Differential and Opposing Regulation of PAI-1 Promoter Activity by Estrogen Receptor α and Estrogen Receptor β in Endothelial Cells

Profiles of Plasminogen Activator Inhibitor-1 Levels in Healthcare Workers with Latent Tuberculosis and Non-Latent Tuberculosis Infections (Healthy Control)

Background: Mycobacterium tuberculosis infection causes the release of proinflammatory cytokines; interleukin IL-1, IL-6, and IL-8, as well as tumor necrosis factor (TNF-α), affecting hemostasis, namely an increase in procoagulation activity, a decrease in anticoagulant factors, and suppression of the fibrinolytic system that causes hypercoagulable states. Methods: This is a cross-sectional study that involves 80 healthcare workers. The study was conducted in two academic medical centers that were part of the healthcare system of Makassar city, South Sulawesi province, Indonesia, from September to October 2021. PAI-1 levels were measured using the enzyme-linked immunosorbent assay technique. The statistical test results were significant if the p values were <0.05. Results: Although there was no statistically significant difference (P > 0.05) in PAI-1 levels, PAI-1 level among participants in the LTBI group was found to be lower (4.9 ng/mL) than in the healthy control group (6.0 ng/mL). In addition, participants in the LTBI group with a history of being infected (9.6 ng/mL) with the COVID-19 had higher PAI-1 levels than those who had never been infected (2.3 ng/mL), which is statistically significant (P = 0.004). Although there was no statistically significant difference (P > 0.05) in PAI-1 levels among participants in the healthy control group, those with a history of being infected (6.7 ng/mL) demonstrated higher PAI-1 levels than those who had never been infected (4.8 ng/mL). Conclusions: PAI-1 levels were lower in LTBI participants than in healthy control participants, which potentially is due to more participants in the healthy control group having a history of COVID-19 infection.

Therapeutic application of estrogen for COVID-19: Attenuation of SARS-CoV-2 spike protein and IL-6 stimulated, ACE2-dependent NOX2 activation, ROS production and MCP-1 upregulation in endothelial cells

The outbreak of COVID-19 has remained uncontained with urgent need for robust therapeutics. We have previously reported sex difference of COVID-19 for the first time indicating male predisposition. Males are more susceptible than females, and more often to develop into severe cases with higher mortality. This predisposition is potentially linked to higher prevalence of cigarette smoking. Nonetheless, we found for the first time that cigarette smoking extract (CSE) had no effect on angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) expression in endothelial cells. The otherwise observed worse outcomes in smokers is likely linked to baseline respiratory diseases associated with chronic smoking. Instead, we hypothesized that estrogen mediated protection might underlie lower morbidity, severity and mortality of COVID-19 in females. Of note, endothelial inflammation and barrier dysfunction are major mediators of disease progression, and development of acute respiratory distress syndrome (ARDS) and multi-organ failure in patients with COVID-19. Therefore, we investigated potential protective effects of estrogen on endothelial cells against oxidative stress induced by interleukin-6 (IL-6) and SARS-CoV-2 spike protein (S protein). Indeed, 17β-estradiol completely reversed S protein-induced selective activation of NADPH oxidase isoform 2 (NOX2) and reactive oxygen species (ROS) production that are ACE2-dependent, as well as ACE2 upregulation and induction of pro-inflammatory gene monocyte chemoattractant protein-1 (MCP-1) in endothelial cells to effectively attenuate endothelial dysfunction. Effects of IL-6 on activating NOX2-dependent ROS production and upregulation of MCP-1 were also completely attenuated by 17β-estradiol. Of note, co-treatment with CSE had no additional effects on S protein stimulated endothelial oxidative stress, confirming that current smoking status is likely unrelated to more severe disease in chronic smokers. These data indicate that estrogen can serve as a novel therapy for patients with COVID-19 via inhibition of initial viral responses and attenuation of cytokine storm induced endothelial dysfunction, to substantially alleviate morbidity, severity and mortality of the disease, especially in men and post-menopause women. Short-term administration of estrogen can therefore be readily applied to the clinical management of COVID-19 as a robust therapeutic option.

The 4G/5G Polymorphism of Plasminogen Activator Inhibitor Type 1 is a Predictor of Moderate-to-Severe Thyroid Eye Disease

Introduction

Thyroid eye disease (TED) is an autoimmune disease of the orbits. Once developed, complete cure is rare. Plasminogen activator inhibitor type 1 (PAI-1) contributes to remodeling of connective tissue and has a central role in the pathogenesis of TED. We aimed to test if the 4G/5G polymorphism of PAI-1 is a predictor of the development of moderate-to-severe TED.

Methods

A total of 185 patients with Graves’ disease, 87 of them with TED, 98 without TED, as well as 201 healthy controls, were studied. Genomic DNA was isolated from peripheral blood samples. The 4G/5G polymorphism of the PAI-1 gene was analyzed by allele-specific PCR, and the distribution of genotypes was calculated in each group. Plasma PAI-1 and thyroid hormone levels were measured by ELISA and ECLIA, respectively.

Results

The 4G/4G genotype was associated with the development of moderate-to-severe TED (OR = 2.54; 95% CI: 1.26–5.14; p < 0.01). The 4G/5G polymorphism of PAI-1 was not a predictor of plasma PAI-1 levels.

Conclusion

The 4G/4G genotype of PAI-1 is a risk factor for the development of moderate-to-severe TED. Patients with Graves’ disease who harbor this genotype may be candidates for special attention towards the development of TED.

Oleuropein is a natural inhibitor of PAI-1-mediated proliferation in human ER-/PR- breast cancer cells

PURPOSE

Elevated expression of PAI-1 has been widely linked with adverse outcomes in a variety of human cancers, such as breast, gastric and ovarian cancers, rendering PAI-1 a prognostic biomarker. As a result, several chemical inhibitors are currently being developed against PAI-1; however, the clinical setting where they might confer survival benefits has not yet been elucidated.

METHODS

RNA sequencing data analysis from the TCGA/GTEx cancer portals (n = 3607 samples). In silico molecular docking analyses to predict functional macromolecule interactions. ER-/PR- (MDA-MB-231) and ER+/PR+ (MCF-7) breast cancer cell lines implemented to assess the effect of oleuropein as a natural inhibitor of PAI-1-mediated oncogenic proliferation.

RESULTS

We show that high PAI-1 levels inversely correlate with ER and PR expressions in a wide panel of estrogen/progesterone-responsive human malignancies. By implementing an in silico molecular docking analysis, we identify oleuropein, a phenolic component of olive oil, as a potent PAI-1-binding molecule displaying increased affinity compared to the other olive oil constituents. We demonstrate that EVOO or oleuropein treatment alone may act as a natural PAI-1 inhibitor by incrementally destabilising PAI-1 levels selectively in ER-/PR- breast cancer cells, accompanied by downstream caspase activation and cell growth inhibition. In contrast, ER+/PR+ breast cancer cells, where PAI-1 expression is absent or low, do not adequately respond to treatment.

CONCLUSIONS

Our study demonstrates an inverse correlation between PAI-1 and ESR1/PGR levels, as well as overall patient survival in estrogen/progesterone-responsive human tumours. With a focus on breast cancer, our data identify oleuropein as a natural PAI-1 inhibitor and suggest that oleuropein-mediated PAI-1 destabilisation may confer clinical benefit only in ER-/PR- tumours.

Effects of 17β-Estradiol on the Plasminogen Activator System in Vascular Smooth Muscle Cells Treated with Lysophophatidylcholine

Objectives

When administered soon after menopause, hormone therapy can prevent coronary heart diseases in women. To explore the mechanism underlying the cardioprotective actions of estrogen, we investigated the effects of 17β-estradiol (17β-E₂) on the plasminogen activator system using cultured vascular smooth muscle cells (VSMCs).

Methods

VSMCs were isolated from rat aortas. Protein expression of plasminogen activator inhibitor type 1 (PAI-1) and tissue-type plasminogen activator (t-PA) were evaluated using Western blotting and enzyme-linked immunosorbent assay, respectively. The enzyme activity of PAI-1 in a conditioned medium was assessed via reverse fibrin overlay zymography and that of t-PA was assessed via fibrin overlay zymography. Gene expression was quantified using real-time reverse transcription-polymerase chain reaction.

Results

Following pre-treatment for 24 hours, 17β-E₂ suppressed both protein expression and enzyme activity of PAI-1 stimulated by lysophosphatidylcholine (lysoPC) in a significant and dose-dependent manner at a near physiological concentration. Moreover, 17β-E₂ (10⁻⁷ M) inhibited PAI-1 gene expression, and ICI 182,780—a specific estrogen receptor antagonist—blocked the effects of 17β-E₂ on the PAI-1 protein. 17β-E₂ did not affect t-PA secretion but significantly enhanced free t-PA activity through reduced binding to PAI-1. Furthermore, 17β-E₂ suppressed intracellular reactive oxygen species production and nuclear factor-κB-mediated transcription.

Conclusions

In VSMCs stimulated with lysoPC, 17β-E₂ reduced PAI-1 expression through a non-receptor-mediated mechanism via antioxidant activity as well as a receptor-mediated mechanism; however, it did not alter t-PA secretion. Of note, 17β-E₂ suppressed PAI-1 activity and concurrently enhanced t-PA activity, suggesting a beneficial influence on fibrinolysis.

Combined but not single treatment with ethinylestradiol/levonorgestrel and spironolactone reduces plasminogen activator inhibitor-1 in insulin-resistant ovariectomised rats

Objective:

Increased circulating level of plasminogen activator inhibitor-1 (PAI-1) is associated with menopausal oestrogen deficiency. We therefore hypothesised that the combined oral contraceptive (COC) with spironolactone (SPL) improves insulin resistance (IR) in ovariectomised (OVX) rats by reducing circulating PAI-1.

Methods:

Twelve-week-old female Wistar rats were divided into sham-operated (SHM), OVX, OVX+SPL (0.25 mg/kg), COC (1.0 µg ethinylestradiol and 5.0 µg levonorgestrel) and OVX+COC+SPL rats treated with COC and SPL daily for eight weeks. IR was assessed by homeostatic model assessment of IR (HOMA-IR).

Results:

Data showed that OVX rats had a higher HOMA-IR value that is associated with increased visceral adiposity, triglycerides (TG), total cholesterol/high-density lipoprotein cholesterol (HDL-C), TG/HDL-C, plasma insulin, GSK-3, corticosterone and decreased 17β-oestradiol. However, these effects were attenuated in OVX+COC, OVX+SPL and OVX+COC+SPL rats compared to OVX rats. OVX rats had lower PAI-1 than SHM rats, whereas the beneficial effect on IR and other parameters by COC or SPL was accompanied with increased PAI-1. Improvement of IR and other parameters with combined COC and SPL in OVX rats was accompanied with reduced PAI-1.

Conclusion:

Taken together, COC or SPL improves IR independent of PAI-1, whereas a combination of COC and SPL in OVX rats ameliorates IR in a PAI-1-dependent manner.

Circulating levels of plasminogen activator inhibitor-1 are associated with metabolic syndrome rather than with menopause

The plasminogen activator inhibitor type 1 (PAI-1) is the major determinant of fibrinolytic activity. PAI-1 concentrations are elevated in obesity, type 2 diabetes and metabolic syndrome (MetS). On the other hand, during menopause, fibrinolytic activity decreases and, consequently, PAI-1 concentration increases; however, it is debated whether menopause is an independent determinant factor of PAI-1 levels. The objective of this study was to evaluate the effect of hormonal and metabolic status on the concentration of PAI-1 in pre-and post-menopausal women. A case-control study was conducted in ninety pre-and post-menopausal women aged 45 to 55 years, matched by body mass index (BMI). Anthropometric measurements and biochemical determinations were performed on all participants. The fibrinolytic activity was determined by measuring PAI-1 by ELISA. Of all the women, 30% presented MetS. Women with MetS had higher values of PAI-1 (36.0 ± 19.1 vs 19.3 ± 14.8 ng/mL, p < .001); in contrast, no differences were observed when compared by hormonal status (20.7 ± 18.10 vs 20.2 ± 17.0 ng/mL, NS). The results of this study suggest that in women, MetS plays a more important role in the deterioration of the fibrinolytic mechanisms rather than their hormonal status. Therefore, the identification of cardio-metabolic factors is relevant to reduce the presence of thrombosis in post-menopausal women.

Is plasminogen activator inhibitor-1 a physiological bottleneck bridging major depressive disorder and cardiovascular disease?

Major depressive disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly comorbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen activator inhibitor-1 (PAI-1) is a prothrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of major depressive disorder as well. In this study, we review candidate pathways implicating MDD in CVD and consider how PAI-1 might act as a mediator by which MDD induces CVD development: chiefly through sleep disruption, adiposity, brain-derived neurotrophic factor (BDNF) metabolism, systemic inflammation and hypothalamic-pituitary-adrenal (HPA)-axis dysregulation. As both MDD and CVD are more prevalent in women than in men, and incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex-specific associations between MDD, PAI-1 and CVD. Of special interest is the role PAI-1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI-1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments.

Hypercoagulability and Migraine

BACKGROUND

A growing body of literature suggests that migraineurs, particularly those with aura, have an increased risk for ischemic stroke, but not via enhanced atherosclerosis. The theory that micro-emboli induced ischemia provokes cortical spreading depression (ie, symptomatic aura) in migraineurs but transient ischemic attacks in others highlights a potential role for hypercoagulability as a link between migraine (with aura) and stroke.

AIM

Our objective is to summarize the literature evaluating the association of migraine with various acquired or inheritable thrombophilic states, including those related to elevated estrogen levels, endothelial activation and dysfunction, antiphospholipid antibodies (aPL), deficiency of coagulation inhibitors, and presence of certain genetic polymorphisms.

FINDINGS

Although definitive studies are lacking, a preponderance of available evidence links migraine, and especially aura, to increased levels of estradiol (eg, oral contraceptive pill [OCP] use, pregnancy), thrombo- and erythrocytosis, von Willebrand factor (vWF) antigen, fibrinogen, tissue plasminogen activator (tPA) antigen, and endothelial microparticles. Studies of a link to migraine are conflicting for aPL, homocysteine, Protein S, and the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism. No association with migraine was found in meta-analyses of Factor V Leiden, and of prothrombin gene mutation. Within a large, young ischemic stroke sample, migraine with aura was associated with a thrombophilic state and with patent foramen ovale (PFO). In the non-stroke population, meta-analyses show an association of PFO and migraine with aura (MA), but two population-based studies do not support the link.

RECOMMENDATIONS

For persons with MA and (1) a personal history or family history of thrombosis, or (2) MRI evidence of micro-vascular ischemia or of stroke, an evaluation for hypercoagulability is warranted. In cases of MA alone, consider screening for markers of endothelial activation (eg, vWF, high sensitivity c-reactive protein [hs CRP], and fibrinogen). Rigorous management of other stroke risk factors is paramount, but efficacy of anti-thrombotic agents in the treatment of migraine is unproven. Closure of PFO is not routinely recommended based on negative randomized trials.

Improvement of Psychotic Symptoms and the Role of Tissue Plasminogen Activator

Tissue plasminogen activator (tPA) mediates a number of processes that are pivotal for synaptogenesis and remodeling of synapses, including proteolysis of the brain extracellular matrix, degradation of adhesion molecules, activation of neurotrophins, and activation of the N-methyl-d-aspartate receptor. Abnormalities in these processes have been consistently described in psychotic disorders. In this paper, we review the physiological roles of tPA, focusing on conditions characterized by low tPA activity, which are prevalent in schizophrenia. We then describe how tPA activity is influenced by lifestyle interventions and nutritional supplements that may ameliorate psychotic symptoms. Next, we analyze the role of tPA in the mechanism of action of hormones and medications effective in mitigating psychotic symptoms, such as pregnenolone, estrogen, oxytocin, dopamine D3 receptor antagonists, retinoic acid, valproic acid, cannabidiol, sodium nitroprusside, N-acetyl cysteine, and warfarin. We also review evidence that tPA participates in the mechanism by which electroconvulsive therapy and cigarette smoking may reduce psychotic symptoms.

Vascular effects of estrogenic menopausal hormone therapy

Cardiovascular disease (CVD) is more common in men and postmenopausal women (Post-MW) than premenopausal women (Pre-MW). Despite recent advances in preventive measures, the incidence of CVD in women has shown a rise that matched the increase in the Post-MW population. The increased incidence of CVD in Post-MW has been related to the decline in estrogen levels, and hence suggested vascular benefits of endogenous estrogen. Experimental studies have identified estrogen receptor ERα, ERβ and a novel estrogen binding membrane protein GPR30 (GPER) in blood vessels of humans and experimental animals. The interaction of estrogen with vascular ERs mediates both genomic and non-genomic effects. Estrogen promotes endothelium-dependent relaxation by increasing nitric oxide, prostacyclin, and hyperpolarizing factor. Estrogen also inhibits the mechanisms of vascular smooth muscle (VSM) contraction including [Ca2+]i, protein kinase C and Rho-kinase. Additional effects of estrogen on the vascular cytoskeleton, extracellular matrix, lipid profile and the vascular inflammatory response have been reported. In addition to the experimental evidence in animal models and vascular cells, initial observational studies in women using menopausal hormonal therapy (MHT) have suggested that estrogen may protect against CVD. However, randomized clinical trials (RCTs) such as the Heart and Estrogen/ progestin Replacement Study (HERS) and the Women's Health Initiative (WHI), which examined the effects of conjugated equine estrogens (CEE) in older women with established CVD (HERS) or without overt CVD (WHI), failed to demonstrate protective vascular effects of estrogen treatment. Despite the initial set-back from the results of MHT RCTs, growing evidence now supports the 'timing hypothesis', which suggests that MHT could increase the risk of CVD if started late after menopause, but may produce beneficial cardiovascular effects in younger women during the perimenopausal period. The choice of an appropriate MHT dose, route of administration, and estrogen/progestin combination could maximize the vascular benefits of MHT and minimize other adverse effects, especially if given within a reasonably short time after menopause to women that seek MHT for the relief of menopausal symptoms.

Differential expression of breast cancer-associated genes between stage- and age-matched tumor specimens from African- and Caucasian-American Women diagnosed with breast cancer

Background

Recent studies suggest that the poorer breast cancer outcome observed in African-American women (AAW) may, in part, result from underlying molecular factors. The purpose of this study was to investigate gene expression differences between Caucasian-American women (CAW) and AAW that may contribute to this poorer prognosis.

Methods

The expression of 84 genes involved in breast carcinoma prognosis, response to therapy, estrogen signaling, and tumor aggressiveness was assessed in age- and stage-matched CAW and AAW paraffin-embedded breast cancer specimens. The Wilcoxon–Mann–Whitney Test was used to identify genes with a significant difference in expression between CAW and AAW. To determine if the differentially expressed genes could segregate between the CAW and AAW, we performed semi-supervised principal component analysis (SSPCA).

Results

Twenty genes were differentially expressed between AAW and CAW. SSPCA incorporating these 20 genes segregated AAW and CAW into two distinct groups. AAW were significantly (p < 0.05) more likely to display aberrations in G₁/S cell-cycle regulatory genes, decreased expression of cell-adhesion genes, and low to no expression of ESR1, PGR, ERBB2 and estrogen pathway targets.

Conclusions

The gene expression differences identified between AAW and CAW may contribute to more aggressive disease, resistance to therapy, enhanced metastatic potential and poor clinical outcome. These findings support the hypothesis that breast cancer specimens collected from AAW display distinct gene expression differences compared to similar tissues obtained from CAW. Additional population-based studies are necessary to determine if these gene expression variations contribute to the highly aggressive and treatment-resistant breast cancer phenotype frequently observed in AAW.

Estrogen regulates endothelial migration via plasminogen activator inhibitor (PAI-1)

Endothelial plasminogen activator inhibitor (PAI-1) controls vascular remodeling, angiogenesis and fibrinolysis. PAI-1 blood levels in women are related to estrogen. The aim of this study was to characterize the signaling pathways through which estrogen regulates PAI-1 in endothelial cells. Furthermore, we aimed to investigate whether PAI-1 is implicated in the control of endothelial migration by estrogen. Cultured human umbilical vein endothelial cells (HUVECs) and ovariectomized rats were used to test the effects of 17β-estradiol (E(2)) on PAI-1 expression and its role on endothelial migration. At physiological concentrations, E(2) increases the expression of PAI-1 in HUVEC within 6-12 h through activation of a signaling cascade initiated by estrogen receptor α and involving G proteins, phosphatidylinositol-3-OH kinase and Rho-associated kinase II. ROCK-II activation turns into an over-expression of c-Jun and c-Fos that is required for E(2)-induced expression of PAI-1. Estrogen-induced PAI-1 expression is implicated in HUVEC horizontal migration. PAI-1 regulation is found also in vivo, in female rats, where ovariectomy is associated with reduced PAI-1 expression, while estrogen replacement counteracts this change. In conclusion, E(2) increases PAI-1 synthesis in human endothelial cells and in rodent aorta through a G protein-initiated signaling that targets early-immediate gene expression. This regulatory pathway is implicated in endothelial cell migration. These findings describe new mechanisms of action of estrogens in the vessels, which may be important for vascular remodeling and hemostasis.

Increased PAI-1 in females compared with males is protective for abdominal aortic aneurysm formation in a rodent model

The serine proteases, along with their inhibitor plasmin activator inhibitor-1 (PAI-1), have been shown to play a role in abdominal aortic aneurysm (AAA) formation. The aim of this study is to determine if PAI-1 may be a protective factor for AAA formation and partially responsible for the gender difference observed in AAAs. Male and female wild-type (WT) C57BL/6 and PAI-1(-/-) mice 8-12 wk of age underwent aortic perfusion with porcine pancreatic elastase. Animals were harvested 14 days following perfusion and analyzed for phenotype, PAI-1 protein levels, and matrix metalloproteinase (MMP)-9 and -2 activity. WT males had an average increase in aortic diameter of 80%, whereas females only increased 32% (P < 0.001). PAI-1(-/-) males increased 204% and females 161%, significantly more than their WT counterparts (P < 0.001). Western blot revealed 61% higher PAI-1 protein levels in the WT females compared with the WT males (P = 0.01). Zymography revealed higher levels of pro-MMP-2 and active MMP-2 in the PAI-1(-/-) males and females compared with their WT counterparts. PAI-1(-/-) females had significantly higher serum plasmin levels compared with WT females (P = 0.003). In conclusion, WT female mice are protected from aneurysm formation and have higher levels of PAI-1 compared with males during experimental aneurysm formation. Additionally, both male and female PAI-1(-/-) animals develop significantly larger aneurysms than WT animals, correlating with higher pro- and active MMP-2 levels. These findings suggest that PAI-1 is protective for aneurysm formation in the elastase model of AAA and plays a role in the gender differences seen in AAA formation.

Association analyses of porcine SERPINE1 reveal sex-specific effects on muscling, growth, fat accretion and meat quality

The serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1), member 1 (SERPINE1) gene encodes plasminogen activator inhibitor type 1 (PAI), which is the major physiological inhibitor of tissue-type and urokinase-type plasminogen activators and plays a role in obesity and insulin resistance in women but not in men. We detected SNP FN396538:g.566G>A in intron 3 and a non-synonymous substitution NM_213910:c.612A>G in exon 3 (p.Ile159Val) and mapped the gene to position 8.4 cM on the linkage map of chromosome 3. Association analyses were conducted on the 12th-15th generation of the Meishan × Large White (MLW) cross (n = 565), with records for weight at the end of test, lifetime daily gain, test time daily gain, loin depth and backfat depth, as well as on a European wild boar × Meishan (W × M) F(2) population (n = 333) with 47 traits recorded for carcass composition and meat quality. Analyses performed across the entire MLW population or in the male animals did not show any trait significantly associated with the loci studied. In female animals, both SNPs were associated with loin depth at nominal P < 0.05 with adjusted P values equal to 0.051 (g.566) and 0.057 (c.612). Differences between homozygotes were up to 0.65 SD. In the entire W × M population and female animals, SERPINE1 was significantly associated at adjusted P < 0.05 in descending order with muscling, growth and fat accretion and in male animals with meat quality (R-value). In the studied populations, allele effects were in opposite directions, which implies that the SNPs are markers that are in linkage disequilibrium with a causative mutation.

Atherosclerosis and sex hormones: current concepts

CVD (cardiovascular disease) is the leading cause of death for women. Considerable progress has been made in both our understanding of the complexities governing menopausal hormone therapy and our understanding of the cellular and molecular mechanisms underlying hormone and hormone receptor function. Understanding the interplay of atherosclerosis and sex steroid hormones and their cognate receptors at the level of the vessel wall has important ramifications for clinical practice. In the present review, we discuss the epidemiology of CVD in men and women, the clinical impact of sex hormones on CVD, and summarize our current understanding of the pathogenesis of atherosclerosis with a focus on gender differences in CVD, its clinical presentation and course, and pathobiology. The critical animal and human data that pertain to the role of oestrogens, androgens and progestins on the vessel wall is also reviewed, with particular attention to the actions of sex hormones on each of the three key cell types involved in atherogenesis: the endothelium, smooth muscle cells and macrophages. Where relevant, the systemic (metabolic) effects of sex hormones that influence atherogenesis, such as those involving vascular reactivity, inflammation and lipoprotein metabolism, are discussed. In addition, four key current concepts in the field are explored: (i) total hormone exposure time and coronary heart disease risk; (ii) the importance of tissue specificity of sex steroid hormones, critical timing and the stage of atherosclerosis in hormone action; (iii) biomarkers for atherosclerosis with regard to hormone therapy; and (iv) the complex role of sex steroids in inflammation. Future studies in this field will contribute to guiding clinical treatment recommendations for women and help define research priorities.

Antioxidant effect of estrogen on bovine aortic endothelial cells

OBJECTIVE

This study discussed the role of estrogen as an antioxidant in the damage of vascular endothelial cells.

DESIGN

We treated bovine aortic endothelial cells (bAEC) either with 1mM of H(2)O(2) alone or with 1 microM of 17beta-estradiol (E(2)) for 24h followed by 1mM of H(2)O(2) for 3h. The cell survival was evaluated by MTT assay, cellular apoptosis by fluorescence activated cell sorter (FACS) and Hoechst 33342 staining, oxidative stress by intracellular reactive oxygen species (ROS) and apoptosis after oxidative stress by western blotting for phospho-p38, p38, and Bcl-2.

RESULTS

MTT assay showed that bAEC viability was reduced to 55.7+/-3.0% and 39.1+/-3.7% after 30 and 60 min of H(2)O(2) treatment, respectively. E(2) and H(2)O(2) treated cells did not show significant decrease in the cell survival. Similarly the FACS analysis and Hoechst 33342 stain showed that the latter decreased cellular apoptosis induced by H(2)O(2). Intracellular ROS increased by 181.6+/-68.9% in the former and by 37.0+/-3.9% in the latter (P<0.05). The expression of phospho-p38 mitogen-activated protein kinase (MAPK) was higher in the latter.

CONCLUSIONS

E(2) mediates antioxidant effects on the oxidative stress induced by H(2)O(2). This antioxidant effect on bAEC may elucidate the scientific basis of hormone therapy for maintaining cardiovascular integrity in postmenopausal women.

Divergent effects of estradiol on gene expression of catecholamine biosynthetic enzymes

Within the catecholaminergic systems, there are contradictory findings regarding ability of estradiol to regulate expression of genes related to catecholamine biosynthesis. Several parameters important for effects of estradiol on the catecholamine (CA) related enzyme gene expression were examined in two CA regions. Ovariectomized (OVX) female rats were given prolonged estradiol treatments, either in a pulsatile fashion by injections or continuously by pellets. The mode affected the response of tyrosine hydroxylase (TH) and GTP cyclohydrolase I (GTPCH) mRNAs differentially in the nucleus of solitary tract (NTS) and the locus coeruleus (LC). In rostral-medial NTS, TH mRNA levels were increased with injections, but declined in rats administered estradiol by pellets. In LC, a significant change was only observed in GTPCH with injections. These differences may reflect activation of different estrogen receptors (ER). The response to estradiol in the presence of ERalpha and ER beta was examined in PC12 cell culture. Estradiol directly regulated promoter activity of TH, GTPCH and dopamine beta-hydroxylase (DBH) genes. With ERalpha, 17 beta-estradiol elevated TH promoter activity, while there was a decline with ERbeta. In contrast, both DBH and GTPCH promoters were enhanced by 17 beta-estradiol over a wide range of concentrations with either ER subtype. Thus, mode of administration, location examined and ER subtype expressed are important considerations in the overall response of catecholamine related enzymes to estradiol.

Long-term estrogen exposure promotes carcinogen bioactivation, induces persistent changes in gene expression, and enhances the tumorigenicity of MCF-7 human breast cancer cells

The cumulative exposure to estrogens is an important determinant in the risk of breast cancer, yet the full range of mechanisms involving estrogens in the genesis and progression of breast cancer remains a subject of debate. Interactions of estrogens and environmental toxicants have received attention as putative factors contributing to carcinogenesis. Mechanistic studies have demonstrated interactions between estrogen receptor alpha (ERalpha) and the aryl hydrocarbon receptor (AhR), with consequences on the genes that they regulate. Many studies of ERalpha and AhR-mediated effects and crosstalk between them have focused on the initial molecular events. In this study, we investigated ERalpha- and AhR-mediated effects in long-term estrogen exposed (LTEE) MCF-7 human breast cancer cells, which were obtained by continuous culturing for at least 12 weeks in medium supplemented with 1 nM of 17beta-estradiol (E(2)). With these LTEE cells and with parallel control cells cultured without E(2) supplementation, we performed an extensive study of cytochrome P450 (CYP) induction, carcinogen bioactivation, global gene expression, and tumorigenicity in immunocompromised mice. We found that LTEE cells, in comparison with control cells, had higher levels of AhR mRNA and protein, greater responsiveness for AhR-regulated CYP1A1 and CYP1B1 induction, a 6-fold higher initial level of benzo(a)pyrene-DNA adducts as determined by liquid chromatography tandem mass spectrometry, marked differences in the expression of numerous genes, and a higher rate of E(2)-dependent tumor growth as xenografts. These studies indicate that LTEE causes adaptive responses in MCF-7 cells, which may reflect processes that contribute to the overall carcinogenic effect of E(2).

Estradiol increases angiotensin II type 1 receptor in hearts of ovariectomized rats

We tested the hypothesis that 17beta-estradiol (E(2)) has dual effects on the heart, increasing levels of proteins thought to have beneficial cardiovascular effects (e.g. endothelial nitric oxide (NO) synthase (eNOS)) as well as those thought to have detrimental cardiovascular effects (e.g. type 1 angiotensin II (AngII) receptor (AT(1)R)). Ovariectomized Wistar rats consuming a high-sodium diet received one of four treatments (n=7 per group): group 1, placebo pellets; group 2, E(2) (0 x 5 mg/pellet, 21-day release); group 3, NOS inhibitor, N(omega)-nitro-L-arginine-methyl-ester (L-NAME; 40 mg/kg per day for 14 days) plus Ang II (0 x 225 mg/kg per day on days 11-14); group 4, E(2) plus L-NAME/Ang II. E(2) increased cardiac levels of estrogen receptors ESR1 and ESR2, an ESR-associated membrane protein caveolin-3, eNOS, and phosphorylated (p)eNOS, thus, exerting potentially beneficial cardiovascular effects on NO. However, E(2) also increased cardiac levels of proteins associated with cardiovascular injury and inflammation including, AT(1)R, protein kinase C delta (PRKCD), phosphorylated PRKC, and phosphorylated extracellular signal regulated kinase (pMAPK)3/1, plasminogen activator inhibitor-1 (PAI-1), osteopontin and ED-1, a monocyte/macrophage-specific protein. E(2) treatment led to similar protein changes in the hearts of L-NAME/Ang II-treated rats except that the increase in peNOS was prevented, and L-NAME/Ang II and E(2) had additive effects in increasing cardiac PRKCD and PAI-1. Thus, the highest levels of cardiac PAI-1 and PRKCD occurred in L-NAME/Ang II-treated rats receiving E(2). In summary, E(2) treatment increased cardiac expression of AT(1)R as well as the expression of pro-inflammatory and prothrombotic factors.

Differential regulation of the inducible nitric oxide synthase gene by estrogen receptors 1 and 2

Estrogen has both rapid and longer term direct effects on cardiovascular tissues mediated by the two estrogen receptors, ESR1 and ESR2. Previous work identified that estrogen regulates the expression of inducible nitric oxide synthase (NOS2A) in vascular smooth muscle cells (VSMC). ESR2 knockout mice have vascular dysfunction due to dysregulation of NOS2A expression and these mice are hypertensive (Zhu et al. Science 2002 295 505-508). Here, we report studies to examine the differential regulation of NOS2A gene expression by ESR1 and 2. Immunoblotting and RT-PCR studies revealed that different VSMC lines expressed different levels of ESR1 and ESR2 protein and mRNA. VSMC from different vascular beds were studied, including aortic VSMC expressing ESR1 and radial (Rad) VSMC expressing ESR2. E(2) inhibited NO production and NOS2A protein expression in aortic VSMC. Human NOS2A promoter-reporter studies revealed suppression of NOS2A reporter activity by E(2) in aortic VSMC, and stimulation of NOS2A reporter activity by E(2) in Rad arterial VSMC. In heterologous expression studies of COS-7 cells lacking endogenous ER, E(2) treatment of COS-7 cells did not alter NOS2A reporter activity in the presence of ESR1, while reporter activity increased 2.3-fold in the presence of ESR2. Similar experiments in COS-7 cells using the selective estrogen receptor modulator raloxifene showed that raloxifene caused a reduction in NOS2A reporter activity with ESR1 coexpression and an increase with ESR2 coexpression. Rat VSMC expressing ESR2 but not ESR1 also showed increased NOS2A reporter activity with E(2) treatment, an effect lost when ESR1 was introduced into the cells. Taken together, these data support that hNOS2A transcription is regulated positively by ESR2 and negatively by ESR1 in VSMC, supporting differential actions of these two estrogen receptors on a physiologically relevant gene in VSMC.

Effect of estrogen therapy on insulin resistance and plasminogen activator inhibitor type 1 concentrations in postmenopausal women

BACKGROUND/AIMS

An elevated thrombotic risk due to abnormal fibrinolysis might be associated with insulin resistance in postmenopause. The aim of this study was to investigate the association of insulin resistance with a biochemical marker of fibrinolysis as well as the effect of transdermal estrogen treatment (ET) on this association.

METHODS

Thirty postmenopausal hysterectomized women received transdermal estradiol during 3 months. 17Beta-estradiol, FSH, LH, plasminogen activator inhibitor type 1 (PAI-1), insulin and glucose were measured in blood samples before and after ET. Insulin resistance was calculated by the use of the homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS

ET induced a significant decrement in both PAI-1 levels and HOMA-IR values. The study also showed that HOMA-IR was a significant predictor for PAI-1 concentrations.

CONCLUSION

Short-term ET improved HOMA-IR values in parallel with a decrease in PAI-1 levels.

Activation of estrogen receptor alpha increases and estrogen receptor beta decreases apolipoprotein E expression in hippocampus in vitro and in vivo

Previous evidence indicates that, in carriers of apolipoprotein E4 (ApoE4), estrogen therapy increased the risk of late-onset Alzheimer's disease (AD), whereas in individuals carrying ApoE2/3, estrogen therapy reduced the risk of AD [Cauley JA, Zmuda JM, Yaffe K, Kuller LH, Ferrell RE, Wisniewski SR, Cummings SR (1999) J Bone Miner Res 14:1175-1181; Yaffe K, Haan M, Byers A, Tangen C, Kuller L (2000) Neurology 54:1949-1954]. Estrogen mechanisms of action are mediated by two estrogen receptors (ERs), ERalpha and ERbeta. In this study, we determined the relationship between ER subtype and estrogen regulation of ApoE expression in HT-22 cells ectopically transfected with ERalpha or ERbeta, in primary cultured rat hippocampal neurons in vitro and in rat hippocampus in vivo by both molecular biological and pharmacological analyses. Results of these analyses demonstrated that activation of ERalpha either by 17beta-estradiol or a specific-agonist, propylpyrazole triol, up-regulated ApoE mRNA and protein expression. In contrast, the ERbeta-selective agonist, diarylpropionitrile, down-regulated ApoE mRNA and protein expression. These results demonstrate that, in vitro and in vivo, ApoE expression can be differentially regulated depending on activation of ER subtypes. These data suggest that use of ER-selective ligands could provide therapeutic benefit to reduce the risk of AD by increasing ApoE expression in ApoE2/3 allele carriers and decreasing ApoE expression in ApoE4 allele carriers.

Estrogens, selective estrogen receptor modulators, and a selective estrogen receptor down-regulator inhibit endothelial production of tissue factor pathway inhibitor 1

Background

Hormone therapy, oral contraceptives, and tamoxifen increase the risk of thrombotic disease. These compounds also reduce plasma content of tissue factor pathway inhibitor-1 (TFPI), which is the physiological inhibitor of the tissue factor pathway of coagulation. The current aim was to study if estrogens and estrogen receptor (ER) modulators may inhibit TFPI production in cultured endothelial cells and, if so, identify possible mechanisms involved.

Methods

Human endothelial cell cultures were treated with 17β-estradiol (E2), 17α-ethinylestradiol (EE2), tamoxifen, raloxifene, or fulvestrant. Protein levels of TFPI in cell media and cell lysates were measured by an enzyme-linked immunosorbent assay, and TFPI mRNA levels were assessed by quantitative PCR. Expression of ERα was analysed by immunostaining.

Results

All compounds (each in a concentration of 10 nM) reduced TFPI in cell medium, by 34% (E2), 21% (EE2), 16% (tamoxifen), and 28% (raloxifene), respectively, with identical inhibitory effects on cellular TFPI levels. Expression of TFPI mRNA was principally unchanged. Treatment with fulvestrant, which was also associated with down-regulation of secreted TFPI (9% with 10 nM and 26% with 1000 nM), abolished the TFPI-inhibiting effect of raloxifene, but not of the other compounds. Notably, the combination of 1000 nM fulvestrant and 10 nM raloxifene increased TFPI secretion, and, conversely, 10 nM of either tamoxifen or raloxifene seemed to partly (tamoxifen) or fully (raloxifene) counteract the inhibitory effect of 1000 nM fulvestrant. The cells did not express the regular nuclear 66 kDa ERα, but instead a 45 kDa ERα, which was not regulated by estrogens or ER modulators.

Conclusion

E2, EE2, tamoxifen, raloxifene, and fulvestrant inhibited endothelial production of TFPI by a mechanism apparently independent of TFPI transcription.

Complex actions of sex steroids in adipose tissue, the cardiovascular system, and brain: Insights from basic science and clinical studies

Recent publications describing the results of the Women's Health Initiative (WHI) and other studies reporting the impact of hormone therapy on aging women have spurred reexamination of the broad use of estrogens and progestins during the postmenopausal years. Here, we review the complex pharmacology of these hormones, the diverse and sometimes opposite effects that result from the use of different estrogenic and progestinic compounds, given via different delivery routes in different concentrations and treatment sequence, and to women of different ages and health status. We examine our new and growing appreciation of the role of estrogens in the immune system and the inflammatory response, and we pose the concept that estrogen's interface with this system may be at the core of some of the effects on multiple physiological systems, such as the adipose/metabolic system, the cardiovascular system, and the central nervous system. We compare and contrast clinical and basic science studies as we focus on the actions of estrogens in these systems because the untoward effects of hormone therapy reported in the WHI were not expected. The broad interpretation and publicity of the results of the WHI have resulted in a general condemnation of all hormone replacement in postmenopausal women. In fact, careful review of the extensive literature suggests that data resulting from the WHI and other recent studies should be interpreted within the narrow context of the study design. We argue that these results should encourage us to perform new studies that take advantage of a dialogue between basic scientists and clinician scientists to ensure appropriate design, incorporation of current knowledge, and proper interpretation of results. Only then will we have a better understanding of what hormonal compounds should be used in which populations of women and at what stages of menopausal/postmenopausal life.

Selective Agonists of Estrogen Receptor Isoforms

The cloning of estrogen receptors (ERs) and generation of ER-deficient mice have increased our understanding of the molecular mechanisms underlying the cardiovascular effects of estrogen. It is conceivable that clinical trials of estrogens so far failed to improve cardiovascular health because of the poor ER isoform selectivity and tissue specificity of endogenous hormones as well as incorrect treatment timing and regimens. Tissue-selective ER modulators (SERMs) may be safer agents than endogenous estrogens for cardiovascular disease. Yet, designing isoform-selective ER ligands (I-SERMs) with agonist or antagonist activity is required to pursue improved pharmacological control of ERs, especially taking into account emerging evidence for the beneficial role of vascular ER alpha activation. Ideally, the quest for unique ER ligands targeted to the vascular wall should lead to compounds that merge the pharmacological profiles of SERM and I-SERM agents. This review highlights the current bases for and approaches to selective ER modulation in the cardiovascular system.

WAY-202196, a selective estrogen receptor-beta agonist, protects against death in experimental septic shock

OBJECTIVE

To determine the effect of an estrogen receptor-beta selective agent in experimental models of systemic infection and sepsis.

DESIGN

WAY-202196, a nonsteroidal selective estrogen receptor-beta agonist, was tested in the murine listeriosis model, the neutropenic rat Pseudomonas aeruginosa infection, and the mouse cecal ligation and puncture sepsis models.

SETTING

University-affiliated biomedical research laboratory.

SUBJECTS

BALB/c mice and Sprague-Dawley rats.

INTERVENTIONS

WAY-202196 or control (vehicle) was administered orally in doses ranging from 1.5 to 50 mg/kg at various time points in the three experimental model systems.

MEASUREMENTS AND MAIN RESULTS

Susceptibility of mice treated with a single oral dose of up to 50 mg/kg WAY-202196 did not differ from those treated with vehicle alone after systemic challenge by Listeria monocytogenes, suggesting a lack of generalized immunosuppression. In the neutropenic rat model, daily administration of WAY-202196 (50 mg/kg) significantly increased survival against an otherwise lethal challenge of P. aeruginosa 12.4.4 compared with the control group (83% vs. 25% survival; p < 0.05). Preservation of intestinal mucosal weight and prevention of histopathologic changes were also observed with the administration of WAY-202196. Similar results were obtained in a cecal ligation and puncture model, in which multiple oral doses of WAY-202196 (50 mg/kg) improved survival (83% vs. 0%; p < 0.05), preserved intestinal epithelial integrity, and significantly reduced systemic bacteremia and peritoneal interleukin-6 and tumor necrosis factor levels. The estrogen receptor-beta agonist provided a comparable level of protection in both male and female animals.

CONCLUSION

These results indicate that oral administration of WAY-202196 preserved gastrointestinal barrier function and improved outcome in experimental models of systemic infection and inflammation. WAY-202196 and similar agents may prove useful clinically as a novel treatment strategy for the treatment or prevention of severe sepsis.

Identification of a peroxisome proliferator responsive element (PPRE)-like cis-element in mouse plasminogen activator inhibitor-1 gene promoter

PAI-1 is expressed and secreted by adipose tissue which may mediate the pathogenesis of obesity-associated cardiovascular complications. Evidence is presented in this report that PAI-1 is not expressed by preadipocyte, but significantly induced during 3T3-L1 adipocyte differentiation and the PAI-1 expression correlates with the induction of peroxisome proliferator-activated receptor gamma (PPARgamma). A peroxisome proliferator responsive element (PPRE)-like cis-element (-206TCCCCCATGCCCT-194) is identified in the mouse PAI-1 gene promoter by electrophoretic mobility shift assay (EMSA) combined with transient transfection experiments; the PPRE-like cis-element forms a specific DNA-protein complex only with adipocyte nuclear extracts, not with preadipocyte nuclear extracts; the DNA-protein complex can be totally competed away by non-labeled consensus PPRE, and can be supershifted with PPARgamma antibody. Mutation of this PPRE-like cis-element can abolish the transactivation of mouse PAI-1 promoter mediated by PPARgamma. Specific PPARgamma ligand Pioglitazone can significantly induce the PAI-1 expression, and stimulate the secretion of PAI-1 into medium.

17Beta-estradiol protects against oxidative stress-induced cell death through the glutathione/glutaredoxin-dependent redox regulation of Akt in myocardiac H9c2 cells

The GSH/glutaredoxin (GRX) system is involved in the redox regulation of certain enzyme activities, and this system protects cells from H2O2-induced apoptosis by regulating the redox state of Akt (Murata, H., Ihara, Y., Nakamura, H., Yodoi, J., Sumikawa, K., and Kondo, T. (2003) J. Biol. Chem. 278, 50226-50233). Estrogens, such as 17beta-estradiol (E2), play an important role in development, growth, and differentiation and appear to have protective effects on oxidative stress mediated by estrogen receptor alpha (ERalpha). However, the role of the ERbeta-mediated pathway in this cytoprotection and the involvement of E2 in the redox regulation are not well understood. In the present study, we demonstrated that E2 protected cardiac H9c2 cells, expressing ERbeta from H2O2-induced apoptosis concomitant with an increase in the activity of Akt. E2 induced the expression of glutaredoxin (GRX) as well as gamma-glutamylcysteine synthetase, a rate-limiting enzyme for the synthesis of GSH. Inhibitors for both gamma-glutamylcysteine synthetase and GRX and ICI182,780, a specific inhibitor of ERs, abolished the protective effect of E2 on cell survival as well as the activity of Akt, suggesting that ERbeta is involved in the cytoprotection and redox regulation by E2. Transcription of the GRX gene was enhanced by E2. The promoter activity of GRX was up-regulated by an ERbeta-dependent element. These results suggest that the GRX/GSH system is involved in the cytoprotective and genomic effects of E2 on the redox state of Akt, a pathway that is mediated, at least in part, by ERbeta. This mechanism may also play an antiapoptotic role in cancer cells during carcinogenesis or chemotherapy.

Transcriptional regulation of tyrosine hydroxylase by estrogen: opposite effects with estrogen receptors alpha and beta and interactions with cyclic AMP

Reported effects of estrogen administration on tyrosine hydroxylase (TH) gene expression are confusing. Therefore, we studied the mechanism of regulation of TH transcription by estrogen with different estradiol receptor (ER) subtypes. PC12 cells, transiently co-transfected with expression vector for ERalpha or ERbeta, and luciferase gene under control of the TH promoter, were treated with 17 beta-estradiol (E2). E2 doubled luciferase activity with ERalpha; however, it was decreased with ERbeta. Mapping the TH promoter showed that the putative half estrogen response element (ERE) motif at - 675, as well as the activation protein 1 motif at - 205, were not required for response to E2 with either ER. The specificity protein 1/early growth response gene 1 (Egr 1) motif was required for the E2-elicited response with ERbeta, but not with ERalpha. Deletion of the cyclic AMP/Ca2+ response element (CRE/CaRE) nearly abolished E2-triggered responses with either ER. Further analysis revealed an imperfect canonical putative ERE overlapping with CRE/CaRE and Nurr1 response element. Oligonucleotides spanning this ERE displayed binding to ER, Cyclic AMP Response Element Binding Protein (CREB) and other proteins. Moreover, E2 attenuated the increase in TH transcription seen with cyclic AMP analogs. Thus, TH is transcriptionally regulated by estradiol in opposite directions depending on ER subtype. The overlapping ERE and CRE/CaRE may integrate interactions elicited by various regulators of TH transcription including cAMP and estrogens.

PAI-1 and atherothrombosis

Plasminogen activator inhibitor-1 (PAI-1) is the major physiologic inhibitor of tissue-type plasminogen activator in plasma, and is elevated in a variety of clinical situations that are associated with increased risk of ischemic cardiovascular events. Recent insights into the biology of PAI-1 suggest that it is more than just an innocent bystander in the pathogenesis of ischemic heart disease. Elevated PAI-1 levels appear to increase the risk of atherothrombotic events and may also promote the progression of vascular disease. The development and testing of specific PAI-1 antagonists will enable basic and clinical investigators the opportunity to test the hypothesis that vascular PAI-1 excess promotes the development of intravascular thrombosis and atherosclerosis.

The sterol response element binding protein regulates cyclooxygenase-2 gene expression in endothelial cells

We previously demonstrated that cholesterol deprivation increases endothelial cyclooxygenase-2 (COX-2)-dependent prostacyclin [prostaglandin I2 (PGI2)] production in vitro. Cholesterol directly regulates gene transcription through the sterol response element binding protein (SREBP). In this work, we demonstrate that SREBP directly regulates COX-2 expression. Cholesterol reduces human COX-2 promoter-luciferase reporter construct activity in transiently transfected endothelial cells. Conversely, cotransfection with a constitutively active mutant SREBP increases COX-2 promoter activity. SREBP-1a and -2 specifically bind a putative sterol response element (SRE) sequence in the COX-2 promoter. This sequence competes for SREBP binding to a low density lipoprotein receptor consensus sequence in an electromobility-shift assay. These data indicate that endothelial COX-2 is regulated by cholesterol via the SREBP pathway. The present study identifies COX-2 as the first vascular gene without a clear role in lipid metabolism transactivated by SREBP, and suggests that enhanced production of PGI2 through this pathway may be an additional benefit of cholesterol-lowering therapies.