Yue Ruichao, Wei Xiaoyuan, Zhao Jiangchao, Zhou Zhanxiang, Zhong Wei
Center for Translational Biomedical Research, University of North Carolina at Greensboro, North Carolina Research Campus, Kannapolis, NC, United States.
Division of Agriculture, Department of Animal Science, University of Arkansas, Fayetteville, AR, United States.
Front Physiol. 2021 Jan 18;11:629141. doi: 10.3389/fphys.2020.629141. eCollection 2020.
The mechanisms by which alcohol provokes bacterial translocation in the development of alcoholic liver disease (ALD) remain incompletely defined. Our previous study demonstrates that impaired gut epithelial antimicrobial defense is critically involved in the pathogenesis of ALD. The study was set to determine the mechanisms of how alcohol inhibits the antimicrobial ability of intestinal epithelial cells (IECs) and to explore possible solutions to this issue. C57BL/6J mice were fed either alcohol or isocaloric dextrin liquid diet for 8 weeks, and intestinal IFN-γ-signal transducer and activator of transcription (STAT) signaling was analyzed. We found that chronic alcohol exposure led to a significant reduction in intestinal IFN-γ levels compared to a control; the protein levels of phosphorylated STAT1 (p-STAT1) and p-STAT3 were both declined by alcohol. We then tested the effects of IFN-γ-STAT signaling on regulating antimicrobial peptides (AMPs), gut microbiota, and disease progression of ALD in a mouse model of chronic alcohol feeding, time-course acute IFN-γ treatment, and and IEC-specific STAT1 or STAT3 knockout mouse models, respectively. Administration of IFN-γ activated intestinal STAT1 and STAT3, upregulated the expression of Reg3 and α-defensins, orchestrated gut microbiota, and reversed alcohol-induced intestinal ZO-1 disruption and systemic endotoxin elevation as well as hepatic inflammation. Meanwhile, acute IFN-γ treatment time-dependently induced AMP expression and α-defensin activation. We then dissected the roles of STAT1 and STAT3 in this progress. Lack of IEC-specific STAT3 inhibited IFN-γ-induced expression of Reg3 and α-defensins and hindered activation of α-defensins inactivating matrix metallopeptidase 7 (MMP7), whereas lack of IEC-specific STAT1 impaired IFN-γ-stimulated expression of α-defensins and the IEC marker, sodium-hydrogen exchanger 3. Lastly, we found that interleukin (IL)-18, a known IFN-γ inducer, was also reduced by alcohol in mice. IL-18 treatment to alcohol-fed mice normalized gut IFN-γ levels and ameliorated organ damages in both the intestine and liver. Taken together, the study reveals that IFN-γ is critically involved in the regulation of AMPs through regulation of STAT1 and STAT3; impaired IFN-γ-STAT signaling provides an explanation for alcohol-induced gut antimicrobial dysfunction and microbial dysbiosis. Therefore, IFN-γ remains a promising host defense-enhancing cytokine with unexplored clinical potential in ALD therapy.
酒精性肝病（ALD）发展过程中酒精引发细菌易位的机制仍未完全明确。我们之前的研究表明，肠道上皮抗菌防御受损在ALD的发病机制中起关键作用。本研究旨在确定酒精抑制肠道上皮细胞（IECs）抗菌能力的机制，并探索解决这一问题的可能方法。将C57BL/6J小鼠分别喂食酒精或等热量的糊精液体饲料8周，并分析肠道干扰素-γ信号转导子和转录激活子（STAT）信号通路。我们发现，与对照组相比，慢性酒精暴露导致肠道干扰素-γ水平显著降低；酒精使磷酸化STAT1（p-STAT1）和p-STAT3的蛋白水平均下降。然后，我们分别在慢性酒精喂养小鼠模型、时间进程急性干扰素-γ治疗以及IEC特异性STAT1或STAT3基因敲除小鼠模型中，测试了干扰素-γ-STAT信号通路对调节抗菌肽（AMPs）、肠道微生物群以及ALD疾病进展的影响。给予干扰素-γ可激活肠道STAT1和STAT3，上调Reg3和α-防御素的表达，协调肠道微生物群，并逆转酒精诱导的肠道紧密连接蛋白1（ZO-1）破坏、全身内毒素升高以及肝脏炎症。同时，急性干扰素-γ治疗可时间依赖性地诱导AMPs表达和α-防御素激活。然后，我们剖析了STAT1和STAT3在这一过程中的作用。缺乏IEC特异性STAT3会抑制干扰素-γ诱导的Reg3和α-防御素表达，并阻碍α-防御素通过使基质金属蛋白酶7（MMP7）失活而激活，而缺乏IEC特异性STAT1则会损害干扰素-γ刺激的α-防御素表达以及IEC标志物钠氢交换体3的表达。最后，我们发现白细胞介素（IL）-18，一种已知的干扰素-γ诱导剂，在小鼠中也因酒精而减少。对喂食酒精的小鼠进行IL-18治疗可使肠道干扰素-γ水平恢复正常，并改善肠道和肝脏的器官损伤。综上所述，该研究表明干扰素-γ通过调节STAT1和STAT3在AMPs的调节中起关键作用；受损的干扰素-γ-STAT信号通路为酒精诱导的肠道抗菌功能障碍和微生物失调提供了解释。因此，干扰素-γ仍然是一种有前景的增强宿主防御的细胞因子，在ALD治疗中具有尚未被探索的临床潜力。
