Leptin is an antiapoptotic effector in placental cells involving p53 down-regulation

AYELÉN TORO; JULIETA L MAYMO; FEDERICO IBARBALZ; ANTONIA PEREZ PEREZ; BERNANDO MASKIN; ALICIA GRACIELA FALETTI; VICTOR SANCHEZ-MARGALETR; CECILIA L VARONE

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014 vol. 9 p. 99187 - 99199

1932-6203

Leptin (Lep), a peripheral signal produced by the adipocyte to regulate energy metabolism, can also be produced by placenta, where it may work as an autocrine hormone. We have previously demonstrated that leptin promotes proliferation and survival of trophoblastic cells. In the present work, we aimed to study the molecular mechanisms that mediate the survival effect of leptin in placenta. We used the human placenta choriocarcinoma BeWo and first trimester Swan-71 cell lines, as well as trophoblastic cells from human placenta. We have assayed the late phase of apoptosis, triggered by serum deprivation, by studying the activation of caspase-3 and DNA fragmentation assay. Recombinant human leptin added to BeWo cell line and human placental explants, showed a decrease on Caspase-3 activation. These effects were dose dependent. Maximal effect was achieved at 250 ng leptin/ml. Moreover, by inhibiting endogenous leptin expression with 2 μM of an antisense oligonucleotide (AS), Caspase-3 activation was diminished. We analyzed the presence of low DNA fragments, product from apoptotic DNA cleavage. Placental explants cultivated in the absence of fetal bovine serum in the culture media increased the apoptotic cleavage of DNA and this effect was prevented by the addition of 100 ng leptin/ml. Taken together these results reinforce the survival effect exerted by leptin on placental cells. To improve the understanding of leptin mechanism in regulating apoptosis process we determined the expression of different intermediates in the apoptosis cascade. We found that under serum deprivation conditions, leptin increased the antiapoptotic Bcl-2 expression, meanwhile downregulated the expression of the proapoptotic Bax protein therefore augmenting Bcl-2/Bax ratio. We also determined that Bid protein expression is decreased by leptin both in Swan-71 and human placental explants. Maximal effect was achieved with 100 ng leptin/ml. Moreover, we have demonstrated that p53, one of the key cell cycle-signaling proteins, is downregulated in the presence of leptin under serum deprivation. On the other hand we determined that leptin reduced the phosphorylation of Ser-46 p53 that plays a pivotal role for apoptotic signaling by p53. In conclusion, we provide evidence that demonstrates that leptin is a trophic factor for trophoblastic cells by virtue of its inhibiting apoptosis and our data suggest that the leptin antiapoptotic effect in placenta is mediated by the p53 pathway.