) is a core signalling protein that drives inflammatory responses and is fundamental to the propagation of signals via numerous immune receptors, including the B cell receptor and Fc receptors (FcRs). Fostamatinib, a small molecule SYK inhibitor, has shown evidence of ameliorating inflammation in RA patients. We sought to understand how the active metabolite of fostamatinib, R406, affects the inflammatory response at the cellular level.

METHODS:

Antigen-specific in vivo systems and in vitro fluorescence microscopy were combined to investigate the effects of fostamatinib on antigen-specific interactions between dendritic cells (DCs) and CD4(+) T cells.

RESULTS:

Although it has previously been shown that R406 reduces the response of DCs to immune complexes (ICs), we found that fostamatinib failed to reduce specific CD4(+) T cell proliferation in mice after immunization with ICs. However, we observed in vitro that R406 reduces both the area and duration of cellular interactions between IC-activated DCs and specific CD4(+) T cells during the initial phase of cellular crosstalk. This led to diminished proliferation of antigen-specific CD4(+) T cells after R406 treatment compared with vehicle controls. This decreased proliferative capacity of CD4(+) T cells was accompanied by reduced expression of the co-stimulatory molecules, inducible T cell co-stimulator (ICOS) and PD-1, and abrogation of the production of inflammatory cytokines such as IFN-γ and IL-17.

CONCLUSION:

Our findings indicate a potential mechanism by which this compound may be effective in inhibiting FcR-driven CD4(+) T cell responses.

• Authors: Andrew M Platt, Robert A Benson, Ross McQueenie, John P Butcher, Martin Braddock, James M Brewer, Iain B McInnes, Paul Garside
• Journal: Rheumatology (Oxford, England) (Rheumatology (Oxford)) Vol. 54 Issue 1 Pg. 169-77 (Jan 2015) ISSN: 1462-0332 [Electronic] England
• PMID: 25065010 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: [email protected].

Chemical References

• Aminopyridines
• Antigen-Antibody Complex
• Chemokines
• Cytokines
• Enzyme Inhibitors
• Intracellular Signaling Peptides and Proteins
• Morpholines
• N4-(2,2-dimethyl-3-oxo-4H-pyrid(1,4)oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine
• Oxazines
• Pyridines
• Pyrimidines
• Protein-Tyrosine Kinases
• Syk Kinase
• Syk protein, mouse
• fostamatinib

Topics

• Administration, Oral
• Aminopyridines
• Animals
• Antigen-Antibody Complex (pharmacology)
• CD4-Positive T-Lymphocytes (drug effects, metabolism, pathology)
• Cell Communication (drug effects)
• Cell Proliferation (drug effects)
• Cells, Cultured
• Chemokines (metabolism)
• Cytokines (metabolism)
• Dendritic Cells (drug effects, metabolism, pathology)
• Enzyme Inhibitors (metabolism, pharmacology)
• In Vitro Techniques
• Intracellular Signaling Peptides and Proteins (antagonists & inhibitors)
• Mice
• Mice, Inbred C57BL
• Mice, Mutant Strains
• Models, Animal
• Morpholines
• Oxazines (administration & dosage, metabolism, pharmacology)
• Protein-Tyrosine Kinases (antagonists & inhibitors)
• Pyridines (administration & dosage, metabolism, pharmacology)
• Pyrimidines
• Syk Kinase