JNK signaling during IL-3-mediated differentiation contributes to the c-kit-potentiated allergic inflammatory capacity of mast cells.

Mast cells are leukocytes that mediate various aspects of immunity and drive allergic hypersensitivity pathologies. Mast cells differentiate from hematopoietic progenitor cells in a manner that is largely IL-3 dependent. However, molecular mechanisms, including the signaling pathways that control this process, have yet to be thoroughly investigated. Here, we examine the role of the ubiquitous and critical MAPK signaling pathway due to its position downstream of the IL-3 receptor. Hematopoietic progenitor cells were harvested from the bone marrow of C57BL/6 mice and differentiated to bone marrow-derived mast cells (BMMCs) in the presence of IL-3 and MAPK inhibitors. Inhibition of the JNK node of the MAPK pathway induced the most comprehensive changes to the mature mast cell phenotype. BMMCs differentiated during impaired JNK signaling express impaired c-kit levels on the mast cell surface, first detected at week 3 of differentiation. Following 1 week of inhibitor withdrawal and subsequent stimulation of IgE-sensitized FcεRI receptors with allergen (TNP-BSA), and c-kit receptors with SCF, JNK-inhibited BMMCs exhibit impediments in early phase mediator release through degranulation (80% of control), as well as late phase secretion of CCL1, CCL2, CCL3, TNF, and IL-6. Experiments with dual stimulation conditions (TNP-BSA + SCF or TNP-BSA alone), show impediments in mediator secretion were found to be mechanistically linked to reduced c-kit surface levels. This study is the first to implicate JNK activity in IL-3-mediated mast cell differentiation, and also identifies development as a critical and functionally determinative period.