Preeclampsia (PE) is a disorder prevalent in 5-7% of pregnancies. It is characterized by maternal hypertension and endothelial dysfunction. While it has been shown that systolic and diastolic function is impaired in women with PE, the exact mechanisms responsible for the cardiac dysfunction in PE have yet to be fully elucidated. PE is thought to develop in response to placental ischemia and ultimately the release of anti-angiogenic and pro-inflammatory factors into the maternal circulation. However, the impact of placental ischemia on cardiac function is unclear. Therefore the aim of this study was to assess cardiac structure and function in response to placental ischemia utilizing the Reduced Uterine Perfusion Pressure (RUPP) rat model. Briefly in this model, silver clips are placed on the abdominal aorta and branches of the ovarian arteries on gestational day (GD) 14 to induce placental ischemia. For this study, the RUPP ( n =8) group underwent surgery on GD 14, and both normal pregnant (NP, n =8) and RUPP rats had carotid catheters placed on GD 18. Blood pressure and echocardiography measurements, and tissue harvest were performed on GD 19. The RUPP group had significantly increased mean arterial pressure compared to the NP group on GD 19 (123±3 vs. 97±2 mmHg, P<0.01). RUPP rats had lower mean left ventricular ejection fraction (60±2 vs. 78±2 %, P<0.01) and fractional shortening (46±3 vs. 56±1 %, P=0.05), in addition to cardiac hypertrophy (0.97±0.04 vs. 0.91±0.02 g, P=0.02). These data were accompanied by increased cardiomyocyte surface area (348±36 vs. 289±23 μm 2 , P=0.03). In conclusion, this study shows that the RUPP rat develops cardiac structural and functional abnormalities after only five days of placental ischemia. Furthermore, these data suggest that the RUPP model could be useful in investigating and understanding the mechanisms which underpin these cardiac changes in PE patients.
Mildly elevated circulating unconjugated bilirubin (UCB) is associated with protection against hypertension and ischemic heart disease. We assessed whether endogenously elevated bilirubin in Gunn rats modifies cardiovascular function and resistance to ischemic insult. Hearts were assessed ex vivo (Langendorff perfusion) and in vivo (Millar catheterization and echocardiography), and left ventricular myocardial gene expression was measured via quantitative real-time PCR. Ex vivo analysis revealed reduced intrinsic contractility in the Gunn myocardium (+dP/d t: 1,976 ± 622 vs. 2,907 ± 334 mmHg/s, P < 0.01; −dP/d t: −1,435 ± 372 vs. −2,234 ± 478 mmHg/s, P < 0.01), which correlated positively with myocardial UCB concentration ( P < 0.05). In vivo analyses showed no changes in left ventricular contractile parameters and ejection (fractional shortening and ejection fraction). However, Gunn rats exhibited reductions in the rate of aortic pressure development (3,008 ± 461 vs. 4,452 ± 644 mmHg/s, P < 0.02), mean aortic velocity (439 ± 64 vs. 644 ± 62 mm/s, P < 0.01), and aortic volume time integral pressure gradient (2.32 ± 0.65 vs. 5.72 ± 0.74 mmHg, P < 0.01), in association with significant aortic dilatation (12–24% increase in aortic diameter, P < 0.05). Ex vivo Gunn hearts exhibited improved ventricular function after 35 min of ischemia and 90 min of reperfusion (63 ± 14 vs. 35 ± 12%, P < 0.01). These effects were accompanied by increased glutathione peroxidase and reduced superoxide dismutase and phospholamban gene expression in Gunn rat myocardium ( P < 0.05). These data collectively indicate that hyperbilirubinemia in Gunn rats 1) reduces intrinsic cardiac contractility, which is compensated for in vivo; 2) induces aortic dilatation, which may beneficially influence aortic ejection velocities and pressures; and 3) may improve myocardial stress resistance in association with beneficial transcriptional changes. These effects may contribute to protection from cardiovascular disease with elevated bilirubin.
Preeclampsia (PE) is a disorder prevalent in 5–7% of pregnancies. It is characterized by maternal hypertension and endothelial dysfunction. PE is thought to develop in response to impaired spiral artery remodelling of the placenta, which leads to placental ischemia and ultimately the release of anti‐angiogenic and pro‐inflammatory factors into the maternal circulation. More recently, it has been shown that cardiac function is impaired in women with PE, including hypertrophy and, systolic and diastolic dysfunction, with symptoms persisting one year post‐partum. In addition to the significant health risks imposed during pregnancy, multiple studies report increased risk of cardiovascular disease for mother and baby later in life. The placental factors, sFlt‐1 and TNF‐α, have been shown to play a role in cardiac dysfunction and the structural abnormalities seen during PE, however, the mechanisms remain unclear. Therefore, it is important to utilise an appropriate model of PE to assess cardiac function and investigate mechanisms of cardiac dysfunction, such as the Reduced Uterine Perfusion Pressure (RUPP) model, where silver clips are placed on the abdominal aorta and branches of the ovarian arteries to induce placental ischemia. We have previously reported that the RUPP model has many of the characteristics seen in women with PE. The aim of this study was to assess cardiac structure and function in RUPP rats during pregnancy and post‐partum to discern any similarities to the human condition. A normal pregnant (NP, n =8) and RUPP ( n =8) group was included in this study. The RUPP group underwent surgery on gestational day (GD) 14 for placement of silver clips. Both the NP and RUPP rats had carotid catheters placed on GD 18, and all initial blood pressure and echocardiography measurements were made on GD 19. A second echocardiography analysis was performed 3 months post‐partum. The RUPP group had significantly increased mean arterial pressure compared to the NP group on GD 19 (123 ± 3 vs. 97 ± 2 mmHg, P<0.01). RUPP hearts also showed reductions in ejection fraction (60 ± 2 vs. 78 ± 2 %, P<0.01) and fractional shortening (46 ± 3 vs. 56 ± 1 %, P=0.05), in addition to cardiac hypertrophy (0.97 ± 0.04 vs.0.91 ± 0.02 g, P=0.02). Interestingly, systolic dysfunction was persistent post‐partum in RUPP hearts, where ejection fraction (67 ± 3 vs.76 ± 2 %, P<0.01) and fractional shortening (50 ± 5 vs. 56 ± 2 %, P=0.05) remained impaired. In conclusion, cardiac dysfunction is present in the RUPP model during pregnancy and post‐partum. Therefore, this model could be useful in understanding the mechanisms which underpin the cardiac structural and functional abnormalities seen in PE patients. Support or Funding Information This study was funded by the NIH (HL51971).
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.
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 ET A 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.
Placental ischemia in preeclampsia (PE) results in hypertension and intrauterine growth restriction (IUGR). Stimulation of soluble guanylate cyclase (sGC) reduces blood pressure in the clinically relevant reduced uterine perfusion pressure (RUPP) rat model of PE, implicating involvement in RUPP-induced hypertension. However, the contribution of sGC in the development of IUGR in PE is not known. Thus, this study demonstrated the efficacy of Riociguat, an sGC stimulator, in IUGR reversion in the RUPP rat model of PE, and tested the hypothesis that improvement in fetal weight occurs in association with improvement in placental perfusion, placental morphology, and placental nutrient transport protein expression. Sham or RUPP surgery was performed at gestational day 14 (G14) with administration of vehicle (Sham or RUPP) or the sGC stimulator (Riociguat, 10 mg/kg/day sc; sGC-treated) until G20. Fetal weight was reduced (P = 0.004) at G20 in RUPP but not in sGC-treated RUPP compared with Sham, the control group. At G20, uterine artery resistance index (UARI) was increased (P = 0.010) in RUPP, indicating poor placental perfusion; proportional junctional zone surface area was elevated (P = 0.035), indicating impaired placental development. These effects were ameliorated in sGC-treated RUPP. Placental protein expression of nutrient transporter heart fatty acid-binding protein (hFABP) was increased (P = 0.008) in RUPP but not in sGC-treated RUPP, suggesting a compensatory mechanism to maintain normal neurodevelopment. Yet, UARI (P < 0.001), proportional junctional zone surface area (P = 0.013), and placental hFABP protein expression (P = 0.008) were increased in sGC-treated Sham, suggesting a potential adverse effect of Riociguat. Collectively, these results suggest sGC contributes to IUGR in PE.
Cardiovascular Disease (CVD) is the world’s greatest killer, claiming the lives of around 17.2 million men and women per year. Bilirubin is a novel antioxidant, which has been cited to reduce ischemia‐reperfusion injury in various tissues; however research into cardiac ischemia‐reperfusion injury is yet to be completed. The aim of this research was to determine whether exogenous bilirubin is capable of reducing ischemia‐reperfusion injury, in the heart. Young male (12 weeks old) Wistar isolated rat hearts were treated with bilirubin (50mM) for a period of 30 minutes before (Pre) or after (Post) a 30 minute no flow ischemic period. As well as functional recovery, tissue damage was measured by collecting effluent samples and quantifying infarct size. The left atria was removed from each heart after their respective treatment periods to allow analysis, through Pearson's correlation, of recovery and bilirubin concentration in the tissue. Diastolic pressure in both Pre and Post treated hearts was most significantly reduced after 90 minutes of reperfusion (Control, 81.01±14.73 mmHg, Pre, 58.92±14.23 mmHg, Post, 64.74±13.21 mmHg). The pre‐treated hearts revealed a significant recovery in left ventricular developed pressure (LVDP) in comparison to controls (Control, 34.72±12.67 %, Pre, 54.32±12.87 %). In addition, biomarkers of tissue damage, as well as infarct area, were significantly reduced in both pre‐treated and post‐treated hearts, in comparison to controls. Although the mechanisms are still unclear, this data suggests that bilirubin loading on the heart, either before or after ischemic insult, can preserve heart tissue and function.
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