Endothelial Mineralocorticoid Receptor Research Articles

Both endothelial mineralocorticoid receptor expression and hyperleptinemia are required for clinical characteristics of placental ischemia in mice.

One of the initiating events in preeclampsia (PE) is placental ischemia. Rodent models of placental ischemia do not present with vascular endothelial dysfunction, a hallmark of PE. We previously demonstrated a role for leptin in endothelial dysfunction in pregnancy in the absence of placental ischemia. We hypothesized that placental ischemia requires hyperleptinemia and endothelial mineralocorticoid receptor (ECMR) expression to induce PE-associated endothelial dysfunction in pregnant mice. We induced placental ischemia via the reduced uterine perfusion pressure (RUPP) procedure in pregnant ECMR-intact (ECMR+/+) and ECMR deletion (ECMR-/-) mice at gestational day (GD) 13. ECMR+/+ RUPP pregnant mice also received concurrent leptin infusion via miniosmotic pump (0.9 mg/kg/day). RUPP increased blood pressure via radiotelemetry and decreased fetal growth in ECMR+/+ pregnant mice. Both increases in blood pressure and reduced fetal growth were abolished in RUPP ECMR-/- mice. Placental ischemia did not decrease endothelial-dependent relaxation to acetylcholine (ACh) but increased phenylephrine (Phe) contraction in mesenteric arteries of pregnant mice, which was ablated by ECMR deletion. Addition of leptin to RUPP mice significantly reduced ACh relaxation in ECMR+/+ pregnant mice, accompanied by an increase in soluble FMS-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PLGF) ratio. In conclusion, our data indicate that high leptin levels drive endothelial dysfunction in PE and that ECMR is required for clinical characteristics of hypertension and fetal growth restriction in placental ischemia PE. Collectively, we show that both ECMR and leptin play a role to mediate PE.NEW & NOTEWORTHY Leptin is a key feature of preeclampsia that initiates vascular endothelial dysfunction in preeclampsia characterized by placental ischemia. Endothelial mineralocorticoid receptor (ECMR) deletion in placental ischemia protects pregnant mice from elevations in blood pressure and fetal growth restriction in pregnancy. Increases in leptin production mediate the key pathological feature of endothelial dysfunction in preeclampsia in rodents. ECMR activation contributes to the increase in blood pressure and fetal growth restriction in preeclampsia.

Eplerenone Reduces Blood Pressure and Improves Vascular Function in a Mouse Model of Leptin-induced Preeclampsia

Preeclampsia is a hypertensive pregnancy disease that increases the risks for adverse outcomes of pregnancy for both mother and baby, notably by reducing fetal growth in utero. We have shown that mid-late gestation leptin infusion induces preeclampsia characteristics in pregnant mice in inducing hypertension, endothelial dysfunction, and fetal growth restriction, which is ablated in mice with endothelial mineralocorticoid receptor deletion (ECMR). However, there is a lack of preclinical data and rationale for MR antagonism for use in preeclampsia in the existing literature. Therefore, we hypothesized that leptin increases ECMR expression and that MR antagonism decreases hypertension, endothelial dysfunction, and fetal growth restriction in leptin-induced preeclamptic mice. We infused timed-pregnant Balb/C mice with saline (sham) or leptin (LEP, 0.9 mg/kg/day) via s.c. osmotic minipump and administered vehicle or eplerenone (EPL, 200mg/kg/day) in drinking water from gestation day (GD)11-18 (n=7-12). We measured mean arterial blood pressure (BP) via radiotelemetry, vascular function in 2nd order mesenteric arteries by wire myography, and pup/placental weights on GD18. We isolated endothelial cells from placentas of our mice via magnetic cell sorting. Pairwise comparisons were by student’s t test and myography curves analyzed by 2-W ANOVA w/RM. Leptin increased ECMR mRNA expression (3.1±0.32 WT LEP vs 1.1±0.48 WT sham, fold change, *p<0.05) compared to WT sham mice in placenta indicating a direct role for leptin to upregulate ECMR in pregnancy. EPL ablated leptin-induced increases in BP (98±4 LEP/EPL vs 113±3 lep/veh mmHg, *p<0.05), and when treated with EPL leptin did not induce endothelial dysfunction, as assessed as a lack of decrease in vascular relaxation to acetylcholine (p>0.05 LEP/EPL vs sham/EPL). Interestingly, EPL treatment did not prevent leptin from decreasing placental effciency in pregnant mice (7.42±0.17 LEP/veh vs 6.71±0.15 LEP/EPL, pup/placenta weight ratio, p>0.05). Collectively, these data show that leptin infusion from GD11-18 in pregnant mice increases ECMR activation by increasing expression. Furthermore, MR antagonism by eplerenone ablates the maternal hypertension and endothelial dysfunction in leptin-induced preeclampsia mice, however, fetal growth is not restored by eplerenone. Therefore, eplerenone may be a promising therapeutic for the maternal cardiovascular syndrome of preeclampsia patients, however, MR antagonism therapies may need additional agents to improve fetal outcomes. 1R01HL169576, 4R00HL146948. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Atlas of cardiac endothelial cell enhancer elements linking the mineralocorticoid receptor to pathological gene expression.

Endothelial cells play crucial roles in physiology and are increasingly recognized as therapeutic targets in cardiovascular disease. Here, we analyzed the regulatory landscape of cardiac endothelial cells by assessing chromatin accessibility, histone modifications, and 3D chromatin organization and confirmed the functional relevance of enhancer-promoter interactions by CRISPRi-mediated enhancer silencing. We used this dataset to explore mechanisms of transcriptional regulation in cardiovascular disease and compared six different experimental models of heart failure, hypertension, or diabetes. Enhancers that regulate gene expression in diseased endothelial cells were enriched with binding sites for a distinct set of transcription factors, including the mineralocorticoid receptor (MR), a known drug target in heart failure and hypertension. For proof of concept, we applied endothelial cell-specific MR deletion in mice to confirm MR-dependent gene expression and predicted direct MR target genes. Overall, we have compiled here a comprehensive atlas of cardiac endothelial cell enhancer elements that provides insight into the role of transcription factors in cardiovascular disease.

Modulation of steroid pathway to preserve corneal transparency

Purpose: Corneal neovascularization (CN) is a major cause of blindness worldwide. We previously showed that endothelial mineralocorticoid receptor (MR) contributed to CN in mice. In this study, we investigated the mechanisms of action of MRA in a rat model of limbal deficiency.Methods: CN was induced in Lewis rats by total corneal de‐epithelialization and limbal scratching. Spironolactone (SPL, 25 mg/kg) or eplerenone was administered daily. Control eyes received vehicle. Rats were euthanized at day 3 and 7, and corneas were dissected for transcriptomic analysis. Proteins extracted from corneas at day 7 were used for western blot. Corneal innervation was evaluated by immunostaining of TUBB3 on corneal flat mounts at day 16. Corneal morphology and CN were assessed in vivo by Micron III optical coherence tomography and fluorescein angiography at day 14.Results: MR antagonists (MRA) favoured epithelial regeneration and nerve growth, reduced corneal angiogenesis, edema and inflammation in a rat model of CN. Transcriptomic analysis showed 75 differentially expressed genes in SPL groups. Gene set enrichment analysis highlighted pathways including wound healing and differentiation, inflammatory and immune responses, hypoxia, angiogenesis and neuroprotection. SPL upregulated Dcn, Col1a1, Timp2 and downregulated Lrg1 at day 3, and induced Pedf at day 7. Increase in DCN protein by SPL was confirmed by western blot.Conclusions: MRA regulates genes/proteins involved in anti‐inflammatory and anti‐angiogenic processes, and improves corneal re‐innervation in CN model. Dcn is one of the downstream regulated targets.

The Mineralocorticoid Receptor in the Vasculature: Friend or Foe?

Originally described as the renal aldosterone receptor that regulates sodium homeostasis, it is now clear that mineralocorticoid receptors (MRs) are widely expressed, including in vascular endothelial and smooth muscle cells. Ample data demonstrate that endothelial and smooth muscle cell MRs contribute to cardiovascular disease in response to risk factors (aging, obesity, hypertension, atherosclerosis) by inducing vasoconstriction, vascular remodeling, inflammation, and oxidative stress. Extrapolating from its role in disease, evidence supports beneficial roles of vascular MRs in the context of hypotension by promoting inflammation, wound healing, and vasoconstriction to enhance survival from bleeding or sepsis. Advances in understanding how vascular MRs become activated are also reviewed, describing transcriptional, ligand-dependent, and ligand-independent mechanisms. By synthesizing evidence describing how vascular MRs convert cardiovascular risk factors into disease (the vascular MR as a foe), we postulate that the teleological role of the MR is to coordinate responses to hypotension (the MR as a friend).

Endothelial MRs mediate Western diet-induced lipid disorders and skeletal muscle insulin resistance in females.

Consumption of a Western diet (WD) consisting of excess fat and carbohydrates activates the renin-angiotensin-aldosterone system, which has emerged as an important risk factor for systemic and tissue insulin resistance. We recently discovered that activated mineralocorticoid receptors (MRs) in diet-induced obesity induces CD36 expression, increases ectopic lipid accumulation, and results in systemic and tissue insulin resistance. Here, we further investigated whether endothelial cell (EC) specific MR (ECMR) activation participates in WD-induced ectopic skeletal muscle lipid accumulation, insulin resistance and dysfunction. Six-week-old female ECMR knockout (ECMR-/-) and wild type (ECMR+/+) mice were fed either a WD or a chow diet for 16 weeks. ECMR-/- mice were found to have decreased WD-induced in vivo glucose intolerance and insulin resistance at 16-weeks. Improved insulin sensitivity was accompanied by increased glucose transporter type 4 (Glut4) expression in conjunction with improved soleus insulin metabolic signaling in phosphoinositide 3-kinases/protein kinase B and endothelial nitric oxide synthase activation. Additionally, ECMR-/- also blunted WD-induced increases in CD36 expression and associated elevations in soleus free fatty acid, total intramyocellular lipid content, oxidative stress, and soleus fibrosis. Moreover, in vitro and in vivo activation of ECMR increased EC derived exosomal CD36 that was further taken up by skeletal muscle cells, leading to increased skeletal muscle CD36 levels. These findings indicate that in the context of an obesogenic WD, enhanced ECMR signaling increases EC derived exosomal CD36 resulting in increased uptake and elevated concentrations of CD36 in skeletal muscle cells, contributing to increased lipid metabolic disorders and soleus insulin resistance.

Abstract 120: Midgestation Eplerenone Treatment Ablates Leptin-induced Hypertension And Endothelial Dysfunction But Not Fetal Growth Restriction In Preeclamptic Mice

Elevated leptin (lep) in pregnant women strongly associates with preeclampsia (PE), a hypertensive pregnancy disorder. Our lab established a mid-late gestation lep-infusion model of PE, which induces endothelial dysfunction, hypertension and fetal growth restriction (FGR); deletion of endothelial mineralocorticoid receptors (MR) ablated these PE characteristics in pregnant mice. Whether pharmacological MR antagonism ablates lep-induced PE, however, is unknown. We hypothesized that MR antagonism (eplerenone) ablates lep-induced PE characteristics in pregnant mice. We infused pregnant BALB/c mice with leptin (lep, 0.9mg/kg/day) or saline (sham) via osmotic minipump alongside eplerenone (Eplr, 200mg/kg/day) or vehicle in drinking water from gestation day (GD)11-18. We measured vascular function via wire myography of 2 nd order mesenteric vessels and pup/placental weights on GD18 (n=5-7). We implanted radiotelemeters in separate mice (n=1-3) prior to mating and measured mean arterial pressure (BP) from GD11-18. Pre-pregnancy BP did not differ between treatment groups. Preliminary data indicates lep increased BP compared to sham from GD11-18 (112.7±4.5 lep vs 89.4 sham mmHg,) and Eplr decreased BP in lep pregnant mice (97.2±7.2 lep+Eplr mmHg, P=0.09 vs lep student’s t-test). Vascular relaxation to endothelial-dependent acetylcholine (ACh) decreased in lep+vehicle compared to sham+vehicle (*P<0.05, 2-Way ANOVA w/ RM). Eplr+lep restored ACh-mediated vascular relaxation (*P<0.05 vs lep+vehicle). LNAME pre-incubation did not ablate differences in ACh-mediated relaxation between lep+vehicle and lep+eplr (P>0.05) indicating that Eplr restored a non-NO mechanism to improve endothelial function. Lep as a variable decreased pup weight in both vehicle and Eplr pregnant mice, however, Eplr did not increase pup weight in either vehicle or lep mice (0.74±0.01sham+veh, 0.71±0.01 lep+veh, 0.70±0.01 sham+eplr, 0.67±0.01 lep+eplr (g), *P<0.05, 2-Way ANOVA). Collectively these data indicate that Eplr improves lep-induced endothelial dysfunction and hypertension, but may not prevent FGR when given from GD11-18. Therefore, further studies will determine whether MR antagonism promises therapeutic potential in lep-induced PE.

Abstract 050: Endothelial Cell Mineralocorticoid Receptor Deletion Improves Endothelial Function, Blood Pressure And Fetal Growth In The RUPP Mouse Model Of Preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy that causes adverse pregnancy outcomes. Progesterone in pregnancy increases endothelial mineralocorticoid receptor (ECMR) expression, which we showed mediates endothelial function in hypertensive female mice, however, whether ablating endothelial dysfunction in PE improves pregnancy outcomes is unknown. We hypothesized that improving endothelial function via ECMR deletion increases fetal growth and ablates hypertension in the reduced uterine perfusion pressure (RUPP) PE mouse. Pregnant ECMR-intact (WT) and -deficient (KO) mice underwent RUPP or sham surgery on GD13 and sacrificed on GD18 (WT Sham=9, WT RUPP=5, KO Sham=6, KO RUPP=6). Vascular function was measured via wire myography on 2 nd order mesenteric arteries and thoracic aorta. Systolic blood pressure (BP) was measured by radiotelemetry in a subset of mice. RUPP did not decrease maternal weights in either WT or KO mice (P>0.05) but decreased pup weight (726±20 WT+Sham vs 660±11mg WT+RUPP, *P<0.05) and fetal demise (16±4 vs 28±4% resoprtions/litter, *P<0.05) in WT pregnant mice, however, not in KO mice (710±15 KO+Sham vs 693±19 mg KO+RUPP, P>0.05, and 13±5 vs 28±12% resoprtions/litter, P>0.05), indicating KO protected fetal growth. RUPP reduced endothelial-dependent, acetylcholine-mediated vascular relaxation (10 -9 -3x10 -5 M) in WT, but not KO pregnant mice (*P<0.05, 2-way ANOVA w/ RM), but not aorta ACh-mediated relaxation (P>0.05). Nitric oxide synthase (NOS) inhibitor LNAME ablated differences in ACh-mediated relaxation between WT Sham and WT RUPP (P>0.05), with no differences observed in KO Sham or KO RUPP, in both aorta and mesenteric arteries, indicating RUPP impaired endothelial function via decreasing NOS activity. Preliminary data demonstrates RUPP increased BP on GD15-17 in WT (127±21 mmHg, N=3), however, not in KO pregnant mice (111±4, N=2). RUPP also ablated circadian rhythm in WT, but not KO, pregnant mice from GD15-18. Collectively, these data indicate that ECMR activation induces reduced pup weight, endothelial dysfunction and hypertension in the RUPP model which may lead to clinical studies for consideration of specific MR antagonists as therapeutic options for endothelial dysfunction in PE pregnancies.

Midgestation Leptin Infusion Induces Characteristics of Clinical Preeclampsia in Mice, Which Is Ablated by Endothelial Mineralocorticoid Receptor Deletion.

Patients with preeclampsia demonstrate increases in placental leptin production in midgestation, and an associated increase in late gestation plasma leptin levels. The consequences of mid-late gestation increases in leptin production in pregnancy is unknown. Our previous work indicates that leptin infusion induces endothelial dysfunction in nonpregnant female mice via leptin-mediated aldosterone production and endothelial mineralocorticoid receptor (ECMR) activation, which is ablated by ECMR deletion. Therefore, we hypothesized that leptin infusion in mid-gestation of pregnancy induces endothelial dysfunction and hypertension, hallmarks of clinical preeclampsia, which are prevented by ECMR deletion. Leptin was infused via miniosmotic pump (0.9 mg/kg per day) into timed-pregnant ECMR-intact (WT) and littermate-mice with ECMR deletion (KO) on gestation day (GD)11-18. Leptin infusion decreased fetal weight and placental efficiency in WT mice compared with WT+vehicle. Radiotelemetry recording demonstrated that blood pressure increased in leptin-infused WT mice during infusion. Leptin infusion reduced endothelial-dependent relaxation responses to acetylcholine (ACh) in both resistance (second-order mesenteric) and conduit (aorta) vessels in WT pregnant mice. Leptin infusion increased placental ET-1 (endothelin-1) production evidenced by increased PPET-1 (preproendothelin-1) and ECE-1 (endothelin-converting enzyme-1) expressions in WT mice. Adrenal aldosterone synthase (CYP11B2) and angiotensin II type 1 receptor b (AT1Rb) expression increased with leptin infusion in pregnant WT mice. KO pregnant mice demonstrated protection from leptin-induced reductions in pup weight, placental efficiency, increased BP, and endothelial dysfunction. Collectively, these data indicate that leptin infusion in midgestation induces endothelial dysfunction, hypertension, and fetal growth restriction in pregnant mice, which is ablated by ECMR deletion.

Endothelial Mineralocorticoid Receptors Constrain Arteriogenesis and Perfusion Recovery Following Chronic Arterial Ligation in a Sex‐specific Manner

Vascular occlusive diseases are major contributors to cardiovascular morbidity and mortality. Prior work has implicated mineralocorticoid receptor (MR) signaling in perfusion recovery following arterial occlusion, however, cell‐specific MR signaling in the associated angiogenic and arteriogenic responses has not been elucidated. Further, accumulating evidence has revealed sex‐specific involvement of MR signaling in a number of cardiovascular disease states. Accordingly, we examined the hypothesis that MR signaling, specifically endothelial cell (EC) MR signaling, attenuates vascular compensation and perfusion recovery following femoral artery excision and that this effect would be more pronounced in females. Unilateral femoral artery ligation and excision was performed in male and female C57BL/6J mice treated with vehicle or the MR antagonist spironolactone (Spiro; 20 mg/kg/d, sc) as well as in male and female MR Intact and EC MR knockout (KO) mice. Serial assessment of hindlimb perfusion for 28 days following surgery revealed enhanced perfusion recovery following Spiro treatment in female, but not male, mice. Interestingly, Spiro increased gastrocnemius capillary density in both the ischemic and sham limb in males and females. Following perfusion fixation, collateral remodeling was assessed by micro‐computed tomography revealing enhanced collateral expansion following Spiro treatment in female, but not male, mice. Additional mechanistic experiments similarly revealed increased perfusion recovery and enhanced collateral expansion in female, not male, EC MR KO mice independent of capillary density. At 28 days post‐surgery, distribution analysis revealed larger overall arteriolar diameters only in the collateral zone of EC MR KO females. Further analysis revealed enhanced early (7 days post‐surgery) collateral expansion in male and female EC MR KO mice. In female, but not male, EC MR KO mice this was associated with increased CD68+ macrophages and CD206+ ‘M2’‐like macrophages in the collateral zone. Together, these data demonstrate that EC MR signaling constrains early arteriogenic collateralization following arterial excision in both sexes and constrains long‐term collateralization only in females involving limitation of pro‐arteriogenic CD206+ ‘M2’‐like macrophages in the collateral zone. To our knowledge, this is the first report of a role for EC MR signaling in arteriogenesis and highlights potential use of MR blockers in the treatment of vascular occlusive events.

Endothelial mineralocorticoid receptor ablation confers protection towards endothelial dysfunction in experimental diabetes in mice.

With diabetes comes a significant risk of macrovascular and microvascular complications. Circulating aldosterone levels increase in patients with diabetes. Aldosterone can directly affect vascular function via activation of the mineralocorticoid receptor (MR). We hypothesized that aldosterone via endothelial MR impairs endothelial function in a murine model of experimental diabetes. Endothelial cell-specific mineralocorticoid receptor knockout MRflox/flox ; Tie2-Cre mice (ECMR-KO) and wild-type FVB littermates were subjected to an experimental type-1 diabetic model by low dose streptozotocin injections (55mg/kg/day) for five consecutive days. After 10weeks of diabetes, second-order mesenteric resistance arteries were perfused ex vivo to evaluate vessel contractility and endothelial function. The effect of ex vivo incubation with aldosterone with and without the antagonist, spironolactone was determined. Diabetic ECMR-KO and wild-type mice had similar, elevated, plasma aldosterone concentration while only diabetic wild-type mice displayed elevated urine albumin excretion and cardiac and kidney hypertrophy at 10weeks. There were no differences in contraction (Emax and EC50 ) to thromboxane receptor agonist (U46619) and elevated K+ between groups. Wild-type diabetic mice showed impaired acetylcholine (ACh)-dependent relaxation, while diabetic ECMR-KO mice had intact ACh-mediated relaxation. Aldosterone incubation ex vivo impaired ACh mediated relaxation and rendered responses similar to diabetic WT arteries. Direct, ex vivo aldosterone effects were absent in ECMR-KO animals. Ex vivo inhibitory effects of aldosterone on endothelial relaxation in arteries from WT were abolished by spironolactone. These findings show that endothelial cell mineralocorticoid receptor activation accounts for diabetes-induced systemic endothelial dysfunction in experimental diabetes and may explain the cardiovascular protection by MR antagonists in diabetes.

Abstract 03: Ablation Of Endothelial Dysfunction Improves Blood Pressure And Fetal Growth Restriction In A Mouse Model Of Preeclampsia-like Hyperleptinemia

Placental ischemia, an initiating event of preeclampsia (PE), increases plasma leptin levels. We recently developed a model of midgestation (gestation day (GD)11-18) leptin infusion mimicking the midgestation rise in leptin levels of PE patients. Our previous work demonstrates that deletion of endothelial mineralocorticoid receptors (ECMR) improves markers of vascular dysfunction in leptin-infused female mice. We hypothesized vascular function improvement with ECMR deletion ablates hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR +/+ (WT) and ECMR -/- (KO) mice were infused with vehicle or leptin by osmotic pump (lep, 0.9mg/kg/day, s.c.) on GD11-18 while implanted with radiotelemeters for conscious blood pressure (BP) measurement and wire myography of thoracic aorta and 2 nd order mesenteric arteries at GD18 (*=P<0.05). Leptin infusion did not decrease maternal weight in any groups. Leptin decreased pup weight (0.86±0.04g WT vs 0.52±0.11 WT+lep*) and placental efficiency (pup/placenta ratio) (9.7±0.7 WT vs 7.9±0.6 WT+lep*) in WT pregnant mice. ECMR deletion prevented leptin-mediated decreases in pup weight (0.91±0.06g KO vs 1.0±0.07 KO+lep) and placental efficiency (9.6±0.5 KO vs 9.4±1.2 KO+lep). Mean arterial pressure (BP) increased in leptin-infused WT (102±3mmHg WT vs 120±12 WT+lep*), but not KO (107±2 KO vs 106±8 KO+lep), mice from GD11-18. Leptin infusion reduced acetylcholine-mediated relaxation in both aorta and mesenteric arteries of WT* and constriction to KCl in mesenteric arteries in WT*, but not KO, pregnant mice (2-way ANOVA, repeated measures). Leptin increased plasma endothelin-1 (ET-1, 1.1±0.3 pg/ml WT vs 4.4±1.8 WT+lep*), placental mRNA expression of prepro-ET-1 (1.9±0.3-fold change from WT*) and ET-1 converting enzyme-1 (1.6±0.3-fold change from WT*) in pregnant WT mice. Leptin infusion also increased adrenal aldosterone-synthase protein (1.4±0.4 WT ratio/β actin vs 3.2±0.3 WT+lep*) and angiotensin II type 1 receptor b (3.5±0.8-fold change from WT*) mRNA in pregnant mice. Collectively, these data indicate that leptin infusion induces hypertension and fetal growth restriction in pregnant mice due to vascular dysfunction and increased ECMR activation in pregnant mice.

Endothelial Mineralocorticoid Receptor Deletion Ablates Leptin-Induced Preeclampsia Characteristics in Pregnancy

Endothelial Mineralocorticoid Receptor Deletion Ablates Leptin-Induced Preeclampsia Characteristics in Pregnancy

Mineralocorticoid and Estrogen Receptors in Endothelial Cells Coordinately Regulate Microvascular Function in Obese Female Mice.

[Figure: see text].

Endothelial mineralocorticoid receptor deletion ablates leptin‐induced cardiovascular and fetal growth preeclampsia characteristics in pregnant mice

Obesity increases the risk for preeclampsia (PE), a hypertensive syndrome of pregnancy characterized by placental ischemia. Obese PE patients demonstrate increases in plasma leptin levels in midgestation due to increased placental leptin production. We have shown that pregnancy increases endothelial mineralocorticoid receptor (ECMR) expression and that ECMR mediates leptin-induced endothelial dysfunction and hypertension in nonpregnant females. We therefore hypothesized that ECMR deletion protects from the development endothelial dysfunction, hypertension and fetal growth restriction in pregnant leptin-infused mice. Pregnant ECMR+/+ (WT) and ECMR-/- (KO) littermate mice were infused with vehicle or leptin (N=4-6/group) by osmotic minipump (0.9mg/kg/day, s.c.) from GD11-18 and thoracic aortas assessed for vascular function by wire myography. Separate groups (N=1-2/group) were implanted with radiotelemeters for systolic blood pressure (BP) measurement. Leptin decreased pup weight (0.86±0.04g WT vs 0.52±0.11g WT+lep, *P<0.05) and placental efficiency (9.7±0.7 WT vs 7.9±0.6 WT+lep, pup/placenta weight ratio, *P<0.05) indicating fetal growth restriction. ECMRdeletion prevented leptin-mediated decreases in pup weight (0.91±0.06g KO vs 1.0±0.07g KO+lep) and placental efficiency (9.6±0.5 KO vs 9.4±1.2 KO+lep). Preliminary data shows that prior to leptin infusion (GD8-11) all groups demonstrated similar BP and circadian rhythm of BP. Leptin infusion increased BP and ablated circadian rhythm (GD11-18, 114 mmHg WT vs 137 mmHg WT+lep), however, ECMR deletion blunted leptin-induced BP increases (112 KO mmHg vs 120 mmHg KO+lep) and preserved circadian rhythm. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of WT, but not KO, pregnant mice (2-way ANOVA, repeated measures, *P<0.05). Relaxation to acetylcholine with LNAME showed restoration of endothelial function in KO+lep mice was NO-dependent. In addition, ECMR deletion protected pregnant mice from leptin-induced increases in vascular α1 receptor-mediated constriction (phenylephrine) (*P<0.05). Endothelial-independent relaxation to sodium nitroprusside was similar across all groups. Moreover, ECMR deletion protected from leptin-mediated increases in placental mRNA expression of: sFlt-1 (WT+leptin: 1.2±0.03-fold from WT, *P<0.05, KO+leptin: 1.1±0.1-fold change from KO), HIF1α (WT+leptin: 1.6±0.1-fold, P=0.09, KO+leptin: 1.5±0.2-fold) and galectin 3 (WT+leptin: 3.2±0.5-fold, *P<0.05, KO+leptin: 0.8±0.1-fold). Collectively, these data indicate that ECMR deletion decreases BP, improves vascular function and placental function in association with increased vascular NO bioavailability and fetal growth in an obesity-associated, leptin-infusion model of PE.

Selective deletion of endothelial mineralocorticoid receptor protects from vascular dysfunction in sodium-restricted female mice

BackgroundRecent evidence by our laboratory demonstrates that women and female mice endogenously express higher endothelial mineralocorticoid receptor (ECMR) than males. Mounting clinical evidence also indicates that aldosterone production is higher in pathological conditions in females compared to males. However, the role for increased activation of ECMR by aldosterone in the absence of a comorbid condition is yet to be explored. The current study hypothesized that increased ECMR activation induced by elevated aldosterone production predisposes healthy female mice to endothelial dysfunction.MethodVascular reactivity was assessed in aortic rings from wild-type (WT) and ECMR KO (KO) mice fed either a normal salt (NSD, 0.4% NaCl) or sodium-restricted diet (SRD, 0.05% NaCl) for 28 days.ResultsSRD elevated plasma aldosterone levels as well as adrenal CYP11B2 and angiotensin II type 1 receptor (AT1R) expressions in female, but not male, WT mice. In baseline conditions (NSD), endothelial function, assessed by vascular relaxation to acetylcholine, was higher while vascular contractility to phenylephrine, serotonin, and KCl lower in female than male WT mice. SRD impaired endothelial function and increased vascular contractility in female, but not male, WT mice effectively ablating the baseline sex differences. NOS inhibition with LNAME ablated endothelial relaxation to a higher extent in male than female mice on NSD and ablated differences in acetylcholine relaxation responses between NSD- and SRD-fed females, indicating a role for NO in SRD-mediated endothelial function. In association, SRD significantly reduced vascular NOX4 expression in female, but not male, mice. Lastly, selective deletion of ECMR protected female mice from SRD-mediated endothelial dysfunction and increased vascular contractility.ConclusionCollectively, these data indicate that female mice develop aldosterone-induced endothelial dysfunction via endothelial MR-mediated reductions in NO bioavailability. In addition, these data support a role for ECMR to promote vascular contractility in female mice in response to sodium restriction.

Female Sex, a Major Risk Factor for Salt-Sensitive Hypertension.

High dietary salt is a significant contributor to essential hypertension in clinical populations. However, although clinical studies indicate a higher prevalence of salt sensitivity in women over men, knowledge of salt-sensitive mechanisms is largely restricted to males, and female-specific mechanisms are presently being elucidated. Male-specific mechanisms of salt-sensitive hypertension are well published and predominantly appear to involve dysfunctional renal physiology. However, emerging novel evidence indicates that aldosterone production is sex-specifically heightened in salt-sensitive hypertensive women and female rodent models, which may be regulated by intra-adrenal renin-angiotensin system activation and sex hormone receptors. In addition, new evidence that young females endogenously express higher levels of endothelial mineralocorticoid receptors (MRs) and that endothelial MR is a crucial mediator of endothelial dysfunction in females indicates that the aldosterone-endothelial MR activation pathway is a novel mediator of salt-sensitive hypertension. Heightened aldosterone levels and endothelial MR expression provide a 2-fold sex-specific mechanism that may underlie the pathology of salt-sensitive hypertension in women. This hypothesis indicates that MR antagonists may be a preferential treatment for premenopausal women diagnosed with salt-sensitive hypertension.

Abstract MP14: Endothelial Mineralocorticoid Receptor Deletion Abrogates Leptin-induced Endothelial Dysfunction And Fetal Growth Restriction In Pregnant Mice

Obesity increases preeclampsia (PE) risk. Plasma leptin levels increase with body weight in women with PE, and in addition, placental ischemia, an initiating event of PE, also increases plasma leptin. Our lab has shown that hyperleptinemia induces endothelial dysfunction and hypertension in female mice via endothelial mineralocorticoid receptor (ECMR) activation and that high progesterone levels of pregnancy increases ECMR expression. We hypothesized that leptin infusion induces PE-like endothelial dysfunction in pregnant mice, which is abrogated by ECMR deletion. Pregnant mice were infused with leptin by miniosmotic pump (0.9mg/kg/day, s.c.) on gestation day (GD) 11-18. Leptin decreased pup wt (0.86±0.04g ECMR +/+ vs 0.52±0.11 ECMR +/+ +leptin, *P&lt;0.05). and increased fetal resorption (3±39% ECMR +/+ vs 42±32 ECMR +/+ +leptin, P=0.09). ECMR deletion rescued pup weight (0.91±0.06g ECMR -/- vs 1.0±0.07 ECMR -/- +leptin) and protected fetal resorptions (2±2% ECMR -/- vs 0±0 ECMR -/- +leptin) in leptin-infused pregnant mice. In association, placental efficiency (pup/placenta ratio) decreased with leptin in ECMR +/+ (9.7±0.7 ECMR +/+ vs 7.9±0.6 ECMR +/+ +leptin, *P&lt;0.05), but not ECMR -/- (9.6±0.5 ECMR -/- vs 9.4±1.2 ECMR -/- +leptin) mice. Leptin infusion reduced endothelial function (acetylcholine-mediated relaxation) in aortas of ECMR +/+ , but not ECMR -/- , pregnant mice (2-way ANOVA, repeated measures, *P&lt;0.05). Relaxation responses to acetylcholine with LNAME showed restoration of endothelial function in ECMR -/- +leptin mice was due to preserved NO bioavailability. No changes in endothelial-independent sodium nitroprusside or contractile responses to phenylephrine, serotonin or KCl were observed. ECMR deletion reduced aorta IL-1β mRNA (0.5±0.1-fold change ECMR +/+ +leptin vs 0.2±0.1-fold change ECMR -/- +leptin, P=0.06) levels and also placental growth factor mRNA (1.0±0.3-fold change ECMR +/+ +leptin vs 01.3±0.1 ECMR -/- +leptin, P=0.05) in placental tissues. Collectively, these data indicate that ECMR deletion protects pregnant mice from adverse fetal growth and demise in association with increasing NO vascular bioavailability, reducing vascular inflammation and improving placental function in a leptin-infused model of PE.

SAT-LB97 MiRNA-99a and mTOR2 Mediate Enhanced Endothelial Mineralocorticoid Receptor Signaling-Induced Activation of Sodium Channel and Endothelium Stiffness

In diet induced obesity enhanced endothelial cell (EC) mineralocorticoid receptor (MR) (ECMR) and downstream sodium channel (EnNaC) activity increases oxidative stress and inflammation, thereby promoting vascular stiffness and associated impaired endothelial mediated relaxation. For example, consumption of a Western diet (WD) containing excess fat (46%) and fructose (17.5%) for 16 weeks elevated plasma aldosterone levels and increased vascular MR expression in conjunction with increased endothelial and vascular stiffness in female mice. EC specific deletion of either the ECMR or EnNaC significantly attenuated this diet induced endothelial/vascular stiffness. Emerging information suggests that abnormal expression of miR-99a may be involved in these processes. To this point, we recently observed that aldosterone (10-7 mol/L) causes a reduction in miR-99a that was prevented by the MR antagonist, spironolactone (10µM) in in vitro ECs. By using RNA sequencing, we also demonstrated that ECMR activation reduced arterial miR-99a expression in diet induced obesity. Since the mammalian target of rapamycin (mTOR2)/SGK1 signaling pathway is involved in aldosterone activation of ENaC we then explored the effects of miR-99a on mTOR2 expression. Indeed, miR-99a reduced mTOR2. We further observed that inhibition of mTOR2 with PP242 inhibited EnNaC activity as determined by patch clamping of ECs. Collectively these data suggest that consumption of a WD induced ECMR activation and increased EnNaC activity and endothelial stiffness, in part, by reducing the tonic inhibitory effects exerted by miR-99a on mTOR2 mediated EnNaC activation.

Attenuation of Mineralocorticoid Receptor Signaling Promotes Vascular Recovery from Hind Limb Ischemia in a Sex Specific Manner

Peripheral arterial disease (PAD) is a growing concern affecting 8.5 million Americans annually and contributing to both fatal and non‐fatal cardiovascular ischemic events. Importantly, available evidence indicates that women experience higher rates of occlusion, reintervention, and mortality than males, however, mechanisms underlying these sex differences remain unclear. Recent evidence has revealed sex‐specific deleterious effects of mineralocorticoid receptor (MR) signaling in a variety of cardiovascular conditions including vascular inflammation and endothelial dysfunction, which have been implicated in PAD. Whether MR signaling differentially impairs microvascular adaptations in males and females following an ischemic insult, however, has not been examined. Accordingly, we evaluated the hypothesis that attenuation of MR signaling promotes microvascular compensation and perfusion recovery following hind limb ischemia (HLI) to a greater extent in females than in males involving enhanced capillary neovascularization and augmented outward remodeling of existing collaterals. Male and female C57BL/6J mice (10–12 weeks old) underwent unilateral femoral artery ligation and excision to induce HLI after implantation of pellets containing either placebo or the MR antagonist spironolactone (20mg/kg/day, sc). The contralateral leg underwent sham surgery with no ligation or excision. Hind limb perfusion was serially assessed for 28 days with laser Doppler imaging. At 28 days post occlusion, the hind limb vasculature was perfusion fixed following maximal dilation and perfused with bismuth for assessment of collateral morphology by micro‐CT imaging. These studies were complemented with immunohistochemistry and angiogenic assay experiments. Additional preliminary HLI experiments were conducted in male mice with endothelial cell‐specific MR (EC MR) deletion. Systemic inhibition of MR signaling enhanced recovery of hind limb perfusion in female, not male, mice. This effect of MR blockade was associated with greater outward collateral remodeling in females compared to males. Interestingly, spironolactone similarly increased skeletal muscle capillary density in both hind limbs of males and females consistent with impairment of VEGF‐stimulated capillary sprouting by the MR agonist aldosterone in an aortic angiogenesis assay. Finally, preliminary studies revealed enhanced recovery of hind limb perfusion in male mice with EC MR deletion and that EC MR deletion enhanced aortic capillary sprouting in vitro. Taken together, these data suggest that MR signaling limits the microvascular response to ischemia and that enhanced perfusion recovery following MR blockade in females involves greater collateral expansion compared to males. Significant vascular cell‐specificity of MR signaling underlying these responses may contribute to these sex differences and warrant further investigation.Support or Funding InformationFunded by HL136386, HL095590, and HL088105.