Sommerhoff C P, Caughey G H, Finkbeiner W E, Lazarus S C, Basbaum C B, Nadel J A
Cardiovascular Research Institute, Department of Medicine, San Francisco, CA 94143.
J Immunol. 1989 Apr 1;142(7):2450-6.
Submucosal glands are the major sources of airway secretions in most mammals. Mast cells are abundant in the environment of airway submucosal glands and are rich sources of secreted proteases. To investigate the hypothesis that mast cell proteases stimulate airway gland secretion, we studied the ability of the two major mast cell granule proteases, chymase and tryptase, to cause secretion of 35S-labeled macromolecules from a line of cultured bovine airway gland serous cells. Mast cell chymase and tryptase were purified from dog mastocytoma cells. Chymase markedly stimulated serous cell secretion in a concentration-dependent fashion with a threshold of 10(-10) M, whereas tryptase had no effect. The response to 10(-8) M chymase (1530 +/- 80% over base line) was approximately 10-fold higher than that evoked by other agonists such as histamine and isoproterenol. The predominant 35S-labeled macromolecule released by chymase was chondroitin sulfate proteoglycan, the glycoconjugate present in serous cell secretory granules. The response to chymase was non-cytotoxic and was blocked by active site inhibitors of chymase (soybean trypsin inhibitor and chymostatin) and by inhibitors of cellular energy metabolism (azide,2,4-dinitrophenol, dicumarol). Supernatant obtained by degranulation of mastocytoma cells caused a secretory response of comparable magnitude to that caused by chymase. These findings demonstrate that chymase, but not tryptase, is a potent secretagogue for airway gland serous cells, and they suggest a possible role for chymase-containing mast cells in the pathogenesis of airway hypersecretion.
在大多数哺乳动物中，黏膜下腺是气道分泌物的主要来源。肥大细胞在气道黏膜下腺环境中大量存在，是分泌蛋白酶的丰富来源。为了研究肥大细胞蛋白酶刺激气道腺体分泌这一假说，我们研究了两种主要的肥大细胞颗粒蛋白酶——糜蛋白酶和类胰蛋白酶，促使一系列培养的牛气道腺体浆液细胞分泌35S标记大分子的能力。肥大细胞糜蛋白酶和类胰蛋白酶从犬肥大细胞瘤细胞中纯化得到。糜蛋白酶以浓度依赖方式显著刺激浆液细胞分泌，阈值为10^(-10) M，而类胰蛋白酶无作用。对10^(-8) M糜蛋白酶的反应（比基线高1530±80%）比组胺和异丙肾上腺素等其他激动剂引起的反应高约10倍。糜蛋白酶释放的主要35S标记大分子是硫酸软骨素蛋白聚糖，即浆液细胞分泌颗粒中存在的糖缀合物。对糜蛋白酶的反应无细胞毒性，且被糜蛋白酶的活性位点抑制剂（大豆胰蛋白酶抑制剂和抑糜酶肽）以及细胞能量代谢抑制剂（叠氮化物、2,4-二硝基苯酚、双香豆素）阻断。肥大细胞瘤细胞脱颗粒获得的上清液引起的分泌反应与糜蛋白酶引起的反应幅度相当。这些发现表明，糜蛋白酶而非类胰蛋白酶是气道腺体浆液细胞的有效促分泌剂，提示含糜蛋白酶的肥大细胞在气道分泌亢进发病机制中可能发挥作用。
