Theophylline and cAMP inhibit lysophosphatidic acid-induced hyperresponsiveness of bovine tracheal smooth muscle cells.
We have established an in vitro model of airway hyperresponsiveness, using a bovine tracheal smooth muscle cell (BTSMC)-embedded collagen gel lattice. When the gel was pretreated with lysophosphatidic acid (LPA), which activates the small G protein RhoA, ATP- and high K+ solution-induced gel contraction was significantly augmented. This was not due to the modulation of Ca2+ mobilizing properties, since ATP- and high K+-induced Ca2+ transients were not significantly different between control and LPA-treated BTSMC. Y-27632, an inhibitor of Rho-kinase, suppressed the LPA-induced augmentation of gel contraction, whereas it did not inhibit the contraction of control gels. Theophylline (> or = 1 microM) reversed the LPA-induced augmentation of gel contraction, whereas it inhibited control gel contraction only with a very high concentration (100 microM). We confirmed that theophylline increased the intracellular concentration of cAMP ([cAMP]i) in BTSMC. Elevation of [cAMP]i with dibutyryl cAMP or forskolin also reversed the LPA-induced augmentation of gel contraction. Furthermore, theophylline, as well as dibutyryl cAMP and forskolin, suppressed the LPA-induced membrane translocation of RhoA, indicating that they prevented airway hyperresponsiveness by inhibiting RhoA. We conclude from these results that theophylline inhibits LPA-induced, RhoA/Rho-kinase-mediated hyperresponsiveness of tracheal smooth muscle cells due to the accumulation of cAMP.
Sakai
Jiro
J
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Oike
Masahiro
M
Hirakawa
Masakazu
M
Ito
Yushi
Y
D000199:Actins / Q000378:metabolism; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000378:metabolism* / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D066298:In Vitro Techniques; D008246:Lysophospholipids / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D013806:Theophylline / Q000494:pharmacology*; D014132:Trachea / Q000166:cytology*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D001993:Bronchodilator Agents; D008246:Lysophospholipids; D013806:Theophylline; D000242:Cyclic AMP; D020742:rhoA GTP-Binding Protein; D002118:Calcium