Endothelin-1 amplifies ventricular repolarization heterogeneities in chronic myocardial infarction pigs

Introduction: Endothelin-1 (ET-1) is a vasoconstrictor peptide secreted by endothelial cells and cardiac myocytes and fibroblasts. It is involved in oxidative stress, apoptosis regulation and ventricular remodeling processes associated with heart failure and ischemic cardiomyopathy, including myocardial hypertrophy, fibrosis and impaired conduction. ET-1 has been shown to influence cardiac electrophysiology by modulation of calcium and potassium currents and to contribute to arrhythmogenesis and sudden cardiac death. Purpose: We aim to characterize the functional role of ET-1 in the electrophysiology of healed myocardial infarction (MI) by analysis of porcine ventricular slices as a highly representative model of ventricular tissue with preserved cellular cross-talks and architecture. Methods: Domestic pigs (60–80 kg, n = 3) were infarcted by temporal occlusion of the left anterior descending coronary artery. 8-12 weeks after infarct induction, animals were cardioplegically arrested under deep anesthesia and sacrificed. All animal procedures conformed to the guidelines from Directive 2010/63/EU and were approved by local authorities. 350 µm-thick ventricular slices were produced from transmural tissue blocks of healed MI ventricles. Tissue blocks were taken from remote, adjacent and border zones of the infarct area. Slices were optically mapped within 8 hours after tissue collection to record transmembrane potential and intracellular calcium. Action Potential Duration (APD) and Calcium Transient Duration (CaTD) were measured at 80% repolarization for 0.5, 1 and 2 Hz pacing frequencies in the presence and absence of 100 nM ET-1. The notation n/N is used to denote n tissue slices from N pigs. Results: ET-1 prolonged the APD at all frequencies in remote zones, with mean prolongation percentages of 30.5%, 32%, 26.2% at 0.5, 1 and 2 Hz, respectively, n/N=7/3. However, only minor effects were observed in adjacent (mean APD prolongation of 3.3%, 4.9% and 10.7%, n/N=5/3) and border zones (7%, 4% and 3.6%, n/N=5/3). ET-1 caused an increase in CaTD at 1 Hz in the three zones, with no significant regional differences in the amount of CaTD increase: mean prolongation of 14.1% (n/N=7/3) in the remote zone, 12.4 % (n/N=5/3) in the adjacent zone and 20.9% (n/N=4/3) in the border zone. Conclusions: In chronic MI pigs, ET-1 induces strong APD and moderate CaTD prolongation of remote normal myocardium at low (0.5 Hz) to high (2 Hz) frequencies. The ET-1-induced effects on the AP of normal tissue, but not on CaT, are disrupted in the border zones of the infarct area and in its proximity. Our results point to ET-1 acting to enhance ventricular repolarization dispersion in chronic MI pigs, which might contribute to increased arrhythmia vulnerability

Sequencing of folding events in Go-like proteins

We have studied folding mechanisms of three small globular proteins: crambin (CRN), chymotrypsin inhibitor 2 (CI2) and the fyn Src Homology 3 domain (SH3) which are modelled by a Go-like Hamiltonian with the Lennard-Jones interactions. It is shown that folding is dominated by a well-defined sequencing of events as determined by establishment of particular contacts. The order of events depends primarily on the geometry of the native state. Variations in temperature, coupling strengths and viscosity affect the sequencing scenarios to a rather small extent. The sequencing is strongly correlated with the distance of the contacting aminoacids along the sequence. Thus $\alpha$-helices get established first. Crambin is found to behave like a single-route folder, whereas in CI2 and SH3 the folding trajectories are more diversified. The folding scenarios for CI2 and SH3 are consistent with experimental studies of their transition states.Comment: REVTeX, 12 pages, 11 EPS figures, J. Chem. Phys (in press

Evaluation of technologies for the extraction of phenolic compounds of cocoa

[SPA] Los antioxidantes del cacao son principalmente flavan 3-oles ((+)-catequina, (-)-epicatequina) y procianidinas, los cuales se reducen durante el proceso de industrialización de los granos. Por esta razón se buscan métodos que permitan concentrar dichos compuestos para el enriquecimiento de productos funcionales. El objetivo de este trabajo fue encontrar la mejor tecnología para la extracción de los compuestos fenólicos del cacao, principalmente los flavan 3-oles. Para este análisis se obtuvo un polvo de cacao sin fermentar el cual fue sometido a diferentes tecnologías de extracción: fluidos supercríticos, extracción asistida por ultrasonido, tratamientos hidrotérmicos (Phytoclean™), sistema de purificación de alto rendimiento (Reveleris®) y extracción por solventes, con el fin de obtener el mayor contenido posible de (+)-catequina y (-)-epicatequina. Se encontró que la mejor extracción fue con solvente ya que concentra de forma superior los flavan 3-oles (20% c.a.) en comparación con en el contenido de inicial de estos compuestos en el polvo de cacao. [ENG] The cocoa antioxidants are mainly flavan 3-ols ((+)-catechin, (-)-epicatechin) and procyanidins, which are reduced during the bean industrialization process. For this reason, there are several methods to concentrate these compounds for the enrichment of functional products. The objective of this work was to find the best technology for the extraction of cocoa phenolic compounds, mainly flavan-3-ols. For this analysis, unfermented cocoa powder was obtained and subjected to different extraction technologies: supercritical fluids, ultrasound-assisted extraction, hydrothermal treatments (Phytoclean™), high-performance purification system (Reveleris®), and solvent extraction, to obtain the highest possible content of (+)-catechin and (-)-epicatechin. It was found that the best extraction was by solvent extraction as it concentrated the flavan 3-ols (20% a.c.) in a superior way compared to the initial content of these compounds in the cocoa powder.Agradecimiento a Compañía Nacional de Chocolates S.A.S por la financiación de este proyect

Conformations of Proteins in Equilibrium

We introduce a simple theoretical approach for an equilibrium study of proteins with known native state structures. We test our approach with results on well-studied globular proteins, Chymotrypsin Inhibitor (2ci2), Barnase and the alpha spectrin SH3 domain and present evidence for a hierarchical onset of order on lowering the temperature with significant organization at the local level even at high temperatures. A further application to the folding process of HIV-1 protease shows that the model can be reliably used to identify key folding sites that are responsible for the development of drug resistance .Comment: 6 pages, 3 eps figure

SK channels contribution to ventricular electrophysiology in heart failure patients

Heart failure (HF) is characterized by deterioration of the electrical and contractile function of the heart due to structural and functional remodelling, leading to development of arrhythmias and increased sudden cardiac death risk. SK channels are a type of calcium-activated potassium channels that do not play a relevant role in normal ventricular electrophysiology. However, it has been hypothesized that these channels become more relevant in pathologies such as HF. Nontheless, their role in human ventricular electrophysiology is not fully characterized

Inhibition of intermediate-conductance calcium-activated K channel (KCa3.1) and fibroblast mitogenesis by a-linolenic acid and alterations of channel expression in the lysosomal storage disorders, fabry disease, and niemann pick C

The calcium/calmodulin-gated KCa3.1 channel regulates normal and abnormal mitogenesis by controlling K+-efflux, cell volume, and membrane hyperpolarization-driven calcium-entry. Recent studies suggest modulation of KCa3.1 by omega-3 fatty acids as negative modulators and impaired KCa3.1 functions in the inherited lysosomal storage disorder (LSD), Fabry disease (FD). In the first part of present study, we characterize KCa3.1 in murine and human fibroblasts and test the impact of omega-3 fatty acids on fibroblast proliferation. In the second, we study whether KCa3.1 is altered in the LSDs, FD, and Niemann-Pick disease type C (NPC). Our patch-clamp and mRNA-expression studies on murine and human fibroblasts show functional expression of KCa3.1. KCa currents display the typical pharmacological fingerprint of KCa3.1: Ca2+-activation, potentiation by the positive-gating modulators, SKA-31 and SKA-121, and inhibition by TRAM-34, Senicapoc (ICA-17043), and the negative-gating modulator, 13b. Considering modulation by omega-3 fatty acids we found that a-linolenic acid (a-LA) and docosahexanenoic acid (DHA) inhibit KCa3.1 currents and strongly reduce fibroblast growth. The a-LA-rich linseed oil and ¿-LA-rich borage oil at 0.5% produce channel inhibition while a-LA/¿-LA-low oils has no anti-proliferative effect. Concerning KCa3.1 in LSD, mRNA expression studies, and patch-clamp on primary fibroblasts from FD and NPC patients reveal lower KCa3.1-gene expression and membrane expression than in control fibroblasts. In conclusion, the omega-3 fatty acid, a-LA, and a-LA/¿-LA-rich plant oils, inhibit fibroblast KCa3.1 channels and mitogenesis. Reduced fibroblast KCa3.1 functions are a feature and possible biomarker of cell dysfunction in FD and NPC and supports the concept that biased lipid metabolism is capable of negatively modulating KCa3.1 expression

Conditional KCa3.1-transgene induction in murine skin produces pruritic eczematous dermatitis with severe epidermal hyperplasia and hyperkeratosis

Ion channels have recently attracted attention as potential mediators of skin disease. Here, we explored the consequences of genetically encoded induction of the cell volume-regulating Ca2+-activated KCa3.1 channel (Kcnn4) for murine epidermal homeostasis. Doxycycline-treated mice harboring the KCa3.1+-transgene under the control of the reverse tetracycline-sensitive transactivator (rtTA) showed 800-fold channel overexpression above basal levels in the skin and solid KCa3.1-currents in keratinocytes. This overexpression resulted in epidermal spongiosis, progressive epidermal hyperplasia and hyperkeratosis, itch and ulcers. The condition was accompanied by production of the pro-proliferative and pro-inflammatory cytokines, IL-ß1 (60-fold), IL-6 (33-fold), and TNFa (26-fold) in the skin. Treatment of mice with the KCa3.1-selective blocker, Senicapoc, significantly suppressed spongiosis and hyperplasia, as well as induction of IL-ß1 (-88%) and IL-6 (-90%). In conclusion, KCa3.1-induction in the epidermis caused expression of pro-proliferative cytokines leading to spongiosis, hyperplasia and hyperkeratosis. This skin condition resembles pathological features of eczematous dermatitis and identifies KCa3.1 as a regulator of epidermal homeostasis and spongiosis, and as a potential therapeutic target

Analysis of age-related left ventricular collagen remodeling in living donors: Implications in arrhythmogenesis

Age-related fibrosis in the left ventricle (LV) has been mainly studied in animals by assessing collagen content. Using second-harmonic generation microscopy and image processing, we evaluated amount, aggregation and spatial distribution of LV collagen in young to old pigs, and middle-age and elder living donors. All collagen features increased when comparing adult and old pigs with young ones, but not when comparing adult with old pigs or middle-age with elder individuals. Remarkably, all collagen parameters strongly correlated with lipofuscin, a biological age marker, in humans. By building patient-specific models of human ventricular tissue electrophysiology, we confirmed that amount and organization of fibrosis modulated arrhythmia vulnerability, and that distribution should be accounted for arrhythmia risk assessment. In conclusion, we characterize the age-associated changes in LV collagen and its potential implications for ventricular arrhythmia development. Consistency between pig and human results substantiate the pig as a relevant model of age-related LV collagen dynamics. © 2022 The Author(s

Tracking antioxidant properties and color changes in low-sugar bilberry jam as effect of processing, storage and pectin concentration

<p>Abstract</p> <p>Background</p> <p>Recently, an increased interest in the identification of valuable possibilities for preserving the antioxidant properties of products obtained by thermal processing of fruits rich in bioactive compounds can be noticed. In this regard, an extensive analysis is necessary in terms of thermal processed products behavior in relation to various factors. The purpose of the present study was to assess the effect which processing and storage at 20°C has on the antioxidant properties and color quality of low-sugar bilberry jam with different low-methoxyl pectin (LMP) concentrations.</p> <p>Results</p> <p>For all measured parameters, it should be noted that thermal processing induced significant alterations reported to the values registered for fresh fruit. Most important losses due to thermal processing were recorded for total monomeric anthocyanins (TMA) (81-84%), followed by L-ascorbic acid (L-AsAc) content (53-58%), total phenolics (TP) content (42-51%) and FRAP (ferric reducing antioxidant power) values (36-47%). Moreover, depreciation of the investigated compounds occurred during storage at 20°C. Jam storage for 7 months resulted in severe losses in TMA content in the range 58-72% from the value recorded one day after processing. This coincided with marked increases in polymeric color percent of these products after 7 months of storage. Also, bilberry jam storage for 7 months resulted in a decrease in L-AsAc content of 40-53% from the value recorded one day after processing, 41-57% in TP content and 33-46% from the value recorded one day after processing for FRAP values. By decreasing of LMP concentration in the jam recipe from 1 to 0.3% there has been an increase in losses of investigated compounds.</p> <p>Conclusion</p> <p>Overall, the results indicated that bilberry jams can also represent a good source of antioxidant compounds, although compared to the fruit, important losses seem to occur. Practical application of this work is that this kind of information will be very useful in optimizing the jam processing technology and storage conditions, in order to improve the quality of these products.</p