Krymskaya V P, Penn R B, Orsini M J, Scott P H, Plevin R J, Walker T R, Eszterhas A J, Amrani Y, Chilvers E R, Panettieri R A
Pulmonary and Critical Care Division, Department of Medicine, University of Pennsylvania Medical Center, Philadelphia, PA 19104-4283, USA.
Am J Physiol. 1999 Jul;277(1):L65-78. doi: 10.1152/ajplung.1999.277.1.L65.
Hypertrophy and hyperplasia of airway smooth muscle (ASM) are important pathological features that contribute to airflow obstruction in chronic severe asthma. Despite considerable research effort, the cellular mechanisms that modulate ASM growth remain unknown. Recent evidence suggests that mitogen-induced activation of phosphoinositide (PI)-specific phospholipase C (PLC) and PI-dependent calcium mobilization are neither sufficient nor necessary to stimulate human ASM proliferation. In this study, we identify phosphatidylinositol (PtdIns) 3-kinase as a key regulator of human ASM proliferation. Pretreatment of human ASM with the PtdIns 3-kinase inhibitors wortmannin and LY-294002 significantly reduced thrombin- and epidermal growth factor (EGF)-induced DNA synthesis (IC(50) approximately 10 nM and approximately 3 microM, respectively). In separate experiments, wortmannin and LY-294002 markedly inhibited PtdIns 3-kinase and 70-kDa S6 protein kinase (pp70(S6k)) activation induced by stimulation of human ASM cells with EGF and thrombin but had no effect on EGF- and thrombin-induced p42/p44 mitogen-activated protein kinase (MAPK) activation. The specificity of wortmannin and LY-294002 was further suggested by the demonstrated inability of these compounds to alter thrombin-induced calcium transients, total PI hydrolysis, or basal cAMP levels. Transient expression of constitutively active PtdIns 3-kinase (p110*) activated pp70(S6k), whereas a dominant-negative PtdIns 3-kinase (Deltap85) blocked EGF- and thrombin-stimulated pp70(S6k) activity. Collectively, these data suggest that activation of PtdIns 3-kinase is required for the mitogenic effect of EGF and thrombin in human ASM cells. Further investigation of the role of PtdIns 3-kinase may offer new therapeutic approaches in the treatment of diseases characterized by smooth muscle cell hyperplasia such as asthma and chronic bronchitis.
气道平滑肌（ASM）肥大和增生是导致慢性重度哮喘气流阻塞的重要病理特征。尽管进行了大量研究，但调节ASM生长的细胞机制仍不清楚。最近的证据表明，有丝分裂原诱导的磷酸肌醇（PI）特异性磷脂酶C（PLC）激活和PI依赖性钙动员对于刺激人ASM增殖既不充分也不必要。在本研究中，我们确定磷脂酰肌醇（PtdIns）3激酶是人ASM增殖的关键调节因子。用PtdIns 3激酶抑制剂渥曼青霉素和LY-294002预处理人ASM可显著降低凝血酶和表皮生长因子（EGF）诱导的DNA合成（IC50分别约为10 nM和约3 μM）。在单独的实验中，渥曼青霉素和LY-294002显著抑制了EGF和凝血酶刺激人ASM细胞诱导的PtdIns 3激酶和70 kDa S6蛋白激酶（pp70S6k）激活，但对EGF和凝血酶诱导的p42/p44丝裂原活化蛋白激酶（MAPK）激活没有影响。渥曼青霉素和LY-294002的特异性进一步体现在这些化合物无法改变凝血酶诱导的钙瞬变、总PI水解或基础cAMP水平。组成型活性PtdIns 3激酶（p110*）的瞬时表达激活了pp70S6k，而显性负性PtdIns 3激酶（Deltap85）阻断了EGF和凝血酶刺激的pp70S6k活性。总体而言，这些数据表明PtdIns 3激酶的激活是人ASM细胞中EGF和凝血酶促有丝分裂作用所必需的。对PtdIns 3激酶作用的进一步研究可能为治疗以平滑肌细胞增生为特征的疾病（如哮喘和慢性支气管炎）提供新的治疗方法。
