Tianjian Laboratory of Advanced Biomedical Sciences, Academy of Medical Sciences, Zhengzhou University, Zhengzhou, Henan 450052, China.
State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Proc Natl Acad Sci U S A. 2024 Jan 2;121(1):e2307395120. doi: 10.1073/pnas.2307395120. Epub 2023 Dec 29.
Oxidative stress, which can be activated by a variety of environmental risk factors, has been implicated as an important pathogenic factor for inflammatory bowel disease (IBD). However, how oxidative stress drives IBD onset remains elusive. Here, we found that oxidative stress was strongly activated in inflamed tissues from both ulcerative colitis patients and Crohn's disease patients, and it caused nuclear-to-cytosolic TDP-43 transport and a reduction in the TDP-43 protein level. To investigate the function of TDP-43 in IBD, we inducibly deleted exons 2 to 3 of Tardbp (encoding Tdp-43) in mouse intestinal epithelium, which disrupted its nuclear localization and RNA-processing function. The deletion gave rise to spontaneous intestinal inflammation by inducing epithelial cell necroptosis. Suppression of the necroptotic pathway with deletion of Mlkl or the RIP1 inhibitor Nec-1 rescued colitis phenotypes. Mechanistically, disruption of nuclear TDP-43 caused excessive R-loop accumulation, which triggered DNA damage and genome instability and thereby induced PARP1 hyperactivation, leading to subsequent NAD depletion and ATP loss, consequently activating mitochondrion-dependent necroptosis in intestinal epithelial cells. Importantly, restoration of cellular NAD levels with NAD or NMN supplementation, as well as suppression of ALKBH7, an α-ketoglutarate dioxygenase in mitochondria, rescued TDP-43 deficiency-induced cell death and intestinal inflammation. Furthermore, TDP-43 protein levels were significantly inversely correlated with γ-H2A.X and p-MLKL levels in clinical IBD samples, suggesting the clinical relevance of TDP-43 deficiency-induced mitochondrion-dependent necroptosis. Taken together, these findings identify a unique pathogenic mechanism that links oxidative stress to intestinal inflammation and provide a potent and valid strategy for IBD intervention.
氧化应激可以被多种环境风险因素激活，被认为是炎症性肠病（IBD）的重要发病因素。然而，氧化应激如何导致 IBD 的发生仍然难以捉摸。在这里，我们发现氧化应激在溃疡性结肠炎和克罗恩病患者的炎症组织中被强烈激活，它导致 TDP-43 从核到细胞质的转运和 TDP-43 蛋白水平的降低。为了研究 TDP-43 在 IBD 中的功能，我们在小鼠肠上皮细胞中诱导性缺失了 Tardbp（编码 Tdp-43）的外显子 2 到 3，这破坏了其核定位和 RNA 处理功能。缺失导致上皮细胞坏死性凋亡，从而自发引起肠道炎症。通过缺失 Mlkl 或 RIP1 抑制剂 Nec-1 抑制坏死性凋亡途径可挽救结肠炎表型。从机制上讲，核 TDP-43 的破坏导致过度的 R 环积累，触发 DNA 损伤和基因组不稳定性，从而导致 PARP1 过度激活，随后 NAD 耗竭和 ATP 损失，从而激活肠道上皮细胞中线粒体依赖性坏死性凋亡。重要的是，用 NAD 或 NMN 补充细胞内 NAD 水平，以及抑制线粒体中的 α-酮戊二酸双加氧酶 ALKBH7，可挽救 TDP-43 缺失诱导的细胞死亡和肠道炎症。此外，TDP-43 蛋白水平与临床 IBD 样本中的 γ-H2A.X 和 p-MLKL 水平呈显著负相关，提示 TDP-43 缺失诱导的线粒体依赖性坏死性凋亡与临床的相关性。总之，这些发现确定了一种将氧化应激与肠道炎症联系起来的独特发病机制，并为 IBD 的干预提供了一种有效策略。
