College of Pharmacy and Research, Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 08826, Korea.
Department of Biochemistry, School of Medicine, Keimyung University, Daegu, 42601, Korea.
Exp Mol Med. 2018 Apr 27;50(4):1-13. doi: 10.1038/s12276-018-0074-5.
Liver fibrosis can be reversed by removing its causative injuries; however, the molecular mechanisms mediating the resolution of liver fibrogenesis are poorly understood. We investigate the role of a scaffold protein, A-Kinase Anchoring Protein 12 (AKAP12), during liver fibrosis onset, and resolution. Biliary fibrogenesis and fibrosis resolution was induced in wild-type (WT) or AKAP12-deficient C57BL/6 mice through different feeding regimens with 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-containing chow. AKAP12 expression in portal fibroblasts (PFs) and liver sinusoidal endothelial cells (LSECs) gradually decreased as fibrosis progressed but was restored after cessation of the fibrotic challenge. Histological analysis of human liver specimens with varying degrees of fibrosis of different etiologies revealed that AKAP12 expression diminishes in hepatic fibrosis from its early stages onward. AKAP12 KO mice displayed reduced fibrosis resolution in a DDC-induced biliary fibrosis model, which was accompanied by impaired normalization of myofibroblasts and capillarized sinusoids. RNA sequencing of the liver transcriptome revealed that genes related to ECM accumulation and vascular remodeling were mostly elevated in AKAP12 KO samples. Gene ontology (GO) and bioinformatic pathway analyses identified that the differentially expressed genes were significantly enriched in GO categories and pathways, such as the adenosine 3',5'-cyclic monophosphate (cAMP) pathway. Knockdown of the AKAP12 gene in cultured primary PFs revealed that AKAP12 inhibited PF activation in association with the adenosine 3',5'-cyclic monophosphate (cAMP) pathway. Moreover, AKAP12 knockdown in LSECs led to enhanced angiogenesis, endothelin-1 expression and alterations in laminin composition. Collectively, this study demonstrates that AKAP12-mediated regulation of PFs and LSECs has a central role in resolving hepatic fibrosis.
肝纤维化可以通过消除其致病损伤来逆转；然而，介导肝纤维化消退的分子机制仍知之甚少。我们研究了支架蛋白 A 激酶锚定蛋白 12（AKAP12）在肝纤维化发生和消退过程中的作用。通过不同的喂养方案，用含有 0.1%3,5-二乙氧基羰基-1,4-二氢吡啶（DDC）的饲料喂养野生型（WT）或 AKAP12 缺陷型 C57BL/6 小鼠，诱导胆管纤维化和纤维化消退。随着纤维化的进展，PFs 和 LSECs 中的 AKAP12 表达逐渐降低，但在纤维化挑战停止后恢复。对不同病因肝纤维化程度不同的人类肝组织标本的组织学分析表明，AKAP12 表达在肝纤维化的早期就开始减少。在 DDC 诱导的胆管纤维化模型中，AKAP12 KO 小鼠的纤维化消退减少，伴随着肌成纤维细胞和毛细血管化窦状内皮细胞的正常化受损。对肝转录组的 RNA 测序显示，与 ECM 积累和血管重塑相关的基因在 AKAP12 KO 样本中大多上调。GO 和生物信息学途径分析表明，差异表达基因在 GO 类别和途径中显著富集，如环磷酸腺苷（cAMP）途径。在培养的原代 PF 中敲低 AKAP12 基因表明，AKAP12 抑制 PF 激活与环磷酸腺苷（cAMP）途径有关。此外，LSEC 中 AKAP12 的敲低导致血管生成、内皮素-1 表达和层粘连蛋白组成的改变。总之，这项研究表明，AKAP12 介导的 PF 和 LSEC 的调节在肝纤维化消退中起核心作用。
