The biased apelin receptor agonist, MM07, reverses Sugen/hypoxia-induced pulmonary arterial hypertension as effectively as the endothelin antagonist macitentan

Introduction: Pulmonary arterial hypertension (PAH) is characterised by endothelial dysfunction and pathological vascular remodelling, resulting in the occlusion of pulmonary arteries and arterioles, right ventricular hypertrophy, and eventually fatal heart failure. Targeting the apelin receptor with the novel, G protein-biased peptide agonist, MM07, is hypothesised to reverse the developed symptoms of elevated right ventricular systolic pressure and right ventricular hypertrophy. Here, the effects of MM07 were compared with the clinical standard-of-care endothelin receptor antagonist macitentan. Methods: Male Sprague-Dawley rats were randomised and treated with either normoxia/saline, or Sugen/hypoxia (SuHx) to induce an established model of PAH, before subsequent treatment with either saline, macitentan (30 mg/kg), or MM07 (10 mg/kg). Rats were then anaesthetised and catheterised for haemodynamic measurements, and tissues collected for histopathological assessment. Results: The SuHx/saline group presented with significant increases in right ventricular hypertrophy, right ventricular systolic pressure, and muscularization of pulmonary arteries compared to normoxic/saline controls. Critically, MM07 was as at least as effective as macitentan in significantly reversing detrimental structural and haemodynamic changes after 4 weeks of treatment. Discussion: These results support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Secondary Amine Catalysis in Enzyme Design: Broadening Protein Template Diversity through Genetic Code Expansion

Secondary amines, due to their reactivity, can transform protein templates into catalytically active entities, accelerating the development of artificial enzymes. However, existing methods, predominantly reliant on modified ligands or N-terminal prolines, impose significant limitations on template selection. In this study, genetic code expansion was used to break this boundary, enabling secondary amines to be incorporated into alternative proteins and positions of choice. Pyrrolysine analogues carrying different secondary amines could be incorporated into superfolder green fluorescent protein (sfGFP), multidrug-binding LmrR and nucleotide-binding dihydrofolate reductase (DHFR). Notably, the analogue containing a D-proline moiety demonstrated both proteolytic stability and catalytic activity, conferring LmrR and DHFR with the desired transfer hydrogenation activity. While the LmrR variants were confined to the biomimetic 1-benzyl-1,4-dihydronicotinamide (BNAH) as the hydride source, the optimal DHFR variant favorably used the pro-R hydride from NADPH for stereoselective reactions (e.r. up to 92 : 8), highlighting that a switch of protein template could broaden the nucleophile option for catalysis. Owing to the cofactor compatibility, the DHFR-based secondary amine catalysis could be integrated into an enzymatic recycling scheme. This established method shows substantial potential in enzyme design, applicable from studies on enzyme evolution to the development of new biocatalysts.

Understanding and Promoting Preventive Health Service Use Among Black Men: Community-Driven and Informed Insights

Black men experience high rates of adverse health that can be prevented or mitigated by the regular use of preventive health services. Efforts are urgently needed to promote this type of health service use among Black men. The U.S. Preventive Services Task Force and the Institute of Medicine indicate that such efforts must align with Black men's values, perspectives, and preferences. However, little guidance exists on how to align these efforts for Black men. The present qualitative study was developed to understand factors associated with preventive health service use among Black men and community-informed strategies to promote preventive health service use among these men. An approach rooted in community-based participatory research and ecological theory was used. A core leadership team consisting of five Black men from the area guided the project's development, implementation, and evaluation. The core leadership team conducted 22 interviews with Black men from their communities. Four themes emerged from these interviews: (1) holistic well-being challenges faced by Black men: interaction of mental, physical, and societal forces; (2) the interplay of financial, informational, and gendered barriers/facilitators to using preventative health services among Black men; (3) the importance of shared identity in peer health education about preventive health service use; and (4) the need for community-centered initiatives to improve preventive health service use among Black men that prioritize accessibility and information. Findings of the present study can be used to tailor preventive health service use efforts for Black men. Such efforts have the potential to promote health and mitigate health disparities.

Evaluation of haem dipstick pad, urine protein, urine pH and urine protein:creatinine ratio results as a marker of bacteriuria in dogs and cats with inactive urine sediment

OBJECTIVES

Evaluation of haem dipstick pad, urine protein, urine pH and urine protein:creatinine ratio results as a marker of bacteriuria in dogs and cats with inactive urine sediment.

MATERIALS AND METHODS

Cats and dogs with contemporaneous urine dipstick, microscopic sediment analysis and microbiological culture and sensitivity results over a four-year period (2016 to 2020) were retrospectively identified. Dogs and cats with active urine sediments (at least five erythrocytes and/or five leukocytes per high-power field) and/or spermaturia were excluded. Association between urine pH, haem dipstick result, protein dipstick result and urine protein:creatinine ratio with bacteriuria were evaluated using binary logistic regression analysis. Likelihood ratios for bacteriuria were calculated at different diagnostic thresholds.

RESULTS

A total of 668 and 169 dog and cat urine samples were included. Of these, 166 dogs (25%) had a positive urine culture, whilst only 29 cats (17%) had a positive urine culture. In dogs and cats, any positive haem dipstick result was significantly associated with bacteriuria, although only a ≥4+ haem positive result in dogs was associated with a small increase in the likelihood of a positive urine culture, and positive likelihood ratios did not support the use of haem dipstick results as a screening test for bacteriuria in cats. pH, urine protein:creatinine ratio and protein dipstick results were not associated with bacteriuria.

CLINICAL SIGNIFICANCE

Our findings provide proof of concept that haem dipstick pad results in dogs with inactive sediment and without spermaturia might be useful as a screening test for bacteriuria, although further studies are required to confirm these findings.

Inducible apelin receptor knockdown reduces differentiation efficiency and contractility of hESC-derived cardiomyocytes

AIMS

The apelin receptor, a G protein-coupled receptor, has emerged as a key regulator of cardiovascular development, physiology, and disease. However, there is a lack of suitable human in vitro models to investigate the apelinergic system in cardiovascular cell types. For the first time we have used human embryonic stem cell-derived cardiomyocytes (hESC-CMs) and a novel inducible knockdown system to examine the role of the apelin receptor in both cardiomyocyte development and to determine the consequences of loss of apelin receptor function as a model of disease.

METHODS AND RESULTS

Expression of the apelin receptor and its ligands in hESCs and hESC-CMs was determined. hESCs carrying a tetracycline-inducible short hairpin RNA targeting the apelin receptor were generated using the sOPTiKD system. Phenotypic assays characterized the consequences of either apelin receptor knockdown before hESC-CM differentiation (early knockdown) or in 3D engineered heart tissues as a disease model (late knockdown). hESC-CMs expressed the apelin signalling system at a similar level to the adult heart. Early apelin receptor knockdown decreased cardiomyocyte differentiation efficiency and prolonged voltage sensing, associated with asynchronous contraction. Late apelin receptor knockdown had detrimental consequences on 3D engineered heart tissue contractile properties, decreasing contractility and increasing stiffness.

CONCLUSIONS

We have successfully knocked down the apelin receptor, using an inducible system, to demonstrate a key role in hESC-CM differentiation. Knockdown in 3D engineered heart tissues recapitulated the phenotype of apelin receptor down-regulation in a failing heart, providing a potential platform for modelling heart failure and testing novel therapeutic strategies.

FXR inhibition may protect from SARS-CoV-2 infection by reducing ACE2

Preventing SARS-CoV-2 infection by modulating viral host receptors, such as angiotensin-converting enzyme 2 (ACE2)1, could represent a new chemoprophylactic approach for COVID-19 that complements vaccination2,3. However, the mechanisms that control the expression of ACE2 remain unclear. Here we show that the farnesoid X receptor (FXR) is a direct regulator of ACE2 transcription in several tissues affected by COVID-19, including the gastrointestinal and respiratory systems. We then use the over-the-counter compound z-guggulsterone and the off-patent drug ursodeoxycholic acid (UDCA) to reduce FXR signalling and downregulate ACE2 in human lung, cholangiocyte and intestinal organoids and in the corresponding tissues in mice and hamsters. We show that the UDCA-mediated downregulation of ACE2 reduces susceptibility to SARS-CoV-2 infection in vitro, in vivo and in human lungs and livers perfused ex situ. Furthermore, we reveal that UDCA reduces the expression of ACE2 in the nasal epithelium in humans. Finally, we identify a correlation between UDCA treatment and positive clinical outcomes after SARS-CoV-2 infection using retrospective registry data, and confirm these findings in an independent validation cohort of recipients of liver transplants. In conclusion, we show that FXR has a role in controlling ACE2 expression and provide evidence that modulation of this pathway could be beneficial for reducing SARS-CoV-2 infection, paving the way for future clinical trials.

Prevalence of depression in amyotrophic lateral sclerosis/motor neuron disease: multi-attribute ascertainment and trajectories over 30 months

Objective: Evidence is equivocal about the prevalence of depression in amyotrophic lateral sclerosis (ALS). This study uses a multi-attribute ascertainment of the prevalence of depression and examines this prevalence over time. Methods: Patients with ALS were recruited into the Trajectories of Outcome in Neurological Conditions (TONiC-ALS) study. Caseness was identified by the Modified-Hospital Anxiety and Depression Scale (M-HADS). In addition, participants provided data on co-morbidities and medication use. A combination of the three was used to derive the estimate for the prevalence of depression, treated or untreated. Longitudinal data were analyzed by trajectory analysis of interval level M-HADS-Depression data. Results: Among 1120 participants, the mean age was 65.0 years (SD 10.7), 60.4% male, and the median duration since diagnosis was 9 months (IQR 4-24). Caseness of probable depression at baseline, defined by M-HADS-Depression, was 6.45% (95%CI: 5.1-8.0). Taken together with antidepressant medication and co-morbidity data, the prevalence of depression was 23.1% (95%CI: 20.7-25.6). Of those with depression, 17.8% were untreated. Trajectory analysis identified three groups, one of which contained the most cases; the level of depression for each group remained almost constant over time. Conclusion: Depression affects almost a quarter of those with ALS, largely confined to a single trajectory group. Prevalence estimates based on screening for current depressive symptoms substantially under-estimate the population experiencing depression. Future prevalence studies should differentiate data based on current symptoms from those including treated patients. Both have their place in assessing depression and the response by the health care system, including medication, depending upon the hypothesis under test.

Expanding the apelin receptor pharmacological toolbox using novel fluorescent ligands

INTRODUCTION

The apelin receptor binds two distinct endogenous peptides, apelin and ELA, which act in an autocrine/paracrine manner to regulate the human cardiovascular system. As a class A GPCR, targeting the apelin receptor is an attractive therapeutic strategy. With improvements in imaging techniques, and the stability and brightness of dyes, fluorescent ligands are becoming increasingly useful in studying protein targets. Here, we describe the design and validation of four novel fluorescent ligands; two based on [Pyr1]apelin-13 (apelin488 and apelin647), and two based on ELA-14 (ELA488 and ELA647).

METHODS

Fluorescent ligands were pharmacologically assessed using radioligand and functional in vitro assays. Apelin647 was validated in high content imaging and internalisation studies, and in a clinically relevant human embryonic stem cell-derived cardiomyocyte model. Apelin488 and ELA488 were used to visualise apelin receptor binding in human renal tissue.

RESULTS

All four fluorescent ligands retained the ability to bind and activate the apelin receptor and, crucially, triggered receptor internalisation. In high content imaging studies, apelin647 bound specifically to CHO-K1 cells stably expressing apelin receptor, providing proof-of-principle for a platform that could screen novel hits targeting this GPCR. The ligand also bound specifically to endogenous apelin receptor in stem cell-derived cardiomyocytes. Apelin488 and ELA488 bound specifically to apelin receptor, localising to blood vessels and tubules of the renal cortex.

DISCUSSION

Our data indicate that the described novel fluorescent ligands expand the pharmacological toolbox for studying the apelin receptor across multiple platforms to facilitate drug discovery.

Urinary extracellular vesicles as a source of protein-based biomarkers in feline chronic kidney disease and hypertension

OBJECTIVES

To validate a methodology for isolating feline urinary extracellular vesicles and characterise the urinary extracellular vesicle population and proteome in cats with normal renal function and cats with normotensive or hypertensive chronic kidney disease.

METHODS

Feline urinary extracellular vesicles were isolated using three different methods (precipitation alone, precipitation followed by size exclusion chromatography and ultrafiltration followed by size exclusion chromatography, which were compared via transmission electron microscopy and nanoparticle tracking analysis. Cats with normal renal function (n=9), normotensive chronic kidney disease (n=10) and hypertensive chronic kidney disease (n=9) were identified and urinary extracellular vesicles isolated from patient urine samples via ultrafiltration followed by size exclusion chromatography. Extracellular vesicle size and concentration were determined using nanoparticle tracking analysis, and subsequently underwent proteomic analysis using liquid chromatography with tandem mass spectrometry to identify differences in protein expression between categories.

RESULTS

Urinary extracellular vesicle preparations contained particles of the expected size and morphology, and those obtained by ultrafiltration + size exclusion chromatography had a significantly higher purity (highest particle: protein ratio). The urinary extracellular vesicle proteomes contained extracellular vesicle markers and proteins originating from all nephron segments. Urinary extracellular vesicle concentration and size were unaffected by renal disease or hypertension. There were no differentially expressed proteins detected when comparing urinary extracellular vesicles derived from cats in the healthy category with the combined chronic kidney disease category, but five differentially expressed proteins were identified between the normotensive chronic kidney disease and hypertensive chronic kidney disease categories.

CLINICAL SIGNIFICANCE

Feline urinary extracellular vesicles can be successfully isolated from stored urine samples. Differentially expressed urinary extracellular vesicle proteins were discovered in cats with hypertensive chronic kidney disease, and warrant further investigation into their utility as biomarkers or therapeutic targets.

Apelin is expressed throughout the human kidney, is elevated in chronic kidney disease & associates independently with decline in kidney function

AIMS

Chronic kidney disease (CKD) is common and cardiovascular disease (CVD) is its commonest complication. The apelin system is a potential therapeutic target for CVD but data relating to apelin in CKD are limited. We examined expression of the apelin system in human kidney, and investigated apelin and Elabela/Toddler (ELA), the endogenous ligands for the apelin receptor, in patients with CKD.

METHODS

Using autoradiography, immunohistochemistry and enzyme-linked immunosorbent assay, we assessed expression of apelin, ELA and the apelin receptor in healthy human kidney, and measured plasma apelin and ELA in 155 subjects (128 patients with CKD, 27 matched controls) followed up for 5 years. Cardiovascular assessments included blood pressure, arterial stiffness (pulse wave velocity) and brachial artery flow-mediated dilation. Surrogate markers of endothelial function (plasma asymmetric dimethylarginine and endothelin-1) and inflammation (C-reactive protein and interleukin-6) were measured.

RESULTS

The apelin system was expressed in healthy human kidney, throughout the nephron. Plasma apelin concentrations were 60% higher in women than men (6.48 [3.62-9.89] vs. 3.95 [2.02-5.85] pg/mL; P < .0001), and increased as glomerular filtration rate declined (R = -0.41, P < .0001), and albuminuria rose (R = 0.52, P < .0001). Plasma apelin and ELA were associated with vascular dysfunction. Plasma apelin associated independently with a 50% decline in glomerular filtration rate at 5 years.

CONCLUSION

We show for the first time that the apelin system is expressed in healthy human kidney. Plasma apelin is elevated in CKD and may be a potential biomarker of risk of decline in kidney function. Clinical studies exploring the therapeutic potential of apelin agonism in CKD are warranted.

Machine Learning-Based Rapid Detection of Volatile Organic Compounds in a Graphene Electronic Nose

Rapid detection of volatile organic compounds (VOCs) is growing in importance in many sectors. Noninvasive medical diagnoses may be based upon particular combinations of VOCs in human breath; detecting VOCs emitted from environmental hazards such as fungal growth could prevent illness; and waste could be reduced through monitoring of gases produced during food storage. Electronic noses have been applied to such problems, however, a common limitation is in improving selectivity. Graphene is an adaptable material that can be functionalized with many chemical receptors. Here, we use this versatility to demonstrate selective and rapid detection of multiple VOCs at varying concentrations with graphene-based variable capacitor (varactor) arrays. Each array contains 108 sensors functionalized with 36 chemical receptors for cross-selectivity. Multiplexer data acquisition from 108 sensors is accomplished in tens of seconds. While this rapid measurement reduces the signal magnitude, classification using supervised machine learning (Bootstrap Aggregated Random Forest) shows excellent results of 98% accuracy between 5 analytes (ethanol, hexanal, methyl ethyl ketone, toluene, and octane) at 4 concentrations each. With the addition of 1-octene, an analyte highly similar in structure to octane, an accuracy of 89% is achieved. These results demonstrate the important role of the choice of analysis method, particularly in the presence of noisy data. This is an important step toward fully utilizing graphene-based sensor arrays for rapid gas sensing applications from environmental monitoring to disease detection in human breath.

Differential expression in humans of the viral entry receptor ACE2 compared with the short deltaACE2 isoform lacking SARS-CoV-2 binding sites

ACE2 is a membrane protein that regulates the cardiovascular system. Additionally, ACE2 acts as a receptor for host cell infection by human coronaviruses, including SARS-CoV-2 that emerged as the cause of the on-going COVID-19 pandemic and has brought unprecedented burden to economy and health. ACE2 binds the spike protein of SARS-CoV-2 with high affinity and shows little variation in amino acid sequence meaning natural resistance is rare. The discovery of a novel short ACE2 isoform (deltaACE2) provides evidence for inter-individual differences in SARS-CoV-2 susceptibility and severity, and likelihood of developing subsequent 'Long COVID'. Critically, deltaACE2 loses SARS-CoV-2 spike protein binding sites in the extracellular domain, and is predicted to confer reduced susceptibility to viral infection. We aimed to assess the differential expression of full-length ACE2 versus deltaACE2 in a panel of human tissues (kidney, heart, lung, and liver) that are implicated in COVID-19, and confirm ACE2 protein in these tissues. Using dual antibody staining, we show that deltaACE2 localises, and is enriched, in lung airway epithelia and bile duct epithelia in the liver. Finally, we also confirm that a fluorescently tagged SARS-CoV-2 spike protein monomer shows low binding at lung and bile duct epithelia where dACE2 is enriched.

Selection for constrained peptides that bind to a single target protein

Peptide secondary metabolites are common in nature and have diverse pharmacologically-relevant functions, from antibiotics to cross-kingdom signaling. Here, we present a method to design large libraries of modified peptides in Escherichia coli and screen them in vivo to identify those that bind to a single target-of-interest. Constrained peptide scaffolds were produced using modified enzymes gleaned from microbial RiPP (ribosomally synthesized and post-translationally modified peptide) pathways and diversified to build large libraries. The binding of a RiPP to a protein target leads to the intein-catalyzed release of an RNA polymerase σ factor, which drives the expression of selectable markers. As a proof-of-concept, a selection was performed for binding to the SARS-CoV-2 Spike receptor binding domain. A 1625 Da constrained peptide (AMK-1057) was found that binds with similar affinity (990 ± 5 nM) as an ACE2-derived peptide. This demonstrates a generalizable method to identify constrained peptides that adhere to a single protein target, as a step towards "molecular glues" for therapeutics and diagnostics.

Human embryonic stem cell-derived cardiomyocyte platform screens inhibitors of SARS-CoV-2 infection

Patients with cardiovascular comorbidities are more susceptible to severe infection with SARS-CoV-2, known to directly cause pathological damage to cardiovascular tissue. We outline a screening platform using human embryonic stem cell-derived cardiomyocytes, confirmed to express the protein machinery critical for SARS-CoV-2 infection, and a SARS-CoV-2 spike-pseudotyped virus system. The method has allowed us to identify benztropine and DX600 as novel inhibitors of SARS-CoV-2 infection in a clinically relevant stem cell-derived cardiomyocyte line. Discovery of new medicines will be critical for protecting the heart in patients with SARS-CoV-2, and for individuals where vaccination is contraindicated.

Histopathological frequency of canine hepatobiliary disease in the United Kingdom

OBJECTIVES

Canine hepatobiliary disease is common; however, data determining disease frequency and breed predispositions are lacking. The primary objective was to identify the frequency of different hepatobiliary disease in a United Kingdom population of dogs and consequently determine breeds at both an increased and decreased risk of hepatobiliary disease.

MATERIALS AND METHODS

Anonymised histopathology reports from a commercial veterinary diagnostic laboratory, which were submitted between August 2013 and February 2018, were analysed. Data were retrospectively categorised into hepatobiliary diseases according to World Small Animal Veterinary Association Standards and the breed, age and genders recorded. Cases with incomplete data or no definitive diagnosis were excluded. Breed predisposition was calculated using odds ratios and 95% confidence intervals against a United Kingdom-based control population of micro-chipped dogs.

RESULTS

Histopathology results from 4584 cases met inclusion criteria. The most frequent histological diagnoses were reactive hepatitis (n=770); chronic hepatitis (n=735) and reversible hepatocellular injury (n=589). A number of breeds were shown to be at an increased or decreased risk of individual liver diseases.

CLINICAL SIGNIFICANCE

This is the first study to document the histopathological frequency of hepatobiliary diseases in a large cohort of dogs in the United Kingdom, as well as novel possible breed and age predispositions. Despite multivariable analysis not being performed to account for confounding factors, this information hopes to inform and support future investigations for hepatic disease in particular breeds and potential predispositions.

A retrospective study of canine idiopathic renal haematuria: clinical findings and outcome following medical treatment

OBJECTIVES

To characterise and document the progression of idiopathic renal haematuria in a large cohort of medically managed UK dogs.

MATERIALS AND METHODS

Retrospective study of 41 client-owned dogs with confirmed (n=14), or suspected (n=27) idiopathic renal haematuria from 4 UK-based referral centres. Clinical findings and outcomes of dogs (2001 to 2018) were determined from the review of medical records and telephone follow-up.

RESULTS

Median survival time from diagnosis was long [1482 (152 to 1825) days] irrespective of treatment and clinical response. Only 1 case was euthanased due to idiopathic renal haematuria, and anaemia or azotaemia occurred infrequently. In total, 25 dogs received angiotensin-converting enzyme-inhibitor or angiotensin receptor blocker therapy, of which 23 received benazepril [0.44 (0.19 to 0.82) mg/kg/24 hours], two received enalapril (0.40 and 0.78 mg/kg/24 hours) and one received telmisartan (1 mg/kg/24 hours). In cases with follow-up urinalyses, complete resolution of haematuria was documented in eight of 19 (42%) dogs following angiotensin-converting enzyme-inhibitor/angiotensin receptor blocker treatment, with partial improvement in five of 19 (26%) and no improvement in six of 19 (31%). Conversely, of the two untreated dogs where outcome was available, one had partial improvement and the other had no improvement.

CLINICAL SIGNIFICANCE

In this study, idiopathic renal haematuria was associated with a good prognosis and low complication rate. Resolution or improvement in haematuria occurred in both angiotensin-converting enzyme-inhibitor/angiotensin receptor blocker-treated and untreated dogs, indicating that further studies are required to evaluate the effectiveness and safety of these interventions.

The G Protein Biased Small Molecule Apelin Agonist CMF-019 is Disease Modifying in Endothelial Cell Apoptosis In Vitro and Induces Vasodilatation Without Desensitisation In Vivo

Signaling through the apelin receptor is beneficial for a number of diseases including pulmonary arterial hypertension. The endogenous small peptides, apelin and elabela/toddler, are downregulated in pulmonary arterial hypertension but are not suitable for exogenous administration owing to a lack of bioavailability, proteolytic instability and susceptibility to renal clearance. CMF-019, a small molecule apelin agonist that displays strong bias towards G protein signaling over β-arrestin (∼400 fold), may be more suitable. This study demonstrates that in addition to being a positive inotrope, CMF-019 caused dose-dependent vasodilatation in vivo (50 nmol 4.16 ± 1.18 mmHg, **p < 0.01; 500 nmol 6.62 ± 1.85 mmHg, **p < 0.01), without receptor desensitization. Furthermore, CMF-019 rescues human pulmonary artery endothelial cells from apoptosis induced by tumor necrosis factor α and cycloheximide (5.66 ± 0.97%, **p < 0.01) by approximately 50% of that observable with rhVEGF (11.59 ± 1.85%, **p < 0.01), suggesting it has disease-modifying potential in vitro. CMF-019 displays remarkable bias at the apelin receptor for a small molecule and importantly recapitulates all aspects of the cardiovascular responses to the endogenous ligand, [Pyr¹]apelin-13, in vivo. Additionally, it is able to protect human pulmonary artery endothelial cells from apoptosis, suggesting that the beneficial effects observed with apelin agonists extend beyond hemodynamic alleviation and address disease etiology itself. These findings support CMF-019 as a G protein biased small molecule apelin agonist in vitro and in vivo that could form the basis for the design of novel therapeutic agents in chronic diseases, such as, pulmonary arterial hypertension.

Transferability of N-terminal mutations of pyrrolysyl-tRNA synthetase in one species to that in another species on unnatural amino acid incorporation efficiency

Genetic code expansion is a powerful technique for site-specific incorporation of an unnatural amino acid into a protein of interest. This technique relies on an orthogonal aminoacyl-tRNA synthetase/tRNA pair and has enabled incorporation of over 100 different unnatural amino acids into ribosomally synthesized proteins in cells. Pyrrolysyl-tRNA synthetase (PylRS) and its cognate tRNA from Methanosarcina species are arguably the most widely used orthogonal pair. Here, we investigated whether beneficial effect in unnatural amino acid incorporation caused by N-terminal mutations in PylRS of one species is transferable to PylRS of another species. It was shown that conserved mutations on the N-terminal domain of MmPylRS improved the unnatural amino acid incorporation efficiency up to five folds. As MbPylRS shares high sequence identity to MmPylRS, and the two homologs are often used interchangeably, we examined incorporation of five unnatural amino acids by four MbPylRS variants at two temperatures. Our results indicate that the beneficial N-terminal mutations in MmPylRS did not improve unnatural amino acid incorporation efficiency by MbPylRS. Knowledge from this work contributes to our understanding of PylRS homologs which are needed to improve the technique of genetic code expansion in the future.

Apelin peptides linked to anti-serum albumin domain antibodies retain affinity in vitro and are efficacious receptor agonists in vivo

The apelin receptor is a potential target in the treatment of heart failure and pulmonary arterial hypertension where levels of endogenous apelin peptides are reduced but significant receptor levels remain. Our aim was to characterise the pharmacology of a modified peptide agonist, MM202, designed to have high affinity for the apelin receptor and resistance to peptidase degradation and linked to an anti-serum albumin domain antibody (AlbudAb) to extend half-life in the blood. In competition, binding experiments in human heart MM202-AlbudAb (pKi  = 9.39 ± 0.09) bound with similar high affinity as the endogenous peptides [Pyr1 ]apelin-13 (pKi  = 8.83 ± 0.06) and apelin-17 (pKi  = 9.57 ± 0.08). [Pyr1 ]apelin-13 was tenfold more potent in the cAMP (pD2  = 9.52 ± 0.05) compared to the β-arrestin (pD2  = 8.53 ± 0.03) assay, whereas apelin-17 (pD2  = 10.31 ± 0.28; pD2  = 10.15 ± 0.13, respectively) and MM202-AlbudAb (pD2  = 9.15 ± 0.12; pD2  = 9.26 ± 0.03, respectively) were equipotent in both assays, with MM202-AlbudAb tenfold less potent than apelin-17. MM202-AlbudAb bound to immobilised human serum albumin with high affinity (pKD  = 9.02). In anaesthetised, male Sprague Dawley rats, MM202-AlbudAb (5 nmol, n = 15) significantly reduced left ventricular systolic pressure by 6.61 ± 1.46 mm Hg and systolic arterial pressure by 14.12 ± 3.35 mm Hg and significantly increased cardiac contractility by 533 ± 170 mm Hg/s, cardiac output by 1277 ± 190 RVU/min, stroke volume by 3.09 ± 0.47 RVU and heart rate by 4.64 ± 2.24 bpm. This study demonstrates that conjugating an apelin mimetic peptide to the AlbudAb structure retains receptor and in vivo activity and may be a new strategy for development of apelin peptides as therapeutic agents.

Enabling protein-hosted organocatalytic transformations

In this review, the development of organocatalytic artificial enzymes will be discussed. This area of protein engineering research has underlying importance, as it enhances the biocompatibility of organocatalysis for applications in chemical and synthetic biology research whilst expanding the catalytic repertoire of enzymes. The approaches towards the preparation of organocatalytic artificial enzymes, techniques used to improve their performance (selectivity and reactivity) as well as examples of their applications are presented. Challenges and opportunities are also discussed.

Evaluation of the Idexx ProCyte Dx® for analysis of canine cerebrospinal fluid

OBJECTIVES

To assess the utility of the Idexx ProCyte Dx® haematology analyser for assessing total nucleated cell count and differential cell counts in canine cerebrospinal fluid.

MATERIALS AND METHODS

Seventy-three client-owned dogs undergoing investigations for pyrexia and/or neurological signs were prospectively included. Cerebrospinal fluid samples were assessed using an Idexx ProCyte Dx® analyser and the results were compared to those obtained with the external laboratory reference standard.

RESULTS

The Idexx ProCyte Dx® performed with good sensitivity (92.6%) and moderate specificity (67.4%) for total nucleated cell count when compared to the reference standard. Qualitative assessment of the Idexx ProCyte Dx® scatter plots, and quantitative assessment of differential cell counts where available, appeared to correlate well with the external laboratory manual differential cell counts, with a good-to-high agreement in 25 of 26 samples (96.2%).

CLINICAL SIGNIFICANCE

The Idexx ProCyte Dx® analyser performed well in determining the total nucleated cell count and differential cell counts in canine cerebrospinal fluid when compared to a reference standard of external laboratory analysis, except for cell counts higher than ~1000/μL. As the Idexx ProCyte Dx® currently only provides a cell count in 10 cells/μL increments, software modification may improve agreement between the two methods. As in human medicine, automated methods may prove useful in the future for cerebrospinal fluid analysis in addition to manual assessment, particularly in an emergency setting.

Apelin-36-[L28A] and Apelin-36-[L28C(30kDa-PEG)] peptides that improve diet induced obesity are G protein biased ligands at the apelin receptor

BACKGROUND

Apelin signalling pathways have important cardiovascular and metabolic functions. Recently, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)], were reported to function independent of the apelin receptor in vivo to produce beneficial metabolic effects without modulating blood pressure. We aimed to show that these peptides bound to the apelin receptor and to further characterise their pharmacology in vitro at the human apelin receptor.

METHODS

[Pyr¹]apelin-13 saturation binding experiments and competition binding experiments were performed in rat and human heart homogenates using [¹²⁵I]apelin-13 (0.1 nM), and/or increasing concentrations of apelin-36, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] (50pM-100μM). Apelin-36 and its analogues apelin-36-[F36A], apelin-36-[L28A], apelin-36-[L28C(30kDa-PEG)], apelin-36-[A28 A13] and [40kDa-PEG]-apelin-36 were tested in forskolin-induced cAMP inhibition and β-arrestin assays in CHO-K1 cells heterologously expressing the human apelin receptor. Bias signaling was quantified using the operational model for bias.

RESULTS

In both species, [Pyr¹]apelin-13 had comparable subnanomolar affinity and the apelin receptor density was similar. Apelin-36, apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] competed for binding of [¹²⁵I]apelin-13 with nanomolar affinities. Apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] inhibited forskolin-induced cAMP release, with nanomolar potencies but they were less potent compared to apelin-36 at recruiting β-arrestin. Bias analysis suggested that these peptides were G protein biased. Additionally, [40kDa-PEG]-apelin-36 and apelin-36-[F36A] retained nanomolar potencies in both cAMP and β-arrestin assays whilst apelin-36-[A13 A28] exhibited a similar profile to apelin-36-[L28C(30kDa-PEG)] in the β-arrestin assay but was more potent in the cAMP assay.

CONCLUSIONS

Apelin-36-[L28A] and apelin-36-[L28C(30kDa-PEG)] are G protein biased ligands of the apelin receptor, suggesting that the apelin receptor is an important therapeutic target in metabolic diseases.

International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.

Using genetically incorporated unnatural amino acids to control protein functions in mammalian cells

Genetic code expansion allows unnatural (non-canonical) amino acid incorporation into proteins of interest by repurposing the cellular translation machinery. The development of this technique has enabled site-specific incorporation of many structurally and chemically diverse amino acids, facilitating a plethora of applications, including protein imaging, engineering, mechanistic and structural investigations, and functional regulation. Particularly, genetic code expansion provides great tools to study mammalian proteins, of which dysregulations often have important implications in health. In recent years, a series of methods has been developed to modulate protein function through genetically incorporated unnatural amino acids. In this review, we will first discuss the basic concept of genetic code expansion and give an up-to-date list of amino acids that can be incorporated into proteins in mammalian cells. We then focus on the use of unnatural amino acids to activate, inhibit, or reversibly modulate protein function by translational, optical or chemical control. The features of each approach will also be highlighted.

Polymer Masked-Unmasked Protein Therapy: Identification of the Active Species after Amylase Activation of Dextrin-Colistin Conjugates

Polymer masked–unmasked protein therapy (PUMPT) uses conjugation of a biodegradable polymer, such as dextrin, hyaluronic acid, or poly(l-glutamic acid), to mask a protein or peptide’s activity; subsequent locally triggered degradation of the polymer at the target site regenerates bioactivity in a controllable fashion. Although the concept of PUMPT is well established, the relationship between protein unmasking and reinstatement of bioactivity is unclear. Here, we used dextrin–colistin conjugates to study the relationship between the molecular structure (degree of unmasking) and biological activity. Size exclusion chromatography was employed to collect fractions of differentially degraded conjugates and ultraperformance liquid chromatography–mass spectrometry (UPLC–MS) employed to characterize the corresponding structures. Antimicrobial activity was studied using a minimum inhibitory concentration (MIC) assay and confocal laser scanning microscopy of LIVE/DEAD-stained biofilms with COMSTAT analysis. In vitro toxicity of the degraded conjugate was assessed using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. UPLC–MS revealed that the fully “unmasked” dextrin–colistin conjugate composed of colistin bound to at least one linker, whereas larger species were composed of colistin with varying lengths of glucose units attached. Increasing the degree of dextrin modification by succinoylation typically led to a greater number of linkers bound to colistin. Greater antimicrobial and antibiofilm activity were observed for the fully “unmasked” conjugate compared to the partially degraded species (MIC = 0.25 and 2–8 μg/mL, respectively), whereas dextrin conjugation reduced colistin’s in vitro toxicity toward kidney cells, even after complete unmasking. This study highlights the importance of defining the structure–antimicrobial activity relationship for novel antibiotic derivatives and demonstrates the suitability of LC–MS to aid the design of biodegradable polymer–antibiotic conjugates.

A novel cyclic biased agonist of the apelin receptor, MM07, is disease modifying in the rat monocrotaline model of pulmonary arterial hypertension

BACKGROUND AND PURPOSE

Apelin is an endogenous vasodilatory and inotropic peptide that is down-regulated in human pulmonary arterial hypertension, although the density of the apelin receptor is not significantly attenuated. We hypothesised that a G protein-biased apelin analogue MM07, which is more stable than the endogenous apelin peptide, may be beneficial in this condition with the advantage of reduced β-arrestin-mediated receptor internalisation with chronic use.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats received either monocrotaline to induce pulmonary arterial hypertension or saline and then daily i.p. injections of either MM07 or saline for 21 days. The extent of disease was assessed by right ventricular catheterisation, cardiac MRI, and histological analysis of the pulmonary vasculature. The effect of MM07 on signalling, proliferation, and apoptosis of human pulmonary artery endothelial cells was investigated.

KEY RESULTS

MM07 significantly reduced the elevation of right ventricular systolic pressure and hypertrophy induced by monocrotaline. Monocrotaline-induced changes in cardiac structure and function, including right ventricular end-systolic and end-diastolic volumes, ejection fraction, and left ventricular end-diastolic volume, were attenuated by MM07. MM07 also significantly reduced monocrotaline-induced muscularisation of small pulmonary blood vessels. MM07 stimulated endothelial NOS phosphorylation and expression, promoted proliferation, and attenuated apoptosis of human pulmonary arterial endothelial cells in vitro.

CONCLUSION AND IMPLICATIONS

Our findings suggest that chronic treatment with MM07 is beneficial in this animal model of pulmonary arterial hypertension by addressing disease aetiology. These data support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Cell-penetrating peptide sequence and modification dependent uptake and subcellular distribution of green florescent protein in different cell lines

Protein therapy holds great promise for treating a variety of diseases. To act on intracellular targets, therapeutic proteins must cross the plasma membrane. This has previously been achieved by covalent attachment to a variety of cell-penetrating peptides (CPPs). However, there is limited information on the relative performance of CPPs in delivering proteins to cells, specifically the cytosol and other intracellular locations. Here we use green fluorescent protein (GFP) as a model cargo to compare delivery capacity of five CPP sequences (Penetratin, R8, TAT, Transportan, Xentry) and cyclic derivatives in different human cell lines (HeLa, HEK, 10T1/2, HepG2) representing different tissues. Confocal microscopy analysis indicates that most fusion proteins when incubated with cells at 10 µM localise to endosomes. Quantification of cellular uptake by flow cytometry reveals that uptake depends on both cell type (10T1/2 > HepG2 > HeLa > HEK), and CPP sequence (Transportan > R8 > Penetratin≈TAT > Xentry). CPP sequence cyclisation or addition of a HA-sequence increased cellular uptake, but fluorescence was still contained in vesicles with no evidence of endosomal escape. Our results provide a guide to select CPP for endosomal/lysosomal delivery and a basis for developing more efficient CPPs in the future.

Dynamic pigmentary and structural coloration within cephalopod chromatophore organs

Chromatophore organs in cephalopod skin are known to produce ultra-fast changes in appearance for camouflage and communication. Light-scattering pigment granules within chromatocytes have been presumed to be the sole source of coloration in these complex organs. We report the discovery of structural coloration emanating in precise register with expanded pigmented chromatocytes. Concurrently, using an annotated squid chromatophore proteome together with microscopy, we identify a likely biochemical component of this reflective coloration as reflectin proteins distributed in sheath cells that envelop each chromatocyte. Additionally, within the chromatocytes, where the pigment resides in nanostructured granules, we find the lens protein Ω- crystallin interfacing tightly with pigment molecules. These findings offer fresh perspectives on the intricate biophotonic interplay between pigmentary and structural coloration elements tightly co-located within the same dynamic flexible organ - a feature that may help inspire the development of new classes of engineered materials that change color and pattern.

Xanthommatin-Based Electrochromic Displays Inspired by Nature

Color is a signature visual feature in nature; however, the ability to trigger color change in the presence of different environmental stimuli is unique to only a handful of species in the animal kingdom. We exploit the natural color-changing properties of the predominant pigment in arthropods and cephalopods-xanthommatin (Xa)-and describe its utility as a new broad-spectrum electrochromic material. To accomplish this goal, we explored the spectroelectrochemical properties of Xa adsorbed to an indium-doped tin oxide-coated substrate chemically modified with poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). We identified a synergistic role between PEDOT:PSS and Xa that contributed to its absorption profile, which could be modulated across multiple cycles. By varying the ratio of the two electroactive components, we also altered the perceived visible color of Xa-based devices, which cycled from different shades of red to yellow under reducing and oxidizing potentials, respectively. Together, our data illustrate the utility of Xa-based devices as new broad-spectrum electrochromic materials.

Carbapenems as water soluble organocatalysts

Background: Identification of organocatalysts functioning in aqueous environments will provide methods for more sustainable chemical transformations and allow tandem reactions with biocatalysts, like enzymes. Here we examine three water-soluble carbapenem antibiotics (meropenem, doripenem, and ertapenem) as secondary amine organocatalysts in aqueous environments. Methods: The Michael addition of nitromethane to cinnamaldehyde was used as the model reaction. The reactions were monitored by 1H NMR, and the enantioselectivity was determined by chiral HPLC.   Results: The effects of buffer components, pH, organic co-solvents and anchoring into a protein scaffold were investigated. Moderate yields of the Michael addition were obtained in buffer alone. The use of methanol as a co-solvent in a ratio of 1:1 increases the yield by 50%. Anchoring of the catalysts into a protein backbone reverses the enatioselectivity of the reaction. Conclusions: Despite only moderate yields and enantioselectivities being obtained, this study lays the foundations for future development of efficient organocatalysis in aqueous environments.

Calcitonin Response to Naturally Occurring Ionized Hypercalcemia in Cats with Chronic Kidney Disease

Background

Hypercalcemia is commonly associated with chronic kidney disease (CKD) in cats.

Objectives

To explore the calcitonin response to naturally occurring ionized hypercalcemia in cats with azotemic CKD, and to assess the relationship of plasma calcitonin with ionized calcium, alkaline phosphatase (ALP), and urinary calcium excretion.

Animals

Thirty‐three client‐owned cats with azotemic CKD and ionized hypercalcemia from first opinion practice.

Methods

Cohort study. Calcitonin was measured with an immunoradiometric assay in heparinized plasma. Simple correlations were assessed with Kendall's rank correlation, and the within‐subject correlations of calcitonin with ionized calcium and other clinicopathological variables were calculated with a bivariate linear mixed effects model.

Results

Calcitonin concentrations above the lower limit of detection (>1.2 pg/mL; range, 1.7–87.2 pg/mL) were observed in 11 of 33 hypercalcemic cats (responders). Blood ionized calcium concentration did not differ significantly between responders (median, 1.59 [1.46, 1.66] mmol/L) and nonresponders (median, 1.48 [1.43, 1.65] mmol/L; P = 0.22). No evidence was found for calcitonin and ionized calcium to correlate between cats (τ_b = 0.14; P = 0.31; n = 33), but significant positive correlation was evident within individual responders over time (within‐subject correlation coefficient [r_within], 0.83; 95% confidence interval [CI], 0.63–0.92). Calcitonin correlated negatively over time with plasma ALP (r_within, −0.55; 95% CI, −0.79 to −0.16).

Conclusions and Clinical Importance

Calcitonin does not appear to have an important role in calcium metabolism in cats with CKD.

Selective targeting of PARP-1 zinc finger recognition domains with Au(iii) organometallics

Insights into gold finger formation by organometallics and implications for targeting pharmacologically relevant zinc-finger proteins.

Elucidation of insulin assembly at acidic and neutral pH: Characterization of low molecular weight oligomers

Deficiency in insulin secretion and function that characterize type 2 diabetes often requires administration of extraneous insulin, leading to injection-site amyloidosis. Insulin aggregation at neutral pH is not well understood. Although oligomer formation is believed to play an important role, insulin oligomers have not been fully characterized yet. Here, we elucidate similarities and differences between in vitro insulin aggregation at acidic and neutral pH for a range of insulin concentrations (2.5-100 μM) by using kinetic thioflavin T fluorescence, circular dichroism, atomic force and electron microscopy imaging. Importantly, we characterize the size distribution of insulin oligomers at different assembly stages by the application of covalent cross-linking and gel electrophoresis. Our results show that at the earliest assembly stage, oligomers comprise up to 40% and 70% of soluble insulin at acidic and neutral pH, respectively. While the highest oligomer order increases with insulin concentration at acidic pH, the opposite tendency is observed at neutral pH, where oligomers up to heptamers are formed in 10 μM insulin. These findings suggest that oligomers may be on- and off-pathway assemblies for insulin at acidic and neutral pH, respectively. Agitation, which is required to induce insulin aggregation at neutral pH, is shown to increase fibril formation rate and fibrillar mass both by an order of magnitude. Insulin incubated under agitated conditions at neutral pH rapidly aggregates into large micrometer-sized aggregates, which may be of physiological relevance and provides insight into injection-site amyloidosis and toxic pulmonary aggregates induced by administration of extraneous insulin.

The Vip3Ag4 Insecticidal Protoxin from Bacillus thuringiensis Adopts A Tetrameric Configuration That Is Maintained on Proteolysis

The Vip3 proteins produced during vegetative growth by strains of the bacterium Bacillus thuringiensis show insecticidal activity against lepidopteran insects with a mechanism of action that may involve pore formation and apoptosis. These proteins are promising supplements to our arsenal of insecticidal proteins, but the molecular details of their activity are not understood. As a first step in the structural characterisation of these proteins, we have analysed their secondary structure and resolved the surface topology of a tetrameric complex of the Vip3Ag4 protein by transmission electron microscopy. Sites sensitive to proteolysis by trypsin are identified and the trypsin-cleaved protein appears to retain a similar structure as an octomeric complex comprising four copies each of the ~65 kDa and ~21 kDa products of proteolysis. This processed form of the toxin may represent the active toxin. The quality and monodispersity of the protein produced in this study make Vip3Ag4 a candidate for more detailed structural analysis using cryo-electron microscopy.

A Method for Extracting Pigments from Squid Doryteuthis pealeii

Cephalopods can undergo rapid and adaptive changes in dermal coloration for sensing, communication, defense, and reproduction purposes. These capabilities are supported in part by the areal expansion and retraction of pigmented organs known as chromatophores. While it is known that the chromatophores contain a tethered network of pigmented granules, their structure-function properties have not been fully detailed. We describe a method for isolating the nanostructured granules in squid Doryteuthis pealeii chromatophores and demonstrate how their associated pigments can be extracted in acidic solvents. To accomplish this, the chromatophore containing dermal layer is first manually isolated using a superficial dissection, and the pigment granules are removed using sonication, centrifugation, and washing cycles. Pigments confined within the purified granules are then extracted via acidic methanol solutions, leaving nanostructures with smaller diameters that are void of visible color. This extraction procedure produces a 58% yield of soluble pigments isolated from granules. Using this method, the composition of the chromatophore pigments can be determined and used to provide insight into the mechanism of adaptive coloration in cephalopods.

Exercise as a Prophylactic Device against Carpal Tunnel Syndrome

The null hupothesis that participation in an on-the-job strength and flexibility exercise program typical of those directed toward prevention of musculoskeletal stress has no prophylactic effect against carpal tunnel syndrome when used as an intervention measure in a population of female garment workers was examined. Grip strength, Phelan's test results, and hand/wrist thermograms obtained by liquid crystal thermography were taken on an experimental group of female employees in a southern garment manufacturing facility before, after five weeks, and after ten weeks of an exercise program and compared with data obtained from a control group. Although the test results suggested the exercise program may have had some benefit, the null hypothesis could not be rejected. An engineering economic analysis, assuming the exercise program was effective and implemented throughout the corporation, indicated the payback period would be approximately eleven years thus casting doubt on its economic efficacy also.

Serum Cystatin C Concentrations in Cats with Hyperthyroidism and Chronic Kidney Disease

Background

Currently, no test can accurately predict the development of azotemia after treatment of hyperthyroidism. Serum cystatin C concentrations (sCysC) might be less influenced by changes in body muscle mass and so better indicate the presence of concurrent chronic kidney disease (CKD) in hyperthyroidism.

Hypotheses

sCysC will be higher in hyperthyroid cats that develop azotemia compared with hyperthyroid cats that remain nonazotemic after treatment; sCysC will be higher in nonhyperthyroid cats with azotemic CKD than healthy older cats and, sCysC will decrease after treatment of hyperthyroidism.

Animals

Ninety‐one cats treated in first opinion practice.

Methods

Case–control study. sCysC were compared between hyperthyroid cats which developed azotemia within 4 months of successful treatment of hyperthyroidism (pre‐azotemic group) and hyperthyroid cats which remained nonazotemic after treatment (nonazotemic group), and between nonhyperthyroid cats with azotemic CKD and healthy older cats. sCysC were also compared between hyperthyroid cats before treatment and at time of establishment of euthyroidism. Data are presented as median [25th, 75th percentile].

Results

Baseline sCysC were not different between the pre‐azotemic and nonazotemic groups (1.9 [1.4, 2.3] mg/L versus 1.5 [1.1, 2.2] mg/L, respectively; P = .22). sCysC in nonhyperthyroid cats with azotemic CKD and healthy older cats were not significantly different (1.5 [1.0, 1.9] mg/L versus 1.2 [0.8, 1.4] mg/L, respectively; P = .16). sCysC did not change significantly after treatment of hyperthyroidism (pretreatment 1.8 [1.2, 2.3] mg/L, after treatment 1.6 [1.1, 2.4] mg/L; P = .82).

Conclusions and Clinical Importance

sCysC do not appear to be a reliable marker of renal function in hyperthyroid cats.

Contributions of Phenoxazone-Based Pigments to the Structure and Function of Nanostructured Granules in Squid Chromatophores

Understanding the structure-function relationships of pigment-based nanostructures can provide insight into the molecular mechanisms behind biological signaling, camouflage, or communication experienced in many species. In squid Doryteuthis pealeii, combinations of phenoxazone-based pigments are identified as the source of visible color within the nanostructured granules that populate dermal chromatophore organs. In the absence of the pigments, granules experience a reduction in diameter with the loss of visible color, suggesting important structural and functional features. Energy gaps are estimated from electronic absorption spectra, revealing highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energies that are dependent upon the varying carboxylated states of the pigment. These results implicate a hierarchical mechanism for the bulk coloration in cephalopods originating from the molecular components confined within in the nanostructured granules of chromatophore organs.

Soluble Prion Protein Binds Isolated Low Molecular Weight Amyloid-β Oligomers Causing Cytotoxicity Inhibition

A growing number of observations indicate that soluble amyloid-β (Aβ) oligomers play a major role in Alzheimer's disease. Recent studies strongly suggest that at least some of the neurotoxic effects of these oligomers are mediated by cellular, membrane-anchored prion protein and that Aβ neurotoxicity can be inhibited by soluble recombinant prion protein (rPrP) and its fragments. However, the mechanism by which rPrP interacts with Aβ oligomers and prevents their toxicity is largely unknown, and studies in this regard are hindered by the large structural heterogeneity of Aβ oligomers. To overcome this difficulty, here we used photoinduced cross-linking of unmodified proteins (PICUP) to isolate well-defined oligomers of Aβ42 and characterize these species with regard to their cytotoxicity and interaction with rPrP, as well the mechanism by which rPrP inhibits Aβ42 cytotoxicity. Our data shows that the addition of rPrP to the assembling Aβ42 results in a shift in oligomer size distribution, decreasing the population of toxic tetramers and higher order oligomers and increasing the population of nontoxic (and possibly neuroprotective) monomers. Isolated oligomeric species of Aβ42 are cytotoxic to primary neurons and cause permeation of model lipid bilayers. These toxic effects, which are oligomer size-dependent, can be inhibited by the addition of rPrP, and our data suggest potential mechanisms of this inhibitory action. This insight should help in current efforts to develop PrP-based therapeutics for Alzheimer's disease.

Stabilization of native amyloid β-protein oligomers by Copper and Hydrogen peroxide Induced Cross-linking of Unmodified Proteins (CHICUP)

Oligomeric assemblies are postulated to be proximate neurotoxic species in human diseases associated with aberrant protein aggregation. Their heterogeneous and transient nature makes their structural characterization difficult. Size distributions of oligomers of several amyloidogenic proteins, including amyloid β-protein (Aβ) relevant to Alzheimer's disease (AD), have been previously characterized in vitro by photo-induced cross-linking of unmodified proteins (PICUP) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Due to non-physiological conditions associated with the PICUP chemistry, Aβ oligomers cross-linked by PICUP may not be representative of in vivo conditions. Here, we examine an alternative Copper and Hydrogen peroxide Induced Cross-linking of Unmodified Proteins (CHICUP), which utilizes naturally occurring divalent copper ions and hydrogen peroxide and does not require photo activation. Our results demonstrate that CHICUP and PICUP applied to the two predominant Aβ alloforms, Aβ40 and Aβ42, result in similar oligomer size distributions. Thioflavin T fluorescence data and atomic force microscopy images demonstrate that both CHICUP and PICUP stabilize Aβ oligomers and attenuate fibril formation. Relative to noncross-linked peptides, CHICUP-treated Aβ40 and Aβ42 cause prolonged disruption to biomimetic lipid vesicles. CHICUP-stabilized Aβ oligomers link the amyloid cascade, metal, and oxidative stress hypotheses of AD into a more comprehensive understanding of the molecular basis of AD pathology. Because copper and hydrogen peroxide are elevated in the AD brain, CHICUP-stabilized Aβ oligomers are biologically relevant and should be further explored as a new therapeutic target.

Europium as an inhibitor of Amyloid-β(1-42) induced membrane permeation

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Europium ions complex with GM1 gangliosides in phospholipid membranes.

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Europium ions cause inhibition Aβ–membrane interactions.

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Europium blocks an Aβ receptor protecting against membrane permeation.

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Discrete Aβ binding events correlate to specific membrane permeation events.

Soluble Amyloid-beta (Aβ) oligomers are a source of cytotoxicity in Alzheimer’s disease (AD). The toxicity of Aβ oligomers may arise from their ability to interact with and disrupt cellular membranes mediated by GM1 ganglioside receptors within these membranes. Therefore, inhibition of Aβ–membrane interactions could provide a means of preventing the toxicity associated with Aβ. Here, using Surface Plasmon field-enhanced Fluorescence Spectroscopy, we determine that the lanthanide, Europium III chloride (Eu³⁺), strongly binds to GM1 ganglioside-containing membranes and prevents the interaction with Aβ42 leading to a loss of the peptides ability to cause membrane permeation. Here we discuss the molecular mechanism by which Eu³⁺ inhibits Aβ42-membrane interactions and this may lead to protection of membrane integrity against Aβ42 induced toxicity.