Bromodomain and extraterminal (BET) proteins regulate biliary-driven liver regeneration

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• 作者：Sungjin Ko¹ ; ^&dagger ; ; Tae-Young Choi¹ ; ^&dagger ; ; Jacquelyn O. Russell² ; Juhoon So¹ ; Satdarshan P.S. Monga² ; Donghun Shin¹ ; ^{donghuns@pitt.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：BEC ; biliary epithelial cell ; CDE ; choline-deficient ; ethionine-supplemented ; BET ; bromodomain and extraterminal domain ; HB-LCs ; hepatoblast-like cells ; LPC ; liver progenitor cell ; Mtz ; metronidazole ; DMSO ; dimethyl sulfoxide ; NTR ; nitroreductase ; CFP ; cyan fluorescent protein ; dpf ; days post-fertilization ; FXR ; farnesoid X receptor ; qPCR ; quantitative polymerase chain reaction ; EdU ; 5-ethynyl-2&rsquo ; -deoxyuridine ; WISH ; whole-mount in situ hybridization ; ALT ; alanine aminotransferase
• 刊名：Journal of Hepatology
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：64
• 期：2
• 页码：316-325
• 全文大小：2868 K

文摘

During liver regeneration, hepatocytes are derived from pre-existing hepatocytes. However, if hepatocyte proliferation is compromised, biliary epithelial cells (BECs) become the source of new hepatocytes. We recently reported on a zebrafish liver regeneration model in which BECs extensively contribute to hepatocytes. Using this model, we performed a targeted chemical screen to identify important factors that regulate BEC-driven liver regeneration, the mechanisms of which remain largely unknown.

Methods

Using Tg(fabp10a:CFP-NTR) zebrafish, we examined the effects of 44 selected compounds on BEC-driven liver regeneration. Liver size was assessed by fabp10a:DsRed expression; liver marker expression was analyzed by immunostaining, in situ hybridization and quantitative PCR. Proliferation and apoptosis were also examined. Moreover, we used a mouse liver injury model, choline-deficient, ethionine-supplemented (CDE) diet.

Results

We identified 10 compounds that affected regenerating liver size. Among them, only bromodomain and extraterminal domain (BET) inhibitors, JQ1 and iBET151, blocked both Prox1 and Hnf4a induction in BECs. BET inhibition during hepatocyte ablation blocked BEC dedifferentiation into hepatoblast-like cells (HB-LCs). Intriguingly, after JQ1 washout, liver regeneration resumed, indicating temporal, but not permanent, perturbation of liver regeneration by BET inhibition. BET inhibition after hepatocyte ablation suppressed the proliferation of newly generated hepatocytes and delayed hepatocyte maturation. Importantly, Myca overexpression, in part, rescued the proliferation defect. Furthermore, oval cell numbers in mice fed CDE diet were greatly reduced upon JQ1 administration, supporting the zebrafish findings.

Conclusions

BET proteins regulate BEC-driven liver regeneration at multiple steps: BEC dedifferentiation, HB-LC proliferation, the proliferation of newly generated hepatocytes, and hepatocyte maturation.