bims-mideyd 2024-12-29 papers

Stem Cells Transl Med. 2024 Dec 27. pii: szae097. [Epub ahead of print]

iPSC-derived retinal pigment epithelium: an in vitro platform to reproduce key cellular phenotypes and pathophysiology of retinal degenerative diseases.

Huirong Li, Ruchi Sharma, Kapil Bharti.

Retinal pigment epithelium (RPE) atrophy is a significant cause of human blindness worldwide, occurring in polygenic diseases such as age-related macular degeneration (AMD) and monogenic diseases such as Stargardt diseases (STGD1) and late-onset retinal degeneration (L-ORD). The patient-induced pluripotent stem cells (iPSCs)-derived RPE (iRPE) model exhibits many advantages in understanding the cellular basis of pathological mechanisms of RPE atrophy. The iRPE model is based on iPSC-derived functionally mature and polarized RPE cells that reproduce several features of native RPE cells, such as phagocytosis of photoreceptor outer segments (POS) and replenishment of visual pigment. When derived from patients, iRPE are able to recapitulate critical cellular phenotypes of retinal degenerative diseases, such as the drusen-like sub-RPE deposits in the L-ORD and AMD models; lipid droplets and cholesterol accumulation in the STGD1 and AMD models. The iRPE model has helped discover the unexpected role of RPE in understanding retinal degenerative diseases, such as a cell-autonomous function of ABCA4 in STGD1. The iRPE model has helped uncover the pathological mechanism of retinal degenerative diseases, including the roles of alternate complement cascades and oxidative stress in AMD pathophysiology, abnormal POS processing in STGD1 and L-ORD, and its association with lipid accumulation. These studies have helped better understand-the role of RPE in retinal degenerative diseases, and molecular mechanisms underlying RPE atrophy, and have provided a basis to discover therapeutics to target RPE-associated diseases.

Keywords: RPE atrophy; cell disease model; iPSCs-derived RPE; retinal degenerative diseases

DOI: https://doi.org/10.1093/stcltm/szae097

Exp Eye Res. 2024 Dec 22. pii: S0014-4835(24)00441-X. [Epub ahead of print]251 110219

How crosstalk between mitochondria, lysosomes, and other organelles can prevent or promote dry age-related macular degeneration.

Aparna Lakkaraju, Patricia Boya, Marie Csete, Deborah A Ferrington, James B Hurley, Alfredo A Sadun, Peng Shang, Ruchi Sharma, Debasish Sinha, Marius Ueffing, Susan E Brockerhoff.

Organelles such as mitochondria, lysosomes, peroxisomes, and the endoplasmic reticulum form highly dynamic cellular networks and exchange information through sites of physical contact. While each organelle performs unique functions, this inter-organelle crosstalk helps maintain cell homeostasis. Age-related macular degeneration (AMD) is a devastating blinding disease strongly associated with mitochondrial dysfunction, oxidative stress, and decreased clearance of cellular debris in the retinal pigment epithelium (RPE). However, how these occur, and how they relate to organelle function both with the RPE and potentially the photoreceptors are fundamental, unresolved questions in AMD biology. Here, we report the discussions of the "Mitochondria, Lysosomes, and other Organelle Interactions" task group of the 2024 Ryan Initiative for Macular Research (RIMR). Our group focused on understanding the interplay between cellular organelles in maintaining homeostasis in the RPE and photoreceptors, how this could be derailed to promote AMD, and identifying where these pathways could potentially be targeted therapeutically.

Keywords: Bioenergetics; Oxidative stress; Photoreceptors; Retinal pigment epithelium; Therapeutics

DOI: https://doi.org/10.1016/j.exer.2024.110219

Int J Biol Macromol. 2024 Dec 22. pii: S0141-8130(24)09888-X. [Epub ahead of print] 139077

The effect of molecular chaperone mediated autophagy on ApoE expression in retinal pigment epithelial cells: Molecular structure and protein action mechanism.

Yifan Zhong, Yun Zhou, Zuoqian Jing, Xianjie Liu, Kaibo Yang, Guijie Ren, Haijie Chen, Siyu Jiang, Xue Shen, Xinying Du, Hongzhe Liu, Yunping Pan, Xiaoli Ma.

Chaperone mediated autophagy (CMA) represents a specialized mechanism of lysosomal protein breakdown, playing a crucial role as a metabolic pathway that helps to regulate and sustain cellular and systemic physiological equilibrium. Within the CMA process, proteins that contain sequences similar to KFERQ are specifically identified by the heat shock cognate protein 70. These proteins are then chaperoned to the lysosomes for subsequent degradation, a process facilitated by the lysosome associated membrane protein 2A. This particular research employed bioinformatics techniques to systematically screen for potential substrates of CMA. ApoE has a KFERQ like motif, which may be a substrate for CMA. Under conditions of starvation, hypoxia, H2O2, PA, and NaIO3, the expression of the rate limiting factor LAMP2A in CMA and ApoE increased significantly (P < 0.05). Under conditions of NaIO3, the expression of CMA related gene mRNA increased significantly (P < 0.05). When we use lysosomal blocker CQ to inhibit CMA activity, the expression level of ApoE in retinal pigment epithelial cells increased, and the difference was statistically significant (P < 0.05). When we inhibit CMA, the accumulation of ApoE in retinal pigment epithelial cells increases and cell viability decreases. When we activate CMA, the accumulation of ApoE decreases and cell viability increases. In retinal pigment epithelial cells, the drusen associated protein ApoE can be degraded through the CMA pathway.

Keywords: Age related macular degeneration; ApoE; LAMP2A; Molecular chaperone autophagy

DOI: https://doi.org/10.1016/j.ijbiomac.2024.139077

Diabetes. 2024 Dec 23. pii: db240040. [Epub ahead of print]

Extracellular Mitochondria Exacerbate Retinal Pigment Epithelium Degeneration in Diabetic Retinopathy.

Keiichi Nishikawa, Tomoaki Murakami, Miyo Yoshida, Noriko Terada, Kenji Ishihara, Yuki Mori, Shinji Ito, Akitaka Tsujikawa.

Advances in fundus imaging are revealing disruptions in the neurovascular unit in diabetic retinopathy (DR). In the era of anti-VEGF treatment, a thorough characterization of neurodegeneration is imperative until DR patients are sufficiently cured. Here we demonstrate that extracellular mitochondria exacerbate retinal pigment epithelium (RPE) degeneration and inflammation in DR. Extracellular mitochondria increased in the vitreous of DR patients and were associated with visual impairment but not with proliferative diabetic retinopathy or diabetic macular edema. Animal experiments demonstrated detrimental effects of extracellular mitochondria on RPE and photoreceptors. Lysosomal cell death induced by extracellular mitochondria in RPE cells required mitochondrial DNA but not its pattern recognition receptors. Furthermore, biochemical screening identified candidates for DNA receptors. Among them, DNA-dependent protein kinase was necessary for extracellular mitochondria-induced cell death in both in vitro and in vivo experiments. Extracellular mitochondria further induced IL-1β and TNF-α expression in RPE cells in a Toll-like receptor 9 dependent manner. RNA sequencing suggested that extracellular mitochondria exacerbate inflammation by promoting the proliferation and migration of macrophages, at least in part. In summary, extracellular mitochondria are designated as a novel exacerbating factor of RPE degeneration in DR.

DOI: https://doi.org/10.2337/db24-0040