Release of non‐neuronal acetylcholine from the isolated human placenta is mediated by organic cation transporters

Abstract

1 The release of acetylcholine was investigated in the human placenta villus, a useful model for the characterization of the non-neuronal cholinergic system. 2 Quinine, an inhibitor of organic cation transporters (OCT), reduced acetylcholine release in a reversible and concentration-dependent manner with an IC 50 value of 5 mM. The maximal e ect, inhibition by 99%, occurred at a concentration of 300 mM. 3 Procaine (100 mM), a sodium channel blocker, and vesamicol (10 mM), an inhibitor of the vesicular acetylcholine transporter, were ine ective. 4 Corticosterone, an inhibitor of OCT subtype 1, 2 and 3 reduced acetylcholine in a concentrationdependent manner with an IC 50 value of 2 mM. 5 Substrates of OCT subtype 1, 2 and 3 (amiloride, cimetidine, guanidine, noradrenaline, verapamil) inhibited acetylcholine release, whereas carnitine, a substrate of subtype OCTN2, exerted no e ect. 6 Long term exposure (48 and 72 h) of villus strips to anti-sense oligonucleotides (5 mM) directed against transcription of OCT1 and OCT3 reduced the release of acetylcholine, whereas OCT2 antisense oliogonucleotides were ine ective. 7 It is concluded that the release of non-neuronal acetylcholine from the human placenta is mediated via organic cation transporters of the OCT1 and OCT3 subtype. IntroductionAcetycholine has been demonstrated in the vast majority of human non-neuronal cells, for example epithelial, endothelial, mesothelial and immune cells as well as smooth muscle ®bres (Grando, 1997;Wessler et al., 1998;Kawashima & Fujii, 2000). In addition, nicotinic and muscarinic receptors are widely expressed on these cells (Brunner & Kukovetz, 1986;Grando et al., 1995;Maus et al., 1998;Costa et al., 1988;Kawashima & Fujii, 2000). Non-neuronal acetylcholine can act as a local cell molecule via paracrine and autocrine mechanisms to control basic cell functions such as proliferation, di erentiation and cell ± cell contact (Grando, 1997;Wessler et al., 1998;Kawashima & Fujii, 2000). The release mechanisms by which non-neuronal cells, for example epithelial cells of the placenta, liberate acetylcholine into the extracellular space, are unknown. The human placenta is not innervated by extrinsic or intrinsic cholinergic neurons (Sastry & Sadavongvivad, 1979;Sastry, 1997). Thus, released acetylcholine is not contaminated by neuronal acetylcholine and can be used as a model for studying the release mechanisms of non-neuronal acetylcholine. Acetylcholine, an organic cation, may be a substrate for organic cation transporters (OCT). OCTs are most widely expressed in di erent cell types including the human placenta (Koepsell, 1998;Dresser et al., 1999). Three organic cation transporters have been cloned which represent high capacity non-neuronal monoamine transporters, OCT subtype 1 (GruÈ ndemann et al., 1994;Nagel et al., 1997), subtype 2 (Okuda et al., 1996 GruÈ ndemann et al., 1997; and subtype 3, the latter also being known as extraneuronal monoamine transporter uptake 2 (GruÈ ndemann et al., 1998;Kekuda et al., 1998;Wu et al., 1998). To ...

Basic and Clinical Aspects of Non-neuronal Acetylcholine: Overview of Non-neuronal Cholinergic Systems and Their Biological Significance

“…Instead, ACh appears to be synthesized and released when necessary, without storage. On the other hand, two polyspecific organic cation transporter subtypes, OCT1 and OCT3, are reportedly involved in the release of ACh in the human placenta (15) and in murine bronchial epithelium (16).…”

Low-affinity uptake of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (4-Di-1-ASP) in BeWo cells

“…Not only did TEA and choline fail to inhibit the uptake of 4-Di-1-ASP, but ergothioneine-a specific substrate for OCTN1 [22]-also showed no inhibitory effects ( Figure 5C). Amiloride [6], MPP + [15], and agmatine [23], three other OCT inhibitors, likewise showed no significant inhibition of 4-Di-1-ASP uptake ( Figure 6). …”

“…In 2001, Wessler et al studied the release of acetylcholine from placental villus and concluded that the process is mediated by OCT1 and OCT3 [6]. The expression of OCT2 in human placenta is reported by multiple authors [7][8][9][10] and refuted by others [11][12][13].…”

Cord Blood Butyrylcholinesterase Activities in Normal Pregnant and Preeclamptic Women

“…OCT activity is modulated by a variety of drugs and endogenous compounds, such as monoamines and steroids. These agents can target the release of non-neuronal acetylcholine under physiological conditions and circulating catecholamines may also affect the release of non-neuronal acetylcholine (23).…”