Darier disease (DD), caused by ATP2A2 mutations, disrupts epidermal adhesion via endoplasmic reticulum (ER) calcium defects. While ER calcium depletion is documented, its impact on mitochondrial calcium homeostasis remains unknown. This study investigates mitochondrial calcium downregulation in DD and evaluates repurposing the ryanodine receptor (RyR) antagonist dantrolene to restore mitochondrial function. Using primary, immortalised DD and ATP2A2 knockout keratinocytes as well as patient fibroblasts, we measured mitochondrial morphology and calcium level. DD models showed fragmented mitochondria and diminished respiratory function. These changes were associated with significantly lower mitochondrial calcium in keratinocytes. Dantrolene increased mitochondrial calcium uptake, partly via the mitochondrial calcium uniporter (MCU), enhancing TCA cycle enzyme activity and improving mitochondrial respiration. This recovery strengthened cell-cell adhesion in DD keratinocytes. Mitochondrial calcium reduction is a critical mediator in DD. Dantrolene ameliorates this calcium dyshomeostasis and disease phenotypes, proposing a therapeutic strategy using an FDA-approved drug.

Malignant hyperthermia (MH) is a rare pharmacogenetic disorder typically triggered by volatile anesthetics or succinylcholine, but its occurrence after total intravenous anesthesia (TIVA) remains exceptional and underreported. Propofol-based TIVA is recommended for MH-susceptible patients to avoid known triggers, yet absolute prevention cannot be guaranteed. A 24-year-old male with prior suspected MH underwent spine surgery under propofol-remifentanil TIVA after strict preventive preparation. Despite stable intraoperative parameters, he developed fever, tachycardia, rigidity, and myoglobinuria 14 hours postoperatively, with markedly elevated creatine kinase and myoglobin levels. Dantrolene administration resulted in rapid clinical improvement. The Malignant Hyperthermia Clinical Grading Scale score of 48 indicated "very likely MH." This case underscores the risk of MH even with TIVA in susceptible patients, emphasizing the need for vigilant monitoring, availability of dantrolene, and preparedness for delayed onset regardless of the anesthetic technique used.

Malignant hyperthermia (MH) is a pharmacogenetic condition triggered by volatile anesthetics, which activate MH susceptible mutants of ryanodine receptor 1 (RyR1). The precise binding sites and mechanisms of the therapeutic dantrolene and MH triggers have remained unclear. Here, we present structures of RyR1 bound to dantrolene and the MH trigger 4-chloro-m-cresol (4CmC), revealing the dantrolene and 4CmC binding sites in atomic detail. Dantrolene binds stacked with ATP or ADP in the RY12 domain at the corner of the receptor, inducing a conformational change. Functional analyses confirm ATP or ADP is required for dantrolene inhibition, and a single point mutation disrupting this peripheral ATP site abolishes this ATP/ADP-dependent inhibition. Strikingly, in the absence of dantrolene, this site selectively binds two ADP molecules even in the presence of excess ATP, indicating a role in ATP/ADP ratio sensing. Additionally, we identified four 4CmC binding sites, revealing one primary binding site in an amphipathic cavity in the core solenoid, and three auxiliary binding sites in the EF-hand, transmembrane, and RY12 domains. These findings offer insights into the binding modes and mechanisms of MH-linked molecules, and reveal the RY12 domain's regulatory role as a promiscuous sensor for adenine nucleotides and small ligands.

Carbon quantum dots (CQDs) are promising fluorescent nanomaterials for analytical applications, but their structure-property relationships remain under-investigated, especially in biomass-derived systems. Herein, we report the ultrafast, one-pot, microwave-assisted synthesis (700 W, 4 min) of highly fluorescent CQDs from gum arabic, a renewable, low-cost, and GRAS-certified polysaccharide. Structural characterization by FTIR spectroscopy and transmission electron microscopy revealed a uniform spherical morphology (3.8 nm) with abundant oxygen-containing functional groups, providing excellent water solubility and high fluorescence quantum yield (35.5%). Spectroscopic studies of the photophysical properties revealed excitation-dependent fluorescence with an optimum λex/λem of 346/425 nm, attributed to surface defect states arising from the functionalized carbon core. Using these structure-derived photophysical properties, a fluorescence nanosensor was developed for the selective determination of dantrolene (DNT), a poorly metabolized muscle relaxant that persists in municipal wastewater. Mechanistic studies showed that fluorescence quenching occurs via the inner filter effect (IFE). The developed method shows excellent analytical performance (linear range of 3.0-60.0 µM and LOD of 0.6 µM) and was successfully applied for the determination of DNT in commercial capsules (recovery of 98.19-102.62%) and tap water samples (recovery of 94.19-96.94%), indicating its selectivity against common excipients, co-administered drugs, and inorganic ions. This work highlights the valorization of underutilized natural gums into high-performance sensing materials, provides clear structure-property-activity correlations in biomass-derived CQDs, and demonstrates their utility as a sustainable spectroscopic probe for environmental and pharmaceutical analysis.

Neuroleptic malignant syndrome (NMS) is an uncommon, but potentially life- threatening complication of antipsychotic therapy, primarily resulting from central dopaminergic blockade. NMS is a clinical diagnosis and occurs rarely in patients receiving atypical antipsychotics agents. Gastrointestinal manifestations, including severe hypomotility and paralytic ileus, are recognized adverse effects of antipsychotic medications. However, paralytic ileus preceding the characteristic neuromuscular and autonomic features of NMS is exceptionally rare and underrecognized as an early manifestation of the syndrome. We report the case of a 49-year-old man who presented with progressive abdominal distension secondary to intestinal pseudo-obstruction as an early manifestation of NMS. This atypical and underreported presentation highlights the importance of maintaining a high index of suspicion for NMS in patients receiving antipsychotic therapy who develop unexplained gastrointestinal dysmotility. Prompt recognition, immediate discontinuation of the offending antipsychotic agent, and early initiation of treatment with dantrolene and bromocriptine resulted in a favorable clinical outcome.

Cardiac surgery in patients with suspected malignant hyperthermia (MH) susceptibility poses a distinct diagnostic and management challenge, as cardiopulmonary bypass (CPB)-induced hypothermia may mask early manifestations of MH. Given the rarity of this clinical scenario, we present our institutional perioperative protocol-encompassing preoperative workstation decontamination, trigger-free total intravenous anesthesia, CPB-specific precautions, and serial creatine kinase surveillance-illustrated through its successful application in a 47-year-old male undergoing elective four-vessel coronary artery bypass grafting. No clinical or biochemical evidence of MH occurred. We outline this structured approach as a practical reference for the cardiac surgical community.

Neuroleptic malignant syndrome (NMS) is a rare but potentially life-threatening neurological emergency, most commonly associated with antipsychotic drugs and other dopamine receptor-blocking agents. Although its incidence has declined over recent decades, NMS remains a diagnostic challenge due to its heterogeneous clinical presentation and overlap with other drug-induced syndromes. The classic clinical picture is defined by a tetrad of hyperthermia, generalized muscle rigidity, altered mental status, and autonomic dysfunction, frequently accompanied by marked creatine kinase elevation secondary to rhabdomyolysis. Diagnosis is primarily clinical and supported by complementary studies aimed at assessing severity, excluding differential diagnoses, and monitoring systemic complications. The underlying pathophysiology involves dopamine D2 receptor blockade within the central nervous system, particularly in the hypothalamus and basal ganglia, leading to impaired thermoregulation and motor control. Management relies on immediate discontinuation of the offending agent, intensive supportive care, and, in moderate to severe cases, pharmacological treatment with benzodiazepines, dopaminergic agents such as bromocriptine or amantadine, and muscle relaxants such as dantrolene. Early recognition and timely treatment are crucial to ensure favorable outcomes and reduce morbidity and mortality.

Although acetylcholine (ACh) released by the vagus nerve can stimulate enterochromaffin cells (ECs) to secrete 5-hydroxytryptamine (5-HT), the precise regulatory mechanism underlying this process and its association with the pathogenesis of ulcerative colitis (UC) remain unclear. In this study, we aimed to investigate whether TRPV4-mediated calcium influx in ECs is involved the process of ACh promoting 5-HT secretion which leads to UC. In vitro experiments, western blotting, cellular calcium imaging, and patch clamp were applied to ECs, and dextran sulfate sodium (DSS)-induced UC of mouse model was used in vivo. Carbachol (CCh), a stable analog of ACh, activated mAChR/IP3/IP3R pathway to increase intracellular [Ca2+]ilevels in ECs, in which both TRPV4 channels and RyR were activated in response to CCh. The selective TRPV4 antagonist HC067047 inhibited the calcium signals and membrane currents induced by IP3/IP3R, as well as 5-HT secretion. In addition, selective blocker of RyR (Dantrolene) also significantly inhibited CCh-induced calcium signals and membrane currents. In vivo experiments, HC067047 significantly suppressed the synthesis and release of 5-HT from ECs and alleviated DSS-induced UC in mice. Taken together, this study reveals a novel mAChR/IP3/IP3R /TRPV4/5-HT pathway in ECs is likely involved in the pathogenesis of UC. Targeting this pathway holds a promise for the potential prevention and treatment of UC.

Malignant hyperthermia is a rare but potentially fatal complication of general anesthesia caused by inhalational anesthetics and depolarizing skeletal muscle relaxants. The mechanism of the disease involves an uncontrolled increase in skeletal muscle metabolism as a result of abnormal calcium regulation. Early diagnosis, immediate discontinuation of the triggering agent, and rapid administration of dantrolene are crucial for patient survival. We present the case of a 32-year-old man who underwent elective rhinoseptoplasty at a city 1-day surgery clinic where dantrolene was not available. During the procedure, the patient experienced an increase in body temperature, followed by cardiac arrest. The patient was transferred to the emergency department of a tertiary care university hospital, where dantrolene treatment was initiated and the patient was qualified for extracorporeal cardiopulmonary resuscitation. Despite several hours of intensive care, the patient died.

TAK-243, an inhibitor of the ubiquitin-activating enzyme UBA1, impairs the ubiquitination of proteins. We investigated its effects on the intracellular Ca[2+] dynamics of human prostate cancer cells DU-145. Live-cell Ca[2+] imaging with Fura2 showed that DU-145 cells exhibited spontaneous Ca[2+] transients that were largely independent of the activity of the Na[+]/Ca[2+] exchanger but were abolished by extracellular Ca[2+] removal, La[3+], Gd[3+], BTP2 (Orai channel blocker), and thapsigargin (which depletes endoplasmic reticulum -ER- Ca[2+] stores). They were also sensitive to U73122 (a phospholipase C inhibitor) and dantrolene (a ryanodine receptor blocker), suggesting the contribution of both store-operated Ca[2+] channels and intracellular Ca[2+] release pathways in the generation and maintenance of these Ca[2+] spikes. At 0.2 μM, TAK-243 augmented the cytosolic concentration of Ca[2+] ([Ca[2+]]i), boosted the Ca[2+] spiking activity, whereas at 10 μM it caused a constitutive Ca[2+] entry through BTP2-sensitive Ca[2+] channels, which further augmented [Ca[2+]]i but reduced the number of spontaneously active cells. Experiments conducted with the genetically encoded Ca[2+] dye CEPIA1er showed that TAK-243 did not empty the ER Ca[2+] stores. Moreover, Förster resonance energy transfer (FRET) experiments on HEK-293 cells transfected with Orai1-CFP and STIM1-YFP indicated that it caused the relocalization of STIM1 and its coupling with Orai1. TAK-243 also increased the membrane potential and the Ca[2+] buffering capacities of mitochondria. Taken together, treating DU-145 cells with TAK-243 to prevent the ubiquitination of proteins activates the entry of Ca[2+] through store-operated Ca[2+] channels independently of the ER Ca[2+] stores and alters mitochondrial functions.

Cases of malignant hyperthermia (MH) are uncommon, but when they are not recognized early, they can be fatal. Early signs include increased heart rate and end tidal CO2 (EtCO2) readings followed by increased temperature. This is the case of 53-year-old man who had a MH crisis after exposure to the volatile anesthetic sevoflurane. His increased EtCO2 and tachycardia coupled with exposure to known trigger is indicative of MH. The condition was quickly recognized, and he was successfully treated with dantrolene. He recovered without significant long-term complications. This case contributes to the literature highlighting the early recognition and use of dantrolene for successful treatment in MH crises along with help from the MH hotline.

Dantrolene is a clinically approved therapeutic used to suppress abnormal calcium release associated with malignant hyperthermia linked to RyR1 mutations. Cryo-electron microscopy studies have revealed a putative dantrolene-binding cavity within the RyR1 P1 domain and highlighted several residues associated with ligand recognition. However, the dynamic molecular interactions governing ligand stabilization within this region remain incompletely understood. MM/GBSA calculations, conformational entropy analyses, and potential of mean force (PMF) profiling were employed to investigate the local binding dynamics of dantrolene within isolated RyR1 P1-domain complexes. Comparative analyses of the P1 domain from open- and closed-state conformations of RyR1 revealed that the closed-state complex provides a more stable binding environment characterized by lower backbone fluctuations, enhanced ligand-protein contacts, stabilization of a distal loop region (residues 1006-1028), and higher ligand dissociation barriers. Per-residue energetic decomposition and interaction analyses identified W882 and W996 as major contributors to ligand stabilization through cooperative hydrogen bonding and π-mediated interactions. Alanine substitution of these residues increased ligand conformational flexibility and substantially reduced the energetic barriers associated with ligand dissociation, whereas R1000 exhibited comparatively smaller contributions to overall binding stability. Overall, these computational findings are consistent with previous experimental observations and provide atomistic insight into the interaction networks and structural determinants underlying state-dependent stabilization of dantrolene in a cryo-EM-derived RyR1 P1-domain binding model.

Ryanodine receptor-like (RyR-like) is a key endoplasmic reticulum (ER) Ca2+ release channel governing intracellular Ca2+ homeostasis and cellular stress responses in invertebrates. However, its function in bivalves under high-temperature stress remains unclear. In the present study, one RyR-like was identified from Yesso scallop Patinopecten yessoensis (PyRyR-like). Its function in regulating intracellular Ca2+, IRE1α-mediated unfolded protein response (UPR) and apoptosis in the mantle after high-temperature (25 °C) treatment was investigated using molecular cloning, qRT-PCR, Western blot, pull-down assay, cellular calcium imaging, TUNEL and histology assays; High temperature treatment significantly increased intracellular Ca2+ content at 1 and 6 h (p < 0.05), but decreased it at 3, 12 and 24 h (p < 0.05); meanwhile, the cAMP level, PyPKA activity, mRNA expression level of PyRyR-like, and protein expression levels of PyFKBP12 and PyGRP78 were significantly increased at different times. However, high temperature did not affect the expression level of PyNVL and PyXBP1(S). The SPRY and RYR domains of PyRyR-like separately interacted with PyFKBP12 and PyPKA. Moreover, RyR antagonist Dantrolene reversed high-temperature-induced alterations in Ca concentration, PKA activity, and core UPR- and apoptosis-related molecules, and suppressed Caspase-3 activity. These findings suggest that PyRyR-like plays an important role in the high-temperature response of scallops by regulating intracellular Ca2+ homeostasis and mediating UPR activation and apoptosis, providing new insight into the molecular mechanism underlying scallop adaptation to high temperature.