Biomedical subjects

Yuichi Hashimoto

Publications and source records attributed to Yuichi Hashimoto.

83 records · Page 5Linked to original sources

PubMed2002

Novel retinoid X receptor antagonists: specific inhibition of retinoid synergism in RXR-RAR heterodimer actions.

Several 2-(arylamino)pyrimidine-5-carboxylic acids were designed as novel retinoid X receptor (RXR) antagonists. Compound 6a or 6b alone did not exhibit differentiation-inducing activity toward HL-60 cells and did not affect the activity of a retinoic acid receptor (RAR) agonist, Am80, but did inhibit the synergistic activity of an RXR agonist, PA024 (3), in the presence of Am80. The activity of 6 was ascribed to selective antagonism at the RXR site of RXR-RAR heterodimers.

2-Naphthylamine↗

PubMed2002

Evidence for in vivo production of Humanin peptide, a neuroprotective factor against Alzheimer's disease-related insults.

An unbiased functional screening with brain cDNA library from an Alzheimer's disease (AD) brain identified a novel 24-residue peptide Humanin (HN), which suppresses AD-related neurotoxicity. As the 1567-base cDNA containing the open reading frame (ORF) of HN is 99% identical to mitochondrial 16S ribosomal RNA as well as registered human mRNA, it was elusive whether HN is produced in vivo. Here, we raised anti-HN antibody and found that long cDNAs containing the ORF of HN (HN-ORF) produced the HN peptide in mammalian cells, dependent on the presence of full-length HN-ORF. Immunoblot analysis detected a 3-kDa protein with HN immunoreactivity in the testis and the colon in 3-week-old mice and in the testis in 12-week-old mice. HN immunoreactivity was also detected in an AD brain, but little in normal brains. This study suggests that HN peptide could be produced in vivo, and would provide a novel insight into the pathophysiology of AD.

Alzheimer Disease↗

PubMed2002

Thalidomide and its analogues as cyclooxygenase inhibitors.

Thalidomide showed cyclooxygenase (COX)-1/2 inhibitory activity with a potency comparable to that of aspirin. Structural development studies of thalidomide resulted in potent COX-1/2 inhibitors, and COX-1-selective and COX-2-selective inhibitors.

Cyclooxygenase 1↗

PubMed2002

Total synthesis of crambescidin 359.

[structure: see text] Crambescidin 359 (4), which is the "vessel part" of the pentacyclic guanidine alkaloid ptilomycalin A (1), was synthesized for the first time based upon successive 1,3-dipolar cycloaddition reaction. This synthesis established the absolute stereochemistry of 4.

Alkaloids↗

PubMed2002

Structural development of biological response modifiers based on thalidomide.

Thalidomide (N-alpha-phthalimidoglutarimide) is a teratogenic hypnotic/sedative agent which was used widely in the late 1950s and the early 1960s. In spite of its withdrawal from the market because of its severe teratogenicity, there has been a resurgence of interest in the drug in recent years due to its potential usefulness for the treatment of various diseases, including acquired immunodeficiency syndrome (AIDS) and various cancers. It has been revealed that thalidomide elicits pleiotropic effects and is a multi-target drug. Our structural development studies of thalidomide, focusing on tumor necrosis factor-alpha(TNF-alpha) production-regulating activity, anti-androgenic activity, puromycin-sensitive aminopeptidase-inhibiting activity, alpha-glucosidase-inhibiting activity, and inhibitory activities toward some other enzymes, are reviewed in relation to the pharmacological effects of thalidomide.

Androgen Antagonists↗

PubMed2002

Novel non-steroidal/non-anilide type androgen antagonists with an isoxazolone moiety.

3-Substituted (Z)-4-(4-N,N-dialkylaminophenylmethylene)-5(4H)-isoxazolones and related compounds were designed and prepared as candidates for structurally novel androgen antagonists. Several compounds showed potent anti-androgenic activity as assessed by nuclear androgen receptor binding assay and growth inhibition assay using androgen-dependent Shionogi carcinoma cells SC-3. They were approximately 10--220 times more potent than flutamide in these assay systems. They also showed anti-androgenic activity toward prostate tumor cell line LNCaP, which has an aberrant nuclear androgen receptor.

Androgen Antagonists↗

PubMed2002

Neurotoxic mechanisms triggered by Alzheimer's disease-linked mutant M146L presenilin 1: involvement of NO synthase via a novel pertussis toxin target.

While it has been reported that familial Alzheimer's disease (FAD)-linked mutants of amyloid precursor protein (APP) and presenilin (PS)2 induce neuronal cytotoxicity in a manner sensitive to antioxidant and pertussis toxin (PTX), little of the mechanism for PS1-mediated neuronal cell death has been characterized. We previously found that multiple mechanisms, different in detail, underlie cytotoxicities by two FAD-linked mutants of APP, using neuronal cells with an ecdysone-controlled expression system. Here we report that this system revealed that (i) low expression of FAD-linked M146L-PS1 caused neuronal cell death, whereas that of wild-type (wt)PS1 did not; (ii) mutation-specific cytotoxicity by M146L-PS1 was sensitive to antioxidant glutathione-ethyl-ester and resistant to Ac-DEVD-CHO; (iii) cytotoxicity by higher expression of wtPS1 was resistant to both; and (iv) cytotoxicity by M146L-PS1 was inhibited by PTX. It was also highly likely that the involved superoxide-generating enzyme was nitric oxide synthase (NOS), and that the PTX-sensitive cytotoxic signal by M146L-PS1 was mediated by none of the G(i/o) proteins. We conclude that M146L-PS1 activates a NOS-mediated cytotoxic pathway via a novel PTX target.

Alzheimer Disease↗

PubMed2002

Neurotoxic mechanisms by Alzheimer's disease-linked N141I mutant presenilin 2.

Although it has been established that oxidative stress mediates cytotoxicity by familial Alzheimer's disease (FAD)-linked mutants of presenilin (PS)1 and that pertussis toxin inhibits cytotoxicity by FAD-linked N141I-PS2, it has not been determined whether oxidative stress is involved in cytotoxicity by N141I-PS2 or which pertussis toxin-sensitive proteins mediate the cytotoxicity. Here we report that low expression of N141I-PS2 caused neuronal cell death, whereas low expression of wild-type PS2 did not. Cytotoxicities by low and high expression of N141I-PS2 occurred through dissimilar mechanisms: the former cytotoxicity was blocked by a cell-permeable caspase inhibitor, and the latter was not. Since both mechanisms were sensitive to a cell-permeable antioxidant, we examined potential sources of reactive oxygen species in each mechanism, and found that the caspase inhibitor-sensitive neurotoxicity by N141I-PS2 was likely through NADPH oxidase and the caspase inhibitor-resistant neurotoxicity by N141I-PS2 through xanthine oxidase. Pertussis toxin greatly suppressed both toxic mechanisms by N141I-PS2, and only Galpha(o), a neuron-enriched pertussis toxin-sensitive G protein, was involved in both mechanisms. We therefore conclude that N141I-PS2 is capable of triggering multiple neurotoxic mechanisms, which can be inhibited by the combination of clinically usable inhibitors of NADPH oxidase and xanthine oxidase. This study thus provides a novel insight into the therapeutic intervention of PS2 mutant-associated FAD.

Alzheimer Disease↗

PubMed2002

Coordination of sodium cation to an oxygen function and olefinic double bond to form molecular adduct ion in fast atom bombardment mass spectrometry.

Steroidal allylic alcohols formed Na+ adduct ion peaks [M+Na]+ by the addition of NaCl in FAB mass spectrometry. A comparison of the intensities of the adduct ion peaks of allylic alcohols with those of the corresponding saturated alcohols and olefin suggested that the olefinic double bond and the proximal hydroxyl group had coordinated to Na+. The adduct ion was stable and did not undergo dehydroxylation. We suggest that the Na+ adduction will be useful for the molecular weight determination of allylic alcohols which are susceptible to dehydroxylation under FAB mass spectrometric conditions. Na+ adduct ions of alpha,beta-unsaturated carbonyl compounds were also investigated.

Alkenes↗

PubMed2002

Structural development of biological response modifiers based on retinoids and thalidomide.

The full-scale commercial appearance of antibiotics in the 1950's caused a shift of the nature of our lethal diseases from infectious/acute to non-infectious/chronic. In this situation, biological response modifiers (BRM's), which are not based on selective toxicity, are expected to be useful. There exist several types of BRM's, including retinoids which act directly on cells at the gene expression level, and thalidomide (and related molecules) which modulate internal circumstances of our body. We have been engaged in medicinal chemical/structural development studies based on these bio-active compounds. Retinoids include all-trans-retinoic acid (ATRA), a major active form of vitamin A (retinol), and its bio-isosters, which elicit their biological effects by binding to their nuclear receptors, RAR's. ATRA has been used in differentiation therapy [typically for the treatment of acute promyelocytic leukemia (APL)] and the treatment of dermatological diseases. Our structural development studies of retinoids, including computer-assisted molecular design has yielded class/subtype-selective agonists, synergists and antagonists of RAR's and their partner nuclear receptors, RXR's. Thalidomide elicits a wide range of pharmacological effects, including anti-cachexia, anti-angiogenic and anti-metastatic activities. We have found that thalidomide is a multi-target drug. Hypothetical target events/molecules of thalidomide include TNF-alpha production, nuclear androgen receptor, aminopeptidases, and alpha-glucosidase. Specific and potent compounds for each of these target phenomena/molecules have been prepared by appropriate modification of the thalidomide structure, and are expected to be superior lead compounds for novel immunomodulators, anti-angiogenic agents, and anti-tumor promoting agents.

Adjuvants, Immunologic↗

PubMedDate not supplied

Molecular mechanisms for neuronal cell death by Alzheimer's amyloid precursor protein-relevant insults.

To develop a therapeutic intervention for Alzheimer's disease (AD), it is necessary to clarify the mechanisms underlying the pathogenesis of AD, in which senile plaques, neurofibrillary tangles and neuronal loss in the cerebrum are the central abnormalities. A number of studies have focused on the major component of the senile plaques, which is amyloid-beta (Abeta) and its precursor protein APP, and have investigated the roles of these molecules in the onset, progression and inhibition of AD. For multiple reasons, however, their roles in AD, especially in neuronal death, remain elusive and a unified concept for their roles has not yet been established. Recently, it has been found that APP functions normally as a neuronal surface transmembrane protein. In this article, we review the molecular mechanisms of neuronal cell death by these APP-relevant insults and discuss the functions of APP in regard to intracellular signal transducers, including c-Jun N-terminal kinase. We also revise the roles of Abeta in neuronal death and survival.

Alzheimer Disease↗