Disturbance Of Calcium Homeostasis Research Articles

Brazilin induces FOXO3A-dependent autophagic cell death by disturbing calcium homeostasis in osteosarcoma cells.

Osteosarcoma is a common primary malignant bone tumour, and its cure rate has stagnated over the past 25-30years. Brazilin, a purified natural product from sappan wood (Caesalpinia sappan L.), has been proved to possess potent anti-cancer effects. In this study, we investigated the anti-cancer effect of brazilin on human osteosarcoma and elucidated the underlying mechanisms. We exposed MG-63 cells to different concentrations of brazilin (5, 10 and 20µM) for 24h. Western blotting, immunocytofluorescence, luciferase reporter assays, and RT-PCR were used to evaluate whether brazilin activates FOXO family-dependent autophagy. Brazilin increased autophagic flux in the human osteosarcoma cell line MG-63, as evidenced by the upregulation of LC3-II and the downregulation of P62/SQSTM1. Moreover, the pharmacological or genetic blockade of autophagy decreased brazilin-induced cell death, indicating that brazilin triggered autophagic cell death in MG-63 cells. Specifically, brazilin induced FOXO3A(Ser7) phosphorylation, activated FOXO3A nuclear translocation and increased FOXO3A reporter activity, which contributed to the expression of autophagy-related genes and subsequently initiated autophagic cell death in MG-63 cells. Importantly, the increased expression and nuclear translocation of FOXO3A were tightly related to the disturbance of calcium homeostasis, which could be prevented by chelating intracellular calcium. Taken together, these data demonstrate that brazilin induces osteosarcoma cell death by inducing excessive autophagy, which is mediated through the Ca2+-FOXO3A pathway. Our study provides a new anti-tumour mechanism for brazilin treatment in osteosarcoma patients.

Role of defective Ca2+ signaling in skeletal muscle weakness: Pharmacological implications.

The misbehaving attitude of Ca2+ signaling pathways could be the probable reason in many muscular disorders such as myopathies, systemic disorders like hypoxia, sepsis, cachexia, sarcopenia, heart failure, and dystrophy. The present review throws light upon the calcium flux regulating signaling channels like ryanodine receptor complex (RyR1), SERCA (Sarco-endoplasmic Reticulum Calcium ATPase), DHPR (Dihydropyridine Receptor) or Cav1.1 and Na+/Ca2+ exchange pump in detail and how remodelling of these channels contribute towards disturbed calcium homeostasis. Understanding these pathways will further provide an insight for establishing new therapeutic approaches for the prevention and treatment of muscle atrophy under stress conditions, targeting calcium ion channels and associated regulatory proteins.

Effect of serum fibroblast growth factor receptor 2 and CAPS proteins on calcium status in β-thalassaemia major patients who are free from overt inflammation

Bone disorders and disturbed calcium (Ca) homeostasis are common disorders in β-thalassaemia major (β-TM). In the present study, two bone related markers are studied in β-TM patients with negative C-reactive protein for the first time; fibroblast growth factor receptor 2 (FGFR2) and CAPS protein. Another goal is to estimate the correlation between the recent parameters and bone biomaterials as a function of iron status parameters in β-TM patients. The results revealed that, in patients with β-TM serum FGFR2, CAPS, alkaline phosphatase (ALP) and Mg significantly increased while serum Ca levels were low as compared with controls. Ca status is correlated with iron overload in β-TM. A significant correlation was present between CAPS and FGFR2. In conclusion, FGFR2 and CAPS associated with Ca status and subsequent bone disturbances in β-TM patients. Their level can be predicted from the equation: CAPS =0.001ALP +0.48FGFR2-1.26Ca – 3.95Pi +12.76 with acceptable applicability.

From Mice to Men: An Evolutionary Conserved Breakdown of the Epidermal Calcium Gradient and Its Impact on the Cornified Envelope

In previous publications, we could establish that a hallmark of human skin aging is the breakdown of the epidermal calcium gradient. This redistribution of calcium has many implications, including a restructuring of the cornified envelope, a reduced epidermal barrier function, a change in lipid composition, a reduced skin hydration, and an increased skin pH. Especially the age-dependent change in the cornified envelope composition was solely studied in human foreskin samples. The aim of this study was to confirm that this effect is neither restricted to UV-protected skin area nor limited to a specific sex. In addition, we wanted to show that the collapse of the epidermal calcium gradient is not only a hallmark of human skin aging, but is also evolutionarily conserved in mammals. By using such techniques as IHC, Western blot analysis, and RT-PCR, we could demonstrate the following: (1) A change in the epidermal calcium gradient is in fact the most important sign of epidermal aging in mammals (as shown in female human eyelids and mouse skin samples of the external ear-shell); (2) The disturbed calcium homeostasis affects the expression and crosslinking of most cornified-envelope-specific genes such as loricrin and filaggrin. In this way, we could establish that the age-dependent altered composition of the cornified envelope is a typical sign of skin aging not only in humans, but in mice, too. This makes the mouse an important model organism to study these changes.

Gadolinium as a new emerging contaminant of aquatic environments.

Since the 1980s, gadolinium (Gd)-based contrast agents (GBCAs) have been routinely used in magnetic resonance imaging as stable chelates of the Gd3+ ion, without toxic effects. Generally, GBCAs are considered some of the safest contrast agents. However, it has been observed that they can accumulate in patient tissue, bone, and probably brain (causing nephrogenic systemic fibrosis in patients with kidney failure or insufficiency and disturbance of calcium homeostasis in the organism). The GBCAs are predominantly removed renally without metabolization. Subsequently, they do not undergo degradation processes in wastewater-treatment plants and are emitted into the aquatic ecosystem. Their occurrence was confirmed in surface waters (up to 1100 ng/L), sediments (up to 90.5 μg/g), and living organisms. Based on a literature review, there is a need to investigate the contamination of different ecosystems and to ascertain the environmental fate of Gd. Long-term ecotoxicological data, degradation, metabolism, bioaccumulation processes, and biochemical effects of the Gd complexes should be explored. These data can be used to assess detailed environmental risks because currently only hotspots with high levels of Gd can be marked as dangerous for aquatic environments according to environmental risk assessments. Environ Toxicol Chem 2018;37:1523-1534. © 2018 SETAC.

Status of calcium homeostasis accompanied by anti- Mullerian hormone level in some primary infertile women in Babylon province

Ionized calcium represents the portion of total calcium and has biologically active; this study has been debated whether the calcium homeostasis status in correlated with anti-Mullerian hormone level how does influence on the reproductive ability in some pre-menopausal women. Eighty volunteer women non-smoking (20-35) years enrolled in this study,some of them (50 women) with primary infertility considered as study group,while the other 30 volunteer parous women considered as control group,non-fasting blood samples were taken from subjects during October 2015 till may 2016. ELISA kit was used to assay the serum level of anti-Mullerian and parathyroid hormone,whereas colorimetric method was used to determine serum total calcium,albumin and inorganic phosphorus,while ionized calcium is calculated by special equation depending on the total calcium and albumin level. Independent T-test analysis was used to determine any significant difference for investigated parameters between control and study group,linear regression analyses were in addition used to explore the association between ionized calcium and anti-Mullerian hormone (AMH) level in both control and infertile groups.infertile group have significantly p<0.001 lower mean serum ionized calcium level (4.31±0.61mg/dl) than in the control group (5.57±0.45mg/dl) accompanied by significantly increase in parathyroid hormone level (94.2±32.2ng/dl) in study groupin comparison with control group where they showed (92.1±22.2 ng/dl) mean concentration,in addition those infertile women had higher significantly (p<0.05) albumin level compared with those in control group,in addition to that,mean serum phosphorus level showed a significantly higher (p<0.01) in study group compared with its level in the control group,however infertile women revealed significantly decrease mean level in anti-Mullerian hormone (2.59±1.38ng/dl)compared with the hormone level in the control group (4.33±1.00ng/dl).As such results of linear regression analyses revealed a significant positive correlation between ionized calcium concentration and AMH level (r=0.58,p=0.000,n=40) in control group, as well,there was a significant strong positive correlation was seen between serum ionized calcium and AMH level for the infertile group (r=0.70,p=0.000,n=50).any physiological process including reproductive ability may need in one way or another to calcium metal. So,it's necessary maintain the concentration of blood calcium within stable normal range to ensure the work of most biological system properly including reproductive capacity and any disturbance in calcium homeostasis may have been altered the ovarian reserve which may in turn,reduce reproductive capacity.

Oxaliplatin Modulates the Characteristics of Voltage-Gated Calcium Channels and Action Potentials in Small Dorsal Root Ganglion Neurons of Rats.

Oxaliplatin is important for treating colorectal cancer. Although oxaliplatin is highly effective, it has severe side effects, of which neurotoxicity in dorsal root ganglion (DRG) neurons is one of the most common. The key mechanisms of this neurotoxicity are still controversial. However, disturbances of calcium homeostasis in DRG neurons have been suggested to mediate oxaliplatin neurotoxicity. By using whole-cell patch-clamp and current-clamp techniques, as well as immunocytochemical staining, we examined the influence of short- and long-term exposure to oxaliplatin on voltage-gated calcium channels (VGCC) and different VGCC subtypes in small DRG neurons of rats in vitro. Exposure to oxaliplatin reduced VGCC currents (ICa(V)) in a concentration-dependent manner (1-500μM; 13.8-63.3%). Subtype-specific measurements of VGCCs showed differential effects on ICa(V). While acute treatment with oxaliplatin led to a reduction in ICa(V) for P/Q-, T-, and L-type VGCCs, ICa(V) of N-type VGCCs was not affected. Exposure of DRG neurons to oxaliplatin (10 or 100μM) for 24h in vitro significantly increased the ICa(V) current density, with a significant influence on L- and T-type VGCCs. Immunostaining revealed an increase of L- and T-type VGCC protein levels in DRG neurons 24h after oxaliplatin exposure. This effect was mediated by calcium-calmodulin-protein kinase II (CaMKII). Significant alterations in action potentials (AP) and their characteristics were also observed. While the amplitude increased after oxaliplatin treatment, the rise time and time-to-peak decreased, and these effects were reversed by treatment with pimozide and nimodipine, which suggests that VGCCs are critically involved in oxaliplatin-mediated neurotoxicity.

Mutational analysis uncovers monogenic bone disorders in women with pregnancy-associated osteoporosis: three novel mutations in LRP5, COL1A1, and COL1A2.

Pregnancy-associated osteoporosis (PAO) is a rare skeletal condition, which is characterized by a reduction in bone mineral density (BMD) in the course of pregnancy and lactation. Typical symptoms include vertebral compression fractures and transient osteoporosis of the hip. Since the etiology is not well understood, this prospective study was conducted in order to elucidate the relevance of pathogenic gene variants for the development of PAO. Seven consecutive cases with the diagnosis of PAO underwent a skeletal assessment (blood tests, DXA, HR-pQCT) and a comprehensive genetic analysis using a custom-designed gene panel. All cases showed a reduced BMD (DXA T-score, lumbar spine - 3.2 ± 1.0; left femur - 2.2 ± 0.5; right femur - 1.9 ± 0.5), while the spine was affected more severely (p < 0.05). The trabecular and cortical thickness was overall reduced in HR-pQCT, while the trabecular number showed no alterations in most cases. The genetic analysis revealed three novel mutations in LRP5, COL1A1, and COL1A2. Our data show that previously unrecognized monogenic bone disorders play an important role in PAO. Pregnancy should be considered a skeletal risk factor, which can promote the initial clinical onset of such skeletal disorders. The underlying increased calcium demand is essential in terms of prophylactic and therapeutic measures, which are especially required in individuals with a genetically determined low bone mass. The implementation of this knowledge in clinical practice can enable the partial recovery of the skeleton. Consistent genetic studies are needed to analyze the frequency of pathogenic variants in women with PAO.

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

BackgroundMajor 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. MethodsDifferences 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. ResultsMDD 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. ConclusionsThe 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.

Neuroprotective potential of spermidine against rotenone induced Parkinson's disease in rats

Parkinson's disease is a leading hypokinetic disorder characterized by selective loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) region of mid-brain. Degeneration of dopaminergic neurons is considered to be due to oxidative stress, neuroinflammation, disturbed calcium homeostasis and glutamate excitotoxicity etc. Spermidine is a polyamine which counteracts age associated cell death by scavenging free radical formation, activates authophagic machinery by enhancing formation of autophagosome, and antagonizes NMDA receptor. In the current study we investigated the neuroprotective potential of spermidine against rotenone induced PD in rats. Rats were treated subcutaneously with rotenone 1.5 mg/kg daily for 28 days. Spermidine 5&10 mg/kg was administered orally 1 h prior to rotenone administration from 15 to 28. Rotenone caused significant reduction in motor functioning and elevated levels of oxidative stress markers and proinflammatory cytokines levels (IL-1β, IL6 and TNF-α). The neurochemical analysis revealed a significant decrease in serotonin, norepinephrine, dopamine and their metabolites accompanied by a significant loss of dopaminergic neurons in the SNpc following ROT injection. However, treatment with spermidine rescued DAergic neurons in SNpc and nerve terminals in the striatum following ROT insult. Spermidine treatment also attenuated oxidative stress, neuroinflammation and restored striatal neurochemistry. Results of our study suggest that spermidine has promising neuroprotective effect against degenerative changes in experimental PD, and the protective effects are mediated through its antioxidant and anti-inflammatory properties.

TRPC1 Channels Are Expressed in Pyramidal Neurons and in a Subset of Somatostatin Interneurons in the Rat Neocortex

Disturbances in calcium homeostasis due to canonical transient receptor potential (TRPC) and/or store-operated calcium (SOC) channels can play a key role in a large number of brain disorders. TRPC channels are plasma membrane cation channels included in the transient receptor potential (TRP) superfamily. The most widely distributed member of the TRPC subfamily in the brain is TRPC1, which is frequently linked to group I metabotropic glutamate receptors (mGluRs) and to the components of SOC channels. Proposing TRPC/SOC channels as a therapeutic target in neurological diseases previously requires a detailed knowledge of the distribution of such molecules in the brain. The aim of our study was to analyze the neuroanatomical distribution of TRPC1 in the rat neocortex. By double- and triple-labeling and confocal microscopy, we tested the presence of TRPC1 by using a series of specific neurochemical markers. TRPC1 was abundant in SMI 32-positive pyramidal neurons, and in some glutamic acid decarboxylase 67 (GAD67) interneurons, but was lacking in glial fibrillary acidic protein (GFAP)-positive glial cells. In neurons it colocalized with postsynaptic marker MAP2 in cell bodies and apical dendritic trunks and it was virtually absent in synaptophysin-immunoreactive terminals. By using a panel of antibodies to classify interneurons, we identified the GABAergic interneurons that contained TRPC1. TRPC1 was lacking in basket and chandelier parvalbumin (PVALB) cells, and a very low percentage of calretinin (CALR) or calbindin (CALB) interneurons expressed TRPC1. Moreover, 63% of somatostatin (SST) expressing-cells and 37% of reelin-positive cells expressed TRPC1. All the SST/TRPC1 double-labeled cells, many of which were presumptive Martinotti cells (MC), were positive for reelin. The presence of TRPC1 in the somata and apical dendritic trunks of neocortical pyramidal cells suggests a role for this channel in sensory processing and synaptic plasticity. Conversely in SST/reelin interneurons, TRPC1 could modulate GABAergic transmission, which is responsible for shaping the coordinated activity of the pyramidal cells in the cortical network. In future studies, it would be relevant to investigate whether TRPC1 could be involved in the expression or processing of reelin in SST inhibitory interneurons.

A retrospective analysis of bone mineral status in patients requiring spinal surgery

BackgroundImpaired bone quality is associated with poor outcome of spinal surgery. The aim of the study was to assess the bone mineral status of patients scheduled to undergo spinal surgery and to report frequencies of bone mineral disorders.MethodsWe retrospectively analyzed the bone mineral status of 144 patients requiring spinal surgery including bone mineral density by dual-energy X-ray absorptiometry (DXA) as well as laboratory data with serum levels of 25-hydroxyvitamin D (25-OH-D), parathyroid hormone, calcium, bone specific alkaline phosphate, osteocalcin, and gastrin. High-resolution peripheral quantitative computed tomography (HR-pQCT) was additionally performed in a subgroup of 67 patients with T-Score below − 1.5 or history of vertebral fracture.ResultsAmong 144 patients, 126 patients (87.5%) were older than 60 years. Mean age was 70.1 years. 42 patients (29.1%) had suffered from a vertebral compression fracture. 12 previously undiagnosed vertebral deformities were detected in 12 patients by vertebral fracture assessment (VFA). Osteoporosis was present in 39 patients (27.1%) and osteopenia in 63 patients (43.8%). Only 16 patients (11.1%) had received anti-osteoporotic therapy, while 54 patients (37.5%) had an indication for specific anti-osteoporotic therapy but had not received it yet. The majority of patients had inadequate vitamin D status (73.6%) and 34.7% of patients showed secondary hyperparathyroidism as a sign for a significant disturbed calcium homeostasis. In a subgroup of 67 patients, severe vertebral deformities were associated with stronger deficits in bone microarchitecture at the distal radius compared to the distal tibia.ConclusionsThis study shows that bone metabolism disorders are highly prevalent in elderly patients scheduled for spinal surgery. Vertebral deformities are associated with a predominant deterioration of bone microstructure at the distal radius. As impaired bone quality can compromise surgical outcome, we strongly recommend an evaluation of bone mineral status prior to operation and anti-osteoporotic therapy if necessary.

Potential role of potassium and chloride channels in regulation of silymarin-induced apoptosis in Candida albicans.

Silymarin, which is derived from the seeds of Silybum marianum, has been widely used to prevent and treat liver diseases. In our previous study, we reported that at concentrations above the minimal inhibitory concentration (MIC), silymarin exhibited antifungal activity against Candida albicans by targeting its plasma membrane. However, the antifungal mechanism at concentration below the MIC remains unknown. Therefore, we aimed to determine the underlying mechanism of antifungal effects of silymarin at concentration below the MIC. To evaluate the inhibitory effects on the ion channels, C. albicans cells were separately pretreated with potassium and chloride channel blockers. The antifungal activity of silymarin at sub-MIC was affected by the ion channel blockers. Potassium channel blockade inhibited the antifungal effects, whereas chloride channel blockade slightly enhanced these effects. Subsequently, we found that silymarin induced disturbances in calcium homeostasis via the cytosolic and mitochondrial accumulation of calcium. Furthermore, apoptotic responses, such as phosphatidylserine exposure, loss of mitochondrial membrane potential (MMP), DNA damage, and caspase activation were induced in response to silymarin treatment. The increases in intracellular calcium level and pro-apoptotic changes were prevented when potassium ion channels were blocked. In contrast, these changes were enhanced upon chloride channels blockade; however, this did not affect the intracellular calcium levels and MMP loss. Thus, we showed that silymarin treatment at concentration below the MIC induced apoptosis in C. albicans; additionally, ion channels contributed these effects. © 2018 IUBMB Life, 70(3):197-206, 2018.

Rapid Electrical Stimulation Increased Cardiac Apoptosis Through Disturbance of Calcium Homeostasis and Mitochondrial Dysfunction in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Background/Aims: Heart failure induced by tachycardia, the most common arrhythmia, is frequently observed in clinical practice. This study was designed to investigate the underlying mechanisms. Methods: Rapid electrical stimulation (RES) at a frequency of 3 Hz was applied on human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for 7 days, with 8 h/day and 24 h/day set to represent short-term and long-term tachycardia, respectively. Age-matched hiPSC-CMs without electrical stimulation or with slow electrical stimulation (1 Hz) were set as no electrical stimulation (NES) control or low-frequency electrical stimulation (LES) control. Following stimulation, JC-1 staining flow cytometry analysis was performed to examine mitochondrial conditions. Apoptosis in hiPSC-CMs was evaluated using Hoechst staining and Annexin V/propidium iodide (AV/PI) staining flow cytometry analysis. Calcium transients and L-type calcium currents were recorded to evaluate calcium homeostasis. Western blotting and qPCR were performed to evaluate the protein and mRNA expression levels of apoptosis-related genes and calcium homeostasis-regulated genes. Results: Compared to the controls, hiPSC-CMs following RES presented mitochondrial dysfunction and an increased apoptotic percentage. Amplitudes of calcium transients and L-type calcium currents were significantly decreased in hiPSC-CMs with RES. Molecular analysis demonstrated upregulated expression of Caspase3 and increased Bax/Bcl-2 ratio. Genes related to calcium re-sequence were downregulated, while phosphorylated Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) was significantly upregulated following RES. There was no significant difference between the NES control and LES control groups in these aspects. Inhibition of CaMKII with 1 µM KN93 partly reversed these adverse effects of RES. Conclusion: RES on hiPSC-CMs disturbed calcium homeostasis, which led to mitochondrial stress, promoted cell apoptosis and caused electrophysiological remodeling in a time-dependent manner. CaMKII played a central role in the damages induced by RES, pharmacological inhibition of CaMKII activity partly reversed the adverse effects of RES on both structural and electrophysiological properties of cells.

Renal phosphate handling and inherited disorders of phosphate reabsorption: an update.

Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.

Disorders of Mechanisms of Calcium Metabolism Control as Potential Risk Factors of Prostate Cancer.

Prostate cancer significantly affects the overall morbidity and mortality of malignant tumours in highly developed countries. Important risk factors include family predisposition and regional, racial and dietary determinants. The scientific literature contains a great deal of data on the role of calcium and dairy products in general in the process of neoplastic transformation of the prostate. This is most likely linked to the fact that changes in the concentration of calcium ions control such varied life processes as secretion of hormones and neurotransmitters, the level of cyclic nucleotides, and cell growth, division and differentiation. Research is conducted to demonstrate that disorders of cell cycle control due to differences in calcium ion concentrations may be crucial for the development and prevention of cancer. Disturbances of calcium homeostasis in the body can be caused by various mechanisms, such as excessive calcium intake in the diet, vitamin D deficiency, structural and functional changes in vitamin D receptor (VDR), Calcium-Sensing Receptor (CaSR), and parathyroid hormone receptor (PTH-1-R), changes in calcium ion channels, phosphate metabolism disorders (phosphatonin and the Klotho protein), changes in the level of parathyroid hormone-related protein (PTHrP), and others. The article presents data on the mechanisms maintaining calcium homeostasis at the molecular level and genetic aspects playing a role in the pathogenesis of prostate cancer. The data cited on the occurrence of abnormal mechanisms of calcium metabolism in prostate cancer suggest the need for individualized intake of this element in the diet, especially in the case of patients with a family history of PCa.

Knockdown of amyloid precursor protein increases calcium levels in the endoplasmic reticulum

Familial Alzheimer’s disease (AD) is caused by mutations in the genes that encode amyloid precursor protein (APP) and presenilins. Disturbances in calcium homeostasis have been observed in various cellular and animal models of AD and are proposed to underlie the pathogenesis of the disease. Furthermore, wildtype presenilins were shown to regulate endoplasmic reticulum (ER) calcium homeostasis, although their precise mechanism of action remains controversial. To investigate whether APP also affects ER calcium levels, we used RNA interference to target the APP gene in cultured T84 cells in combination with two types of ER calcium sensors. Using a genetically encoded calcium indicator, GEM-CEPIA1er, we found that APP-deficient cells exhibited elevated resting calcium levels in the ER and prolonged emptying of ER calcium stores upon the cyclopiazonic acid-induced inhibition of sarco-endoplasmic reticulum calcium-ATPase. These effects could be ascribed to lower ER calcium leakage rates. Consistent with these results, translocation of the endogenous ER calcium sensor STIM1 to its target channel Orai1 was delayed following ER calcium store depletion. Our data suggest a physiological function of APP in the regulation of ER calcium levels.

Inhibition of the mitochondrial calcium uniporter inhibits Aβ-induced apoptosis by reducing reactive oxygen species-mediated endoplasmic reticulum stress in cultured microglia

Amyloid-beta (Aβ) has been shown to induce microglial apoptosis, which is itself sensitive to disturbed mitochondrial calcium (Ca2+) homeostasis. The mitochondrial calcium uniporter (MCU) plays an important regulatory role in mitochondrial Ca2+ homeostasis, but its role in Aβ-induced microglia apoptosis is unknown. In this study, we found increased mitochondrial Ca2+ concentration in Aβ-treated primary microglia and BV-2 cells; also, the MCU inhibitor Ru360 significantly attenuated Aβ-induced microglial apoptosis, whereas the MCU activator spermine augmented it. In addition, Ru360 significantly attenuated Aβ-induced mitochondrial reactive oxygen species (ROS) production, as well as endoplasmic reticulum (ER) stress characterized by glucose-regulated protein 78 (GRP78) and C/-EBP homologous protein (CHOP) expression. Spermine, however, exerted the opposite effects on mitochondrial ROS production and ER stress. We also found that mitochondria-targeted antioxidant (Mito-TEMPO) treatment decreased GRP78 and CHOP expression in Aβ-treated microglia. Moreover, blocking endogenous CHOP expression using a CHOP small interfering RNA (siRNA) attenuated Aβ-induced cell death. Altogether, our data suggested that 1) inhibition of MCU exerts a neuroprotective effect on Aβ-induced microglia apoptosis, and 2) that the underlying mechanism may be related to reducing mitochondrial ROS-mediated ER stress.

Contribution of VMA5 to vacuolar function, stress response, ion homeostasis and autophagy in Candida albicans.

V-ATPase is a conservative multi-subunit enzyme in eukaryotes and modulates several cellular responses. This study aimed to illustrate the roles of Vma5 in vacuolar function, oxidative stress response, calcium homeostasis, autophagy and virulence. The vma5Δ/Δ mutant was obtained using PCR-mediated homologous recombination. The functions of Vma5 were investigated by a series of biochemical and systemic infection methods. Disruption of VMA5 led to growth inhibition, vacuolar dysfunction, disturbance of calcium homeostasis and inhibition of calcium-related oxidative stress response. Furthermore, its deletion caused defects in autophagy completion and hyphal development, and resulted in attenuated Candida albicans virulence. Our findings provide new insights into V-ATPase functions in C. albicans, and reveal a potential candidate for development of antifungal drugs.

KCa1.1 channels regulate β1-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes.

Large-conductance calcium-activated potassium channel (KCa1.1; BK, Slo1, MaxiK, KCNMA1) is the predominant potassium channel expressed at the plasma membrane of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) isolated from the synovium of patients with RA. It is a critical regulator of RA-FLS migration and invasion and therefore represents an attractive target for the therapy of RA. However, the molecular mechanisms by which KCa1.1 regulates RA-FLS invasiveness have remained largely unknown. Here, we demonstrate that KCa1.1 regulates RA-FLS adhesion through controlling the plasma membrane expression and activation of β1 integrins, but not α4, α5, or α6 integrins. Blocking KCa1.1 disturbs calcium homeostasis, leading to the sustained phosphorylation of Akt and the recruitment of talin to β1 integrins. Interestingly, the pore-forming α subunit of KCa1.1 coimmunoprecipitates with β1 integrins, suggesting that this physical association underlies the functional interaction between these molecules. Together, these data outline a new signaling mechanism by which KCa1.1 regulates β1-integrin function and therefore invasiveness of RA-FLSs.-Tanner, M. R., Pennington, M. W., Laragione, T., Gulko, P. S., Beeton, C. KCa1.1 channels regulate β1-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes.