Gene Expression in Brain and Liver Produced by Three Different Regimens of Alcohol Consumption in Mice: Comparison with Immune Activation

Chronically available alcohol escalates drinking in mice and a single injection of the immune activator lipopolysaccharide can mimic this effect and result in a persistent increase in alcohol consumption. We hypothesized that chronic alcohol drinking and lipopolysaccharide injections will produce some similar molecular changes that play a role in regulation of alcohol intake. We investigated the molecular mechanisms of chronic alcohol consumption or lipopolysaccharide insult by gene expression profiling in prefrontal cortex and liver of C57BL/6J mice. We identified similar patterns of transcriptional changes among four groups of animals, three consuming alcohol (vs water) in different consumption tests and one injected with lipopolysaccharide (vs. vehicle). The three tests of alcohol consumption are the continuous chronic two bottle choice (Chronic), two bottle choice available every other day (Chronic Intermittent) and limited access to one bottle of ethanol (Drinking in the Dark). Gene expression changes were more numerous and marked in liver than in prefrontal cortex for the alcohol treatments and similar in the two tissues for lipopolysaccharide. Many of the changes were unique to each treatment, but there was significant overlap in prefrontal cortex for Chronic-Chronic Intermittent and for Chronic Intermittent-lipopolysaccharide and in liver all pairs showed overlap. In silico cell-type analysis indicated that lipopolysaccharide had strongest effects on brain microglia and liver Kupffer cells. Pathway analysis detected a prefrontal cortex-based dopamine-related (PPP1R1B, DRD1, DRD2, FOSB, PDNY) network that was highly over-represented in the Chronic Intermittent group, with several genes from the network being also regulated in the Chronic and lipopolysaccharide (but not Drinking in the Dark) groups. Liver showed a CYP and GST centered metabolic network shared in part by all four treatments. We demonstrate common consequences of chronic alcohol consumption and immune activation in both liver and brain and show distinct genomic consequences of different types of alcohol consumption.

长期供给酒精可升高小鼠的饮酒量，而单次注射免疫激活剂脂多糖（lipopolysaccharide）可模拟该效应，导致饮酒量持续升高。本研究假设，长期饮酒与脂多糖注射可诱导产生若干相似的分子变化，这些变化在饮酒量调控中发挥作用。本研究通过对C57BL/6J小鼠的前额叶皮层（prefrontal cortex）与肝脏进行基因表达谱分析，探究了长期饮酒或脂多糖刺激的分子机制。我们在四组小鼠中发现了相似的转录变化模式：其中三组在不同的饮酒检测范式中摄入酒精（相较于饮水组），另一组接受脂多糖注射（相较于溶媒（vehicle）对照组）。三种饮酒检测范式分别为：持续慢性双瓶选择（Chronic）、隔日双瓶选择（慢性间歇性，Chronic Intermittent）以及单瓶乙醇限量摄入（黑暗饮酒，Drinking in the Dark）。酒精处理组的肝脏中基因表达变化数量更多、程度更显著，而脂多糖处理组在两种组织中的基因表达变化程度相似。多数变化为各处理组所特有，但前额叶皮层中，慢性组与慢性间歇性组、慢性间歇性组与脂多糖组之间存在显著的基因表达重叠；而肝脏中所有处理组配对均存在表达重叠。计算机模拟（in silico）细胞类型分析显示，脂多糖对大脑小胶质细胞与肝脏库普弗细胞（Kupffer cells）的作用最为显著。通路分析发现，慢性间歇性组中显著富集了以多巴胺相关基因为核心的前额叶皮层网络（PPP1R1B、DRD1、DRD2、FOSB、PDNY），该网络中的若干基因在慢性组与脂多糖组中同样受到调控，但未在黑暗饮酒组中出现调控变化。肝脏中存在以CYP与GST为核心的代谢网络，该网络在四种处理组中均存在部分共享的调控变化。本研究证实了长期饮酒与免疫激活在肝脏与大脑中均存在共同的效应，并揭示了不同饮酒范式所产生的特异性基因组学变化。