Molecular and cellular biology in vitro and in vivo of the development, regulation, and function of mast cells and the cysteinyl leukotriene pathway.
The central focus of the laboratory continues to be on the molecular and cellular biology of the mast cell, the pathways of arachidonic acid metabolism to cysteinyl leukotrienes and prostanoids, and the cytokine regulation of the action of each of these components of allergic inflammation. We have used stem cell factor together with Th2 cell cytokines to develop mast cells from mouse bone marrow and human cord blood. Mast cells respond to Fc-epsilonRI-mediated activation with generation of prostaglandin (PG) D2 and leukotriene (LT) C4. Interleukin-4 regulates expression of the gene for the outer nuclear membrane protein LTC4 synthase responsible for the production of LTC4. The cloning of the cDNA for human LTC4 synthase (LTC4S) followed by the determination of the crystal structure in atomic detail revealed the basis for the profound specificity of the catalytic mechanism and its novel constitutive binding of glutathione for conjugation to newly generated LTA4. We have used LTC4 synthase null mice together with CysLTl and CysLT2 receptor null strains, respectively, on a C57B/6 background to evaluate local and systemic biologic responses to tissue-generated cysLTs. The CysLT1 receptor mediates the increment in intravascular permeability to cysLTs. In contrast, the CysLT2 receptor mediates the cysLT dependent portion of bleomycin-induced pulmonary fibrosis. The hematopoietic stem cell and monocyte lineage derived fibrocytes express LTC4 synthase and respond with directed migration via the cysLTs receptors; how they regulate fibroblast function is under study. In order to study the role of cysLTs in Th2 cell-mediated pulmonary inflammation, we also developed null strains on a BALB/c background. The sensitized and inhalation challenged LTC4S null strain exhibits markedly attenuated responses that suggest a role for the CysLTs in the afferent limb of the immune response distinct from their smooth muscle effector limb functions.