BLT2 Is Upregulated in Allergen-Stimulated Mast Cells and Mediates the Synthesis of Th2 Cytokines

Abstract

Mast cells are effector cells that mediate the allergic response through Ag stimulation of IgE bound to FcεRI. In allergic reactions, cross-linking of the surface receptors for IgE on mast cells results in the synthesis of Th2 cytokines such as IL-4 and IL-13, which are critical for the initiation and progression of the allergic response. Despite the important roles of these cytokines, the signaling mechanism by which Ag stimulation mediates the production of IL-4 and IL-13 in mast cells is not clearly understood. In the present study, we found that Ag-stimulated bone marrow-derived mast cells (BMMCs) highly upregulated the expression of BLT2, a leukotriene B4 receptor, and that blockade of BLT2 with the specific antagonist LY255283 or small interfering RNA knockdown completely abolished the production of Th2 cytokines. Furthermore, BMMCs overexpressing BLT2 showed significantly enhanced production of Th2 cytokines compared with wild-type BMMCs. Additionally, we found that the generation of Nox1-derived reactive oxygen species occurs downstream of BLT2, thus mediating the synthesis of Th2 cytokines. Taken together, our results suggest that the BLT2-Nox1-reactive oxygen species cascade is a previously unsuspected mediatory signaling mechanism to Th2 cytokine production in Ag-stimulated BMMCs, thus contributing to allergic response.

Bioactive Lipoxygenase Metabolites Stimulation of NADPH Oxidases and Reactive Oxygen Species

“…The BLT2-mediated NOX1 upregulation-dependent pathway has also been shown to promote the secretion of IL-8 from human mast cells in response to the pro-inflammatory cytokine IL1beta, contributing to angiogenesis (Kim et al, 2010d). Another study indicated that BLT2-stimulated NOX1 upregulation is a downstream signaling route that mediates the synthesis of Th2 cytokines (IL-4 and IL-13) in antigen-stimulated bone marrowderived mast cells (Cho et al, 2010). The mechanism through which BLT2 mediates NOX upregulation has not yet been clearly demonstrated.…”

International Union of Basic and Clinical Pharmacology. LXXXIV: Leukotriene Receptor Nomenclature, Distribution, and Pathophysiological Functions

“…A subsequent study also described BLT 2 R mRNA in BMMC after 4 weeks of culture and indicated that either the BLT 1 R antagonist U75302 or the BLT 2 receptor antagonist LY255283 inhibited LTB 4 -induced BMMC chemotaxis, although no additive effect was observed after combination of the two receptor antagonists (Lundeen et al, 2006). In addition, antigen stimulation increased BLT 2 R expression in murine BMMCs (Cho et al, 2010a). In support of a functional murine MC BLT 2 receptor, the BLT 2 receptor agonists 12-HHT and 12(S)-HETE have also been reported to induce BMMC migration (Lundeen et al, 2006;Okuno et al, 2008).…”

Ras Promotes Transforming Growth Factor-β (TGF-β)-induced Epithelial-Mesenchymal Transition via a Leukotriene B4 Receptor-2-linked Cascade in Mammary Epithelial Cells

“…The amplification protocol for both the first round and nested PCR included 27 cycles of denaturation 95°C for 30 s, annealing at 61°C for 40 s, and elongation at 72°C for 45 s. For Nox1, the size of amplification product is 305 bp. The primers for mouse BLT1 were 5Ј-GCATGTCCCTGT-CTCGTT-3Ј (forward) and 5Ј-CGGGCAAAGGCCTTAGT-ACG-3Ј (reverse), and the primers for mouse BLT2 were 5Ј-CAGCATGTACGCCAGCGTGC-3Ј (forward) and 5Ј-CGAT-GGCGCTCACCAGACG-3Ј (reverse) (25). The PCR protocol for mouse BLT1/2 entailed 35 cycles of denaturation at 94°C for 30 s, annealing at 68°C for 30 s, and elongation at 72°C for 30 s followed by extension at 72°C for 10 min.…”