T Helper Cell Type 2 Cytokines Coordinately Regulate Immunoglobulin E–Dependent Cysteinyl Leukotriene Production by Human Cord Blood–Derived Mast Cells

Abstract

Human mast cells (hMCs) derived in vitro from cord blood mononuclear cells exhibit stem cell factor (SCF)-dependent comitogenic responses to T helper cell type 2 (Th2) cytokines. As cysteinyl leukotriene (cys-LT) biosynthesis is a characteristic of immunoglobulin (Ig)E-activated mucosal hMCs, we speculated that Th2 cytokines might regulate eicosanoid generation by hMCs. After passive sensitization for 5 d with IgE in the presence of SCF, anti-IgE–stimulated hMCs elaborated minimal cys-LT (0.1 ± 0.1 ng/106 hMCs) and abundant prostaglandin (PG)D2 (16.2 ± 10.3 ng/106 hMCs). Priming of hMCs by interleukin (IL)-4 with SCF during passive sensitization enhanced their anti-IgE–dependent histamine exocytosis and increased their generation of both cys-LT (by 27-fold) and PGD2 (by 2.5-fold). Although priming with IL-3 or IL-5 alone for 5 d with SCF minimally enhanced anti-IgE–mediated cys-LT generation, these cytokines induced further six- and fourfold increases, respectively, in IgE-dependent cys-LT generation when provided with IL-4 and SCF; this occurred without changes in PGD2 generation or histamine exocytosis relative to hMCs primed with IL-4 alone. None of these cytokines, either alone or in combination, substantially altered the levels of cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), or 5-LO activating protein (FLAP) protein expression by hMCs. In contrast, IL-4 priming dramatically induced the steady-state expression of leukotriene C4 synthase (LTC4S) mRNA within 6 h, and increased the expression of LTC4S protein and functional activity in a dose- and time-dependent manner, with plateaus at 10 ng/ml and 5 d, respectively. Priming by either IL-3 or IL-5, with or without IL-4, supported the localization of 5-LO to the nucleus of hMCs. Thus, different Th2-derived cytokines target distinct steps in the 5-LO/LTC4S biosynthetic pathway (induction of LTC4S expression and nuclear import of 5-LO, respectively), each of which is necessary for a full integrated functional response to IgE-dependent activation, thus modulating the effector phenotype of mature hMCs.

Role of STAT6 and Mast Cells in IL-4- and IL-13-Induced Alterations in Murine Intestinal Epithelial Cell Function

“…It remains to be determined whether STAT6 signaling is required to induce mast cells to release specific mediators that promote increased responsiveness to PGE 2 and histamine, or whether there is a separate, STAT6-dependent effect of IL-4 on intestinal epithelial cells that acts with a STAT6-independent mast cell effect to increase intestinal epithelial responsiveness. In support of the latter possibility, IL-4 has been shown to act through a STAT6-dependent mechanism to: 1) increase responsiveness to platelet-activating factor, histamine, 5-HT, and leukotriene C 4 in an anaphylaxis model (33,34); 2) induce increased expression of a receptor for cysteinyl leukotrienes (35); and 3) promote mast cell-dependent expulsion of Trichinella spiralis by infected mice through an effect on non-bone marrow-derived cells (24).…”

Prostaglandins Inhibit 5-Lipoxygenase-Activating Protein Expression and Leukotriene B4 Production from Dendritic Cells Via an IL-10-Dependent Mechanism

“…Another possibility is modulating the expression and activity of the enzymatic components through transcriptional or posttranscriptional mechanisms. It has also been demonstrated that the nuclear import of 5-LO can modulate LT biosynthesis, because nuclear import of 5-LO can strongly enhance (48) or suppress (49) 5-LO activity. Recently, Flammand et al (50) have reported that PGE 2 and other cAMPelevating agents down-regulated LT biosynthesis by inhibiting 5-LO translocation to the nuclear envelope in human polymorphonuclear leukocytes (PMN).…”

Cysteinyl leukotriene receptor 1 is also a pyrimidinergic receptor and is expressed by human mast cells

“…Total RNA was extracted from hMCs at 6-8 wk of culture with TRI Reagent (Molecular Research, Cincinnati), and RNA blotting was performed under high stringency conditions as previously described (23). For RT-PCR, RNA samples were primed with oligo(dT) and reverse transcribed in accordance with the manufacturer's protocol in an RT kit (CLONTECH).…”

“…When stimulated ex vivo by cross-linkage of their high-affinity Fc receptors for IgE (Fc RI), dispersed human lung MCs generate cys-LTs (22). When human MCs (hMCs), derived in vitro from cord blood, are primed with recombinant human IL-4 (10 ng͞ml), they express both the terminal biosynthetic enzyme, LTC 4 S, and Fc RI, thereby markedly up-regulating their generation of cys-LTs in response to Fc RI cross-linkage (23). Thus, the pivotal Th2 cytokine IL-4 regulates functions of MCs that are directly pertinent to their effector role in allergic inflammation.…”