Rehan Virender K, Sakurai Reiko, Wang Ying, Santos Jamie, Huynh Kyle, Torday John S
Department of Pediatrics, Harbor-UCLA Medical Center, Los Angeles Biomedical Research Institute at Harbor-UCLA, David Geffen School of Medicine at UCLA, 1124 West Carson St., RB1, California, Torrance 90502, USA.
Lung. 2007 May-Jun;185(3):151-9. doi: 10.1007/s00408-007-9007-0.
Nicotine exposure disrupts the parathyroid hormone-related protein (PTHrP)-driven alveolar epithelial-mesenchymal paracrine-signaling pathway, resulting in the transdifferentiation of pulmonary lipofibroblasts (LIFs) to myofibroblasts (MYFs), which seems to be central to altered pulmonary development and function in infants born to mothers who smoke during pregnancy. Modulation of PTHrP-driven signaling can almost completely prevent nicotine-induced LIF-to-MYF transdifferentiation. However, once this process has occurred, whether it can be reversed is not known. Our objective was to determine if nicotine-induced LIF-to-MYF transdifferentiation could be reversed by specifically targeting the PTHrP-mediated alveolar epithelial-mesenchymal paracrine signaling. WI38 cells, a human embryonic pulmonary fibroblast cell line, were initially treated with nicotine for 7 days and LIF-to-MYF transdifferentiation was confirmed by determining the downregulation of the key lipogenic marker, peroxisome proliferator-activated receptor gamma (PPARgamma) and upregulation of the key myogenic marker, alpha-smooth muscle actin (alphaSMA). Because downregulation of the PPARgamma signaling pathway is the key determinant of LIF-to-MYF transdifferentiation, cells were treated with three agonists of this pathway, PTHrP, dibutryl cAMP (DBcAMP), or rosiglitazone (RGZ) for 7 days, and the expression of the PTHrP receptor, PPARgamma, alphaSMA, and calponin was determined by Western analysis and immunohistochemistry. Simultaneously, fibroblast function was characterized by measuring their capacity to take up triglycerides. Nicotine-induced LIF-to-MYF transdifferentiation was almost completely reversed by treatment with RGZ, PTHrP, or DBcAMP, as determined by protein and functional assays. Using a specific molecular approach and targeting specific molecular intermediates in the PTHrP signaling pathway, to our knowledge, this for the first time, demonstrates the reversibility of nicotine-induced LIF-to-MYF transdifferentiation, suggesting not only the possibility of prevention but also the potential for reversal of nicotine-induced lung injury.
尼古丁暴露会破坏甲状旁腺激素相关蛋白（PTHrP）驱动的肺泡上皮-间充质旁分泌信号通路，导致肺脂肪成纤维细胞（LIFs）向肌成纤维细胞（MYFs）转分化，这似乎是孕期吸烟母亲所生婴儿肺部发育和功能改变的核心因素。对PTHrP驱动的信号进行调节几乎可以完全阻止尼古丁诱导的LIF向MYF转分化。然而，一旦这个过程发生，它是否可以逆转尚不清楚。我们的目标是确定通过特异性靶向PTHrP介导的肺泡上皮-间充质旁分泌信号，尼古丁诱导的LIF向MYF转分化是否可以逆转。WI38细胞是一种人胚胎肺成纤维细胞系，最初用尼古丁处理7天，通过测定关键脂肪生成标志物过氧化物酶体增殖物激活受体γ（PPARγ）的下调和关键肌生成标志物α-平滑肌肌动蛋白（αSMA）的上调来确认LIF向MYF的转分化。由于PPARγ信号通路的下调是LIF向MYF转分化的关键决定因素，用该通路的三种激动剂PTHrP、二丁酰环磷腺苷（DBcAMP）或罗格列酮（RGZ）处理细胞7天，并通过蛋白质印迹分析和免疫组织化学测定PTHrP受体、PPARγ、αSMA和钙调蛋白的表达。同时，通过测量成纤维细胞摄取甘油三酯的能力来表征其功能。蛋白质和功能测定表明，用RGZ、PTHrP或DBcAMP处理几乎完全逆转了尼古丁诱导的LIF向MYF转分化。据我们所知，使用特定的分子方法并靶向PTHrP信号通路中的特定分子中间体，首次证明了尼古丁诱导的LIF向MYF转分化的可逆性，这不仅提示了预防的可能性，也提示了逆转尼古丁诱导的肺损伤的潜力。
