Background & Aims

Patients with ulcerative colitis have low concentrations of the major membrane lipid phosphatidylcholine (PC) in gastrointestinal mucus, suggesting that defects in colonic PC metabolism might be involved in the development of colitis. To determine the precise role that PC plays in colonic barrier function, we examined mice with intestinal epithelial cell (IEC)-specific deletion of the rate-limiting enzyme in the major pathway for PC synthesis: cytidine triphosphate:phosphocholine cytidylyltransferase-α (CTα^IKO mice).

Methods

Colonic tissue of CTα^IKO mice and control mice was analyzed by histology, immunofluorescence, electron microscopy, quantitative polymerase chain reaction, Western blot, and thin-layer chromatography. Histopathologic colitis scores were assigned by a pathologist blinded to the experimental groupings. Intestinal permeability was assessed by fluorescein isothiocyanate–dextran gavage and fecal microbial composition was analyzed by sequencing 16s ribosomal RNA amplicons. Subsets of CTα^IKO mice and control mice were treated with dietary PC supplementation, antibiotics, or 4-phenylbutyrate.

Results

Inducible loss of CTα in the intestinal epithelium reduced colonic PC concentrations and resulted in rapid and spontaneous colitis with 100% penetrance in adult mice. Colitis development in CTα^IKO mice was traced to a severe and unresolving endoplasmic reticulum stress response in IECs with altered membrane phospholipid composition. This endoplasmic reticulum stress response was linked to the necroptotic death of IECs, leading to excessive loss of goblet cells, formation of a thin mucus barrier, increased intestinal permeability, and infiltration of the epithelium by microbes.

Conclusions

Maintaining the PC content of IEC membranes protects against colitis development in mice, showing a crucial role for IEC phospholipid equilibrium in colonic homeostasis. SRA accession number: PRJNA562603.

中文翻译：

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肠道磷脂不平衡引发 ER 应激反应，导致小鼠杯状细胞坏死和自发性结肠炎

背景与目标

溃疡性结肠炎患者胃肠道粘液中的主要膜脂磷脂酰胆碱 (PC) 浓度较低，这表明结肠 PC 代谢缺陷可能与结肠炎的发生有关。为了确定 PC 在结肠屏障功能中的确切作用，我们检查了具有肠上皮细胞 (IEC) 特异性缺失 PC 合成主要途径中的限速酶的小鼠：胞苷三磷酸：磷酸胆碱胞苷酰转移酶-α (CTα ^IKO老鼠）。

方法

通过组织学、免疫荧光、电子显微镜、定量聚合酶链反应、蛋白质印迹和薄层色谱分析CTα ^{IKO小鼠和对照小鼠的结肠组织。}组织病理学结肠炎评分由对实验分组不知情的病理学家分配。通过异硫氰酸荧光素-葡聚糖管饲法评估肠道通透性，并通过对 16s 核糖体 RNA 扩增子进行测序分析粪便微生物组成。CTα ^IKO小鼠和对照小鼠的亚组用膳食 PC 补充剂、抗生素或 4-苯基丁酸盐治疗。

结果

肠上皮中 CTα 的可诱导损失降低了结肠 PC 浓度，并导致成年小鼠快速自发性结肠炎，外显率为 100%。^{CTα IKO}小鼠的结肠炎发展可追溯到具有改变的膜磷脂成分的 IEC 中严重且无法解决的内质网应激反应。这种内质网应激反应与 IEC 的坏死性死亡有关，导致杯状细胞过度损失、形成薄的粘液屏障、增加肠道通透性和微生物对上皮的浸润。

结论

维持 IEC 膜的 PC 含量可防止小鼠发生结肠炎，显示出 IEC 磷脂平衡在结肠稳态中的关键作用。SRA 登录号：PRJNA562603。