Tanaka H, Watanabe K, Tamaru N, Yoshida M
Second Department of Internal Medicine, Fukuoka University School of Medicine, Japan.
Lung. 1995;173(6):347-61. doi: 10.1007/BF00172142.
To elucidate the signal transduction system in the production of prostaglandin E2 (PGE2) by porcine tracheal smooth muscle cells in culture (PTSMC), we examined the pattern of arachidonic acid metabolites released from PTSMC and the relationship between bradykinin-stimulated rises in intracellular calcium concentration ([Ca2+]i) and PGE2 production by PTSMC. We next examined the effect of dexamethasone on these parameters. Bradykinin induced a dose-dependent increase in both the rise in [Ca2+]i and PGE2 production by PTSMC. The increase in [Ca2+]i paralleled an increase in PGE2 production. High-performance liquid chromatography (HPLC) revealed that dexamethasone-treated PTSMC were suppressed to release arachidonic acid metabolites such as PGE2 and prostaglandin F2 alpha (PGF2 alpha). Incubation of PTSMC with 10(-6)M dexamethasone for 24 h significantly suppressed both the rise in [Ca2+]i and PGE2 production by PTSMC in response to bradykinin, and also significantly suppressed bradykinin-stimulated release of radioactivity from PTSMC prelabeled with 3H-labeled arachidonic acid (3H-AA). When PTSMC pretreated with dexamethasone were incubated with 170 nM prostaglandin H2 (PGH2) or 20 microM arachidonic acid; PTSMC synthesized less PGE2 than control PTSMC. Results suggest that bradykinin stimulates PTSMC to produce PGE2 via the signal transduction system including Ca2+, and dexamethasone appeared to suppress PGE2 production by reducing the activity of cytosolic phospholipase A2 (cPLA2) and PGE2 synthase. However, we failed to demonstrate the suppression of the activity of cyclooxygenase in PTSMC by dexamethasone. Since the elevation of [Ca2+]i is necessary for the contraction of airway smooth muscles, dexamethasone seems to reduce the contraction of airway smooth muscles by suppressing the rise in [Ca2+]i and the release of arachidonic acid metabolites. Reduced production of arachidonic acid metabolites may also contribute to improvement in the bronchial inflammation.
为阐明培养的猪气管平滑肌细胞（PTSMC）产生前列腺素E2（PGE2）的信号转导系统，我们检测了PTSMC释放的花生四烯酸代谢产物模式，以及缓激肽刺激引起的细胞内钙浓度（[Ca2+]i）升高与PTSMC产生PGE2之间的关系。接下来，我们检测了地塞米松对这些参数的影响。缓激肽诱导PTSMC的[Ca2+]i升高和PGE2产生呈剂量依赖性增加。[Ca2+]i的增加与PGE2产生的增加平行。高效液相色谱（HPLC）显示，地塞米松处理的PTSMC释放花生四烯酸代谢产物如PGE2和前列腺素F2α（PGF2α）受到抑制。用10(-6)M地塞米松孵育PTSMC 24小时，可显著抑制PTSMC对缓激肽反应的[Ca2+]i升高和PGE2产生，也显著抑制缓激肽刺激的预先用3H标记花生四烯酸（3H-AA）标记的PTSMC释放放射性。当用170 nM前列腺素H2（PGH2）或20 μM花生四烯酸孵育预先用地塞米松处理的PTSMC时，PTSMC合成的PGE2比对照PTSMC少。结果表明，缓激肽通过包括Ca2+的信号转导系统刺激PTSMC产生PGE2，地塞米松似乎通过降低胞质磷脂酶A2（cPLA2）和PGE2合酶的活性来抑制PGE2产生。然而，我们未能证明地塞米松对PTSMC中环氧化酶活性的抑制作用。由于[Ca2+]i升高是气道平滑肌收缩所必需的，地塞米松似乎通过抑制[Ca2+]i升高和花生四烯酸代谢产物释放来减少气道平滑肌收缩。花生四烯酸代谢产物产生减少也可能有助于改善支气管炎症。
