Vitamin D,calcium homeostasis and aging

Osteoporosis is characterized by low bone mass and microarchitecture deterioration of bone tissue, leading to enhanced bone fragility and consequent increase in fracture risk. Evidence is accumulating for an important role of calcium deficiency as the process of aging is associated with disturbed calcium balance. Vitamin D is the principal factor that maintains calcium homeostasis. Increasing evidence indicates that the reason for disturbed calcium balance with age is inadequate vitamin D levels in the elderly. In this article, an overview of our current understanding of vitamin D, its metabolism, and mechanisms involved in vitamin D-mediated maintenance of calcium homeostasis is presented. In addition, mechanisms involved in age-related dysregulation of 1,25（OH）2D3 action, recommended daily doses of vitamin D and calcium, and the use of vitamin D analogs for the treatment of osteoporosis （which remains controversial） are reviewed. Elucidation of the molecular pathways of vitamin D action and modifications that occur with aging will be an active area of future research that has the potential to reveal new therapeutic strategies to maintain calcium balance.

Fenvalerate-induced Alterations in Calcium Homeostasis in Rat Ovary

Objective To observe the effects of fenv＇,derate on calcium homeostasis in rat ovary. Methods Female SpragueDawley rats were orally given fenvalerate at dally doses of 0.00, 1.91, 9.55, and 31.80 mg/kg for four weeks. The ovary ultrastucture was observed by electron microscopy. Serum free calcium concentration was measured by atomic absorption spectrophotometry. The activities of phosphorylase a in rat ovary were evaluated by the chromatometry. The total content of calmodulin in ovary was estimated by ELISA at each stage of estrous cycle. Radioimmunoassay （R/A） was used to evaluate the level of serum progesterone. Results Histopathologically, damages of ovarian corpus luteum cells were observed. An increase in serum fi＇ee calcium concentration was observed in rats treated with 31.80mg/kg fenvalerate. The activities of phosphorylase a enhanced in all treated groups, and fenvalerate increased the total content of calmodulin significantly in estrus period. Serum progesterone levels declined in fenvalerate exposed rats in diestrus. Conclusion Fenvalerate interferes with calcium homeostasis in rat ovary. Also, the inhibitory effects of fenvalerate on serum progesterone levels may be mediated partly through calcium signals.

Mitochondrial Oxidative Stress Enhances Vasoconstriction by Altering Calcium Homeostasis in Cerebrovascular Smooth Muscle Cells under Simulated Microgravity

Objective Exposure to microgravity results in postflight cardiovascular deconditioning in astronauts.Vascular oxidative stress injury and mitochondrial dysfunction have been reported during this process.To elucidate the mechanism for this condition,we investigated whether mitochondrial oxidative stress regulates calcium homeostasis and vasoconstriction in hindlimb unweighted(HU)rat cerebral arteries.Methods Three-week HU was used to simulate microgravity in rats.The contractile responses to vasoconstrictors,mitochondrial fission/fusion,Ca^(2+) distribution,inositol 1,4,5-trisphosphate receptor(IP3 R)abundance,and the activities of voltage-gated K+channels(KV)and Ca^(2+)-activated K+channels(BKCa)were examined in rat cerebral vascular smooth muscle cells(VSMCs).Results An increase of cytoplasmic Ca^(2+) and a decrease of mitochondrial/sarcoplasmic reticulum(SR)Ca^(2+) were observed in HU rat cerebral VSMCs.The abundance of fusion proteins(mitofusin 1/2[MFN1/2])and fission proteins(dynamin-related protein 1[DRP1]and fission-mitochondrial 1[FIS1])was significantly downregulated and upregulated,respectively in HU rat cerebral VSMCs.The cerebrovascular contractile responses to vasoconstrictors were enhanced in HU rats compared to control rats,and IP3 R protein/mRNA levels were significantly upregulated.The current densities and open probabilities of KV and BKCa decreased and increased,respectively.Treatment with the mitochondrial-targeted antioxidant mitoTEMPO attenuated mitochondrial fission by upregulating MFN1/2 and downregulating DRP1/FIS1.It also decreased IP3 R expression levels and restored the activities of the KV and BKCa channels.MitoTEMPO restored the Ca^(2+) distribution in VSMCs and attenuated the enhanced vasoconstriction in HU rat cerebral arteries.Conclusion The present results suggest that mitochondrial oxidative stress enhances cerebral vasoconstriction by regulating calcium homeostasis during simulated microgravity.

Latest assessment methods for mitochondrial homeostasis in cognitive diseases

Mitochondria play an essential role in neural function,such as supporting normal energy metabolism,regulating reactive oxygen species,buffering physiological calcium loads,and maintaining the balance of morphology,subcellular distribution,and overall health through mitochondrial dynamics.Given the recent technological advances in the assessment of mitochondrial structure and functions,mitochondrial dysfunction has been regarded as the early and key pathophysiological mechanism of cognitive disorders such as Alzheimer’s disease,Parkinson’s disease,Huntington’s disease,mild cognitive impairment,and postoperative cognitive dysfunction.This review will focus on the recent advances in mitochondrial medicine and research methodology in the field of cognitive sciences,from the perspectives of energy metabolism,oxidative stress,calcium homeostasis,and mitochondrial dynamics(including fission-fusion,transport,and mitophagy).

KCTD4 interacts with CLIC1 to disrupt calcium homeostasis and promote metastasis in esophageal cancer

Increasing evidences suggest the important role of calcium homeostasis in hallmarks of cancer,but its function and regulatory network in metastasis remain unclear.A comprehensive investigation of key regulators in cancer metastasis is urgently needed.Transcriptome sequencing(RNA-seq)of primary esophageal squamous cell carcinoma(ESCC)and matched metastatic tissues and a series of gain/loss-of-function experiments identified potassium channel tetramerization domain containing 4(KCTD4)as a driver of cancer metastasis.KCTD4 expression was found upregulated in metastatic ESCC.High KCTD4 expression is associated with poor prognosis in patients with ESCC and contributes to cancer metastasis in vitro and in vivo.Mechanistically,KCTD4 binds to CLIC1 and disrupts its dimerization,thus increasing intracellular Ca^(2+)level to enhance NFATc1-dependent fibronectin transcription.KCTD4-induced fibronectin secretion activates fibroblasts in a paracrine manner,which in turn promotes cancer cell invasion via MMP24 signaling as positive feedback.Furthermore,a lead compound K279-0738 significantly suppresses cancer metastasis by targeting the KCTD4-CLIC1 interaction,providing a potential therapeutic strategy.Taken together,our study not only uncovers KCTD4 as a regulator of calcium homeostasis,but also reveals KCTD4/CLIC1-Ca^(2+)-NFATc1-fibronectin signaling as a novel mechanism of cancer metastasis.These findings validate KCTD4 as a potential prognostic biomarker and therapeutic target for ESCC.

ARTC1-mediated VAPB ADP-ribosylation regulates calcium homeostasis

Mono-ADP-ribosylation(MARylation)is a post-translational modification that regulates a variety of biological processes,including DNA damage repair,cell proliferation,metabolism,and stress and immune responses.In mammals,MARylation is mainly catalyzed by ADP-ribosyltransferases(ARTs),which consist of two groups:ART cholera toxin-like(ARTCs)and ART diphtheria toxin-like(ARTDs,also known as PARPs).The human ARTC(hARTC)family is composed of four members:two active mono-ADP-ARTs(hARTC1 and hARTC5)and two enzymatically inactive enzymes(hARTC3 and hARTC4).In this study,we systematically examined the homology,expression,and localization pattern of the hARTC family,with a particular focus on hARTC1.Our results showed that hARTC3 interacted with hARTC1 and promoted the enzymatic activity of hARTC1 by stabilizing hARTC1.We also identified vesicle-associated membrane protein-associated protein B(VAPB)as a new target of hARTC1 and pinpointed Arg50 of VAPB as the ADP-ribosylation site.Furthermore,we demonstrated that knockdown of hARTC1 impaired intracellular calcium homeostasis,highlighting the functional importance of hARTC1-mediated VAPB Arg50 ADP-ribosylation in regulating calcium homeostasis.In summary,our study identified a new target of hARTC1 in the endoplasmic reticulum and suggested that ARTC1 plays a role in regulating calcium signaling.

Inhibition of the cGAS–STING pathway:contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS–STING pathway plays an important role in ischemia-reperfusion injury in the heart,liver,brain,and kidney,but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed.Here,we outline the components of the cGAS–STING pathway and then analyze its role in autophagy,ferroptosis,cellular pyroptosis,disequilibrium of calcium homeostasis,inflammatory responses,disruption of the blood–brain barrier,microglia transformation,and complement system activation following cerebral ischemia-reperfusion injury.We further analyze the value of cGAS–STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms.Inhibition of the cGAS–STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

Aluminum neurotoxicity effects on intracellular Ca^(2+) homeostasis in the rat cerebral cortex

Studies have suggested that aluminum, a neurotoxic metal, is involved in the progression of neurodegenerative diseases. Previous studies have confirmed that aluminum influences intracellular Ca^2＋ homeostasis. However, it remains unclear whether aluminum increases or decreases intracellular Ca^2＋ concentrations. The present study demonstrated that Al^3＋ competitively binds to calmodulin （CAM）, together with Ca^2＋, which resulted in loss of capacity of CaM to bind to Ca^2＋, leading to increased [Ca^2＋]i. Al^3＋ stimulated voltage-gated calcium channels on cell membranes, which allowed a small quantity of Ca^2＋ into the cells. Al^3＋ also promoted calcium release from organelles by stimulating L-Ca^2＋αlc to trigger calcium-induced calcium release. Although Al^3＋ upregulated expression of Na＋/Ca^2＋exchanger mRNA, increased levels of Ca^2＋ and Na＋/Ca^2＋ exchanger did not maintain a normal Ca^2＋ balance. Al^3＋ resulted in disordered intracellular calcium homeostasis by affecting calcium channels, calcium buffering, and calcium expulsion.

Calcium channel blockers and Alzheimer's disease

Alzheimer＇s disease is characterized by two pathological hallmarks： amyloid plaques and neurofibrillary tangles. In addition, calcium homeostasis is disrupted in the course of human aging Recent research shows that dense plaques can cause functional alteration of calcium signals in mice with Alzheimer＇s disease. Calcium channel blockers are effective therapeutics for treating Alzheimer＇s disease. This review provides an overview of the current research of calcium channel blockers involved in Alzheimer＇s disease theraov.

Mitochondria in Huntington’s disease:implications in pathogenesis and mitochondrial-targeted therapeutic strategies

Huntington’s disease is a genetic disease caused by expanded CAG repeats on exon 1 of the huntingtin gene located on chromosome 4.Compelling evidence implicates impaired mitochondrial energetics,altered mitochondrial biogenesis and quality control,disturbed mitochondrial trafficking,oxidative stress and mitochondrial calcium dyshomeostasis in the pathogenesis of the disorder.Unfortunately,conventional mitochondrial-targeted molecules,such as cysteamine,creatine,coenzyme Q10,or triheptanoin,yielded negative or inconclusive results.However,future therapeutic strategies,aiming to restore mitochondrial biogenesis,improving the fission/fusion balance,and improving mitochondrial trafficking,could prove useful tools in improving the phenotype of Huntington’s disease and,used in combination with genome-editing methods,could lead to a cure for the disease.

LncRNA CCRR maintains Ca^(2+)homeostasis against myocardial infarction through the FTO-SERCA2a pathway

Cardiac conduction regulatory RNA(CCRR)has been documented as an antiarrhythmic lncRNA in our earlier investigation.This study aimed to evaluate the effects of CCRR on SERCA2a and the associated Ca^(2+)homeostasis in myocardial infarction(MI).Overexpression of CCRR via AAV9-mediated delivery not only partially reversed ischemia-induced contractile dysfunction but also alleviated abnormal Ca^(2+)homeostasis and reduced the heightened methylation level of SERCA2a following MI.These effects were also observed in CCRR overexpressing transgenic mice.A conserved sequence domain of CCRR mimicked the protective function observed with the full length.Furthermore,silencing CCRR in healthy mice led to intracellular Ca^(2+)overloading of cardiomyocytes.CCRR increased SERCA2a protein stability by upregulating FTO expression.The direct interaction between CCRR and FTO protein was characterized by RNA-binding protein immunoprecipitation(RIP)analysis and RNA pulldown experiments.Activation of NFATc3 was identified as an upstream mechanism responsible for CCRR downregulation in MI.This study demonstrates that CCRR is a protective lncRNA that acts by maintaining the function of FTO,thereby reducing the m^(6)A RNA methylation level of SERCA2a,ultimately preserving calcium homeostasis for myocardial contractile function in MI.Therefore,CCRR may be considered a promising therapeutic strategy with a beneficial role in cardiac pathology.

Ca^(2+) cytochemical changes of hepatotoxicity caused by halothane and sevoflurane in enzyme-induced hypoxic rats

AIM： To investigat the relation between hepatotoxicity of halothane and sevoflurane and altered hepatic calcium homeostasis in enzyme-induced hypoxic rats. METHODS： Forty-eight rats were pretreated with phenobarbital and randomly divided into six groups （eight in each group） and exposed to O2/N2/1.2 MAC anesthetics for 1 h： normal control （NC）, 21% O2/79% N2; hypoxic control （HC）, 14% O2/86% N2; normal sevoflurane （NS）, 21% O2/ N2/1.2MAC sevoflurane; hypoxic sevoflurane （HS）, 14% O2/N2/1.2MAC sevoflurane; normal halothane （NH）21%O2/79%N2/1.2MAC halothane; hypoxic halothane （HH）, 14%O2/N2/1.2MAC halothane. Liver specimens and blood were taken 24 h after exposure to calcium and determined by EDX microanalysis. RESULTS： The liver of all rats given halothane （14% O2） had extensive centrilobular necrosis and denaturation. Morphologic damage was accompanied with an increase in serum glutarnic pyruvic transminase. In groups NH and HH, more calcium was precipitated in cytoplasm and mitochondria. CONCLUSION： These results suggest that halothane increases cytosolic Ca^2＋ concentration in hepatocytes. Elevation in Ca^2＋ concentration is implicated in the mechanism of halothane-induced hepatotoxicity. sevoflurane is less effective in affecting hepatic calcium homeostasis than halothane.

Resveratrol corrects aberrant splicing of RYR1 pre-mRNA and Ca2+ signal in myotonic dystrophy type 1 myotubes

Myotonic dystrophy type 1(DM1) is a spliceopathy related to the mis-splicing of several genes caused by sequestration of nuclear transcriptional RNA-binding factors from non-coding CUG repeats of DMPK pre-mRNAs. Dysregulation of ryanodine receptor 1(RYR1), sarcoplasmatic/endoplasmatic Ca^2+-ATPase(SERCA) and α1 S subunit of voltage-gated Ca^2+ channels(Cav1.1) is related to Ca^2+ homeostasis and excitation-contraction coupling impairment. Though no pharmacological treatment for DM1 exists, aberrant splicing correction represents one major therapeutic target for this disease. Resveratrol(RES, 3,5,4′-trihydroxy-trans-stilbene) is a promising pharmacological tools for DM1 treatment for its ability to directly bind the DNA and RNA influencing gene expression and alternative splicing. Herein, we analyzed the therapeutic effects of RES in DM1 myotubes in a pilot study including cultured myotubes from two DM1 patients and two healthy controls. Our results indicated that RES treatment corrected the aberrant splicing of RYR1, and this event appeared associated with restoring of depolarization-induced Ca^2+ release from RYR1 dependent on the electro-mechanical coupling between RYR1 and Cav1.1. Interestingly, immunoblotting studies showed that RES treatment was associated with a reduction in the levels of CUGBP Elav-like family member 1, while RYR1, Cav1.1 and SERCA1 protein levels were unchanged. Finally, RES treatment did not induce any major changes either in the amount of ribonuclear foci or sequestration of muscleblind-like splicing regulator 1. Overall, the results of this pilot study would support RES as an attractive compound for future clinical trials in DM1. Ethical approval was obtained from the Ethical Committee of IRCCS Fondazione Policlinico Universitario A. Gemelli, Rome, Italy(rs9879/14) on May 20, 2014.

The Prevenlive-Therapeutic Effects of Reduqing (热毒清)on Endotoxin-Induced DIC in Rabbits (Continued)Protection of Hepatocytic Microsomes, Maintenance of CalciumHomeostasis and Reduction of Oxygen Free Radicals

Disseminated intravascular coagulation (DIC) model of rabbits was made by the injectionof endotoxin. Cytochrome P-450 content and aniline hydroxylase activity in hepatocytic microsomes in DICrabbits were significantly reduced. The microviscosity of mitochondrial membrane was elevated, whilethe fluidity of the membrane, and the activities of calcium-magnesium-adenosine triphosphatase and calci-um-adenosine triphosphatase were reduced. Lipid peroxide and xanthine oxidase activities were in-creased. while superoxide dismutase and glutathione peroxidase activities were significantly decreased(P<0.05 or <0. 01) . The changes in the Reduqing test group were not prominent. and the parameters ofthe test group were close to those of the control group. This study suggests that in endotoxin induced DICrabbits the hepatocytic microsomes are injured. calcium homeostasis is disturbed and oxygen free radicalsare notably accumulated. Whereas Reduqing may have a protective effect on hepatocytic microsomestrom the injury, maintain calcium homeostasis and reduce oxygen free radicals in DIC rabbits.

Hypercalcaemia after treatment with denosumab in children:bisphosphonates as an option for therapy and prevention?

Background Pharmacologic options for treatment of osteolytic diseases especially in children are limited.Although not licensed for use,denosumab,a fully humanized antibody to RANKL,is used in children with good effects.Among others,one possible indication are giant cell tumors and aneurysmatic bone cysts.However,there are reports of severe hypercalcemia during weeks to months after termination of denosumab,that are rarely seen in adults.Methods We collected data of four patients,aged 6-17 years,who experienced severe hypercalcemia after completion of treatment with denosumab for unresectable giant cell tumors of bone or aneurysmal bone cysts and methods of their treatment.The detailed case information were described.Results One patient was treated with long-term,high-dose steroid therapy,leading to typical Cushing's syndrome.Another patient was restarted on denosumab repeatedly due to relapses of hypercalcemia after every stop.Finally,in two patients,hypercalcemia ceased definitely after treatment with bisphosphonates.However,several applications were necessary to stabilize calcium levels.Conclusions There is a considerable risk of hypercalcemia as an adverse effect after denosumab treatment in children.Therapeutic and,preferably,preventive strategies are needed.Bisphosphonates seem to be an option for both,but effective proceedings still remain to be established.

Generation of Calhm1 knockout mouse and characterization of calhm1 gene expression

Alzheimer’s disease(AD)is the most common neurode-generative disease among elderly people worldwide.Several genes have been validated to be associated with AD,and calcium homeostasis modulator 1(Calhm1)is the latest suspected one.To investigate the biological and pathological function of Calhm1 systematically,we generated a Calhm1 conventional knockout mouse.However,both the male and female of elderly Calhm1 knockout(KO)mice showed similar ability to their wild type littermates in spatial learning and memory retrieving.Surprisingly,we found that Calhm1 mRNA could not be detected in mouse brains at different ages,although it is expressed in the human brain tissues.We further found that CpG islands(CGIs)of both mouse and human Calhm1 were hypermethylated,whereas CGI of mouse Calhm2 was hypomethylated.In addition,transcriptional active marker H3K4Di occupied on promoters of human Calhm1 and mouse Calhm2 at a considerable level in brain tissues,while the occupancy of H3K4Di on pro-moter of mouse Calhm1 was rare.In sum,we found that mouse Calhm1 was of rare abundance in brain tissues.So it might not be suitable to utilize the knockout murine model to explore biological function of Calhm1 in the pathogenesis of AD.