Role of endothelial cells in pulmonary fibrosis via SREBP2 activation
Marcy Martin, Jiao Zhang, Yifei Miao, Ming He, Jian Kang, Hsi-Yuan Huang, Chih-Hung Chou, Tse-Shun Huang, Hsiao-Chin Hong, Shu-Han Su, Simon S. Wong, Rebecca L. Harper, Lingli Wang, Rakesh Bhattacharjee, Hsien-Da Huang, Zhen Bouman Chen, Atul Malhotra, Marlene Rabinovitch, James S. Hagood, John Y-J. Shyy
Marcy Martin, Jiao Zhang, Yifei Miao, Ming He, Jian Kang, Hsi-Yuan Huang, Chih-Hung Chou, Tse-Shun Huang, Hsiao-Chin Hong, Shu-Han Su, Simon S. Wong, Rebecca L. Harper, Lingli Wang, Rakesh Bhattacharjee, Hsien-Da Huang, Zhen Bouman Chen, Atul Malhotra, Marlene Rabinovitch, James S. Hagood, John Y-J. Shyy
View: Text | PDF
Research Article Pulmonology Vascular biology

Role of endothelial cells in pulmonary fibrosis via SREBP2 activation

Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with limited treatment options. Despite endothelial cells (ECs) comprising 30% of the lung cellular composition, the role of EC dysfunction in pulmonary fibrosis (PF) remains unclear. We hypothesize that sterol regulatory element-binding protein 2 (SREBP2) plays a critical role in the pathogenesis of PF via EC phenotypic modifications. Transcriptome data demonstrate that SREBP2 overexpression in ECs led to the induction of the TGF, Wnt, and cytoskeleton remodeling gene ontology pathways and the increased expression of mesenchymal genes, such as snail family transcriptional repressor 1 (snai1), α-smooth muscle actin, vimentin, and neural cadherin. Furthermore, SREBP2 directly bound to the promoter regions and transactivated these mesenchymal genes. This transcriptomic change was associated with an epigenetic and phenotypic switch in ECs, leading to increased proliferation, stress fiber formation, and ECM deposition. Mice with endothelial-specific transgenic overexpression of SREBP2 (EC-SREBP2[N]-Tg mice) that were administered bleomycin to induce PF demonstrated exacerbated vascular remodeling and increased mesenchymal transition in the lung. SREBP2 was also found to be markedly increased in lung specimens from patients with IPF. These results suggest that SREBP2, induced by lung injury, can exacerbate PF in rodent models and in human patients with IPF.

Authors

Marcy Martin, Jiao Zhang, Yifei Miao, Ming He, Jian Kang, Hsi-Yuan Huang, Chih-Hung Chou, Tse-Shun Huang, Hsiao-Chin Hong, Shu-Han Su, Simon S. Wong, Rebecca L. Harper, Lingli Wang, Rakesh Bhattacharjee, Hsien-Da Huang, Zhen Bouman Chen, Atul Malhotra, Marlene Rabinovitch, James S. Hagood, John Y-J. Shyy

×

Figure 6

BLM-induced SREBP2 promotes EC phenotypic switch and partial EndoMT in mice.

Options: View larger image (or click on image) Download as PowerPoint
BLM-induced SREBP2 promotes EC phenotypic switch and partial EndoMT in m...
(A) Lung microvascular ECs were isolated from age-matched EC-SREBP2(N)-Tg mice and compared with their WT littermates (pooled from n = 5 per group). The level of indicated mRNA was measured using qPCR. (B–E) Age-matched EC-SREBP2(N)-Tg and WT littermates, or EC-specific tdTomato-expressing mice driven with tamoxifen inducible VE-Cad–Cre (EC-tdTomato mice) were administered BLM (8 units/injection) on days 0, 4, 7, 10, and 14 through i.p. injection. Twenty-eight days after BLM administration, lungs were harvested. (B) Frozen lung sections were immunostained for the EC marker VE-Cad (green) and the mesenchymal marker αSMA (red). Nuclei were counter stained with DAPI (blue). Scale bar: 20 μm. Quantitative analysis showing the number of αSMA+ cells compared with total VE-Cad+ cells in the intima is graphed below the representative images. (C–E) Lineage-tracing experiments were performed with EC-specific expression of tdTomato (red), counterstained with αSMA (green) (C), vimentin (green) (D), or SREBP2 (green) (E). Nuclei are labeled with DAPI (blue). Scale bar: 20 μm. Quantitative analysis showing αSMA+, Vim+, or SREBP2+ cells are compared with total tdTomato+ cells in the intima, which is graphed on the right of the representative images. Data in B were analyzed by 2-way ANOVA with Kruskal-Wallis post hoc; data are represented as mean ± SEM from n = 6 mice per group. Data in C–E were analyzed by 2-tailed Student’s t test; data are represented as mean ± SEM from n = 6 mice per group. *P < 0.05 between the indicated groups. Col1A1, collagen 1 type 1; FN1, fibronectin 1; KDR, kinase insert domain receptor; KLF2, Krüppel-like factor 2; N-Cad, neural cadherin; Snai1, snail family transcriptional repressor 1; VE-Cad, vascular endothelial cadherin; Vim, vimentin; Wnt, wingless integration site).