triprolidine and Inflammation

We report that gp49B1, a mast cell membrane receptor with two immunoreceptor tyrosine-based inhibitory motifs (ITIM), constitutively inhibits mast cell activation-secretion induced by stem cell factor (SCF), a tissue-derived cytokine that also regulates mast cell development. The intradermal injection of SCF into the ears of gp49B1 null (gp49B(-/-)) mice elicited approximately 4- and 2.5-fold more degranulating mast cells and tissue swelling caused by edema, respectively, than in gp49B(+/+) mice. SCF did not induce tissue swelling in mast cell-deficient mice, and the responsiveness of gp49B(-/-) mice to mast cell-associated amine and lipid mediators was unaltered. When gp49B(+/+) and gp49B(-/-) mice were pretreated with antagonists of the amines, SCF-induced tissue swelling was reduced by >90% and 60%, respectively, and it was reduced by >90% in both genotypes when a cysteinyl leukotriene receptor antagonist was also provided. Hence, the dominant contribution of secretory granule amines to SCF-induced tissue swelling is the result of gp49B1-mediated inhibition of the production of cysteinyl leukotrienes by mast cells. Our findings also provide the first example of an ITIM-bearing receptor that constitutively suppresses inflammation generated in vivo independently of the adaptive immune response by a receptor that signals through intrinsic tyrosine kinase activity rather than immunoreceptor tyrosine-based activation motifs.

Topics: Animals; Cell Degranulation; Chromones; Edema; Female; Inflammation; Male; Mast Cells; Membrane Glycoproteins; Metergoline; Mice; Mice, Inbred BALB C; Mice, Knockout; Mice, Mutant Strains; Receptors, Immunologic; Recombinant Proteins; Stem Cell Factor; Triprolidine

Dispase-dissociated primary cultures of human conjunctival epithelial (HCE) cells were stimulated with histamine and the generation of inositol phosphates ([3H]IPs) from [3H]phosphoinositide (PI) hydrolysis and the mobilization of intracellular calcium ([Ca2+]i) were studied using ion exchange chromatography and Fura-2 fluorescence techniques, respectively. Histamine (100 microM) maximally stimulated PI turnover in HCE cells by 210 +/- 10% (n = 21) above basal levels and with a potency (EC50) of 3.3 microM (n = 4). Histamine (EC50 = 5.8 microM, n = 3) rapidly mobilized [Ca2+]i which peaked within 10 sec but which was still significantly elevated 20 min after stimulation. The histamine-induced [Ca2+]i responses did not desensitize upon repeated applications of histamine. The effects of histamine (100 microM) on PI turnover and [Ca2+]i were potently antagonized by the H1-antagonists, emedastine (IC50 = 1.6-2.9 nM), triprolidine (IC50 = 3.1 nM) and levocabastine (IC50 = 8 nM), but weakly by the H2-(ranitidine/cimetidine) and H3-(thioperamide) antagonists (IC50s = 10-100 microM). In conclusion, HCE cells have been shown to possess functional H1-histamine receptors that couple to inositol phosphates generation which then mobilize intracellular calcium. These intracellular signaling mechanisms may be intimately linked with the process of inflammatory cytokine secretion from the HCE cells after stimulation by histamine released from the conjunctival mast cells. The current results strongly suggest that the HCE cells are active participants in mediating, and perhaps amplifying, the pro-inflammatory and allergic effects of histamine which is released from conjunctival mast cells during ocular allergic and inflammatory reactions.

Topics: Benzimidazoles; Calcium; Cells, Cultured; Chromatography, Ion Exchange; Conjunctiva; Cytokines; Epithelium; Eye Diseases; Histamine; Histamine Antagonists; Humans; Hypersensitivity; Inflammation; Phosphatidylinositols; Piperidines; Receptors, Histamine H1; Stimulation, Chemical; Triprolidine

Topics: Aminocaproates; Animals; Antigens; Aprotinin; Aspirin; Blood Coagulation Tests; Capillary Permeability; Cell Migration Inhibition; Cells, Cultured; Esters; Guinea Pigs; Heparin; Hydrocortisone; Immunization; Indomethacin; Inflammation; Isoflurophate; Kymography; Lymph Nodes; Lymphocytes; Mercuribenzoates; Muscle, Smooth; Mycobacterium tuberculosis; Phenylbutazone; Protamines; Skin Tests; Thiocarbamates; Triprolidine; Trypsin Inhibitors

Interaction in free solution of highly purified preparations of human C'1 esterase, C'4, C'2, and C'3, in the presence of Mg(2+), resulted in rapid generation of an activity indistinguishable by biological criteria from anaphylatoxin. The formation of anaphylatoxin was associated with immunoelectrophoretic conversion of C'3 to anodically faster migrating proteins and was unaffected by the presence or absence of added C'5. The biological properties of human anaphylatoxin prepared in this manner include: contraction and desensitization of isolated guinea pig ileum, failure to contract isolated rat uterus, enhancement of vascular permeability in guinea pig skin, degranulation of mast cells in guinea pig mesentery preparations, and liberation of histamine from suspensions of rat peritoneal mast cells. The smooth muscle-contracting and permeability enhancing properties were fully blocked by an antihistaminic drug, triprolidine. No cross-desensitizing activity on guinea pig ileum was demonstrable between rat and human or guinea pig and human anaphylatoxins but a closer biological relationship between rat and guinea pig anaphylatoxins was observed. It is concluded that anaphylatoxin is a product of the complement system. Its possible relationship to apparently similar activities currently being obtained in other laboratories has been discussed.

Topics: Anaphylaxis; Capillary Permeability; Chemical Phenomena; Chemistry; Complement System Proteins; Edetic Acid; Esterases; Histamine; Immunoelectrophoresis; Inflammation; Mast Cells; Muscle Contraction; Muscle, Smooth; Toxins, Biological; Triprolidine