Search Results (141)

Hydrolyzed collagen (HC) derived from salmon skin is a promising source of bioactive peptides. In this study, the vasorelaxant effects and potential mechanisms of action of HC on isolated rat thoracic aorta rings were investigated using the organ bath technique. The vasorelaxant properties of HC were evaluated using aortic rings from Wistar rats pre-contracted with phenylephrine (PE) or potassium chloride (KCl). HC induced significant vasorelaxation in both endothelium-intact and endothelium-denuded rings, indicating that its mechanism of action was independent of the endothelium and involved direct effects on vascular smooth muscle cells. The vasorelaxant effect of HC was reduced when pre-contraction was induced by tetraethylammonium chloride (TEA). However, the vasodilatory effects of HC were not significantly inhibited by all K⁺ channel blockers, including glibenclamide, barium chloride (BaCl₂), or 4-aminopyridine (4-AP). Additionally, pre-incubation with prazosin, an α-adrenoceptor blocker, significantly reduced the vasorelaxation induced by HC, whereas propranolol, a β-adrenoceptor blocker, had no effect. In addition, HC inhibited CaCl₂-induced contractions induced by both PE and caffeine in a Ca²⁺-free solution. Therefore, HC exhibited the vasorelaxant effects through an endothelium-independent mechanism. The vasodilatory effects of HC were associated with the activation of K_Ca channels, suppression of PE-induced contraction via α₁-adrenergic receptor pathways, and inhibition of CaCl₂-induced contractions by modulating intracellular Ca²⁺ release and extracellular Ca²⁺ influx in vascular cells. Full article

Kv11.1 (hERG1) channels, encoded by KCNH2, mediate the rapid delayed rectifier potassium current (I_Kr) crucial for cardiac repolarization. Disruptions, via mutations or antiarrhythmic drugs like dofetilide cause severe arrhythmogenic disorders, including Long QT Syndrome Type 2 (LQT2), Brugada Syndrome (BrS), and Torsades de Pointes (TdP). While Kv11.1’s role in channelopathies and drug-induced arrhythmias is established, understanding its complex regulation and therapeutic targeting remains a challenge. This review synthesizes the structural, functional, and regulatory aspects of Kv11.1 channels and their clinical implications. Recent studies using iPSC-derived cardiomyocytes highlight regulation by PI3K/Akt, PKC, and PKA signaling via phosphorylation (Ser283, Ser890) and interactions with proteins like 14-3-3. Beyond electrophysiology, Kv11.1 influences pathological hypertrophy and non-cardiac functions including insulin secretion. Pharmacological efforts focus on activators to shorten action potential duration and suppress TdP, and blockers with overdose risks. Mutation heterogeneity, exemplified by trafficking impairment (G785D) in LQT2 and gain-of-function (R397C) in BrS, complicates precision therapy. Clinically, systematic risk stratification using electrocardiographic parameters and genotype-specific approaches enables personalized management. Beta-blockers remain first-line therapy for LQTS2, while rigorous avoidance of QT-prolonging medications and electrolyte monitoring form the cornerstones of preventive care. Advancing Kv11.1-targeted therapies with approaches like CRISPR-Cas9 and pharmacological chaperones (e.g., lumacaftor) holds promise for personalized treatments, ultimately reducing arrhythmic events and sudden cardiac death. Full article

Background/Objectives: Type 2 diabetes mellitus (T2DM) is characterized by chronic hyperglycemia and insulin resistance, leading to progressive metabolic dysfunction. Flavonoids, such as astragalin, have reported antidiabetic potential; however, their direct effects on pancreatic β-cell ionic mechanisms and insulin secretion remain unclear. This study aimed to investigate the effects of astragalin on glucose uptake, insulin secretion, and membrane ionic currents in pancreatic β-cell lines. Methods: Murine MIN6 and rat INS-1 pancreatic β-cells were used as experimental models. Following astragalin treatment, glucose uptake was quantified by bioluminescence, and insulin secretion was measured by ELISA. Ionic currents were analyzed using the whole-cell patch-clamp technique. Selective pharmacological blockers targeting ATP-sensitive K⁺ channels (KATP), voltage-dependent K⁺ channels (K_v), and L-type voltage-dependent Ca²⁺ channels were applied to elucidate the underlying mechanisms. Results: Astragalin increased glucose uptake in a time-dependent manner, reaching a plateau between 3 and 5 h. Insulin secretion was significantly enhanced after 1 h of exposure to 100 µM astragalin. Patch-clamp recordings demonstrated that astragalin reduced potassium channel currents in pancreatic β-cells. Pharmacological modulation confirmed the involvement of KATP, K_v, and L-type Ca²⁺ channels. Verapamil attenuated the insulinotropic effect, supporting the role of calcium influx in astragalin-induced insulin exocytosis. Conclusions: Astragalin enhances glucose uptake and stimulates insulin secretion in pancreatic β-cells through modulation of potassium and calcium channels, promoting calcium-dependent exocytosis. These findings support its potential as a candidate for antidiabetic therapeutic strategies. Full article

The patch-clamp technique is widely regarded as the gold standard in cellular electrophysiology and can be applied in several configurations. In the cell-attached (C-A) mode, it enables the recording of single-channel currents, whereas the whole-cell (W-C) mode allows for the measurement of macroscopic currents, representing the collective activity of many channels. When the recording configuration was switched from C-A to W-C on the same cell, the current amplitude increased dramatically, while action currents (ACs) were completely abolished, indicating a profound alteration in the cell’s electrophysiological response under the new setup. In excitable cells, the occurrence of ACs, representing propagated action potentials, can interfere with C-A single-channel recordings. To address this, a high-K⁺ solution is typically applied to the bath to suppress the ACs. The inwardly rectifying K⁺ (Kir), ATP-sensitive K⁺ (K_ATP) and large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels are crucial members of the K⁺ channel family that facilitate the efflux of K⁺ ions, driven by the K⁺ electrochemical gradient. These channels are primarily distinguished by their rectification properties and gating kinetics. For instance, K_ATP channels exhibit a bursting kinetic pattern with inward rectifying property, while BK_Ca channels display strong outward rectification. Mitoxantrone, which belongs to a class of drugs called anthracenediones, can suppress the activity of Kir channels in differentiated RAW 264.7 cells, with no change in single-channel conductance. The respiratory stimulator GAL-021 acts as a BK_Ca channel inhibitor, and it suppresses channel activity and shifts the activation curve to the right, suggesting a voltage-dependent blockade that stabilizes the channel in a closed state. GAL-021 does not change the single-channel conductance, indicating it is a gating modifier rather than an open-pore blocker. The functional roles of ion channels are fundamentally important. Correspondingly, the field is transitioning to artificial intelligence for automated single-cell patch-clamp experiments, though brain slice recordings still require manual techniques. Full article

Potassium (K⁺) channel blockers are promising anticancer agents but suffer from off-target toxicities. We designed cross-linked poly-2-Hydroxyethyl methacrylate (HEMA)–pectin nanogels (HPN) to deliver two model blockers—dofetilide (Dof) and azimilide (Azi)—and evaluated their physicochemical properties, release behavior, and in vitro anticancer activity. HPN was synthesized by surfactant-assisted aqueous nanogel polymerization and comprehensively characterized (FTIR, DLS, TEM/SEM, XRD, BET). The particles were monodispersed with a mean diameter ~230 nm, compatible with tumor accumulation via the Enhanced Permeability and Retention (EPR) effect, and exhibited a microporous matrix suitable for controlled release. Drug loading was higher for Dof than for Azi, with DL% values of 82.30 ± 3.1% and 17.84 ± 2.9%, respectively. Release kinetics diverged: Azi-HPN followed primarily first-order diffusion with a rapid burst, whereas Dof-HPN showed mixed zero/first-order behavior. Cytotoxicity was assessed in A549 lung cancer and BEAS-2B bronchial epithelial cells. Both free and nano-formulated blockers were selectively toxic to A549 with minimal effects on BEAS-2B. Notably, a hormesis-like pattern (low-dose stimulation/high-dose inhibition in MTT) was evident for free Dof and Azi; encapsulation attenuated this effect for Dof but not for Azi. Co-administration with paclitaxel (Ptx) potentiated Dof-HPN cytotoxicity in A549 but did not enhance Azi-HPN, suggesting mechanism-dependent drug-drug interactions. Overall, HPN provides a biocompatible platform that improves K⁺ blocker delivery. Full article

Magnesium ions regulate synaptic and nonsynaptic neuronal excitability from intracellular (Mg²⁺_i) and extracellular (Mg²⁺_o) domains, modulating voltage- and ligand-gated ion channels. K+ inward rectifier (Kir) channel inward rectification arises from Mg²⁺_i blocking the pore and outward K⁺ current, while Mg²⁺_o targets external sites. Mg²⁺_i causes voltage-dependent Ca²⁺ voltage-gated (Ca_V) and Na⁺ voltage-gated (Na_V) channel block while phosphorylation modulates channel activity. Mg²⁺_o elicits direct voltage-dependent Ca_V channel block, and screens surface charge, and in Na_V channels reduces conduction and may cause depolarization by quantum tunneling across closed channels. Mg²⁺_i is an allosteric large conductance Ca²⁺-activated K⁺ (BK) channel activator, binding to low-affinity sites to alter Ca²⁺ and voltage sensitivity but reduces small conductance Ca²⁺-activated K⁺ (SK) channels’ outward K⁺ current and induces inward rectification. N-Methyl-D-aspartate receptor (NMDAR) channels are inhibited by Mg²⁺_i binding within the pore, while Mg²⁺_o stabilizes excitability through voltage-dependent block, Mg²⁺_o forms Mg-ATP complex modifying purinergic P2X receptor (P2XR) channel affinity and gating and directly blocks the pore. Mg²⁺_o reduces gamma-aminobutyric acid type A receptor (GABA_AR) channel Cl⁻ current amplitude and augments susceptibility to blockers. Mg²⁺_o and Mg²⁺_i block nicotinic acetylcholine receptor (nAChR) channels through voltage-dependent pore binding and surface charge screening, impeding current flow and altering gating. Full article

Background: Hypertension and its complications are a major global health problem, and natural compounds with vasorelaxant effects are being investigated as potential antihypertensive agents. Objective: This study aimed to determine whether rosmarinic acid (RA) induces vasorelaxation in the rat thoracic aorta and to elucidate the underlying mechanisms. Methods: Isolated thoracic aortic rings, with or without endothelium, were precontracted with phenylephrine and subsequently exposed to cumulative concentrations of RA. The roles of endothelium-derived factors, potassium channels, and calcium signaling were evaluated using selective pharmacological inhibitors and activators. In addition, the involvement of the AMPK pathway, adenylate cyclase/cAMP pathway, PKC signaling, β-adrenergic receptors, muscarinic receptors, and angiotensin II in RA-induced vasorelaxation was investigated. Results: RA induced a concentration-dependent vasorelaxation in endothelium-intact thoracic aortic rings (p < 0.001; pD₂ = 7.67 ± 0.04). The vasorelaxant effect of RA was attenuated in endothelium-denuded vessels (pD2: 5.26 ± 0.18). The relaxation response was significantly attenuated by inhibitors of the PI3K/Akt/eNOS/NO/cGMP pathway and by blockers of BK_Ca, IK_Ca, and Kv potassium channels (p < 0.001). Furthermore, RA markedly inhibited both extracellular Ca²⁺ influx and intracellular Ca²⁺ release from the sarcoplasmic reticulum (p < 0.001). RA incubation also significantly reduced the contractions induced by angiotensin II (Ang II) and by the PKC activator PMA (p < 0.001). Other tested pathways had no significant influence on the vasorelaxant effect of RA (p > 0.05). Conclusions: These findings demonstrate that rosmarinic acid induces both endothelium-dependent and endothelium-independent vasorelaxation in the rat thoracic aorta through activation of the PI3K/Akt/eNOS/NO/cGMP pathway, opening of BK_Ca, IK_Ca, and Kv potassium channels, and suppression of Ca²⁺ mobilization. Additionally, inhibition of PKC- and angiotensin II-mediated vascular contraction contributes to RA-induced vasorelaxation. RA may therefore have therapeutic potential in the management of hypertension. Full article

Calcium (Ca²⁺) release from the sarcoplasmic reticulum is central to excitation–contraction coupling and plays a critical role in the development of skeletal muscle fatigue. Altered Ca²⁺ dynamics may affect not only contractile function but also neuromuscular excitability. This study examined the effects of pharmacological modulation of Ca²⁺ channels on fatigue development and spinal reflex activity in rats. Using the Hoffmann reflex (H-reflex) as an indicator of motoneuron excitability, we evaluated the effects of Ca²⁺ channel blockers (Amiloride, Nifedipine) and an activator ((−)-Bay K8644) on the reflex responses of the plantar muscle before and after fatigue induction. The ratio of the maximum H-reflex to maximum M-wave (H_max/M_max) was used to assess alterations in spinal excitability. Compared with the control, both Amiloride and Nifedipine markedly reduce the H_max/M_max ratio (77% and 60%, respectively), whereas (−)-Bay K8644 elicited a robust 129% increase. These findings demonstrate that pharmacological modulation of Ca²⁺ channels has distinct and divergent effects on spinal excitability during fatigue. These results highlight the close interaction between intramuscular Ca²⁺ regulation and reflex pathways and suggest potential strategies for enhancing muscle performance through targeted Ca²⁺ channel modulation. Full article

This study aimed to elucidate the vasorelaxant mechanism of action for apigenin 7-glucoside (A7G) by integrating computational and ex vivo pharmacological approaches. Molecular docking simulations were conducted to predict the binding affinities and interactions of A7G with key vascular proteins, specifically human endothelial nitric oxide synthase (eNOS-PDB ID: 1M9M), and human intermediate (IKCa-PDB ID: 9ED1) and small-conductance (SKCa-PDB ID: 6CNN) Ca²⁺-activated K⁺ channels. The vasodilatory properties of A7G were subsequently evaluated in isolated mesenteric vascular beds (MVBs) from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). The in silico analysis indicated that A7G possesses favorable binding affinities for the 1M9M, 9ED1, and 6CNN protein targets. Pharmacological assessments demonstrated that A7G induced a dose- and endothelium-dependent reduction in perfusion pressure in MVBs from WKY and SHR rats. The vasodilatory response to A7G was completely abrogated by perfusion with a high-potassium solution or a non-selective K⁺ channel blocker. Furthermore, co-administration of apamin and TRAM-34, selective inhibitors of SKCa and IKCa, respectively, also abolished the vasorelaxant effects of A7G. Collectively, these findings suggest that the vascular effects of A7G in both WKY and SHR rats involve an endothelium-dependent mechanism, likely initiated by the activation of the NO/cGMP pathway, which culminates in the opening of IKCa and SKCa channels. Full article

The vascular 5-HT sympatho-modulation may involve inhibitory or potentiating pathways: nitric oxide (NO), endothelium-dependent hyperpolarization (EDH)-K⁺ channels, prostanoids, angiotensin II (Ang-II), or endothelin. Compared to males, female rats show differences in the serotonergic sympatho-regulation; therefore, we aimed to study the involvement of indirect pathways via 5-HT_1D-mediated inhibition and 5-HT_2A/3-mediated potentiation of vascular noradrenergic neurotransmission in females. An i.v. bolus of different inhibitors/blockers of modulators/mediators (NO, K⁺ channels, prostanoids, Ang-II, or endothelin) was administered prior to the infusion of the agonists, L-694,247 (5-HT_1D), TCB-2 (5-HT_2A), or 1-PBG (5-HT₃), in female pithed rats. In these conditions, the vascular sympathetic outflow was electrically stimulated to assess the vasopressor responses. The L-694,247 vascular sympatho-inhibition was abolished by a non-selective K⁺ channel blocker, tetraethylammonium. The 1-PBG sympatho-excitatory vascular effect was not modified by any of the inhibitors tested, whereas TCB-2 sympatho-potentiation was blocked solely by losartan (Ang-II type 1 receptor antagonist). Moreover, Ang-II levels were increased after TCB-2 infusion in females. The EDH pathway mediates the 5-HT_1D-induced sympatho-inhibition, while the 5-HT_2A-evoked sympatho-excitatory effect is associated with Ang-II. In contrast, the 5-HT₃ sympatho-potentiation does not involve any indirect pathway. These findings advance current understanding of the complex interactions between 5-HT and vascular homeostasis in female rats. Full article

Alphaviruses are transmitted by Aedes mosquitoes and cause large-scale epidemics worldwide. Chikungunya virus (CHIKV) infection can cause febrile seizures known as chikungunya fever (CHIKF), which ultimately leads to severe joint pain and myalgia. While a vaccine has recently been introduced against CHIKV, at present, no anti-viral drug is available. CHIKV, like other alphaviruses, has a short 6K protein capable of forming an ion channel. Blocking this ion channel with drugs can therefore serve as a potential way to curtail CHIKV infection. To that end, we screened a repurposed drug library using three bacteria-based channel assays to detect blockers against 6K viroporin, yielding several hits. Interestingly, several of the blockers were able to inhibit the 6K protein from the similar Eastern equine encephalitis virus (EEEV), while others were not, pointing to structural specificity which may be explained by modeling studies. In conclusion, our study provides a starting point for developing a new route to potentially inhibit CHIKV. Full article

Background: Epilepsy is a high-burden neurological disorder worldwide, and several sedative drugs are used as therapy. Topiramate is among the more recent drugs shown to be effective in some patients, although its benefits are limited. Two carbohydrate derivatives, FB1 (from D-fructose) and AB1 (from D-arabinose), as well as phenylboronic acid, were recently reported as sedative and safe agents in mice. Their sedative properties and structural similarity to topiramate suggest potential antiseizure activity. Objective: The objective of this study was to evaluate the antiseizure potential of FB1 and AB1. Methods: Boron-containing compounds were administered to mice with seizures induced by pentylenetetrazol (a GABA-A receptor antagonist), 4-aminopyridine (a non-selective K⁺ channel blocker), or pilocarpine (a muscarinic agonist) to assess efficacy across models and explore potential mechanisms of action. Neuronal and glial toxicity was evaluated both in vitro and in vivo. Results: AB1 reduced seizure activity after intraperitoneal administration, whereas FB1 did not exhibit anticonvulsant effects, although it modified motor performance and limited neuronal loss. The effect of AB1 was comparable to that of topiramate across all three seizure models. Docking studies suggested that these compounds can interact with GABA-A (chloride), NMDA (glutamate), calcium, and potassium channels. Toxicity assays indicated that the concentrations required to affect neurons or glial cells were ≥300 µM, supporting the safety of these compounds. Conclusions: This preliminary evaluation demonstrates the antiseizure potential of AB1. Further experimental studies are needed to clearly establish its mechanism(s) of action. Full article

The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in the kidney participate in reabsorbing potassium (K⁺) and ammonium (NH₄⁺) in the nephron, contributing to the acid–base balance. Acidosis is a metabolic condition of renal tubular acidosis and chronic kidney disease. Acidosis stimulates the production of mitochondrial reactive oxygen species (mROS), activating protective mechanisms dependent on mitochondrial membrane potential (Δψm) such as autophagy. The HCN3 channel is expressed in the plasma membrane, mitochondria (mitoHCN3), and lysosomes (lysoHCN3) of the rat proximal tubule. In this work we aimed to investigate the role of HCN3 in autophagy, mROS production, and Δψm in cultured rat proximal tubule cells (NRK-52E) exposed to ammonium chloride (NH₄Cl). NH₄Cl arrested autophagic flux and produced extracellular acidosis and, under this condition, mitoHCN3 and lysoHCN3 were up-regulated. NH₄Cl or/and ZD7288, a specific blocker of HCN channels, enhanced mROS. ZD7288 in NH₄Cl conditions at 24 h stimulated autophagy by reducing Beclin1, LC3BII, p62, and Parkin in an mROS- or Δψm independent pathway. Therefore, ZD7288 reverted NH₄Cl inhibited autophagy through lysoHCN3 inhibition. Oxidative stress induced by H₂O₂ up-regulated mitoHCN3 expression, while Tiron had the opposite effect. In conclusion, inhibition of mito- and lysoHCN3 channels by ZD7288 can protect against mitochondrial oxidative stress and stimulate the lysosome–autophagy pathway in response to NH₄Cl treatment. Full article

Cancer has recently been proposed as a type of channelopathy due to the aberrant expression of various ion channels. Voltage-gated potassium (K⁺) channels (VGKCs) are notably upregulated during tumor proliferation, while voltage-gated sodium (Na⁺) channels are predominantly associated with the invasive stage of cancer progression. Among these, the Kv10.1 channel has been found to be overexpressed in breast cancer, making it a promising therapeutic target. 4-Aminopyridine (4-AP), a non-selective voltage-gated potassium channel blocker, has emerged as a potential novel agent for breast cancer treatment. In this study, we aimed to elucidate the mechanism of action of 4-aminopyridine in breast cancer cells. To investigate the involvement of various cell death pathways, cycloheximide (CHX) (a paraptosis inhibitor), Z-VAD-FMK (a pan-caspase inhibitor), and 2-Aminoethoxydiphenyl borate (2-APB) (a phosphoinositide 3-kinase [PI3K] inhibitor) were employed. Experiments were conducted using the MCF-7 human breast cancer cell line and the L929 mouse fibroblast cell line as a healthy control. Assessments included cell viability assays, intracellular calcium (Ca²⁺) and K⁺ concentration measurements, and plasma membrane potential analysis. Our findings aim to contribute to the understanding of the therapeutic potential and cellular effects of VGKC blockers, particularly 4-aminopyridine, in breast cancer treatment strategies. Full article

We used molecular docking as a computational tool to predict the binding affinities and interactions of quercetin 3-O-malonylglucoside (Q3MG) with vascular target proteins. First, the proteins 1M9M (human endothelial nitric oxide synthase; eNOS) and 6ND0 (human large-conductance voltage- and calcium-activated K⁺ channels; BK_Ca) were downloaded from the Protein Data Bank and submitted to molecular docking studies, revealing Q3MG binding affinities for both proteins. The vascular effect of Q3MG was investigated in the perfused mesenteric vascular beds (MVBs) of spontaneously hypertensive rats. In preparations with functional endothelium, Q3MG dose-dependently reduced the perfusion pressure in MVBs. Removal of the endothelium or inhibition of the nitric oxide synthase enzyme by L-NAME blocked the vasodilation induced by Q3MG. Perfusion with a physiological solution containing high KCl or the use of a non-selective blocker of K⁺ channels, as well as perfusion with iberiotoxin, completely abolished the vasodilatory effects of Q3MG. The data obtained suggest that the vascular effects of Q3MG involve the activation of the NO/cGMP pathway followed by the opening of BK_Ca. Full article