Intracellular Calcium Measurements Research Articles

Cannabidiol inhibits transient receptor potential canonical 4 and modulates excitability of pyramidal neurons in mPFC.

Cannabidiol (CBD), a non-psychoactive compound derived from the cannabis plant, has been extensively studied for its potential therapeutic effects on various central nervous system (CNS) disorders, including epilepsy, chronic pain, Parkinson's disease, and stress-related neuropsychiatric disorders. However, the pharmacological mechanisms of CBD have not been fully elucidated due to the complexity of their targets. In this study, we reported that the transient receptor potential canonical 4 (TRPC4) channel, a calcium-permeable, non-selective cation channel, could be inhibited by CBD. TRPC4 is highly abundant in the central nervous system and plays a critical role in regulating axonal regeneration, neurotransmitter release, and neuronal network activity. Here, we used whole-cell electrophysiology and intracellular calcium measurements to identify the inhibitory effects of CBD on TRPC4, in which CBD was found to inhibit TRPC4 channel with an IC50 value of 1.52μM TRPC4 channels function as receptor-operated channels (ROC) and could be activated by epinephrine (EP) via G proteins. We show that CBD can inhibit EP-evoked TRPC4 current in vitro and EP-evoked neuronal excitability in the medial prefrontal cortex (mPFC). These results are consistent with the action of TRPC4-specific inhibitor Pico145, suggesting that TRPC4 works as a functional ionotropic receptor of CBD. This study identified TRPC4 as a novel target for CBD in the CNS and suggested that CBD could reduce the pyramidal neuron excitability by inhibiting TRPC4-containing channels in the mPFC.

Abstract 4139187: Electrophysiological and Mechanical Characterization of Human Ventricular Myocardium from Patients with Primary or Secondary Cardiac Hypertrophy

Left-ventricular hypertrophy (LVH) is an adaptive condition to hemodynamic stress often involving the left ventricle (LV). This pathological condition is associated with clinical complications such as ventricular arrhythmias and diastolic dysfunction, the molecular and cellular mechanisms of which have been poorly investigated in the human heart. We collected myocardial samples from the upper interventricular septum of 132 patients with hypertrophic cardiomyopathy (HCM), 42 patients with aortic stenosis and severe LVH (AoS-LVH) and 12 non-failing non-hypertrophic patients with valve disease (NF-NH), who underwent myectomy operations at our cardiac surgery center. Samples were used to isolate single viable cardiomyocytes from the left ventricle to perform patch-clamp electrophysiological studies and intracellular calcium measurements with fluorescent dyes. Intact trabeculae were also dissected to perform isometric force measurements of electrically-stimulated twitches. Single-cell patch-clamp studies revealed a marked prolongation of action potential duration (APD) in HCM (N=82, mean APD at 90% repolarization=763±252ms at 0.5Hz) and AoS-LVH (N=22, APD90%=579±147ms) samples with respect to NF-NH (N=12, APD90%=447±88ms). In both HCM and AoS-LVH cardiomyocytes, APD prolongation was associated with increased late-Na + current with respect to NF-NH, while L-type Ca 2+ current was enlarged only in HCM samples. Ca 2+ -fluorescence studies revealed markedly slower Ca-transient (CaT) kinetics in myocardial samples from HCM (N=38, mean CaT 50% decay time at 0.5 Hz = 658±179ms) and AoS-LVH patients (N=9, CaT50%= 568±187ms), when compared with NF-NH samples (N=8, CaT50%=283±59ms), paralleled by elevated diastolic [Ca 2+ ]. Twitch force measurements in intact trabeculae revealed prolonged isometric contractions in HCM (N=78, overall twitch duration at 0.5Hz= 730±147ms) and in AoS-LVH patient-samples (N=24, TwD=669±116ms), as compared with NF-NH (N=7, TwD=511±73ms). Force-frequency relationship was flat in pathological samples, while NF-NH trabeculae showed a clear increase in twitch amplitude while increasing pacing rate to 2Hz. Our results suggest that the main features of functional cardiomyocyte remodeling (that is, changes in the expression and/or function of ion-channel and EC-coupling proteins) are qualitatively similar in primary vs. secondary LVH, albeit abnormalities are quantitatively more extensive in HCM samples.

Abstract 4136448: A Novel Cardiomyocyte Targeting Peptide Enhances Calcium Handling

Introduction: Intracellular calcium handling plays a central role in cardiac contractility and relaxation. Genes such as the Ca 2+ -ATPase pump (SERCA2a) and the Dihydropteridine reductase (DHPR) enzyme are especially important in the cycling of intracellular calcium. As prior research has established a link between treatment with our cardiac targeting peptide (CTP: a 12-amino acid, cardiomyocyte-specific cell penetrating peptide) and upregulation of calcium-handling genes such as SERCA2a and DHPR, we hypothesized that treatment with our novel hybrid cardiac targeting peptide (hCTP: positions #3 and 11 replaced with the D-enantiomer form of the amino acids) will improve intracellular calcium handling in human cardiomyocytes (CMCs) by increasing expression of key calcium handling genes instrumental in sequestering calcium in diastole and lowering cytosolic levels. Methods: To test hCTP’s calcium handling abilities, CMCs were plated on day 1 and allowed to settle for 24 hours, after which they received daily treatment with various concentrations of hCTP (1-25µM) for three days. On day 5, cells underwent either intracellular calcium measurements using the FLIPR 6 Calcium assay or were prepared for western blotting. Western blotting was performed to determine the protein concentrations of SERCA2a and DHPR, as compared to a GAPDH control. To test hCTP’s intrinsic calcium handling abilities, various concentrations of hCTP were mixed with a constant amount of elemental calcium dissolved in water. After 20 min at 37 o C, the concentration of free Ca 2+ was measured with an ABL90 Flex Plus radiometer. Results: In CMCs, treatment with hCTP led to a decrease in cytosolic calcium in a dose dependent fashion; concentrations as low as 1µM led to a significant decrease in cytosolic calcium (p< 0.0001 for all groups). Western blots performed on the treated CMCs revealed an increase in expression of both DHPR and SERCA2a, normalized to GAPDH control. Outside of the cellular environment, hCTP did not appear to display inherent calcium sequestring properties, suggesting that improvements in calcium handling are due to upregulation of gene expression. Conclusion: hCTP appears to lower cytosolic calcium and improve calcium handling through upregulation of SERCA2a and DHPR. Our data indicates that hCTP is worth pursuing as a stand-alone, cardio-selective therapy for cardiomyopathies involving calcium mishandling.

Monitoring Calcium-Sensing Receptor (CaSR)-Induced Intracellular Calcium Flux Using an Indo-1 Flow Cytometry Assay.

The calcium-sensing receptor (CaSR) has a critical role in maintaining serum calcium concentrations within the normal physiological range, and mutations in the receptor, or components of its signaling and trafficking pathway, cause disorders of calcium homeostasis. Inactivating mutations cause neonatal severe hyperparathyroidism or familial hypocalciuric hypercalcemia (FHH), while gain-of-function mutations cause autosomal dominant hypocalcemia (ADH). Characterizing the functional impact of mutations of the CaSR, and components of the CaSR-signaling pathway, is clinically important to enable correct diagnoses of FHH and ADH, optimize management, and prevent inappropriate parathyroidectomy or vitamin D supplementation. CaSR signals predominantly by activating the G-alpha subunit-11 to mobilize calcium release from intracellular stores. Thus, measurement of CaSR-induced intracellular calcium (Ca2+i) signaling is the gold standard method to investigate the pathogenicity of CaSR genetic variants. This protocol describes a method to assess CaSR-induced Ca2+I signaling using the Indo-1 calcium indicator dye and flow cytometry. This method has been used to assess multiple genetic variants in CaSR and components of its signaling and trafficking pathway in HEK293 cells.

Mechanism of sensory perception unveiled by simultaneous measurement of membrane voltage and intracellular calcium

Measuring neuronal activity is important for understanding neuronal function. Ca2+ imaging by genetically encoded calcium indicators (GECIs) is a powerful way to measure neuronal activity. Although it revealed important aspects of neuronal function, measuring the neuronal membrane voltage is important to understand neuronal function as it triggers neuronal activation. Recent progress of genetically encoded voltage indicators (GEVIs) enabled us fast and precise measurements of neuronal membrane voltage. To clarify the relation of the membrane voltage and intracellular Ca2+, we analyzed neuronal activities of olfactory neuron AWA in Caenorhabditis elegans by GCaMP6f (GECI) and paQuasAr3 (GEVI) responding to odorants. We found that the membrane voltage encodes the stimuli change by the timing and the duration by the weak semi-stable depolarization. However, the change of the intracellular Ca2+ encodes the strength of the stimuli. Furthermore, ODR-3, a G-protein alpha subunit, was shown to be important for stabilizing the membrane voltage. These results suggest that the combination of calcium and voltage imaging provides a deeper understanding of the information in neural circuits.

Techniques for evaluating the ATP-gated ion channel P2X7 receptor function in macrophages and microglial cells

Resident macrophages are tissue-specific innate immune cells acting as sentinels, constantly patrolling their assigned tissue to maintain homeostasis, and quickly responding to pathogenic invaders or molecular danger signals molecules when necessary. Adenosine triphosphate (ATP), when released to the extracellular medium, acts as a danger signal through specific purinergic receptors. Interaction of ATP with the purinergic receptor P2X7 activates macrophages and microglial cells in different pathological conditions, triggering inflammation. The highly expressed P2X7 receptor in these cells induces cell membrane permeabilization, inflammasome activation, cell death, and the production of inflammatory mediators, including cytokines and nitrogen and oxygen-reactive species. This review explores the techniques to evaluate the functional and molecular aspects of the P2X7 receptor, particularly in macrophages and microglial cells. Polymerase chain reaction (PCR), Western blotting, and immunocytochemistry or immunohistochemistry are essential for assessing gene and protein expression in these cell types. Evaluation of P2X7 receptor function involves the use of ATP and selective agonists and antagonists and diverse techniques, including electrophysiology, intracellular calcium measurements, ethidium bromide uptake, and propidium iodide cell viability assays. These techniques are crucial for studying the role of P2X7 receptors in immune responses, neuroinflammation, and various pathological conditions. Therefore, a comprehensive understanding of the functional and molecular aspects of the P2X7 receptor in macrophages and microglia is vital for unraveling its involvement in immune modulation and its potential as a therapeutic target. The methodologies presented and discussed herein offer valuable tools for researchers investigating the complexities of P2X7 receptor signaling in innate immune cells in health and disease.

Anandamide modulation of monocyte-derived Langerhans cells: implications for immune homeostasis and skin inflammation.

The endocannabinoid system (ECS), named after the chemical compounds found in the cannabis plant, is a regulatory network of neurotransmitters, receptors, and enzymes that plays crucial roles in skin health and disease. Endogenous ligands of the ECS, called endocannabinoids, have proven to be important regulators of immune responses. One of the most prevalent endocannabinoids, arachidonoylethanolamide (also known as anandamide), is known for its anti-inflammatory effects. Langerhans cells (LCs) are the sole antigen-presenting cells present in the human epidermis. They serve as the first line of defense against pathogens and are essential for the skin's specific immune responses and play a critical role in maintaining tissue homeostasis; however, little is known about the effect of endocannabinoids on these cells. Our research aimed to provide the connection between monocyte-derived Langerhans cells (moLCs) and the ECS, shedding light on their collaborative roles in immune homeostasis and inflammation. Human monocytes were differentiated into moLCs using established protocols. Anandamide was applied during the differentiation process to test its effect on the viability, marker expression, and cytokine production of the cells, as well as in short term treatments for intracellular calcium measurement. TLR ligands applied after the differentiation protocol were used to activate moLCs. The impact of anandamide on the functionality of moLCs was further assessed using differential gene expression analysis of bulk RNA-Seq data, moLC-T cell cocultures, while ELISpot was employed to determine polarization of T cells activated in the aforementioned cocultures. Anandamide did not significantly affect the viability of moLCs up to 10 µM. When applied during the differentiation process it had only a negligible effect on CD207 expression, the prototypic marker of LCs; however, there was an observed reduction in CD1a expression by moLCs. Anandamide had no significant effects on the maturation status of moLCs, nor did it affect the maturation induced by TLR3 and TLR7/8 agonists. MoLCs differentiated in the presence of anandamide did however show decreased production of CXCL8, IL-6, IL-10 and IL-12 cytokines induced by TLR3 and TLR7/8 activation. Anandamide-treated moLCs showed an increased capability to activate naïve T cells; however, not to the level seen with combined TLR agonism. RNA sequencing analysis of moLCs differentiated with anandamide showed modest changes compared to control cells but did reveal an inhibitory effect on oxidative phosphorylation specifically in activated moLCs. Anandamide also promoted the polarization of naïve T cells towards a Th1 phenotype. Our results show that anandamide has nuanced effects on the differentiation, maturation, cytokine secretion, metabolism and function of activated moLCs. Among these changes the decrease in CD1a expression on moLCs holds promise to selectively dampen inflammation induced by CD1a restricted T cells, which have been implicated as drivers of inflammation in common inflammatory skin conditions such as psoriasis, atopic dermatitis and contact dermatitis.

Synthesis and Characterization of Thymoquinone‐Oxime (TQ‐Ox) from Thymoquinone and Evaluation of its Cytotoxic, Genotoxic, and Apoptotic Potential in Lung Cancer Cells (A549) in vitro

AbstractIntro: Thymoquinone(TQ), a compound derived from Nigella sativa, has been found to impede cancer progression, including proliferation, migration, and invasion. Previous research has explored the potential benefits of augmenting TQ with functional groups to enhance its activity, particularly when combined with traditional drugs. The aim of our study was to investigate the therapeutic effects of Thymoquinone‐Oxime(TQ−Ox) on lung cancer cell lines. Methods: To determine the structure of the novel TQ−Ox substance, we employed NMR spectroscopy. We also performed in vitro assays to assess the anti‐cancer mechanisms of TQ−Ox on lung cancer cells(A549) and healthy lung cells(BEAS‐2B). These assays included assessments of cytotoxicity, genotoxicity, and apoptosis, as well as measurements of intracellular Reactive Oxygen Species(iROS), intracellular Calcium(iCa2+), and Mitochondrial Membrane Potential(MMP). Results: Our results demonstrate that TQ−Ox induces dose‐dependent cytotoxicity, genotoxicity, and apoptosis in cancer cells, along with an increase in iROS production. The IC50 values for A549 and BEAS‐2B cells were 41.01 μM and 48.71 μM, respectively. We also observed that as iCa2+ levels increased, there was a decrease in MMP levels(p<0.001). Conclusion: TQ−Ox shows potential as a therapeutic option for lung cancer, justifying further in vitro and in vivo research to explore its clinical applications.

Inhibition of TRPM8 function by prostacyclin receptor agonists requires coupling to Gq/11 proteins.

The TRPM8 ion channel is involved in innocuous cold sensing and has a potent anti-inflammatory action. Its activation by lower temperature or chemical agonists such as menthol and icilin induces analgesic effects, reversing hypersensitivity and reducing chronic pain. On the other hand, prostacyclin (PGI2) enhances pain and inflammation by activating the IP receptors. Due to the critical roles of TRPM8 and IP receptors in the regulation of inflammatory pain, and considering their overlapping expression pattern, we analysed the functional interaction between human TRPM8 and IP receptors. We transiently expressed human TRPM8 channels and IP receptors in HEK293T cells and carried out intracellular calcium and cAMP measurements. Additionally, we cultured neurons from the dorsal root ganglia (DRGs) of mice and determined the increase in intracellular calcium triggered by the TRPM8 agonist, icilin, in the presence of the IP receptor agonist cicaprost, the IP receptor antagonist Cay10441, and the Gq/11 inhibitor YM254890. Activation of IP receptors by selective agonists (cicaprost, beraprost, and iloprost) inhibited TRPM8 channel function, independently of the Gs-cAMP pathway. The potent inhibition of TRPM8 channels by IP receptor agonists involved Gq/11 coupling. These effects were also observed in neurons isolated from murine DRGs. Our results demonstrate an unusual signalling pathway of IP receptors by coupling to Gq/11 proteins to inhibit TRPM8 channel function. This pathway may contribute to a better understanding of the role of TRPM8 channels and IP receptors in regulating pain and inflammation.

Calcium regulates cortex contraction in Physarum polycephalum

The tubular network-forming slime mold Physarum polycephalum is able to maintain long-scale contraction patterns driven by an actomyosin cortex. The resulting shuttle streaming in the network is crucial for the organism to respond to external stimuli and reorganize its body mass giving rise to complex behaviors. However, the chemical basis of the self-organized flow pattern is not fully understood. Here, we present ratiometric measurements of free intracellular calcium in simple morphologies of Physarum networks. The spatiotemporal patterns of the free calcium concentration reveal a nearly anti-correlated relation to the tube radius, suggesting that calcium is indeed a key regulator of the actomyosin activity. We compare the experimentally observed phase relation between the radius and the calcium concentration to the predictions of a theoretical model including calcium as an inhibitor. Numerical simulations of the model suggest that calcium indeed inhibits the contractions in Physarum, although a quantitative difference to the experimentally measured phase relation remains. Unraveling the mechanism underlying the contraction patterns is a key step in gaining further insight into the principles of Physarum’s complex behavior.

Essential role of CD38 in platelet aggregation through the PKC-mediated internalization and activation.

CD38 is a multifunctional enzyme with a potent Ca2+ mobilizing effect, cyclic ADP-ribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP). Here, we aimed to demonstrate the role of CD38 in platelets via protein kinase C (PKC)-mediated internalization and activation. Mouse platelets were used in this study. Thrombin, an agonist of platelet function, provoked a prompt and long-lasting increase in intracellular Ca2+ concentration ([Ca2+]i), resulting from an interplay of multifold Ca2+ mobilizing messengers.The signaling pathway was delineated using different inhibitors and techniques such as platelet aggregation assay, intracellular calcium measurements, immunoprecipitation, immunoblotting, and flow cytometry. We observed a sequential formation of cADPR and NAADP through CD38 activation by PKC of non-muscle myosin heavy chain IIA (MHCIIA), resulting in phospholipase C (PLC) activation in the thrombin-stimulated platelets. These findings reveal that PKC is fundamental in activating CD38 and elicits a physiological response in the murine platelets. PKC is involved in many signaling pathways. Specifically, PKC is involved in the internalization of CD38 via MHCIIA in CD38+/+ wild-type (WT) and CD38-/- knockout mice (KO). CD38 generates calcium-mobilizing agents that act on specific receptors of the calcium stores. Calcium triggered platelet aggregation while serving as a secondary messenger.

Heimdall, an alternative protein issued from a ncRNA related to kappa light chain variable region of immunoglobulins from astrocytes: a new player in neural proteome

The dogma “One gene, one protein” is clearly obsolete since cells use alternative splicing and generate multiple transcripts which are translated into protein isoforms, but also use alternative translation initiation sites (TISs) and termination sites on a given transcript. Alternative open reading frames for individual transcripts give proteins originate from the 5′- and 3′-UTR mRNA regions, frameshifts of mRNA ORFs or from non-coding RNAs. Longtime considered as non-coding, recent in-silico translation prediction methods enriched the protein databases allowing the identification of new target structures that have not been identified previously. To gain insight into the role of these newly identified alternative proteins in the regulation of cellular functions, it is crucial to assess their dynamic modulation within a framework of altered physiological modifications such as experimental spinal cord injury (SCI). Here, we carried out a longitudinal proteomic study on rat SCI from 12 h to 10 days. Based on the alternative protein predictions, it was possible to identify a plethora of newly predicted protein hits. Among these proteins, some presented a special interest due to high homology with variable chain regions of immunoglobulins. We focus our interest on the one related to Kappa variable light chains which is similarly highly produced by B cells in the Bence jones disease, but here expressed in astrocytes. This protein, name Heimdall is an Intrinsically disordered protein which is secreted under inflammatory conditions. Immunoprecipitation experiments showed that the Heimdall interactome contained proteins related to astrocyte fate keepers such as “NOTCH1, EPHA3, IPO13” as well as membrane receptor protein including “CHRNA9; TGFBR, EPHB6, and TRAM”. However, when Heimdall protein was neutralized utilizing a specific antibody or its gene knocked out by CRISPR-Cas9, sprouting elongations were observed in the corresponding astrocytes. Interestingly, depolarization assays and intracellular calcium measurements in Heimdall KO, established a depolarization effect on astrocyte membranes KO cells were more likely that the one found in neuroprogenitors. Proteomic analyses performed under injury conditions or under lipopolysaccharides (LPS) stimulation, revealed the expression of neuronal factors, stem cell proteins, proliferation, and neurogenesis of astrocyte convertor factors such as EPHA4, NOTCH2, SLIT3, SEMA3F, suggesting a role of Heimdall could regulate astrocytic fate. Taken together, Heimdall could be a novel member of the gatekeeping astrocyte-to-neuroprogenitor conversion factors.

A sulfonamide chalcone AMPK activator ameliorates hyperglycemia and diabetic nephropathy in db/db mice

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus (DM), which currently lacks effective treatments. AMP-activated protein kinase (AMPK) stimulation by chalcones, a class of polyphenols abundantly found in plants, is proposed as a promising therapeutic approach for DM. This study aimed to identify novel chalcone derivatives with improved AMPK-stimulating activity in human podocytes and evaluate their mechanisms of action as well as in vivo efficacy in a mouse model of DN. Among 133 chalcone derivatives tested, the sulfonamide chalcone derivative IP-004 was identified as the most potent AMPK activator in human podocytes. Western blot analyses, intracellular calcium measurements and molecular docking simulation indicated that IP-004 activated AMPK by mechanisms involving direct binding at allosteric site of calcium-dependent protein kinase kinase β (CaMKKβ) without affecting intracellular calcium levels. Interestingly, eight weeks of intraperitoneal administration of IP-004 (20 mg/kg/day) significantly decreased fasting blood glucose level, activated AMPK in the livers, muscles and glomeruli, and ameliorated albuminuria in db/db type II diabetic mice. Collectively, this study identifies a novel chalcone derivative capable of activating AMPK in vitro and in vivo and exhibiting efficacy against hyperglycemia and DN in mice. Further development of AMPK activators based on chalcone derivatives may provide an effective treatment of DN.

The regulation of TRPA1 expression and function by Th1 and Th2-type inflammation in human A549 lung epithelial cells

BackgroundTransient Receptor Potential Ankyrin 1 (TRPA1) is a cation channel that mediates pain, itch, cough, and neurogenic inflammation in response to pungent compounds such as acrolein in cigarette smoke. TRPA1 is also activated by endogenous factors and promotes inflammation in asthma models. We have recently shown that TRPA1 is upregulated by inflammatory cytokines in A549 human lung epithelial cells. Here, we explored the effects of Th1 and Th2-type inflammation on TRPA1.Methods and resultsTRPA1 expression and function was studied in A549 human lung epithelial cells. To induce inflammation, the cells were exposed to a combination of cytokines TNF-α and IL-1β; and to model Th1 or Th2-type responses, IFN-γ or IL-4/IL-13 was added, respectively. TRPA1 expression (measured by RT-PCR and Western blot) and function (assessed by Fluo-3AM intracellular calcium measurement) was enhanced under the influence of TNF-α + IL-1β. IFN-γ further enhanced TRPA1 expression and function, whereas IL-4 and IL-13 suppressed them. The effects of IFN-γ and IL-4 on TRPA1 expression were reversed by the Janus kinase (JAK) inhibitors baricitinib and tofacitinib, and those of IL-4 also by the STAT6 inhibitor AS1517499. The glucocorticoid dexamethasone downregulated TRPA1 expression, whereas the PDE4 inhibitor rolipram had no effect. Under all conditions, TRPA1 blockade was found to reduce the production of LCN2 and CXCL6.ConclusionsTRPA1 expression and function in lung epithelial cells was upregulated under inflammatory conditions. IFN-γ further increased TRPA1 expression while IL-4 and IL-13 suppressed that in a JAK-STAT6 dependent manner which is novel. TRPA1 also modulated the expression of genes relevant to innate immunity and lung disease. We propose that the paradigm of Th1 and Th2 inflammation is a major determinant of TRPA1 expression and function, which should be considered when targeting TRPA1 for pharmacotherapy in inflammatory (lung) disease.

Automated Dual-Mode Cell Monitoring To Simultaneously Explore Calcium Dynamics and Contraction-Relaxation Kinetics within Drug-Treated Stem Cell-Derived Cardiomyocytes.

This manuscript proposes a new dual-mode cell imaging system for studying the relationships between calcium dynamics and the contractility process of cardiomyocytes derived from human-induced pluripotent stem cells. Practically, this dual-mode cell imaging system provides simultaneously both live cell calcium imaging and quantitative phase imaging based on digital holographic microscopy. Specifically, thanks to the development of a robust automated image analysis, simultaneous measurements of both intracellular calcium, a key player of excitation-contraction coupling, and the quantitative phase image-derived dry mass redistribution, reflecting the effective contractility, namely, the contraction and relaxation processes, were achieved. Practically, the relationships between calcium dynamics and the contraction-relaxation kinetics were investigated in particular through the application of two drugs─namely, isoprenaline and E-4031─known to act precisely on calcium dynamics. Specifically, this new dual-mode cell imaging system enabled us to establish that calcium regulation can be divided into two phases, an early phase influencing the occurrence of the relaxation process followed by a late phase, which although not having a significant influence on the relaxation process affects significantly the beat frequency. In combination with cutting-edge technologies allowing the generation of human stem cell-derived cardiomyocytes, this dual-mode cell monitoring approach therefore represents a very promising technique, particularly in the fields of drug discovery and personalized medicine, to identify compounds likely to act more selectively on specific steps that compose the cardiomyocyte contractility.

Protective Effect of Trillium tschonoskii Maxim Components Against Glutamate-Induced SH-SY5Y Cells Damage Through Regulating Apoptosis.

Among the Tujia people, the root or rhizome of Trillium tschonoskii Maxim.in Bull.Acad (TTM) is considered a miraculous herb for headaches. Previous studies have shown ethyl acetate extract (TTM1) can protect SH-SY5Y cells against glutamate injury. This study clarified TTM1's mechanism against glutamate-induced cell damage, focusing on the regulation of apoptosis. The compounds were separated, identified, and performed molecular docking with pro-apoptotic proteins. SH-SY5Y cells were treated with glutamate (2mM) for 12hour, and the effect of TTM1 (2.5, 5, 10, and 20μg/mL) was evaluated with MTT and LDH release assays, taking EGb761(40μg/mL) as a control. Cell apoptosis was detected with Hoechst 33258 and Annexin V-FITC and measurements of intracellular calcium and caspase-3. The major components were separated and identified by LCMS-IT-TOF and NMR, then the proapoptotic activity of TTM1 was confirmed by molecular docking method. TTM1 protected SH-SY5Y cells by resisting apoptosis, TTM1 (10 and 20μg/mL) decreased apoptotic bodies and nuclear fragments, increased the proportion of normal cells to 68.38 ± 5.63% and 92.80 ± .88%, decreased VA cells to 4.30 ± .76% and 3.58 ± .45% and caspase-3 to .365 ± .034 and .344 ± .047ng/mL.TTM1 (10μg/mL) decreased intracellular free calcium to 2.77 ± .40. Polyphyllin VI and pennogenin 3-O-β-chacotrioside were identified in TTM1 at 15.04% and 2.84%, and had potential anti-apoptosis activities. Folk records of TTM for headache may be related to its anti-apoptosis of nerve cells. Identification and content determination of index components based on effective extract provides research paradigms for rare and endangered ethnic plants.

The inhibitory effect of escitalopram on mouse detrusor contractility: The role of L-type calcium channels

Selective serotonin reuptake inhibitors (SSRIs) are associated with urinary problems attributed to their central effects. ESC is a preferred SSRI and several case reports described that ESC is related to urinary retention. However, the direct effect of ESC on detrusor contractility is still not completely elucidated. Thus, we investigated the effect of ESC on detrusor contractility and mechanism(s) of its action in isolated mouse detrusor strips. Molecular docking and measurement of intracellular calcium were performed to determine the possible calcium channel blocking effect of ESC. The contractile responses to carbachol (CCh), KCl and electrical field stimulation of detrusor strips were significantly abolished by ESC (10 or 100 μM). ESC relaxed KCl-precontracted detrusor strips concentration-dependently, which was not affected by tetraethylammonium, glibenclamide, 4-aminopyridine, propranolol, L-NAME or methylene blue. ESC (10 or 100 μM) reduced both the CaCl2- and CCh-induced contractions under calcium-free conditions, indicating the role of calcium-involved mechanisms in ESC-mediated relaxation. Furthermore, ESC significantly decreased Bay K8644-induced contraction and the cytosolic calcium level in fura-2-loaded A7r5 cells. Molecular docking study also revealed the potential of ESC to bind L-type calcium (Cav1) channels. Our results demonstrate that ESC inhibits detrusor contractility via blocking Cav1 channels, which provides evidence for the direct effect of ESC on detrusor contractility and its mechanism.

High throughput 3D gel-based neural organotypic model for cellular assays using fluorescence biosensors

Three-dimensional (3D) organotypic models that capture native-like physiological features of tissues are being pursued as clinically predictive assays for therapeutics development. A range of these models are being developed to mimic brain morphology, physiology, and pathology of neurological diseases. Biofabrication of 3D gel-based cellular systems is emerging as a versatile technology to produce spatially and cell-type tailored, physiologically complex and native-like tissue models. Here we produce 3D fibrin gel-based functional neural co-culture models with human-iPSC differentiated dopaminergic or glutamatergic neurons and astrocytes. We further introduce genetically encoded fluorescence biosensors and optogenetics activation for real time functional measurements of intracellular calcium and levels of dopamine and glutamate neurotransmitters, in a high-throughput compatible plate format. We use pharmacological perturbations to demonstrate that the drug responses of 3D gel-based neural models are like those expected from in-vivo data, and in some cases, in contrast to those observed in the equivalent 2D neural models.

Elevated and Sustained Intracellular Calcium Signalling Is Necessary for Efficacious Induction of the Human Sperm Acrosome Reaction.

Progesterone and prostaglandin E1 are postulated to trigger the human sperm acrosome reaction (AR). However, their reported efficacy is very variable which likely, in part, reflects the plethora of experimental conditions and methodologies used to detect this physiologically relevant event. The purpose of this study was to develop an assay for the robust induction and objective measurement of the complete AR. Sperm from healthy volunteers or patients undertaking IVF were treated with a variety of ligands (progesterone, prostaglandin E1 or NH4Cl, alone or in combinations). AR, motility and intracellular calcium measurements were measured using flow cytometry, computer-assisted sperm analysis (CASA) and fluorimetry, respectively. The AR was significantly increased by the simultaneous application of progesterone, prostaglandin E1 and NH4Cl, following an elevated and sustained intracellular calcium concentration. However, we observed notable inter- and intra-donor sample heterogeneity of the AR induction. When studying the patient samples, we found no relationship between the IVF fertilization rate and the AR. We conclude that progesterone and prostaglandin E1 alone do not significantly increase the percentage of live acrosome-reacted sperm. This assay has utility for drug discovery and sperm toxicology studies but is not predictive for IVF success.

α-Subunit Tyrosine Phosphorylation Is Required for Activation of the Large Conductance Ca2+-Activated Potassium Channel in the Rabbit Sphincter of Oddi

Large conductance Ca2+-activated potassium (BKCa) channels are regulated by intracellular free Ca2+ concentrations ([Ca2+]i) and channel protein phosphorylation. In hypercholesterolemia (HC), motility impairment of the sphincter of Oddi (SO) is associated with abnormal [Ca2+]i accumulation in smooth muscle cells of the rabbit SO (RSOSMCs), which is closely related to BKCa channel activity. However, the underlying mechanisms regulating channel activity remain unclear. In this study, an HC rabbit model was generated and used to investigate BKCa channel activity of RSOSMCs via SO muscle tone measurement invitro and manometry invivo, electrophysiological recording, intracellular calcium measurement, and Western blot analyses. BKCa channel activity was decreased, which correlated with [Ca2+]i overload and reduced tyrosine phosphorylation of the BKCa α-subunit in the HC group. The abnormal [Ca2+]i accumulation and decreased BKCa channel activity were partially restored by Na3VO4 pretreatment but worsened by genistein in RSOSMCs in the HC group. This study suggests that α-subunit tyrosine phosphorylation is required for [Ca2+]i to activate BKCa channels, and there is a negative feedback between the BKCa channel and the L-type voltage-dependent Ca2+ channel that regulates [Ca2+]i. This study provides direct evidence that tyrosine phosphorylation of BKCa α-subunits is required for [Ca2+]i to activate BKCa channels in RSOSMCs, which may be the underlying physiological and pathologic mechanism regulating the activity of BKCa channels in SO cells.