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Hypothyroidism is the most frequent endocrine pathology. Although clinical or overt hypothyroidism has been traditionally associated to low T3 / T4 and high thyrotropin (TSH) circulating levels, other forms exist such as subclinical hypothyroidism, characterized by normal blood T3 / T4 and high TSH. In its different forms is estimated to affect approximately 10% of the population, especially women, in a 5:1 ratio with respect to men. Among its consequences are alterations in cardiac electrical activity, especially in the repolarization phase, which is accompanied by an increased susceptibility to cardiac arrhythmias. Although these alterations have traditionally been attributed to thyroid hormone deficiency, recent studies, both clinical trials and experimental models, demonstrate a fundamental role of TSH in cardiac electrical remodeling. Thus, both metabolic thyroid hormones and TSH regulate cardiac ion channel expression in many and varied ways. This means that the different combinations of hormones that predominate in different types of hypothyroidism (overt, subclinic, primary, central) can generate different forms of cardiac electrical remodeling. These new findings are raising the relevant question of whether serum TSH reference ranges should be redefined., (© 2023. The Author(s).)

Purpose: Kv1.3 channel regulates the activity of lymphocytes, macrophages, or adipose tissue and its blockade reduces inflammatory cytokine secretion and improves insulin sensitivity in animals with metabolic syndrome and in genetically obese mice. Thus, Kv1.3 blockade could be a strategy for the treatment of type 2 diabetes. Elevated circulating levels of TNFα and IL-1b mediate the higher susceptibility to cardiac arrhythmia in type 2 diabetic rats. We hypothesized that Kv1.3 channel blockade with the psoralen PAP1 could have immunomodulatory properties that prevent QTc prolongation and reduce the risk of arrhythmia in type 2 diabetic rats., Methods: Type 2 diabetes was induced to Sprague-Dawley rats by high-fat diet and streptozotocin injection. Diabetic animals were untreated, treated with metformin, or treated with PAP1 for 4 weeks. Plasma glucose, insulin, cholesterol, triglycerides, and cytokine levels were measured using commercial kits. ECG were recorded weekly, and an arrhythmia-inducing protocol was performed at the end of the experimental period. Action potentials were recorded in isolated ventricular cardiomyocytes., Results: In diabetic animals, PAP1 normalized glycaemia, insulin resistance, adiposity, and lipid profile. In addition, PAP1 prevented the diabetes-induced repolarization defects through reducing the secretion of the inflammatory cytokines IL-10, IL-12p70, GM-CSF, IFNγ, and TNFα. Moreover, compared to diabetic untreated and metformin-treated animals, those treated with PAP1 had the lowest risk of developing the life-threatening arrhythmia Torsade de Pointes under cardiac challenge., Conclusion: Kv1.3 inhibition improves diabetes and diabetes-associated low-grade inflammation and cardiac electrical remodeling, resulting in more protection against cardiac arrhythmia compared to metformin., (© 2021. The Author(s).)

The present study describes a detailed neuroanatomical distribution map of the cannabinoid type 1 (CB 1 ) receptor, along with the biochemical characterization of the expression and functional coupling to their cognate G i/o proteins in the medial prefrontal cortex (mPCx) of the obese Zucker rats. The CB 1 receptor density was higher in the prelimbic (PL) and infralimbic (IL) subregions of the mPCx of obese Zucker rats relative to their lean littermates which was associated with a higher percentage of CB 1 receptor immunopositive excitatory presynaptic terminals in PL and IL. Also, a higher expression of CB 1 receptors and WIN55,212-2-stimulated [ 35 S]GTPγS binding was observed in the mPCx but not in the neocortex (NCx) and hippocampus of obese rats. Low-frequency stimulation in layers II/III of the mPCx induced CB 1 receptor-dependent long-term synaptic plasticity in IL of area obese Zucker but not lean rats. Overall, the elevated 2-AG levels, up-regulation of CB 1 receptors, and increased agonist-stimulated [ 35 S]GTPγS binding strongly suggest that hyperactivity of the endocannabinoid signaling takes place at the glutamatergic terminals of the mPCx in the obese Zucker rat. These findings could endorse the importance of the CB 1 receptors located in the mPCx in the development of obesity in Zucker rats., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest., (Copyright © 2022 Echeazarra, Barrondo, García del Caño, Bonilla-Del Río, Egaña-Huguet, Puente, Aretxabala, Montaña, López de Jesús, González-Burguera, Saumell-Esnaola, Goicolea, Grandes and Sallés.)

Background: Replacement of radioligand binding assays with antibody-antigen interaction-based approaches for quantitative analysis of G protein-coupled receptor (GPCR) levels requires the use of purified protein standards containing the antigen. GPCRs in general and cannabinoid CB 1 receptor in particular show a progressive tendency to aggregate and precipitate in aqueous solution outside of their biological context due to the low solubility that the hydrophobic nature imprinted by their seven transmembrane domains. This renders full-length recombinant GPCRs useless for analytical purposes, a problem that can be overcome by engineering soluble recombinant fragments of the receptor containing the antigen., Results: Here we generated highly soluble and stable recombinant protein constructs GST-CB1 414-472 and GST-CB1 414-442 containing much of the human CB 1 receptor C-terminal tail for use as standard and negative control, respectively, in quantitative Western blot analysis of CB 1 receptor expression on crude synaptosomes of the adult rat brain cortex. To this end we used three different antibodies, all raised against a peptide comprising the C-terminal residues 443-473 of the mouse CB 1 receptor that corresponds to residues 442-472 in the human homolog. Estimated values of CB 1 receptor density obtained by quantitative Western blot were of the same order of magnitude but slightly higher than values obtained by the radioligand saturation binding assay., Conclusions: Collectively, here we provide a suitable Western blot-based design as a simple, cost-effective and radioactivity-free alternative for the quantitative analysis of CB 1 receptor expression, and potentially of any GPCR, in a variety of biological samples. The discrepancies between the results obtained by quantitative Western blot and radioligand saturation binding techniques are discussed in the context of their particular theoretical bases and methodological constraints., (© 2022. The Author(s).)

Metformin is the first choice drug for the treatment of type 2 diabetes due to positive results in reducing hyperglycaemia and insulin resistance. However, diabetic patients have higher risk of ventricular arrhythmia and sudden cardiac death, and metformin failed to reduce ventricular arrhythmia in clinical trials. In order to explore the mechanisms responsible for the lack of protective effect, we investigated in vivo the effect of metformin on cardiac electrical activity in non-diabetic rats; and in vitro in isolated ventricular myocytes, HEK293 cells expressing the hERG channel and human induced pluripotent stem cells derived cardiomyocytes (hIPS-CMs). Surface electrocardiograms showed that long-term metformin treatment (7 weeks) at therapeutic doses prolonged cardiac repolarization, reflected as QT and QTc interval duration, and increased ventricular arrhythmia during the caffeine/dobutamine challenge. Patch-clamp recordings in ventricular myocytes isolated from treated animals showed that the cellular mechanism is a reduction in the cardiac transient outward potassium current (I to ). In vitro, incubation with metformin for 24 h also reduced I to , prolonged action potential duration, and increased spontaneous contractions in ventricular myocytes isolated from control rats. Metformin incubation also reduced I hERG in HEK293 cells. Finally, metformin incubation prolonged action potential duration at 30% and 90% of repolarization in hIPS-CMs, which is compatible with the reduction of I to and I hERG . Our results show that metformin directly modifies the electrical behavior of the normal heart. The mechanism consists in the inhibition of repolarizing currents and the subsequent decrease in repolarization capacity, which prolongs AP and QTc duration.

Specific and selective anti-CB 1 antibodies are among the most powerful research tools to unravel the complex biological processes mediated by the CB 1 receptor in both physiological and pathological conditions. However, low performance of antibodies remains a major source of inconsistency between results from different laboratories. Using a variety of techniques, including some of the most commonly accepted ones for antibody specificity testing, we identified three of five commercial antibodies against different regions of CB 1 receptor as the best choice for specific end-use purposes. Specifically, an antibody against a long fragment of the extracellular amino tail of CB 1 receptor (but not one against a short sequence of the extreme amino-terminus) detected strong surface staining when applied to live cells, whereas two different antibodies against an identical fragment of the extreme carboxy-terminus of CB 1 receptor (but not one against an upstream peptide) showed acceptable performance on all platforms, although they behaved differently in immunohistochemical assays depending on the tissue fixation procedure used and showed different specificity in Western blot assays, which made each of them particularly suitable for one of those techniques. Our results provide a framework to interpret past and future results derived from the use of different anti-CB 1 antibodies in the context of current knowledge about the CB 1 receptor at the molecular level, and highlight the need for an adequate validation for specific purposes, not only before antibodies are placed on the market, but also before the decision to discontinue them is made., (© 2021. The Author(s).)

Hypertension is a chronic condition that can lead to serious health problems. Patients with High Blood Pressure (HBP) are often asked to have their BP checked at home. The traditional at-home procedure has some drawbacks, such as forgetting to check or write down the values, errors in transcribing the numbers, or the impossibility of immediately notifying medical staff of out-of-range BP values. To facilitate self-measurements by patients at home we devised TensioBot, a Telegram based chatbot. The bot sends patients reminders to check their BP, advice on good monitoring practices, measurement tracking, medical alerts and allows healthcare professionals to access up-to-date measurement information. TensioBot has been tested for two years in a randomized controlled trial with 112 patients (55 using the bot and 57 in the control group). We found that, although the bot group showed similar results in terms of adherence to the BP checking schedule, bot users scored better in terms of knowledge and skills on BP checking best practices. Participants rated the bot very positively, perceived it as useful and easy to use, and continued to use it after the intervention. Moreover, all data being equal, we describe some other benefits of using a chatbot for self-managed in-house BP control, both for patients and healthcare professionals and systems.

The electrophysiological behavior of the zebrafish heart is very similar to that of the human heart. In fact, most of the genes that codify the channels and regulatory proteins required for human cardiac function have their orthologs in the zebrafish. The high fecundity, small size, and easy handling make the zebrafish embryos/larvae an interesting candidate to perform whole animal experiments within a plate, offering a reliable and low-cost alternative to replace rodents and larger mammals for the study of cardiac physiology and pathology. The employment of zebrafish embryos/larvae has widened from basic science to industry, being of particular interest for pharmacology studies, since the zebrafish embryo/larva is able to recapitulate a complete and integrated view of cardiac physiology, missed in cell culture. As in the human heart, I Kr is the dominant repolarizing current and it is functional as early as 48 h post fertilization. Finally, genome editing techniques such as CRISPR/Cas9 facilitate the humanization of zebrafish embryos/larvae. These techniques allow one to replace zebrafish genes by their human orthologs, making humanized zebrafish embryos/larvae the most promising in vitro model, since it allows the recreation of human-organ-like environment, which is especially necessary in cardiac studies due to the implication of dynamic factors, electrical communication, and the paracrine signals in cardiac function., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Echeazarra, Hortigón-Vinagre, Casis and Gallego.)

Background/aims: To test whether the physiological regulation of the cardiac Kv4 channels by the Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) is restricted to lipid rafts and whether the interactions observed in rat cardiomyocytes also occur in the human ventricle., Methods: Ventricular myocytes were freshly isolated from Sprague-Dawley rats. I to was recorded by the whole-cell Patch-Clamp technique. Membrane rafts were isolated by centrifugation in a discontinuous sucrose density gradient. The presence of the proteins of interest was analysed by western blot. Immunogold staining and electron microscopy of heart vibrosections was performed to localize Kv4.2/Kv4.3 and CaMKII proteins. Protein-protein interactions were determined by co-immunoprecipitation experiments in rat and human ventricular mycoytes., Results: Patch-Clamp recordings in control conditions and after lipid raft or caveolae disruption show that the CaMKII-Kv4 channel complex must associate in non-caveolar lipid rafts to be functional. Separation in density gradients, co-immunoprecipitation and electron microscopy show that there are two Kv4 channel populations: one located in caveolae, that is CaMKII independent, and another one located in planar membrane rafts, which is bound to CaMKII., Conclusion: CaMKII regulates only the Kv4 channel population located in non-caveolar lipid rafts. Thus, the regulation of cardiac Kv4 channels in rat and human ventricle depends on their subcellular localization., Competing Interests: The authors declare that they have no competing interests., (© Copyright by the Author(s). Published by Cell Physiol Biochem Press.)

Background: Hypothyroidism, the most common endocrine disease, induces cardiac electrical remodeling that creates a substrate for ventricular arrhythmias. Recent studies report that high thyrotropin (TSH) levels are related to cardiac electrical abnormalities and increased mortality rates. The aim of the present work was to investigate the direct effects of TSH on the heart and its possible causative role in the increased incidence of arrhythmia in hypothyroidism. Methods: A new rat model of central hypothyroidism (low TSH levels) was created and characterized together with the classical propylthiouracil-induced primary hypothyroidism model (high TSH levels). Electrocardiograms were recorded in vivo , and ionic currents were recorded from isolated ventricular myocytes in vitro by the patch-clamp technique. Protein and mRNA were measured by Western blot and quantitative reverse transcription polymerase chain reaction in rat and human cardiac myocytes. Adult human action potentials were simulated in silico to incorporate the experimentally observed changes. Results: Both primary and central hypothyroidism models increased the L-type Ca 2+ current (I Ca-L ) and decreased the ultra-rapid delayed rectifier K + current (I Kur ) densities. However, only primary but not central hypothyroidism showed electrocardiographic repolarization abnormalities and increased ventricular arrhythmia incidence during caffeine/dobutamine challenge. These changes were paralleled by a decrease in the density of the transient outward K + current (I to ) in cardiomyocytes from animals with primary but not central hypothyroidism. In vitro treatment with TSH for 24 hours enhanced isoproterenol-induced spontaneous activity in control ventricular cells and diminished I to density in cardiomyocytes from control and central but not primary hypothyroidism animals. In human myocytes, TSH decreased the expression of KCND3 and KCNQ1 , I to , and the delayed rectifier K + current (I Ks ) encoding proteins in a protein kinase A-dependent way. Transposing the changes produced by hypothyroidism and TSH to a computer model of human ventricular action potential resulted in enhanced occurrence of early afterdepolarizations and arrhythmia mostly in primary hypothyroidism, especially under β-adrenergic stimulation. Conclusions: The results suggest that suppression of repolarizing K + currents by TSH underlies most of the electrical remodeling observed in hypothyroidism. This work demonstrates that the activation of the TSH-receptor/protein kinase A pathway in the heart is responsible for the cardiac electrical remodeling and arrhythmia generation seen in hypothyroidism.

This work proposes a liquid chromatography-electrospray ionization ion trap mass spectrometry (LC-ESI-ITMS) method, for the quantification of sildenafil (SDF), tadalafil (TDF) and vardenafil (VDF) and their metabolites N-desmethylSDF, O-desethylSDF and N-desethylVDF, preceded by a sample preparation step based on protein and phospholipid elimination. A C8 column (150 mm × 4.6 mm, 5 μm) with ammonium formate (20mM) and acetonitrile as the mobile phase components have been used. This method has been validated, obtaining limits of quantification ranged from 1 to 2.5 ng/mL and 2 to 5 ng/g in serum and brain tissue respectively, while limits of detection ranged from 0.3 to 0.9 ng/mL in serum and 0.6 to 1.9 ng/g in brain tissue. Assay recoveries for low level QC samples were higher than 83% and the matrix effect ranged between 91% and 108% in serum and between 98% and 107% in brain tissue. The method has been applied to the quantification of these compounds in the serum and brain tissue of rats treated intraperitoneally with 10 mg/kg of SDF, TDF or VDF., (Copyright © 2012 Elsevier B.V. All rights reserved.)