RESUMEN
The cholinergic anti-inflammatory pathway is recognized as one of the main mechanisms of neuromodulation of the immune system. Activation of the α7 nicotinic acetylcholine receptor (nAchRα7) suppresses cytokine synthesis in distinct immune cells but the molecular mechanisms behind this effect remain to be fully described. Mast cells (MCs) are essential players of allergic reactions and innate immunity responses related to chronic inflammation. Activation of TLR4 receptor in MCs leads to the rapid secretion of pre-synthesized TNF from intracellular pools and to the activation of NFκB, necessary for de novo synthesis of TNF and other cytokines. Here we report that the nAchRα7 receptor specific agonist GTS-21 inhibits TLR4-induced secretion of preformed TNF from MCs in vivo and in vitro. Utilizing bone marrow-derived mast cells (BMMCs) it was found that GTS-21 also diminished secretion of de novo synthesized TNF, TNF mRNA accumulation and IKK-dependent p65-NFκB phosphorylation in response to LPS. nAchRα7 triggering prevented TLR4-induced ERK1/2 phosphorylation, which resulted an essential step for TNF secretion due to the phosphorylation of the metallopeptidase responsible for TNF maturation (TACE). Main inhibitory actions of GTS-21 were prevented by AG490, an inhibitor of JAK-2 kinase. Our results show for the first time, that besides the prevention of NFκB-dependent transcription, inhibitory actions of nAchRα7 triggering include the blockade of pathways leading to exocytosis of granule-stored cytokines in MCs.
Asunto(s)
Mastocitos/inmunología , Mastocitos/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Receptor Nicotínico de Acetilcolina alfa 7/metabolismo , Proteína ADAM17/inmunología , Proteína ADAM17/metabolismo , Animales , Activación Enzimática/inmunología , Inflamación/inmunología , Inflamación/metabolismo , Lipopolisacáridos/farmacología , Sistema de Señalización de MAP Quinasas/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Factor de Necrosis Tumoral alfa/inmunología , Receptor Nicotínico de Acetilcolina alfa 7/inmunologíaRESUMEN
OBJECTIVE AND DESIGN: To characterize the effects of swim stress on the early mast cell (MC)-dependent peritoneal production of TNF in response to lipopolysaccharide (LPS) administration in mice, identifying the neuroendocrine mediators involved. SUBJECTS: Ten to twelve-week-old Swiss Webster, C57BL/6 J or c-Kit (Wsh/Wsh) mice were used. TREATMENT: Animals were intraperitoneally challenged with LPS at different times after forced swimming (FS) and peak TNF production was determined in peritoneal washes at optimal time after LPS administration. Selective blockage of main neuroendocrine pathways was performed before swim stress. METHODS: TNF concentrations were determined by ELISA. RESULTS: FS provoked an immediate and transient inhibition of LPS-elicited, MC-dependent TNF accumulation in peritoneum, which lasted around 30 min. Suppresive effects of FS were absent on MC-deficient c-Kit (Wsh/Wsh) mice but were recovered after reconstitution with MC. Adrenalectomy or DSP4 administration increased basal ip TNF levels and enhanced LPS-induced TNF release without any effect on stress-induced inhibitory effects, mifepristone did not produce any change on stress-induced inhibition, whereas mecamylamine administration increased basals and attenuated stress effects. CONCLUSIONS: Swim stress transiently inhibits the canonical MC-dependent response of TNF production in response to LPS in murine peritoneal cavity with the main participation of the cholinergic anti-inflammatory reflex.