Estimates of the Nutritional Impact of Non-Participation in the National School Lunch Program during COVID-19 School Closures

The COVID-19 pandemic resulted in widespread school closures, reducing access to school meals for millions of students previously participating in the US Department of Agriculture (USDA) National School Lunch Program (NSLP). School-prepared meals are, on average, more nutritious than home-prepared meals. In the absence of recent data measuring changes in children's diets during the pandemic, this article aims to provide conservative, back-of-the-envelope estimates of the nutritional impacts of the pandemic for school-aged children in the United States. We used administrative data from the USDA on the number of NSLP lunches served in 2019 and 2020 and nationally representative data from the USDA School Nutrition and Meal Cost Study on the quality of school-prepared and home-prepared lunches. We estimate changes in lunchtime calories and nutrients consumed by NSLP participants from March to November 2020, compared to the same months in 2019. We estimate that an NSLP participant receiving no school meals would increase their caloric consumption by 640 calories per week and reduce their consumption of nutrients such as calcium and vitamin D. Because 27 to 78 million fewer lunches were served per week in March-November 2020 compared to the previous year, nationally, students may have consumed 3 to 10 billion additional calories per week. As students return to school, it is vital to increase school meal participation and update nutrition policies to address potentially widening nutrition disparities.

School Closures During COVID-19: Opportunities for Innovation in Meal Service

In 2019, the National School Lunch Program and School Breakfast Program served approximately 15 million breakfasts and 30 million lunches daily at low or no cost to students.Access to these meals has been disrupted as a result of long-term school closures related to the COVID-19 pandemic, potentially decreasing both student nutrient intake and household food security. By the week of March 23, 2020, all states had mandated statewide school closures as a result of the pandemic, and the number of weekly missed breakfasts and lunches served at school reached a peak of approximately 169.6 million; this weekly estimate remained steady through the final week of April.We highlight strategies that states and school districts are using to replace these missed meals, including a case study from Maryland and the US Department of Agriculture waivers that, in many cases, have introduced flexibility to allow for innovation. Also, we explore lessons learned from the pandemic with the goal of informing and strengthening future school nutrition policies for out-of-school time, such as over the summer.

Wellness School Assessment Tool Version 3.0: An Updated Quantitative Measure of Written School Wellness Policies

Schools play an important role in promoting student wellness. As directed by the Healthy Hunger-Free Kids Act, the US Department of Agriculture updated the requirements for written school wellness policies in 2016. The WellSAT (Wellness School Assessment Tool) is an online tool that provides a quantitative score for wellness policy comprehensiveness and strength. The WellSAT has been updated 3 times over the past decade to remain current with federal law and best practices. In this article, we describe the process of updating to WellSAT 3.0. The steps included: reviewing the language of each item linked to a federal provision; adding and deleting items based on frequencies from the National Wellness Policy Study and the empirical support for specific policies; gathering feedback from a survey of experts (N = 77) about best practices and measure usability; and establishing intercoder reliability in a national sample (N = 50) of policies. We conclude with recommendations and guidance for the use of WellSAT 3.0.

Implementing School-Based Policies to Prevent Obesity: Cluster Randomized Trial

INTRODUCTION

Healthier school environments can benefit students, and school wellness policies may result in meaningful enhancements. Schools participating in federal child nutrition programs must implement wellness policies as mandated by law. The primary study objective is to assess effectiveness of implementing school-based nutrition and physical activity policies on student BMI trajectories.

STUDY DESIGN

Cluster randomized trial using 2 × 2 factorial design.

SETTING/PARTICIPANTS

Twelve randomly selected schools in an urban district. Students were followed for 3 years through middle school, fifth to eighth grades (2011-2015, n=595 students, 92.3% participation, 85.2% retention).

INTERVENTION

Specific to randomized condition, support was provided for implementation of nutrition policies (e.g., alternatives to food-based rewards/celebrations) and physical activity policies (e.g., opportunities for physical activity during/after school).

MAIN OUTCOME MEASURES

Sex-/age-adjusted BMI percentile and BMI z-score; behavioral indicators. Data collected via standardized protocols.

RESULTS

Analyses followed intention-to-treat principles, with planned secondary analyses (conducted 2016-2018). Students at schools randomized to receive support for nutrition policy implementation had healthier BMI trajectories over time (F=3.20, p=0.02), with a greater magnitude over time and cumulatively significant effects 3 years post-intervention (β=-2.40, p=0.04). Overall, students at schools randomized to receive the nutrition intervention had an increase in BMI percentile of <1%, compared with students in other conditions, whereas BMI percentile increased 3%-4%. There was no difference in student BMI between those in schools with and without physical activity policy implementation. Examining behavioral correlates in eighth grade, students at schools randomized to the nutrition condition consumed fewer unhealthy foods and sugar-sweetened beverages, and ate less frequently at fast-food restaurants (all p<0.03).

CONCLUSIONS

This cluster randomized trial demonstrated effectiveness of providing support for implementation of school-based nutrition policies, but not physical activity policies, to limit BMI increases among middle school students. Results can guide future school interventions.

TRIAL REGISTRATION

This study is registered at www.clinicaltrials.gov NCT02043626.

Impact of the Smoothened inhibitor, IPI-926, on smoothened ciliary localization and Hedgehog pathway activity

A requisite step for canonical Hedgehog (Hh) pathway activation by Sonic Hedgehog (Shh) ligand is accumulation of Smoothened (Smo) to the primary cilium (PC). Activation of the Hh pathway has been implicated in a broad range of cancers, and several Smo antagonists are being assessed clinically, one of which is approved for the treatment of advanced basal cell carcinoma. Recent reports demonstrate that various Smo antagonists differentially impact Smo localization to the PC while still exerting inhibitory activity. In contrast to other synthetic small molecule Smo antagonists, the natural product cyclopamine binds to and promotes ciliary accumulation of Smo and “primes” cells for Hh pathway hyper-responsiveness after compound withdrawal. We compared the properties of IPI-926, a semi-synthetic cyclopamine analog, to cyclopamine with regard to potency, ciliary Smo accumulation, and Hh pathway activity after compound withdrawal. Like cyclopamine, IPI-926 promoted accumulation of Smo to the PC. However, in contrast to cyclopamine, IPI-926 treatment did not prime cells for hyper-responsiveness to Shh stimulation after compound withdrawal, but instead demonstrated continuous inhibition of signaling. By comparing the levels of drug-induced ciliary Smo accumulation with the degree of Hh pathway activity after compound withdrawal, we propose that a critical threshold of ciliary Smo is necessary for “priming” activity to occur. This “priming” appears achievable with cyclopamine, but not IPI-926, and is cell-line dependent. Additionally, IPI-926 activity was evaluated in a murine tumor xenograft model and a pharmacokinetic/pharmacodynamic relationship was examined to assess for in vivo evidence of Hh pathway hyper-responsiveness. Plasma concentrations of IPI-926 correlated with the degree and duration of Hh pathway suppression, and pathway activity did not exceed baseline levels out to 96 hours post dose. The overall findings suggest that IPI-926 possesses unique biophysical and pharmacological properties that result in Hh pathway inhibition in a manner that differentiates it from cyclopamine.

Discovery of a potent and orally active hedgehog pathway antagonist (IPI-926)

Recent evidence suggests that blocking aberrant hedgehog pathway signaling may be a promising therapeutic strategy for the treatment of several types of cancer. Cyclopamine, a plant Veratrum alkaloid, is a natural product antagonist of the hedgehog pathway. In a previous report, a seven-membered D-ring semisynthetic analogue of cyclopamine, IPI-269609 (2), was shown to have greater acid stability and better aqueous solubility compared to cyclopamine. Further modifications of the A-ring system generated three series of analogues with improved potency and/or solubility. Lead compounds from each series were characterized in vitro and evaluated in vivo for biological activity and pharmacokinetic properties. These studies led to the discovery of IPI-926 (compound 28), a novel semisynthetic cyclopamine analogue with substantially improved pharmaceutical properties and potency and a favorable pharmacokinetic profile relative to cyclopamine and compound 2. As a result, complete tumor regression was observed in a Hh-dependent medulloblastoma allograft model after daily oral administration of 40 mg/kg of compound 28.

Development of 17-allylamino-17-demethoxygeldanamycin hydroquinone hydrochloride (IPI-504), an anti-cancer agent directed against Hsp90

Heat shock protein 90 (Hsp90) is an emerging therapeutic target of interest for the treatment of cancer. Its role in protein homeostasis and the selective chaperoning of key signaling proteins in cancer survival and proliferation pathways has made it an attractive target of small molecule therapeutic intervention. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), the most studied agent directed against Hsp90, suffers from poor physical-chemical properties that limit its clinical potential. Therefore, there exists a need for novel, patient-friendly Hsp90-directed agents for clinical investigation. IPI-504, the highly soluble hydroquinone hydrochloride derivative of 17-AAG, was synthesized as an Hsp90 inhibitor with favorable pharmaceutical properties. Its biochemical and biological activity was profiled in an Hsp90-binding assay, as well as in cancer-cell assays. Furthermore, the metabolic profile of IPI-504 was compared with that of 17-AAG, a geldanamycin analog currently in clinical trials. The anti-tumor activity of IPI-504 was tested as both a single agent as well as in combination with bortezomib in myeloma cell lines and in vivo xenograft models, and the retention of IPI-504 in tumor tissue was determined. In conclusion, IPI-504, a potent inhibitor of Hsp90, is efficacious in cellular and animal models of myeloma. It is synergistically efficacious with the proteasome inhibitor bortezomib and is preferentially retained in tumor tissues relative to plasma. Importantly, it was observed that IPI-504 interconverts with the known agent 17-AAG in vitro and in vivo via an oxidation-reduction equilibrium, and we demonstrate that IPI-504 is the slightly more potent inhibitor of Hsp90.

Microvascular effects of corticotropin-releasing hormone in human skin vary in relation to estrogen concentration during the menstrual cycle

Females have a significantly greater life expectancy than males, which in part may be due to the cardio-protective effects of the female sex hormone, estrogen, on vascular function. However, the sex-specific mechanisms contributing to these differences are complex and not fully understood. Previously we have reported that corticotropin-releasing hormone (CRH) has potent dilator effects in the female skin circulation via mast cell degranulation. Furthermore the dilator response to CRH was more enhanced in females than in age-matched males, suggesting that estrogens may be involved. In this study we examined whether CRH-induced dilation and endothelial cell-dependent dilation in the skin circulation of pre-menopausal females were associated with changes in estrogen during the menstrual cycle. CRH-induced dilation (1 nM) was enhanced in the presence of high circulating concentrations of estrogen and a positive correlation was identified between CRH-induced dilation and plasma estrogen concentrations. Endothelial cell-dependent dilation was examined using acetylcholine. Acetylcholine-induced dilation (1 nM) was not correlated with circulating concentrations of estrogen. These data suggest the variation in CRH-induced dilation in the skin microvasculature during the menstrual cycle may be due to estrogenic effects on mast cell function and not due to direct changes in endothelial cell function.

G-quadruplexes as therapeutic targets

The ends of chromosomes (telomeres) consist of tandem repeats of guanine-rich sequences. In eukaryotics, telomeric DNA is single stranded for the final few hundred bases. These single-stranded sequences can fold into a variety of four-stranded structures (quadruplexes) held together by quartets of hydrogen-bonded guanine bases. The reverse transcriptase enzyme telomerase is responsible for maintaining telomeric DNA length in over 85% of cancer cells by catalyzing the synthesis of further telomeric repeats. Its substrate is the single-stranded 3'-telomeric end. Inhibition of telomere maintenance can be achieved by stabilization of a quadruplex structure for the telomere end. A variety of small molecules have been devised to achieve this, ranging from anthraquinones to porphyrins, acridines, and complex polycyclic systems. Structural and mechanistic aspects of these quadruplex complexes are reviewed here, together with a discussion of the issues of selectivity/potency for quadruplex DNAs vs duplex DNA.

An intact NEDD8 pathway is required for Cullin-dependent ubiquitylation in mammalian cells

Skp1-Cdc53/Cul1-F-box (SCF) complexes constitute a class of E3 ubiquitin ligases. Recently, a multiprotein complex containing pVHL, elongin C and Cul2 (VEC) was shown to structurally and functionally resemble SCF complexes. Cdc53 and the Cullins can become covalently linked to the ubiquitin-like molecule Rub1/NEDD8. Inhibition of neddylation inhibits SCF function in vitro and in yeast and plants. Here we show that ongoing neddylation is likewise required for VEC function in vitro and for the degradation of SCF and VEC targets in mammalian cells. Thus, neddylation regulates the activity of two specific subclasses of mammalian ubiquitin ligases.

Vasoactive effects of 8-epi-prostaglandin F(2alpha)in isolated human placental conduit and resistance blood vessels in vitro

The effects of 8-epi-prostaglandin F(2alpha)(8-epi-PGF(2alpha)) and the thromboxane A(2)-mimetic U46619 were examined on isolated human fetal placental arteries obtained from normal pregnancies and from those complicated by pre-eclampsia. The effects of these agents were examined on both conduit and resistance arteries. 8-epi-PGF(2alpha)was found to be markedly less potent than U46619 in constricting both size vessels. Vasoconstrictor EC(50)s for 8-epi PGF(2alpha)were 4.10x10(-7) m (2.02-8.35x10(-7) m) (mean, 95 per cent CI and 2.05x10(-6) m (0.43-9.89 x10(-6) m) in conduit and resistance arteries, respectively. The maximum vasoconstriction produced by 8-epi-PGF(2alpha)(112+/-17 per cent), (relative to maximum KCl induced vasoconstriction) in conduit vessels was significantly less than that caused by U46619 (152+/-20 per cent). In resistance vessels the maximum vasoconstrictor effects to 8-epi-PGF(2alpha)(208+/-10 per cent) and U46619 (201+/-19 per cent) were similar, and in both cases significantly greater than the maximal effects seen in conduit vessels. U46619 displayed a similar vasoconstrictor potency in both conduit (EC(50)=1.21x10(-9) m, 0.58-2.51x10(-9) m) and resistance arteries [EC(50)=5.95x10(-9) m, (0.81-43.60x10(-9) m] as was found for 8-epi PGF(2alpha). 8-epi-PGF(2alpha)was equipotent in resistance arteries obtained from women with severely pre-eclamptic pregnancies (EC(50)=1.25x10(-6) m, 0.25-6.17x10(-6) m) compared with normotensive controls. However, the maximum vasoconstrictor effect induced by 8-epi-PGF(2alpha)in placental resistance arteries was significantly reduced (99+/-20 per cent) in vessels obtained from severely pre-eclamptic compared with normal pregnancies. These results indicate that 8-epi-PGF(2alpha)displays differential vasoconstrictor activity in the fetal-placental vasculature. Furthermore the vasoconstrictor effects of 8-epi-PGF(2alpha)are reduced in pre-eclampsia, the effect being selective to placental resistance vessels. This reduction may occur as a result of more serious disturbances in the placental microcirculation with the disease process in pre-eclampsia.

Effects of nitrovasodilators on the human fetal-placental circulation in vitro

This study examines the vasorelaxation of isolated human placental chorionic plate arteries and the perfused fetal-placental vasculature, in vitro, to a variety of nitrovasodilator compounds including glyceryl trinitrate (GTN) sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), S-nitroso-N-glutathione (SNG) and NaNO(2). The effects of these compounds were also examined under conditions of high (>450 mmHg) and low oxygen (<50 mmHg) tension. In a separate series of experiments the effects of GTN and NaNO(2)were further investigated with addition of the antioxidants cysteine (100 microm), glutathione (100 microm) or superoxide dismutase (SOD) (30 I.U./ml). The order of nitrovasodilator potency, when added directly to isolated fetal vessels was GTN=SNP>SNAP=SNG>NaNO(2). The order under low oxygen tension was similar, GTN=SNP>SNG= SNAP>or=NaNO(2). SNG ( approximately fourfold) and NaNO(2)( approximately 50-fold) were significantly more potent under low oxygen conditions. Cysteine, glutathione and SOD were without effect on GTN induced vasodilatation. However, all three agents significantly enhanced (six- to ninefold) the effects of NaNO(2)under similar conditions. When infused directly into the fetal-placental circulation during in vitro perfusion experiments the order of potency was GTN>SNP>or=SNG>or=SNAP>or=NaNO(2). When the nitrovasodilators were infused indirectly via the maternal intervillous space the order of potency was GTN>or=SNP>or=NaNO(2)>or=SNAP=SNG. Our observations suggest that there are important differences in the action of different classes of nitrovasodilator compounds on the fetal-placental circulation. The changes observed with SNG and NaNO(2)may be influenced by levels of tissue oxygenation.

Structural characterization of a guanine-quadruplex ligand complex

The inhibition of telomerase by molecules such as disubstituted amidoanthraquinones is believed to be due to their stabilization of guanine-quadruplex complexes. The characterization is reported of a complex with the intermolecular parallel quadruplex formed from the sequence TGGGGT and a 1,4-bis-piperidino amidoanthraquinone. Crystals obtained did not give single-crystal diffraction; the fiber-like pattern has been interpreted in terms of a repeating unit with four guanine-quartets and two stacked/intercalated ligand molecules. The two categories of possible structures for the complex consistent with this interpretation have been examined by molecular dynamics simulations, with fully solvated environments and 1000 ps simulation times. The two central guanine-quartets in the intercalation model rapidly became highly distorted, whereas the two types of models with ligand stacked externally on the ends of the quadruplex remained very stable. It was concluded that the externally bound ligand complexes best represent the structure of this quadruplex complex, in agreement with earlier NMR results on related systems.

A novel inhibitor of human telomerase derived from 10H-indolo[3,2-b]quinoline

The bis-dimethylaminoethyl derivative of quindoline (10H-indolo[3,2-b]quinoline), an alkaloid from the West African shrub Cryptolepis sanguinolenta, has been synthesised. This has been shown to have modest cytotoxicity, as well as inhibitory activity against the telomerase enzyme. It is hypothesised that the latter activity is due to stabilisation of an intermediate guanine-quadruplex complex, in accordance with computer modelling.

Fetal placental vascular responses to corticotropin-releasing hormone in vitro. Effects of variation in oxygen tension

In this study, using the human placenta perfused in vitro with Krebs' bicarbonate solution, we have examined the effects of changes in oxygen tension on the vasoreactivity of fetal placental blood vessels to corticotropin releasing hormone (CRH). Vasodilatory responses to human synthetic CRH were measured during sub-maximal vasoconstriction of the fetal placental circulation with prostaglandin F(2alpha)(PGF(2alpha)) (1-100 micrometer). Decreases in fetal placental arterial perfusion pressure (FAP) were obtained with CRH under conditions of high oxygen or low oxygen tension, >/=450 mmHg and </=50 mmHg, respectively. Secretion of CRH into the maternal and fetal placental circulations was measured during changes in oxygen tension in normal placentae and placentae from abnormal pregnancies complicated by pre-eclampsia. The change from high to low oxygen perfusion resulted in a small increase in the basal perfusion pressure (21+/-3.6 to 28.3+/-2.6 mmHg; (P</= 0.001, Student's paired t -test). During high oxygen perfusion, CRH (0. 3-3000 p m) caused a concentration dependent reduction of the PGF(2alpha)induced increase in FAP. However, during low oxygen perfusion, the vasodilatory effects of CRH were completely inhibited (P</= 0.05, regression analysis, ANOVA). The effect of the NO synthase inhibitor l -nitro-omega-arginine methyl ester (l -NAME, 1-100 micrometer), on basal FAP during high and low oxygen conditions was also established. Low oxygen perfusion significantly attenuated l -NAME-induced increases in perfusion pressure (P</= 0.05, regression analysis, ANOVA). Low oxygen perfusion was associated with an increase in CRH secretion into the maternal but not fetal circulation. CRH release into either the maternal or fetal circulations of abnormal placentae were not significantly different from normal controls. In conclusion CRH-induced vasodilatation of the fetal placental vasculature in vitro is inhibited during low oxygen perfusion. This effect may be related to reduced NO production. Reduced CRH induced vasodilation is associated with increased secretion of the CRH into the maternal but not fetal circulation.

Evidence for a hormonal tactic maximizing green turtle reproduction in response to a pervasive ecological stressor

Mortality of breeding sea turtles due to excessive heat exposure after nesting activities is an unusual feature of the Raine Island green turtle rookery. Breeding turtles that fail to return to the ocean after oviposition can experience increasing body temperatures that exceed lethal limits (>39 degrees C) as ambient temperatures rise after sunrise. We investigated how acute increases in body temperature influenced plasma corticosterone (B) concentrations of individual turtles. Furthermore, interactions between progesterone (P) and testosterone (T) and increasing body temperature and the glucocorticoid corticosterone were examined for negative correlations. Breeding green turtles exhibited a 16-fold mean increase in plasma corticosterone concentration as body temperature (cloacal) rose from 28.2 to 40.7 degrees C in less than 6 h. However, the absolute increase in plasma B was small and much less than expected, despite the lethal stressor. Comparatively, the maximal B response to lethal heat stress was similar to plasma B concentrations obtained from breeding female turtles exposed to 8 h of capture stress. However, the maximal B response of breeding turtles exposed to heat and capture stressors was significantly less than the B response of nonbreeding adult female turtles subjected to an 8-h capture stressor. No negative correlations were observed between plasma T and plasma B, between plasma T and body temperature, between plasma P and plasma B, or between plasma P and body temperature. Our findings provide further evidence that reduced adrenocortical function operates in breeding green turtles in the presence of even the most pervasive of environmental stressors.

Nedd8 modification of cul-1 activates SCF(beta(TrCP))-dependent ubiquitination of IkappaBalpha

Regulation of NF-kappaB occurs through phosphorylation-dependent ubiquitination of IkappaBalpha, which is degraded by the 26S proteasome. Recent studies have shown that ubiquitination of IkappaBalpha is carried out by a ubiquitin-ligase enzyme complex called SCF(beta(TrCP)). Here we show that Nedd8 modification of the Cul-1 component of SCF(beta(TrCP)) is important for function of SCF(beta(TrCP)) in ubiquitination of IkappaBalpha. In cells, Nedd8-conjugated Cul-1 was complexed with two substrates of SCF(beta(TrCP)), phosphorylated IkappaBalpha and beta-catenin, indicating that Nedd8-Cul-1 conjugates are part of SCF(beta(TrCP)) in vivo. Although only a minute fraction of total cellular Cul-1 is modified by Nedd8, the Cul-1 associated with ectopically expressed betaTrCP was highly enriched for the Nedd8-conjugated form. Moreover, optimal ubiquitination of IkappaBalpha required Nedd8 and the Nedd8-conjugating enzyme, Ubc12. The site of Nedd8 ligation to Cul-1 is essential, as SCF(beta(TrCP)) containing a K720R mutant of Cul-1 only weakly supported IkappaBalpha ubiquitination compared to SCF(beta(TrCP)) containing WT Cul-1, suggesting that the Nedd8 ligation of Cul-1 affects the ubiquitination activity of SCF(beta(TrCP)). These observations provide a functional link between the highly related ubiquitin and Nedd8 pathways of protein modification and show how they operate together to selectively target the signal-dependent degradation of IkappaBalpha.

Structure-activity relationships among guanine-quadruplex telomerase inhibitors

The ribonucleoprotein telomerase is responsible for maintaining the length of telomeric ends of chromosomes in tumour cells. It is activated in over 85% of the tumour cells, and is emerging as a major target for cancer chemotherapy. A range of molecules containing tricyclic and tetracyclic aromatic chromophores has been shown to inhibit the telomerase enzyme system at the micromolar level. There is evidence that they do so via stabilisation of a guanine-quadruplex structure, which provides a stop signal for further telomere elongation. The known structure-activity relationships for these compounds are summarised, and pointers for the development of future molecules with enhanced selectivity are described.

Molecular modeling studies on G-quadruplex complexes of telomerase inhibitors: structure-activity relationships

Inhibition of the ability of the enzyme telomerase to add telomeric repeats to the end of chromosomes is a novel target for potential anticancer therapy. This paper examines the hypothesis that compounds possessing a planar aromatic chromophore inhibit telomerase via stabilization of, and binding to, a folded guanine quadruplex structure. Two series of telomerase inhibitors have been designed based on the 2,6-disubstituted amidoanthracene-9,10-dione and 3,6-disubstituted acridine chromophores in order to investigate structure-activity relationships between biological activity and substituent group size. The relative binding energies between these compounds and the folded human telomere DNA quadruplex were determined using molecular simulation methods, involving explicitly solvated structures. The results obtained are in excellent agreement with the biological activity as measured in vitro using a modified TRAP assay and in general agreement with the ranking order of binding enthalpies found in isothermal titration calorimetry studies. This broad agreement provides strong support for the hypothesis that guanine quadruplexes are the primary target for telomerase inhibitors with extended planar chromophores.

Crystal structure of human DT-diaphorase: a model for interaction with the cytotoxic prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954)

The crystal structure of human DT-diaphorase (NAD(P)H oxidoreductase (quinone); EC 1.6.99.2) has been determined to 2.3 A resolution. There are only minor differences in shape and volume between the active sites of the rat and human enzymes and in the hydrophobic environment in the vicinity of the substrate. The isoalloxazine ring of the bound FAD is more buried in the human structure. Molecular modeling was used to examine optimal positions for the antitumor prodrug CB1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide) in both the human and rat enzyme active sites. This suggests that the position of CB1954 in the active site of the human enzyme is very similar to that in the rat, although there are detailed differences in the predicted patterns of hydrogen bonding between side chains and the drug. Some of the differences are a consequence of the shift in position for the FAD molecule and may contribute to the observed differences in rate of the two-electron reduction of CB1954.

A new model of cancer cachexia: contribution of the ubiquitin-proteasome pathway

A new model of cachexia is described in which muscle protein metabolism related to the ubiquitin-proteasome pathway was investigated. Cloning of the colon-26 tumor produced a cell line, termed R-1, which induced cytokine (noninterleukin-1beta, interleukin-6 and tumor necrosis factor-alpha)-independent cachexia. Implantation of R-1 cells in mice elicited significant (20-30%) weight loss and decreased blood glucose by 70%, and adipose tissue levels declined by 95% and muscle weights decreased by 20-25%. Food intake was unaffected. The decrease in muscle weight reflected a decline in insoluble, but not soluble, muscle protein that was associated with a significant increase in net protein degradation. The rate of ubiquitin conjugation of proteins was significantly elevated in muscles of cachectic mice. Furthermore, the proteasome inhibitor lactacystin blocked the increase in protein breakdown but had no significant effect on proteolysis. Several markers of the ubiquitin-proteasome pathway, E2(14k) mRNA and E2(14k) protein and ubiquitin-protein conjugates, were not elevated. Future investigations with this new model should gain further insights into the mechanisms of cachexia and provide a background to evaluate novel and more efficacious therapies.

Stabilization of DNA triple helices by a series of mono- and disubstituted amidoanthraquinones

We have used quantitative DNase I footprinting to measure the relative affinities of four disubstituted and two monosubstituted amidoanthraquinone compounds for intermolecular DNA triplexes, and have examined how the position of the attached base-functionalized substituents affects their ability to stabilize DNA triplexes. All four isomeric disubstituted derivatives examined stabilize DNA triplexes at micromolar or lower concentrations. Of the compounds studied the 2,7-disubstituted amidoanthraquinone displayed the greatest triplex affinity. The order of triplex affinity for the other disubstituted ligands decreases in the order 2,7 > 1,8 = 1,5 > 2,6, with the equivalent monosubstituted compounds being at least an order of magnitude less efficient. The 1,5-disubstituted derivative also shows some interaction with duplex DNA. These results have been confirmed by molecular modelling studies, which provide a rational basis for the structure-activity relationships. These suggest that, although all of the compounds bind through an intercalative mode, the 2,6, 2,7 and 1,5 disubstituted isomers bind with their two side groups occupying adjacent triplex grooves, in contrast with the 1,8 isomer which is positioned with both side groups in the same triplex groove.

Design, synthesis and evaluation of human telomerase inhibitors based upon a tetracyclic structural motif

There is currently significant interest in the development of inhibitors of human telomerase for the treatment of cancer. We describe here the design and synthesis of a new class of mono-substituted small-molecule inhibitors of human telomerase based upon a tetracyclic structural motif. In contrast to the structurally related molecule 9-hydroxyellipticine, recently shown to inhibit telomerase activity in cell cultures but found to be inactive in a cell-free system, we demonstrate direct inhibition of the telomerase enzyme by the tetracyclic compounds in a modified cell-free TRAP assay. The most potent compounds exhibit activity in the low micromolar range and are thus comparable with some of the more active small-molecule telomerase inhibitors based on planar aromatic chromophores, previously described by ourselves and others. These compounds may represent useful leads for the development of more potent inhibitors of human telomerase.

2,7-Disubstituted amidofluorenone derivatives as inhibitors of human telomerase

Telomerase is a major new target for the rational design of novel anticancer agents. We have previously identified anthraquinone-based molecules capable of inhibiting telomerase by stabilizing G-quadruplex structures formed by the folding of telomeric DNA. In the present study we describe the synthesis and biological evaluation of a series of analogous fluorenone-based compounds with the specific aims of, first, determining if the anthraquinone chromophore is a prerequisite for activity and, second, whether the conventional cytotoxicity inherent to anthraquinone-based molecules may be reduced by rational design. This fluorenone series of compounds exhibits a broad range of telomerase inhibitory activity, with the most potent inhibitors displaying levels of activity (8-12 microM) comparable with other classes of G-quadruplex-interactive agents. Comparisons with analogous anthraquinone-based compounds reveal a general reduction in the level of cellular cytotoxicity. Molecular modeling techniques have been used to compare the interaction of fluorenone- and analogous anthraquinone-based inhibitors with a human G-quadruplex structure and to rationalize their observed biological activities.

U46619-mediated vasoconstriction of the fetal placental vasculature in vitro in normal and hypertensive pregnancies

OBJECTIVES

To measure in-vitro responses to the thromboxane A2 (TxA2) mimetic U46619 in the fetal placental vasculature of human placentae from normotensive women and those with pre-eclampsia. Furthermore, to compare fetal vascular responses to endothelin-1,5-hydroxytryptamine, potassium chloride (KCl) and prostacyclin (PGI2) in placentae from normal or pre-eclamptic pregnancies.

METHODS

Single placental lobules of intact placentae were bilaterally perfused in situ (fetal and maternal) with constant flows of Krebs' solution. Changes in fetal arterial perfusion pressure during intra-arterial infusion of vasoactive agents were recorded. Fetal placental vasoconstrictor concentration response curves were obtained to U46619 (0.01-300 nmol/l), endothelin-1 (0.4-160 nmol/l), KCl (3-300 mmol/l) and 5-hydroxytryptamine (0.03-30 mumol/l). In addition, vasodilator concentration response curves were obtained for PGI2 (1.2-350 nmol/l) in the fetal placental circulation during submaximal increases in perfusion pressure with prostaglandin F2 alpha (PGF2 alpha; 0.7-2.0 mumol/l).

RESULTS

The maximum increase in perfusion pressure caused by U46619 in placentae from normotensive women was 194 +/- 25 mmHg. The maximum response to U46619 was significantly reduced in the placentae from women with pre-eclampsia (104 +/- 21 mmHg). In contrast, there were no differences in constrictor responses to endothelin-1,5-hydroxytryptamine and KCl, or in dilator responses to PGI2 in placentae obtained from either normotensive women or those with pre-eclampsia.

CONCLUSION

TxA2 receptor-mediated vasoconstriction is reduced in the fetal vasculature of placentae from women with pre-eclampsia, possibly to compensate for the increased levels of TxA2 seen in these conditions.

Human, rat and crocodile liver microsomal monooxygenase activities measured using diazepam and nifedipine: effects of CYP3A inhibitors and relationship to immunochemically detected CYP3A apoprotein

Nifedipine oxidase and diazepam C3-hydroxylase were tested as activities for selectively measuring CYP3A enzymes using liver microsomes from male and female human organ donors, male and female Wistar rats and male and female estuarine crocodiles. The association between CYP3A enzymes and these monooxygenations was confirmed for the human samples. Male rat samples had lower specific contents of CYP3A apoprotein than the human samples but had equivalent (nifedipine) or higher (diazepam) monooxygenase specific activities. CYP3A apoprotein was undetectable in female rat samples which had very low activities towards both substrates. Enzyme inhibition studies showed that diazepam C3-hydroxylase of male rat liver was attributable to CYP3A but corresponding results for female rats suggested a contribution from non-CYP3A enzyme. Western blotting with immunochemical detection using anti-CYP3A4 IgG suggested the presence of putative CYP3A apoprotein in male and female crocodile liver samples and inhibition studies with diazepam as substrate suggested the presence of CYP3A subfamily monooxygenase activity in these enzyme preparations. Results for nifedipine oxidase with male and female rat liver and male crocodile liver suggested major contributions to catalysis from non-CYP3A enzymes. Inhibition studies suggested that a higher proportion of nifedipine oxidase in female crocodile liver may be attributable to the putative CYP3A enzyme(s) than in male crocodile liver. These results show the need for care in the assessment of CYP3A activity of fractionated tissues when using these substrates in cross-species studies and where gender is a variable.

Vasodilator actions of urocortin and related peptides in the human perfused placenta in vitro

Urocortin, is a recently isolated peptide belonging to the CRH family that binds with high affinity to the CRH2 receptor. Like CRH, urocortin causes hypotension in the rat, but its vasoactive actions have not yet been studied in the human. We have compared the vasoactive properties of urocortin, CRH, and urotensin-1 in the human fetal placental vasculature in vitro. Single placental lobules were bilaterally perfused (maternal and fetal sides, 5 mL/min each; 95% O2-5% CO2; 37 C), and changes in fetal arterial perfusion pressure were recorded. Submaximal vasoconstriction was induced by PGF2alpha (4+/-0.7 micromol/L), which increased perfusion pressure from 19.6+/-1.4 to 100.7+/-3.1 mm Hg (n=38; P < 0.001). Subsequent fetal arterial infusion of urocortin (0.001-1 nmol/L) caused concentration-dependent vasodilatation. Urocortin was equipotent with urotensin-1 and 25 times more potent than CRH in causing vasodilatation. Nevertheless, the maximum vasodilator responses to each of the peptides were similar (P > 0.05). The CRH receptor antagonist, alpha-helical CRH-(9-41) (0.2 nmol/L) significantly attenuated the vasodilatation produced by urocortin, urotensin-1, and CRH (P < 0.05). These results indicate a possible physiological role for urocortin in the modulation of human fetal placental vascular tone by activation of CRH2-like receptors.

Human telomerase inhibition by regioisomeric disubstituted amidoanthracene-9,10-diones

Telomerase is an attractive target for the design of new anticancer drugs. We have previously described a series of 1,4- and 2, 6-difunctionalized amidoanthracene-9,10-diones that inhibit human telomerase via stabilization of telomeric G-quadruplex structures. The present study details the preparation of three further, distinct series of regioisomeric difunctionalized amidoanthracene-9,10-diones substituted at the 1,5-, 1,8-, and 2,7-positions, respectively. Their in vitro cytotoxicity and Taq DNA polymerase and human telomerase inhibition properties are reported and compared with those of their 1,4- and 2,6-isomers. Potent telomerase inhibition (telIC50 values 1.3-17.3 microM) is exhibited within each isomeric series. In addition, biophysical and molecular modeling studies have been conducted to examine binding to the target G-quadruplex structure formed by the folding of telomeric DNA. These studies indicate that the isomeric diamidoanthracene-9,10-diones bind to the human telomeric G-quadruplex structure with a stoichiometry of 1:1. Plausible G-quadruplex-ligand complexes have been identified for each isomeric family, with three distinct modes of intercalative binding being proposed. The exact mode of intercalative binding is dictated by the positional placement of substituent side chains. Furthermore, in contrast to previous studies directed toward triplex DNA, it is evident that stringent control over positional attachment of substituents is not a necessity for effective telomerase inhibition.

Effects of Bufo marinus skin toxins on human fetal extracorporeal blood vessels

The effects of extracts of Bufo marinus toad skin toxin on human isolated umbilical arterial rings and the fetal vessels of perfused placentae were examined and compared with those of ouabain, an inhibitor of Na+/K(+)-ATPase. Umbilical artery rings and fetal vessels of the perfused placenta responded to extracts, or ouabain, with constriction which persisted after the removal of each agent. Extraction of the skin, using various solvents, revealed that the umbilical artery constriction was due mainly to the effects of water-soluble, polar compounds. Fractionation of a water extract and bioassay on the rat isolated aorta revealed maximum vasoconstrictor activity in a low mol. wt fraction. During Na+/K(+)-ATPase inactivation in the fetal circulation of the human placenta, by perfusion with K(+)-free Kreb's solution, reactivation of the enzyme by K+ infusion caused vasodilatation. This effect was inhibited both by water extracts of load skin and by ouabain. Thus, properties of some of the endogenous compounds in B. marinus skin resemble those of ouabain, by causing persistent constriction of human fetal blood vessels. A component of the vasoconstrictor response probably results from inhibition of vascular smooth muscle Na+/K(+)-ATPase, but it is likely that a contribution is also made by additional vasoconstrictor substances contained in B. marinus toxin.

Tumor necrosis factor alpha-induced E-selectin expression is activated by the nuclear factor-kappaB and c-JUN N-terminal kinase/p38 mitogen-activated protein kinase pathways

E-selectin expression by endothelium is crucial for leukocyte recruitment during inflammatory responses. Transcriptional regulation of the E-selectin promoter by tumor necrosis factor alpha (TNFalpha) requires multiple nuclear factor-kappaB (NF-kappaB) binding sites and a cAMP-responsive element/activating transcription factor-like binding site designated positive domain II (PDII). Here we characterize the role of the stress-activated family of mitogen-activated protein (MAP) kinases in induced expression of this adhesion molecule. By UV cross-linking and immunoprecipitation, we demonstrated that a heterodimer of transcription factors ATF-2 and c-JUN is constitutively bound to the PDII site. TNFalpha stimulation of endothelial cells induces transient phosphorylation of both ATF-2 and c-JUN and induces marked activation of the c-JUN N-terminal kinase (JNK1) and p38 but not extracellular signal-regulated kinase (ERK1). JNK and p38 are constitutively present in the nucleus, and DNA-bound c-JUN and ATF-2 are stably contacted by JNK and p38, respectively. MAP/ERK kinase kinase 1 (MEKK1), an upstream activator of MAP kinases, increases E-selectin promoter transcription and requires an intact PDII site for maximal induction. MEKK1 can also activate NF-kappaB -dependent gene expression. The effects of dominant interfering forms of the JNK/p38 signaling pathway demonstrate that activation of these kinases is critical for cytokine-induced E-selectin gene expression. Thus, TNFalpha activates two signaling pathways, NF-kappaB and JNK/p38, which are both required for maximal expression of E-selectin.

Postinduction transcriptional repression of E-selectin and vascular cell adhesion molecule-1

TNF-alpha induction of the E-selectin and vascular cell adhesion molecule-1 (VCAM-1) genes leads to transient accumulation of high levels of mRNA in endothelial cells. The increase in these mRNAs after induction is due to an increase in the rate of gene transcription, which is maintained for several hours in the continuous presence of cytokine. Cytokine-induced transcriptional activation of these genes requires the transcription factor, nuclear factor-kappaB. Following removal of TNF-alpha, there is rapid postinduction transcriptional repression common to both of these genes. The repression is protein synthesis dependent and correlates with protein synthesis-dependent loss of both the p50 and p65 subunits of nuclear factor-kappaB from the nucleus. IkappaBalpha is capable of specifically displacing endothelial-derived heterodimeric p50/p65 from the E-selectin and VCAM-1 kappaB elements, while having no effect on binding of p50 homodimer. In the presence of agents that block proteasomal degradation of IkappaBalpha, endogenous IkappaBalpha can be visualized in the nucleus of both resting and TNF-alpha-activated endothelial cells. Endogenous IkappaBalpha is readily detected in the nucleus of HeLa cells, and its nuclear localization is increased following removal of TNF-alpha. Repression of E-selectin and VCAM-1 transcription following cytokine removal requires the loss of nuclear p50 and p65, and involves IkappaBalpha. This postinduction transcription repression mechanism may be one component of a program that prevents inappropriate and prolonged expression of adhesion molecules.

Postinduction transcriptional repression of E-selectin and vascular cell adhesion molecule-1

TNF-alpha induction of the E-selectin and vascular cell adhesion molecule-1 (VCAM-1) genes leads to transient accumulation of high levels of mRNA in endothelial cells. The increase in these mRNAs after induction is due to an increase in the rate of gene transcription, which is maintained for several hours in the continuous presence of cytokine. Cytokine-induced transcriptional activation of these genes requires the transcription factor, nuclear factor-kappaB. Following removal of TNF-alpha, there is rapid postinduction transcriptional repression common to both of these genes. The repression is protein synthesis dependent and correlates with protein synthesis-dependent loss of both the p50 and p65 subunits of nuclear factor-kappaB from the nucleus. IkappaBalpha is capable of specifically displacing endothelial-derived heterodimeric p50/p65 from the E-selectin and VCAM-1 kappaB elements, while having no effect on binding of p50 homodimer. In the presence of agents that block proteasomal degradation of IkappaBalpha, endogenous IkappaBalpha can be visualized in the nucleus of both resting and TNF-alpha-activated endothelial cells. Endogenous IkappaBalpha is readily detected in the nucleus of HeLa cells, and its nuclear localization is increased following removal of TNF-alpha. Repression of E-selectin and VCAM-1 transcription following cytokine removal requires the loss of nuclear p50 and p65, and involves IkappaBalpha. This postinduction transcription repression mechanism may be one component of a program that prevents inappropriate and prolonged expression of adhesion molecules.

Actions of magnesium, nifedipine and clonidine on the fetal vasculature of the human placenta

The anticonvulsant magnesium and the antihypertensives clonidine and nifedipine are extensively used for the clinical treatment of preeclampsia and eclampsia. Little, however, is known about the possible effects of these agents on human fetal-placental vascular resistance. We therefore examined the actions of these agents on the human fetal placental vascular bed in vitro relating the concentrations causing any vasoactive effects to the maternal blood levels attained during treatment. Placentas (n = 24) were obtained within 20 minutes of delivery from women (aged 30.2 +/- 0.9 years). In each a placental lobule was bilaterally perfused with Krebs' solution (5 mL/minute, 37 degrees C, 95% O2, 5% CO2) and fetal arterial inflow pressure (FAP) monitored. Submaximal vasoconstriction of the fetal vascular bed was induced by continuous infusion of prostaglandin F2 alpha (4.2 +/- 0.5 microM) which increased FAP from 25.9 +/- 3.9 to 95.1 +/- 6.2 mm Hg. Using a group of placentas for each drug, the effects of MgCl2, nifedipine and clonidine, were examined. Magnesium (0.3-100 mM) (n = 4) dilated the placental fetal circulation with an IC50 of 8.1 mM and a maximal response of 89.7 +/- 3.6% (n = 4). This effect of Mg2+ was not changed during concomitant infusion of the cyclo-oxygenase inhibitor, indomethacin (3 microM). Nifedipine (3-10,000 nM) also produced vasodilatation (maximum response 42 +/- 9%, n = 5). Clonidine (3-1,000 nM) caused no significant change (p < 0.05 n = 5) in vascular resistance (maximum response 11.2-5.7%) relaxation), when compared to controls. Thus in concentrations likely to be therapeutically present in maternal blood, magnesium causes a greater degree of placental fetal vasodilatation than does nifedipine, whereas clonidine is unlikely to have any effect on fetal placental vascular resistance.

Salicylates inhibit I kappa B-alpha phosphorylation, endothelial-leukocyte adhesion molecule expression, and neutrophil transmigration

The expression of leukocyte adhesion molecules on endothelial cells is induced by TNF-alpha and other inflammatory cytokines. This induction of endothelial-leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 requires the transcription factor nuclear factor-kappa B (NF-kappa B). Recent work has suggested that some nonsteroidal anti-inflammatory agents, including sodium salicylate and aspirin, can inhibit NF-kappa B-dependent gene activation. We studied the effects of salicylates on expression of adhesion molecules in HUVECs. We found that sodium salicylate inhibited activation of NF-kappa B (p50/p65 and p65/p65) by preventing phosphorylation and subsequent degradation of the inhibitor 1 kappa B-alpha. Salicylate treatment had no effect on TNF-alpha-induced phosphorylation of the transcription factor ATF-2. Salicylate blocked the TNF-alpha-induced increase in mRNA levels of adhesion molecules and gave a dose-dependent inhibition of TNF-alpha-induced surface expression of vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 with higher doses required to inhibit endothelial-leukocyte adhesion molecule-1 expression. Indomethacin, a nonsalicylate cyclooxygenase inhibitor, had no effect on surface expression of adhesion molecules, suggesting that the effects were not due to inhibition of cyclooxygenase. Treatment of endothelial cell monolayers with sodium salicylate inhibited transendothelial migration of neutrophils but had no significant effect on neutrophil adhesion under flow conditions. The clinical importance of high-dose salicylates in inflammation may be due, in part, to the ability to prevent expression of inducible adhesion molecules and recruitment of leukocytes.

Salicylates inhibit I kappa B-alpha phosphorylation, endothelial-leukocyte adhesion molecule expression, and neutrophil transmigration

The expression of leukocyte adhesion molecules on endothelial cells is induced by TNF-alpha and other inflammatory cytokines. This induction of endothelial-leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 requires the transcription factor nuclear factor-kappa B (NF-kappa B). Recent work has suggested that some nonsteroidal anti-inflammatory agents, including sodium salicylate and aspirin, can inhibit NF-kappa B-dependent gene activation. We studied the effects of salicylates on expression of adhesion molecules in HUVECs. We found that sodium salicylate inhibited activation of NF-kappa B (p50/p65 and p65/p65) by preventing phosphorylation and subsequent degradation of the inhibitor 1 kappa B-alpha. Salicylate treatment had no effect on TNF-alpha-induced phosphorylation of the transcription factor ATF-2. Salicylate blocked the TNF-alpha-induced increase in mRNA levels of adhesion molecules and gave a dose-dependent inhibition of TNF-alpha-induced surface expression of vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 with higher doses required to inhibit endothelial-leukocyte adhesion molecule-1 expression. Indomethacin, a nonsalicylate cyclooxygenase inhibitor, had no effect on surface expression of adhesion molecules, suggesting that the effects were not due to inhibition of cyclooxygenase. Treatment of endothelial cell monolayers with sodium salicylate inhibited transendothelial migration of neutrophils but had no significant effect on neutrophil adhesion under flow conditions. The clinical importance of high-dose salicylates in inflammation may be due, in part, to the ability to prevent expression of inducible adhesion molecules and recruitment of leukocytes.

Adrenocorticotropin causes vasodilatation in the human fetal-placental circulation

During human pregnancy, ACTH is produced by both the placenta and fetal pituitary. ACTH has been shown to cause vasodilatation in the adrenal cortex in vitro. In this context we have investigated the vasoactive effects of ACTH in the human fetal-placental circulation. Single lobules of term human placentas were bilaterally perfused in vitro with Krebs solution (maternal and fetal, 5 mL/min; 95% O2-5% CO2; 37 C; pH 7.3), and changes in fetal placental arterial perfusion pressure (FAP) were measured. ACTH (40-4000 pmol/L; n = 5) caused a dose-dependent reduction of both KC1 and PGF2alpha-induced increases in FAP in the fetal placental circulation. The reductions were of a similar magnitude in the presence of either constrictor agent. ACTH was 187.4 (95% confidence limits, 162.7-215.9) times more potent than prostacyclin (PGI2; 1.2-1180 nmol/L; n = 6), which is a known vasodilator of the fetal-placental circulation. The threshold concentrations for ACTH and PGI2 were 40 pmol/L and 1.2 nmol/L, respectively. ACTH-induced reductions in PGF2alpha-induced increases in FAP in the fetal placental circulation were not inhibited by the nitric oxide synthase inhibitor, N omega-nitro-L-arginine (100 micromol/L; n = 5), the cyclooxygenase inhibitor indomethacin (3 micromol/L; n = 5), or a guanylate cyclase inhibitor LY83583(1 micromol/L; n = 5). The inhibitory effect of ACTH was attenuated by the antagonist, ACTH-(7-38) (240 pmol/L; n = 4), and a polyclonal ACTH antiserum (1:1000 dilution; n = 4). We have demonstrated that ACTH causes a reduction in fetal placental vascular resistance in the human fetal-placental circulation in vitro. The mechanism by which it exerts these effects has not been defined, but neither nitric oxide nor PG-mediated pathways appear to be involved.

Effects of variation in oxygen tension on responses of the human fetoplacental vasculature to vasoactive agents in vitro

The human placenta perfused in vitro with Krebs' solution has been used to examine the effects of low oxygen tension on the vasoreactivity of the fetal placental vessels to several vasodilator and vasocontrictor autacoids. Increases in fetal arterial perfusion pressure (FAP) produced by endothelin-1 (ET-1, human), the thromboxane A2-mimetic U46619, 5-hydroxytryptamine (5-HT), angiotensin II (A II) and bradykinin (BK) were examined under conditions of high ( >or= 450 mmHg) and low <or= 50 mmHg) O2 tension. Similarly, decreases in pressure produced by adenosine triphosphate (ATP) and arachidonic acid (AA) were examined. The effects of these autacoids on the fetoplacental vasculature during low oxygen perfusion was compared to that obtained following nitric oxide synthase inhibition with N omega-nitro-L-arginine, (L-NOARG, 100 microns). Increases in FAP caused by ET-1, U46619, and 5-HT on fetoplacental blood vessels were not altered significantly at low oxygen tension, although that in response to BK was enhanced. Increases in FAP caused by A II were unchanged at low oxygen tension. ATP-induced decreases in FAP were reduced whereas AA-mediated changes were unchanged. Both low oxygen tension and L-NOARG produced an elevation in basal perfusion pressure. Perfusion of the human placenta with Krebs' solution of low oxygen tension may compromise placental vascular function. Impaired placental oxygenation may contribute to the development and severity of vasoconstriction in the placenta associated with pre-eclampsia/pregnancy induced hypertension.

Corticotropin-releasing hormone-induced vasodilatation in the human fetal-placental circulation: involvement of the nitric oxide-cyclic guanosine 3',5'-monophosphate-mediated pathway

This study has used an in vitro perfusion method to investigate the mechanism by which CRH causes vasodilatation in the human fetal-placental circulation. In normal term placentas, vasodilatory responses to human CRH (24-7000 pmol/L) were examined during submaximal vasoconstriction (100-120 mm Hg) of the fetal-placental vasculature induced by prostaglandin F2 alpha (0.7-2 mumol/L), KCl (50-100 mmol/L), or the thromboxane A2 mimetic, U46619 (0.05-0.5 mumol/L). Infusion of CRH caused a concentration-dependent vasodilatation that was similar in the presence of each constrictor agent (P > 0.05). The CRH antagonist, alpha-helical CRH-(9-41) (200 pmol/L), and a polyclonal CRH antiserum significantly inhibited CRH-induced vasodilatation during constriction with prostaglandin F2 alpha (P < 0.05). Vasodilatory responses to CRH were attenuated by the nitric oxide synthase inhibitor, N omega-nitro-L-arginine (100 mumol/L; P < 0.05), and the guanylate cyclase inhibitor, LY 83583 (1 mumol/L; P < 0.05), but not by the cyclooxygenase inhibitor, indomethacin (3 mumol/L; P > 0.05). In placentas of women with increased fetal vascular resistance, as demonstrated by Doppler ultrasound waveforms in vivo, CRH-induced vasodilatation was significantly reduced (P < 0.05). These results indicate that in the human fetal-placental circulation, CRH causes a vasodilatory response via a nitric oxide-/cGMP-dependent pathway. CRH may play a role in the control of vascular resistance to blood flow in the normal human placenta, and there may be a deficiency in the CRH signaling pathway of placentas with increased fetal vascular resistance.

Transcriptional regulation of endothelial cell adhesion molecules: NF-kappa B and cytokine-inducible enhancers

Transcription of endothelial-leukocyte adhesion molecule-1 (E-selectin or ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) is induced by the inflammatory cytokines interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha). The positive regulatory domains required for maximal levels of cytokine induction have been defined in the promoters of all three genes. DNA binding studies reveal a requirement for nuclear factor-kappa B (NF-kappa B) and a small group of other transcriptional activators. The organization of the cytokine-inducible element in the E-selectin promoter is remarkably similar to that of the virus-inducible promoter of the human interferon-beta gene in that both promoters require NF-kappa B, activating transcription factor-2 (ATF-2), and high mobility group protein I(Y) for induction. Based on this structural similarity, a model has been proposed for the cytokine-induced E-selectin enhancer that is similar to the stereospecific complex proposed for the interferon-beta gene promoter. In these models, multiple DNA bending proteins facilitate the assembly of higher order complexes of transcriptional activators that interact as a unit with the basal transcriptional machinery. The assembly of unique enhancer complexes from similar sets of transcriptional factors may provide the specificity required to regulate complex patterns of gene expression and correlate with the distinct patterns of expression of the leukocyte adhesion molecules.

Endothelial interferon regulatory factor 1 cooperates with NF-kappa B as a transcriptional activator of vascular cell adhesion molecule 1

Transcription of the vascular cell adhesion molecule 1 (VCAM-1) gene in endothelial cells is induced by lipopolysaccharide and the inflammatory cytokines interleukin-1 beta and tumor necrosis factor alpha (TNF-alpha). Previous studies have demonstrated that tandem binding sites for the inducible transcription factor NF-kappa B are necessary but not sufficient for full cytokine-mediated transcriptional activation. Herein, we demonstrate that full cytokine-induced accumulation of VCAM1 transcript requires protein synthesis. We report the definition of a functional regulatory element in the VCAM1 promoter interacting with the transcriptional activator interferon regulatory factor 1 (IRF-1). DNA-protein binding studies with endothelial nuclear extracts revealed that IRF-1 is cytokine inducible and binds specifically to a consensus sequence motif located 3' of the TATA element. We have identified heterodimeric p65 and p50 as the NF-kappa B species binding to the VCAM1 promoter in TNF-alpha-activated endothelial cells. Experiments with recombinant proteins showed that p50/p65 and high-mobility-group I(Y) protein cooperatively facilitated the binding of IRF-1 to the VCAM1 IRF binding site and that IRF-1 physically interacted with p50 and with high-mobility-group I(Y) protein. Transient transfection assay in endothelial cells showed that overexpressed IRF-1 resulted in superinduction of TNF-alpha-stimulated transcription. Site-directed mutations in the IRF binding element decreased TNF-alpha-induced activity and totally abolished superinduction. Cotransfection assays in P19 embryonal carcinoma cells revealed that IRF-1 synergized with p50/p65 NF-kappa B to activate the VCAM1 promoter or heterologous promoter constructs bearing isolated VCAM1 NF-kappa B and IRF binding motifs. Cytokine inducibility of VCAM1 in endothelial cells utilizes the interaction of heterodimeric p50/p65 proteins with IRF-1.

The proteasome pathway is required for cytokine-induced endothelial-leukocyte adhesion molecule expression

Multiple cell adhesion proteins are up-regulated in vascular endothelial cells in response to TNF alpha and other inflammatory cytokines. This increase in cell adhesion gene expression is thought to require the transcription factor NF-kappa B. Here, we show that peptide aldehyde inhibitors of the proteasome, a multicatalytic protease recently shown to be required for the activation of NF-kappa B, block TNF alpha induction of the leukocyte adhesion molecules E-selectin, VCAM-1, and ICAM-1. Striking functional consequences of this inhibition were observed in analyses of leukocyte-endothelial interactions under defined flow conditions. Lymphocyte attachment to TNF alpha-treated endothelial monolayers was totally blocked, while neutrophil attachment was partially reduced but transmigration was essentially prevented.

Vascular responses to sodium nitroprusside in the human fetal-placental circulation

This study examined the activity of sodium nitroprusside (SNP) in the human fetal-placental circulation in vitro in pathological and experimental conditions in which vascular function may be impaired. SNP (13-3400 nM) caused a concentration-dependent reduction in fetal arterial perfusion pressure (FAP) in Krebs' perfused placental cotyledons, at basal tone and following pre-constriction with prostaglandin F2 alpha (PGF2 alpha). SNP-induced reduction in FAP in the PGF2 alpha pre-constricted fetal-placental circulation was enhanced approximately six-fold (5.85) in those placentae pre-treated with the nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine (100 microM). Reductions in FAP in the preconstricted fetal-placental vasculature caused by SNP were not altered by prior infusion of ouabain (100 nM) into the fetal circulation or during low oxygen perfusion (O2 tension < 50 mmHg). No differences were observed in the responses obtained to SNP in placentae obtained from women with normotensive pregnancies or those associated with (i) pregnancy-induced hypertension, (ii) intra-uterine growth retardation, or (iii) an elevated umbilical-artery Doppler-ultrasound systolic/diastolic ratio, in either preconstricted placentae or those at basal tone. These findings are consistent with an up-regulation of guanylate cyclase/cGMP-mediated vasodilatation in the fetal-placental vasculature following complete blockade of endogenous NO production.

A striking similarity in the organization of the E-selectin and beta interferon gene promoters

Transcription of the endothelial leukocyte adhesion molecule 1 (E-selectin or ELAM-1) gene is induced by the inflammatory cytokines interleukin-1 beta and tumor necrosis factor alpha (TNF-alpha). In this report, we identify four positive regulatory domains (PDI to PDIV) in the E-selectin promoter that are required for maximal levels of TNF-alpha induction in endothelial cells. In vitro DNA binding studies reveal that two of the domains contain novel adjacent binding sites for the transcription factor NF-kappa B (PDIII and PDIV), a third corresponds to a recently described CRE/ATF site (PDII), and a fourth is a consensus NF-kappa B site (PDI). Mutations that decrease the binding of NF-kappa B to any one of the NF-kappa B binding sites in vitro abolished cytokine-induced E-selectin gene expression in vivo. Previous studies demonstrated a similar correlation between ATF binding to PDII and E-selectin gene expression. Here we show that the high-mobility-group protein I(Y) [HMG I(Y)] also binds specifically to the E-selectin promoter and thereby enhances the binding of both ATF-2 and NF-kappa B to the E-selectin promoter in vitro. Moreover, mutations that interfere with HMG I(Y) binding decrease the level of cytokine-induced E-selectin expression. The organization of the TNF-alpha-inducible element of the E-selectin promoter is remarkably similar to that of the virus-inducible promoter of the human beta interferon gene in that both promoters require NF-kappa B, ATF-2, and HMG I(Y). We propose that HMG I(Y) functions as a key architectural component in the assembly of inducible transcription activation complexes on both promoters.

Autacoids and control of human placental blood flow

1. Humans have a haemochorial, villous placenta. Uterine blood passes through maternal sinuses, bathing placental villi through which fetal blood circulates. Blood flow through each circulation is high and vascular resistance low. This haemodynamic situation is essential for efficient placental function. 2. The low placental vascular resistance is due to a lack of nervous influences together with pregnancy-induced changes promoting vasodilatation. Increases occur in output of the vasodilators prostacyclin and nitric oxide and also in membrane sodium pump activity. 3. Many autacoids are present in umbilical blood. Fetal vessels of the placenta develop intense vasoconstriction in the presence of some autacoids, such as thromboxane A2 and prostaglandins F2 alpha and E2, and respond weakly to others, such as angiotensin II and 5-hydroxytryptamine. Nevertheless, vasodilator influences predominate. 4. The diseases of pre-eclampsia and fetal growth retardation are associated with reduced output of nitric oxide and prostacyclin and with increased production of thromboxane A2 and endothelin-1. These changes promote vasoconstriction, increased vascular sensitivity to vasoconstrictor stimuli, platelet aggregation and intravascular coagulation, retarding blood flow and feto-placental growth. 5. Aspirin and glyceryl trinitrate have been investigated for possible therapeutic use in pre-eclampsia and fetal growth retardation. Improved drug therapy is likely as knowledge increases of the importance of autacoids in normal placental function and in the changes that occur during disease.

Effect of inhibition of nitric oxide synthase and guanylate cyclase on hydralazine-induced vasodilatation of the human fetal placental circulation

1. The vasodilator effects of hydralazine in vitro, using the Krebs' perfused human placental lobule was studied. Single placental lobules were bilaterally perfused (maternal and fetal sides 5 mL/min each, 95% O2, 5% CO2, 37 degrees C) and changes in fetal arterial pressure (FAP) and venous outflow (VO) were recorded. 2. Submaximal vasoconstriction was induced by KCl (20-50 mmol/L), which increased basal FAP from 22.8 +/- 1.7 to 91.3 +/- 3.9 mmHg (n = 9, P < 0.001), and decreased VO from 4.1 +/- 0.6 to 0.2 +/- 0.1 mL/min (n = 6, P < 0.01). 3. Hydralazine caused vasodilatation (IC50 1.9 mmol/L, n = 9) and increased VO in the presence of KCl-induced vasoconstriction. 4. Infusion of N omega-nitro-L-arginine (100 mumol/L) to block nitric oxide synthase caused the basal FAP to increase from 30.9 +/- 5.9 to 47.4 +/- 6.7 (n = 6, P < 0.05) and significantly potentiated hydralazine-induced vasodilatation (n = 7, P < 0.05). 5. The soluble guanylate cyclase inhibitor LY 83583 (6-anilino-5,8-quinolinedione) (1 mumol/L) significantly antagonized the vasodilatation produced by hydralazine (n = 5, P < 0.05). 6. Thus, Hydralazine appears to activate guanylate cyclase, leading to increased cyclic GMP in fetal arterial vascular smooth muscle to cause vasorelaxation. No evidence was obtained to suggest that hydralazine exerted its action by either releasing nitric oxide from endothelial cells in the placenta or acting as a nitric oxide donor.