ABSTRACT
The involvement of serotonin (5-HT) in chronic pain mechanisms is established. 5-HT inhibits central painful stimuli, but recent data suggests that 5-HT could also enhance pain stimulus from the periphery, where mast cells play an important role. We aimed in our study to clarify the influence of selected tricyclic antidepressants (TCAs) on mast cell function: secretion, uptake, and reuptake of 5-HT, that could interfere with 5-HT levels and in this way contribute to the generation of pain. As an experimental model, we used isolated rat peritoneal mast cells and incubated them with selected TCAs (clomipramine, amitriptyline, doxepin, and imipramine) under different experimental conditions. 5-HT release, uptake, and reuptake were determined spectrofluorometrically. We showed that TCAs were able to inhibit 5-HT secretion from mast cells, as well as uptake of exogenous 5-HT and reuptake of secreted 5-HT back into mast cells. The effects of TCAs were concentration dependent; higher concentrations of TCAs inhibited the secretion of 5-HT induced by compound 48/80, whereas lower concentrations of TCAs inhibited 5-HT uptake. The most effective TCA was halogenated clomipramine. As TCAs are well introduced in chronic pain treatment, the insight into mechanisms of action is important for an understanding of their effect in various pain conditions.
Subject(s)
Antidepressive Agents, Tricyclic/pharmacology , Chronic Pain/metabolism , Mast Cells/metabolism , Serotonin/metabolism , Amitriptyline/pharmacology , Animals , Biological Transport/drug effects , Cells, Cultured , Clomipramine/pharmacology , Imipramine/pharmacology , Mast Cells/drug effects , Rats , Rats, WistarABSTRACT
The common structural feature of LK direct thrombin inhibitors is a strong basic group attached to the azaphenylalanine scaffold, which is important for the appropriate interaction at the thrombin active site. Our previous results have shown that this basic group could be responsible for a reduction of tracheal air flow and a fall of mean arterial pressure in anaesthetized rats, an undesired effect of direct thrombin inhibitors which correlated with their ability to release histamine from mast cells. In the present study, we investigated the mechanism of LK direct thrombin inhibitors-induced histamine release from rat peritoneal mast cells. We demonstrated that thrombin inhibitors with basic character (LK-732, LK-639 and LK-6063) provoked release of histamine from mast cells, while less basic analogs (LK-658, LK-633 and LK-6062) had no effect. Histamine released by LK-732 and LK-639 was suppressed by removal of sialic acid residues by neuraminidase and by pertussis toxin, an inhibitor of G(i) protein activity. Additional demonstration that G proteins are the targets of LK-732 and LK-639 was provided by the increase of GTPgammaS binding rate to G proteins in rat brain cortical membranes. Our results indicate that basic direct thrombin inhibitors LK-732 and LK-639 provoke release of histamine from mast cells by direct activation of G(i) proteins through the similar biochemical pathway as basic secretagogues.
Subject(s)
Aniline Compounds/pharmacology , GTP-Binding Protein alpha Subunits, Gi-Go/metabolism , Histamine Release/drug effects , Naphthalenes/pharmacology , Phenylalanine/analogs & derivatives , Thrombin/antagonists & inhibitors , Analysis of Variance , Aniline Compounds/chemical synthesis , Animals , Cell Survival/drug effects , Cells, Cultured , Dose-Response Relationship, Drug , Guanosine 5'-O-(3-Thiotriphosphate)/metabolism , Histamine/metabolism , Male , Mast Cells/cytology , Mast Cells/drug effects , Mast Cells/metabolism , Naphthalenes/chemical synthesis , Pertussis Toxin/pharmacology , Phenylalanine/chemical synthesis , Phenylalanine/pharmacology , Protein Binding/drug effects , Rats , Rats, Wistar , Structure-Activity RelationshipABSTRACT
It has been demonstrated that the release of histamine from mast cells by cytokines is strongly dependent on extracellular Ca2+ and Na+ ions. The results of our current research indicate that the removal of extracellular Na+ enhances NGF induced histamine release, but reduces induction by compound 48/80, suggesting that different mechanisms are involved in the secretory process induced by these agents.
