PL74, a Novel Member of the Transforming Growth Factor-β Superfamily, Is Overexpressed in Preeclampsia and Causes Apoptosis in Trophoblast Cells

PL74, a novel member of the TGFbeta superfamily that has highest expression in placenta, is a multifunctional peptide that can induce differentiation, inhibit inflammatory stimulation of TNFalpha, and execute apoptosis after p53 overexpression and cytotoxic injury. To study its expression and function in placenta and preeclampsia, we first determined mRNA expression in nine normal and 10 preeclamptic placentas. PL74 mRNA was overexpressed by 57.3% in preeclampsia. Transfection of PL74 into term cytotrophoblasts resulted in increased apoptosis by terminal uridine deoxynucleotidyl nick end labeling labeling (control, 2.8 +/- 0.5%; PL74, 19.1 +/- 0.2%; P < 0.005). Addition of PL74 protein to HTR8/SVneo extravillous cytotrophoblast cells showed a dose-response (0-100 ng/ml) inhibition of [3H]thymidine uptake and increase in apoptosis shown by terminal uridine deoxynucleotidyl nick end labeling and histone-associated DNA fragment ELISA (control, 0.11 +/- 0.01 absorbance units; PL74, 0.21 +/- 0.01; P < 0.01). PL74 did not alter cytotrophoblast invasion using a Matrigel in vitro invasion assay. Cytokine regulation of PL74 mRNA expression in term cytotrophoblasts showed that epidermal growth factor and IFNgamma increased PL74 expression, but TGFbeta and TNFalpha had no effect. Transfection of antisense PL74 into term cytotrophoblast cells resulted in an inhibition of spontaneous differentiation at 2 and 24 h of culture (control vector, 30.8 +/- 3.1% and 26.4 +/- 1.2%; antisense PL74, 17.6 +/- 1.8%and 12.6 +/- 1.4% syncytial units, at 2 and 24 h respectively; P < 0.01). We conclude that PL74 is overexpressed in preeclampsia and may thus promote apoptosis of cytotrophoblasts at the expense of differentiation. PL74 secretion is induced by IFNgamma and may play a role in abnormal placental responses in preeclampsia.