Neutralization of Natural Killer Cell Associated Cytokines Improves Vascular Function and Reduces Blood Pressure in Placental Ischemic Rats

Abstract

Women with preeclampsia (PE) have increased cytolytic NK cells (cNKs), interferon gamma (IFNγ) and tumor necrosis factor alpha (TNFα) in the circulation and placenta. In previous studies, adoptive transfer of placental cNKs from the Reduced Uterine Perfusion Pressure (RUPP) model of PE into normal pregnant Sprague Dawley (SD) rats caused increased IFNγ and TNFα, and induced vascular dysfunction, hypertension (HTN), and restricted fetal growth (IUGR) similar to what is observed in PE patients. The purpose of this study was to examine the roles of IFNγ and TNFα in RUPP and PE pathophysiology. We hypothesized that neutralization of IFNγ or TNFα would attenuate PE-associated pathophysiology in RUPP rats. Pregnant SD rats underwent RUPP or Sham procedure on Gestation Day (GD) 14. On GD 15 and 18, a subset of Sham and RUPP rats received vehicle or 10μg/kg anti-IFNγ monoclonal antibody (IFNy-ab; n=9/group) i.p. On GD18, Uterine Artery Resistance Index (UARI) was measured via Doppler Ultrasound and on GD19, mean arterial pressure (MAP), fetal and placental weight were measured, and blood and tissues were processed for analysis. MAP was 105±2 mmHg and 108±2 mmHg in Sham and Sham+IFNγ-ab respectively, was elevated to 125±1 mmHg in RUPP (p<0.05 vs Sham), and reduced to 112±2 mmHg in RUPP+ IFNγ-ab (p<0.05 vs RUPP). Fetal and placental weights were significantly reduced in RUPP and remained so in RUPP+IFNγ-ab (p<0.05 vs Sham). UARI was 0.6±0.02 in Sham and Sham+ IFNγ-ab, was elevated to 0.73±0.02 in RUPP (p<0.05 vs Sham), and was normalized to 0.6±0.02 in RUPP+ IFNγ-ab (p<0.05 vs RUPP). Both placental ROS and plasma soluble Fms-like Tyrosine kinase 1 (sFlt-1) were elevated in RUPP (p<0.05 vs Sham) and were normalized in RUPP+IFNγ-ab (p<0.05 vs RUPP). In separate experiments, pregnant SD rats underwent RUPP or Sham procedure on GD 14. On GD 15 and 18, a subset of Sham and RUPP rats received vehicle or 0.4 mg/kg of Etanercept (ETA), a soluble TNFα receptor (n=10/group) i.p. Analyses were performed as described above. MAP was elevated in RUPP (127±2 mmHg) compared to Sham (105±3 mmHg) and Sham+ETA (109±2 mmHg, p<0.05) and was normalized to 109±3 mmHg in RUPP+ETA (p<0.05 vs RUPP). Both fetal and placental weights were significantly reduced in RUPP rats (p<0.05 vs Sham) and were normalized in RUPP+ETA (p<0.05 vs RUPP). UARI was 0.6±0.02 in Sham and 0.6±0.01 in Sham+ETA. UARI was elevated in RUPP (0.72±0.02, p<0.05 vs Sham) and was normalized to 0.61±0.02 in RUPP+ETA (p<0.05 vs RUPP). Plasma total nitrate was significantly reduced in RUPP (p<0.05 vs Sham) and was normalized in RUPP+ETA (p<0.05 vs RUPP). Placental ROS was elevated in RUPP (p<0.05 vs Sham) and remained so in RUPP+ETA (p>0.05 vs RUPP). Plasma sFlt-1 was 92±34 pg/mL in Sham and 53±9 pg/mL in Sham+ETA, was elevated to 1039±211 pg/mL in RUPP (p<0.05 vs Sham), and was normalized to 145±33 pg/mL in RUPP+ETA (p<0.05 vs RUPP). The results of this study suggest that increased secretion of IFNγ and TNFα by cNKs mediate vascular dysfunction to cause maternal HTN and IUGR in RUPP and PE pathophysiology. IFNγ and TNFα are potential therapeutic targets for treatment in PE.