Abstract 208: TLR3-Induced Placental miR-210 Down-Regulates the STAT6/IL-4 Pathway

Abstract

Several clinical studies have reported differential expression of microRNAs (miRs) in placentas from women with preeclampsia (PE) compared to normotensive women. Whether or not miRs play a role in the etiology of PE is unknown. Given the important role of maternal immune system activation and inflammation in PE, we developed a mouse model of PE via activation of Toll-like receptor 3 (TLR3) which exhibit hypertension, endothelial dysfunction, and proteinuria only when pregnant. miR-210 is increased in placentas of women with PE, but whether TLR3 activation in pregnant mice and human cytotrophoblasts (CTBs) increases miR-210 and the effects on miR-210 targets related to inflammation are unknown. miR-210 expression was up-regulated in placentas of poly I:C-treated control mice (P-PIC: 4.9 fold, p<0.05 vs. controls) similar to that in women with PE. Both HIF-1α and NF-κB p50 are known to bind to the promoter of miR-210 and induce its expression. HIF-1α (1.5 fold, p<0.05 vs. controls) and NF-κB p50 (2.7 fold, p<0.05 vs. controls) expression were increased significantly in placentas of P-PIC mice. Target identification algorithms and gene ontology predicted STAT6 as a target of miR-210 related to inflammation and STAT6 was decreased significantly in placentas of P-PIC mice. Increased production of the anti-inflammatory cytokine IL-4, which is regulated by STAT6, plays a critical role during normotensive pregnancy but failed to increase in P-PIC mice. Pregnant TLR3 KO mice treated with poly I:C, which did not develop hypertension, did not have increased placental expression of HIF-1α, NF-κB p50, and miR-210 or decreased expression of STAT6 and IL-4. To determine the placental etiology, human CTBs were treated with poly I:C and HIF-1α, NF-κB p50, and miR-210 expression were increased significantly while STAT6 and IL-4 expression decreased significantly. Inhibition of miR-210 in CTBs using anti-miR-210 significantly increased STAT6 and IL-4 expression and overexpression of miR-210 decreased STAT6 and IL-4 expression in CTBs. Taken together our data suggest that TLR3 activation induces placental miR-210 via HIF-1α and NF-κB p50 which in turn decreases STAT6 and IL-4 expression and may contribute to the development of PE.