Serotonin Uptake Is Largely Mediated by Platelets versus Lymphocytes in Peripheral Blood Cells

Beikmann, Brendan Stephen; Tomlinson, Ian; Rosenthal, Sandra J.; Andrews, Anne M.

doi:10.1021/cn300146w

Cited by 50 publications

(48 citation statements)

References 62 publications

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“…APP+ is a DAT, NET, and SERT substrate as demonstrated in cell lines transfected with rat or human monoamine transporters and thus provides a useful reporter substrate for these transporters. 32,33 As recently described, APP+ enabled examination of endogenously expressed SERT in platelets and lymphocytes, 38 as well as in an immortalized serotonergic neural cell line. 37 In the present study, we examined APP+ in acute brain tissue and found that it labeled catecholamine neuronal somata in the midbrain (SN/VTA and LC) as well as dopaminergic axonal processes and presynaptic terminals in the dorsal striatum.…”

Section: ■ Discussionmentioning

confidence: 98%

“…Previous studies investigating APP+ uptake by cells have been limited to cultured cells transfected with plasma membrane monoamine transporters, 32,33 cultured cells endogenously expressing SERT, 37 or platelets and lymphocytes. 38 We therefore examined labeling characteristics of APP+ in acute mouse brain slices containing the midbrain region. The labeling selectivity was determined by colocalization of the APP+ and GFP signals in brain tissue obtained from mice expressing GFP under the control of tyrosine hydroxylase (TH) promoter (TH-GFP mice), 39 via two-photon microscopy ( Figure 4).…”

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confidence: 99%

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APP+, a Fluorescent Analogue of the Neurotoxin MPP+, Is a Marker of Catecholamine Neurons in Brain Tissue, but Not a Fluorescent False Neurotransmitter

Karpowicz

Dunn

Sulzer

et al. 2013

ACS Chem. Neurosci.

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ABSTRACT:We have previously introduced fluorescent false neurotransmitters (FFNs) as optical reporters that enable visualization of individual dopaminergic presynaptic terminals and their activity in the brain. In this context, we examined the fluorescent pyridinium dye 4-(4-dimethylamino)phenyl-1-methylpyridinium (APP+), a fluorescent analogue of the dopaminergic neurotoxin MPP+, in acute mouse brain tissue. APP+ is a substrate for the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT), and as such represented a candidate for the development of new FFN probes. Here we report that APP+ labels cell bodies of catecholaminergic neurons in the midbrain in a DAT-and NET-dependent manner, as well as fine dopaminergic axonal processes in the dorsal striatum. APP+ destaining from presynaptic terminals in the dorsal striatum was also examined under the conditions inducing depolarization and exocytotic neurotransmitter release. Application of KCl led to a small but significant degree of destaining (approximately 15% compared to control), which stands in contrast to a nearly complete destaining of the new generation FFN agent, FFN102. Electrical stimulation of brain slices at 10 Hz afforded no significant change in the APP+ signal. These results indicate that the majority of the APP+ signal in axonal processes originates from labeled organelles including mitochondria, whereas only a minor component of the APP+ signal represents the releasable synaptic vesicular pool. These results also show that APP+ may serve as a useful probe for identifying catecholaminergic innervations in the brain, although it is a poor candidate for the development of FFNs.

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Section: ■ Discussionmentioning

confidence: 98%

mentioning

confidence: 99%

APP+, a Fluorescent Analogue of the Neurotoxin MPP+, Is a Marker of Catecholamine Neurons in Brain Tissue, but Not a Fluorescent False Neurotransmitter

Karpowicz

Dunn

Sulzer

et al. 2013

ACS Chem. Neurosci.

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“…In the periphery, serotonin (5-HT) 3 is produced by enterochromaffin cells in the gastrointestinal tract, released into the plasma, and quickly taken up by platelets via the plasma membrane serotonin transporter (SERT). Following uptake, 5-HT is stored in dense granules by the actions of the vesicular monoamine transporter 2 (1)(2)(3)(4).…”

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confidence: 99%

Loss of Serotonin Transporter Function Alters ADP-mediated Glycoprotein αIIbβ3 Activation through Dysregulation of the 5-HT2A Receptor

Oliver

Duvernay

Hamm

et al. 2016

Journal of Biological Chemistry

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Reduced platelet aggregation and a mild bleeding phenotype have been observed in patients chronically taking selective serotonin reuptake inhibitors (SSRIs). However, it remains unclear how SSRIs, which inhibit the plasma membrane serotonin transporter (SERT), modulate hemostasis. Here, we examine how sustained inhibition of SERT activity alters serotonergic signaling and influences platelet activation and hemostasis. In the periphery, serotonin (5-HT) 3 is produced by enterochromaffin cells in the gastrointestinal tract, released into the plasma, and quickly taken up by platelets via the plasma membrane serotonin transporter (SERT). Following uptake, 5-HT is stored in dense granules by the actions of the vesicular monoamine transporter 2 (1-4). Chronic inhibition of SERT through selective serotonin reuptake inhibitors (SSRIs) (e.g. citalopram and paroxetine) leads to dramatically reduced platelet 5-HT granule content (5, 6), altering peripheral 5-HT homeostasis and potentially modifying multiple physiological processes including hemostasis (7-10). Clinically, increased bleeding risk has been observed in patients taking SSRIs, and platelet aggregation is disrupted (5, 11). Here, we have characterized a similar effect in two distinct mouse models of lost SERT function, suggesting that sustained loss of SERT function influences hemostasis. Pharmaceutical blockade (citalopram dosing) or genetic ablation (SERTPlatelet dense granules contain 5-HT along with other platelet agonists including adenosine diphosphate (ADP), thromboxane (TXA2), and histamine. Appropriate platelet activation depends on the timely release of these factors (4, 5, 12). Platelet aggregation is crucial early in thrombus formation (4, 5, 13). Aggregation, which is the bridging of platelet-platelet contacts, requires a conformational alteration in the glycoprotein ␣IIb␤3, leading to its activation and fibrinogen binding. 5-HT has been shown to enhance aggregation in a 5-HT 2A receptor (5-HT 2A R)-dependent manner (4, 14 -17). The 5-HT 2A R is the only serotonergic receptor found on platelets and potentiates platelet responses to weak agonists like ADP (18). Subthreshold concentrations of two different platelet agonists can exert a synergistic effect on platelet activation. One example includes dual ADP and 5-HT activation leading to increases in cytosolic [Ca 2ϩ ] (13). However, the role of 5-HT during in vivo hemostasis remains unclear, particularly in the context of chronic SERT inhibition.To elucidate the underlying mechanisms of SSRI effects on platelet aggregation, a better understanding of acute versus chronic inhibition of SERT function during platelet activation is required. Acute and chronic blockage of SERT function results in distinct scenarios regarding the effects on 5-HT homeostasis. Acute inhibition of SERT blocks the amount of

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“…4A). To verify this result independently, CYAM-treated slices were imaged before and after incubation with IDT307 (also called APP + ), a fluorescent substrate of plasma membrane monoamine transporters (7)(8)(9). Because the DA transporter (DAT) is the only somatic monoamine transporter in the SNc, somatic IDT307 labeling identifies DA neurons.…”

Section: Resultsmentioning

confidence: 99%

“…In experiments for which it was important to localize CYAM puncta to monoaminergic neurons, the fluorescent monoamine transporter substrate, IDT307 (also known as APP + ) was used (7)(8)(9). IDT307 has a wide 2P excitation spectrum ranging from ∼700-950 nm, with a peak at 870 nm (8).…”

Section: Methodsmentioning

confidence: 99%

Action potentials and amphetamine release antipsychotic drug from dopamine neuron synaptic VMAT vesicles

Tucker

Block

Levitan

2015

Proc. Natl. Acad. Sci. U.S.A.

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Based on lysotracker red imaging in cultured hippocampal neurons, antipsychotic drugs (APDs) were proposed to accumulate in synaptic vesicles by acidic trapping and to be released in response to action potentials. Because many APDs are dopamine (DA) D2 receptor (D2R) antagonists, such a mechanism would be particularly interesting if it operated in midbrain DA neurons. Here, the APD cyamemazine (CYAM) is visualized directly by two-photon microscopy in substantia nigra and striatum brain slices. CYAM accumulated slowly into puncta based on vacuolar H + -ATPase activity and dispersed rapidly upon dissipating organelle pH gradients. Thus, CYAM is subject to acidic trapping and released upon deprotonation. In the striatum, Ca 2+ -dependent reduction of the CYAM punctate signal was induced by depolarization or action potentials. Striatal CYAM overlapped with the dopamine transporter (DAT). Furthermore, parachloroamphetamine (pCA), acting via vesicular monoamine transporter (VMAT), and a charged VMAT, substrate 1-methyl-4-phenylpyridinium (MPP + ), reduced striatal CYAM. In vivo CYAM administration and in vitro experiments confirmed that clinically relevant CYAM concentrations result in vesicular accumulation and pCA-dependent release. These results show that some CYAM is in DA neuron VMAT vesicles and suggests a new drug interaction in which amphetamine induces CYAM deprotonation and release as a consequence of the H + countertransport by VMAT that accompanies vesicular uptake, but not by inducing exchange or acting as a weak base. Therefore, in the striatum, APDs are released with DA in response to action potentials and an amphetamine. This synaptic corelease is expected to enhance APD antagonism of D2Rs where and when dopaminergic transmission occurs.M ost antipsychotic drugs (APDs) are competitive dopamine (DA) D2 receptor (D2R) antagonists (1, 2). The standard view is that APDs, by being weak bases that are in equilibrium with an uncharged form, cross the blood-brain barrier to access extracellular receptor binding sites from the circulation. However, because APDs are weak bases, they have been proposed to accumulate also in acidic intracellular organelles by acidic trapping (i.e., the less abundant uncharged basic hydrophobic form enters organelles passively and then is protonated to become membrane-impermeant). This hypothesis was first explored by examining a D2 antagonist with a covalently added fluorophore and APD displacement of acridine orange (3). More recently, APDs were found to be released from brain tissue by depolarization, which is expected for any positively charged drug. However, follow-up experiments in hippocampal neuron cultures showed that APDs displace the acidophilic dye lysotracker red, implying there is overlap in intracellular distribution between APDs and lysotracker red. Furthermore, lysotracker red was found to accumulate in hippocampal neuron synaptic vesicles by acidic trapping without displacing native neurotransmitter and to be released in response to electrical stimulation. Thus, b...

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Serotonin Uptake Is Largely Mediated by Platelets versus Lymphocytes in Peripheral Blood Cells

Cited by 50 publications

References 62 publications

APP+, a Fluorescent Analogue of the Neurotoxin MPP+, Is a Marker of Catecholamine Neurons in Brain Tissue, but Not a Fluorescent False Neurotransmitter

APP+, a Fluorescent Analogue of the Neurotoxin MPP+, Is a Marker of Catecholamine Neurons in Brain Tissue, but Not a Fluorescent False Neurotransmitter

Loss of Serotonin Transporter Function Alters ADP-mediated Glycoprotein αIIbβ3 Activation through Dysregulation of the 5-HT2A Receptor

Action potentials and amphetamine release antipsychotic drug from dopamine neuron synaptic VMAT vesicles

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