112: Neutralization of Fas Ligand reduces placental inflammation and endothelial damage in an animal model of HELLP syndrome

Abstract

The Fas ligand (FasL) system has an impact on inflammation and hypertension during pregnancy and is dysregulated in women with severe preeclampsia and HELLP syndrome. We have recently reported that endothelin antagonism impacted the Fas/FasL system, therefore in the current study we tested the hypothesis that neutralization of FasL in an animal model of HELLP syndrome decreases inflammation, improves endothelial damage and in turn improves hypertension. Mini-osmotic pumps infusing anti-angiogenic factors sFlt-1 and sEng were placed into normal pregnant (NP) rats on gestational day (GD) 12 to induce HELLP syndrome (n=15). On GD13, 7 of these HELLP rats were infused with 500ng/kg of MFL4 via the jugular vein to inhibit FasL. Untreated NP rats (n=5) served as controls. On GD19 mean arterial pressure (MAP) was measured and all rats were euthanized. Maternal tissues were collected, placentas were cultured under normal culture conditions and media collected (conditioned media - CM) and placed over human umbilical vein endothelial cells (HUVECs) for 24hrs. Administration of FasL to HP rats significant decreased MAP (p=0.03) compared to untreated HP rats. However there was not a significant change in LDH (p=0.164), AST (p=0.52) or platelets (p=0.746) due to attenuation of FasL in HELLP rats compared to untreated HELLP rats. Circulating FasL was significantly increased in HELLP rats compared to NP rats (p=0.0006) but was attenuated with infusion of MFL4 (p=0.0005). Placental protein expression of TNF-alpha, measured via ELISA, was significantly reduced due to MFL4 infusion in HELLP rats (p=0.0009). Finally, HUVECs exposed to CM from HP+MFL4 rats secreted significantly less endothelin-1 compared to HUVECs exposed to CM from HP placentas (p=0.004) and CM from NP placentas (p=0.02). These data suggest that neutralization of FasL decreases MAP and improves placental inflammation and endothelial damage in an animal model of HELLP syndrome. However FasL neutralization does not improve the symptomology of HELLP syndrome, suggesting that FasL may only contribute to the inflammatory pathway.