Inhibition of amino acid transport system a by interleukin-1beta in trophoblasts.
OBJECTIVE
The current study sought to investigate the influence of interleukin-1beta (IL-1beta) on the function of the amino acid transport system A in trophoblasts.


METHODS
BeWo choriocarcinoma cells were exposed to recombinant human IL-1beta in serum-free medium. Cells incubated with serum-free medium in the absence of IL-1beta were used as control. System A activity was determined in control and treated cells by measuring the uptake of alpha-(methylamino)isobutyric acid. The results obtained were confirmed by measuring system A activity in placental brush border membrane vesicles isolated from pregnant rats injected with IL-1beta.


RESULTS
Treatment of BeWo cells with IL-1beta resulted in a time- and dose- dependent inhibition of system A. Treatment with IL-1beta also inhibited the uptake of arginine, and glutamate but had no significant effect on the uptake of leucine, tryptophan, and ascorbate. The inhibition of system A activity by IL-1beta was abolished in the presence of IL-1beta receptor antagonist. The inhibitory effect was associated with a decrease in the maximal velocity of the transport system with no effect on the substrate affinity. Steady-state levels of both SNAT1 and SNAT2 mRNA were reduced by IL-1beta treatment as evidenced by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. In rat placental brush border membrane vesicles isolated from IL-1beta-treated pregnant rats, system A activity was found to be decreased by approximately 40% compared to activity in control membrane vesicles.


CONCLUSIONS
IL-1beta decreases SNAT1 and SNAT2 mRNA levels in trophoblasts, which is associated with a decrease in system A-mediated transport activity at the functional level. These findings may have important consequences under both physiologic conditions and pathologic conditions during pregnancy that are associated with elevated levels of IL-1beta.
Thongsong
Boonrit
B
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912-2100, USA.
Subramanian
Radhika K
RK
Ganapathy
Vadivel
V
Prasad
Puttur D
PD
D026924:Amino Acid Transport System A / Q000502:physiology*; D026962:Amino Acid Transport System ASC / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007375:Interleukin-1 / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D014327:Trophoblasts / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000473:pathology; D014594:Uterine Neoplasms / Q000473:pathology
D026924:Amino Acid Transport System A; D026962:Amino Acid Transport System ASC; D007375:Interleukin-1; D012333:RNA, Messenger