Regulation of Pregnancy-Associated Plasma Protein A2 (PAPPA2) in a Human Placental Trophoblast Cell Line (BeWo)

Background: Pregnancy-associated plasma protein A2 (PAPPA2) is an insulin-like growth factor-binding protein(IGFBP) protease expressed at high levels in the placenta and upregulated in pregnancies complicated bypreeclampsia and HELLP (Hemolytic anemia, Elevated Liver enzymes, and Low Platelet count) syndrome. However,it is unclear whether elevated PAPPA2 expression causes abnormal placental development, or whetherupregulation compensates for placental pathology. In the present study, we investigate whether PAPPA2expression is affected by hypoxia, oxidative stress, syncytialization factors or substances known to affect theexpression of PAPPA2’s paralogue, PAPPA.Methods: BeWo cells, a model of placental trophoblasts, were treated with one of the following: hypoxia (2% O2),oxidative stress (20 microM hydrogen peroxide), forskolin (10 microM and 100 microM), TGF-beta (10 and 50 ng/mL),TNF-alpha (100 ng/mL), IL-1beta (100 ng/mL) or PGE2 (1 microM). We used quantitative RT-PCR (qRT-PCR) to quantifythe mRNA levels of PAPPA2, as well as those of PAPPA and ADAM12 since these proteases have similar substrates andare also highly expressed in the placenta. Where we observed significant effects on PAPPA2 mRNA levels, we tested foreffects at the protein level using an in-cell Western assay.Results: Hypoxia, but not oxidative stress, caused a 47-fold increase in PAPPA2 mRNA expression, while TNF-alpharesulted in a 6-fold increase, and both of these effects were confirmed at the protein level. PGE2 resulted in a14-fold upregulation of PAPPA2 mRNA but this was not reflected at the protein level. Forskolin, TGF-beta andIL-1beta had no significant effect on PAPPA2 mRNA expression. We observed no effects of any treatment onPAPPA or ADAM12 expression.Conclusion: Our study demonstrates that factors previously known to be highly expressed in preeclampticplacentae (PGE2 and TNF-alpha), contribute to the upregulation of PAPPA2. Hypoxia, known to occur inpreeclamptic placentae, also increased PAPPA2 expression. These results are consistent with the hypothesis thatPAPPA2 is upregulated as a consequence of placental pathology, rather than elevated PAPPA2 levels being a causeof preeclampsia.