ABSTRACT
The vasoactive intestinal peptide (VIP) and its G protein-coupled receptors VPAC1 and VPAC2 prominently mediate diverse physiological functions in the neural, endocrine, and immune systems. A deletion variant of mouse VPAC2 has been identified in immune cells that lacks amino acids 367-380 at the carboxyl-terminal end of the seventh transmembrane domain. When expressed at equivalent levels in a human Jurkat T cell line, which has very low endogenous expression of human VPAC1 and VPAC2, wild-type and deletion-variant VPAC2 bound the same amount of 125I-VIP with similar affinity. Unlike wild-type VPAC2, however, deletion-variant VPAC2 did not transduce VIP-elicited increases in intracellular concentration of cyclic AMP, chemotaxis, or suppression of generation of interleukin-2. Natural deletion of part of the last transmembrane domain of VPAC2 thus abrogates signaling functions without apparent alterations of expression or ligand binding.
Subject(s)
Receptors, G-Protein-Coupled/chemistry , Receptors, Vasoactive Intestinal Peptide/chemistry , Vasoactive Intestinal Peptide/chemistry , Animals , Chemotaxis , Cyclic AMP/metabolism , Female , Gene Deletion , Humans , Interleukin-2/metabolism , Jurkat Cells , Ligands , Mice , Mice, Inbred C57BL , Mutation , Protein Binding , Protein Structure, Tertiary , RNA, Messenger/metabolism , Receptors, G-Protein-Coupled/metabolism , Receptors, Vasoactive Intestinal Peptide/metabolism , Receptors, Vasoactive Intestinal Peptide, Type II , Signal Transduction , Transfection , Vasoactive Intestinal Peptide/metabolismABSTRACT
Sphingosine 1-phosphate (S1P) in blood, lymph, and immune tissues stimulates and regulates T cell migration through their S1P(1) (endothelial differentiation gene encoded receptor-1) G protein-coupled receptors. We show now that S1P(1)Rs also mediate suppression of T cell proliferation and cytokine production. Uptake of [(3)H]thymidine by mouse CD4 T cells stimulated with anti-CD3 mAbs plus either anti-CD28 or IL-7 was inhibited up to 50% by 10(-9)-10(-6) M S1P. Suppression by S1P required Ca(2+) signaling and was reduced by intracellular cAMP. S1P decreased CD4 T cell generation of IFN-gamma and IL-4, without affecting IL-2. A Th1 line from D011.10 TCR transgenic mice without detectable S1P(1) was refractory to S1P until introduction of S1P(1) by retroviral transduction. S1P then evoked chemotaxis, inhibited chemotaxis to CCL-5 and CCL-21, and suppressed Ag-stimulated proliferation and IFN-gamma production. Thus, S1P(1) signals multiple immune functions of T cells as well as migration and tissue distribution.
Subject(s)
Lysophospholipids , Receptors, G-Protein-Coupled/physiology , Signal Transduction/genetics , Signal Transduction/immunology , Sphingosine/analogs & derivatives , Sphingosine/physiology , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism , Adjuvants, Immunologic/genetics , Adjuvants, Immunologic/pharmacology , Adjuvants, Immunologic/physiology , Animals , CD4-Positive T-Lymphocytes/cytology , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , Cell Division/genetics , Cell Division/immunology , Cell Line , Cell Line, Tumor , Cell Movement/genetics , Cell Movement/immunology , Female , Growth Inhibitors/pharmacology , Humans , Interferon-gamma/antagonists & inhibitors , Interferon-gamma/metabolism , Interleukin-2/biosynthesis , Interleukin-4/antagonists & inhibitors , Interleukin-4/metabolism , Lymphocyte Activation/genetics , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Transgenic , Rats , Receptors, Antigen, T-Cell/physiology , Receptors, G-Protein-Coupled/genetics , Receptors, Lysophospholipid , Sphingosine/genetics , Sphingosine/metabolism , Sphingosine/pharmacology , T-Lymphocyte Subsets/cytology , Transduction, Genetic/methodsABSTRACT
Vasoactive intestinal peptide (VIP) and its two G protein-coupled receptors, VPAC1 and VPAC2, are quantitatively prominent and functionally critical in the immune system. Transgenic (T) mice constitutively expressing VPAC2 selectively in CD4 T cells, at levels higher than those found after maximal induction in CD4 T cells of wild-type (N) mice, have elevated blood concentrations of IgE, IgG1, and eosinophils; enhanced immediate-type hypersensitivity; and reduced delayed-type hypersensitivity. In contrast, VPAC2-null (K) mice manifest decreased immediate-type hypersensitivity and enhanced delayed-type hypersensitivity. The phenotypes are attributable to opposite skewing of the Th2/Th1 cytokine ratio, but no studies were conducted on the roles of T cell-derived VIP and altered expansion of the Th subsets. Dependence of the Th phenotype of T mice, but not of N or K mice, on T cell-derived VIP now is proven by showing that eliminating VIP from TCR-stimulated T cell cultures with VIPase IgG normalizes the elevated number of IL-4-secreting CD4 T cells, decreases the secretion of IL-4 and IL-10, and increases the secretion of IFN-gamma. Flexible responsiveness of CD4 T cells from N and K mice, but not T mice, to exogenous VIP in vitro and in vivo is shown by increased numbers of IL-4-secreting CD4 T cells, greater secretion of IL-4 and IL-10, and lesser secretion of IFN-gamma after TCR stimulation with VIP. The level of VIP recognized by CD4 T cells thus is a major determinant of the relative contributions of Th subsets to the immune effector phenotype.
Subject(s)
Gene Expression Regulation/immunology , Immunophenotyping , Receptors, Vasoactive Intestinal Peptide/biosynthesis , Receptors, Vasoactive Intestinal Peptide/genetics , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism , Vasoactive Intestinal Peptide/pharmacology , Animals , Antibodies, Catalytic/metabolism , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , Cells, Cultured , Cytokines/biosynthesis , Cytokines/metabolism , Humans , Hypersensitivity, Delayed/genetics , Hypersensitivity, Immediate/genetics , Lymphocyte Activation/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Peptide Biosynthesis/genetics , Peptide Biosynthesis/immunology , Receptors, Antigen, T-Cell/physiology , Receptors, Vasoactive Intestinal Peptide/deficiency , Receptors, Vasoactive Intestinal Peptide, Type II , Vasoactive Intestinal Peptide/chemical synthesis , Vasoactive Intestinal Peptide/immunology , Vasoactive Intestinal Peptide/metabolismABSTRACT
Vasoactive intestinal peptide (VIP) and its two G protein-coupled receptors, VPAC1R and VPAC2R, are prominent in the immune system and potently affect T cells and macrophages. VPAC1Rs are expressed constitutively by blood and tissue T cells, with an order of prevalence of Th2>Th1>>Ts, and transmit signals suppressive for migration, proliferation and cytokine production. Immune activation of T cells downregulates VPAC1Rs and upregulates VPAC2Rs. VPAC2Rs mediate T cell chemotaxis, stimulation of some Th2-type cytokines, and inhibition of some Th1-type cytokines. A tentative hypothesis that the VIP-VPAC2R axis is the major neuroregulator of Th2/Th1 balance has been confirmed by finding an increased ratio in CD4 T cells of transgenic (TG) mice, expressing high levels of VPAC2Rs, and a decreased ratio in CD4 T cells of VPAC2R-null (K/O) mice. VPAC2R TG mice exhibit an allergic phenotype, whereas the K/O mice are hypoallergic and have heightened delayed-type hypersensitivity. The mechanisms of VIP-VPAC2R effects include decreased Th2 apoptosis, increased Th2-type cytokine production, and greater generation of Th2 memory cells. VPAC2R antagonists are being developed to alleviate allergic diseases and strengthen effector Th1 cell-mediated immunoprotection.
