Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada.
Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada.
Biochim Biophys Acta Gen Subj. 2019 Nov;1863(11):129400. doi: 10.1016/j.bbagen.2019.07.009. Epub 2019 Jul 22.
Chronic activation of glial cells contributes to neurodegenerative diseases. Cytochrome c (CytC) is a soluble mitochondrial protein that can act as a damage-associated molecular pattern (DAMP) when released into the extracellular space from damaged cells. CytC causes immune activation of microglia in a toll-like receptor (TLR) 4-dependent manner. The effects of extracellular CytC on astrocytes are unknown. Astrocytes, which are the most abundant glial cell type in the brain, express TLR 4 and secrete inflammatory mediators; therefore, we hypothesized that extracellular CytC can interact with the TLR 4 of astrocytes inducing their release of inflammatory molecules and cytotoxins.
Experiments were conducted using primary human astrocytes, U118 MG human astrocytic cells, BV-2 murine microglia, and SH-SY5Y human neuronal cells.
Extracellularly applied CytC increased the secretion of interleukin (IL)-1β, granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-12 p70 by cultured primary human astrocytes. Anti-TLR 4 antibodies blocked the CytC-induced secretion of IL-1β and GM-CSF by astrocytes. Supernatants from CytC-activated astrocytes were toxic to human SH-SY5Y neuronal cells. We also demonstrated CytC release from damaged glial cells by measuring CytC in the supernatants of BV-2 microglia after their exposure to cytotoxic concentrations of staurosporine, amyloid-β peptides (Aβ42) and tumor necrosis factor-α.
CytC can be released into the extracellular space from damaged glial cells causing immune activation of astrocytes in a TLR 4-dependent manner.
Astrocyte activation by CytC may contribute to neuroinflammation and neuronal death in neurodegenerative diseases. Astrocyte TLR 4 could be a potential therapeutic target in these diseases.
神经胶质细胞的慢性激活会导致神经退行性疾病。细胞色素 c（CytC）是一种可溶性线粒体蛋白，当从受损细胞释放到细胞外空间时，它可以作为一种损伤相关分子模式（DAMP）。CytC 通过 Toll 样受体（TLR）4 依赖性方式引起小胶质细胞的免疫激活。细胞外 CytC 对星形胶质细胞的影响尚不清楚。星形胶质细胞是大脑中最丰富的神经胶质细胞类型，表达 TLR 4 并分泌炎症介质；因此，我们假设细胞外 CytC 可以与星形胶质细胞的 TLR 4 相互作用，诱导其释放炎症分子和细胞毒素。
使用原代人星形胶质细胞、U118 MG 人星形胶质细胞、BV-2 鼠小胶质细胞和 SH-SY5Y 人神经元细胞进行实验。
细胞外 CytC 增加了培养的原代人星形胶质细胞分泌白细胞介素（IL）-1β、粒细胞-巨噬细胞集落刺激因子（GM-CSF）和 IL-12 p70。抗 TLR 4 抗体阻断了 CytC 诱导的星形胶质细胞分泌 IL-1β 和 GM-CSF。来自 CytC 激活的星形胶质细胞的上清液对人 SH-SY5Y 神经元细胞有毒。我们还通过测量暴露于细胞毒性浓度的星形胶质细胞毒性因子（如星形胶质细胞）后 BV-2 小胶质细胞上清液中的 CytC 来证明 CytC 从受损的胶质细胞中释放。细胞毒素-α、淀粉样β肽（Aβ42）。
细胞外 CytC 可从受损的神经胶质细胞中释放到细胞外空间，以 TLR 4 依赖性方式引起星形胶质细胞的免疫激活。
CytC 对星形胶质细胞的激活可能导致神经退行性疾病中的神经炎症和神经元死亡。星形胶质细胞 TLR 4 可能是这些疾病的潜在治疗靶点。
