Search Results (97)

Atrial fibrillation (AF) is the most prevalent sustained arrhythmia and is increasingly driven by cardiometabolic disease, including type 2 diabetes mellitus (T2DM), obesity, and insulin resistance. These conditions promote atrial electrical instability and a permissive substrate through mitochondrial dysfunction, oxidative stress, inflammation, calcium-handling abnormalities, and profibrotic signaling, culminating in atrial fibrosis and conduction heterogeneity. Metformin, the foundational glucose-lowering therapy for T2DM, exerts pleiotropic actions that intersect with these upstream pathways. Beyond glycemic control, metformin induces mild mitochondrial complex I modulation with reduction of reverse electron transfer-derived reactive oxygen species, activates adenosine monophosphate (AMP) activated protein kinase, and attenuates nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-mediated cytokine signaling; experimental data further suggest favorable effects on adiponectin–sarcoendoplasmic reticulum calcium adenosine triphosphatase (SERCA) 2a-dependent calcium cycling, connexin expression, small-conductance Ca²⁺-activated K+ channel remodeling, lipid handling, and transforming growth factor-β (TGF)-β-associated fibrotic remodeling. Observational cohort studies have reported associations between metformin exposure and a modest reduction in incident AF, particularly with longer treatment duration and in higher-risk metabolic phenotypes; device-based surveillance cohorts support a preventive association for new-onset AF rather than reduction of established AF burden. Data after catheter ablation suggest improved freedom from recurrence in metformin-treated patients, whereas evidence in postoperative AF is largely neutral, likely reflecting distinct acute mechanisms. Collectively, metformin may be best conceptualized as a potential substrate-modifying, upstream therapy candidate; however, confounding, exposure misclassification, and heterogeneity in comparators limit causal inference, underscoring the need for prospective randomized trials with AF endpoints. In practice, integration with comprehensive risk-factor modification (blood pressure, weight, sleep apnea, and glycemic optimization) remains essential when considering AF prevention strategies. Full article

Ventricular remodeling occurring in heart failure (HF) involves structural disarray of the sarcolemma T-tubule (TT)–sarcoplasmic reticulum (SR) dyad junctions, thereby disrupting the close apposition of L-type Ca²⁺ channels (Ca_V1.2) with ryanodine receptors (RyR2) that trigger SR Ca²⁺ release and myofilament contraction. In a rat ischemic heart failure model expressing low thyroid hormone (TH) function, we used 3D stochastic optical reconstruction microscopy (STORM) to image RyR2 clusters with Ca_V1.2 channels, and the associated protein junctophilin-2 (Jph2). We tested whether treatment with T3, the biologically active form of TH, throughout progression of the disease would preserve T-tubule structure and dyadic ion channel organization. Confocal microscopy of isolated cardiomyocytes (CMs) stained with ANEPPS membrane dye showed significantly decreased TT density in diseased CMs while T3 treatment attenuated TT disorganization. 3D STORM images of dyadic ion channels labeled with fluorescent-tagged antibodies to RyR-Dylight550, Jph-CF647 and Ca_V1.2/IgG-Dylight488 were captured. A density-based algorithm defined RyR2 clusters, and a 400 nm spherical 3D volume of interest around each RyR2 cluster’s centroid determined the number of Ca_V1.2 and Jph2 localizations associated with each RyR2 cluster. Analysis revealed significant reduction in RyR2 cluster size and number with reduced co-localized Jph2 in failing CMs. T3 treatment increased RyR2 cluster numbers and cluster volumes albeit non-significantly, with increased co-clustering of Jph2. The number of Ca_V1.2 co-localized with RyR2 clusters trended lower in the failing CMs. These results support maintaining TH homeostasis in optimizing the nanoscale organization of Ca²⁺ ion channels in triggering Ca²⁺ release and myofibrillar contraction in patients with heart disease. Full article

Health, social, and ethical considerations highlight the need for new male contraceptives. Pimozide is an FDA approved drug known to block T-type calcium channels and which shares structural similarities with mibefradil, a proven antagonist of the CatSper channel. In this study, we examined the effect of pimozide on CatSper, a key target for non-hormonal male contraception. Molecular docking and molecular dynamics simulations were carried out to assess how pimozide binds within the channel pore, and binding energies were estimated using MM-GBSA. To determine its impact on sperm function, we evaluated hyperactivation, the acrosome reaction, and CatSper activity. Our computational analyses indicate that pimozide functions as a pore blocker of the CatSper channel. Experimental findings further support this, showing that pimozide inhibits CatSper activity, and impairs hyperactivation and the acrosome reaction in human spermatozoa. Overall, these results identify pimozide as a novel CatSper antagonist and propose a binding mode, offering a basis for the rational design of reversible, non-hormonal male contraceptives that target the CatSper channel. Full article

Background: In patients with type 2 diabetes mellitus (T2DM), angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin receptor blockers (ARBs) are first-line antihypertensive treatments with important cardiovascular benefits, but their impacts on coronary-specific inflammation are unknown. Pericoronary adipose tissue (PCAT) attenuation, as assessed by coronary computed tomography angiography (CCTA), serves as a specific biomarker for coronary inflammation. Here, we aim to assess whether treatment with ACE-I or ARB is correlated with lower PCAT attenuation. Methods: In this retrospective observational study, we analyzed 223 patients with T2DM and coronary atherosclerosis who underwent CCTA from 1 January 2017 to 1 September 2024 at our institution. PCAT attenuation was measured in the proximal right coronary artery. Propensity score matching and multivariate linear regression analyses were performed for comparisons. Results: Of the 223 patients (mean age of 64.9 ± 8.8 years, 69.1% male), 122 patients were on ACE-I or ARB (ACE-I/ARB). ACE-I/ARB users had similar PCAT attenuation as their counterparts after propensity score matching (−72.1 ± 7.5 and −71.7 ± 8.1 HU, respectively; p = 0.722). Subgroup analysis in patients with glomerular filtration rate (GFR) < 90 mL/min revealed lower PCAT attenuation in ACE-I/ARB users (−74.8 ± 6.6 vs. −71.4 ± 7.1 HU; p = 0.038), with a significant interaction between these two factors in the multivariate analysis (p = 0.047). Other antihypertensive treatments (beta blockers, dihydropyridine calcium channel blockers, and thiazides) were not linked with lower coronary inflammation. Conclusions: In T2DM patients with coronary atherosclerosis, we did not find an association between ACE-I/ARB treatment and lower coronary inflammation as defined by PCAT attenuation, although such a relationship may exist in those with reduced GFRs. Full article

Retinal neurovascular unit (RNVU) dysfunction underlies major blinding and neurodegenerative conditions including glaucoma, diabetic retinopathy (DR), age-related macular degeneration (AMD), retinal ischemia–reperfusion (RIR) injury, and Alzheimer’s disease (AD)-associated retinopathy. Within the RNVU, calcium ions coordinate neurotransmission, glial activation, vascular tone, and blood–retinal barrier maintenance, and calcium dysregulation is emerging as a unifying pathogenic hub across these conditions. Although upstream triggers differ, including mechanical stress in glaucoma, hyperglycemia in DR, oxidative damage in AMD, ischemic energy failure in RIR, and amyloid-β–driven endoplasmic reticulum stress in AD, all converge on disruption of intracellular calcium homeostasis, producing shared downstream consequences including excitotoxic injury of retinal ganglion cells (RGCs), Müller cell reactive gliosis, and pericyte hypercontraction. Broad-spectrum calcium channel blockade has shown limited clinical success, underscoring the need for cell-type-specific and pathway-selective approaches. This review therefore catalogs key interventional nodes, including transient receptor potential (TRP) channel antagonists, T-type calcium channel inhibitors, calcium/calmodulin-dependent protein kinase II (CaMKII) suppressors, and mitochondrial permeability transition pore (mPTP) inhibitors, and discusses how precision targeting of these pathways may restore RNVU homeostasis and open a therapeutic window into central nervous system (CNS) degenerative disorders. Full article

How do ryanodine receptors (RyRs) open simultaneously to trigger the contraction of whole myofibrils within a large skeletal muscle cell? One possible answer is the uniformity of mechanosensitive RyRs, which is mechanically forced by the neighboring environment, including proteins. Here, we review papers addressing this proposed “mechanical sarcoplasmic reticulum (SR) paradigm”. Crystals of the molecular complexes comprising RyR and L-type voltage-gated Ca²⁺ channels were observed at the T-tubule/SR junction in situ using cryo-electron tomography. Observations of the SR vesicles isolated from rabbit and scallop cross-striated muscles using negative staining and transmission electron microscope raised a hypothesis of dynamic rearrangement of the Ca²⁺-ATPase (ATPase) molecules in response to cytoplasmic calcium concentration, as follows: (i) At a low calcium concentration where the ratio of operating ATPase molecules to the total molecules is at a submaximal level, the ATPase molecules form, at least in part, their cylindrical crystals in the SR membrane with the help of ATP; this results in the elongation of the SR vesicles. (ii) High concentrations of calcium, at which the ratio of operating ATPase molecules is maximal, reversibly collapse the ATPase crystals to transform the elongated vesicles into round forms comprising tightly attached crystal patches. These data further lead to the idea that the reversible growth of cylindrical ATPase crystals provides a dynamic crystalline network, which acts as an “SR membrane-endoskeletal motor” to manipulate the SR movement. The possibility of interactions between ATPase crystals and neighboring RyR crystals is also discussed. Full article

Background/Objectives: Familial hyperaldosteronism type IV (FH-IV) is an extremely rare, clinically heterogeneous condition representing the least characterized familial subtype of primary aldosteronism (PA) caused by germline gain-of-function CACNA1H mutations. Despite growing molecular insights, optimal diagnostic and therapeutic strategies remain poorly defined. This systematic review aims to synthesize available evidence regarding the clinical, biochemical, and genetic characteristics of FH-IV, and to evaluate the efficacy of current pharmacological and surgical treatments. Methods: A systematic review was conducted in accordance with PRISMA guidelines and preregistered in PROSPERO (CRD420261324945). A comprehensive search of MEDLINE, Embase, and Web of Science identified studies reporting genetically confirmed FH-IV patients. Data concerning clinical phenotypes, diagnostic evaluations, treatment outcomes, and genetic backgrounds were extracted and analyzed. Results: The primary cohort included 31 fully characterized symptomatic patients, alongside 8 mutation-positive relatives (4 asymptomatic carriers and 4 symptomatic individuals). The genetic landscape was remarkably heterogeneous, encompassing 17 distinct CACNA1H mutations. Clinically, diagnosis was frequently delayed, often complicated by atypical normokalaemic presentations and misleading adrenal imaging. Surgical treatment was generally ineffective, frequently resulting in persistent or recurrent hypertension and biochemical dysregulation. Pharmacologically, patients often required multiple antihypertensive drugs, most frequently a combination of mineralocorticoid receptor antagonists (MRAs) and calcium channel blockers (CCBs). Conclusions: FH-IV is best conceptualized as a systemic adrenal channelopathy. While standard screening parameters are usually elevated, atypical biochemical profiles and misleading structural imaging can complicate the diagnostic process. Optimal management relies on multigene Next-Generation Sequencing (NGS) panels for definitive diagnosis and cascade screening of relatives. Finally, while the combination of MRAs and CCBs is commonly used in PA, it represents a valuable therapy for FH-IV, with dual L-/T-type CCBs emerging as a potential disease-specific option. 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 purinergic ionotropic receptor P2X7 stands out from other members of the P2X family due to its ability to form a macropore, activate multiple intracellular signaling pathways, and, as more recently reported, to mediate scavenger activity toward apoptotic cells. In addition, P2X7 exhibits a high number of single nucleotide polymorphisms (SNPs) and splice variants, several of which have been shown to impair ATP-mediated macropore formation. The aim of this study was to determine whether specific SNPs or deletion variants that have lost channel conductance or macropore activity retain other reported P2X7 functions. To address this, we analyzed the following variants: P2X7A (wild-type), P2X7B (unable to activate the macropore), P2X7 T283M (lacking conductance and macropore formation), P2X7 with N-terminal deletion (∆N; deficient in signal transduction), and P2X7 DN (dominant-negative double mutant W167A/C168A, lacking all known activities). We evaluated calcium influx, macropore formation, ERK and p38 signaling, and scavenger activity. Our results indicate that macropore formation depends on channel conductance, in contrast to what has been previously reported for P2X7B. Moreover, all modifications tested impaired signaling pathway activation. Strikingly, none of the mutations affected receptor-mediated phagocytic activity. These findings suggest that loss of conductance or macropore formation does not necessarily entail loss of other P2X7 functions, and our data reveals a functional independence between scavenger activity and the canonical roles of P2X7 (channel/macropore, MAPKs). This modular view provides a framework to reconcile the apparently discordant phenotypes of P2X7 variants observed across diverse pathophysiological settings. Full article

While persistent firing in glutamatergic neurons has been well-characterized, the intrinsic and synaptic mechanisms driving this phenomenon in neurogliaform cells (NGFCs), a subtype of GABAergic interneurons, remain unclear. This study investigates the mechanisms underlying persistent firing in hippocampal NGFCs. Whole-cell current-clamp recordings were performed on acute brain slices from C57BL/6J mice to examine the electrophysiological properties of NGFCs in the hippocampal stratum lacunosum-moleculare (SLM). Pharmacological interventions, including T-type calcium channel blocker ML218 and 5-hydroxytryptamine (5-HT) receptor antagonist olanzapine, were used to dissect the mechanisms of persistent firing. Biocytin labeling and confocal microscopy were employed to confirm neuronal morphology and location. The study revealed that persistent firing in NGFCs is induced by a long-lasting delayed afterdepolarization (L-ADP), which depends on T-type calcium channels (intrinsic mechanism) and is modulated by 5-HT receptors (synaptic mechanism). Persistent firing was observed in 62.96% of SLM neurons and was abolished by ML218 or olanzapine. The findings bridge a gap in understanding how inhibitory interneurons contribute to memory processes. The dual-mechanism framework (T-type channels and 5-HT receptors) aligns with prior work on glutamatergic systems but highlights unique features of GABAergic persistent firing. These insights advance the understanding of inhibitory circuit dynamics and their potential role in cognitive functions, paving the way for further research into interneuron-specific memory encoding. Full article

Blarina paralytic peptides (BPPs), neurotoxins from shrew saliva that paralyze mealworms, share high sequence similarity with human synenkephalin [1–53] (hSYN), a peptide released from proenkephalin together with opioid peptides that mediate analgesic and antidepressant effects in the brain. Both synthetic BPP2 and hSYN induce a hyperpolarizing shift in the human T-type voltage-gated calcium channel (hCa_v3.2) at sub-micromolar concentrations, although only BPP2 causes paralysis in insects. To gain insight into the functions of these insectivorous animal-specific neurotoxins and the largely uncharacterized brain peptides, we investigated the structure prediction of BPPs and SYNs and their interactions with hCa_v3.2. AlphaFold 3 modeling complemented available cryo-EM data and accurately reproduced the overall channel architecture; however, this inactivated-state model proved unsuitable for predicting agonistic binding of BPPs and SYNs. In contrast, docking simulations using an activated-state hCa_v3.2 homology model revealed distinct ligand-dependent differences in binding energies, affinity, and conformational flexibility. Notably, the C-terminal tail of BPPs—particularly its variable length and flexibility—was identified as a key determinant for the interactions with the S4 voltage-sensing domain of the channel. These findings provide new insights into the evolutionary adaptation of venom peptides in mammals and into potential therapeutic strategies targeting neurological disorders. Full article

Migraine is a prevalent neurological disorder that affects over 1 billion individuals worldwide. The pathogenesis of migraine remains incompletely understood, though evidence suggests a multifactorial etiology involving genetic factors. The CACNA1A gene has been implicated in rare forms of Familial Hemiplegic Migraine (FHM). This study aimed to investigate the role of CACNA1A variants in individuals with and without a family history of migraine. We genotyped 150 subjects (100 migraine patients: 50 with migraine without aura (MO), 50 with migraine with aura (MA) and 50 controls) for six CACNA1A variants using Sanger sequencing. Statistical analyses were performed in Statistica (p < 0.05). The CADD v1.7 model was used to assess the potential pathogenicity of novel variants. Three variants described in databases (rs10405121, rs894252513, and rs1012663275) and three novel variants (ch19:13228374 G > C, ch19:13228428 G > C, and ch19:13228348 A > T) were identified. The rs10405121 variant was associated with both migraine types, with the homozygous AA genotype exclusively found in familial cases. Abnormal genotype of rs894252513 and rs1012663275 were detected only in familial cases with MO. The novel variants were observed exclusively in patients with a family history of migraine, suggesting their potential relevance to inherited migraine pathogenesis. Novel variants may contribute to migraine pathogenesis by altering calcium channel function and lowering the threshold for cortical spreading depression (CSD). Full article

Although opioids are effective in treating pain, they cause serious side effects. The use of regional anesthesia, although effective in the perioperative period, may not be suitable if mobility and lack of numbness is desired. Hence, there is a clear need for novel pain therapies. Low-voltage activated (T-type) calcium channels (Ca_V3.2 isoform) could be a promising therapeutic target for the development of novel pain therapies. Indeed, our published findings suggest that novel neuroactive steroid (NAS) analogs that modulate the activity of Ca_V3.2 channels have unique anti-nociceptive properties. However, the concern with current NASs appears to be their hypnotic/sedative properties, thus potentially hindering the future development of NASs for novel pain therapies. Hence, we developed a new line of NASs that are effective blockers of neuronal Ca_V3.2 channels in pain pathways while having more favorable pharmacodynamic properties, i.e., lack of sedative/hypnotic side effects. We present two promising novel analogs of NASs—B372 ((3β,5α,17β)-3-Hydroxyandrostan-17-carbonitrile) and YX23 ((3β,5α,17β)-3-Methoxyestran-17-ol). Using an in vitro approach, we show that B372 and YX23 are effective in blocking Ca_V3.2 channels. Using an in vivo approach, we show that they are effective anti-nociceptives in wild-type but not Ca_V3.2 knock-out mice. Importantly, we show that they lack sedative/hypnotic effects. Full article

Calcium channel blockers (CCBs), originally developed for cardiovascular indications, have gained attention for their therapeutic potential in neuropsychiatric, endocrine, and pain-related disorders. In neuropsychiatry, nimodipine and isradipine, both L-type CCBs, show mood-stabilizing and neuroprotective effects, with possible benefits in depression, bipolar disorder, and schizophrenia. In endocrinology, verapamil, a non-dihydropyridine L-type blocker, has been associated with the preservation of pancreatic β-cell function and reduced insulin dependence in diabetes. CCBs may also aid in managing primary aldosteronism and pheochromocytoma, particularly in patients with calcium signaling mutations. In pain medicine, α2δ ligands and selective blockers of N-type and T-type channels demonstrate efficacy in neuropathic and inflammatory pain. However, their broader use is limited by challenges in central nervous system (CNS) penetration, off-target effects, and heterogeneous trial outcomes. Future research should focus on pharmacogenetic stratification, novel delivery platforms, and combination strategies to optimize repurposing of CCBs across disciplines. Full article

The L-type calcium channels (LTCCs) function as the main entry points that convert myocyte membrane depolarization into calcium transients, which drive every heartbeat. There is increasing evidence to show that maladaptive remodeling of these channels is the cause of heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF). Recent experimental, translational, and clinical studies have improved our understanding of the roles LTCC expression, micro-domain trafficking, and post-translational control have in disrupting excitation–contraction coupling, provoking arrhythmias, and shaping phenotype specific hemodynamic compromise. We performed a systematic search of the PubMed and Google Scholar databases (2015–2025, English) and critically evaluated 17 eligible publications in an effort to organize the expanding body of work. This review combines existing data about LTCC density and T-tubule architecture with β-adrenergic and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) signaling and downstream sarcoplasmic reticulum crosstalk to explain how HFrEF presents with contractile insufficiency and how HFpEF shows diastolic calcium overload and stiffening. Additionally, we highlight the emerging therapeutic strategies aimed at restoring calcium homeostasis such as CaMKII inhibitors, ryanodine receptor type 2 (RyR2) stabilizers, and selective LTCC modulators without compromising systolic reserve. The review establishes LTCC dysregulation as a single mechanism that causes myocardial dysfunction while remaining specific to each phenotype, thus offering clinicians and researchers a complete reference for current concepts and future precision therapy approaches in heart failure. Full article