In vivo release of non‐neuronal acetylcholine from the human skin as measured by dermal microdialysis: effect of botulinum toxin

Abstract

1 Acetylcholine is synthesized in the majority of non-neuronal cells, for example in human skin. In the present experiments, the in vivo release of acetylcholine was measured by dermal microdialysis. 2 Two microdialysis membranes were inserted intradermally at the medial shank of volunteers. Physiological saline containing 1 mM neostigmine was perfused at a constant rate of 4 ml min À1 and the effluent was collected in six subsequent 20 min periods. Acetylcholine was measured by high-pressure liquid chromatography (HPLC) combined with bioreactors and electrochemical detection. 3 Analysis of the effluent by HPLC showed an acetylcholine peak that disappeared, when the analytical column was packed with acetylcholine-specific esterase, confirming the presence of acetylcholine. 4 In the absence of neostigmine, 71751 pmol acetylcholine (n ¼ 4) was found during a 120 min period. The amount increased to 183743 pmol (n ¼ 34), when the perfusion medium contained 1 mM neostigmine. 5 Injection of 100 MU botulinum toxin subcutaneously blocked sweating completely, but the release of acetylcholine was not affected (botulinum toxin treated skin: 116770 pmol acetylcholine/120 min; untreated skin: 50720 pmol; n ¼ 4). 6 Quinine (1 mM), inhibitor of organic cation transporters, and carnitine (0.1 mM), substrate of the Na þ -dependent carnitine transporter OCTN2, tended to reduce acetylcholine release (by 40%, not significant). 7 Our experiments demonstrate, for the first time, the in vivo release of non-neuronal acetylcholine in human skin. Organic cation transporters are not predominantly involved in the release of non-neuronal acetylcholine from the human skin.

Immuno-detection of OCTN1 (SLC22A4) in HeLa cells and characterization of transport function

“…The involvement of mediatophore in acetylcholine release from T cells has also been proposed [2]. However, microdialysis experiments on human skin suggested that other transporters should also be involved in non-neuronal acetylcholine release [19]. More recently human OCTN1 has been found to be competent for acetylcholine transport [16,17].…”

Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ

“…The role of acetylcholine as an important regulator of sweating is well explored (721)(722)(723) (see also Table 2). In contrast, the exact role of autonomic nerve-derived neuropeptides such as CGRP, VIP, and galanin, for example, is only poorly understood (160, 341,558,574).…”

Acetylcholine release by human colon cancer cells mediates autocrine stimulation of cell proliferation

“…However, emerging evidence indicates that normal and neoplastic nonneuronal cells also produce and release ACh. Strong evidence for nonneuronal ACh production is reported in human keratinocytes and small cell lung cancer cells (7,20,24), indicating in these tissues that ACh may act as an autocrine or paracrine growth factor. Likewise, ACh production by spermatozoa (19), parotid gland epithelium (11), human vascular endothelium (12), and small intestinal mucosa (27) is suggested.…”