Molecular and pharmacological modulation of CALHM1 promote neuroprotection against oxygen and glucose deprivation in a model of hippocampal slices

Calcium homeostasis modulator 1 (CALHM1) is a calcium channel involved in the regulation of cytosolic Ca2+ levels. From a physiological point of view, the open state of CALHM1 depends not only on voltage but also on the extracellular concentration of calcium ([Ca2+]) ions. At low [Ca2+]e or depolarization, the channel is opened, allowing Ca2+ influx; however, high extracellular [Ca2+]e or hyperpolarization promote its resting state. The unique Ca2+ permeation of CALHM1 relates to the molecular events that take place in brain ischemia, such as depolarization and extracellular changes in [Ca2+]e, particularly during the reperfusion phase after the ischemic insult. In this study, we attempted to understand its role in an in vitro model of ischemia, namely oxygen and glucose deprivation, followed by reoxygenation (OGD/Reox). To this end, hippocampal slices from wild-type Calhm1+/+, Calhm1+/-, and Calhm1-/- mice were subjected to OGD/Reox. Our results point out to a neuroprotective effect when CALHM1 is partially or totally absent. Pharmacological manipulation of CALHM1 with CGP37157 reduced cell death in Calhm1+/+ slices but not in that of Calhm1-/- mice after exposure to the OGD/Reox protocol. This ionic protection was also verified by measuring reactive oxygen species production upon OGD/Reox in Calhm1+/+ and Calhm1-/- mice, resulting in a downregulation of ROS production in Calhm1-/- hippocampal slices and increased expression of HIF-1α. Taken together, we can conclude that genetic or pharmacological inhibition of CALHM1 results in a neuroprotective effect against ischemia, due to an attenuation of the neuronal calcium overload and downregulation of oxygen reactive species productionThis research was funded by the Spanish Ministry of Science, Innovation and Universities Ref RTI2018-095793-B-I00 and Comunidad Autónoma de Madrid Ref. B2017/BMD-3827 to MGL. ETN PURINESDX Research and Innovation Agreement Nº 766124. Program under the Marie Sklodowska-Curie and Proyectos Santander-Universidad Autónoma de Madrid 2017, to MFC

Central activation of alpha7 nicotinic signaling attenuates lps-induced neuroinflammation and sickness behavior in adult but not in aged animals

We previously reported that lipopolysaccharide (LPS) challenge caused microglial-mediated neuroinflammation and sickness behavior that was amplified in aged mice. As α7 nAChRs are im-plicated in the “Cholinergic anti-inflammatory pathway”, we aimed to determine how α7 nAChR stimulation modulates microglial phenotype in an LPS-induced neuroinflammation model in adult and aged mice. For this, BALB/c mice were injected intraperitoneally with LPS (0.33 mg/kg) and treated with the α7 nAChR agonist PNU282987, using different administration protocols. LPS challenge reduced body weight and induced lethargy and social withdrawal in adult mice. Peripheral (intraperitoneal) co-administration of the α7 nAChR agonist PNU282987 with LPS, attenuated body weight loss and sickness behavior associated with LPS challenge in adult mice, and reduced microglial activation with suppression of IL-1β and TNFα mRNA levels. Furthermore, central (intracerebroven-tricular) administration of the α7 nAChR agonist, even 2 h after LPS injection, attenuated the decrease in social exploratory behavior and microglial activation induced by peripheral administration of LPS, although this recovery was not achieved if activation of α7 nAChRs was performed peripherally. Finally, we observed that the positive results of central activation of α7 nAChRs were lost in aged mice. In conclusion, we provide evidence that stimulation of α7 nAChR signaling reduces microglial activation in an in vivo LPS-based model, but this cholinergic-dependent regulation seems to be dysfunctional in microglia of aged mice.This work was supported by the Spanish Ministry of Science, innovation and Universities Ref. SAF2015-63935-R and Ref. RTI2018-095793-B-I00 and General Council for Research and Innovation of the Community of Madrid and European Structural Funds Ref. B2017/BMD–3827–NRF24ADCM to M.G.L. Aging studies were supported by an NIA grant (R01-AG-033028) to J.P.G

Synthesis and pharmacology of alkanediguanidinium compounds that block the neuronal nicotinic acetylcholine receptor

Taking as models the polyamine toxin fraction FTX from the funnel-web spider venom, and the guanidinium moiety of guanethidine, a series of azaalkane-1,omega-diguanidinium salts were obtained. Some of them blocked ion fluxes through the neuronal nicotinic receptors for acetylcholine (nAChR). The blockade was exerted at submicromolar concentrations, suggesting a highly selective interaction with the nAChR. In fact, the active compounds on the nAChR ion channel did not recognize the voltage-dependent Na+ or Ca2+ channels of bovine adrenal chromaffin cells. Therefore, these compounds may be useful tools to clarify the functions of nAChR receptors in the central and peripheral nervous systems.Fundación Ramón Arece

CALHM1 and its polymorphism P86L differentially control Ca²⁺ homeostasis, mitogen-activated protein kinase signaling, and cell vulnerability upon exposure to amyloid β

The mutated form of the Ca2+ channel CALHM1 (Ca2+ homeostasis modulator 1), P86L-CALHM1, has been correlated with early onset of Alzheimer’s disease (AD). P86L-CALHM1 increases production of amyloid beta (Ab) upon extracellular Ca2+ removal and its subsequent addback. The aim of this study was to investigate the effect of the overexpression of CALHM1 and P86L-CALHM, upon Ab treatment, on the following: (i) the intracellular Ca2+ signal pathway; (ii) cell survival proteins ERK1/2 and Ca2+/cAMP response element binding (CREB); and (iii) cell vulnerability after treatment with Ab. Using aequorins to measure the effect of nuclear Ca2+ concentrations ([Ca2+]n) and cytosolic Ca2+ concentrations ([Ca2+]c) on Ca2+ entry conditions, we observed that baseline [Ca2+]n was higher in CALHM1 and P86L-CALHM1 cells than in control cells. Moreover, exposure to Ab affected [Ca2+]c levels in HeLa cells overexpressing CALHM1 and P86L-CALHM1 compared with control cells. Treatment with Ab elicited a significant decrease in the cell survival proteins p-ERK and p-CREB, an increase in the activity of caspases 3 and 7, and more frequent cell death by inducing early apoptosis in P86L-CALHM1- overexpressing cells than in CALHM1 or control cells. These results suggest that in the presence of Ab, P86L-CALHM1 shifts the balance between neurodegeneration and neuronal survival toward the stimulation of pro-cytotoxic pathways, thus potentially contributing to its deleterious effects in AD.This work was partly supported by the following grants: Ministerio de Economía y Competitividad, FPU Program, Refs. AP2009/0343 (AJMO) and AP2010/1219 (IB). ARN: FIS PI10/01426. MGL: Ministerio de Economía y Competitividad, Ref. SAF2012-23332. MFCA: Consolidación de grupos de investigación UAM-CAM 1004040047. We also thank Fundación Teófilo Hernando, Madrid, Spain, for their continued suppor

Calcium signalling mediated through a7 and non-a7 nAChR stimulation is differentially regulated in bovine chromaffin cells to induce catecholamine release

Producción CientíficaCa2+ signalling and exocytosis mediated by nicotinic receptor (nAChR) subtypes, especially the a7 nAChR, in bovine chromaffin cells are still matters of debate.We have used chromaffin cell cultures loaded with Fluo-4 or transfected with aequorins directed to the cytosol or mitochondria, several nAChR agonists (nicotine, 5-iodo-A-85380, PNU282987 and choline), and the a7 nAChR allosteric modulator PNU120596. Minimal [Ca2+]c transients, induced by low concentrations of selective a7 nAChR agonists and nicotine, were markedly increased by the a7 nAChR allosteric modulator PNU120596. These potentiated responses were completely blocked by the a7 nAChR antagonist a-bungarotoxin (a7-modulated-response). Conversely, high concentrations of the a7 nAChR agonists, nicotine or 5-iodo-A-85380 induced larger [Ca2+]c transients, that were blocked by mecamylamine but were unaffected by a-bungarotoxin (non-a7 response). [Ca2+]c increases mediated by a7 nAChR were related to Ca2+ entry through non-L-type Ca2+ channels, whereas non-a7 nAChR-mediated signals were related to L-type Ca2+ channels; Ca2+-induced Ca2+-release contributed to both responses. Mitochondrial involvement in the control of [Ca2+]c transients, mediated by either receptor, was minimal. Catecholamine release coupled to a7 nAChRs was more efficient in terms of catecholamine released/[Ca2+]c.2015-09-1

Reactive oxygen-related diseases: therapeutic targets and emerging clinical indications

SIGNIFICANCE Enhanced levels of reactive oxygen species (ROS) have been associated with different disease states. Most attempts to validate and exploit these associations by chronic antioxidant therapies have provided disappointing results. Hence, the clinical relevance of ROS is still largely unclear. RECENT ADVANCES We are now beginning to understand the reasons for these failures, which reside in the many important physiological roles of ROS in cell signaling. To exploit ROS therapeutically, it would be essential to define and treat the disease-relevant ROS at the right moment and leave physiological ROS formation intact. This breakthrough seems now within reach. CRITICAL ISSUES Rather than antioxidants, a new generation of protein targets for classical pharmacological agents includes ROS-forming or toxifying enzymes or proteins that are oxidatively damaged and can be functionally repaired. FUTURE DIRECTIONS Linking these target proteins in future to specific disease states and providing in each case proof of principle will be essential for translating the oxidative stress concept into the clinic. Antioxid. Redox Signal. 23, 1171-1185

Adipose tissue as a therapeutic target for vascular damage in Alzheimer's disease

Adipose tissue has recently been recognized as an important endocrine organ that plays a crucial role in energy metabolism and in the immune response in many metabolic tissues. With this regard, emerging evidence indicates that an important crosstalk exists between the adipose tissue and the brain. However, the contribution of adipose tissue to the development of age-related diseases, including Alzheimer's disease, remains poorly defined. New studies suggest that the adipose tissue modulates brain function through a range of endogenous biologically active factors known as adipokines, which can cross the blood–brain barrier to reach the target areas in the brain or to regulate the function of the blood–brain barrier. In this review, we discuss the effects of several adipokines on the physiology of the blood–brain barrier, their contribution to the development of Alzheimer's disease and their therapeutic potential.Funding for open access charge; Universidad de Málaga / CBU

Metastable polymorphic phases in monolayer TaTe2

Polymorphic phases and collective phenomena—such as charge density waves (CDWs)—in transition metal dichalcogenides (TMDs) dictate the physical and electronic properties of the material. Most TMDs naturally occur in a single given phase, but the fine-tuning of growth conditions via methods such as molecular beam epitaxy (MBE) allows to unlock otherwise inaccessible polymorphic structures. Exploring and understanding the morphological and electronic properties of new phases of TMDs is an essential step to enable their exploitation in technological applications. Here, scanning tunneling microscopy (STM) is used to map MBE-grown monolayer (ML) TaTe2. This work reports the first observation of the 1H polymorphic phase, coexisting with the 1T, and demonstrates that their relative coverage can be controlled by adjusting synthesis parameters. Several superperiodic structures, compatible with CDWs, are observed to coexist on the 1T phase. Finally, this work provides theoretical insight on the delicate balance between Te…Te and Ta–Ta interactions that dictates the stability of the different phases. The findings demonstrate that TaTe2 is an ideal platform to investigate competing interactions, and indicate that accurate tuning of growth conditions is key to accessing metastable states in TMD

Microglial Hemoxygenase-1 Deletion Reduces Inflammation in the Retina of Old Mice with Tauopathy

Tauopathies such as Alzheimer’s disease are characterized by the accumulation of neurotoxic aggregates of tau protein. With aging and, especially, in Alzheimer’s patients, the inducible enzyme heme oxygenase 1 (HO-1) progressively increases in microglia, causing iron accumulation, neuroinflammation, and neurodegeneration. The retina is an organ that can be readily accessed and can reflect changes that occur in the brain. In this context, we evaluated how the lack of microglial HO-1, using mice that do not express HO-1 in microglia (HMO-KO), impacts retinal macro and microgliosis of aged subjects (18 months old mice) subjected to tauopathy by intrahippocampal delivery of AAV-hTauP301L (TAU). Our results show that although tauopathy, measured as anti-TAUY9 and anti-AT8 positive immunostaining, was not observed in the retina of WT-TAU or HMO-KO+TAU mice, a morphometric study of retinal microglia and macroglia showed significant retinal changes in the TAU group compared to the WT group, such as: (i) increased number of activated microglia, (ii) retraction of microglial processes, (iii) increased number of CD68+ microglia, and (iv) increased retinal area occupied by GFAP (AROA) and C3 (AROC3). This retinal inflammatory profile was reduced in HMO-KO+TAU mice. Conclusion: Reduction of microglial HO-1 could be beneficial to prevent tauopathy-induced neuroinflammation.Depto. de Inmunología, Oftalmología y ORLUnidad Docente de Inmunología, Oftalmología y ORLFac. de MedicinaFac. de Óptica y OptometríaTRUEMinisterio de Ciencia e Innovación de EspañaMinisterio de Ciencia, Innovación y Universidades de EspañaUniversidad Complutense de Madridpu