Search Results (86)

The overdose mortality landscape has shifted from predominantly opioid exposures to a polysubstance epidemic increasingly driven by illicit fentanyl and fentanyl analogs combined with other centrally active agents. Among the co-intoxicants, veterinary α₂-adrenoceptor (α₂AR) agonists such as xylazine have emerged as clinically confounding adulterants. Recent reports from forensic toxicology, medical examiners, and border/interdiction agencies indicate that medetomidine, a veterinary sedative racemate with the highly selective α₂AR agonist enantiomer dexmedetomidine, is increasingly being detected together with fentanyl and its analogs in seized materials and postmortem assays. Prior reviews have covered these aspects. The current review synthesizes current evidence and clinical experience relevant to fentanyl + medetomidine co-exposure-induced respiratory depression—a primary cause of death. We focus on convergent µ-opioid receptor (MOR) and α₂AR signaling within key physiological substrates, including respiratory rhythm-generating networks, ascending arousal pathways, chemosensory reflex control of ventilation, and autonomic cardiovascular regulation, integrating mechanistic pharmacology, respiratory and cardiovascular toxicology, emergency-room treatment, and emerging public-health implications. Available evidence supports a model in which combined MOR and α₂AR activation produces additive-to-synergistic suppression of ventilation and consciousness, attenuation of hypoxic ventilatory drive and CO₂ responsiveness, with marked sympatholysis manifested as bradycardia and hypotension, all of which can persist beyond presumptive opioid reversal with a MOR antagonist. We discuss the implications for prehospital and emergency care. In sum, the increasing detection of medetomidine in the illicit fentanyl supply represents an emerging and potentially high-risk co-exposure pattern that may be only partially naloxone-responsive. Lastly, we highlight potential future pharmacologic countermeasures for polysubstance overdose, such as the BK-channel antagonist ENA-001, which may address naloxone-insensitive ventilatory suppression in opioid-dominant polysubstance overdose. 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

Dietary polyphenols are recognized as crucial modulators of gastrointestinal motility, holding therapeutic promise for conditions like irritable bowel syndrome, postoperative ileus, and functional dyspepsia. However, their reported effects are heterogeneous, ranging from spasmolytic to prokinetic. This review aims to clarify these inconsistencies by synthesizing experimental evidence on structure–activity relationships and underlying mechanisms. Relevant publications were identified in PubMed and Google Scholar using terms related to polyphenols and gastrointestinal motility. References were selected for relevance, and the narrative review integrates findings from in vitro, ex vivo, in vivo, and clinical studies. Across various experimental models, polyphenols function as multi-target modulators of gastrointestinal smooth muscle. The primary mechanisms identified involve the blockade of voltage-dependent L-type Ca²⁺ channels, activation of K⁺ channels (BK, K_ATP), and modulation of the NO/cGMP and cAMP/PKA pathways. Flavones and multiple flavonols consistently demonstrate spasmolytic activity via Ca²⁺ channel antagonism. In contrast, flavanones engage BK and K_ATP channels to induce membrane hyperpolarization. Complex extracts from plants like ginger and turmeric exhibit mixed pro- or antimotility effects, reflecting the diverse profiles of their constituent compounds. While robust ex vivo pharmacology and some in vivo and human data exist, a high degree of dataset heterogeneity and inconsistent reporting impedes direct translational efforts. Polyphenols are promising multi-mechanistic modulators of gastrointestinal motility with clear structure–activity patterns. To advance their clinical application, future research must focus on establishing standardized in vivo pharmacokinetics, conducting targeted structure–activity studies, employing bioassay-guided fractionation, and designing rigorous clinical trials. Full article

As we found earlier, paxilline (a Penicillium paxilli mycotoxin and blocker of Ca²⁺-activated big-conductance potassium channels, BK(Ca)s) attenuated Cd²⁺-induced cytotoxic effects, whereas BK(Ca) activators (NS004, NS1619) and Cd²⁺ were able to induce apoptosis, which was enhanced when used together. In this work, molecular mechanisms underlying the aforementioned effects were studied using two rat cell lines, PC12 and AS-30D, flow cytometry, and spectrofluorometric and polarographic techniques. Both NS004 and NS1619 were found to have time- and dose-dependent effects on cell viability, respiration, mitochondrial membrane potential, and intracellular reactive oxygen species (ROS) production. In PC12 cells, BK(Ca) openers exerted an uncoupling effect after 3 h, increasing the resting respiration, while they partially inhibited the maximal respiration after 5 and 24 h; in addition, after 3 h, a transient protection by NS004/NS1619 against Cd²⁺-induced decrease of cell viability was observed. In both cell types, NS004/NS1619 increased ROS production after 3 h and counteracted the mitigating effect of paxilline against Cd²⁺-induced necrosis. In turn, paxilline reduced NS004/NS1619-induced apoptosis in AS-30D cells and ROS increase produced by NS004/NS1619 and/or Cd²⁺ in PC12 cells. As a result, the involvement of the mitochondrial respiratory chain, ROS, and, very likely, BK(Ca)s, in the mechanisms of the modulatory effects of the BK(Ca) blocker/opener(s) used in the absence and presence of Cd²⁺ was revealed. Full article

Understanding the functional modulation of ion channels by multiple activating substances is critical to grasping stimulus-specific gating mechanisms and possible synergistic or competitive interactions. This study investigates the activation of large-conductance, voltage- and Ca²⁺-activated potassium channels (BK) in the plasma membrane of human bronchial epithelial cells by Ca²⁺ and quercetin (Que), both individually and in combination. Patch-clamp recordings were analyzed using open state probability, dwell-time distributions, Shannon entropy, sample entropy, power spectral density (PSD), and empirical mode decomposition (EMD). Our results reveal concentration-dependent alterations in gating kinetics, particularly at a low concentration of quercetin ([Que] = 10 μM) compared with [Que] = 100 μM, where some Que-related effects are strongly attenuated in the presence of Ca²⁺. We also identify specific frequency bands where oscillatory components are most sensitive to the considered stimuli. Our findings highlight the complex reciprocal interplay between Ca²⁺ and Que in modulating BK channel function, and demonstrate the interpretative power of entropic and signal-decomposition approaches in characterizing stimulus-specific gating dynamics. Full article

Large-conductance, voltage- and calcium-activated potassium (BK) channels are crucial regulators of cellular excitability, influenced by various signaling molecules, including heme. The BK channel contains a heme-sensitive motif located at the sequence ⁶¹²CKACH⁶¹⁶, which is a conserved heme regulatory motif (HRM) found in the cytochrome c protein family. This motif is situated within a linker region of approximately 120 residues that connect the RCK1 and RCK2 domains, and it also includes terminal α-helices similar to those found in cytochrome c family proteins. However, much of this region has yet to be structurally defined. We conducted a sequence alignment of the BK linker region with mitochondrial cytochrome c and cytochrome c domains from various hemoproteins to better understand this functionally significant region. In addition to the HRM motif, we discovered that important structural and functional elements of cytochrome c proteins are conserved in the BK RCK1-RCK2 linker. Firstly, the part of the BK region that is resolved in available atomic structures shows similarities in secondary structural elements with cytochrome c domain proteins. Secondly, the Met80 residue in cytochrome c domains, which acts as the second axial ligand to the heme iron, aligns with the BK channel. Beyond its role in electron shuttling, cytochrome c domains exhibit various catalytic properties, including peroxidase activity—specifically, the oxidation of suitable substrates using peroxides. Our findings reveal that the linker region endows human BK channels with peroxidase activity, showing an apparent H₂O₂ affinity approximately 40-fold greater than that of mitochondrial cytochrome c under baseline conditions. This peroxidase activity was reduced when substitutions were made at ⁶¹²CKACH⁶¹⁶ and other relevant sites. These results indicate that the BK channel possesses a novel module similar to the cytochrome c domains of hemoproteins, which may give rise to unique physiological functions for these widespread ion channels. Full article

Fibrosis represents a pivotal pathological process in numerous diseases, characterized by excessive deposition of extracellular matrix (ECM) that disrupts normal tissue architecture and function. In the heart, cardiac fibrosis significantly impairs both structural integrity and functional capacity, contributing to the progression of heart failure. Central to this process are cardiac fibroblasts (CFs), which, upon activation, differentiate into contractile myofibroblasts, driving pathological ECM accumulation. Transforming growth factor-beta (TGFβ) is a well-established regulator of fibroblast activation; however, the precise molecular mechanisms, particularly the involvement of ion channels, remain poorly understood. Emerging evidence highlights the regulatory role of ion channels, including calcium-activated potassium (K_Ca) channels, in fibroblast activation. This study elucidates the role of ion channels and investigates the mechanism by which Yoda1, an agonist of the mechanosensitive ion channel Piezo1, modulates TGFβ-induced fibroblast activation. Using NIH/3T3 fibroblasts, we demonstrated that TGFβ-induced activation is regulated by tetraethylammonium (TEA)-sensitive potassium channels, but not by specific K⁺ channel subtypes such as BK, SK, or IK channels. Intriguingly, Yoda1 was found to inhibit TGFβ-induced fibroblast activation through a Piezo1-independent mechanism. Transcriptomic analysis revealed that Yoda1 modulates fibroblast activation by altering gene expression pathways associated with fibrotic processes. Bromodomain-containing protein 4 (BRD4) was identified as a critical mediator of Yoda1’s effects, as pharmacological inhibition of BRD4 with JQ1 or ZL0454 suppressed TGFβ-induced expression of the fibroblast activation marker Periostin (Postn). Conversely, BRD4 overexpression attenuated the inhibitory effects of Yoda1 in both mouse and rat CFs. These results provide novel insights into the pharmacological modulation of TGFβ-induced cardiac fibroblast activation and highlight promising therapeutic targets for the treatment of fibrosis-related cardiac pathologies. Full article

Multi-anthelmintic resistance in hookworms poses a significant challenge to both human and veterinary health, underscoring the need for novel treatment strategies. In this study, we evaluated the in vitro efficacy of three anthelmintics—pyrantel, ivermectin, and emodepside—against L3 larvae of drug-susceptible (WMD) and triple-anthelmintic-resistant (BCR) isolates of Ancylostoma caninum. While pyrantel was largely ineffective and ivermectin induced high mortality in both isolates, emodepside displayed a surprising trend: the drug-resistant BCR isolate was more susceptible than the drug-susceptible WMD isolate. To explore the underlying mechanism, we performed survival assays in the presence of penitrem A, a BK channel (SLO-1) inhibitor. The addition of penitrem A reversed the enhanced emodepside sensitivity in BCR, implicating elevated basal expression of SLO-1 channels as a potential factor. These findings suggest that emodepside, via its action on SLO-1, may offer a promising therapeutic avenue to combat multidrug-resistant hookworm infections. Full article

Calcium- and voltage-gated potassium channels of large conductance (BK channels) in smooth muscle (SM) act as part of a negative feedback mechanism on SM contraction and associated decrease in cerebral artery diameter. Functional BK channels result from tetrameric association of α subunits encoded by KCNMA1 (Slo1). Ionic current from slo1 channels is inhibited by cholesterol in artificial lipid bilayers, an effect significantly reduced by the slo1 Y450F substitution. Whether such substitution affects cholesterol action on cerebral artery SM BK channel function and diameter remains unknown. Using the KCNMA1Y450F knock-in (K/I) mouse, we determined the effect of cholesterol enrichment on BK currents in native SM cells from middle cerebral artery using patch-clamp electrophysiology and the artery diameter ex vivo response to cholesterol. Results show that the KCNMA1Y450F K/I mutation modifies both basal function and the channel’s response to cholesterol enrichment. Such modifications are detectable solely in SM cells from males, demonstrating sexual dimorphism. Unexpectedly, the modifications introduced by the Y450F substitution do not translate into observable changes in middle cerebral artery diameter ex vivo, suggesting that mechanisms at the SM level compensate for changes driven by the KCNMA1 point mutation under study. Full article

Podocytes express large-conductance Ca²⁺-activated K⁺ channels (BK channels) and at least two different pore-forming KCa1.1 subunit C-terminal splice variants, known as VEDEC and EMVYR, along with auxiliary β and γ subunits. Podocyte KCa1.1 subunits interact directly with TRPC6 channels and BK channels become active in response to Ca²⁺ influx through TRPC6. Here, we confirmed that Ca²⁺ influx through TRPC channels is reduced following the blockade of BK channels by paxilline. The overall abundance of KCa1.1 subunits, as well as that of β4 and γ3 subunits, were increased in glomeruli isolated from Sprague Dawley rats during chronic puromycin aminonucleoside (PAN) nephrosis. Exposing cultured mouse podocytes for 24 h to recombinant TNFα, a circulating factor implicated in pediatric nephrotic syndromes, did not affect the total abundance of KCa1.1, but did evoke significant increases in both β4 and γ3. However, TNFα evoked a marked increase in the surface abundance of KCa1.1 subunits, similar to that of its previously reported effects on TRPC6 channels. The effect of TNFα on the surface expression of KCa1.1 was eliminated following siRNA knockdown of the β4 subunits, suggesting a role for this subunit in KCa1.1 trafficking to the cell surface. By contrast, treating podocytes with suPAR did not affect the total or surface expression of KCa1.1. The coordinated activation of KCa1.1 channels may promote Ca²⁺ influx through TRPC channels during normal and abnormal podocyte function by maintaining a membrane potential that allows for the efficient permeation of divalent cations through TRPC pores. Full article

Alcohol use disorder (AUD) is the most common substance use disorder and poses a significant global health challenge. Despite pharmacological advances, no single drug effectively treats all AUD patients. This study explores the protective potential of hispidol, a 6,4′-dihydroxyaurone, for AUD using the Caenorhabditis elegans model system. Our findings demonstrate that hispidol-fed worms exhibited more pronounced impairments in thrashes, locomotory speed, and bending amplitude, indicating that hispidol exacerbated the detrimental effects of acute ethanol exposure. However, hispidol significantly improved ethanol withdrawal behaviors, such as locomotory speed and chemotaxis performance. These beneficial effects were absent in slo-1 worms (the ortholog of mammalian α-subunit of BK channel) but were restored with the slo-1(+) or hslo(+) transgene, suggesting the involvement of BK channel activity. Additionally, hispidol increased fluorescence intensity and puncta in the motor neurons of slo-1::mCherry-tagged worms, indicating enhanced BK channel expression and clustering. Notably, hispidol did not alter internal ethanol concentrations, suggesting that its action is independent of ethanol metabolism. In the mouse models, hispidol treatment also demonstrated anxiolytic activity against ethanol withdrawal. Overall, these findings suggest hispidol as a promising candidate for targeting the BK channel in AUD treatment. Full article

With the rapid development of mobile edge computing (MEC) and wireless power transfer (WPT) technologies, the MEC-WPT system makes it possible to provide high-quality data processing services for end users. However, in a real-world WPT-MEC system, the channel gain decreases with the transmission distance, leading to “double near and far effect” in the joint transmission of wireless energy and data, which affects the quality of the data processing service for end users. Consequently, it is essential to design a reasonable system model to overcome the “double near and far effect” and make reasonable scheduling of multi-dimensional resources such as energy, communication and computing to guarantee high-quality data processing services. First, this paper designs a relay collaboration WPT-MEC resource scheduling model to improve wireless energy utilization efficiency. The optimization goal is to minimize the normalization of the total communication delay and total energy consumption while meeting multiple resource constraints. Second, this paper imports a BK-means algorithm to complete the end terminals cluster to guarantee effective energy reception and adapts the whale optimization algorithm with adaptive mechanism (AWOA) for mobile vehicle path-planning to reduce energy waste. Third, this paper proposes an immune differential enhanced deep deterministic policy gradient (IDDPG) algorithm to realize efficient resource scheduling of multiple resources and minimize the optimization goal. Finally, simulation experiments are carried out on different data, and the simulation results prove the validity of the designed scheduling model and proposed IDDPG. Full article

K⁺ channels do play a role in cell shape changes observed during cell proliferation and apoptosis. Research suggested that the dynamics of the aggregation of Aquaporin-4 (AQP4) into AQP4-OAP isoforms can trigger cell shape changes in malignant glioma cells. Here, we investigated the relationship between AQP4 and some K⁺ channels in the malignant glioma U87 line. The U87 cells transfected with the human M1-AQP4 and M23-AQP4 isoforms were investigated for morphology, the gene expression of KCNJ8, KCNJ11, ABCC8, ABCC9, KCNMA1, and Cyclin genes by RT-PCR, recording the whole-cell K⁺ ion currents by patch-clamp experiments. AQP4 aggregation into OAPs increases the plasma membrane functional expression of the Kir6.2 and SUR2 subunits of the KATP channels and of the KCNMA1 of the BK channels in U87 cells leading to a large increase in inward and outward K⁺ ion currents. These changes were associated with changes in morphology, with a decrease in cell volume in the U87 cells and an increase in the ER density. These U87 cells accumulate in the mitotic and G2 cell cycle. The KATP channel blocker zoledronic acid reduced cell proliferation in both M23 AQP4-OAP and M1 AQP4-tetramer-transfected cells, leading to early and late apoptosis, respectively. The BK channel sustains the efflux of K⁺ ions associated with the M23 AQP4-OAP expression in the U87 cells, but it is downregulated in the M1 AQP4-tetramer cells. The KATP channels are effective in the M1 AQP4-tetramer and M23 AQP4-OAP cells. Zoledronic acid can be effective in targeting pathogenic M1 AQP4-tetramer cell phenotypes inhibiting KATP channels and inducing early apoptosis. Full article

It has been reported that, in the spontaneously hypertensive rat (SHR) model of hypertension, different components of the G-protein/adenylate cyclase (AC)/Calcium-activated potassium channel of high conductance (BK) channel signaling pathway are altered differently. In the upstream part of the pathway (G-protein/AC), a comparatively low efficacy has been established, whereas downstream BK currents seem to be increased. Thus, the overall performance of this signaling pathway in SHR is elusive. For a better understanding, we focused on one aspect, the direct targeting of the BK channel by the G-protein/AC pathway and tested the hypothesis that the comparatively low AC pathway efficacy in SHR results in a reduced agonist-induced stimulation of BK currents. This hypothesis was investigated using freshly isolated smooth muscle cells from WKY and SHR rat tail artery and the patch-clamp technique. It was observed that: (1) single BK channels have similar current–voltage relationships, voltage-dependence and calcium sensitivity; (2) BK currents in cells with a strong buffering of the BK channel activator calcium have similar current–voltage relationships; (3) the iloprost-induced concentration-dependent increase of the BK current is larger in WKY compared to SHR; (4) the effects of activators of the PKA pathway, the catalytic subunit of PKA and the potent and selective cAMP-analogue Sp-5,6-DCl-cBIMPS on BK currents are similar. Thus, our data suggest that the lower iloprost-induced stimulation of the BK current in freshly isolated rat tail artery smooth muscle cells from SHR compared with WKY is due to the lower efficacy of upstream elements of the G-Protein/AC/BK channel pathway. Full article

Apolipoprotein L1 (APOL1) nephropathy results from several podocyte dysfunctions involving morphological and motility changes, mitochondrial perturbations, inflammatory stress, and alterations in cation channel activity. I propose that this phenotype results from increased hydrophobicity of the APOL1 risk variants, which induces two distinct types of podocyte dysfunctions. On one hand, increased hydrophobic interactions with APOL3 cause intracellular variant isoforms to impair both APOL3 control of Golgi PI(4)P kinase-B (PI4KB) activity and APOL3 control of mitochondrial membrane fusion, triggering actomyosin reorganisation together with mitophagy and apoptosis inhibition (hit 1). On the other hand, increased hydrophobic interactions with the podocyte plasma membrane may cause the extracellular variant isoforms to activate toxic Ca²⁺ influx and K⁺ efflux by the TRPC6 and BK channels, respectively (hit 2), presumably due to APOL1-mediated cholesterol clustering in microdomains. I propose that hit 2 depends on low HDL-C/high extracellular APOL1 ratio, such as occurs in cell culture in vitro, or during type I-interferon (IFN-I)-mediated inflammation. Full article