L-serine restored lysosomal failure in cells derived from patients with BPAN reducing iron accumulation with eliminating lipofuscin

Hye Eun Lee; Minkyo Jung; Kiju Choi; Jae Hyuck Jang; Su-Kyeong Hwang; Sehyun Chae; Jae-Hyeok Lee; Ji Young Mun

doi:10.1016/j.freeradbiomed.2024.05.017

L-serine restored lysosomal failure in cells derived from patients with BPAN reducing iron accumulation with eliminating lipofuscin

Free Radic Biol Med. 2024 May 11:S0891-5849(24)00452-0. doi: 10.1016/j.freeradbiomed.2024.05.017. Online ahead of print.

Authors

Hye Eun Lee¹, Minkyo Jung², Kiju Choi³, Jae Hyuck Jang⁴, Su-Kyeong Hwang⁵, Sehyun Chae⁶, Jae-Hyeok Lee⁷, Ji Young Mun⁸

Affiliations

¹ Neural circuit research group, Korea Brain Research Institute, Daegu, South Korea; School of Medicine, Kyungpook National University, Daegu, South Korea.
² Neural circuit research group, Korea Brain Research Institute, Daegu, South Korea.
³ Division of Structural Biology, Baobab AiBIO, Incheon, South Korea.
⁴ Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, South Korea; Electron Microscopy Group for Materials Science, Korea Basic Science Institute, Daejeon, South Korea.
⁵ Department of Pediatrics, School of Medicine, Kyungpook National University, Daegu, South Korea; Astrogen Inc., Techno-Building 313, Kyungpook National University, Daegu 41566, South Korea.
⁶ Neurovascular Unit Research Group, Korea Brain Research Institute, Daegu 41068, Korea. Electronic address: hbchoi@kbri.re.kr.
⁷ Department of Neurology, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan 50612, Korea; Medical Research Institute, Pusan National University School of Medicine, Yangsan 50612, South Korea. Electronic address: jhlee.neuro@pusan.ac.kr.
⁸ Neural circuit research group, Korea Brain Research Institute, Daegu, South Korea. Electronic address: mjy1026@gmail.com.

PMID: 38740102
DOI: 10.1016/j.freeradbiomed.2024.05.017

Abstract

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.

Keywords: BPAN; iron; lipid; lysosome; oxidative stress.