Progesterone-induced blocking factor improves blood pressure, inflammation, and pup weight in response to reduced uterine perfusion pressure (RUPP).

Preeclampsia (PE) is characterized by new-onset hypertension in association with elevated natural killer (NK) cells and inflammatory cytokines, which are likely culprits for decreased fetal weight during PE pregnancies. As progesterone increases during normal pregnancy, it stimulates progesterone-induced blocking factor (PIBF). PIBF has been shown to decrease inflammation and cytolytic NK cells, both of which are increased during PE. We hypothesized that PIBF reduces inflammation as a mechanism to improve hypertension in the preclinical reduced uterine perfusion pressure (RUPP) rat model of PE. PIBF (2.0 µg/mL) was administered intraperitoneally on gestational day 15 to either RUPP or normal pregnant (NP) rats. On day 18, carotid catheters were inserted. Mean arterial blood pressure (MAP) and samples were collected on day 19. MAP in NP rats (n = 11) was 100 ± 2 mmHg and 105 ± 3 mmHg in NP + PIBF rats (n = 8) and 122 ± 1 mmHg in RUPP rats (n = 10), which improved to 110 ± 2 mmHg in RUPP + PIBF rats (n = 11), P < 0.05. Pup weight was 2.4 ± 0.1 g in NP, 2.5 ± 0.1 g in NP + PIBF, 1.9 ± 0.1 g in RUPP, and improved to 2.1 ± 0.1 g in RUPP + PIBF rats. Circulating and placental cytolytic NK cells, IL-17, and IL-6 were significantly reduced while IL-4 and T helper (TH) 2 cells were significantly increased in RUPP rats after PIBF administration. Importantly, vasoactive pathways preproendothelin-1, nitric oxide, and soluble fms-Like tyrosine Kinase-1 (sFlt-1) were normalized in RUPP + PIBF rats compared with RUPP rats, P < 0.05. Our findings suggest that PIBF normalized IL-4/TH2 cells, which was associated with improved inflammation, fetal growth restriction, and blood pressure in the RUPP rat model of PE.