Akinori Arimura

Antifibrotic action of pirfenidone and prednisolone : Different effects on pulmonary cytokines and growth factors in bleomycin-induced murine pulmonary fibrosis

Pirfenidone, a broad-spectrum antifibrotic agent, is known to have efficacy in certain fibrotic disease models, and is under clinical trials in patients with idiopathic pulmonary fibrosis. We investigated the antifibrotic effect of pirfenidone, and its regulatory effect on various pulmonary cytokines, in bleomycin-induced lung fibrosis in mice at the protein level, using prednisolone as a reference agent. Pirfenidone attenuated the bleomycin-induced pulmonary fibrosis at a minimum effective dose of 30 mg/kg/day t.i.d. from the analysis of lung hydroxyproline content. Both pirfenidone (30, 100 mg/kg/day t.i.d) and prednisolone (3, 15 mg/kg/day q.d.) suppressed lung inflammatory edema; however, prednisolone failed to suppress pulmonary fibrosis, which was significantly suppressed only by pirfenidone. Both pirfenidone and prednisolone suppressed the increase in lung interleukin (IL)-1beta, IL-6, IL-12p40 and monocyte chemoattractant protein (MCP)-1 levels induced by bleomycin. On the other hand, pirfenidone prevented the bleomycin-induced decrease in lung interferon (IFN)-gamma levels, while prednisolone had no such effect. Furthermore, pirfenidone suppressed elevation of lung basic-fibroblast growth factor (bFGF) and transforming growth factor (TGF)-beta1 levels, but prednisolone had no such effect. The increases in lung stroma cell derived factor (SDF)-1alpha and IL-18 were also suppressed. These findings suggest that pirfenidone exerts its antifibrotic effect through regulation of lung IFN-gamma, bFGF and TGF-beta1 levels during the development of bleomycin-induced pulmonary fibrosis in mice. The effect on SDF-1alpha and IL-18 levels may also be related to the antifibrotic effects of pirfenidone.

Synthesis and Biological Activity of Various Derivatives of a Novel Class of Potent, Selective, and Orally Active Prostaglandin D2 Receptor Antagonists. 2. 6,6-Dimethylbicyclo[3.1.1]heptane Derivatives

In an earlier paper, we reported that novel prostaglandin D(2) (PGD(2)) receptor antagonists having the bicyclo[2.2.1]heptane ring system as a prostaglandin skeleton were a potent new class of antiallergic agents and suppressed various allergic inflammatory responses such as those observed in conjunctivitis and asthma models. In the present study, we synthesized PGD(2) receptor antagonists having the 6,6-dimethylbicyclo[3.1.1]heptane ring system. These derivatives have the amide moiety, in contrast to those with the bicyclo[2.2.1]heptane ring system, which have the sulfonamide group. The derivatives having the 6,6-dimethylbicyclo[3.1.1]heptane ring also exhibited strong activity in PGD(2) receptor binding and cAMP formation assays. In in vivo assays such as allergic rhinitis, conjunctivitis, and asthma models, these series of derivatives showed excellent pharmacological profiles. In particular, compound 45 also effectively suppressed eosinophil infiltration in allergic rhinitis and asthma models. This compound (45, S-5751) is now being developed as a promising alternative antiallergic drug candidate.

A Method for Evaluating Anti-Allergic Drugs by Simultaneously Induced Passive Cutaneous Anaphylaxis and Mediator Cutaneous Reactions

Homologous passive cutaneous anaphylaxis (PCA) was induced by IgE antibody and, simultaneously, cutaneous reactions were induced by some allergic mediators such as histamine, serotonin and leukotriene (LT) C4 on rat back skin. Disodium cromoglycate and tranilast with inhibitory actions on mediator release inhibited PCA specifically, whereas antihistaminics, including ketotifen, azelastine, mequitazine and diphenhydramine, inhibited histamine- and serotonin-induced cutaneous reactions as well as PCA. Anti-slow-reacting substance of anaphylaxis drugs, KC-404 and FPL-55712, significantly inhibited PCA and histamine- and serotonin-induced reactions, but at the same doses they did not produce significant inhibition of the LTC4-induced reaction. All reactions tested were strongly inhibited dose dependently with the beta stimulants, salbutamol and isoproterenol, and a xanthine derivative, theophylline, which are known to increase the intracellular cyclic AMP level. We think that this method enables the determination of the properties of anti-allergic drugs.

Antiasthmatic Activity of a Novel Thromboxane A2 Antagonist, S-1452, in Guinea Pigs

We examined the effect of a potent thromboxane (Tx) A2 receptor antagonist, calcium (1R, 2S, 3S, 4S)-(5Z)-7-(((phenylsulfonyl)amino)bicyclo[2.2.1] hept-2-yl)-5-heptenoate dihydrate (S-1452), on antigen- and various allergic-spasmogen-induced contractions of guinea pig lung parenchymal strips and on the increase in insufflation pressure, an index of bronchoconstriction, in anesthetized guinea pigs. In isolated guinea pig lung parenchymal strips, S-1452 showed competitive antagonism of the contractile activity of U-46619, a TxA2 mimetic, with a pA2 value of 8.9. The compound also inhibited the contraction induced by prostaglandin (PG) D2 and PGF2 alpha, but a TxA2 synthetase inhibitor, OKY-046, did not. In contrast, both drugs inhibited not only leukotriene (LT) D4-induced contraction but also antigen-induced contraction in the presence of a histamine antagonist. In anesthetized guinea pigs, oral administration of S-1452 markedly inhibited the bronchoconstrictions induced by intravenous injection of U-46619, PGD2, PGF2 alpha, LTD4 and platelet-activating factor (PAF) with ED50 values of 0.006, 0.031, 0.112, 0.033 and 0.115 mg/kg, respectively, but OKY-046 inhibited only that by LTD4 and PAF. Additionally, bronchoconstriction following intravenous injection of antigen was almost completely suppressed by S-1452 (0.1 mg/kg) and partially by OKY-046 (300 mg/kg) in passively sensitized guinea pigs which were treated with diphenydramine and propranolol. The inhibitory effect of S-1452 against U-46619-induced broncho-constriction persisted up to 7 h after oral administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Discovery of S-777469: an orally available CB2 agonist as an antipruritic agent.

The discovery of novel CB2 ligands based on the 3-carbamoyl-2-pyridone derivatives by adjusting the size of side chain at 1-, 5- and 6-position is reported. The structure-activity relationship around this template lead to the identification of S-777469 as a selective CB2 receptor agonist, which exhibited the significant inhibition of scratching induced by Compound 48/80 at 1.0 mg/kg po and 10 mg/kg po (55% and 61%, respectively).

Total Synthesis of Terprenin, a Highly Potent and Novel Immunoglobulin E Antibody Suppressant

Regioselective halogenations and Suzuki reactions ensure proper linkage of the aromatic rings in two total syntheses of terprenin (1). Both routes make it possible to prepare 1 efficiently and in large quantity.

Involvement of thromboxane A2 in bronchial hyperresponsiveness but not lung inflammation induced by bacterial lipopolysaccharide in guinea pigs.

We examined both a possible association of bronchial hyperresponsiveness with lung inflammatory responses and the role of thromboxane (Tx) A2 in these responses after lipopolysaccharide (LPS) exposure in guinea pigs treated with metyrapone, a cortisol synthesis inhibitor. The increase in bronchial responsiveness to i.v. acetylcholine was transient, with a peak at 2 h after LPS exposure, which was associated with increases in TxB2 and tumor necrosis factor in bronchoalveolar lavage (BAL) fluid. However, the levels of 6-keto-prostaglandin (PG) F1 alpha, interleukin-1 and interleukin-6 in BAL fluid, and the influx of leukocytes in airway and pulmonary edema were not associated with bronchial hyperresponsiveness. Oral administration of S-1452, a selective TxA2 receptor antagonist, markedly suppressed bronchial hyperresponsiveness without affecting cellular responses, pulmonary edema and production of PGs and cytokines. These findings suggest that LPS-induced bronchial hyperresponsiveness is dependent on secondarily generated TxA2, which appears to be independent of lung inflammation.

Involvement of Thromboxane A2 in Antigen-Induced Nasal Blockage in Guinea Pigs

To estimate the involvement of thromboxane (Tx) A2 in the onset of nasal blockage, we examined the effect of the selective TxA2 receptor antagonist, S-1452, as well as an H1-antihistamine, diphenhydramine, on the antigen-induced increase in intranasal pressure, as an index of nasal blockage, in anesthetized guinea pigs actively sensitized by inhalation of aerosolized ovalbumin (OA). Oral administration of S-1452 or intravenous administration of diphenhydramine significantly but incompletely reduced the increase in intranasal pressure following exposure of the nasal cavity of guinea pigs to aerosolized OA. In combination, the two agents were more effective than either alone, but there was no significant difference between them. The TxB2 level was significantly elevated in nasal lavage fluid 15 and 30 min after antigen challenge. Exposure of the nasal cavity of guinea pigs to aerosolized U-46619, a TxA2 mimetic, also resulted in a marked increase in intranasal pressure, and this could be almost completely suppressed by S-1452. These findings suggest that TxA2 contributes to antigen-induced nasal blockage in guinea pigs.

Inhibitory Effect of a Potent and Selective Cytosolic Phospholipase A2α Inhibitor RSC-3388 on Skin Inflammation in Mice

Cytosolic phospholipase A2α (cPLA2α) preferentially hydrolyzes membrane phospholipids containing arachidonic acid, resulting in the biosynthesis of eicosanoids such as prostaglandins and leukotrienes. To examine the contribution of cPLA2α to skin inflammation, we evaluated the effect of (E)-N-[(2S,4R)-4-[N-(biphenyl-2-ylmethyl)-N-2-methylpropylamino]-1-[2-(2,4-difluorobenzoyl)benzoyl]pyrrolidin- 2-yl]methyl-3-[4-(2,4-dioxothiazolidin-5-ylidenemethyl) phenyl]acrylamide (RSC-3388), a potent and selective cPLA2α inhibitor, on 2,4,6-trinitro-1-chlorobenzene (TNCB)-induced ear inflammation and mite antigen-induced dermatitis in mice. Topical application of RSC-3388 showed a significant inhibitory activity against TNCB-induced ear swelling and eicosanoid production in mice. Comprehensive expression analysis using Gene-Chip technology and subsequent experiments concerning mRNA and protein expression demonstrated that RSC-3388 clearly reduced the levels of interleukin-1β, macrophage inflammatory protein-1α (MIP-1α) and MIP-1β in a TNCB-induced mouse model. In addition, RSC-3388 ointment significantly alleviated atopic dermatitis-like skin lesions induced by repeated application of mite antigen. Furthermore, increased expression of cPLA2α, assessed by anti-phospho-cPLA2α antibody, was observed in the skin lesions of mite-antigen-induced dermatitis. These results indicate that cPLA2α is involved in the development of skin inflammation in mice, and RSC-3388 is expected to be useful for the treatment of inflammatory skin disorders such as atopic dermatitis.

Amyloid β protein impairs motor function via thromboxane A2 in the rat striatum

Abstract Amyloid β protein (Aβ) deposits are found in the striatum of patients with Alzheimer disease (AD) showing extrapyramidal motor dysfunction, but neuronal cell loss has not yet been detected. To clarify how Aβ impairs motor function, we analyzed intrastriatally Aβ-injected rats. Unilateral injection of Aβ(25-35) enhanced apomorphine-induced circling in an ipsilateral direction, indicating ipsilateral dysfunction of dopaminergic nigrostriatal pathways. Volumes of lesion in the Aβ(25-35)-injected striata were significantly higher than those in the saline-injected ones. The correlation between lesion volume and circling behavior was close to significance, but slightly too low, suggesting the possible involvement of other factors in the striatal dysfunction. Aβ(25-35) significantly elevated the level of thromboxane A2 (TXA2). A stable TXA2 agonist, U46619, enhanced circling behavior, and TXA2 receptor antagonists attenuated U46619- and Aβ(25-35)-enhanced circling behavior. This study demonstrated that Aβ(25-35) impairs the motor function of dopaminergic neurons via neuronal cell loss and TXA2. It also sheds light on the therapeutic potential of TXA2 receptor blockers for the neurotoxicity of Aβ.