Biomedical subjects

H Kagechika

Publications and source records attributed to H Kagechika.

At least 37 records · Page 2Linked to original sources

PubMed1997

A mutation mimicking ligand-induced conformational change yields a constitutive RXR that senses allosteric effects in heterodimers.

Mutations of a single residue in the retinoid X receptor alpha (RXRalpha) ligand-binding pocket (LBP) generate constitutive, ligand-binding-competent mutants with structural and functional characteristics similar to those of agonist-bound wild-type RXR. Modelling of the mouse RXRalphaF318A LBP suggests that, like agonist binding, the mutation disrupts a cluster of van der Waals interactions that maintains helix H11 in the apo-receptor location, thereby shifting the thermodynamic equilibrium to the holo form. Heterodimerization with some apo-receptors (retinoic acid, thyroid hormone and vitamin D3 receptors) results in 'silencing' of RXRalphaF318A constitutive activity, which, on the other hand, efficiently contributes to synergistic transactivation within NGFI-B-RXR heterodimers. RAR mutants disabled for corepressor binding and/or lacking a functional AF-2 activation domain, do not relieve RXR 'silencing'. Not only RAR agonists, but also the RAR antagonist BMS614 induce conformational changes allowing RXR to exert constitutive (RXRalphaF318A) or agonist-induced (wild-type RXR) activity in heterodimers. Interestingly, the RXRalphaF318A constitutive activity generated within heterodimers in the presence of BMS614 requires the integrity of both RXR and RAR AF-2 domains. These observations suggest that, within RXR-RAR heterodimers, RAR can adopt a structure distinct from that of the active holo-RAR, thus allowing RXR to become transcriptionally responsive to agonists.

Allosteric Regulation↗

PubMed1997

Action mechanism of retinoid-synergistic dibenzodiazepines.

4-[5H-2,3-(2,5-Dimethyl-2,5-hexano)-5-methyldibenzo[b,e][1,4 ]diazepin-11-yl]benzoic acid (HX600), as well as its oxa- (HX620) and thia- (HX630) analogs, enhanced the activity of retinoic acid and a receptor alpha (RAR alpha)-selective agonist Am80 in HL-60 cell differentiation assays. HX600 synergizes with Am80 by binding to, and transactivating through, the RXR subunit of the RXR-RAR heterodimer. HX600 exhibited RXR pan-agonist activity in transient transfections with a DR1-based reporter gene and synergized with RA-bound RAR alpha and RAR beta in inducing transcription from a DR5-based reporter. In addition, all three compounds at high concentrations acted as RAR pan-antagonists in stably transfected RAR "reporter cells." These efficient synergists bind only weakly with RXRs in vitro, suggesting that they are RXR-RAR heterodimer-selective activators. These HX retinoids exhibited dual functionality, since they affected signalling through both retinoid receptor families (RARs and RXRs).

Benzoates↗

PubMed1997

Inhibition of IL-1-induced IL-6 production by synthetic retinoids.

The effects of retinoids and retinoid antagonists on IL-6 production in MC3T3-E1 cells were investigated. None of the synthetic retinoids examined stimulated IL-6 production, but all of them strongly inhibited IL-6 production induced by mouse IL-1 alpha. Their inhibitory activities correlated well with their differentiation-inducing activities in HL-60 assay or their binding affinities to nuclear retinoic acid receptors (RARs). Among three retinoid antagonists, two weak antagonists exhibited similar inhibition of mouse IL-1 alpha-induced IL-6 production, whereas a potent retinoid antagonist, 4-(13H-10,11,12,13-tetrahydro-10,10,13,13,15-pentamethyl-dinaph tho[2,3-b] [1,2-e]diazepin-7-yl)benzoic acid (LE540, 14), enhanced IL-6 production under the same conditions.

3T3 Cells↗

PubMed1997

Photoaffinity labeling of the ligand-interacting helix of the retinoic acid receptor alpha.

Two photoaffinity-labeling probes for retinoic acid receptor (RAR) alpha, 4-[(3-(3-(trifluoromethyl)-3H-diazirin-3-yl)phenyl)carboxamido]ben zoic acid (3DIAM) and its para-isomer (4DIAM), were designed and synthesized. Both compounds possess high affinity for recombinant RAR alpha (MBP-RAR alpha/E) and bind covalently to its cognate ligand-binding site. The labeled site of MBP-RAR alpha/E with 3DIAM was determined, by the endoproteinase combination method, to be located in helix 11 of the ligand-binding domain of RAR alpha, which is the position at which the ligand is considered to bind, on the basis of the reported crystal structure of the retinoic acid/RAR gamma complex.

Azirines↗

PubMed1997

Polyenylidene thiazolidinedione derivatives with retinoidal activities.

Several polyenylidene thiazolidine or 2-thioxo-4-thiazolidinone derivatives were synthesized and their retinoidal activities were examined in terms of the differentiation-inducing ability towards human promyelocytic leukemia HL-60 cells and inhibitory effect on interleukin (IL)-1 alpha-induced IL-6 production in MC3T3-E1 cells. Compounds containing a trimethylcyclohexenyl ring induced HL-60 cell differentiation with weaker activity than retinoic acid (1a) by one or two orders of magnitude. The thiazolidinedione derivatives (2, 5, 7) showed stronger activity than the corresponding 2-thioxo-4-thiazolidinone derivatives (3, 6, 8). The effects of a retinoid antagonist (LE540) and synergists (retinoid X receptor (RXR) agonists, HX600 or HX630) on the activities of thiazolidine derivatives indicate that these compounds elicit their activities through the nuclear retinoic acid receptors (RARs). All the thiazolidines examined also inhibited IL-1 alpha-induced IL-6 production with IC50 values of 10 nM order. The retinoidal activities of the thiazolidines are significant, considering that replacement of the carboxylic acid in retinoid structures with bioisosteric functional groups is generally ineffective, as seen in the structure-activity relationships of retinoidal benzoic acids.

Cell Differentiation↗

PubMed1996

Evaluation of differentiation-inducing activity of retinoids on human leukemia cell lines HL-60 and NB4.

Retinoids, including all-trans-retinoic acid (ATRA), its isomers, and fifty synthetic retinoids (retinobenzoic acids), were tested for differentiation-inducing activity on human leukemia cell lines HL-60 and NB4. Binding activity of typical retinoids to nuclear retinoic acid receptors (RARs) was also investigated. A good linear correlation between the ED50 values of differentiation-inducing activity towards HL-60 cells and those towards NB4 cells was found. Binding activities of retinoids to RAR alpha and RAR beta also correlated well to the differentiation-inducing activities.

Benzoates↗

PubMed1996

Novel aromatic urea derivatives with DNA-binding ability.

Several aromatic urea derivatives were designed and synthesized as DNA-targeting agents. N,N'-Dimethyl-N,N'-bis[(4-amidylphenyl)aminocarbonyl]-2,6-di aminopyridine (1) and 1,3-bis[5-(glycylamino)pyrid-2-yl]urea (3) showed remarkable DNA-binding abilities as determined by ultrafiltration assay using calf thymus DNA, their potencies being equal to and half that of netropsin, respectively. Compound 1 inhibited the proliferation of both L1210 cells and KB cells with similar IC50 values to netropsin.

Animals↗

PubMed1996

[Retinoid antagonists].

Retinoids, retinoic acid and its bioisosters, regulate many biological functions such as cell differentiation, proliferation and embryonic development in vertebrates, through binding to and activating their specific nuclear receptors. There are two classes of nuclear receptors for retinoids, retinoic acid receptors (RAR alpha, beta, gamma) and retinoid X receptors (RXR alpha, beta, gamma). Several retinoid antagonists, which bind to but not activate RARs, have been reported. Among them, 4-(5H-7,8,9,10-tetrahydro-5,7,7,10,10-pentamethylbenzo[e]naphtho [2,3-b][1,4]diazepin-13-yl)benzoic acid (LE135, 20) is a RAR beta-selective retinoid antagonist. Structure-activity relationships of LE135 (20) showed that the naphthalenyl analogs [LE540 (21) and LE550 (22)] are more potent retinoid antagonists in HL-60 assay. Contrary to the antagonistic activity of LE135 (20), an isomer of LE135 (20), 4-[5H-2,3-(2,5-dimethyl-2,5-hexano)-5-methyldibenzo- [b,e][1,4]diazepin-11-yl)benzoic acid (HX600, 39) enhanced the activities of retinoids. Although the synergistic activity of HX600 (39) can be explained by the binding to RXRs and the further activation of RAR/RXR heterodimer activated by retinoid (RAR ligand), the significantly different biological character of HX600 (39) from the typical RXR-selective ligand suggested the possibility of the participation of other nuclear receptors or cofactors in the retinoid synergism.

Animals↗

PubMed1995

Possible involvement of retinoid-like cofactor in serum in hemin/protoporphyrin-IX-induced differentiation of human leukemia K562 cells.

Serum is generally added to media used for mammalian cell culture and for investigation of in vitro cell differentiation induction. Erythroid differentiation of human leukemia cell line K562 is induced by hemin or protoporphyrin IX in the presence of fetal bovine serum (FBS). Addition to the medium of retinoids enhanced the differentiation, and addition of retinoid antagonists suppressed the differentiation. Making the added FBS retinoid-free, i.e., treatment of the serum with charcoal, also reduced the efficiency of the cell differentiation induced by hemin or protoporphyrin IX. These facts suggest that retinoids or retinoid-like cofactor(s) in serum are necessary for hemin/protoporphyrin-IX-induced erythroid differentiation of K562 cells.

Cell Differentiation↗

PubMed1995

Correlation of differentiation-inducing activity of retinoids on human leukemia cell lines HL-60 and NB4.

Retinoids, including all-trans-retinoic acid, its isomers, and fifty synthetic retinoids (retinobenzoic acids), were tested for differentiation-inducing activity on human leukemia cell lines HL-60 and NB4. A good linear correlation, with an r value of 0.91, between the ED50 values for the differentiation-inducing activity towards HL-60 cells and that towards NB4 cells was found.

Cell Differentiation↗

PubMed1995

Synergists for retinoid in cellular differentiation of human promyelocytic leukemia cells HL-60.

4-[5H-2,3-(2,5-Dimethyl-2,5-hexano)-5-methyldibenzo[b, e]diazepin-11-yl]benzoic acid (4) enhanced the differentiation-inducing activity of retinoic acid (1) and of a synthetic retinoid Am80 (2) toward human promyelocytic leukemia cells HL-60, although 4 alone did not induce differentiation. The synergistic effect of 4 on the activities of retinoids was also seen in suppression of proliferation of HL-60 cells.

Cell Differentiation↗

PubMed1995

Synthesis of oligopeptides as polynucleotide analogs.

Several dipeptides which have a nucleic acid base in their side chains were designed as water-soluble nucleotide analogs. Amino acids having a uracil or adenine moiety in the gamma-position were synthesized and were connected with another amino acid (spacer) to afford dipeptides. The oligopeptides were prepared from the dipeptides as monomer units. Although all the oligopeptides having uracil moieties examined were water-soluble as expected, these exhibited no hypochromic effect with poly A or poly dA. Contrary, the oligopeptides with adenines exhibited large hypochromicity (ca. 30%) base-specifically with poly dT or poly U.

Molecular Structure↗

PubMed1994

Retinobenzoic acids. 6. Retinoid antagonists with a heterocyclic ring.

Several candidate retinoid antagonists were designed on the basis of the ligand superfamily concept and synthesized. Retinoidal activities of these benzimidazole and benzodiazepine derivatives were examined by assay of differentiation-inducing activity on human promyelocytic leukemia cell line HL-60. The parent benzimidazole derivative, 4-(5,6,7,8-tetrahydro-5,5,8,8- tetramethylnaphth-[2,3-d]imidazol-2-yl)benzoic acid (7a), and related compounds with a small alkyl group instead of the hydrogen on the nitrogen (1N) atom of the imidazole ring exhibited retinoidal activity, and the potency strongly depended on the bulkiness of the substituent. The compounds having a phenyl or benzyl group on the nitrogen lacked differentiation-inducing activity on HL-60 cells and acted as antagonists to the potent retinoid 4-[(5,6,7,8-tetrahydro-5,5,8,8- tetramethyl-2-naphthalenyl)carbamoyl]benzoic acid (Am80). Among the compounds possessing a seven-membered heterocyclic ring as a linking group, 4-(5H-7,8,9,10-tetrahydro-5,7,7,10,10- pentamethylbenzo[e]- naphtho[2,3-b][1,4]diazepin-13-yl)benzoic acid (16) also exhibited the antagonistic activity. The binding abilities of these compounds to retinoic acid receptors alpha and beta were consistent with their potency for the inhibition of HL-60 cell differentiation induced by the retinoid Am80.

Benzimidazoles↗

PubMed1994

Synthesis and biological activity of carboxyphenylquinolines and related compounds as new potent retinoids. Retinobenzoic acids. VII.

A series of new quinoline, quinolone, and quinazolinedione derivatives was synthesized and tested for retinoid activity in the human promyelocytic cell line HL-60 differentiation assay. All the quinoline compounds exhibited significant activity, depending on the substituent on the heterocycle. However, the quinolone and quinazolinedione derivatives were poor inducers of the differentiation of the HL-60 cells, the activity depending strongly on the polarity of the molecule.

Benzoates↗

PubMed1994

[Novel synthetic retinoid agonists and antagonists].

Retinoic acid acts as a specific modulator of cellular differentiation and proliferation. Its natural and synthetic analogs, classified as retinoids, can be applied to the chemotherapy in the field of dermatology and oncology. Various benzoic acid derivatives exhibited the specific biological responses of retinoic acid and were named retinobenzoic acids. Especially, the aromatic amides such as Am80 and Am580 have better therapeutic effects than retinoic acid. N-Methylation of these highly active aromatic secondary amides caused the disappearance of the activity due to the change of the amide conformation from trans into cis. From such observations, the conformation of the linking group between alkyl-substituted benzene ring and benzoic acid moiety is an important factor for the activity. Some retinobenzoic acids do not bind to the cellular-retinoic acid-binding protein, but bind to nuclear retinoic acid receptors (RARs) with the binding affinity corresponding to the potency of their biological activities. Among them, Am80 can bind to two of the three RAR subtypes (RAR alpha and beta). The selectivity is favorable for the clinical application of retinoid since it has possibility to elicit a part of a number of the biological activities of retinoic acid.

Cell Differentiation↗

PubMed1994

[Stereochemistry of benzanilides and N-methylbenzanilides].

Conformations of benzanilide , N-methylbenzanilide and those with a methyl group(s) ortho to the amide bond in solution and in the crystal have been studied. N-Methylbenzanilide exists in cis-amide (E) form in the crystal. In CDCl3 solution, cis-amide form is also predominant (99%), while benzanilide exists in trans-amide (Z) form in the crystal and in solution. In the crystal, all the methyl-substituted benzanilides exist in trans-amide conformation and the introduction of an ortho-methyl group(s) makes the interplanar angles of the aromatic rings and the amide group (Aramide) larger. N-Methylbenzanilides exist in cis form in the crystal except the compound which has four methyl groups ortho to the amide bond. For the N-methylbenzanilides, the effects of introduction of one or two ortho-methyl groups on the dihedral angles of Ar-amide are smaller than that for the secondary benzanilides. In solution, benzanilides exist exclusively in trans conformation except for the compound 12 which has a minor cis conformer (3%) in CDCl3, whereas N-methylbenzanilides exist in equilibrium between the major cis-form and the minor trans-form. The tetramethyl derivative exists in trans conformation in solution as observed in the crystal. For N-methylbenzanilides, an introduction of a methyl group(s) ortho to the amide bond seems to destabilize the cis-amide conformation in solution, resulting in an increased ratio of the trans-amide conformation.

Anilides↗

PubMed1993

Expression of the ligand-binding domain-containing region of retinoic acid receptors alpha, beta and gamma in Escherichia coli and evaluation of ligand-binding selectivity.

The complete molecule or the ligand-binding domain-containing region of each of the three subtypes of human retinoic acid receptors (hRAR alpha, hRAR beta and hRAR gamma) was expressed in Escherichia coli. The expressed recombinant RARs (rRARs: rRAR alpha/E, rRAR beta/E and rRAR gamma) showed nearly the same magnitude of binding affinity toward [3H]retinoic acid (RA) as hRARs extracted from human cells (Ka values: 6.0 x 10(9) M-1 for rRAR alpha/E and 2.7 x 10(10) M-1 for both rRAR beta/E and rRAR gamma). Therefore, the ligand-binding selectivity of the rRARs toward RA and synthetic retinoids (4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenylcarbamoyl )benzoic acid (Am80), (E)-4-[3-(3,5-di-tert-butylphenyl)-3-oxo-1-propenyl]benzoic acid (Ch55)) was examined. Am80 bound rRAR alpha/E preferentially and showed no binding activity toward rRAR gamma, which is consistent with the case of hRAR gamma. Ch55 bound all three subtypes of rRARs, preferentially rRAR beta/E. These results suggest that the intrinsic nature of the binding of each retinoid can be investigated by usage of the rRARs. However, rRARs show quantitatively different ligand-selectivity from that of hRARs: RA showed higher binding affinity toward rRARs than both Am80 and Ch55, but Ch55 binds all three subtypes of hRARs stronger than RA and Am80, which binds hRAR beta stronger than RA.

Base Sequence↗

PubMed1992

Differentiation-inducing activity of retinoic acid isomers and their oxidized analogs on human promyelocytic leukemia HL-60 cells.

Retinoidal activity of retinoic acid isomers [all-trans-retinoic acid (ATRA), 9-cis-retinoic acid (9CRA) and 13-cis-retinoic acid (13CRA)] and their oxidized derivatives [19-hydroxy and 19-oxo derivatives of ATRA (19-hydroxy-ATRA and 19-oxo-ATRA), 19-oxo derivative of 9CRA (19-oxo-9CRA), and 19-hydroxy derivative of 13CRA (19-hydroxy-13CRA)] was evaluated by means of a human promyelocytic leukemia HL-60 cell differentiation induction assay. All the compounds examined showed this activity with ED50 values of 2-30 nM, which are in accordance with their binding activity to nuclear retinoic acid receptors (RARs).

Binding, Competitive↗