Nav1.7 as a chondrocyte regulator and therapeutic target for osteoarthritis

Osteoarthritis (OA) is the most common joint disease. Currently there are no effective methods that simultaneously prevent joint degeneration and reduce pain1. Although limited evidence suggests the existence of voltage-gated sodium channels (VGSCs) in chondrocytes2, their expression and function in chondrocytes and in OA remain essentially unknown. Here we identify Nav1.7 as an OA-associated VGSC and demonstrate that human OA chondrocytes express functional Nav1.7 channels, with a density of 0.1 to 0.15 channels per µm2 and 350 to 525 channels per cell. Serial genetic ablation of Nav1.7 in multiple mouse models demonstrates that Nav1.7 expressed in dorsal root ganglia neurons is involved in pain, whereas Nav1.7 in chondrocytes regulates OA progression. Pharmacological blockade of Nav1.7 with selective or clinically used pan-Nav channel blockers significantly ameliorates the progression of structural joint damage, and reduces OA pain behaviour. Mechanistically, Nav1.7 blockers regulate intracellular Ca2+ signalling and the chondrocyte secretome, which in turn affects chondrocyte biology and OA progression. Identification of Nav1.7 as a novel chondrocyte-expressed, OA-associated channel uncovers a dual target for the development of disease-modifying and non-opioid pain relief treatment for OA.

The dietary sweetener sucralose is a negative modulator of T cell-mediated responses

Artificial sweeteners are used as calorie-free sugar substitutes in many food products and their consumption has increased substantially over the past years1. Although generally regarded as safe, some concerns have been raised about the long-term safety of the consumption of certain sweeteners2-5. In this study, we show that the intake of high doses of sucralose in mice results in immunomodulatory effects by limiting T cell proliferation and T cell differentiation. Mechanistically, sucralose affects the membrane order of T cells, accompanied by a reduced efficiency of T cell receptor signalling and intracellular calcium mobilization. Mice given sucralose show decreased CD8+ T cell antigen-specific responses in subcutaneous cancer models and bacterial infection models, and reduced T cell function in models of T cell-mediated autoimmunity. Overall, these findings suggest that a high intake of sucralose can dampen T cell-mediated responses, an effect that could be used in therapy to mitigate T cell-dependent autoimmune disorders.

Magnolol and honokiol target TRPC4 to regulate extracellular calcium influx and relax intestinal smooth muscle

ETHNOPHARMACOLOGICAL RELEVANCE

Magnolia officinalis Cortex (M. officinalis) is a classical traditional Chinese medicine (TCM) widely used to treat digestive system diseases. It effectively regulates gastrointestinal motility to improve abdominal pain, abdominal distension and other symptoms. Magnolol (MAG) and honokiol (HON) are the main pharmacodynamic components responsible for the gastrointestinal activity of M. officinalis.

AIM OF THE STUDY

The transient receptor potential (TRP) family is highly expressed in the gastrointestinal tract and participates in the regulation of gastrointestinal motility, visceral hypersensitivity, visceral secretion and other physiological activities. In this study, the calcium-lowering mechanisms of MAG and HON contributing to the smooth muscle relaxation associated with TRP are discussed.

MATERIALS AND METHODS

The relaxation smooth muscle effects of MAG and HON were tested by the isolated intestine tone tests. A synthetic MAG probe (MAG-P) was used to target fishing for their possible target. The distribution of MAG on the smooth muscle was identified by a molecular tracer based on chemical biology. Ca²⁺ imaging and dual-luciferase reporter assays were used to determine the effects on the target proteins. Finally, the calcium-mediating effects of MAG and HON on smooth muscle cells and TRPC4-knockdown cells were compared to verify the potential mechanism.

RESULTS

After confirming the smooth muscle relaxation in the small intestine induced by MAG and HON, the relaxation effect was identified mainly due to the downregulation of intracellular calcium by controlling external calcium influx. Although MAG and HON inhibited both TRPV4 and TRPC4 channels to reduce calcium levels, the inhibitory effect on TRPC4 channels is an important mechanism of their smooth muscle relaxation effect, since TRPC4 is widely expressed in the small intestinal smooth muscle cells.

CONCLUSIONS

The inhibition of MAG and HON on TRPC4 channels contributes to the relaxation of intestinal smooth muscle.

Capsaicin and Zinc Promote Glucose Uptake in C2C12 Skeletal Muscle Cells through a Common Calcium Signalling Pathway

Capsaicin and zinc have recently been highlighted as potential treatments for glucose metabolism disorders; however, the effect of these two natural compounds on signalling pathways involved in glucose metabolism is still uncertain. In this study, we assessed the capsaicin- or zinc- induced activation of signalling molecules including calcium/calmodulin-dependent protein kinase 2 (CAMKK2), cAMP-response element-binding protein (CREB), and target of rapamycin kinase complex 1 (TORC1). Moreover, the expression status of genes associated with the control of glucose metabolism was measured in treated cells. The activation of cell signalling proteins was then evaluated in capsaicin- or zinc treated cells in the presence or absence of cell-permeant calcium chelator (BAPTA-AM) and the CAMKK inhibitor (STO-609). Finally, capsaicin- and zinc-induced glucose uptake was measured in the cells pre-treated with or without BAPTA-AM. Our results indicate that calcium flux induced by capsaicin or zinc led to activation of calcium signalling molecules and promoting glucose uptake in skeletal muscle cells. Pharmacological inhibition of CAMKK diminished activation of signalling molecules. Moreover, we observed an increase in intracellular cAMP levels in the cells after treatment with capsaicin and zinc. Our data show that capsaicin and zinc mediate glucose uptake in C2C12 skeletal muscle cells through the activation of calcium signalling.

A novel assay to assess the effects of estrogen on the cardiac calmodulin binding equilibrium

AIMS

The Ca²⁺-binding protein calmodulin (CaM) modulates numerous target proteins but is produced insufficiently to bind all of them, generating a limiting CaM equilibrium. Menopause increases cardiac morbidity; however, it is unknown if the cardiac CaM equilibrium is affected by estrogen. We devised an assay to assess the effects of ovariectomy and estrogen treatment on the cardiac CaM equilibrium.

MATERIALS AND METHODS

Sprague-Dawley rats received sham surgery or ovariectomy, followed by 2-week treatment with vehicle or 17β-estradiol. Ca²⁺-saturated left ventricular (LV) lysates were processed through CaM sepharose columns, which retained CaM-binding proteins unoccupied by endogenous CaM. Eluants therefrom were subjected to a competitive binding assay against purified CaM and a CaM biosensor to assess the amounts of unoccupied CaM-binding sites. LV cellular composition was assessed by immunohistochemistry.

KEY FINDINGS

LV eluants processed from sham animals reduce biosensor response by ~32%, indicating baseline presence of unoccupied CaM-binding sites and a limiting CaM equilibrium. Ovariectomy exacerbates the limiting CaM equilibrium, reducing biosensor response by ~65%. 17β-estradiol treatment equalizes the difference between sham and ovariectomized animals. These changes reflect whole tissue responses and are not mirrored by changes in total surface areas of cardiomyocytes and fibroblasts. Consistently, Ca²⁺-dependent, but not Ca²⁺-independent, interaction between CaM and the cardiac inositol trisphosphate receptor (IP₃R) is reduced following ovariectomy and is restored by subsequent 17β-estradiol treatment.

SIGNIFICANCE

Our assay provides a new parameter to assess tissue CaM equilibrium. The exacerbated limiting CaM equilibrium following estrogen loss may contribute to cardiac morbidity and is prevented by estrogen treatment.

A Central Role for TRPM4 in Ca2+-Signal Amplification and Vasoconstriction

Transient receptor potential melastatin-4 (TRPM4) is activated by an increase in intracellular Ca2+ concentration and is expressed on smooth muscle cells (SMCs). It is implicated in the myogenic constriction of cerebral arteries. We hypothesized that TRPM4 has a general role in intracellular Ca2+ signal amplification in a wide range of blood vessels. TRPM4 function was tested with the TRPM4 antagonist 9-phenanthrol and the TRPM4 activator A23187 on the cardiovascular responses of the rat, in vivo and in isolated basilar, mesenteric, and skeletal muscle arteries. TRPM4 inhibition by 9-phenanthrol resulted in hypotension and a decreased heart rate in the rat. TRPM4 inhibition completely antagonized myogenic tone development and norepinephrine-evoked vasoconstriction, and depolarization (high extracellular KCl concentration) evoked vasoconstriction in a wide range of peripheral arteries. Vasorelaxation caused by TRPM4 inhibition was accompanied by a significant decrease in intracellular Ca2+ concentration, suggesting an inhibition of Ca2+ signal amplification. Immunohistochemistry confirmed TRPM4 expression in the smooth muscle cells of the peripheral arteries. Finally, TRPM4 activation by the Ca2+ ionophore A23187 was competitively inhibited by 9-phenanthrol. In summary, TRPM4 was identified as an essential Ca2+-amplifying channel in peripheral arteries, contributing to both myogenic tone and agonist responses. These results suggest an important role for TRPM4 in the circulation. The modulation of TRPM4 activity may be a therapeutic target for hypertension. Furthermore, the Ca2+ ionophore A23187 was identified as the first high-affinity (nanomolar) direct activator of TRPM4, acting on the 9-phenanthrol binding site.

NGF Enhances CGRP Release Evoked by Capsaicin from Rat Trigeminal Neurons: Differential Inhibition by SNAP-25-Cleaving Proteases

Nerve growth factor (NGF) is known to intensify pain in various ways, so perturbing pertinent effects without negating its essential influences on neuronal functions could help the search for much-needed analgesics. Towards this goal, cultured neurons from neonatal rat trigeminal ganglia—a locus for craniofacial sensory nerves—were used to examine how NGF affects the Ca²⁺-dependent release of a pain mediator, calcitonin gene-related peptide (CGRP), that is triggered by activating a key signal transducer, transient receptor potential vanilloid 1 (TRPV1) with capsaicin (CAP). Measurements utilised neurons fed with or deprived of NGF for 2 days. Acute re-introduction of NGF induced Ca²⁺-dependent CGRP exocytosis that was inhibited by botulinum neurotoxin type A (BoNT/A) or a chimera of/E and/A (/EA), which truncated SNAP-25 (synaptosomal-associated protein with Mr = 25 k) at distinct sites. NGF additionally caused a Ca²⁺-independent enhancement of the neuropeptide release evoked by low concentrations (<100 nM) of CAP, but only marginally increased the peak response to ≥100 nM. Notably, BoNT/A inhibited CGRP exocytosis evoked by low but not high CAP concentrations, whereas/EA effectively reduced responses up to 1 µM CAP and inhibited to a greater extent its enhancement by NGF. In addition to establishing that sensitisation of sensory neurons to CAP by NGF is dependent on SNARE-mediated membrane fusion, insights were gleaned into the differential ability of two regions in the C-terminus of SNAP-25 (181–197 and 198–206) to support CAP-evoked Ca²⁺-dependent exocytosis at different intensities of stimulation.

Evodiamine induces ROS-Dependent cytotoxicity in human gastric cancer cells via TRPV1/Ca2+ pathway

Evodiamine (EVO), a key active ingredient of the fruit of Evodiae fructus, is provided with antitumor effects (mainly cytotoxic effect) including proliferation inhibition, cell cycle arrest, apoptosis, and metastasis inhibition. Our study aims to explain the underlying role of TRPV1/Ca²⁺ in EVO-induced cytotoxicity in human gastric cancer cells. Human gastric cancer line BGC-823 was used to study EVO-induced cytotoxicity. Cell viability was examined using CCK-8 assay. Apoptosis was examined using Annexin V-FITC/PI staining assay. Intracellular ROS ([ROS]i) levels were examined using DCFH-DA assay. Mitochondrial morphology was examined using Mitotracker Green staining. Mitochondrial membrane potential (Δψm) were examined using JC-1 assay. Intracellular Ca²⁺ levels ([Ca²⁺]i) were examined using Fluo-4 AM assay. Mitochondrial ROS ([ROS]m)levels were examined using Mitotracker Green/MitoSOX Red staining. Mitochondrial Ca²⁺ ([Ca²⁺]m)levels were examined using Mitotracker Green/Rhod-2 Red staining. The protein levels was detected by Western blot. EVO exposure causes significant ROS generation and apoptotic cell death. Pretreatment of EUK134 significantly ameliorated EVO-induced apoptotic cell death. Furthermore, EVO exposure induced [ROS]i generation and mitochondrial dysfunction, including [ROS]m generation and Δψm dissipation, which can be significantly attenuated by pre-incubation of rotenone indicating that [ROS]m is the main source of EVO-induced intracellular ROS generation. Importantly, EVO-induced cytotoxicity was significantly ameliorated by intracellular Ca²⁺ chelation, confirming that EVO induces cell death through Ca²⁺ overload. Pharmacological and genetic inhibition of TRPV1 could significantly attenuate Ca²⁺ influx, ROS generation and apoptotic cell death induced by EVO exposure, while exogenous TRPV1 overexpression could augment the EVO-induced cytotoxicity. Moreover, genetic inhibition of mitochondrial calcium uniporter (MCU) attenuated EVO-induced cell death and mitochondrial dysfunction. EVO exposure induced endoplasmic reticulum (ER) stress demonstrated by the activation of PERK/CHOP in cells exposed to EVO, and PERK/CHOP activation was depleted by EUK134 pre-treatment. Our results support the concept that EVO induces ROS-dependent cytotoxicity via TRPV1/Ca²⁺ Pathway.

OXER1 mediates testosterone-induced calcium responses in prostate cancer cells

In prostate cancer, calcium homeostasis plays a significant role in the disease's development and progression. Intracellular calcium changes are an important secondary signal, triggered by a variety of extracellular stimuli, that controls many cellular functions. One of the main events affecting calcium is androgen signaling. Indeed, via calcium changes, androgens regulate cell processes like cell growth, differentiation and motility. In the present work we explored the nature of the receptor involved in calcium response induced by membrane-acting testosterone in prostate cancer cells. We report that testosterone, independently of the presence of the classical androgen receptor, can rapidly increase intracellular calcium from calcium stores, through the oxoeicosanoid receptor 1 (OXER1) and a specific signaling cascade that triggers calcium release from the endoplasmic reticulum. These findings reveal for the first time the receptor involved in the rapid calcium changes induced by androgens. Moreover, they further support the notion that androgens, even in the absence of AR, can still exert specific effects that regulate cancer cell fate.

Ryanodine receptors mediate high intracellular Ca2+ and some myocyte damage following eccentric contractions in rat fast-twitch skeletal muscle

Eccentric contractions (ECC) facilitate cytosolic calcium ion (Ca2+) release from the sarcoplasmic reticulum (SR) and Ca2+ influx from the extracellular space. Ca2+ is a vital signaling messenger that regulates multiple cellular processes via its spatial and temporal concentration ([Ca2+]i) dynamics. We hypothesized that 1) a specific pattern of spatial/temporal intramyocyte Ca2+ dynamics portends muscle damage following ECC and 2) these dynamics would be regulated by the ryanodine receptor (RyR). [Ca2+]i in the tibialis anterior muscles of anesthetized adult Wistar rats was measured by ratiometric (i.e., ratio, R, 340/380 nm excitation) in vivo bioimaging with Fura-2 pre-ECC and at 5 and 24 h post-ECC (5 × 40 contractions). Separate groups of rats received RyR inhibitor dantrolene (DAN; 10 mg/kg ip) immediately post-ECC (+DAN). Muscle damage was evaluated by histological analysis on hematoxylin-eosin stained muscle sections. Compared with control (CONT, no ECC), [Ca2+]i distribution was heterogeneous with increased percent total area of high [Ca2+]i sites (operationally defined as R ≥ 1.39, i.e., ≥1 SD of mean control) 5 h post-ECC (CONT, 14.0 ± 8.0; ECC5h: 52.0 ± 7.4%, P < 0.01). DAN substantially reduced the high [Ca2+]i area 5 h post-ECC (ECC5h + DAN: 6.4 ± 3.1%, P < 0.01) and myocyte damage (ECC24h, 63.2 ± 1.0%; ECC24h + DAN: 29.1 ± 2.2%, P < 0.01). Temporal and spatially amplified [Ca2+]i fluctuations occurred regardless of DAN (ECC vs. ECC + DAN, P > 0.05). These results suggest that the RyR-mediated local high [Ca2+]i itself is related to the magnitude of muscle damage, whereas the [Ca2+]i fluctuation is an RyR-independent phenomenon.

Two-hit mechanism of cardiac arrhythmias in diabetic hyperglycaemia: reduced repolarization reserve, neurohormonal stimulation, and heart failure exacerbate susceptibility

AIMS

Diabetic hyperglycaemia is associated with increased arrhythmia risk. We aimed to investigate whether hyperglycaemia alone can be accountable for arrhythmias or whether it requires the presence of additional pathological factors.

METHODS AND RESULTS

Action potentials (APs) and arrhythmogenic spontaneous diastolic activities were measured in isolated murine ventricular, rabbit atrial, and ventricular myocytes acutely exposed to high glucose. Acute hyperglycaemia increased the short-term variability (STV) of action potential duration (APD), enhanced delayed afterdepolarizations, and the inducibility of APD alternans during tachypacing in both murine and rabbit atrial and ventricular myocytes. Hyperglycaemia also prolonged APD in mice and rabbit atrial cells but not in rabbit ventricular myocytes. However, rabbit ventricular APD was more strongly depressed by block of late Na+ current (INaL) during hyperglycaemia, consistent with elevated INaL in hyperglycaemia. All the above proarrhythmic glucose effects were Ca2+-dependent and abolished by CaMKII inhibition. Importantly, when the repolarization reserve was reduced by pharmacological inhibition of K+ channels (either Ito, IKr, IKs, or IK1) or hypokalaemia, acute hyperglycaemia further prolonged APD and further increased STV and alternans in rabbit ventricular myocytes. Likewise, when rabbit ventricular myocytes were pretreated with isoproterenol or angiotensin II, hyperglycaemia significantly prolonged APD, increased STV and promoted alternans. Moreover, acute hyperglycaemia markedly prolonged APD and further enhanced STV in failing rabbit ventricular myocytes.

CONCLUSION

We conclude that even though hyperglycaemia alone can enhance cellular proarrhythmic mechanisms, a second hit which reduces the repolarization reserve or stimulates G protein-coupled receptor signalling greatly exacerbates cardiac arrhythmogenesis in diabetic hyperglycaemia.

The Protective Mechanism of Deuterated Linoleic Acid Involves the Activation of the Ca2+ Signaling System of Astrocytes in Ischemia In Vitro

Ischemia-like (oxygen-glucose deprivation, OGD) conditions followed by reoxygenation (OGD/R) cause massive death of cerebral cortex cells in culture as a result of the induction of necrosis and apoptosis. Cell death occurs as a result of an OGD-induced increase in Ca²⁺ ions in the cytosol of neurons and astrocytes, an increase in the expression of genes encoding proapoptotic and inflammatory genes with suppression of protective genes. The deuterated form of linoleic polyunsaturated fatty acid (D4-Lnn) completely inhibits necrosis and greatly reduces apoptotic cell death with an increase in the concentration of fatty acid in the medium. It was shown for the first time that D4-Lnn, through the activation of the phosphoinositide calcium system of astrocytes, causes their reactivation, which correlates with the general cytoprotective effect on the cortical neurons and astrocytes in vitro. The mechanism of the cytoprotective action of D4-Lnn involves the inhibition of the OGD-induced calcium ions, increase in the cytosolic and reactive oxygen species (ROS) overproduction, the enhancement of the expression of protective genes, and the suppression of damaging proteins.

The signatures of organellar calcium

Recent insights about the transport mechanisms involved in the in and out of calcium ions in plant organelles, and their role in the regulation of cytosolic calcium homeostasis in different signaling pathways.

The mechanisms of calcium mobilization by procyanidins, flavonols and flavonoids from Cecropia glaziovii Sneth in pulmonary endothelial cell cultures endorse its popular use as vasodilator phytomedicine

The hypotensive and antihypertensive activities of the aqueous extract (AE) and butanolic fraction (ButF) isolated from Cecropia glaziovii Sneth have been demonstrated in previous studies in animal models. This study aimed to evaluate the molecular mechanism of action responsible for the vasodilatory effect of procyanidins, flavanols, and flavonoids found in C. glaziovii in endothelial cell culture. For this purpose, we analyzed the effect of procyanidin B2 and B3 compounds, catechin, epicatechin, orientin, isoorientin, and isovitexin in the mobilization of Ca2+ in rat endothelial cell cultures. Parallel associations with different antagonists were examined by considering the following in vivo hypotensive mechanisms: blockage of L-type calcium channels, action on β-2 adrenergic receptors, and vasodilation via the nitric oxide pathway. All measurements of calcium mobilization were carried out by using the fluorescence measurement methodology in a Flexstation M3 spectrophotometer. The results indicate that some of the compounds have mixed actions, acting through different calcium mobilization pathways. The mobilization induced by such compounds significantly decreased when they were incubated with their corresponding antagonists. Taken together, our data suggest that the beneficial effects seen with the popular use of Cecropia glaziovii Sneth in pathological conditions, such as systemic arterial hypertension, seem to be related to the plant's hypotensive effect, very probably promoted by the actions of flavonols, flavonoids, and procyanidins, by different pathways of calcium mobilization.

Mechanism and potential treatment of the "no reflow" phenomenon after acute myocardial infarction: role of pericytes and GPR39

The "no reflow" phenomenon, where the coronary artery is patent after treatment of acute myocardial infarction (AMI) but tissue perfusion is not restored, is associated with worse outcome. The mechanism of no reflow is unknown. We hypothesized that pericytes contraction, in an attempt to maintain a constant capillary hydrostatic pressure during reduced coronary perfusion pressure, causes capillary constriction leading to no reflow and that this effect is mediated through the orphan receptor, GPR39, present in pericytes. We created AMI (coronary occlusion followed by reperfusion) in GPR39 knock out mice and littermate controls. In a separate set of experiments, we treated wild-type mice undergoing coronary occlusion with vehicle or VC43, a specific inhibitor of GPR39, before reperfusion. We found that no reflow zones were significantly smaller in the GPR39 knockouts compared with controls. Both no reflow and infarct size were also markedly smaller in animals treated with VC43 compared with vehicle. Immunohistochemistry revealed greater capillary density and larger capillary diameter at pericyte locations in the GPR39-knockout and VC43-treated mice compared with controls. We conclude that GPR39-mediated pericyte contraction during reduced coronary perfusion pressure causes capillary constriction resulting in no reflow during AMI and that smaller no reflow zones in GPR39-knockout and VC43-treated animals are associated with smaller infarct sizes. These results elucidate the mechanism of no reflow in AMI, as well as providing a therapeutic pathway for the condition.NEW & NOTEWORTHY The mechanism of "no reflow" phenomenon, where the coronary artery is patent after treatment of acute myocardial infarction but tissue perfusion is not restored, is unknown. This condition is associated with worse outcome. Here, we show that GPR39-mediated pericyte contraction during reduced coronary perfusion pressure causes capillary constriction resulting in no reflow. Smaller no-reflow zones in GPR39-knockout animals and those treated with a GPR39 inhibitor are associated with smaller infarct size. These results could have important therapeutic implications.

CaMK4 is a downstream effector of the α1G T-type calcium channel to determine the angiogenic potential of pulmonary microvascular endothelial cells

Pulmonary microvascular endothelial cells (PMVECs) uniquely express an α1G-subtype of voltage-gated T-type Ca2+ channel. We have previously revealed that the α1G channel functions as a background Ca2+ entry pathway that is critical for the cell proliferation, migration, and angiogenic potential of PMVECs, a novel function attributed to the coupling between α1G-mediated Ca2+ entry and constitutive Akt phosphorylation and activation. Despite this significance, mechanism(s) that link the α1G-mediated Ca2+ entry to Akt phosphorylation remain incompletely understood. In this study, we demonstrate that Ca2+/calmodulin-dependent protein kinase (CaMK) 4 serves as a downstream effector of the α1G-mediated Ca2+ entry to promote the angiogenic potential of PMVECs. Notably, CaMK2 and CaMK4 are both expressed in PMVECs. Pharmacological blockade or genetic knockdown of the α1G channel led to a significant reduction in the phosphorylation level of CaMK4 but not the phosphorylation level of CaMK2. Pharmacological inhibition as well as genetic knockdown of CaMK4 significantly decreased cell proliferation, migration, and network formation capacity in PMVECs. However, CaMK4 inhibition or knockdown did not alter Akt phosphorylation status in PMVECs, indicating that α1G/Ca2+/CaMK4 is independent of the α1G/Ca2+/Akt pathway in sustaining the cells' angiogenic potential. Altogether, these findings suggest a novel α1G-CaMK4 signaling complex that regulates the Ca2+-dominated angiogenic potential in PMVECs.

Role of Store-Operated Ca2+ Entry in the Pulmonary Vascular Remodeling Occurring in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe and multifactorial disease. PAH pathogenesis mostly involves pulmonary arterial endothelial and pulmonary arterial smooth muscle cell (PASMC) dysfunction, leading to alterations in pulmonary arterial tone and distal pulmonary vessel obstruction and remodeling. Unfortunately, current PAH therapies are not curative, and therapeutic approaches mostly target endothelial dysfunction, while PASMC dysfunction is under investigation. In PAH, modifications in intracellular Ca2+ homoeostasis could partly explain PASMC dysfunction. One of the most crucial actors regulating Ca2+ homeostasis is store-operated Ca2+ channels, which mediate store-operated Ca2+ entry (SOCE). This review focuses on the main actors of SOCE in human and experimental PASMC, their contribution to PAH pathogenesis, and their therapeutic potential in PAH.

Evidence of G-Protein-Coupled Receptors (GPCR) in the Parasitic Protozoa Plasmodium falciparum-Sensing the Host Environment and Coupling within Its Molecular Signaling Toolkit

Throughout evolution, the need for single-celled organisms to associate and form a single cluster of cells has had several evolutionary advantages. In complex, multicellular organisms, each tissue or organ has a specialty and function that make life together possible, and the organism as a whole needs to act in balance and adapt to changes in the environment. Sensory organs are essential for connecting external stimuli into a biological response, through the senses: sight, smell, taste, hearing, and touch. The G-protein-coupled receptors (GPCRs) are responsible for many of these senses and therefore play a key role in the perception of the cells' external environment, enabling interaction and coordinated development between each cell of a multicellular organism. The malaria-causing protozoan parasite, Plasmodium falciparum, has a complex life cycle that is extremely dependent on a finely regulated cellular signaling machinery. In this review, we summarize strong evidence and the main candidates of GPCRs in protozoan parasites. Interestingly, one of these GPCRs is a sensor for K+ shift in Plasmodium falciparum, PfSR25. Studying this family of proteins in P. falciparum could have a significant impact, both on understanding the history of the evolution of GPCRs and on finding new targets for antimalarials.

Abnormal Calcium Handling in Atrial Fibrillation Is Linked to Changes in Cyclic AMP Dependent Signaling

Both, the decreased L-type Ca²⁺ current (I_Ca,L) density and increased spontaneous Ca²⁺ release from the sarcoplasmic reticulum (SR), have been associated with atrial fibrillation (AF). In this study, we tested the hypothesis that remodeling of 3′,5′-cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) signaling is linked to these compartment-specific changes (up- or down-regulation) in Ca²⁺-handling. Perforated patch-clamp experiments were performed in atrial myocytes from 53 patients with AF and 104 patients in sinus rhythm (Ctl). A significantly higher frequency of transient inward currents (I_TI) activated by spontaneous Ca²⁺ release was confirmed in myocytes from AF patients. Next, inhibition of PKA by H-89 promoted a stronger effect on the I_TI frequency in these myocytes compared to myocytes from Ctl patients (7.6-fold vs. 2.5-fold reduction), while the β-agonist isoproterenol (ISO) caused a greater increase in Ctl patients (5.5-fold vs. 2.1-fold). I_Ca,L density was larger in myocytes from Ctl patients at baseline (p < 0.05). However, the effect of ISO on I_Ca,L density was only slightly stronger in AF than in Ctl myocytes (3.6-fold vs. 2.7-fold). Interestingly, a significant reduction of I_Ca,L and Ca²⁺ sparks was observed upon Ca²⁺/Calmodulin-dependent protein kinase II inhibition by KN-93, but this inhibition had no effect on I_TI. Fluorescence resonance energy transfer (FRET) experiments showed that although AF promoted cytosolic desensitization to β-adrenergic stimulation, ISO increased cAMP to similar levels in both groups of patients in the L-type Ca²⁺ channel and ryanodine receptor compartments. Basal cAMP signaling also showed compartment-specific regulation by phosphodiesterases in atrial myocytes from 44 Ctl and 43 AF patients. Our results suggest that AF is associated with opposite changes in compartmentalized PKA/cAMP-dependent regulation of I_Ca,L (down-regulation) and I_TI (up-regulation).

Trans-Ned 19-Mediated Antagonism of Nicotinic Acid Adenine Nucleotide-Mediated Calcium Signaling Regulates Th17 Cell Plasticity in Mice

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca2+ mobilizing agent and its inhibition proved to inhibit T-cell activation. However, the impact of the NAADP signaling on CD4+ T-cell differentiation and plasticity and on the inflammation in tissues other than the central nervous system remains unclear. In this study, we used an antagonist of NAADP signaling, trans-Ned 19, to study the role of NAADP in CD4+ T-cell differentiation and effector function. Partial blockade of NAADP signaling in naïve CD4+ T cells in vitro promoted the differentiation of Th17 cells. Interestingly, trans-Ned 19 also promoted the production of IL-10, co-expression of LAG-3 and CD49b and increased the suppressive capacity of Th17 cells. Moreover, using an IL-17A fate mapping mouse model, we showed that NAADP inhibition promotes conversion of Th17 cells into regulatory T cells in vitro and in vivo. In line with the results, we found that inhibiting NAADP ameliorates disease in a mouse model of intestinal inflammation. Thus, these results reveal a novel function of NAADP in controlling the differentiation and plasticity of CD4+ T cells.

Baicalin attenuates angiotensin II-induced blood pressure elevation and modulates MLCK/p-MLC signaling pathway

Scutellaria baicalensis Georgi is an extensively used medicinal herb for the treatment of hypertension in traditional Chinese medicine. Baicalin, is an important flavonoid in Scutellaria baicalensis Georgi extracts, which exhibits therapeutic effects on anti-hypertension, but its underlying mechanisms remain to be further explored. Therefore, we investigated the effects and molecular mechanisms of Baicalin on anti-hypertension. In vivo studies revealed that Baicalin treatment significantly attenuated the elevation in blood pressure, the pulse propagation and thickening of the abdominal aortic wall in C57BL/6 mice infused with Angiotensin II (Ang II). Moreover, RNA-sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses identified 537 differentially expressed transcripts and multiple enriched signaling pathways (including vascular smooth muscle contraction and calcium signaling pathway). Consistently, we found that Baicalin pretreatment significantly alleviated the Ang II induced constriction of abdominal aortic ring, while promoted NE pre-contracted vasodilation of abdominal aortic ring at least partly dependent on L-type calcium channel. In addition, Ang II stimulation significantly increased cell viability and PCNA expression, while were attenuated after Baicalin treatment. Moreover, Baicalin pretreatment attenuated Ang II-induced intracellular Ca2+ release, Angiotensin II type 1 receptor (AT1R) expression and activation of MLCK/p-MLC pathway in vascular smooth muscle cells (VSMCs). The present work further addressed the pharmacological and mechanistic insights on anti-hypertension of Baicalin, which may help better understand the therapeutic effect of Scutellaria baicalensis Georgi on anti-hypertension.

Monitoring mitochondrial calcium and metabolism in the beating MCU-KO heart

Optical methods for measuring intracellular ions including Ca2+ revolutionized our understanding of signal transduction. However, these methods are not extensively applied to intact organs due to issues including inner filter effects, motion, and available probes. Mitochondrial Ca2+ is postulated to regulate cell energetics and death pathways that are best studied in an intact organ. Here, we develop a method to optically measure mitochondrial Ca2+ and demonstrate its validity for mitochondrial Ca2+ and metabolism using hearts from wild-type mice and mice with germline knockout of the mitochondria calcium uniporter (MCU-KO). We previously reported that germline MCU-KO hearts do not show an impaired response to adrenergic stimulation. We find that these MCU-KO hearts do not take up Ca2+, consistent with no alternative Ca2+ uptake mechanisms in the absence of MCU. This approach can address the role of mitochondrial Ca2+ to the myriad of functions attributed to alterations in mitochondrial Ca2+.

Spontaneous Calcium Oscillations through Differentiation: A Calcium Imaging Analysis of Rat Cochlear Nucleus Neural Stem Cells

Causal therapies for the auditory-pathway and inner-ear diseases are still not yet available for clinical application. Regenerative medicine approaches are discussed and examined as possible therapy options. Neural stem cells could play a role in the regeneration of the auditory pathway. In recent years, neural stem and progenitor cells have been identified in the cochlear nucleus, the second nucleus of the auditory pathway. The current investigation aimed to analyze cell maturation concerning cellular calcium activity. Cochlear nuclei from PND9 CD rats were microscopically dissected and propagated as neurospheres in free-floating cultures in stem-cell medium (Neurobasal, B27, GlutaMAX, EGF, bFGF). After 30 days, the dissociation and plating of these cells took place under withdrawal of the growth factors and the addition of retinoic acid, which induces neural cell differentiation. Calcium imaging analysis with BAPTA-1/Oregon Green was carried out at different times during the differentiation phase. In addition, the influence of different voltage-dependent calcium channels was analyzed through the targeted application of inhibitors of the L-, N-, R- and T-type calcium channels. For this purpose, comparative examinations were performed on CN NSCs, and primary CN neurons. As the cells differentiated, a significant increase in spontaneous neuronal calcium activity was demonstrated. In the differentiation stage, specific frequencies of the spontaneous calcium oscillations were measured in different regions of the individual cells. Initially, the highest frequency of spontaneous calcium oscillations was ascertainable in the maturing somata. Over time, these were overtaken by calcium oscillations in the axons and dendrites. Additionally, in the area of the growth cones, an increasing activity was determined. By inhibiting voltage-dependent calcium channels, their expression and function in the differentiation process were confirmed. A comparable pattern of maturation of these channels was found in CN NSCs and primary CN neurons. The present results show that neural stem cells of the rat cochlear nucleus differentiated not only morphologically but also functionally. Spontaneous calcium activities are of great relevance in terms of neurogenesis and integration into existing neuronal structures. These functional aspects of neurogenesis within the auditory pathway could serve as future targets for the exogenous control of neuronal regeneration.

Influence of calcium channel modulators on the production of serotonin, gentisic acid, and a few other biosynthetically related phenolic metabolites in seedling leaves of salt tolerant rice variety Nonabokra

Rice, a most salt-sensitive cereal plant, adopts diverse pathways to withstand sodium chloride-induced salinity-related adversities. During the present study, attempt was made to understand the role of calcium on metabolite profile of the leaves of salt tolerant rice seedlings of variety of Nonabokra under sodium chloride induced salinity, by Gas Chromatography-Mass Spectrometry-based metabolomics approach. Calcium availability in the seedlings was reduced or enhanced applying inhibitors (vanadyl sulfate, lanthanum chloride, and verapamil) or promoters of calcium influx (calcimycin also known as calcium ionophore A23187) in the sodium chloride (100 mM) supplemented growth medium. Growth medium of ten-day-old seedlings was replaced by sodium chloride supplemented hydroponic solution with promotor or inhibitors of calcium channel. Fifteen days old seedlings were harvested. It was observed that depletion of calcium availability increased the level of serotonin and gentisic acid whereas increased calcium level decreased these metabolites. It was concluded from the results that production of the signaling molecules serotonin and gentisic acids was elevated in calcium-deficient seedlings under salt stress the condition that was considered as control during the experiment. The two signaling molecules probably help this tolerant rice variety Nonabokra to withstand the salt-induced adversities.

MCU overexpression evokes disparate dose-dependent effects on mito-ROS and spontaneous Ca2+ release in hypertrophic rat cardiomyocytes

Cardiac dysfunction in heart failure (HF) and diabetic cardiomyopathy (DCM) is associated with aberrant intracellular Ca2+ handling and impaired mitochondrial function accompanied with reduced mitochondrial calcium concentration (mito-[Ca2+]). Pharmacological or genetic facilitation of mito-Ca2+ uptake was shown to restore Ca2+ transient amplitude in DCM and HF, improving contractility. However, recent reports suggest that pharmacological enhancement of mito-Ca2+ uptake can exacerbate ryanodine receptor-mediated spontaneous sarcoplasmic reticulum (SR) Ca2+ release in ventricular myocytes (VMs) from diseased animals, increasing propensity to stress-induced ventricular tachyarrhythmia. To test whether chronic recovery of mito-[Ca2+] restores systolic Ca2+ release without adverse effects in diastole, we overexpressed mitochondrial Ca2+ uniporter (MCU) in VMs from male rat hearts with hypertrophy induced by thoracic aortic banding (TAB). Measurement of mito-[Ca2+] using genetic probe mtRCamp1h revealed that mito-[Ca2+] in TAB VMs paced at 2 Hz under β-adrenergic stimulation is lower compared with shams. Adenoviral 2.5-fold MCU overexpression in TAB VMs fully restored mito-[Ca2+]. However, it failed to improve cytosolic Ca2+ handling and reduce proarrhythmic spontaneous Ca2+ waves. Furthermore, mitochondrial-targeted genetic probes MLS-HyPer7 and OMM-HyPer revealed a significant increase in emission of reactive oxygen species (ROS) in TAB VMs with 2.5-fold MCU overexpression. Conversely, 1.5-fold MCU overexpression in TABs, that led to partial restoration of mito-[Ca2+], reduced mitochondria-derived reactive oxygen species (mito-ROS) and spontaneous Ca2+ waves. Our findings emphasize the key role of elevated mito-ROS in disease-related proarrhythmic Ca2+ mishandling. These data establish nonlinear mito-[Ca2+]/mito-ROS relationship, whereby partial restoration of mito-[Ca2+] in diseased VMs is protective, whereas further enhancement of MCU-mediated Ca2+ uptake exacerbates damaging mito-ROS emission.NEW & NOTEWORTHY Defective intracellular Ca2+ homeostasis and aberrant mitochondrial function are common features in cardiac disease. Here, we directly compared potential benefits of mito-ROS scavenging and restoration of mito-Ca2+ uptake by overexpressing MCU in ventricular myocytes from hypertrophic rat hearts. Experiments using novel mito-ROS and Ca2+ biosensors demonstrated that mito-ROS scavenging rescued both cytosolic and mito-Ca2+ homeostasis, whereas moderate and high MCU overexpression demonstrated disparate effects on mito-ROS emission, with only a moderate increase in MCU being beneficial.

Role of L-Type Voltage-Gated Calcium Channels in Epileptiform Activity of Neurons

Epileptic discharges manifest in individual neurons as abnormal membrane potential fluctuations called paroxysmal depolarization shift (PDS). PDSs can combine into clusters that are accompanied by synchronous oscillations of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in neurons. Here, we investigate the contribution of L-type voltage-gated calcium channels (VGCC) to epileptiform activity induced in cultured hippocampal neurons by GABA(A)R antagonist, bicuculline. Using KCl-induced depolarization, we determined the optimal effective doses of the blockers. Dihydropyridines (nifedipine and isradipine) at concentrations ≤ 10 μM demonstrate greater selectivity than the blockers from other groups (phenylalkylamines and benzothiazepines). However, high doses of dihydropyridines evoke an irreversible increase in [Ca²⁺]_i in neurons and astrocytes. In turn, verapamil and diltiazem selectively block L-type VGCC in the range of 1–10 μM, whereas high doses of these drugs block other types of VGCC. We show that L-type VGCC blockade decreases the half-width and amplitude of bicuculline-induced [Ca²⁺]_i oscillations. We also observe a decrease in the number of PDSs in a cluster and cluster duration. However, the pattern of individual PDSs and the frequency of the cluster occurrence change insignificantly. Thus, our results demonstrate that L-type VGCC contributes to maintaining the required [Ca²⁺]_i level during oscillations, which appears to determine the number of PDSs in the cluster.

Cyclic GMP-Dependent Regulation of Vascular Tone and Blood Pressure Involves Cysteine-Rich LIM-Only Protein 4 (CRP4)

The cysteine-rich LIM-only protein 4 (CRP4), a LIM-domain and zinc finger containing adapter protein, has been implicated as a downstream effector of the second messenger 3',5'-cyclic guanosine monophosphate (cGMP) pathway in multiple cell types, including vascular smooth muscle cells (VSMCs). VSMCs and nitric oxide (NO)-induced cGMP signaling through cGMP-dependent protein kinase type I (cGKI) play fundamental roles in the physiological regulation of vascular tone and arterial blood pressure (BP). However, it remains unclear whether the vasorelaxant actions attributed to the NO/cGMP axis require CRP4. This study uses mice with a targeted deletion of the CRP4 gene (CRP4 KO) to elucidate whether cGMP-elevating agents, which are well known for their vasorelaxant properties, affect vessel tone, and thus, BP through CRP4. Cinaciguat, a NO- and heme-independent activator of the NO-sensitive (soluble) guanylyl cyclase (NO-GC) and NO-releasing agents, relaxed both CRP4-proficient and -deficient aortic ring segments pre-contracted with prostaglandin F2α. However, the magnitude of relaxation was slightly, but significantly, increased in vessels lacking CRP4. Accordingly, CRP4 KO mice presented with hypotonia at baseline, as well as a greater drop in systolic BP in response to the acute administration of cinaciguat, sodium nitroprusside, and carbachol. Mechanistically, loss of CRP4 in VSMCs reduced the Ca2+-sensitivity of the contractile apparatus, possibly involving regulatory proteins, such as myosin phosphatase targeting subunit 1 (MYPT1) and the regulatory light chain of myosin (RLC). In conclusion, the present findings confirm that the adapter protein CRP4 interacts with the NO-GC/cGMP/cGKI pathway in the vasculature. CRP4 seems to be part of a negative feedback loop that eventually fine-tunes the NO-GC/cGMP axis in VSMCs to increase myofilament Ca2+ desensitization and thereby the maximal vasorelaxant effects attained by (selected) cGMP-elevating agents.

Uterotonic Effects of Aqueous and Methanolic Extracts of Lannea acida in Wistar Rats: An In Vitro Study

Lannea acida (Anacardiaceae), commonly called Kikié in the Noun division (West-Cameroon), is a tree whose bark is used locally to facilitate delivery. This study was aimed at evaluating the in vitro uterotonic effects of aqueous and methanol extracts of L. acida in Wistar rats. Uterine strips isolated from rats pretreated with 5 μg estradiol (48 h) were mounted in a single-organ bath containing aerated and thermostated De Jalon solution (37 °C). After equilibration, non-cumulative effects of L. acida extracts were recorded after application. The effect of the methanol extract (the most active extract) was monitored in the presence of atosiban (a competitive antagonist of oxytocin receptors), atropine (a specific type 3 muscarinic receptor antagonist), nifedipine (an L-type calcium channel antagonist), and 2-Aminoethoxydiphenyl borate (2-ADB, a specific antagonist of inositol 1,4,5-triphosphate receptors type 1), and in calcium-free medium containing EGTA to elucidate its mechanism of action. L. acida induced uterine contraction in a concentration-dependent manner with the methanol extract (1.506 ± 0.032 gf) being the most effective. Administration of atosiban (2 μmol/L) and atropine (1 μmol/L) reduced the contractile effect of L. acida. Complete inhibition was observed with nifedipine, 2-APB, and calcium-free medium containing EGTA. These results suggest that L. acida possesses uterotonic effects mediated through oxytocin receptors with mobilization of extracellular calcium.

Activation of RAGE leads to the release of glutamate from astrocytes and stimulates calcium signal in neurons

The receptor for advanced glycation end products (RAGE) is a signal receptor first shown to be activated by advanced glycation end products, but also by a variety of signal molecules, including pathological advanced oxidation protein products and β-amyloid. However, most of the RAGE activators have multiple intracellular targets, making it difficult to unravel the exact pathway of RAGE activation. Here, we show that the cell-impermeable RAGE fragment sequence (60-76) of the V-domain of the receptor is able to activate RAGE present on the plasma membrane of neurons and, preferentially, astrocytes. This leads to the exocytosis of vesicular glutamate transporter vesicles and the release of glutamate from astrocytes, which stimulate NMDA and AMPA/kainate receptors, resulting in calcium signals predominantly in neurons. Thus, we show a specific mechanism of RAGE activation by the RAGE fragment and propose a mechanism by which RAGE activation can contribute to the neuronal-astrocytic communication in physiology and pathology.

COVID19-associated cardiomyocyte dysfunction, arrhythmias and the effect of Canakinumab

Background

Cardiac injury associated with cytokine release frequently occurs in SARS-CoV-2 mediated coronavirus disease (COVID19) and mortality is particularly high in these patients. The mechanistic role of the COVID19 associated cytokine-storm for the concomitant cardiac dysfunction and associated arrhythmias is unclear. Moreover, the role of anti-inflammatory therapy to mitigate cardiac dysfunction remains elusive.

Aims and methods

We investigated the effects of COVID19-associated inflammatory response on cardiac cellular function as well as its cardiac arrhythmogenic potential in rat and induced pluripotent stem cell derived cardiomyocytes (iPS-CM). In addition, we evaluated the therapeutic potential of the IL-1β antagonist Canakinumab using state of the art in-vitro confocal and ratiometric high-throughput microscopy.

Results

Isolated rat ventricular cardiomyocytes were exposed to control or COVID19 serum from intensive care unit (ICU) patients with severe ARDS and impaired cardiac function (LVEF 41±5%; 1/3 of patients on veno-venous extracorporeal membrane oxygenation; CK 154±43 U/l). Rat cardiomyocytes showed an early increase of myofilament sensitivity, a decrease of Ca²⁺ transient amplitudes and altered baseline [Ca²⁺] upon exposure to patient serum. In addition, we used iPS-CM to explore the long-term effect of patient serum on cardiac electrical and mechanical function. In iPS-CM, spontaneous Ca²⁺ release events were more likely to occur upon incubation with COVID19 serum and nuclear as well as cytosolic Ca²⁺ release were altered. Co-incubation with Canakinumab had no effect on pro-arrhythmogenic Ca²⁺ release or Ca²⁺ signaling during excitation-contraction coupling, nor significantly influenced cellular automaticity.

Conclusion

Serum derived from COVID19 patients exerts acute cardio-depressant and chronic pro-arrhythmogenic effects in rat and iPS-derived cardiomyocytes. Canakinumab had no beneficial effect on cellular Ca²⁺ signaling during excitation-contraction coupling. The presented method utilizing iPS-CM and in-vitro Ca²⁺ imaging might serve as a novel tool for precision medicine. It allows to investigate cytokine related cardiac dysfunction and pharmacological approaches useful therein.

Tannic acid attenuates vascular calcification-induced proximal tubular cells damage through paracrine signaling

Vascular calcification is common in chronic kidney disease; however, the extent to which such condition can affect the renal microvasculature and the neighboring cell types is unclear. Our induced-calcification model in renal proximal tubular (PT) cells exhibited endoplasmic reticulum (ER) stress and oxidative damage, leading to apoptosis. Here, we utilized such calcification in mouse vascular smooth muscle (MOVAS-1) cells as a vascular calcification model, because it exhibited reactive oxygen species (ROS) generation, ER and oxidative stress, inflammatory, and apoptotic gene expressions. To demonstrate whether the vascular calcification condition can dictate the function of the adjacent PT cell layer, we utilized a Transwell multilayer culture system by combining those MOVAS-1 cells in the bottom chamber and polarized PT cells in the upper chamber to show the dimensional cross-signaling effect. Interestingly, calcification of MOVAS-1 cells, in this co-culture, induced H2O2 and lactate dehydrogenase (LDH) release leading to store-operated Ca2+ entry, ROS generation, and activation of oxidative, inflammatory, and apoptotic gene expressions in PT cells through paracrine signaling. Interestingly, application of tannic acid (TA) to either calcified MOVAS-1 or uncalcified PT cells diminished such detrimental pathway activation. Furthermore, the TA-mediated protection was much higher in the PT cells when applied on the calcified MOVAS-1 cells, and the delayed the pathological effects in neighboring PT cells can well be via paracrine signaling. Together, these results provide evidence of vascular calcification-induced PT cell damage, and the protective role of TA in preventing such pathological consequences, which can potentially be used as a nephroprotective remedy.

Ellagic Acid Prevents Ca2+ Dysregulation and Improves Functional Abnormalities of Ventricular Myocytes via Attenuation of Oxidative Stress in Pathological Cardiac Hypertrophy

The aim of this study was to investigate whether ellagic acid (EA) treatment can prevent changes in contractile function and Ca2+ regulation of cardiomyocytes in pathologic cardiac hypertrophy. Groups were assigned as Con group; an ISO group in which the rats received isoproterenol alone (5 mg/kg/day); and an ISO + EA group in which the rats received isoproterenol and EA (20 mg/kg/day) for 4 weeks. Subsequently, fractional shortening, intracellular Ca2+ signals, and L-type Ca2+ currents of isolated ventricular myocytes were recorded. Protein expression levels were also determined by the Western blotting method. The survival rate was increased, and the upregulated cardiac hypertrophy markers were significantly attenuated with the EA treatment. The fractional shortening and relaxation rate of myocytes was decreased in the ISO group, whereas EA significantly improved these changes. Ventricular myocytes of the ISO + EA rats displayed lower diastolic Ca2+ levels, higher Ca2+ transients, shorter Ca2+ decay, and higher L-type Ca2+ currents than those of ISO rats. Protein expression analyses indicated that the upregulated p-PLB and p-CaMKII expressions were restored by EA treatment, suggesting improved calcium handling in the ISO + EA rat heart. Moreover, ISO rats displayed significantly increased expression of p-22phox and p47phox subunits of NOX2 protein. Expression of the p22phox subunit was reduced with EA administration, while the decrease in p47phox did not reach a significant level. The increased ROS impairs Ca2+ homeostasis and contractile activity of cardiac myocytes, whereas chronic EA administration prevents Ca2+ dysregulation and functional abnormalities associated with pathological cardiac hypertrophy via the diminution of oxidative stress.

Stromal interaction molecule 1 (STIM1) knock down attenuates invasion and proliferation and enhances the expression of thyroid-specific proteins in human follicular thyroid cancer cells

Stromal interaction molecule 1 (STIM1) and the ORAI1 calcium channel mediate store-operated calcium entry (SOCE) and regulate a multitude of cellular functions. The identity and function of these proteins in thyroid cancer remain elusive. We show that STIM1 and ORAI1 expression is elevated in thyroid cancer cell lines, compared to primary thyroid cells. Knock-down of STIM1 or ORAI1 attenuated SOCE, reduced invasion, and the expression of promigratory sphingosine 1-phosphate and vascular endothelial growth factor-2 receptors in thyroid cancer ML-1 cells. Cell proliferation was attenuated in these knock-down cells due to increased G1 phase of the cell cycle and enhanced expression of cyclin-dependent kinase inhibitory proteins p21 and p27. STIM1 protein was upregulated in thyroid cancer tissue, compared to normal tissue. Downregulation of STIM1 restored expression of thyroid stimulating hormone receptor, thyroid specific proteins and increased iodine uptake. STIM1 knockdown ML-1 cells were more susceptible to chemotherapeutic drugs, and significantly reduced tumor growth in Zebrafish. Furthermore, STIM1-siRNA-loaded mesoporous polydopamine nanoparticles attenuated invasion and proliferation of ML-1 cells. Taken together, our data suggest that STIM1 is a potential diagnostic and therapeutic target for treatment of thyroid cancer.

2-Aminoethyl diphenylborinate inhibits bleomycin-induced skin and pulmonary fibrosis via interrupting intracellular Ca2+ regulation

BACKGROUND

Systemic sclerosis (SSc) causes progressive fibrosis of multiple organs with the low efficacy of immunosuppressive therapies. Our previous study indicated the SSc pathological pathways are closely correlated with Ca2+ signals, and blockage of the intracellular Ca2+ elevation facilitates inhibition of SSc pathogenesis.

OBJECTIVE

Transforming growth factor β (TGF-β)-modulated SMAD signaling is crucial in regulating SSc pathogenesis. Whether Ca2+ signals are involved in TGF-β1/SMAD signaling-induced fibrotic process has been further investigated.

METHODS

We utilized TGF-β1-induced myofibroblasts as a model to detect how Ca2+ signals affected SSc pathogenesis, and investigated the combination of treatment with store-operated Ca2+ entry (SOCE) associated inhibitors, 2-aminoethyl diphenylborinate (2-APB) and SKF96365 to restrain the increased Ca2+ signaling in myofibroblasts. In addition, the SSc bleomycin mouse model was used to detect the effect of 2-APB on SSc pathogenesis in vivo.

RESULTS

Our findings revealed increased levels of TGF-β1 production in SSc was associated with intracellular Ca2+ activity, and inhibition of intracellular Ca2+ regulation by 2-APB resulted in the dedifferentiation of TGF-β1-induced myofibroblasts. This was due to the fact that 2-APB restrained the expression fibrotic markers, α-SMA, fibronectin and vimentin through inhibiting TGF-β1/SMAD3 signaling. Thus, subcutaneous injection of 2-APB improved bleomycin-induced skin and pulmonary fibrosis.

CONCLUSION

2-APB is a potential candidate for treating fibrosis, by disrupting intracellular Ca2+ regulation in SSc to induce the dedifferentiation of myofibroblasts and meliorates fibrosis pathogenesis via inhibiting TGF-β1/SMAD3 signaling.

Amelioration of circadian disruption and calcium-handling protein defects by choline alleviates cardiac remodeling in abdominal aorta coarctation rats

The key pathophysiological process leading to heart failure is cardiac remodeling, a term referring to cardiac hypertrophy, fibrosis, and apoptosis. We explored circadian rhythm disruption and calcium dyshomeostasis in cardiac remodeling and investigated the cardioprotective effect of choline. The experiments were conducted using a model of cardiac remodeling by abdominal aorta coarctation (AAC) in Sprague-Dawley rats. In vitro cardiomyocyte remodeling was induced by exposing neonatal rat cardiomyocytes to angiotensin II. The circadian rhythms of the transcript levels of the seven major components of the mammalian clock (Bmal1, Clock, Rev-erbα, Per1/2, and Cry1/2) were altered in AAC rat hearts during a normal 24 h light/dark cycle. AAC also upregulated the levels of proteins that mediate store-operated Ca2+ entry/receptor-operated Ca2+ entry (stromal interaction molecule 1 [STIM1], Orai1, and transient receptor potential canonical 6 [TRPC6]) in rat hearts. Moreover, choline ameliorated circadian rhythm disruption, reduced the upregulated protein levels of STIM1, Orai1, and TRPC6, and alleviated cardiac dysfunction and remodeling (evidenced by attenuated cardiac hypertrophy, fibrosis, and apoptosis) in AAC rats. In vitro analyses showed that choline ameliorated calcium overload, downregulated STIM1, Orai1, and TRPC6, and inhibited thapsigargin-induced store-operated Ca2+ entry and 1-oleoyl-2-acetyl-sn-glycerol-induced receptor-operated Ca2+ entry in angiotensin II-treated cardiomyocytes. In conclusion, choline attenuated AAC-induced cardiac remodeling and cardiac dysfunction, which was related to amelioration of circadian rhythm disruption and attenuation of calcium-handling protein defects. Modulation of vagal activity by choline targeting the circadian rhythm and calcium homeostasis may have therapeutic potential for cardiac remodeling and heart failure.

Purinergic Receptors Crosstalk with CCR5 to Amplify Ca2+ Signaling

Many G protein-coupled receptors (GPCRs) signal through more than one subtype of heterotrimeric G proteins. For example, the C-C chemokine receptor type 5 (CCR5), which serves as a co-receptor to facilitate cellular entry of human immunodeficiency virus 1 (HIV-1), normally signals through the heterotrimeric G protein, Gi. However, CCR5 also exhibits G protein signaling bias and certain chemokine analogs can cause a switch to Gq pathways to induce Ca2+ signaling. We want to understand how much of the Ca2+ signaling from Gi-coupled receptors is due to G protein promiscuity and how much is due to transactivation and crosstalk with other receptors. We propose a possible mechanism underlying the apparent switching between different G protein signaling pathways. We show that chemokine-mediated Ca2+ flux in HEK293T cells expressing CCR5 can be primed and enhanced by ATP pretreatment. In addition, agonist-dependent lysosomal exocytosis results in the release of ATP to the extracellular milieu, which amplifies cellular signaling networks. ATP is quickly degraded via ADP and AMP to adenosine. ATP, ADP and adenosine activate different cell surface purinergic receptors. Endogenous Gq-coupled purinergic P2Y receptors amplify Ca2+ signaling and allow for Gi- and Gq-coupled receptor signaling pathways to converge. Associated secretory release of GPCR ligands, such as chemokines, opioids, and monoamines, should also lead to concomitant release of ATP with a synergistic effect on Ca2+ signaling. Our results suggest that crosstalk between ATP-activated purinergic receptors and other Gi-coupled GPCRs is an important cooperative mechanism to amplify the intracellular Ca2+ signaling response.

Calcium activity in response to nAChR ligands in murine bone marrow granulocytes with different Gr-1 expression

Polymorphonuclear neutrophilic granulocytes (PMNs) are the largest proportion of leukocytes in adult human blood that perform numerous functions, including phagocytosis, degranulation, generation of reactive oxygen species, and NETosis. Excessive neutrophil activity associates with hyperinflammation and tissue damage during pathologies such as inflammatory bowel disease, diabetes mellitus, tuberculosis, and coronavirus disease 2019. Nicotinic acetylcholine receptors (nAChRs) can modulate immune cells, including neutrophils, functions, therefore, nAChR ligands are considered as the potent agents for therapy of inflammation. Earlier it was shown, that about 30% of PMNs from the acute inflammatory site responded to nicotine by calcium spikes. In this study, we studied the generation of calcium spikes in murine granulocytes with different maturity level (evaluated by Gr-1 expression) isolated from bone marrow in response to ligands of nAChRs in control and under chronic nicotine consumption. It was found that nearly 20%-25% cells in the granulocyte population responded to nicotine or selective antagonists of different type of nAChRs (α-cobratoxin, GIC, and Vc1.1). We demonstrated that in the control group Ca2+ -mobilizing activity was regulated through α7 and α9α10 nAChRs in immature granulocytes (Gr-1int ), whereas in mature granulocytes (Gr-1hi ) it was regulated through α7, α3β2, and α9-contained nAChRs. Sensitivity of PMNs to nicotine depended on their maturity level after chronic nicotine consumption. Gr-1int cells responded to nicotine through α7 and α9-contained nAChRs, while Gr-1hi did not respond to nicotine. Thus, calcium response to nAChR ligands in bone marrow PMNs depends on their maturity level.

κ‑opioid receptor agonist, U50488H, inhibits pyroptosis through NLRP3 via the Ca2+/CaMKII/CREB signaling pathway and improves synaptic plasticity in APP/PS1 mice

Alzheimer's disease (AD) is a progressive neurodegenerative brain disorder with slow onset in most cases. Clinically, dementia associated with AD is characterized by memory disorders, aphasia, executive dysfunction and personality and behavior changes. Currently, treatment strategies attempt to reduce certain symptoms, however there is no cure for AD. The aim of the present study was to identify a novel treatment strategy for AD. Thus, the protective effects of a κ‑opioid receptor (KOR) agonist, U50488H on neural damage in AD mice were investigated. The underlying mechanism of the Ca2+/calcium/calmodulin‑dependent protein kinase II/cyclic adenosine monophosphate‑response element binding protein (Ca2+/CaMKII/CREB) signaling pathway was evaluated. Amyloid precursor protein (APP)/presenilin‑1 (PS1) mice were treated subcutaneously with a KOR agonist for 28 days. The learning and memory abilities of the APP/PS1 mice were evaluated using the Morris water maze test. Damage to hippocampal neurons was assessed using hematoxylin and eosin staining. Inflammatory factors and brain injury markers were detected using ELISA. Neurons were examined using immunofluorescence and dendritic spines were observed using Golgi‑Cox staining. Western blotting was used to detect NOD‑, LRR‑ and pyrin domain‑containing protein 3, microglial ptosis and the Ca2+/CaMKII/CREB‑related protein pathway. The KOR agonist significantly improved the brain injury observed in APP/PS1 mice, inhibited microglia pyroptosis and improved the synaptic plasticity of APP/PS1 mice, which was reversed by a KOR antagonist. Thus, the KOR agonist improved the symptoms of APP/PS1 mice by inhibiting the Ca2+/CaMKII/CREB signaling pathway.

Calcium/calmodulin-dependent regulation of Rac GTPases and Akt in histamine-induced chemotaxis of mast cells

Histamine induces chemotaxis of mast cells through the histamine H4 receptor. This involves the activation of small GTPases, Rac1 and Rac2, downstream of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). Activation of the H4 receptor also results in phospholipase C (PLC)-mediated calcium mobilization; however, it is unclear whether the PLC‑calcium pathway interacts with the PI3K-Rac pathway. Here, we demonstrated that calcium mobilization regulates the PI3K-dependent activation of Rac GTPases through calmodulin. A PLC inhibitor (U73122) and an intracellular calcium chelator (BAPTA-AM) suppressed the histamine-induced activation of Rac, whereas the calcium ionophore ionomycin increased the active Rac GTPases, suggesting that intracellular calcium regulates the activation of Rac. The calmodulin antagonist (W-7) inhibited the histamine-induced activation of Rac and migration of mast cells, indicating that calmodulin mediates the effect of calcium. Inhibition of calcium/calmodulin signaling suppressed histamine-induced phosphorylation of Akt. The Akt inhibitor MK-2206 attenuated histamine-induced migration of mast cells. However, it did not suppress the activation of Rac GTPases. These results suggest that Rac GTPases and Akt play independent roles in the histamine-induced chemotaxis of mast cells. Our findings enable further elucidation of the molecular mechanism of histamine-induced chemotaxis of mast cells and help identify therapeutic targets for allergic and inflammatory conditions involving mast cell accumulation.

Opioid Receptor Regulation of Neuronal Voltage-Gated Calcium Channels

Neuronal voltage-gated calcium channels play a pivotal role in the conversion of electrical signals into calcium entry into nerve endings that is required for the release of neurotransmitters. They are under the control of a number of cellular signaling pathways that serve to fine tune synaptic activities, including G-protein coupled receptors (GPCRs) and the opioid system. Besides modulating channel activity via activation of second messengers, GPCRs also physically associate with calcium channels to regulate their function and expression at the plasma membrane. In this mini review, we discuss the mechanisms by which calcium channels are regulated by classical opioid and nociceptin receptors. We highlight the importance of this regulation in the control of neuronal functions and their implication in the development of disease conditions. Finally, we present recent literature concerning the use of novel μ-opioid receptor/nociceptin receptor modulators and discuss their use as potential drug candidates for the treatment of pain.

Bioactivity-guided isolation of immunomodulatory compounds from the fruits of Ligustrum lucidum

ETHNOPHARMACOLOGICAL RELEVANCE

The fruits of Ligustrum lucidum (FLL) W.T. Aiton (Oleaceae) is included in the 2020 "Chinese Pharmacopoeia" and is widely used in traditional Chinese medicine as a tonic. In recent years, FLL has been reported to improve immune function, but the bioactive compounds and mechanisms of FLL remain poorly characterized.

AIM OF THE STUDY

To identify FFL compounds with strong immune activity and explore their molecular mechanisms.

MATERIALS AND METHODS

The phagocytic activity of RAW264.7 macrophages and proliferation activity of spleen lymphocytes were used to guide the isolation of bioactive compounds from FLL extracts. Lymphocyte subpopulations, Ca²⁺ concentrations, and surface molecule expression were analyzed using flow cytometry. Cytokine secretion was examined using ELISA. FITC-OVA uptake was observed using fluorescence microscopy. NF-κB activation was analyzed using western blotting.

RESULTS

The extraction and isolation produced ten compounds, namely oleuropeinic acid, nuezhenide, isonuezhenide, salidroside, isoligustrosidic acid, ligulucidumosides A, 8(E)-nuezhenide, hydroxytyrosol, oleuropein, and p-hydroxyphenethyl 7-β-D-glucosideelenolic acid ester were isolated and identified from FLL-Bu-30%. Immunoactivity experiments showed that hydroxytyrosol had the strongest macrophage phagocytotic and lymphocyte proliferation-promoting activities. Further studies showed that hydroxytyrosol could significantly enhance lymphocyte subsets CD3⁺, CD4⁺/CD8⁺, and CD3⁺CD4^-CD8^-, promote IL-4, IFN-γ, and TNF-α secretion, and increase intracellular Ca²⁺ concentrations. In addition, the results from RAW264.7 macrophages showed that hydroxytyrosol increased FITC-OVA uptake, induced TNF-α and IL-1β production, upregulated MHC-II, CD80, and CD86 expression, promoted cytoplasmic IκB-α degradation, and increased nuclear NF-κB p65 levels.

CONCLUSION

Our study provides substantial evidence regarding the mechanism of the immunomodulatory effects of compounds from FLL.

Triiodothyronine maintains cardiac transverse-tubule structure and function

Subclinical hypothyroidism and low T3 syndrome are commonly associated with an increased risk of cardiovascular disease (CVD) and mortality. We examined effects of T3 on T-tubule (TT) structures, Ca²⁺ mobilization and contractility, and clustering of dyadic proteins. Thyroid hormone (TH) deficiency was induced in adult female rats by propyl-thiouracil (PTU; 0.025%) treatment for 8 weeks. Rats were then randomized to continued PTU or triiodo-L-thyronine (T3; 10 μg/kg/d) treatment for 2 weeks (PTU + T3). After in vivo echocardiographic and hemodynamic recordings, cardiomyocytes (CM) were isolated to record Ca²⁺ transients and contractility. TT organization was assessed by confocal microscopy, and STORM images were captured to measure ryanodine receptor (RyR2) cluster number and size, and L-type Ca²⁺ channel (LTCC, Ca_v1.2) co-localization. Expressed genes including two integral TT proteins, junctophilin-2 (Jph-2) and bridging integrator-1 (BIN1), were analyzed in left ventricular (LV) tissues and cultured CM using qPCR and RNA sequencing. The T3 dosage used normalized serum T3, and reversed adverse effects of TH deficiency on in vivo measures of cardiac function. Recordings of isolated CM indicated that T3 increased rates of Ca²⁺ release and re-uptake, resulting in increased velocities of sarcomere shortening and re-lengthening. TT periodicity was significantly decreased, with reduced transverse tubules but increased longitudinal tubules in TH-deficient CMs and LV tissue, and these structures were normalized by T3 treatment. Analysis of STORM data of PTU myocytes showed decreased RyR2 cluster numbers and RyR localizations within each cluster without significant changes in Ca_v1.2 localizations within RyR clusters. T3 treatment normalized RyR2 cluster size and number. qPCR and RNAseq analyses of LV and cultured CM showed that Jph2 expression was T3-responsive, and its increase with treatment may explain improved TT organization and RyR-LTCC coupling.

Dual Mode of Action of Acetylcholine on Cytosolic Calcium Oscillations in Pancreatic Beta and Acinar Cells In Situ

Cholinergic innervation in the pancreas controls both the release of digestive enzymes to support the intestinal digestion and absorption, as well as insulin release to promote nutrient use in the cells of the body. The effects of muscarinic receptor stimulation are described in detail for endocrine beta cells and exocrine acinar cells separately. Here we describe morphological and functional criteria to separate these two cell types in situ in tissue slices and simultaneously measure their response to ACh stimulation on cytosolic Ca2+ oscillations [Ca2+]c in stimulatory glucose conditions. Our results show that both cell types respond to glucose directly in the concentration range compatible with the glucose transporters they express. The physiological ACh concentration increases the frequency of glucose stimulated [Ca2+]c oscillations in both cell types and synchronizes [Ca2+]c oscillations in acinar cells. The supraphysiological ACh concentration further increases the oscillation frequency on the level of individual beta cells, inhibits the synchronization between these cells, and abolishes oscillatory activity in acinar cells. We discuss possible mechanisms leading to the observed phenomena.

Nimodipine inhibits intestinal and aortic smooth muscle contraction by regulating Ca2+-activated Cl- channels

Nimodipine is a clinically used dihydropyridine L-type calcium channel antagonist that effectively inhibits transmembrane Ca2+ influx following the depolarization of smooth muscle cells, but the detailed effect on smooth muscle contraction is not fully understood. Ca2+-activated Cl- channels (CaCCs) in vascular smooth muscle cells (VSMCs) may regulate vascular contractility. We found that nimodipine can inhibit transmembrane protein 16A (TMEM16A) activity in a concentration-dependent manner by cell-based fluorescence-quenching assay and short-circuit current analysis, with an IC50 value of ~5 μM. Short-circuit current analysis also showed that nimodipine prevented Ca2+-activated Cl- current in both HT-29 cells and mouse colonic epithelia accompanied by significantly decreased cytoplasmic Ca2+ concentrations. In the absence of extracellular Ca2+, nimodipine still exhibited an inhibitory effect on TMEM16A/CaCCs. Additionally, the application of nimodipine to CFTR-expressing FRT cells and mouse colonic mucosa resulted in mild activation of CFTR-mediated Cl- currents. Nimodipine inhibited basolateral CCh-activated K+ channel activity with no effect on Na+/K+-ATPase activity. Evaluation of intestinal smooth muscle contraction showed that nimodipine inhibits intestinal smooth muscle contractility and frequency, with an activity pattern that was similar to that of non-specific inhibitors of CaCCs. In aortic smooth muscle, the expression of TMEM16A in thoracic aorta is higher than that in abdominal aorta, corresponding to stronger maximum contractility in thoracic aorta smooth muscle stimulated by phenylephrine (PE) and Eact. Nimodipine completely inhibited the contraction of aortic smooth muscle stimulated by Eact, and partially inhibited the contraction stimulated by PE. In summary, the results indicate that nimodipine effectively inhibits TMEM16A/CaCCs by reduction transmembrane Ca2+ influx and directly interacting with TMEM16A, explaining the mechanisms of nimodipine relaxation of intestinal and aortic smooth muscle contraction and providing new targets for pharmacological applications.

Transient Receptor Potential C 1/4/5 Is a Determinant of MTI-101 Induced Calcium Influx and Cell Death in Multiple Myeloma

Multiple myeloma (MM) is a currently incurable hematologic cancer. Patients that initially respond to therapeutic intervention eventually relapse with drug resistant disease. Thus, novel treatment strategies are critically needed to improve patient outcomes. Our group has developed a novel cyclic peptide referred to as MTI-101 for the treatment of MM. We previously reported that acquired resistance to HYD-1, the linear form of MTI-101, correlated with the repression of genes involved in store operated Ca²⁺ entry (SOCE): PLCβ, SERCA, ITPR3, and TRPC1 expression. In this study, we sought to determine the role of TRPC1 heteromers in mediating MTI-101 induced cationic flux. Our data indicate that, consistent with the activation of TRPC heteromers, MTI-101 treatment induced Ca²⁺ and Na⁺ influx. However, replacing extracellular Na⁺ with NMDG did not reduce MTI-101-induced cell death. In contrast, decreasing extracellular Ca²⁺ reduced both MTI-101-induced Ca²⁺ influx as well as cell death. The causative role of TRPC heteromers was established by suppressing STIM1, TRPC1, TRPC4, or TRPC5 function both pharmacologically and by siRNA, resulting in a reduction in MTI-101-induced Ca²⁺ influx. Mechanistically, MTI-101 treatment induces trafficking of TRPC1 to the membrane and co-immunoprecipitation studies indicate that MTI-101 treatment induces a TRPC1-STIM1 complex. Moreover, treatment with calpeptin inhibited MTI-101-induced Ca²⁺ influx and cell death, indicating a role of calpain in the mechanism of MTI-101-induced cytotoxicity. Finally, components of the SOCE pathway were found to be poor prognostic indicators among MM patients, suggesting that this pathway is attractive for the treatment of MM.

Activation of L-type calcium channels and attenuation of oxidative stress are involved in the improving effect of methyl jasmonate on learning and memory and its anxiolytic property in rats

The present study was designed to evaluate the effect of plant bioactive compound methyl jasmonate on learning and memory, anxiety-like behaviors, and brain oxidative stress in rats. It has been indicated that methyl jasmonate stimulates calcium-binding protein expression and increases intracellular calcium (Ca2+). Therefore, we investigated the potential role of L-type calcium channel on methyl jasmonate effects. The animals were intracerebroventriculary (i.c.v.) injected with different doses of methyl jasmonate (0.5, 2.5, and 5 µg/rat). L-type calcium channel blocker (nifedipine 5 µg/rat, i.c.v.) was injected 30 min before methyl jasmonate (5 µg/rat). Shuttle box apparatus was used to evaluate passive avoidance memory. Anxiety-like behaviors were assessed by open field and elevated plus maze tests. Lastly, oxidative stress-related indices were assessed in hippocampus and prefrontal cortex. The data showed that methyl jasmonate dose-dependently could improve passive avoidance learning and memory and reduce anxiogenic behaviors. The methyl jasmonate effects were significantly prevented by nifedipine. Furthermore, central microinjection of methyl jasmonate significantly decreased hydrogen peroxide concentration, and increased reactive oxygen species scavenger activity (catalase and peroxide enzymes) in rats' hippocampus as well as prefrontal cortex. Indeed, the results indicated that the beneficial effects of methyl jasmonate on learning and memory and anxiety might be partly associated with L-type calcium channel and partly on the inhibition of oxidant indices.

Differential inhibitory effects of resveratrol on excitotoxicity and synaptic plasticity: involvement of NMDA receptor subtypes

Objectives: The neuroprotective effects of resveratrol against excitatory neurotoxicity have been associated with N-methyl-D-aspartate receptor (NMDAR) inhibition. This study examined the differential inhibitory effects of resveratrol on NMDAR-mediated responses in neuronal cells with different NMDAR subtype composition.Methods: The effects of resveratrol on NMDA-induced cell death and calcium influx in immature and mature rat primary cortical neurons were determined and compared. Moreover, the potencies and efficacies of resveratrol to inhibit NR1/NR2A, NR1/NR2B, NR1/NR2C, and NR1/NR2D NMDAR expressed in HEK 293 cells were evaluated.Results: Resveratrol significantly attenuated NMDA-induced cell death in mature neurons, but not in immature neurons. Resveratrol also concentration-dependently reduced NMDA-induced calcium influx among all NMDAR subtypes, but displayed NR2 subunit selectivity, with a potency rank order of NR2B = NR2D > NR2A = NR2C and an efficacy rank order of NR2B = NR2C > NR2A = NR2D. Data show the stronger inhibitory effects of resveratrol on NR1/NR2B than other subtypes. Moreover, resveratrol did not affect hippocampal long-term potentiation (LTP), but impaired long-term depression (LTD).Discussion: These findings reveal the specific NMDAR modulating profile of resveratrol, providing further insight into potential mechanisms underlying the protective effects of resveratrol on neurological disorders.

Drugs that inhibit TMEM16 proteins block SARS-CoV-2 spike-induced syncytia

COVID-19 is a disease with unique characteristics that include lung thrombosis1, frequent diarrhoea2, abnormal activation of the inflammatory response3 and rapid deterioration of lung function consistent with alveolar oedema4. The pathological substrate for these findings remains unknown. Here we show that the lungs of patients with COVID-19 contain infected pneumocytes with abnormal morphology and frequent multinucleation. The generation of these syncytia results from activation of the SARS-CoV-2 spike protein at the cell plasma membrane level. On the basis of these observations, we performed two high-content microscopy-based screenings with more than 3,000 approved drugs to search for inhibitors of spike-driven syncytia. We converged on the identification of 83 drugs that inhibited spike-mediated cell fusion, several of which belonged to defined pharmacological classes. We focused our attention on effective drugs that also protected against virus replication and associated cytopathicity. One of the most effective molecules was the antihelminthic drug niclosamide, which markedly blunted calcium oscillations and membrane conductance in spike-expressing cells by suppressing the activity of TMEM16F (also known as anoctamin 6), a calcium-activated ion channel and scramblase that is responsible for exposure of phosphatidylserine on the cell surface. These findings suggest a potential mechanism for COVID-19 disease pathogenesis and support the repurposing of niclosamide for therapy.

Generation of GCaMP6s-Expressing Zebrafish to Monitor Spatiotemporal Dynamics of Calcium Signaling Elicited by Heat Stress

The ability of organisms to quickly sense and transduce signals of environmental stresses is critical for their survival. Ca²⁺ is a versatile intracellular messenger involved in sensing a wide variety of stresses and regulating the subsequent cellular responses. So far, our understanding for calcium signaling was mostly obtained from ex vivo tissues and cultured cell lines, and the in vivo spatiotemporal dynamics of stress-triggered calcium signaling in a vertebrate remains to be characterized. Here, we describe the generation and characterization of a transgenic zebrafish line with ubiquitous expression of GCaMP6s, a genetically encoded calcium indicator (GECI). We developed a method to investigate the spatiotemporal patterns of Ca²⁺ events induced by heat stress. Exposure to heat stress elicited immediate and transient calcium signaling in developing zebrafish. Cells extensively distributed in the integument of the head and body trunk were the first batch of responders and different cell populations demonstrated distinct response patterns upon heat stress. Activity of the heat stress-induced calcium signaling peaked at 30 s and swiftly decreased to near the basal level at 120 s after the beginning of exposure. Inhibition of the heat-induced calcium signaling by LaCl₃ and capsazepine and treatment with the inhibitors for CaMKII (Ca²²/calmodulin-dependent protein kinase II) and HSF1 (Heat shock factor 1) all significantly depressed the enhanced heat shock response (HSR). Together, we delineated the spatiotemporal dynamics of heat-induced calcium signaling and confirmed functions of the Ca²⁺-CaMKII-HSF1 pathway in regulating the HSR in zebrafish.

The Role of G Protein-Coupled Receptors (GPCRs) and Calcium Signaling in Schizophrenia. Focus on GPCRs Activated by Neurotransmitters and Chemokines

Schizophrenia is a common debilitating disease characterized by continuous or relapsing episodes of psychosis. Although the molecular mechanisms underlying this psychiatric illness remain incompletely understood, a growing body of clinical, pharmacological, and genetic evidence suggests that G protein-coupled receptors (GPCRs) play a critical role in disease development, progression, and treatment. This pivotal role is further highlighted by the fact that GPCRs are the most common targets for antipsychotic drugs. The GPCRs activation evokes slow synaptic transmission through several downstream pathways, many of them engaging intracellular Ca²⁺ mobilization. Dysfunctions of the neurotransmitter systems involving the action of GPCRs in the frontal and limbic-related regions are likely to underly the complex picture that includes the whole spectrum of positive and negative schizophrenia symptoms. Therefore, the progress in our understanding of GPCRs function in the control of brain cognitive functions is expected to open new avenues for selective drug development. In this paper, we review and synthesize the recent data regarding the contribution of neurotransmitter-GPCRs signaling to schizophrenia symptomology.