Peptide Inhibitors of Kv1.5: An Option for the Treatment of Atrial Fibrillation

Abstract: The human voltage gated potassium channel Kv1.5 that conducts the IKurcurrent is akey determinant of the atrial action potential. Its mutations have been linked to hereditary formsof atrial fibrillation (AF), and the channel is an attractive target for the management of AF. Thedevelopment of IKurblockers to treat AF resulted in small molecule Kv1.5 inhibitors. The selectivityof the blocker for the target channel plays an important role in the potential therapeutic applicationof the drug candidate: the higher the selectivity, the lower the risk of side effects. In this respect,small molecule inhibitors of Kv1.5 are compromised due to their limited selectivity. A wide range ofpeptide toxins from venomous animals are targeting ion channels, including mammalian channels.These peptides usually have a much larger interacting surface with the ion channel compared tosmall molecule inhibitors and thus, generally confer higher selectivity to the peptide blockers. Wefound two peptides in the literature, which inhibited IKur: Ts6 and Osu1. Their affinity and selectivityfor Kv1.5 can be improved by rational drug design in which their amino acid sequences could bemodified in a targeted way guided by in silico docking experiments

Elucidation of the binding mode of organic polysulfides on the human TRPA1 receptor

Introduction: Previous studies have established that endogenous inorganic polysulfides have significant biological actions activating the Transient Receptor Potential Ankyrin 1 (TRPA1) receptor. Organic polysulfides exert similar effects, but they are much more stable molecules, therefore these compounds are more suitable as drugs. In this study, we aimed to better understand the mechanism of action of organic polysulfides by identification of their binding site on the TRPA1 receptor.Methods: Polysulfides can readily interact with the thiol side chain of the cysteine residues of the protein. To investigate their role in the TRPA1 activation, we replaced several cysteine residues by alanine via site-directed mutagenesis. We searched for TRPA1 mutant variants with decreased or lost activating effect of the polysulfides, but with other functions remaining intact (such as the effects of non-electrophilic agonists and antagonists). The binding properties of the mutant receptors were analyzed by in silico molecular docking. Functional changes were tested by in vitro methods: calcium sensitive fluorescent flow cytometry, whole-cell patch-clamp and radioactive calcium-45 liquid scintillation counting.Results: The cysteines forming the conventional binding site of electrophilic agonists, namely C621, C641 and C665 also bind the organic polysulfides, with the key role of C621. However, only their combined mutation abolished completely the organic polysulfide-induced activation of the receptor.Discussion: Since previous papers provided evidence that organic polysulfides exert analgesic and anti-inflammatory actions in different in vivo animal models, we anticipate that the development of TRPA1-targeted, organic polysulfide-based drugs will be promoted by this identification of the binding site

The conservation status of the world's freshwater molluscs

With the biodiversity crisis continuing unchecked, we need to establish levels and drivers of extinction risk, and reassessments over time, to effectively allocate conservation resources and track progress towards global conservation targets. Given that threat appears particularly high in freshwaters, we assessed the extinction risk of 1428 randomly selected freshwater molluscs using the IUCN Red List Categories and Criteria, as part of the Sampled Red List Index project. We show that close to one-third of species in our sample are estimated to be threatened with extinction, with highest levels of threat in the Nearctic, Palearctic and Australasia and among gastropods. Threat levels were higher in lotic than lentic systems. Pollution (chemical and physical) and the modification of natural systems (e.g. through damming and water abstraction) were the most frequently reported threats to freshwater molluscs, with some regional variation. Given that we found little spatial congruence between species richness patterns of freshwater molluscs and other freshwater taxa, apart from crayfish, new additional conservation priority areas emerged from our study. We discuss the implications of our findings for freshwater mollusc conservation, the adequacy of a sampled approach and important next steps to estimate trends in freshwater mollusc extinction risk over time

Slovak Experience After 10 Years from the Introduction of the Euro as Globalization Factor

One of Slovakia’s globalization tendencies is the successful introduction of the Eurocurrency. It has been 10 years since the introduction of the euro in Slovakia. It is a sufficient time for us to continuously assess the real situation and attitudes of the citizens in this area. There are several publicly available studies, research findings conducted by Eurobarometer, Fincenter or the National bank, which focus on advantages and disadvantages of the euro currency. The most frequently mentioned advantages are price stability, transaction cost decrease in foreign trade and tourism, Slovak export increase and the removal of exchange rate risk. On the other side, Slovakia has lost its independent monetary policy and the member country is also expected to participate in the euro area rescue mechanism. Similarly the research team of the Faculty of Economics of J. Selye University was invited by Hungarian Pallas Athene Domus Educationis Foundation to participate in the research project named ten years of euro – Slovak experience. Based on this project initiative, the aim of the paper is to find out the experience regarding the euro among citizens, also with an emphasis on cross-border activity. In order to achieve the research objectives we applied primary data collection to obtain information about the researched issue. An anonymous questionnaire survey was conducted among the respondents. Data collection among the residents was realized with a help of an agent, but also an online questionnaire was provided for the respondents in 2018. Statistic indicators were used to verify our assumptions

How to improve agricultural value-added in the MENA region? Implementation of Diamond Porter's theory in agriculture

The global economy in recent decades has experienced frequent shocks. Many regions must improve their competitiveness and value-added to deal with this. One of them is in the Middle East and North Africa (MENA), where a rise in agricultural value-added (AVA) can produce more jobs than in other sectors. It is necessary to consider increasing AVA in the MENA region. Hence, the aim of this study is identifying the determinant factors of AVA in the MENA region. We employed 13 countries in the MENA region as samples in this study. The study's data spans 45 years, from 1975 to 2019. Static panel data regression analysis was employed in this study. AVA can growth by increasing the irrigated land, credit, and human capital. Meanwhile, growing inflation and economic globalization will reduce AVA. Therefore, we recommend that countries in the MENA region have to increase irrigation infrastructure, expand agricultural credit availability, encourage farmers to get a good education, improve research and development, control inflation, and find the best way to implement economic globalization

Evolution of a dextral lineage by left-right reversal in Cristataria (Gastropoda, Pulmonata, Clausiliidae)

It has long been debated whether mirror image-like similarity in shell morphology between enantiomorphic pairs of dextral and sinistral taxa represents their sister relationship, or each of them is closer related to other congeners with the same coiling direction. The obligate rock-dwelling genus Cristataria Vest, 1867 of the eastern Mediterranean region belongs to the Alopiinae subfamily of door snails (Clausiliidae). Cristataria and a few other genera of this subfamily include enantiomorphic pairs that are conchologically very similar to each other. Dextral C. colbeauiana (Pfeiffer, 1861) and its sinistral counterpart of such an enantiomorphic pair occur nearby one another in southern Turkey. However, the latter has been classified either as the sinistral subspecies C. colbeauiana inversa Szekeres, 1998 or as a form of sinistral C. leprevieri (Pallary, 1922). To examine the phylogenetic relationship of this enantiomorphic pair, we carried out molecular phylogenetic analysis of all the Turkish and two other Cristataria taxa based on both mitochondrial and nuclear DNA markers. Our results show that dextral C. colbeauiana and its sinistral counterpart are closest related to one another. This supports the classification of this enantiomorphic pair as dextral C. colbeauiana colbeauiana and sinistral C. colbeauiana inversa. Our results also reveal that these taxa and C. intersita Nemeth & Szekeres, 1995, sharing a characteristic collar behind the aperture of the shell, represent a monophyletic lineage. By contrast, the Cristataria species of non-collared shells belong to another clade

Caveolin-1 limits the contribution of BK(Ca) channel to EDHF-mediated arteriolar dilation: implications in diet-induced obesity

AIMS: Caveolin-1 (Cav-1) interacts with large conductance Ca(2+)-activated potassium channels (BKCa) and likely exerts a negative regulatory effect on the channel activity. We investigated the role of Cav-1 in modulating BK(Ca) channel-mediated, endothelium-derived hyperpolarizing factor (EDHF)-dependent arteriolar dilation in normal condition and in an experimental model of obesity. METHODS AND RESULTS: In isolated, pressurized (80 mmHg) gracilis muscle arterioles (approximately 100 microm) of Cav-1 knockout mice, acetylcholine (ACh)-induced, EDHF-mediated dilations were enhanced and were significantly reduced by the BK(Ca) channel inhibitor, iberiotoxin (IBTX), whereas IBTX had no effect on EDHF-mediated dilations in the wild-type mice. Dilations to the selective BK(Ca) channel opener, NS-1619 were augmented in the Cav-1 knockout mice. In high-fat diet-treated, obese rats ACh-induced coronary arteriolar dilations were preserved, whereas IBTX-sensitive, ACh-induced and also NS-1619-evoked vasodilations were augmented when compared with lean animals. In coronary arterioles of obese rats a reduced protein expression of Cav-1 was detected by western immunoblotting and immunohistochemistry. Moreover, in coronary arterioles of lean rats, disruption of caveolae with methyl-beta-cyclodextrin augmented IBTX-sensitive, ACh-induced, and also NS-1619-evoked dilations. CONCLUSION: Thus, under normal conditions, Cav-1 limits the contribution of the BK(Ca) channel to EDHF-mediated arteriolar dilation. In obesity, a reduced expression of Cav-1 leads to greater contribution of the BK(Ca) channel to EDHF-mediated response, which seems essential for maintained coronary dilation

Activation of prostaglandin E2 EP1 receptor increases arteriolar tone and blood pressure in mice with type 2 diabetes

AIMS: Type 2 diabetes mellitus is frequently associated with hypertension, but the underlying mechanisms are not completely understood. We tested the hypothesis that activation of type 1 prostaglandin E(2) (PGE(2)) receptor (EP1) increases skeletal muscle arteriolar tone and blood pressure in mice with type 2 diabetes. METHODS AND RESULTS: In 12-week-old, male db/db mice (with homozygote mutation in leptin receptor), systolic blood pressure was significantly elevated, compared with control heterozygotes. Isolated, pressurized gracilis muscle arterioles ( approximately 90 microm) of db/db mice exhibited an enhanced pressure- and angiotensin II (0.1-10 nM)-induced tone, which was reduced by the selective EP1 receptor antagonist, AH6809 (10 microM), to the level observed in arterioles of control mice. Exogenous application of PGE(2) (10 pM-100 nM) or the selective agonist of the EP1 receptor, 17-phenyl-trinor-PGE(2) (10 pM-100 nM), elicited arteriolar constrictions that were significantly enhanced in db/db mice (max: 31 +/- 4 and 29 +/- 5%), compared with controls (max: 20 +/- 2 and 14 +/- 3%, respectively). In the aorta of db/db mice, an increased protein expression of EP1, but not EP4, receptor was also detected by western immunoblotting. Moreover, we found that oral administration of the EP1 receptor antagonist, AH6809 (10 mg/kg/day, for 4 days), significantly reduced the systolic blood pressure in db/db, but not in control mice. CONCLUSION: Activation of EP1 receptors increases arteriolar tone, which could contribute to the development of hypertension in the db/db mice

Functional Voltage-Gated Sodium Channels Are Present in the Human B Cell Membrane

B cells express various ion channels, but the presence of voltage-gated sodium (NaV) channels has not been confirmed in the plasma membrane yet. In this study, we have identified several NaV channels, which are expressed in the human B cell membrane, by electrophysiological and molecular biology methods. The sensitivity of the detected sodium current to tetrodotoxin was between the values published for TTX-sensitive and TTX-insensitive channels, which suggests the co-existence of multiple NaV1 subtypes in the B cell membrane. This was confirmed by RT-qPCR results, which showed high expression of TTX-sensitive channels along with the lower expression of TTX-insensitive NaV1 channels. The biophysical characteristics of the currents also supported the expression of multiple NaV channels. In addition, we investigated the potential functional role of NaV channels by membrane potential measurements. Removal of Na+ from the extracellular solution caused a reversible hyperpolarization, supporting the role of NaV channels in shaping and maintaining the resting membrane potential. As this study was mainly limited to electrophysiological properties, we cannot exclude the possible non-canonical functions of these channels. This work concludes that the presence of voltage-gated sodium channels in the plasma membrane of human B cells should be recognized and accounted for in the future

Functional Voltage-Gated Sodium Channels Are Present in the Human B Cell Membrane

B cells express various ion channels, but the presence of voltage-gated sodium (NaV) channels has not been confirmed in the plasma membrane yet. In this study, we have identified several NaV channels, which are expressed in the human B cell membrane, by electrophysiological and molecular biology methods. The sensitivity of the detected sodium current to tetrodotoxin was between the values published for TTX-sensitive and TTX-insensitive channels, which suggests the co-existence of multiple NaV1 subtypes in the B cell membrane. This was confirmed by RT-qPCR results, which showed high expression of TTX-sensitive channels along with the lower expression of TTX-insensitive NaV1 channels. The biophysical characteristics of the currents also supported the expression of multiple NaV channels. In addition, we investigated the potential functional role of NaV channels by membrane potential measurements. Removal of Na+ from the extracellular solution caused a reversible hyperpolarization, supporting the role of NaV channels in shaping and maintaining the resting membrane potential. As this study was mainly limited to electrophysiological properties, we cannot exclude the possible non-canonical functions of these channels. This work concludes that the presence of voltage-gated sodium channels in the plasma membrane of human B cells should be recognized and accounted for in the future