Keratin 23通过PPARα/c-Myc轴的调控促进肝纤维化进展的机制研究

Keratin23(Krt23), as a type I acidic cytokeratin, which expresses on cholangiocytes and hepatocytes in liver. It will be up-regulated as well as ductular reaction and hepatocyte proliferation during chronic hepatitis and liver fibrosis. Especially interesting, Krt23 may be a potential non-invasive diagnostic marker of cirrhosis since it can be detected in the serum of patients with cirrhosis. But the role and modulation of Krt23 in the mechanism of liver fibrogenesis is unknown so far. Our previous work showed the expression level of Krt23 in liver is correlated with the degree of liver fibrosis in the patients with chronic hepatitis B and cirrhosis due to HBV infection. Further basic research results indicated c-Myc is the upstream of Krt23，Wy14643 treatment up regulates the expression of Krt23. Based on our previous work we have a hypothesis that PPARalpha/c-Myc signaling modulates Krt23 to promote liver fibrogenesis. Next, we will confirm Krt23 level in serum and liver tissue have a good correlation with the degree of fibrosis using the larger samples and then we will use Krt23-/-, Myc-/-, PPARA-/- hepatocyte-specific knockout mice and primary hepatocyte to study the role and mechanism of Krt23 regulated by PPARalpha/c-Myc signaling in vivo and in vitro. By this research, we will clarify Krt23 can be a useful promising non-invasive diagnostic marker/warning biomarker of early stage of cirrhosis and PPARalpha/c-Myc signaling via modulating Keratin 23 promotes liver fibrogenesis.

角蛋白23（Krt23/K23）为近年新发现的一种酸性角蛋白，在慢性肝炎伴发胆管反应和肝细胞再生时K23表达显著上调。令人感兴趣的是肝硬化患者血清中可检测到K23。作为一种潜在肝硬化无创诊断标志物，目前Krt23与肝纤维化程度相关性以及调控机制尚不清楚。我们的前期工作发现肝内K23表达水平与肝硬化患者不同纤维化病理分期相关；基础实验提示Myc是K23上游基因；PPARα激动剂可上调K23。据此我们推测K23可促进肝纤维化进展，PPARα/Myc轴可调控K23的表达进而参与了肝纤维化。本课题拟首先扩大样本进一步验证血清及肝内K23表达水平与肝硬化患者纤维化程度相关；利用PPARα和Myc细胞特异敲除小鼠，胆管结扎以及DDC喂养建立肝纤维化模型，经体内外实验阐明K23可促进肝纤维化，PPARα/Myc轴调控K23表达的分子机制。本课题的实施将为Krt23作为临床肝纤维化无创诊断标志奠定理论基础

肝纤维化是各种肝损伤性疾病向不可逆性肝硬化发展的关键阶段，但其发生发展机制并不明确，导致临床上对肝硬化的干预手段有限。本项目立足于药物性肝损伤、酒精性肝损伤及自身免疫性肝损伤临床队列，旨在寻找反映肝纤维化进展的关键分子标志物及促进肝硬化进展的关键节点。研究结果显示，在药物性肝损伤患者肝组织中，代谢性核受体PPARa（过氧化物酶体增殖物激活受体a）表达明显下调，且与肝脏损伤程度呈负相关。机制研究中，我们发现敲除肝细胞PPAR并不影响引起肝损伤的常见药物对乙酰氨基酚APAP在肝脏的代谢活化和解毒，也并不能改善APAP诱导的肝组织GSH的耗竭；但却明显降低APAP诱导的氧化应激的产生；进一步实验显示，敲除肝细胞PPARa可上调IL-6/STAT3从而促进肝细胞增殖{Wang Y et al. Int J Biol Sci. 2022 Mar 6;18(6):2317-2328.}。另外，在髓系敲除PPARα小鼠中建立部分肝切除动物模型，结果显示，部分肝切除32小时后，髓系PPARα敲除小鼠肝细胞增殖及有丝分裂均显著上调，中性粒细胞及巨噬细胞局部浸润增加，巨噬细胞M1极化，通过下游IL-6及TNFα表达水平上调， 进一步激活STAT3信号通路促进肝再生{Wang Y et al. Hepatobiliary Surg Nutr. 2022 Apr;11(2):199-211.}。上述结果提示，PPARα在不同细胞类型中发挥着迥异的作用；PPARα通过调控IL-6/STAT3在不同肝脏疾病模型、不同疾病阶段发挥着诱导肝损伤或促进肝再生的重要作用。