1 Department of Physiology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana; and.
Am J Respir Cell Mol Biol. 2014 Jan;50(1):106-14. doi: 10.1165/rcmb.2013-0204OC.
Heparan sulfate proteoglycans (HSPGs) are integral components of the lung. Changes in HSPGs have been documented in idiopathic pulmonary fibrosis (IPF). Many of the biological functions of HSPGs are mediated by heparan sulfate (HS) side chains, and little is understood about these side chains in the pathogenesis of IPF. The aims of this study were to compare HS structure between normal and IPF lungs and to examine how changes in HS regulate the fibrotic process. HS disaccharide analysis revealed that HS 6-O-sulfation was significantly increased in IPF lungs compared with normal lungs, concomitant with overexpression of HS 6-O-sulfotransferases 1 and 2 (HS6ST1/2) mRNA. Immunohistochemistry revealed that HS6ST2 was specifically expressed in bronchial epithelial cells, including those lining the honeycomb cysts in IPF lungs, whereas HS6ST1 had a broad expression pattern. Lung fibroblasts in the fibroblastic foci of IPF lungs expressed HS6ST1, and overexpression of HS6ST1 mRNA was observed in primary lung fibroblasts isolated from IPF lungs compared with those from normal lungs. In vitro, small interference RNA-mediated silencing of HS6ST1 in primary normal lung fibroblasts resulted in reduced Smad2 expression and activation and in reduced expression of collagen I and α-smooth muscle actin after TGF-β1 stimulation. Similar results were obtained in primary IPF lung fibroblasts. Furthermore, silencing of HS6ST1 in normal and IPF lung fibroblasts resulted in significant down-regulation of TβRIII (betaglycan). In summary, HS 6-O-sulfation is up-regulated in IPF with overexpression of HS6ST1 and HS6ST2, and overexpression of HS6ST1 in lung fibroblasts may regulate their fibrotic responses to TGF-β1.
硫酸乙酰肝素蛋白聚糖 (HSPGs) 是肺的重要组成部分。在特发性肺纤维化 (IPF) 中已记录到 HSPGs 的变化。HSPGs 的许多生物学功能是由硫酸乙酰肝素 (HS) 侧链介导的，而对于 IPF 发病机制中的这些侧链知之甚少。本研究的目的是比较正常肺和 IPF 肺中的 HS 结构，并研究 HS 变化如何调节纤维化过程。HS 二糖分析显示，与正常肺相比，IPF 肺中的 HS 6-O-硫酸化显著增加，同时 HS6ST1/2 mRNA 的表达也增加。免疫组织化学显示 HS6ST2 特异性表达于支气管上皮细胞，包括 IPF 肺中蜂窝状囊肿的衬里细胞，而 HS6ST1 则具有广泛的表达模式。IPF 肺的纤维母细胞灶中的肺成纤维细胞表达 HS6ST1，并且从 IPF 肺中分离的原代肺成纤维细胞中观察到 HS6ST1 mRNA 的过表达，而从正常肺中分离的原代肺成纤维细胞中则没有。在体外，通过小干扰 RNA 介导的 HS6ST1 在原代正常肺成纤维细胞中的沉默导致 Smad2 表达和激活减少，以及 TGF-β1 刺激后胶原 I 和 α-平滑肌肌动蛋白的表达减少。在原代 IPF 肺成纤维细胞中也获得了类似的结果。此外，正常和 IPF 肺成纤维细胞中 HS6ST1 的沉默导致 TβRIII (β 型转化生长因子受体 III，betaglycan) 的显著下调。总之，HS 6-O-硫酸化在 IPF 中上调，伴有 HS6ST1 和 HS6ST2 的过表达，肺成纤维细胞中 HS6ST1 的过表达可能调节它们对 TGF-β1 的纤维化反应。
