A comprehensive review on ecology, life cycle and use of Tecoma stans (bignoneaceae)

Tecoma stans is a widely distributed tall ornamental shrub in the plains of Indian subcontinent and is considered an invasive species across Argentina, Australia, South Africa, Pacific Islands and tropical regions of Asia. Besides having an ornamental significance, T. stans has been extensively investigated for its pharmaceutical applications as a source of bioactive compounds. In addition, the shrub is cultivated commercially as a potted flowering plant. We believe that T. stans, being a hardy, invasive and aggressively growing species, holds a considerable potential and a promising solution for re-greening waste and degraded lands outside its invasive range, due to its wider adaptability and drought tolerant characteristics. The shrub is an excellent source of pollen and nectar, that attracts diverse insect-pollinators and several species of birds. The prudent plantation of this shrub has the potential to restore the ecology of barren landscapes, that can change its perspective of 'being invasive' to 'being ecologically healthy' across the tropical, semi-arid and subtropical regions worldwide. This paper reviews the current updates on ecology, life cycle including morphology, plant growth characteristics, flowering phenology, reproductive biology, breeding system and fruiting of T. stans. In addition, details on insect-pollinator diversity and natural regeneration potential have also been discussed, besides highlighting its therapeutic and landscape use.

Multi-objective Genetic Algorithm Based Deep Learning Model for Automated COVID-19 Detection Using Medical Image Data

Purpose

In early 2020, the world is amid a significant pandemic due to the novel coronavirus disease outbreak, commonly called the COVID-19. Coronavirus is a lung infection disease caused by the Severe Acute Respiratory Syndrome Coronavirus 2 virus (SARS-CoV-2). Because of its high transmission rate, it is crucial to detect cases as soon as possible to effectively control the spread of this pandemic and treat patients in the early stages. RT-PCR-based kits are the current standard kits used for COVID-19 diagnosis, but these tests take much time despite their high precision. A faster automated diagnostic tool is required for the effective screening of COVID-19.

Methods

In this study, a new semi-supervised feature learning technique is proposed to screen COVID-19 patients using chest CT scans. The model proposed in this study uses a three-step architecture, consisting of a convolutional autoencoder based unsupervised feature extractor, a multi-objective genetic algorithm (MOGA) based feature selector, and a Bagging Ensemble of support vector machines based binary classifier. The proposed architecture has been designed to provide precise and robust diagnostics for binary classification (COVID vs.nonCOVID). A dataset of 1252 COVID-19 CT scan images, collected from 60 patients, has been used to train and evaluate the model.

Results

The best performing classifier within 127 ms per image achieved an accuracy of 98.79%, the precision of 98.47%, area under curve of 0.998, and an F1 score of 98.85% on 497 test images. The proposed model outperforms the current state of the art COVID-19 diagnostic techniques in terms of speed and accuracy.

Conclusion

The experimental results prove the superiority of the proposed methodology in comparison to existing methods.The study also comprehensively compares various feature selection techniques and highlights the importance of feature selection in medical image data problems.

Increased tracheostomy rates in head and neck cancer surgery during the COVID-19 pandemic

Surgical practice during the coronavirus disease 2019 (COVID-19) pandemic has changed significantly, without supporting data. With increasing experience, a dichotomy of practice is emerging, challenging existing consensus guidelines. One such practice is elective tracheostomy. Here, we share our initial experience of head and neck cancer surgery in a COVID-19 tertiary care centre, emphasizing the evolved protocol of perioperative care when compared to pre-COVID-19 times. This was a prospective study of 21 patients with head and neck cancers undergoing surgery during the COVID-19 pandemic, compared to 193 historical controls. Changes in anaesthesia, surgery, and operating room practices were evaluated. A strict protocol was followed. One patient tested positive for COVID-19 preoperatively. There was a significant increase in pre-induction tracheostomies (28.6% vs 6.7%, P = 0.005), median hospital stay (10 vs 7 days, P = 0.001), and postponements of surgery (57.1% vs 27.5%, P = 0.01), along with a significant decrease in flap reconstructions (33.3% vs 59.6%, P = 0.03). There was no mortality and no difference in postoperative morbidity. No healthcare personnel became symptomatic for COVID-19 during this period. Tracheostomy is safe during the COVID-19 pandemic and rates have increased. Despite increased rescheduling of surgeries and longer hospital stays, definitive cancer care surgery has not been deferred and maximum patient and healthcare worker safety has been ensured.

Comparative study of glycated hemoglobin by ion exchange chromatography and affinity binding nycocard reader in type 2 diabetes mellitus

The aim of this study was to compare the level of glycated hemoglobin (HbA1c) in type 2 Diabetes Mellitus (DM) patients by two different methods namely Ion Exchange Chromatography and Affinity Binding Nycocard Reader. This is a cross-sectional study conducted on confirmed type 2 diabetes mellitus patients (n = 100) who visited Out Patients Department of the Universal College of Medical Sciences Teaching hospital, Bhairahawa, Nepal from November 2012 to March 2013. The diagnosis of diabetes mellitus was done on the basis of their fasting (164.46 ± 45.33 mg/dl) and random (187.93 ± 78.02 mg/dl) serum glucose level along with clinical history highly suggestive of type 2 DM. The HbA1c values of (7.8 ± 1.9%) and (8.0 ± 2.2%) were found in DM patients as estimated by those two different methods respectively. The highest frequency was observed in HbA1c > 8.0% indicating maximum cases were under very poor glycemic control. However, there were no significant differences observed in HbA1c value showing both methods are comparable in nature and can be used in lab for ease of estimation. The significant raised in HbA1c indicates complications associated with DM and monitoring of therapy become hard for those patients. Despite having standard reference method for HbA1c determination, the availability of report at the time of the patient visit can be made easy by using Nycocard Reader and Ion Exchange Chromatography techniques without any delay in communicating glycemic control, clinical decision-making and changes in treatment regimen.

A Comparative Study of Propofol and Isoflurane Anaesthesia using Butorphanol in Neurosurgery

SUMMARY

Propofol and isoflurane have well proven roles as intravenous and inhalational anaesthetics respectively in neurosurgery. We conducted this study to know the outcome using butorphanol as an intraoperative analgesic. Sixty craniotomy patients randomly divided into two groups of 30 each were included in this study. Group A patients were induced and maintained with propofol. Group B patients were induced with thiopentone and maintained with isoflurane. All patients were administered 30mug.kg(-1) butorphanol intravenously 10 minutes before induction of anaesthesia, followed by slow injection of 30mug.kg(-1) midazolam. All were assessed for sedation, respiratory insufficiency, postoperative nausea and vomiting (PONV) and other side effects in the recovery room. We found no difference in demographic parameters between the groups. The fall in HR was maintained in the post induction / intubation period and throughout the intraoperative period in Group A, unlike Group B patients in whom it rose significantly following intubation. Butorphanol was found to be a safe intraoperative analgesic in neurosurgical patients. In addition, it was associated with statistically better haemodynamics and earlier recovery when used with propofol as compared to thiopentone-isoflurane anaesthesia.

2-Hydroxyestradiol attenuates the development of obesity, the metabolic syndrome, and vascular and renal dysfunction in obese ZSF1 rats

A pandemic of obesity is contributing importantly to the prevalence of the metabolic syndrome characterized by hypertension, insulin resistance, and hyperlipidemia. In turn, the metabolic syndrome is contributing to vascular disease and the accelerating epidemic of chronic renal failure. Currently, pharmacological approaches to attenuate obesity and its cardiovascular/renal sequelae are limited. The purpose of this study was to determine the effects of 2-hydroxyestradiol, a metabolite of 17beta-estradiol with minimal estrogenic activity, on the development of obesity, the metabolic syndrome, and heart, vascular, and renal dysfunction in obese ZSF1 rats, a well-characterized genetic model of obesity and the metabolic syndrome with concomitant heart, vascular, and kidney disease. ZSF1 rats were treated, beginning at 12 weeks of age, for 26 weeks with vehicle or 2-hydroxyestradiol (10 microg/kg/h). At baseline and after 24 weeks of treatment, animals were placed in metabolic cages, and food intake, water intake, urine output, and urinary excretion of proteins and glucose were determined. Next, in fasting animals, plasma cholesterol was measured, an oral glucose tolerance test was conducted, and total glycated hemoglobin levels were determined. At the end of the study, animals were anesthetized and instrumented for assessment of heart performance, renal hemodynamics, and mesenteric vascular reactivity. 2-Hydroxyestradiol attenuated the development of obesity and improved endothelial function, decreased nephropathy, decreased the severity of diabetes, lowered arterial blood pressure, and reduced plasma cholesterol. 2-Hydroxyestradiol may be an important lead for the development of safe and effect drugs to attenuate obesity and its metabolic, vascular, and renal sequelae.

Catecholamines abrogate antimitogenic effects of 2-hydroxyestradiol on human aortic vascular smooth muscle cells

Catechol-O-methyltransferase (COMT)-mediated methylation of 2-hydroxyestradiol (endogenous estradiol metabolite) to 2-methoxyestradiol (angiogenesis inhibitor) may be responsible for the antimitogenic effects of 2-hydroxyestradiol on vascular smooth muscle cells (VSMCs). Catecholamines are also substrates for COMT, and increased levels of catecholamines are associated with vasoocclusive disorders. We hypothesize that catecholamines may abrogate the vasoprotective effects of 2-hydroxyestradiol by competing for COMT and inhibiting 2-methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic effects of 0.001 to 0.1 micromol/L of 2-hydroxyestradiol on human aortic VSMC proliferation (cell number and DNA synthesis), collagen synthesis, and migration in the presence and absence of catecholamines. Norepinephrine, epinephrine, and isoproterenol concentration-dependently abrogated the inhibitory effects of 2-hydroxyestradiol on cell number, DNA synthesis, collagen synthesis, and cell migration. These modulatory/attenuating effects of catecholamines were not abrogated in the presence of the alpha- and beta-adrenergic receptor antagonists, phentolamine mesylate and propranolol, respectively. In contrast to 2-hydroxyestradiol, the antimitogenic effects of 2-methoxyestradiol (0.1 micromol/L) were not attenuated by isoproterenol (1 micromol/L) or quercetin (competitive inhibitor of COMT, 10 micromol/L). Norepinephrine, epinephrine, and isoproterenol concentration-dependently (10 to 500 micromol/L) inhibited the metabolism of 2-hydroxyestradiol (0.25 to 2 micromol/L) to 2-methoxyestradiol, and the potency of the catecholamines to reverse 2-hydroxyestradiol-induced inhibition of VSMC proliferation, collagen synthesis, and migration was correlated with their ability to inhibit 2-methoxyestradiol formation. Our findings suggest that catecholamines within the vasculature may abrogate the anti-vaso-occlusive effects of estradiol and 2-hydroxyestradiol by blocking 2-methoxyestradiol formation.

Cardiovascular protective effects of 17beta-estradiol metabolites

17beta-estradiol (estradiol), the most abundant endogenous estrogen, affords cardiovascular protection. However, in a given cohort of postmenopausal women, estradiol replacement therapy provides cardiovascular protection in only a subset. The reasons for this variable action can only be understood once the mechanisms by which estradiol induces its cardiovascular protective effects are known. Because most biological effects of estradiol are mediated via estrogen receptors (ERs) and the heart and blood vessels contain both ER-alpha and ER-beta, the prevailing view is that ERs mediate estradiol-induced cardiovascular protection. However, recent findings that estradiol protects against vascular injury in arteries of mice lacking either ER-alpha or ER-beta seriously challenges this concept. Thus other non-ER mechanisms may be operative. Endogenous estradiol is enzymatically converted to several nonestrogenic metabolites, and some of these metabolites induce potent biological effects via ER-independent mechanisms. Therefore, it is conceivable that the cardiovascular protective effects of estradiol are mediated via its endogenous metabolites. On the basis of the evidence cited in this review, the cardiovascular protective effects of estradiol are both ER dependent and independent. The purpose of this article is to review the evidence regarding the cardiovascular protective effects of estradiol metabolites and to discuss the cellular, biochemical, and molecular mechanisms involved.

Role of the extracellular cAMP-adenosine pathway in renal physiology

Adenosine exerts physiologically significant receptor-mediated effects on renal function. For example, adenosine participates in the regulation of preglomerular and postglomerular vascular resistances, glomerular filtration rate, renin release, epithelial transport, intrarenal inflammation, and growth of mesangial and vascular smooth muscle cells. It is important, therefore, to understand the mechanisms that generate extracellular adenosine within the kidney. In addition to three "classic" pathways of adenosine biosynthesis, contemporary studies are revealing a novel mechanism for renal adenosine production termed the "extracellular cAMP-adenosine pathway." The extracellular cAMP-adenosine pathway is defined as the egress of cAMP from cells during activation of adenylyl cyclase, followed by the extracellular conversion of cAMP to adenosine by the serial actions of ecto-phosphodiesterase and ecto-5'-nucleotidase. This mechanism of extracellular adenosine production may provide hormonal control of adenosine levels in the cell-surface biophase in which adenosine receptors reside. Tight coupling of the site of adenosine production to the site of adenosine receptors would permit a low-capacity mechanism of adenosine biosynthesis to have a large impact on adenosine receptor activation. The purposes of this review are to summarize the physiological roles of adenosine in the kidney; to describe the classic pathways of renal adenosine biosynthesis; to review the evidence for the existence of the extracellular cAMP-adenosine pathway; and to describe possible physiological roles of the extracellular cAMP-adenosine pathway, with particular emphasis on the kidney.

Liposomal atp or NAD+ protects human endothelial cells from energy failure in a cell culture model of sepsis

Sepsis depletes intracellular stores of ATP and NAD+, leading to cellular energy failure. Liposome encapsulation improves intracellular delivery of bulky, charged molecules and substrates susceptible to extracellular enzyme degradation. We hypothesized that treatments with liposome encapsulated ATP or NAD+ would protect human endothelial cells exposed to endotoxin (LPS) and interferon-gamma (IFN-gamma) from energy failure. Liposomal ATP and NAD+ were prepared by a modification of the thin film method. Human endothelial cells were exposed to LPS 50 microg/ml and IFN-gamma 50 ng/ml for 72 hours, and liposomal ATP and NAD+ treatments were dosed at 0 and 24 hours. Energy state was determined by rate of mitochondrial respiration as measured by WST-1 assay. Mitochondrial respiration significantly decreased to 57% +/- 3 of control in LPS/IFN-gamma exposed cells after 72 hours. Liposomal ATP (200 microM) and NAD+ (100 microM) completely reversed this respiratory depression while empty liposomes, free ATP (200 microM). and free NAD+ (100 microM) did not. These results support the hypothesis that treatments with liposome encapsulated ATP or NAD+ protect human endothelial cells from energy failure in a cell culture model of sepsis and potentially may provide a novel therapy for use in clinical sepsis.

Endogenous cyclic AMP-adenosine pathway regulates cardiac fibroblast growth

Our previous studies show that cardiac fibroblasts express the extracellular "cAMP-adenosine pathway," that is, the generation of adenosine from extracelluar cAMP. The goal of this study was to assess whether activation of the cAMP-adenosine pathway by stimulation of endogenous cAMP synthesis regulates cardiac fibroblast growth. Cardiac fibroblasts in 3D cultures were used as the model system. Treatment of cardiac fibroblasts with forskolin, isoproterenol, or norepinephrine increased cAMP production and extracellular levels of adenosine, and these effects were prevented by inhibition of adenylyl cyclase (2',5'-dideoxyadenosine). Treatment with forskolin, isoproterenol, or norepinephrine for 24 hours inhibited DNA synthesis ((3)H-thymidine incorporation), and this effect was enhanced by combined inhibition of adenosine deaminase (erythro-9-[2-hydroxy-3-nonyl] adenine) plus adenosine kinase (iodotubercidin). Inhibition of adenylyl cyclase or adenosine receptors (1,3-dipropyl-8-p-sulfophenylxanthine or KF17837) prevented the effects of forskolin, isoproterenol, and norepinephrine on DNA synthesis. Forskolin also inhibited protein synthesis ((3)H-leucine incorporation) and cell proliferation, and these effects were blocked by adenosine receptor antagonism. Treatment of cardiac fibroblasts with norepinephrine for >48 hours but not <48 hours increased DNA synthesis, protein synthesis, and cell number. However, blockade of adenylyl cyclase or antagonism of adenosine receptors caused norepinephrine to induce proliferation in <48 hours. Our findings indicate that the endogenous cAMP-adenosine pathway regulates cardiac fibroblast growth.

Estrogen-induced cardiorenal protection: potential cellular, biochemical, and molecular mechanisms

A number of cellular and biochemical processes are involved in the pathophysiology of glomerular and vascular remodeling, leading to renal and vascular disorders, respectively. Although estradiol protects the renal and cardiovascular systems, the mechanisms involved remain unclear. In this review we provide a discussion of the cellular, biochemical, and molecular mechanisms by which estradiol may exert protective effects on the kidneys and vascular wall. In this regard, we consider the possible role of genomic vs. nongenomic mechanisms and estrogen receptor-dependent vs. estrogen receptor-independent mechanisms in mediating the protective effects of estradiol on the renal and cardiovascular systems.

Increased 2-methoxyestradiol production in human coronary versus aortic vascular cells

Estradiol may be cardioprotective; however, the mechanisms involved remain unclear. Recent findings that estradiol attenuates neointima formation in estrogen receptor knockout mice suggest that the cardioprotective effects of estradiol may be mediated through estrogen receptor-independent mechanisms. Because 2-methoxyestradiol, an endogenous metabolite of estradiol with no affinity for estrogen receptors, is more potent than estradiol in inhibiting vascular smooth muscle cell growth, it is feasible that 2-methoxyestradiol mediates in part the cardioprotective effects of estradiol. To address this hypothesis, we examined the kinetics of 2-methoxyestradiol synthesis in vascular smooth muscle cells and endothelial cells. In human aortic smooth muscle cells, the V(max), K(m), and V(max)/K(m) ratio values for conversion of 2-hydroxyestradiol to 2-methoxyestradiol were 19+/-0.69 pmol. min(-1) per 10(6) cells, 0.52+/-0.085 micromol/L, and 44+/-4.9 pmol. min(-1). micromol/L per 10(6) cells, respectively. In human coronary artery vascular smooth muscle cells, the V(max), K(m), and V(max)/K(m) ratio values for conversion of 2-hydroxyestradiol to 2-methoxyestradiol were 16+/-0.59 pmol. min(-1) per 10(6) cells, 0.23+/-0.011 micromol/L, and 69+/-3.6 pmol. min(-1). micromol/L per 10(6) cells, respectively (all values significantly different compared with human aortic smooth muscle cells). Also, in human aortic versus coronary artery endothelial cells, the V(max) (33+/-0.24 versus 22+/-0.33 pmol. min(-1) per 10(6) cells, respectively), K(m) (0.20+/-0.010 versus 0.099+/-0.014 micromol/L, respectively), and V(max)/K:(m) (163+/-7.7 versus 243+/-41 pmol. min(-1). micromol/L per 10(6) cells, respectively) values were significantly different. Our results indicate that vascular smooth muscle and endothelial cells effectively metabolize 2-hydroxyestradiol to 2-methoxyestradiol. The lower K(m) and higher V(max)/K(m) ratio of human coronary versus aortic cells indicate a faster rate of local metabolism of 2-hydroxyestradiol to 2-methoxyestradiol in the coronary circulation at low levels of 2-hydroxyestradiol.

Estradiol metabolites inhibit endothelin synthesis by an estrogen receptor-independent mechanism

Estradiol inhibits endothelin-1 synthesis, an effect that may contribute to the cardiovascular protective effects of estradiol. Recent findings that estradiol inhibits neointima formation in mice lacking estrogen receptors suggests that the cardiovascular protective effects of estradiol may be mediated by means of an estrogen receptor-independent mechanism. Because 2-hydroxyestradiol and 2-methoxyestradiol, metabolites of estradiol with little/no affinity for estrogen receptors, are more potent than estradiol in inhibiting vascular smooth muscle cell growth, we investigated whether these metabolites also inhibit endothelin-1 synthesis by means of an receptor-independent mechanism. Treatment of porcine coronary artery endothelial cells for 4 to 24 hours with 0.001 to 1 micromol/L of estradiol, 2-hydroxyestradiol, or 2-methoxyestradiol concentration-dependently inhibited basal as well as serum-induced (2.5%), TNFalpha-induced (10 ng/mL), angiotensin II-induced (100 nmol/L), and thrombin-induced (4 U/mL) endothelin-1 synthesis. Estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol also inhibited serum-induced mitogen-activated protein kinase activity. As compared with estradiol, its metabolites were more potent in inhibiting endothelin-1 secretion and mitogen activated protein kinase activity. The inhibitory effects of 2-hydroxyestradiol and 2-methoxyestradiol on endothelin-1 release and mitogen-activated protein kinase activity were not blocked by ICI182780 (50 micromol/L), an estrogen receptor antagonist. Our findings indicate that the estradiol metabolites 2-hydroxyestradiol and 2-methoxyestradiol potently inhibit endothelin-1 synthesis by means of an estrogen receptor-independent mechanism. This effect of estradiol metabolites may be mediated by inhibition of mitogen activated protein kinase activity and may contribute to the cardioprotective effects of estradiol.

Effects of estradiol and its metabolites on glomerular endothelial nitric oxide synthesis and mesangial cell growth

Reduced nitric oxide synthesis by glomerular endothelial cells and increased proliferation of glomerular mesangial cells is associated with glomerular remodeling that leads to accelerated glomerulosclerosis. Estradiol induces nitric oxide synthesis and slows the progression of renal disease. Because the estradiol metabolites 2-hydroxyestradiol and 2-methoxyestradiol are more potent than estradiol in inhibiting growth of vascular smooth muscle cells, which are phenotypically similar to mesangial cells, we compared the effects of estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol on growth of glomerular mesangial cells and on basal nitric oxide synthesis by glomerular endothelial cells. In human glomerular mesangial cells, estradiol and its metabolites concentration-dependently (1 nmol/L to 10 micromol/L) inhibited serum (2.5%)-induced DNA synthesis, cell proliferation, and collagen synthesis with the order of potency being 2-methoxyestradiol > 2-hydroxyestradiol > estradiol. ICI182780 (100 micromol/L, an estrogen receptor antagonist) blocked the growth inhibitory effects of estradiol but not 2-hydroxyestradiol or 2-methoxyestradiol. Treatment with estradiol, but not 2-hydroxyestradiol and 2-methoxyestradiol, induced nitric oxide synthesis (P<0.05, assayed by the formation of (3)H-L-citrulline from (3)H-L-arginine) in human glomerular endothelial cells, and these effects were blocked by ICI182780 and L-NMA (a nitric oxide synthesis inhibitor). In conclusion, estradiol may attenuate glomerulosclerosis by inducing nitric oxide synthesis via an estrogen receptor-dependent mechanism and by conversion to 2-hydroxyestradiol and 2-methoxyestradiol, which inhibit glomerular mesangial cell proliferation independent of estrogen receptors.

A(2b) receptors mediate the antimitogenic effects of adenosine in cardiac fibroblasts

Adenosine inhibits growth of cardiac fibroblasts; however, the adenosine receptor subtype that mediates this antimitogenic effect remains undefined. Therefore, the goals of this study were to determine which adenosine receptor subtype mediates the antimitogenic effects of adenosine and to investigate the signal transduction mechanisms involved. In rat left ventricular cardiac fibroblasts, PDGF-BB (25 ng/mL) stimulated DNA synthesis ((3)H-thymidine incorporation), cellular proliferation (cell number), collagen synthesis ((3)H-proline incorporation), and MAP kinase activity. The adenosine receptor agonists 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, but not N(6)-cyclopentyladenosine, 4-aminobenzyl-5'-N-methylcarboxamidoadenosine, or CGS21680, inhibited the growth effects of PDGF-BB, an agonist profile consistent with an A(2B) receptor-mediated effect. The adenosine receptor antagonists KF17837 and 1,3-dipropyl-8-p-sulfophenylxanthine, but not 8-cyclopentyl-1,3-dipropylxanthine, blocked the growth-inhibitory effects of 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, an antagonist profile consistent with an A(2) receptor-mediated effect. Antisense, but not sense or scrambled, oligonucleotides to the A(2B) receptor stimulated basal and PDGF-induced DNA synthesis, cell proliferation, and collagen synthesis. Moreover, the growth-inhibitory effects of 2-chloroadenosine, 5'-N-methylcarboxamidoadenosine, and erythro-9-(2-hydroxy-3-nonyl) adenine plus iodotubericidin (inhibitors of adenosine deaminase and adenosine kinase, respectively) were abolished by antisense, but not scrambled or sense, oligonucleotides to the A(2B) receptor. Our findings strongly support the hypothesis that adenosine causes inhibition of CF growth by activating A(2B) receptors coupled to inhibition of MAP kinase activity. Thus, A(2B) receptors may play a critical role in regulating cardiac remodeling associated with CF proliferation. Pharmacologic or molecular biological activation of A(2B) receptors may prevent cardiac remodeling associated with hypertension, myocardial infarction, and myocardial reperfusion injury after ischemia.

Methoxyestradiols mediate the antimitogenic effects of estradiol on vascular smooth muscle cells via estrogen receptor-independent mechanisms

Estrogen receptors (ERs) are widely held to mediate the ability of 17 beta-estradiol (estradiol) to attenuate injury-induced proliferation of vascular smooth muscle cells (VSMCs) leading to vascular lesions. However, recent findings that estradiol prevents injury-induced vascular lesion formation in knock-out mice lacking either ER alpha or ER beta seriously challenge this concept. Here we report that the local metabolism of estradiol to methoxyestradiols, endogenous metabolites of estradiol with no affinity for ERs, is responsible for the ER-independent inhibitory effects of locally applied estradiol on rat VSMC growth. These finding imply that local vascular estradiol metabolism may be an important determinant of the cardiovascular protective effects of circulating estradiol. Thus, interindividual differences, either genetic or acquired, in the vascular metabolism of estradiol may define a given female's risk of cardiovascular disease and influence the cardiovascular benefit she receives from estradiol replacement therapy in the postmenopausal state. These findings also imply that nonfeminizing estradiol metabolites may confer cardiovascular protection in both women and men.

Cardiac fibroblasts express the cAMP-adenosine pathway

The extracellular "cAMP-adenosine pathway" refers to the local production of adenosine mediated by cAMP egress into the extracellular space, conversion of cAMP to AMP by ectophosphodiesterase, and the metabolism of AMP to adenosine by ecto-5'-nucleotidase. The goal of this study was to assess whether the cAMP-adenosine pathway limits cardiac fibroblast growth. Studies were conducted in ventricular cardiac fibroblasts maintained in 3-dimensional cultures. Addition of exogenous cAMP to cardiac fibroblasts increased extracellular levels of AMP, adenosine, and inosine in a concentration-dependent and time-dependent manner. This effect was attenuated by blockade of total phosphodiesterase activity (3-isobutyl-1-methylxanthine), ectophosphodiesterase activity (high concentration of 1, 3-dipropyl-8-p-sulfophenylxanthine), or ecto-5'-nucleotidase (alpha, beta-methylene-adenosine-5'-diphosphate). Treatment with exogenous cAMP inhibited cell growth as assessed by DNA synthesis ((3)H-thymidine incorporation), cell proliferation (cell counts), and protein synthesis ((3)H-leucine incorporation). Antagonism of A(2) (KF17837) or A(1)/A(2) (low concentration of 1, 3-dipropyl-8-p-sulfophenylxanthine), but not A(1) (8-cyclopentyl-1, 3-dipropylxanthine), adenosine receptors blocked the growth-inhibitory effects of exogenous cAMP, but not the growth inhibitory effects of 8-bromo-cAMP (stable cAMP analogue). The growth-inhibitory effects of exogenous cAMP were enhanced by the combined inhibition of adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl) adenine] and adenosine kinase (iodotubercidin). In conclusion, the extracellular cAMP-adenosine pathway exists in cardiac fibroblasts and attenuates cell growth. Pharmacological augmentation of this pathway could abate pathological cardiac remodeling in heart disease.

Cellular and biochemical mechanisms by which environmental oestrogens influence reproductive function

The biology and physiology of the male as well as female reproductive system is hormonally regulated. Abnormalities in the dynamics of hormone production, metabolism and elimination, as well as their binding to certain target tissues, has been associated with pathophysiological conditions of the reproductive system. Although oestrogens are known to be one of the major hormone groups in regulating the reproductive function and the fertilization process, the cellular and biochemical mechanism or mechanism(s) via which oestrogens induce their effects are still not fully defined. Moreover, in a modern environment we are also exposed to a wide battery of environmental agents which are structurally similar to oestrogens, and termed 'environmental oestrogens'. Because environmental oestrogens have been shown to mimic some of the effects of oestradiol, it has been postulated that these exogenous chemicals may influence or interfere with the oestrogen-dependent reproductive processes, and may be associated with beneficial as well as deleterious effects on the reproductive system. In this regard, two classes of environmental oestrogens have been widely studied, i.e. phyto-oestrogens (plant-derived dietary oestrogens) and xeno-oestrogens (industrial chemicals, including polychlorinated biphenyls, DDT, TCDD, dioxins, etc.). The main focus of this review is to provide an overview on the cellular and biochemical mechanism(s) by which xeno-oestrogens and phyto-oestrogens influence the oestrogen-dependent reproductive functions and induce their deleterious or protective effects on the reproductive system.

Clinically used estrogens differentially inhibit human aortic smooth muscle cell growth and mitogen-activated protein kinase activity

Some estrogenic compounds modify vascular smooth muscle cell (SMC) biology; however, whether such effects are mediated in part by estrogen receptors is unknown. The purpose of this study was to evaluate whether the actions of clinically used estrogens on human aortic SMC biology are mediated by estrogen receptors. We examined the effects of various clinically used estrogens in the presence and absence of ICI 182,780, an estrogen receptor antagonist, on cultured human aortic SMC DNA synthesis ([(3)H]thymidine incorporation), cellular proliferation (cell counting), cell migration (modified Boyden chamber), collagen synthesis ([(3)H]proline incorporation), and mitogen-activated protein kinase activity. FCS-induced DNA synthesis, cell proliferation, collagen synthesis, platelet-derived growth factor-induced SMC migration, and mitogen-activated protein kinase activity were significantly inhibited by physiological (10(-9) mol/L) concentrations of 17beta-estradiol and low concentrations (10(-8) to 10(-7) mol/L) of 17beta-estradiol, estradiol valerate, estradiol cypionate, and estradiol benzoate but not by estrone, estriol, 17alpha-estradiol, or estrone sulfate. The inhibitory effects of 17beta-estradiol and other inhibitory estrogens were completely reversed by 100 micromol/L ICI 182,780, and the rank-order potency of various estrogens to inhibit SMC biology matched their rank-order affinity for estrogen receptors. The inhibitory effects of estrogens on SMC biology are in part receptor-mediated. Because the cardioprotective effects of hormone replacement therapy are most likely mediated by modification of SMC biology, whether hormone replacement therapy protects a given postmenopausal woman against cardiovascular disease will depend partially on the affinity of the estrogen for estrogen receptors in vascular SMCs.

Sustained reduction in myocardial reperfusion injury with an adenosine receptor antagonist: possible role of the neutrophil chemoattractant response

Recent studies have demonstrated that three membrane-permeant A(1) receptor antagonists reduced infarct size in a model of ischemia followed by brief reperfusion. However, it was not determined whether cardioprotection was mediated by nonspecific intracellular effects of these highly lipophilic drugs and whether the antagonists only delayed myocardial necrosis without affecting the ultimate infarct size. In the present study, closed-chest dogs were subjected to 90 min of left anterior descending coronary artery occlusion and 72 h of reperfusion and received either a nonmembrane-permeant adenosine receptor blocker that is devoid of direct intracellular effects and is 6-fold selective for the A(1) receptor [1, 3-dipropyl-8-p-sulfophenylxanthine (DPSPX); n = 11] or vehicle (n = 12). DPSPX was administered as three 200-mg boluses 60 min before and 30 and 120 min after reperfusion. The area of necrosis was determined histologically and expressed as a percentage of the area at risk. Baseline predictors of infarct size were similar in the two groups. The ratio of the area of necrosis to the area at risk was less in the DPSPX group (17.8 +/- 4.3% versus 35.0 +/- 1.9%; P =. 012), and DPSPX improved regional ventricular function. Under both basal and stimulated (formyl-Met-Leu-Phe) conditions, suspensions of human neutrophils generated extracellular adenosine levels (approximately 50 nM) sufficient to activate A(1) receptors. Moreover, both DPSPX and 1,3-dipropyl-8-cyclopentylxanthine, a selective A(1) receptor antagonist, significantly reduced the chemoattractant response of neutrophils to formyl-Met-Leu-Phe. We conclude that blockade of A(1) adenosine receptors attenuates myocardial ischemic/reperfusion injury, possibly in part by decreasing the chemoattractant response of neutrophils.

Estradiol inhibits smooth muscle cell growth in part by activating the cAMP-adenosine pathway

Estradiol inhibits smooth muscle cell growth; however, the mechanisms involved remain unclear. Because estradiol stimulates cAMP synthesis and adenosine inhibits cell growth, we hypothesized that the conversion of cAMP to adenosine (ie, the cAMP-adenosine pathway) mediates in part the inhibitory effects of estradiol on vascular smooth muscle cell growth. To test this hypothesis, we examined the effects of estradiol (0.001 to 1 micromol/L) on serum-induced DNA, collagen, and total protein synthesis and cell number in the absence and presence of 1, 3-dipropyl-8-p-sulfophenylxanthine (10 nmol/L; A(1)/A(2) adenosine receptor antagonist), KF17837 (10 nmol/L; selective A(2) adenosine receptor antagonist), 8-cyclopentyl-1,3-dipropylxanthine (10 nmol/L; selective A(1) adenosine receptor antagonist), and 2', 5'-dideoxyadenosine (10 micromol/L; adenylyl cyclase inhibitor). Estradiol inhibited all measures of cell growth, and the concentration-dependent inhibitory curves for estradiol were shifted to the right (P<0.05) by 1,3-dipropyl-8-p-sulfophenylxanthine, KF17837, and 2',5'-dideoxyadenosine but not by 8-cyclopentyl-1, 3-dipropylxanthine. Moreover, the inhibitory effects of estradiol were enhanced by stimulation of adenylyl cyclase with forskolin and by inhibition of adenosine metabolism with erythro-9-(2-hydroxy-3-nonyl)adenine plus iodotubericidin (adenosine deaminase and kinase inhibitors, respectively). Estradiol also increased levels of cAMP and adenosine, and these effects were blocked by 2',5'-dideoxyadenosine (P<0.05). Our results support the hypothesis that estradiol stimulates cAMP synthesis and cAMP-derived adenosine regulates smooth muscle cell growth via A(2) adenosine receptors. Thus, the cAMP-adenosine pathway may contribute importantly to the antivasooclusive effects of estradiol.

A(2B) receptors mediate antimitogenesis in vascular smooth muscle cells

Adenosine inhibits growth of vascular smooth muscle cells. The goals of this study were to determine which adenosine receptor subtype mediates the antimitogenic effects of adenosine and to investigate the signal transduction mechanisms involved. In rat aortic vascular smooth muscle cells, platelet-derived growth factor-BB (PDGF-BB) (25 ng/mL) stimulated DNA synthesis ([(3)H]thymidine incorporation), cellular proliferation (cell number), collagen synthesis ([(3)H]proline incorporation), total protein synthesis ([(3)H]leucine incorporation), and mitogen-activated protein (MAP) kinase activity. The adenosine receptor agonists 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, but not N(6)-cyclopentyladenosine or CGS21680, inhibited the growth effects of PDGF-BB, an agonist profile consistent with an A(2B) receptor-mediated effect. The adenosine receptor antagonists KF17837 and 1,3-dipropyl-8-p-sulfophenylxanthine, but not 8-cyclopentyl-1, 3-dipropylxanthine, blocked the growth-inhibitory effects of 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, an antagonist profile consistent with an A(2) receptor-mediated effect. Antisense, but not sense or scrambled, oligonucleotides to the A(2B) receptor stimulated basal and PDGF-induced DNA synthesis, cell proliferation, and MAP kinase activity. Moreover, the growth-inhibitory effects of 2-chloroadenosine, 5'-N-methylcarboxamidoadenosine, and erythro-9-(2-hydroxy-3-nonyl) adenine plus iodotubericidin (inhibitors of adenosine deaminase and adenosine kinase, respectively) were abolished by antisense, but not scrambled or sense, oligonucleotides to the A(2B) receptor. Our findings strongly support the hypothesis that adenosine causes inhibition of vascular smooth muscle cell growth by activating A(2B) receptors coupled to inhibition of MAP kinase activity. Pharmacological or molecular biological activation of A(2B) receptors may prevent vascular remodeling associated with hypertension, atherosclerosis, and restenosis following balloon angioplasty.

Significance of charge on lysine residue of ovine luteinizing hormone on immunological and biological properties of the hormone

In order to understand the significance of positive charge of lysine residues of ovine luteinizing hormone (oLH) on immunological and biological activity, the epsilon-NH2 group(s) of ovine LH were sequentially modified with 2-iminothiolane (2IT) that preserves the positive charge of the lysine while the overall charge of the hormone remains unchanged. These studies have also been compared with the oLH modified by N-succinimidyl 3-(2 pyridyldithio) propionate (SPDP) and succinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (LC-SPDP) that abolish positive charge of lysine residues. The modification primarily occurs in the alpha-subunit. Sequential modification led to progressive reduction in receptor binding and immunological activities. However, the steroidogenic activity was substantially retained. The immunoreactivity and receptor binding properties of 2IT modified oLH (oLH-2IT) were less affected when compared to SPDP (oLH-SPDP) or LC-SPDP (oLH-LC-SPDP) modified derivatives suggesting that increase in hydrophobic carbon chain in oLH-LC-SPDP molecule resulted in drastic inhibition in immunological and biological properties. But the steroidogenic potential of oLH-2IT, oLH-LC-SPDP or oLH-SPDP was relatively comparable. This suggests that a single -NH2 group modification with 2IT would generate the site in the hormone for conjugation to the toxin/carrier proteins that may retain better immunological and biological activity compared to that of SPDP or LC-SPDP modified oLH.

Role of adenosine A(1) receptors in modulating extracellular adenosine levels

The purpose of this investigation was to test the hypothesis that A(1) receptors modulate extracellular levels of adenosine in cardiovascular tissues. Rat cardiac fibroblasts and human aortic vascular smooth muscle cells were cultured to confluence and various pharmacological agents were applied to the cultures. The extracellular fluid was extracted and adenosine concentrations were measured by HPLC. Three selective A(1) receptor antagonists, namely 8-cyclopentyl-1,3-dipropylxanthine, xanthine amine congener, and N-0840, at a concentration of 10 nM significantly increased extracellular levels of adenosine in both rat cardiac fibroblasts and human aortic vascular smooth muscle cells. Further studies in rat cardiac fibroblasts revealed that the effects of A(1) receptor blockade on extracellular adenosine levels were concentration dependent and prevented by inhibition of G(i) proteins with pertussis toxin or blockade of ecto-5'-nucleotidase with alpha, beta-methyleneadenosine-5'-diphosphate. In cardiac fibroblasts in which the extracellular levels of endogenous adenosine were increased, the ability of A(1) receptor blockade to augment extracellular adenosine was attenuated. A time-course study revealed a time lag of several hours between blockade of A(1) receptors and increases in extracellular adenosine levels. These data suggest that A(1) receptors function to detect the long-term levels of extracellular adenosine, and appropriately adjust extracellular adenosine levels by a slow-onset mechanism involving G(i) proteins and ecto-5'nucleotidase.

Xeno-oestrogens and phyto-oestrogens induce the synthesis of leukaemia inhibitory factor by human and bovine oviduct cells

In bovine oviduct cells 17beta-oestradiol can induce the synthesis of leukaemia inhibitory factor (LIF), a glycoprotein essential for embryo implantation. Therefore substances which are structurally similar to 17beta-oestradiol and possess oestrogenic activity may also modulate LIF synthesis and influence the reproductive process. We used primary cultures of bovine and human oviduct cells (epithelial cells:fibroblasts 1:1) to compare the effects of 17beta-oestradiol, phyto-oestrogens (genistein, biochanin A, daidzein, formononetin, and equol) and xeno-oestrogens [polychlorinated biphenyls (PCB): trichlorobiphenyl, 4-hydroxy-trichlorobiphenyl and 4-hydroxy-dichlorobiphenyl] on LIF synthesis. Immunoreactive LIF-enzyme-linked immunosorbent assay was used to determine the concentration of LIF in the culture medium. Similar to 17beta-oestradiol, genistein (0.02-2 micromol/l) induced LIF synthesis in bovine oviduct cells in a concentration-dependent manner. Equol, biochanin A and daidzein (2 micromol/l), 4-hydroxy-trichlorobiphenyl and 4-hydroxy-dichlorobiphenyl (0.01-10 micromol/l) but not formononetin (2 micromol/l) also induced LIF synthesis in bovine cells. Phyto-oestrogens and xeno-oestrogens also induced LIF synthesis in human oviduct cells (P < 0.05). The stimulatory effects of PCB, phyto-oestrogens and 17beta-oestradiol were blocked by ICI 182,780 (1 micromol/l). Moreover, 17beta-oestradiol, 4-hydroxy-trichlorobiphenyl, 4-hydroxy-dichlorobiphenyl, genistein, tamoxifen and ICI 182,780 displaced [(3)H]17beta-oestradiol from cytosolic oestrogen receptors in bovine oviduct cells. These results suggest that phyto-oestrogens and PCB mimic the effects of oestradiol in inducing LIF synthesis by bovine and human oviduct cells and that these stimulatory effects are oestrogen receptor-mediated. Environmental oestrogens act as endocrine modulators/disrupters and may induce deleterious effects on the reproductive process by influencing LIF synthesis in a non-cyclic fashion leading to tubal infertility.

Purification and characterisation of gelonin from seeds of Gelonium multiflorum

Gelonin, a ribosome-inactivating protein has been isolated from the seeds of Gelonium multifluorum of Euphorbiaceae family by two methods and the results are compared. In method-I conventional aqueous extraction, cation-exchange and gel-filtration chromatography has been used. In method-II S-Sepharose fast flow gel has been used to purify the proteins from the seed extract, followed by ammonium sulfate fractionation, cation-exchange and gel-filtration chromatography. Extensive physico-chemical and immunological characterizations show that molecular weight of gelonin as determined by gel-filtration chromatography and SDS-PAGE is approximately 30 kDa. The non-proteinous material which binds to CMC-gel in association with gelonin in method-I is substantially removed when gelonin is purified by method-II. Cation exchange, G-100 chromatography, RP-HPLC and SDS-PAGE show that method-II yields 50% more purified gelonin when compared to the yield by method-I. The immunoreactivity of gelonin obtained by methods I and II vary from 22-26% and 50-66% respectively and the ribosome-inactivating property vary from 46-56% and 70-87% respectively.

Angiotensin receptor subtype 1 mediates angiotensin II enhancement of isoproterenol-induced cyclic AMP production in preglomerular microvascular smooth muscle cells

In a previous study, we found that angiotensin (Ang) II enhances beta-adrenoceptor-induced cAMP production in cultured preglomerular microvascular smooth muscle cells (PMVSMCs) obtained from spontaneously hypertensive rats. The purpose of the present investigation was to identify the Ang receptor subtypes that mediate this effect. In our first study, we compared the ability of Ang II, Ang III, Ang (3-8), and Ang (1-7) to increase cAMP production in isoproterenol (1 microM)-treated PMVSMCs. Each peptide was tested at 0.1, 1, 10, 100, and 1000 nM. Both Ang II and Ang III increased intracellular (EC50s, 1 and 11 nM, respectively) and extracellular (EC50s, 2 and 14 nM, respectively) cAMP levels in a concentration-dependent fashion. In contrast, Ang (3-8) and Ang (1-7) did not enhance either intracellular or extracellular cAMP levels at any concentration tested. In our second study, we examined the ability of L 158809 [a selective Ang receptor subtype 1 (AT1) receptor antagonist] to inhibit Ang II (100 nM) and Ang III (100 nM) enhancement of isoproterenol (1 microM)-induced cAMP production in PMVSMCs. L 158809 (10 nM) abolished or nearly abolished (p <.001) Ang II and Ang III enhancement of isoproterenol-induced intracellular and extracellular cAMP levels. In contrast, PD 123319 (300 nM; a selective AT2 receptor antagonist) did not significantly alter Ang II enhancement of isoproterenol-induced intracellular or extracellular cAMP levels. We conclude that AT1 receptors, but not AT2, Ang (3-8), nor Ang (1-7) receptors mediate Ang II and Ang III enhancement of beta-adrenoceptor-induced cAMP production in cultured PMVSMCs.

Estrogen and tamoxifen metabolites protect smooth muscle cell membrane phospholipids against peroxidation and inhibit cell growth

The goal of this study was to test the hypothesis that antioxidant estrogens, by a mechanism independent of the estrogen receptor, protect phospholipids residing in the plasma membrane of vascular smooth muscle cells from peroxidation and peroxidation-induced cell growth and migration. Peroxidation of membrane phospholipids was assessed by HPLC analysis of phospholipids extracted from rat aortic vascular smooth muscle cells prelabeled with cis-parinaric acid (a fatty acid that is susceptible to peroxidation, which quenches its fluorescent properties). Incubation of cells for 2 hours with the peroxyl radical donor 2,2'-azobis-2,4-dimethylvaleronitrile (AMVN) caused peroxidation of all measured membrane phospholipids. This effect was attenuated by pretreating cells for 15 minutes with 50 to 5000 ng/mL of 2-hydroxyestradiol (strong antioxidant but weak estrogen-receptor ligand) or 4-hydroxytamoxifen (strong antioxidant and potent estrogen-receptor ligand), but not by estrone or droloxifene (both weak antioxidants but potent estrogen-receptor ligands). Moreover, pretreatment of cells for 20 hours with physiological concentrations (0.3 ng/mL) of 2-hydroxyestradiol or pharmacologically relevant concentrations of 4-hydroxytamoxifen (40 ng/mL) also decreased AMVN-induced phospholipid peroxidation. Both 2-hydroxyestradiol and 4-hydroxytamoxifen were as effective as 2,2,5, 7,8-pentamethyl-6-hydrochromane (an antioxidant homolog of vitamin E) in attenuating AMVN-induced peroxidation of membrane phospholipids. Also, physiological concentrations of 2-hydroxyestradiol, but not estrone, and pharmacologically relevant concentrations of 4-hydroxytamoxifen attenuated AMVM-induced DNA synthesis, cell proliferation, and cell migration. These studies demonstrate in vascular smooth muscle cells that antioxidant estrogens via a non-estrogen receptor-dependent mechanism attenuate peroxidation of membrane phospholipids and peroxidation-induced cell growth and migration.

Phytoestrogens inhibit growth and MAP kinase activity in human aortic smooth muscle cells

-Estrogens are known to induce cardioprotective effects by inhibiting smooth muscle cell (SMC) growth and neointima formation. However, the use of estrogens as cardioprotective agents is limited by carcinogenic effects in women and feminizing effects in men. If noncarcinogenic and nonfeminizing estrogenlike compounds, such as natural phytoestrogens, afford cardioprotection, this would provide a safe method for prevention of cardiovascular disease in both men and women. Therefore, we evaluated and compared in human aortic SMCs the effects of phytoestrogens (formononetin, genistein, biochanin A, daidzein, and equol) on 2.5% fetal calf serum-induced proliferation (3H-thymidine incorporation and cell number), collagen synthesis (3H-proline incorporation), and total protein synthesis (3H-leucine incorporation) and on PDGF-BB (25 ng/mL)-induced migration (modified Boydens chambers). Moreover, the effects of phytoestrogens on PDGF-BB (25 ng/mL)-induced mitogen-activated protein kinase (MAP kinase) activity in SMCs was also studied. Phytoestrogens inhibited proliferation, collagen and total protein synthesis, migration, and MAP kinase activity in a concentration-dependent manner and in the following order of potency: biochanin A>genistein>equol>daidzein>formononetin. In conclusion, our studies provide the first evidence that in human aortic SMCs phytoestrogens inhibit mitogen-induced proliferation, migration and extracellular matrix synthesis and inhibit/downregulate MAP kinase activity. Thus, phytoestrogens may confer protective effects on the cardiovascular system by inhibiting vascular remodeling and neointima formation and may be clinically useful as a safer substitute for feminizing estrogens in preventing cardiovascular disease in both women and men.

Peroxidase-catalyzed pro- versus antioxidant effects of 4-hydroxytamoxifen: enzyme specificity and biochemical sequelae

Some studies have shown the potential relevance of the oxidation products of 4-hydroxytamoxifen (4OHTAM) in carcinogenesis. Other studies show 4OHTAM has antioxidant properties. We characterized the one-electron oxidative activation reactions of 4OHTAM and three other phenolics, 3-hydroxytamoxifen (3OHTAM), 1-(4-hydroxyphenyl)-1, 2-diphenylethene, and phenol (PhOH), catalyzed by myeloperoxidase (MPx), horseradish peroxidase (HRP), lactoperoxidase, mushroom tyrosinase, and nonenzymatic initiators in vitro under a variety of conditions and in cells. Differences in activation of the phenolics by the enzymes were directly compared using cis-parinaric acid (PnA)-loaded human serum albumin. All phenolics were substrates for the enzymes, but MPx only weakly activated 4OHTAM to its phenoxyl radical. In HL60 cells loaded metabolically with PnA so that effects on phospholipids could be monitored by HPLC with fluorescence detection, PhOH plus H2O2 caused massive oxidation across all phospholipid classes. 4OHTAM dose-dependently protected phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine against both H2O2-induced and normal metabolic oxidation. This suggested 4OHTAM is a poor substrate for intracellular MPx. In rat aorta smooth muscle cells loaded with PnA, 4OHTAM also protected against AMVN-induced peroxidation of those three phospholipids and sphingomyelin, whereas 3OHTAM did not. Spin trapping of glutathionyl radicals (GS*) with DMPO and quantifying the ESR-silent nitrone form of the GS-DMPO adduct by HPLC showed that neither 3OHTAM plus H2O2 nor 4OHTAM plus H2O2 caused a significant level of GSH oxidation with isolated MPx, nor did the latter in HL60 cells, whereas PhOH plus H2O2 was a potent source of GS* in both systems. Both 4OHTAM and 3OHTAM formed the nitrone adduct under cell-free conditions when activated with HRP. The data show that the substrate specificity of a given (myelo)peroxidase determines if a phenolic exerts pro- (through generation of reactive phenoxyl radicals) or antioxidant (through radical scavenging) properties in intracellular environments.

Adenosine inhibits collagen and total protein synthesis in vascular smooth muscle cells

-The objective of this study was to characterize the effects of exogenous, drug-induced and cAMP-adenosine pathway-derived adenosine on collagen synthesis by and hypertrophy of vascular smooth muscle cells (SMCs). Confluent vascular SMCs were stimulated with 2.5% fetal calf serum in the presence and absence of adenosine receptor agonists [adenosine, 2-chloroadenosine, N6-cyclopentyladenosine, 5'-N-ethylcarboxamidoadenosine, 5'-N-methylcarboxamidoadenosine, and 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamino adenosine], drugs that increase levels of endogenous adenosine [erythro-9-(2-hydroxy-3-nonyl) adenine, dipyridamole, and iodotubericidin], and cAMP (increases adenosine by conversion to AMP and hence to adenosine via the cAMP-adenosine pathway). Adenosine receptor agonists inhibited fetal calf serum-induced collagen and total protein synthesis (as assessed by [3H]proline and [3H]leucine incorporation, respectively) with a relative potency profile consistent with the effects being mediated by adenosine A2B receptors. Erythro-9-(2-hydroxy-3-nonyl) adenine, dipyridamole, iodotubericidin, and cAMP also inhibited collagen and total protein synthesis. The effects of 2-chloroadenosine, erythro-9-(2-hydroxy-3-nonyl) adenine, iodotubericidin, and cAMP on collagen and total protein synthesis were attenuated by KF17837 and 1,3-dipropyl-8-p-sulfophenylxanthine (selective and nonselective A2 receptor antagonists, respectively) but not by 8-cyclopentyl-1, 3-dipropylxanthine (selective A1 receptor antagonist). These studies indicate that exogenous, drug-induced and cAMP-adenosine pathway-derived adenosine inhibit vascular SMC collagen synthesis and hypertrophy via A2B receptors. Thus, exogenous A2B receptor agonists and drugs that modulate endogenous adenosine levels may protect against vasoocclusive disorders by attenuating extracellular matrix synthesis by and cellular hypertrophy of vascular SMCs. Moreover, the cAMP-adenosine pathway may protect against vascular hypertrophy.

Angiotensin II and insulin induce growth of ciliary artery smooth muscle: effects of AT1/AT2 antagonists

PURPOSE

Abnormal growth of smooth muscle cells (SMCs) in small arteries of the eye is associated with hypertension and diabetes, and the complications that they induce. Migration and proliferation of SMCs into the intima are primary mechanisms involved in neointima formation. In aortic SMCs, angiotensin II (AII)-induced proliferation is inhibited by angiotensin type 1 (AT1) receptor antagonist. However, in small artery SMCs, in particular in the circulation of the eye, the effects of AII on migration and proliferation are unknown.

METHODS

The effects of AII (10(-6) to 10(-10) M) on migration and proliferation of growth-arrested SMCs of porcine ciliary arteries were studied in the presence and absence of insulin (5 x 10(-10) M) by assaying DNA synthesis (3H-thymidine incorporation), cell number, and movement of SMCs across the membrane of a modified Boyden chamber.

RESULTS

In the absence of insulin, only high concentrations (10(-6) to 10(-8) M) of AII induced DNA synthesis and increased cell number (P < 0.05); however, in the presence of insulin (5 x 10(-10) M), AII induced DNA synthesis and cell number at low concentrations (10(-10) M) and in a concentration-dependent manner (P < 0.05). In contrast to proliferation, AII induced SMC migration in a concentration-dependent manner in the absence of insulin (P < 0.05). The AT1 antagonist CGP48933 (10(-8) to 10(-12) M), but not the AT2 antagonist CGP42112 (10(-8) to 10(-12) M), inhibited AII (10(-8) M)-induced proliferation and migration in a concentration-dependent manner (P < 0.05).

CONCLUSIONS

Our results suggest that AII is a potent mitogen for SMCs of ophthalmic arteries, an effect that is enhanced in the presence of insulin, and that it may be an important contributor to structural vascular changes in the ophthalmic circulation in hypertension associated with non-insulin dependent diabetes. The inhibition of AII-induced growth by an AT1 antagonist suggests that these drugs may be important therapeutic tools to prevent structural vascular changes in the ophthalmic vasculature under these conditions.

Modulation by angiotensin II of isoproterenol-induced cAMP production in preglomerular microvascular smooth muscle cells from normotensive and genetically hypertensive rats

The objectives of the present study were to determine whether angiotensin II (Ang II) modifies beta-adrenoceptor-induced cAMP production in preglomerular microvascular smooth muscle cells (PMVSMCs), to determine whether the Ang II/beta-adrenoceptor interaction on cAMP production differs in PMVSMCs from normotensive Wistar-Kyoto (WKY) rats vs. PMVSMCs from spontaneously hypertensive rats (SHR), and to elucidate the mechanism of Ang II/beta-adrenoceptor interactions on cAMP production in PMVSMCs. In cultured PMVSMCs, isoproterenol increased cAMP levels and this effect was markedly enhanced by Ang II. The Ang II enhancement of isoproterenol-induced cAMP was significantly greater in SHR PMVSMCs compared with WKY PMVSMCs. Neither inhibition of calcineurin with FK506, inhibition of calcium-calmodulin with W-7 and calmidazolium, nor inhibition of Gi proteins with pertussis toxin attenuated Ang II enhancement of isoproterenol-induced cAMP in PMVSMCs from either SHR or WKY rats. Moreover, the effect of Ang II on isoproterenol-induced cAMP was not mimicked by alpha-2 adrenoceptor stimulation. In contrast, chelation of intracellular calcium with BAPTA-AM attenuated, increasing intracellular calcium with A23187 augmented, and inhibition of protein kinase C with either calphostin C or chelerythrine chloride abolished Ang II enhancement of isoproterenol-induced cAMP. We conclude that in cultured PMVSMCs Ang II enhances the cAMP response to beta-adrenoceptor agonists via a mechanism that involves coincident activation of adenylyl cyclase by stimulatory G proteins and protein kinase C. Thus, protein kinase C-mediated activation of adenylyl cyclase may attenuate Ang II-induced vasoconstriction in the renal microcirculation by raising the intracellular levels of cAMP, and this mechanism may be augmented in genetic hypertension.

Guanine nucleotide-binding inhibitory protein-mediated inhibition of adenylyl cyclase is enhanced in spontaneously hypertensive rat preglomerular arteriolar smooth muscle cells

The purpose of our study was to determine whether Gi-mediated control over adenylyl cyclase in preglomerular arteriolar smooth muscle cells (PGASMC) is enhanced in the spontaneously hypertensive rat (SHR). PGASMC were cultured from preglomerular microvessels isolated from adult SHR (14-15 wk of age) and age-matched WKY rats. Confluent monolayers of cells in third passage were used for the experiments. cAMP released into the media (30 min) as well as cellular levels of cAMP were measured in the presence of a phosphodiesterase inhibitor, 1-isobutyl-3-methyl-xanthine (IBMX; 100 microM) and expressed as pmol/mg protein. Total (released + cellular) cAMP was significantly lower in SHR (14.19 +/- 2.30 pmol/mg protein) as compared with WKY (28.3 +/- 3.04 pmol/mg protein). Correspondingly, the released (4.6 +/- 0.4 pmol/mg protein) as well as cellular (9.78 +/- 2.18 pmol/mg protein) cAMP levels were also significantly lower in SHR when compared with WKY (8.85 +/- 1.26 and 18.86 +/- 2.0 pmol/mg protein, respectively). The steady-state levels of none of the Gi alpha subunits, namely Gi alpha 1, Gi alpha 2 and Gi alpha 3, were higher in the SHR PGASMC. Pertussis toxin treatment (PTX; 100 ng/ml; 24 hr) caused complete ADP-ribosylation of Gi alpha subunits in both WKY and SHR PGASMC. The same treatment of PTX also produced a significant increase in total cAMP in SHR, but not in WKY, such that the total cAMP levels after PTX treatment were not significantly different between the two strains. Interestingly, PTX significantly increased the released (20.26 +/- 0.90 pmol/mg protein) but not the cellular (13.63 +/- 1.63 pmol/mg protein) cAMP in SHR. Forskolin (1 microM) induced similar increases in total cAMP and isoproterenol (1 microM) caused greater increases in total cAMP in SHR cells compared with WKY cells. These data strongly suggest that in SHR PGASMC total adenylyl cyclase activity is not altered. Furthermore, steady-state expressions of Gi alpha-1, Gi alpha-2 and Gi alpha-3 are not increased whereas Gi-mediated inhibition of adenylyl cyclase is augmented in SHR PGASMC.

Adenosine inhibits collagen and protein synthesis in cardiac fibroblasts: role of A2B receptors

The objective of this study was to characterize the effects of exogenous and endogenous (cardiac fibroblast-derived) adenosine on [3H]proline and [3H]leucine incorporation, which are reliable markers of collagen and total protein synthesis, respectively, in rat left ventricular cardiac fibroblasts. Growth-arrested confluent cardiac fibroblast monolayers were stimulated with 2.5% fetal calf serum (FCS) in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), or modulators of adenosine levels including (1) erythro-9-(2-hydroxy-3-nonyl) adenine (adenosine deaminase inhibitor), (2) dipyridamole (adenosine transport blocker), and (3) iodotubericidin (adenosine kinase inhibitor). All agents inhibited in a concentration-dependent fashion FCS-induced [3H]proline and [3H]leucine incorporation. These effects were blocked by KF17837 (selective A2 antagonist) and 1,3-dipropyl-8-(p-sulfophenyl)xanthine (A1/A2 receptor antagonist) but not by 8-cyclopentyl-1,3-dipropylxanthine (selective A1 antagonist), thus excluding the participation of A1 receptors. The lack of effect of CGS21680 (selective A2A agonist) excluded involvement of A2A receptors, thus suggesting a major role for A2B receptors. Comparisons of the inhibitory potencies of N6-cyclopentyladenosine (selective A1 agonist), 5'-N-ethylcarboxamidoadenosine (A1/A2 agonist), and 5'-N-methylcarboxamidoadenosine (A1/A2 agonist) were consistent with that of an A2B receptor subtype mediating the inhibitory effects. We conclude that adenosine inhibits FCS-induced collagen and total protein synthesis in cardiac fibroblasts via activation of A2B receptors. These studies suggest, but do not prove, that endogenous adenosine may protect against cardiac fibrosis.

Synthesis and regulation of leukaemia inhibitory factor in cultured bovine oviduct cells by hormones

Leukaemia inhibitory factor (LIF) is an essential factor for embryo implantation. Factors generated by the oviduct cells (epithelial cells and fibroblasts) create the microenvironment for fertilization and first embryo stage development. Hence, it is feasible that the oviduct cells also synthesize LIF to promote and condition the embryo for implantation in the uterus. In the present study, we investigated whether cultured bovine oviduct epithelial cells and fibroblasts synthesize LIF. LIF production was measured in the conditioned medium of oviduct epithelial cells and fibroblasts, using LIF enzyme-linked immunosorbent assay. Moreover, expression of LIF mRNA was confirmed by LIF reverse transcriptase-polymerase chain reaction in extracts of RNA from oviduct epithelial/fibroblast cells. Quantitatively similar amounts of LIF were detected in the culture medium of epithelial cells and fibroblasts. In cells cultured for 1-7 days, the levels of LIF in the medium increased in a time-dependent manner. As compared to untreated cells, treatment of cells with 17beta-oestradiol (1-100 ng/ ml), but not progesterone (1-100 ng/ml) and insulin (20 ng/ml), increased the levels of LIF in a concentration-dependent manner (P < 0.05). Similarly, tumour necrosis factor-alpha (100 ng/ml) significantly induced the levels of LIF. The effects of 17beta-oestradiol (50 ng/ml) on LIF synthesis were enhanced and not blocked in the presence of tamoxifen (1 microg/ml), an oestrogen receptor antagonist, suggesting that the stimulatory effects of 17beta-oestradiol on LIF synthesis are not receptor-mediated. In conclusion 17beta-oestradiol, but not progesterone, induces LIF synthesis by bovine oviduct epithelial cells and fibroblasts and this may play an important role in the biology of early embryo development. However, the exact pathophysiological role of LIF within the oviduct needs to be further investigated.

Adenosine inhibits growth of human aortic smooth muscle cells via A2B receptors

Adenosine inhibits rat vascular smooth muscle cell (SMC) growth. However, the effects of adenosine on human vascular SMC proliferation and synthesis of extracellular matrix proteins, such as collagen, are unknown. The objective of this study was to characterize the effects of exogenous and endogenous (SMC-derived) adenosine on human aortic SMC proliferation and collagen synthesis. Growth-arrested SMCs were stimulated with 2.5% fetal calf serum (FCS) in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), and with agents that increase endogenous adenosine levels, including erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), dipyridamole, and iodotubericidin. All of these agents inhibited in a concentration-dependent manner FCS-induced SMC proliferation as assessed by DNA synthesis (3H-thymidine incorporation) and cell counting, as well as collagen synthesis (3H-proline incorporation). EHNA, dipyridamole, and iodotubericidin increased extracellular levels of adenosine by 1.7-fold to 18-fold when added separately to SMCs, and EHNA+iodotubericidin and EHNA+iodotubericidin+dipyridamole increased extracellular adenosine levels by more than 392-fold. Both KF17837 (selective A2 antagonist) and DPSPX (A1/A2 antagonist), but not DPCPX (selective A1 antagonist), blocked the antimitogenic effects of 2-chloroadenosine, EHNA, and dipyridamole on DNA and collagen synthesis, suggesting the involvement of A2A and/or A2B, but excluding the participation of A1, receptors. The lack of effect of CGS21680 (selective A2A agonist), excluded involvement of A2A receptors and suggested a major role for A2B receptors. A comparison of the inhibitory potencies of 2-chloroadenosine, N6-cyclopentyladenosine (selective A1 agonist), NECA (A1/A2 agonist), and MECA (A1/A2 agonist) were consistent with an A2B receptor subtype mediating the inhibitory effects of adenosine on human aortic SMC proliferation. In conclusion, human aortic SMCs synthesize adenosine, and exogenous as well as endogenous (SMC-derived) adenosine inhibits SMC proliferation and collagen synthesis via activation of A2B receptors.

Cyclic AMP-adenosine pathway induces nitric oxide synthesis in aortic smooth muscle cells

The main purpose of this investigation was to evaluate whether the cyclic AMP-adenosine pathway, ie, the conversion of cAMP to AMP and, hence, to adenosine, is involved in the regulation of nitric oxide (NO) synthesis by vascular smooth muscle cells (SMCs). Treatment of confluent monolayers of SMCs with adenosine, 2-chloroadenosine (stable analog of adenosine), and agents that elevate endogenous (SMC-derived) adenosine (EHNA and iodotubericidin) increased nitrite/nitrate (stable metabolites of NO) levels in the medium and enhanced the conversion of 3H-L-arginine to 3H-L-citrulline by cytosolic extracts obtained from the pretreated SMCs. The stimulatory effects of adenosine were not mimicked by low (1 to 100 nmol/L) concentrations of CGS21680, an A2A receptor agonist, or CPA, a selective A1 receptor agonist. The stimulatory effects of 2-chloroadenosine and EHNA plus iodotubericidin were significantly inhibited by KF17837, a selective A2 receptor antagonist, and by DPSPX, an A1/A2 receptor antagonist, but not by DPCPX, a selective A1 receptor antagonist. DDA (adenylyl cyclase inhibitor) and Rp-cyclic AMP (protein kinase A inhibitor) did not block the effects of adenosine on NO synthesis. Incubation of SMCs with exogenous cyclic AMP, at concentrations previously shown to elevate levels ofadenosine in the medium, also increased nitrite/nitrate levels and 3H-L-citrulline formation, and the effects of cyclic AMP on NO synthesis were blocked by DPSPX and KF17837, but not by DPCPX. These findings provide evidence that exogenous and SMC-derived adenosine induce NO synthesis via A2B receptors linked to a pathway not involving adenylyl cyclase/protein kinase A. Moreover, extracellular cyclic AMP induces NO synthesis via conversion to adenosine and activation of A2B adenosine receptors. The cyclic AMP-adenosine pathway may be importantly involved in the vascular production of NO.

Role of nitric oxide in the biology, physiology and pathophysiology of reproduction

Following its benchmark discovery, nitric oxide (NO) is now known to play important functional roles in a variety of physiological systems. Within the vasculature, NO induces vasodilation, inhibits platelet aggregation, prevents neutrophil/platelet adhesion to endothelial cells, inhibits smooth muscle cell proliferation and migration, regulates programmed cell death (apoptosis) and maintains endothelial cell barrier function. NO generated by neurons acts as a neurotransmitter, whereas NO generated by macrophages in response to invading microbes acts as an antimicrobial agent. Because neurons, blood vessels and cells of the immune system are integral parts of the reproductive organs, and in view of the important functional role that NO plays in those systems, it is likely that NO is an important regulator of the biology and physiology of the reproductive system. Indeed, in the past 10 years, NO has established itself as a polyvalent molecule which plays a decisive role in regulating multiple functions within the female as well as the male reproductive system. This review provides an overview of the role of NO in various reproductive organs under physiological and pathological conditions.

17Beta-estradiol, its metabolites, and progesterone inhibit cardiac fibroblast growth

Postmenopausal women (PMW) have increased incidence of cardiovascular disease, and estrogen substitution therapy has been shown to have cardioprotective effects. Since abnormal growth of cardiac fibroblasts (CFs) is associated with hypertension and myocardial infarction and estrogen inhibits vascular smooth muscle cell (SMC) growth, it is feasible that estrogen may attenuate cardiac remodeling by inhibiting CF growth, and this possibility was investigated by using cultured CFs. 17Beta-estradiol and progesterone, but not 17alpha-estradiol, estrone, or estriol, inhibited 2.5% FCS-induced proliferation (DNA synthesis and cell number) and collagen synthesis (3H-proline incorporation) in a concentration-dependent manner and to a similar extent in male and female CFs. Compared to 17beta-estradiol, its metabolites 2-hydroxyestradiol and 2-methoxyestradiol were more potent in inhibiting FCS-induced DNA synthesis, collagen synthesis, and cell proliferation. The inhibitory effects of 17beta-estradiol and its metabolites were enhanced in presence of progesterone and 4-hydroxytamoxifen (high-affinity estrogen receptor ligand). Moreover, like estrogens, the dietary phytoestrogens biochanin A and daidzein inhibited FCS-induced growth of CFs. In conclusion, 17beta-estradiol, its metabolites, and progesterone inhibit CF growth in a gender-independent fashion. Moreover, hormone replacement therapy using 17beta-estradiol and progesterone may protect PMW against cardiovascular disease by inhibiting CF growth and cardiac remodeling; whereas estrogens that do not inhibit CF growth may be less effective in protecting PMW against cardiovascular disease. Finally, our studies provide evidence that phytoestrogens inhibit CF growth and may be clinically useful as a substitute for feminizing estrogens in preventing cardiovascular disease in both women and men.

Phosphodiesterases in the rat renal vasculature

The objective this investigation was to determine the relative importance of type I, III, and IV phosphodiesterases in the regulation of cyclic adenosine monophosphate (cAMP) in the renal circulation. In the first experimental series, four groups of isolated rat kidneys perfused with Tyrode's solution were stimulated with isoproterenol (3 microM) and then treated with increasing concentrations (from the approximately IC50 to 30 times the approximately IC50 in threefold increments) of one of four phosphodiesterase inhibitors: group 1, 3-isobutyl-1-methylxanthine, a "broad-spectrum" phosphodiesterase inhibitor (10-300 microM); group 2, Ro 20-1724, a selective type IV phosphodiesterase inhibitor (3-100 microM); group 3, 8-methoxymethyl-3-isobutyl-1-methylxanthine, a selective type I phosphodiesterase inhibitor (3-100 microM); and group 4, milrinone, a selective type III phosphodiesterase inhibitor (0.3-10 microM). In the second experimental series, five groups of cultured preglomerular (interlobular and afferent arteriolar) vascular smooth-muscle cells were stimulated with isoproterenol (1 microM) and treated with vehicle or supramaximal concentrations (30 times IC50) of either 3-isobutyl-1-methylxanthine (300 microM), Ro 20-1724 (100 microM), 8-methoxymethyl-3-isobutyl-1-methylxanthine (100 microM), or milrinone (10 microM). In perfused kidneys and cultured pre-glomerular vascular smooth-muscle cells, 3-isobutyl-1-methylxanthine and Ro 20-1724 similarly increased renal cAMP release and total cellular (extracellular + intracellular) cAMP levels, respectively. In contrast, neither 8-methoxymethyl-3-isobutyl-1-methylxanthine nor milrinone affected renal cAMP release or total cellular cAMP levels. These data indicate that in the renal circulation, type IV phosphodiesterase is the predominant phosphodiesterase isozyme.

Exogenous and endogenous adenosine inhibits fetal calf serum-induced growth of rat cardiac fibroblasts: role of A2B receptors

BACKGROUND

Because proliferation of cardiac fibroblasts participates in cardiac hypertrophy/remodeling associated with hypertension and myocardial infarction, it is important to elucidate factors regulating cardiac fibroblast proliferation. Adenosine, a nucleoside abundantly produced by cardiac cells, is antimitogenic vis-à-vis vascular smooth muscle cells; however, the effect of adenosine on cardiac fibroblast proliferation is unknown. The objective of this study was to characterize the effects of exogenous and endogenous (cardiac fibroblast-derived) adenosine on cardiac fibroblast proliferation.

METHODS AND RESULTS

Growth-arrested cardiac fibroblasts were stimulated with 2.5% FCS in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), or modulators of adenosine levels, including (1) erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; adenosine deaminase inhibitor); (2) dipyridamole (adenosine transport blocker); and (3) iodotubericidin (adenosine kinase inhibitor). All of these agents inhibited, in a concentration-dependent manner, FCS-induced cardiac fibroblast proliferation as assessed by DNA synthesis ([3H]thymidine incorporation) and cell counting. EHNA, dipyridamole, and iodotubericidin increased extracellular levels of adenosine by 2.3- to 5.6-fold when added separately to cardiac fibroblasts, and EHNA+iodotubericidin or EHNA+iodotubericidin+dipyridamole increased extracellular adenosine levels by >690-fold. Both KF17837 (selective A2 antagonist) and DPSPX (nonselective A2 antagonist) but not DPCPX (selective A1 antagonist) blocked the antimitogenic effects of 2-chloroadenosine, EHNA, and dipyridamole on DNA synthesis, suggesting the involvement of A2A and/or A2B but excluding the participation of A1 receptors. The lack of effect of CGS21680 (selective A2A agonist) excluded involvement of A2A receptors and suggested a major role for A2B receptors. This conclusion was confirmed by the rank order potencies of four adenosine analogues.

CONCLUSIONS

Cardiac fibroblasts synthesize adenosine, and exogenous and cardiac fibroblast-derived adenosine inhibits cardiac fibroblast proliferation via activation of A2B receptors. Cardiac fibroblast-derived adenosine may regulate cardiac hypertrophy and/or remodeling by modulating cardiac fibroblast proliferation.

Amphotericin B as an intracellular antioxidant: protection against 2,2'-azobis(2,4-dimethylvaleronitrile)-induced peroxidation of membrane phospholipids in rat aortic smooth muscle cells

The antifungal activity of amphotericin B (AmB) and its side-effects (e.g. nephrotoxicity and hemolytic action) are suggested to be associated with its prooxidant effects in target cells. To test this hypothesis, we have undertaken studies to examine the role of AmB in oxidative stress in cultured rat aortic smooth muscle cells (SMC) incubated in the absence or in the presence of a lipid-soluble azo-initiator of peroxyl radicals, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). No changes in the pattern of membrane phospholipids could be detected by two-dimensional high performance thin-layer chromatography (HPTLC) after oxidative stress induced by AMVN in which the cells remained viable, as judged by trypan blue exclusion. To improve the sensitivity of detection of oxidative stress in the cells, cis-parinaric acid (PnA) was incorporated biosynthetically into the membrane phospholipids [using PnA-human serum albumin (hSA) complex]. Incubation of the cells under aerobic conditions in the presence of up to 10 microM AmB showed no significant change in the pattern of PnA-labeled phospholipids, suggesting that AmB was not affecting the oxidative state of the cells. In contrast, treatment with AMVN (0.5 mM, incubation in the dark for 2 hr at 37 degrees--conditions in which the viability of the cells was maintained) caused a significant reduction of all fluorescently labeled phospholipid fractions separated by HPLC. When PnA-labeled cells were subjected to oxidative stress by incubation with 0.5 mM AMVN in the presence of AmB, the loss of fluorescent phospholipids was reduced in a concentration-dependent manner over a concentration range of 0.25 to 10 microM. Thus, AmB does not produce any prooxidant effect but rather acts as an intracellular antioxidant.

Metabolism of cAMP to adenosine in the renal vasculature

We recently demonstrated that cAMP added to the perfusate increased the renal venous recovery of adenosine in the isolated rat kidney, an effect blocked by inhibition of ecto-phosphodiesterase and ecto-5'-nucleotidase. Although our previous study established the cAMP-adenosine pathway, i.e., the conversion of cAMP to adenosine, as a viable metabolic pathway within the kidney, that study did not determine whether conversion of arterial cAMP to adenosine recoverable in the venous effluent occurred in the tubules versus nontubular sites. In the current study, we addressed this issue by determining the effects of blocking cAMP transport into the renal tubules with probenecid (0.1, 0.3 and 1 mM) on the increase in renal venous output of adenosine induced by adding cAMP (30 microM) to the perfusate of isolated rat kidneys. Addition of cAMP to the perfusate caused a marked increase in renal venous secretion of adenosine, an effect that was augmented, rather than inhibited, by probenecid. To test the hypothesis that the renal vasculature supports a cAMP-adenosine pathway, cultured rat preglomerular vascular smooth muscle cells were incubated with cAMP (30 microM) for 1 hr in the presence and absence of 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). Incubation with cAMP increased extracellular adenosine levels 41-fold, and this effect was abolished by 3-isobutyl-1-methylxanthine. In a third experimental series, addition of cAMP (0.3, 1, 3, 10 and 30 microM) to the perfusate of isolated rat kidneys and mesenteric vascular beds increased the renal venous, but not mesenteric venous, output of AMP, adenosine and inosine. We conclude that the renal vasculature supports a cAMP-adenosine pathway, that administering cAMP into the renal artery and measuring adenosine in the venous effluent of the perfused rat kidney most likely monitors primarily the renal vascular cAMP-adenosine pathway and that the quantitative importance of the cAMP-adenosine pathway is not equivalent in all vascular compartments.

Differential effects of hormone-replacement therapy on endogenous nitric oxide (nitrite/nitrate) levels in postmenopausal women substituted with 17 beta-estradiol valerate and cyproterone acetate or medroxyprogesterone acetate

Increased incidence of cardiovascular disease in postmenopausal women (PMW) is accompanied by ovarian dysfunction; hormone replacement therapy (HRT) can have cardioprotective effects. Because hypertension and atherosclerosis are associated with impaired release of endothelium-derived nitric oxide (NO) and increased levels of low-density lipoproteins (LDL), we investigated whether HRT augments NO release, and whether these increases are accompanied by a decrease in LDL levels in PMW. We determined serum nitrite/ nitrate (NO2-/NO3-) and LDL levels at baseline (before initiation of HRT) and during the 6th and 12th months of the study. The PMW (n = 26) received continuous oral administration of estradiol valerate (Progynova, 2 mg daily) for 21 days supplemented with either oral cyproterone acetate (CPA; 1 mg; n = 11) or medroxyprogesterone acetate (MPA; 5 mg; n = 15) on days 12-21 of each treatment cycle. Blood samples in the PMW receiving HRT were collected at times while the subjects were taking estradiol valerate alone and estradiol valerate plus CPA or MPA. Compared with the samples collected at baseline, serum NO2-/NO3- levels increased significantly from 20.1 +/- 1.58 mumol/L at baseline to 30 +/- 3.7 mumol/L (P < 0.01) in samples collected after 12 months of HRT while the PMW were not taking progestins (CPA or MPA), and to 25.4 +/- 2 mumol/L (P < 0.05) when all the samples, regardless of the treatment with CPA or MPA, were included in the analysis. Moreover, > 30% increase in serum NO2-/NO3- levels were observed only in 13 (responders) out of 26 PMW substituted with estradiol valerate, suggesting that estradiol may improve endogenous NO synthesis in a differential fashion. Compared with baseline, no significant increases in serum NO2-/NO3- were observed in samples collected while the estradiol-treated responders were taking either CPA or MPA. In contrast to NO2-/NO3- serum LDL levels were significantly reduced in samples collected after 12 months of HRT (P < 0.05 vs. baseline). Furthermore, levels of NO2-/NO3 showed a significant negative correlation with the levels of LDL (r2 = 0.17; P < 0.05) in the responders but not in nonresponders. These results indicate that oral administration of estradiol valerate in PMW for HRT increases circulating NO levels, an effect that may contribute to the cardioprotective effects of HRT in PMW. In addition, our data suggests but does not prove that concomitant administration of a progestin may attenuate the beneficial effects of estrogen replacement therapy with regard to NO release. Finally, our data provides evidence for the existence of responders and nonresponders to postmenopausal estrogen treatment with respect to improvement of endogenous NO levels, suggesting that a significant number, but not all, of the hormonally substituted PMW profit fully from the beneficial properties of a HRT.