Neural Circuit Research Group, Korea Brain Research Institute, Daegu, South Korea; School of Medicine, Kyungpook National University, Daegu, South Korea.
Neural Circuit Research Group, Korea Brain Research Institute, Daegu, South Korea.
Free Radic Biol Med. 2024 Aug 20;221:273-282. doi: 10.1016/j.freeradbiomed.2024.05.017. Epub 2024 May 11.
Defective mitochondria and autophagy, as well as accumulation of lipid and iron in WDR45 mutant fibroblasts, is related to beta-propeller protein-associated neurodegeneration (BPAN). In this study, we found that enlarged lysosomes in cells derived from patients with BPAN had low enzyme activity, and most of the enlarged lysosomes had an accumulation of iron and oxidized lipid. Cryo-electron tomography revealed elongated lipid accumulation, and spectrometry-based elemental analysis showed that lysosomal iron and oxygen accumulation superimposed with lipid aggregates. Lysosomal lipid aggregates superimposed with autofluorescence as free radical generator, lipofuscin. To eliminate free radical stress by iron accumulation in cells derived from patients with BPAN, we investigated the effects of the iron chelator, 2,2'-bipyridine (bipyridyl, BIP). To study whether the defects in patient-derived cells can be rescued by an iron chelator BIP, we tested whether the level of iron and reactive oxygen species (ROS) in the cells and genes related to oxidative stress were rescued BIP treatment. Although BIP treatment decreased some iron accumulation in the cytoplasm and mitochondria, the accumulation of iron in the lysosomes and levels of cellular ROS were unaffected. In addition, the change of specific RNA levels related to free radical stress in patient fibroblasts was not rescued by BIP. To alleviate free radical stress, we investigated whether l-serine can regulate abnormal structures in cells derived from patients with BPAN through the regulation of free radical stress. l-serine treatment alleviated increase of enlarged lysosomes and iron accumulation and rescued impaired lysosomal activity by reducing oxidized lipid accumulation in the lysosomes of the cells. Lamellated lipids in the lysosomes of the cells were identified as lipofuscin through correlative light and electron microscopy, and l-serine treatment reduced the increase of lipofuscin. These data suggest that l-serine reduces oxidative stress-mediated lysosomal lipid oxidation and iron accumulation by rescuing lysosomal activity.
缺陷的线粒体和自噬，以及脂质和铁在 WDR45 突变成纤维细胞中的积累，与β-三叶蛋白相关的神经退行性变（BPAN）有关。在这项研究中，我们发现 BPAN 患者来源的细胞中的扩大的溶酶体酶活性较低，并且大多数扩大的溶酶体积累了铁和氧化脂质。冷冻电子断层扫描显示伸长的脂质积累，基于光谱的元素分析表明溶酶体铁和氧积累与脂质聚集体重叠。溶酶体脂质聚集体与自由基生成剂脂褐素的自体荧光重叠。为了消除 BPAN 患者来源的细胞中铁积累引起的自由基应激，我们研究了铁螯合剂 2,2'-联吡啶（bipyridyl，BIP）的作用。为了研究铁螯合剂 BIP 是否可以挽救患者来源细胞的缺陷，我们测试了 BIP 处理是否可以挽救细胞中铁和活性氧物种（ROS）的水平以及与氧化应激相关的基因。尽管 BIP 处理降低了细胞质和线粒体中铁的一些积累，但溶酶体中铁的积累和细胞 ROS 水平不受影响。此外，BIP 处理不能挽救患者成纤维细胞中与自由基应激相关的特定 RNA 水平的变化。为了减轻自由基应激，我们研究了 l-丝氨酸是否可以通过调节自由基应激来调节患者来源的细胞中的异常结构。l-丝氨酸处理通过减少溶酶体中氧化脂质的积累，减轻了细胞中溶酶体的扩大和铁积累的增加，并挽救了受损的溶酶体活性。通过相关的光镜和电镜，细胞溶酶体中的层状脂质被鉴定为脂褐素，l-丝氨酸处理减少了脂褐素的增加。这些数据表明，l-丝氨酸通过挽救溶酶体活性来减少氧化应激介导的溶酶体脂质氧化和铁积累。
