Regulation of the effects of TGF-β1 by activation of latent TGF-β1 and differential expression of TGF-β receptors (TβR-I and TβR-II) in idiopathic pulmonary fibrosis
Regulation of the effects of TGF-β1 by activation of latent TGF-β1 and differential expression of TGF-β receptors (TβR-I and TβR-II) in idiopathic pulmonary fibrosis
复制标题
DOI：
10.1136/thorax.56.12.907
复制
发表时间：
2001-12-01
期刊：
影响因子：
10
通讯作者：
Gold, LI
中科院分区：
文献类型：
--
作者：
Khalil, N;Parekh, TV;Gold, LI
背景-特发性肺纤维化（IPF）的特征是胸膜下纤维化，其进展涉及肺的所有区域。转化生长因子β 1的表达。在IPF患者的肺切片中，结缔组织合成的强效调节因子TGF-β 1增加。TGF-β 1通常以生物学潜伏形式（L-TGF-β 1）释放。在具有生物活性之前，TGF-β必须转化为其活性形式，并与I型和II型TGF-β受体（T β R-I和T β R-II）相互作用。TGF-β潜伏期结合蛋白1（LTBP-1），促进L-TGF-β 1的释放和激活，在TGF-β 1的生物学中也很重要。方法：对IPF患者和正常对照的开放性肺活检样本进行检查，以定位T β R-I、T β R-II和LTBP-1。肺泡巨噬细胞（AM）和支气管肺泡灌洗（BAL）液进行了检查，使用CCL-64生物测定，以确定是否TGF-β是目前在其活性形式在肺的IPF患者。结果免疫反应性L-TGF-β 1存在于所有肺细胞的IPF患者除了成纤维细胞在蜂窝状囊肿的上皮下区域。LTBP-1主要在晚期IPF区域的AM和内衬蜂窝囊肿的上皮细胞中检测到。在正常肺组织中，少数AM可见LTBP-1免疫反应。来自IPF患者肺上叶和肺下叶的AM分别分泌1.6（0.6）fmol和4.1（1.9）fmol活性TGF-β，而来自对照患者肺下叶的AM不分泌活性TGF-β（来自IPF患者肺下叶的AM与正常对照相比，条件培养基中TGF-β的p值小于或等于0.01）。IPF患者肺下叶和对照组肺下叶AM分泌的活性TGF-β百分比差异显著（p <0.01），但肺下叶分泌的总TGF-β之间差异不显著。IPF患者上叶和下叶AM条件培养基中活性TGF-β的差异也无统计学意义。IPF患者上叶和下叶的BAL液中分别含有0.7（0.2）fmol和2.9（1.2）fmol活性TGF-β（p ≤ 0.03）。上叶和下叶中活性TGF-β的百分比分别为17.6（1.0）%和78.4（1.6）%（p ≤ 0.03）。相比之下，来自对照患者的BAL液含有少量的L-TGF-β。使用免疫染色，T β R-I和T β R-II均存在于正常肺的所有细胞上，但除了IPF患者肺中的间质肌成纤维细胞外，蜂窝囊肿区域的大多数细胞中的T β R-I显著降低。TGF-β 1抑制上皮细胞增殖，蜂窝囊肿衬里上皮细胞缺乏T β R-I表达将促进上皮细胞增殖对肺泡的修复。然而，成纤维细胞上两种T β R的存在可能导致对TGF-β 1的反应，用于合成结缔组织蛋白。我们的研究结果表明，具有生物活性的TGF-β 1仅存在于IPF患者的肺部。此外，TGF-β 1对细胞的影响可能进一步调节T β Rs的表达。结论激活L-TGF-β 1和T β Rs的差异表达可能是重要的IPF的重塑和纤维化的发病机制。
Background-Idiopathic pulmonary fibrosis (IPF) is characterised by subpleural fibrosis that progresses to involve all areas of the lung. The expression of transforming growth factor-beta1. (TGF-beta1), a potent regulator of connective tissue synthesis, is increased in lung sections of patients with IPF. TGF-beta1 is generally released in a biologically latent form (L-TGF-beta1). Before being biologically active, TGF-P must be converted to its active form and interact with both TGF-beta receptors type I and II (T betaR-I and T betaR-II). TGF-beta latency binding protein 1 (LTBP-1), which facilitates the release and activation of L-TGF-beta1, is also important in the biology of TGF-beta1.Methods-Open lung biopsy samples from patients with IPF and normal controls were examined to localise T betaR-I, T betaR-II, and LTBP-1. Alveolar macrophages (AM) and bronchoalveolar lavage (BAL) fluid were examined using the CCL-64 bioassay to determine if TGF-beta is present in its active form in the lungs of patients with IPF.Results-Immunoreactive L-TGF-beta1 was present in all lung cells of patients with IPF except for fibroblasts in the subepithelial regions of honeycomb cysts. LTBP-1 was detected primarily in AM and epithelial cells lining honeycomb cysts in areas of advanced IPF. In normal lungs LTBP-1 immunoreactivity was observed in a few AM. AM from the upper and lower lobes of patients with IPF secreted 1.6 (0.6) fmol and 4.1 (1.9) fmol active TGF-beta, respectively, while AM from the lower lobes of control patients secreted no active TGF-beta (p less than or equal to0.01 for TGF-beta in the conditioned media from AM obtained from the lower lobes of IPF patients v normal controls). The difference in percentage active TGF-beta secreted by AM from the lower lobes of patients with IPF and the lower lobes of control patients was significant (p less than or equal to0.01), but the difference between the total TGF-beta secreted from these lobes was not significant. The difference in active TGF-beta in conditioned media of AM from the upper and lower lobes of patients with IPF was also not statistically significant. BAL fluid from the upper and lower lobes of patients with IPF contained 0.7 (0.2) fmol and 2.9 (1.2) fmol active TGF-beta, respectively (p less than or equal to0.03). The percentage of active TGF-beta in the upper and lower lobes was 17.6 (1.0)% and 78.4 (1.6)%, respectively (p less than or equal to0.03). In contrast, BAL fluid from control patients contained small amounts of L-TGF-beta. Using immunostaining, both T betaR-I and T betaR-II were present on all cells of normal lungs but T betaR-I was markedly reduced in most cells in areas of honeycomb cysts except for interstitial myofibroblasts in lungs of patients with IPF. TGF-beta1 inhibits epithelial cell proliferation and a lack of T betaR-I expression by epithelial cells lining honeycomb cysts would facilitate repair of the alveoli by epithelial cell proliferation. However, the presence of both T beta Rs on fibroblasts is likely to result in a response to TGF-beta1 for synthesis of connective tissue proteins. Our findings show that biologically active TGF-beta1 is only present in the lungs of patients with IPF. In addition, the effects of TGF-beta1 on cells may be further regulated by the expression of T beta Rs.Conclusion-Activation of L-TGF-beta1 and the differential expression of T beta Rs may be important in the pathogenesis of remodelling and fibrosis in IPF.