Down-regulation of Rac-1 GTPase by Estrogen

Inhibition of Rac1 GTPase Decreases Vascular Oxidative Stress, Improves Endothelial Function, and Attenuates Atherosclerosis Development in Mice

Aims: Oxidative stress and inflammation contribute to atherogenesis. Rac1 GTPase regulates pro-oxidant NADPH oxidase activity, reactive oxygen species (ROS) formation, actin cytoskeleton organization and monocyte adhesion. We investigated the vascular effects of pharmacological inhibition of Rac1 GTPase in mice.

Methods and Results: We treated wild-type and apolipoprotein E-deficient (ApoE^−/−) mice with Clostridium sordellii lethal toxin (LT), a Rac1 inhibitor, and assessed vascular oxidative stress, expression and activity of involved proteins, endothelial function, macrophage infiltration, and atherosclerosis development. LT-treated wild-type mice displayed decreased vascular NADPH oxidase activity and ROS production. Therapeutic LT doses had no impact on behavior, food intake, body weight, heart rate, blood pressure, vascular and myocardial function, differential blood count, and vascular permeability. ApoE^−/− mice were fed a cholesterol-rich diet and were treated with LT or vehicle. LT treatment led to decreased aortic Rac1 GTPase activity, NADPH oxidase activity and ROS production, but had no impact on expression and membrane translocation of NADPH oxidase subunits and RhoA GTPase activity. LT-treated mice showed improved aortic endothelium-dependent vasodilation, attenuated atherosclerotic lesion formation and reduced macrophage infiltration of atherosclerotic plaques. Concomitant treatment of cholesterol-fed ApoE^−/− mice with LT, the specific synthetic Rac1 inhibitor NSC 23766 or simvastatin comparably reduced aortic Rac1 activity, NADPH oxidase activity, oxidative stress, endothelial dysfunction, atherosclerosis development, and macrophage infiltration.

Conclusions: These findings identify an important role of the small GTPase Rac1 in atherogenesis and provide a potential target for anti-atherosclerotic therapy.

Protective Effects of Estrogen on Cardiovascular Disease Mediated by Oxidative Stress

Perimenopause is an important stage of female senescence. Epidemiological investigation has shown that the incidence of cardiovascular disease in premenopausal women is lower than that in men, and the incidence of cardiovascular disease in postmenopausal women is significantly higher than that in men. This phenomenon reveals that estrogen has a definite protective effect on the cardiovascular system. In the cardiovascular system, oxidative stress is considered important in the pathogenesis of atherosclerosis, myocardial dysfunction, cardiac hypertrophy, heart failure, and myocardial ischemia. From the perspective of oxidative stress, estrogen plays a regulatory role in the cardiovascular system through the estrogen receptor, providing strategies for the treatment of menopausal women with cardiovascular diseases.

G Protein-Coupled Estrogen Receptor Regulates Actin Cytoskeleton Dynamics to Impair Cell Polarization

Mechanical forces regulate cell functions through multiple pathways. G protein-coupled estrogen receptor (GPER) is a seven-transmembrane receptor that is ubiquitously expressed across tissues and mediates the acute cellular response to estrogens. Here, we demonstrate an unidentified role of GPER as a cellular mechanoregulator. G protein-coupled estrogen receptor signaling controls the assembly of stress fibers, the dynamics of the associated focal adhesions, and cell polarization via RhoA GTPase (RhoA). G protein-coupled estrogen receptor activation inhibits F-actin polymerization and subsequently triggers a negative feedback that transcriptionally suppresses the expression of monomeric G-actin. Given the broad expression of GPER and the range of cytoskeletal changes modulated by this receptor, our findings position GPER as a key player in mechanotransduction.

Nox1 downregulators: A new class of therapeutics

Chronic non-communicable diseases share the pathomechanism of increased reactive oxygen species (ROS) production by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, known as Nox. The recent discovery that expression of Nox1, a Nox isoform that has been implicated in the pathogenesis of cardiovascular and kidney disease and cancer is regulated by the expression and activity of G protein-coupled estrogen receptor (GPER) led to the identification of orally active small-molecule GPER blockers as selective Nox1 downregulators (NDRs). Preclinical studies using NDRs have demonstrated beneficial effects in vascular disease, hypertension, and glomerular renal injury. These findings suggest the therapeutic potential of NDRs, which reduce Nox1 protein levels, not only for cardiovascular disease conditions including arterial hypertension, pulmonary hypertension, heart failure with preserved ejection fraction (HFpEF), and chronic renal disease, but also for other non-communicable diseases, such as cerebrovascular disease and vascular dementia, Alzheimer's disease, autoimmune diseases and cancer, in which elevated Nox1-derived ROS production plays a causal role.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

ARHGAP15 in Human Breast Carcinoma: A Potent Tumor Suppressor Regulated by Androgens

Rho GTPase activating protein 15 (ARHGAP15) is a recently identified GTPase activating protein which enhances intrinsic hydrolysis of GTP-bound Ras-related C3 botulinus toxin substrate (Rac1), resulting in inactivation of Rac1. Although a lot of studies have pointed out the pivotal roles of the Rac1 pathway in the progression of breast carcinomas, the clinical significance of ARHGAP15 has remained largely unknown in human breast carcinomas. Therefore, we immunolocalized ARHGAP15 in one hundred breast carcinoma tissues. ARHGAP15 immunoreactivity was frequently detected in the cytoplasm of carcinoma cells, and was positively correlated with that of Rac1 and androgen receptor labeling index. Furthermore, ARHGAP15 immunoreactivity was significantly correlated with decreased risk of recurrence and improved prognosis, and multivariate analyses demonstrated that ARHGAP15 immunoreactivity was an independent prognostic factor for both disease-free and breast-cancer-specific survival of the patients. In addition, exogenous overexpression of ARHGA15 suppressed cell proliferation and migration of MCF-7 cells and SK-BR-3 cells. On the other hand, ARHGAP15 mRNA was significantly induced by dihydrotestosterone. These findings suggest that ARHGAP15 is an androgen-induced gene and has anti-tumorigenic roles associated with the Rac1 pathway. ARHGAP15 immunoreactivity is therefore considered a potent prognostic factor in human breast carcinomas.

GPER blockers as Nox downregulators: A new drug class to target chronic non-communicable diseases

Oxidative stress is a hallmark of chronic non-communicable diseases such as arterial hypertension, coronary artery disease, diabetes, and chronic renal disease. Cardiovascular diseases are characterized by increased production of reactive oxygen species (ROS) by NAPDH oxidase 1 (Nox1) and additional Nox isoforms among other sources. Activation of the G protein-coupled estrogen receptor (GPER) can mediate multiple salutary effects on the cardiovascular system. However, GPER also has constitutive activity, e.g. in the absence of specific agonists, that was recently shown to promote hypertension and aging-induced tissue damage by promoting Nox1-derived production of ROS. Furthermore, the small molecule GPER blocker (GRB) G36 reduces blood pressure and vascular ROS production by selectively down-regulating Nox1 expression. These unexpected findings revealed GRBs as first in class Nox downregulators capable to selectively reduce the increased expression and activity of Nox1 in disease conditions. Here, we will discuss the paradigm shift from selective GPER activation to ligand-independent, constitutive GPER signaling as a key regulator of Nox-derived oxidative stress, and the surprising identification of GRBs as the first Nox downregulators for the treatment of chronic non-communicable diseases.

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

Quantitative proteomic analyses of mammary organoids reveals distinct signatures after exposure to environmental chemicals

Common environmental contaminants such as bisphenols and phthalates and persistent contaminants such as polychlorinated biphenyls are thought to influence tissue homeostasis and carcinogenesis by acting as disrupters of endocrine function. In this study we investigated the direct effects of exposure to bisphenol A (BPA), mono-n-butyl phthalate (Pht), and polychlorinated biphenyl 153 (PCB153) on the proteome of primary organotypic cultures of the mouse mammary gland. At low-nanomolar doses each of these agents induced distinct effects on the proteomes of these cultures. Although BPA treatment produced effects that were similar to those induced by estradiol, there were some notable differences, including a reduction in the abundance of retinoblastoma-associated protein and increases in the Rho GTPases Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle protein CDC42. Both Pht and PCB153 induced changes that were distinct from those induced by estrogen, including decreased levels of the transcriptional corepressor C-terminal binding protein 1. Interestingly, the three chemicals appeared to alter the abundance of distinct splice forms of many proteins as well as the abundance of several proteins that regulate RNA splicing. Our combined results indicate that the three classes of chemical have distinct effects on the proteome of normal mouse mammary cultures, some estrogen-like but most estrogen independent, that influence diverse biological processes including apoptosis, cell adhesion, and proliferation.

G-protein-coupled estrogen receptor as a new therapeutic target for treating coronary artery disease

Coronary heart disease (CHD) continues to be the greatest mortality risk factor in the developed world. Estrogens are recognized to have great therapeutic potential to treat CHD and other cardiovascular diseases; however, a significant array of potentially debilitating side effects continues to limit their use. Moreover, recent clinical trials have indicated that long-term postmenopausal estrogen therapy may actually be detrimental to cardiovascular health. An exciting new development is the finding that the more recently discovered G-protein-coupled estrogen receptor (GPER) is expressed in coronary arteries-both in coronary endothelium and in smooth muscle within the vascular wall. Accumulating evidence indicates that GPER activation dilates coronary arteries and can also inhibit the proliferation and migration of coronary smooth muscle cells. Thus, selective GPER activation has the potential to increase coronary blood flow and possibly limit the debilitating consequences of coronary atherosclerotic disease. This review will highlight what is currently known regarding the impact of GPER activation on coronary arteries and the potential signaling mechanisms stimulated by GPER agonists in these vessels. A thorough understanding of GPER function in coronary arteries may promote the development of new therapies that would help alleviate CHD, while limiting the potentially dangerous side effects of estrogen therapy.

Expression and activity of Rac1 is negatively affected in the dehydroepiandrosterone induced polycystic ovary of mouse

Background

Polycystic ovarian syndrome (PCOS) is characterized by the presence of multiple follicular cysts, giving rise to infertility due to anovulation. This syndrome affects about 10% of women, worldwide. The exact molecular mechanism leading to PCOS remains obscure. RhoGTPase has been associated with oogenesis, but its role in PCOS remains unexplored. Therefore, we attempted to elucidate the Vav-Rac1 signaling in PCOS mice model.

Methods

We generated a PCOS mice model by injecting dehydroepiandrosterone (DHEA) for a period of 20 days. The expression levels of Rac1, pRac1, Vav, pVav and Caveolin1 were analyzed by employing immuno-blotting and densitometry. The association between Vav and Rac1 proteins were studied by immuno-precipitation. Furthermore, we analyzed the activity of Rac1 and levels of inhibin B and 17β-estradiol in ovary using biochemical assays.

Results

The presence of multiple follicular cysts in ovary were confirmed by histology. The activity of Rac1 (GTP bound state) was significantly reduced in the PCOS ovary. Similarly, the expression levels of Rac1 and its phosphorylated form (pRac1) were decreased in PCOS in comparison to the sham ovary. The expression level and activity (phosphorylated form) of guanine nucleotide exchanger of Rac1, Vav, was moderately down-regulated. We observed comparatively increased expressions of Caveolin1, 17β-estradiol, and inhibin B in the polycystic ovary.

Conclusion

We conclude that hyperandrogenization (PCOS) by DHEA diminishes ovarian Rac1 and Vav expression and activity along with an increase in expression of Caveolin1. This is accompanied by an increase in the intra-ovarian level of '17 β-estradiol and inhibin B.

Rac1-mediated effects of HMG-CoA reductase inhibitors (statins) in cardiovascular disease

SIGNIFICANCE

HMG-CoA reductase inhibitors (statins) lower serum cholesterol concentrations and are beneficial in the primary and secondary prevention of coronary heart disease. The positive clinical effects have only partially been reproduced with other lipid-lowering interventions suggesting potential statin effects in addition to cholesterol lowering. In experimental models, direct beneficial cardiovascular effects that are mediated by the inhibition of isoprenoids have been documented, which serve as lipid attachments for intracellular signaling molecules such as small Rho guanosine triphosphate-binding proteins, whose membrane localization and function are dependent on isoprenylation.

RECENT ADVANCES

Rac1 GTPase is an established master regulator of cell motility through the cortical actin reorganization and of reactive oxygen species generation through the regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.

CRITICAL ISSUES

Observations in cells, animals, and humans have implicated the activation of Rac1 GTPase as a key component of cardiovascular pathologies, including the endothelial dysfunction, cardiac hypertrophy and fibrosis, atrial fibrillation, stroke, hypertension, and chronic kidney disease. However, the underlying signal transduction remains incompletely understood.

FUTURE DIRECTIONS

Based on the recent advance made in Rac1 research in the cardiovascular system by using mouse models with transgenic overexpression of activated Rac1 or conditional knockout, as well as Rac1-specific small molecule inhibitor NSC 23766, the improved understanding of the Rac1-mediated effects statins may help to identify novel therapeutic targets and strategies.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.

Inhibition of XO or NOX attenuates diethylstilbestrol-induced endothelial nitric oxide deficiency without affecting its effects on LNCaP cell invasion and apoptosis

Oestrogen protects cardiovascular health partially via an up-regulation of NO• (NO radical) production. Its synthetic analogue DES (diethylstilbestrol), used as a potent androgen deprivation therapy for patients with prostate cancer, is however associated with high incidence of thromboembolic events. Exposure of BAECs (bovine aortic endothelial cells) to pharmacologically relevant dosage (12.5 μmol/l, 24 h) of DES resulted in a marked reduction in endothelial NO• bioavailability determined by ESR (electron spin resonance), while 17β-oestradiol instead increased NO• production as expected. Intriguingly, endothelial O(2)•- (superoxide anion) production was up-regulated by DES in vitro and in vivo, which was, however, attenuated by the ER (oestrogen receptor) antagonist ICI 182780, the XO (xanthine oxidase) inhibitor oxypurinol or the NOX (NADPH oxidase) inhibitor NSC23766. These agents also restored NO• production. DES alone in a cell-free system did not produce any ESR-sound O(2)•- signal. Of note, eNOS (endothelial NO synthase) mRNA and protein remained unchanged in response to DES. These results suggest that receptor-dependent activation of XO or NOX, and subsequent production of O(2)•-, mediate DES-induced NO• deficiency. This could represent a previously unrecognized mechanism that is responsible for cardiovascular complications of DES administration. Importantly, DES-induced suppression of LNCaP cell invasion and apoptosis were not affected by XO or NOX inhibitor. Therefore combinatorial therapy of DES and XO/NOX inhibitor may prove to be an innovative and useful therapeutic option in eliminating cardiovascular complications of DES, while preserving its anti-cancer effects, benefiting patients with advanced cancer who do not respond well to any other treatments but DES.

Antiproliferative effect of estrogen in vascular smooth muscle cells is mediated by Kruppel-like factor-4 and manganese superoxide dismutase

The mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) and the zinc finger transcription factor Kruppel-like factor-4 (KLF4) are involved in the regulation of redox homeostasis, apoptosis and cell proliferation. We have shown that estrogen exerts antioxidative actions via induction of MnSOD in cultured rat aortic vascular smooth muscle cells (VSMC). The purpose of the present study was to investigate whether estrogen inhibits VSMC proliferation via alteration of KLF4 and MnSOD expression. In cultured rat aortic VSMC, estrogen binding to estrogen receptor-alpha led to rapid increase in KLF4 expression and reduction of cell proliferation by 50%. Protein separation revealed that KLF4 was shifted to the nucleus when VSMC were treated with estrogen. Estrogen-mediated induction of KLF4 and the antiproliferative effect involved activation of PI-3 kinase, Akt phosphorylation and induction of NO synthase activity. Experiments in freshly isolated denuded aortic segments revealed an increase in KLF4 abundance after estrogen treatment and demonstrated that eNOS is expressed in the media at low levels. Transfection experiments showed that estrogen-induced overexpression of MnSOD required KLF4 and that both KLF4 and MnSOD were indispensable for the observed antiproliferative effect of estrogen in VSMC. To confirm these data in vivo, we investigated neointima formation after carotid artery injury in wild-type (WT) and MnSOD+/- mice. Estrogen deficiency led to enhanced neointima formation and higher numbers of Ki67-positive proliferating cells in the neointima of ovariectomized WT and MnSOD+/- mice. Moreover, MnSOD+/- mice showed more extensive neointima formation and Ki67 immunostaining. Interestingly, estrogen replacement prevented neointima formation in WT mice but failed to completely inhibit neointima formation in MnSOD+/- mice. Cultured VSMC derived from MnSOD+/- mice showed enhanced proliferation as compared to WT VSMC, and estrogen treatment failed to inhibit proliferation in MnSOD+/- VSMC. In conclusion, these data demonstrate the importance of MnSOD and KLF4 for proliferation control in VSMC. Our results provide novel insights into how proliferation of VSMC is regulated by estrogen and may help to identify novel targets for the treatment of vascular diseases such as restenosis.

The physical ability of elderly female Japanese patients with cerebrovascular disease correlates with telomere length in their peripheral blood leukocytes

BACKGROUND AND AIMS

The telomere length of peripheral blood leukocytes has been reported to be inversely correlated with many kinds of pathophysiological conditions. However, correlations between telomere length in peripheral blood leukocytes and patients' physical ability are not known.

METHODS

To address this problem, the physical ability of patients with cerebrovascular disease admitted to the chronic disease ward of Kyushu University Hospital was assessed with the Barthel index (BI) and the telomere length of their peripheral blood leukocytes was determined.

RESULTS AND CONCLUSIONS

Women exhibited a significant correlation between the Barthel score and the expression of long telomeres (>9.4 Kb), in contrast with men who revealed no such correlation. The physical ability of older women was positively correlated with the lengths of their somatic telomeres. Among the BI items, the scores of more difficult physical performances tended to correlate with the presence of terminal restriction fragments longer than 9.4 Kb.

Statin-induced apoptosis linked with membrane farnesylated Ras small G protein depletion, rather than geranylated Rho protein

Rhabdomyolysis is a severe adverse effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins). This myopathy is strongly enhanced by the combination with statins and fibrates, another hypolipidaemic agent. We have evaluated the initial step of statin-induced apoptosis by the detection of membrane flip-flop using flow cytometric analysis. L6 rat myoblasts were treated with various statins (atorvastatin (3 μm), cerivastatin (3 μm), fluvastatin (3 μm), pravastatin (3 mm), or simvastatin (3 μm)) for 2, 4 or 6 h followed by reacting with FITC-conjugated annexin V for the detection of initial apoptosis signal (flip-flop). Various statin-treated myoblasts were significantly stained with FITC-annexin V at 6 h, whereas they were not detected at 2 h. Moreover, immunoblot analysis indicated that when the cells were treated with cerivastatin (3 μm), membrane-associated Ras protein was activated and detached until 6 h, resulting in cell death through the consequent activation of caspase-8. On the other hand, since cytosolic Ras activation did not activate, there is still an unknown mechanism in statin-related Ras depletion. In conclusion, statin-induced apoptosis in muscular tissue was directly initiated by the farnesyl-anchored Ras protein depletion from cell membrane with subsequent apoptosis.

17beta-estradiol inhibits oleic acid-induced rat VSMC proliferation and migration by restoring PGC-1alpha expression

Estrogen shows a vasoprotective role through inhibiting the proliferation and migration of vascular smooth muscle cells (VSMCs). The mechanism underlying the effect of estrogen, however, is not completely understood. Here, we explored the role of peroxisome proliferator-activated receptor-gamma (PPARgamma) coactivator-1alpha (PGC-1alpha) in estrogen-mediated vasoprotection. Firstly, we showed that oleic acid (OA) decreased PGC-1alpha expression while stimulating VSMC proliferation and migration. In contrast, administration of VSMCs with 17beta-estradiol (E(2), 1 or 10nM) significantly restored OA-decreased PGC-1alpha expression, treatment with 10nM E(2) almost completely abolished OA-induced VSMC proliferation and migration. Secondly, by using PGC-1alpha siRNA, the inhibitory effect of E(2) on VSMC growth is strongly reduced via suppressing PGC-1alpha expression, indicating that E(2) may exert its role through restoring PGC-1alpha. Finally, E(2) (10nM) treatment inhibits OA-induced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, however, suppression of PGC-1alpha expression abolishes this inhibitory effect of E(2). Our findings demonstrate for the first time that in OA-stimulated rat VSMCs, treatment with E(2) (1 or 10nM) diminishes VSMC proliferation and migration via restoring OA-decreased PGC-1alpha expression. This observation offers a novel molecular basis of the vasoprotective effect of estrogen.

RhoA and Rac1 changes in the atherosclerotic lesions of WHHLMI rabbits

AIM

The activation of RhoA and Rac1 is crucial for the pathogenesis of atherosclerosis. This study investigated the changes of unprocessed and mature forms of RhoA and Rac1 in the progression of atherosclerosis.

METHODS

Unprocessed and geranylgeranylated forms of RhoA and Rac1 in aortic atherosclerotic lesions were separated by the Triton X-114 partition method using Watanabe heritable hyperlipidemic (WHHLMI) rabbits prone to myocardial infarction. The activation of RhoA and Rac1 was determined by membrane translocation and pull-down assays.

RESULTS

The levels of unprocessed RhoA and Rac1 of the aortas were higher at 7 months than 3 months, accompanied by increased levels of total RhoA and Rac1. Membrane-bound RhoA and Rac1 levels of the aortas at 7 months were significantly increased compared with those at 3 months, consistent with the results of GTP-loading. Unprocessed and activated forms of RhoA and Rac1 had gradually decreas at 15 and 24 months compared to 7 months.

CONCLUSIONS

We show evidence of marked increases in unprocessed RhoA and Rac1 with enhanced activities in the progression of atherosclerosis in WHHLMI rabbits. This is important for better understanding of the pathogenesis of hyperlipidemia-dependent atherosclerosis.

Effects of Oral Estrogen on Aortic ROS-Generating and -Scavenging Enzymes and Atherosclerosis in apoE-Deficient Mice

The effect of hormone replacement therapy (HRT) on cardiovascular diseases remains controversial. Studies conducted on postmenopausal women indicate that oral HRT increases risk factors that may counteract the atheroprotective effect of estrogen. However, the effects of estrogen on atherosclerosis have been examined using subcutaneous estrogen in most animal studies, which points to the need for evaluating the effect of oral estrogen. Reactive oxygen species (ROS) have emerged as critical factors in the pathogenesis of atherosclerosis. This study examined the effect of long-term oral estrogen treatment on aortic oxidative stress and atherosclerosis in female apoE−/− mice to mimic HRT in humans. Ovariectomized apoE−/− mice were given 6 μg/day of oral 17β-estradiol (E2) or control vehicle for 12 weeks. Estrogen treatment reduced atherosclerotic lesions by 38% (E2: 0.20 ± 0.01 mm2/section; control vehicle: 0.32 ± 0.02 mm2/section) and intima by 32% (E2: 0.44 ± 0.02 mm2/section; control vehicle: 0.65 ± 0.04 mm2/section) in the aortic root. Serum levels of total and low-density lipoprotein cholesterol were significantly decreased after estrogen treatment. Aortic superoxide anion levels and the expression of NAD(P)H oxidase subunit p22phox markedly decreased, and two ROS scavenging enzymes, Cu/ZnSOD and MnSOD, were upregulated after estrogen treatment. Estrogen at physiological concentration inhibited tumor necrosis factor-α-stimulated NAD(P)H oxidase activity in both cultured smooth muscle cells and peritoneal macrophages. These results showed that long-term oral estrogen treatment reduces ROS levels and atherosclerosis progression in apoE−/− mice. Oral estrogen alters ROS-generating and -scavenging enzyme expression, suggesting that anti-oxidative actions in the vessel wall contribute to atheroprotective effects of estrogen.

Isoproterenol inhibits angiotensin II-stimulated proliferation and reactive oxygen species production in vascular smooth muscle cells through heme oxygenase-1

Heme oxygenase (HO)-1 is a well-known cytoprotectant against oxidative stress and exhibits an antiproliferative effect in vascular smooth muscle cells (VSMCs). The purpose of the present study was to test whether isoproterenol, one of the synthetic catecholamines having beta-adrenergic activity, affected angiotensin II (Ang II)-induced cell proliferation and reactive oxygen species (ROS) production. Also, the presumptive underlying signaling pathways in VSMCs were studied. Aortic VSMCs from 11-week-old male Sprague-Dawley rats were used. Isoproterenol dose-dependently increased HO-1 expression through beta(2)-adrenoceptor (AR) and protein kinase A (PKA) pathway, and isoproterenol concentration-dependently increased beta(2)-AR mRNA expression. Isoproterenol attenuated Ang II-induced cell proliferation, as evidenced by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. This effect of isoproterenol was inhibited by pretreatment of the cells with beta(2)-AR antagonist butoxamine, PKA inhibitor H-89 and HO inhibitor Tin Protoporphyrin IX (SnPP IX), respectively. Isoproterenol inhibited phosphorylation level of Ang II-induced extracellular signal-regulated kinase (ERK1/2). Isoproterenol significantly inhibited Ang II-induced ROS production through the ERK1/2 pathway. These findings suggest that isoproterenol, via induction of HO-1, inhibits Ang II-stimulated proliferation and ROS production in cultured VSMCs.

Inhibitory effect of estrogen on Rac1-expression in monocytes

Recruitment of circulating monocytes into the vasculature and release of reactive oxygen species (ROS) promote atherogenesis. Rac1-GTPase is an essential component of the superoxide-producing NADPH-oxidase complex. Estrogens inhibit production of vascular reactive oxygen species. Angiotensin II as well as overexpression of the constitutively active mutant RacL61 increased ROS production in monocytes. AngII-mediated ROS release was completely inhibited by overexpression of the dominant negative mutant RacN17 or treatment with 17beta-estradiol. 17beta-Estradiol reduced Rac1-expression concentration- and time-dependently and decreased basal, as well as AngII-induced Rac1 activity. The effects of 17beta-estradiol were receptor-mediated. In vivo, down-regulation of Rac1 by 17beta-estradiol was observed in human mononuclear cells of women with elevated 17beta-estradiol levels after controlled ovarian hyperstimulation. In summary, the data show that down-regulation of Rac1-GTPase contributes to the inhibition of angiotensin II-mediated superoxide release by 17beta-estradiol in monocytes.

Rac1 mediates sex difference in cardiac tumor necrosis factor-alpha expression via NADPH oxidase-ERK1/2/p38 MAPK pathway in endotoxemia

The purpose of this study was to investigate the role of Rac1 and estrogen in sex difference of cardiac tumor necrosis factor-alpha (TNF-alpha) expression during endotoxemia. Endotoxemia was induced in male and female mice by peritoneal injection of lipopolysaccharide (LPS, 4 mg/kg). Compared with female mice, male mice produced more TNF-alpha in the heart 4 h after LPS treatment, which were correlated with higher Rac1 and NADPH oxidase activity, more phosphorylation of ERK1/2 and p38 MAPK, and up-regulation of toll-like receptor-4 (TLR-4) expression in male mice. Cardiac specific Rac1 knockout or administration of 17beta-estradiol down-regulated Rac1 expression, attenuated gp91(phox)-NADPH oxidase expression and activity, decreased phosphorylation of ERK1/2/p38 MAPK and inhibited cardiac TNF-alpha expression induced by LPS, suggesting an important role of Rac1 and estrogen in LPS-stimulated TNF-alpha expression in the heart. More importantly, the sex difference in TNF-alpha expression was abrogated by Rac1 knockout or gp91(phox) knockout and by administration of apocynin or N-acetylcysteine in LPS-stimulated mice. To investigate the functional significance of sex difference in endotoxemia, heart function was measured in isolated hearts with a Langendorff system. Male mice exhibited worse myocardial dysfunction compared with female in endotoxemia. Treatment of male mice with 17beta-estradiol attenuated myocardial dysfunction during endotoxemia. In conclusion, LPS induces Rac1 activation, which contributes to NADPH oxidase activity and phosphorylation of ERK1/2/p38 MAPK, leading to TNF-alpha expression in the heart. The sex difference in TNF-alpha expression is estrogen-dependent and mediated via Rac1 dependent NADPH oxidase/ERK1/2 and p38 MAPK pathway in LPS-stimulated hearts.

Effects of oral contraception with ethinylestradiol and drospirenone on oxidative stress in women 18-35 years old

BACKGROUND

Oral contraceptives (OCs) with estrogens and progestins may affect oxidative stress (OS) status.

STUDY DESIGN

A group of 32 women using oral contraceptives (OCU) containing 0.03 mg ethinylestradiol and 3 mg drospirenone have been compared to a matched control group of 30 noncontraception users (NCU). Blood levels of antioxidants, trace elements and markers of lipid peroxidation were assessed by biochemical methods. A microarray analysis of whole blood mRNA levels of 200 genes involved in OS-dependant pathway was also performed.

RESULTS

Levels of zinc, vitamin E and antibodies to oxidized low-density lipoproteins (LDLs) were not significantly different between the two groups. On the other hand, significant increases in the mean levels of lipid peroxides (+176%, p<.001), oxidized LDLs (+145%, p<.002), copper (+103%, p<.001), Cu/Zn ratio (+100%, p<.001) and a significant decrease in the mean level of beta-carotene (-41%, p<.01) were observed in the OCU compared to NCU. There was a highly significant positive correlation between the lipid peroxide levels and the copper-to-zinc ratio. From the 200 genes tested by microarray, one coding for HSP70 was significantly up-regulated (log(2) fold change=+ 0.45, p<.02) and one coding for inducible nitric oxide synthase significantly down-regulated (log(2) fold change=-0.24, p<.05) in the OCU compared to the NCU.

CONCLUSIONS

The recently introduced combination of ethinylestradiol and drospirenone induced the heightening of lipid peroxidation correlated with high levels of copper, a situation that could be associated with increased cardiovascular risk.

Rapid enhancement of two-step wiring plasticity by estrogen and NMDA receptor activity

Cortical information storage requires combined changes in connectivity and synaptic strength between neurons, but the signaling mechanisms underlying this two-step wiring plasticity are unknown. Because acute 17beta-estradiol (E2) modulates cortical memory, we examined its effects on spine morphogenesis, AMPA receptor trafficking, and GTPase signaling in cortical neurons. Acute E2 application resulted in a rapid, transient increase in spine density, accompanied by temporary formation of silent synapses through reduced surface GluR1. These rapid effects of E2 were dependent on a Rap/AF-6/ERK1/2 pathway. Intriguingly, NMDA receptor (NMDAR) activation after E2 treatment potentiated silent synapses and elevated spine density for as long as 24 h. Hence, we show that E2 transiently increases neuronal connectivity by inducing dynamic nascent spines that "sample" the surrounding neuropil and that subsequent NMDAR activity is sufficient to stabilize or "hold" E2-mediated effects. This work describes a form of two-step wiring plasticity relevant for cortical memory and identifies targets that may facilitate recovery from brain injuries.

Central estrogen inhibition of angiotensin II-induced hypertension in male mice and the role of reactive oxygen species

It has been shown that reactive oxygen species (ROS) contribute to the central effect of ANG II on blood pressure (BP). Recent studies have implicated an antihypertensive action of estrogen in ANG II-infused female mice. The present study used in vivo telemetry recording and in vitro living mouse brain slices to test the hypothesis that the central activation of estrogen receptors in male mice inhibits ANG II-induced hypertension via the modulation of the central ROS production. In male wild-type mice, the systemic infusion of ANG II induced a significant increase in BP (Delta30.1 +/- 2.5 mmHg). Either central infusion of Tempol or 17beta-estradiol (E2) attenuated the pressor effect of ANG II (Delta10.9 +/- 2.3 and Delta4.5 +/- 1.4 mmHg), and the protective effect of E2 was prevented by the coadministration of an estrogen receptor, antagonist ICI-182780 (Delta23.6 +/- 3.1 mmHg). Moreover, the ganglionic blockade on day 7 after the start of ANG II infusions resulted in a smaller reduction of BP in central Tempol- and in central E2-treated males, suggesting that estrogen inhibits the central ANG II-induced increases in sympathetic outflow. In subfornical organ slices, the application of ANG II resulted in a 21.5 +/- 2.5% increase in ROS production. The coadministration of irbesartan, an ANG II type 1 receptor antagonist, or the preincubation of brain slices with Tempol blocked ANG II-induced increases in ROS production (-1.8 +/- 1.6% and -1.0 +/- 1.8%). The ROS response to ANG II was also blocked by E2 (-3.2 +/- 2.4%). The results suggest that the central actions of E2 are involved in the protection from ANG II-induced hypertension and that estrogen modulation of the ANG II-induced effects may involve interactions with ROS production.

Effect of gender and sex hormones on vascular oxidative stress

1. It is well documented that the incidence and severity of several vascular diseases, such as hypertension, atherosclerosis and stroke, are lower in premenopausal women than men of similar age and post-menopausal women. The mechanisms responsible for gender differences in the incidence and severity of vascular disease are not well understood. However, emerging evidence suggests that sex hormone-dependent differences in vascular oxidative stress may play an important role. The aim of the present brief review is to provide an insight into the effect of gender and sex hormones on vascular oxidative stress. 2. When production of reactive oxygen species (ROS) is enhanced and/or their metabolism by anti-oxidant enzymes is impaired, a condition known as 'oxidative stress' can develop. Oxidative stress is believed to play an important role in both the initiation and progression of a variety of vascular diseases, including hypertension and atherosclerosis. NADPH oxidases are believed to be the major source of vascular ROS. Moreover, excessive production of ROS by NADPH oxidases has been linked to the development of vascular oxidative stress. 3. Increasing evidence suggests that levels of vascular ROS may be lower in women than men during health and disease. Indeed, the activity and expression of vascular NADPH oxidase is lower in female versus male animals under healthy, hypertensive and atherosclerotic conditions. 4. Gonadal sex hormones may play an important role in the regulation of vascular oxidative stress. For example, oestrogens, which are present in highest levels in premenopausal women, have been reported to lower vascular oxidative stress by modulating the expression and function of NADPH oxidases, as well as anti-oxidant enzymes. 5. Further studies are needed to clarify whether lower vascular oxidative stress in women in fact protects against the initiation and development of vascular disease and to further define the roles of gonadal sex hormones in such an effect. Knowledge gained from these studies may potentially lead to advances in the clinical diagnosis and treatment of vascular disease in both genders.

Up-regulation of Rac1 by epidermal growth factor mediates COX-2 expression in recurrent respiratory papillomas

Recurrent respiratory papillomas are epithelial tumors of the airway caused by human papillomaviruses. We previously reported that the epidermal growth factor receptor (EGFR) is overexpressed in papilloma cells, that cyclooxygenase-2 (COX-2) is induced, and that COX-2 expression in primary papilloma cells requires activation of the EGFR but not Erk. Rac1, a member of the Rho family of GTPases, is a key signaling element that is known to control multiple pathways downstream of the EGFR. Here we report that Rac1 is overexpressed in papilloma cells compared with normal laryngeal epithelial cells and that the increased levels of Rac1 are mediated by EGFR activation. Transfecting cells with Rac1-specific siRNA suppressed COX-2 expression. Surprisingly, Rac1 mediated phosphorylation of p38 mitogen-activated kinase in papilloma cells but not normal cells, and inhibition of p38 with the specific inhibitor SB202190 suppressed COX-2 expression in papilloma cells but had no effect on low-level COX-2 expression in normal cells. Thus, the signaling cascades that regulate COX-2 expression are different in HPV-infected papilloma cells, with a significant contribution by the EGFR-- Rac1-->p38 pathway.

Up-regulation of Rac1 by epidermal growth factor mediates COX-2 expression in recurrent respiratory papillomas

Recurrent respiratory papillomas are epithelial tumors of the airway caused by human papillomaviruses. We previously reported that the epidermal growth factor receptor (EGFR) is overexpressed in papilloma cells, that cyclooxygenase-2 (COX-2) is induced, and that COX-2 expression in primary papilloma cells requires activation of the EGFR but not Erk. Rac1, a member of the Rho family of GTPases, is a key signaling element that is known to control multiple pathways downstream of the EGFR. Here we report that Rac1 is overexpressed in papilloma cells compared with normal laryngeal epithelial cells and that the increased levels of Rac1 are mediated by EGFR activation. Transfecting cells with Rac1-specific siRNA suppressed COX-2 expression. Surprisingly, Rac1 mediated phosphorylation of p38 mitogen-activated kinase in papilloma cells but not normal cells, and inhibition of p38 with the specific inhibitor SB202190 suppressed COX-2 expression in papilloma cells but had no effect on low-level COX-2 expression in normal cells. Thus, the signaling cascades that regulate COX-2 expression are different in HPV-infected papilloma cells, with a significant contribution by the EGFR-- Rac1-->p38 pathway.

Inhibition of apoptosis-regulated signaling kinase-1 and prevention of congestive heart failure by estrogen

BACKGROUND

Epidemiological studies have shown gender differences in the incidence of congestive heart failure (CHF); however, the role of estrogen in CHF is not known. We hypothesize that estrogen prevents cardiomyocyte apoptosis and the development of CHF.

METHODS AND RESULTS

17Beta-estradiol (E2, 0.5 mg/60-day release) or placebo pellet was implanted subcutaneously into male G alpha q transgenic (Gq) mice. After 8 weeks, E2 treatment decreased the extent of cardiac hypertrophy and dilation and improved contractility in Gq mice. E2 treatment also attenuated nicotinamide adenine dinucleotide phosphate oxidase activity and superoxide anion production via downregulation of Rac1. This correlated with reduced apoptosis in cardiomyocytes of Gq mice. The antioxidative properties of E2 were also associated with increased expression of thioredoxin (Trx), Trx reductases, and Trx reductase activity in the hearts of Gq mice. Furthermore, the activation of apoptosis signal-regulating kinase 1 and its downstream effectors, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase, in the hearts of Gq mice was reduced by long-term E2 treatment. Indeed, E2 (10 nmol/L)-treated cardiomyocytes were much more resistant to angiotensin II-induced apoptosis. These antiapoptotic and cardioprotective effects of E2 were blocked by an estrogen receptor antagonist (ICI 182,780) and by a Trx reductase inhibitor (azelaic acid).

CONCLUSIONS

These findings indicate that long-term E2 treatment improves CHF by antioxidative mechanisms that involve the upregulation of Trx and inhibition of Rac1-mediated attenuated nicotinamide adenine dinucleotide phosphate oxidase activity and apoptosis signal-regulating kinase 1 /c-Jun N-terminal kinase/p38 mitogen-activated protein kinase-mediated apoptosis. These results suggest that estrogen may be a useful adjunctive therapy for patients with CHF.

Effect of gender on NADPH-oxidase activity, expression, and function in the cerebral circulation: role of estrogen

BACKGROUND AND PURPOSE

This study tested whether NADPH-oxidase activity, expression, and functional effects on vascular tone are influenced by gender in the rat cerebral circulation and whether such differences are estrogen-dependent.

METHODS

NADPH-stimulated superoxide production by cerebral (basilar [BA]; middle cerebral) arteries from male and female Sprague-Dawley rats was measured using lucigenin-enhanced chemiluminescence and dihydroethidium. Protein expression of Nox1, Nox2, Nox4, superoxide dismutase 1 (SOD1), SOD2, and SOD3 was measured using Western blotting. Vascular responses of BA to NADPH were assessed in a myograph. Some female rats were ovariectomized and treated with either vehicle (dimethyl sulfoxide) or 17beta-estradiol.

RESULTS

NADPH-stimulated superoxide production by BA and middle cerebral arteries from males was approximately 2-fold greater than vessels from females. Superoxide production was virtually abolished by the NADPH-oxidase inhibitor, diphenyleneiodonium. Protein expression of Nox1 and Nox4 in BA was also higher in males than in females (2.4- and 2.8-fold, respectively), whereas Nox2, SOD1, SOD2, and SOD3 expression did not differ between genders. NADPH induced greater vasorelaxant effects in BA from males versus females (P<0.05). The hydrogen peroxide scavenger, catalase, abolished these NADPH-induced relaxations. NADPH-stimulated superoxide production by BA from ovariectomized rats treated with vehicle was 3-fold greater than levels in intact females. Treatment of ovariectomized rats with 17beta-estradiol decreased superoxide production (P<0.05). NADPH-induced relaxations of BA were smaller in 17beta-estradiol-treated than in vehicle-treated ovariectomized rats (P<0.05).

CONCLUSIONS

NADPH-oxidase activity and function are lower in cerebral arteries of female rats. These gender differences are estrogen-dependent and are associated with lower Nox1 and Nox4 expression.

Regulation of antioxidant and oxidant enzymes in vascular cells and implications for vascular disease

Data from numerous studies demonstrate that oxidative stress plays an important role in the pathogenesis of vascular disease. Oxidative stress leads to many pathologic events, such as inactivation of nitric oxide, lipid oxidation, enhanced mitogenicity and apoptosis of vascular cells, and increased expression and activation of redox-sensitive genes, which contribute to atherogenesis at all stages of the disease. Multiple enzymes are expressed in vascular cells that are involved in the elimination and production of reactive oxygen species, including the superoxide dismutases, catalase, thioredoxin reductase, glutathione peroxidase, NAD(P)H oxidase, xanthine oxidase, myeloperoxidase, and endothelial nitric oxide synthase. Several agonists and pathologic conditions that predispose to vascular disease induce changes in the expression and activity levels of these antioxidant and oxidant enzyme systems, leading to modulation of vascular oxygen radical load. Identification of key enzymes and mechanisms of vascular oxidative stress is important for the development of novel, specific pharmacologic interventions.

Angiotensin II-induced NADPH oxidase activation impairs insulin signaling in skeletal muscle cells

The renin-angiotensin system (RAS) and reactive oxygen species (ROS) have been implicated in the development of insulin resistance and its related complications. There is also evidence that angiotensin II (Ang II)-induced generation of ROS contributes to the development of insulin resistance in skeletal muscle, although the precise mechanisms remain unknown. In the present study, we found that Ang II markedly enhanced NADPH oxidase activity and consequent ROS generation in L6 myotubes. These effects were blocked by the angiotensin II type 1 receptor blocker losartan, and by the NADPH oxidase inhibitor apocynin. Ang II also promoted the translocation of NADPH oxidase cytosolic subunits p47phox and p67phox to the plasma membrane within 15 min. Furthermore, Ang II abolished insulin-induced tyrosine phosphorylation of insulin receptor substrate 1 (IRS1), activation of protein kinase B (Akt), and glucose transporter-4 (GLUT4) translocation to the plasma membrane, which was reversed by pretreating myotubes with losartan or apocynin. Finally, small interfering RNA (siRNA)-specific gene silencing targeted specifically against p47phox (p47siRNA), in both L6 and primary myotubes, reduced the cognate protein expression, decreased NADPH oxidase activity, restored Ang II-impaired IRS1 and Akt activation as well as GLUT4 translocation by insulin. These results suggest a pivotal role for NADPH oxidase activation and ROS generation in Ang II-induced inhibition of insulin signaling in skeletal muscle cells.

Antiproliferative Effect of Isosteviol on Angiotensin-II-Treated Rat Aortic Smooth Muscle Cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. The aims of this study were to examine whether isosteviol alters angiotensin-II-induced cell proliferation in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with isosteviol, then stimulated with angiotensin II, after which [(3)H]thymidine incorporation and endothelin-1 secretion were examined. Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II on extracellular signal-regulated kinase (ERK) phosphorylation were found reversed with isosteviol and antioxidants such as N-acetylcysteine. In summary, we speculate that isosteviol inhibits angiotensin-II-induced cell proliferation and endothelin-1 secretion via attenuation of reactive oxygen species generation. Thus, this study provides important insights that may contribute to the effects of isosteviol on the cardiovascular system.

AT1 receptor antagonism improves endothelial dysfunction in postmenopausal women

The menopause is associated with an increased incidence of atherosclerotic disease. Estrogen deficiency causes AT1 receptor overexpression which is involved in the development of vascular dysfunction. The effect of a 6 week-treatment with the AT1 receptor antagonist candesartan (16 mg/d) on endothelium-dependent vasorelaxation was compared to the treatment with placebo or the calcium channel antagonist felodipine (5 mg/d) in 29 postmenopausal women in the absence or presence of hormone replacement therapy (HRT) in a prospective, double-blind, randomized cross-over study. Endothelial function was assessed by measurement of forearm blood flow (FBF) by venous occlusion plethysmography. FBF during reactive hyperemia was significantly improved by candesartan in patients without HRT (hyperemic peak flow and area under the FBF curve), whereas felodipine and placebo exerted no effect. In patients with HRT, no treatment regimen showed a significant effect on endothelial function. Nitroglycerin-induced vasorelaxation and basal FBF were not significantly altered in all groups. AT1 receptor antagonism improves vascular function in postmenopausal women without HRT. Thus, AT1 receptor blockade may resemble an efficient approach for the prevention of vascular dysfunction in estrogen-deficient women.

Tetramethylpyrazine downregulates angiotensin II-induced endothelin-1 gene expression in vascular endothelial cells

1. Tetramethylpyrazine (TMP) is one of the active ingredients of the Chinese herb Ligusticum wallichii Franchat. It is well documented that TMP exerts a cardiovascular protective effect. The aims of the present study were to examine whether TMP alters angiotenisn (Ang) II-induced endothelin (ET)-1 gene expression and to identify the putative underlying signalling pathways in vascular endothelial cells. 2. Cultured vascular endothelial cells were pre-incubated with TMP, stimulated with AngII and ET-1 gene expression was then examined. The effects of TMP pretreatment on AngII-induced extracellular signal-regulated kinase (ERK) phosphorylation were investigated to elucidate the intracellular mechanism responsible for the effects of TMP on ET-1 gene expression. 3. Tetramethylpyrazine inhibited AngII-induced ET-1 gene expression, as revealed by nothern blotting and a promoter activity assay. Tetramethylpyrazine also inhibited the AngII-induced increase in intracellular reactive oxygen species (ROS), as measured by the redox sensitive fluorescent dye 2' 7'-dichlorofluorescin diacetate and ERK phosphorylation. 4. In summary, we have demonstrated, for the first time, that TMP inhibits AngII-induced ROS generation, ERK phosphorylation and ET-1 gene expression in vascular endothelial cells. Thus, the present study delivers important new insights into the molecular pathways that may contribute to the proposed beneficial effects of TMP in the cardiovascular system.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

Progesterone Antagonizes the Vasoprotective Effect of Estrogen on Antioxidant Enzyme Expression and Function

Oxidative stress plays an important role in the pathogenesis of atherosclerosis and can be effectively influenced by radical scavenging enzymes. Estrogens exert antioxidative effects in the vasculature; however, cotreatment with progesterone may abrogate the vasoprotective effects of estrogen. Therefore, the effects of progesterone on the production of reactive oxygen species (ROS) and expression and function of antioxidant and oxidant enzymes were investigated in cultured vascular smooth muscle cells (VSMCs) and vascular tissue of mice. Progesterone time- and concentration-dependently downregulated extracellular superoxide dismutase (ecSOD) and manganese superoxide dismutase (MnSOD) expression and enzyme activity and reversed 17β-estradiol–induced overexpression of ecSOD and MnSOD in VSMCs. Nuclear run-on assays revealed that progesterone decreases MnSOD and ecSOD transcription rates. Consequently, progesterone increased ROS release in VSMCs that was prevented by concomitant treatment with 17β-estradiol. Estrogen deficiency in ovariectomized mice was associated with an increase in vascular superoxide release and NADPH oxidase activity. Estrogen replacement prevented this increase, whereas progesterone substitution enhanced ROS production and NADPH oxidase activity. The modulation of superoxide release coincided with decreased expression of ecSOD and MnSOD and upregulation of the p22phox and p67phox subunits of the NADPH oxidase complex in progesterone-treated animals. Furthermore, administration of progesterone to ovariectomized mice treated with 17β-estradiol abrogated the antioxidative effects of estrogen. Progesterone antagonizes the vasoprotective effects of estrogen on ecSOD and MnSOD expression and increases NADPH oxidase activity. These findings may in part explain why hormone replacement therapy with estrogen plus progesterone displayed no beneficial effect on cardiovascular event rates in the prospective clinical trials.

17Beta-estradiol attenuates PDGF signaling in vascular smooth muscle cells at the postreceptor level

Estrogens are known to display significant vasoprotective effects in premenopausal women. PDGF is an important mediator of vascular smooth muscle cell (VSMC) migration and proliferation, and thus atherogenesis. We analyzed the effects of 17beta-estradiol (E2) on beta-PDGF receptor (beta-PDGFR) expression/activation and PDGF-dependent VSMC proliferation, migration, and downstream signaling events. Pretreatment of VSMCs with E2 (0.3 microM-0.1 mM) for 24 h concentration-dependently inhibited PDGF-induced proliferation and migration up to 85.5 +/- 15.8% and 79.4 +/- 9.8%, respectively (both P < 0.05). These effects were prevented by coincubation with the ER antagonist ICI-182780. E2 did not alter beta-PDGFR expression, nor did it impair the ligand-induced tyrosine phosphorylation of the beta-PDGFR and consecutive binding of the receptor-associated signaling molecules Src homology region 2-containing phosphatase-2, PLC-gamma, phosphatidylinositol 3-kinase, and RasGAP. Thus estrogens inhibited PDGF-induced cellular responses at the postreceptor level. Although stimulation of VSMCs with PDGF-BB led to a transient increase of rac-1 activity, pretreatment with E2 for 24 h concentration-dependently inhibited PDGF-induced rac-1 activation. Furthermore, inhibition of rac-1 by Clostridium sordellii lethal toxin or overexpression of dominant-negative rac-1 (rac-N17) significantly inhibited PDGF-induced VSMC migration, indicating that rac-1 activity is essential for PDGF-dependent cellular responses. E2 did not further reduce PDGF-induced migration in rac-N17-overexpressing cells, suggesting that it diminishes VSMC migration by altering rac-1 activity. We conclude that E2 attenuates PDGF-dependent cellular functions of VSMCs downstream of the beta-PDGFR via inhibition of rac-1. These observations offer a molecular explanation for the vasoprotective effects of estrogens.

Resveratrol and curcumin reduce the respiratory burst of Chlamydia-primed THP-1 cells

The intracellular bacterium Chlamydia pneumoniae is involved in the inflammation process of atherosclerosis. We previously demonstrated that C. pneumonia infected monocytes (THP-1 cells) responded to stimulation by an increased respiratory burst linked to an increased NADPH oxidase (NOX) activity. We now tested agents acting on the assembly of the NOX subunits or on protein kinase C, a trigger of NOX activity. Apocynin, resveratrol, rutin, quercetin, curcumin, and tocopherols were tested. The cells were pre-incubated with Chlamydia and the agent for 19 h, and then stimulated with phorbol myristate acetate. The NOX activity was monitored by measuring the hydrogen peroxide production. Resveratrol and curcumin (10(-4)-10(-6) M) were better inhibitors than apocynin. alpha-Tocopherol was inactive, and gamma-tocopherol inhibitor at 10(-4) M only. Quercetin was inactive, and rutin a moderate but significant inhibitor. The inhibition by resveratrol was increased by 10(-6) M rutin or quercetin. Resveratrol and curcumin thus appeared to be interesting for atherosclerosis treatment.

Delayed mechanism for induction of gamma-glutamylcysteine synthetase heavy subunit mRNA stability by oxidative stress involving p38 mitogen-activated protein kinase signaling

Expression of the gamma-glutamylcysteine synthetase heavy subunit (gamma-GCSh), which encodes the rate-limiting enzymes for glutathione biosynthesis, is regulated by many cytotoxic agents. Moreover, gamma-GCSh mRNA expression is elevated in colorectal cancer, but how gamma-GCSh expression is regulated is not completely understood. By using actinomycin D, which inhibits new RNA synthesis, we showed that treatment of human colorectal cancer cells with the prooxidant sulindac increased the half-life of gamma-GCSh mRNA. By using a tetracycline-regulated gamma-GCSh mRNA assay system, we systematically dissected the cis-acting sequence and trans-acting factors that regulate the stability of gamma-GCSh by cytotoxic prooxidants. We demonstrated that a HuR recognition sequence, AUUUA, in the 3'-untranslated region is responsible for the decay of gamma-GCSh mRNA. Oxidative stress enhanced cytoplasmic content of HuR. Overexpression of HuR by transfection stabilized gamma-GCSh mRNA, whereas overexpression of a dominant-negative HuR mutant suppressed the induced stability. Furthermore, prooxidant-induced gamma-GCSh mRNA stabilization and HuR binding were blocked by p38 mitogen-activated protein kinase inhibitors. We provide the first evidence that reduction-oxidation regulation of gamma-GCSh expression, itself a reduction-oxidation sensor and regulator, is mediated at least in part by the p38 mitogen-activated protein kinase signaling through the HuR RNA-binding protein.

Inhibition of angiotensin II induced endothelin-1 gene expression by 17-beta-oestradiol in rat cardiac fibroblasts

OBJECTIVE

To examine whether 17-beta-oestradiol (E(2)) may alter angiotensin II (Ang II) induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts.

DESIGN

Cultured rat cardiac fibroblasts were preincubated with E(2) then stimulated with Ang II. [(3)H]Thymidine incorporation and endothelin-1 (ET-1) gene expression were examined. The effect of E(2) on Ang II induced NADPH oxidase activity, reactive oxygen species (ROS) formation, and extracellular signal regulated kinase (ERK) phosphorylation were tested to elucidate the intracellular mechanism of E(2) in proliferation and ET-1 gene expression.

RESULTS

Ang II increased DNA synthesis, which was inhibited with E(2) (1-100 nmol/l). E(2), but not 17-alpha-oestradiol, inhibited Ang II induced ET-1 gene expression as shown by northern blotting and promoter activity assay. This effect was prevented by co-incubation with the oestrogen receptor antagonist ICI 182,780 (1 micromol/l). E(2) also inhibited Ang II increased NADPH oxidase activity, ROS formation, ERK phosphorylation, and activator protein-1 mediated reporter activity.

CONCLUSIONS

The results suggest that E(2) inhibits Ang II induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway through attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of oestrogen on the cardiovascular system.

Resveratrol inhibits angiotensin II-induced endothelin-1 gene expression and subsequent proliferation in rat aortic smooth muscle cells

Resveratrol is a phytoestrogen naturally found in grapes and is the major constituent of wine thought to have a cardioprotective effect. The aims of this study were to examine whether resveratrol alters angiotenisn II-induced cell proliferation and endothelin-1 gene expression and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with resveratrol then stimulated with angiotensin II, after which [3H]thymidine incorporation and endothelin-1 gene expression were examined. The intracellular mechanism of resveratrol in cellular proliferation and endothelin-1 gene expression was elucidated by examining the phosphorylation level of angiotensin II-induced extracellular signal-regulated kinase (ERK). The inhibitory effects of resveratrol (1-100 microM) on angiotensin II-induced DNA synthesis and endothelin-1 gene expression were demonstrated with Northern blot and promoter activity assays. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-senstive fluorescent dye, showed a resveratrol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II and H2O2 on ERK phosphorylation and activator protein-1-mediated reporter activity were found reversed with resveratrol and antioxidants such as N-acetyl-cysteine. In summary, we speculate that resveratrol inhibits angiotensin II-induced cell proliferation and endothelin-1 gene expression, and does so in a manner which involves the disruption of the ERK pathway via attenuation of reactive oxygen species generation. Thus, this study provides important insight into the molecular pathways that may contribute to the proposed beneficial effects of resveratrol on the cardiovascular system.

Downregulation of Rac1 activation by caffeic acid in aortic smooth muscle cells

Caffeic acid, a dietary phenol from coffee, fruits and vegetables, is an efficient antioxidant. However, little is known about its anti-oxidative mechanism in the modulation of fundamental cellular processes. In this study, we investigated whether caffeic acid regulates Rac1 GTPase activity, a partner of NADPH oxidase. Our results showed that caffeic acid decrease Rac1 protein level under basal conditions and incubation with angiotensin II (ANG II) in vascular smooth muscle cells. In a Rac-bound-to-PAK pull down assay, caffeic acid clearly inhibited Rac1 activity. We also observed that caffeic acid suppressed the generation of superoxide anion stimulated by ANG II that activates NADPH oxidase. On the other hand, co-incubation with caffei caid and cycloheximide significantly accelerated the Rac1 degradation. In addition, pretreatment with caffeic acid for 24 hours was able to prevent phosphorylation of MLC and HSP27, when cells were challenged with ANG II through the redox sensitive pathway. These results support the hypothesis that caffeic acid reduces Rac1 GTPase protein and activity level, followed by a down-regulation of NADPH oxidase activity.