<i>In Vivo</i> Zonal Variation and Liver Cell-Type Specific NF-κB Localization after Chronic Adaptation to Ethanol and following Partial Hepatectomy

NF-κB is a major inflammatory response mediator in the liver, playing a key role in the pathogenesis of alcoholic liver injury. We investigated zonal as well as liver cell type-specific distribution of NF-κB activation across the liver acinus following adaptation to chronic ethanol intake and 70% partial hepatectomy (PHx). We employed immunofluorescence staining, digital image analysis and statistical distributional analysis to quantify subcellular localization of NF-κB in hepatocytes and hepatic stellate cells (HSCs). We detected significant spatial heterogeneity of NF-κB expression and cellular localization between cytoplasm and nucleus across liver tissue. Our main aims involved investigating the zonal bias in NF-κB localization and determining to what extent chronic ethanol intake affects this zonal bias with in hepatocytes at baseline and post-PHx. Hepatocytes in the periportal area showed higher NF-κB expression than in the pericentral region in the carbohydrate-fed controls, but not in the ethanol group. However, the distribution of NF-κB nuclear localization in hepatocytes was shifted towards higher levels in pericentral region than in periportal area, across all treatment conditions. Chronic ethanol intake shifted the NF-κB distribution towards higher nuclear fraction in hepatocytes as compared to the pair-fed control group. Ethanol also stimulated higher NF-κB expression in a subpopulation of HSCs. In the control group, PHx elicited a shift towards higher NF-κB nuclear fraction in hepatocytes. However, this distribution remained unchanged in the ethanol group post-PHx. HSCs showed a lower NF-κB expression following PHx in both ethanol and control groups. We conclude that adaptation to chronic ethanol intake attenuates the liver zonal variation in NF-κB expression and limits the PHx-induced NF-κB activation in hepatocytes, but does not alter the NF-κB expression changes in HSCs in response to PHx. Our findings provide new insights as to how ethanol treatment may affect cell-type specific processes regulated by NF-κB activation in liver cells.核因子κB（NF-κB）是肝脏中主要的炎症反应介质，在酒精性肝损伤的发病机制中发挥关键作用。本研究聚焦慢性乙醇摄入适应及70%肝部分切除术（PHx）后，肝腺泡内核因子κB激活的分区分布与肝细胞类型特异性分布特征。我们采用免疫荧光染色、数字图像分析及统计分布分析手段，对肝细胞与肝星状细胞（HSCs）内核因子κB的亚细胞定位进行定量检测。检测发现，肝组织内核因子κB的表达水平及细胞质与细胞核间的细胞定位存在显著空间异质性。本研究的核心目标为探究核因子κB定位的分区偏好性，并明确基线水平及肝部分切除术后，慢性乙醇摄入对肝细胞内该分区偏好性的影响程度。在碳水化合物喂养的对照组中，门静脉周区域的肝细胞核因子κB表达水平高于中央静脉周区域，但该现象在乙醇喂养组中并未观察到。然而，所有处理组的肝细胞内核因子κB核定位分布均向中央静脉周区域偏移，且该区域的核定位水平高于门静脉周区域。与配对喂养对照组相比，慢性乙醇摄入使肝细胞内核因子κB的核分布占比向更高水平偏移。此外，乙醇还可促进肝星状细胞亚群的核因子κB表达上调。对照组中，肝部分切除术可使肝细胞内核因子κB的核分布占比向更高水平偏移，但该变化在乙醇喂养组的肝部分切除术后并未发生。乙醇喂养组与对照组中，肝部分切除术后肝星状细胞的核因子κB表达均出现下调。本研究结论表明，慢性乙醇摄入适应可减弱肝脏内核因子κB表达的分区差异，并抑制肝部分切除术诱导的肝细胞内核因子κB激活，但不会改变肝星状细胞在肝部分切除术后的核因子κB表达变化。本研究结果为阐明乙醇如何调控肝脏细胞中核因子κB激活所介导的细胞类型特异性过程提供了新的见解。