Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232.
Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232.
J Immunol. 2020 Aug 15;205(4):1125-1134. doi: 10.4049/jimmunol.1900820. Epub 2020 Jun 29.
NF-κB is a reduction-oxidation-sensitive transcription factor that plays a key role in regulating the immune response. In these studies, we intended to investigate the role of mitochondrial-derived reactive oxygen species in regulating NF-κB activation by studying transgenic mice that overexpress mitochondrial-targeted human catalase (mCAT). We treated wild-type (WT) and mCAT mice with intratracheal instillation of LPS and found that mCAT mice had exaggerated NF-κB activation in the lungs, increased neutrophilic alveolitis, and greater lung inflammation/injury compared with WT mice. Additional studies using bone marrow chimeras revealed that this hyperinflammatory phenotype was mediated by immune/inflammatory cells. Mechanistic studies using bone marrow-derived macrophages (BMDMs) showed that LPS treatment induced a sustained increase in NF-κB activation and expression of NF-κB-dependent inflammatory mediators in mCAT BMDMs compared with WT BMDMs. Further investigations showed that cytoplasmic, but not mitochondrial, hydrogen peroxide levels were reduced in LPS-treated mCAT BMDMs. However, mCAT macrophages exhibited increased glycolytic and oxidative metabolism, coupled with increased ATP production and an increased intracellular NADH/NAD ratio compared with BMDMs from WT mice. Treatment of BMDMs with lactate increased the intracellular NADH/NAD ratio and upregulated NF-κB activation after LPS treatment, whereas treatment with a potent inhibitor of the mitochondrial pyruvate carrier (UK5099) decreased the NADH/NAD ratio and reduced NF-κB activation. Taken together, these findings point to an increased availability of reducing equivalents in the form of NADH as an important mechanism by which metabolic activity modulates inflammatory signaling through the NF-κB pathway.
NF-κB 是一种氧化还原敏感的转录因子，在调节免疫反应中发挥关键作用。在这些研究中，我们旨在通过研究过表达线粒体靶向人过氧化氢酶（mCAT）的转基因小鼠，研究线粒体来源的活性氧在调节 NF-κB 激活中的作用。我们用气管内滴注 LPS 处理野生型（WT）和 mCAT 小鼠，发现 mCAT 小鼠的肺部 NF-κB 激活过度，中性粒细胞性肺泡炎增加，与 WT 小鼠相比，肺部炎症/损伤更大。使用骨髓嵌合体的进一步研究表明，这种过度炎症表型是由免疫/炎症细胞介导的。使用骨髓来源的巨噬细胞（BMDM）进行的机制研究表明，与 WT BMDM 相比，LPS 处理诱导 mCAT BMDM 中 NF-κB 激活和 NF-κB 依赖性炎症介质的表达持续增加。进一步的研究表明，LPS 处理的 mCAT BMDM 中细胞质而非线粒体的过氧化氢水平降低。然而，与 WT 小鼠的 BMDM 相比，mCAT 巨噬细胞表现出增强的糖酵解和氧化代谢，伴随着增加的 ATP 产生和增加的细胞内 NADH/NAD 比。用乳酸处理 BMDM 可增加细胞内 NADH/NAD 比，并在上皮素处理后上调 NF-κB 激活，而用一种有效的线粒体丙酮酸载体（UK5099）抑制剂处理可降低 NADH/NAD 比并减少 NF-κB 激活。综上所述，这些发现表明，作为一种重要机制，还原当量以 NADH 的形式增加，从而通过 NF-κB 途径调节炎症信号。
