Transcriptome of human primary macrophages from X-linked adrenoleukodystrophy patients and healthy controls

Saturated very long-chain fatty acids (VLCFA, = C22), enriched in brain myelin and innate immune cells, accumulate in X-linked adrenoleukodystrophy (X-ALD). The severest form, inherited dysfunction of the VLCFA transporter ABCD1, underlying X-ALD, causes brain myelin destruction with infiltration of pro-inflammatory skewed monocytes/macrophages. How VLCFA levels relate to macrophage activation is unclear. Using whole transcriptome sequencing of X-ALD macrophages, we revealed that VLCFAs prime human macrophage membranes for inflammation and increase factors involved in chemotaxis and invasion. When applied externally, mimicking lipid destruction in X-ALD lesions, VLCFAs did not activate toll-like receptors in healthy cells but provoked pro-inflammatory responses through scavenger receptor CD36-mediated uptake, cumulating in JNK signalling and expression of matrix degrading enzymes and chemokine release. Following pro-inflammatory LPS-activation, VLCFA accumulated in healthy macrophages but were rapidly cleared with onset of resolution by increasing VLCFA degradation through liver-X-receptor mediated upregulation of ABCD1. ABCD1 deficiency impaired VLCFA homeostasis and prolonged pro-inflammatory gene expression. Our study uncovers a pivotal role for ABCD1, a protein linked to neuroinflammation, and associated peroxisomal VLCFA degradation in regulating macrophage plasticity. Overall design: Comparative gene expression profiling analysis of RNA-seq data for macrophages derived from X-ALD patients and control blood-isolated monocytes.

饱和超长链脂肪酸（very long-chain fatty acids, VLCFA，碳链长度≥C22）富集于大脑髓鞘与固有免疫细胞，在X连锁肾上腺脑白质营养不良（X-linked adrenoleukodystrophy, X-ALD）中会发生异常蓄积。X-ALD的致病核心为VLCFA转运蛋白ABCD1的遗传性功能缺陷，其中最严重的亚型可引发大脑髓鞘破坏，并伴随促炎极化的单核细胞/巨噬细胞浸润。目前，VLCFA水平与巨噬细胞活化之间的关联机制仍不明确。本研究通过对X-ALD患者来源的巨噬细胞开展全转录组测序，发现VLCFA可致敏人类巨噬细胞膜以促进炎症反应，并上调趋化与侵袭相关因子的表达。当外源性给予VLCFA以模拟X-ALD病灶中的脂质破坏环境时，健康细胞内的Toll样受体（Toll-like receptors, TLR）并未被激活，但VLCFA可通过清道夫受体CD36介导的摄取途径诱发促炎反应，最终激活JNK信号通路，上调基质降解酶的表达并促进趋化因子释放。在经促炎型脂多糖（lipopolysaccharide, LPS）激活巨噬细胞后，健康巨噬细胞内会出现VLCFA蓄积，但随着炎症消退进程启动，肝脏X受体（liver-X-receptor, LXR）介导的ABCD1表达上调可增强VLCFA的降解能力，从而快速清除胞内蓄积的VLCFA。ABCD1功能缺陷会破坏VLCFA的细胞稳态，并延长促炎基因的表达持续时间。本研究揭示了与神经炎症相关的蛋白ABCD1及其介导的过氧化物酶体VLCFA降解通路在调控巨噬细胞可塑性中的关键作用。总体实验设计：对X-ALD患者与健康对照者外周血分离单核细胞诱导分化得到的巨噬细胞的RNA-seq数据进行比较基因表达谱分析。