Miwa Misawa

Astrocyte stellation induced by Rho kinase inhibitors in culture.

To understand the role of Rho kinases in regulation of astrocyte morphology, we investigated the effects of Rho kinase inhibitors on the morphology of cultured rat cortical astrocytes. Cultured astrocytes exhibited flattened, polygonal morphology in the absence of stimulation, but changed into process-bearing stellate cells following treatment with the selective Rho kinase inhibitor Y-27632 (1-10 microM). The Y-27632-induced astrocyte stellation was abolished by treatment with colchicine, indicating that the response requires reorganization of cytoskeletal elements. The effect of Y-27632 was mimicked by another Rho kinase inhibitor HA1077, but not by the protein kinase C inhibitor GF-109203X or the protein kinase A inhibitor KT5720. These results suggest that Rho kinases are in an activated state in the absence of stimuli and contribute to the maintenance of polygonal morphology of cultured astrocytes.

Amyloid β protein enhances the clearance of extracellular l-glutamate by cultured rat cortical astrocytes

To explore the impact of Alzheimers disease amyloid beta protein (Abeta) on astrocyte functions, we investigated the effect of Abeta on glutamate clearance capacity of cultured rat cortical astrocytes. When L-glutamate (50-200 microM) was added to astrocyte cultures and incubated, the extracellular L-glutamate concentration declined with time. The time-dependent decline of extracellular L-glutamate was significantly faster in cultures treated with 10-20 microM Abeta for 24 h than in intact cultures, suggesting that Abeta enhances the L-glutamate clearance capacity of astrocytes. The effect of Abeta was not affected by antioxidants including catalase, propyl gallate or Trolox. Relatively long treatment time (8-48 h) was required for Abeta to exert this effect. Western blot analysis revealed that expression level of the glutamate transporter GLAST was increased by treatment with 10-20 microM Abeta for 8-48 h. These results suggest that Abeta upregulates a glutamate uptake system of astrocytes and enhances the clearance of extracellular L-glutamate.

Hyperresponsiveness of bronchial but not tracheal smooth muscle in a murine model of allergic bronchial asthma.

Abstract.Objective: To determine a change in airway smooth muscle contractility in a murine model of allergic asthma, the responsiveness of airway smooth muscles isolated from ovalbumin (OA)-sensitized and -challenged mice was compared with that from control animals.Methods: Actively sensitized mice were repeatedly challenged by ovalbumin (OA) antigen inhalation. Twenty-four h after the last antigen challenge, tracheal and bronchial smooth muscle responsiveness to acetylcholine (ACh) and endothelin-1 (ET-1) were measured. Airway microvascular leakage and histochemistry were also determined as indices of airway inflammation.Results: Both the ACh and ET-1 responsiveness of bronchial, but not tracheal, smooth muscles were significantly augmented in OA-challenged mice, whereas no significant change in the expression levels of M2, M3 and ETB receptors was observed. The Evans blue dye extravasation in the main bronchial, but not tracheal, tissue of OA-challenged mice was significantly increased as compared with that of sensitized control animals. A marked inflammatory cells infiltration was also observed in bronchial but not tracheal tissues of OA-challenged mice.Conclusion: Repeated antigen challenge to sensitized mice caused a hyperresponsiveness of bronchial, but not tracheal, smooth muscle accompanied with bronchial tissue inflammation.

Effect of sodium azulene sulfonate on capsaicin-induced pharyngitis in rats.

Abstract: Sodium azulene sulfonate is a water‐soluble derivative of azulene which is an antiinflammatory component of chamomile of the family of Asteraceae. Sodium azulene sulfonate is clinically used as a therapeutic agent in the treatment of pharyngitis as well as other inflammatory diseases such as tonsillitis, stomatitis and conjunctivitis. There has been no documentation on the effect of sodium azulene sulfonate on pharyngitis in laboratory models, probably because of no availability of such models. We recently established a pharyngitis model using capsaicin application on pharyngeal mucosa in rats. The present study investigated the antipharyngitis activity of sodium azulene sulfonate comparing with those of ruthenium red (vanilloid receptor antagonist, 8.5 and 85 mg/ml), ascorbic acid (antioxidative compound, 100 μg/ml), povidone iodine (gargle as disinfectant, oxidative compound, 5 and 20 mg/ml) and diclofenac sodium (cyclooxygenase inhibitor, 0.1 and 1 mg/ml). As an antipharyngeal effect, the capsaicin‐induced plasma exudation in the pharyngeal mucosa of the rat was evaluated. The capsaicin‐induced plasma exudation in the pharyngeal mucosa was inhibited by sodium azulene sulfonate (100 and 200 μg/ml) as well as ruthenium red and ascorbic acid, but not by povidone iodine and dicrofenac sodium; povidone iodine rather promoted the plasma exudation. In conclusion, the antipharyngitis effect of sodium azulene sulfonate was demonstrated for the first time in a laboratory model. Although the mechanism by which sodium azulene sulfonate inhibited the capsaicin‐induced pharyngitis is not yet unraveled, antioxidative effect, but not inhibitory effect on cyclooxygenase pathway, might be involved.