Transcriptome network analysis identifies protective role of the LXR/SREBP-1c axis in murine pulmonary fibrosis
Shigeyuki Shichino, Satoshi Ueha, Shinichi Hashimoto, Mikiya Otsuji, Jun Abe, Tatsuya Tsukui, Shungo Deshimaru, Takuya Nakajima, Mizuha Kosugi-Kanaya, Francis H.W. Shand, Yutaka Inagaki, Hitoshi Shimano, Kouji Matsushima
Shigeyuki Shichino, Satoshi Ueha, Shinichi Hashimoto, Mikiya Otsuji, Jun Abe, Tatsuya Tsukui, Shungo Deshimaru, Takuya Nakajima, Mizuha Kosugi-Kanaya, Francis H.W. Shand, Yutaka Inagaki, Hitoshi Shimano, Kouji Matsushima
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Research Article Inflammation Pulmonology

Transcriptome network analysis identifies protective role of the LXR/SREBP-1c axis in murine pulmonary fibrosis

Abstract

Pulmonary fibrosis (PF) is an intractable disorder with a poor prognosis. Although lung fibroblasts play a central role in PF, the key regulatory molecules involved in this process remain unknown. To address this issue, we performed a time-course transcriptome analysis on lung fibroblasts of bleomycin- and silica-treated murine lungs. We found gene modules whose expression kinetics were associated with the progression of PF and human idiopathic PF (IPF). Upstream analysis of a transcriptome network helped in identifying 55 hub transcription factors that were highly connected with PF-associated gene modules. Of these hubs, the expression of Srebf1 decreased in line with progression of PF and human IPF, suggesting its suppressive role in fibroblast activation. Consistently, adoptive transfer and genetic modification studies revealed that the hub transcription factor SREBP-1c suppressed PF-associated gene expression changes in lung fibroblasts and PF pathology in vivo. Moreover, therapeutic pharmacological activation of LXR, an SREBP-1c activator, suppressed the Srebf1-dependent activation of fibroblasts and progression of PF. Thus, SREBP-1c acts as a protective hub of lung fibroblast activation in PF. Collectively, the findings of the current study may prove to be valuable in the development of effective therapeutic strategies for PF.

Authors

Shigeyuki Shichino, Satoshi Ueha, Shinichi Hashimoto, Mikiya Otsuji, Jun Abe, Tatsuya Tsukui, Shungo Deshimaru, Takuya Nakajima, Mizuha Kosugi-Kanaya, Francis H.W. Shand, Yutaka Inagaki, Hitoshi Shimano, Kouji Matsushima

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Figure 6

Pharmacological activation of LXR suppresses fibroblast activation and collagen deposition in murine pulmonary fibrosis.

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Pharmacological activation of LXR suppresses fibroblast activation and c...
(A) Experimental scheme of the treatment of bleomycin- and silica-induced pulmonary fibrosis by the LXR agonist T0901317. (B) qPCR analysis of Srebf1 expression in lung fibroblasts. (C) Changes in the number of lung fibroblasts and myofibroblasts in bleomycin- or silica-treated right lungs following T0901317 administration. (D) qPCR analysis of expression changes of trSrebf1c-targeted genes (detected by intratracheal transfer model of bleomycin-treated lungs; see Figure 5D) in the fibroblasts of bleomycin-treated lungs. (E) qPCR analysis of Nr1h3 expression in activated lung fibroblasts. (F) Changes in hydroxyproline content in the whole left lung of bleomycin- or silica-treated Col-GFP mice following T0901317 administration. (G) Changes in hydroxyproline content in the whole right lung of bleomycin-treated Srebf1–/–Col-GFP mice following T0901317 administration. (B and D) Graphs show the mean ± SEM (n = 6, DMSO; n = 5, T0901317). (C) Graphs show the mean ± SEM (n = 4, BLM day14 DMSO fibroblast number; n = 5, BLM day14 T0901317 and SiO2 day21 fibroblast number; n = 6, BLM day14 and SiO2 day21 DMSO, % of α-SMA; n = 5, SiO2 day21 T0901317, % of α-SMA). (E) Graphs show the mean ± SEM of n = 5 (UT, day 0; BLM, days 7, 63; SiO2, day 63), n = 6 (SiO2, day 7), n = 7 (BLM, day 14; SiO2, day 14). (F) Graphs show the mean ± SEM (n = 6, BLM, day14; n = 5, SiO2, day21). (G) Graphs show the mean ± SEM (n = 6, DMSO; n = 5, T0901317). Representative results of 3 (B–D and F) or 2 (E and G) independent experiments is shown. (B–D, F, and G) Statistical significance is indicated as follows: *P < 0.05; **P < 0.01, ***P < 0.001 (2-tailed unpaired Student’s t-test). Effect size (d) is shown on the bottom of the graph. (E) Statistical significance is indicated as follows: *P < 0.05, **P < 0.01 (untreated vs. bleomycin group), and †††P < 0.001(untreated vs. silica group) from 2-way ANOVA followed by the post hoc Tukey-Kramer’s multiple comparison test. Effect size (d) (compared with untreated group) is indicated at the bottom of the graph. Col-GFP, Col1a2-GFP reporter; BLM, bleomycin model, SiO2, silica model; SSC, side scatter.