Preeclampsia is characterized by increased uterine artery resistance index, chronic immune activation, and decreased circulating nitric oxide levels. 17-?-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.
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.
Several studies suggest a link between autoimmunity and essential hypertension in humans. However, whether autoimmunity can drive the development of hypertension remains unclear. The autoimmune disease systemic lupus erythematosus is characterized by autoantibody production, and the prevalence of hypertension is increased markedly in this patient population compared with normal healthy women. We hypothesized that preventing the development of autoimmunity would prevent the development of hypertension in a mouse model of lupus. Female lupus (NZBWF1) and control mice (NZW) were treated weekly with anti-CD20 or immunoglobulin G antibodies (both 10 mg/kg, IV) starting at 20 weeks of age for 14 weeks. Anti-CD20 therapy markedly attenuated lupus disease progression as evidenced by reduced CD45R+ B cells and lower double-stranded DNA autoantibody activity. In addition, renal injury in the form of urinary albumin, glomerulosclerosis, and tubulointerstitial fibrosis, as well as tubular injury (indicated by renal cortical expression of neutrophil gelatinase-associated lipocalin) was prevented by anti-CD20 therapy in lupus mice. Finally, lupus mice treated with anti-CD20 antibody did not develop hypertension. The protection against the development of hypertension was associated with lower renal cortical tumor necrosis factor-? expression, a cytokine that has been previously reported by us to contribute to the hypertension in this model, as well as renal cortical monocyte chemoattractant protein-1 expression and circulating T cells. These data suggest that the development of autoimmunity and the resultant increase in renal inflammation are an important underlying factor in the prevalent hypertension that occurs during systemic lupus erythematosus.
Preeclampsia is a multisystem disorder recognized as hypertension with proteinuria developing >20 weeks' gestation. Preeclampsia is associated with chronic immune activation characterized by increased T and B lymphocytes, cytokines, and antibodies activating the angiotensin II type I receptor (AT1-AA). Hypertension in response to elevated interleukin (IL)-6 during pregnancy occurs with increased renin activity and AT1-AA, and reduced kidney function.
Eclampsia, defined as unexplained seizure in a woman with preeclampsia, is a life-threatening complication of pregnancy with unclear etiology. Magnesium sulfate (MgSO4) is the leading eclamptic seizure prophylactic, yet its mechanism of action remains unclear. Here, we hypothesized severe preeclampsia is a state of increased seizure susceptibility due to blood-brain barrier (BBB) disruption and neuroinflammation that lowers seizure threshold. Further, MgSO4 decreases seizure susceptibility by protecting the BBB and preventing neuroinflammation. To model severe preeclampsia, placental ischemia (reduced uteroplacental perfusion pressure; RUPP) was combined with a high cholesterol diet (HC) to cause maternal endothelial dysfunction. RUPP+HC rats developed symptoms associated with severe preeclampsia, including hypertension, oxidative stress, endothelial dysfunction and fetal and placental growth restriction. Seizure threshold was determined by quantifying the amount of pentylenetetrazole (PTZ; mg/kg) required to elicit seizure in RUPP+HC±MgSO4 and compared to normal pregnant controls (n?=?6/group; gestational day 20). RUPP+HC rats were more sensitive to PTZ with seizure threshold being ?65% lower vs. control (12.4±1.7 vs. 36.7±3.9 mg/kg PTZ; p<0.05) that was reversed by MgSO4 (45.7±8.7 mg/kg PTZ; p<0.05 vs. RUPP+HC). BBB permeability to sodium fluorescein, measured in-vivo (n?=?5-7/group), was increased in RUPP+HC vs. control rats, with more tracer passing into the brain (15.9±1.0 vs. 12.2±0.3 counts/gram ×1000; p<0.05) and was unaffected by MgSO4 (15.6±1.0 counts/gram ×1000; p<0.05 vs. controls). In addition, RUPP+HC rats were in a state of neuroinflammation, indicated by 35±2% of microglia being active compared to 9±2% in normal pregnancy (p<0.01; n?=?3-8/group). MgSO4 treatment reversed neuroinflammation, reducing microglial activation to 6±2% (p<0.01 vs. RUPP+HC). Overall, RUPP+HC rats were in a state of augmented seizure susceptibility potentially due to increased BBB permeability and neuroinflammation. MgSO4 treatment reversed this, increasing seizure threshold and decreasing neuroinflammation, without affecting BBB permeability. Thus, reducing neuroinflammation may be one mechanism by which MgSO4 prevents eclampsia during severe preeclampsia.
Preeclampsia, new onset hypertension with proteinuria during pregnancy, is associated with chronic inflammation and placental oxidative stress (ROS). Chronic interleukin-17 (IL-17) increases blood pressure, autoantibodies (angiotensin II type I receptor [AT1-AA]), and ROS during pregnancy. The objective of this study was to determine whether T-helper 17 (TH17) suppression via IL-17 recombinant receptor C (IL-17RC) decreases pathophysiology associated with placental ischemia (reduced uterine perfusion pressure [RUPP]). On gestation day 14, miniosmotic pumps infusing 100 pg of IL-17RC per day were implanted into pregnant rats undergoing RUPP. On gestation day 18, carotid catheters were inserted. On gestation day 19, mean arterial pressure was recorded and TH17 cells, oxidative stress, and AT1-AA were measured and analyzed via 1-way ANOVA. Mean arterial pressure increased from 101 ± 2 mm Hg in normal pregnant rats (n = 19) to 120 ± 1 mm Hg in RUPP rats (n = 17) but decreased to 110 ± 2 mm Hg in RUPP+IL-17RC rats (n = 22). Pup weight decreased from 2.28 ± 0.2 g in normal pregnant rats to 1.96 ± 0.3 g in RUPP rats but was significantly increased to 2.01 ± 0.1 in RUPP+IL-17RC rats. TH17 cells were 1.77% in RUPP rats but decreased to 0.65% in RUPP+IL-17RC rats. Urinary isoprostanes were normalized in RUPP+IL-17RC rats (52 pg/µg) compared with 89 pg/µg in RUPP controls. Placental ROS was 652 relative light units in RUPP rats but decreased to 337 relative light units in RUPP+IL-17RC rats. AT1-AA was 17.27 ± 0.7 bpm in RUPP rats but decreased to 5.00 ± 0.5 bpm in RUPP+IL-17RC rats. With this study, we show that infusion of IL-17RC blunts TH17s, oxidative stress, AT1-AA, and hypertension in the RUPP model of preeclampsia, indicating that TH17 cells may play an important role in disease pathophysiology.
Hypertension during preeclampsia is associated with increased maternal vascular sensitivity to angiotensin II (ANGII). This study was designed to determine mechanisms whereby agonistic autoantibodies to the ANGII type I receptor (AT1-AA) enhance blood pressure (mean arterial pressure [MAP]) and renal vascular sensitivity to ANGII during pregnancy. First, we examined MAP and renal artery resistance index in response to chronic administration of ANGII or AT1-AA or AT1-AA+ANGII in pregnant rats compared with control pregnant rats. To examine mechanisms of heightened sensitivity in response to AT1-AA during pregnancy, we examined the role of endogenous ANGII in AT1-AA-infused pregnant rats, and that of endothelin-1 and oxidative stress in AT1-AA+ANGII-treated rats. Chronic ANGII increased MAP from 95±2 in normal pregnant rats to 115±2 mm?Hg; chronic AT1-AA increased MAP to 118±1 mm?Hg in normal pregnant rats, which further increased to 123±2 mm?Hg with AT1-AA+ANGII. Increasing ANGII from 10(-11) to 10(-8) decreased afferent arteriole diameter from 15% to 20% but sharply decreased afferent arteriole diameter to 60% in AT1-AA-pretreated vessels. Renal artery resistance index increased from 0.67 in normal pregnant rats to 0.70 with AT1-AA infusion, which was exacerbated to 0.74 in AT1-AA+ANGII-infused rats. AT1-AA-induced hypertension decreased with enalapril but was not attenuated. Both tissue endothelin-1 and reactive oxygen species increased with AT1-AA+ANGII compared with AT1-AA alone, and blockade of either of these pathways had significant effects on MAP or renal artery resistance index. These data support the hypothesis that AT1-AA, via activation of endothelin-1 and oxidative stress and interaction with endogenous ANGII, is an important mechanism whereby MAP and renal vascular responses are enhanced during preeclampsia.
Blood pressure management is recommended to avoid maternal cerebrovascular or cardiovascular compromise during pregnancy. Current antihypertensive treatment during pregnancy with positive safety profiles includes labetalol, hydralazine, methyldopa and nifedipine.
Preeclampsia is associated with hypertension and increased infant and maternal morbidity and mortality. The underlying cause of preeclampsia is largely unknown, but it is clear that an immunological component plays a key pathophysiological role. This review will highlight immunological key players in the pathology of preeclampsia and discuss their role in the pathophysiology observed in the reduced placental perfusion (RUPP) rat model of preeclampsia.
Preeclampsia (PE) is associated with hypertension and elevated endothelin (ET-1), an indicator of endothelial cell activation and dysfunction. Reduction of uteroplacental perfusion (RUPP) in the pregnant rat model of PE is characterized by elevated mean arterial pressure, inflammatory cytokines, and activation of the ET-1 system. We aim to determine whether 17-alpha-hydroxyprogesterone caproate (17-OHPC) or progesterone suppresses these pathways.
Administration of dexamethasone to the hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome patients (10 mg intravenously [IV] every 12 hours) shortens the disease course and reduces maternal morbidity in patients treated at the University of Mississippi Medical Center (UMMC), associated with this severe form of preeclampsia. However, the pathophysiological mechanisms involved with this intervention remain unclear.
Pre-eclampsia is defined as new onset hypertension with proteinuria during pregnancy. Pre-eclampsia is also characterized by endothelial cell activation and dysfunction and intrauterine growth restriction. Preeclamptic women display a chronic inflammatory response characterized by elevated inflammatory cytokines, circulating monocytes, neutrophils, and T and B lymphocytes secreting autoantibodies that activate the angiotensin II type I receptor (AT1-AA). Although the pathophysiology of pre-eclampsia is becoming more defined, the genesis of the disease is still largely unknown. Furthermore, the only treatment for extreme forms of the disease is bed rest and administration of magnesium sulfate to sustain the pregnancy a few days prior to early delivery of the fetus, which can lead to devastating neurological and physical effects for the newborn. Administration of magnesium sulfate is routinely given without adverse effects. The focus of this review is to discuss the cascade of events leading to cytokines, specifically interleukin-6 (IL-6), in stimulating vasoactive substances such as AT1-AA (Figure 1) and to examine the mechanism whereby administration of magnesium sulfate can be beneficial during pre-eclampsia. One area is to decrease vascular resistance index parameters determined by Doppler velocimetry. Another potential area of benefit with magnesium sulfate administration may be to decrease inflammatory responses or decrease cardiovascular mechanisms stimulated by overexpression of inflammatory cytokines in response to placental ischemia or animal models of elevated IL-6 during pregnancy. Further studies identifying IL-6-driven mechanisms playing a role in the development of hypertension during pregnancy and how administration of magnesium sulfate can suppress them are critical to improve decisions affecting patient care in women with pre-eclampsia. The results of these types of studies will be advantageous to further our knowledge of the pathophysiological ramifications associated with pre-eclampsia and to further therapeutic development for this disease.
BACKGROUND: Increases in interleukin 6 (IL-6) and agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA) are proposed to be important links between placental ischemia and hypertension in preeclampsia. METHODS: The purpose of this study was to determine whether IL-6 (5 ng/day), infused into normal pregnant (NP) rats, increased mean arterial pressure (MAP) and AT1-AA. MAP was analyzed in the presence and absence of an angiotensin type 1 receptor (AT1R) antagonist, losartan, L. RESULTS: MAP and AT1-AA increased from 102 ± 2 to 118 ± 4 mmHg and 0.7 ± 0.3 NP to 14.1 ± 1.4 chronotropic units with chronic IL-6 infusion. MAP responses to IL-6 were abolished in losartan pretreated rats (85 ± 4 in NP + L vs 85 ± 3 mmHg in IL-6 + L). CONCLUSION: These data indicate that IL-6 stimulates AT1-AA and that activation of the AT1R mediates IL-6 induced hypertension during pregnancy.
While soluble fms-like tyrosine kinase-1 (sFlt-1) and endothelin-1 (ET-1) have been implicated in the pathogenesis of preeclampsia (PE), the mechanisms whereby increased sFlt-1 leads to enhanced ET-1 production and hypertension remain unclear. It is well documented that nitric oxide (NO) production is reduced in PE; however, whether a reduction in NO synthesis plays a role in increasing ET-1 and blood pressure in response to chronic increases in plasma sFlt-1 remains unclear. The purpose of this study was to determine the role of reduced NO synthesis in the increase in blood pressure and ET-1 in response to sFlt-1 in pregnant rats. sFlt-1 was infused into normal pregnant (NP) Sprague-Dawley rats (3.7 ?g·kg(-1)·day(-1) for 6 days beginning on day 13 of gestation) treated with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (100 mg/l for 4 days) or supplemented with 2% L-Arg (in drinking water for 6 days beginning on day 15 of gestation). Infusion of sFlt-1 into NP rats significantly elevated mean arterial pressure compared with control NP rats: 116 ± 2 vs. 103 ± 1 mmHg (P < 0.05). NO synthase inhibition had no effect on the blood pressure response in sFlt-1 hypertensive pregnant rats (121 ± 3 vs. 116 ± 2 mmHg), while it significantly increased mean arterial pressure in NP rats (128 ± 4 mmHg, P < 0.05). In addition, NO production was reduced ?70% in isolated glomeruli from sFlt-1 hypertensive pregnant rats compared with NP rats (P < 0.05). Furthermore, prepro-ET-1 in the renal cortex was increased ?3.5-fold in sFlt-1 hypertensive pregnant rats compared with NP rats. Supplementation with L-Arg decreased the sFlt-1 hypertension (109 ± 3 mmHg, P < 0.05) but had no effect on the blood pressure response in NP rats (109 ± 3 mmHg) and abolished the enhanced sFlt-1-induced renal cortical prepro-ET expression. In conclusion, a reduction in NO synthesis may play an important role in the enhanced ET-1 production in response to sFlt-1 hypertension in pregnant rats.
One potential mechanism contributing to the increased risk for encephalopathies in women with preeclampsia is altered cerebral vascular autoregulation resulting from impaired myogenic tone. Whether placental ischemia, a commonly proposed initiator of preeclampsia, alters cerebral vascular function is unknown. This study tested the hypothesis that placental ischemia in pregnant rats (caused by reduced uterine perfusion pressure [RUPP]) leads to impaired myogenic responses in middle cerebral arteries. Mean arterial pressure was increased by RUPP (135±3 mm Hg) compared with normal pregnant rats (103±2 mm Hg) and nonpregnant controls (116±1 mm Hg). Middle cerebral arteries from rats euthanized on gestation day 19 were assessed in a pressure arteriograph under active (+Ca(2+)) and passive (0 Ca(2+)) conditions, whereas luminal pressure was varied between 25 and 150 mm Hg. The slope of the relationship between tone and pressure in the middle cerebral artery was 0.08±0.01 in control rats and was similar in normal pregnant rats (0.05±0.01). In the RUPP model of placental ischemia, this relationship was markedly reduced (slope=0.01±0.00; P<0.05). Endothelial dependent and independent dilation was not different between groups, nor was there evidence of vascular remodeling assessed by the wall:lumen ratio and calculated wall stress. The impaired myogenic response was associated with brain edema measured by percentage of water content (RUPP P<0.05 versus control and normal pregnant rats). This study demonstrates that placental ischemia in pregnant rats leads to impaired myogenic tone in the middle cerebral arteries and that the RUPP model is a potentially important tool to examine mechanisms leading to encephalopathy during preeclamptic pregnancies.
Although it is well established that the renal endothelin (ET-1) system plays an important role in regulating sodium excretion and blood pressure through activation of renal medullary ET(B) receptors, the role of this system in Dahl salt-sensitive (DS) hypertension is unclear. The purpose of this study was to determine whether the DS rat has abnormalities in the renal medullary endothelin system when maintained on a high sodium intake. The data indicate that Dahl salt-resistant rats (DR) on a high-salt diet had a six-fold higher urinary endothelin excretion than in the DR rats with low Na(+) intake (17.8 ± 4 pg/day vs. 112 ± 44 pg/day). In sharp contrast, urinary endothelin levels increased only twofold in DS rats in response to a high Na(+) intake (13 ± 2 pg/day vs. 29.8 ± 5.5 pg/day). Medullary endothelin concentration in DS rats on a high-Na(+) diet was also significantly lower than DR rats on a high-Na(+) diet (31 ± 2.8 pg/mg vs. 70.9 ± 5 pg/mg). Furthermore, DS rats had a significant reduction in medullary ET(B) receptor expression compared with DR rats while on a high-Na(+) diet. Finally, chronic infusion of ET-1 directly into the renal medulla blunted Dahl salt-sensitive hypertension. These data indicate that a decrease in medullary production of ET-1 in the DS rat could play an important role in the development of salt-sensitive hypertension observed in the DS rat.
Chronic reduction of uteroplacental perfusion pressure (RUPP) in pregnant rats leads to placental ischemia, maternal endothelial cell dysfunction, hypertension and elevated levels of tumor necrosis factor-alpha (TNF-?). In this study we investigated the hypothesis that placental ischemia in pregnant rat, a model of preeclampsia, stimulates cardiac hypertrophy and fibrosis via a TNF-?-dependent mechanism.
Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and reactive oxygen species (ROS) are implicated in the pathophysiology of preeclampsia. The objective of this study was to determine the role of AT1-AA to stimulate placental oxidative stress in vivo and role ROS in mediating hypertension in response to AT1-AA during pregnancy.
We have shown that hypertension in response to chronic placental ischemia is associated with elevated inflammatory cytokines and CD4(+) T cells. However, it is unknown whether these cells play an important role in mediating hypertension in response to placental ischemia. Therefore, we hypothesize that reduced uterine perfusion pressure (RUPP)-induced CD4(+) T cells increase blood pressure during pregnancy. To answer this question, CD4(+) T cells were isolated from spleens at day 19 of gestation from control normal pregnant (NP) and pregnant RUPP rats, cultured, and adjusted to 10(6) cells per 100 ?L of saline for intraperitoneal injection into NP rats at day 13 of gestation. On day 18, in the experimental groups of rats, arterial catheters were inserted, and on day 19 mean arterial pressure was analyzed. Inflammatory cytokines and antiangiogenic factor soluble fms-like tyrosine kinase 1 were determined via ELISA. Mean arterial pressure increased from 104±2 mm Hg in NP rats to 124±2 mm Hg in RUPP rats (P<0.001) and to 118±1 mm Hg in rats receiving RUPP CD4(+) T cells (P<0.001). Circulating tumor necrosis factor-? and soluble fms-like tyrosine kinase 1 were elevated in recipients of RUPP CD4(+) T cells to levels similar to control RUPP rats. In contrast, virgin rats injected with NP or RUPP CD4(+) T cells exhibited no blood pressure changes compared with control virgin rats. Importantly, mean arterial pressure did not change in recipients of NP CD4(+) T cells (109±3 mm Hg). These data support the hypothesis that RUPP-induced CD4(+) T cells play an important role in the pathophysiology of hypertension in response to placental ischemia.
Preeclampsia is associated with innate inflammatory response resulting in elevated tumor necrosis factor-?, agonistic autoantibodies to the angiotensin II type I receptor, and activation of endothelin 1 (ET-1). This study was designed to determine the role of B-cell depletion, resulting in agonistic autoantibodies to the angiotensin II type I receptor suppression to mediate hypertension via activation of ET-1 in the placental ischemic reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. To achieve this goal we examined the effect of RUPP on mean arterial pressure and ET-1 in the presence and absence of chronically infused rituximab (R; 250 mg/kg), a B-lymphocyte-suppressive agent used clinically to treat autoimmune diseases. Mean arterial pressure was 103±1 mm Hg in normal pregnant (NP) rats; 103±3 mm Hg in NP+R versus 133±2 mm Hg in RUPP rats, and 118±2 mm Hg in RUPP+R rats (P<0.001 vs RUPP controls). B lymphocytes decreased from 6.0±0.5% gated cells in RUPP to 3.7±0.8% gated cells in RUPP+R rats. Importantly, agonistic autoantibodies to the angiotensin II type I receptor decreased from 18±1 bpm in RUPP rats to 10±1 bpm in RUPP+R rats. ET-1 decreased 1.5-fold in kidneys and 4-fold in the placenta (P<0.01) of RUPP+R versus RUPP rats. Media ET-1 excretion from endothelial cells exposed to serum from NP, RUPP, NP+R, or RUPP+R rats was determined. ET-1 from endothelial cells treated with NP serum was 53+13 pg/mg and increased to 75+10 pg/mg with RUPP serum. In contrast, ET-1 secretion decreased in response to B-cell-depleted RUPP serum to 50±8 pg/mg and was unchanged in response to NP+R sera (46±12 pg/mg). These data demonstrate the important roles that B-lymphocyte activation and agonistic autoantibodies to the angiotensin II type I receptors play in the pathophysiology of hypertension in response to placental ischemia.
We sought to determine the effect of an endothelin type A receptor antagonist (ETA) on uterine artery resistive index (UARI) and mean arterial pressure (MAP) in a placental ischemia rat model of preeclampsia produced by reduction in uterine perfusion pressure (RUPP).
Previous investigations suggested that agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) might mediate a hypertensive response through dysregulation of the endothelin-1 system. AT1-AA induced hypertension was attenuated by the AT1 receptor and/or endothelin-1 type A receptor antagonists.
Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of preeclampsia are unclear. One important initiating event in preeclampsia is thought to be reduced placental perfusion leading to the production of a variety of factors that cause widespread dysfunction of the maternal vasculature. The major objective of this review is to discuss the potential role of a novel agonistic autoantibody to the angiotensin II type I receptor (AT1-AA) in mediating hypertension during pregnancy. Although animal studies suggest that increasing plasma AT1-AA concentration in pregnant rats to levels observed in preeclamptic women or placental ischemic rats result in significant increases in arterial pressure, the quantitative importance of AT1-AA in the pathophysiology of preeclampsia in humans has yet to be fully elucidated.
Preeclampsia is associated with increased levels of reactive oxygen species (ROS) and the antiangiogenic factor, soluble fms-like tyrosine kinase-1 (sFlt-1). Moreover, recent studies have indicated that chronic sFlt-1 excess causes hypertension in pregnant animals. The purpose of this study was to evaluate the role of ROS in mediating sFlt-1-induced hypertension in the pregnant rat.
Chronic inflammation has been implicated in the pathology of hypertension; however, the role for specific cytokines remains unclear. We tested whether tumor necrosis factor-? blockade with etanercept (Etan) reduces mean arterial pressure in a female mouse model of systemic lupus erythematosus (SLE). SLE is a chronic inflammatory disorder with prevalent hypertension. Thirty-week-old SLE (NZBWF1) and control mice (NZW/LacJ) received Etan (0.8 mg/kg SC weekly) for 4 weeks or vehicle. Mean arterial pressure (in millimeters of mercury) was increased in SLE mice (150±5 versus 113±5 in controls; P<0.05) and was lower in Etan-treated SLE mice (132±3) but not controls (117±5). Albuminuria (in micrograms per milligram of creatinine) was elevated in SLE mice (28 742±9032 versus 1075±883; P<0.05) and was lower in Etan-treated SLE mice (8154±3899) but not control animals (783±226). Glomerulosclerosis (in percentage of glomeruli) was evident in SLE mice (2.5±1.6 versus 0.0±0.0 in controls; P<0.05) and was ameliorated in Etan-treated SLE mice (0.1±0.1). Renal cortex CD68(+) cell staining (in percentage of area) was elevated in SLE mice (4.75±0.80 versus 0.79±0.12 in controls; P<0.05) and was lower in Etan-treated SLE mice (2.28±0.32) but not controls (1.43±0.25). Renal cortex NADPH oxidase activity (relative light units per milligram of protein) was higher in SLE mice compared with controls (10 718±1276 versus 7584±229; P<0.05) and lowered in Etan-treated SLE mice (6645±490). Renal cortex nuclear factor ?B (phosphorylated and nonphosphorylated) was increased in SLE mice compared with controls and lower in Etan-treated SLE mice. These data suggest that TNF-? mechanistically contributes to the development of hypertension in a chronic inflammatory disease through increased renal nuclear factor ?B, oxidative stress, and inflammation.
Preeclampsia is considered a disease of immunological origin associated with abnormalities in inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), and activated lymphocytes secreting autoantibodies to the angiotensin II receptor (AT1-AA). Recent studies have also demonstrated that an imbalance of angiogenic factors, soluble fms-like tyrosine kinase (sFlt-1), and sEndoglin, exists in preeclampsia; however, the mechanisms that initiate their overproduction are unclear.
Although soluble fms-like tyrosine kinase 1 (sFlt-1), an antagonist of vascular endothelial growth factor and placental growth factor, has been implicated in the pathogenesis of hypertension during preeclampsia, the mechanisms whereby enhanced sFlt-1 production leads to hypertension remain unclear. Both sFlt-1 and endothelin 1 productions are elevated in women with preeclampsia and in placental ischemic animal models of preeclampsia; however, the importance of endothelin 1 and sFlt-1 interactions in the control of blood pressure during pregnancy is unknown. The purpose of this study was to determine the role of endothelin 1 in mediating sFlt-1-induced hypertension in pregnant rats. To achieve this goal, sFlt-1 (3.7 microg/kg per day for 6 days) was infused into normal pregnant rats and pregnant rats treated with a selective endothelin type A receptor antagonist, ABT 627 (5 mg/kg per day for 6 days). Plasma concentration of sFlt-1 increased from 735+/-34 pg/mL in normal pregnant rats to 2498+/-645 pg/mL (P<0.05) with infusion of sFlt-1. Arterial pressure increased from 100+/-1 mm Hg in normal pregnant rats to 122+/-3 mm Hg (P<0.05) in sFlt-1-infused rats. Chronic increases in plasma sFlt-1 in normal pregnant rats increased preproendothelin mRNA expression in the renal cortices by approximately 3-fold. In addition, chronic endothelin type A receptor blockade completely abolished the blood pressure response to sFlt-1 in pregnant rats (104+/-3 versus 100+/-1 mm Hg; P<0.05), whereas the endothelin A receptor antagonist had no effect on arterial pressure in NP rats (105+/-2 versus 100+/-1 mm Hg). In conclusion, this study demonstrates that endothelin 1, via endothelin type A receptor activation, plays an important role in mediating the hypertension in response to excess sFlt-1 during pregnancy.
Postmenopausal women (PMW) are at greater risk for salt-sensitive hypertension and insulin resistance than premenopausal women. Peroxisome-proliferator-activated receptor-gamma (PPARgamma) agonists reduce blood pressure (BP) and insulin resistance in humans. As in PMW, ovariectomy (OVX) increases salt sensitivity of BP and body weight in Dahl salt-sensitive (DS) rats. This study addressed whether rosiglitazone (ROSI), a PPARgamma agonist, attenuates salt-sensitive hypertension in intact (INT) and OVX DS rats, and if so, whether insulin resistance, nitric oxide (NO), oxidative stress, and/or renal inflammation were contributing mediators. Telemetric BP was similar in OVX and INT on low salt diet (0.3% NaCl), but was higher in OVX than INT on high salt (8% NaCl). ROSI reduced BP in OVX and INT on both low and high salt diet, but only attenuated salt sensitivity of BP in OVX. Nitrate/nitrite excretion (NO(x); index of NO) was similar in INT and OVX on low salt diet, and ROSI increased NO(x) in both groups. High salt diet increased NO(x) in all groups but ROSI only increased NO(x) in OVX rats. OVX females exhibited insulin resistance, increases in body weight, plasma leptin, cholesterol, numbers of renal cortical macrophages, and renal MCP-1 and osteopontin mRNA expression compared to INT. ROSI reduced cholesterol and macrophage infiltration in OVX, but not INT. In summary, PPARgamma activation reduces BP in INT and OVX females, but attenuates the salt sensitivity of BP in OVX only, likely due to increases in NO and in part to reductions in renal resident macrophages and inflammation.
Inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) may be an important link between placental ischemia and hypertension in preeclampsia. We examined the effect of 17-hydroxyprogesterone caproate (17-OHP) on TNF-alpha-stimulated endothelin (ET) production and hypertension during pregnancy.
Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and endothelin -1 (ET-1) are suggested to be important links between placental ischemia and hypertension during preeclampsia. Activation of the angiotensin II type 1 receptor (AT1R) increases endothelial cell production of ET-1; however, the importance of ET-1 in response to AT1-AA-mediated AT1 R activation during preeclampsia is unknown. Furthermore, the role of AT1-AA-mediated increases in blood pressure during pregnancy remains unclear. The objective of this study was to test the hypothesis that AT1-AA, increased to levels observed in preeclamptic women and placental ischemic rats, increases mean arterial pressure (MAP) by activation of the ET-1 system. Chronic infusion of purified rat AT1-AA into normal pregnant (NP) rats for 7 days increased AT1-AA from 0.68+/-0.5 to 10.88+/-1.1 chronotropic units (P<0.001). The increased AT1-AA increased MAP from 99+/-1 to 119+/-2 mm Hg (P<0.001). The hypertension was associated with significant increases in renal cortices (11-fold) and placental (4-fold) ET-1. To determine whether ET-1 mediates AT1-AA-induced hypertension, pregnant rats infused with AT1-AA and NP rats were treated with an ET(A) receptor antagonist. MAP was 100+/-1 mm Hg in AT1-AA+ET(A) antagonist-treated rats versus 98+/-2 mm Hg in ET(A) antagonist-treated rats. Collectively, these data support the hypothesis that one potential pathway whereby AT1-AAs increase blood pressure during pregnancy is by an ET-1-dependent mechanism.
An elevated plasma level of homocysteine (hyperhomocysteinemia) is thought to be an important risk factor for a variety of cardiovascular diseases including preeclampsia. Although clinical studies have reported a two- to threefold elevation in plasma levels of homocysteine in women who developed preeclampsia, the importance of hyperhomocysteinemia in causing endothelial dysfunction and increases in arterial pressure during pregnancy is unknown.
Uterine fibroids are the most prevalent benign tumors in women of reproductive age. The current knowledge on the fibroid disease mechanism has derived from studies of the Eker rat model where a unique germ line defect in the tuberous sclerosis 2 (Tsc2) tumor suppressor gene leads to the development of leiomyosarcoma, leiomyoma, and renal cancer. To study fibroids of human origin, we sought to establish fibroid xenografts in immune-compromised mice. We determined that lentiviral-mediated transduction of a green fluorescence protein (GFP)-luciferase (LUC) fusion gene and bioluminescence-based whole animal imaging allowed for the monitoring of transplanted fibroid cells in mice. We used this in vivo imaging approach to test a series of transplantation protocols and found that only freshly dissociated fibroid cells, but not the fibroid-derived smooth muscle cells grown in ex vivo cultures, can generate stable xenografts in subcutaneous Matrigel implants. Formation of the fibroid-xenografts requires the implantation of 17betaestradiol-releasing pellets in the recipient mice. Furthermore, freshly dissociated myometrial cells do not form xenografts under the experimental conditions. The xenograft protocol developed from this study provides an avenue for investigating the pathogenesis and drug responses of human fibroids.
Reduction in uteroplacental perfusion (RUPP) in pregnant rats is associated with hypertension, elevated cytokines, and activation of the endothelin (ET-1) system. Our objective was to determine whether the antiinflammatory properties of 17-alpha-hydroxyprogesterone caproate (17 OHP) reduce cytokine-stimulated vasoactive pathways that are associated with hypertension in response to placental ischemia.
Autoantibodies can cause complications in pregnancy. Preeclampsia is the leading cause of maternal and fetal morbidity and mortality during pregnancy. Overall, 5-10% of all pregnancies worldwide develop preeclampsia. Women who developed preeclampsia and their children have an increased risk to suffer from cardiovascular diseases later in life. In preeclampsia, agonistic autoantibodies against the angiotensin II type 1 receptor autoantibodies (AT1-AA) are described. They induce NADPH oxidase and the MAPK/ERK pathway leading to NF-?B and tissue factor activation. AT1-AA are detectable in animal models of preeclampsia and are responsible for elevation of soluble fms-related tyrosine kinase-1 (sFlt1) and soluble endoglin (sEng), oxidative stress, and endothelin-1, all of which are enhanced in preeclamptic women. AT1-AA can be detected in pregnancies with abnormal uterine perfusion and increased resistance index as well as in patients with systemic sclerosis and renal allograft rejection. This review discusses the current knowledge about the AT1-AA, its signaling, and their impact in pregnancy complications and other autoimmune disorders.
Although abnormal soluble fms-like tyrosine kinase-1 (sFlt-1) production is thought to be an important factor in the pathogenesis of preeclampsia (PE), the mechanisms that regulate the production of sFlt-1 during PE are unclear. While our laboratory has shown tumor necrosis factor-? (TNF-?) and sFlt-1 to be elevated in pregnant rats in response to placental ischemia, the importance of TNF-? in the regulation of sFlt-1 production is unknown. Therefore, the purpose of this study was to determine the role of TNF-? in mediating the increase in sFlt-1 in response to placental ischemia or hypoxia. Reductions in uterine perfusion pressure in pregnant rats significantly increased plasma levels of sFlt-1 and tended to increase TNF-?, an effect markedly attenuated by pretreatment with a TNF-? inhibitor etanercept (0.4 mg/kg). To further assess chronic interactions between TNF-? and sFlt-1, we examined a chronic effect of TNF-? infusion (50 ng/day) into normal pregnant rats to increase plasma sFlt-1 levels, as well as the effects of acute hypoxia on placental sFlt-1 production in the absence and presence of TNF-? blockade. Placental explants exposed to hypoxic conditions had enhanced TNF-? levels versus normoxic conditions, as well as increased sFlt-1 production. Pretreatment of placental explants with etanercept (15 ?M) significantly reduced TNF-? levels in response to hypoxia but did not attenuate sFlt-1 production. These data suggest that while TNF-? may not play an important role in stimulating sFlt-1 production in response to acute hypoxia, a more chronic hypoxia, or placental ischemia may be an important stimulus for enhanced sFlt-l production.
Preeclampsia is a multisystem disorder of pregnancy, originating in the placenta. Cytochrome P450 (CYP)-dependent eicosanoids regulate vascular function, inflammation, and angiogenesis, which are mechanistically important in preeclampsia.
Preeclampsia is associated with autoimmune cells T(H)17, secreting interleukin-17, autoantibodies activating the angiotensin II type I receptor (AT1-AA), and placental oxidative stress (ROS). The objective of our study was to determine whether chronic IL-17 increases blood pressure by stimulating ROS and AT1-AAs during pregnancy. To answer this question four groups of rats were examined: normal pregnant (NP, n = 20), NP+IL-17 (n = 12), NP+tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (n = 7) (a superoxide dismutase mimetic that scavenges ROS), and NP+IL-17+tempol (n = 11). IL-17 (150 pg/day) was infused into NP rats while tempol was administered via the drinking water ad libitum. On day 19 blood pressure (MAP) was recorded, and plasma, urine, and tissue were collected for isolation of ROS detected by chemilluminescent technique. Urinary isoprostane was measured by ELISA. AT1-AAs were determined via cardiomyocyte assay and expressed as beats per minute. MAP increased from 98 ± 3 mmHg in NP to 123 ± 3 mmHg in IL-17-infused NP rats. Urinary isoprostane increased from 1,029 ± 1 in NP to 3,526 ± 2 pg·mg(-1)·day(-1) in IL-17-infused rats (P < 0.05). Placental ROS was 436 ± 4 RLU·ml(-1)·min(-1) (n = 4) in NP and 702 ± 5 (n = 5) RLU·ml(-1)·min(-1) in IL-17-treated rats. Importantly, AT1-AA increased from 0.41 ± 0.05 beats/min in NP rats (n = 8) to 18.4 ± 1 beats/min in IL-17 rats (n = 12). Administration of tempol attenuated the hypertension (101 ± 3 mmHg) ROS (459 ± 5 RLU·ml(-1)·min(-1)) and blunted AT1-AAs (7.3 ± 0.6 beats/min) in NP+IL-17+tempol-treated rats. Additionally, AT1 receptor blockade inhibited IL-17-induced hypertension and placental oxidative stress. MAP was 105 ± 5 mmHg and ROS was 418 ± 5 RLU·ml(-1)·min(-1) in NP+IL 17-treated with losartan. These data indicate that IL-17 causes placental oxidative stress, which serves as stimulus modulating AT1-AAs that may play an important role in mediating IL-17-induced hypertension during pregnancy.
We have shown that adoptive transfer of CD4(+) T cells from placental ischemia (reduction in uteroplacental perfusion, RUPP) rats causes hypertension and elevated inflammatory cytokines during pregnancy. In this study we tested the hypothesis that adoptive transfer of RUPP CD4(+) T cells was associated with endothelin-1 activation as a mechanism to increase blood pressure during pregnancy. CD4(+) T cells from RUPP or normal pregnant (NP) rats were adoptively transferred into NP rats on gestational day 13. Mean arterial pressure (MAP) was analyzed on gestational day 19, and tissues were collected for endothelin-1 analysis. MAP increased in placental ischemic RUPP rats versus NP rats (124.1 ± 3 vs. 96.2 ± 3 mmHg; P = 0.0001) and increased in NP recipients of RUPP CD4(+) T cells (117.8 ± 2 mmHg; P = 0.001 compared with NP). Adoptive transfer of RUPP CD4(+) T cells increased placental preproendothelin-1 mRNA 2.1-fold compared with NP CD4(+) T cell rats and 1.7-fold compared with NP. Endothelin-1 secretion from endothelial cells exposed to NP rat serum was 52.2 ± 1.9 pg·mg(-1)·ml(-1), 77.5 ± 4.3 pg·mg(-1)·ml(-1) with RUPP rat serum (P = 0.0003); 47.2 ± .16 pg·mg(-1)·ml(-1) with NP+NP CD4(+) T cell serum, and 62.2 ± 2.1 pg·mg(-1)·ml(-1) with NP+RUPP CD4(+) T cell serum (P = 0.002). To test the role of endothelin-1 in RUPP CD4(+) T cell-induced hypertension, pregnant rats were treated with an endothelin A (ET(A)) receptor antagonist (ABT-627, 5 mg/kg) via drinking water. MAP was 92 ± 2 mmHg in NP+ET(A) blockade and 108 ± 3 mmHg in RUPP+ET(A) blockade; 95 ± 5 mmHg in NP+NP CD4(+) T cells+ET(A) blockade and 102 ± 2 mmHg in NP+RUPP CD4(+) T cells+ET(A) blockade. These data indicate the importance of endothelin-1 activation to cause hypertension via chronic exposure to activated CD4(+) T cells in response to placental ischemia.
Preeclampsia is defined as new-onset hypertension with proteinuria after 20 wk gestation and is hypothesized to be due to shallow trophoblast invasion in the spiral arteries thus resulting in progressive placental ischemia as the fetus grows. Many animal models have been developed that mimic changes in maternal circulation or immune function associated with preeclampsia. The model of reduced uterine perfusion pressure in pregnant rats closely mimics the hypertension, immune system abnormalities, systemic and renal vasoconstriction, and oxidative stress in the mother, and intrauterine growth restriction found in the offspring. The model has been successfully used in many species; however, rat and primate are the most consistent in comparison of characteristics with human preeclampsia. The model suffers, however, from lack of the ability to study the mechanisms responsible for abnormal placentation that ultimately leads to placental ischemia. Despite this limitation, the model is excellent for studying the consequences of reduced uterine blood flow as it mimics many of the salient features of preeclampsia during the last weeks of gestation in humans. This review discusses these features.
Preeclampsia (PE), new-onset hypertension with proteinuria during pregnancy, is associated with increased reactive oxygen species, the vasoactive peptide endothelin-1 (ET-1), T and B lymphocytes, soluble antiangiogenic factors sFlt-1 and sEndoglin (sFlt-1 and sEng), and agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA).
Hypertension in rats with chronic placental ischemia (reduced uterine perfusion pressure, RUPP) is associated with elevated inflammatory cytokines, agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and CD4(+) T cells; all of which are elevated in preclamptic women. Additionally, we have shown that adoptive transfer of RUPP CD4(+) T cells increases blood pressure, inflammatory cytokines, and sFlt-1. The objective of this study was to determine the long-term effects of RUPP CD4(+) T cells on AT1-AA, renal and systemic hemodynamics in pregnant rats. To answer this question CD4(+) T splenocytes were magnetically isolated on day 19 of gestation from control RUPP and normal pregnant (NP) rats and injected into a new group of NP rats at day 13 of gestation. On day 19 of gestation mean arterial pressure (MAP) and renal function (glomerular filtration rates, GFR) were analyzed and serum collected for AT1-AA analysis. To determine a role for AT1-AA to mediate RUPP CD4(+) T cell-induced blood pressure increases, MAP was analyzed in a second group of rats treated with AT1 receptor blockade losartan (10 mg·kg(-1)·day(-1)) and in a third group of rats treated with rituximab, a B cell-depleting agent (250 mg/kg) we have shown previously to decrease AT1-AA production in RUPP rats. MAP increased from 101 ± 2 mmHg NP to 126 ± 2 mmHg in RUPP rats (P < 0.001) and to 123 ± 1 mmHg in NP rats injected with RUPP CD4(+) T cells (NP+RUPP CD4(+)T cells) (P < 0.001). Furthermore, GFR decreased from 2.2 ml/min (n = 7) in NP rats to 1.0 ml/min (n = 5) NP+RUPP CD4(+)T cell. Circulating AT1-AA increased from 0.22 ± 0.1 units in NP rats to 13 ± 0.7 (P < 0.001) units in NP+RUPP CD4(+)T cell-treated rats but decreased to 8.34 ± 1 beats/min in NP+RUPP CD4(+) T cells chronically treated with rituximab. Hypertension in NP+RUPP CD4(+)T cell group was attenuated by losartan (102 ± 4 mmHg) and with B cell depletion (101 ± 5 mmHg). Therefore, we conclude that one mechanism of hypertension in response to CD4(+) T lymphocytes activated during placental ischemia is via AT1 receptor activation, potentially via AT1-AA during pregnancy.
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