Molecular and Cellular Pathology, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Division of Molecular and Translational Biomedicine, Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Genes (Basel). 2022 Aug 24;13(9):1514. doi: 10.3390/genes13091514.
Nuclear factor, erythroid 2 like 2 (Nfe2l2 or Nrf2), is a transcription factor that protects cells by maintaining a homeostatic redox state during stress. The constitutive expression of Nrf2 (CaNrf2-TG) was previously shown to be pathological to the heart over time. We tested a hypothesis that the cardiac-specific expression of full length Nrf2 (mNrf2-TG) would moderately increase the basal antioxidant defense, triggering a pro-reductive environment leading to adaptive cardiac remodeling. Transgenic and non-transgenic (NTG) mice at 7−8 months of age were used to analyze the myocardial transcriptome, structure, and function. Next generation sequencing (NGS) for RNA profiling and qPCR-based validation of the NGS data, myocardial redox levels, and imaging (echocardiography) were performed. Transcriptomic analysis revealed that out of 14,665 identified mRNAs, 680 were differently expressed (DEG) in TG hearts. Of 680 DEGs, 429 were upregulated and 251 were downregulated significantly (FC > 2.0, p < 0.05). Gene set enrichment analysis revealed that the top altered pathways were (a) Nrf2 signaling, (b) glutathione metabolism and (c) ROS scavenging. A comparative analysis of the glutathione redox state in the hearts demonstrated significant differences between pro-reductive vs. hyper-reductive conditions (233 ± 36.7 and 380 ± 68.7 vs. 139 ± 8.6 µM/mg protein in mNrf2-TG and CaNrf2-TG vs. NTG). Genes involved in fetal development, hypertrophy, cytoskeletal rearrangement, histone deacetylases (HDACs), and GATA transcription factors were moderately increased in mNrf2-TG compared to CaNrf2-TG. Non-invasive echocardiography analysis revealed an increase in systolic function (ejection fraction) in mNrf2-TG, suggesting an adaptation, as opposed to pathological remodeling in CaNrf2-TG mice experiencing a hyper-reductive stress, leading to reduced survival (40% at 60 weeks). The effects of excess Nrf2-driven antioxidant transcriptome revealed a pro-reductive condition in the myocardium leading to an adaptive cardiac remodeling. While pre-conditioning the myocardial redox with excess antioxidants (i.e., pro-reductive state) could be beneficial against oxidative stress, a chronic pro-reductive environment in the myocardium might transition the adaptation to pathological remodeling.
核因子，红系 2 相关 2（Nfe2l2 或 Nrf2）是一种转录因子，可在应激过程中通过维持稳态氧化还原状态来保护细胞。Nrf2 的组成型表达（CaNrf2-TG）先前被证明随着时间的推移对心脏具有病理性。我们提出了一个假设，即全长 Nrf2（mNrf2-TG）的心脏特异性表达将适度增加基础抗氧化防御，引发有利于还原性的环境，从而导致适应性心脏重塑。在 7-8 个月大时，使用转基因（TG）和非转基因（NTG）小鼠来分析心肌转录组、结构和功能。进行了下一代测序（NGS）以进行 RNA 分析，并通过 qPCR 验证 NGS 数据、心肌氧化还原水平和成像（超声心动图）。转录组分析显示，在鉴定出的 14665 个 mRNAs 中，有 680 个在 TG 心脏中表达不同（DEG）。在 680 个 DEG 中，有 429 个上调，251 个显著下调（FC > 2.0，p < 0.05）。基因集富集分析显示，改变最明显的途径是（a）Nrf2 信号，（b）谷胱甘肽代谢和（c）ROS 清除。对心脏中谷胱甘肽氧化还原状态的比较分析表明，还原性条件与超还原性条件之间存在显著差异（mNrf2-TG 和 CaNrf2-TG 与 NTG 相比，233 ± 36.7 和 380 ± 68.7 与 139 ± 8.6 µM/mg 蛋白）。与 CaNrf2-TG 相比，mNrf2-TG 中涉及胎儿发育、肥大、细胞骨架重排、组蛋白去乙酰化酶（HDAC）和 GATA 转录因子的基因适度增加。非侵入性超声心动图分析显示，mNrf2-TG 的收缩功能（射血分数）增加，表明适应性重塑，而 CaNrf2-TG 小鼠经历超还原性应激时则为病理性重塑，导致存活率降低（60 周时为 40%）。过量 Nrf2 驱动的抗氧化转录组的作用揭示了心肌中的还原性条件导致适应性心脏重塑。虽然用过量抗氧化剂预先调节心肌氧化还原（即还原性状态）可能有助于抵抗氧化应激，但心肌中的慢性还原性环境可能会将适应性转化为病理性重塑。
