Department of Gastroenterology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan.
Department of Gastroenterology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan.
Life Sci. 2019 Mar 15;221:293-300. doi: 10.1016/j.lfs.2019.02.040. Epub 2019 Feb 20.
Cathepsin L (Ctsl) plays a pivotal role in lysosomal and autophagic proteolysis. Previous investigations revealed that partial hepatectomy (PH) decreases biosynthesis of cathepsins in liver, followed by suppression of lysosomal and autophagic proteolysis during liver regeneration. Conversely, it was reported that autophagy-deficiency suppressed liver regeneration. Thus, the purpose of this study is to determine if Ctsl deficiency affects liver regeneration after PH.
70% of PH was performed in male Ctsl-deficient mice (Ctsl-/-) and wild-type littermates (Ctsl +/+) after PH. Mice were sacrificed and wet weight of the whole remaining liver was measured. Bromodeoxyuridine (BrdU)-immunostaining of liver sections was performed. Expression of cyclin D1, p62, LC-3, Nrf2, cleaved-Notch1, Hes1 was evaluated by western blot analysis. NQO1 mRNA expression was measured by realtime-PCR.
After a 70% of PH, the liver mass was significantly restored within 5 days in Ctsl-/- mice compared to wild-type. Ctsl-deficiency enhanced the increases in both the rate of BrdU-positive cells and cyclin D1 expression after PH more than wild-type mice. On the other hand, Ctsl-deficiency upregulated p62, cleaved-Notch1 and Hes1 expression after PH. Moreover, the protein level of Nrf2 in the nucleus and mRNA expression of NQO1 in the liver after PH was also up-regulated in Ctsl-/- mice.
These findings suggest that accumulation of p62 due to loss of Ctsl plays an important role in liver regeneration through activation of Nrf2-Notch1 signaling. Taken together, Ctsl might be a new therapeutic target on disorder of liver regeneration.
组织蛋白酶 L（Ctsl）在溶酶体和自噬性蛋白水解中发挥关键作用。先前的研究表明，部分肝切除术（PH）会降低肝脏中组织蛋白酶的生物合成，随后在肝再生期间抑制溶酶体和自噬性蛋白水解。相反，据报道自噬缺陷会抑制肝再生。因此，本研究旨在确定 Ctsl 缺乏是否会影响 PH 后的肝再生。
在 PH 后，雄性 Ctsl 缺陷型（Ctsl-/-）和野生型同窝仔鼠（Ctsl +/+）中进行 70%的 PH。处死小鼠，测量整个剩余肝脏的湿重。对肝组织切片进行溴脱氧尿苷（BrdU）免疫染色。通过 Western blot 分析评估 cyclin D1、p62、LC-3、Nrf2、裂解 Notch1、Hes1 的表达。通过实时 PCR 测量 NQO1 mRNA 表达。
在 70%的 PH 后，与野生型相比，Ctsl-/-小鼠的肝质量在 5 天内显著恢复。与野生型相比，Ctsl 缺乏增强了 PH 后 BrdU 阳性细胞和 cyclin D1 表达的增加。另一方面，Ctsl 缺乏增加了 PH 后 p62、裂解 Notch1 和 Hes1 的表达。此外，PH 后 Ctsl-/-小鼠核内 Nrf2 蛋白水平和肝内 NQO1 mRNA 表达也上调。
这些发现表明，由于 Ctsl 的缺失导致 p62 的积累在通过激活 Nrf2-Notch1 信号通路在肝再生中发挥重要作用。总之，Ctsl 可能是肝再生障碍的新治疗靶点。
