Jun Hiroi

Comparison of the cardiovascular effect of FR34235, a new dihydropyridine, with other calcium antagonists.

We compared the cardiovascular effect of FR34235, a new dihydropyridine derivative, with the effects of nifedipine, nicardipine, and diltiazem on the dog using in vitro and in vivo preparations. FR34235 reduced the amplitude of coronary arterial contraction induced by K+ more so than that induced by norepinephrine in in vitro preparations. The ID50 values of FR34235 for various arterial strips contracted by K+ were smaller (1/5–1/426) than those of nifedipine and diltiazem, and almost the same as those of nicardipine. There was a greater increase in both the coronary and vertebral blood flow than in the other peripheral arterial flow in anesthetized dogs administered FR34235 (0.32–100 μg/kg i.v.), and the duration of effect was about two to three times longer than that of the other drugs. To obtain a vasodilating effect by the intraduodenal route, 10–30 times the intravenous dose of FR34235 was required, far lower than that required of nicardipine. In atrioventricular (AV) and sinoatrial node preparations, FR34235 was weaker in impairing AV conduction than nifedipine, in spite of their similar potencies in increasing coronary flow and decreasing sinus rate. FR34235 was more potent than diltiazem in increasing coronary flow, in spite of their similar potencies on AV conduction. It is concluded that FR34235 has: (a) potent vasodilating activity, probably due to inhibition of Ca2+ influx into the cells; (b) selective and long-lasting effects on the coronary and cerebral arteries in vivo; (c) a wide difference between doses that cause vasodilation and an impairing effect on AV conducting tissues; and (d) therapeutic effects after absorption from the intestinal tract.

Bone-specific delivery and sustained release of diclofenac, a non-steroidal anti-inflammatory drug, via bisphosphonic prodrug based on the Osteotropic Drug Delivery System (ODDS).

We have newly synthesized osteotropic diclofenac with bisphosphonic moiety (DIC-BP) based on the concept of Osteotropic Drug Delivery System (ODDS) and investigated its potency of site-specific and controlled delivery of diclofenac to the bone in rats. After intravenous injection into rats, DIC-BP was predominantly distributed in the skeleton. DIC-BP once incorporated in the bone was gradually eliminated (t(1/2)=9.7 days), releasing diclofenac into the bone compartment. As a result, the bone concentration of regenerated diclofenac was apparently constant over 28 days. Furthermore, we evaluated the anti-inflammatory effects of DIC-BP compared with diclofenac (sodium salt) in adjuvant-induced arthritic rats. The mean effective doses (ED(50)) were 0.55 mg/kg and 1.3 mg/kg for daily oral administration of diclofenac and weekly intravenous injection of DIC-BP, respectively. Considering the frequency of medication of 17 times for diclofenac and 4 times for DIC-BP in the experimental period, ED(50) was corrected to 9.4 and 5.2 mg/kg (per experimental period) for diclofenac and DIC-BP, respectively. Moreover, DIC-BP exhibited no side effects of gastrointestinal damage, typical of non-steroidal anti-inflammatory drugs. Thus, ODDS of diclofenac shows promise as an approach for highly potent and non-toxic therapy of diclofenac, with less frequent medication.

Functional neurokinin NK-1 receptor expression in rat peritoneal mast cells.

Objective and Design: Recently, Ogawa et al. [17] reported that the peritoneal mast cells (PMCs) of rats can release histamine by substance P (SP) in a receptor-dependent manner. In the present study, we confirmed and extended their findings.¶Material: PMCs were isolated from six strains of rats. In some experiments, peritoneal cells in the non-MC fraction were used.¶Methods: PMCs were incubated with SP, neurokinin (NK) receptor agonists or antagonists, and histamine content in the supernatant was measured. In the binding assay, PMCs were incubated with [125I]BH-SP together with SP or NK receptor antagonists. NK-1 receptor mRNA was detected using a reverse transcription-polymerase chain reaction (RT-PCR) assay.¶Results: PMCs from Slc:Wistar and F344/NSlc were highly sensitive to SP, leading to histamine release, whereas those from Slc:SD and three other strains were not. PMCs from Slc:Wistar and F344/NSlc also released histamine in the presence of an NK-1 agonist. The histamine release induced by SP and the NK-1 agonist was inhibited by the NK-1 receptor antagonists, FK888 and CP-99,994. [125I]BH-SP binding experiments revealed that PMCs from Slc:Wistar rats possessed a single high affinity binding site for SP and that the binding was blocked by NK-1 receptor antagonists. Peritoneal cells in the non-MC fraction exhibited no appreciable binding. In the RT-PCR assay, expression of NK-1 receptor mRNA was evident in Slc:Wistar PMCs, but not in the non-MC fraction from Slc:Wistar or Slc:SD PMCs.¶Conclusion: These data demonstrate the existence of functional NK-1 receptors on freshly isolated PMCs in at least some strains of rats.

Effects of specific tachykinin receptor antagonists on citric acid-induced cough and bronchoconstriction in unanesthetized guinea pigs

We compared the effects of a tachykinin NK1 receptor antagonist, FK888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl-L-prolyl]-N-methy l-N -phenylmethyl-3-(2-naphthyl)-L-alaninamide), and a tachykinin NK2 receptor antagonist, SR48968 ((S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl)butyl]benzamide]), on citric acid-induced cough and bronchoconstriction in conscious guinea pigs. FK888 and SR48968 inhibited the cough dose dependently. Combination of FK888 and SR48968 showed a small additive effect compared with that of FK888 or SR48968 alone. SR48968 but not FK888 inhibited the bronchoconstriction dose dependently. These results indicate that tachykinin NK1 receptors as well as tachykinin NK2 receptors are involved in the citric acid-induced cough response. The antitussive activity of the tachykinin NK1 receptor antagonist appeared not to depend on the anti-bronchoconstrictor effects.

Genetic analyses for dermatitis and IgE hyperproduction in the NC/Nga mouse

Atopic dermatitis (AD) is a severe problem in the human species, and many approaches have been taken to reveal the causes of the disease and to develop therapeutical methods to combat it. However, the fundamental causes of AD are still unknown, and no radical therapy exists (Leung 1997; van Bever 1992), mainly due to lack of a suitable animal model for studying the mechanisms through which AD arises. We recently determined that the NC/Nga (NC) mice would be an excellent animal model for human AD, because they show severe hereditary dermatitis with hyperproduction of immunoglobulin E (IgE), similar to the situation in humans (Matsuda et al. 1997). The NC strain was established as an inbred strain by K. Kondo in 1957 based on Japanese fancy mice (Festing 1996; Kondo 1984), and is now a highly inbred strain (more than 100 generations). The dermatitis and IgE hyperproduction occur spontaneously in all NC mice reared under non-sterile (conventional) conditions, but no genetic analyses for these characters have been done so far. When trying to use the NC mice as an efficient animal model for human AD, it is necessary to reveal the mode of inheritance of the expression of dermatitis and IgE hyperproduction, and we describe it in this paper. All animals used in this study were handled according to the rules described in Guide for the Care and Use of Laboratory Animals (NIH publication no. 86-23, 1985); Standards Relating to the Care and Management of Experimental Animals, Prime Ministers Office, Japan, 1980; and Guide for the Use of Experimental Animals in Universities, The Ministry of Education, Science, and Culture, Japan, 1987. NC and BALB/cA (BALB) strains and their crossbreds were used, with the BALB mice serving as a control. All mice were raised in a clean, conventional animal room with temperature and relative humidity adjusted to 23+2 °C and 50+10%, respectively. The room was illuminated by fluorescent light from 5 am until 9 pm. Mice were kept in a polycarbonate cage (Clea Japan, Inc., Osaka, Japan) that was bedded with clean wood chips (Clea Japan, Inc.), and tap water and a commercial diet for small rodents (CE-2, Clea Japan, Inc.) were provided for ad libitum consumption. We reciprocally paired NC mice with BALB mice to produce F1 progeny. Subsequently, F2 and backcross generations were also produced. In these mice, we scored the incidence of abnormal mice showing dermatitis or high levels of plasmic total IgE at 12 weeks of age. The resulting segregation ratios were analyzed by the chi-square test. To obtain segregation data for the mice with dermatitis, we classified the animals on the basis of the absence or presence of scratching, erythema, hemorrhage, edema, superficial erosion, deep excoriation, and/or scaling and dryness of the skin, because all conventional NC mice are characterized by these symptoms. The BALB mice, however, showed no such symptoms even though they were reared together with the severely lesioned NC mice in the same cage for several months (Matsuda et al. 1997). To obtain segregation data for the mice showing IgE hyperproduction, we classified the animals with an IgE level less than 1500 ng/ml as a low-level group and those with more than 9000 ng/ml as a high-level group, because the F2 and M. Tsudzuki ( ) Laboratory of Animal Breeding and Genetics, Faculty of Applied Biological Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739, Japan

A 5-lipoxygenase inhibitor, FR110302, inhibits ozone-induced airway hyperresponsiveness in guinea pigs and dogs

Airway hyperresponsiveness is a key feature of asthma, and attenuating airway hyperresponsiveness is an important part of asthma therapy. In the present study we examined the inhibitory effect of a potent 5-lipoxygenase inhibitor, FR 110302, on airway hyperresponsiveness induced by ozone exposure in guinea pigs and dogs. Respiratory resistance (Rrs) was measured by a forced oscillation method. Airway responsiveness was determined from the dose-response curve ofRrs to acetylcholine. Guinea pigs were exposed to 2.5 ppm ozone for 1 h. In a control group of guinea pigs, Δlog PC100 (the index of the ozone-induced airway hyperresponsiveness) was 0.58±0.04 (log mg/ml). Treatment with FR110302 (10 or 100 mg/kg p.o.) significantly diminished Δlog PC100 (10 mg/kg; 0.22±0.10; 100 mg/kg; 0.11±0.06). Dogs were exposed to 3 ppm ozone for 2 h. In a control group of dogs, ΔlogDmin (another index of the ozone-induced airway hyperresponsiveness) was 1.24±0.15 (log unit). Treatment with FR110302 (1 or 3.2 mg/kg p.o.) significantly diminished ΔlogDmin (1 mg/kg: 0.60±0.18; 3.2 mg/kg: 0.27±0.12). These results suggest that FR110302 may be a useful drug for attenuating airway hyperresponsiveness in asthmatic patients.

アトピー性皮膚炎治療薬タクロリムス軟膏(プロトピック®軟膏)の薬理学的特性と臨床効果

Atopic dermatitis (AD) is thought to be induced by a complex of various allergic reactions and T cells are implicated in its etiology. Since tacrolimus strongly inhibits T cell activation, tacrolimus ointment has been developed as a novel drug for AD throughout the world. Tacrolimus inhibits mast cell and eosinophil activation and antigen presenting activity of Langerhans cells in vitro. In the in vivo experimental animal models of AD, such as contact and spontaneous dermatitis in mice and repeated hapten treated skin inflammation in rats, tacrolimus ointment showed inhibitory activity. In clinical studies with AD patients in Japan, USA and Europe, tacrolimus ointment showed a marked effect. In comparative studies in Japan, it showed the same efficacy as a strong class steroid ointment on eczema at the trunk and extremities and superior efficacy at the face and neck compared to a medium class steroid. The most prominent adverse event is experienced at the local application site with reactions such as a burning sensation and erythema. Systemic side effects were rarely observed. While there is a possibility of skin infections when using tacrolimus, skin atrophy, even after long term treatment, was not observed. Thus tacrolimus ointment could be an efficient alternative to steroid ointment for AD.