Search Results (485)

This review examines and hypothesizes cytoprotection as a conceptual therapeutic criterion for antiarrhythmic drugs, referring to the possibility of suppressing arrhythmias while avoiding adverse electrophysiological or systemic effects. Toward a theoretically complete cytoprotective profile—preserving benefits and eliminating toxicity—the criterion was the degree of counteraction of arrhythmias (i.e., bradycardia, tachycardia, atrioventricular (AV) block, ventricular tachycardia (VT), ST-segment changes, prolonged P, PR, QRS, and QT/QTc intervals, and repolarization). Conventional and new antiarrhythmics share class I–IV ≈ partial cytoprotection/narrow range; late INa inhibitors, IKs enhancers, RyR2 stabilizers, gap junction modulators, and atrial-selective antiarrhythmics ≈ partial cytoprotection/more extended range. Still predominantly in preclinical models, stable gastric pentadecapeptide BPC 157, in the clinic, has not demonstrated adverse effects in available human trials (non-cardiac) to date. As a prominent cytoprotection mediator (LD1 not achieved in toxicology studies), it demonstrates well-matched cytoprotective–antiarrhythmic effects, BPC 157 ≈ full cytoprotection/wide-range homeostasis. In vivo, this was across models of hypo-/hyperkalemia, hypermagnesemia, ischemia–reperfusion, myocardial infarction, drug-induced arrhythmias (including local anesthetics), and vascular occlusion. BPC 157 restores sinus rhythm, normalizes P/QRS/QT intervals, prevents AV block, suppresses VT, attenuates ST-segment changes, and stabilizes heart rate, even when insults are advanced. In vitro, HEK293 studies confirm direct membrane-stabilizing actions: BPC 157 prevents hypokalemia-induced hyperpolarization, reduces hyperkalemia- and hypermagnesemia-induced depolarization, and mitigates local anesthetic-induced Na⁺/Ca²⁺ dysregulation, reflecting bidirectional homeostatic modulation of membrane potential. Thus, to confirm the hypothesis, these BPC 157 conditional, not constitutive effects, in rodent models or in vitro systems (HEK293 cells), mandate expansion of now limited clinical data and mechanisms in human investigated as a translational cytoprotective strategy for complex arrhythmias. Full article

Breast cancer screening, while vital for reducing mortality, faces significant limitations in sensitivity and specificity, particularly in dense breasts. Current modalities primarily detect anatomical changes, often missing biologically aggressive tumors at their earliest stages. The altered metabolism of cancer cells establishes a characteristic inverted pH gradient that drives tumor invasion, metastasis, and treatment resistance. This makes tumor acidity a compelling, functional biomarker for early detection. This review synthesizes the emerging role of pH as a diagnostic biomarker and provides a critical evaluation of advanced imaging techniques for its non-invasive or minimal measurement. We detail the biological underpinnings of tumor acidosis, emphasizing its regulation through glycolytic reprogramming and dysregulated proton transport. Our analysis encompasses a broad spectrum of pH-sensitive imaging modalities, including magnetic resonance methods such as Chemical Exchange Saturation Transfer (CEST) MRI for extracellular pH mapping and multi-nuclear Magnetic Resonance Spectroscopy (MRS) using ¹H, ³¹P, and ¹⁹F nuclei to probe various cellular compartments. Furthermore, we examine hyperpolarized ¹³C MRI for real-time metabolic flux imaging, where metrics such as the lactate-to-pyruvate ratio demonstrate significant predictive value for treatment response. The review also assesses optical and photoacoustic imaging techniques, which offer high sensitivity but are often constrained to superficial tumors. Imaging tumor pH provides a powerful functional window into the earliest metabolic shifts in breast cancer, far preceding macroscopic anatomical changes. The ongoing development and evidence support the role of the pH-sensitive imaging techniques in diagnosis, lesion characterization, and therapy. Additionally, it holds promise for supplementing breast cancer screening by enabling earlier, more specific detection and personalized risk stratification, ultimately aiming to improve patient outcomes. Full article

Glucagon is an endogenous peptide that is produced in the pancreas. Via glucagon receptors, glucagon increases the beating rate in cultured rat neonatal cardiomyocytes and also in isolated right atrial preparations from adult rats. Moreover, in living adult mice, injections of glucagon can elevate the heart rate. It is unknown whether these effects of glucagon in living adult mice are mediated via central glucagon receptors or via a direct effect on cardiac glucagon receptors. Thus, we tested the hypothesis that glucagon can exert a direct positive chronotropic effect in the adult mouse heart. We measured the contractile effects of cumulatively increasing concentrations of glucagon (0.1–100 nM) in isolated paced (1 Hz) left atrial preparations, in isolated spontaneously beating right atrial preparations and in isolated spontaneously beating retrogradely perfused whole hearts. We detected in isolated right atrial preparations time- and concentration-dependent positive chronotropic effects of glucagon that were reversed by the glucagon receptor antagonists SC203972 and desglucagon. The positive chronotropic effects of glucagon were also attenuated by 1 µM of ivabradine, an inhibitor of the hyperpolarization-activated cation channels (HCN), but not by 100 nM rolipram, a phosphodiesterase 4 inhibitor, nor by 10 µM of propranolol, a β-adrenoceptor antagonist. Moreover, the positive chronotropic effects of glucagon were also attenuated by stimulation of the A₁-adenosine receptor or muscarinic receptors. Glucagon decreased the force of contraction in right atrial preparations. In left atrial preparations, glucagon failed to alter the force of contraction. In isolated adult mouse hearts perfused in the Langendorff mode, 10 nM of glucagon increased the beating rate and reduced left ventricular force of contraction. The gene expression of the glucagon receptors was lowest in the left atrium, higher in the ventricle and highest in the right atrium of adult mice. In summary, glucagon exerted a positive chronotropic effect in the mouse heart via glucagon receptors, mediated, at least in part, via HCN channels in the sinus node. Full article

The “athlete’s heart” phenotype, featuring resting bradycardia, has traditionally been viewed as a benign adaptation. However, emerging evidence associates prolonged, high-intensity endurance training with an increased risk of clinical sinoatrial node dysfunction. This systematic review synthesizes evidence on exercise-induced intrinsic Sinoatrial Node (SAN) electrophysiological remodelling and evaluates its dual nature along the adaptation–pathology continuum. Following PRISMA guidelines, a systematic search of PubMed, Web of Science, and Google Scholar (2000–2025) identified 17 eligible studies. Analysis revealed that in humans, rodents, and rabbits, exercise induces intrinsic SAN electrophysiological remodelling—a “membrane clock” reset characterized by coordinated downregulation of pacemaker currents, notably Hyperpolarization-activated cyclic nucleotide-gated cation channel (I_f), via the Nkx2.5-miR-423-5p transcription factor pathway. Evidence for “calcium clock” involvement remains inconsistent. In contrast, large animal models (e.g., dogs, horses) show only parasympathetic-mediated bradycardia without intrinsic remodelling. Training loads may induce structural changes (e.g., fibrosis), providing an anatomical substrate for pathology. Moderating factors such as training type and ageing contribute to a phenotype of “acquired SAN reserve reduction. Exercise-induced intrinsic SAN remodelling is a physiological adaptation mechanism that, under certain conditions, can cross a threshold to become a pathological cause of clinical dysfunction. Recognizing this continuum is essential for risk stratification and future therapeutic innovation. Full article

Background: Diabetes mellitus is a multifactorial disease characterized by complex metabolic dysfunctions and chronic complications induced by hyperglycaemia. The design of multitarget ligands, capable of simultaneously controlling different pathogenic processes, was proposed as a promising approach to identify novel antidiabetic drugs endowed with improved efficacy. Methods: (5-Arylidene-4-oxothiazolidin-3-yl)alkanoic acid derivatives 1a–g and 2a–g were synthesized as potential multitarget antidiabetic agents. They were tested in vitro as inhibitors of both human recombinant AKR1B1 and PTP1B, and kinetic studies and molecular docking simulations for both enzymes were performed. Their effects on cellular glucose uptake, insulin signalling, and mitochondrial potential were assayed in cultures of murine C2C12 myocytes. A lipid accumulation assay was performed in HepG2 liver cells. The effects on high glucose-induced sorbitol accumulation were evaluated in lens HLE and retinal MIO-M1 cells. Results: All compounds displayed excellent AKR1B1 inhibitory activity (IC₅₀ 0.03–0.46 μM 1a–g; IC₅₀ 0.48–6.30 μM 2a–g); 1g and 2e–g also appreciably inhibited PTP1B at micromolar concentrations. Propanoic derivatives 2e–g significantly stimulated glucose uptake in C2C12 myocytes, in an insulin-independent way, reduced lipid accumulation in HepG2 liver cells, and caused hyperpolarization of C2C12 mitochondria at 10 μM concentration. Derivative 2e significantly reduced sorbitol accumulation in both HLE and MIO-M1 cells at a 5 μM concentration. Conclusions: The results reported here provided new insights into the mechanisms of action and structure/activity relationships of 4-thiazolidinone derivatives, underscoring the capability of compounds 2e–g of eliciting insulin-mimetic effects independent of hormone signalling. Among them, compound 2e also proved to inhibit AKR1B1-dependent sorbitol accumulation and, thus, emerged as a promising multitarget agent that can be considered for further investigations. Full article

Background: Pediatric thoracic magnetic resonance imaging (MRI) has evolved into a valuable diagnostic modality that offers high-resolution morphological and functional assessment. While conventional radiography and computed tomography (CT) remain standard, their radiation exposure poses significant risks in children requiring repeated imaging. Technological innovations have addressed prior MRI limitations such as low lung proton density and motion artifacts, expanding its role in pediatric thoracic imaging. Methods: A review of the recent literature was performed, focusing on technical advancements, key MRI sequences and clinical applications in pediatric thoracic imaging. Emphasis was placed on ultrashort echo time (UTE), phase-resolved functional lung (PREFUL) MRI, hyperpolarized xenon-129 MRI, radial imaging, compressed sensing, parallel imaging and respiratory gating techniques. Results: Modern MRI sequences provide both detailed anatomic visualization and quantitative functional assessment of the pediatric thorax. UTE and PREFUL enable evaluation of lung parenchyma, ventilation, and perfusion, while hyperpolarized gas imaging offers high-resolution functional mapping. Radial, compressed sensing and parallel imaging reduce motion artifacts and acquisition times, enhancing feasibility in uncooperative children. Clinical indications include assessment of congenital malformations, chronic lung disease like cystic fibrosis, infectious and inflammatory disorders, tumors and selected traumatic injuries. Conclusions: Recent technical advances have established pediatric thoracic MRI as a versatile, patient-friendly alternative, as well as a complementary method to CT in selected clinical scenarios. Ongoing developments in acquisition speed, motion compensation and functional imaging are expected to further improve diagnostic accuracy and clinical utility, supporting broader adoption in routine pediatric thoracic evaluation. Full article

Triarylmethyl radicals (TAMs) have recently emerged as highly effective polarizing agents in dynamic nuclear polarization (DNP) under viscous conditions, enabling substantial hyperpolarization via the solid-effect (SE) DNP mechanism even at room temperature. A comparable, though less pronounced, enhancement was observed for BDPA radicals embedded in phosphocholine-based lipid bilayers. Given the increasing interest in elucidating the structure and dynamics of biopolymers and their high-molecular-weight assemblies—such as cell membranes—this study focuses on the design, synthesis, and characterization of paramagnetic agents tailored for DNP-based structural biology. To this end, we synthesized a series of TAM derivatives functionalized with lipophilic substituents and characterized their magnetic resonance properties, including isotropic hyperfine interaction (HFI) constants on carbon nuclei and electron spin relaxation times (T₁ and T_m) at low temperatures (80 K). Echo-detected EPR spectra and electron spin echo envelope modulations (ESEEM) were recorded for novel TAM incorporated into liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). These low-temperature measurements revealed that the radicals are localized either at the liposome surface or within the lipid bilayer, ensuring optimal accessibility to water molecules. Crucially, the presence of a single cholesterol moiety provides strong noncovalent anchoring within the hydrophobic core of the bilayer. Guided by these findings, we identify an amphiphilic TAM bearing a single cholesterol group and polar carboxyl functionalities as a highly promising candidate for DNP applications in membrane biology, combining efficient polarization transfer, bilayer integration, and aqueous accessibility. Full article

Parahydrogen-induced hyperpolarization (PHIP), introduced nearly four decades ago, provides an elegant solution to one of the fundamental limitations of nuclear magnetic resonance (NMR)—its notoriously low sensitivity. By converting the spin order of parahydrogen into nuclear spin polarization, NMR signals can be boosted by several orders of magnitude. Here we present a portable, compact, and cost-effective setup that brings PHIP and Signal Amplification by Reversible Exchange (SABRE) experiments within easy reach, operating seamlessly across ultra-low-field (0–10 μT) and high-field (>1 T) conditions at 50% parahydrogen enrichment. The system provides precise control over bubbling pressure, temperature, and gas flow, enabling systematic studies of how these parameters shape hyperpolarization performance. Using the benchmark Chloro(1,5-cyclooctadiene)[1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene]iridium(I) (Ir–IMes) catalyst, we explore the catalyst activation time and response to parahydrogen flow and pressure. Polarization transfer experiments from hydrides to [1-¹³C]pyruvate leading to the estimation of heteronuclear J-couplings are also presented. We further demonstrate the use of Chloro(1,5-cyclooctadiene)[1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene]iridium(I) (Ir–SIPr), a recently introduced catalyst that can also be used for pyruvate hyperpolarization. The proposed design is robust, reproducible, and easy to implement in any laboratory, widening the route to explore and expand the capabilities of parahydrogen-based hyperpolarization. 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

The endothelium, once considered merely a vascular lining responsible for selective permeability to water and electrolytes, is now recognised as a key regulator of vascular tone through the release of mediators such as oxylipins, nitric oxide, and hyperpolarizing factors. This in vitro study investigated the biological activity of Vesvein, a natural formulation containing Diosmin/Hesperidin, Ruscus aculeatus, Bromelain, and Ananas comosus, on intestinal and endothelial cells. Vesvein enhanced intestinal cell viability and preserved barrier integrity, as demonstrated by increased tight junction expression at both single and double concentrations. In endothelial cells, the compound improved parameters linked to venous insufficiency, elevating nitric oxide production by approximately 1.39-fold at a single dose and 1.65-fold at a double dose. These findings indicate a potential role for Vesvein in supporting endothelial health and vascular function in vitro. Preliminary evidence from intestinal models further suggests preserved barrier properties, which may positively influence absorption and bioavailability, thereby enhancing its vascular benefits. Full article

Genipin, a natural compound derived from Gardenia jasminoides, is widely used as an inhibitor of uncoupling protein 2 (UCP2), a protein located in the inner mitochondrial membrane (IMM) that plays a crucial role in regulating oxidative stress and cellular metabolism. Pharmacological inhibition of UCP2 has been explored as a strategy to modulate reactive oxygen species (ROS) and inflammatory responses. However, the utility of genipin is limited by its relatively low bioavailability and dose-dependent toxicity. To address these limitations, we developed mito-genipin, a mitochondria-targeted genipin derivative incorporating a triphenylphosphonium (TPP⁺) moiety, designed to enhance mitochondrial accumulation and thereby increase efficacy. In macrophages, mito-genipin induced mitochondrial hyperpolarization, elevated ROS production, and amplified pro-inflammatory cytokine expression compared with control or genipin treatment. In cells lacking UCP2, mito-genipin did not enhance ROS production. Our data identify mito-genipin as an effective modulator of oxidative stress and inflammation, supporting a putative link to UCP2 inhibition and highlighting potential implications in redox biology and immunomodulation. Full article

Background: Standard imaging in neurosurgery often fails to visualize infiltrative tumor regions that extend beyond contrast enhancement. Metabolic imaging using hyperpolarized 13C-MRI may offer new intraoperative insights into tumor biology. Objective: To systematically assess the clinical and technical evidence on hyperpolarized MRI for metabolic tumour characterization in patients with malignant brain tumors. Eligibility criteria: We included original human studies reporting on hyperpolarized 13C-MRI for perioperative and diagnostic use in brain tumor patients. Reviews, animal studies, and technical-only reports were excluded. Information sources: Searches were conducted in PubMed, Embase, and Web of Science on 26 December 2024. Risk of bias: Methodological quality was assessed using the QUADAS-2 tool. Synthesis of results: A qualitative synthesis was performed, and where feasible, random-effects meta-analysis was used to calculate standardized mean differences (SMDs) and heterogeneity statistics. Results: Three studies (n = 15 patients) met inclusion criteria. The bicarbonate-to-pyruvate ratio showed a significant difference between tumor and non-tumour brain (SMD = 1.34, p = 0.002), whereas pyruvate-to-lactate ratio (kPL) values showed minimal difference (SMD = 0.06, p = 0.730). Asmall effect was observed for kPL between tumor and normal-appearing white matter (SMD = –0.33). One study provided qualitative data only. Overall heterogeneity was high (I² = 69.4%). Limitations: Limitations include small sample sizes, heterogeneous methodologies, and limited availability of patient-level data. Interpretation: Hyperpolarized 13C-MRI shows metabolic differentiation between tumor and healthy tissue in certain parameters, especially bicarbonate metabolism. While promising, the technology requires further clinical validation before routine intraoperative application. Full article

Despite a specific histone mutation defining the unique genetic makeup, diffuse midline gliomas are heterogeneous tumors with a wide range of morphologic and molecular spectrum. We investigated the feasibility of using hyperpolarized carbon-13(¹³C) MR metabolic imaging to differentiate distinctive molecular features from two H3K27M-mutant, biopsy-originated diffuse midline glioma xenografts. ¹³C MR metabolic imaging data were acquired on a 3T scanner from 12 rats that had been implanted with SF8628 or SF7761 diffuse midline glioma cells in brainstem, following injection of hyperpolarized [1-¹³C]pyruvate. Despite the two tumors’ similar appearance of T₂-hyperintensity throughout the cerebellum and pons without contrast enhancement, ¹³C metabolic imaging data revealed that SF8627 had significantly higher ratios of lactate to pyruvate, lactate to total carbon, and normalized lactate than SF7761. Elevated lactate levels in SF8628 were associated with large amounts of lactate dehydrogenase (LDH)-A and carbonic anhydrase-IX staining in SF8628 compared to SF7761, which implied that the highly hypoxic condition in SF8628 appeared to contribute to the high level of LDH-A enzyme activity, which, in turn, induced the large conversion from hyperpolarized pyruvate to lactate. Our findings suggest that this advanced metabolic imaging technique may be used for the noninvasive characterization of molecular hypoxia and lactate dehydrogenase-A activity in these pediatric brainstem gliomas. 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

Pharmaceuticals can be found in the aquatic environment and cause unwanted effects on organisms. The present work aimed to characterize the toxic mode of action of the antidepressant fluoxetine (FLX) on the freshwater microalga Raphidocelis subcapitata. With this aim, the microalga was exposed to low levels (µg/L) of FLX for 72 h. Exposure to 20–30 µg/L FLX arrested algal growth, which can be explained by the blockage of algal nuclear division. In addition, FLX (15–30 µg/L) deeply altered the alga’s metabolism, which was reflected by an increase in esterase activity, mitochondrial dysfunction (hyperpolarization of inner mitochondrial membrane), and reduction in the content of photosynthetic pigments: chlorophyll a (chla) and carotenoids (car). A sharp decline in photosynthetic performance, revealed by the reduction in maximum photochemical quantum yield (F_v/F_m), effective photochemical quantum yield (ΦPSII), and photosynthetic electron transport rate (ETR) of photosystem II (PSII), was also observed. FLX, at 30 µg/L, induced the intracellular accumulation of reactive oxygen species (ROS) and lipid peroxidation, with a marginal loss (1%) of cell membrane integrity. The results presented here contribute to the elucidation of the toxic mode of action of FLX on the microalgae R. subcapitata and, simultaneously, warn of the negative impact of the presence of pharmaceutical compounds in freshwater aquatic environments. Full article