Zinc Deficiency Decreases Neurite Extension via CRMP2 Signal Pathway.

Previous reports indicated that zinc deficiency could increase the risk of infectious diseases and developmental retardation in children. In experimental study, it has been reported that zinc deficiency during the embryonic period inhibited fetal growth, and disturbed neural differentiation and higher brain function later in adulthood. Although it has been suggested that zinc deficiency during development can have significant effects on neuronal differentiation and maturation, the molecular mechanisms of the effects of low zinc on neuronal differentiation during development have not been elucidated in detail. This study was performed to determine the effects of low zinc status on neurite outgrowth and collapsin response mediator protein 2 (CRMP2) signal pathway. Low zinc suppressed neurite outgrowth, and caused increase levels of phosphorylated CRMP2 (pCRMP2) relative to CRMP2, and decrease levels of phosphorylated glycogen synthase kinase 3ß (pGSK3ß) relative to GSK3ß in human neuroblastoma cell line (SH-SY5Y) cells on days 1, 2, and 3 of neuronal differentiation induction. Neurite outgrowth inhibited by low zinc was restored by treatment with the GSK3ß inhibitor CHIR99021. These results suggested that low zinc causes neurite outgrowth inhibition via phosphorylation of CRMP2 by GSK3ß. In conclusion, this study is the first to demonstrate that CRMP signaling is involved in the suppression of neurite outgrowth by low zinc.

Role of phosphate transporter PiT-2 in the pathogenesis of primary brain calcification.

Primary brain calcification (PBC), also known as idiopathic basal ganglia calcification (IBGC), primary familial brain calcification (PFBC) and so on, is a rare intractable disease characterized by abnormal mineral deposits, including mostly calcium in the basal ganglia, thalamus, and cerebellum. The causative gene of familial PBC is SLC20A2, which encodes the phosphate transporter PiT-2. Despite this knowledge, the molecular mechanism underlying SLC20A2-associated PBC remains unclear. In the present study, we investigated whether haploinsufficiency or a dominant-negative mechanism reduced Pi uptake in two PiT-2 variants (T115 M and R467X). We demonstrated that the presence of T115 M or R467X had no dominant-negative effect on Pi transport activity of wild-type (WT). In addition, the subcellular localization of R467X completely differed from that of WT, indicating that there is no interaction between R467X and WT. Conversely, T115 M and WT showed almost the same localization. Therefore, we examined the interaction between T115 M and WT using the bioluminescence resonance energy transfer (BRET) method. Although WT and T115 M interact with each other, T115 M does not inhibit WT's Pi transport activity. These results suggest that the role of SLC20A2 in the pathogenesis of PBC may involve decreased intracellular Pi uptake by a haploinsufficiency mechanism rather than a dominant-negative mechanism; agents promoting PiT-2 dimerization may be promising potential therapeutic agents for PBC.

Molecular Imaging of Labile Heme in Living Cells Using a Small Molecule Fluorescent Probe.

Labile heme (LH) is a complex of Fe(II) and protoporphyrin IX, an essential signaling molecule in various biological systems. Most of the subcellular dynamics of LH remain unclear because of the lack of efficient chemical tools for detecting LH in cells. Here, we report an activity-based fluorescence probe that can monitor the fluctuations of LH in biological events. H-FluNox is a selective fluorescent probe that senses LH using biomimetic N-oxide deoxygenation to trigger fluorescence. The selectivity of H-FluNox to LH is >100-fold against Fe(II), enabling the discrimination of LH from the labile Fe(II) pool in living cells. The probe can detect the acute release of LH upon NO stimulation and the accumulation of LH by inhibiting the heme exporter. In addition, imaging studies using the probe revealed a partial heme-export activity of the ATP-binding cassette subfamily G member 2 (ABCG2), potential LH pooling ability of G-quadruplex, and involvement of LH in ferroptosis. The successful use of H-FluNox in identifying fluctuations of LH in living cells offers opportunities for studying the physiology and pathophysiology of LH in living systems.

PDGF-BB is involved in phosphate regulation via the phosphate transporters in human neuroblastoma SH-SY5Y cells.

Inorganic phosphate (Pi) is the second most abundant inorganic ion in the body. Since abnormalities in Pi metabolism are risk factors for various diseases, serum Pi levels are strictly controlled. Type-III sodium-dependent Pi transporters, PiT-1 (encoded by SLC20A1) and PiT-2 (encoded by SLC20A2), are distributed throughout the tissues of the body, including the central nervous system, and are known to be responsible for extracellular to intracellular Pi transport. Platelet-derived growth factor (PDGF) is a major growth factor of mesenchymal cells. PDGF-BB, a homodimer of PDGF-B, regulates intracellular Pi by increasing PiT-1 expression in vascular smooth muscle cells. However, the effects of PDGF-BB on Pi transporters in neurons have yet to be reported. Here, we investigated the effect of PDGF-BB on Pi transporters in human neuroblastoma SH-SY5Y cells. PDGF-BB did not induce SLC20A1 mRNA expression, but it increased the intracellular uptake of Pi via PiT-1 in SH-SY5Y cells. Among the signaling pathways associated with PDGF-BB, AKT signaling was shown to be involved in the increase in Pi transport. In addition, the PDGF-BB-induced increase in Pi mediated neuroprotective effects in SLC20A2-suppressed cells, in an in vitro model of the pathological condition found in idiopathic basal ganglia calcification. Moreover, the increase in Pi uptake was found to occur through promotion of intracellular PiT-1 translocation to the plasma membrane. Overall, these results indicate that PDGF-BB exerts neuroprotective effects via Pi transport, and they demonstrate the potential utility of PDGF-BB against abnormal Pi metabolism in neurons.

Characteristics and therapeutic potential of sodium-dependent phosphate cotransporters in relation to idiopathic basal ganglia calcification.

Type-III sodium-dependent phosphate transporters 1 and 2 (PiT 1 and PiT 2, respectively) are proteins encoded by SLC20A1 and SLC20A2, respectively. The ubiquitous distribution of SLC20A1 and SLC20A2 mRNAs in mammalian tissues supports the housekeeping maintenance and homeostasis of intracellular inorganic phosphate (Pi), which is absorbed from interstitial fluid for normal cellular functions. SLC20A2 variants have been found in patients with idiopathic basal ganglia calcification (IBGC), also known as Fahr's disease or primary familial brain calcification (PFBC). Thus, disrupted Pi homeostasis is considered one of the major factors in the pathogenic mechanism of IBGC. In this paper, among the causative genes of IBGC, we focused specifically on PiT2, and its potential for a therapeutic target of IBGC.

DNA methyltransferase- and histone deacetylase-mediated epigenetic alterations induced by low-level methylmercury exposure disrupt neuronal development.

Methylmercury (MeHg) is a chemical substance that causes adverse effects on fetal development. However, the molecular mechanisms by which environmental MeHg affects fetal development have not been clarified. Recently, it has been suggested that the toxic effects of chemicals on fetal development are related alterations in epigenetics, such as DNA methylation and histone modification. In order to analyze the epigenetic effects of low-level MeHg exposure on neuronal development, we evaluated neuronal development both in vivo and in vitro. Pregnant mice (C57BL/6J) were orally administrated 3 mg/kg of MeHg once daily from embryonic day 12-14. Fetuses were removed on embryonic day 19 and brain tissues were collected. LUHMES cells were treated with 1 nM of MeHg for 6 days and collected on the last day of treatment. In both in vivo and in vitro samples, MeHg significantly suppressed neurite outgrowth. Decreased acetylated histone H3 (AcH3) levels and increased histone deacetylase (HDAC) 3 and HDAC6 levels were observed in response to MeHg treatment in both in vivo and in vitro experiments. In addition, increased DNA methylation and DNA methyltransferase 1 (DNMT1) levels were observed in both in vivo and in vitro experiments. The inhibition of neurite outgrowth resulting from MeHg exposure was restored by co-treatment with DNMT inhibitor or HDAC inhibitors. Our results suggest that neurological effects such as reduced neurite outgrowth due to low-level MeHg exposure result from epigenetic changes, including a decrease in AcH3 via increased HDAC levels and an increase in DNA methylation via increased DNMT1 levels.

Kaempferol Has Potent Protective and Antifibrillogenic Effects for α-Synuclein Neurotoxicity In Vitro.

Aggregation of α-synuclein (α-Syn) is implicated in the pathogenesis of Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Therefore, the removal of α-Syn aggregation could lead to the development of many new therapeutic agents for neurodegenerative diseases. In the present study, we succeeded in generating a new α-Syn stably expressing cell line using a piggyBac transposon system to investigate the neuroprotective effect of the flavonoid kaempferol on α-Syn toxicity. We found that kaempferol provided significant protection against α-Syn-related neurotoxicity. Furthermore, kaempferol induced autophagy through an increase in the biogenesis of lysosomes by inducing the expression of transcription factor EB and reducing the accumulation of α-Syn; thus, kaempferol prevented neuronal cell death. Moreover, kaempferol directly blocked the amyloid fibril formation of α-Syn. These results support the therapeutic potential of kaempferol in diseases such as synucleinopathies that are characterized by α-Syn aggregates.

Neuroprotective effects of 5-aminolevulinic acid against neurodegeneration in rat models of Parkinson's disease and stroke.

Oxidative stress is associated with the progression of the neurodegenerative diseases Parkinson's disease (PD) and cerebral ischemia. Recently, 5-aminolevulinic acid (5-ALA), an intermediate in the porphyrin synthesis pathway, was reported to exert antioxidative effects on macrophages and cardiomyocytes. Here, we demonstrated the neuroprotective effects of 5-ALA using rat models of PD and ischemia as well as in vitro in SH-SY5Y cells. 5-ALA partially prevented neurodegeneration in each condition. These results suggest that 5-ALA has a potential for promising therapeutic agent to protect against neurodegeneration exacerbated by oxidative stress.

MicroRNA-5572 Is a Novel MicroRNA-Regulating SLC30A3 in Sporadic Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease caused by the loss of motor neurons. Although the pathogenesis of sporadic ALS (sALS) remains unclear, it has recently been suggested that disorders of microRNA (miRNA) may be involved in neurodegenerative conditions. The purpose of this study was to investigate miRNA levels in sALS and the target genes of miRNA. Microarray and real-time RT-PCR analyses revealed significantly-decreased levels of miR-139-5p and significantly increased levels of miR-5572 in the spinal cords of sALS patients compared with those in controls. We then focused on miR-5572, which has not been reported in ALS, and determined its target gene. By using TargetScan, we predicted SLC30A3 as the candidate target gene of miR-5572. In a previous study, we found decreased SLC30A3 levels in the spinal cords of sALS patients. We revealed that SLC30A3 was regulated by miR-5572. Taken together, these results demonstrate that the level of novel miRNA miR-5572 is increased in sALS and that SLC30A3 is one of the target genes regulated by miR-5572.

The Novel gem-Dihydroperoxide 12AC3O Suppresses High Phosphate-Induced Calcification via Antioxidant Effects in p53LMAco1 Smooth Muscle Cells.

The excessive intake of phosphate (Pi), or chronic kidney disease (CKD), can cause hyperphosphatemia and eventually lead to ectopic calcification, resulting in cerebrovascular diseases. It has been reported that reactive oxygen species (ROS), induced by high concentrations of Pi loading, play a key role in vascular calcification. Therefore, ROS suppression may be a useful treatment strategy for vascular calcification. 12AC3O is a newly synthesized gem-dihydroperoxide (DHP) that has potent antioxidant effects. In the present study, we investigated whether 12AC3O inhibited vascular calcification via its antioxidative capacity. To examine whether 12AC3O prevents vascular calcification under high Pi conditions, we performed Alizarin red and von Kossa staining, using the mouse aortic smooth muscle cell line p53LMAco1. Additionally, the effect of 12AC3O against oxidative stress, induced by high concentrations of Pi loading, was investigated using redox- sensitive dyes. Further, the direct trapping effect of 12AC3O on reactive oxygen species (ROS) was investigated by ESR analysis. Although high concentrations of Pi loading exacerbated vascular smooth muscle calcification, calcium deposition was suppressed by the treatment of both antioxidants and 12AC3O, suggesting that the suppression of ROS may be a candidate therapeutic approach for treating vascular calcification induced by high concentrations of Pi loading. Importantly, 12AC3O also attenuated oxidative stress. Furthermore, 12AC3O directly trapped superoxide anion and hydroxyl radical. These results suggest that ROS are closely involved in high concentrations of Pi-induced vascular calcification and that 12AC3O inhibits vascular calcification by directly trapping ROS.

SLC20A2 variants cause dysfunctional phosphate transport activity in endothelial cells induced from Idiopathic Basal Ganglia Calcification patients-derived iPSCs.

Idiopathic Basal Ganglia Calcification (IBGC) is a rare neuropsychiatric illness also known as Fahr's disease or Primary Familial Brain Calcification (PFBC). IBGC is caused by SLC20A2 variants, which encodes the inorganic phosphate (Pi) transporter PiT-2, a transmembrane protein associated with Pi homeostasis. We have reported novel SLC20A2 variants in the Japanese population and established an induced pluripotent stem cells (iPSCs) from an IBGC patient carrying a SLC20A2 variant. To investigate the effect of these SLC20A2 variants identified in our previous study, we used Chinese hamster ovary (CHO) cells expressing these variant proteins using the Flp-In system (Flp-In CHO cells), and showed that variant SLC20A2 proteins significantly disrupted the Pi transport activity in Flp-In CHO cells. Endothelial cells (ECs) represent important target cells for elucidating the pathology of IBGC. Using patient-derived iPSCs in this study, we differentiated these cells into ECs and found no significant difference in their differentiation capacity into ECs compared with control iPSCs. However, the Pi transport activity of IBGC patient-derived iPS-ECs was significantly decreased compared with that of control iPS-ECs without changing the gene expression of the other SLC 20 family members. We confirmed that SLC20A2 variants caused the loss of function of the Pi transport activity in both Flp-In CHO cells and disease-specific iPSCs. This is the first report to show an in vitro model of iPSCs in IBGC with patient-identified SLC20A2 variants. These useful tools will help in elucidating IBGC pathogenesis and can be used for screening drug candidates.

Effects of gem-dihydroperoxides against mutant copper­zinc superoxide dismutase-mediated neurotoxicity.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive muscle weakness, paralysis, and death. Although its neuropathology is well investigated, currently, effective treatments are unavailable. The mechanism of ALS involves the aggregation and accumulation of several mutant proteins, including mutant copper­zinc superoxide dismutase (SOD1), TAR DNA binding protein 43 kDa (TDP-43) and fused in sarcoma (FUS) proteins. Previous reports have shown that excessive oxidative stress, associated with mitochondrial dysfunction and mutant protein accumulation, contributes to ALS pathology. The present study focuses on the promotion of SOD1 misfolding and aggregation by oxidative stress. Having recently synthesized novel organic gem-dihydroperoxides (DHPs) with high anti-oxidant activity, we now examined whether DHPs reduce the mutant SOD1-induced intracellular aggregates involved in oxidative stress. We found that, among DHPs, 12AC2O significantly inhibited mutant SOD1-induced cell death and reduced the intracellular mutant SOD1 aggregates. Moreover, immunofluorescence staining with redox-sensitive dyes showed that 12AC2O reduced the excessive level of intracellular mutant SOD1-induced reactive oxygen species (ROS). Additionally, ESR analysis showed that 12AC2O exerts a direct scavenging effect against the hydroxyl radical (OH) and the superoxide anion (O2-). These results suggest that 12AC2O is a very useful agent in combination with other agents against ALS.

p-Coumaric Acid Has Protective Effects against Mutant Copper-Zinc Superoxide Dismutase 1 via the Activation of Autophagy in N2a Cells.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective death of motor neurons. In previous our study, an ethanol extract of Brazilian green propolis (EBGP) prevented mutant copper-zinc superoxide dismutase 1 (SOD1mut)-induced neurotoxicity. This paper aims to reveal the effects of p-coumaric acid (p-CA), an active ingredient contained in EBGP, against SOD1mut-induced neurotoxicity. We found that p-CA reduced the accumulation of SOD1mut subcellular aggregation and prevented SOD1mut-associated neurotoxicity. Moreover, p-CA attenuated SOD1mut-induced oxidative stress and endoplasmic reticulum stress, which are significant features in ALS pathology. To examine the mechanism of neuroprotective effects, we focused on autophagy, and we found that p-CA induced autophagy. Additionally, the neuroprotective effects of p-CA were inhibited by chloroquine, an autophagy inhibiter. Therefore, these results obtained in this paper suggest that p-CA prevents SOD1mut-induced neurotoxicity through the activation of autophagy and provides a potential therapeutic approach for ALS.

Methylmercury causes epigenetic suppression of the tyrosine hydroxylase gene in an in vitro neuronal differentiation model.

Methylmercury (MeHg) is the causative substance of Minamata disease, which is associated with various neurological disorders such as sensory disturbance and ataxia. It has been suggested low-level dietary intake of MeHg from MeHg-containing fish during gestation adversely affects the fetus. In our study, we investigated the toxicological effects of MeHg exposure on neuronal differentiation focusing on epigenetics. We used human fetal brain-derived immortalized cells (LUHMES cells) as a human neuronal differentiation model. Cell viability, neuronal, and catecholamine markers in LUHMES cells were assessed after exposure to MeHg (0-1000 nM) for 6 days (from day 2 to day 8 of neuronal differentiation). Cell viability on day 8 was not affected by exposure to 1 nM MeHg for 6 days. mRNA levels of AADC, DBH, TUJ1, and SYN1 also were unaffected by MeHg exposure. In contrast, levels of TH, the rate-limiting enzyme for dopamine synthesis, were significantly decreased after MeHg exposure. Acetylated histone H3, acetylated histone H3 lysine 9, and tri-methyl histone H3 lysine 9 levels at the TH gene promoter were not altered by MeHg exposure. However, tri-methylation of histone H3 lysine 27 levels, related to transcriptional repression, were significantly increased at the TH gene promotor after MeHg exposure. In summary, MeHg exposure during neuronal differentiation led to epigenetic changes that repressed TH gene expression. This study provides useful insights into the toxicological mechanisms underlying the effects of developmental MeHg exposure during neuronal differentiation.

Protective function of SLC30A10 induced via PERK-ATF4 pathway against 1-methyl-4-phenylpyridinium.

Solute carrier family 30 member 10 (SLC30A10) has been known as manganese transporter. It has been suggested that neurodegenerative diseases are related with cellular stress such as oxidative stress or endoplasmic reticulum (ER) stress. However, it remains unknown whether SLC30A10 is actually involved in several intracellular stress. We found that the level of Slc30a10 was increased in midbrain of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Therefore, we further investigated the role of SLC30A10 in the 1-methyl-4-phenylpiridium ion (MPP+)-induced intracellular stress, and the molecular mechanism underlying SLC30A10 induction by MPP+ treatment. In human neuroblastoma cell line (SH-SY5Y) treated with MPP+ (1 mM), the SLC30A10 mRNA level was significantly increased, and in addition, the expression of CHOP, which is known as one of ER stress markers, was significantly increased by MPP+. Interestingly, the level of SLC30A10 mRNA was significantly increased by tunicamycin as an ER stressor, suggesting that the induction of SLC30A10 by MPP+ was caused via ER stress. Considering that PKR-like endoplasmic reticulum kinase (PERK) pathway is activated under ER stress induced by MPP+, we investigated whether the expression of SLC30A10 is increased through ATF4, which is major transcription factor in PERK pathway. The increase of SLC30A10 expression in MPP+-treated cells was eliminated by ATF4 knockdown. And the protective role of SLC30A10 against MPP+-induced ER stress was confirmed by measuring cell viability in SLC30A10 knockdown cells. In conclusion, SLC30A10 is thought to have protective role for MPP+-induced toxicity via PERK-ATF4 pathway.

Fluorodopa is a Promising Fluorine-19 MRI Probe for Evaluating Striatal Dopaminergic Function in a Rat Model of Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra projecting to the striatum. It has been estimated that approximately 80% of the striatal dopamine and 50% of nigral dopaminergic neurons are lost before the onset of typical motor symptoms, indicating that early diagnosis of PD using noninvasive imaging is feasible. Fluorine-19 (19 F) magnetic resonance imaging (MRI) represents a highly sensitive, easily available, low-background, and cost-effective approach to evaluate dopaminergic function using non-radioactive fluorine-containing dopaminergic agents. The aim of this study was to find a potent 19 F MRI probe to evaluate dopaminergic presynaptic function in the striatum. To select candidates for 19 F MRI probes, we investigated the following eight non-radioactive fluorine-containing dopaminergic agents: fluorodopa (F-DOPA), F-tyrosine, haloperidol, GBR13069 duhydrochloride, GBR12909 duhydrochloride, 3-bis-(4-fluorophenyl) methoxytropane hydrochloride, flupenthixol, and fenfluramine. In 19 F nuclear magnetic resonance measurements, F-tyrosine and F-DOPA displayed a relatively higher signal-to-noise ratio value in brain homogenates than in others. F-DOPA, but not F-tyrosine, induced the rotational behavior in a 6-hydroxydopamine (6-OHDA)-induced hemiparkinsonian rat model. In addition, a significantly high amount of F-DOPA accumulated in the ipsilateral striatum of hemiparkinsonian rats after the injection. We performed 19 F MRI in PC12 cells and isolated rat brain using a 7T MR scanner. Our findings suggest that F-DOPA is a promising 19 F MRI probe for evaluating dopaminergic presynaptic function in the striatum of hemiparkinsonian rats. © 2016 Wiley Periodicals, Inc.

DJ-1/PARK7: A New Therapeutic Target for Neurodegenerative Disorders.

DJ-1, encoded in a causative gene of familial Parkinson's disease (PARK7), has multiple functions: it works as an antioxidant, in transcriptional regulation, as a molecular chaperone and in protein degradation. Three types of pathogenic mutants of DJ-1 (M26I, D149A and L166P) have been reported to disrupt proper structures and lead to a loss of function. DJ-1 receives oxidation at the cysteine residue, and the degree of oxidation at the C106 residue determines DJ-1 activity. In this decade, DJ-1 has been reported to suppress the progression of various neurodegenerative disorders in animal models. The administration of recombinant wild-type DJ-1 protein suppresses the neuronal loss associated with both Parkinson's disease and ischemic stroke in rats. Furthermore, in studies focused on DJ-1 as the therapeutic target, compounds that have the capacity of binding to DJ-1 at the C106 residue have been reported to exert therapeutic effects on various neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease and ischemic stroke. DJ-1 and DJ-1-targeting molecules/compounds will be useful therapeutic targets for various neurodegenerative disorders due to their various functions such as antioxidant capacity, chaperone function and as a proteolytic pathway.

Therapeutic Activities of DJ-1 and Its Binding Compounds Against Neurodegenerative Diseases.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that is primarily characterized by the degeneration of dopaminergic neurons in the nigrostriatal pathway. Loss-of-function mutations in the gene encoding PARK7/DJ-1 were identified in familial PD. Wild-type DJ-1 acts as an oxidative stress sensor in neural cells. Previously, we identified binding compounds of DJ-1, including UCP0045037/compound A, UCP0054278/compound B, and compound-23 (comp-23), by in silico virtual screening. These compounds prevented oxidative stress-induced dopaminergic neuronal death and restored locomotion defects in animal models of PD. In addition, these binding partners reduced infarct size in cerebral ischemia in rats. The neuroprotective effects of these compounds are lost in DJ-1-knockdown cells and DJ-1-knockout animal. These results suggest that these compounds interact with endogenous DJ-1 and then produce antioxidant and neuroprotective responses in both animal models for PD and cerebral ischemia in rats. This raises the possibility that interaction partners of DJ-1, such as UCP0045037, UCP0054278, and comp-23, may represent a novel dopaminergic neuroprotective drug for the treatment of PD.

Protective roles of SLC30A3 against endoplasmic reticulum stress via ERK1/2 activation.

Endoplasmic reticulum (ER) stress has been thought to be involved to neurodegenerative diseases such as Alzheimer's disease (AD) or Amyotrophic lateral sclerosis (ALS). The previous studies have shown that SLC30A3 level is decreased in prefrontal cortex of AD patients. In addition, we have shown that level of zinc (Zn) is increased in cerebrospinal fluid and SLC30A3 level is decreased in spinal cord of ALS patients. It was thought that both SLC30A3 and ER stress could be related to the cause of AD and ALS, however the relationship between ER stress and SLC30A3 has not been elucidated. Therefore we investigated that the role of SLC30A3 against ER stress. The level of SLC30A3 mRNA was significantly increased by tunicamycin treatment in human neuroblastoma cell line (SH-SY5Y) and human embryonic kidney cell line (HEK293). Cell viability under tunicamycin treatment was significantly decreased in SLC30A3 knockdown cells by siRNA in comparison with negative control (NC) cells. Cleaved caspase-3 level was significantly increased in SLC30A3 knockdown cells, not in NC cells. These results showed that SLC30A3 has a protective role to ER stress-induced toxicities. The previous study has shown that SLC30A3 protect cells from oxidative stress in ERK1/2 signal dependent manner, thus we determined the activity of ERK1/2 in SLC30A3 knockdown cells under ER stress condition. The level of ERK1/2 phosphorylation was significantly increased by tunicamycin treatment in NC cells, not in SLC30A3 knockdown cells. The ERK1/2 pathway is thought to have an association with defensive effects of SLC30A3 on cellular stress such as ER stress. In conclusion, this study suggested that SLC30A3 is supposed to play a protective role against ER stress, which is related to ERK1/2 activation.

Zinc transporters ZnT3 and ZnT6 are downregulated in the spinal cords of patients with sporadic amyotrophic lateral sclerosis.

The loss of homeostasis of essential metals is associated with various diseases, including neurodegenerative diseases. Previous studies have shown that the levels of zinc (Zn) are significantly higher in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis (ALS). Zn transporters and metallothioneins tightly control intracellular and extracellular Zn levels. This study investigated the protein levels of ZnT, a Zn transporter family, in ALS patients and model mice. The mRNA expression of ZnT1, -3, -4, -5, -6, -7, and -10 was assessed in the spinal cords of human control subjects. ZnT3 and ZnT6 protein levels were significantly diminished in the spinal cords of sporadic ALS patients compared with controls. Furthermore, immunohistochemical staining demonstrated decreased ZnT3 and ZnT6 immunoreactivity in the ventral horn of the spinal cords in ALS patients. Moreover, immunohistochemical analysis revealed that all ZnTs expressed in the spinal cords were localized in a distinct subset of motor neurons. In addition, ZnT3 and ZnT6 protein levels were not altered in SOD1 (G93A) mutant transgenic mice before or after the onset of ALS symptoms compared with controls. These results suggest that ZnT3 and ZnT6 protein levels are decreased in the spinal cords of sporadic ALS patients; however, this did not occur merely via loss of motor neurons.