NLRP3 Plays a Causative Role in Vascular and Renal Dysfunction and Hypertension in Placental Ischemic Pregnancy

Abstract

Preeclampsia is a multi-system disorder of pregnancy characterized by hypertension (HTN), intrauterine growth restriction (IUGR), organ dysfunction, and inflammation. The NLRP3 inflammasome is a multi-protein complex that initiates the inflammatory response, and has been implicated in chronic kidney disease, AKI, and heart failure. The purpose of the present study was to determine if NLRP3 activation plays a causative role in preeclampsia pathophysiology. We hypothesized that inhibition of NLRP3 activation would attenuate hypertension and IUGR in response to placental ischemia. Pregnant Sprague Dawley rats underwent Sham or Reduced Uterine Perfusion Pressure (RUPP; model of preeclampsia) procedure on Gestation Day (GD) 14. A subset of Sham and RUPP rats received i.p. injections of the specific NLRP3 inhibitor MCC950 (20mg/kg/day) from GD14-GD19. On GD18, Uterine Artery Resistance Index (UARI) was measured via Doppler Ultrasound. On GD19, mean arterial pressure (MAP), mean fetal and placental weight were measured, and blood and tissues were processed for additional analysis. MAP (mmHg) was significantly elevated in RUPP (130±1, n=8) compared to Sham (105±1, n=8; p<0.05). Treatment with MCC950 decreased MAP in RUPP+MCC950 (113±2, n=8; p<0.05 vs RUPP). Fetal and placental weights were significantly reduced in RUPP compared to Sham, and treatment with MCC950 had no effect. UARI was significantly increased in RUPP versus Sham (0.70±0.03 vs. 0.56±0.01, respectively; p<0.05) and was normalized to 0.52±0.03 in RUPP+ MCC950. T-helper 17 cells (TH17s) and cytolytic NK cells (cNKs) in the circulation, placenta, and kidney were evaluated by flow cytometry. Circulating TH17s (% gated) were significantly increased in RUPP (2.1±1) vs Sham (0.5±0.2; p<0.05 vs RUPP). Inhibition of NLRP3 significantly reduced circulating TH17s in RUPP+MCC950 (0.4±0.1; p<0.05 vs RUPP). Similar trends were also observed in TH17 populations in placentas and kidneys from each group. Circulating cNKs (% gated) increased from 2.3±0.3 in Sham to 6.4±0.8 in RUPP (p<0.05), and was significantly reduced to 2.3±0.6 in RUPP+MCC950 (p<0.05 vs RUPP). In a separate set of animals, renal function studies were performed to study the impact of MCC950 treatment on renal blood flow (RBF), glomerular filtration rate (GFR), and renal vascular resistance (RVR) in all groups. RBF (mL/min/g) was markedly reduced in RUPP (n=4) compared to Sham (n=5) (4±1 vs. 7±1, respectively). Importantly, treatment with MCC950 normalized RBF in RUPP+MCC950 (8±3, n=3) while having no effect in Sham (9±2, n=3). GFR (μL/min/g) was reduced from 1320±177 in Sham and 1117±240 in Sham+MCC950 to 829±124 in RUPP and remained low at 744±180 in RUPP+MCC950. RVR (mmHg/mL/min/g) was markedly increased in RUPP compared to values measured in Sham (42±8 vs. 23±4, respectively) and was normalized to 26±3 in RUPP after treatment with MCC950. The results of this study implicate NLRP3 in directly mediating inflammation, immune cell activation, vascular and renal dysfunction to cause maternal HTN in RUPP. These data suggest that NLRP3 is a potential therapeutic target for treatment in PE.