CD4+ T Cells Play a Critical Role in Mediating Hypertension in Response to Placental Ischemia

Reduced uterine perfusion pressure as a model for preeclampsia and fetal growth restriction in murine: a systematic review and meta-analysis

The reduced uterine perfusion pressure (RUPP) model is frequently used to study preeclampsia and fetal growth restriction. An improved understanding of influential factors might improve reproducibility and reduce animal use considering the variability in RUPP phenotype. We performed a systematic review and meta-analysis by searching Medline and Embase (until 28 March, 2023) for RUPP studies in murine. Primary outcomes included maternal blood pressure (BP) or proteinuria, fetal weight or crown-rump length, fetal reabsorptions, or antiangiogenic factors. We aimed to identify influential factors by meta-regression analysis. We included 155 studies. Our meta-analysis showed that the RUPP procedure results in significantly higher BP (MD = 24.1 mmHg; [22.6; 25.7]; n = 148), proteinuria (SMD = 2.3; [0.9; 3.8]; n = 28), fetal reabsorptions (MD = 50.4%; [45.5; 55.2]; n = 42), circulating soluble FMS-like tyrosine kinase-1 (sFlt-1) (SMD = 2.6; [1.7; 3.4]; n = 34), and lower fetal weight (MD = -0.4 g; [-0.47; -0.34]; n = 113. The heterogeneity (variability between studies) in primary outcomes appeared ≥90%. Our meta-regression identified influential factors in the method and time point of BP measurement, randomization in fetal weight, and type of control group in sFlt-1. The RUPP is a robust model considering the evident differences in maternal and fetal outcomes. The high heterogeneity reflects the observed variability in phenotype. Because of underreporting, we observed reporting bias and a high risk of bias. We recommend standardizing study design by optimal time point and method chosen for readout measures to limit the variability. This contributes to improved reproducibility and thereby eventually improves the translational value of the RUPP model.

Placental CD4+ T cells from preeclamptic patients cause autoantibodies to the angiotensin II type I receptor and hypertension in a pregnant rat model of preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy associated with activated CD4+ T cells and autoantibodies to angiotensin II type 1 receptor (AT1-AA). We have previously shown that CD4+ T cells isolated from women with PE cause hypertension, increased tumor necrosis factor alpha (TNF-α), endothelin-1, and soluble fms-like tyrosine kinase-1 (sFlt-1) when injected into pregnant nude-athymic rats compared to CD4+ T cells from normal pregnant (NP) women. However, the role of PE CD4+ T cells to cause AT1-AA as a mechanism of hypertension is not known. Aim: Our goal was to determine if PE CD4+ T cells stimulate AT1-AA in pregnant nude-athymic rats. CD4+ T cells were isolated from human NP and PE placentasand injected into nude-athymic rats on gestational day (GD) 12. In order to examine the role of the PE CD4+ T cells to stimulate B cell secretion of AT1-AA, a subset of the rats receiving PE CD4+ T cells were treated with rituximab on GD 14 or anti-CD40 ligand (anti-CD40L) on GD 12. On GD 19, mean arterial pressure (MAP) and tissues were obtained MAP [114 ± 1 mmHg (n = 9)] and AT1-AA [19.8 ± 0.9 beats per minute (bpm, n = 4)] were increased in NP nude + PE CD4+ T cells compared to NP nude + NP CD4+ T cells [98 ± 2 mmHg (n = 7, P < 0.05) and 1.3 ± 0.9 bpm (n = 5, P < 0.05)]. Rituximab (103 ± 2 mmHg, n = 3, P < 0.05) and anti-CD40L (102 ± 1 mmHg, n = 3, P < 0.05) lowered MAP compared to NP nude + PE CD4+ T cells. Circulating a proliferation-inducing ligand (APRIL) and placental angiotensin-converting enzyme 2 (ACE-2) activity was increased in response to PE CD4+ T cells. These results show that placental CD4+ T cells play an important role in the pathophysiology of PE, by activating B cells secreting AT1-AA to cause hypertension during pregnancy.

Progesterone Induced Blocking Factor Reduces Hypertension and Placental Mitochondrial Dysfunction in Response to sFlt-1 during Pregnancy

Preeclampsia (PE) is characterized by new onset hypertension in association with placental ischemia, reduced fetal weight, elevated soluble fms-like tyrosine kinase-1 (sFlt-1), and placental mitochondrial (mt) dysfunction and oxidative stress (ROS). Progesterone induced blocking factor (PIBF) is a product of progesterone signaling that blocks inflammatory processes and we have previously shown PIBF to lower mean arterial blood pressure (MAP) and sFlt-1 in a rat model of PE. Infusion of sFlt-1 causes hypertension and many characteristics of PE in pregnant rodents, however, its role in causing mt dysfunction is unknown. Therefore, we hypothesize that PIBF will improve mt function and MAP in response to elevated sFlt-1 during pregnancy. We tested our hypothesis by infusing sFlt-1 via miniosmotic pumps in normal pregnant (NP) Sprague-Dawley rats (3.7 μg·kg-1·day-1) on gestation days (GD) 13-19 in the presence or absence of PIBF (2.0 µg/mL) injected intraperitoneally on GD 15 and examined mean arterial blood pressure (MAP) and placental mt ROS on GD 19. sFlt-1 increased MAP to 112 + 2 (n = 11) compared to NP rats (98 + 2 mmHg, n = 15, p < 0.05), which was lowered in the presence of sFlt-1 (100 + 1 mmHg, n = 5, p < 0.05). Placental mtATP was reduced in sFlt-1 infused rats versus NP controls, but was improved with PIBF. Placental mtROS was elevated with sFlt-1 compared to NP controls, but was reduced with PIBF. Sera from NP + sFlt-1 increased endothelial cell mtROS, which was attenuated with PIBF. These data demonstrate sFlt-1 induced HTN during pregnancy reduces placental mt function. Importantly, PIBF improved placental mt function and HTN, indicating the efficacy of improved progesterone signaling as potential therapeutics for PE.

Adoptive transfer of placental ischemia-stimulated natural killer cells causes a preeclampsia-like phenotype in pregnant rats

PROBLEM

The Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia recapitulates many characteristics of preeclampsia including maternal hypertension, intrauterine growth restriction (IUGR), and increased cytolytic natural killer cells (cNKs). While we have previously shown a 5-fold higher cytotoxicity of RUPP NKs versus normal pregnant NKs, their role in RUPP pathophysiology remains unclear. In this study, we tested the hypotheses that (1) adoptive transfer of RUPP-stimulated NKs will induce maternal hypertension and IUGR in normal pregnant control (Sham) rats and (2) adoptive transfer of Sham NKs will attenuate maternal hypertension and IUGR in RUPP rats.

METHOD OF STUDY

On gestation day (GD)14, vehicle or 5 × 106 RUPP NKs were infused i.v. into a subset of Sham rats (Sham+RUPP NK), and vehicle or 5 × 106 Sham NKs were infused i.v. into a subset of RUPP rats (RUPP+Sham NK; n = 12/group). On GD18, Uterine Artery Resistance Index (UARI) was measured. On GD19, mean arterial pressure (MAP) was measured, animals were sacrificed, and blood and tissues were collected for analysis.

RESULTS

Adoptive transfer of RUPP NKs into Sham rats resulted in elevated NK activation, UARI, placental oxidative stress, and preproendothelin expression as well as reduced circulating nitrate/nitrite. This led to maternal hypertension and IUGR. RUPP recipients of Sham NKs demonstrated normalized NK activation, sFlt-1, circulating and placental VEGF, and UARI, which led to improved maternal blood pressure and normal fetal growth.

CONCLUSION

These data suggest a direct role for cNKs in causing preeclampsia pathophysiology and a role for normal NKs to improve maternal outcomes and IUGR during late gestation.

CD4+ T cells cause renal and placental mitochondrial oxidative stress as mechanisms of hypertension in response to placental ischemia

The reduced uterine perfusion pressure (RUPP) rat model and normal pregnant (NP) rat recipients of RUPP CD4+ T cells recapitulate many characteristics of preeclampsia such as hypertension and oxidative stress. We have shown an important hypertensive role for natural killer (NK) cells to cause mitochondrial dysfunction in RUPP rats; however, the role for RUPP CD4+ T cells to stimulate NK cells is unknown. Therefore, we hypothesized that RUPP-induced CD4+ T cells activate NK cells to cause mitochondrial dysfunction/reactive oxygen species (ROS) as mechanisms of hypertension during pregnancy. We tested our hypothesis by adoptive transfer of RUPP CD4+ T cells into NP rats or by inhibiting the activation of RUPP CD4+ T cells with Orencia (abatacept) and examining hypertension, NK cells, and mitochondrial function. RUPP was performed on gestation day (GD) 14, and splenic CD4+ T cells were isolated on GD 19 and injected into NP rats on GD 13. In a separate group of rats, Orencia was infused and the RUPP procedure was performed. Mean arterial pressure and placental and renal mitochondrial ROS increased in RUPP (n = 7, P < 0.05) and NP + RUPP CD4+ T-cell recipients (n = 13, P < 0.05) compared with control NP (n = 7) and NP + NP CD4+ T-cell recipients (n = 5) but was reduced with Orencia (n = 13, P < 0.05). Placental and renal respiration was reduced in RUPP (n = 6, P < 0.05) and NP + RUPP CD4+ T-cell recipients (n = 6, state 3 P < 0.05) compared with NP (n = 5) and NP + NP CD4+ T-cell recipients (n = 5) but improved with Orencia (n = 9, n = 8 P < 0.05). These data indicate that CD4+ T cells, independent of NK cells, cause mitochondrial dysfunction/ROS contributing to hypertension in response to placental ischemia during pregnancy.

Neurodevelopmental Outcomes of Prenatal Preeclampsia Exposure

Preeclampsia is a dangerous hypertensive disorder of pregnancy with known links to negative child health outcomes. Here, we review epidemiological and basic neuroscience work from the past several decades linking prenatal preeclampsia to altered neurodevelopment. This work demonstrates increased rates of neuropsychiatric disorders [e.g., increased autism spectrum disorder, attention deficit hyperactivity disorder (ADHD)] in children of preeclamptic pregnancies, as well as increased rates of cognitive impairments [e.g., decreased intelligence quotient (IQ), academic performance] and neurological disease (e.g., stroke and epilepsy). We also review findings from multiple animal models of preeclampsia. Manipulation of key clinical preeclampsia processes in these models (e.g., placental hypoxia, immune dysfunction, angiogenesis, oxidative stress) causes various disruptions in offspring, including ones in white matter/glia, glucocorticoid receptors, neuroimmune outcomes, cerebrovascular structure, and cognition/behavior. This animal work implicates potentially high-yield targets that may be leveraged in the future for clinical application.

Hypertension, Anxiety, and Blood-Brain Barrier Permeability Are Increased in Postpartum Severe Preeclampsia/Hemolysis, Elevated Liver Enzymes, and Low Platelet Count Syndrome Rats

Hypertension and inflammation during pregnancy are suggested to contribute to the development of postpartum depression and anxiety. Using a rat model of severe preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome, which displays both hypertension and inflammation during pregnancy, we evaluated whether rats were prone to develop depression or anxiety in the postpartum period. On gestational day 12, miniosmotic pumps infusing sFlt-1 (soluble fms-like tyrosine kinase-1) and sEng (soluble endoglin) were placed into rats, a subset of these rats was infused with 2 mg/kg of Orencia (abatacept) the following day to determine whether immune suppression via T-cell depletion prevented any changes in maternal depression or anxiety-like behavior. All rats, including normal pregnant (NP) controls, delivered between gestational days 21 and 22. Postpartum severe preeclamptic rats buried significantly more marbles compared with NP rats ( P=0.002) and Orencia-treated rats ( P=0.05). Severe preeclamptic rats spent significantly more time in closed arms of the elevated plus maze compared with NP rats ( P=0.009) and Orencia-treated rats ( P=0.05). Severe preeclamptic rats were hypertensive compared with NP ( P=0.03) and Orencia-treated rats ( P=0.01). Finally, severe preeclamptic rats had increased blood-brain barrier permeability compared with NP rats ( P=0.03), which was reversed in Orencia-treated rats ( P=0.008). These results suggest that severe preeclampsia/hemolysis, elevated liver enzymes, and low platelet count syndrome during pregnancy contributes to an increase in anxiety-like behavior, blood-brain barrier permeability, and hypertension in the postpartum. The current results suggest that T-cell suppression during pregnancy can also help prevent chronic hypertension and increased anxiety in the postpartum period.

Placental CD4+ T cells isolated from preeclamptic women cause preeclampsia-like symptoms in pregnant nude-athymic rats

Preeclampsia (PE), new onset hypertension during pregnancy, is associated with a proinflammatory profile compared to normal pregnancy (NP). We hypothesize that CD4⁺ T cells from PE patient placentas cause PE symptoms during pregnancy compared to those from NP women. CD4⁺ T cells were isolated from placentas of PE and NP women using anti-CD4 magnetic separation, cultured in TexMACS medium at 37 °C in 5% CO₂, and injected intraperitoneally into nude-athymic rats on day 12 of gestation. On day 18, carotid catheters were implanted and on day 19, mean arterial pressure (MAP) was measured and blood and tissues were collected. MAP was 125 ± 2 mmHg in rats with NP CD4⁺ T cells but increased to 140 ± 4 mmHg in rats with PE CD4⁺ T cells. Significant differences in circulating cytokines tumor necrosis factor-alpha (TNF-α), interleukin-17 (IL-17) and soluble fms-like tyrosine kinase-1 (sFlt-1) were found with PE vs NP CD4⁺ T cells (TNF-α- PE = 167.4 pg/mL, NP = 79.4 pg/mL; IL-17-PE = 7.054 pg/mL, NP = 3.185 pg/mL; sFlt-1-PE = 90.7 pg/mL, NP = 58.2 pg/mL. In addition, renal cortical endothelin-1 (ET-1) mRNA expression increased 4.5 fold in rats with PE CD4⁺ T cells versus those receiving to NP CD4⁺ T cells. These data indicate an important role for placental PE CD4⁺ T cells to cause many characteristics of PE during pregnancy.

Pre-eclampsia: the role of highly active antiretroviral therapy and immune markers

PURPOSE OF THE REVIEW

This review highlights the role immune cells and markers such as natural killer (NK) cells, cytokines and human leukocyte antigen (HLA-G) play in predisposing HIV-infected women who are on HAART to develop PE, thus contributing to a better understanding and early diagnosis of PE with a subsequent reduction in maternal foetal and neonatal deaths.

RECENT FINDINGS

Pregnant women infected with the Human Immunodeficiency Virus (HIV) have a 25% risk of mother to child transmission. This risk, however, decreases to 2% if the women is on treatment. Highly active antiretroviral therapy (HAART) is the recommended treatment for both pregnant and non-pregnant women infected with HIV. Treatment with HAART is reported to potentiate predisposition to the development of hypertensive disorders of pregnancy such as pre-eclampsia (PE). Pre-eclampsia accounts for 7-10% of abnormal pregnancies worldwide. Studies demonstrate that pregnant women with HIV have PE at lower frequencies than uninfected women, however, the converse is observed upon HAART initiation. HIV-infected women on HAART exhibit a greater tendency to develop PE, emanating from immune reconstitution induced by HAART. There is paucity of information as to the pathogenesis of PE upon HAART initiation and there are, therefore, controversial data as to whether HAART predisposes women to a lower, equal or higher risk of PE development compared to the general population, further investigations on the impact of HIV infection and HAART on the immune response and rate of PE development in HIV infected pregnant women are urgently needed.

Preeclampsia: From Inflammation to Immunoregulation

Preeclampsia (PE) affects 5% to 7% of pregnant women each year worldwide, accounts for up to 18% of maternal deaths in the United States each year, and is the number 1 cause of premature births. Preeclampsia is associated with hypertension after the 20th week of gestation with or without proteinuria, in conjunction with fetal growth restriction, maternal endothelial dysfunction, and chronic immune activation. The mechanisms leading to the development of PE are unclear. However, it is thought that shallow trophoblast invasion and insufficient remodeling of uterine spiral arteries result in placental ischemia. Consequently, an immune imbalance characterized by increases in proinflammatory CD4⁺ T cells and cytokines along with decreases in regulatory T cells and anti-inflammatory cytokines occurs. This imbalance leads to chronic inflammation and ensuing oxidative stress, proinflammatory cytokines, and autoantibodies. Studies performed in our laboratories, using the Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia, have demonstrated a role for this immune imbalance to mediate PE pathophysiology and identified potential mechanisms of immunoregulation that may be of benefit in the treatment of PE. Therefore, the purpose of this commentary is to review studies demonstrating the positive effects of immunoregulatory factors in the RUPP rat model of PE. Restoration of the immune balance in PE may be a potential strategy for the development of therapeutic interventions that could improve maternal and fetal outcomes associated with this maternal syndrome.

Immune regulation of systemic hypertension, pulmonary arterial hypertension, and preeclampsia: shared disease mechanisms and translational opportunities

Systemic hypertension, preeclampsia, and pulmonary arterial hypertension (PAH) are diseases of high blood pressure in the systemic or pulmonary circulation. Beyond the well-defined contribution of more traditional pathophysiological mechanisms, such as changes in the renin-angiotensin-aldosterone system, to the development of these hypertensive disorders, there is substantial clinical evidence supporting an important role for inflammation and immunity in the pathogenesis of each of these three conditions. Over the last decade, work in small animal models, bearing targeted deficiencies in specific cytokines or immune cell subsets, has begun to clarify the immune-mediated mechanisms that drive changes in vascular structure and tone in hypertensive disease. By summarizing the clinical and experimental evidence supporting a contribution of the immune system to systemic hypertension, preeclampsia, and PAH, the current review highlights the cellular and molecular pathways that are common to all three hypertensive disorders. These mechanisms are centered on an imbalance in CD4⁺ helper T cell populations, defined by excessive Th17 responses and impaired T_reg activity, as well as the excessive activation or impairment of additional immune cell types, including macrophages, dendritic cells, CD8⁺ T cells, B cells, and natural killer cells. The identification of common immune mechanisms in systemic hypertension, preeclampsia, and PAH raises the possibility of new therapeutic strategies that target the immune component of hypertension across multiple disorders.

Inhibition of T-cell activation attenuates hypertension, TNFα, IL-17, and blood-brain barrier permeability in pregnant rats with angiogenic imbalance

PROBLEM

Angiogenic imbalance during pregnancy is associated with immune activation, hypertension, increased T cell infiltration, and neurological insults.

METHOD OF STUDY

On gestational day (GD) 12, timed-pregnant rats were infused with anti-angiogenic factors sFlt-1 and sEndoglin (4.7 and 7 μg/kg) to create HELLP syndrome via mini-osmotic pumps for 8 days, with a subset of these rats having Orencia (2 mg/kg) infused on GD13. On GD19, blood-brain barrier (BBB) permeability was evaluated via Evan's Blue infusion, blood was collected for T-cell measurements, inflammatory cytokine secretion. Brain tissues were also collected to examine inflammatory cytokine infiltration.

RESULTS

T-cell attenuation with Orencia decreased circulating CD4(+) and CD8(+) T cells, circulating tumor necrosis factor alpha (TNFα) and IL-17, BBB permeability and significantly decreased biochemical evidence of HELLP compared to untreated HELLP rats.

CONCLUSIONS

These data support the hypothesis that T cells have a critical role in contributing to the pathophysiology that is seen in angiogenic imbalance during pregnancy.

Serelaxin improves the pathophysiology of placental ischemia in the reduced uterine perfusion pressure rat model of preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy that has limited therapeutic options. In healthy pregnancy, relaxin plays an important vasodilatory role to maintain vascular compliance; however, currently, there is no preclinical evidence to support the use of relaxin during preeclampsia. Therefore, the goal of this study was to test the hypothesis that recombinant human relaxin-2 (Serelaxin, Novartis; RLX) could reduce mean arterial pressure (MAP) and improve uterine artery resistance index (UARI) and nitric oxide bioavailability, and/or decrease prepro-endothelin-1 (PPET-1), soluble fms-like tyrosine kinase-1 (sFlt-1), and TNF-α) in the reduced uterine perfusion pressure (RUPP) model of preeclampsia. On day 14 of gestation (GD14), pregnant rats were assigned to normal pregnant (NP), RUPP, RUPP+RLX, or NP+RLX groups. Treated rats received RLX at 0.4 μg/h or RLX2 4 μg/h RLX via minipump implanted on GD14. On GD18, carotid arterial catheters were inserted, and on GD19, MAP and tissues were collected. MAP was increased in RUPP rats compared with NP but was lowered with either dose of RLX. UARI and sFlt-1 were significantly improved in both treated RUPP groups. Total circulating nitrate-nitrite improved and placental PPET-1 and TNF-α were significantly decreased with the higher dose of RLX. Renal cortex PPET-1 was reduced with both doses of RLX. In conclusion, Serelaxin improved blood pressure, sFlt-1, TNF-α, UARI, and nitric oxide bioavailability and PPET-1 in a rat model of preeclampsia, thereby suggesting a potential therapeutic role for RLX in maintaining maternal health and prolonging pregnancy in the face of placental ischemia.

Identifying immune mechanisms mediating the hypertension during preeclampsia

Preeclampsia (PE) is a pregnancy-associated disorder that affects 5-8% of pregnancies and is a major cause of maternal, fetal, and neonatal morbidity and mortality. Hallmark characteristics of PE are new onset hypertension after 20 wk gestation with or without proteinuria, chronic immune activation, fetal growth restriction, and maternal endothelial dysfunction. However, the pathophysiological mechanisms that lead to the development of PE are poorly understood. Recent data from studies of both clinical and animal models demonstrate an imbalance in the subpopulations of CD4+ T cells and a role for these cells as mediators of inflammation and hypertension during pregnancy. Specifically, it has been proposed that the imbalance between two CD4+ T cell subtypes, regulatory T cells (Tregs) and T-helper 17 cells (Th17s), is involved in the pathophysiology of PE. Studies from our laboratory highlighting how this imbalance contributes to vasoactive factors, endothelial dysfunction, and hypertension during pregnancy will be discussed in this review. Therefore, the purpose of this review is to highlight hypertensive mechanisms stimulated by inflammatory factors in response to placental ischemia, thereby elucidating a role.

Placental Ischemia and Resultant Phenotype in Animal Models of Preeclampsia

Preeclampsia is new onset (or worsening of preexisting) hypertension that occurs during pregnancy. It is accompanied by chronic inflammation, intrauterine growth restriction, elevated anti-angiogenic factors, and can occur with or without proteinuria. Although the exact etiology is unknown, it is thought that preeclampsia begins early in gestation with reduced uterine spiral artery remodeling leading to decreased vasculogenesis of the placenta as the pregnancy progresses. Soluble factors, stimulated by the ischemic placenta, shower the maternal vascular endothelium and are thought to cause endothelial dysfunction and to contribute to the development of hypertension during pregnancy. Due to the difficulty in studying such soluble factors in pregnant women, various animal models have been designed. Studies from these models have contributed to a better understanding of how factors released in response to placental ischemia may lead to increased blood pressure and reduced fetal weight during pregnancy. This review will highlight various animal models and the major findings indicating the importance of placental ischemia to lead to the pathophysiology observed in preeclamptic patients.

The role of inflammation in the pathology of preeclampsia

Preeclampsia (PE) affects 5-7% of all pregnancies in the United States and is the leading cause of maternal and prenatal morbidity. PE is associated with hypertension after week 20 of gestation, decreased renal function and small-for-gestational-age babies. Women with PE exhibit chronic inflammation and production of autoantibodies. It is hypothesized that during PE, placental ischaemia occurs as a result of shallow trophoblast invasion which is associated with an immune imbalance where pro-inflammatory CD4(+) T-cells are increased and T regulatory cells (Tregs) are decreased. This imbalance leads to chronic inflammation characterized by oxidative stress, pro-inflammatory cytokines and autoantibodies. Studies conducted in our laboratory have demonstrated the importance of this immune imbalance in causing hypertension in response to placental ischaemia in pregnant rats. These studies confirm that increased CD4(+) T-cells and decreased Tregs during pregnancy leads to elevated inflammatory cytokines, endothelin (ET-1), reactive oxygen species (ROS) and agonistic autoantibodies to the angiotensin II (Ang II), type 1 receptor (AT1-AA). All of these factors taken together play an important role in increasing the blood pressure during pregnancy. Specifically, this review focuses on the decrease in Tregs, and their associated regulatory cytokine interleukin (IL)-10, which is seen in response to placental ischaemia during pregnancy. This study will also examine the effect of regulatory immune cell repopulation on the pathophysiology of PE. These studies show that restoring the balance of the immune system through increasing Tregs, either by adoptive transfer or by infusing IL-10, reduces the blood pressure and pathophysiology associated with placental ischaemia in pregnant rats.

Vitamin D supplementation improves pathophysiology in a rat model of preeclampsia

Deficiency of vitamin D (VD) is associated with preeclampsia (PE), a hypertensive disorder of pregnancy characterized by proinflammatory immune activation. We sought to determine whether VD supplementation would reduce the pathophysiology and hypertension associated with the reduced uterine perfusion pressure (RUPP) rat model of PE. Normal pregnant (NP) and RUPP rats were supplemented with VD2 or VD3 (270 IU and 15 IU/day, respectively) on gestation days 14-18 and mean arterial pressures (MAPs) measured on day 19. MAP increased in RUPP to 123 ± 2 mmHg compared with 102 ± 3 mmHg in NP and decreased to 113 ± 3 mmHg with VD2 and 115 ± 3 mmHg with VD3 in RUPP rats. Circulating CD4+ T cells increased in RUPP to 7.90 ± 1.36% lymphocytes compared with 2.04 ± 0.67% in NP but was lowered to 0.90 ± 0.19% with VD2 and 4.26 ± 1.55% with VD3 in RUPP rats. AT1-AA, measured by chronotropic assay, decreased from 19.5 ± 0.4 bpm in RUPPs to 8.3 ± 0.5 bpm with VD2 and to 15.4 ± 0.7 bpm with VD3. Renal cortex endothelin-1 (ET-1) expression was increased in RUPP rats (11.6 ± 2.1-fold change from NP) and decreased with both VD2 (3.3 ± 1.1-fold) and VD3 (3.1 ± 0.6-fold) supplementation in RUPP rats. Plasma-soluble FMS-like tyrosine kinase-1 (sFlt-1) was also reduced to 74.2 ± 6.6 pg/ml in VD2-treated and 91.0 ± 16.1 pg/ml in VD3-treated RUPP rats compared with 132.7 ± 19.9 pg/ml in RUPP rats. VD treatment reduced CD4+ T cells, AT1-AA, ET-1, sFlt-1, and blood pressure in the RUPP rat model of PE and could be an avenue to improve treatment of hypertension in response to placental ischemia.

Blockade of CD40 ligand for intercellular communication reduces hypertension, placental oxidative stress, and AT1-AA in response to adoptive transfer of CD4+ T lymphocytes from RUPP rats

Preeclampsia (PE) is associated with altered immune activation during pregnancy. We have previously shown that adoptive transfer of CD4(+) T cells from the reduced uterine perfusion pressure (RUPP) rat model of PE increases blood pressure, oxidative stress (ROS), and inflammation in normal pregnant recipient rats. The objective of this study was to determine if blockade of communication via the CD40-CD40 ligand (CD40L) interaction between placental ischemia-induced CD4(+) T cells with endogenous normal pregnant (NP) cells would improve pathophysiology that was previously observed in NP recipient rats of RUPP CD4(+) T cells. Splenic CD4(+) T lymphocytes were magnetically separated, incubated with 2.5 μg/ml anti-CD40 ligand (αCD40L) overnight, and transferred into NP rats on day 12 of gestation (NP+RUPP CD4(+) T+anti-CD40L). On day 19 of gestation, blood pressure (MAP), blood, and tissues were collected. MAP was 99 ± 2 in NP (n = 13), 116 ± 4 in NP+RUPP CD4(+) T cells (n = 7; P < 0.01); MAP only increased to 104 ± 2 in NP+RUPP CD4(+) T cells+CD40L (n = 24) (P < 0.05 vs. NP+RUPP CD4(+) T cells). Mechanisms of hypertension in response to RUPP CD4(+) T cells include endothelin-1 (ET-1), ROS, and angiotensin II type I receptor (AT1-AA) were analyzed. Inhibition of CD40L binding reduced placental ET-1 to 2.3-fold above NP rats and normalized placental ROS from 318.6 ± 89 in NP+RUPP CD4(+) T cells (P < 0.05) to 118.7 ± 24 in NP+RUPP CD4(+) T+anti-CD40L (P < 0.05). AT1-AA was also normalized with inhibition of CD40L. These data suggest that placental ischemia-induced T-cell communication via the CD40L is one important mechanism leading to much of the pathophysiology of PE.

An increased population of regulatory T cells improves the pathophysiology of placental ischemia in a rat model of preeclampsia

The reduced uterine perfusion pressure (RUPP) rat model of preeclampsia exhibits much of the pathology characterizing this disease, such as hypertension, inflammation, suppressed regulatory T cells (TRegs), reactive oxygen species (ROS), and autoantibodies to the ANG II type I receptor (AT1-AA) during pregnancy. The objective of this study was to determine whether supplementation of normal pregnant (NP) TRegs into RUPP rats would attenuate the pathophysiology associated with preeclampsia during pregnancy. CD4(+)/CD25(+) T cells were isolated from spleens of NP and RUPP rats, cultured, and injected into gestation day (GD) 12 normal pregnant rats that underwent the RUPP procedure on GD 14. On GD 1, mean arterial pressure (MAP) was recorded, and blood and tissues were collected for analysis. One-way ANOVA was used for statistical analysis. MAP increased from 99 ± 2 mmHg in NP (n = 12) to 127 ± 2 mmHg in RUPP (n = 21) but decreased to 118 ± 2 mmHg in RUPP+NP TRegs (n = 17). Circulating IL-6 and IL-10 were not significantly changed, while circulating TNF-α and IL-17 were significantly decreased after supplementation of TRegs. Placental and renal ROS were 339 ± 58.7 and 603 ± 88.1 RLU·min(-1)·mg(-1) in RUPP and significantly decreased to 178 ± 27.8 and 171 ± 55.6 RLU·min(-1)·mg(-1), respectively, in RUPP+NP TRegs; AT1-AA was 17.81 ± 1.1 beats per minute (bpm) in RUPP but was attenuated to 0.50 ± 0.3 bpm with NP TRegs. This study demonstrates that NP TRegs can significantly improve inflammatory mediators, such as IL-17, TNF-α, and AT1-AA, which have been shown to increase blood pressure during pregnancy.

17-hydroxyprogesterone caproate significantly improves clinical characteristics of preeclampsia in the reduced uterine perfusion pressure rat model

Preeclampsia is characterized by increased uterine artery resistance index, chronic immune activation, and decreased circulating nitric oxide levels. 17-α-Hydroxyprogesterone caproate (17-OHPC) is a synthetic metabolite of progesterone used for the prevention of recurrent preterm birth. We hypothesized that 17-OHPC could reduce mean arterial pressure by decreasing inflammation, whereas improving vasodilation by increasing nitric oxide bioavailability and uterine artery resistance index during late gestation in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. 17-OHPC (3.32 mg/kg) was intraperitoneally administered on gestation day 18 into RUPP rats, carotid catheters inserted, and mean arterial pressure, blood, and tissues were collected on day 19. Mean arterial pressure in normal pregnant (NP; n=13) was 92±2.0 and increased to123±2.0 in RUPP (n=18; P<0.0001), which was improved to 116±1.5 mm Hg in RUPP+17-OHPC (n=10; P<0.05). Circulating CD4+ T cells were 1.19%±1.0% of gated cells in NP (n=7), which increased to 8.52%±2.4% in RUPP rats (n=10; P<0.05) but was reduced to 2.72%±0.87% (n=14; P<0.05) in RUPP+17-OHPC. Circulating nitrate/nitrite was 26.34±3.5 µmol/L in NP (n=12) but was reduced to14.58±3.1 in RUPP rats (n=8; P=0.03) and increased to 22.69±1.62 in RUPP+17-OHPC (n=7; P=0.05). Endothelial nitric oxide synthase expression was 0.65±0.11 AU in NP (n=4), which decreased to 0.33±0.01 in RUPP rats (n=4; P=0.05) but increased to 0.57±0.01 in RUPP+17-OHPC (n=5; P=0.03). Uterine artery resistance index was 0.54±0.02 in NP (n=3), 0.78±0.03 in RUPP (n=4), and 0.63±0.038 in RUPP+17-OHPC (n=8; both P<0.05). Our findings demonstrate that even though modest, lowering blood pressure with 17-OHPC could be a viable treatment option for suppressing inflammation, uterine artery vasoconstriction while improving litter size.

CD4+ T cells are important mediators of oxidative stress that cause hypertension in response to placental ischemia

Preeclampsia is associated with oxidative stress, which is suspected to play a role in hypertension, placental ischemia, and fetal demise associated with the disease. Various cellular sources of oxidative stress, such as neutrophils, monocytes, and CD4(+) T cells have been suggested as culprits in the pathophysiology of preeclampsia. The objective of this study was to examine a role of circulating and placental CD4(+) T cells in oxidative stress in response to placental ischemia during pregnancy. CD4(+) T cells and oxidative stress were measured in preeclamptic and normal pregnant women, placental ischemic and normal pregnant rats, and normal pregnant recipient rats of placental ischemic CD4(+) T cells. Women with preeclampsia had significantly increased circulating (P=0.02) and placental CD4(+) T cells (P=0.0001); lymphocyte secretion of myeloperoxidase (P=0.004); and placental reactive oxygen species (P=0.0004) when compared with normal pregnant women. CD4(+) T cells from placental ischemic rats cause many facets of preeclampsia when injected into normal pregnant recipient rats on gestational day 13. On gestational day 19, blood pressure increased in normal pregnant recipients of placental ischemic CD4(+) T cells (P=0.002) compared with that in normal pregnant rats. Similar to preeclamptic patients, CD4(+) T cells from placental ischemic rats secreted significantly more myeloperoxidase (P=0.003) and induced oxidative stress in cultured vascular cells (P=0.003) than normal pregnant rat CD4(+)Tcells. Apocynin, a nicotinamide adenine dinucleotide phosphate inhibitor, attenuated hypertension and all oxidative stress markers in placental ischemic and normal pregnant recipient rats of placental ischemic CD4(+)Tcells (P=0.05). These data demonstrate an important role for CD4(+) T cells in mediating another factor, oxidative stress, to cause hypertension during preeclampsia.