cyclic-gmp and azelastine

Azelastine (1-300 microM) inhibited contractions of isolated porcine trachea induced by high K+, carbachol and endothelin-1 (ET-1) with a decrease in [Ca2+]cyt (as measured by fura-2-fluorescence). Verapamil (0.1-10 microM) also inhibited the high K(+)-induced increases in [Ca2+]cyt and contraction, although it only partially inhibited the responses evoked by carbachol or ET-1. In the absence of extracellular Ca2+ (with 0.5 mM EGTA), carbachol induced a transient increase in [Ca2+]cyt and force by releasing Ca2+ from cellular stores. Azelastine (100 microns) completely inhibited these contransient changes. In the absence of extracellular Ca2+, carbachol and 12-deoxyphorbol 13-isobutyrate (DPB) induced small sustained contractions without increasing [Ca2+]cyt. Azelastine inhibited these contractions. In muscle permeabilized with alpha-toxin, Ca2+ (0.3-3 microM) induced contraction in a concentration-dependent manner. DPB (without GTP) and carbachol or ET-1 (with GTP) enhanced the Ca(2+)-induced contraction. Azelastine partially inhibited the contraction induced by 0.3 microM Ca2+ but not the contraction induced by 3 microM Ca2+, and strongly inhibited the potentiating effects of DPB, carbachol and ET-1. Azelastine had no effect on the content of cyclic AMP or cyclic GMP. These results suggest that azelastine inhibits smooth muscle contraction by (i) decreasing [Ca2+]cyt, by inhibition of Ca2+ channels, (ii) decreasing agonist-induced Ca2+ release, and (iii) direct inhibition of contractile elements.

Topics: Animals; Bronchodilator Agents; Carbachol; Cyclic AMP; Cyclic GMP; Endothelins; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Phthalazines; Potassium; Swine; Trachea; Verapamil

To investigate the mechanism by which azelastine may be effective therapeutically in asthma, we studied its ability to inhibit anti-IgE- and calcium ionophore A23187-stimulated histamine release from human lung and to alter lung cyclic nucleotide levels. Significant inhibition of histamine release from both anti-IgE- and A23187-stimulated human tissue was apparent after 30 minutes preincubation of the lung tissue in azelastine. Significant inhibition of anti-IgE-stimulated histamine release was consistently seen in azelastine concentrations greater than or equal to 5 microM, and was dose dependent (r = 0.71, p less than 0.05) with maximal mean inhibition of 53 +/- 11%. For A23187-stimulated lung tissue, consistent inhibition of histamine release was not found until we used 30 microM azelastine, mean 35 +/- 11%. Inhibition in azelastine concentrations below 30 microM was variable and not significant. Lung cyclic AMP and cyclic GMP content was not significantly altered by incubation of lung tissue in 100 microM azelastine. We conclude that azelastine inhibits stimulated histamine release from human lung tissue in vitro but does not alter cyclic nucleotide content.

Topics: Antibodies, Anti-Idiotypic; Calcimycin; Cyclic AMP; Cyclic GMP; Histamine H1 Antagonists; Histamine Release; Humans; Immunoglobulin E; Lung; Phthalazines; Pyridazines