YM872: a selective,potent and highly water-soluble alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist

This review focuses on the in vitro and in vivo neuropharmacology of YM872, a potential neuroprotective agent currently undergoing clinical trials in the United States (trial name: AMPA Receptor Antagonist Treatment in Ischemic Stroke - ARTIST). Its neuroprotective properties in rats and cats with induced focal cerebral ischemia are described. YM872, [2,3-dioxo-7-(1H-imidazol-1-yl)-6-nitro-1,2,3,4-tetrahydroquinoxalin-1-yl]-acetic acid monohydrate, is a selective, potent and highly water-soluble competitive alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor antagonist. YM872 has a potent inhibitory effect on [(3)H]AMPA binding with a K(i) value of 0.096 microM. In contrast, YM872 has very low affinity for other ionotropic glutamate receptors. The solubility of YM872 is approximately 500 to 1000 times higher than that of the other competitive AMPA antagonists: YM90K, NBQX, or CNQX. The neuroprotective efficacy of YM872 was investigated in rats and cats subjected to permanent occlusion of the left middle cerebral artery. The animals were assessed either histologically or neurologically following ischemia. In rats with occluded middle cerebral artery (MCAO) YM872, by i.v. infusion, significantly reduced infarct volume measured at 24 h and 1 week after ischemia. Significant neuroprotection was maintained even when drug administration was delayed for up to 2 h after ischemia. In addition, YM872 significantly improved neurological deficit measured at 1 week after ischemia. In cats with MCAO YM872, by i.v. infusion, dose-dependently reduced infarct volume at 6 h after ischemia. YM872 produced no behavioral abnormalities and was not nephrotoxic. The evidence for the neuroprotective efficacy of YM872 suggests its therapeutic potential in the treatment of acute stroke in humans.     

Molecular and cellular mechanism of glutamate receptors in relation to amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of the central nervous system (CNS) with an unknown etiology. This disorder is characterized clinically by muscular weakness and wasting, and pathologically by selective degeneration of the corticospinal tracts and motor neurons of the brain stem and spinal cord. Median survival following onset is 3 to 5 years. Riluzole, an antiglutamatergic agent has been shown to have modest beneficial effects on survival. Glutamate is the main excitatory neurotransmitter in the CNS and excessive activation of glutamate receptors is excitotoxic to neurons. Glutamate receptor-mediated excitotoxicity has been proposed to explain the pattern of selective neuronal cell death and clinical manifestation of ALS. Activation of glutamate receptors leading to elevation of intracellular calcium may play a major role. This review will focus on the current understanding of the molecular and cellular mechanisms of glutamate receptors in relation to ALS.     

Cyclotheonamide E4 and E5, new potent tryptase inhibitors from an Ircinia species of sponge

Tryptase is a protease released from mast cells and is believed to contribute to the inflammatory process in allergic diseases including asthma. In the course of screening to find tryptase inhibitors, we isolated two new tryptase inhibitors, cyclotheonamide E4 (3) and E5 (4), from a marine sponge of the genus Ircinia. The structures of these molecules were determined by interpretation of 1H and 13C NMR spectra, and they were shown to be closely related to the previously reported cyclotheonamides E (1), E2, and E3 (2). These molecules contain two unusual amino acids, vinylogous tyrosine and alpha-ketohomoarginine, which are involved in strong activities against serine proteases. Cyclotheonamide E4 showed potent inhibitory activity against human tryptase (IC50 5.1 nM). Therefore, cyclotheonamide E4 may be useful as a therapeutic agent in the treatment of allergic diseases including asthma.     

Dissociation of E-4031 from the HERG channel caused by mutations of an amino acid results in greater block at high stimulation frequency

OBJECTIVE: We have reported identification of the amino acid whose mutation reduces effects of quinidine on the HERG channel. Although the residue (isoleucine at 647) is not in the recently reported methanesulfonanilide binding site, a single concentration of E-4031 (10 microM) was less effective to I647 mutant channels than wild type HERG channel. We designed the present experiment to further investigate influence of mutations at 647 on the effects of methanesulfonanilides. METHODS AND RESULTS: HERG channels were expressed in Xenopus oocytes and their currents were measured by a two-microelectrode voltage clamp method. Of the two mutations initially studied (I647A and I647F), the I647F had a greater influence and differentially affected the effects of dofetilide and E-4031. The IC(50) for dofetilide of the two mutant channels (I647A and I647F) was increased only 2-fold, but the IC(50) for E-4031 was increased 6-fold (I647A) and 14-fold (I647F). Aromatic residues other than phenylalanine were then substituted for I647, and found to reduce the effects of E-4031. Whereas E-4031 dissociated from the mutant channels during rested state, dofetilide little dissociated. The mutant channels that showed recovery from E-4031 block were inhibited greater at 1 Hz than at 0.1 Hz. CONCLUSIONS: The present results indicate that dissociation of a drug from the HERG channel results in greater block at high frequency. Although the mechanism by which the mutations cause the dissociation of E-4031 is uncertain, it is noteworthy that one methanesulfonanilide dissociates from the channel more easily than another.     

Association of phosphorylation site of tau protein with neuronal apoptosis in Alzheimer's disease

In addition to neuritic changes and amyloid deposits, neuronal and glial cell apoptosis is an important pathological feature of Alzheimer's disease (AD). Several factors have been postulated as causes or triggers of cellular apoptotic change. This study focused on a quantifiable relationship between phosphorylation sites of tau protein in the neurofibrillary tangles (NFT) and neuronal apoptosis. Five monoclonal anti-tau antibodies (AT180, AT8, HT7, Tau2 and Tau5) for NFT labeling and TdT-mediated UTP nick-end labeling (TUNEL) for localizing apoptotic change were employed. TUNEL-stained neuronal nuclei showed significantly high density in the entorhinal cortex, cornu ammonis (CA) and the parietal cortex. In all regions, density of TUNEL-stained neuronal nuclei showed significantly direct correlation with that of AT8-, AT180- and Tau2-positive neurons. Correlation of TUNEL-stained neuronal nuclei with tau-positive neurons differed depending on the cerebral regions. Density of TUNEL-stained neuronal nuclei showed inverse correlation with that of both AT8-positive and Gallyas-stained NFT in the CA and showed significantly direct correlation with AT8- and HT7-positive neurons in the frontal cortex. Density of tau-positive and Gallyas-stained NFT was higher than that of TUNEL-stained nuclei. We conclude that phosphorylation sites of tau, 159-163 and 202-205, are probably associated with neuronal apoptosis and apoptotic change follows abnormal phosphorylation of tau.     

Anxiety in school refusal children with indefinite complaints: psychological estimation using State-Trait Anxiety Inventory and therapy by serotonin reuptake inhibitors

Using State-Trait Anxiety Inventory (STAI) we examined 13 junior high school students with school refusal and indefinite complaints. Significant increase of the anxiety levels was higher in these children than in the control group. Serotonin reuptake inhibitors (SSRIs) were administered to 19 elementary and junior high school students with school refusal and indefinite complaints. The indefinite symptoms improved markedly in 2 children, moderately in 11, and mildly in 6. We conclude that high anxiety may cause indefinite symptoms in children with school refusal and that the treatment of indefinite symptoms with SSRI is an effective supportive therapy.     

A SNARE complex containing SGR3/AtVAM3 and ZIG/VTI11 in gravity-sensing cells is important for Arabidopsis shoot gravitropism

Plants can sense the direction of gravity and change the growth orientation of their organs. The molecular mechanisms of gravity sensing and signal transduction during gravitropism are not well known. We have isolated several shoot gravitropism (sgr) mutants of Arabidopsis. The sgr3-1 mutant exhibits a reduced gravitropic response in the inflorescence stems. In the inflorescence stems of Arabidopsis, gravity is sensed in endodermal cells that contain sedimentable amyloplasts. In sgr3-1, some amyloplasts in the endodermis failed to sediment in the direction of gravity. SGR3 encodes a syntaxin, AtVAM3, which had previously been cloned as a homologue of yeast Vam3p. AtVAM3 is localized to the prevacuolar compartment and vacuole and is suggested to function in vesicle transport to the vacuole. We have also cloned another soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE), ZIG/AtVTI11, a mutation that causes abnormal gravitropism. This mutant displayed an abnormal distribution of amyloplasts in the endodermal cells similar to that in sgr3-1. Endodermis-specific expression of SGR3 and ZIG by using the SCR promoter could complement the abnormal shoot gravitropism of each mutant. Protein-protein interaction between AtVAM3 and AtVTI11 in the endodermal cells was detected immunologically. The sgr3-1 mutation appeared to reduce the affinity of AtVAM3 for AtVTI11 or SYP5. These results suggest that vesicle transport to the prevacuolar compartment/vacuole in the endodermal cells, mediated by a specific SNARE complex containing AtVAM3 and AtVTI11, plays an important role in shoot gravitropism.     

A traditional healers' training model in rural Nepal: strengthening their roles in community health

In this paper, we evaluated a western medical training model for traditional healers (THs) in rural Nepal. We used semi-structured interviews to compare 48 trainees with 30 randomly selected untrained THs, 1 year after the training was completed. We asked them about their knowledge of the causes, prevention and treatment of common illnesses and HIV/AIDS, and their relationship with government health workers (GHWs) in the area. Nine GHWs were also interviewed about their perceptions of THs. We found that trained THs had a better knowledge of allopathic medicine, practised modern treatment using first aid kits, and were more likely to refer patients to GHWs. They also improved their relationships with the GHWs. Up-scaling this model is a challenge for improving community health care in Nepal in the future.     

Age-related changes in peroxisomal membrane protein 70 and superoxide dismutase 1 in transgenic G93A mice

Peroxisomal membrane protein 70 (PMP70) and Cu/Zn superoxide dismutase (SOD1) were examined in the spinal cords of transgenic (Tg) mice expressing a human mutant SOD1 protein (G93A) and their age-matched controls at 8, 20 and 32 weeks by immunohistochemistry. At pre-symptomatic 20 weeks and symptomatic 32 weeks, PMP70 was reduced in the cytoplasm of motor neurons in Tg animals and increased in glial cells in anterior horn at late age. SOD1 showed a progressive increase of dot-like deposits in the neuropil of anterior horn of Tg mice, and a late decrease of signal intensity in the white matter and motor neurons at 32 weeks. It is conceivable that reduction of PMP70 might underlie decrease in peroxisomal functions and increase in oxidative stress that is well documented in this animal model.