Haploinsufficiency of Hedgehog interacting protein causes increased emphysema induced by cigarette smoke through network rewiring. Mus musculus

BACKGROUND: The HHIP gene, encoding Hedgehog interacting protein, has been implicated in chronic obstructive pulmonary disease (COPD) by genome-wide association studies (GWAS), and our subsequent studies identified a functional upstream genetic variant that decreased HHIP transcription. However, little is known about how HHIP contributes to COPD pathogenesis. METHODS: Here, we exposed Hhip haploinsufficient mice (Hhip+/-) to cigarette smoke (CS) for 6 months to model the biological consequences caused by CS in human COPD risk-allele carriers at the HHIP locus. Gene expression profiling in murine lungs was performed followed by an integrative network inference analysis, PANDA (Passing Attributes between Networks for Data Assimilation) analysis. RESULTS: We detected more severe airspace enlargement in Hhip+/- mice vs. wild-type littermates (Hhip+/+) exposed to CS. Gene expression profiling in murine lungs suggested enhanced lymphocyte activation pathways in CS-exposed Hhip+/- vs. Hhip+/+ mice, which was supported by increased numbers of lymphoid aggregates and enhanced activation of CD8+ T cells after CS-exposure in the lungs of Hhip+/- mice compared to Hhip+/+ mice. Mechanistically, results from PANDA network analysis suggested a rewired and dampened Klf4 signaling network in Hhip+/- mice after CS exposure. CONCLUSIONS: In summary, HHIP haploinsufficiency exaggerated CS-induced airspace enlargement, which models CS-induced emphysema in human smokers carrying COPD risk alleles at the HHIP locus. Network modeling suggested rewired lymphocyte activation signaling circuits in the HHIP haploinsufficiency state. Overall design: Total RNA was obtained from the lung tissue of C57BL/6J mice exposed to cigarette smoke (CS) or filtered air (air) for 6 months. Six mice from each of four groups with different genotypes (Hhip+/+ or Hhip+/-) and treatments (air or CS) were randomly chosen for gene expression profiling

背景：编码刺猬相互作用蛋白（Hedgehog interacting protein）的HHIP基因，已通过全基因组关联研究（Genome-Wide Association Studies, GWAS）被证实与慢性阻塞性肺疾病（Chronic Obstructive Pulmonary Disease, COPD）相关；本团队后续研究进一步鉴定出一种可降低HHIP转录水平的功能性上游遗传变异。然而，目前关于HHIP如何参与COPD的发病机制仍知之甚少。方法：本研究将Hhip单倍体不足小鼠（Hhip+/-）暴露于香烟烟雾（Cigarette Smoke, CS）中6个月，以模拟携带HHIP位点COPD风险等位基因的人群中香烟烟雾所引发的生物学效应。随后对小鼠肺部开展基因表达谱分析，并进一步进行整合网络推断分析——即数据同化网络间属性传递（Passing Attributes between Networks for Data Assimilation, PANDA）分析。结果：相较于野生型同窝对照小鼠（Hhip+/+），香烟烟雾暴露后的Hhip+/-小鼠出现了更为严重的肺泡腔扩大。小鼠肺部基因表达谱分析显示，香烟烟雾暴露的Hhip+/-小鼠中淋巴细胞活化通路激活增强，这一结果得到了进一步验证：与Hhip+/+小鼠相比，香烟烟雾暴露后Hhip+/-小鼠肺部的淋巴聚集灶数量增多、CD8+ T细胞活化程度更高。从机制层面来看，PANDA网络分析结果显示，香烟烟雾暴露后的Hhip+/-小鼠体内Klf4信号网络发生重连且活性被抑制。结论：综上，HHIP单倍体不足会加剧香烟烟雾诱导的肺泡腔扩大，该模型可模拟携带HHIP位点COPD风险等位基因的人类吸烟者中香烟烟雾诱导的肺气肿。网络建模结果显示，HHIP单倍体不足状态下淋巴细胞活化信号通路发生重连。实验整体设计：从暴露于香烟烟雾（CS）或过滤空气（空气对照）6个月的C57BL/6J小鼠肺组织中提取总RNA；按基因型（Hhip+/+、Hhip+/-）与处理方式（空气对照、CS暴露）分为4组，每组随机选取6只小鼠进行基因表达谱分析。