Disruption of zinc homeostasis and the pathogenesis of senile dementia.

Zinc (Zn) is an essential trace element that is abundantly present in the brain. Although Zn plays crucial roles in learning and memory, numerous studies have indicated that the disruption of Zn homeostasis, namely both depletion and excess Zn, causes severe damage to neurons and is linked with various neurodegenerative diseases including Alzheimer's disease and vascular dementia. Here, we review the current understanding of the role of Zn in the pathogenesis of these neurodegenerative diseases. Based on our findings and other numerous studies, Zn acts as a contributor to Alzheimer's disease in the oligomerization, and as a protector in the neurotoxicity of Alzheimer's ß-amyloid protein. Furthermore, Zn plays a central role in ischemia-induced neuronal death and the pathogenesis of vascular dementia. Involvement of Ca(2+) dyshomeostasis and endoplasmic reticulum (ER) stress in the mechanism of Zn-induced neurotoxicity are suggested. We also discuss the possible role of carnosine (ß-alanyl histidine), a dipeptide that is present in the brain, as a protective substance for neuronal injury.

D-histidine and L-histidine attenuate zinc-induced neuronal death in GT1-7 cells.

Although zinc (Zn) is an essential trace element, excess Zn causes neuronal death following transient global ischemia and plays a central role in the pathogenesis of vascular-type dementia. In this study, we developed a rapid and convenient screening system for substances that prevent Zn-induced neurotoxicity by using GT1-7 cells (immortalized hypothalamic neurons), with the aim of identifying a treatment for vascular-type dementia. Among tested, we found a protective substance in the extract of round herring (Etrumeus teres), and determined its structure as l-histidine. Analysis of the structure-activity relationship by using histidine analogues revealed that both l-histidine and d-histidine exhibit the same neuroprotective activity. Furthermore, we investigated the molecular mechanisms underlying the protective effect of histidine on Zn-induced neurotoxicity using Zn imaging and gene expression analysis, and found that histidine protects against Zn-induced neurotoxicity not by inhibiting Zn chelation, thereby preventing increases in intracellular Zn(2+). Moreover, it is also suggested that endoplasmic reticulum (ER) stress and activity-regulated cytoskeleton associated protein (Arc) are implicated in Zn-induced degeneration of neurons.

Oral clarithromycin enhances airway immunoglobulin A (IgA) immunity through induction of IgA class switching recombination and B-cell-activating factor of the tumor necrosis factor family molecule on mucosal dendritic cells in mice infected with influenza A virus.

We previously reported that the macrolide antibiotic clarithromycin (CAM) enhanced the mucosal immune response in pediatric influenza, particularly in children treated with the antiviral neuraminidase inhibitor oseltamivir (OSV) with low production of mucosal antiviral secretory IgA (S-IgA). The aims of the present study were to confirm the effects of CAM on S-IgA immune responses, by using influenza A virus (IAV) H1N1-infected mice treated with or without OSV, and to determine the molecular mechanisms responsible for the induction of mucosal IgA class switching recombination in IAV-infected CAM-treated mice. The anti-IAV S-IgA responses and expression levels of IgA class switching recombination-associated molecules were examined in bronchus-lymphoid tissues and spleens of infected mice. We also assessed neutralization activities of S-IgA against IAV. Data show that CAM enhanced anti-IAV S-IgA induction in the airway of infected mice and restored the attenuated antiviral S-IgA levels in OSV-treated mice to the levels in the vehicle-treated mice. The expression levels of B-cell-activating factor of the tumor necrosis factor family (BAFF) molecule on mucosal dendritic cells as well as those of activation-induced cytidine deaminase and Iµ-Cα transcripts on B cells were enhanced by CAM, compared with the levels without CAM treatment, but CAM had no effect on the expression of the BAFF receptor on B cells. Enhancement by CAM of neutralization activities of airway S-IgA against IAV in vitro and reinfected mice was observed. This study identifies that CAM enhances S-IgA production and neutralizing activities through the induction of IgA class switching recombination and upregulation of BAFF molecules in mucosal dendritic cells in IAV-infected mice.

Quantification of structural alterations of L-Asp and L-Asn residues in peptides related to neuronal diseases by reversed-phase high-performance liquid chromatography.

A method for analyzing the structural alterations in Asn or Asp residues was developed by using the peptides related to neuronal conformational diseases, i.e., the prion protein (PrP)(106-126) and the Alzheimer's amyloid beta (A beta) protein(6-28). The alterations were analyzed by reversed-phase (RP) HPLC, because the peptides containing the structurally altered residues were diastereoisomers of each other, and they were separated with the mobile phase containing an MeCN/sodium phosphate solution and NaCl. The amount of L-Asp, L-isoAsp, D-Asp, or D-isoAsp residues in each PrP peptide isomer was simultaneously quantified by carrying out single HPLC analysis; these residues were generated by the deamidation of the Asn residue. Only 0.3% of the newly generated peptide containing the D-Asp residue was detected. Furthermore, the investigation of the partial fragment of the A beta protein revealed that the present method possessed the ability of simultaneous analysis of the isomerizations of two Asp residues. These results implied that the present method was highly sensitive and reduced the time required for the analysis. This method may accelerate the elucidation of the PrP and A beta protein functions, because the structural alterations of Asn and Asp have been reported to influence these functions.

Protective substances against zinc-induced neuronal death after ischemia: carnosine as a target for drug of vascular type of dementia.

Recent studies have indicated the significance of zinc in neurodegeneration after transient global ischemia. After ischemia, excess glutamate and zinc, which are released in the synaptic clefts, cause the apoptotic death of the target neurons, and finally lead the pathogenesis of vascular type of dementia. Considering the removal of zinc using zinc-sensitive chelators was effective in the prevention of neuronal death after transient global ischemia, it is highly possible that substances which protect against zinc-induced neuronal death will become a candidate for drugs of vascular type of dementia. Based on this 'zinc hypothesis', we have searched for such substances among various agricultural products including fruits, vegetables, and fishes using our developed in vitro screening system. Among tested, we found that carnosine (beta-alanyl histidine) protected against zinc-induced death of cultured neurons, and have applied for the patent as a drug of ischemia-induced neuronal death and the treatment/prevention for vascular type of dementia (application No. 2006-145857) in Japan. Here, we review the perspective of protective substances of zinc-induced neuronal death as a drug of vascular type of dementia based on our studies and other numerous studies.

Effect of cordycepin (3'-deoxyadenosine) on hematogenic lung metastatic model mice.

We investigated the anti-metastatic effect of cordycepin (3'-deoxyadenosine) on a hematogenic metastatic mouse model which was intravenously injected with B16-BL6 melanoma cells. A 3-hour exposure to various concentrations of cordycepin (0.3, 1 and 3 microg/ml) dose-dependently reduced the number of nodules formed in lung at 15 days after the tumor injection. To elucidate the mechanism of this anti-metastatic effect, we examined the effect of cordycepin on the invasiveness of B16-BL6 cells using a chemo-invasion chamber in vitro. The B16-BL6 cells pretreated with cordycepin (3 microg/ml) for 3 hours showed a significant decrease in invasiveness. Under the same conditions, however, cordycepin did not influence the growth curve of B16-BL6 cells at concentrations up to 3 microg/ml. These results suggest that cordycepin exerts an anti-metastatic action, in part, by inhibiting the invasiveness of mouse melanoma cells.

Combined effects of Cordyceps sinensis and methotrexate on hematogenic lung metastasis in mice.

We investigated antitumor effects of water extracts of Cordyceps sinensis (WECS). WECS (100 microg/ml) induced apoptosis of B16 melanoma cells after 48 h exposure in vitro as determined by both the TUNEL (TdT-mediated dUTP-biotin nick end labeling) method and the detection of a DNA ladder. In vivo, combined treatment with WECS and methotrexate (MTX) in mice intravenously inoculated with B16 melanoma cells was conducted. Although MTX caused a significant and severe decrease in body weight compared with that in control mice starting 16 days after the start of administration, the mice given both MTX and WECS did not show a significant decrease in body weight. The mean survival time (days) of the control mice, MTX-treated mice (15 mg/kg/day, s.c.), and WECS-treated mice (200 mg/kg/day, p.o.) was 25.0 +/- 0.3, 25.6 +/- 1.3, and 25.7 +/- 1.0 (mean +/- S.E.M. of 6-7 mice), respectively. On the other hand, mean survival time (days) of mice given the combination of MTX and WECS was 28.2 +/- 0.7, significantly longer than the control value. WECS might be beneficial in the prevention of tumor metastasis as an adjuvant agent in cancer chemotherapy.