Abstract 128: Interleukin-17 Mediates Hypertension, Intrauterine Growth Restriction, Cytolytic Natural Killer Cells and Vascular Dysfunction in Pregnant Rats

Preeclampsia is a hypertensive disorder of pregnancy characterized by intrauterine growth restriction (IUGR), vascular dysfunction, and chronic immune activation including increased T H 17s and cytolytic NK cells (NK C ). We recently developed a novel model of preeclampsia in which placental ischemia (PI)-induced T H 17s cause a preeclampsia-like phenotype in pregnant rats characterized by hypertension, IUGR, oxidative stress (ROS), and increased cytolytic NK cells (NK C ). In the current study we investigated a novel role for IL-17, the main cytokine secreted from T H 17s, to directly induce IUGR, NK C activation, and vascular dysfunction in pregnancy. IL-17 (150 pg/day) was chronically infused into a subset of normal pregnant (NP) rats from gestation day (GD) 12-19 (NP+IL-17) via i.p. minipump. On GD 18 carotid catheters were implanted and on GD 19 MAP, fetal weight, placental weight, placental NK C , and NK C -associated proteins were measured and vascular reactivity of uterine arteries was assessed. Data are expressed as mean±SEM. MAP significantly increased from 100±3 mmHg in NP (n=9) to 115±1 mmHg in NP+IL-17 (n=12). Fetal weight significantly decreased from 2.5±0.04 g in NP to 2.3±0.03 g in NP+IL-17 (p<0.05). Placental weight significantly decreased from 0.62±0.02 g in NP to 0.55±0.01 g in NP+IL-17 (p<0.05). Placental ROS significantly increased 1353±337 RLU/min/mg in NP to 2210±180 RLU/min/mg in NP+IL-17 (p<0.05). Placental NK C increased from 2.6±1.6% of the total NK population in NP to 11.3±2.2% in NP+IL-17 (p<0.05). Placental granzyme B increased from 22.7±1.6 pg/mg in NP to 30.2±2 pg/mg in NP+IL-17 (p<0.05). Placental granzyme A increased from 3067±225 pg/mg in NP to 3926±210 pg/mg (p<0.05). Additionally, placental levels of VEGF, an important pro-angiogenic factor secreted by non-cytolytic uterine NK cells significantly decreased from 77.6±6.5 pg/mg in NP to 54.2±3.2 pg/mg in NP+IL-17 (p<0.05). We also observed impaired relaxation of uterine arteries in response to acetylcholine. These data suggest a shift from non-cytolytic NK to NK C cells in the placentas of NP+IL17. In addition to hypertension and ROS, this study demonstrates novel roles for IL-17 to directly mediate IUGR, NK C activation, and endothelial vascular dysfunction during pregnancy.

Abstract 012: Brain Endoplasmic Reticulum (ER) Stress Reduces Appetite and Increases Blood Pressure Independent of the Melanocortin-4 Receptor in Rats

Although there is evidence that chronic endoplasmic reticulum (ER) stress affects hypothalamic pathways that regulate food intake, body weight and blood pressure (BP), the specific mechanisms are unclear. One key pathway for controlling energy balance and BP is the central nervous system (CNS) melanocortin system. However, the importance of this system in mediating the effects of ER stress on metabolic and cardiovascular function is unclear. In this study we examined the role of the melanocortin-4 receptor (MC4R) in controlling blood pressure (BP) and metabolic functions during chronic brain ER stress. MC4R knockout (MC4R -/- , n=5) and control wild-type Wistar Hannover rats (WT, n=5) were implanted with blood pressure (BP) telemetry transmitters and an intracerebroventricular (ICV) cannula was inserted into the third ventricle at 22 weeks of age. After 10 days of recovery, food intake, BP and HR were measured 24-hrs/day. After stable baseline measurements for 4 days, thapsigargin (TG, 5μg/5μl, ICV) was injected daily for 3 consecutive days to induce ER stress. At baseline, MC4R -/- rats ate 23% more food and were 41% heavier than WT rats. MAP was slightly higher (115±3 vs. 109±2 mmHg) and HR was lower (318±10 vs. 363±6 bpm) in MC4R-/- rats. Induction of brain ER stress decreased food intake (26%) while causing no changes in blood glucose levels (WT: 94±4 vs. 98±3 and MC4R-/-: 110±6 vs.116±4 mg/dl) or HR in both groups. Induction of brain ER stress also raised BP in both groups (7 and 5 mmHg, respectively for WT and MC4R -/- rats). These results suggest that chronic brain ER stress-induced reductions in appetite and increases in BP are independent of MC4R signaling. (NHLBI-PO1HL51971, NIGMS- P20GM104357 and AHA SDG5680016)

Abstract 211: Inhibition of Heme Oxygenase-1 (HO-1) Induces Mild Hypertension in Pregnant Rats

In the preeclamptic patient, inadequate remodeling of the maternal vasculature exacerbates this effect, causing dramatically increased oxidative stress in the placenta, which has been shown to be an important component of the maternal hypertension. There is also increasing awareness that HO-1 may act as an important regulator of placental function during normal pregnancy and decreases in HO-1 activity have been implicated in the pathogenesis of preeclampsia. While previous work in pregnant mice demonstrated that pharmacological inhibition of HO-1 leads to elevations in blood pressure, the mechanisms involved in the hypertension are unclear. The purpose of this study was to test the hypothesis that HO inhibition in late gestation leads to increases in maternal blood pressure by altering angiogenic balance and increasing placental oxidative stress in pregnant rats. HO activity was inhibited with tin mesoporphyrin (SnMP) was administered on gestational day 14, and blood pressure was measured on gestational day 19 by indwelling carotid catheter before sacrifice. In response to SnMP treatment, maternal MAP was significantly increased (99±1 vs 113±2 mmHg, p<0.05, n=15 per group). Placental sFlt-1 (631±47 vs 648±26 pg/mg, p=0.76) levels in the placenta were not affected by HO inhibition. Additionally, there was no significant difference in free VEGF in the maternal circulation (287±22 vs 329±14 pg/ml, p=0.11). There was, however, a significant increase in placental NADPH oxidase activity in SnMP treated rats (2021±238 vs 3005±301 RLU/min/mg, p<0.05) as determined by NADPH dependent lucigenin luminescence. This is likely due to decreased production of bilirubin, which is known to inhibit NADPH oxidase activity, and suggests an important role for HO-1 as an antioxidant in the developing placenta.