Melatonin alters the excitability of mouse cerebellar granule neurons by inhibiting voltage-gated sodium, potassium, and calcium channels.

Besides its role in the circadian rhythm, the pineal gland hormone melatonin (MLT) also possesses antiepileptogenic, antineoplastic, and cardioprotective properties, among others. The dosages necessary to elicit beneficial effects in these diseases often far surpass physiological concentrations. Although even high doses of MLT are considered to be largely harmless to humans, the possible side effects of pharmacological concentrations are so far not well investigated. In the present study, we report that pharmacological doses of MLT (3 mM) strongly altered the electrophysiological characteristics of cultured primary mouse cerebellar granule cells (CGCs). Using whole-cell patch clamp and ratiometric Ca2+ imaging, we observed that pharmacological concentrations of MLT inhibited several types of voltage-gated Na+ , K+ , and Ca2+ channels in CGCs independently of known MLT-receptors, altering the character and pattern of elicited action potentials (APs) significantly, quickly and reversibly. Specifically, MLT reduced AP frequency, afterhyperpolarization, and rheobase, whereas AP amplitude and threshold potential remained unchanged. The altered biophysical profile of the cells could constitute a possible mechanism underlying the proposed beneficial effects of MLT in brain-related disorders, such as epilepsy. On the other hand, it suggests potential adverse effects of pharmacological MLT concentrations on neurons, which should be considered when using MLT as a pharmacological compound.

Modeling of Calcium-dependent Low Intensity Low Frequency Ultrasound Modulation of a Hodgkin-Huxley Neuron.

Non-invasive low intensity, low frequency ultrasound is a progressive neuromodulation approach that can reach deep brain areas with peak spatial and temporal resolution for highly-targeted diagnostic and therapeutic purposes. Coupling the ultrasound mechanical effects to the neural membrane comprises different mechanisms that are, to-date, still a topic of debate. The availability of calcium ions in the extracellular medium is of high significance when it comes to the effect of ultrasound on the neural tissue. Whereby the generated calcium influx can directly affect the voltage-gated ion channels, amplifying their action. We modeled the flexoelectric-induced effects of ultrasound to a single firing neuron, taking into consideration the effect of calcium channel embedding into the neural membrane on the neuron's firing rate, latency response, peak-to-peak voltage, and general shape of the action potential.Clinical Relevance- Upon Ultrasound sonication, the mechanical waves interact with the neural membrane and alter the kinetics of the calcium channels, thus changing the neural response.

Hipertensión pulmonar: señalización mediada por canales de calcio, dianas farmacológicas presentes y futuras / Pulmonary hypertension: calcium channel-mediated signaling, present and future pharmacological targets

La hipertensión arterial pulmonar se caracteriza por una presión arterial pulmonar media y resistencia vascular pulmonar elevadas y remodelado patológico de las arterias pulmonares. La entrada de calcio desde el espacio extracelular al intracelular a través de canales dependientes e independientes de voltaje juega un rol fundamental en el aumento de la contractilidad de las arterias pulmonares y la pérdida de regulación del comportamiento proliferativo de las células de las distintas capas de la pared de las arterias pulmonares. De esta manera, estos canales contribuyen con la vasoconstricción exacerbada de las arterias pulmonares y a su remodelado patológico. El objetivo de esta revisión es recapitular la evidencia obtenida desde modelos celulares y animales respecto a la contribución de los principales canales de calcio de membrana plasmática en estos mecanismos fisiopatológicos claves en el desarrollo de la hipertensión pulmonar, discutiendo su valor potencial como diana farmacológica para terapias presentes y futuras.

Pulmonary arterial hypertension is characterized by increased mean pulmonary arterial pressure, resistance, and pathological remodeling of pulmonary arteries. Calcium entry from the extracellular to the intracellular space through voltage-dependent and -independent channels play a major role in the increase of contractility of pulmonary arteries and in the loss of regulation of the proliferative behavior of the cells from the different layers of the pulmonary arterial wall. In doing so, these channels contribute to enhanced vasoconstriction of pulmonary arteries and their pathological remodeling. This review aims to summarize the evidence obtained from animal and cellular models regarding the involvement of the main plasma membrane calcium channels in these key pathophysiological processes for pulmonary arterial hypertension, discussing the potential value as pharmacological targets for therapies in the present and the future.

Millimeter (MM) wave and microwave frequency radiation produce deeply penetrating effects: the biology and the physics.

Millimeter wave (MM-wave) electromagnetic fields (EMFs) are predicted to not produce penetrating effects in the body. The electric but not magnetic part of MM-EMFs are almost completely absorbed within the outer 1 mm of the body. Rodents are reported to have penetrating MM-wave impacts on the brain, the myocardium, liver, kidney and bone marrow. MM-waves produce electromagnetic sensitivity-like changes in rodent, frog and skate tissues. In humans, MM-waves have penetrating effects including impacts on the brain, producing EEG changes and other neurological/neuropsychiatric changes, increases in apparent electromagnetic hypersensitivity and produce changes on ulcers and cardiac activity. This review focuses on several issues required to understand penetrating effects of MM-waves and microwaves: 1. Electronically generated EMFs are coherent, producing much higher electrical and magnetic forces then do natural incoherent EMFs. 2. The fixed relationship between electrical and magnetic fields found in EMFs in a vacuum or highly permeable medium such as air, predicted by Maxwell's equations, breaks down in other materials. Specifically, MM-wave electrical fields are almost completely absorbed in the outer 1 mm of the body due to the high dielectric constant of biological aqueous phases. However, the magnetic fields are very highly penetrating. 3. Time-varying magnetic fields have central roles in producing highly penetrating effects. The primary mechanism of EMF action is voltage-gated calcium channel (VGCC) activation with the EMFs acting via their forces on the voltage sensor, rather than by depolarization of the plasma membrane. Two distinct mechanisms, an indirect and a direct mechanism, are consistent with and predicted by the physics, to explain penetrating MM-wave VGCC activation via the voltage sensor. Time-varying coherent magnetic fields, as predicted by the Maxwell-Faraday version of Faraday's law of induction, can put forces on ions dissolved in aqueous phases deep within the body, regenerating coherent electric fields which activate the VGCC voltage sensor. In addition, time-varying magnetic fields can directly put forces on the 20 charges in the VGCC voltage sensor. There are three very important findings here which are rarely recognized in the EMF scientific literature: coherence of electronically generated EMFs; the key role of time-varying magnetic fields in generating highly penetrating effects; the key role of both modulating and pure EMF pulses in greatly increasing very short term high level time-variation of magnetic and electric fields. It is probable that genuine safety guidelines must keep nanosecond timescale-variation of coherent electric and magnetic fields below some maximum level in order to produce genuine safety. These findings have important implications with regard to 5G radiation.

Mutations That Affect the Surface Expression of TRPV6 Are Associated with the Upregulation of Serine Proteases in the Placenta of an Infant.

Recently, we reported a case of an infant with neonatal severe under-mineralizing skeletal dysplasia caused by mutations within both alleles of the TRPV6 gene. One mutation results in an in frame stop codon (R510stop) that leads to a truncated, nonfunctional TRPV6 channel, and the second in a point mutation (G660R) that, surprisingly, does not affect the Ca2+ permeability of TRPV6. We mimicked the subunit composition of the unaffected heterozygous parent and child by coexpressing the TRPV6 G660R and R510stop mutants and combinations with wild type TRPV6. We show that both the G660R and R510stop mutant subunits are expressed and result in decreased calcium uptake, which is the result of the reduced abundancy of functional TRPV6 channels within the plasma membrane. We compared the proteomic profiles of a healthy placenta with that of the diseased infant and detected, exclusively in the latter two proteases, HTRA1 and cathepsin G. Our results implicate that the combination of the two mutant TRPV6 subunits, which are expressed in the placenta of the diseased child, is responsible for the decreased calcium uptake, which could explain the skeletal dysplasia. In addition, placental calcium deficiency also appears to be associated with an increase in the expression of proteases.

Key Signaling Pathways Regulate the Development and Survival of Auditory Hair Cells.

The loss of auditory sensory hair cells (HCs) is the most common cause of sensorineural hearing loss (SNHL). As the main sound transmission structure in the cochlea, it is necessary to maintain the normal shape and survival of HCs. In this review, we described and summarized the signaling pathways that regulate the development and survival of auditory HCs in SNHL. The role of the mitogen-activated protein kinase (MAPK), phosphoinositide-3 kinase/protein kinase B (PI3K/Akt), Notch/Wnt/Atoh1, calcium channels, and oxidative stress/reactive oxygen species (ROS) signaling pathways are the most relevant. The molecular interactions of these signaling pathways play an important role in the survival of HCs, which may provide a theoretical basis and possible therapeutic interventions for the treatment of hearing loss.

Inward Ca2+ current through the polycystin-2-dependent channels of renal primary cilia.

In 15% of cases, autosomal dominant polycystic kidney disease arises from defects in polycystin-2 (PC2). PC2 is a member of the polycystin transient receptor potential subfamily of cation-conducting channels and is expressed in the endoplasmic reticulum and primary cilium of renal epithelial cells. PC2 opposes a procystogenic influence of the cilium, and it has been proposed that this beneficial effect is mediated in part by a flow of Ca2+ through PC2 channels into the primary cilium. However, previous efforts to determine the permeability of PC2 channels to Ca2+ have yielded widely varying results. Here, we report the mean macroscopic Ca2+ influx through native PC2 channels in the primary cilia of mIMCD-3 cells, which are derived from the murine inner medullary collecting duct. Under conditions designed to isolate inward Ca2+ currents, a small inward Ca2+ current was detected in cilia with active PC2 channels but not in cilia lacking those channels. The current was activated by the addition of 10 µM internal Ca2+, which is known to activate ciliary PC2 channels. It was blocked by 10 µM isosakuranetin, which blocks the same channels. On average, the current amplitude was -1.8 pA at -190 mV; its conductance from -50 to -200 mV averaged 20 pS. Thus, native PC2 channels of renal primary cilia are able to conduct a small but detectable Ca2+ influx under the conditions tested. The possible consequences of this influx are discussed.NEW & NOTEWORTHY In autosomal dominant polycystic kidney disease, it is proposed that Ca2+ entering the primary cilium through polycystin-2 (PC2) channels may limit the formation of cysts. Recent studies predict that any macroscopic Ca2+ influx through these channels should be small. We report that the native PC2 channels in primary cilia of cultured renal epithelial cells can allow a small macroscopic calcium influx. This may allow a significant accumulation of Ca2+ in the cilium in vivo.

Exploring the Ion Channel TRPV2 and Testicular Macrophages in Mouse Testis.

The cation channel TRPV2 is known to be expressed by murine macrophages and is crucially involved in their functionality. Macrophages are frequent cells of the mouse testis, an immune-privileged and steroid-producing organ. TRPV2 expression by testicular macrophages and possible changes associated with age or inflammation have not been investigated yet. Therefore, we studied testes of young adult and old wild-type (WT) and AROM+ mice, i.e., transgenic mice overexpressing aromatase. In these animals, inflammatory changes are described in the testis, involving active macrophages, which increase with age. This is associated with impaired spermatogenesis and therefore AROM+ mice are a model for male infertility associated with sterile inflammation. In WT animals, testicular TRPV2 expression was mapped to interstitial CD206+ and peritubular MHC II+ macrophages, with higher levels in CD206+ cells. Expression levels of TRPV2 and most macrophage markers did not increase significantly in old mice, with the exception of CD206. As the number of TRPV2+ testicular macrophages was relatively small, their possible involvement in testicular functions and in aging in WT mice remains to be further studied. In AROM+ testis, TRPV2 was readily detected and levels increased significantly with age, together with macrophage markers and TNF-α. TRPV2 co-localized with F4/80 in macrophages and further studies showed that TRPV2 is mainly expressed by unusual CD206+MHC II+ macrophages, arising in the testis of these animals. Rescue experiments (aromatase inhibitor treatment and crossing with ERαKO mice) restored the testicular phenotype and also abolished the elevated expression of TRPV2, macrophage and inflammation markers. This suggests that TRPV2+ macrophages of the testis are part of an inflammatory cascade initiated by an altered sex hormone balance in AROM+ mice. The changes in testis are distinct from the described alterations in other organs of AROM+, such as prostate and spleen. When we monitored TRPV2 levels in another immune-privileged organ, namely the brain, we found that levels of TRPV2 were not elevated in AROM+ and remained stable during aging. In the adrenal, which similar to the testis produces steroids, we found slight, albeit not significant increases in TRPV2 in both AROM+ and WT mice, which were associated with age. Thus, the changes in the testis are specific for this organ.

Vasorelaxant property of Plectranthus vettiveroides root essential oil and its possible mechanism.

ETHNOPHARMACOLOGICAL RELEVANCE: Plectranthus vettiveroides (Jacob) N.P. Singh & B.D. Sharma is a traditional medicinal plant used in Siddha System of Medicine and its aromatic root is used to reduce the elevated blood pressure. AIM: The aim of the present study was to study vasorelaxant property of the root essential oil nanoemulsion (EON) of P. vettiveroides. METHODS: The EON was formulated to enhance the solubility and bioavailability and characterized. The preliminary screening was performed by treating the EON with aortic rings pre-contracted with phenylephrine (1 µM) and potassium chloride (80 mM). The role of K⁺ channels in EON induced vasorelaxation was investigated by pre-incubating the aortic rings with different K⁺ channel inhibitors namely, glibenclamide (a non-specific ATP sensitive K⁺ channel blocker, 10 µM), TEA (a Ca2⁺ activated non-selective K⁺ channel blocker, 10-2 M), 4-AP (a voltage-activated K⁺ channel blocker, 10-3 M) and barium chloride (inward rectifier K⁺ channel blocker, 1 mM). The involvement of extracellular Ca2+ was performed by adding cumulative dose of extracellular calcium in the presence and absence of EON and the concentration-response curve (CRC) obtained is compared. Similarly, the role of nitric oxide synthase, muscarinic and prostacyclin receptors on EON induced vasorelaxation were evaluated by pre-incubating the aortic rings with their inhibitors and the CRC obtained in the presence and absence of inhibitor were compared. RESULTS: The GC-MS and GC-FID analyses of the root essential oil revealed the presence of 62 volatile compounds. The EON exhibited significant vasorelaxant effect through nitric oxide-mediated pathway, G-protein coupled muscarinic (M3) receptor pathway, involvement of K+ channels (KATP, KIR, KCa), and blocking of the calcium influx by receptor-operated calcium channel. CONCLUSION: It is concluded that the root essential oil of P. vettiveroides is possessing marked vasorelaxant property. The multiple mechanisms of action of the essential oil of P. vettiveroides make it a potential source of antihypertensive drug.

Pharmacological basis of the anxiolytic and antidepressant properties of Silexan®, an essential oil from the flowers of lavender.

Silexan®, a proprietary essential oil manufactured by steam distillation from Lavandula angustifolia flowers showed pronounced anxiolytic effects in patients with subthreshold anxiety disorders and was also efficacious in patients with Generalized Anxiety disorder (GAD). Moreover, evidences for antidepressant-like properties of Silexan® have been observed in anxious patients suffering from comorbid depressive symptoms and in patients with mixed anxiety-depression disorder (ICD-10 F41.2). In accordance with the clinical data Silexan® is active in several behavioral models in rodents at rather low concentrations indicating potent anxiolytic and antidepressive properties. As possible mechanism of action a moderate inhibition of voltage dependent calcium channels (VDCC) has been found showing some similarities to the anxiolytic drug pregabalin. However, while pregabalin mainly inhibits P/Q-type channels by binding to a modulatory subunit, Silexan® moderately inhibits mainly T-type and N-type channels and to some extent P/Q-type channels. Unlike pregabalin Silexan® is free of hypnotic or sedative side effects and seems to be devoid of any abuse potential. With respect to its specific antidepressant like properties Silexan® improves several aspects of neuroplasticity which seems to be the common final pathway of all antidepressant drugs. As a potential mechanism of its effects on neuroplasticity an activation of the transcription factor CREB via activation of intracellular signaling kinases like PKA and MAPK has been found. Since the concentrations of Silexan® needed to inhibit VDCC function and to improve neuroplasticity are quite similar, the effects of Silexan® on PKA or MAPK could constitute a common intracellular signaling cascade leading to VDCC modulation as well as CREB activation and improved neuroplasticity.

Proteotranscriptomic Insights into the Venom Composition of the Wolf Spider Lycosa tarantula.

Spider venoms represent an original source of novel compounds with therapeutic and agrochemical potential. Whereas most of the research efforts have focused on large mygalomorph spiders, araneomorph spiders are equally promising but require more sensitive and sophisticated approaches given their limited size and reduced venom yield. Belonging to the latter group, the genus Lycosa ("wolf spiders") contains many species widely distributed throughout the world. These spiders are ambush predators that do not build webs but instead rely strongly on their venom for prey capture. Lycosa tarantula is one of the largest species of wolf spider, but its venom composition is unknown. Using a combination of RNA sequencing of the venom glands and venom proteomics, we provide the first overview of the peptides and proteins produced by this iconic Mediterranean spider. Beside the typical small disulfide rich neurotoxins, several families of proteins were also identified, including cysteine-rich secretory proteins (CRISP) and Hyaluronidases. Proteomic analysis of the electrically stimulated venom validated 30 of these transcriptomic sequences, including nine putative neurotoxins and eight venom proteins. Interestingly, LC-MS venom profiles of manual versus electric stimulation, as well as female versus male, showed some marked differences in mass distribution. Finally, we also present some preliminary data on the biological activity of L. tarantula crude venom.

Relaxant Effect of Monoterpene (-)-Carveol on Isolated Human Umbilical Cord Arteries and the Involvement of Ion Channels.

Carveol is a monoterpene present in the structure of many plant products. It has a variety of biological activities: antioxidant, anticancer and vasorelaxation. However, studies investigating the effect of monoterpenoids on human vessels have not yet been described. Thus, the present study aimed to characterize the effect of (-)-carveol on human umbilical arteries (HUAs). HUA ring preparations were isolated and subjected to isometric tension recordings of umbilical artery smooth muscle contractions. (-)-Carveol exhibited a significant vasorelaxant effect on KCl and 5-HT-induced contractions, obtaining EC50 values of 344.25 ± 8.4 and 175.82 ± 4.05 µM, respectively. The participation of calcium channels in the relaxation produced by (-)-carveol was analyzed using vessels pre-incubated with (-)-carveol (2000 µM) in a calcium-free medium, where the induction of contractions was abolished. The vasorelaxant effect of (-)-carveol on HUAs was reduced by tetraethylammonium (TEA), which increased the (-)-carveol EC50 to 484.87 ± 6.55 µM. The present study revealed that (-)-carveol possesses a vasorelaxant activity in HUAs, which was dependent on the opening of calcium and potassium channels. These results pave the way for further studies involving the use of monoterpenoids for the vasodilatation of HUAs. These molecules have the potential to treat diseases such as pre-eclampsia, which is characterized by resistance in umbilical arteries.

Role of Two-Pore Channels in Embryonic Development and Cellular Differentiation.

Since the identification of nicotinic acid adenine dinucleotide phosphate (NAADP) and its putative target, the two-pore channel (TPC), the NAADP/TPC/Ca2+ signaling pathway has been reported to play a role in a diverse range of functions in a variety of different cell types. TPCs have also been associated with a number of diseases, which arise when their activity is perturbed. In addition, TPCs have been shown to play key roles in various embryological processes and during the differentiation of a variety of cell types. Here, we review the role of NAADP/TPC/Ca2+ signaling during early embryonic development and cellular differentiation. We pay particular attention to the role of TPC2 in the development and maturation of early neuromuscular activity in zebrafish, and during the differentiation of isolated osteoclasts, endothelial cells, and keratinocytes. Our aim is to emphasize the conserved features of TPC-mediated Ca2+ signaling in a number of selected examples.

Vasorelaxation elicited by endogenous and exogenous hydrogen sulfide in mouse mesenteric arteries.

H2S causes vasorelaxation however there is considerable heterogeneity in the reported pharmacological mechanism of this effect. This study examines the contribution of endogenously released H2S in the regulation of vascular tone and the mechanism of H2S-induced vasorelaxation in small resistance-like arteries. Mesenteric arteries from C57 and eNOS-/- mice were mounted in myographs to record isometric force. Vasorelaxation responses to NaHS were examined in the presence of various inhibitors of vasorelaxation pathways. Expression and activity of the H2S-producing enzyme, cystathionine-γ-lyase (CSE), were also examined. CSE was expressed in vascular smooth muscle and perivascular adipose cells from mouse mesenteric artery. The substrate for CSE, L-cysteine, caused a modest vasorelaxation (35%) in arteries from C57 mice and poor vasorelaxation (10%) in arteries from eNOS-/- mice that was sensitive to the CSE inhibitor DL-propargylglycine. The fast H2S donor, NaHS, elicited a full and biphasic vasorelaxation response in mesenteric arteries (EC50 (1) 8.7 µM, EC50 (2) 0.6 mM), which was significantly inhibited in eNOS-/- vessels (P < 0.05), unaffected by endothelial removal, or blockers at any point in the NO via soluble guanylate cyclase and cGMP (NO-sGC-cGMP) vasorelaxation pathway. Vasorelaxation to NaHS was significantly inhibited by blocking K+ channels of the KCa and KV subtypes and the Cl-/HCO3- exchanger (P < 0.05). Further experiments showed that NaHS can significantly inhibit voltage-gated Ca2+ channel function (P < 0.05). The vasorelaxant effect of H2S in small resistance-like arteries is complex, involving eNOS, K+ channels, Cl-/HCO3- exchanger, and voltage-gated Ca2+ channels. CSE is present in the smooth muscle and periadventitial adipose tissue of these resistance-like vessels and can be activated to cause modest vasorelaxation under these in vitro conditions.

Lipid-gated monovalent ion fluxes regulate endocytic traffic and support immune surveillance.

Despite ongoing (macro)pinocytosis of extracellular fluid, the volume of the endocytic pathway remains unchanged. To investigate the underlying mechanism, we used high-resolution video imaging to analyze the fate of macropinosomes formed by macrophages in vitro and in situ. Na+, the primary cationic osmolyte internalized, exited endocytic vacuoles via two-pore channels, accompanied by parallel efflux of Cl- and osmotically coupled water. The resulting shrinkage caused crenation of the membrane, which fostered recruitment of curvature-sensing proteins. These proteins stabilized tubules and promoted their elongation, driving vacuolar remodeling, receptor recycling, and resolution of the organelles. Failure to resolve internalized fluid impairs the tissue surveillance activity of resident macrophages. Thus, osmotically driven increases in the surface-to-volume ratio of endomembranes promote traffic between compartments and help to ensure tissue homeostasis.

Pathogenic roles of altered calcium channels and transporters in colon tumorogenesis.

Cytosolic calcium [Ca2+]cyt signaling plays a critical role in the regulation of multiple cellular functions, and Ca2+ channels/transporters are important to regulate calcium homeostasis whose abnormality may contribute human tumorogenesis including colorectal cancer (CRC). In this review, we summarized and discussed the current knowledge on pathogenic roles of the altered [Ca2+]cyt and Ca2+ channels/transporters like SOCE, TRP channels, SERCA and Na+/Ca2+ exchangers in CRC tumorigenesis and progression. Understanding the detailed molecular mechanisms underlying the effects of [Ca2+]cyt on CRC is essential to develop Ca2+ channels/transporters as diagnostic and therapeutic targets. Targeting Ca2+ signaling for cancer therapy has become an emerging research area nowadays, although our knowledge about the roles of Ca2+ channels/transporters in tumorigenesis is still in the early stage, we still believe that they will act as novel preventive/therapeutic targets for CRC with potentially extensive clinical significance.

Intercalated Cells of the Kidney Collecting Duct in Kidney Physiology.

The epithelium of the kidney collecting duct (CD) is composed mainly of two different types of cells with distinct and complementary functions. CD principal cells traditionally have been considered to have a major role in Na+ and water regulation, while intercalated cells (ICs) were thought to largely modulate acid-base homeostasis. In recent years, our understanding of IC function has improved significantly owing to new research findings. Thus, we now have a new model for CD transport that integrates mechanisms of salt and water reabsorption, K+ homeostasis, and acid-base status between principal cells and ICs. There are three main types of ICs (type A, type B, and non-A, non-B), which first appear in the late distal convoluted tubule or in the connecting segment in a species-dependent manner. ICs can be detected in CD from cortex to the initial part of the inner medulla, although some transport proteins that are key components of ICs also are present in medullary CD, cells considered inner medullary. Of the three types of ICs, each has a distinct morphology and expresses different complements of membrane transport proteins that translate into very different functions in homeostasis and contributions to CD luminal pro-urine composition. This review includes recent discoveries in IC intracellular and paracrine signaling that contributes to acid-base regulation as well as Na+, Cl-, K+, and Ca2+ homeostasis. Thus, these new findings highlight the potential role of ICs as targets for potential hypertension treatments.

Bronchial Epithelial Calcium Metabolism Impairment in Smokers and Chronic Obstructive Pulmonary Disease. Decreased ORAI3 Signaling.

The airway epithelium represents a fragile environmental interface potentially disturbed by cigarette smoke (CS), the major risk factor for developing chronic obstructive pulmonary disease (COPD). CS leads to bronchial epithelial damage on ciliated, goblet, and club cells, which could involve calcium (Ca2+) signaling. Ca2+ is a key messenger involved in virtually all fundamental physiological functions, including mucus and cytokine secretion, cilia beating, and epithelial repair. In this study, we analyzed Ca2+ signaling in air-liquid interface-reconstituted bronchial epithelium from control subjects and smokers (with and without COPD). We further aimed to determine how smoking impaired Ca2+ signaling. First, we showed that the endoplasmic reticulum (ER) depletion of Ca2+ stores was decreased in patients with COPD and that the Ca2+ influx was decreased in epithelial cells from smokers (regardless of COPD status). In addition, acute CS exposure led to a decrease in ER Ca2+ release, significant in smoker subjects, and to a decrease in Ca2+ influx only in control subjects. Furthermore, the differential expression of 55 genes involved in Ca2+ signaling highlighted that only ORAI3 expression was significantly altered in smokers (regardless of COPD status). Finally, we incubated epithelial cells with an ORAI antagonist (GSK-7975A). GSK-7975A altered Ca2+ influx and ciliary beating, but not mucus and cytokine secretion or epithelial repair, in control subjects. Our data suggest that Ca2+ signaling is impaired in smoker epithelia (regardless of COPD status) and involves ORAI3. Moreover, ORAI3 is additionally involved in ciliary beating.

Mitochondrial calcium uniporter complex modulation in cancerogenesis.

Aberrations in mitochondrial Ca2+ homeostasis have been associated with different pathological conditions, including neurological defects, cardiovascular diseases, and, in the last years, cancer. With the recent molecular identification of the mitochondrial calcium uniporter (MCU) complex, the channel that allows Ca2+ accumulation into the mitochondrial matrix, alterations in the expression levels or functioning in one or more MCU complex members have been linked to different cancers and cancer-related phenotypes. In this review, we will analyze the role of the uniporter and mitochondrial Ca2+ derangements in modulating cancer cell sensitivity to death, invasiveness, and migratory capacity, as well as cancer progression in vivo. We will also discuss some critical points and contradictory results to highlight the consequence of MCU complex modulation in tumor development.

AMPK-mediated activation of MCU stimulates mitochondrial Ca2+ entry to promote mitotic progression.

The capacity of cells to alter bioenergetics in response to the demands of various biological processes is essential for normal physiology. The coordination of energy sensing and production with highly energy-demanding cellular processes, such as cell division, is poorly understood. Here, we show that a cell cycle-dependent mitochondrial Ca2+ transient connects energy sensing to mitochondrial activity for mitotic progression. The mitochondrial Ca2+ uniporter (MCU) mediates a rapid mitochondrial Ca2+ transient during mitosis. Inhibition of mitochondrial Ca2+ transients via MCU depletion causes spindle checkpoint-dependent mitotic delay. Cellular ATP levels drop during early mitosis, and the mitochondrial Ca2+ transients boost mitochondrial respiration to restore energy homeostasis. This is achieved through mitosis-specific MCU phosphorylation and activation by the mitochondrial translocation of energy sensor AMP-activated protein kinase (AMPK). Our results establish a critical role for AMPK- and MCU-dependent mitochondrial Ca2+ signalling in mitosis and reveal a mechanism of mitochondrial metabolic adaptation to acute cellular energy stress.