Interleukin-17 signaling mediates cytolytic natural killer cell activation in response to placental ischemia

Abstract

T-helper (TH)17s, IL-17, and cytolytic natural killer cells (cNKs) are increased in preeclampsia and contribute to the hypertension, inflammation, and fetal growth restriction that occurs in response to placental ischemia in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. As IL-17 stimulates NK cytotoxicity in vitro, we tested the hypothesis that IL-17 inhibition in RUPP rats would decrease cNK activation as a mechanism to improve maternal and fetal outcomes. On gestation day (GD) 14, rats undergoing RUPP received a miniosmotic pump infusing IL-17RC (100 pg/day), a soluble IL-17 receptor (RUPP + IL-17RC). On GD19, mean arterial pressure (MAP) was measured in normal pregnant (NP), RUPP, and RUPP + IL-17RC rats ( n = 10–12/group), animals were euthanized, and blood and tissues were collected for analysis. MAP was 30% higher in RUPP compared with NP ( P < 0.0001) and was 12% lower in RUPP + IL-17RC ( P = 0.0007 vs. RUPP). Placental cytolytic NK cells were 132% higher in RUPP than in NP ( P = 0.04 vs. NP) and were normalized in RUPP + IL-17RC ( P = 0.03 vs. RUPP). Placental levels of TNF-α, a cNK-secreted cytokine, and macrophage inflammatory protein-3α (MIP-3α), a cNK chemokine, were higher in RUPP vs. NP and lower after IL-17 blockade. Placental VEGF was lower in RUPP vs. NP and was normalized in RUPP + IL-17RC. In vitro cytolytic activity of RUPP placental NKs was higher compared with NP and was blunted in RUPP + IL-17RC NKs. Finally, both fetal weight and placental weight were lower in RUPP compared with NP, and were improved in RUPP + IL-17RC. These data identify IL-17 as a mediator of cNK activation in response to placental ischemia during pregnancy.

Adoptive transfer of placental ischemia‐stimulated natural killer cells causes a preeclampsia‐like phenotype in pregnant rats

“…Similar to what we have previously shown, 21,22 total circulating NKs were elevated in RUPP with a value of 40 ± 4% compared to 13 ± 5% in Sham (p = .0008 vs. Sham). Total circulating NKs were elevated in Sham rats that received RUPP NKs at 38 ± 3% (p = .0032 vs. Sham) and were reduced in RUPP rats that received Sham NKs at 17 ± 6% (p = .005 vs. RUPP; Figure 1A).…”

“…20 We have previously published that cNKs are significantly increased in RUPP rats compared to their normal pregnant counterparts. 21,22 We also showed a 5-fold increase in cytotoxicity of placental NKs from RUPP compared to those from their normal pregnant counterparts. 22 Additionally, we previously depleted NKs in RUPP and saw a significant reduction in maternal blood pressure and improved fetal weight.…”

“…21,22 We also showed a 5-fold increase in cytotoxicity of placental NKs from RUPP compared to those from their normal pregnant counterparts. 22 Additionally, we previously depleted NKs in RUPP and saw a significant reduction in maternal blood pressure and improved fetal weight. 21 However, because this study depleted all subsets of NKs, it did not reveal the precise role that cNKs play in the pathophysiology observed in RUPP animals.…”

“…CD3 − CD161 + NKs were isolated using (MS) columns (Miltenyi Biotec) according to the manufacturer's protocol prior to culture and expansion. The collected cells were resuspended in NK cell activation media (RPMI, 10% FBS, 1% Pen/Strep, 2 ng/ml IL-2), [25][26][27] and allowed to expand in culture for 48 h.…”

“…Superoxide production in the placenta was measured using the lucigenin technique as previously described. [22][23][24]30 Each sample was run in triplicate and the average was used for data transformation. The protein concentration was measured using a protein assay with BSA standards (Pierce), and the data are expressed as RLUs/min/mg.…”