Xie Shaoping, Sukkar Maria B, Issa Razao, Khorasani Nadia M, Chung Kian Fan
Airway Disease Section, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Am J Physiol Lung Cell Mol Physiol. 2007 Jul;293(1):L245-53. doi: 10.1152/ajplung.00068.2007. Epub 2007 Apr 27.
Airway smooth muscle (ASM) hyperplasia is a characteristic feature of the asthmatic airway, but the underlying mechanisms that induce ASM hyperplasia remain unknown. Because transforming growth factor (TGF)-beta is a potent regulator of ASM cell proliferation, we determined its expression and mitogenic signaling pathways in ASM cells. We obtained ASM cells by laser capture microdissection of bronchial biopsies and found that ASM cells from asthmatic patients expressed TGF-beta1 mRNA and protein to a greater extent than nonasthmatic individuals using real-time RT-PCR and immunohistochemistry, respectively. TGF-beta1 stimulated the growth of nonconfluent and confluent ASM cells either in the presence or absence of serum in a time- and concentration-dependent manner. The mitogenic activity of TGF-beta1 on ASM cells was inhibited by selective inhibitors of TGF-beta receptor I kinase (SD-208), phosphatidylinositol 3-kinase (PI3K, LY-294002), ERK (PD-98059), JNK (SP-600125), and NF-kappaB (AS-602868). On the other hand, p38 MAPK inhibitor (SB-203580) augmented TGF-beta1-induced proliferation. To study role of the Smads, we transduced ASM cells with an adenovirus vector-expressing Smad4, Smad7, or dominant-negative Smad3 and found no involvement of these Smads in TGF-beta1-induced proliferation. Dexamethasone caused a dose-dependent inhibition in TGF-beta1-induced proliferation. Our findings suggest that TGF-beta1 may act in an autocrine fashion to induce ASM hyperplasia, mediated by its receptor and several kinases including PI3K, ERK, and JNK, whereas p38 MAPK is a negative regulator. NF-kappaB is also involved in the TGF-beta1 mitogenic signaling, but Smad pathway does not appear important.
气道平滑肌（ASM）增生是哮喘气道的一个特征性表现，但诱导ASM增生的潜在机制仍不清楚。由于转化生长因子（TGF）-β是ASM细胞增殖的有效调节因子，我们测定了其在ASM细胞中的表达及促有丝分裂信号通路。我们通过激光捕获显微切割支气管活检组织获得ASM细胞，分别使用实时逆转录聚合酶链反应（RT-PCR）和免疫组织化学方法发现，哮喘患者的ASM细胞比非哮喘个体表达更多的TGF-β1信使核糖核酸（mRNA）和蛋白。TGF-β1在有或无血清的情况下，均以时间和浓度依赖性方式刺激未融合和融合的ASM细胞生长。TGF-β1受体I激酶（SD-208）、磷脂酰肌醇3激酶（PI3K，LY-294002）、细胞外信号调节激酶（ERK，PD-98059）、c-Jun氨基末端激酶（JNK，SP-600125）和核因子κB（NF-κB，AS-602868）的选择性抑制剂可抑制TGF-β1对ASM细胞的促有丝分裂活性。另一方面，p38丝裂原活化蛋白激酶（MAPK）抑制剂（SB-203580）增强了TGF-β1诱导的增殖。为了研究Smads的作用，我们用表达Smad4、Smad7或显性负性Smad3的腺病毒载体转导ASM细胞，发现这些Smads不参与TGF-β1诱导的增殖。地塞米松对TGF-β1诱导的增殖有剂量依赖性抑制作用。我们的研究结果表明，TGF-β1可能以自分泌方式通过其受体和包括PI3K、ERK和JNK在内的几种激酶介导诱导ASM增生，而p38 MAPK是负调节因子。NF-κB也参与TGF-β1促有丝分裂信号传导，但Smad途径似乎并不重要。
