Brown J K, Tyler C L, Jones C A, Ruoss S J, Hartmann T, Caughey G H
Pulmonary and Critical Care Medicine Section, VA Medical Center, San Francisco, CA 94121, USA.
Am J Respir Cell Mol Biol. 1995 Aug;13(2):227-36. doi: 10.1165/ajrcmb.13.2.7626290.
Hyperplasia of airway smooth muscle cells is present in the airways of asthmatic patients and may contribute to the development of the bronchial hyperresponsiveness that occurs in these patients. Because tryptase is an abundant component of mast cell granules and has demonstrated growth-stimulatory effects in other mesenchymal cells (J. Clin. Invest. 1991; 88:493-499), the goal of our study was to determine whether tryptase is a mitogen for airway smooth muscle cells. The mitogenic effects of tryptase were tested in passages 1 through 5 of dog tracheal smooth muscle cells, either by counting smooth muscle cells or by monitoring uptake of bromodeoxyuridine (BrdU) into cellular DNA during S-phase. With respect to its efficacy, at a near maximal concentration (4 nM), tryptase increased cell numbers 2.1 +/- 0.2- or 2.8 +/- 0.6-fold above controls after 2 or 4 days, respectively, and these increases were approximately the same as those induced by platelet-derived growth factor (50 ng/ml) or 10% calf serum. With respect to potency, tryptase caused concentration-dependent increases in BrdU uptake, as detected in an enzyme-linked immunosorbent assay or by counting BrdU-labeled nuclei, with an EC50 of 2 nM. Pretreatment of tryptase with diisopropylfluorophosphate, to reduce markedly its catalytic as a activity as a proteinase, attenuated its growth-stimulated effects by 58 +/- 16%. Tryptase-induced mitogenesis was not a nonspecific effect of all serine proteinases, because thrombin, another proteinase with mitogenicity for fibroblasts, stimulated neither increases in cell counts nor BrdU uptake in our cells. We conclude that tryptase is a potent mitogen for airway smooth muscle cells in culture.
气道平滑肌细胞增生存在于哮喘患者的气道中，可能促成这些患者出现的支气管高反应性。因为类胰蛋白酶是肥大细胞颗粒的丰富成分，并且已在其他间充质细胞中显示出生长刺激作用（《临床研究杂志》1991年；88:493 - 499），我们研究的目的是确定类胰蛋白酶是否是气道平滑肌细胞的有丝分裂原。通过对犬气管平滑肌细胞第1至5代进行计数或监测S期细胞DNA中溴脱氧尿苷（BrdU）的摄取，来测试类胰蛋白酶的促有丝分裂作用。就其效力而言，在接近最大浓度（4 nM）时，类胰蛋白酶在2天或4天后分别使细胞数量比对照增加2.1±0.2倍或2.8±0.6倍，这些增加与血小板衍生生长因子（50 ng/ml）或10%小牛血清诱导的增加大致相同。就其效价而言，如在酶联免疫吸附测定中检测到的或通过计数BrdU标记的细胞核，类胰蛋白酶使BrdU摄取呈浓度依赖性增加，半数有效浓度（EC50）为2 nM。用二异丙基氟磷酸预处理类胰蛋白酶，以显著降低其作为蛋白酶的催化活性，其生长刺激作用减弱了58±16%。类胰蛋白酶诱导的有丝分裂不是所有丝氨酸蛋白酶的非特异性作用，因为凝血酶是另一种对成纤维细胞有促有丝分裂作用的蛋白酶，在我们的细胞中既不刺激细胞计数增加也不刺激BrdU摄取。我们得出结论，类胰蛋白酶是培养的气道平滑肌细胞的一种强效有丝分裂原。
