Center for Biomedical Imaging, EPFL, Lausanne, Switzerland; Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland.
Center for Biomedical Imaging, EPFL, Lausanne, Switzerland; Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland.
Free Radic Biol Med. 2022 Jan;178:295-307. doi: 10.1016/j.freeradbiomed.2021.12.011. Epub 2021 Dec 8.
The role and coexistence of oxidative stress (OS) and inflammation in type C hepatic encephalopathy (C HE) is a subject of intense debate. Under normal conditions the physiological levels of intracellular reactive oxygen species are controlled by the counteracting antioxidant response to maintain redox homeostasis. Our previous in-vivoH-MRS studies revealed the longitudinal impairment of the antioxidant system (ascorbate) in a bile-duct ligation (BDL) rat model of type C HE. Therefore, the aim of this work was to examine the course of central nervous system (CNS) OS and systemic OS, as well as to check for their co-existence with inflammation in the BDL rat model of type C HE. To this end, we implemented a multidisciplinary approach, including ex-vivo and in-vitro electron paramagnetic resonance spectroscopy (EPR) spin-trapping, which was combined with UV-Vis spectroscopy, and histological assessments. We hypothesized that OS and inflammation act synergistically in the pathophysiology of type C HE. Our findings point to an increased CNS- and systemic-OS and inflammation over the course of type C HE progression. In particular, an increase in the CNS OS was observed as early as 2-weeks post-BDL, while the systemic OS became significant at week 6 post-BDL. The CNS EPR measurements were further validated by a substantial accumulation of 8-Oxo-2'-deoxyguanosine (Oxo-8-dG), a marker of oxidative DNA/RNA modifications on immunohistochemistry (IHC). Using IHC, we also detected increased synthesis of antioxidants, glutathione peroxidase 1 (GPX-1) and superoxide dismutases (i.e.Cu/ZnSOD (SOD1) and MnSOD (SOD2)), along with proinflammatory cytokine interleukin-6 (IL-6) in the brains of BDL rats. The presence of systemic inflammation was observed already at 2-weeks post-surgery. Thus, these results suggest that CNS OS is an early event in type C HE rat model, which seems to precede systemic OS. Finally, our results suggest that the increase in CNS OS is due to enhanced formation of intra- and extra-cellular ROS rather than due to reduced antioxidant capacity, and that OS in parallel with inflammation plays a significant role in type C HE.
氧化应激 (OS) 和炎症在 C 型肝性脑病 (C HE) 中的作用和共存是一个激烈争论的话题。在正常情况下，细胞内活性氧的生理水平通过抗氧化剂反应来控制，以维持氧化还原平衡。我们之前的体内 H-MRS 研究揭示了在 C 型 HE 的胆管结扎 (BDL) 大鼠模型中抗氧化系统 (抗坏血酸) 的纵向损伤。因此，这项工作的目的是检查中枢神经系统 (CNS) OS 和全身 OS 的过程，并检查它们在 C 型 HE 的 BDL 大鼠模型中与炎症的共存。为此，我们采用了多学科方法，包括离体和体内电子顺磁共振波谱 (EPR) 自旋陷阱，结合紫外可见光谱和组织学评估。我们假设 OS 和炎症在 C 型 HE 的病理生理学中协同作用。我们的研究结果表明，在 C 型 HE 进展过程中，CNS 和全身 OS 以及炎症均增加。特别是，在 BDL 后 2 周即可观察到 CNS OS 增加，而在 BDL 后 6 周时，全身 OS 变得显著。CNS EPR 测量结果通过免疫组织化学 (IHC) 中氧化 DNA/RNA 修饰的标志物 8-氧-2'-脱氧鸟苷 (Oxo-8-dG) 的大量积累得到进一步验证。通过 IHC，我们还检测到 BDL 大鼠大脑中抗氧化剂谷胱甘肽过氧化物酶 1 (GPX-1) 和超氧化物歧化酶 (即 Cu/ZnSOD (SOD1) 和 MnSOD (SOD2)) 的合成增加，以及促炎细胞因子白细胞介素-6 (IL-6) 的合成增加。在手术后 2 周即可观察到全身炎症的存在。因此，这些结果表明，CNS OS 是 C 型 HE 大鼠模型中的早期事件，似乎先于全身 OS。最后，我们的结果表明，CNS OS 的增加是由于细胞内和细胞外 ROS 形成增加而不是由于抗氧化能力降低所致，并且 OS 与炎症一起在 C 型 HE 中发挥重要作用。
