Nicotine attenuates activation of tissue resident macrophages in the mouse stomach through the beta2 nicotinic acetylcholine receptor.

BACKGROUND: The cholinergic anti-inflammatory pathway is an endogenous mechanism by which the autonomic nervous system attenuates macrophage activation via nicotinic acetylcholine receptors (nAChR). This concept has however not been demonstrated at a cellular level in intact tissue. To this end, we have studied the effect of nicotine on the activation of resident macrophages in a mouse stomach preparation by means of calcium imaging. METHODS: Calcium transients ([Ca(2+)]i) in resident macrophages were recorded in a mouse stomach preparation containing myenteric plexus and muscle layers by Fluo-4. Activation of macrophages was achieved by focal puff administration of ATP. The effects of nicotine on activation of macrophages were evaluated and the nAChR involved was pharmacologically characterized. The proximity of cholinergic nerves to macrophages was quantified by confocal microscopy. Expression of beta2 and alpha7 nAChR was evaluated by beta2 immunohistochemistry and fluorophore-tagged alpha-bungarotoxin. RESULTS: In 83% of macrophages cholinergic varicose nerve fibers were detected at distances {\textless}900 nm. The ATP induced [Ca(2+)]i increase was significantly inhibited in 65% or 55% of macrophages by 100 microM or 10 microM nicotine, respectively. This inhibitory effect was reversed by the beta2 nAChR preferring antagonist dihydro-beta-eryhtroidine but not by hexamethonium (non-selective nAChR-antagonist), mecamylamine (alpha3beta4 nAChR-preferring antagonist), alpha-bungarotoxin or methyllycaconitine (both alpha7 nAChR-preferring antagonist). Macrophages in the stomach express beta2 but not alpha7 nAChR at protein level, while those in the intestine express both receptor subunits. CONCLUSION: This study is the first in situ demonstration of an inhibition of macrophage activation by nicotine suggesting functional signaling between cholinergic neurons and macrophages in the stomach. The data suggest that the beta2 subunit of the nAChR is critically involved in the nicotine-induced inhibition of these resident macrophages.     «

BACKGROUND: The cholinergic anti-inflammatory pathway is an endogenous mechanism by which the autonomic nervous system attenuates macrophage activation via nicotinic acetylcholine receptors (nAChR). This concept has however not been demonstrated at a cellular level in intact tissue. To this end, we have studied the effect of nicotine on the activation of resident macrophages in a mouse stomach preparation by means of calcium imaging. METHODS: Calcium transients ([Ca(2+)]i) in resident macrophag...     »

Mice, Inbred C57BL, Microscopy, Confocal, Immunohistochemistry, Animals, Calcium/metabolism, Mice, Male, Adenosine Triphosphate/pharmacology, Aniline Compounds/metabolism, Enteric Nervous System/cytology/drug effects/metabolism, Ganglionic Stimulants/pharmacology, Macrophage Activation/drug effects, Macrophages/*drug effects/metabolism, Myenteric Plexus/drug effects/metabolism, Neurons/drug effects/metabolism, Nicotine/*pharmacology, Receptors, Nicotinic/*metabolism, Stomach/*drug effects/innervation/metabolism, Xanthenes/metabolism     «

Mice, Inbred C57BL, Microscopy, Confocal, Immunohistochemistry, Animals, Calcium/metabolism, Mice, Male, Adenosine Triphosphate/pharmacology, Aniline Compounds/metabolism, Enteric Nervous System/cytology/drug effects/metabolism, Ganglionic Stimulants/pharmacology, Macrophage Activation/drug effects, Macrophages/*drug effects/metabolism, Myenteric Plexus/drug effects/metabolism, Neurons/drug effects/metabolism, Nicotine/*pharmacology, Receptors, Nicotinic/*metabolism, Stomach/*drug effects/innerv...     »