Molecular Biology and Cancer Research Laboratory, Department of Biochemistry, University of Ibadan, Ibadan, Nigeria.
Environ Toxicol. 2014 Aug;29(8):867-75. doi: 10.1002/tox.21814. Epub 2012 Sep 20.
Kupffer cells (KCs) are important in hepatic homeostasis and responses to xenobiotics. KCs are activated on interaction with endotoxin, releasing cytokines, and reactive oxygen species normally associated with increased gene expression, cellular growth, or hepatic injury. Ethanol-induced endotoxemia is one means of KC activation. We propose that KC depletion attenuates the effect of EtOH-induced endotoxemia to impact the hepatic growth response. Hepatic DNA synthesis was examined in KC competent (KC+) or KC-depleted (KC-) C57BL/6 mice fed EtOH-containing diet in the presence or absence of polyphenol-60 antioxidant. KC depletion was assessed by F4/80 antigen, and DNA synthesis was assessed by 5-bromo-2'-deoxyuridine incorporation. Tumor necrosis factor alpha (TNF-α) messenger RNA released was quantified by RT-PCR/electrophoresis. ERK1/2 phosphorylation was evaluated by Western blotting, and Nrf2 and CYP2E1protein were also assayed. Apoptosis and hepatic injury were examined by the Tunnel assay and hepatic transaminases in serum, respectively. Hepatic transaminases in serum (AST and ALT) were within normal range. Over 90% of KC was depleted by clodronate treatment. KC depletion decreased TNF-α mRNA release, ERK1/2 phosphorylation, and hepatocyte DNA synthesis. KC depletion is associated with increased numbers of apoptotic cells bodies in KC- mice. Antioxidant treatment decreased DNA synthesis, Nrf2, and CYP2E1 protein expression in EtOH-consuming mice. Our data indicate that upon ethanol exposure, KC participates in hepatic DNA synthesis and growth responses. Collectively, these observations suggest that KC depletion attenuates the downstream effect of ethanol-induced endotoxemia by reduced cytokine and reactive oxygen species production with its concomitant effect on MAPK-signaling pathway on hepatocyte DNA synthesis.
枯否细胞（KCs）在肝脏稳态和对外源物的反应中起着重要作用。KCs 在与内毒素相互作用时被激活，释放细胞因子和活性氧物质，通常与基因表达、细胞生长或肝损伤增加相关。乙醇诱导的内毒素血症是 KC 激活的一种手段。我们提出，KC 耗竭可减弱乙醇诱导的内毒素血症的作用，从而影响肝脏生长反应。在存在或不存在多酚-60 抗氧化剂的情况下，用含乙醇的饮食喂养 KC 功能正常（KC+）或 KC 耗竭（KC-）的 C57BL/6 小鼠，检查肝 DNA 合成。通过 F4/80 抗原评估 KC 耗竭，通过 5-溴-2'-脱氧尿苷掺入评估 DNA 合成。通过 RT-PCR/电泳定量释放肿瘤坏死因子-α（TNF-α）信使 RNA。通过 Western 印迹评估 ERK1/2 磷酸化，还检测 Nrf2 和 CYP2E1 蛋白。通过隧道试验和血清中转氨酶分别检查细胞凋亡和肝损伤。血清中转氨酶（AST 和 ALT）在正常范围内。用氯膦酸盐处理可耗竭超过 90%的 KC。KC 耗竭减少 TNF-αmRNA 释放、ERK1/2 磷酸化和肝细胞 DNA 合成。KC 耗竭与 KC-小鼠中凋亡细胞体数量增加有关。抗氧化剂治疗降低了乙醇消耗小鼠的 DNA 合成、Nrf2 和 CYP2E1 蛋白表达。我们的数据表明，在乙醇暴露下，KC 参与了肝 DNA 合成和生长反应。总的来说，这些观察结果表明，KC 耗竭通过减少细胞因子和活性氧物质的产生，减弱了乙醇诱导的内毒素血症的下游效应，从而对 MAPK 信号通路对肝细胞 DNA 合成产生了伴随的影响。
