Dalton Shana R, Wiegert Robert L, Baldwin Cheryl R, Kassel Karen M, Casey Carol A
Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68198-2000, USA.
Biochem Pharmacol. 2003 Feb 15;65(4):535-43. doi: 10.1016/s0006-2952(02)01555-1.
During receptor-mediated endocytosis (RME), extracellular molecules are internalized after being recognized and bound to specific cell surface receptors. In previous studies of the asialoglycoprotein receptor (ASGPR) in rats, we showed that ethanol impairs RME at multiple ASGPR sites. Ethanol administration has been shown to increase apoptosis, and we demonstrated increased sensitization to apoptotic induction in hepatocytes from ethanol-fed rats. Although a physiological role for the ASGPR has not been identified, investigators have shown its involvement in the uptake/clearance of apoptotic cells in vitro. This suggests a potential role for the ASGPR in the removal of apoptotic cells, and the recent availability of an ASGPR-deficient mouse strain provides an excellent opportunity to examine the role of the ASGPR during ethanol impairment. In this study, we examined ethanol-impaired RME in mice and began the characterization of ASGPR-deficient mice for use in ethanol studies. Similar to our findings with rats, ligand binding, internalization, and degradation were decreased 45-50% in hepatocytes from ethanol-fed wild-type mice. In ASGPR-deficient mice, these parameters did not vary among the chow-fed, pair-fed control, or ethanol groups and were negligible compared with those of wild-type mice. TUNEL analysis of liver sections showed an ethanol-induced increase in apoptotic bodies in all mouse strains with a significant difference in the receptor-deficient mice. Further, the livers of ASGPR-deficient mice had three times more apoptotic bodies, in all feeding groups, compared with wild-type mice. These results support the use of the ASGPR-deficient mouse model for studying ethanol-induced liver injury, specifically ethanol-induced apoptosis.
在受体介导的内吞作用（RME）过程中，细胞外分子在被识别并结合到特定细胞表面受体后被内化。在先前对大鼠去唾液酸糖蛋白受体（ASGPR）的研究中，我们发现乙醇会在多个ASGPR位点损害RME。乙醇给药已被证明会增加细胞凋亡，并且我们证明了乙醇喂养大鼠的肝细胞对凋亡诱导的敏感性增加。尽管尚未确定ASGPR的生理作用，但研究人员已表明其在体外参与凋亡细胞的摄取/清除。这表明ASGPR在清除凋亡细胞中可能发挥作用，并且最近获得的ASGPR缺陷小鼠品系为研究乙醇损伤期间ASGPR的作用提供了绝佳机会。在本研究中，我们研究了乙醇对小鼠RME的损害，并开始对用于乙醇研究的ASGPR缺陷小鼠进行表征。与我们在大鼠中的发现相似，乙醇喂养的野生型小鼠肝细胞中的配体结合、内化和降解减少了45-50%。在ASGPR缺陷小鼠中，这些参数在正常饮食、配对喂养对照或乙醇组之间没有差异，与野生型小鼠相比可以忽略不计。肝脏切片的TUNEL分析显示，所有小鼠品系中乙醇均诱导凋亡小体增加，受体缺陷小鼠中有显著差异。此外，在所有喂养组中，ASGPR缺陷小鼠肝脏中的凋亡小体数量是野生型小鼠的三倍。这些结果支持使用ASGPR缺陷小鼠模型来研究乙醇诱导的肝损伤，特别是乙醇诱导的细胞凋亡。
