27-OR

Objectives Upregulation of placental soluble fms-like tyrosine kinase 1 (sFlt1) contributes to the pathogenesis of preeclampsia. Our aim was to evaluate novel upstream pathways that regulate placental sFlt1 production. Methods We screened a library of natural compounds ( N = 502) in primary cytotrophoblasts and placental villous cultures and characterized molecules that had biological activity in the nanomolar range. sFlt1 production was assayed by ELISA. Immunoblot analysis, Co-immunoprecipitation, RT-PCR were employed in Characterizing the sFlt1, HIF AND hsp27 proteins and RNA. Pregnancy-induced hypertension rats were used as animal models. Results Here we report three compounds in the cardiac glycoside family, ouabain, gitoxigenin and digitoxin that inhibited placental sFlt1 production at nanomolar concentrations in vitro. We further characterized ouabain and demonstrate that it inhibits sFlt1 mRNA and protein expression in human placental cytotrophoblasts and explant cultures in a dose and time dependent manner. Ouabain down-regulated sFlt1 production by inhibiting hypoxia inducible factor 1 (HIF-1 α ) protein expression in the placenta. Furthermore, we found that phosphorylation of heat shock protein 27 (HSP27) was necessary for ouabain to inhibit HIF-1 α translation. In a rat model of pregnancy-induced hypertension, ouabain reduced mean arterial pressure and enhanced placental HSP27 phosphorylation without any adverse effects on pups. Conclusions Collectively we show that ouabain inhibits placental sFlt1 production through a HIF-1 α / HSP27 dependent pathway. Further studies are needed to explore the usefulness of targeting HIF-1 α /HSP27 pathway in preeclampsia. Disclosures S. Rana: None. A. Rajakumar: None. C. Geahchan: None. S. Salahuddin: None. A. Cerdeira: None. S.D. Burke: None. E. George: None. J. Granger: None. S. Karumanchi: co-inventor on multiple patents for preeclampsia markers and reports service as a consultant to Siemens Diagnostics, and has financial interest in Aggamin LLC.