Search Results (98)

S-nitrosoglutathione (GSNO), a promising S-nitrosothiol, has been recognized for its ability to modulate vascular tone through its vasodilatory, antiplatelet, and antiproliferative effects. However, data on its vasodilatory effects in human vessels remain limited, and its mechanisms of action have yet to be fully elucidated. In this study, we aimed to investigate the vasorelaxant effect of GSNO and its underlying mechanisms, with particular focus on the soluble guanylate cyclase (sGC)/nitric oxide (NO) pathway and potassium channels in isolated human saphenous veins (SVs) obtained from patients undergoing coronary artery bypass grafting (CABG). GSNO (10⁻⁸–10⁻⁴ M) produced concentration-dependent relaxations in SV rings precontracted with phenylephrine. These relaxations were unaffected by NO synthase inhibition with L-NAME (10⁻⁴ M, 30 min) or NO scavenging with PTIO (10⁻⁴ M, 30 min), but were significantly reduced by the sGC inhibitor, ODQ (10⁻⁵ M, 30 min). Inhibition of ATP-sensitive (glibenclamid; 10⁻⁵ M, 30 min.), high-conductance Ca²⁺-activated (charybdotoxin; 10⁻⁷ M, 30 min), small-conductance Ca²⁺-activated (apamin; 10⁻⁶ M, 30 min), or voltage-dependent (4-aminopyridine; 10⁻³ M, 30 min) potassium channels did not alter the maximum relaxant responses to GSNO. Furthermore, pretreatment with GSNO (10⁻⁴ M, 30 min) significantly attenuated both the contractile response and sensitivity to phenylephrine. Collectively, these findings demonstrate that GSNO exerts acute vasorelaxant and modulatory effects in human SV primarily via cGMP-dependent mechanisms, highlighting its potential as a local therapeutic agent for preventing graft spasm in CABG. Full article

Neuropathic pain is a chronic and debilitating disorder of the somatosensory system that affects a significant proportion of the population and is characterized by abnormal responses such as hyperalgesia and allodynia. Voltage-gated ion channels, including sodium (Na_V), calcium (Ca_V), and potassium (K_V) channels, play a pivotal role in modulating neuronal excitability and pain signal transmission following nerve injury. This review intends to provide a comprehensive analysis of the molecular and cellular mechanisms by which dysregulation in the expression, localization, and function of specific Na_V channel subtypes (mainly Na_V1.7 and Na_V1.8) and their auxiliary subunits contributes to aberrant neuronal activation, the generation of ectopic discharges, and sensitization in neuropathic pain. Likewise, special emphasis is placed on the crucial role of Ca_V channels, particularly Ca_V2.2 and the auxiliary subunit Ca_Vα₂δ, whose overexpression increases calcium influx, neurotransmitter release, and neuronal hyperexcitability, thus maintaining persistent pain states. Furthermore, K_V channels (particularly K_V7 channels) function as brakes on neuronal excitability, and their dysregulation facilitates the development and maintenance of neuropathic pain. Therefore, targeting specific K_V channel subtypes to restore their function is also a promising therapeutic strategy for alleviating neuropathic pain symptoms. On the other hand, recent advances in the development of small molecules as selective modulators or inhibitors targeting voltage-gated ion channels are also discussed. These agents have improved efficacy and safety profiles in preclinical and clinical studies by attenuating pathophysiological channel activity and restoring neuronal function. This review seeks to contribute to guiding future research and drug development toward more effective mechanism-based treatments by discussing the molecular mechanisms underlying neuropathic pain and highlighting translational therapeutic opportunities. Full article

Small conductance Ca²⁺-activated K⁺ (SK) channels are expressed in atria and ventricles. However, the data on the contribution of SK channels to atrial action potential (AP) repolarization are inconsistent. We investigated the effect of SK channel modulators on AP morphology in rabbit atrial myocytes and tested the hypothesis that pharmacological activation of SK channels suppresses pacing-induced Ca²⁺ transient (CaT) and AP duration (APD) alternans. At the cellular level, alternans are observed as beat-to-beat alternations in contraction, APD, and CaT amplitude, representing a risk factor for arrhythmias, including atrial fibrillation. Our results show that SK channel inhibition by apamin did not affect atrial APD under basal conditions. However, SK channel activation by NS309 significantly shortened APD, indicating the expression of functional SK channels. Moreover, the activation of SK channels reduced CaT amplitude and sarcoplasmic reticulum Ca²⁺ load. Activation of SK channels also suppressed pacing-induced CaT and APD alternans. K_V7.1 potassium channel inhibition, simulating long QT syndrome type-1 conditions, increased the risk of atrial CaT alternans, which was abolished by the activation of SK channels. In summary, our data suggest that pharmacological modulation of SK channels can potentially reduce atrial arrhythmia risk arising from pathological APD prolongation. Full article

Pancreatic beta cells regulate insulin secretion in response to glucose by generating ATP, which modulates ATP-sensitive potassium channels (K_ATP) channel activity and Ca²⁺ dynamics. We present a model of ATP production in pancreatic beta cells, focusing on ATP dynamics within the bulk cytosol, submembrane region, and microdomains near K_ATP channels. ATP is generated through glycolysis, mitochondrial oxidative phosphorylation (OxPhos), and glycolytic pyruvate kinase-mediated phosphoenolpyruvate (PEP) production, supported by PEP cycling between mitochondria and the cytosol. The model examines ATP production in relation to Ca²⁺ oscillations, elucidating their interdependent dynamics. Our findings demonstrate that both mitochondrial OxPhos and PEP-mediated ATP production contribute substantially to cellular ATP levels. Specifically, glycolysis and mitochondrial OxPhos are crucial for the initial (first-phase) increase in bulk and subplasmalemmal ATP, effectively “filling up” the ATP pool in beta cells. In the second phase, coordinated cycling between OxPhos and PEP pathways enables cost-effective fine-tuning of ATP levels, with localized effects in the K_ATP channel microdomains. This model addresses and clarifies the recent debate regarding the mechanisms by which sufficient ATP concentrations are achieved to close K_ATP channels in glucose-stimulated beta cells, offering novel insights into the regulation of energy production and K_ATP channel activity. Full article

Primary aldosteronism is characterised by the excessive production of aldosterone, which is a key regulator of salt metabolism, and is the most common cause of secondary hypertension. Studies have investigated the association between primary aldosteronism and genetic alterations, with pathogenic mutations being identified. This includes a glycine-to-arginine substitution at position 151 (G151R) of the G protein-activated inward rectifier potassium (K⁺) channel 4 (GIRK4), which is encoded by the KCNJ5 gene. Mutations in GIRK4 have been found to reduce the selectivity for K⁺ ions, resulting in membrane depolarisation, the activation of voltage-gated Ca²⁺ channels, and an increase in aldosterone secretion. As a result, there is an interest in identifying and exploring the mechanisms of action of small molecule modulators of wildtype (WT) and mutant channels. In order to investigate the potential modulation of homotetrameric GIRK4^WT and GIRK4^G151R channels, homology models were generated. Molecular dynamics (MD) simulations were performed, followed by a cluster analysis to extract starting structures for molecular docking. The central cavity has been previously identified as a binding site for small molecules, including natural compounds. The OliveNet^TM database, which consists of over 600 compounds from Olea europaea, was subsequently screened against the central cavity. The binding affinities and interactions of the docked ligands against the GIRK4^WT and GIRK4^G151R channels were then examined. Based on the results, luteolin-7-O-rutinoside, pheophorbide a, and corosolic acid were identified as potential lead compounds. The modulatory activity of olive-derived compounds against the WT and mutated forms of the GIRK4 channel can be evaluated further in vitro. Full article

The pulmonary vein wall contains a myocardial layer whose ectopic automaticity is the major cause of atrial fibrillation. This review summarizes the results obtained in isolated pulmonary vein myocardium from small experimental animals, focusing on the studies with the guinea pig. The diversity in the action potential waveform reflects the difference in the repolarizing potassium channel currents involved. The diastolic depolarization, the trigger of automatic action potentials, is caused by multiple membrane currents, including the Na⁺-Ca²⁺ exchanger current and late I_Na. The action potential waveform and automaticity are affected differentially by α- and β-adrenoceptor stimulation. Class I antiarrhythmic drugs block the propagation of ectopic electrical activity of the pulmonary vein myocardium through blockade of the peak I_Na. Some of the class I antiarrhythmic drugs block the late I_Na and inhibit pulmonary vein automaticity. The negative inotropic and chronotropic effects of class I antiarrhythmic drugs could be largely attributed to their blocking effect on the Ca²⁺ channel rather than the Na⁺ channel. Such a comprehensive understanding of pulmonary vein automaticity and class I antiarrhythmic drugs would lead to an improvement in pharmacotherapy and the development of novel therapeutic agents for atrial fibrillation. Full article

Background/Objectives: Hemodialysis-induced myocardial stunning (HIMS) is a frequent complication in patients undergoing maintenance hemodialysis, characterized by transient left ventricular dysfunction due to ischemic episodes. Mitochondrial dysfunction and fluctuations in key ions such as potassium (K⁺) and calcium (Ca²⁺) are implicated in the pathogenesis of HIMS. This study aims to investigate the role of mitochondrial dysfunction and the protective potential of mitochondrial ATP-sensitive potassium channels (mitoK_ATP) in mitigating HIMS. Methods: A 5/6 nephrectomy rat model was established to mimic chronic kidney disease and the subsequent HIMS. The effects of mitoK_ATP channel modulators were evaluated by administering diazoxide (DZX), a mitoK_ATP opener, and 5-hydroxydecanoate (5-HD), a mitoK_ATP blocker, before hemodialysis. Mitochondrial function was assessed by measuring membrane potential, ATP synthase activity, and intramitochondrial Ca²⁺ levels. Myocardial function was evaluated using speckle tracking echocardiography. Results: Rats undergoing hemodialysis exhibited significant reductions in left ventricular strain and synchrony. DZX administration significantly improved mitochondrial function and reduced myocardial strain compared to controls. Conversely, 5-HD worsened mitochondrial swelling and disrupted myocardial function. Higher K⁺ and Ca²⁺ concentrations in the dialysate were associated with improved mitochondrial energy metabolism and myocardial strain. Conclusions: Mitochondrial dysfunction and ion imbalances during hemodialysis are key contributors to HIMS. The activation of mitoK_ATP channels provides mitochondrial protection and may serve as a potential therapeutic strategy to mitigate HIMS. Full article

Regulating membrane potential is key to cellular function. For many animal cells, resting membrane potential is predominantly driven by a family of K2P (two-pore domain) potassium channels. These channels are commonly referred to as leak channels, as their presence results in the membrane being permeable to K⁺ ions. These channels, along with various pumps and exchangers, keep the cell resting membrane potential (Rp) relatively close to potassium’s equilibrium potential (E_K); however, in many cells, the resting membrane potential is more depolarized than the E_K due to a small Na⁺ ion leak. Raising [Ca²⁺]_O (extracellular Ca²⁺ concentration) can result in hyperpolarization of the membrane potential from the resting state. The mechanism for this hyperpolarization likely lies in the blockage of a Na⁺ leak channel (NALCN) and/or voltage-gated Na⁺ channels. The effects may also be connected to calcium-activated potassium channels. Using Drosophila melanogaster, we here illustrate that changing [Ca²⁺]_O from 0.5 to 3 mM hyperpolarizes the muscle. Replacing NaCl with LiCl or choline chloride still led to hyperpolarization when increasing [Ca²⁺]_O. Replacing CaCl₂ with BaCl₂ results in depolarization. K2P channel overexpression in the larval muscle greatly reduces the effects of [Ca²⁺]_O on cell membrane potential, likely because potential is heavily driven by the E_K in these muscles. These experiments provide an understanding of the mechanisms behind neuronal hypo-excitability during hypercalcemia, as well as the effects of altered expression of K2P channels on membrane potential. Full article

Antispasmodic agents are crucial in managing gastrointestinal motility disorders by modulating muscle contractions and reducing symptoms like cramping and diarrhea. This study investigated the antispasmodic potential of different coffee bean extracts, including light coffee (LC), medium coffee (MC), and dark coffee (DC), on ileum contractions induced by potassium chloride (KCl), and elucidated their mechanisms of action using in vitro isolated tissue techniques. The results demonstrated that all coffee extracts reduced spontaneous contractions of rat ileum tissue in a dose-dependent manner. Among these, LC showed the most significant reduction in ileum contractions, particularly at higher concentrations. The key findings reveal that LC at 5 mg/mL significantly reduced CaCl₂-induced contractions in isolated rat ileum tissue, indicating that LC may inhibit calcium influx or interfere with calcium signaling pathways. The presence of nifedipine, propranolol, and N-nitro-L-arginine methyl ester (L-NAME) have been confirmed in their involvement; they block calcium influx and calcium channels and activate β-adrenergic pathways as part of LC’s mechanism of action. The presence of their active compounds, particularly chlorogenic acid and caffeine, likely contributes to the observed antispasmodic effects. These findings suggest that LC exerts its antispasmodic effects by targeting key mechanisms involved in muscle spasms and intestinal motility, providing a potential for managing such conditions. Full article

Neuroplasticity in the amygdala and its central nucleus (CeA) is linked to pain modulation and pain behaviors, but cellular mechanisms are not well understood. Here, we addressed the role of small-conductance Ca²⁺-activated potassium (SK) channels in pain-related amygdala plasticity. The facilitatory effects of the intra-CeA application of an SK channel blocker (apamin) on the pain behaviors of control rats were lost in a neuropathic pain model, whereas an SK channel activator (NS309) inhibited pain behaviors in neuropathic rats but not in sham controls, suggesting the loss of the inhibitory behavioral effects of amygdala SK channels. Brain slice electrophysiology found hyperexcitability of CeA neurons in the neuropathic pain condition due to the loss of SK channel-mediated medium afterhyperpolarization (mAHP), which was accompanied by decreased SK2 channel protein and mRNA expression, consistent with a pretranscriptional mechanisms. The underlying mechanisms involved the epigenetic silencing of the SK2 gene due to the increased DNA methylation of the CpG island of the SK2 promoter region and the change in methylated CpG sites in the CeA in neuropathic pain. This study identified the epigenetic dysregulation of SK channels in the amygdala (CeA) as a novel mechanism of neuropathic pain-related plasticity and behavior that could be targeted to control abnormally enhanced amygdala activity and chronic neuropathic pain. Full article

Oocyte–cumulus cell interaction is essential for oocyte maturation and competence. The bidirectional crosstalk network mediated by gap junctions is fundamental for the metabolic cooperation between these cells. As cumulus cells exhibit a more glycolytic phenotype, they can provide metabolic substrates that the oocyte can use to produce ATP via oxidative phosphorylation. The impairment of mitochondrial activity plays a crucial role in ovarian aging and, thus, in fertility, determining the success or failure of assisted reproductive techniques. This review aims to deepen the knowledge about the electro-metabolic coupling of the cumulus–oocyte complex and to hypothesize a putative role of potassium channel modulators in order to improve fertility, promote intracellular Ca²⁺ influx, and increase the mitochondrial biogenesis and resulting ATP levels in cumulus cells. Full article

Alterations in intraocular and external pressure critically involve the pathogenesis of glaucoma, traumatic retinal injury (TRI), and other retinal disorders, and retinal neurons have been reported to express multiple mechanical-sensitive channels (MSCs) in recent decades. However, the role of MSCs in visual functions and pressure-related retinal conditions has been unclear. This review will focus on the variety and functional significance of the MSCs permeable to K⁺, Na⁺, and Ca²⁺, primarily including the big potassium channel (BK); the two-pore domain potassium channels TRAAK and TREK; Piezo; the epithelial sodium channel (ENaC); and the transient receptor potential channels vanilloid TRPV1, TRPV2, and TRPV4 in retinal photoreceptors, bipolar cells, horizontal cells, amacrine cells, and ganglion cells. Most MSCs do not directly mediate visual signals in vertebrate retinas. On the other hand, some studies have shown that MSCs can open in physiological conditions and regulate the activities of retinal neurons. While these data reasonably predict the crossing of visual and mechanical signals, how retinal light pathways deal with endogenous and exogenous mechanical stimulation is uncertain. Full article

Ca²⁺ binding to the ubiquitous Ca²⁺ sensing protein calmodulin (CaM) activates the intermediate conductance Ca²⁺-activated SK4 channel. Potential hydrophilic pockets for CaM binding have been identified at the intracellular HA and HB helices in the C-terminal of SK4 from the three published cryo-EM structures of SK4. Single charge reversal substitutions at either site, significantly weakened the pull-down of SK4 by CaM wild-type (CaM), and decreased the TRAM-34 sensitive outward K⁺ current densities in native HEK293T cells when compared with SK4 WT measured under the same conditions. Only the doubly substituted SK4 R352D/R355D (HB helix) obliterated the CaM-mediated pull-down and thwarted outward K⁺ currents. However, overexpression of CaM E84K/E87K, which had been predicted to face the arginine doublet, restored the CaM-mediated pull-down of SK4 R352D/R355D and normalized its whole-cell current density. Virtual analysis of the putative salt bridges supports a unique role for the positively charged arginine doublet at the HB helix into anchoring the interaction with the negatively charged CaM glutamate 84 and 87 CaM. Our findings underscore the unique contribution of electrostatic interactions in carrying CaM binding onto SK4 and support the role of the C-terminal HB helix to the Ca²⁺-dependent gating process. Full article

During pregnancy, uterine vasculature undergoes significant circumferential growth to increase uterine blood flow, vital for the growing feto-placental unit. However, this process is often compromised in conditions like maternal high blood pressure, particularly in preeclampsia (PE), leading to fetal growth impairment. Currently, there is no cure for PE, partly due to the adverse effects of anti-hypertensive drugs on maternal and fetal health. This study aimed to investigate the vasodilator effect of extra virgin olive oil (EVOO) phenols on the reproductive vasculature, potentially benefiting both mother and fetus. Isolated uterine arteries (UAs) from pregnant rats were tested with EVOO phenols in a pressurized myograph. To elucidate the underlying mechanisms, additional experiments were conducted with specific inhibitors: L-NAME/L-NNA (10⁻⁴ M) for nitric oxide synthases, ODQ (10⁻⁵ M) for guanylate cyclase, Verapamil (10⁻⁵ M) for the L-type calcium channel, Ryanodine (10⁻⁵ M) + 2-APB (3 × 10⁻⁵ M) for ryanodine and the inositol triphosphate receptors, respectively, and Paxilline (10⁻⁵ M) for the large-conductance calcium-activated potassium channel. The results indicated that EVOO-phenols activate Ca²⁺ signaling pathways, generating nitric oxide, inducing vasodilation via cGMP and BKCa²⁺ signals in smooth muscle cells. This study suggests the potential use of EVOO phenols to prevent utero-placental blood flow restriction, offering a promising avenue for managing PE. Full article

Psoriasis is a chronic inflammatory skin disease characterized by the rapid abnormal growth of skin cells in the epidermis, driven by an overactive immune system. Consequently, a complex interplay among epidermal cells, immune cells, and sensory neurons contributes to the development and progression of psoriasis. In these cellular contexts, various ion channels, such as acetylcholine receptors, TRP channels, Ca²⁺ release-activated channels, chloride channels, and potassium channels, each serve specific functions to maintain the homeostasis of the skin. The dysregulation of ion channels plays a major role in the pathophysiology of psoriasis, affecting various aspects of epidermal cells, immune responses, and sensory neuron signaling. Impaired function of ion channels can lead to altered calcium signaling, inflammation, proliferation, and sensory signaling, all of which are central features of psoriasis. This overview summarizes the pathophysiological roles of ion channels in epidermal cells, immune cells, and sensory neurons during early and late psoriatic processes, thereby contributing to a deeper understanding of ion channel involvement in the interplay of psoriasis and making a crucial advance toward more precise and personalized approaches for psoriasis treatment. Full article