Use of Induced Pluripotent Stem Cells to Build Isogenic Systems and Investigate Type 1 Diabetes

Type 1 diabetes (T1D) is a disease that arises due to complex immunogenetic mechanisms. Key cell-cell interactions involved in the pathogenesis of T1D are activation of autoreactive T cells by dendritic cells (DC), migration of T cells across endothelial cells (EC) lining capillary walls into the islets of Langerhans, interaction of T cells with macrophages in the islets, and killing of β-cells by autoreactive CD8⁺ T cells. Overall, pathogenic cell-cell interactions are likely regulated by the individual's collection of genetic T1D-risk variants. To accurately model the role of genetics, it is essential to build systems to interrogate single candidate genes in isolation during the interactions of cells that are essential for disease development. However, obtaining single-donor matched cells relevant to T1D is a challenge. Sourcing these genetic variants from human induced pluripotent stem cells (iPSC) avoids this limitation. Herein, we have differentiated iPSC from one donor into DC, macrophages, EC, and β-cells. Additionally, we also engineered T cell avatars from the same donor to provide an in vitro platform to study genetic influences on these critical cellular interactions. This proof of concept demonstrates the ability to derive an isogenic system from a single donor to study these relevant cell-cell interactions. Our system constitutes an interdisciplinary approach with a controlled environment that provides a proof-of-concept for future studies to determine the role of disease alleles (e.g. IFIH1, PTPN22, SH2B3, TYK2) in regulating cell-cell interactions and cell-specific contributions to the pathogenesis of T1D.

A hypertension patient-derived iPSC model demonstrates a role for G protein-coupled estrogen receptor in hypertension risk and development

Hypertension (HTN) is a polyfactorial disease that can manifest severe cardiovascular pathologies such as heart failure or stroke. Genome-wide association studies (GWAS) of HTN indicate that single-nucleotide polymorphisms (SNPs) contribute to increased risk for HTN and resistance to some HTN drug regimens (Hiltunen TP et al., J Am Heart Assoc 4: e001521, 2015; Le MT et al., PLoS One 8: e52062, 2013; McDonough CW et al., J Hypertens 31: 698-704, 2013; Vandell AG et al., Hypertension 60: 957-964, 2012). However, cellular mechanistic insights of such SNPs remain largely unknown. Using a bank of induced pluripotent stem cells (iPSCs) derived from patients with HTN and CRISPR/Cas9-mediated gene-editing approach, we investigated the effects of a female HTN risk-associated SNP (rs1154431) of the G protein-coupled estrogen receptor (GPER) (Bassuk SS, Manson JE., Clin Chem 60: 68-77, 2014) in vascular endothelial cells. Although GPER1 deletion reduced endothelial nitric oxide synthase (eNOS) activation in iPSC-derived endothelial cells (iECs), the polymorphism itself did not significantly affect eNOS and NO production in a comparison of isogenic hemizygous iECs expressing either normal (P16) or HTN-associated (L16) GPER. Interestingly, we demonstrate for the first time that GPER plays a role in regulation of adhesion molecule expression and monocyte adhesion to iECs. Moreover, the L16 iECs had higher expression of inflammation genes than P16 iECs, implying that the risk variant may affect carrier individuals through increased inflammatory activity. This study further indicates that iPSCs are a useful platform for exploring mechanistic insights underlying hypertension GWAS endeavors.

Abstract P261: GPER is Required for Age-dependent Albuminuria and Glomerulosclerosis: Evidence for its Role in Podocyte Injury and Mesangial Nox1 Regulation

We recently found that the G-protein coupled estrogen receptor (GPER) exerts constitutive effects on cell proliferation and fibrosis in heart failure and arterial hypertension via the NADPH oxidase isoform Nox1 (Sci Signal 2016; 9(452): ra105). Whether GPER affects glomerulosclerosis or podocyte function is unknown. Thus, the present study investigated the effects of GPER in a model of age-dependent spontaneous focal segmental glomerulosclerosis and studied effects of GPER inhibition in mesangial cells and podocytes. Albuminuria and kidney histology were studied in male wild-type (WT) and GPER-deficient ( Gper -/- ) mice at 4 and 24 months of age. Aged Gper -/- mice were largely protected from albuminuria (albumin/creatinine-ratio, 0.9±0.4 vs. 3.5±1.0, -74 %, p<0.05 vs. WT). Gper deficiency had no effect at 4 months of age, but largely prevented age-dependent increases in kidney weight (306±11 vs. 554±94 mg), and glomerulosclerosis index (1.3±0.2 vs. 2.9±0.4, p<0.05 vs. WT). All changes were independent of blood pressure. In human podocytes exposed to TGFβ-1, treatment with the selective GPER blocker G36 markedly reduced mRNA expression of injury markers nephrin, collagen-4, and Wilms-tumor-1 (all p<0.01). Gper knock-down in rat mesangial cells reduced Nox1 protein expression by approx. 50% (p<0.05) while Nox2 and Nox4 expression remained unchanged. These results indicate that constitutive activity of Gper maintains Nox1 expression and contributes to podocyte injury in vitro and that Gper is essential for age-dependent podocyte injury, subsequent albuminuria, fibrosis and glomerulosclerosis in vivo. Nox1 downregulators such as G36 represent a new class of drugs that may offer therapeutic potential for patients with chronic renal diseases and other forms of chronic non-communicable diseases involving inflammation and fibrosis.

Genome Wide Association Study Identifies the HMGCS2 Locus to be Associated With Chlorthalidone Induced Glucose Increase in Hypertensive Patients

Background

Thiazide and thiazide‐like diuretics are first‐line medications for treating uncomplicated hypertension. However, their use has been associated with adverse metabolic events, including hyperglycemia and incident diabetes mellitus, with incompletely understood mechanisms. Our goal was to identify genomic variants associated with thiazide‐like diuretic/chlorthalidone‐induced glucose change.

Methods and Results

Genome‐wide analysis of glucose change after treatment with chlorthalidone was performed by race among the white (n=175) and black (n=135) participants from the PEAR‐2 (Pharmacogenomic Evaluation of Antihypertensive Responses‐2). Single‐nucleotide polymorphisms with P<5×10⁻⁸ were further prioritized using in silico analysis based on their expression quantitative trait loci function. Among blacks, an intronic single‐nucleotide polymorphism (rs9943291) in the HMGCS2 was associated with increase in glucose levels following chlorthalidone treatment (ß=12.5; P=4.17×10⁻⁸). G‐allele carriers of HMGCS2 had higher glucose levels (glucose change=+16.29 mg/dL) post chlorthalidone treatment compared with noncarriers of G allele (glucose change=+2.80 mg/dL). This association was successfully replicated in an independent replication cohort of hydrochlorothiazide‐treated participants from the PEAR study (ß=5.54; P=0.023). A meta‐analysis of the 2 studies was performed by race in Meta‐Analysis Helper, where this single‐nucleotide polymorphism, rs9943291, was genome‐wide significant with a meta‐analysis P value of 3.71×10⁻⁸. HMGCS2, a part of the HMG‐CoA synthase family, is important for ketogenesis and cholesterol synthesis pathways that are essential in glucose homeostasis.

Conclusions

These results suggest that HMGCS2 is a promising candidate gene involved in chlorthalidone and Hydrochlorothiazide (HCTZ)‐induced glucose change. This may provide insights into the mechanisms involved in thiazide‐induced hyperglycemia that may ultimately facilitate personalized approaches to antihypertensive selection for hypertension treatment.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00246519 and NCT01203852.

Role of GPER in estrogen-dependent nitric oxide formation and vasodilation

Estrogens are potent regulators of vasomotor tone, yet underlying receptor- and ligand-specific signaling pathways remain poorly characterized. The primary physiological estrogen 17β-estradiol (E2), a non-selective agonist of classical nuclear estrogen receptors (ERα and ERβ) as well as the G protein-coupled estrogen receptor (GPER), stimulates formation of the vasodilator nitric oxide (NO) in endothelial cells. Here, we studied the contribution of GPER signaling in E2-dependent activation of endothelial NO formation and subsequent vasodilation. Employing E2 and the GPER-selective agonist G-1, we investigated eNOS phosphorylation and NO formation in human endothelial cells, and endothelium-dependent vasodilation in the aortae of wild-type and Gper-deficient mice. Both E2 and G-1 induced phosphorylation of eNOS at the activation site Ser1177 to similar extents. Endothelial NO production to E2 was comparable to that of G-1, and was substantially reduced after pharmacological inhibition of GPER. Similarly, the clinically used ER-targeting drugs 4OH-tamoxifen, raloxifene, and ICI182,780 (faslodex, fulvestrant™) induced NO formation in part via GPER. We identified c-Src, EGFR, PI3K and ERK signaling pathways to be involved in GPER-dependent NO formation. In line with activation of NO formation in cells, E2 and G-1 induced equally potent vasodilation in the aorta of wild-type mice. Gper deletion completely abrogated the vasodilator response to G-1, while reducing the response to E2 by ∼50%. These findings indicate that a substantial portion of E2-induced endothelium-dependent vasodilation and NO formation is mediated by GPER. Thus, selective targeting of vascular GPER may be a suitable approach to activate the endothelial NO pathway, possibly leading to reduced vasomotor tone and inhibition of atherosclerotic vascular disease.

Concise Review: Induced Pluripotent Stem Cell Research in the Era of Precision Medicine

Recent advances in DNA sequencing technologies are revealing how human genetic variations associate with differential health risks, disease susceptibilities, and drug responses. Such information is now expected to help evaluate individual health risks, design personalized health plans and treat patients with precision. It is still challenging, however, to understand how such genetic variations cause the phenotypic alterations in pathobiologies and treatment response. Human induced pluripotent stem cell (iPSC) technologies are emerging as a promising strategy to fill the knowledge gaps between genetic association studies and underlying molecular mechanisms. Breakthroughs in genome editing technologies and continuous improvement in iPSC differentiation techniques are particularly making this research direction more realistic and practical. Pioneering studies have shown that iPSCs derived from a variety of monogenic diseases can faithfully recapitulate disease phenotypes in vitro when differentiated into disease-relevant cell types. It has been shown possible to partially recapitulate disease phenotypes, even with late onset and polygenic diseases. More recently, iPSCs have been shown to validate effects of disease and treatment-related single nucleotide polymorphisms identified through genome wide association analysis. In this review, we will discuss how iPSC research will further contribute to human health in the coming era of precision medicine. Stem Cells 2017;35:545-550.

Obligatory role for GPER in cardiovascular aging and disease

Pharmacological activation of the heptahelical G protein-coupled estrogen receptor (GPER) by selective ligands counteracts multiple aspects of cardiovascular disease. We thus expected that genetic deletion or pharmacological inhibition of GPER would further aggravate such disease states, particularly with age. To the contrary, we found that genetic ablation of Gper in mice prevented cardiovascular pathologies associated with aging by reducing superoxide (⋅O₂^-) formation by NADPH oxidase (Nox) specifically through reducing the expression of the Nox isoform Nox1 Blocking GPER activity pharmacologically with G36, a synthetic, small-molecule, GPER-selective blocker (GRB), decreased Nox1 abundance and ⋅O₂^- production to basal amounts in cells exposed to angiotensin II and in mice chronically infused with angiotensin II, reducing arterial hypertension. Thus, this study revealed a role for GPER activity in regulating Nox1 abundance and associated ⋅O₂^--mediated structural and functional damage that contributes to disease pathology. Our results indicated that GRBs represent a new class of drugs that can reduce Nox abundance and activity and could be used for the treatment of chronic disease processes involving excessive ⋅O₂^- formation, including arterial hypertension and heart failure.

GPER is required for the age-dependent upregulation of the myocardial endothelin system

AIMS

Cardiac aging is associated with progressive structural changes and functional impairment, such as left ventricular hypertrophy, fibrosis and diastolic dysfunction. Aging also increases myocardial activity of endothelin-1 (ET-1), a multifunctional peptide with growth-promoting and pro-fibrotic activity. Because the G protein-coupled estrogen receptor (GPER) regulates vascular responsiveness to ET-1, we investigated whether GPER also plays a role in the regulation of the myocardial endothelin system with aging.

MAIN METHODS

Young (4month-old) and aged (24month-old) wild-type and Gper-deficient (Gper(-/-)) mice were studied. Gene expression levels of prepro-ET-1, endothelin converting enzymes ECE-1 and ECE-2, and endothelin ETA and ETB receptors were determined by qPCR in left ventricular myocardium.

KEY FINDINGS

Aging markedly increased steady-state mRNA expression levels of ECE-1, ECE-2, ETA and ETB receptors (each p<0.001 vs. young mice). Deletion of Gper inhibited the age-dependent increase in ECE-2 and ETB receptor mRNA levels (57% and 40% reduction, respectively, each p<0.01 vs. wild-type mice), whereas gene expression of prepro-ET-1, ECE-1, and the ETA receptor was unaffected in Gper(-/-) mice.

SIGNIFICANCE

We identified a novel regulatory mechanism through which the endogenous Gper facilitates the age-dependent increase in myocardial expression of ECE-2 and the ETB receptor, which is compatible with an activating role of GPER for the local endothelin system with aging. Targeting GPER signaling by selective antagonists may therefore be considered a new therapeutic approach to reduce age-dependent increased ET-1 activity and the associated development of left ventricular hypertrophy, fibrosis and heart failure.

G protein-coupled estrogen receptor inhibits vascular prostanoid production and activity

Complications of atherosclerotic vascular disease, such as myocardial infarction and stroke, are the most common causes of death in postmenopausal women. Endogenous estrogens inhibit vascular inflammation-driven atherogenesis, a process that involves cyclooxygenase (COX)-derived vasoconstrictor prostanoids such as thromboxane A2. Here, we studied whether the G protein-coupled estrogen receptor (GPER) mediates estrogen-dependent inhibitory effects on prostanoid production and activity under pro-inflammatory conditions. Effects of estrogen on production of thromboxane A(2) were determined in human endothelial cells stimulated by the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-α). Moreover, Gper-deficient (Gper(-/-)) and WT mice were fed a pro-inflammatory diet and underwent ovariectomy or sham surgery to unmask the role of endogenous estrogens. Thereafter, contractions to acetylcholine-stimulated endothelial vasoconstrictor prostanoids and the thromboxane-prostanoid receptor agonist U46619 were recorded in isolated carotid arteries. In endothelial cells, TNF-α-stimulated thromboxane A2 production was inhibited by estrogen, an effect blocked by the GPER-selective antagonist G36. In ovary-intact mice, deletion of Gper increased prostanoid-dependent contractions by twofold. Ovariectomy also augmented prostanoid-dependent contractions by twofold in WT mice but had no additional effect in Gper(-/-) mice. These contractions were blocked by the COX inhibitor meclofenamate and unaffected by the nitric oxide synthase inhibitor l-N(G)-nitroarginine methyl ester. Vasoconstrictor responses to U46619 did not differ between groups, indicating intact signaling downstream of thromboxane-prostanoid receptor activation. In summary, under pro-inflammatory conditions, estrogen inhibits vasoconstrictor prostanoid production in endothelial cells and activity in intact arteries through GPER. Selective activation of GPER may therefore be considered as a novel strategy to treat increased prostanoid-dependent vasomotor tone or vascular disease in postmenopausal women.

Abstract P607: Deletion of GPER Protects from Age-related Renovascular Dysfunction and Tubulo-interstitial Injury

Aging is associated with reduced vasodilatory capacity in renal arteries. Activation of the G protein-coupled estrogen receptor (GPER) induces vasodilation and improves hypertensive renal injury in rats. Moreover, GPER, as observed with many G protein-coupled receptors, likely exhibits “basal activity” independent of ovarian estrogen production, which may become relevant in disease-like states such as aging. We hypothesized that deletion of basal GPER activity would further aggravate vasodilatory dysfunction in renal arteries and the associated tubulo-interstitial injury. In young (4 month-old) and senescent (24 month-old) male wild-type and GPER-deficient ( Gper -/- ) mice, blood pressure and endothelium-dependent vasodilation to acetylcholine in renal arteries were determined. In addition, vascular injury (VIS score) and tubulo-interstitial injury (TIS score) including staining for amyloid were quantified in histologic sections. In wild-type mice, aging markedly reduced renal artery vasodilation to acetylcholine (from 77±5% to 28±4% of precontraction, n=4-5, p<0.001 vs. young mice), and increased vascular injury (VIS: 0.42±0.07 vs. 0.04±0.03), tubulo-interstitial injury (TIS: 2.9±0.6 vs. 0.3±0.1), and amyloid staining (2.8±0.7 vs. 0±0, all n=6-8, p<0.001 vs. young mice). Contrary to our hypothesis, vasodilatory responses to acetylcholine were largely preserved in renal arteries from senescent Gper -/- mice (63±4 vs. 28±4% of precontraction, n=4-5, p<0.001 vs. wild-type mice). Similarly, in senescent Gper -/- mice, vascular injury (VIS) was reduced by 46% (n=6-7, p=0.09 vs. wild-type mice), as were tubulo-interstitial injury (TIS) and amyloid staining by 77% and 92%, respectively (both n=6-7, p<0.01 vs. wild-type mice). Deletion of Gper had no effect on blood pressure in either senescent (110±5/83±1 vs. 114±2/87±2 mmHg) or young animals (117±2/90±1 vs. 119±2/91±2 mmHg, both n=5-12, p=n.s. vs. wild-type mice). These results indicate a novel role for GPER expression in age-related impaired vasodilatory capacity in renal arteries and the associated tubulo-interstitial injury independent of blood pressure, as well as a pathophysiologically relevant activity of GPER in male mice, possibly independent of estrogen.

Prostanoid-mediated contractions of the carotid artery become Nox2-independent with aging

Aging is a major risk factor for carotid artery disease that may lead to stroke and dementia. Vascular effects associated with aging include increased vasomotor tone, as well as enhanced contractility to endothelial vasoconstrictor prostanoids and reduced nitric oxide (NO) bioactivity partly due to increased oxidative stress. We hypothesized that vascular NADPH oxidase (Nox)-derived superoxide may be involved in prostanoid- and NO-related functional aging. NO-mediated relaxations and prostanoid-mediated contractions to acetylcholine as well as phenylephrine-dependent contractions were investigated in the carotid artery from young (4 months) and aged mice (24 months). Gene expression of Nox subunits and endothelial NO synthase (eNOS) was determined in the carotid artery and aorta. In young mice, the thromboxane-prostanoid receptor antagonist SQ 29,548 fully blocked acetylcholine-induced contractions while reducing responses to phenylephrine by 75 %. The Nox2-targeted inhibitor Nox2ds-tat and the superoxide scavenger tempol reduced acetylcholine-stimulated, prostanoid-mediated contractions by 85 and 75 %, respectively, and phenylephrine-dependent contractions by 45 %. Unexpectedly, in aged mice, the substantial Nox2-dependent component of acetylcholine- and phenylephrine-induced, prostanoid-mediated contractions was abolished. In addition, endothelium-dependent, NO-mediated relaxations were impaired with aging. The expression of Nox subunits was greater in the aorta compared with the carotid artery, in which Nox1 was undetectable. eNOS gene expression was reduced in the aorta of aged compared to young mice. In conclusion, aging decreases prostanoid-mediated contractility in the carotid artery involving a loss of Nox2 activity and is associated with impaired endothelium-dependent, NO-mediated relaxation. These findings may contribute to a better understanding of the pathophysiology of carotid artery disease and the aging process.

G protein-coupled estrogen receptor protects from atherosclerosis

Coronary atherosclerosis and myocardial infarction in postmenopausal women have been linked to inflammation and reduced nitric oxide (NO) formation. Natural estrogen exerts protective effects on both processes, yet also displays uterotrophic activity. Here, we used genetic and pharmacologic approaches to investigate the role of the G protein-coupled estrogen receptor (GPER) in atherosclerosis. In ovary-intact mice, deletion of gper increased atherosclerosis progression, total and LDL cholesterol levels and inflammation while reducing vascular NO bioactivity, effects that were in some cases aggravated by surgical menopause. In human endothelial cells, GPER was expressed on intracellular membranes and mediated eNOS activation and NO formation, partially accounting for estrogen-mediated effects. Chronic treatment with G-1, a synthetic, highly selective small molecule agonist of GPER, reduced postmenopausal atherosclerosis and inflammation without uterotrophic effects. In summary, this study reveals an atheroprotective function of GPER and introduces selective GPER activation as a novel therapeutic approach to inhibit postmenopausal atherosclerosis and inflammation in the absence of uterotrophic activity.

Abstract 653: Stimulation Of Endothelial Nitric Oxide Production And Dilation By The G Protein-coupled Estrogen Receptor

Endogenous estrogens mediate protective effects in the cardiovascular system in part due to rapid activation of endothelial nitric oxide synthase (eNOS), which involves the classical estrogen receptor (ER) α. Estrogen-dependent increases in NO bioactivity may also be mediated by the G protein-coupled estrogen receptor (GPER/GPR30), although the contribution of GPER to the overall response to estrogen and the mechanisms involved remain unclear. We have investigated GPER-mediated NO signaling in telomerase-immortalized human umbilical vein endothelial (TIVE) cells as well as estrogen-dependent, GPER-mediated relaxation in mouse aortae. Similar to the non-selective ER agonist 17β-estradiol (E2), the GPER-selective agonist G-1 stimulated phosphorylation of eNOS (ser1171) at 100 nM vs. 0.01% DMSO vehicle (53 +/-7 vs. 19+/-4, p=0.035, n=4). Colorimetric detection of nitric oxide demonstrated that Acetylcholine (Ach) (536 +/-18), E2 (425+/- 18) and G-1 (308 +/-18) also increased NO production in TIVEs (vs. veh 94.0 +/-5, p= 0.006, n=4-6). Pharmacologic inhibition of GPER (G36) reduced NO production in response to E2 by 57% (407 +/-29 vs. 235 +/- 15, p=0.009, n=6), but not to Ach (543+/-12 vs. 533+/-9, p=0.838, n=5-8). In contrast, inhibition of EGFR signaling with AG1478 did not reduce GPER-mediated (G-1) eNOS phosphorylation or G-1-induced NO production (172 +/-8 and 201 +/-12, p=0.120, n=3). Myography studies of endothelium-intact aorta from GPER KO showed a 46% reduction in the relaxation response to E2 compared to WT (-32.3 +/-8.1% and -59.2 +/-3.2 %, p=0.009, n=4-5). Relaxation responses to Ach were similar in GPER KO and WT (-88.0 +/- 1.2 mg and -90.6 +/-1.4 mg, p=0.204, n=5), and WT aorta showed similar relaxation to both E2 and G-1 (59.2 +/- 3.21% and 62.03 +/-6.24%, p=0.71, n=7). These findings suggest that in addition to ERα, the activity of GPER is likely required for full eNOS activation and vasodilation in response to E2, and thus may contribute to the estrogen-mediated protective effects in the cardiovascular system.

Endothelin-1 but not angiotensin II contributes to functional aging in murine carotid arteries

AIMS

Aging is a major risk factor for carotid artery disease and stroke. Endothelin-1 (ET-1) and angiotensin II (Ang II) are important modifiers of vascular disease, partly through increased activity of NADPH oxidase and vasoconstrictor prostanoids. Since the renin-angiotensin and endothelin systems become activated with age, we hypothesized that aging affects NADPH oxidase- and prostanoid-dependent contractions to ET-1 and Ang II.

MAIN METHODS

Carotid artery rings of young (4 month-old) and old (24 month-old) C57BL6 mice were pretreated with the NO synthase inhibitor L-NAME to exclude differential effects of NO. Contractions to ET-1 and Ang II were determined in the presence and absence of the NADPH oxidase-selective inhibitor gp91ds-tat or the thromboxane-prostanoid receptor antagonist SQ 29,548. Gene expression of endothelin and angiotensin receptors was measured by qPCR.

KEY FINDINGS

Aging reduced ET-1-induced contractions and diminished ETA but increased ETB receptor gene expression levels. Gp91ds-tat inhibited contractions to ET-1 in young and to a greater extent in old animals, whereas SQ 29,548 had no effect. Ang II-induced contractions were weak compared to ET-1 and unaffected by aging, gp91ds-tat, and SQ 29,548. Aging had also no effect on AT1A and AT1B receptor gene expression levels.

SIGNIFICANCE

Aging in carotid arteries decreases ETA receptor gene expression and responsiveness to ET-1, which nevertheless becomes increasingly dependent upon NAPDH oxidase activity with age; responses to Ang II and gene expression of its receptors are however unaffected. These findings suggest that physiological aging differentially regulates functional responses to G protein-coupled receptor agonists and the signaling pathways associated with their activation.

Regulation of vascular smooth muscle tone by adipose-derived contracting factor

Obesity and arterial hypertension, important risk factors for atherosclerosis and coronary artery disease, are characterized by an increase in vascular tone. While obesity is known to augment vasoconstrictor prostanoid activity in endothelial cells, less is known about factors released from fat tissue surrounding arteries (perivascular adipose). Using lean controls and mice with either monogenic or diet-induced obesity, we set out to determine whether and through which pathways perivascular adipose affects vascular tone. We unexpectedly found that in the aorta of obese mice, perivascular adipose potentiates vascular contractility to serotonin and phenylephrine, indicating activity of a factor generated by perivascular adipose, which we designated “adipose-derived contracting factor” (ADCF). Inhibition of cyclooxygenase (COX) fully prevented ADCF-mediated contractions, whereas COX-1 or COX-2-selective inhibition was only partially effective. By contrast, inhibition of superoxide anions, NO synthase, or endothelin receptors had no effect on ADCF activity. Perivascular adipose as a source of COX-derived ADCF was further confirmed by detecting increased thromboxane A₂ formation from perivascular adipose-replete aortae from obese mice. Taken together, this study identifies perivascular adipose as a novel regulator of arterial vasoconstriction through the release of COX-derived ADCF. Excessive ADCF activity in perivascular fat under obese conditions likely contributes to increased vascular tone by antagonizing vasodilation. ADCF may thus propagate obesity-dependent hypertension and the associated increased risk in coronary artery disease, potentially representing a novel therapeutic target.

Abstract 621: The G Protein-Coupled Estrogen Receptor GPER is Required for Induction of Nox Activity in Mice

The Nox family of NADPH oxidases is a major source of reactive oxygen species (ROS) such as superoxide (O 2 - ) and hydrogen peroxide (H 2 O 2 ), which importantly influence cardiovascular function. Vasoactive agonists such as angiotensin II can stimulate Nox-dependent ROS production, whereas endogenous estrogens act as antioxidants under certain conditions. We hypothesized that the intracellular transmembrane G protein-coupled estrogen receptor GPER is involved in the regulation of Nox activity. Using GPER -/- and WT mice, we determined the effect of angiotensin II on O 2 - production in isolated vascular smooth muscle cells (VSMC) by lucigenin-enhanced chemiluminescence, and on contractile responses in renal arteries prepared for recording of isometric tension. The contribution of NADPH oxidases was assessed using its specific inhibitor gp91ds-tat (3 μmol/L). Angiotensin II (100 nmol/L) acutely increased O 2 - production in WT VSMC, an effect blocked by gp91ds-tat (6.6±2.1 AU vs. -0.8±2.2 AU after 20 min, n =4-5, p <0.05). Surprisingly, angiotensin II was unable to induce O 2 - formation in GPER -/- VSMC (-0.2±1.0 AU vs. 6.6±2.1 AU, n =5, p <0.05 vs. WT). Following administration of NADPH (100 μmol/L), maximal NADPH oxidase activity in GPER -/- VSMC was also reduced by 73% (442±185 AU vs. 1617±468 AU, n =5, p <0.05 vs. WT), indicating that the induction of Nox activity is largely impaired by GPER deficiency. In line with these findings, contraction to angiotensin II was 1.9-fold less potent in GPER -/- renal arteries (35±4% vs. 66±11% of contraction to 60 mmol/L KCl, n =5, p <0.05 vs. WT); this difference was abolished by gp91ds-tat, which decreased the contractile response in WT by 47% ( p <0.05), but had no effect in GPER -/- arteries. In conclusion, these data indicate that GPER is required for induction of vascular Nox activity in mice, and suggest that estrogen-dependent regulation of ROS production may not be limited to antioxidative effects.