Department of Human Pathology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan.
Lab Invest. 2010 Jun;90(6):835-43. doi: 10.1038/labinvest.2010.56. Epub 2010 Mar 8.
Recent studies disclosed that autophagy is induced during and facilitates the process of senescence. Given that biliary epithelial cells (BECs) in damaged small bile ducts in primary biliary cirrhosis (PBC) show senescent features, we examined an involvement of autophagy in the process of biliary epithelial senescence in PBC. We examined immunohistochemically the expression of microtubule-associated proteins-light chain 3beta (LC3), a marker of autophagy, in livers taken from the patients with PBC (n=37) and control livers (n=75). We also examined the co-localization of LC3 with autophagy-related cathepsin D, lysosome-associated membrane protein-1 (LAMP-1), and senescent markers, p16(INK4a) and p21(WAF1/Cip1). We examined the effect of autophagy inhibitor (3-methyladenine) on the induction of cellular senescence and senescence-associated secretion (CCL2 and CX3CL1) in cultured murine BECs. The expression of LC3 was specifically seen in vesicles in BECs in the inflamed and damaged small bile ducts in PBC, when compared with non-inflamed small bile ducts in PBC and in control livers (P<0.01). The expression of LC3 was closely related to the expression of cathepsin D, LAMP-1, and senescent markers. In cultured BECs, oxidative stress, DNA damage, and serum deprivation induced cellular senescence, when compared with control and the inhibition of autophagy significantly decreased the stress-induced cellular senescence (P<0.01). Furthermore, the secretion level of CCL2 and CX3CL1 increased significantly by various stress and suppressed by the inhibition of autophagy (P<0.01). In conclusion, autophagy is specifically seen in the damaged small bile ducts along with cellular senescence in PBC. The inhibition of autophagy suppressed cellular senescence in cultured cells. These findings suggest that autophagy may mediate the process of biliary epithelial senescence and involve in the pathogenesis of bile duct lesions in PBC.
最近的研究表明，自噬在衰老过程中被诱导并促进衰老过程。鉴于原发性胆汁性肝硬化（PBC）中小胆管损伤时的胆管上皮细胞（BEC）表现出衰老特征，我们研究了自噬在 PBC 胆管上皮细胞衰老过程中的作用。我们用免疫组织化学方法检测了来自 PBC 患者（n=37）和对照组肝脏（n=75）的 LC3（自噬的标志物）的表达。我们还检查了 LC3 与自噬相关的组织蛋白酶 D、溶酶体相关膜蛋白-1（LAMP-1）和衰老标志物 p16(INK4a)和 p21(WAF1/Cip1)的共定位。我们检测了自噬抑制剂（3-甲基腺嘌呤）对培养的鼠 BEC 中细胞衰老和衰老相关分泌（CCL2 和 CX3CL1）的诱导作用。与 PBC 中的非炎症性小胆管和对照组肝脏相比（P<0.01），LC3 在 PBC 中小胆管炎症和损伤部位的 BEC 中可见于囊泡内。LC3 的表达与组织蛋白酶 D、LAMP-1 和衰老标志物的表达密切相关。在培养的 BEC 中，与对照组相比，氧化应激、DNA 损伤和血清剥夺诱导细胞衰老，自噬的抑制显著降低应激诱导的细胞衰老（P<0.01）。此外，CCL2 和 CX3CL1 的分泌水平显著增加各种应激诱导，并被自噬抑制所抑制（P<0.01）。总之，自噬在 PBC 中小胆管损伤的同时与细胞衰老一起被特异性观察到。自噬的抑制抑制了培养细胞的细胞衰老。这些发现表明自噬可能介导胆管上皮细胞衰老过程，并参与 PBC 胆管损伤的发病机制。
