Mid-late gestation leptin infusion induces placental mitochondrial and endoplasmic reticulum unfolded protein responses in a mouse model of preeclampsia.

INTRODUCTION: Preeclamptic patients, both lean and obese, present with elevated leptin levels which are associated with the development of maternal endothelial dysfunction and adverse fetal outcomes, such as growth restriction, leading to low birth weight. Recent studies in pregnant mice demonstrate that mid-late gestation leptin infusion induces clinical characteristics of preeclampsia, including elevated maternal blood pressure, maternal endothelial dysfunction and fetal growth restriction. However, whether leptin triggers placental stress responses that contribute to adverse fetal outcomes as in preeclampsia is unknown. METHODS: In the current study we measured the expression of proteins involved in the endoplasmic reticulum (UPR(er)) and mitochondrial (UPR(mt)) unfolded protein responses in placentas of wild-type sham normal pregnant and leptin-infused preeclamptic mice. RESULTS: The data show that mid-late gestation leptin infusion induced activation of indices of placental UPR(er) and UPR(mt), while reducing placental repair mechanisms to UPR(mt) in preeclamptic mice. Mid-late gestation infusion with leptin upregulated markers of placental oxidative stress, reduced the placental expression levels of mitochondrial electron transport chain complexes I and II and increased the expression of placental endothelin-1 (ET-1) in preeclamptic mice. The leptin-induced activation of several placental UPR(mt) markers as well as ET-1 levels correlated with fetal growth restriction and impaired maternal endothelial function in preeclamptic mice. DISCUSSION: Collectively, these data indicate that elevated levels of leptin in mid-late pregnancy in mice promote placental stress responses, akin to those in pregnant women with preeclampsia.