Increased platelet mitochondrial function correlates with clot strength in a rodent fracture model

BACKGROUND

Thromboelastographic measures of clot strength increase early after injury, portending higher risks for thromboembolic complications during recovery. Understanding the specific role of platelets is challenging because of a lack of clinically relevant measures of platelet function. Platelet mitochondrial respirometry may provide insight to global platelet function but has not yet been correlated with functional coagulation studies.

METHODS

Wistar rats underwent anesthesia and either immediate sacrifice for baseline values (n = 6) or (1) bilateral hindlimb orthopedic injury (n = 12), versus (2) sham anesthesia (n = 12) with terminal phlebotomy/hepatectomy after 24 hours. High-resolution respirometry was used to measure basal respiration, mitochondrial leak, maximal oxidative phosphorylation, and Complex IV activity in intact platelets; Complex I- and Complex II-driven respiration was measured in isolated liver mitochondria. Results were normalized to platelet number and protein mass, respectively. Citrated native thromboelastography (TEG) was performed in triplicate.

RESULTS

Citrated native TEG maximal amplitude was significantly higher (81.0 ± 3.0 vs. 73.3 ± 3.5 mm, p < 0.001) in trauma compared with sham rats 24 hours after injury. Intact platelets from injured rats had higher basal oxygen consumption (17.7 ± 2.5 vs. 15.1 ± 3.2 pmol O 2 /[s × 10 8 cells], p = 0.045), with similar trends in mitochondrial leak rate ( p = 0.19) when compared with sham animals. Overall, platelet basal respiration significantly correlated with TEG maximal amplitude ( r = 0.44, p = 0.034). As a control for sex-dependent systemic mitochondrial differences, females displayed higher liver mitochondria Complex I-driven respiration (895.6 ± 123.7 vs. 622.1 ± 48.7 mmol e - /min/mg protein, p = 0.02); as a control for systemic mitochondrial effects of injury, no liver mitochondrial respiration differences were seen.

CONCLUSION

Platelet mitochondrial basal respiration is increased after injury and correlates with clot strength in this rodent hindlimb fracture model. Several mitochondrial-targeted therapeutics exist in common use that are underexplored but hold promise as potential antithrombotic adjuncts that can be sensitively evaluated in this preclinical model.

Luteolin prevents TNF-α-induced NF-κB activation and ROS production in cultured human placental explants and endothelial cells

INTRODUCTION

Preeclampsia (PE) is a serious hypertensive pregnancy disorder and a leading cause of maternal and perinatal morbidity and mortality. Despite the prevalence and complications, there are no approved therapeutics to relieve PE symptoms. Inflammation, oxidative stress, and angiogenic imbalance have been shown to contribute to the PE pathophysiology, though there is a lack of understanding in how best to target these pathways in PE. We recently demonstrated that the bioflavonoid luteolin is a potent inhibitor of the anti-angiogenic and pro-hypertensive soluble fms-like tyrosine kinase 1 (sFlt-1), and here we aimed to determine if luteolin was also capable of reducing inflammation and oxidative stress pathways.

METHODS

Tumor necrosis factor (TNF)-α, which is upregulated in PE, was utilized to stimulate these pathways in human placental explants and endothelial cells. Endothelin-1 (ET-1) and interleukin (IL)-6 in the media from explants and cells were measured via ELISA, and NF-κB localization and reactive oxygen species were detected via fluorescence microscopy.

RESULTS

Pretreatment with luteolin demonstrated significant reductions in NF-κB activation, reactive oxygen species, superoxide, and IL-6 and ET-1 expression in endothelial cells. We also saw a significant reduction in phosphorylation of NF-κB in human placental explants.

DISCUSSION

These data demonstrate that luteolin inhibits pathways implicated in the development of PE and should be explored further for its potential as a PE therapeutic.

Bioflavonoid luteolin prevents sFlt-1 release via HIF-1α inhibition in cultured human placenta

Preeclampsia (PE) is a serious hypertensive complication of pregnancy and is a leading cause of maternal death and major contributor to maternal and perinatal morbidity, including establishment of long-term complications. The continued prevalence of PE stresses the need for identification of novel treatments which can target prohypertensive factors implicated in the disease pathophysiology, such as soluble fms-like tyrosine kinase 1 (sFlt-1). We set out to identify novel compounds to reduce placental sFlt-1 and determine whether this occurs via hypoxia-inducible factor (HIF)-1α inhibition. We utilized a commercially available library of natural compounds to assess their ability to reduce sFlt-1 release from primary human placental cytotrophoblast cells (CTBs). Human placental explants from normotensive (NT) and preeclamptic (PE) pregnancies were treated with varying concentrations of luteolin. Protein and mRNA expression of sFlt-1 and upstream mediators were evaluated using ELISA, western blot, and real-time PCR. Of the natural compounds examined, luteolin showed the most potent inhibition of sFlt-1 release, with >95% reduction compared to vehicle-treated. Luteolin significantly inhibited sFlt-1 in cultured placental explants compared to vehicle-treated in a dose- and time-dependent manner. Additionally, significant decreases in HIF-1α expression were observed in luteolin-treated explants, suggesting a mechanism for sFlt-1 downregulation. The ability of luteolin to inhibit HIF-1α may be mediated through the Akt pathway, as inhibitors to Akt and its upstream regulator phosphatidylinositol-3 kinase (PI3K) resulted in significant HIF-1α reduction. Luteolin reduces anti-angiogenic sFlt-1 through inhibition of HIF-1α, making it a novel candidate for the treatment of PE.

Increased NOS coupling by the metabolite tetrahydrobiopterin (BH4) reduces preeclampsia/IUGR consequences

Preeclampsia (PE) is a high-prevalence pregnancy disease characterized by placental insufficiency, gestational hypertension, and proteinuria. Overexpression of the A isoform of the STOX1 transcription factor (STOX1A) recapitulates PE in mice, and STOX1A overexpressing trophoblasts recapitulate PE patients hallmarks in terms of gene expression and pathophysiology. STOX1 overexpression induces nitroso-redox imbalance and mitochondrial hyper-activation. Here, by a thorough analysis on cell models, we show that STOX1 overexpression in trophoblasts alters inducible nitric oxide synthase (iNOS), nitric oxide (NO) content, the nitroso-redox balance, the antioxidant defense, and mitochondrial function. This is accompanied by specific alterations of the Krebs cycle leading to reduced l-malate content. By increasing NOS coupling using the metabolite tetrahydrobiopterin (BH4) we restore this multi-step pathway in vitro. Moving in vivo on two different rodent models (STOX1 mice and RUPP rats, alike early onset and late onset preeclampsia, respectively), we show by transcriptomics that BH4 directly reverts STOX1-deregulated gene expression including glutathione metabolism, oxidative phosphorylation, cholesterol metabolism, inflammation, lipoprotein metabolism and platelet activation, successfully treating placental hypotrophy, gestational hypertension, proteinuria and heart hypertrophy. In the RUPP rats we show that the major fetal issue of preeclampsia, Intra Uterine Growth Restriction (IUGR), is efficiently corrected. Our work posits on solid bases BH4 as a novel potential therapy for preeclampsia.

Placental Ischemia Says "NO" to Proper NOS-Mediated Control of Vascular Tone and Blood Pressure in Preeclampsia

In this review, we first provide a brief overview of the nitric oxide synthase (NOS) isoforms and biochemistry. This is followed by describing what is known about NOS-mediated blood pressure control during normal pregnancy. Circulating nitric oxide (NO) bioavailability has been assessed by measuring its metabolites, nitrite (NO₂) and/or nitrate (NO₃), and shown to rise throughout normal pregnancy in humans and rats and decline postpartum. In contrast, placental malperfusion/ischemia leads to systemic reductions in NO bioavailability leading to maternal endothelial and vascular dysfunction with subsequent development of hypertension in PE. We end this article by describing emergent risk factors for placental malperfusion and ischemic disease and discussing strategies to target the NOS system therapeutically to increase NO bioavailability in preeclamptic patients. Throughout this discussion, we highlight the critical importance that experimental animal studies have played in our current understanding of NOS biology in normal pregnancy and their use in finding novel ways to preserve this signaling pathway to prevent the development, treat symptoms, or reduce the severity of PE.

Impact of hyperleptinemia during placental ischemia-induced hypertension in pregnant rats

The prevalence of preeclampsia and obesity have increased. Although obesity is a major risk factor for preeclampsia, the mechanisms linking these morbidities are poorly understood. Circulating leptin levels increase in proportion to fat mass. Infusion of this adipokine elicits hypertension in nonpregnant rats, but less is known about how hyperleptinemia impacts blood pressure during placental ischemia, an initiating event in the pathophysiology of hypertension in preeclampsia. We tested the hypothesis that hyperleptinemia during reduced uterine perfusion pressure (RUPP) exaggerates placental ischemia-induced hypertension. On gestational day (GD) 14, Sprague-Dawley rats were implanted with osmotic mini-pumps delivering recombinant rat leptin (1 µg/kg/min iv) or vehicle concurrently with the RUPP procedure to induce placental ischemia or Sham. On GD 19, plasma leptin was elevated in Sham + Leptin and RUPP + Leptin. Leptin infusion did not significantly impact mean arterial pressure (MAP) in Sham. MAP was increased in RUPP + Vehicle vs. Sham + Vehicle. In contrast to our hypothesis, placental ischemia-induced hypertension was attenuated by leptin infusion. To examine potential mechanisms for attenuation of RUPP-induced hypertension during hyperleptinemia, endothelial-dependent vasorelaxation to acetylcholine was similar between Sham and RUPP; however, endothelial-independent vasorelaxation to the nitric oxide (NO)-donor, sodium nitroprusside, was increased in Sham and RUPP. These findings suggest that NO/cyclic guanosine monophosphate (cGMP) signaling was increased in the presence of hyperleptinemia. Plasma cGMP was elevated in Sham and RUPP hyperleptinemic groups compared with vehicle groups but plasma and vascular NO metabolites were reduced. These data suggest that hyperleptinemia during placental ischemia attenuates hypertension by compensatory increases in NO/cGMP signaling.NEW & NOTEWORTHY Ours is the first study to examine the impact of hyperleptinemia on the development of placental ischemia-induced hypertension using an experimental animal model.

Circulating Total Cell-Free DNA Levels Are Increased in Hypertensive Disorders of Pregnancy and Associated with Prohypertensive Factors and Adverse Clinical Outcomes

Previous studies have described increased circulating cell-free DNA (cfDNA) in hypertensive disorders of pregnancy (HDP). Here, we aimed first to confirm this information using a simple, but sensible fluorescent assay, and second to investigate whether total cfDNA is associated with circulating factors known to be linked to the pathophysiology of HDP as well as with poor maternal-fetal outcomes. We studied 98 women with healthy pregnancies (HP), 88 with gestational hypertension (GH), and 91 with preeclampsia (PE). Total DNA was extracted from plasma using the QIAamp DNA blood mini kit and quantified using Quant-iT™ PicoGreen® dsDNA fluorescent detection kit. We found higher total cfDNA levels in GH and PE (197.0 and 174.2 ng/mL, respectively) than in HP (140.5 ng/mL; both p < 0.0001). Interestingly, total cfDNA levels were elevated in both male and female-bearing pregnancies diagnosed with either HDP, and in more severe versus less severe HDP cases, as classified according to responsiveness to antihypertensive therapy. In addition, total cfDNA was independently associated with HDP, and a cutoff concentration of 160 ng/mL provided appropriate sensitivity and specificity values for diagnosing GH and PE compared to HP (70-85%, both p < 0.0001). Moreover, high total cfDNA was associated with adverse clinical outcomes (high blood pressure, low platelet count, preterm delivery, fetal growth restriction) and high prohypertensive factors (sFLT-1, sEndoglin, MMP-2). These findings represent a step towards to the establishment of cfDNA as a diagnostic tool and the need to understand its role in HDP.

Preeclampsia: Linking Placental Ischemia with Maternal Endothelial and Vascular Dysfunction

Preeclampsia (PE), a hypertensive disorder, occurs in 3% to 8% of pregnancies in the United States and affects over 200,000 women and newborns per year. The United States has seen a 25% increase in the incidence of PE, largely owing to increases in risk factors, including obesity and cardiovascular disease. Although the etiology of PE is not clear, it is believed that impaired spiral artery remodeling of the placenta reduces perfusion, leading to placental ischemia. Subsequently, the ischemic placenta releases antiangiogenic and pro-inflammatory factors, such as cytokines, reactive oxygen species, and the angiotensin II type 1 receptor autoantibody (AT1-AA), among others, into the maternal circulation. These factors cause widespread endothelial activation, upregulation of the endothelin system, and vasoconstriction. In turn, these changes affect the function of multiple organ systems including the kidneys, brain, liver, and heart. Despite extensive research into the pathophysiology of PE, the only treatment option remains early delivery of the baby and importantly, the placenta. While premature delivery is effective in ameliorating immediate risk to the mother, mounting evidence suggests that PE increases risk of cardiovascular disease later in life for both mother and baby. Notably, these women are at increased risk of hypertension, heart disease, and stroke, while offspring are at risk of obesity, hypertension, and neurological disease, among other complications, later in life. This article aims to discuss the current understanding of the diagnosis and pathophysiology of PE, as well as associated organ damage, maternal and fetal outcomes, and potential therapeutic avenues. © 2021 American Physiological Society. Compr Physiol 11:1315-1349, 2021.

Chronic CNS-mediated cardiometabolic actions of leptin: potential role of sex differences

Previous studies using male rodents showed the adipocyte-derived hormone leptin acts in the brain to regulate cardiovascular function, energy balance, and glucose homeostasis. The importance of sex differences in cardiometabolic responses to leptin, however, is still unclear. We examined potential sex differences in leptin's chronic central nervous system (CNS)-mediated actions on blood pressure (BP), heart rate (HR), appetite, and glucose homeostasis in normal and type 1 diabetic rats. Female and male Sprague-Dawley (SD) rats were instrumented with intracerebroventricular cannulas for continuous 7-day leptin infusion (15 µg/day), and BP and HR were measured by telemetry 24 h/day. At baseline, females had lower mean arterial pressure (MAP) (96 ± 3 vs. 104 ± 4 mmHg, P < 0.05) but higher HR (375 ± 5 vs. 335 ± 5 beats/min, P < 0.05) compared with males. After leptin treatment, we observed similar increases in BP (∼3 mmHg) and HR (∼25 beats/min) in both sexes. Females had significantly lower body weight (BW, 283 ± 2 vs. 417 ± 7 g, P < 0.05) and caloric intake (162 ± 20 vs. 192 ± 9 kcal/kg of body wt, P < 0.05) compared with males, and leptin infusion reduced BW (-10%) and caloric intake (-62%) similarly in both sexes. In rats with streptozotocin-induced diabetes (n = 5/sex), intracerebroventricular leptin treatment for 7 days completely normalized glucose levels. The same dose of leptin administered intraperitoneally did not alter MAP, HR, glucose levels, or caloric intake in normal or diabetic rats. These results show that leptin's CNS effects on BP, HR, glucose regulation, and energy homeostasis are similar in male and female rats. Therefore, our results provide no evidence for sex differences in leptin's brain-mediated cardiovascular or metabolic actions.

Luteolin-induced vasorelaxation in uterine arteries from normal pregnant rats

BACKGROUND

The flavonoid, luteolin, promotes vasorelaxation in various arteries through endothelial-dependent and independent mechanisms. Although there is growing interest in the vasoactive effects of flavonoids on maternal vascular function during pregnancy, it is unknown whether luteolin elicits vasorelaxation in the uterine circulation. We tested the hypothesis that luteolin induces vasorelaxation via endothelial-dependent mechanisms in uterine arteries from normal pregnant rats during late gestation.

METHODS

Uterine arteries and aortas were isolated from Sprague-Dawley rats at gestational day 19 and prepared for wire myography.

RESULTS

The potency of luteolin-induced vasorelaxation was examined between uterine arteries and the aortas. By 50 µM of luteolin, there was complete relaxation (100.5 ± 5.2%) in uterine arteries as compared to aortas (27.5 ± 10.0%). Even the highest concentration of 100 µM luteolin produced less than half relaxation (43.6 ± 8.6%) in aortas compared to uterine arteries. We then explored if luteolin-induced vasorelaxation in uterine arteries from pregnant rats was mediated by endothelial-dependent vasorelaxation pathways, including nitric oxide synthase (NOS), cyclooxygenase (COX), or potassium (K⁺) channels. Blocking these pathways with N(G)-Nitro-l-arginine methyl ester hydrochloride (L-NAME), indomethacin, or tetraethylammonium (TEA)/high potassium chloride (KCl), respectively, did not alter luteolin responses in uterine arteries from pregnant rats. These findings suggested that endothelial factors may not mediate luteolin-induced vasorelaxation in uterine arteries during pregnancy. Indeed, experiments where the endothelium was removed did not alter luteolin-induced vasorelaxation in uterine arteries during pregnancy.

CONCLUSIONS

Luteolin directly promotes vasorelaxation in the medial smooth muscle layer of uterine arteries during normal pregnancy.

Abstract P215: Hyperglycemic Rats Have Increased Fetal Demise But Not Hypertension During Pregnancy

While obesity is a major cause for pregnancy complications including preeclampsia and fetal demise, it is not exactly clear the precise obesity-related metabolic factors that promote these adverse outcomes. Epidemiological studies have pointed toward hyperglycemia as one such factor. Therefore, we tested the hypothesis that hyperglycemic rats have hypertension and fetal demise during pregnancy. For this purpose, we utilized the type II diabetic model, the Goto-Kakizaki (GK) rat (N=16), compared to normoglycemic Wistar Hannover (WH) rats (N=9), which were maintained on Envigo 8640 standard chow. The GK rat allows for assessment of hyperglycemia on pregnancy without confounding obesity. Maternal fasting glucose levels were significantly greater (P<0.05) in GK (97±8 mg/dL) vs. WH (72±9 mg/dL) rats by gestational day 19. Body weight was lower (P<0.05) in GK (248±4 g) versus WH (289±4 g) pregnant rats, whereas perirenal fat (1.56±0.07 g vs. 1.38±0.07 g, P>0.05) and circulating levels of the adipokine, leptin (1.6±0.2 ng/mL vs. 2.2±0.3 ng/mL, P>0.05) were similar between GK and WH pregnant groups, respectively. Endothelial-dependent relaxation to acetylcholine (sensitivity as logEC50: -5.2±0.3 M vs -5.2±0.4 M) and endothelial-independent relaxation to the nitric oxide-donor sodium nitroprusside (logEC50: -7.2±0.2 M vs. -7.5±0.1 M) were similar (P>0.05) in uterine arteries isolated from GK and WH rats, respectively. It was then determined if reduced uterine perfusion pressure (RUPP)-induced placental ischemia, a significant contributor to the development of preeclampsia, promoted greater maternal hypertension in GK rats. RUPP was conducted on gestational day 14 and blood pressure assessed on day 19. RUPP produced hypertension to a similar extent (P>0.05) in GK (116±5 mmHg vs. Sham 102±5 mmHg) and WH (124±4 mmHg vs. Sham 100±2 mmHg) groups. Blood pressure was similar under Sham conditions. Fetal demise was already greater in Sham GK vs. Sham WH pregnant rats (% absorptions: 13±2 vs. 2±2, P<0.05) but increased similarly following RUPP in GK (61±11 %) and WH (65±5 %) pregnant rats. In conclusion, these data suggest that high glucose levels promote fetal demise during pregnancy but do not exaggerate the outcomes of placental ischemia-induced hypertension.

High-fat diet from parental generation exaggerates body and adipose tissue weights in pregnant offspring

Parental high-fat diet (HFD) programs for obesity and hypertension in female offspring in rats, but it is unknown how the pregnancies of these offspring are impacted. Therefore, the hypothesis was tested that parental HFD exaggerates obesity and hypertension during pregnancy of the offspring. Wistar Hannover rat dams (the parental, P generation) were maintained on normal-fat diet (NFD) or HFD from weaning and were kept on respective diets through pregnancy and lactation. Their offspring (the first filial, F1 generation) were weaned onto the same diet as the P generation, or they were changed to the other diet to determine if combined HFD in the P and F1 generations exaggerates body weight and blood pressure levels during pregnancy in these offspring. This diet paradigm resulted in the following groups of pregnant F1 offspring: P-NFD/F1-NFD, P-HFD/F1-NFD, P-NFD/F1-HFD, and P-HFD/F1-HFD. Maternal body and adipose tissue weights were greatest in the P-HFD/F1-HFD group compared to the other 3 groups by the end of pregnancy. Plasma leptin and conscious mean arterial blood pressure were not significantly different between any group, although there was a main effect for increased blood pressure in the F1-HFD groups. Circulating levels of the antihypertensive pregnancy factor, placental growth factor (PlGF), were assessed. Although average PlGF levels were similar among all groups, correlative studies revealed that lower levels of PlGF were associated with higher blood pressure only in the P-HFD/F1-HFD group. In summary, HFD feeding from the P generation exaggerated HFD-induced body and adipose tissue weights in the pregnant offspring.

Melanocortin-4 Receptor Deficiency Attenuates Placental Ischemia-Induced Hypertension in Pregnant Rats

Preeclampsia is a pregnancy-specific disorder of new-onset hypertension linked to placental ischemia. While obesity is a major risk factor for preeclampsia, not all obese pregnant women develop pregnancy-induced hypertension or preeclampsia. Previously, we reported that placental ischemia-induced hypertension is dependent upon intact signaling of the sympathetic nervous system. Moreover, in various models of obesity, blockade of MC4R (melanocortin-4 receptor) signaling protects against the development of hypertension via suppression of the sympathetic nervous system. Less is known about this pathway during obese pregnancy. Although blockade of MC4R may lead to increased body weight during pregnancy, we tested the hypothesis that placental ischemia-induced hypertension is attenuated in obese MC4R-deficient pregnant rats. On gestational day 14, MC4R wild-type or heterozygous-deficient (MC4R-def) rats were subjected to chronic placental ischemia via the reduced uterine perfusion pressure procedure or Sham surgery then examined on gestational day 19. In Sham MC4R-def versus Sham wild-type pregnant rats, there was increased body weight, fat mass, and circulating leptin levels but they had similar fetus weights. Reduced uterine perfusion pressure reduced fetus weights in both strains. Reduced uterine perfusion pressure increased blood pressure in wild-type rats but this response was significantly attenuated in MC4R-def rats, although blood pressure was elevated in Sham MC4R-def over Sham wild-type. These data indicate that while obese MC4R-def pregnant rats have higher blood pressure during pregnancy, placental ischemia-induced hypertension is attenuated in obese MC4R-def pregnant rats. Thus, obese women with abnormal MC4R signaling may be less susceptible to the development of placental ischemia-induced hypertension.

Abstract P3046: Elevated Free Fatty Acids During Pregnancy Promote Vascular Impairment, Uteroplacental Dysfunction And Angiogenic Imbalance In Rats

Preeclampsia (PE) is a pregnancy-specific syndrome affecting 5-8% of pregnancies and is associated with vascular dysfunction and an increase in anti-angiogenic factors. Recent studies have shown that obese women are 4 times more likely to develop preeclampsia, and obesity/preeclampsia has been shown to increase circulating free fatty acids (FA). However, the role of FA on preeclamptic characteristics, such as uteroplacental and vascular dysfunction, as well as angiogenic imbalance has yet to be determined. To test the hypothesis that FAs induce a placental ischemic-like phenotype, pregnant rats were infused daily (IV) from gestational days (GD) 13-18 with specific free FA: 10mM Oleate and Palmitate, 4mM Linoleic Acid, and 0.8mM Arachadonic Acid. On GD 19, MAP, blood and tissues were collected. Third order mesentery arteries and aortas were used for vascular reactivity studies. Placental villi from normal pregnant rats exposed to FA ex vivo were examined for production of angiogenic factors. While infusion of FA resulted in no change in MAP, pup or placental weight, there was a trend for an increase in fetal reabsorption (9.7±3.3% vs 2.4±1.3%; p=0.07) and decrease in plasma PlGF in FA-infused rats (506±22vs 583±35 pg/mL; p=0.07), indicating moderate impairment in uteroplacental function in FA-infused pregnant rats compared to vehicle normal pregnant rats. Aortas of FA-infused pregnant rats revealed impaired Phe-induced vasoconstriction beginning at 3E -6.5 M of Phe (31.3±7.5 vs 70.8±11.4; p=<0.02), while vasorelaxation was attenuated in mesenteric arteries of FA-infused pregnant rats compared to normal pregnant rats (p<0.01). Moreover, FA caused an increase in sFlt-1 (533±34 vs 181±7 pg/mL; p<0.01) and sFlt-1:PlGF ratio (4.8±.1 vs 3.2±.2; p<0.01) in placental explants compared to vehicle. These data suggest that elevated FA during pregnancy, at levels comparable to those observed in preeclampsia, promote uteroplacental dysfunction, angiogenic imbalance, and impaired vascular reactivity in rats. Further studies to examine the mechanisms associated with FA-induced uteroplacental outcomes in pregnancy could elucidate the role of elevated FA as a risk factor for placental ischemia.

Abstract 150: Obese Hypertensive Pregnant Rats Have Reduced Placental Growth Factor Whereas Increasing It's Levels Decreases Their Blood Pressure

While epidemiological studies have repeatedly shown that overweight and obesity are associated with hypertension during pregnancy, the mechanisms linking these co-morbidities are not as explored. Reports show reduced levels of the anti-hypertensive and pregnancy-related factor, placental growth factor (PlGF), in obese hypertensive pregnant humans. We tested the hypothesis that obese hypertensive pregnant rats have reduced PlGF whereas increasing its levels reduces their blood pressure. We utilized a genetic model of obesity in rats having heterozygous deficiency of the melanocortin-4 receptor (MC4R-def) compared to wild-type lean controls. By gestational day 19, body mass (341±8 vs 311±7 g), periaortic adipose tissue (10.9±1.1 vs 8.2±0.5 mg), retroperitoneal adipose tissue (4.4±0.4 vs 2.5±0.2 g), circulating levels of leptin (10±1 vs 6±1 ng/mL), and mean arterial blood pressure (116±2 vs 105±2 mmHg) were greater (all P<0.05) in obese (N=17) compared to lean (N=14) pregnant rats. PlGF levels were lower (P<0.05) in serum (61±6 vs. 78±7 pg/mL) and secreted from placental (58±3 vs 71±3 pg/mg) and periaortic adipose tissue (7±1 vs 15±2 pg/mL) explants in obese compared to lean groups. PlGF secretion from retroperitoneal adipose tissue was similar between obese (78±10 pg/mL) and lean (62±12 pg/mL) groups. Vascular expression of the PlGF receptor, vascular endothelial growth factor receptor 1 (VEGFR1), was lower (P<0.05) in aortic tissue (832±60 vs 1106±91 pg/mg) but higher (P<0.05) in small mesenteric arteries (214±23 vs. 151±17 pg/mg) from the obese pregnant rats. Chronic administration of recombinant human (rh)PlGF (180 ug/kg per day) from gestational day 13-19 produced detectable levels of human PlGF in serum from both lean (33±4 pg/mL) and obese (43±4 pg/mL) pregnant rats and reduced (P<0.05) blood pressure in obese (102±3 mmHg) but not in lean (101±3 mmHg) groups. The treatment did not alter maternal body or fat masses or circulating leptin. In summary, PlGF is reduced in MC4R-def obese hypertensive pregnant rats, similar to findings in obese pregnant humans, whereas increasing the levels of PlGF reduced their hypertensive phenotype. Thus, treatment with rhPlGF may prove beneficial in attenuating blood pressure in obese hypertensive pregnancies.

Prenatal Sildenafil Therapy Improves Cardiovascular Function in Fetal Growth Restricted Offspring of Dahl Salt-Sensitive Rats

Fetal growth restriction (FGR) is associated with increased risk for cardiovascular and renal disorders in later life. Prenatal sildenafil improves birth weight in FGR animal models. Whether sildenafil treatment protects against long-term cardiovascular and renal disease in these offspring is unknown. The aim of this study is to test the hypothesis that prenatal sildenafil ameliorates cardiovascular and renal function in FGR offspring of Dahl salt-sensitive rats. Sildenafil citrate (60 mg/kg per day) or control gel diet (containing 0.3% salt) was administered from gestational day ten until birth. In male and female offspring, the mean arterial pressure was measured by telemetry in 1 subset from week 5 until week twenty. Echocardiographic parameters, glomerular filtration rate, and fractional electrolyte excretion were determined in another subset at week 9. Aortic and mesenteric artery rings were prepared to assess endothelial-dependent (acetylcholine) and -independent (sodium nitroprusside) vasorelaxation (week 10). The rise in mean arterial pressure per week was attenuated in treated versus untreated male offspring. Mesenteric arteries showed an increased endothelium-dependent relaxation and improved endothelium-independent relaxation in treated versus control male offspring. No differences in aortic relaxation, echocardiographic parameters or renal function were observed between groups. Prenatal sildenafil treatment subtly improves cardiovascular but not renal function in the offspring of this FGR rat model. Translationally, in utero treatment could be beneficial for cardiovascular programming in a sex-specific manner; however, caution is warranted since recent human trials have been halted because of potentially deleterious neonatal side effects when treating pregnancies complicated with severe FGR with sildenafil.

Role of melanocortin 4 receptor in hypertension induced by chronic intermittent hypoxia

AIM

We previously demonstrated that central nervous system (CNS) melanocortin 4 receptors (MC4R) play a key role in regulating blood pressure (BP) in some conditions associated with increased SNS activity, including obesity. In this study, we examined whether activation of CNS MC4R contributes to chronic intermittent hypoxia (CIH)-induced hypertension and ventilatory responses to hypercapnia.

METHODS

Rats were instrumented with an intracerebroventricular (ICV) cannula in the lateral cerebral ventricle for continuous infusion of MC4R antagonist (SHU-9119) and telemetry probes for measuring mean arterial pressure (MAP) and heart rate (HR). Untreated and SHU-9119-treated rats as well as obese and lean MC4R-deficient rats were exposed to CIH for 7-18 consecutive days.

RESULTS

Chronic intermittent hypoxia reduced cumulative food intake by 18 ± 5 g while MAP and HR increased by 10 ± 3 mm Hg and 9 ± 5 bpm in untreated rats. SHU-9119 increased food intake (from 15 ± 1 to 46 ± 3 g) and prevented CIH-induced reduction in food intake. CIH-induced hypertension was not attenuated by MC4R antagonism (average increase of 10 ± 1 vs 9 ± 1 mm Hg for untreated and SHU-9119 treated rats). In obese MC4R-deficient rats, CIH for 7 days raised BP by 11 ± 4 mm Hg. However, when MC4R-deficient rats were food restricted to prevent obesity, CIH-induced hypertension was attenuated by 32%. We also found that MC4R deficiency was associated with impaired ventilatory responses to hypercapnia independently of obesity.

CONCLUSION

These results show that obesity and the CNS melanocortin system interact in complex ways to elevate BP during CIH and that MC4R may be important in the ventilatory responses to hypercapnia.

Chronic infusion of interleukin-17 promotes hypertension, activation of cytolytic natural killer cells, and vascular dysfunction in pregnant rats

Previous studies by our lab have established that placental-ischemia stimulated T-helper 17 cells (TH 17s) cause increased cytolytic natural killer (cNK) cell proliferation and activation during pregnancy; however, the exact mechanism is unknown. The objective of this study was to investigate the role of interlukin 17 (IL-17) in inducing cNK cell activation in pregnancy. We infused 150 pg/day of recombinant IL-17 into a subset of normal pregnant (NP) Sprague Dawley rats from gestation day (GD) 12-19 (NP+IL-17). On GD 19, mean arterial pressure (MAP), fetal and placental weights, cytokines, cNK cell activation, cytotoxic enzymes, and vascular reactivity were assessed. MAP significantly increased from 99 ± 3 mmHg in NP to 120 ± 1 mmHg in NP+IL-17 (P < 0.05). Fetal weight significantly decreased from 2.52 ± 0.04 g in NP to 2.32 ± 0.03 g in NP+IL-17 as did placental weight (NP: 0.65 ± 0.03 g; NP+IL-17: 0.54 ± 0.01 g, P < 0.05). Plasma levels of TNF-α increased to 281.4 ± 55.07 pg/mL in NP+IL-17 from 145.3 ± 16.03 pg/mL in NP (P < 0.05) while placental levels of VEGF decreased from 74.2 ± 6.48 pg/mg in NP to 54.2 ± 3.19 pg/mg in NP+IL-17. Total NK cells were increased in the placenta (NP: 14.3 ± 3.49%; NP+IL-17: 29.33 ± 2.76%, P < 0.05) as were cytolytic NK cells (NP: 3.31 ± 1.25%; NP+IL-17: 13.41 ± 1.81%, P < 0.05). A similar trend was observed in circulating NK cells. Plasma granzyme K increased from 3.55 ± 2.29 pg/mL in NP to 20.9 ± 7.76 pg/mL in NP+IL-17 (P < 0.05), and plasma granzyme B increased from 10.95 ± 0.64 pg/mL in NP to 14.9 ± 0.98 pg/mL in NP+IL-17(P < 0.05). In the placenta, both granzyme A (NP: 246.1 ± 16.7 pg/mg; NP+IL-17: 324.3 ± 15.07 pg/mg, P < 0.05) and granzyme B (NP: 15.18 ± 3.79 pg/mg; NP+IL-17: 27.25 ± 2.34 pg/mg, P < 0.05) increased in response to IL-17 infusion. Finally, vascular reactivity of uterine arteries was significantly impaired in response to IL-17 infusion. The results of this study suggest that IL-17 plays a significant role in the activation of cNK cells during pregnancy.

Sympathetic nervous system control of vascular function and blood pressure during pregnancy and preeclampsia

: Proper vascular tone and blood pressure regulation during pregnancy are important for immediate and long-term cardiovascular health of the mother and her offspring. Preeclampsia is clinically defined as new-onset maternal hypertension accompanied by cardiovascular, renal, and/or neural abnormalities presenting in the second half of pregnancy. There is strong evidence to support that preeclampsia is mediated by attenuations in uteroplacental vascular remodeling and increases in vasoconstriction with subsequent placental ischemia/reperfusion-induced release of hypertensive substances into the maternal circulation. These include antiangiogenic and pro-inflammatory factors. There is also evidence implicating increased sympathetic nervous system activity (SNA) in this maternal disorder, but this mostly includes data correlating severity of disease with catecholamine levels and elevated muscle SNA. These measurements have not confirmed a causative role for SNA in the pathogenesis of preeclampsia. Therefore, studies are needed to provide a comprehensive understanding of SNA and its control of vascular function and blood pressure regulation during normal pregnancy in order to set the stage for exploring the mechanisms mediating the exaggerated SNA and signaling during preeclampsia. This review examines the role of SNA in control of uteroplacental vascular tone and blood pressure regulation during normal pregnancy. Furthermore, it is proposed that over-activation of the SNA contributes to altered uteroplacental vascular tone and perfusion leading to placental ischemic events and modulates the systemic vasoconstriction and hypertensive responses to soluble placenta ischemic factors. Recognizing the integrative role and importance of SNA in the pathophysiology of preeclampsia will advance our understanding of this maternal disorder.

Developmental origins of nonalcoholic fatty liver disease as a risk factor for exaggerated metabolic and cardiovascular-renal disease

Intrauterine growth restriction (IUGR) is linked to increased risk for chronic disease. Placental ischemia and insufficiency in the mother are implicated in predisposing IUGR offspring to metabolic dysfunction, including hypertension, insulin resistance, abnormalities in glucose homeostasis, and nonalcoholic fatty liver disease (NAFLD). It is unclear whether these metabolic disturbances contribute to the developmental origins of exaggerated cardiovascular-renal disease (CVRD) risk accompanying IUGR. IUGR impacts the pancreas, adipose tissue, and liver, which are hypothesized to program for hepatic insulin resistance and subsequent NAFLD. NAFLD is projected to become the major cause of chronic liver disease and contributor to uncontrolled type 2 diabetes mellitus, which is a leading cause of chronic kidney disease. While NAFLD is increased in experimental models of IUGR, lacking is a full comprehension of the mechanisms responsible for programming of NAFLD and whether this potentiates susceptibility to liver injury. The use of well-established and clinically relevant rodent models, which mimic the clinical characteristics of IUGR, metabolic disturbances, and increased blood pressure in the offspring, will permit investigation into mechanisms linking adverse influences during early life and later chronic health. The purpose of this review is to propose mechanisms, including those proinflammatory in nature, whereby IUGR exacerbates the pathogenesis of NAFLD and how these adverse programmed outcomes contribute to exaggerated CVRD risk. Understanding the etiology of the developmental origins of chronic disease will allow investigators to uncover treatment strategies to intervene in the mother and her offspring to halt the increasing prevalence of metabolic dysfunction and CVRD.

Maternal separation enhances anticontractile perivascular adipose tissue function in male rats on a high-fat diet

Clinical studies have shown that obesity negatively impacts large arteries' function. We reported that rats exposed to maternal separation (MatSep), a model of early life stress, display enhanced angiotensin II (ANG II)-induced vasoconstriction in aortic rings cleaned of perivascular adipose tissue (PVAT) under normal diet (ND) conditions. We hypothesized that exposure to MatSep promotes a greater loss of PVAT-mediated protective effects on vascular function and loss of blood pressure (BP) rhythm in rats fed a high-fat diet (HFD) when compared with controls. MatSep was performed in male Wistar-Kyoto rats from days 2 to 14 of life. Normally reared littermates served as controls. On ND, aortic rings from MatSep rats with PVAT removed showed increased ANG II-mediated vasoconstriction versus controls; however, rings from MatSep rats with intact PVAT displayed blunted constriction. This effect was exacerbated by an HFD in both groups; however, the anticontractile effect of PVAT was greater in MatSep rats. Acetylcholine-induced relaxation was similar in MatSep and control rats fed an ND, regardless of the presence of PVAT. HFD impaired aortic relaxation in rings without PVAT from MatSep rats, whereas the presence of PVAT improved relaxation in both groups. On an HFD, immunolocalization of vascular smooth muscle-derived ANG-(1-7) and PVAT-derived adiponectin abundances were increased in MatSep. In rats fed an HFD, 24-h BP and BP rhythms were similar between groups. In summary, MatSep enhanced the ability of PVAT to blunt the heightened ANG II-induced vasoconstriction and endothelial dysfunction in rats fed an HFD. This protective effect may be mediated via the upregulation of vasoprotective factors within the adipovascular axis.

Abstract 013: Soluble Guanylate Cyclase Activators Improve Vascular Function and Attenuate Placental Ischemia-Induced Hypertension

Preeclampsia (PE) is a pregnancy specific disorder associated with maternal hypertension and endothelial dysfunction caused by the release of anti-angiogenic and pro-inflammatory factors from the ischemic placenta. In addition, PE is associated with depletion of nitric oxide (NO), which, during normal pregnancy, binds to soluble guanylate cyclase (sGC), and synthesizes cGMP, to facilitate vasodilation. A recently developed drug, sGC activators have been shown to bind to the sGC molecule and increase activity independently of NO. However, whether these drugs might have therapeutic potential in PE is not known. We tested the hypothesis that sGC activators attenuates blood pressure in a placental ischemic rat by improving vascular function. Sprague-Dawley rats underwent Sham or RUPP (Reduced Uterine Perfusion Pressure) surgery on gestational day (GD) 14, where silver clips were placed on the abdominal aorta and branches of the ovarian artery to induce placental ischemia. Animals were then placed on placebo (P) or sGC activator (80 ppm, BAY 60-2770) -supplemented (sGC-A) diets, ad libitum, from GD14-19. To determine the effect of sGC activators on vascular function, uterine arteries were isolated from Sham and RUPP operated rats and mounted on a wire myograph. Vessels were pre-constricted and vasodilation was assessed by increasing doses of the sGC activator (Cinaciguat; Sigma, St Louis, MO). On GD19, RUPP surgery had significantly increased mean arterial blood pressure as expected (Sham+P, n =6, 100±6 mmHg; RUPP+P, n =6, 117±4 mmHg; P<0.01), and was attenuated by treatment with the sGC activator (RUPP+sGC-A, n =6, 108±6 mmHg; P=0.02). Interestingly, in the presence of sGC activators (Cinaciguat), uterine arteries isolated from RUPP rats exhibited significantly improved vasodilation at doses of 1μM (Sham, n =5, 7±0.5 %; RUPP, n =3, 25±0.8 %; P<0.01) and 5μM (Sham, n =5, 7±0.5 %; RUPP, n =3, 28±1 %; P<0.01) compared to the Sham group. The results of this study demonstrate that activating sGC can reduce blood pressure by improving vascular function in the RUPP rat. In conclusion, these findings suggest there could be a therapeutic potential for treating preeclampsia with sGC activators.

Adrenergic receptor blockade attenuates placental ischemia-induced hypertension

Preeclampsia (PE), a disorder of new-onset maternal hypertension and vascular dysfunction during pregnancy, is thought to be linked to placental ischemia-induced release of prohypertensive factors and reductions of vasoprotective factors in the maternal circulation. Although markers of sympathetic nervous activity are elevated in experimental models of placental ischemia-induced hypertension and women with PE compared with their normal pregnant counterparts, the importance of adrenergic receptor signaling in the development of hypertension in PE is unknown. Therefore, we tested the hypothesis that adrenergic receptor blockade attenuates the development of placental ischemia-induced hypertension in rats. Wistar Hannover rats underwent reduced uterine perfusion pressure (RUPP) or Sham surgeries on gestational day 14. By day 19, mean arterial blood pressure (MAP) was increased in RUPP over Sham rats. Groups of RUPP and Sham pregnant rats received terazosin and propranolol (3 mg/kg per day of each via subcutaneous osmotic minipump) to block α1- and β-adrenergic receptors, respectively, beginning on gestational day 14. Adrenergic blockade significantly attenuated the development of hypertension in the RUPP rats with a slight blood pressure-lowering response in the Sham, normal pregnant rats by day 19. In conclusion, these data implicate that placental ischemia-induced hypertension involves adrenergic receptor signaling to promote increases in blood pressure during PE.

Abstract P179: Placental Ischemia-Induced Hypertension is Attenuated in Melanocortin-4 Receptor (MC4R)-Deficient Pregnant Rats

The incidence of preeclampsia (PE), a pregnancy-specific disorder of new-onset hypertension that is linked to placental ischemia, has increased over the last several decades. While obesity is a major risk factor for PE, the mechanisms whereby obesity impacts placental ischemia-induced hypertension are not fully understood. We recently reported that placental ischemia-induced hypertension is partially dependent upon an intact sympathetic nervous system (SNS). In various hypertensive models including obesity, blockade of MC4R signaling leads to increased food intake and body weight but protects against the development of hypertension via suppression of the SNS. Although blockade of MC4R may lead to increased body weight during pregnancy, we tested the hypothesis that placental ischemia-induced hypertension is attenuated in obese MC4R-deficient pregnant rats. Wild-type (WT) and MC4R heterozygous-deficient rats were mated with genotype-matched males at ~12 wks old. All rats were maintained on NIH31 chow diet. On gestational day 14, rats were subjected to chronic placental ischemia via the reduced uterine perfusion pressure (RUPP) procedure or Sham surgery. By day 19, conscious mean arterial blood pressure (MAP, carotid catheter) was elevated in RUPP WT (N=21) over Sham WT rats (N=14) (117±2 vs. 101±1 mmHg, P<0.05) with reduced average fetus (1.71±0.04 vs. 1.89±0.05 g, P<0.05) but no change in average placenta weights (0.46±0.02 vs. 0.47±0.01 g), respectively. In Sham MC4R-def vs. Sham WT, respectively, there was increased (P<0.05) body weight (366±8 vs. 337±6 g), total body fat mass (72±4 vs. 44±2 g), and circulating leptin adipokine levels (6.9±0.7 vs. 3.3±0.3 ng/mL) but with similar average fetus (1.92±0.02 vs. 1.89±0.05 g) and placenta weights (0.49±0.01 vs. 0.47±0.01 g). Even though blood pressure was elevated in Sham MC4R-def (109±2 mmHg, P<0.05) over Sham WT, the hypertensive response to RUPP was attenuated in MC4R-def rats (114±2 mmHg). RUPP did not alter leptin levels in MC4R-def rats (6.4±1 ng/mL). In conclusion, these data suggest that MC4R heterozygous-def pregnant rats are obese and have higher blood pressure during pregnancy. However, placental ischemia may require a full complement of MC4R expression to elicit a hypertensive response.

Heme oxygenase-1 is a potent inhibitor of placental ischemia-mediated endothelin-1 production in cultured human glomerular endothelial cells

Preeclampsia is a pregnancy-specific disorder of maternal hypertension and reduced renal hemodynamics linked to reduced endothelial function. Placental ischemia is thought to be the culprit of this disease, as it causes the release of factors like tumor necrosis factor (TNF)-α that induce vascular endothelin-1 (ET-1) production. Interestingly, placental ischemia-induced hypertension in rats [reduced uterine perfusion pressure (RUPP) model] is abolished by ETA receptor blockade, suggesting a critical role for ET-1. Although it has been found that systemic induction of heme oxygenase (HO)-1 is associated with reduced ET-1 production and attenuated hypertension, it is unclear whether HO-1 directly modulates the increased ET-1 response to placental factors. We tested the hypothesis that HO-1 or its metabolites inhibit ET-1 production in human glomerular endothelial cells induced by serum of RUPP rats or TNF-α. Serum (5%) from RUPP hypertensive (mean arterial blood pressure 119 ± 9 mmHg) vs. normotensive pregnant (NP, 101 ± 6 mmHg, P < 0.001) rats increased ET-1 production (RUPP 168.8 ± 18.1 pg/ml, NP 80.3 ± 22.7 pg/ml, P < 0.001, n = 12/group). HO-1 induction [25 µM cobalt photoporphyrin (CoPP)] abolished RUPP serum-induced ET-1 production (1.6 ± 0.8 pg/ml, P < 0.001), whereas bilirubin (10 µM) significantly attenuated ET-1 release (125.3 ± 5.2 pg/ml, P = 0.005). Furthermore, TNF-α-induced ET-1 production (TNF-α 31.0 ± 8.4 vs. untreated 7.5 ± 0.4 pg/ml, P < 0.001) was reduced by CoPP (1.5 ± 0.8 pg/ml, P < 0.001) and bilirubin (10.5 ± 4.3 pg/ml, P < 0.001). These results suggest that circulating factors released during placental ischemia target the maternal glomerular endothelium to increase ET-1, and that pharmacological induction of HO-1 or bilirubin could be a treatment strategy to block this prohypertensive pathway in preeclampsia.

Abstract 037: Exaggerated Placental Ischemia-induced Hypertension in Endothelin Receptor Type B (ETB)-deficient Pregnant Rats s Independent of Increased sFlt-1 or ROS Levels

While the pathogenesis of preeclampsia is not fully understood, studies implicate placental ischemia. Reduced uterine perfusion pressure (RUPP)-induced placental ischemia/hypoxia in animal models stimulates release of factors like antiangiogenic sFlt-1 into the maternal circulation increasing vascular-renal ET-1. ET-1 promotes hypertension via reactive oxygen species (ROS). Blockade of vasoconstrictive ETA abolishes RUPP hypertension. Deficiency of vasodilatory ETB in rats leads to increased blood pressure in pregnancy. While ETB deficiency markedly enhances RUPP hypertension, it is unknown if there is exaggerated RUPP-induced sFlt-1, ET-1 or ROS levels in ETB-def rats. The hypothesis was tested that placental ischemia/hypoxia-induced release of sFlt-1 and circulating ET-1 and ROS are greater in ETB-def rats. Eighteen-week-old ETB-def and transgenic (Tg) control pregnant rats were generated with Wistar Hannover males. RUPP or Sham surgeries were on gestational day 14 and assessment of plasmas and placentas at day 19. RUPP increased placental sFlt-1 (pg/mg) similarly in RUPP ETB-def (781±113, N=5) vs Sham ETB-def (573±54, N=12) and RUPP Tg (631±62, N=5) vs Sham Tg (547±31, N=12) (P<0.05). In placental explant cultures, acute hypoxia (48 h 1% O2 vs normoxia 6% O2) stimulated a comparable release of sFlt-1 (pg/mg) in Sham ETB-def (2577±135 vs 2070±78) and Sham Tg (3208±318 vs 2553±107) (P<0.05). Unexpectedly, plasma sFlt-1 (pg/mL) was lower in RUPP ETB-def (153±48) vs Sham ETB-def (476±125) and RUPP Tg (238±32) vs Sham Tg (463±102) (P<0.05). Plasma ET-1 (fmol/L) was exaggerated in RUPP ETB-def (954±70) and greater in Sham ETB-def (735±43) vs RUPP Tg (122±14) or Sham Tg (142±41) (P<0.05). Plasma H2O2 (umol/L) was not exaggerated in RUPP ETB-def (5.4±1.2) or RUPP Tg (4.0±0.5) but was greater (P<0.05) in Sham ETB-def (6.2±0.3) vs Sham Tg (3.6±0.3). In conclusion, these data suggest in 1) normal pregnancy, ETB is crucial for blood pressure control by regulating bioavailable ET-1 to prevent ROS production and 2) placental ischemia, ETB reduces excess ET-1 to buffer hypertension independently of sFlt-1 or ROS. These data support ETB physiology as important in controlling blood pressure in pregnancy and its loss in mediating hypertension in preeclampsia.

Role of Nitric Oxide Synthase on Blood Pressure Regulation and Vascular Function in Pregnant Rats on a High-Fat Diet

BACKGROUND

While obesity is a leading risk factor for preeclampsia, the mechanisms whereby obese women are more susceptible to pregnancy-induced hypertension are unclear. As high-fat diet (HFD) is an important contributor to the development of obesity, we tested the hypothesis that pregnant rats on HFD have hypertension and endothelial dysfunction due to reduced nitric oxide synthase (NOS).

METHODS

Twelve-week-old Sprague-Dawley female rats were fed normal diet (ND, 13% fat kcal) or HFD (40% fat kcal) for 9 weeks. Timed-pregnant rats were then generated and the effect of HFD on mean arterial blood pressure (MAP) and vascular function was assessed on gestational day (GD) 19.

RESULTS

MAP was not different between HFD and ND pregnant rats. Intriguingly, sensitivity to acetylcholine-induced endothelium-dependent vasorelaxation was enhanced in small mesenteric arteries of HFD dams compared to ND controls (logEC50 -7.9 ± 0.3 vs. -6.7 ± 0.3 M; P < 0.05). Additionally, HFD dams exhibited higher mesenteric artery expression of NOS3 and plasma levels of NO metabolites than ND controls (1738.0 ± 316.4 vs. 1094.0 ± 82.5 pg/mg and 72.5 ± 8.7 vs. 39.7 ± 4.5 µM, respectively; both P < 0.05). Further, to determine the role of NOS in modulating blood pressure in HFD pregnant rats, animals were treated with the nonselective inhibitor Nω-Nitro-l-arginine methyl ester hydrochloride (100 mg/l, drinking water) from GD 14 to 19. It was found that NOS inhibition increased MAP equally in HFD and ND groups.

CONCLUSIONS

Contrary to our initial hypothesis, HFD dams were normotensive and presented increased endothelial function and NO/NOS3 levels. This enhanced NOS-mediated vascular function does not appear to have a major impact on blood pressure regulation of HFD-fed pregnant rats.

Exposure to placental ischemia impairs postpartum maternal renal and cardiac function in rats

Women with a history of preeclampsia (PE) have an increased risk to develop cardiovascular and renal diseases later in life, but the mechanisms underlying this effect are unknown. In rats, we assessed whether placental ischemia results in long-term effects on the maternal cardiovascular and renal systems using the reduced uterine perfusion pressure (RUPP) model for PE. Sprague-Dawley rats received either a Sham or RUPP operation at gestational day 14 The rats were followed for 8 wk after delivery (Sham n = 12, RUPP n = 21) at which time mean arterial pressure (MAP; conscious), 24-h albuminuria, glomerular filtration rate (GFR; transcutaneous, FITC-sinistrin), and cardiac function (Vevo 770 system) were assessed. Subsequently, all rats were euthanized for mesenteric artery vasorelaxation and histology of heart and kidney. At 8 wk after delivery, there was no difference in MAP and albuminuria. However, RUPP rats showed a significantly reduced GFR [2.61 ± 0.53 vs. 3.37 ± 0.74 ml/min; P = 0.01]. Ultrasound showed comparable cardiac structure, but RUPP rats had a lower left ventricular ejection fraction (62 ± 7 vs. 69 ± 10%; P = 0.04). Heart and kidney histology was not different between Sham or RUPP rats. Furthermore, there were no differences in endothelial-dependent or -independent vasorelaxation. We show that exposure to placental ischemia in rats is accompanied by functional disturbances in maternal renal and cardiac function 8 wk after a preeclamptic pregnancy. However, these changes were not dependent on differences in blood pressure, small artery vasorelaxation, or cardiac and renal structure at this time point postpartum.

Metabolic abnormalities and obesity's impact on the risk for developing preeclampsia

Preeclampsia (PE), a hypertensive disorder of pregnancy, is increasing as a major contributor to perinatal and long-term morbidity of mother and offspring. PE is thought to originate from ischemic insults in the placenta driving the release of prohypertensive anti-angiogenic [soluble fms-like tyrosine kinase-1 (sFlt-1)] and proinflammatory [tumor necrosis factor-α (TNF-α)] factors into the maternal circulation. Whereas the increased incidence of PE is hypothesized to be largely due to the obesity pandemic, the mechanisms whereby obesity increases this risk are unknown. The maternal endothelium is targeted by placental and adipose tissue-derived factors like sFlt-1 and TNF-α that promote hypertension during pregnancy, resulting in vascular dysfunction and hypertension. Interestingly, not all obese pregnant women develop PE. Data suggest that obese pregnant women with the greatest metabolic abnormalities have the highest incidence of PE. Identifying obesity-related mechanisms driving hypertension in some obese pregnant women and pathways that protect normotensive obese pregnant women, may uncover novel protocols to treat PE. Metabolic abnormalities, such as increased circulating leptin, glucose, insulin, and lipids, are likely to increase the risk for PE in obese women. It is not only important to understand whether each of these metabolic factors contribute to the increased risk for PE in obesity, but also their cumulative effects. This is particularly relevant to obese pregnant women with gestational diabetes mellitus (GDM) where all of these factors are increased and the risk for PE is highest. It is speculated that these factors potentiate the anti-angiogenic and proinflammatory mechanisms of placental ischemia-induced vascular dysfunction thereby contributing to the increasing incidence of PE.

Abstract P175: Soluble Guanylate Cyclase Activator Attenuates Tumor Necrosis Factor- α Induced Production of Endothelin-1 from Human Glomerular Endothelial Cells

Preeclampsia (PE) is a disorder associated with maternal hypertension, endothelial dysfunction and reductions in renal hemodynamics. Placental ischemia leads to increases in circulating maternal anti-angiogenic and pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) that induce endothelin-1 (ET-1), a potent vasoconstrictor. PE is also associated with depletion of nitric oxide, a facilitator of vasodilation, which binds to soluble guanylate cyclase (sGC), and synthesizes cGMP. In addition to promoting vasodilation, sGC activators and stimulators inhibit smooth muscle proliferation, leukocyte recruitment and platelet aggregation and are therefore, currently in clinical trials for treating cardiopulmonary disease. Although it is known that activating the nitric oxide signalling pathway induces vasodilation, its ability to inhibit TNF-α induced renal glomerular endothelial ET-1 production is unknown. We tested the hypothesis that cinaciguat, a sGC activator, attenuates ET-1 production induced by TNF-α in conditionally immortalized human glomerular endothelial cells. Cells were cultured; starved for 48 h; and treated for 12 h resulting in the following 4 groups having N=6/group: 1) Untreated, 2) 10 ng TNF-α 3) 10 μM cinaciguat + 10 ng TNF-α, and 4) 20 μM cinaciguat + 10 ng TNF-α. TNF-α (10 ng, 67.25±3.2 pg/mL) significantly increased ET-1 production compared to the untreated group (43.6±4.3 pg/mL, P<0.01). Interestingly, both cinaciguat treatment groups attenuated TNF-α induced ET-1 production, with significant reductions at a higher dose (20 μM, 57.38±1.42 pg/mL, P=0.02; 10 μM, 58.6±2.32 pg/mL, P=0.07). The results of this study demonstrate that activating sGC can attenuate ET-1 production. In conclusion, these findings suggest there is a therapeutic potential for treating preeclampsia with sGC activators.

Abstract P133: Melanocortin 4 Receptor is Required for the Effect of Testosterone Supplement on Metabolic Parameters and Blood Pressure

Melanocortin 4 receptor (MC4R) activation causes appetite suppression and sympathetic nervous system activation. Blockade of MC4R increases food intake and in some cases, decreases BP. MC4R has been implicated as playing a role in obesity and hypertension. Previously we observed that testosterone supplementation in male Zucker rats improved insulin resistance and the characteristics of metabolic syndrome, but increased BP. Similarly, testosterone increases BP in male SHR, and blockade of the MC4R reduces BP in both young and old male SHR. In the present study we tested the hypothesis that testosterone supplementation (T) requires activated MC4R to attenuate metabolic parameters, and to increase BP. Male obese MC4R -/- and Wistar Hannover rats (WT) were treated with T (MC4R-KO+T vs WT+T: 22 mg/10 mm silastic pellet) or placebo (empty pellets; MC4R-KO+P, and WT+P), beginning at 10 wks of age for 6 weeks. In WT animals, T reduced body weight by 13% compared to placebo (367 gr vs 432gr; p<0.05), but had no effect on food intake (WT+P: 19±7 gr/d vs WT+T: 16±5 gr/d, n=3, p:NS). In MC4R-KO rats, body weight and food intake were similar in both placebo and T rats (BW: 555±20 gr vs 526±18 gr, and FI: 26±1 gr vs 28±2; n=3, p:NS, respectively). T reduced fat mass (measured by ECHO-MRI ® ) in WT+T by 38% compared to placebo (50±2.9 gr vs 31±3.2 gr; p<0.05); however, there was no effect on fat mass in MC4R-KO + T (149±8 gr vs 147±11 gr; n=3, p:NS). Lean mass (by ECHO-MRI ® ) was not affected by T in either MC4R-KO+T or WT+T (p:NS). Finally, unlike our previous studies in obese Zucker and SHR males, T failed to affect mean arterial pressure or heart rate (by telemetry) in MC4R-KO+T rats compared to control MC4R-KO+P (MAP: 122±2 mmHg vs 122±1 mmHg; n=3, p:NS; HR:309±5 bpm vs 320±17 bpm; n=3, p:NS). These data suggest that the effect of T on metabolic parameters and BP may be mediated at least in part by MC4R since in the absence of active MC4R, T is not able to affect either body composition or BP. Also, these data gave a potential new insight into the mechanism by which T contributes to BP control and adipose tissue regulation. More studies are necessary to clarify the role of MC4R in mediating the effects of testosterone. Supported by NIH-R01HL66072, R01HL69194, PO1HL51971 (JFR), 14POST18640015 (ROM).

Abstract 132: Adrenergic Receptor Blockade Prevents Placental Ischemia-induced Hypertension

Hypertensive disorders of pregnancy are the number one cause of pregnancy-related deaths in the United States. Preeclampsia is a disorder of maternal hypertension and cardiovascular dysfunction typically presenting in the second half of pregnancy along with fetal growth restriction. There are no steadfast therapies besides early delivery of the fetus and ischemic placenta, which releases factors into the maternal circulation promoting hypertension. Although sympathetic nervous activity was found to be increased in preeclamptic versus normal pregnant women, it is unknown if sympathetic nervous system plays a role in placental ischemia-induced hypertension. To address this question, we tested the hypothesis that adrenergic receptor blockade prevents placental ischemia-induced hypertension. Wistar rats were randomized to receive reduced uterine perfusion pressure, (RUPP, n=6) or Sham (n=5) surgeries on gestational day 14 and examined at day 19. In RUPP vs Sham rats, respectively, mean arterial blood pressure (115 ± 4 vs 103 ±2 mmHg, P<0.05) and the number of absorbed fetuses (6 ± 1 vs 1 ± 1, P<0.05) were greater whereas average fetal weight was lower (1.7 ± 0.1 vs 2.0 ± 0.2, P<0.05) with similar placental weights (0.49 ± 0.03 vs 0.52 ± 0.03). In RUPP vs Sham rats, renal cortical norepinephrine content (HPLC) was higher (183 ± 15 vs 150 ± 8 pg/mg wet weight, P<0.05) and vasoconstriction to phenylephrine was greater in small, third order mesenteric arteries (Emax: 262 ± 19 vs 160 ± 26% of KCl response). A subset of RUPP rats (n=3) received terazosin and propranolol (3 mg/kg per day each, subcutaneous osmotic minipump) to block alpha- and beta-adrenergic receptors, respectively, beginning the day of RUPP surgery. At day 19, adrenergic blockade prevented the development of hypertension (100 ± 4 mmHg, P<0.05) and did not alter number of fetal absorptions (8 ± 1). Average fetal weight was higher (2 ± 0.1, P<0.05) and placental weight lower (0.41 ± 0.03, P<0.05) compared to the untreated RUPP rats. In conclusion, placental ischemia-induced hypertension depends on activation of the sympathetic nervous system. The mechanism for this enhanced sympathetic nerve activity is unknown but may involve factors released from the ischemic placenta.

Nitric oxide synthase-mediated blood pressure regulation in obese melanocortin-4 receptor-deficient pregnant rats

Although obesity increases the risk for hypertension in pregnancy, the mechanisms responsible are unknown. Increased nitric oxide (NO) production results in vasodilation and reduced blood pressure during normal pregnancy in lean rats; however, the role of NO is less clear during obese pregnancies. We examined the impact of obesity on NO synthase (NOS)-mediated regulation of blood pressure during pregnancy by testing the hypothesis that NOS activity, expression, and regulation of vascular tone and blood pressure are reduced in obese pregnant rats. At gestational day 19, melanocortin-4 receptor (MC4R)-deficient obese rats (MC4R) had greater body weight and fat mass with elevated blood pressure and circulating sFlt-1 levels compared with MC4R pregnant rats. MC4R pregnant rats also had less circulating cGMP levels and reduced total NOS enzymatic activity and expression in mesenteric arteries. Despite decreased biochemical measures of NO/NOS in MC4R rats, NOS inhibition enhanced vasoconstriction only in mesenteric arteries from MC4R rats, suggesting greater NOS-mediated tone. To examine the role of NOS on blood pressure regulation in obese pregnant rats, MC4R and MC4R pregnant rats were administered the nonselective NOS inhibitor N^G-nitro-l-arginine methyl ester (l-NAME, 100 mg/l) from gestational day 14 to 19 in drinking water. The degree by which l-NAME raised blood pressure was similar between obese and lean pregnant rats. Although MC4R obese pregnant rats had elevated blood pressure associated with reduced total NOS activity and expression, they had enhanced NOS-mediated attenuation of vasoconstriction, with no evidence of alterations in NOS-mediated regulation of blood pressure.

Placental Growth Factor Administration Abolishes Placental Ischemia-Induced Hypertension

Preeclampsia is a pregnancy-specific disorder of new-onset hypertension. Unfortunately, the most effective treatment is early delivery of the fetus and placenta. Placental ischemia appears central to the pathogenesis of preeclampsia because placental ischemia/hypoxia induced in animals by reduced uterine perfusion pressure (RUPP) or in humans stimulates release of hypertensive placental factors into the maternal circulation. The anti-angiogenic factor soluble fms-like tyrosine kinase-1 (sFlt-1), which antagonizes and reduces bioavailable vascular endothelial growth factor and placental growth factor (PlGF), is elevated in RUPP rats and preeclampsia. Although PlGF and vascular endothelial growth factor are both natural ligands for sFlt-1, vascular endothelial growth factor also has high affinity to VEGFR2 (Flk-1) causing side effects like edema. PlGF is specific for sFlt-1. We tested the hypothesis that PlGF treatment reduces placental ischemia-induced hypertension by antagonizing sFlt-1 without adverse consequences to the mother or fetus. On gestational day 14, rats were randomized to 4 groups: normal pregnant or RUPP±infusion of recombinant human PlGF (180 μg/kg per day; AG31, a purified, recombinant human form of PlGF) for 5 days via intraperitoneal osmotic minipumps. On day 19, mean arterial blood pressure and plasma sFlt-1 were higher and glomerular filtration rate lower in RUPP than normal pregnant rats. Infusion of recombinant human PlGF abolished these changes seen with RUPP along with reducing oxidative stress. These data indicate that the increased sFlt-1 and reduced PlGF resulting from placental ischemia contribute to maternal hypertension. Our novel finding that recombinant human PlGF abolishes placental ischemia-induced hypertension, without major adverse consequences, suggests a strong therapeutic potential for this growth factor in preeclampsia.

Dahl SS rats demonstrate enhanced aortic perivascular adipose tissue-mediated buffering of vasoconstriction through activation of NOS in the endothelium

Perivascular adipose tissue (PVAT) mediates buffering of vasoconstriction through activation of endothelium-derived factors. We hypothesized that the PVAT of Dahl salt-sensitive (Dahl SS) rats has reduced ability to buffer vasoconstriction. Vascular reactivity experiments were performed on aortic rings with PVAT intact (+PVAT) or removed (-PVAT), and endothelium intact (+ENDO) or removed (-ENDO) from Dahl SS rats and control SS.13(BN) rats (Dahl SS rats that have had chromosome 13 completely replaced with that of the Brown Norway rat, rendering this strain insensitive to high-salt or high-fat diet-induced hypertension). Endothelial dysfunction, assessed by ACh-mediated vasorelaxation, was confirmed in aortic rings of Dahl SS rats. The +PVAT+ENDO aortic rings had indistinguishable phenylephrine-induced vasoconstriction between genotypes. In both strains, removal of PVAT significantly enhanced vasoconstriction. Dahl SS rat -PVAT+ENDO aortic rings displayed exaggerated vasoconstriction to phenylephrine vs. SS.13(BN) rats, indicating that PVAT-mediated buffering of vasoconstriction was greater in Dahl SS rats. Removal of both the ENDO and PVAT restored vasoconstriction in both strains. The nitric oxide synthase (NOS) inhibitor, N(ω)-nitro-L-arginine methyl ester (L-NAME), produced a similar effect as that seen with -ENDO. These data indicate that the function of the PVAT to activate endothelium-derived NOS is enhanced in Dahl SS compared with SS.13(BN) rats and, most likely, occurs through a pathway that is distinct from ACh-mediated activation of NOS. PVAT weight and total PVAT leptin levels were greater in Dahl SS rats. Leptin induced a significantly decreased vasoconstriction in -PVAT+ENDO aortic rings from Dahl SS rats, but not SS.13(BN) rats. In contrast to our initial hypothesis, PVAT in Dahl SS rats buffers vasoconstriction by activating endothelial NOS via mechanisms that may include the involvement of leptin. Thus, the PVAT serves a vasoprotective role in Dahl SS rats on normal-salt diet.

Immune Mechanisms Linking Obesity and Preeclampsia

Preeclampsia (PE) is characterized by hypertension occurring after the twentieth week of pregnancy. It is a significant contributor to maternal and perinatal morbidity and mortality in developing countries and its pervasiveness is increasing within developed countries including the USA. However, the mechanisms mediating the pathogenesis of this maternal disorder and its rising prevalence are far from clear. A major theory with strong experimental evidence is that placental ischemia, resulting from inappropriate remodeling and widening of the maternal spiral arteries, stimulates the release of soluble factors from the ischemic placenta causing maternal endothelial dysfunction and hypertension. Aberrant maternal immune responses and inflammation have been implicated in each of these stages in the cascade leading to PE. Regarding the increased prevalence of this disease, it is becoming increasingly evident from epidemiological data that obesity, which is a state of chronic inflammation in itself, increases the risk for PE. Although the specific mechanisms whereby obesity increases the rate of PE are unclear, there are strong candidates including activated macrophages and natural killer cells within the uterus and placenta and activation in the periphery of T helper cells producing cytokines including TNF-α, IL-6 and IL-17 and the anti-angiogenic factor sFlt-1 and B cells producing the agonistic autoantibodies to the angiotensin type 1 receptor (AT1-aa). This review will focus on the immune mechanisms that have been implicated in the pathogenesis of hypertension in PE with an emphasis on the potential importance of inflammatory factors in the increased risk of developing PE in obese pregnancies.

Increased risk for the development of preeclampsia in obese pregnancies: weighing in on the mechanisms

Preeclampsia (PE) is a pregnancy-specific disorder typically presenting as new-onset hypertension and proteinuria. While numerous epidemiological studies have demonstrated that obesity increases the risk of PE, the mechanisms have yet to be fully elucidated. Growing evidence from animal and human studies implicate placental ischemia in the etiology of this maternal syndrome. It is thought that placental ischemia is brought about by dysfunctional cytotrophoblast migration and invasion into the uterus and subsequent lack of spiral arteriole widening and placental perfusion. Placental ischemia/hypoxia stimulates the release of soluble placental factors into the maternal circulation where they cause endothelial dysfunction, particularly in the kidney, to elicit the clinical manifestations of PE. The most recognized of these factors are the anti-angiogenic sFlt-1 and pro-inflammatory TNF-α and AT1-AA, which promote endothelial dysfunction by reducing levels of the provasodilator nitric oxide and stimulating production of the potent vasoconstrictor endothelin-1 and reactive oxygen species. We hypothesize that obesity-related metabolic factors increase the risk for developing PE by impacting various stages in the pathogenesis of PE, namely, 1) cytotrophoblast migration and placental ischemia; 2) release of soluble placental factors into the maternal circulation; and 3) maternal endothelial and vascular dysfunction. This review will summarize the current experimental evidence supporting the concept that obesity and metabolic factors like lipids, insulin, glucose, and leptin affect placental function and increase the risk for developing hypertension in pregnancy by reducing placental perfusion; enhancing placental release of soluble factors; and by increasing the sensitivity of the maternal vasculature to placental ischemia-induced soluble factors.

Abstract 049: Preeclampsia in the Dahl Salt Sensitive Rat is Associated with Increased Uterine Artery Resistance and Reduced Placental Microvascular Density

We showed that the Dahl salt sensitive (Dahl S) rat is a spontaneous model of preeclampsia superimposed on chronic kidney disease and hypertension. This model exhibits intrauterine growth restriction, decreased pup weight, increased fetal death, and placental hypoxia; however, the underlying mechanisms are unknown. We hypothesized that a pathological remodeling and rarefaction in the maternal placental bed drives the development of preeclampsia in this model. Pregnant Dahl S and Sprague-Dawley (SD) rats were used in this study. Uterine artery resistance index (UARI) was calculated via Doppler ultrasound (Vevo 770) on day 18 of pregnancy (UARI=(peak systolic flow velocity - end diastolic flow velocity)/ peak systolic flow velocity). On day 20 of pregnancy, placentas were perfused through the uterine circulation with a silicon-polymer contrast (Microfil MV122). Individual placentas were then excised, scanned using a micro-CT scanner (SkyScan 1076), and 3D reconstructed for analysis and quantification of the placental vasculature on the maternal side. Microvascular density was calculated for vessels of diameters in the 0-500 μm ranges. UARI was higher in the Dahl S compared to the SD (0.71±0.02 vs 0.51±0.02, n=4-12, p<0.05). Density of placental microvessels in the 200-500 μm range was significantly decreased in placentas from Dahl S rats, and we observed a strong trend towards a decrease in density of microvessels in the 0-200 μm range (n=3-5, Figure). These results suggest that the impaired fetal growth and placental hypoxia in the Dahl S rat may be mediated by insufficient placental vascularization and reduced blood flow to the feto-placental unit.

Abstract P613: The Effect of Metabolic Factors on Hypoxia-Induced sFlt-1 Secretion in Rat Placental Villi

Although the etiology of preeclampsia (PE) remains unclear, evidence indicates that impaired trophoblast invasion followed by placental ischemia/hypoxia promotes the release of placental anti-angiogenic factors, such as soluble fms-like tyrosine kinase-1 (sFlt-1), into the maternal circulation. sFlt-1 blocks the pro-angiogenic actions of vascular endothelial growth factor to elicit maternal endothelial dysfunction and ultimately hypertension. Obesity is a major risk factor for PE. In addition, increased circulating metabolic factors, such as leptin and insulin have been associated with PE. However, the mechanisms whereby obesity and its related metabolic factors increase the risk for the development of PE are unknown. The aim of this study was to evaluate whether chronic leptin or insulin exposure exacerbate hypoxia-induced sFlt-1 secretion from rat placental villi. In order to address this question, placental villous explants were isolated from placentas of normal pregnant rats (n=4, 3 placentas per rat) and pregnant rats treated with either leptin (0.5 mg/kg/min i.p.; n=3, 3 placentas per rat) or insulin (1.5 mU/kg/min s.c.) supplemented with 20% glucose in drinking water (n=3, 3 placentas per rat) from gestational day 14 to 19. Placental explants were then incubated for 48 h at 37 °C under normoxia (6% O2) or hypoxia (1% O2) and sFlt-1 secretion in cultured media was measured by ELISA. While hypoxia significantly enhanced sFlt-1 release of explants from normal pregnant rats compared with normoxia (3224±224 vs 4251±236 pg/mg; P<0.05), explants from chronic hyperleptinemic (3197±178 vs. 3762±317 pg/mg) or euglycemic hyperinsulinemic (4066±186 vs. 4251±213 pg/mg) pregnant rats secreted similar sFlt-1 levels under normoxic and hypoxic conditions, respectively. Additionally, chronic leptin or insulin treatments did not exacerbate the effect of hypoxia on sFlt-1 release. In conclusion, our in vitro studies with placental villi from chronic hyperleptinemic or euglycemic hyperinsulinemic pregnant rats showed no exacerbation of hypoxia-induced sFlt-1 secretion.

Abstract 038: Placental Growth Factor Supplementation Abolishes Placental Ischemia-induced Hypertension

Preeclampsia (PE) is a pregnancy-specific disorder of new-onset hypertension. Unfortunately, the most effective treatment is early delivery of the fetus and placenta. Progress toward potential therapeutic targets has found that placental ischemia/hypoxia induced in animals by reduced uterine perfusion pressure (RUPP) or in human patients stimulates the release of hypertensive placental factors into the maternal circulation. For example, the antiangiogenic factor sFlt-1, which antagonizes and reduces bioavailable vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), is significantly elevated in PE patients and RUPP rats. It is clear that reductions in VEGF promote hypertension in RUPP rats as supplementation with recombinant VEGF at 180 ug/kg/day abolished the hypertension. However, it is unknown if reductions in PlGF levels also contribute to the hypertensive response. Thus, we tested the hypothesis that PlGF treatment would reduce placental ischemia-induced hypertension. On gestational day 14, Sprague Dawley rats were randomized to three groups: normal pregnant (NP, N=6), RUPP (N=5) and RUPP + 180 ug/kg/day PlGF (N=7). The rPlGF (AG31, a purified-recombinant human PlGF) was infused via i.p. osmotic minipump. Mean arterial blood pressure (MAP, carotid catheter) and pregnancy weights were assessed on day 19. MAP was significantly higher in RUPP than NP rats (123±4 vs. 104±1, P<0.05). PlGF reversed these levels to NP values (105±3, P<0.05 vs. RUPP). Placental weights (NP: 0.5±0.02; RUPP: 0.51±0.04; and RUPP+rPlGF: 0.5±0.05) and fetal weights (NP: 2.30±0.07; RUPP: 2.00±0.15; and RUPP+rPlGF: 2.09±0.07) were similar among all groups. The number of live fetuses was reduced in RUPP than NP rats (5±2 vs. 12±1, P<0.05) with a slight increase in the RUPP+rPlGF group (8±1). The number of fetal absorptions was increased in RUPP than NP rats (9±2 vs. 2±1, P<0.05) with a slight increase in the RUPP+rPlGF group (5±1). In conclusion, these data indicate that the reductions in PlGF that occur as a result of placental ischemia contribute to the development of maternal hypertension. Our novel finding that rPlGF abolishes placental ischemia-induced hypertension suggests a strong role and therapeutic potential for this growth factor in PE.