Cannabinoid receptors and their role in the regulation of the serotonin transporter in human placenta.
OBJECTIVE
We sought to investigate the expression of cannabinoid receptors in human placenta and BeWo choriocarcinoma cells and study their role in the regulation of the serotonin transporter.


METHODS
Expression of the 2 types of cannabinoid receptors (CB1 and CB2) in human placenta and BeWo cells was investigated by reverse transcriptase-polymerase chain reaction and Northern blot analysis. The involvement of the receptors in the regulation of the serotonin transporter expression was studied by using a cannabinoid receptor agonist (WIN 55212-2). BeWo cells were treated with the agonist in the presence or absence of forskolin, and the serotonin transporter activity was measured by assessing paroxetine-sensitive serotonin transport. Serotonin transporter density in cell membranes was monitored by measuring paroxetine-sensitive binding of RTI-55, a specific high-affinity ligand for the transporter. Agonist-induced changes in intracellular levels of cyclic adenosine monophosphate were also monitored.


RESULTS
Reverse transcriptase-polymerase chain reaction and Northern blot analysis demonstrated unequivocally that human placenta and BeWo cells express both types of cannabinoid receptors. Treatment of BeWo cells with the receptor agonist blocked the activity of the constitutive, as well as the forskolin-induced, serotonin transporter without affecting the serotonin transporter density. This effect is not mediated by alterations in intracellular cyclic adenosine monophosphate levels.


CONCLUSIONS
The results show that cannabinoid receptors are expressed in human placenta and BeWo cells and play a role in the regulation of the serotonin transporter activity. Human placenta is therefore a direct target for cannabinoids, and marijuana use during pregnancy is likely to affect the placental clearance of serotonin through the serotonin transporter.
Kenney
S P
SP
Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, USA.
Kekuda
R
R
Prasad
P D
PD
Leibach
F H
FH
Devoe
L D
LD
Ganapathy
V
V
D048588:Benzoxazines; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002822:Choriocarcinoma / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009419:Nerve Tissue Proteins; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050486:Serotonin Plasma Membrane Transport Proteins; D014407:Tumor Cells, Cultured
D048588:Benzoxazines; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009025:Morpholines; D009281:Naphthalenes; D009419:Nerve Tissue Proteins; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D000242:Cyclic AMP