Retracted: At diabetes‐like concentration, glucose down‐regulates the placental serotonin transport system in a cell‐cycle‐dependent manner
Authors: R Unal
E A Reece
J T Harney
B C Jeffus
B A Ahmed
Y-K Wu
F Kilic
T C Chambers
C S Lyle
Journal: Journal of Neurochemistry (2007)
Discipline: NEUROSCIENCE & BEHAVIOR
Keywords: Serotonin; 5HT transporter; placental trophoblast cells; glucose; diabetic pregnancy
Affiliations: Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA., Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA

Abstract:  Serotonin [5-hydroxytryptamine (5HT)] is a vasoconstrictor that also acts as a developmental signal early in embryogenesis. The 5HT transporter (SERT) on the membranes of the placental trophoblast cells controls 5HT levels in the maternal bloodstream to maintain stable transplacental blood flow and simultaneously provide 5HT to the embryo. The 5HT uptake rate of placental SERT is important for both the mother and the developing embryo. The impact of glucose on the placental SERT system during diabetic pregnancy is not known. The present in vitro study investigated this important issue in human placental choriocarcinoma (JAR) cells that were cultured for 24-96 h in a medium containing either 5.5 (physiologic concentration) or 25 mmol/L D-glucose (diabetic-like concentration). The 5HT uptake rates of the cultured cells were not altered at exogenous D-glucose concentrations in the range of 5.5-15 mmol/L, but were decreased significantly at a diabetic-like concentration (&gt;or=25 mmol/L). To understand better the role of glucose on the placental 5HT system, we first characterized SERT in JAR cells at different cell-cycle phases and then determined the expression levels of SERT on the plasma membrane and in the intracellular pools of JAR cells at the late-S and G2 phases, where the uptake rates were decreased 73% under diabetic-like glucose concentrations. Finally, the importance of self-association of SERT molecules was examined. In JAR cells co-expressing Flag- and myc-tagged SERT, myc-antibody precipitated 70% of Flag-SERT, indicating that a large percentage of SERT proteins exist as oligomers in situ. Under diabetic conditions, myc-antibody no longer precipitated Flag-SERT, suggesting a disruption in the aggregation of SERT molecules. Therefore, we propose that under uncontrolled diabetic conditions, glucose down-regulates 5HT uptake rates of placental SERT by interfering with its functional expression in a cell-cycle-dependent manner. 

Retracted: Yes

PubPeer comments:
 This paper is one of several from this research group at the Department of Biochemistry and Biotechnology of Annamalai University that report measurements with an unexpectedly narrow range of standard deviations (SDs). Together, these cast serious doubts over the existence of real, replicate measurements in studies by this group. Tables 1 through 3 in this paper together show 24 measurements with SDs. Here, for example, is a screenshot of Tables 2 and 3. ![file] The majority of SDs fall between 7 and 8% of their measurement. Here is a histogram of the SD percentages, showing an unexpected narrow range of values. ![file] This is a very unusual distribution of SDs in biological measurements. Could the authors please explain? ,