An orally available Cav2.2 calcium channel inhibitor for the treatment of neuropathic pain.

BACKGROUND AND PURPOSE: Neuropathic pain affects up to 10% of the global population and is caused by an injury or a disease affecting the somatosensory, peripheral, or central nervous system. NP is characterized by chronic, severe and opioid-resistant properties. Therefore, its clinical management remains very challenging. The N-type voltage-gated calcium channel, Cav2.2, is a validated target for therapeutic intervention in chronic and neuropathic pain. The conotoxin ziconotide (Prialt®) is an FDA-approved drug that blocks Cav2.2 channel but needs to be administered intrathecally. Thus, although being principally efficient, the required application route is very much in disfavour. EXPERIMENTAL APPROACH AND KEY RESULTS: Here, we describe an orally available drug candidate, RD2, which competes with ziconotide binding to Cav2.2 at nanomolar concentrations and inhibits Cav2.2 almost completely reversible. Other voltage-gated calcium channel subtypes, like Cav1.2 and Cav3.2, were affected by RD2 only at concentrations higher than 10 µM. Data from sciatic inflammatory neuritis rat model demonstrated the in vivo proof of concept, as low-dose RD2 (5 mg·kg-1) administered orally alleviated neuropathic pain compared with vehicle controls. High-dose RD2 (50 mg·kg-1) was necessary to reduce pain sensation in acute thermal response assessed by the tail flick test. CONCLUSIONS AND IMPLICATIONS: Taken together, these results demonstrate that RD2 has antiallodynic properties. RD2 is orally available, which is the most convenient application form for patients and caregivers. The surprising and novel result from standard receptor screens opens the room for further optimization into new promising drug candidates, which address an unmet medical need.

Aging impairs the neurovascular interface in the heart.

Aging is a major risk factor for impaired cardiovascular health. Because the aging myocardium is characterized by microcirculatory dysfunction, and because nerves align with vessels, we assessed the impact of aging on the cardiac neurovascular interface. We report that aging reduces nerve density in the ventricle and dysregulates vascular-derived neuroregulatory genes. Aging down-regulates microRNA 145 (miR-145) and derepresses the neurorepulsive factor semaphorin-3A. miR-145 deletion, which increased Sema3a expression or endothelial Sema3a overexpression, reduced axon density, mimicking the aged-heart phenotype. Removal of senescent cells, which accumulated with chronological age in parallel to the decline in nerve density, rescued age-induced denervation, reversed Sema3a expression, preserved heart rate patterns, and reduced electrical instability. These data suggest that senescence-mediated regulation of nerve density contributes to age-associated cardiac dysfunction.

Sex-specific repolarization heterogeneity in mouse left ventricle: Optical mapping combined with mathematical modeling predict the contribution of specific ionic currents.

Ventricular repolarization shows notable sex-specificity, with female sex being associated with longer QT-intervals in electrocardiography irrespective of the species studied. From a clinical point of view, women are at a greater risk for drug-induced torsade de pointes and symptomatic long-QT syndrome. Here, we present an optical mapping (OM) approach to reveal sex-specific action potential (AP) heterogeneity in a slice preparation of mouse hearts. Left ventricular epicardial repolarization in female versus male mice shows longer and, interindividually, more variable AP duration (APD), yielding a less prominent transmural APD gradient. By combining OM with mathematical modeling, we suggest a significant role of IKto,f and IKur in AP broadening in females. Other transmembrane currents, including INaL , only marginally affect basal APD. As in many cardiac pathophysiologies, increasing [Ca2+ ]i poses a risk for arrhythmia, the response of AP morphology to enhanced activation of L-type calcium channels (LTCC) was assessed in a sex-selective manner. Both APD and its variation increased significantly more in female versus male mice after pharmacological LTCC activation, which we hypothesize to be due to sex-specific INaL expression based on mathematical modeling. Altogether, we demonstrate a more delayed repolarization of LV epicardium, a leveled LV transmural APD gradient, and a more pronounced epicardial APD response to Ca2+ influx in females versus males. Mathematical modeling quantifies the relative contributions of selected ionic currents to sex-specific AP morphology under normal and pathophysiological conditions.

The NMDA receptor regulates integrin activation, ATP release and arterial thrombosis through store-operated Ca2+ entry in platelets.

Introduction: Platelet activation and thrombus formation is crucial for hemostasis, but also trigger arterial thrombosis. Calcium mobilization plays an important role in platelet activation, because many cellular processes depend on the level of intracellular Ca2+ ([Ca2+](i)), such as integrin activation, degranulation, cytoskeletal reorganization. Different modulators of Ca2+ signaling have been implied, such as STIM1, Orai1, CyPA, SGK1, etc. Also, the N-methyl-D-aspartate receptor (NMDAR) was identified to contribute to Ca2+ signaling in platelets. However, the role of the NMDAR in thrombus formation is not well defined. Methods: In vitro and in vivo analysis of platelet-specific NMDAR knock-out mice. Results: In this study, we analyzed Grin1fl/fl-Pf4-Cre+ mice with a platelet-specific knock-out of the essential GluN1 subunit of the NMDAR. We found reduced store-operated Ca2+ entry (SOCE), but unaltered store release in GluN1-deficient platelets. Defective SOCE resulted in reduced Src and PKC substrate phosphorylation following stimulation of glycoprotein (GP)VI or the thrombin receptor PAR4 followed by decreased integrin activation but unaltered degranulation. Consequently, thrombus formation on collagen under flow conditions was reduced ex vivo, and Grin1fl/fl-Pf4-Cre+ mice were protected against arterial thrombosis. Results from human platelets treated with the NMDAR antagonist MK-801 revealed a crucial role of the NMDAR in integrin activation and Ca2+ homeostasis in human platelets as well. Conclusion: NMDAR signaling is important for SOCE in platelets and contributes to platelet activation and arterial thrombosis. Thus, the NMDAR represents a novel target for anti-platelet therapy in cardiovascular disease (CVD).

Extracellular flux analysis in intact cardiac tissue slices-A novel tool to investigate cardiac substrate metabolism in mouse myocardium.

AIM: Cardiac pathologies are accompanied by alterations in substrate metabolism, and extracellular flux analysis is a standard tool to investigate metabolic disturbances, especially in immortalized cell lines. However, preparations of primary cells, such as adult cardiomyocytes require enzymatic dissociation and cultivation affecting metabolism. Therefore, we developed a flux analyzer-based method for the assessment of substrate metabolism in intact vibratome-sliced mouse heart tissue. METHODS: Oxygen consumption rates were determined using a Seahorse XFe24-analyzer and "islet capture plates." We demonstrate that tissue slices are suitable for extracellular flux analysis and metabolize both free fatty acids (FFA) and glucose/glutamine. Functional integrity of tissue slices was proven by optical mapping-based assessment of action potentials. In a proof-of-principle approach, the sensitivity of the method was tested by analyzing substrate metabolism in the remote myocardium after myocardial infarction (I/R). RESULTS: Here, I/R increased uncoupled OCR compared with sham animals indicating a stimulated metabolic capacity. This increase was caused by a higher glucose/glutamine metabolism, whereas FFA oxidation was unchanged. CONCLUSION: In conclusion, we describe a novel method to analyze cardiac substrate metabolism in intact cardiac tissue slices by extracellular flux analysis. The proof-of-principle experiment demonstrated that this approach has a sensitivity allowing the investigation of pathophysiologically relevant disturbances in cardiac substrate metabolism.

Cardiac ischemia and reperfusion in mice: a comprehensive hemodynamic, electrocardiographic and electrophysiological characterization.

Malignant ventricular arrhythmias (VA) after acute myocardial infarction remain a major threat. Aim of this study was to characterize the electrophysiological and autonomic sequelae of cardiac ischemia and reperfusion (I/R) in mice during the first week post incident. Left ventricular function was serially assessed using transthoracic echocardiography. VA were quantified by telemetric electrocardiogram (ECG) recordings and electrophysiological studies on the 2nd and 7th day after I/R. Cardiac autonomic function was evaluated by heart rate variability (HRV) and heart rate turbulence (HRT). Infarct size was quantified by planimetric measures. I/R caused significant myocardial scarring and diminished left ventricular ejection fraction. The ECG intervals QRS, QT, QTc, and JTc were prolonged in I/R mice. Both spontaneous VA scored higher and the inducibility of VA was raised in I/R mice. An analysis of HRV and HRT indicated a relative reduction in parasympathetic activity and disturbed baroreflex sensitivity up to 7 days after I/R. In summary, during the first week after I/R, the murine heart reflects essential features of the human heart after myocardial infarction, including a greater vulnerability for VA and a decreased parasympathetic tone accompanied by decelerated depolarization and repolarization parameters.

Respiratory and heart rate dynamics during peripheral chemoreceptor deactivation compared to targeted sympathetic and sympathetic/parasympathetic (co-)activation.

BACKGROUND: The importance of peripheral chemoreceptors for cardiorespiratory neural control is known for decades. Pure oxygen inhalation deactivates chemoreceptors and increases parasympathetic outflow. However, the relationship between autonomic nervous system (ANS) activation and resulting respiratory as well as heart rate (HR) dynamics is still not fully understood. METHODS: In young adults the impact of (1) 100 % pure oxygen inhalation (hyperoxic cardiac chemoreflex sensitivity (CHRS) testing), (2) the cold face test (CFT) and (3) the cold pressor test (CPT) on heart rate variability (HRV), hemodynamics and respiratory rate was investigated in randomized order. Baseline ANS outflow was determined assessing respiratory sinus arrhythmia via deep breathing, baroreflex sensitivity and HRV. RESULTS: Baseline ANS outflow was normal in all participants (23 ± 1 years, 7 females, 3 males). Hyperoxic CHRS testing decreased HR (after 60 ± 3 vs before 63 ± 3 min-1, p = 0.004), while increasing total peripheral resistance (1053 ± 87 vs 988 ± 76 dyne*s + m2/cm5, p = 0.02) and mean arterial blood pressure (93 ± 4 vs 91 ± 4 mm Hg, p = 0.02). HRV indicated increased parasympathetic outflow after hyperoxic CHRS testing accompanied by a decrease in respiratory rate (15 ± 1vs 19 ± 1 min-1, p = 0.001). In contrast, neither CFT nor CPT altered the respiratory rate (18 ± 1 vs 18 ± 2 min-1, p = 0.38 and 18 ± 1 vs 18 ± 1 min-1, p = 0.84, respectively). CONCLUSION: Changes in HR characteristics during deactivation of peripheral chemoreceptors but not during the CFT and CPT are related with a decrease in respiratory rate. This highlights the need of respiratory rate assessment when evaluating adaptations of cardiorespiratory chemoreceptor control.

Peripherally active dextromethorphan derivatives lower blood glucose levels by targeting pancreatic islets.

Dextromethorphan (DXM) acts as cough suppressant via its central action. Cell-protective effects of this drug have been reported in peripheral tissues, making DXM potentially useful for treatment of several common human diseases, such as type 2 diabetes mellitus (T2DM). Pancreatic islets are among the peripheral tissues that positively respond to DXM, and anti-diabetic effects of DXM were observed in two placebo-controlled, randomized clinical trials in humans with T2DM. Since these effects were associated with central side effects, we here developed chemical derivatives of DXM that pass the blood-brain barrier to a significantly lower extent than the original drug. We show that basic nitrogen-containing residues block central adverse events of DXM without reducing its anti-diabetic effects, including the protection of human pancreatic islets from cell death. These results show how to chemically modify DXM, and possibly other morphinans, as to exclude central side effects, while targeting peripheral tissues, such as pancreatic islets.

Characterization of the HCN Interaction Partner TRIP8b/PEX5R in the Intracardiac Nervous System of TRIP8b-Deficient and Wild-Type Mice.

The tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b/PEX5R) is an interaction partner and auxiliary subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are key for rhythm generation in the brain and in the heart. Since TRIP8b is expressed in central neurons but not in cardiomyocytes, the TRIP8b-HCN interaction has been studied intensely in the brain, but is deemed irrelevant in the cardiac conduction system. Still, to date, TRIP8b has not been studied in the intrinsic cardiac nervous system (ICNS), a neuronal network located within epicardial fat pads. In vitro electrophysiological studies revealed that TRIP8b-deficient mouse hearts exhibit increased atrial refractory and atrioventricular nodal refractory periods, compared to hearts of wild-type littermates. Meanwhile, heart rate, sino-nodal recovery time, and ventricular refractory period did not differ between genotypes. Trip8b mRNA was detected in the ICNS by quantitative polymerase chain reaction. RNAscope in situ hybridization confirmed Trip8b localization in neuronal somata and nerve fibers. Additionally, we found a very low amount of mRNAs in the sinus node and atrioventricular node, most likely attributable to the delicate fibers innervating the conduction system. In contrast, TRIP8b protein was not detectable. Our data suggest that TRIP8b in the ICNS may play a role in the modulation of atrial electrophysiology beyond HCN-mediated sino-nodal control of the heart.

Disease-associated HCN4 V759I variant is not sufficient to impair cardiac pacemaking.

The hyperpolarization-activated cation current If is a key determinant for cardiac pacemaker activity. It is conducted by subunits of the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel family, of which HCN4 is predominant in mammalian heart. Both loss-of-function and gain-of-function mutations of the HCN4 gene are associated with sinus node dysfunction in humans; however, their functional impact is not fully understood yet. Here, we sought to characterize a HCN4 V759I variant detected in a patient with a family history of sick sinus syndrome. The genomic analysis yielded a mono-allelic HCN4 V759I variant in a 49-year-old woman presenting with a family history of sick sinus syndrome. This HCN4 variant was previously classified as putatively pathogenic because genetically linked to sudden infant death syndrome and malignant epilepsy. However, detailed electrophysiological and cell biological characterization of HCN4 V759I in Xenopus laevis oocytes and embryonic rat cardiomyocytes, respectively, did not reveal any obvious abnormality. Voltage dependence and kinetics of mutant channel activation, modulation of cAMP-gating by the neuronal HCN channel auxiliary subunit PEX5R, and cell surface expression were indistinguishable from wild-type HCN4. In good agreement, the clinically likewise affected mother of the patient does not exhibit the reported HCN4 variance. HCN4 V759I resembles an innocuous genetic HCN channel variant, which is not sufficient to disturb cardiac pacemaking. Once more, our work emphasizes the importance of careful functional interpretation of genetic findings not only in the context of hereditary cardiac arrhythmias.

Location, Dissection, and Analysis of the Murine Stellate Ganglion.

The autonomic nervous system is a substantial driver of cardiac electrophysiology. Especially the role of its sympathetic branch is an ongoing matter of investigation in the pathophysiology of ventricular arrhythmias (VA). Neurons in the stellate ganglia (SG) - bilateral star-shaped structures of the sympathetic chain - are an important component of the sympathetic infrastructure. The SG are a recognized target for treatment via cardiac sympathetic denervation in patients with therapy-refractory VA. While neuronal remodeling and glial activation in the SG have been described in patients with VA, the underlying cellular and molecular processes that potentially precede the onset of arrhythmia are only insufficiently understood and should be elucidated to improve autonomic modulation. Mouse models allow us to study sympathetic neuronal remodeling, but identification of the murine SG is challenging for the inexperienced investigator. Thus, in-depth cellular and molecular biological studies of the murine SG are lacking for many common cardiac diseases. Here, we describe a basic repertoire for dissecting and studying the SG in adult mice for analyses at RNA level (RNA isolation for gene expression analyses, in situ hybridization), protein level (immunofluorescent whole mount staining), and cellular level (basic morphology, cell size measurement). We present potential solutions to overcome challenges in the preparation technique, and how to improve staining via quenching of autofluorescence. This allows for the visualization of neurons as well as glial cells via established markers in order to determine cell composition and remodeling processes. The methods presented here allow characterizing the SG to gain further information on autonomic dysfunction in mice prone to VA and can be complemented by additional techniques investigating neuronal and glial components of the autonomic nervous system in the heart.

Hepatic encephalopathy is linked to alterations of autophagic flux in astrocytes.

BACKGROUND: Hepatic encephalopathy (HE) is a severe neuropsychiatric syndrome caused by various types of liver failure resulting in hyperammonemia-induced dysfunction of astrocytes. It is unclear whether autophagy, an important pro-survival pathway, is altered in the brains of ammonia-intoxicated animals as well as in HE patients. METHODS: Using primary rat astrocytes, a co-culture model of primary mouse astrocytes and neurons, an in vivo rat HE model, and post mortem brain samples of liver cirrhosis patients with HE we analyzed whether and how hyperammonemia modulates autophagy. FINDINGS: We show that autophagic flux is efficiently inhibited after administration of ammonia in astrocytes. This occurs in a fast, reversible, time-, dose-, and ROS-dependent manner and is mediated by ammonia-induced changes in intralysosomal pH. Autophagic flux is also strongly inhibited in the cerebral cortex of rats after acute ammonium intoxication corroborating our results using an in vivo rat HE model. Transglutaminase 2 (TGM2), a factor promoting autophagy, is upregulated in astrocytes of in vitro- and in vivo-HE models as well as in post mortem brain samples of liver cirrhosis patients with HE, but not in patients without HE. LC3, a commonly used autophagy marker, is significantly increased in the brain of HE patients. Ammonia also modulated autophagy moderately in neuronal cells. We show that taurine, known to ameliorate several parameters caused by hyperammonemia in patients suffering from liver failure, is highly potent in reducing ammonia-induced impairment of autophagic flux. This protective effect of taurine is apparently not linked to inhibition of mTOR signaling but rather to reducing ammonia-induced ROS formation. INTERPRETATION: Our data support a model in which autophagy aims to counteract ammonia-induced toxicity, yet, as acidification of lysosomes is impaired, possible protective effects thereof, are hampered. We propose that modulating autophagy in astrocytes and/or neurons, e.g. by taurine, represents a novel strategy to treat liver diseases associated with HE. FUNDING: Supported by the DFG, CRC974 "Communication and Systems Relevance in Liver Injury and Regeneration", Düsseldorf (Project number 190586431) Projects A05 (DH), B04 (BG), B05 (NK), and B09 (ASR).

Sign Inversion in Photopharmacology: Incorporation of Cyclic Azobenzenes in Photoswitchable Potassium Channel Blockers and Openers.

Photopharmacology relies on ligands that change their pharmacodynamics upon photoisomerization. Many of these ligands are azobenzenes that are thermodynamically more stable in their elongated trans-configuration. Often, they are biologically active in this form and lose activity upon irradiation and photoisomerization to their cis-isomer. Recently, cyclic azobenzenes, so-called diazocines, have emerged, which are thermodynamically more stable in their bent cis-form. Incorporation of these switches into a variety of photopharmaceuticals could convert dark-active ligands into dark-inactive ligands, which is preferred in most biological applications. This "pharmacological sign-inversion" is demonstrated for a photochromic blocker of voltage-gated potassium channels, termed CAL, and a photochromic opener of G protein-coupled inwardly rectifying potassium (GIRK) channels, termed CLOGO.

Isoform-specific Inhibition of N-methyl-D-aspartate Receptors by Bile Salts.

The N-methyl-D-aspartate subfamily of ionotropic glutamate receptors (NMDARs) is well known for its important roles in the central nervous system (CNS), e.g. learning and memory formation. Besides the CNS, NMDARs are also expressed in numerous peripheral tissues including the pancreas, kidney, stomach, and blood cells, where an understanding of their physiological and pathophysiological roles is only evolving. Whereas subunit composition increases functional diversity of NMDARs, a great number of endogenous cues tune receptor signaling. Here, we characterized the effects of the steroid bile salts cholate and chenodeoxycholate (CDC) on recombinantly expressed NMDARs of defined molecular composition. CDC inhibited NMDARs in an isoform-dependent manner, preferring GluN2D and GluN3B over GluN2A and GluN2B receptors. Determined IC50 values were in the range of bile salt serum concentrations in severe cholestatic disease states, pointing at a putative pathophysiological significance of the identified receptor modulation. Both pharmacological and molecular simulation analyses indicate that CDC acts allosterically on GluN2D, whereas it competes with agonist binding on GluN3B receptors. Such differential modes of inhibition may allow isoform-specific targeted interference with the NMDAR/bile salt interaction. In summary, our study provides further molecular insight into the modulation of NMDARs by endogenous steroids and points at a putative pathophysiological role of the receptors in cholestatic disease.

Cardiac glial cells release neurotrophic S100B upon catheter-based treatment of atrial fibrillation.

Atrial fibrillation (AF), the most common sustained heart rhythm disorder worldwide, is linked to dysfunction of the intrinsic cardiac autonomic nervous system (ICNS). The role of ICNS damage occurring during catheter-based treatment of AF, which is the therapy of choice for many patients, remains controversial. We show here that the neuronal injury marker S100B is expressed in cardiac glia throughout the ICNS and is released specifically upon catheter ablation of AF. Patients with higher S100B release were more likely to be AF free during follow-up. Subsequent in vitro studies revealed that murine intracardiac neurons react to S100B with diminished action potential firing and increased neurite growth. This suggests that release of S100B from cardiac glia upon catheter-based treatment of AF is a hallmark of acute neural damage that contributes to nerve sprouting and can be used to assess ICNS damage.

Heterogeneity of the astrocytic AMPA-receptor transcriptome.

Astrocytes form the largest class of glial cells in the central nervous system. They serve plenty of diverse functions that range from supporting the formation and proper operation of synapses to controlling the blood-brain barrier. For many of them, the expression of ionotropic glutamate receptors of the AMPA subtype (AMPARs) in astrocytes is of key importance. AMPARs form as macromolecular protein complexes, whose composition of the pore-lining GluA subunits and of an extensive set of core and peripheral complex constituents defines both their trafficking and gating behavior. Although astrocytic AMPARs have been reported to exhibit heterogeneous properties, their molecular composition is largely unknown. In this study, we sought to quantify the astrocytic AMPAR transcriptome during brain development and with respect to selected brain regions. Whereas the early postnatal pattern of AMPAR mRNA expression showed minor variation over time, it did show significant heterogeneity in different brain regions. Cerebellar astrocytes express a combination of AMPAR complex constituents that is remarkably distinct from the one in neocortical or hippocampal astrocytes. Our study provides a workflow and a first reference for future investigations into the molecular and functional diversity of glial AMPARs.

Human Autoantibodies against the AMPA Receptor Subunit GluA2 Induce Receptor Reorganization and Memory Dysfunction.

AMPA receptors are essential for fast excitatory transmission in the CNS. Autoantibodies to AMPA receptors have been identified in humans with autoimmune encephalitis and severe defects of hippocampal function. Here, combining electrophysiology and high-resolution imaging with neuronal culture preparations and passive-transfer models in wild-type and GluA1-knockout mice, we analyze how specific human autoantibodies against the AMPA receptor subunit GluA2 affect receptor function and composition, synaptic transmission, and plasticity. Anti-GluA2 antibodies induce receptor internalization and a reduction of synaptic GluA2-containing AMPARs followed by compensatory ryanodine receptor-dependent incorporation of synaptic non-GluA2 AMPARs. Furthermore, application of human pathogenic anti-GluA2 antibodies to mice impairs long-term synaptic plasticity in vitro and affects learning and memory in vivo. Our results identify a specific immune-neuronal rearrangement of AMPA receptor subunits, providing a framework to explain disease symptoms.

A modified approach for programmed electrical stimulation in mice: Inducibility of ventricular arrhythmias.

BACKGROUND: Electrophysiological studies in mice, the prevailing model organism in the field of basic cardiovascular research, are impeded by the low yield of programmed electrical stimulation (PES). OBJECTIVE: To investigate a modified approach for ventricular arrhythmia (VA) induction and a novel scoring system in mice. METHOD: A systematic review of literature on current methods for PES in mice searching the PubMed database revealed that VA inducibility was low and ranged widely (4.6 ± 10.7%). Based on this literature review, a modified PES protocol with 3 to 10 extrastimuli was developed and tested in comparison to the conventional PES protocol using up to 3 extrastimuli in anesthetized wildtype mice (C57BL/6J, n = 12). Induced VA, classified according to the Lambeth Convention, were assessed by established arrhythmia scores as well as a novel arrhythmia score based on VA duration. RESULTS: PES with the modified approach raised both the occurrence and the duration of VA compared to conventional PES (0% vs 50%; novel VA score p = 0.0002). Particularly, coupling of >6 extrastimuli raised the induction of VA. Predominantly, premature ventricular complexes (n = 6) and ventricular tachycardia <1s (n = 4) were observed. Repeated PES after adrenergic stimulation using isoprenaline resulted in enhanced induction of ventricular tachycardia <1s in both protocols. CONCLUSION: Our findings suggest that the presented approach of modified PES enables effective induction and quantification of VA in wildtype mice and may well be suited to document and evaluate detailed VA characteristics in mice.

Optical control of L-type Ca2+ channels using a diltiazem photoswitch.

L-type Ca2+ channels (LTCCs) play a crucial role in excitation-contraction coupling and release of hormones from secretory cells. They are targets of antihypertensive and antiarrhythmic drugs such as diltiazem. Here, we present a photoswitchable diltiazem, FHU-779, which can be used to reversibly block endogenous LTCCs by light. FHU-779 is as potent as diltiazem and can be used to place pancreatic ß-cell function and cardiac activity under optical control.