Suppression of TH17 Cells Blunts Preeclampsia‐Associated Cytolytic Natural Killer Cells during Pregnancy

Abstract

The Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia mimics many of the characteristics of preeclampsia (PE) including hypertension, intrauterine growth restriction (IUGR), and increases in T‐helper 17 cells, (TH17s), IL‐17, and placental cytolytic natural killer cells (cNKs). We have previously demonstrated that placental ischemia (PI)‐stimulated TH17s mediate cNK activation and cause hypertension and IUGR in pregnant rats similar to that seen in RUPP and human PE. In this study we tested the hypothesis that suppression of TH17s via blockade of IL‐17 signaling would inhibit activation of cNKs and decrease cytolytic proteins (perforin, granzymes) to improve blood pressure and fetal growth during placental ischemia. On gestation day (GD) 14 mini osmotic pumps infusing 100 pg/d of IL‐17 RC, a soluble receptor for IL‐17, were implanted into pregnant rats undergoing RUPP (RUPP+IL17 RC). On GD 19, circulating and placental TH17s and placental total NK cells and cNKs were quantified via flow cytometry in normal pregnant (NP), RUPP, and RUPP+IL17 RC rats. MAP, fetal and placental weights, placental reactive oxygen species (ROS), perforin, and granzymes were also measured. As we have previously shown, both circulating and placental TH17 populations were significantly increased in RUPP compared to NP rats. Treatment with IL‐17 RC suppressed TH17 populations in RUPP+IL17 RC rats. Circulating TH17s (% gated): NP (n=9)– 2.5±1.2%, RUPP (n=9)– 7.4±1.4%, RUPP+IL17 RC (n=10)– 0.9±0.4% (p<0.05 vs RUPP). Placental TH17s: NP–8.5±3.8%, RUPP– 23.1±3.9%, RUPP+IL17 RC– 8.3±3.1% (p<0.05 vs RUPP). Placental total NKs and cNKs, were significantly increased after RUPP and normalized with IL‐17 blockade. Total NKs (% gated): NP– 23.6±6.7%, RUPP– 46.8±5.1%, RUPP+IL17 RC‐23.5±4.6 % (p<0.05 vs RUPP). cNKs: NP– 7.2±2.8%, RUPP– 16.6±3.3%, RUPP+IL17 RC–6.9±1.5% (p<0.05 vs RUPP). MAP increased from 93 mmHg in NP to 119 mmHg in RUPP, and significantly decreased to 105 mmHg in RUPP+IL17 RC (p<0.05 vs RUPP). Fetal weight decreased from 2.4±0.04 g in NP to 2.1±0.04 g in RUPP and increased to 2.3±0.05 g in RUPP+IL17 RC (p<0.05 vs RUPP). Placental weight decreased from 0.55±0.01 g in NP to 0.43±0.01 g in RUPP and increased to 0.52±0.03 g in RUPP+IL17 RC (p<0.05 vs RUPP). Placental ROS increased from 890.1±218.1 relative light units (RLUs) in NP to 2240±318.9 RLUs in RUPP and decreased to 11458±136.7 RLUs in RUPP+IL17 RC (p<0.05 vs RUPP). Placental NK cytolytic proteins were significantly increased in response to RUPP and were not decreased after IL‐17 RC administration. Importantly in vitro cytotoxicity of RUPP NK cells increased 5‐fold compared to NP NK cells, and IL‐17 blockade blunted cytotoxic activity of RUPP NK. These data identify TH17/IL‐17 signaling as a mechanism of NK cytotoxic activation in response to placental ischemia during pregnancy. Therefore, targeting TH17s and IL‐17 may be a therapeutic strategy to normalize polarization of the NK population during PE and improve maternal and fetal outcomes associated with this maternal disorder.Support or Funding InformationFunding: National Institutes of Health/National Heart Lung and Blood Institute grant R00HL130456 to DCCThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.