Ikuhisa Yakuo

The role of thromboxane A2 [TxA2] in liver injury in mice

The role of thromboxane A2 (TxA2) in CCl4-induced liver disease was investigated in mice. Significant elevation of TxB2 in the liver was observed 6 hours after the injection of CCl4. Administration of OKY-046, a selective TxA2 synthetase inhibitor (10 and 50 mg/kg) and ONO-3708, a TxA2 receptor antagonist, (0.5, 1 and 2 mg/Kg) suppressed the elevation of serum GOT and GPT levels and histopathological changes of the liver. In addition, OKY-046 inhibited the elevation of TxB2 in the liver. When U-46619, a stable TxA2 mimetic was injected i.v. into the mice, clear elevation of serum GOT and GPT levels and histopathological score of the liver were observed. These results suggest that TxA2 play a role for the onset of CCl4-induced liver injury in mice.

Role of peptide-leukotrienes in liver injury in mice.

The role of peptide leukotrienes (p-LTs), especially LTC4 and LTD4 in liver disease, was investigated in mice experimental liver injury models. The liver injury was induced by the injection of bacterial lipopolysaccharide (LPS) intoCorynebacterium parvum pretreated mice. Carbon tetrachloride (CCl4)-induced liver injury in mice was used as a standard model. In both injury models, extensive liver parenchymal cell damage was observed by the elevation of glutamate transaminase (GOT and GPT) activity and confirmed by significant histopathological changes in the liver. Moreover, significant elevation of LTC4 in the liver was observed in both models 1 and 6 h after the onset of disease. Administration of AA-861, a selective 5-lipoxy-genase inhibitor (0.5, 1, and 2 mg/kg) and LY-171883, a p-LT receptor antagonist (50 and 200 mg/kg) suppressed the elevation of serum GOT and GPT levels and histopathological changes in both experimental liver injury models. In addition, when authentic LTC4 or LTD4 was injected into the mouse, clear elevation of serum GOT and GPT and histopathological changes of the liver were observed. These results suggest that p-LTs play a role in the onset of liver diseases in mice.

The equivalent bronchodilator effects of salbutamol formulated in chlorofluorocarbon and hydrofluoroalkane-134a metered dose inhalers on the histamine-induced pulmonary response in dogs.

AbstractPurpose. The bronchodilator effect of salbutamol formulated in hydrofluoroalkane-134a (HFA-134a), a Chlorofluorocarbon (CFC)-free propellant for metered dose inhalation (MDI) devices, was compared with that of salbutamol formulated in CFC in anesthetized dogs. Methods. Bronchospasms were induced by the intravenous injection of histamine, and bronchial resistance was measured by the method of Konzett and Rossler. Results. While the placebo vehicles (HFA-134a and CFC propellants) had no significant effect on histamine-induced bronchospasms, the salbutamol/HFA-134a and salbutamol/CFC MDI formulations had equivalent dose-related inhibitory effects. Conclusions. These data indicated that salbutamol formulated in HFA-134a and that in CFC propellant are bioequivalent.

Role of thromboxane (Tx) A2 in guinea pig forssman shock and the effect of OKY-046, TX A2 synthetase inhibitor

To study the role of thromboxane (Tx) A2 in Forssman systemic shock (FSS) in guinea pig, the effect of (E)-3-[p-(1H-Imidazol-1-ylmethyl)phenyl]-2-propenoic acid hydrochloride (OKY-046), a specific Tx A2 synthetase inhibitor, was studied. OKY-046 administered intravenously clearly prolonged survival time and protected against fatal shock. In shocked animals, definite decreases in serum complement hemolytic activity (CH50), leucocyte counts and platelet counts and an increase in lactate dehydrogenase (LDH) activity were observed. In addition, a significant increase of Tx B2 and incoagulability of blood were observed after shock. Whereas OKY-046 had no effect on the decreases in CH50, platelet counts and leucocyte counts, it inhibited the increase of Tx B2 and increased the amount of 6-keto PG F1 alpha. When Forssman antibody (half a lethal dose) was injected, a diphasic increase in airway resistance was observed. OKY-046 inhibited this diphasic increase in airway resistance. These data suggest a pathophysiological role for Tx A2 in FSS. OKY-046 inhibited the Forssman antibody induced respiratory disorders probably due to the inhibition of Tx A2 synthesis after shock.

Effect of cinnarizine on IgE antibody‐mediated experimental allergic reactions in guinea pigs

The anti‐allergic activity and mechanism of cinnarizine was investigated in guinea pigs. Nifedipine, a calcium antagonist, and tranilast, a potent, orally active anti‐allergic agent, were used as comparative drugs. 1) Cinnarizine protected against fatal systemic anaphylactic shock in guinea pigs passively sensitized with IgE antibody. Cinnarizine reduced many of the features of severe respiratory disorders. Nifedipine and tranilast showed similar effects. 2) Cinnarizine and nifedipine inhibited the contractile response to antigen of sensitized tracheal smooth muscle when the challenge was carried out at low antigen concentrations. Tranilast showed a tendency to inhibit the antigen‐induced contraction of tracheal smooth muscle. 3) Cinnarizine and nifedipine inhibited Ca‐induced contraction in potassium‐depolarized tracheal smooth muscle, tranilast had no effect. 4) Cinnarizine showed antagonistic action to the contraction by histamine or leukotriene D4 (LTD4) of tracheal muscle. Nifedipine showed similar antagonistic action, although its potency is lower than cinnarizine. Tranilast showed slight antagonistic action to LTD4. 5) Antigen‐induced release of histamine and slow reacting substance of anaphylaxis (SRS‐A) from sensitized lung tissues was inhibited by nifedipine and tranilast but not by cinnarizine. 6) The release of histamine and SRS‐A from lung tissues by calcium ionophore A23187 was inhibited by nifedipine and tranilast but not by cinnarizine. These results suggest that the anti‐allergic action of cinnarizine is mainly due to the antagonistic action to allergic mediators and not by interfering with die release of mediators. Cinnarizines mechanism seems to be related to its antagonistic action to Ca in smooth muscle, but not to the transport of Ca in releasing the anaphylactic chemical mediators in mast cells and other target cells.

The role of thromboxane A2 (TxA2) in allergic cutaneous reactions and the effect of (E)-3-[p-(1H-Imidazol-1-ylmethyl) phenyl]-2-propenoic acid hydrochloride (OKY-046), a TxA2 synthetase inhibitor

To study the role of thromboxane A2 (TxA2) in cutaneous allergic reactions, the effect of (E)-3-[p-(1H-Imidazol-1-ylmethyl)phenyl]-2-propenoic acid hydrochloride (OKY-046), a selective TxA2 synthetase inhibitor, on cutaneous reactions in rats and mice was studied. Simultaneously, the effect of 9,11-methanoepoxy-prostaglandin H2 (U-46619), a stable analogue of TxA2, on capillary permeability in mouse and rat skin was investigated. Passive cutaneous anaphylaxis (PCA) in mouse ear was clearly inhibited by OKY-046 but not by indomethacin. The inhibitory action of OKY-046 was not influenced by pretreatment with indomethacin. Moreover, prostaglandin I2, which accumulated as a result of the inhibition of TxA2 synthetase, did not affect the PCA. But, the dye leakages caused by histamine, serotonin and leukotriene C4 in mouse ear were clearly inhibited by OKY-046. In addition, OKY-046 inhibited rat reversed cutaneous anaphylaxis, but its inhibitory action was not affected by pretreatment with indomethacin. Contrary to the above results, rat footpad passive Arthus reaction and mouse footpad tuberculin delayed hypersensitivity reaction were not affected by OKY-046. Additionally, U-46619 did not cause an increase of capillary permeability in either mouse and rat skin. These results suggest a slight role of TxA2 in cutaneous allergic reactions in mice and rats and the efficacy of OKY-046 on Type I and II reactions regardless of the inhibition of TxA2 synthetase activity.

Morphological studies on nephrotoxic serum nephritis accelerated with rabbit IgG in mice.

A glomerulonephritis was induced in mice by injection of subnephrotoxic dose of nephrotoxic serum (NTS) after preimmunization with rabbit IgG. In order to characterize this glomerulonephritis, light, electron and immunofluorescence microscopic studies were carried out 15 days after NTS injection, the time when increases in urinary protein and serum cholesterol and a decrease in serum albumin were apparent.Characteristic changes were widespread thickening of capillary walls and narrowing of the capillary lumen owing to widening of mesangial areas. In those capillary walls, the mesangial interposition into subendothelial areas was often noted ultrastructurally and double track was confirmed on sections stained with PAM. Linear deposition of mouse IgG was detected in capillary walls by immunofluorescence. In severely affected glomeruli, PAS-positive hyaline nodular lesion was observed light microscopically and massive mesangial deposits ultrastructurally.Visceral epithelial cells demonstrated fusion of the foot processes, microvilli formation, occasional proliferation and enlargement. Parietal epithelial cells proliferated, forming cellular or fibrocellular crescent.Based on these characteristics, it appears this nephritic model shares a common pathology with human membranoproliferative glomerulonephritis type 1 and crescentic glomerulonephritis and can be considered an appropriate model for producing severe nephritis for short periods.

Pathological studies on nephrotoxic serum nephritis accelerated with rabbit γ-globulin in mice.

In order to characterize nephrotoxic serum nephritis accelerated with rabbit γ-globulin in mice, histopathological studies were carried out 15 days after NTS injection, the time when increases in urinary protein and serum cholesterol and a decrease in serum albumin were apparent. Characteristic changes were widespread thickening of glomerular capillary walls and widening of mesangial areas, owing to deposits of mesangial matrixlike substances. The mesangial interposition into subendothelial areas and the resultant narrowing of the capillary lumen were shown ultrastructurally. In severely affected glomeruli, a hyaline nodular lesion was observed. Visceral epithelial cells demonstrated fusion of the foot processes, microvilli formation, occasional proliferation, and enlargement. Parietal epithelial cells proliferated, forming a cellular crescent. Based on these characteristics, it appears this nephritic model shares a common pathology with human membranoproliterative glomerulonephritis type 1 and crescentic glomerulonephritis and can be considered an appropriate model for producing severe nephritis for short periods.

Inhibition of Antigen-Induced Contraction of Guinea Pig Isolated Tracheal Muscle with 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indene (MDI-A), indane (MDI-B) and 8-(diethylamino)octyl-3,4,5-trimethoxy benzoate hydrochloride (TMB-8)

The effects of three intracellular calcium antagonists on antigen-induced contraction of sensitized guinea pig tracheal muscle were investigated. The agents employed were: 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indene hydrochloride (MDI-A), 2-n-butyl-3-dimethylamino-5,6-methylenedioxy indane hydrochloride (MDI-B) and 8-(diethylamino)octyl-3,4,5-trimethoxy benzoate hydrochloride (TMB-8). Each of these agents caused a concentration-dependent inhibition of the antigen-induced contraction of sensitized tracheal smooth muscle. Moreover, in histamine and leukotriene D4 (LTD4) incited contractions of guinea pig tracheal muscle, they showed antagonistic action. The induced tracheal muscle contraction, achieved through the addition of compound 48/80 to a solution of ethylene glycol bis (beta-aminoethylether)-N,N,N1, N1-tetraacetic acid (EGTA) in a contained Ca-free medium, was completely inhibited by individual pretreatment with MDI-A, MDI-B and TMB-8. In the case of tracheal muscle contraction induced by CaCl2 in a high potassium, Ca-free medium, only TMB-8 inhibited contraction. Lastly, none of these three intracellular calcium antagonists affected the antigen-induced release of histamine and slow reacting substance of anaphylaxis (SRS-A). These results suggest that MDI-A and MDI-B inhibit the antigen-induced contraction of sensitized guinea pig tracheal muscle by interfering with the contractile responses caused by histamine and LTD4.