Hiroshi Kayakiri

The identification of an orally active, nonpeptide bradykinin B2 receptor antagonist, FR173657

1 An orally active, nonpeptide bradykinin (BK) B2 receptor antagonist, FR173657 (E)‐3‐(6‐acetamido‐3‐pyridyl)‐N‐[N‐[2‐4‐dichloro‐3‐[(2‐methyl‐8‐quinolinyl) oxymethyl]phenyl]‐N‐methylaminocarbonyl‐methyl]acrylamide) has been identified. 2 This compound displaced [3H]‐BK binding to B2 receptors present in guinea‐pig ileum membranes with an IC50 of 5.6 × 10−10 M and in rat uterus with an IC50 of 1.5 × 10−9 M. It did not inhibit different specific radio‐ligand binding to other receptor sites. 3 In human lung fibroblast IMR‐90 cells, FR173657 displaced [3H]‐BK binding to B2 receptors with an IC50 of 2.9 × 10−9 M and a Ki of 3.6 × 10−10 M, but did not reduce [3H]‐des‐Arg10‐kallidin binding to B1, receptors. 4 In guinea‐pig isolated preparations, FR173657 antagonized BK‐induced contractions with an IC50 of 7.9 × 10−9 M, but did not antagonize acetylcholine or histamine‐induced contractions even at a concentration of 10−6 M. FR173657 caused parallel rightward shifts of the concentration‐response curves to BK at concentrations of 10−9 M and 3.2 × 10−9 M, and a little depression of the maximal response in addition to the parallel rightward shift of the concentration‐response curve at a concentration of 10−8 M. Analysis of the data yield a pA2 of 9.2 ± 0.2 (n = 5) and a slope of 1.5 ± 0.2 (n = 5). 5 In vivo, the oral administration of FR173657 inhibited BK‐induced bronchoconstriction dose‐dependently in guinea‐pigs with an ED50 of 0.075 mg kg−1, but did not inhibit histamine‐induced bronchoconstriction even at 1 mg kg−1. FR173657 also inhibited carrageenin‐induced paw oedema with an ED50 of 6.8 mg kg−1 2 h after the carrageenin injection in rats. 6 These results show that FR173657 is a potent, selective, and orally active bradykinin B2 receptor antagonist.

The β-lactam antibiotics, penicillin-G and cefoselis have different mechanisms and sites of action at GABAA receptors

The action of the β‐lactam antibiotics, penicillin‐G (PCG) and cefoselis (CFSL) on GABAA receptors (GABAA‐R) was investigated using the two‐electrode voltage clamp technique and Xenopus oocyte expressed murine GABAA‐R. Murine GABAA‐Rs were expressed in Xenopus oocytes by injecting cRNA that encoded for each subunit (α1, β2, and γ2) and the effects of PCG and CFSL on the α1β2γ2s subunit receptors were examined using two‐electrode voltage clamp. Using the α1β2γ2s GABAA‐R, PCG and CFSL inhibited GABA‐induced currents in a concentration‐dependent manner, with IC50s of 557.1±125.4 and 185.0±26.6 μM, respectively. The inhibitory action of PCG on GABA‐induced currents was non‐competitive whereas that of CFSL was competitive. Mutation of tyrosine to phenylalanine at position 256 in the β2 subunit (β2Y256F), which is reported to abolish the inhibitory effect of picrotoxin, drastically reduced the potency of PCG (IC50=28.4±1.42 mM) for the α1β2Y256Fγ2s receptor without changing the IC50 of CFSL (189±26.6 μM). These electrophysiological data indicate that PCG and CFSL inhibit GABAA‐R in a different manner, with PCG acting non‐competitively and CFSL competitively. The mutational study indicates that PCG might act on an identical or nearby site to that of picrotoxin in the channel pore of the GABAA‐R.

Pharmacological characterization of a nonpeptide bradykinin B2 receptor antagonist, FR165649, and agonist, FR190997.

The nonpeptide bradykinin (BK) B2 receptor antagonist, FR165649 (8‐[2,6‐dichloro‐3‐[N‐[(E)‐4‐(N‐ methylcarbamoyl)cinnamidoacetyl] ‐N‐methylamino] benzyloxy] ‐2 ‐ methylquinoline), and agonist, FR190997 (8‐[2,6‐dichloro‐3‐[N‐[(E)‐4‐(N‐methylcarbamoyl) cinnamidoacetyl]‐N‐methylamino]benzyloxy]‐2‐methyl‐4‐(2‐pyridylmethoxy)quinoline) have been identified. These compounds have a common chemical structure, and the 2‐pyridylmethoxy group is the only structural difference between them. Both FR165649 and FR190997 displaced [3H]‐BK binding to B2 receptors in guinea‐pig ileum membranes, with an IC50 of 4.7×10−10 M and 1.5×10−9 M, respectively. They also displaced [3H]‐BK binding to B2 receptors in human lung fibroblast IMR‐90 cells, with an IC50 of 1.6×10−9 M and 9.8×10−10 M, respectively. In guinea‐pig isolated ileum‐preparations, FR165649 had no agonistic effect on contraction and caused parallel rightward shifts of the concentration‐response curves to BK on contraction. Analysis of the data produced a nominal pA2 value of 9.2±0.1 (n=5) and a slope of 1.4±0.1 (n=5). On the other hand, FR190997 induced concentration‐dependent contraction of guinea‐pig ilea with a pD2 of 7.9±0.2 and the contraction was inhibited by a specific peptide bradykinin B2 receptor antagonist, Hoe 140 (D‐Arg‐[Hyp3, Thi5, D‐Tic7, Oic8]BK) in a non‐competitive manner. In IMR‐90 cells, FR165649 had no agonistic effect on phosphatidyl inositol (PI) hydrolysis and caused parallel rightward shifts (approximately 200 fold shift at 10−7 M) of the concentration‐response curves to BK on PI hydrolysis. FR190997 induced concentration‐dependent PI hydrolysis in IMR‐90 cells with a pD2 of 8.4±0.1, and this effect was inhibited by Hoe 140. These results indicate that FR165649 and FR190997 are, respectively, a potent bradykinin B2 receptor antagonist and agonist, and that the agonistic activity depends on the small part of the nonpeptide ligand. FR165649 and FR190997 may be useful tools for studying the relationship between ligands and receptors.

Structure of FR 900483, a new immunomodulator isolated from a fungus

The structure of the immunomodulator FR 900483 (C5H9NO3) has been shown to be 1 on the basis of chemical and spectroscopic evidence and confirmed by a synthesis from D-glucose.

Pharmacological characterization of a novel, orally active, nonpeptide bradykinin B2 receptor antagonist, FR167344

To investigate the pathophysiological role of bradykinin and to develop a drug for inflammatory diseases, we discovered an orally active, nonpeptide bradykinin B2 receptor antagonist, FR167344, N-[N-[3-[(3-bromo-2-methylimidazo[1,2-a]pyridin-8-yl)oxymethyl]-2, 4dichlorophenyl]-N-methylaminocarbonylmethyl]-4-(dimethyl aminocarbonyl) cinnamylamide hydrochloride. This compound competitively displaced [3H]bradykinin binding to bradykinin B2 receptors present in guinea-pig ileum membrane with an IC50 value of 6.6 X 10(-10) M. In isolated guinea-pig ileum preparations, it also antagonized bradykinin-induced contraction with a pA2 value of 9.3. In human lung fibroblast IMR-90 cells, FR167344 displaced [3H]bradykinin binding to human bradykinin B2 receptors with an IC50 value of 1.3 X 10(-8) M, but not [3H]des-Arg10-kallidin binding to human bradykinin B1 receptors. In vivo, oral administration of FR167344 inhibited bradykinin-induced bronchoconstriction in guinea pigs and the bradykinin-induced hypotensive response for 6 h in rats. These results show that FR167344 is a potent, selective, orally active and long acting bradykinin B2 receptor antagonist.

Discovery of orally active nonpeptide bradykinin B2 receptor antagonists.

Orally active nonpeptide bradykinin (BK) B2 receptor antagonists have been discovered by using directed random screening and chemical modification. These compounds displaced [3H]BK binding to B2 receptors in guinea-pig ileum membranes, rat uterus membranes and human lung fibroblasts with nanomolar IC50s. They did not inhibit different specific radio-ligand bindings to other receptor sites including B2 receptors. In isolated guinea-pig ileum preparations, these compounds had no agonistic effect on smooth muscle contraction at 10(-6) M, and caused parallel rightward shifts of the concentration-response curves to BK on contraction with higher p A2 values. They also blocked human B2 receptor-mediated phosphatidylinositol hydrolysis without agonistic effect. In vivo, the oral administrations of these antagonists potently inhibited BK-induced bronchoconstriction in guinea-pigs. They also reduced carrageenin-induced paw edema and caerulein-induced pancreatitis in rats. Moreover, these compounds alleviated kaolin-induced pain in mice by oral administration. These results show that our compounds are potent, selective, and orally active BK B2 receptor antagonists and that they may have therapeutic potential against inflammatory diseases and pain.

Synthesis of kifunensine, an immunomodulating substance isolated from microbial source

Abstract A synthesis of kifunensine ( 1 ) has been achieved by a route involving, as a key step, a double cyclization of aldehyde 3 with ammonia.

A new synthetic approach to aminolycoside antibiotics by use of oxidative decarboxylation and reductive deacetoxylation as key-reactions

Abstract By use of a decarboxylation reaction with lead tetraacetate and a deacetoxylation reaction with sodium borohydride as key-reactions, paromamine ( 12 and tri-N-benzyloxycarbonylparomamine ( 12a ) were synthesized from D-glucosamine.

Nonpeptide mimic of bradykinin with long-acting properties.

Kinins, members of a family of peptides released from kininogens by the action of kallikreins, have been implicated in a variety of biological activities including vasodilation, increased vascular permeability, contraction of smooth muscle cells and activation of sensory neurons. However, investigation of the physiological actions of kinins have been greatly hampered because its effects are curtailed by rapid proteolytic degradation. We examined the pharmacological characteristics of the first nonpeptide bradykinin receptor agonist 8-[2,6-dichloro-3-[N-[(E)-4-(N-methylcarbamoyl)cinnamidoacetyl+ ++]-N-methylamino]benzyloxy]-2-methyl-4-(2-pyridylmethoxy)quinolin e (FR190997). FR190997, whose structure is quite different from the natural peptide ligand, but is similar to the nonpeptide antagonists FR165649, FR167344 and FR173657, potently and selectively interacts with the human B2 receptor and markedly stimulates inositol phosphate formation in transfected Chinese hamster ovary (CHO) cells. FR190997 induces concentration-dependent contraction of isolated guinea pig ileum. In vivo, FR190997 mimics the biological action of bradykinin and induces hypotensive responses in rats with prolonged duration, presumably as a consequence of its resistance to proteolytic degradation. Therefore, FR190997 is a highly potent and subtype-selective nonpeptide agonist which displays high intrinsic activity at the bradykinin B2 receptor. This compound represents a powerful tool for further investigation of the physiology and pathophysiology of bradykinin receptors.