The importance of being subtle: small changes in calcium homeostasis control cognitive decline in normal aging

The neonicotinoid, imidacloprid, disrupt the chicken sperm quality through calcium efflux

Imidacloprid (IMI), an insecticide from the neonicotinoid group widely used in agriculture, has drawn attention due to its potential harmful effects on non-target species, including bird populations. In the present work, we investigated the effect of IMI on avian semen by in vitro exposure of rooster spermatozoa to this pesticide. The semen was collected twice a week. Samples collected on one day were pooled and incubated with the following IMI concentrations: 0 mM, 0.5 mM, 5 mM, 10 mM, and 50 mM at 36°C for 3 h. Comprehensive semen analysis was carried out after 1 h and 3 h of incubation, evaluating sperm motility parameters with the CASA system and using flow cytometry to assess membrane integrity, mitochondrial activity, acrosome integrity, chromatin structure, intracellular calcium level and apoptosis markers such as: early apoptosis and caspase activation and lipid peroxidation. The results of the first experiment suggest that low concentrations of IMI have a different effect on sperm motility compared to higher concentrations. In IMI samples, we also observed a lower percentage of cells with a high level of calcium ions compared to the control, and a lower level of lipid peroxidation. We concluded that IMI may act as a blocker of calcium channels, preventing the influx of these ions into the cell. To confirm this mechanism, we conducted a second experiment with calcium channel blockers: SNX 325, MRS-1845, and Nifedipine. The results of this experiment confirmed that the mechanism of action of IMI largely relies on the blockade of calcium channels in rooster sperm. Blocking the influx of calcium ions into the cell prevents the formation of Ca²⁺-dependent pores, thereby preventing an increase in cell membrane permeability, ultimately blocking early apoptosis and lipid peroxidation in chicken spermatozoa.

Innovative approaches to Alzheimer's therapy: Harnessing the power of heterocycles, oxidative stress management, and nanomaterial drug delivery system

Alzheimer's disease (AD) presents a complex pathology involving amyloidogenic proteolysis, neuroinflammation, mitochondrial dysfunction, and cholinergic deficits. Oxidative stress exacerbates AD progression through pathways like macromolecular peroxidation, mitochondrial dysfunction, and metal ion redox potential alteration linked to amyloid-beta (Aβ). Despite limited approved medications, heterocyclic compounds have emerged as promising candidates in AD drug discovery. This review highlights recent advancements in synthetic heterocyclic compounds targeting oxidative stress, mitochondrial dysfunction, and neuroinflammation in AD. Additionally, it explores the potential of nanomaterial-based drug delivery systems to overcome challenges in AD treatment. Nanoparticles with heterocyclic scaffolds, like polysorbate 80-coated PLGA and Resveratrol-loaded nano-selenium, show improved brain transport and efficacy. Micellar CAPE and Melatonin-loaded nano-capsules exhibit enhanced antioxidant properties, while a tetra hydroacridine derivative (CHDA) combined with nano-radiogold particles demonstrates promising acetylcholinesterase inhibition without toxicity. This comprehensive review underscores the potential of nanotechnology-driven drug delivery for optimizing the therapeutic outcomes of novel synthetic heterocyclic compounds in AD management. Furthermore, the inclusion of various promising heterocyclic compounds with detailed ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) data provides valuable insights for planning the development of novel drug delivery treatments for AD.

Upregulated ECM genes and increased synaptic activity in Parkinson's human DA neurons with PINK1/ PRKN mutations

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease. Primary symptoms of PD arise with the loss of dopaminergic (DA) neurons in the Substantia Nigra Pars Compacta, but PD also affects the hippocampus and cortex, usually in its later stage. Approximately 15% of PD cases are familial with a genetic mutation. Two of the most associated genes with autosomal recessive (AR) early-onset familial PD are PINK1 and PRKN. In vitro studies of these genetic mutations are needed to understand the neurophysiological changes in patients' neurons that may contribute to neurodegeneration. In this work, we generated and differentiated DA and hippocampal neurons from human induced pluripotent stem cells (hiPSCs) derived from two patients with a double mutation in their PINK1 and PRKN (one homozygous and one heterozygous) genes and assessed their neurophysiology compared to two healthy controls. We showed that the synaptic activity of PD neurons generated from patients with the PINK1 and PRKN mutations is impaired in the hippocampus and dopaminergic neurons. Mutant dopaminergic neurons had enhanced excitatory post-synaptic activity. In addition, DA neurons with the homozygous mutation of PINK1 exhibited more pronounced electrophysiological differences compared to the control neurons. Signaling network analysis of RNA sequencing results revealed that Focal adhesion and ECM receptor pathway were the top two upregulated pathways in the mutant PD neurons. Our findings reveal that the phenotypes linked to PINK1 and PRKN mutations differ from those from other PD mutations, suggesting a unique interplay between these two mutations that drives different PD mechanisms.

Antihypertensive medication and dementia risk in patients with hypertension: A nationwide population-based study

The claim between hypertension and dementia needs more evidence due to limited data. We aim to examine the risk of dementia in patients with hypertension, and determine whether the use of antihypertensive medications (AHMs) could decrease the incidence of dementia diagnosed following the onset of hypertension. We employed the Taiwan National Health Insurance Research Database from 2000 to 2016 and performed a retrospective cohort study. We also carried out a case-control study to see if AHMs could reduce the incidence of newly diagnosed dementia in hypertensive patients. In the retrospective cohort study, we selected 587,762 participants with age and gender matched in experimental and control groups. The hypertension group had significantly higher adjusted hazard ratios (aHRs) of getting newly diagnosed dementia, including all-cause dementia, Alzheimer's disease, and vascular dementia (aHR, 2.86; 95 % confidence interval (CI), 2.74-2.99) than the control group. Three kinds of specific AHMs, namely, angiotensin II receptor blockers (aHR, 0.55; 95 % CI, 0.53-0.57), calcium channel blockers (aHR, 0.76; 95 % CI, 0.73-0.80), and diuretics (aHR,0.93; 95 % CI, 0.89-0.97) could significantly decrease the incidence of getting newly diagnosed dementia. Also, the application of traditional Chinese medicine (TCM) significantly associates with the lower aHRs of newly diagnosed dementia in hypertensive patients compared to patients without TCM (aHR, 0.90; 95 % CI, 0.81-1.00). Hypertension may be a significant risk factor for dementia. Both AHMs and TCM significantly associate with the lower incidence of newly diagnosed dementia in hypertensive patients.

The 3-(3-oxoisoindolin-1-yl)pentane-2,4-dione (ISOAC1) as a new molecule able to inhibit Amyloid β aggregation and neurotoxicity

Amyloid β 1-42 (Aβ1-42) protein aggregation is considered one of the main triggers of Alzheimer's disease (AD). In this study, we examined the in vitro anti-amyloidogenic activity of the isoindolinone derivative 3-(3-oxoisoindolin-1-yl)pentane-2,4-dione (ISOAC1) and its neuroprotective potential against the Aβ1-42 toxicity. By performing the Thioflavin T fluorescence assay, Western blotting analyses, and Circular Dichroism experiments, we found that ISOAC1 was able to reduce the Aβ1-42 aggregation and conformational transition towards β-sheet structures. Interestingly, in silico studies revealed that ISOAC1 was able to bind to both the monomer and a pentameric protofibril of Aβ1-42, establishing a hydrophobic interaction with the PHE19 residue of the Aβ1-42 KLVFF motif. In vitro analyses on primary cortical neurons showed that ISOAC1 counteracted the increase of intracellular Ca2+ levels and decreased the Aβ1-42-induced toxicity, in terms of mitochondrial activity reduction and increase of reactive oxygen species production. In addition, confocal microscopy analyses showed that ISOAC1 was able to reduce the Aβ1-42 intraneuronal accumulation. Collectively, our results clearly show that ISOAC1 exerts a neuroprotective effect by reducing the Aβ1-42 aggregation and toxicity, hence emerging as a promising compound for the development of new Aβ-targeting therapeutic strategies for AD treatment.

The effect of serum calcium on the association of depression with infertility among U.S. women

This study aimed to explored the association between depressive symptoms and infertility among U.S. women, and the effect of serum calcium on this association. We used data from the National Health and Nutrition Examination Survey (2013-2018), relating to women aged 20-45 years. Depressive symptoms were determined using the nine-item Patient Health Questionnaire (PHQ-9 scores ≥10), and interview data were used to identify self-reported infertility. Of 2708 women (mean age: 32.7 ± 7.5 years), 274 were depressed and 12.0 % self-reported being "ever-infertile." Depressive symptoms were associated with infertility in multivariable logistic regression (OR, 1.62; 95 % CI, 1.11-2.38). Depressive symptoms were associated with infertility among participants who were obese (OR, 1.68; 95 % CI, 1.03-2.74), had not received psychological counseling (OR, 1.60; 95 % CI, 1.03-2.50), were antidepressant users (OR 3.22; 95 % CI, 1.15-9.00), and had high serum calcium levels (OR, 2.05; 95 % CI, 1.25-3.35). A significant interaction between serum calcium and depression was observed for infertility (P = .038, interaction likelihood ratio test). In sensitivity analyses, the association between depressive symptoms and infertility remained after excluding women aged ≥35 years (OR, 1.87; 95 % CI, 1.08-3.23), lowering the cut-off for PHQ-9 scores (≥5) (OR, 1.48; 95 % CI, 1.12-1.96), excluding women with some gynecological diseases (OR, 1.63; 95 % CI, 1.07-2.49), and using inverse probability of treatment weighting (OR, 1.64; 95 % CI, 1.17-2.31).

Conclusion

Our findings indicate that depression is associated with infertility among U.S. women and serum calcium may have an effect on the association. Interventions such as serum calcium reduction, weight management and psychosocial counseling for infertility treatment in individuals with depression may be integrated into routine clinical practice. Additionally, more caution could be exercised when using antidepressants.

Unravelling the Collective Calcium Dynamics of Physiologically Aged Astrocytes under a Hypoxic State In Vitro

Astrocytes serve many functions in the brain related to maintaining nerve tissue homeostasis and regulating neuronal function, including synaptic transmission. It is assumed that astrocytes are crucial players in determining the physiological or pathological outcome of the brain aging process and the development of neurodegenerative diseases. Therefore, studies on the peculiarities of astrocyte physiology and interastrocytic signaling during aging are of utmost importance. Calcium waves are one of the main mechanisms of signal transmission between astrocytes, and in the present study we investigated the features of calcium dynamics in primary cultures of murine cortical astrocytes in physiological aging and hypoxia modeling in vitro. Specifically, we focused on the assessment of calcium network dynamics and the restructuring of the functional network architecture in primary astrocytic cultures. Calcium imaging was performed on days 21 ("young" astrocyte group) and 150 ("old" astrocyte group) of cultures' development in vitro. While the number of active cells and frequency of calcium events were decreased, we observed a reduced degree of correlation in calcium dynamics between neighboring cells, which was accompanied by a reduced number of functionally connected cells with fewer and slower signaling events. At the same time, an increase in the mRNA expression of anti-apoptotic factor Bcl-2 and connexin 43 was observed in "old" astrocytic cultures, which can be considered as a compensatory response of cells with a decreased level of intercellular communication. A hypoxic episode aggravates the depression of the connectivity of calcium dynamics of "young" astrocytes rather than that of "old" ones.

Ageing in the brain: mechanisms and rejuvenating strategies

Ageing is characterized by the progressive loss of cellular homeostasis, leading to an overall decline of the organism's fitness. In the brain, ageing is highly associated with cognitive decline and neurodegenerative diseases. With the rise in life expectancy, characterizing the brain ageing process becomes fundamental for developing therapeutic interventions against the increased incidence of age-related neurodegenerative diseases and to aim for an increase in human life span and, more importantly, health span. In this review, we start by introducing the molecular/cellular hallmarks associated with brain ageing and their impact on brain cell populations. Subsequently, we assess emerging evidence on how systemic ageing translates into brain ageing. Finally, we revisit the mainstream and the novel rejuvenating strategies, discussing the most successful ones in delaying brain ageing and related diseases.

Cigarette smoke triggers calcium overload in mouse hippocampal neurons via the ΔFOSB-CACNA2D1 axis to impair cognitive performance

A growing body of evidence shows that cigarette smoking impairs cognitive performance. The 'Calcium Hypothesis' theory of neuronopathies reveals a critical role of aberrant calcium signaling in compromised cognitive functions. However, the underlying implications of abnormalities in calcium signaling in the neurotoxicity induced by cigarette smoke (CS) have not yet been identified. CACNA2D1, an important auxiliary subunit involved in the composition of voltage-gated calcium channels (VGCCs), was reported to affect the calcium signaling in neurons by facilitating VGCCs-mediated Ca²⁺ influx. ΔFOSB, an alternatively-spliced product of the Fosb gene, is an activity-dependent transcription factor induced robustly in the brain in response to environmental stimuli such as CS. Interestingly, our preliminary bioinformatics analysis revealed a significant co-expression between ΔFOSB and CACNA2D1 in brain tissues of patients with neurodegenerative diseases characterized by progressive cognitive decline. Therefore, we hypothesized that the activation of the ΔFOSB-CACNA2D1 axis in response to CS exposure might cause dysregulation of calcium homeostasis in hippocampal neurons via VGCCs-mediated Ca²⁺ influx, thereby contributing to cognitive deficits. To this end, the present study established a CS-induced mouse model of hippocampus-dependent cognitive impairment, in which the activation of the ΔFOSB-CACNA2D1 axis accompanied by severe calcium overload was observed in the mouse hippocampal tissues. More importantly, ΔFOSB knockdown-/overexpression-mediated inactivation/activation of the ΔFOSB-CACNA2D1 axis interdicted/mimicked CS-induced dysregulation of calcium homeostasis followed by severe cellular damage in HT22 mouse hippocampal neurons. Mechanistically speaking, a further ChIP-qPCR assay confirmed the physical interaction between transcription factor ΔFOSB and the Cacna2d1 gene promoter, suggesting a direct transcriptional regulation of the Cacna2d1 gene by ΔFOSB. Overall, our current work aims to deliver a unique insight into the neurotoxic mechanisms induced by CS to explore potential targets for intervention.

Vimar/RAP1GDS1 promotes acceleration of brain aging after flies and mice reach middle age

Brain aging may accelerate after rodents reach middle age. However, the endogenous mediator that promotes this acceleration is unknown. We predict that the mediator may be expressed after an organism reaches middle age and dysregulates mitochondrial function. In the neurons of wild-type Drosophila (flies), we observed that mitochondria were fragmented in aged flies, and this fragmentation was associated with mitochondrial calcium overload. In a previous study, we found that mitochondrial fragmentation induced by calcium overload was reversed by the loss of Vimar, which forms a complex with Miro. Interestingly, Vimar expression was increased after the flies reached middle age. Overexpression of Vimar in neurons resulted in premature aging and mitochondrial calcium overload. In contrast, downregulation of Vimar in flies older than middle age promoted healthy aging. As the mouse homolog of Vimar, RAP1GDS1 expression was found to be increased after mice reached middle age; RAP1GDS1-transgenic and RAP1GDS1-knockdown mice displayed similar responses to flies with overexpressed and reduced Vimar expression, respectively. This research provides genetic evidence of a conserved endogenous mediator that promotes accelerated brain aging.

Layer-specific vulnerability is a mechanism of topographic map aging

Topographic maps form a critical feature of cortical organization, yet are poorly described with respect to their microstructure in the living aging brain. We acquired quantitative structural and functional 7T-MRI data from younger and older adults to characterize layer-wise topographic maps of the primary motor cortex (M1). Using parcellation-inspired techniques, we show that quantitative T1 and Quantitative Susceptibility Maps values of the hand, face, and foot areas differ significantly, revealing microstructurally distinct cortical fields in M1. We show that these fields are distinct in older adults and that myelin borders between them do not degenerate. We further show that the output layer 5 of M1 shows a particular vulnerability to age-related increased iron, while layer 5 and the superficial layer show increased diamagnetic substance, likely reflecting calcifications. Taken together, we provide a novel 3D model of M1 microstructure, where body parts form distinct structural units, but layers show specific vulnerability toward increased iron and calcium in older adults. Our findings have implications for understanding sensorimotor organization and aging, in addition to topographic disease spread.

PINK1 deficiency with Ca2+ changes in the hippocampus exacerbates septic encephalopathy in mice

PTEN-induced putative kinase 1 (PINK1) is a mitochondrial kinase that protects against oxidative stress-induced cellular death. PINK1 deletion, on the other hand, disrupts mitochondrial calcium (Ca²⁺) homeostasis in various brain disorders. This study looked at how PINK1 affects hippocampal intracellular Ca²⁺ changes in mice with septic encephalopathy. Mice were injected intraperitoneally with lipopolysaccharide (LPS, 5 mg/kg) to induce septic encephalopathy; then, fiber photometry was used to record hippocampal Ca²⁺ transients during behavioral tests in freely moving mice. Basal cytoplasmic Ca²⁺ levels were detected under a fluorescent microscope. LPS induced PINK1 expression and neuronal loss in the hippocampus of mice, whereas no difference in neuronal counts was shown between PINK1 knockout LPS mice and WT LPS mice. PINK1 deficiency led to inhibited Ca²⁺ transients and increased intracellular Ca²⁺ levels in the hippocampus of mice, thus, significantly aggravating the cognitive dysfunction in septic mice. An analysis of Parkin and PLC-γ1, downstream effectors of PINK1, showed that they are associated with the effects of PINK1. These results demonstrate that PINK1 deficiency disrupts intracellular Ca²⁺ homeostasis and exacerbates septic encephalopathy. This observation suggests a protective role of PINK1 in septic encephalopathy.

Aging reduces calreticulin expression and alters spontaneous calcium signals in astrocytic endfeet of the mouse dorsolateral striatum

Aging-related impairment of the blood brain barrier (BBB) and neurovascular unit (NVU) increases the risk for neurodegeneration. Among various cells that participate in BBB and NVU function, calcium signals in astrocytic endfeet are crucial for maintaining BBB and NVU integrity. To assess if aging is associated with altered calcium signals within astrocytic endfeet of the dorsolateral striatum (DLS), we expressed GCaMP6f in DLS astrocytes of young (3-4 months), middle-aged (12-15 months) and aging (20-30 months) mice. Compared to endfeet in young mice, DLS endfeet in aging mice demonstrated decreased calreticulin expression, and alterations to both spontaneous membrane-associated and mitochondrial calcium signals. While young mice required both extracellular and endoplasmic reticulum calcium sources for endfoot signals, middle-aged and aging mice showed heavy dependence on endoplasmic reticulum calcium. Thus, astrocytic endfeet show significant changes in calcium buffering and sources throughout the lifespan, which is important for understanding mechanisms by which aging impairs the BBB and NVU.

Age-associated alterations of brain mitochondria energetics

The study aimed to explore the role of age-associated elevated cytosolic Ca²⁺ in changes of brain mitochondria energetic processes. Two groups of rats, young adults (4 months) and advanced old (24 months), were evaluated for potential alterations of mitochondrial parameters, the oxidative phosphorylation (OxPhos), membrane potential, calcium retention capacity, activity of glutamate/aspartate carrier (aralar), and ROS formation. We demonstrated that the brain mitochondria of older animals have a lower resistance to Ca²⁺ stress with resulting consequences. The suppressed complex I OxPhos and decreased membrane potential were accompanied by reduction of the Ca²⁺ threshold required for induction of mPTP. The Ca²⁺ binding sites of mitochondrial aralar mediated a lower activity of old brain mitochondria. The altered interaction between aralar and mPTP may underlie mitochondrial dysregulation leading to energetic depression during aging. At the advanced stages of aging, the declined metabolism is accompanied by the diminished oxidative background.

Chronic Fatigue, Depression and Anxiety Symptoms in Long COVID Are Strongly Predicted by Neuroimmune and Neuro-Oxidative Pathways Which Are Caused by the Inflammation during Acute Infection

BACKGROUND

Long-term coronavirus disease 2019 (long COVID) is associated with physio-somatic (chronic fatigue syndrome and somatic symptoms) and affective (depression and anxiety) symptoms. The severity of the long COVID physio-affective phenome is largely predicted by increased peak body temperature (BT) and lowered oxygen saturation (SpO2) during the acute infectious phase. This study aims to delineate whether the association of BT and SpO2 during the acute phase and the long COVID physio-affective phenome is mediated by neurotoxicity (NT) resulting from activated immune-inflammatory and oxidative stress pathways.

METHODS

We recruited 86 patients with long COVID (3-4 months after the acute phase) and 39 healthy controls and assessed serum C-reactive protein (CRP), caspase 1, interleukin (IL) 1β, IL-18, IL-10, myeloperoxidase (MPO), advanced oxidation protein products (AOPPs), total antioxidant capacity (TAC), and calcium (Ca), as well as peak BT and SpO2 during the acute phase.

RESULTS

Cluster analysis revealed that a significant part (34.9%) of long COVID patients (n = 30) show a highly elevated NT index as computed based on IL-1β, IL-18, caspase 1, CRP, MPO, and AOPPs. Partial least squares analysis showed that 61.6% of the variance in the physio-affective phenome of long COVID could be explained by the NT index, lowered Ca, and peak BT/SpO2 in the acute phase and prior vaccinations with AstraZeneca or Pfizer. The most important predictors of the physio-affective phenome are Ca, CRP, IL-1β, AOPPs, and MPO.

CONCLUSION

The infection-immune-inflammatory core of acute COVID-19 strongly predicts the development of physio-affective symptoms 3-4 months later, and these effects are partly mediated by neuro-immune and neuro-oxidative pathways.

Astrocytes as a Therapeutic Target in Alzheimer's Disease-Comprehensive Review and Recent Developments

Alzheimer's disease (AD) is a frequent and disabling neurodegenerative disorder, in which astrocytes participate in several pathophysiological processes including neuroinflammation, excitotoxicity, oxidative stress and lipid metabolism (along with a critical role in apolipoprotein E function). Current evidence shows that astrocytes have both neuroprotective and neurotoxic effects depending on the disease stage and microenvironmental factors. Furthermore, astrocytes appear to be affected by the presence of amyloid-beta (Aβ), with alterations in calcium levels, gliotransmission and proinflammatory activity via RAGE-NF-κB pathway. In addition, astrocytes play an important role in the metabolism of tau and clearance of Aβ through the glymphatic system. In this review, we will discuss novel pharmacological and non-pharmacological treatments focused on astrocytes as therapeutic targets for AD. These interventions include effects on anti-inflammatory/antioxidant systems, glutamate activity, lipid metabolism, neurovascular coupling and glymphatic system, calcium dysregulation, and in the release of peptides which affects glial and neuronal function. According to the AD stage, these therapies may be of benefit in either preventing or delaying the progression of the disease.

The calcium-iron connection in ferroptosis-mediated neuronal death

Iron, through its participation in oxidation/reduction processes, is essential for the physiological function of biological systems. In the brain, iron is involved in the development of normal cognitive functions, and its lack during development causes irreversible cognitive damage. Yet, deregulation of iron homeostasis provokes neuronal damage and death. Ferroptosis, a newly described iron-dependent cell death pathway, differs at the morphological, biochemical, and genetic levels from other cell death types. Ferroptosis is characterized by iron-mediated lipid peroxidation, depletion of the endogenous antioxidant glutathione and altered mitochondrial morphology. Although iron promotes the emergence of Ca²⁺ signals via activation of redox-sensitive Ca²⁺ channels, the role of Ca²⁺ signaling in ferroptosis has not been established. The early dysregulation of the cellular redox state observed in ferroptosis is likely to disturb Ca²⁺ homeostasis and signaling, facilitating ferroptotic neuronal death. This review presents an overview of the role of iron and ferroptosis in neuronal function, emphasizing the possible involvement of Ca²⁺ signaling in these processes. We propose, accordingly, that the iron-ferroptosis-Ca²⁺ association orchestrates the progression of cognitive dysfunctions and memory loss that occurs in neurodegenerative diseases. Therefore, to prevent iron dyshomeostasis and ferroptosis, we suggest the use of drugs that target the abnormal Ca²⁺ signaling caused by excessive iron levels as therapy for neurological disorders.

Lockdown of mitochondrial Ca2+ extrusion and subsequent resveratrol treatment kill HeLa cells by Ca2+ overload

Anticancer effect of resveratrol and the role of sodium/lithium/calcium exchanger in context with calcium ions are studied in human cervical cancer cell line. This therapeutic approach using siNCLX mediated gene silencing and drug therapy with resveratrol indicates the disruption of calcium homeostasis, increase in caspase (-3, 8, 9) mRNA expressions and DNA damage leading to apoptotic cell death. Monitoring the intracellular Ca2+ changes using fluo-4AM indicates highest rise in [Ca2+] level in sodium/lithium/calcium exchanger silenced group with five different stages, that is distinguishable based on the fluorescence intensity. In resveratrol treated and siNCLX + resveratrol treated groups no such cell staging differences were observed, despite uniform Ca2+ rise followed by decrease in the intensity. Integrating RNAi gene silencing of sodium/lithium/calcium exchanger with resveratrol can form the most interesting, efficient and promising therapeutic strategy in the treatment of cancer.

Chronic Stress Weakens Connectivity in the Prefrontal Cortex: Architectural and Molecular Changes

Chronic exposure to uncontrollable stress causes loss of spines and dendrites in the prefrontal cortex (PFC), a recently evolved brain region that provides top-down regulation of thought, action, and emotion. PFC neurons generate top-down goals through recurrent excitatory connections on spines. This persistent firing is the foundation for higher cognition, including working memory, and abstract thought. However, exposure to acute uncontrollable stress drives high levels of catecholamine release in the PFC, which activates feedforward calcium-cAMP signaling pathways to open nearby potassium channels, rapidly weakening synaptic connectivity to reduce persistent firing. Chronic stress exposures can further exacerbate these signaling events leading to loss of spines and resulting in marked cognitive impairment. In this review, we discuss how stress signaling mechanisms can lead to spine loss, including changes to BDNF-mTORC1 signaling, calcium homeostasis, actin dynamics, and mitochondrial actions that engage glial removal of spines through inflammatory signaling. Stress signaling events may be amplified in PFC spines due to cAMP magnification of internal calcium release. As PFC dendritic spine loss is a feature of many cognitive disorders, understanding how stress affects the structure and function of the PFC will help to inform strategies for treatment and prevention.

Decreased Interactions between Calmodulin and a Mutant Huntingtin Model Might Reduce the Cytotoxic Level of Intracellular Ca2+: A Molecular Dynamics Study

Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with significant effects on the intracellular calcium levels by altering the specific calcium-mediated signals. Furthermore, the mutant huntingtin proteins show great affinity for CaM that can lead to a further stabilization of the mutant huntingtin aggregates. In this context, the present study focuses on describing the interactions between CaM and two huntingtin mutants from a biophysical point of view, by using classical Molecular Dynamics techniques. The huntingtin models consist of a wild-type structure, one mutant with 45 glutamine residues and the second mutant with nine additional key-point mutations from glutamine residues into proline residues (9P(EM) model). Our docking scores and binding free energy calculations show higher binding affinities of all HTT models for the C-lobe end of the CaM protein. In terms of dynamic evolution, the 9P(EM) model triggered great structural changes into the CaM protein’s structure and shows the highest fluctuation rates due to its structural transitions at the helical level from α-helices to turns and random coils. Moreover, our proposed 9P(EM) model suggests much lower interaction energies when compared to the 45Qs-HTT mutant model, this finding being in good agreement with the 9P(EM)’s antagonistic effect hypothesis on highly toxic protein–protein interactions.

Mitochondrial Calcium Signaling as a Therapeutic Target for Alzheimer's Disease

Mitochondria absorb calcium (Ca2+) at the expense of the electrochemical gradient generated during respiration. The influx of Ca2+ into the mitochondrial matrix helps maintain metabolic function and results in increased cytosolic Ca2+ during intracellular Ca2+ signaling. Mitochondrial Ca2+ homeostasis is tightly regulated by proteins located in the inner and outer mitochondrial membranes and by the cross-talk with endoplasmic reticulum Ca2+ signals. Increasing evidence indicates that mitochondrial Ca2+ overload is a pathological phenotype associated with Alzheimer's Disease (AD). As intracellular Ca2+ dysregulation can be observed before the appearance of typical pathological hallmarks of AD, it is believed that mitochondrial Ca2+ overload may also play an important role in AD etiology. The high mitochondrial Ca2+ uptake can easily compromise neuronal functions and exacerbate AD progression by impairing mitochondrial respiration, increasing reactive oxygen species formation and inducing apoptosis. Additionally, mitochondrial Ca2+ overload can damage mitochondrial recycling via mitophagy. This review will discuss the molecular players involved in mitochondrial Ca2+ dysregulation and the pharmacotherapies that target this dysregulation. As most of the current AD therapeutics are based on amyloidopathy, tauopathy, and the cholinergic hypothesis, they achieve only symptomatic relief. Thus, determining how to reestablish mitochondrial Ca2+ homeostasis may aid in the development of novel AD therapeutic interventions.

Altered hippocampal astroglial metabolism is associated with aging and preserved spatial learning and memory

An age-related decrease in hippocampal metabolism correlates with cognitive decline. Hippocampus-dependent learning and memory requires glutamatergic neurotransmission supported by glutamate-glutamine (GLU-GLN) cycling between neurons and astrocytes. We examined whether GLU-GLN cycling in hippocampal subregions (dentate gyrus and CA1) in Fischer 344 rats was altered with age and cognitive status. Hippocampal slices from young adult, aged cognitively-unimpaired (AU) and aged cognitively-impaired (AI) rats were incubated in artificial cerebrospinal fluid (aCSF) containing 1-13C-glucose to assess neural metabolism. Incorporation of 13C-glucose into glutamate and glutamine, measured by mass spectroscopy/liquid chromatography tandem mass spectroscopy, did not significantly differ between groups. However, when 13C-acetate, a preferential astrocytic metabolite, was used, a significant increase in 13C-labeled glutamate was observed in slices from AU rats. Taken together, the data suggest that resting state neural metabolism and GLU-GLN cycling may be preserved during aging when sufficient extracellular glucose is available, but that enhanced astroglial metabolism can occur under resting state conditions. This may be an aging-related compensatory change to maintain hippocampus-dependent cognitive function.

Elevating the Levels of Calcium Ions Exacerbate Alzheimer's Disease via Inducing the Production and Aggregation of β-Amyloid Protein and Phosphorylated Tau

Alzheimer’s disease (AD) is a neurodegenerative disease with a high incidence rate. The main pathological features of AD are β-amyloid plaques (APs), which are formed by β-amyloid protein (Aβ) deposition, and neurofibrillary tangles (NFTs), which are formed by the excessive phosphorylation of the tau protein. Although a series of studies have shown that the accumulation of metal ions, including calcium ions (Ca²⁺), can promote the formation of APs and NFTs, there is no systematic review of the mechanisms by which Ca²⁺ affects the development and progression of AD. In view of this, the current review summarizes the mechanisms by which Ca²⁺ is transported into and out of cells and organelles, such as the cell, endoplasmic reticulum, mitochondrial and lysosomal membranes to affect the balance of intracellular Ca²⁺ levels. In addition, dyshomeostasis of Ca²⁺ plays an important role in modulating the pathogenesis of AD by influencing the production and aggregation of Aβ peptides and tau protein phosphorylation and the ways that disrupting the metabolic balance of Ca²⁺ can affect the learning ability and memory of people with AD. In addition, the effects of these mechanisms on the synaptic plasticity are also discussed. Finally, the molecular network through which Ca²⁺ regulates the pathogenesis of AD is introduced, providing a theoretical basis for improving the clinical treatment of AD.

Calcium Dyshomeostasis in Alzheimer's Disease Pathogenesis

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disorder that is characterized by amyloid β-protein deposition in senile plaques, neurofibrillary tangles consisting of abnormally phosphorylated tau protein, and neuronal loss leading to cognitive decline and dementia. Despite extensive research, the exact mechanisms underlying AD remain unknown and effective treatment is not available. Many hypotheses have been proposed to explain AD pathophysiology; however, there is general consensus that the abnormal aggregation of the amyloid β peptide (Aβ) is the initial event triggering a pathogenic cascade of degenerating events in cholinergic neurons. The dysregulation of calcium homeostasis has been studied considerably to clarify the mechanisms of neurodegeneration induced by Aβ. Intracellular calcium acts as a second messenger and plays a key role in the regulation of neuronal functions, such as neural growth and differentiation, action potential, and synaptic plasticity. The calcium hypothesis of AD posits that activation of the amyloidogenic pathway affects neuronal Ca²⁺ homeostasis and the mechanisms responsible for learning and memory. Aβ can disrupt Ca²⁺ signaling through several mechanisms, by increasing the influx of Ca²⁺ from the extracellular space and by activating its release from intracellular stores. Here, we review the different molecular mechanisms and receptors involved in calcium dysregulation in AD and possible therapeutic strategies for improving the treatment.

Astrocyte dystrophy in ageing brain parallels impaired synaptic plasticity

Little is known about age-dependent changes in structure and function of astrocytes and of the impact of these on the cognitive decline in the senescent brain. The prevalent view on the age-dependent increase in reactive astrogliosis and astrocytic hypertrophy requires scrutiny and detailed analysis. Using two-photon microscopy in conjunction with 3D reconstruction, Sholl and volume fraction analysis, we demonstrate a significant reduction in the number and the length of astrocytic processes, in astrocytic territorial domains and in astrocyte-to-astrocyte coupling in the aged brain. Probing physiology of astrocytes with patch clamp, and Ca2+ imaging revealed deficits in K+ and glutamate clearance and spatiotemporal reorganisation of Ca2+ events in old astrocytes. These changes paralleled impaired synaptic long-term potentiation (LTP) in hippocampal CA1 in old mice. Our findings may explain the astroglial mechanisms of age-dependent decline in learning and memory.

The aging mouse brain: cognition, connectivity and calcium

Aging is a complex process that differentially impacts multiple cognitive, sensory, neuronal and molecular processes. Technological innovations now allow for parallel investigation of neuronal circuit function, structure and molecular composition in the brain of awake behaving adult mice. Thus, mice have become a critical tool to better understand how aging impacts the brain. However, a more granular systems-based approach, which considers the impact of age on key features relating to neural processing, is required. Here, we review evidence probing the impact of age on the mouse brain. We focus on a range of processes relating to neuronal function, including cognitive abilities, sensory systems, synaptic plasticity and calcium regulation. Across many systems, we find evidence for prominent age-related dysregulation even before 12 months of age, suggesting that emerging age-related alterations can manifest by late adulthood. However, we also find reports suggesting that some processes are remarkably resilient to aging. The evidence suggests that aging does not drive a parallel, linear dysregulation of all systems, but instead impacts some processes earlier, and more severely, than others. We propose that capturing the more fine-scale emerging features of age-related vulnerability and resilience may provide better opportunities for the rejuvenation of the aged brain.

Increased Calbindin D28k Expression via Long-Term Alternate-Day Fasting Does Not Protect against Ischemia-Reperfusion Injury: A Focus on Delayed Neuronal Death, Gliosis and Immunoglobulin G Leakage

Calbindin-D28k (CB), a calcium-binding protein, mediates diverse neuronal functions. In this study, adult gerbils were fed a normal diet (ND) or exposed to intermittent fasting (IF) for three months, and were randomly assigned to sham or ischemia operated groups. Ischemic injury was induced by transient forebrain ischemia for 5 min. Short-term memory was examined via passive avoidance test. CB expression was investigated in the Cornu Ammonis 1 (CA1) region of the hippocampus via western blot analysis and immunohistochemistry. Finally, histological analysis was used to assess neuroprotection and gliosis (microgliosis and astrogliosis) in the CA1 region. Short-term memory did not vary significantly between ischemic gerbils with IF and those exposed to ND. CB expression was increased significantly in the CA1 pyramidal neurons of ischemic gerbils with IF compared with that of gerbils fed ND. However, the CB expression was significantly decreased in ischemic gerbils with IF, similarly to that of ischemic gerbils exposed to ND. The CA1 pyramidal neurons were not protected from ischemic injury in both groups, and gliosis (astrogliosis and microgliosis) was gradually increased with time after ischemia. In addition, immunoglobulin G was leaked into the CA1 parenchyma from blood vessels and gradually increased with time after ischemic insult in both groups. Taken together, our study suggests that IF for three months increases CB expression in hippocampal CA1 pyramidal neurons; however, the CA1 pyramidal neurons are not protected from transient forebrain ischemia. This failure in neuroprotection may be attributed to disruption of the blood–brain barrier, which triggers gliosis after ischemic insults.

High neural activity accelerates the decline of cognitive plasticity with age in Caenorhabditis elegans

The ability to learn progressively declines with age. Neural hyperactivity has been implicated in impairing cognitive plasticity with age, but the molecular mechanisms remain elusive. Here, we show that chronic excitation of the Caenorhabditis elegans O₂-sensing neurons during ageing causes a rapid decline of experience-dependent plasticity in response to environmental O₂ concentration, whereas sustaining lower activity of O₂-sensing neurons retains plasticity with age. We demonstrate that neural activity alters the ageing trajectory in the transcriptome of O₂-sensing neurons, and our data suggest that high-activity neurons redirect resources from maintaining plasticity to sustaining continuous firing. Sustaining plasticity with age requires the K⁺-dependent Na⁺/Ca²⁺ (NCKX) exchanger, whereas the decline of plasticity with age in high-activity neurons acts through calmodulin and the scaffold protein Kidins220. Our findings demonstrate directly that the activity of neurons alters neuronal homeostasis to govern the age-related decline of neural plasticity and throw light on the mechanisms involved.

Cell shape regulates subcellular organelle location to control early Ca2+ signal dynamics in vascular smooth muscle cells

The shape of the cell is connected to its function; however, we do not fully understand underlying mechanisms by which global shape regulates a cell's functional capabilities. Using theory, experiments and simulation, we investigated how physiologically relevant cell shape changes affect subcellular organization, and consequently intracellular signaling, to control information flow needed for phenotypic function. Vascular smooth muscle cells going from a proliferative and motile circular shape to a contractile fusiform shape show changes in the location of the sarcoplasmic reticulum, inter-organelle distances, and differential distribution of receptors in the plasma membrane. These factors together lead to the modulation of signals transduced by the M3 muscarinic receptor/Gq/PLCβ pathway at the plasma membrane, amplifying Ca2+ dynamics in the cytoplasm, and the nucleus resulting in phenotypic changes, as determined by increased activity of myosin light chain kinase in the cytoplasm and enhanced nuclear localization of the transcription factor NFAT. Taken together, our observations show a systems level phenomenon whereby global cell shape affects subcellular organization to modulate signaling that enables phenotypic changes.

Ca2+-permeable TRPV1 pain receptor knockout rescues memory deficits and reduces amyloid-β and tau in a mouse model of Alzheimer's disease

The transient receptor potential vanilloid 1 (TRPV1) protein is a pain receptor that elicits a hot sensation when an organism eats the capsaicin of red chili peppers. This calcium (Ca2+)-permeable cation channel is mostly expressed in the peripheral nervous system sensory neurons but also in the central nervous system (e.g. hippocampus and cortex). Preclinical studies found that TRPV1 mediates behaviors associated with anxiety and depression. Loss of TRPV1 functionality increases expression of genes related to synaptic plasticity and neurogenesis. Thus, we hypothesized that TRPV1 deficiency may modulate Alzheimer's disease (AD). We generated a triple-transgenic AD mouse model (3xTg-AD+/+) with wild-type (TRPV1+/+), hetero (TRPV1+/-) and knockout (TRPV1-/-) TRPV1 to investigate the role of TRPV1 in AD pathogenesis. We analyzed the animals' memory function, hippocampal Ca2+ levels and amyloid-β (Aβ) and tau pathologies when they were 12 months old. We found that compared with 3xTg-AD-/-/TRPV1+/+ mice, 3xTg-AD+/+/TRPV1+/+ mice had memory impairment and increased levels of hippocampal Ca2+, Aβ and total and phosphorylated tau. However, 3xTg-AD+/+/TRPV1-/- mice had better memory function and lower levels of hippocampal Ca2+, Aβ, tau and p-tau, compared with 3xTg-AD+/+/TRPV1+/+ mice. Examination of 3xTg-AD-derived primary neuronal cultures revealed that the intracellular Ca2+ chelator BAPTA/AM and the TRPV1 antagonist capsazepine decreased the production of Aβ, tau and p-tau. Taken together, these results suggested that TRPV1 deficiency had anti-AD effects and promoted resilience to memory loss. These findings suggest that drugs or food components that modulate TRPV1 could be exploited as therapeutics to prevent or treat AD.

Targeting of intracellular Ca2+ stores as a therapeutic strategy against age-related neurotoxicities

Calcium dysregulation often underlies pathologies associated with aging and age-associated neurodegenerative diseases. Cells express a unique pattern of Ca²⁺ channels and pumps geared to fulfill specific physiological requirements and there is a decline in the fidelity of these processes with age and age-associated diseases. J147 is an Alzheimer’s disease (AD) drug candidate that was identified using a phenotypic screening platform based upon age-related brain toxicities that are mediated by changes in calcium metabolism. The molecular target for J147 is the α-F1-ATP synthase (ATP5A). J147 has therapeutic efficacy in multiple mouse models of AD and accelerated aging and extends life span in flies. A bioinformatics analysis of gene expression in rapidly aging SAMP8 mice during the last quadrant of their life span shows that J147 has a significant effect on ion transport pathways that are changed with aging, making their expression look more like that of younger animals. The molecular basis of these changes was then investigated in cell culture neurotoxicity assays that were the primary screen in the development of J147. Here we show that J147 and its molecular target, ATP synthase, regulate the maintenance of store-operated calcium entry (SOCE) and cell death during acute neurotoxicity.

Intranasal lipid nanocapsules for systemic delivery of nimodipine into the brain: In vitro optimization and in vivo pharmacokinetic study

Nimodipine (NM) is FDA-approved drug for treating subarachnoid haemorrhage induced vasospasm. Intravenous (IV) administration, the most common route of NM, causes several side effects such as hypotension, bradycardia, arrhythmias and inflammation at site of administration. The aim of this study was to investigate the capability of intranasal (IN) lipid nanocapsules (LNCs) for effective delivery of NM into the brain. NM LNCs were prepared by solvent free phase inversion temperature technique using D-Optimal mixture design studying the effects of three formulation variables on the properties of the prepared LNCs. The prepared particles were evaluated for particle size, drug payload, PDI, Zeta potential and in-vitro drug release. The optimized NM loaded LNC showed particle size of 35.94 ± 0.14 nm and PDI of 0.146 ± 0.045. The in-vivo pharmacokinetic behaviour of IN NM loaded LNC in blood and brain was compared with NM-solution after IV administration in rats. Results show that IN NM loaded LNC was capable to deliver the same amount of NM at brain tissue with lower drug levels in blood compared with IV administration of the NM solution which is greatly beneficial to minimize the cardiovascular side effects of NM. Contrary to most IN nanocarriers, systemic pathway rather than olfactory pathway plays the major role in brain delivery following IN administration of LNCs. The appropriate brain delivery with lower blood levels and slow elimination propose that intranasal LNCs could provide effective systemic delivery of NM into brain with lower frequency of administration and minimal side effects.

Intestinal expression of toll-like receptor gene changes early after gastric bypass surgery and association with type 2 diabetes remission

OBJECTIVES

Abnormal activation of toll-like receptors (TLRs) is observed in obese rodents and is correlated with local dysbiosis and increased gut permeability. These purported changes trigger systemic inflammation associated with obesity-related comorbidities, including type 2 diabetes (T2D). Roux-en-Y gastric bypass (RYGB) surgery is an effective treatment for severe obesity and known to induce changes in the gut microbiota and decrease systemic inflammation in humans. This study examined the intestinal expression of TLR-encoding genes in obese women (n = 20) treated with RYGB surgery and the relationship of these genes with T2D remission (T2Dr METHODS: Intestinal biopsies were performed before and 3 months after RYGB surgery. Partial and complete T2Dr after 1 year was assessed using the American Diabetes Association criteria. Affymetrix Human GeneChip 1.0 ST array (microarray) and TaqMan assay (real-time quantitative polymerase chain reaction) were used to analyze intestinal gene expression, and associations with systemic markers of energy homeostasis were examined.

RESULTS

Patients experienced significant weight loss (P < 0.001) and altered gut TLR gene expression 3 months after surgery. The main effects were a reduction in jejunal TLR4 expression in patients with complete and partial T2Dr (P < 0.05). There was a postoperative decrease in jejunal TLR7 expression in patients with complete T2Dr that correlated inversely with high-density lipoprotein cholesterol and positively with triglyceride concentrations, but not with weight loss.

CONCLUSIONS

RYGB-induced weight loss-independent changes in the expression of intestinal TLR-encoding genes in obese women and complete T2Dr that was correlated with systemic markers of energy homeostasis. The modulation of intestinal TLRs may mediate inflammatory mechanisms linked to T2Dr after RYGB surgery.

Altered Mitochondrial Dynamics in Motor Neuron Disease: An Emerging Perspective

Mitochondria plays privotal role in diverse pathways that regulate cellular function and survival, and have emerged as a prime focus in aging and age-associated motor neuron diseases (MNDs), such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Accumulating evidence suggests that many amyloidogenic proteins, including MND-associated RNA/DNA-binding proteins fused in sarcoma (FUS) and TAR DNA binding protein (TDP)-43, are strongly linked to mitochondrial dysfunction. Animal model and patient studies have highlighted changes in mitochondrial structure, plasticity, replication/copy number, mitochondrial DNA instability, and altered membrane potential in several subsets of MNDs, and these observations are consistent with the evidence of increased excitotoxicity, induction of reactive oxygen species, and activation of intrinsic apoptotic pathways. Studies in MND rodent models also indicate that mitochondrial abnormalities begin prior to the clinical and pathological onset of the disease, suggesting a causal role of mitochondrial dysfunction. Our recent studies, which demonstrated the involvement of specific defects in DNA break-ligation mediated by DNA ligase 3 (LIG3) in FUS-associated ALS, raised a key question of its potential implication in mitochondrial DNA transactions because LIG3 is essential for both mitochondrial DNA replication and repair. This question, as well as how wild-type and mutant MND-associated factors affect mitochondria, remain to be elucidated. These new investigation avenues into the mechanistic role of mitochondrial dysfunction in MNDs are critical to identify therapeutic targets to alleviate mitochondrial toxicity and its consequences. In this article, we critically review recent advances in our understanding of mitochondrial dysfunction in diverse subgroups of MNDs and discuss challenges and future directions.

The Na+/Ca2+exchanger in Alzheimer's disease

As a pivotal player in regulating sodium (Na⁺) and calcium (Ca²⁺) homeostasis and signalling in excitable cells, the Na⁺/Ca²⁺ exchanger (NCX) is involved in many neurodegenerative disorders in which an imbalance of intracellular Ca²⁺ and/or Na⁺ concentrations occurs, including Alzheimer's disease (AD). Although NCX has been mainly implicated in neuroprotective mechanisms counteracting Ca²⁺ dysregulation, several studies highlighted its role in the neuronal responses to intracellular Na⁺ elevation occurring in several pathophysiological conditions. Since the alteration of Na⁺ and Ca²⁺ homeostasis significantly contributes to synaptic dysfunction and neuronal loss in AD, it is of crucial importance to analyze the contribution of NCX isoforms in the homeostatic responses at neuronal and synaptic levels. Some studies found that an increase of NCX activity in brains of AD patients was correlated with neuronal survival, while other research groups found that protein levels of two NCX subtypes, NCX2 and NCX3, were modulated in parietal cortex of late stage AD brains. In particular, NCX2 positive synaptic terminals were increased in AD cohort while the number of NCX3 positive terminals were reduced. In addition, NCX1, NCX2 and NCX3 isoforms were up-regulated in those synaptic terminals accumulating amyloid-beta (Aβ), the neurotoxic peptide responsible for AD neurodegeneration. More recently, the hyperfunction of a specific NCX subtype, NCX3, has been shown to delay endoplasmic reticulum stress and apoptotic neuronal death in hippocampal neurons exposed to Aβ insult. Despite some issues about the functional role of NCX in synaptic failure and neuronal loss require further studies, these findings highlight the putative neuroprotective role of NCX in AD and open new strategies to develop new druggable targets for AD therapy.

Role of endolysosomes and inter-organellar signaling in brain disease

Endosomes and lysosomes (endolysosomes) are membrane bounded organelles that play a key role in cell survival and cell death. These acidic intracellular organelles are the principal sites for intracellular hydrolytic activity required for the maintenance of cellular homeostasis. Endolysosomes are involved in the degradation of plasma membrane components, extracellular macromolecules as well as intracellular macromolecules and cellular fragments. Understanding the physiological significance and pathological relevance of endolysosomes is now complicated by relatively recent findings of physical and functional interactions between endolysosomes with other intracellular organelles including endoplasmic reticulum, mitochondria, plasma membranes, and peroxisomes. Indeed, evidence clearly indicates that endolysosome dysfunction and inter-organellar signaling occurs in different neurodegenerative diseases including Alzheimer's disease (AD), HIV-1 associated neurocognitive disease (HAND), Parkinson's disease (PD) as well as various forms of brain cancer such as glioblastoma multiforme (GBM). These findings open new areas of cell biology research focusing on understanding the physiological actions and pathophysiological consequences of inter-organellar communication. Here, we will review findings of others and us that endolysosome de-acidification and dysfunction coupled with impaired inter-organellar signaling is involved in the pathogenesis of AD, HAND, PD, and GBM. A more comprehensive appreciation of cell biology and inter-organellar signaling could lead to the development of new drugs to prevent or cure these diseases.

Calcium Signaling During Brain Aging and Its Influence on the Hippocampal Synaptic Plasticity

Calcium (Ca²⁺) ions are highly versatile intracellular signaling molecules and are universal second messenger for regulating a variety of cellular and physiological functions including synaptic plasticity. Ca²⁺ homeostasis in the central nervous system endures subtle dysregulation with advancing age. Research has provided abundant evidence that brain aging is associated with altered neuronal Ca²⁺ regulation and synaptic plasticity mechanisms. Much of the work has focused on the hippocampus, a brain region critically involved in learning and memory, which is particularly susceptible to dysfunction during aging. The current chapter takes a specific perspective, assessing various Ca²⁺ sources and the influence of aging on Ca²⁺ sources and synaptic plasticity in the hippocampus. Integrating the knowledge of the complexity of age-related alterations in neuronal Ca²⁺ signaling and synaptic plasticity mechanisms will positively shape the development of highly effective therapeutics to treat brain disorders including cognitive impairment associated with aging and neurodegenerative disease.

Total and ionized calcium and magnesium are significantly lowered in drug-naïve depressed patients: effects of antidepressants and associations with immune activation

Major depressive disorder (MDD) is associated with alterations in calcium (Ca) and magnesium (Mg), as well as circulating pro- and anti-inflammatory cytokines. Anti-inflammatory drugs are commonly used as adjuvant treatments for MDD. However, no studies examined the effects of a combinatorial treatment with sertraline and ketoprofen, an anti-inflammatory drug, on Ca and Mg levels in MDD. The present study examined a) differences in both cations between drug-naïve MDD patients and controls, and b) the effects of sertraline and ketoprofen on Ca and Mg (both total and ionized). In the same patients, we also examined the associations between both cations and IL-1β, IL-4, IL-6, IL-18, IFN-γ, TGF-β1, zinc, and indoleamine 2,3-dioxygenase (IDO). Clinical improvement was assessed using the Beck Depression Inventory-II (BDI-II) at baseline and after follow up for 2 months. Serum Ca and Mg (total and ionized) were significantly lower in MDD patients as compared with controls, while treatment significantly increased calcium but decreased magnesium levels. There were significant and inverse correlations between the BDI-II scores from baseline to endpoint and Ca (both total and ionized), but not Mg, levels. The effects of calcium on the BDI-II score remained significant after considering the effects of zinc, IDO and an immune activation z unit-weighted composite score based on the sum of all cytokines. There was a significant and inverse association between this immune activation index and calcium levels from baseline to endpoint. In conclusion, lowered levels of both cations play a role in the pathophysiology of major depression. Antidepressant-induced increases in Ca are associated with clinical efficacy and attenuation of the immune response. The suppressant effect of antidepressants on Mg levels is probably a side effect of those drugs. New antidepressant treatments should be developed that increase the levels both Ca and Mg. Graphical abstract.

Resveratrol Directly Controls the Activity of Neuronal Ryanodine Receptors at the Single-Channel Level

Calcium ion dyshomeostasis contributes to the progression of many neurodegenerative diseases and represents a target for the development of neuroprotective therapies, as reported by Duncan et al. (Molecules 15(3):1168-95, 2010), LaFerla (Nat Rev Neurosci 3(11):862-72, 2002), and Niittykoshi et al. (Invest Ophthalmol Vis Sci 51(12):6387-93, 2010). Dysfunctional ryanodine receptors contribute to calcium ion dyshomeostasis and potentially to the pathogenesis of neurodegenerative diseases by generating abnormal calcium ion release from the endoplasmic reticulum, according to Bruno et al. (Neurobiol Aging 33(5):1001 e1-6, 2012) and Stutzmann et al. (J Neurosci 24(2):508-13, 2004). Since ryanodine receptors share functional and structural similarities with potassium channels, as reported by Lanner et al. (Cold Spring Harb Perspect Biol 2(11):a003996, 2010), and small molecules with anti-oxidant properties, such as resveratrol (3,5,4'-trihydroxy-trans-stilbene), directly control the activity of potassium channels, according to Wang et al. (J Biomed Sci 23(1):47, 2016), McCalley et al. (Molecules 19(6):7327-40, 2014), Novakovic et al. (Mol Hum Reprod 21(6):545-51, 2015), Li et al. (Cardiovasc Res 45(4):1035-45, 2000), Gopalakrishnan et al. (Br J Pharmacol 129(7):1323-32, 2000), and Hambrock et al. (J Biol Chem 282(5):3347-56, 2007), we hypothesized that trans-resveratrol can modulate intracellular calcium signaling through direct binding and functional regulation of ryanodine receptors. The goal of our study was to identify and measure the control of ryanodine receptor activity by trans-resveratrol. Mechanisms of calcium signaling mediated by the direct interaction between trans-resveratrol and ryanodine receptors were identified and measured with single-channel electrophysiology. Addition of trans-resveratrol to the cytoplasmic face of the ryanodine receptor increased single-channel activity at physiological and elevated pathophysiological cytoplasmic calcium ion concentrations. The open probability of the channel increases after interacting with the small molecule in a dose-dependent manner, but remains also dependent on the concentration of its physiological ligand, cytoplasmic-free calcium ions. This study provides the first evidence of a direct functional interaction between trans-resveratrol and ryanodine receptors. Such functional control of ryanodine receptors by trans-resveratrol as a novel mechanism of action could provide additional rationales for the development of novel therapeutic strategies to treat and prevent neurodegenerative diseases.

Astroglial Calcium Signaling in Aging and Alzheimer's Disease

Astrocytes are the homeostatic and protective cells of the central nervous system (CNS). In neurological diseases, astrocytes undergo complex changes, which are subclassified into (1) reactive astrogliosis, an evolutionary conserved defensive rearrangement of cellular phenotype aimed at neuroprotection; (2) pathological remodeling, when astrocytes acquire new features driving pathology; and (3) astrodegeneration, which is manifested by astroglial atrophy and loss of homeostatic functions. In aging brains as well as in the brains affected by Alzheimer's disease (AD), astrocytes acquire both atrophic and reactive phenotypes in a region- and disease-stage-dependent manner. Prevalence of atrophy overreactivity, observed in certain brain regions and in terminal stages of the disease, arguably facilitates the development of neurological deficits. Astrocytes exhibit ionic excitability mediated by changes in intracellular concentration of ions, most importantly of Ca²⁺ and Na⁺, with intracellular ion dynamics triggered by the activity of neural networks. AD astrocytes associated with senile plaques demonstrate Ca²⁺ hyperactivity in the form of aberrant Ca²⁺ oscillations and pathological long-range Ca²⁺ waves. Astroglial Ca²⁺ signaling originating from Ca²⁺ release from the endoplasmic reticulum is a key factor in initiating astrogliotic response; deficient Ca²⁺ signaling toolkits observed in entorhinal and prefrontal cortices of AD model animals may account for vulnerability of these regions to the pathology.

Alternative Splicing at N Terminus and Domain I Modulates CaV1.2 Inactivation and Surface Expression

The Ca_V1.2 L-type calcium channel is a key conduit for Ca²⁺ influx to initiate excitation-contraction coupling for contraction of the heart and vasoconstriction of the arteries and for altering membrane excitability in neurons. Its α_1C pore-forming subunit is known to undergo extensive alternative splicing to produce many Ca_V1.2 isoforms that differ in their electrophysiological and pharmacological properties. Here, we examined the structure-function relationship of human Ca_V1.2 with respect to the inclusion or exclusion of mutually exclusive exons of the N-terminus exons 1/1a and IS6 segment exons 8/8a. These exons showed tissue selectivity in their expression patterns: heart variant 1a/8a, one smooth-muscle variant 1/8, and a brain isoform 1/8a. Overall, the 1/8a, when coexpressed with Ca_Vβ_2a, displayed a significant and distinct shift in voltage-dependent activation and inactivation and inactivation kinetics as compared to the other three splice variants. Further analysis showed a clear additive effect of the hyperpolarization shift in V_1/2inact of Ca_V1.2 channels containing exon 1 in combination with 8a. However, this additive effect was less distinct for V_1/2act. However, the measured effects were β-subunit-dependent when comparing Ca_Vβ_2a with Ca_Vβ₃ coexpression. Notably, calcium-dependent inactivation mediated by local Ca²⁺-sensing via the N-lobe of calmodulin was significantly enhanced in exon-1-containing Ca_V1.2 as compared to exon-1a-containing Ca_V1.2 channels. At the cellular level, the current densities of the 1/8a or 1/8 variants were significantly larger than the 1a/8a and 1a/8 variants when coexpressed either with Ca_Vβ_2a or Ca_Vβ₃ subunit. This finding correlated well with a higher channel surface expression for the exon 1-Ca_V1.2 isoform that we quantified by protein surface-expression levels or by gating currents. Our data also provided a deeper molecular understanding of the altered biophysical properties of alternatively spliced human Ca_V1.2 channels by directly comparing unitary single-channel events with macroscopic whole-cell currents.

Effects of sustained cognitive activity on white matter microstructure and cognitive outcomes in healthy middle-aged adults: A systematic review

Adults who remain cognitively active may be protected from age-associated changes in white matter (WM) and cognitive decline. To determine if cognitive activity is a precursor for WM plasticity, the available literature was systematically searched for Region of Interest (ROI) and whole-brain studies assessing the efficacy of cognitive training (CT) on WM microstructure using Diffusion Tensor Imaging (DTI) in healthy adults (> 40 years). Seven studies were identified and included in this review. Results suggest there are beneficial effects to WM microstructure after CT in frontal and medial brain regions, with some studies showing improved performance in cognitive outcomes. Benefits of CT were shown to be protective against age-related WM microstructure decline by either maintaining or improving WM after training. These results have implications for determining the capacity for training-dependent WM plasticity in older adults and whether CT can be utilised to prevent age-associated cognitive decline. Additional studies with standardised training and imaging protocols are needed to confirm these outcomes.

Familial Alzheimer's disease-linked presenilin mutants and intracellular Ca2+ handling: A single-organelle, FRET-based analysis

An imbalance in Ca²⁺ homeostasis represents an early event in the pathogenesis of Alzheimer's disease (AD). Presenilin-1 and -2 (PS1 and PS2) mutations, the major cause of familial AD (FAD), have been extensively associated with alterations in different Ca²⁺ signaling pathways, in particular those handled by storage compartments. However, FAD-PSs effect on organelles Ca²⁺ content is still debated and the mechanism of action of mutant proteins is unclear. To fulfil the need of a direct investigation of intracellular stores Ca²⁺ dynamics, we here present a detailed and quantitative single-cell analysis of FAD-PSs effects on organelle Ca²⁺ handling using specifically targeted, FRET (Fluorescence/Förster Resonance Energy Transfer)-based Ca²⁺ indicators. In SH-SY5Y human neuroblastoma cells and in patient-derived fibroblasts expressing different FAD-PSs mutations, we directly measured Ca²⁺ concentration within the main intracellular Ca²⁺ stores, e.g., Endoplasmic Reticulum (ER) and Golgi Apparatus (GA) medial- and trans-compartment. We unambiguously demonstrate that the expression of FAD-PS2 mutants, but not FAD-PS1, in either SH-SY5Y cells or FAD patient-derived fibroblasts, is able to alter Ca²⁺ handling of ER and medial-GA, but not trans-GA, reducing, compared to control cells, the Ca²⁺ content within these organelles by partially blocking SERCA (Sarco/Endoplasmic Reticulum Ca²⁺-ATPase) activity. Moreover, by using a cytosolic Ca²⁺ probe, we show that the expression of both FAD-PS1 and -PS2 reduces the Ca²⁺ influx activated by stores depletion (Store-Operated Ca²⁺ Entry; SOCE), by decreasing the expression levels of one of the key molecules, STIM1 (STromal Interaction Molecule 1), controlling this pathway. Our data indicate that FAD-linked PSs mutants differentially modulate the Ca²⁺ content of intracellular stores yet leading to a complex dysregulation of Ca²⁺ homeostasis, which represents a common disease phenotype of AD.

Neuroglia in Ageing

Ageing reduces the functional capacity of all organs, so does that of the nervous system; the latter is evident in the reduction of cognitive abilities, learning and memory. While the exact mechanisms of ageing of the nervous system remain elusive, it is without doubt that morpho-functional changes in a variety of neuroglial cells contribute to this process. The age-dependent changes in neuroglia are characterised by a progressive loss of function. This reduces glial ability to homeostatically nurture, protect and regenerate the nervous tissue. Such neuroglial paralysis also facilitates neurodegenerative processes. Ageing of neuroglia is variable and can be affected by environmental factors and comorbidities.

Astroglia in Alzheimer's Disease

Alzheimer's disease is the most common cause of dementia. Cellular changes in the brains of the patients suffering from Alzheimer's disease occur well in advance of the clinical symptoms. At the cellular level, the most dramatic is a demise of neurones. As astroglial cells carry out homeostatic functions of the brain, it is certain that these cells are at least in part a cause of Alzheimer's disease. Historically, Alois Alzheimer himself has recognised this at the dawn of the disease description. However, the role of astroglia in this disease has been understudied. In this chapter, we summarise the various aspects of glial contribution to this disease and outline the potential of using these cells in prevention (exercise and environmental enrichment) and intervention of this devastating disease.

Ageing reduces the reproductive performance of male white shrimp Litopenaeus vannamei by altering sperm intracellular Ca2+ concentrations and interfering with sperm apoptosis

Although the effects of age on the reproductive performance of various invertebrates, including white shrimp Litopenaeus vannamei are increasingly well documented, the mechanisms manifesting these impacts remain poorly understood. To ascertain the mechanisms of age on reproductive performance, the sperm quality, intracellular contents of Ca²⁺, insemination and hatching rates, and status of sperm apoptosis in terms of the expression of key regulatory genes were investigated in 11 and 16 month old male L. vannamei. The aged male individuals (16 months) had lesser reproductive performance in terms of fertilization and hatching rates. In addition, fewer and less viable sperm were detected in aged shrimp, which may be due to the altered expression of apoptosis-related genes. Furthermore, the aged males had lesser intracellular contents of Ca²⁺ in the sperm which may decrease the capacity of these gametes to undergo a complete acrosome reaction. In general, due to the decrease in intracellular contents of Ca²⁺ and alterations in the process of apoptosis, aged L. vannamei have relatively lesser quality sperm and may, therefore, have lesser reproductive performance.

Serum calcium levels and neuropsychological performance in depression and matched healthy controls: Reversal of correlation a marker of the aging cognitive clock?

BACKGROUND

Major depressive disorder (MDD) is associated with cognitive impairment, that might be related to disturbed calcium homeostasis. Calcium-related processes have also been implicated in age related cognitive decline. Since serum calcium and brain interstitial fluids maintain long-term equilibrium under normal physiological states, serum calcium levels could affect neuronal and hence cognitive function. High serum calcium has been associated with cognitive decline in geriatric populations, whereas evidence for MDD and healthy populations is less consistent.

METHODS

Differences in neuropsychological (NPS) performance and their relationship with serum calcium (total, ionized, total to ionized ratio) in (partially) remitted MDD patients (n = 59) and healthy controls (HC) (n = 59) individually matched for age, gender and education (age-range 19-60 years) were examined. Modulation of study parameters and their interaction by the factor age was investigated, with subgroups young and old divided at median = 37 years. Participants provided blood samples and completed an extensive NPS test battery.

RESULTS

MDD showed significantly poorer NPS performance compared to HC. Serum calcium associated positively with NPS performance in HC and negatively in MDD for entire age-range samples. While younger MDD and HC showed positive NPS-calcium correlations, older MDD and HC exhibited negative NPS-calcium correlations ('correlation reversal'). Age had a significant effect on cognition and ionized calcium and interacted with illness-status, with an exaggerated influence on cognition in MDD compared to HC.

CONCLUSIONS

The results place calcium 'correlation reversal' to early middle-age time window, which may be accelerated for MDD and highlight the central role of calcium pathways in normal and pathological cognitive aging.

Vitamin D deficiency accelerates ageing and age-related diseases: a novel hypothesis

Ageing can occur at different rates, but what controls this variable rate is unknown. Here I have developed a hypothesis that vitamin D may act to control the rate of ageing. The basis of this hypothesis emerged from studyng the various cellular processes that control ageing. These processes such as autophagy, mitochondrial dysfunction, inflammation, oxidative stress, epigenetic changes, DNA disorders and alterations in Ca²⁺ and reactive oxygen species (ROS) signalling are all known to be regulated by vitamin D. The activity of these processes will be enhanced in individuals that are deficient in vitamin D. Not only will this increase the rate of ageing, but it will also increase the probability of developing age-related diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and cardiovascular disease. In individual with normal vitamin D levels, these ageing-related processes will occur at lower rates resulting in a reduced rate of ageing and enhanced protection against these age-related diseases.

Vitamin D, reactive oxygen species and calcium signalling in ageing and disease

Vitamin D is a hormone that maintains healthy cells. It functions by regulating the low resting levels of cell signalling components such as Ca(2+) and reactive oxygen species (ROS). Its role in maintaining phenotypic stability of these signalling pathways depends on the ability of vitamin D to control the expression of those components that act to reduce the levels of both Ca(2+) and ROS. This regulatory role of vitamin D is supported by both Klotho and Nrf2. A decline in the vitamin D/Klotho/Nrf2 regulatory network may enhance the ageing process, and this is well illustrated by the age-related decline in cognition in rats that can be reversed by administering vitamin D. A deficiency in vitamin D has also been linked to two of the major diseases in man: heart disease and Alzheimer's disease (AD). In cardiac cells, this deficiency alters the Ca(2+) transients to activate the gene transcriptional events leading to cardiac hypertrophy and the failing heart. In the case of AD, it is argued that vitamin D deficiency results in the Ca(2+) landscape that initiates amyloid formation, which then elevates the resting level of Ca(2+) to drive the memory loss that progresses to neuronal cell death and dementia.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.