Glucocorticoids induce endothelin release from vascular smooth muscle cells but not endothelial cells

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

Apitherapy combination improvement of blood pressure, cardiovascular protection, and antioxidant and anti-inflammatory responses in dexamethasone model hypertensive rats

Hypertension-induced ventricular and vascular remodeling causes myocardial infarction, heart failure, and sudden death. Most available pharmaceutical products used to treat hypertension lead to adverse effects on human health. Limited data is available on apitherapy (bee products) combinations for treatment of hypertension. This study aims to evaluate the antihypertensive effects of combinations of natural apitherapy compounds used in the medical sector to treat a variety of diseases. Rats were assigned into six groups consisting of one control group and five hypertensive groups where hypertension (blood pressure > 140/90) was induced with dexamethasone. One of these groups was used as a hypertension model, while the remaining four hypertensive groups were treated with a propolis, royal jelly, and bee venom combination (PRV) at daily oral doses of 0.5, 1.0, and 2.0 mg/kg, and with losartan 10 mg/kg. The PRV combination at all doses decreased arterial blood pressure below the suboptimal value (p < 0.001), and PRV combination treatment improved dexamethasone-induced-ECG changes. The same treatment decreased angiotensin-II, endothelin-1, and tumor growth factor β serum levels in hypertensive rats. Additionally, PRV combination improved histopathological structure, and decreased serum levels of NF-kB and oxidative stress biomarkers. We concluded that PRV combination therapy may be used as a potential treatment for a variety of cardiovascular diseases.

ET-1 as a Sex-Specific Mechanism Impacting Age-Related Changes in Vascular Function

Aging is a primary risk factor for cardiovascular disease (CVD), which is the leading cause of death in developed countries. Globally, the population of adults over the age of 60 is expected to double by the year 2050. CVD prevalence and mortality rates differ between men and women as they age in part due to sex-specific mechanisms impacting the biological processes of aging. Measures of vascular function offer key insights into cardiovascular health. Changes in vascular function precede changes in CVD prevalence rates in men and women and with aging. A key mechanism underlying these changes in vascular function is the endothelin (ET) system. Studies have demonstrated sex and sex hormone effects on endothelin-1 (ET-1), and its receptors ETA and ETB. However, with aging there is a dysregulation of this system resulting in an imbalance between vasodilation and vasoconstriction. Thus, ET-1 may play a role in the sex differences observed with vascular aging. While most research has been conducted in pre-clinical animal models, we describe more recent translational data in humans showing that the ET system is an important regulator of vascular dysfunction with aging and acts through sex-specific ET receptor mechanisms. In this review, we present translational evidence (cell, tissue, animal, and human) that the ET system is a key mechanism regulating sex-specific changes in vascular function with aging, along with therapeutic interventions to reduce ET-mediated vascular dysfunction associated with aging. More knowledge on the factors responsible for the sex differences with vascular aging allow for optimized therapeutic strategies to attenuate CVD risk in the expanding aging population.

Glucocorticoids: Fuelling the Fire of Atherosclerosis or Therapeutic Extinguishers?

Glucocorticoids are steroid hormones with key roles in the regulation of many physiological systems including energy homeostasis and immunity. However, chronic glucocorticoid excess, highlighted in Cushing's syndrome, is established as being associated with increased cardiovascular disease (CVD) risk. Atherosclerosis is the major cause of CVD, leading to complications including coronary artery disease, myocardial infarction and heart failure. While the associations between glucocorticoid excess and increased prevalence of these complications are well established, the mechanisms underlying the role of glucocorticoids in development of atheroma are unclear. This review aims to better understand the importance of glucocorticoids in atherosclerosis and to dissect their cell-specific effects on key processes (e.g., contractility, remodelling and lesion development). Clinical and pre-clinical studies have shown both athero-protective and pro-atherogenic responses to glucocorticoids, effects dependent upon their multifactorial actions. Evidence indicates regulation of glucocorticoid bioavailability at the vasculature is complex, with local delivery, pre-receptor metabolism, and receptor expression contributing to responses linked to vascular remodelling and inflammation. Further investigations are required to clarify the mechanisms through which endogenous, local glucocorticoid action and systemic glucocorticoid treatment promote/inhibit atherosclerosis. This will provide greater insights into the potential benefit of glucocorticoid targeted approaches in the treatment of cardiovascular disease.

Dose-dependent and time-dependent metabolic, hemodynamic, and redox disturbances in dexamethasone-treated Wistar rats

OBJECTIVES

Dexamethasone is used experimentally to induce insulin resistance and type 2 diabetes. However, data concerning the dose, the duration of treatment, and the associated comorbidities are inconsistent. The aim of this study was to compare the effects of different doses of dexamethasone and the duration of treatment necessary for the development of a model of insulin resistance that mimics the clinical condition with the associated comorbidities.

METHODS

Dexamethasone was administered intramuscularly to male Wistar rats, at doses of 500 and 1,000 µg/kg/day for the subchronic treatment (eight consecutive days) and at doses of 5, 25, 50, and 100 µg/kg/day in chronic treatment (28 consecutive days). Effects on body weight, metabolism, hemodynamics, renal function, and redox status were evaluated.

RESULTS

Both treatments induced a progressive body weight loss that was drastic in subchronic treatment, improved glucose tolerance without affecting fasting glycemia. Doses of 1,000 and 100 µg/kg were associated with hypertriglyceridemia, hypertension, and increased heart rate, cardiac and renal hypertrophy. Increased creatinemia associated with reduced creatinuria were observed in sub-chronic treatment while increased proteinuria and reduced creatinuria were noticed in chronic treatment. 1,000 µg/kg dexamethasone caused an increase in hepatic, and renal malondialdehyde (MDA) and glutathione (GSH) coupled with a reduction in catalase activity. The dose of 100 µg/kg induced a rise in GSH and catalase activity but reduced MDA levels in the kidney.

CONCLUSIONS

Doses of 1,000 µg/kg for subchronic and 100 µg/kg for chronic treatment exhibited similar effects and are the best doses to respective time frames to induce the model.

Impact of Acute and Chronic Stress on Thrombosis in Healthy Individuals and Cardiovascular Disease Patients

Psychological stress induces different alterations in the organism in order to maintain homeostasis, including changes in hematopoiesis and hemostasis. In particular, stress-induced hyper activation of the autonomic nervous system and hypothalamic–pituitary–adrenal axis can trigger cellular and molecular alterations in platelets, coagulation factors, endothelial function, redox balance, and sterile inflammatory response. For this reason, mental stress is reported to enhance the risk of cardiovascular disease (CVD). However, contrasting results are often found in the literature considering differences in the response to acute or chronic stress and the health condition of the population analyzed. Since thrombosis is the most common underlying pathology of CVDs, the comprehension of the mechanisms at the basis of the association between stress and this pathology is highly valuable. The aim of this work is to give a comprehensive review of the studies focused on the role of acute and chronic stress in both healthy individuals and CVD patients, focusing on the cellular and molecular mechanisms underlying the relationship between stress and thrombosis.

Macitentan in the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an uncommon but lethal and progressive disease in which prostacyclin, nitric oxide and endothelin-1 pathways are disturbed and contribute to the pathophysiology of this disease. Endothelin receptor antagonists are a class of drugs that have been approved as PAH therapy. Macitentan is a lipophilic, tissue specific, dual receptor antagonist with a higher potency than bosentan and a reduced risk of hepatic injury. Macitentan has shown a reduction in morbidity and mortality due to PAH at long-term follow-up and improvements in hemodynamics, exercise capacity and functional class at the short term. Its main adverse events are nasopharyngitis, bronchitis and an increased risk of anemia. We review the clinical data of macitentan and its use in PAH.

Acute psychological stress, autonomic function, and arterial stiffness among women

This study aimed to investigate the effect of acute psychological stress on autonomic function and arterial stiffness, and to test a mediating role of changes in autonomic function between acute stress and arterial stiffness. Eighty-five healthy female adults were randomized into either an experimental or control group. The Trier Social Stress Test (TSST) was used to induce acute psychological stress. Autonomic function (measured by pre-ejection period [PEP] from cardiac impedance and high frequency [HF] of heart rate variability [HRV]) and arterial stiffness (measured by carotid and femoral pulse wave velocity [cfPWV] and augmentation index [AIx]) were assessed before and after the TSST. The mean age of the participants was 28.78 (±9.84) years old. Experimental group participants had a significant increase in cfPWV (p = .025) and AIx (p = .017) following the stressor, compared with those in the control group, after controlling for age, body mass index, and systolic blood pressure. However, no significant group differences were observed in changes in PEP (p = .181) and HF (p = .058). Changes in PEP and HF were neither associated with changes in cfPWV (p = .975 and p = .654, respectively), nor in AIx (p = .376 and p = .323, respectively). The results suggest that even a brief period of mild to moderate stress, which does not cause sustainable changes in autonomic function, may still exert significant adverse effects on arterial stiffness. The changes in arterial stiffness were not related to changes in autonomic function. Future experimental studies with several measurement points are recommended to identify distinct effects of stress on autonomic function and arterial stiffness.

Perinatal programming of metabolic diseases: The role of glucocorticoids

The worldwide increase in metabolic diseases has urged the scientific community to improve our understanding about the mechanisms underlying its cause and effects. A well supported area of studies had related maternal stress with early programming to the later metabolic diseases. Mechanisms upon origins of metabolic disturbances are not yet fully understood, even though stressful factors rising glucocorticoids have been put out as pivotal trigger by programming metabolic diseases as long-term consequence. Considering energy balance and glucose homeostasis, by producing and/or sensing regulator signals, hypothalamus-pituitary-adrenal axis and endocrine pancreas are directly affected by glucocorticoids excess. We focus on the evidences reporting the role of increased glucocorticoids due to perinatal insults on the physiological systems involved in the metabolic homeostasis and in the target organs such as endocrine pancreas, white adipose tissue and blood vessels. Besides, we review some mechanisms underlining the malprogramming of type 2 diabetes, obesity and hypertension. Studies on this field are currently ongoing and even there is a good understanding regarding the effects of glucocorticoids addressing metabolic diseases, few is known about the relationship between maternal insults rising glucocorticoids to pups' metabolic disturbances, a thorough understanding about that may provide pivotal clinical clues regarding those disorders.

Anti-inflammatory and vasoconstrictive properties of Potentilla erecta - A traditional medicinal plant from the northern hemisphere

ETHNOPHARMACOLOGICAL RELEVANCE

Potentilla erecta (L.) Raeusch is a medicinal plant of the Northern hemisphere belonging to the plant family of roses (Rosaceae). It has traditionally been used to treat inflammatory disorders of the skin and mucous membranes as well as chronic diarrhea.

AIM OF THE STUDY

In the present study we analyzed the anti-inflammatory and vasoconstrictive effect of a Potentilla erecta extract (PE) and questioned if PE is similar effective as mild corticosteroids. Then we analyzed if PE acts in the skin via a similar mode of action as corticosteroids.

MATERIAL AND METHODS

The anti-inflammatory effect of PE was analyzed in irradiated HaCaT keratinocytes by measuring the formation of IL-6 and PGE₂. Additionally the effect of PE on TNF-α induced NF-κB activation was determined. As the anti-inflammatory effect of corticosteroids correlates with their vasoconstrictive properties we tested if PE displays also vasoconstriction. Therefore we performed an occlusive patch test and a collagen contraction assay. Furthermore the binding of PE to the glucocorticoid receptor was determined with stainings and reporter assays. The interaction of PE on the nitric oxide (NO) content was examined with radical scavenging and endothelial NO synthase (eNOS) reporter assays.

RESULTS

In irradiated or TNF-α stimulated HaCaT cells the formation of IL-6 and PGE₂ or NF-κB activation was strongly reduced by PE. Furthermore PE showed a blanching effect comparable to hydrocortisone. However, in contrast to glucocorticoids, PE did not cause nuclear translocation of the glucocorticoid receptor in HaCaT cells. The blanching effect of PE was at least partly attributable to a scavenging effect of NO and inhibition of eNOS.

CONCLUSIONS

PE displays anti-inflammatory and vasoconstrictive effects and might therefore be beneficial for the topical treatment of inflammatory skin disorders.

Glucocorticoid-induced fetal origins of adult hypertension: Association with epigenetic events

Hypertension is a predominant risk factor for cardiovascular diseases and a major health care burden. Accumulating epidemiological and experimental evidence suggest that adult-onset hypertension may have its origins during early development. Upon exposure to glucocorticoids, the fetus develops hypertension, and the offspring may be programmed to continue the hypertensive trajectory into adulthood. Elevated oxidative stress and deranged nitric oxide system are not only hallmarks of adult hypertension but are also observed earlier in life. Endothelial dysfunction and remodeling of the vasculature, which are robustly associated with increased incidence of hypertension, are likely to have been pre-programmed during fetal life. Apparently, genomic, non-genomic, and epigenomic factors play a significant role in the development of hypertension, including glucocorticoid-driven effects on blood pressure. In this review, we discuss the involvement of the aforementioned participants in the pathophysiology of hypertension and suggest therapeutic opportunities for targeting epigenome modifiers, potentially for personalized medicine.

Glucocorticoids (as an Etiologic Factor)

Adrenocortical hormones were first prepared from the adrenal gland as a new compound by Kendall in 1935 [1]. Thirteen years later, Hench et al. [2] observed a miraculous effect of cortisone in a patient with severe rheumatoid arthritis, which opened new doors to innovative treatments for a variety of inflammatory diseases. Against this background, Kendall, Hench, and Reichstein were awarded the 1950 Nobel Prize for Physiology or Medicine. Since then, glucocorticoids have been used as a first-line therapy for immune-mediated conditions or as an adjunctive therapy in many inflammatory, infectious, or malignant diseases.

The impact of acute mental stress on vascular endothelial function: evidence, mechanisms and importance

Cardiovascular disease is a principle cause of morbidity and mortality worldwide, and it has a complex etiology that involves lifestyle factors such as psychosocial stress. Recent evidence suggests that temporary impairments in vascular endothelial cell function may contribute to the relationship between stress and cardiovascular disease. Indeed, impaired endothelial function has been observed to occur transiently (lasting up to 1.5h) following mental stress, and such periods of impairment could accumulate to become clinically relevant over the long term. The finding of acute stress induced endothelial dysfunction is not universal however, and both physiological (e.g. sympathetic nervous system and hypothalamic-pituitary-adrenal axis reactivity), and methodological factors contribute to the conflicting results. A clear understanding of the interaction between stress response activation and endothelial function is critical to elucidating the complexities of the relationship between psychosocial stress and cardiovascular disease. Therefore, the purpose of this review is: 1) to briefly describe the importance of vascular endothelial function and how it is assessed, 2) to review the literature investigating the impact of acute mental stress on endothelial function in humans, identifying factors that may explain contradictory results, and 3) to summarize our current understanding of the mechanisms that may mediate an acute mental stress-endothelial function interaction.

Slow receptor dissociation kinetics differentiate macitentan from other endothelin receptor antagonists in pulmonary arterial smooth muscle cells

Two endothelin receptor antagonists (ERAs), bosentan and ambrisentan, are currently approved for the treatment of pulmonary arterial hypertension (PAH), a devastating disease involving an activated endothelin system and aberrant contraction and proliferation of pulmonary arterial smooth muscle cells (PASMC). The novel ERA macitentan has recently concluded testing in a Phase III morbidity/mortality clinical trial in PAH patients. Since the association and dissociation rates of G protein-coupled receptor antagonists can influence their pharmacological activity in vivo, we used human PASMC to characterize inhibitory potency and receptor inhibition kinetics of macitentan, ambrisentan and bosentan using calcium release and inositol-1-phosphate (IP₁) assays. In calcium release assays macitentan, ambrisentan and bosentan were highly potent ERAs with K_b values of 0.14 nM, 0.12 nM and 1.1 nM, respectively. Macitentan, but not ambrisentan and bosentan, displayed slow apparent receptor association kinetics as evidenced by increased antagonistic potency upon prolongation of antagonist pre-incubation times. In compound washout experiments, macitentan displayed a significantly lower receptor dissociation rate and longer receptor occupancy half-life (ROt_1/2) compared to bosentan and ambrisentan (ROt_1/2∶17 minutes versus 70 seconds and 40 seconds, respectively). Because of its lower dissociation rate macitentan behaved as an insurmountable antagonist in calcium release and IP₁ assays, and unlike bosentan and ambrisentan it blocked endothelin receptor activation across a wide range of endothelin-1 (ET-1) concentrations. However, prolongation of the ET-1 stimulation time beyond ROt_1/2 rendered macitentan a surmountable antagonist, revealing its competitive binding mode. Bosentan and ambrisentan behaved as surmountable antagonists irrespective of the assay duration and they lacked inhibitory activity at high ET-1 concentrations. Thus, macitentan is a competitive ERA with significantly slower receptor dissociation kinetics than the currently approved ERAs. Slow dissociation caused insurmountable antagonism in functional PASMC-based assays and this could contribute to an enhanced pharmacological activity of macitentan in ET-1-dependent pathologies.

Autocrine Effects of Endothelin on In Vitro Proliferation of Vascular Smooth Muscle Cells from Spontaneously Hypertensive and Normotensive Rats

According to previous studies, endothelin-1 (ET-1) is the most potent growth factor in the regulation of vascular smooth muscle cell (VSMC) proliferation in spontaneously hypertensive rats (SHR). To evaluate if the dominant effect of ET-1-induced VSMC proliferation is achieved by autocrine regulation, aortic smooth muscle cells from four-week-old SHR and WKY (Wistar-Kyoto) rats were cultured in 24-well dishes, and the effects of ET-1 on VSMC proliferation were determined by (a) 3H-thymidine incorporation assays with different ET-1 blocking treatments, including a specific anti-ET-1 antibody; BQ-123, an ETA receptor blocker; and BQ-788, an ETB receptor blocker; and (b) examining the ET-1 blockade on the effects of treatment with other growth factors, including thrombin and angiotension II (AT-II). These results demonstrated that the anti-ET-1 antibody, BQ-123, BQ-788, and BQ-123 plus BQ-788 all caused dose-dependent inhibition of proliferation. A 90% inhibitory effect was observed at the maximum doses used except for BQ-123. The ET-1 receptor blockers inhibited thrombin-induced VSMC growth; however, they did not efficiently inhibit AT-II-induced VSMC growth. These results indicate that the autocrine effects of ET-1 play a predominant role in the proliferation of VSMCs from SHR and WKY rats. They also suggest that thrombin-induced VSMC growth is mediated by the autocrine effects of ET-1, and angiotensin II-induced VSMC growth is mediated by other signal pathways.

Stress – the battle for hearts and minds: links between depression, stress and ischemic heart disease

Depression and ischemic heart disease (IHD) are strongly related common disorders. Depression itself is an independent cardiac risk factor and is associated with a two- to threefold increase in IHD mortality. Attention has now shifted to identifying the common underlying mechanisms that could make individuals susceptible to both disorders. Abnormalities that have been implicated in this relationship include abnormal platelet activation, decreased baroreceptor sensitivity and endothelial dysfunction. Depression and IHD both have a high association with environmental stress, and depression is characterized by abnormalities of the stress-hormone axis. This review provides a brief overview of some recent developments in our understanding of the pathophysiological links between stress, depression and IHD.

Thermographic study of in vivo modulation of vascular responses to phenylephrine and endothelin-1 by dexamethasone in the horse

REASONS FOR PERFORMING STUDY

In vitro, glucocorticoids potentiate vasoconstriction of equine digital vessels to catecholamines and this has been implicated as a mechanism of glucocorticoid-induced laminitis. This observation has never been confirmed in vivo.

OBJECTIVES

To study the effects of glucocorticoid therapy on vasoconstrictor responsiveness in the horse in vivo.

METHODS

In a blinded, randomised cross-over experiment, 9 horses were treated with either dexamethasone (0.1 mg/kg bwt i.v. q. 24 h) or saline i.v. for 6 days. The changes in local average skin temperature before (baseline) and after intradermal injections of the alpha1-adrenoceptor agonist phenylephrine (PHE; 10(-4), 10(-5), 10(-6), 10(-7) and 10(-8) mol/l), endothelin-1 (ET-1; 10(-5), 10(-6), 10(-7), 10(-8) and 10(-9) mol/l) or ET-1 plus a blocker (BQ-123 10(-6) mol/l; RES-701 10(-6) mol/l; and L-NAME 10(-4) mol/l) were investigated with a thermograph.

RESULTS

Dexamethasone (DEX) decreased baseline skin temperatures, suggesting reduced blood flow as a consequence of an increase in vasomotor tone. This was accompanied by potentiation of the response to PHE as demonstrated by a left shift in the dose-response curve and a decrease in the EC50. Dexamethasone did not potentiate ET-1, but the interplay with the lower baseline temperature resulted in a significantly lower skin temperature for this vasoconstrictor after DEX. The different ET-1 blockers had no effect on ET-1 modulated skin temperatures.

CONCLUSIONS

Dexamethasone decreases skin perfusion. This is accompanied by a potentiated alpha1-adrenoceptor agonist response and a greater response to ET-1.

POTENTIAL RELEVANCE

Glucocorticoid therapy probably decreases perfusion of the equine hoof. During disease states that already are characterised by hypoperfusion and/or increased levels of circulating catecholamines, glucocorticoid therapy could, according to the vascular model of laminitis, tilt the balance in favour of laminitis.

Endothelin-1 promotes cell survival in renal cell carcinoma through the ET(A) receptor

Endothelin-1 (ET-1) is a potent vasoconstrictor that has been shown to significantly impact many benign and malignant tissues by signaling through its two cognate receptors: ET(A) and ET(B). As ET-1 has a role in both normal and diseased kidney, we initiated studies to investigate endothelin axis expression and function in renal cell carcinoma (RCC). In this study, relatively high levels of ET-1 were detected in all six human RCC cell lines investigated. RT-PCR and Southern analyses revealed that all six RCC cell lines expressed ET(A) receptor mRNA, while 3/6 cell lines also expressed ET(B) mRNA. High affinity ET-1 binding occurred in all but one RCC cell line and quantitative RT-PCR demonstrated ET(A) mRNA expression in all six cell lines. Methylation of the ET(B) promoter (EDNRB) in 4/6 RCC cell lines was observed, suggesting a mechanism for repressed ET(B) expression. Moreover, methylation occurred in 32/48 of renal tumors and in 27/55 of histologically normal adjacent tissue samples studied, while no methylation was evident in any normal tissue isolated from nephrectomy or at autopsy. Functionally, ET-1 significantly inhibited paclitaxel-induced apoptosis in RCC cells through binding ET(A) with the ET-1 signaling mediated via the PI3-kinase/Akt pathway. Collectively, these data support the therapeutic targeting of the ET(A) receptor as a novel treatment strategy for RCC.

IMPACT OF CORTISOL ON alpha-ACTIN CONTENT IN VASCULAR SMOOTH MUSCLE CELLS OF FETAL SHEEP

The effects of gestation on a-actin levels in vascular smooth muscle aortae were studied in 31 fetal sheep, aged 66-144 days (term=150 days). Aortae were collected post-mortem. 2. Aortae, carotid and femoral arteries from two groups of chronically catheterized fetal sheep (110-114 days) were also examined. One group was infused with cortisol (n=6; hydrocortisone sodium succinate, total dose 16.8 mg in 48 h) and the control group received saline (0.15 mol/L, 0.33 mL/h, n=7). 3. Vascular homogenate protein was separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western transfer. a-Actin was identified using a monoclonal mouse anti-a actin antibody and standardized against tissue protein and DNA content. 4. Between 60 and 144 days gestation, there was an exponential increase in the a-actin content of vascular smooth muscle cells from fetal sheep aorta (P<0.0001). a-Actin concentration (densitometry units (U) relative to DNA 260 nm absorbance (Abs)) was significantly (P<0.05) higher in the aortae of cortisol-infused (12,601+/- 2,499 U/Abs) fetal sheep compared with those that were saline-infused (4,514+/-670 U/Abs). a-Actin (relative to DNA absorbance) of carotid and femoral vessels in cortisol-infused animals (20,659+/- 4,812 U/Abs) compared with those that were saline-infused (14,461+/- 2,645 U/Abs) was increased, but the difference was not significant. 5. Therefore, the a-actin concentration of the vascular smooth muscle of the aorta increases throughout gestation. Cortisol treatment is associated with further increases in a-actin concentration in the fetal aorta, indicating that the development of large conduit vessels can be altered by this glucocorticoid.

Inhibition of Cortisol Production With Metyrapone Prevents Mental Stress-Induced Endothelial Dysfunction and Baroreflex Impairment

OBJECTIVES

This study was designed to investigate the role of cortisol in stress-induced endothelial dysfunction and impaired baroreflex sensitivity (BRS) by blocking cortisol production with metyrapone before subjecting healthy volunteers to mental stress.

BACKGROUND

Mental stress raises cortisol levels and is associated with increased coronary heart disease (CHD) morbidity and mortality, especially from sudden cardiac death. It also causes endothelial dysfunction and impaired BRS.

METHODS

We measured brachial artery flow-mediated dilation (FMD), a measure of endothelial function, and BRS in 36 subjects without CHD risk factors who were then randomized in a double-blind fashion to oral metyrapone 750 mg x 2 or placebo. Five hours later we subjected subjects to mental stress and then remeasured endothelial function and BRS.

RESULTS

Prestress cortisol levels were significantly higher in the placebo group at 270.5 (30.9) nmol/l versus 89.1 (11.8) nmol/l (p = 0.01), and the increase with stress was higher at 57.9 (17.9) nmol/l versus 11.2 (2.2) nmol/l (p < 0.001). In the placebo group, compared to baseline, FMD and BRS fell significantly from 4.5% (0.7%) to 1.4% (1.1%) (p = 0.02) and 21.4 (2.3) ms/mmHg to 16.3 (1.5) ms/mmHg (p = 0.04), respectively. In the metyrapone group, FMD and BRS were unchanged from baseline: 4.3% (0.9%) versus 5.1% (0.8%) (p = 0.48) and 26.4 (2.9) ms/mmHg versus 24.9 (2.6) ms/mmHg (p = 0.62), respectively. Analysis of covariation showed a significant effect of metyrapone on change in both FMD (p = 0.009) and BRS (p = 0.024).

CONCLUSIONS

Stress-related endothelial dysfunction and BRS impairment can be prevented by blocking cortisol production with metyrapone, demonstrating a direct or facilitative role for cortisol in these phenomena and suggesting mechanisms by which stress contributes to CHD and sudden cardiac death.

Suppression of cytokine-induced expression of adrenomedullin and endothelin-1 by dexamethasone in T98G human glioblastoma cells

There is accumulating evidence showing that glial cells and gliomas secrete some neuropeptides and vasoactive peptides, such as adrenomedullin and endothelin-1. We have previously shown that expression of these two peptides is induced by inflammatory cytokines in T98G human glioblastoma cells. Glucocorticoids are frequently used for the treatment of inflammatory diseases and glioblastomas. We therefore studied effects of dexamethasone on expression of adrenomedullin and endothelin-1 in T98G human glioblastoma cells. Dexamethasone dose-dependently increased adrenomedullin mRNA levels and immunoreactive-adrenomedullin levels in the medium in T98G cells, whereas it decreased immunoreactive-endothelin levels in the medium. A combination of three cytokines, interferon-gamma (100 U/ml), tumor necrosis factor-alpha (20 ng/ml) and interleukin-1beta (10 ng/ml) induced expression of adrenomedullin and endothelin-1 in T98G cells. Dexamethasone (10(-8) mol/l) suppressed increases in expression of both adrenomedullin and endothelin-1 induced by these three cytokines. Thus, dexamethasone alone increased adrenomedullin expression whereas it suppressed the cytokine-induced expression of adrenomedullin in T98G cells. These findings raised the possibility that effects of dexamethasone on brain inflammation and glioblastomas may be partly mediated or modulated by its effects on expression of adrenomedullin and endothelin-1.

Dexamethasone regulates endothelin-1 and endothelin receptors in human non-pigmented ciliary epithelial (HNPE) cells

Endothelin-1 (ET-1) lowers intraocular pressure (IOP) in animal models by regulating aqueous humour dynamics through both inflow and outflow mechanisms. Moreover, ET's concentration is elevated in glaucoma patients and in animal models of glaucoma. Glucocorticoid therapy often can lead to increase IOP in susceptible individuals including patients with primary open angle glaucoma (POAG). In this study, we examined the effects of dexamethasone (Dex), a frequently used anti-inflammatory glucocorticoid, on the synthesis and release of endothelin-1 and on the expression of endothelin receptors in human non-pigmented ciliary epithelial (HNPE) cells, an established source for ET-1 in the anterior chamber. As measured by ET-1 immunoreactivity, ET-1 was concentration-dependently increased following 24hr Dex treatment, with a maximum concentration (100 nM) causing a threefold increase of ET-1 release. Western blot analysis of HNPE cells showed the expression of endothelin receptor A (ET(A)) and endothelin receptor B (ET(B)) with approximate molecular weights of 40 kDa. Dex treatment decreased ET(A) receptor expression at all Dex doses, but up-regulated ET(B) receptors with 10nM Dex having the greatest effect. Quantitative PCR demonstrated that Dex also increased the mRNA of pre-pro-ET-1 (ppET-1) and ET(B) but decreased the mRNA of ET(A). RU486, a glucocorticoid receptor antagonist, was able to block Dex's actions on ET release and ET(B) receptor expression, but did not block its action on ET(A) receptor expression. Endothelin receptors were minimally expressed in HNPE cells as determined in binding experiments (B(max): ET(A) 17, ET(B) 25 fmolmg(-1) membrane protein). However Dex treatment stimulated a dramatic increase in ET(B) receptor density while decreasing ET(A) receptors (B(max): ET(A) 11, ET(B) 116 fmolmg(-1) membrane protein). The regulation of endothelin and its receptors could be a novel mechanism associated with glucocorticoid's effects on intraocular pressure. The increase in ET-1 and disproportionate regulation in ET receptor expression by Dex could promote dysregulation in ET's mechanism on both inflow and outflow, thus affecting aqueous humour dynamics in the anterior chamber of the eye.

Inhibition of in vivo constriction of fetal ductus arteriosus by endothelin receptor blockade in rats

The fetal ductus can be constricted by drugs, including cyclooxygenase inhibitors (indomethacin), nitric oxide synthesis antagonists [N-nitro-L-arginine monomethyl ester (L-NAME)], and glucocorticoid hormones (dexamethasone). Constriction of the fetal ductus by endothelin (ET) 1 was reported in an in vitro study. We studied the preventive effect of a dual ET receptor antagonist (bosentan) and a selective ET-A blocker (CI-1020) on pharmacologic fetal ductal constriction in rats. Near-term pregnant Wistar rats at d 21 and preterm rats at d 19 were used. The fetal ductus was constricted by four medications: orogastric administration of indomethacin (10 mg/kg) on fetal d 21, orogastric indomethacin 1 mg/kg combined with muscular injection of L-NAME (10 mg/kg) on fetal d 21, and muscular injection of L-NAME or dexamethasone (1 mg/kg) on fetal d 19. Bosentan (0.1, 1, 10, or 100 mg/kg) was injected intraperitoneally either simultaneously with indomethacin, L-NAME, or dexamethasone, or 4 h after administration of 10 mg/kg indomethacin. CI-1020 (0.01, 0.1, 1, or 10 mg/kg) was injected intraperitoneally simultaneously with indomethacin. After maternal atlas dislocation, cesarean section, fetal whole-body freezing, and cutting on the freezing microtome, measurements were made of the inner diameters of the ductus, main pulmonary artery, and ascending aorta. Bosentan blocked fetal ductal constriction by indomethacin, indomethacin plus L-NAME in the near-term rats, and constriction by L-NAME and dexamethasone in the preterm rats dose dependently. Fetal ductal constriction was nearly completely blocked by simultaneously administered 100 mg/kg of bosentan or 10 mg/kg of CI-1020. Dual ET receptor antagonist (bosentan) and selective ET-A blocker (CI-1020) prevent constriction of the fetal ductus arteriosus induced by ductus-constricting agents in rats, indicating that ET and ET-A receptors are essential in fetal ductal constriction.

Long-term adrenomedullin administration in experimental heart failure

Short-term administration of adrenomedullin, a recently discovered peptide with potent vasodilator, natriuretic, and aldosterone-inhibitory actions, has beneficial effects in experimental and clinical heart failure. The effects of prolonged adrenomedullin administration have not previously been assessed in this setting. Consequently, in 16 sheep with pacing-induced heart failure, we infused either adrenomedullin (10 ng/kg per minute; n=8) or a vehicle control (Hemaccel; n=8) for 4 days. Compared with control data, infusion of adrenomedullin persistently increased circulating levels of the peptide (by approximately 9.5 pmol/L; P<0.001), in association with prompt (15 minutes) and sustained (4 days) increases in cardiac output (day 4, 27%), and reductions in peripheral resistance (30%), mean arterial pressure (13%), and left atrial pressure (24%; all, P<0.001). Adrenomedullin also significantly enhanced urinary sodium excretion (day 4, 3-fold; P<0.05), creatinine excretion (1.2-fold; P<0.001), and creatinine clearance (1.4-fold; P<0.001) over the 4 days of treatment, whereas urine volume and cAMP excretion tended to be elevated (both, 0.1>P>0.05). Plasma renin activity was increased (P<0.05), whereas aldosterone levels were reduced in a sustained fashion (P<0.01). Plasma endothelin rose transiently (hours 1 to 6) after initiation of treatment (P<0.05). Despite substantial cardiac unloading, plasma concentrations of the natriuretic peptides were not significantly different from control. In conclusion, long-term administration of adrenomedullin induces pronounced and sustained cardiovascular and renal effects in experimental heart failure, including reductions in cardiac preload and afterload, as well as augmentation of cardiac output, sodium excretion, and glomerular filtration. These findings support the concept of adrenomedullin as a protective hormone during hemodynamic compromise with therapeutic potential in heart failure.

Evidence for microvascular dysfunction after prenatal dexamethasone at 0.7, 0.75, and 0.8 gestation in sheep

Dexamethasone (DM) was administered to pregnant ewes as three weekly courses of four injections of 2 mg at 12-h intervals. DM (n = 7) or saline (n = 7) was given starting at 103 days of gestation (dGA; term approximately 149 days). Fetal femoral arteries (approximately 300-microm internal diameter) were evaluated using wire myography at 119 dGA. DM-exposed fetuses were significantly smaller than saline-exposed fetuses. DM exposure increased maximal contraction to 125 mM KCl, and maximum tension developed along with sensitivity to endothelin-1 and relaxation to bradykinin. Preincubation with the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester shifted the dose-response curves to endothelin-1 and acetylcholine to the right in controls but not in the DM-exposed group. Relaxation to acetylcholine and to the nitric oxide donor sodium nitroprusside was similar in both groups. The combination of enhanced endothelin-induced vasoconstriction, abnormal endothelium-dependent relaxation, and normal endothelium-independent relaxation indicates microvessel dysfunction following antenatal DM administration. Because such dysfunction is associated with several forms of adult hypertension, our results indicate the potential for consequences of antenatal glucocorticoid exposure on adult cardiovascular health.

Association of hypertension and hypokalemia with Cushing's syndrome caused by ectopic ACTH secretion: a series of 58 cases

Cushing's syndrome is associated with hypertension in approximately 80% of cases. Hypertension contributes to the marked increased mortality risk of past or current Cushing's syndrome, largely because of increased cardiovascular risk. Observation of the pathophysiological effect of chronically elevated ACTH and cortisol values in patients with ectopic ACTH secretion complements the available data from acute studies of the effects of ACTH and glucocorticoid infusions in normal volunteers. In a retrospective case review, we identified 58 patients with Cushing's syndrome caused by ectopic ACTH secretion, who were treated at the National Institutes of Health between 1983-1997. The diagnosis of an ectopic ACTH cause was confirmed by inferior petrosal sinus sampling and/or pathologic examination of tumor. The commonest causes were bronchial carcinoid (40%) and thymic carcinoid (10%), but 18 of 58 (31%) patients had an unknown source of ectopic ACTH. Hypertension (systolic blood pressure >140 mmHg and/or diastolic blood pressure >90 mmHg in adults) was noted in 45 of 58 (78%) ectopic Cushing's patients, a prevalence similar to that noted in other endogenous Cushing's syndrome etiologies. Hypertension was severe, deemed to require 3 or more drugs by the treating physicians, in 26 of 58 (45%) patients. Hypokalemia was much more prevalent than in patients with other causes of Cushing's syndrome, affecting 33 of 58 (57%) patients. The range of plasma ACTH (17-1557 pg/mL, normal <60) and 24-hour urine cortisol (UC) excretion (192-1600 mcg/24 hr, normal <90) allowed analysis of the influence of these hormones on blood pressure and plasma potassium. There was a significant relationship between 24-hour UC excretion and the presence of hypokalemia (P = 0.003). Eight of nine patients with a UC >6000 mcg/24 hr had hypokalemia. There was no relation between ACTH level and hypokalemia. In addition, we did not find blood pressure severity to be related to UC excretion or ACTH levels. Urine and plasma cortisol and cortisol metabolite measurements suggest that cortisol may act as a mineralocorticoid when in excess, perhaps by saturating the 11beta-hydroxysteroid-dehydrogenase (11beta-HSD2 enzyme) that inactivates cortisol at the renal tubule. The current data suggest that high cortisol levels may be the principal cause of hypokalemic alkalosis in Cushing's syndrome, rather than inhibition of the 11betaHSD2 enzyme by ACTH or the effects of adrenal steroid biosynthetic intermediaries with mineralococorticoid activity.

Paradoxical sleep deprivation increases plasma endothelin levels

The endothelins (ET-1, 2 and 3) constitute a family of 21 amino acid peptides with potent biological activities. ET-1 is one of the most potent endogenous vasoconstrictors so far identified and its increased concentration in plasma appears to be closely related to the pathogenesis of arterial hypertension as well as to obstructive sleep apnea (OSA). OSA patients exhibit repetitive episodes of apnea and hypopnea that result in hypoxia and consecutive arousals. These patients are chronically sleep deprived, which may aggravate the hypertensive features, since literature data show that sleep deprivation results in hypertension both in humans and in animals. Based on the reported relationship between ET-1, hypertension and sleep deprivation consequences, the purpose of the present study was to determine plasma ET concentrations in paradoxical sleep-deprived animals. Male Wistar rats, 3 to 4 months old (N = 10 per group), were deprived of sleep for 24 and 96 h by the platform technique and plasma ET-(1/2) was measured by radioimmunoassay. Analysis of plasma revealed that 96 h of sleep deprivation induced a significant increase in ET-(1/2) release (6.58 fmol/ml) compared to control (5.07 fmol/ml). These data show that sleep deprivation altered plasma ET-(1/2) concentrations, suggesting that such an increase may participate in the genesis of arterial hypertension and cardiorespiratory changes observed after sleep deprivation.

Effect of in vivo fetal infusion of dexamethasone at 0.75 GA on fetal ovine resistance artery responses to ET-1

At 110-111 days gestation, instrumented fetal sheep were administered saline or dexamethasone (2.2 microgram. kg(-1). h(-1) iv) for 48 h. Measurement of fetal blood pressure showed a greater increase in dexamethasone-treated (n = 6) compared with control (n = 5) fetuses (7.3 +/- 2.3 vs. 0.6 +/- 2.3 mmHg, P < 0.05). Fetuses were delivered by cesarean section, and the femoral muscle and brain were obtained under halothane anesthesia. Femoral and middle cerebral arteries (approximately 320-micrometer internal diameter) were evaluated using wire myography. Sensitivity to KCl (2.5-125 mM) and the magnitude of the maximal vasoconstriction to 125 mM K(+) were similar in femoral and middle cerebral arteries from dexamethasone-treated vs. control fetuses. Acetylcholine-induced vasorelaxation was similar in femoral arteries from control and dexamethasone-treated fetuses. Middle cerebral arteries did not relax to acetylcholine. Sensitivity to endothelin-1 (ET-1; 0.1 pM-0.1 microM) and magnitude of the ET-1-induced vasoconstriction were greater in femoral arteries from dexamethasone-treated vs. control fetuses (P < 0.05). Autoradiographical studies with receptor-specific ligands demonstrated increased ET(A)-receptor binding, the principal receptor subtype, in femoral muscle vessels (P < 0.001) but decreased ET(A)-receptor binding in middle cerebral arteries (P < 0.01) from dexamethasone-treated compared with control fetuses. Relatively little ET(B)-receptor binding was evident in all tissues examined. We conclude that hyperreactivity to ET-1, due to increased ET(A)-receptor binding, may be involved in the dexamethasone-induced increase in peripheral vascular resistance in fetal sheep in vivo.

Vascular protective effects of angiotensin converting enzyme inhibitors and their relation to clinical events

Endothelial cells are a rich source of a variety of vasoactive substances, which either cause vasodilation or vasoconstriction. Important endothelium-derived vasodilators are prostacyclin, bradykinin, nitric oxide and endothelium-derived hyperpolarizing factor. In particular, nitric oxide inhibits cellular growth and migration. In concert with prostacyclin. nitric oxide exerts potent anti-atherogenic and thromboresistant properties by preventing platelet aggregation and cell adhesion. Endothelium-derived contracting factors include the 21 amino acid peptide endothelin (ET). vasoconstrictor prostanoids such as thromboxane A2 and prostaglandin H2, as well as free radicals and components of the renin angiotensin system. In hypertension, elevated blood pressure transmits into cardiovascular disease by causing endothelial dysfunction. Hence, modem therapeutic strategies in human hypertension focus on preserving or restoring endothelial integrity. Angiotensin converting enzyme (ACE) inhibitors are a primary candidate for that concept as they inhibit the circulating and local renin angiotensin system. Angiotensin converting enzyme is an endothelial enzyme which converts angiotensin-I (A-I) into angiotensin-II (A-II). This effect of the ACE inhibitor prevents direct effects of angiotensin-II such as vasoconstriction and proliferation in the vessel wall but also prevents activation of the ET system and of plasminogen activator inhibitor. Furthermore, inhibition of ACE prolongs the half-life of bradykinin and stabilizes bradykinin receptors linked to the formation of nitric oxide and prostacyclin. In isolated arteries ACE inhibitors prevent the contractions induced by angiotensin II and enhance relaxation induced by bradykinin. Chronic treatment of experimental hypertension with ACE inhibitors normalizes endothelium-dependent relaxation to acetylcholine and other agonists. In addition, the dilator effects of exogenous nitric oxide donors are enhanced, at least in certain models of hypertension. In humans with essential hypertension ACE inhibitors augment endothelium-dependent relaxation to bradykinin, while those to acetylcholine remain unaffected, at least in the time frame of the published studies, i.e. 3-6 months. In patients with coronary artery disease, however, paradoxical vasoconstriction to acetylcholine is markedly reduced after 6 months of ACE inhibition. After myocardial infarction ACE inhibitors reduce the development of overt heart failure, the occurrence of reinfarction and cardiovascular death in hypertensive patients. These effects have also been demonstrated in a subgroup analysis of the SOLVD (Studies of Left Ventricular Dysfunction) trial. Thus, in summary, ACE inhibitors are an important class of drugs providing cardiovascular protection in patients with increased cardiovascular risk.

Transforming growth factor-beta1 induces endothelin-1 in a bovine pulmonary artery endothelial cell line and rat lungs via cAMP

We investigated the mechanism of Endothelin-1 regulation by transforming growth factor-beta1 (TGF-beta1) in bovine pulmonary artery endothelial cells (BPAECs) and in isolated perfused rat lungs. Our data show that TGF-beta1 induces ET-1 gene expression and ET-1 peptide synthesis in BPAECs. The induction of preproET-1 mRNA level was due to de novo transcription, as well as mRNA stabilization, and new protein synthesis was not required for this induction. To investigate the role of cAMP-protein kinase A pathway in TGF-beta1-stimulated-ET-1 induction, we exposed BPAECs to various compounds which modulate this pathway. Dibutyryl-cAMP led to an increase in preproET-1 mRNA and Rp-cAMP abolished the induction of preproET-1 mRNA and ET-1 peptide by TGF-beta1. TGF-beta1 increased cAMP in BPAECs. Dexamethasone up-regulated preproET-1 mRNA expression and ET-1 peptide synthesis under basal and TGF-beta1-stimulated conditions. In isolated perfused rat lungs, TGF-beta1 increased preproET-1 mRNA abundance whereas Rp-cAMP inhibited the TGF-beta1-induced ET-1 gene activation. Thus our data suggest that TGF-beta1 stimulates ET-1 gene expression in BPAECs and in rat lungs via a cAMP dependent mechanism.

Regulation of endothelin-1 production in cultured rat vascular smooth muscle cells

Endothelin-1 (ET-1) is secreted from all rat vascular smooth muscle cells (VSMCs) examined, in addition to endothelial cells (ECs). An average secretion rate of ET-1 from rat VSMCs was determined to be 10% that excreted from ECs. We examined the effects of 22 substances on ET-1 secretion from VSMCs and compared them with those from ECs. Transforming growth factor-beta1 (TGF-beta), acidic and basic fibroblast growth factors, epidermal growth factor, angiotensin II, and adrenaline stimulated ET-1 secretion from VSMCs, whereas forskolin, thrombin, and platelet-derived growth factor-BB reduced it. Only TGF-beta and phorbol ester elicited consistent effects on ET-1 secretion from VSMCs and ECs. Regulation of ET-1 and adrenomedullin secretion from VSMCs was distinctly different. These data suggest that ET- 1 production in VSMCs is regulated by a mechanism separate from that in ECs and from adrenomedullin production in VSMCs. Chromatographic analysis showed immunoreactive ET-1 secreted from VSMCs was mainly composed of big ET- 1, whereas approximately 90% of that from ECs was ET-1. By TGF-beta stimulation of VSMCs, the ratio of big ET-1 to ET-1 was further increased. Because big ET-1 is converted into ET-1 only on the surface of the ECs in the culture system, big ET-1 secreted from the VSMCs may function as a mediator transmitting a signal from VSMCs to ECs in vivo.

Endothelin-1 plasma concentrations in depressed patients and healthy controls

Depression and cardiovascular morbidity are known to be associated. So far, however, the pathophysiological link between these conditions is unclear. We tested the hypothesis that in depressed hypercortisolemic patients endothelin-1 (ET-1) plasma concentrations are increased and contribute to the cardiovascular risk. Diurnal plasma concentrations of cortisol and ET-1 were measured in 29 healthy controls and 22 depressed patients. ANCOVA did not reveal a significant effect of diagnosis or age upon ET-1 concentrations. However, only in depressed patients, cortisol plasma concentrations tended to be positively related to ET-1 concentrations. We conclude that ET-1 is not increased in depressed patients, but within this group, hypercortisolemia may be associated with increased ET-1 concentrations.

Glucocorticoids regulate the expression of the human osteoblastic endothelin A receptor gene

The endothelial cell-derived peptide endothelin 1 (ET1) stimulates cell proliferation and differentiated functions of human osteoblastic cells (HOC), and HOC constitutively express the endothelin A receptor (ETRA). Therefore, ET1 may play an important role in the regulation of bone cell metabolism. As glucocorticoids (GC) exert a profound influence on bone metabolism and increase the effects of ET1 on bone cell metabolism in vitro, the effects of GC on ETRA expression in HOC were investigated. Dexamethasone (DEX) increased ETRA mRNA levels in a dose- and time-dependent fashion. The effects of dexamethasone, prednisolone, and deflazacort on the increase of ETRA mRNA levels correlate positively with their binding affinity to the GC receptor. Scatchard analysis of ET1 binding data to HOC revealed that DEX increased the binding capacity for ET1 from 25,300 to 62,800 binding sites per osteoblastic cell, leading to an enhanced mitogenic effect of ET1 on HOC after preincubation with DEX. Transiently transfected primary HOC with a reporter gene construct, containing the 5'-flanking region of the ETRA gene fused to luciferase gene, showed a promoter-dependent expression of the reporter gene and the induction of reporter gene expression by DEX treatment. Total RNA extracts of femoral head biopsies with osteonecrotic lesions from GC-treated patients showed threefold higher ETRA mRNA levels compared with extracts of bone biopsies from patients with traumatically induced osteonecrosis and coxarthrosis. Furthermore, GC treatment increased plasma ET1 levels by 50% compared with pretreatment values. These findings suggest that GC induced upregulation of ETRA, and ET1 plasma levels enhance ET1's anabolic action on bone cell metabolism. Increased ET1 concentrations may also impair bone perfusion by vasoconstriction in a metabolically activated skeletal region.

Dexamethasone modulates the expression of endothelin-1 and -A receptors in A7r5 vascular smooth muscle cells

Endothelin-1 (ET-1) is synthesized and released by vascular smooth-muscle cells (VSMCs). Glucocorticoids induce the release of ET-1 from VSMCs into the medium. We investigated whether glucocorticoids modulate ET-1 action by an autocrine production of ET-1 in A7r5 VSMCs. Dexamethasone (100 nM) stimulated the release of ET-1 into the medium. Treatment with 100 nM dexamethasone for 24 h reduced the peak increase of intracellular free Ca2+ induced by ET-1 (100 nM) by 50%, an effect that was dose-dependently inhibited by the specific ET(A)-receptor antagonist FR139317. Scatchard plots of [125I]-ET-1 binding revealed that dexamethasone reduced the number of maximal ET-1 binding sites without altering their binding affinity. FR139317 reversed the decrease in ET-1 binding capacity induced by dexamethasone. Northern blot analysis revealed that dexamethasone increased the level of prepro-ET-1 messenger RNA (mRNA) and decreased the level of ET(A)-receptor mRNA. FR139317 prevented the decrease in the level of ET(A)-receptor mRNA induced by dexamethasone. Results indicate that dexamethasone downregulates ET(A) receptors in A7r5 VSMCs at the mRNA level, in part by the autocrine production of ET-1.

Glucocorticoids increase preproendothelin-1 expression in rat aorta

Glucocorticoids play an important role in circulatory homeostasis. They modulate peripheral resistance by their direct action on blood vessels. We have previously shown that glucocorticoids increase preproendothelin-1 gene transcription rate in vascular smooth muscle cells (Morin C et al. 1998, BBRC 244:583). Endothelin-1 is a potent vasoactive peptide involved in the maintenance of vascular tone as well as in pathophysiological states. In this report we show that glucocorticoids increase preproendothelin-1 expression in rat aorta. The rise in preproendothelin-1 steady state mRNA level is dose-dependent with a maximal 2.3-fold stimulation 8 hours following a 0.35 and a 2.5 mg/kg dexamethasone injection. A lower dose of dexamethasone (0.13 mg/kg) also increased preproendothelin-1 expression in rat aorta. Since endothelin-1 levels are regulated at the transcriptional step, the increase in mRNA is likely to be paralleled by increased protein synthesis and vasoconstrictor action. Moreover, systolic blood pressure was significantly elevated in rats who received the 0.35 and 2.5 mg/kg doses of dexamethasone. Together, our results strongly suggest that the increase in preproendothelin-1 expression by glucocorticoids contributes to the regulatory action of these corticosteroids on blood pressure in health and disease.

Transcriptional regulation of pre-pro-endothelin-1 gene by glucocorticoids in vascular smooth muscle cells

Endothelin is a potent vasoactive peptide involved in the maintenance of vascular tone and in pathophysiological states. Endothelin-1 synthesis is controlled at the transcriptional level. We report that glucocorticoids increase the pre-pro-endothelin-1 gene transcription rate in vascular smooth muscle cells. The effect of glucocorticoids is dose-dependent (EC50 approximately 2-3 nM) and completely blocked by co-incubation with the glucocorticoid antagonist RU 38486. The rise in pp-Et-1 steady state mRNA levels is rapid and transient with a maximal three-fold stimulation within one hour of glucocorticoid administration. Glucocorticoid treatment does not affect the half-life of pre-pro-endothelin-1 mRNA as shown by actinomycin D studies. Furthermore, cycloheximide treatment concomitantly with RU 28362 did not reverse the stimulatory effect of glucocorticoids on pre-pro-endothelin-1 mRNA levels. Nuclear run-on analysis shows that glucocorticoids increase the transcription rate of pre-pro-endothelin-1. Our results suggest a role for glucocorticoids in the regulation of biosynthesis and action of this important vasoactive peptide in vascular smooth muscle cells.

Expression of endothelin-1 in human broncho-epithelial and monocytic cell lines: influence of tumor necrosis factor-alpha and dexamethasone

Abnormal endothelin-1 (ET-1) expression has been observed in bronchial asthma and systemic sclerosis with lung involvement. The purpose of this study was to analyze the synthesis of ET-1 in human airway epithelial cells and macrophages under basal conditions and after challenge with tumor necrosis factor-alpha (TNF alpha) or with the glucocorticoid dexamethasone. The ET-1 mRNA level and peptide release were measured in the broncho-epithelial cells BEAS-2B and the monocytic cell line U937. At baseline, U937 cells released low amounts of ET-1 peptide, whereas ET-1 was not detectable in BEAS-2B cells. After TNF alpha treatment, BEAS-2B cells, but not U937 cells, showed a significant increase in ET-1 expression, both at the mRNA and peptide levels. In contrast, dexamethasone elicited an increased amount of ET-1 peptide in U937 medium, but not in BEAS-2B cells. In this latter cell line, dexamethasone pretreatment was unable to inhibit the TNF alpha-induced expression. We conclude that response to TNF alpha and glucocorticoids is cell-type specific with respect to ET-1 production. The response of lung tissue to these agents in vivo is likely to be the overall balance of induction and inhibition in local microenvironments.

The role of endothelins in the paracrine control of the secretion and growth of the adrenal cortex

Endothelins (ETs) are a family of vasoactive peptides (ET-1, ET-2, and ET-3) mainly secreted by vascular endothelium and widely distributed in the various body systems, where they play major autocrine/paracrine regulatory functions, acting via two subtypes of receptors (ETA and ETB): Adrenal cortex synthesizes and releases ETS and expresses both ETA and ETB. Zona glomerulosa possesses both ETA and ETB, whereas zona fasciculata/reticularis is almost exclusively provided with ETB. ETS exert a strong mineralocorticoid and a less intense glucocorticoid secretagogue action, mainly via ETB receptors. ETS also appear to enhance the growth and steroidogenic capacity of zona glomerulosa and to stimulate its proliferative activity. This trophic action of ETS is likely to be mediated mainly by ETA receptors. The intraadrenal release of ETS undergoes a multiple regulation, with the rise in blood flow rate and the local release of nitric oxide being the main stimulatory factors. Data are also available that indicate that ETS may also have a role in the pathophysiology of primary aldosteronism caused by adrenal adenomas and carcinomas.

Increased concentrations of endothelin-1 messenger RNA in tissues and endothelin-1 peptide in plasma in septic pigs: modulation by betamethasone

OBJECTIVES

To study the expression of preproendothelin-1 messenger RNA (mRNA) in tissue after Escherichia coli lipopolysaccharide challenge and to evaluate the possible effects of betamethasone both regarding endothelin-1 production as well as hemodynamic and vascular effects during E. coli lipopolysaccharide infusion in pigs in vivo.

DESIGN

Prospective trial.

SETTING

Laboratory at a university medical center.

SUBJECTS

Ten domestic pigs, weighing 18 to 25 kg.

INTERVENTIONS

Anesthetized pigs were given continuous infusions of E. coli lipopolysaccharide (15 micrograms/kg/hr for 3 hrs), with or without prior treatment with betamethasone (0.5 mg/kg im 12 hrs before the start of the surgical preparation and 0.5/kg iv at the start of the preparation).

MEASUREMENTS AND MAIN RESULTS

The E. coli lipopolysaccharide infusion evoked the characteristic cardiovascular changes observed in septic shock: decreased mean arterial pressure and cardiac output; increased heart rate and increased pulmonary vascular resistance. Large increases in both arterial plasma concentrations of endothelin-1-like immunoreactivity, as well as preproendothelin-1 mRNA concentrations in tissues, were also observed during the E. coli lipopolysaccharide infusion. Treatment with betamethasone significantly attenuated the E. coli lipopolysaccharide-induced increase in endothelin-1 plasma concentrations, whereas the increased mRNA concentrations were only slightly affected. Furthermore, betamethasone treatment also affected cardiovascular parameters, with significant attenuation of the E. coli lipopolysaccharide-induced increase in heart rate and a higher cardiac output after 60 mins of the E. coli lipopolysaccharide infusion. The urine production, which was markedly decreased during the E. coli lipopolysaccharide infusion, was significantly higher in the betamethasone-treated group compared with the control group.

CONCLUSIONS

The present results indicate that the increased concentrations of endothelin-1-like immunoreactivity that are observed in septic shock may have negative effects on both cardiovascular parameters as well as renal function, which is in agreement with a possible role for endothelin-1 in the pathogenesis of septic shock.

Increased levels of endothelin-1 in bronchoalveolar lavage fluid of patients with lung allografts

The aim of the present study was to determine levels of endothelin-1 in bronchoalveolar lavage fluid and in plasma in patients with lung and heart-lung allografts. The aim was based on the hypothesis that levels of endothelin-1 are elevated in the bronchoalveolar lavage fluid of patients with lung allografts. Patients (n = 23) undergoing heart-lung (n = 8), single-lung (n = 10), or bilateral lung (n = 5) transplantation were included in the study. In patients with single-lung allografts, endothelin-1 levels were analyzed in bronchoalveolar lavage fluid from both the transplanted and the nontransplanted, native lung. The level of endothelin-1 was also analyzed in bronchoalveolar lavage fluid from 12 patients who did not undergo transplantation. Transbronchial biopsies and bronchoalveolar lavage were done routinely or when clinically indicated on 64 different occasions, between 2 and 104 weeks after transplantation. The level of endothelin-1 was measured in bronchoalveolar lavage fluid and plasma by radioimmunoassay. Immunoreactive endothelin-1 was detectable in bronchoalveolar lavage fluid from all patients. The concentration of endothelin-1 in bronchoalveolar lavage fluid from transplanted lungs (2.94 +/- 0.30 pg/ml, n = 64) was significantly higher compared with that in bronchoalveolar lavage fluid from patients without allografts (0.86 +/- 0.20 pg/ml, n = 12, p < 0.01). In patients who received single-lung transplantation because of emphysema, the level of endothelin-1 in bronchoalveolar lavage fluid from the transplanted lung was significantly greater than that from the native lung (5.61 +/- 1.9 versus 0.39 +/- 0.05 pg/ml, p < 0.05). Concentrations of endothelin-1 in bronchoalveolar lavage fluid did not correlate with grade of rejection, infection, or time after transplant. Plasma levels of endothelin-1 were unchanged with pulmonary rejection. These results indicate that endothelin-1 is released into bronchi of transplanted human lungs. The release is not associated with rejection or infection. Because of its potent mitogenic properties, endothelin-1 may have a potential impact in the development of posttransplant complications such as bronchiolitis obliterans.

Endothelin-1 and in vitro evidence of renal artery vasoconstriction after liver transplantation

Twelve pigs underwent orthotopic liver transplantation. The mean endothelin-1 (ET-1) levels in the serum samples of the recipient animals 1 h after reperfusion of the graft (6.2 +/- 1.5 pg/ml) was significantly higher (P < 0.05) than in pretransplantation samples (3.2 +/- 0.6 pg/ml). Serum blood urea nitrogen (BUN) 24 h after transplantation was 13.8 +/- 5.9 mg/dl, which was significantly higher than before transplantation (6.4 +/- 2.2 mg/dl). There was a positive correlation between the serum BUN and ET-1 (r = 0.62, P < 0.05). An in vitro isometric tension study was performed for the contractility response rate of the intact renal artery in the bath chamber containing the serum of the corresponding recipient animals. The mean contractility response rates were higher with the serum obtained after reperfusion of the graft (66.9 +/- 32.4%) than with those obtained before transplantation (18.3 +/- 9.2%) when compared to a standard contractility rate of 100% with 40 mM KCI. Moreover, these contractility response rates were significantly reduced (32.8 +/- 21.0%) with the addition of the ET-1 receptor antagonist FR139317. The results of the present study demonstrated that the liver transplantation was associated with elevation of ET-1 in the serum of the recipient animals. It was considered that ET-1 in the serum caused a direct vasoconstriction of the renal artery in vitro. This may help to explain the renal dysfunction that is often seen in the recipients of clinical liver transplantation.

Dexamethasone down-regulates the expression of endothelin B receptor mRNA in the rat brain

The present study was designed to examine effects of dexamethasone on the steady state level of endothelin B(ETB) receptor mRNA in in vivo the rat brain. ETB receptor mRNA was very high at the hypothalamus and cerebellum but was comparatively low at the striatum and amygdala. Dexamethasone, 1 and 7 mg/kg, i.p., markedly and dose-relatedly decreased ETB receptor mRNA level with slow onset of 8hr at the hypothalamus and cerebellum, but did not induced a marked decrease at other areas. On the contrary, dexamethasone produced an increase of ET-1 mRNA which preceded to the decrease of ETB receptor mRNA at the same brain areas. Phosphoramidon, a endothelin-converting enzyme inhibitor, did not antagonized but potentiated the effect of dexamethasone. Besides, phosphoramidon per se markedly stimulated the expression of ET-1 mRNA. The results suggested that dexamethasone down-regulates ETB receptor mRNA level at the hypothalamus and cerebellum of rat brain and these effects may be involved in the increase of ET-1 peptide gene transcription.

Dexamethasone down-regulates endothelin receptors in human cerebromicrovascular endothelial cells

Human cerebromicrovascular endothelial cells (HBEC) in culture express high affinity ETA receptors coupled to phospholipase C activation. Pretreatment of HBEC with 1 microM dexamethasone for 24 h decreased the number of the ET-1 binding sites (Bmax) on HBEC (96 fmol/mg protein vs 57 fmol/mg protein) without changing the binding affinity (KD) (101 pM vs 92 pM) or displacing profile (ET-1 = ET-2 > ET-3 > S6c). Dexamethasone-pretreated HBEC also exhibited a 40% reduction in the maximal ET-1-stimulated inositol triphosphate (IP3) production, whereas half-maximal stimulatory concentration (EC50) was not affected. This effect of dexamethasone was concentration-dependent, and most pronounced after 24 h of pretreatment. The inhibitory effect of dexamethasone on the ET-1-induced IP3 production was abolished by glucocorticoid-receptor antagonist cortexolone. In contrast, vasopressin-mediated IP3 response in HBEC was not changed by dexamethasone. Cyclo-oxygenase inhibitors indomethacin and acetylsalicylic acid did not influence the ET-1-induced IP3 production by HBEC. The down-regulation of ETA receptors in HBEC by dexamethasone, may represent one of the mechanisms involving the described effects of glucocorticoids on cerebromicrovascular function (i.e. changes in blood brain barrier properties, secretion of vasoactive factors, vascular morphogenesis).

Vasoconstrictive peptides induce endothelin-1 and prostanoids in human cerebromicrovascular endothelium

Vasoconstrictive peptides and prostanoids have been implicated in the pathogenesis of hypertension and vasospasm. Recently, we have shown that human cerebromicrovascular endothelium [human brain endothelial cells (HBEC)] constitutively produces both endothelin-1 (ET-1) and prostanoids. The vasoactive peptides, arginine vasopressin (AVP) or angiotensin II (ANG II), stimulated secretion of both immunoreactive ET-1 and prostanoids from HBEC by a receptor-mediated induction of phospholipase C (PLC) and PLA2. The release of constitutive or AVP- or ANG II-induced ET-1 occurred at different rates during the 24-h incubation of HBEC in serum-free medium. The temporal profile of AVP-stimulated production of prostanoids differed from that of ANG II. AVP-induced release of prostaglandin D2 (PGD2) persisted for 24 h, whereas ANG II-stimulated PGD2 was only seen during the first 4 h of incubation. ANG II maximally stimulated PGI2 secretion during the 4- to 8-h interval, whereas AVP did not stimulate PGI2 secretion. Dexamethasone (Dxm), indomethacin (Indo), and nordihydroguaiaretic acid, the respective inhibitors of PLA2-cyclooxygenase II, cyclooxygenase, and lipoxygenase, increased both constitutive and AVP- or ANG II-stimulated secretion of ET-1. Dxm also decreased AVP- or ANG II-stimulated production of PGD2 and PGF2 alpha. These results indicate an interrelationship between HBEC production of ET-1 and prostanoids, which may play a role in regulating cerebral microcirculation.