Network Analysis for Formative Evaluation of Collaborative, Team Science Research Partnerships.

Cancer health disparities persist across the cancer care continuum despite decades of effort to eliminate them. Among the strategies currently used to address these disparities are multi-institution research initiatives that engage multiple stakeholders and change efforts. Endemic to the theory of change of such programs is the idea that collaboration-across institutions, research disciplines, and academic ranks-is necessary to improve outcomes. Despite this emphasis on collaboration, however, it is not often a focus of evaluation for these programs and others like them. In this paper we describe a method for evaluating collaboration within the Meharry-Vanderbilt-Tennessee State University Cancer Partnership using network analysis. Specifically, we used network analysis of co-authorship on academic publications to visualize the growth and patterns of scientific collaboration across partnership institutions, research disciplines, and academic ranks over time. We presented the results of the network analysis to internal and external advisory groups, creating the opportunity to discuss partnership collaboration, celebrate successes, and identify opportunities for improvement. We propose that basic network analysis of existing data along with network visualizations can foster conversation and feedback and are simple and effective ways to evaluate collaboration initiatives.

Rational Design of Hydrogel Networks with Dynamic Mechanical Properties to Mimic Matrix Remodeling.

Engineered hydrogels are increasingly used as extracellular matrix (ECM) surrogates for probing cell function in response to ECM remodeling events related to injury or disease (e.g., degradation followed by deposition/crosslinking). Inspired by these events, this work establishes an approach for pseudo-reversible mechanical property modulation in synthetic hydrogels by integrating orthogonal, enzymatically triggered crosslink degradation, and light-triggered photopolymerization stiffening. Hydrogels are formed by a photo-initiated thiol-ene reaction between multiarm polyethylene glycol and a dually enzymatically degradable peptide linker, which incorporates a thrombin-degradable sequence for triggered softening and a matrix metalloproteinase (MMP)-degradable sequence for cell-driven remodeling. Hydrogels are stiffened by photopolymerization using a flexible, MMP-degradable polymer-peptide conjugate and multiarm macromers, increasing the synthetic matrix crosslink density while retaining degradability. Integration of these tools enables sequential softening and stiffening inspired by matrix remodeling events within loose connective tissues (Young's modulus (E) ≈5 to 1.5 to 6 kPa with >3x ΔE). The cytocompatibility and utility of this approach is examined with breast cancer cells, where cell proliferation shows a dependence on the timing of triggered softening. This work provides innovative tools for 3D dynamic property modulation that are synthetically accessible and cell compatible.

Rate-based approach for controlling the mechanical properties of 'thiol-ene' hydrogels formed with visible light.

The mechanical properties of synthetic hydrogels traditionally have been controlled with the concentration, molecular weight, or stoichiometry of the macromolecular building blocks used for hydrogel formation. Recently, the rate of formation has been recognized as an important and effective handle for controlling the mechanical properties of these water-swollen polymer networks, owing to differences in network heterogeneity (e.g., defects) that arise based on the rate of gelation. Building upon this, in this work, we investigate a rate-based approach for controlling mechanical properties of hydrogels both initially and temporally with light. Specifically, synthetic hydrogels are formed with visible light-initiated thiol-ene 'click' chemistry (PEG-8-norbornene, dithiol linker, LAP photoinitiator with LED lamp centered at 455 nm), using irradiation conditions to control the rate of formation and the mechanical properties of the resulting hydrogels. Further, defects within these hydrogels were subsequently exploited for temporal modulation of mechanical properties with a secondary cure using low doses of long wavelength UV light (365 nm). The elasticity of the hydrogel, as measured with Young's and shear moduli, was observed to increase with increasing light intensity and concentration of photoinitiator used for hydrogel formation. In situ measurements of end group conversion during hydrogel formation with magic angle spinning (MAS 1H NMR) correlated with these mechanical properties measurements, suggesting that both dangling end groups and looping contribute to the observed mechanical properties. Dangling end groups provide reactive handles for temporal stiffening of hydrogels with a secondary UV-initiated thiol-ene polymerization, where an increase in Young's modulus by a factor of ~ 2.5x was observed. These studies demonstrate how the rate of photopolymerization can be tuned with irradiation wavelength, intensity, and time to control the properties of synthetic hydrogels, which may prove useful in a variety of applications from coatings to biomaterials for controlled cell culture and regenerative medicine.

Design of synthetic extracellular matrices for probing breast cancer cell growth using robust cyctocompatible nucleophilic thiol-yne addition chemistry.

Controlled, three-dimensional (3D) cell culture systems are of growing interest for both tissue regeneration and disease, including cancer, enabling hypothesis testing about the effects of microenvironment cues on a variety of cellular processes, including aspects of disease progression. In this work, we encapsulate and culture in three dimensions different cancer cell lines in a synthetic extracellular matrix (ECM), using mild and efficient chemistry. Specifically, harnessing the nucleophilic addition of thiols to activated alkynes, we have created hydrogel-based materials with multifunctional poly(ethylene glycol) (PEG) and select biomimetic peptides. These materials have definable, controlled mechanical properties (G' = 4-10 kPa) and enable facile incorporation of pendant peptides for cell adhesion, relevant for mimicking soft tissues, where polymer architecture allows tuning of matrix degradation. These matrices rapidly formed in the presence of sensitive breast cancer cells (MCF-7) for successful encapsulation with high cell viability, greatly improved relative to that observed with the more widely used radically-initiated thiol-ene crosslinking chemistry. Furthermore, controlled matrix degradation by both bulk and local mechanisms, ester hydrolysis of the polymer network and cell-driven enzymatic hydrolysis of cell-degradable peptide, allowed cell proliferation and the formation of cell clusters within these thiol-yne hydrogels. These studies demonstrate the importance of chemistry in ECM mimics and the potential thiol-yne chemistry has as a crosslinking reaction for the encapsulation and culture of cells, including those sensitive to radical crosslinking pathways.

Isolation and Identification of Proteins Secreted by Cells Cultured within Synthetic Hydrogel-Based Matrices.

Cells interact with and remodel their microenvironment, degrading large extracellular matrix (ECM) proteins (e.g., fibronectin, collagens) and secreting new ECM proteins and small soluble factors (e.g., growth factors, cytokines). Synthetic mimics of the ECM have been developed as controlled cell culture platforms for use in both fundamental and applied studies. However, how cells broadly remodel these initially well-defined matrices remains poorly understood and difficult to probe. In this work, we have established methods for widely examining both large and small proteins that are secreted by cells within synthetic matrices. Specifically, human mesenchymal stem cells (hMSCs), a model primary cell type, were cultured within well-defined poly(ethylene glycol) (PEG)-peptide hydrogels, and these cell-matrix constructs were decellularized and degraded for subsequent isolation and analysis of deposited proteins. Shotgun proteomics using liquid chromatography and mass spectrometry identified a variety of proteins, including the large ECM proteins fibronectin and collagen VI. Immunostaining and confocal imaging confirmed these results and provided visualization of protein organization within the synthetic matrices. Additionally, culture medium was collected from the encapsulated hMSCs, and a Luminex assay was performed to identify secreted soluble factors, including vascular endothelial growth factor (VEGF), endothelial growth factor (EGF), basic fibroblast growth factor (FGF-2), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-α). Together, these methods provide a unique approach for studying dynamic reciprocity between cells and synthetic microenvironments and have the potential to provide new biological insights into cell responses during three-dimensional (3D) controlled cell culture.

Reduced Amplitude of Low-Frequency Brain Oscillations in the Psychosis Risk Syndrome and Early Illness Schizophrenia.

Low-frequency oscillations (LFOs) of the blood oxygen level-dependent (BOLD) signal are gaining interest as potential biomarkers sensitive to neuropsychiatric pathology. Schizophrenia has been associated with alterations in intrinsic LFOs that covary with cognitive deficits and symptoms. However, the extent to which LFO dysfunction is present before schizophrenia illness onset remains unknown. Resting-state FMRI data were collected from clinical high-risk (CHR; n=45) youth, early illness schizophrenia (ESZ; n=74) patients, and healthy controls (HCs; n=85) aged 12-35 years. Age-adjusted voxelwise fractional amplitude of low-frequency fluctuations (fALFF; 0.01-0.08 Hz) of the BOLD signal was compared among the three groups. Main effects of Group (p<0.005 height threshold, familywise error cluster-level corrected p<0.05) were followed up via Tukey-corrected pairwise comparisons. Significant main effects of Group (p<0.05) revealed decreased fALFF in ESZ and CHR groups relative to HCs, with values in the CHR group falling between those of ESZ and HC groups. These differences were identified primarily in posterior cortex, including temporoparietal regions, extending into occipital and cerebellar lobes. Less LFO activity was related to greater symptom severity in both CHR and ESZ groups in several of these posterior cortical regions. These data support an intermediate phenotype of reduced posterior cortical LFO amplitude in CHR individuals, with resting fALFF values smaller than in HCs but higher than in ESZ patients. Findings indicate that LFO magnitude alterations relate to clinical symptoms and predate psychosis onset but are more pronounced in the early stages of schizophrenia.

Pharmacological characterization of AZD5069, a slowly reversible CXC chemokine receptor 2 antagonist.

In normal physiologic responses to injury and infection, inflammatory cells enter tissue and sites of inflammation through a chemotactic process regulated by several families of proteins, including inflammatory chemokines, a family of small inducible cytokines. In neutrophils, chemokines chemokine (CXC motif) ligand 1 (CXCL1) and CXCL8 are potent chemoattractants and activate G protein-coupled receptors CXC chemokine receptor 1 (CXCR1) and CXCR2. Several small-molecule antagonists of CXCR2 have been developed to inhibit the inflammatory responses mediated by this receptor. Here, we present the data describing the pharmacology of AZD5069 [N-(2-(2,3-difluorobenzylthio)-6-((2R,3S)-3,4-dihydroxybutan-2-yloxy)[2,4,5,6-(13)C4, 1,3-(15)N2]pyrimidin-4-yl)azetidine-1-sulfonamide,[(15)N2,(13)C4]N-(2-(2,3-difluoro-6-[3H]-benzylthio)-6-((2R,3S)-3,4-dihydroxybutan-2-yloxy)pyrimidin-4-yl)azetidine-1-sulfonamide], a novel antagonist of CXCR2. AZD5069 was shown to inhibit binding of radiolabeled CXCL8 to human CXCR2 with a pIC50 value of 9.1. Furthermore, AZD5069 inhibited neutrophil chemotaxis, with a pA2 of approximately 9.6, and adhesion molecule expression, with a pA2 of 6.9, in response to CXCL1. AZD5069 was a slowly reversible antagonist of CXCR2 with effects of time and temperature evident on the pharmacology and binding kinetics. With short incubation times, AZD5069 appeared to have an antagonist profile with insurmountable antagonism of calcium response curves. This behavior was also observed in vivo in an acute lipopolysaccharide-induced lung inflammation model. Altogether, the data presented here show that AZD5069 represents a novel, potent, and selective CXCR2 antagonist with potential as a therapeutic agent in inflammatory conditions.

An Age-Related Dissociation of Short-Term Memory for Facial Identity and Facial Emotional Expression.

BACKGROUND: Memory for both facial emotional expression and facial identity was explored in younger and older adults in 3 experiments using a delayed match-to-sample procedure. METHOD: Memory sets of 1, 2, or 3 faces were presented, which were followed by a probe after a 3-s retention interval. RESULTS: There was very little difference between younger and older adults in memory for emotional expressions, but memory for identity was substantially impaired in the older adults. DISCUSSION: Possible explanations for spared memory for emotional expressions include socioemotional selectivity theory as well as the existence of overlapping yet distinct brain networks for processing of different emotions.

Longitudinal characterization of a model of chronic allergic lung inflammation in mice using imaging, functional and immunological methods.

The present study investigated the role that imaging could have for assessing lung inflammation in a mouse model of HDM (house dust mite)-provoked allergic inflammation. Inflammation is usually assessed using terminal procedures such as BAL (bronchoalveolar lavage) and histopathology; however, MRI (magnetic resonance imaging) and CT (computed tomography) methods have the potential to allow longitudinal, repeated study of individual animals. Female BALB/c mice were administered daily either saline, or a solution of mixed HDM proteins sufficient to deliver a dose of 12 or 25 µg total HDM protein±budesonide (1 mg/kg of body weight, during weeks 5-7) for 7 weeks. AHR (airway hyper-responsiveness) and IgE measurements were taken on weeks 3, 5 and 7. Following imaging sessions at weeks 3, 5 and 7 lungs were prepared for histology. BAL samples were taken at week 7 and lungs prepared for histology. MRI showed a gradual weekly increase in LTI (lung tissue intensity) in animals treated with HDM compared with control. The 25 µg HDM group showed a continual significant increase in LTI between weeks 3 and 7, the 12 µg HDM-treated group showed a similar rate of increase, and plateaued by week 5. A corresponding increase in AHR, cell counts and IgE were observed. CT showed significant increases in lung tissue density from week 1 of HDM exposure and this was maintained throughout the 7 weeks. Budesonide treatment reversed the increase in tissue density. MRI and CT therefore provide non-invasive sensitive methods for longitudinally assessing lung inflammation. Lung tissue changes could be compared directly with the classical functional and inflammatory readouts, allowing more accurate assessments to be made within each animal and providing a clinically translatable approach.

Functional magnetic resonance imaging identifies somatotopic organization of nociception in the human spinal cord.

Functional magnetic resonance imaging (fMRI) is a technique that uses blood oxygen-level-dependent (BOLD) signals to elucidate discrete areas of neuronal activity. Despite the significant number of fMRI human brain studies, few researchers have applied fMRI technology to investigating neuronal activity within the human spinal cord. Our study goals were to demonstrate that fMRI could reveal the following: (i) appropriate somatotopic activations in response to noxious stimuli in the deep and superficial dorsal horn of the human cervical spinal cord, and (ii) lateralization of fMRI activations in response to noxious stimulation in the right and left upper extremity. We subjected healthy participants to noxious stimulation during fMRI scans. Using a spiral in-out image sequence and retrospective correction for physiologic noise, we demonstrated that fMRI can create high-resolution, neuronal activation maps of the human cervical spinal cord. During nociceptive stimulation of all 4 sites (left deltoid, right deltoid, left thenar eminence and right thenar eminence), we found ipsilateral dorsal horn activation. Stimulation of the deltoid activated C5, whereas stimulation of the thenar eminence activated C6. Our study contributes to creating an objective analysis of pain transmission; other investigators can use these results to further study central nervous system changes that occur in patients with acute and chronic pain.

Identification of a putative intracellular allosteric antagonist binding-site in the CXC chemokine receptors 1 and 2.

The chemokine receptors CXCR1 and CXCR2 are G-protein-coupled receptors (GPCRs) implicated in mediating cellular functions associated with the inflammatory response. Potent CXCR2 receptor antagonists have been discovered, some of which have recently entered clinical development. The aim of this study was to identify key amino acid residue differences between CXCR1 and CXCR2 that influence the relative antagonism by two compounds that have markedly different chemical structures. By investigating the effects of domain switching and point mutations, we found that the second extracellular loop, which contained significant amino acid sequence diversity, was not important for compound antagonism. We were surprised to find that switching the intracellular C-terminal 60 amino acid domains of CXCR1 and CXCR2 caused an apparent reversal of antagonism at these two receptors. Further investigation showed that a single amino acid residue, lysine 320 in CXCR2 and asparagine 311 in CXCR1, plays a predominant role in describing the relative antagonism of the two compounds. Homology modeling studies based on the structure of bovine rhodopsin indicated a potential intracellular antagonist binding pocket involving lysine 320. We conclude that residue 320 in CXCR2 forms part of a potential allosteric binding pocket on the intracellular side of the receptor, a site that is distal to the orthosteric site commonly assumed to be the location of antagonist binding to GPCRs. The existence of a common intracellular allosteric binding site at GPCRs related to CXCR2 may be of value in the design of novel antagonists for therapeutic intervention.

Endothelin-mediated vasoconstriction in early atherosclerosis is markedly increased in ApoE-/- mouse but prevented by atorvastatin.

We have discovered that endothelin-1 (ET-1) vasoconstriction is significantly enhanced in aortas of young (8-16-week-old) apolipoprotein E-deficient (ApoE-/-) mice devoid of atherosclerotic lesions (maximum response expressed as a percentage of the mean response to 100 mM KCl (E(MAX)) = 55.7% +/- 19.5% KCl, n = 5) compared to age-matched C57BL/6/J control animals (E(MAX) = 12.6% +/- 2.5% KCl, n = 8), indicating that alterations in the endothelin system may contribute to disease progression, at least in this animal model. There was no difference in the potency of ET-1 to contract aorta from the two groups (C57BL/6/J pD2 = 8.74 +/- 0.30; ApoE-/- pD2 = 8.50 +/- 0.15, P > 0.05). This increased response was specific to ET-1, as it was not observed with phenylephrine or U46619, nor was it due to a non-receptor mediated increase in contractile sensitivity, as there was no change in response to KCl between the two groups. [125I]ET-1 bound with subnanomolar affinity (K(D)) to aorta (K(D) = 0.018 +/- 0.002 nM, n = 4) and, with an order of magnitude lower affinity, to heart (K(D) = 0.47 +/- 0.05, n = 5) of C57BL/6/J mice with binding densities (B(MAX)) of 9.3 +/- 2.4 fmol mg(-1)protein and 100 +/- 14 fmol mg(-1) protein, respectively. Alterations in vascular reactivity to ET-1 could not be explained by increased endothelin receptor density or affinity, as these were not altered in aorta (K(D) = 0.011 +/- 0.003 nM; B(MAX) = 10.1 +/- 3.9 fmol mg(-1), n = 4) and heart (K(D) = 0.43 +/- 0.04 nM; B(MAX) = 115 +/- 26 fmol mg(-1), n == 6) of ApoE-/- animals. The ratio of ET(A) to ET(B) receptors in heart of control and ApoE-/- mice was similar, comprising 89% and 85% ET(A) receptors, respectively. In isolated aorta from ApoE-/- mice on the Western diet, which more closely resembled more advanced stages of the disease in man, the augmented ET-1 vasoconstrictor response was maintained (E(MAX) = 25.2% +/- 6.8% KCl, n = 9); however, it was completely prevented in animals that had received 10 weeks of oral atorvastatin (30 mg kg(-1) day(-1)) (E(MAX) = 4.0% +/- 1.5% KCl, n = 5), a concentration that was chosen because it did not affect plasma cholesterol and triglyceride levels. Therefore, this protective prevention of enhanced ET-1 vasoconstriction in ApoE-/- mice by atorvastatin was independent of its lipid-lowering properties.

Regional hemodynamic actions of selective corticotropin-releasing factor type 2 receptor ligands in conscious rats.

In conscious male Sprague-Dawley rats, we compared regional hemodynamic actions of the selective corticotropin-releasing factor type 2 (CRF(2)) receptor ligands human and mouse urocortin 2 (hUCN2 and mUCN2, respectively) with those of CRF. Bolus i.v. doses of 3 and 30 pmol kg(-1) hUCN2, mUCN2, or CRF had no significant hemodynamic actions, but at doses of 300 and 3000 pmol kg(-1), all three peptides caused dose-dependent tachycardia and hypotension, with rapid-onset, short-duration, mesenteric vasodilatation and slower-onset, more prolonged hindquarters vasodilatation but little or no change in renal vascular conductance. Pretreatment with the nonselective CRF receptor antagonist astressin or the selective CRF(2) receptor antagonist antisauvagine 30 abolished all the cardiovascular actions of all three peptides. Indomethacin had no effect on responses to hUCN2, and there was no evidence for any involvement of nitric oxide (NO) in the vasodilator actions of hUCN2. There was no evidence that recruitment of angiotensin- and endothelin-mediated vasoconstrictor mechanisms counteracted the vascular actions of hUCN2. The results indicate that the hemodynamic effects of i.v. hUCN2, mUCN2, and CRF depend on activation of CRF(2) receptors and do not involve NO or prostanoids.

Cellular distribution of immunoreactive urotensin-II in human tissues with evidence of increased expression in atherosclerosis and a greater constrictor response of small compared to large coronary arteries.

We detected urotensin-II-like immunoreactivity in the endothelium of normal human blood vessels from heart, kidney, placenta, adrenal, thyroid and umbilical cord. Immunoreactivity was also detected in endocardial endothelial and kidney epithelial cells. In atherosclerotic coronary artery, immunoreactivity localized to regions of macrophage infiltration. Urotensin-II constricted human atherosclerotic epicardial coronary arteries with pD2=10.58 +/- 0.46 (mean +/- S.E.M.) and Emax=11.4 +/- 4.2% KCl and small coronary arteries with pD2=9.25 +/- 0.38 and Emax=77 +/- 16% KCl. Small coronary arteries clearly exhibited a greater maximum response to urotensin-II than epicardial vessels. This enhanced responsiveness may be of importance in heart failure, where circulating concentrations of U-II are increased, or in atherosclerosis where focally up-regulated urotensin-II production may act down stream to produce significant vasospasm, compromising blood flow to the myocardium. We conclude that urotensin-II is a locally released vasoactive mediator that may be an important regulator of blood flow particularly to the myocardium and may have a specific role in human atherosclerosis.

CRF2 receptors are highly expressed in the human cardiovascular system and their cognate ligands urocortins 2 and 3 are potent vasodilators.

1. Systemic infusions of urocortin 1 produce a decrease in mean arterial pressure. This effect may be mediated by a direct action on novel corticotropin-releasing factor type 2 (CRF(2)) receptors predicted to be expressed in blood vessels and the heart. Our objectives were to determine the presence of CRF(2) receptors in the human cardiovascular system using the selective radioligand [(125)I]antisauvagine 30. We also investigated the potential functional roles of novel CRF(2) ligands in the regulation of vascular tone in human arteries in vitro. 2. Radioligand binding techniques were used to characterise the CRF(2) receptor. [(125)I]antisauvagine 30 bound specifically, saturably, reversibly and with high affinity to CRF(2) receptors in human left ventricle (K(D) 0.21+/-0.03 nm, B(MAX) 0.80+/-0.18 fmol mg(-1) protein), and no change in receptor density or affinity was observed in the dilated cardiomyopathy group. 3. Autoradiographical studies revealed highly localised binding of [(125)I]antisauvagine 30 to intramyocardial blood vessels. Binding sites were also detected in the myocardium and in the medial layer of internal mammary arteries. 4. In endothelium-denuded human internal mammary artery in vitro, all peptides tested produced a potent and sustained vasodilator response reversing endothelin-1-induced constrictions (10 nm) (urocortin 1: pD(2) 8.39+/-0.32, E(MAX) 46+/-7.7%; urocortin 2: pD(2) 8.27+/-0.17, E(MAX) 60+/-8.5%; urocortin 3: pD(2) 8.61+/-0.25, E(MAX) 61+/-7.2%; CRF: pD(2) 8.28+/-0.27, E(MAX): 40+/-10%). 5. We have demonstrated the presence of CRF(2) receptors in the human cardiovascular system and a direct, endothelium-independent vasodilator action of urocortins 2 and 3, which may counter-balance the centrally mediated pressor effects of CRF and urocortin 1.

Identification of a prostate cancer susceptibility locus on chromosome 7q11-21 in Jewish families.

Results from over a dozen prostate cancer susceptibility genome-wide scans, encompassing some 1,500 hereditary prostate cancer families, indicate that prostate cancer is an extremely heterogeneous disease with multiple loci contributing to overall susceptibility. In an attempt to reduce locus heterogeneity, we performed a genomewide linkage scan for prostate cancer susceptibility genes with 36 Jewish families, which represent a stratification of hereditary prostate cancer families with potentially increased locus homogeneity. The 36 Jewish families represent a combined dataset of 17 Jewish families from the Fred Hutchinson Cancer Research Center-based Prostate Cancer Genetic Research Study dataset and 19 Ashkenazi Jewish families collected at Johns Hopkins University. All available family members, including 94 affected men, were genotyped at markers distributed across the genome with an average interval of <10 centimorgans. Nonparametric multipoint linkage analyses were the primary approach, although parametric analyses were performed as well. Our strongest signal was a significant linkage peak at 7q11-21, with a nonparametric linkage (NPL) score of 3.01 (P = 0.0013). Simulations indicated that this corresponds to a genomewide empirical P = 0.006. All other regions had NPL P values >/=0.02. After genotyping additional markers within the 7q11-21 peak, the NPL score increased to 3.35 (P = 0.0004) at D7S634 with an allele-sharing logarithm of odds of 3.12 (P = 0.00007). These studies highlight the utility of analyzing defined sets of families with a common origin for reducing locus heterogeneity problems associated with studying complex traits.

Endothelin receptor pharmacology and function in the mouse: comparison with rat and man.

The endothelin system was characterized in the C57BL/6J mouse, a strain commonly used in genetically manipulated models of cardiovascular disease. Functional responses to endothelin-1 (ET-1) were measured in segments of aorta mounted in wire myographs. Endothelin-1 produced a potent vasoconstriction [EC50: 0.49 nM (0.18-1.3 nM), n = 5], and the maximum response was 11 +/- 2.9% KCl response. Competition binding assays (0.1 nM [I]-ET-1 vs 2 pM to 100 microM PD156707) were conducted on cryostat sections of mouse heart and brain. The endothelin-A (ETA) selective antagonist bound to mouse heart with two affinities, yielding a KDETA of 1.1 +/- 0.2 nM (BMAX 130 +/- 16 fmol/mg protein) and a KDETB (endothelin-B) of 0.51 +/- 0.09 microM (BMAX 14.0 +/- 1.1 fmol/mg protein) (n = 5). ETA receptors were predominant in the heart, with competition assays yielding receptor ratios of 90:10 ETA:ETB. Contrastingly, mouse brain was ETB-rich, although PD156707 also competed with two affinities (ETA: KD 0.97 +/- 0.87 nM, BMAX 61.7 +/- 10 fmol/mg protein; ETB: KD 0.87 +/- 0.08 microM, BMAX 132 +/- 6.7 fmol/mg protein). In conclusion, we have shown that endothelin-1 is a potent constrictor of mouse aorta and endothelin receptors are highly expressed in mouse heart and brain.

Comparison of the effects of atherosclerosis and nitrate therapy on responses to nitric oxide and endothelin-1 in human arteries in vitro.

The effect of previous nitrate therapy on vascular responses to endothelin-1 (ET-1) and NO was investigated in human internal mammary artery (IMA) in vitro. Cumulative concentration-response curves to ET-1 were constructed in rings of IMA and the data grouped into IMA from patients given nitrates prior to the bypass graft operation (nitrate group) and IMA from patients who were not prescribed nitrates (control group). No significant differences were observed between the two groups, either in EC(50) value [P>0.05; 3.5 nM (2.4-5.3 nM; 95% confidence interval) and 4.8 (2.2-10 nM), nitrate and control groups respectively] or E(max) (P>0.05; 78+/-7.5% and 85+/-9.5%, nitrate and control group respectively). No significant differences in concentration-response curves to the NO-donor diethylamine NONOate (DEA/NO) in rings of IMA pre-constricted with 10 nM ET-1 were observed between control and nitrate groups [P>0.05; EC(50) values 0.59 (0.21-1.7) microM and 0.17 (0.03-0.87) microM; E(max) 110+/-5.7% and 112+/-4.5%, nitrate and control groups respectively]. Concentration-response curves to DEA/NO constructed in normal coronary artery were not significantly different from those in coronary artery obtained from patients with ischaemic heart disease (IHD) [P>0.05; E(max) 124+/-11% and 138+/-20%; EC(50) 0.08 (0.02-0.30) microM and 0.23 (0.02-24) microM, normal and IHD respectively]. These data indicate that nitrate therapy does not induce long-term changes in the ET signalling pathway. Furthermore, the tolerance to nitrate therapy is likely to be because of impaired bio-transformation of the drug rather than reduced sensitivity of the media to NO. The similar responses to DEA/NO in normal and atherosclerotic coronary artery suggests that the reduced vasodilator responses in IHD is because of a dysfunctional endothelium and is not mediated by changes in the NO signalling pathway of the smooth muscle.

Comparison of vasodilators in human internal mammary artery: ghrelin is a potent physiological antagonist of endothelin-1.

1 The potential vasodilator function of the peptide ghrelin, recently identified as the endogenous ligand of the growth hormone secretagogue orphan receptor (GHS-R), was investigated in human endothelium-denuded internal mammary artery. The peptide endothelin-1 (ET-1) is a potent and long-lasting vasoconstrictor. Comparisons were made with established and putative endogenous vasodilators to determine if any could reverse ET-1-induced vasoconstriction in this vessel. 2 Ghrelin (0.1-300 nM) potently dilated 10 nM ET-1-induced constrictions (pD(2) 8.39+/-0.29; E(MAX) 63+/-5.6%; n=9/14, responders/total). 3 ANP (pD(2) 7.75+/-0.14; E(MAX) 106+/-2.0; n=5/5) and CGRP (pD(2) 8.08+/-0.17; E(MAX) 76+/-15% n=5/6) both produced complete reversal of the constrictor response to ET-1 (E(MAX) not significantly different from 100%, P>0.05 one-sample t-test). 4 The following caused partial reversal of the ET-1 response: Adrenomedullin (n=9/9) and two peptides derived from proadrenomedullin, PAMP-12 (n=6/7) and PAMP-20 (n=9/9) (pD(2) values 7.63+/-0.28, 7.97+/-0.23 and 8.51+/-0.29; E(MAX) 58+/-7.3, 54+/-10 and 51+/-7.8% respectively). Unexpectedly, amylin was only 2 fold less potent than CGRP, although there was less than 50% reversal of the ET-1 constriction (pD(2) 7.86+/-0.30; E(MAX) 41+/-5.4%; n=7/9). CNP (n=6/6) also partially reversed constrictions to ET-1 (E(MAX) 53+/-6.3; pD(2) 8.07+/-0.38). 5 BNP (n=4/5) and PGI(2) (n=6/8) were weak vasodilators, since concentration-response curves failed to reach a maximum within the range tested. PGE(2) caused a small dilatation in some vessels (E(MAX) 17+/-2.1%; pD(2) 8.63+/-0.36; n=4/8). 6 We have demonstrated ghrelin to be an effective, endothelium-independent vasodilator of the long-lasting constrictor ET-1 in human arteries producing responses similar to those of adrenomedullin (P>0.05, ANOVA). British Journal of Pharmacology (2002) 136, 1146-1152