bims-mideyd 2024-03-24 papers

Issue of 2024‒03‒24
four papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Biol Pharm Bull. 2024 ;47(3): 641-651

Oxidized-LDL Induces Metabolic Dysfunction in Retinal Pigment Epithelial Cells.

Manami Tomomatsu, Naoto Imamura, Hoshimi Izumi, Masatsugu Watanabe, Masataka Ikeda, Tomomi Ide, Shohei Uchinomiya, Akio Ojida, Mirinthorn Jutanom, Kazushi Morimoto, Ken-Ichi Yamada.

Recently, mitochondrial dysfunction has gained attention as a causative factor in the pathogenesis and progression of age-related macular degeneration (AMD). Mitochondrial damage plays a key role in metabolism and disrupts the balance of intracellular metabolic pathways, such as oxidative phosphorylation (OXPHOS) and glycolysis. In this study, we focused on oxidized low-density lipoprotein (ox-LDL), a major constituent of drusen that accumulates in the retina of patients with AMD, and investigated whether it could be a causative factor for metabolic alterations in retinal pigment epithelial (RPE) cells. We found that prolonged exposure to ox-LDL induced changes in fatty acid β-oxidation (FAO), OXPHOS, and glycolytic activity and increased the mitochondrial reactive oxygen species production in RPE cells. Notably, the effects on metabolic alterations varied with the concentration and duration of ox-LDL treatment. In addition, we addressed the limitations of using ARPE-19 cells for retinal disease research by highlighting their lower barrier function and FAO activity compared to those of induced pluripotent stem cell-derived RPE cells. Our findings can aid in the elucidation of mechanisms underlying the metabolic alterations in AMD.

Keywords: age-related macular degeneration; metabolic change; mitochondrial dysfunction; oxidized low-density lipoprotein (ox-LDL); retinal pigment epithelium

DOI: https://doi.org/10.1248/bpb.b23-00849

bioRxiv. 2024 Mar 04. pii: 2024.03.04.583371. [Epub ahead of print]

Activating soluble adenylyl cyclase protects mitochondria, rescues retinal ganglion cells, and ameliorates visual dysfunction caused by oxidative stress.

Tonking Bastola, Guy A Perkins, Viet Anh Nguyen Huu, Saeyeon Ju, Keun-Young Kim, Ziyao Shen, Dorota Skowronska-Krawczyk, Robert N Weinreb, Won-Kyu Ju.

Oxidative stress is a key factor causing mitochondrial dysfunction and retinal ganglion cell (RGC) death in glaucomatous neurodegeneration. The cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway is involved in mitochondrial protection, promoting RGC survival. Soluble adenylyl cyclase (sAC) is one of the key regulators of the cAMP/PKA signaling pathway. However, the precise molecular mechanisms underlying the sAC-mediated signaling pathway and mitochondrial protection in RGCs that counter oxidative stress are not well characterized. Here, we demonstrate that sAC plays a critical role in protecting RGC mitochondria from oxidative stress. Using mouse models of oxidative stress, we found that activating sAC protected RGCs, blocked AMP-activated protein kinase activation, inhibited glial activation, and improved visual function. Moreover, we found that this is the result of preserving mitochondrial dynamics (fusion and fission), promoting mitochondrial bioenergetics and biogenesis, and preventing metabolic stress and apoptotic cell death in a paraquat oxidative stress model. Notably, sAC activation ameliorated mitochondrial dysfunction in RGCs by enhancing mitochondrial biogenesis, preserving mitochondrial structure, and increasing ATP production in oxidatively stressed RGCs. These findings suggest that activating sAC enhances the mitochondrial structure and function in RGCs to counter oxidative stress, consequently promoting RGC protection. We propose that modulation of the sAC-mediated signaling pathway has therapeutic potential acting on RGC mitochondria for treating glaucoma and other retinal diseases.

DOI: https://doi.org/10.1101/2024.03.04.583371

Transl Vis Sci Technol. 2024 Mar 01. 13(3): 19

Sirt3 Protects Retinal Pigment Epithelial Cells From High Glucose-Induced Injury by Promoting Mitophagy Through the AMPK/mTOR/ULK1 Pathway.

Wei Yang, Chen Qiu, Hongbin Lv, Zhiru Zhang, Tianyu Yao, Li Huang, Guihong Wu, Xueqin Zhang, Jie Chen, Yue He.

Purpose: The regulation of mitophagy by Sirt3 has rarely been studied in ocular diseases. In the present study, we determined the effects of Sirt3 on AMPK/mTOR/ULK1 signaling pathway-mediated mitophagy in retinal pigment epithelial (RPE) cells in a high glucose environment.Methods: The mRNA expression levels of Sirt3, AMPK, mTOR, ULK1, and LC3B in RPE cells under varying glucose conditions were measured by real-time polymerase chain reaction (RT-PCR). The expressions of Sirt3, mitophagy protein, and AMPK/mTOR/ULK1 signaling pathway-related proteins were detected by Western blotting. Lentivirus (LV) transfection mediated the stable overexpression of Sirt3 in cell lines. The experimental groups were NG (5.5 mM glucose), hypertonic, HG (30 mM glucose), HG + LV-GFP, and HG + LV-Sirt3. Western blotting was performed to detect the expressions of mitophagy proteins and AMPK/mTOR/ULK1-related proteins in a high glucose environment during the overexpression of Sirt3. Reactive oxygen species (ROS) production in a high glucose environment was measured by DCFH-DA staining. Mitophagy was detected by labeling mitochondria and lysosomes with MitoTracker and LysoTracker probes, respectively. Apoptosis was detected by flow cytometry.
Results: Sirt3 expression was reduced in the high glucose group, inhibiting the AMPK/mTOR/ULK1 pathway, with diminished mitophagy and increased intracellular ROS production. The overexpression of Sirt3, increased expression of p-AMPK/AMPK and p-ULK1/ULK1, and decreased expression of p-mTOR/mTOR inhibited cell apoptosis and enhanced mitophagy.
Conclusions: Sirt3 protected RPE cells from high glucose-induced injury by activating the AMPK/mTOR/ULK1 signaling pathway.
Translational Relevance: By identifying new targets of action, we aimed to establish effective therapeutic targets for diabetic retinopathy treatment.

DOI: https://doi.org/10.1167/tvst.13.3.19

J Ocul Pharmacol Ther. 2024 Mar 22.

Inhibition of Connective Tissue Growth Factor Expression in Adult Retinal Pigment Epithelial-19 Cells by Blocking Yes-Associated Protein/Transcriptional Coactivator with PDZ-Binding Motif Activity.

Yoko Murakami, Toshiyasu Imaizumi, Kouhei Hashizume, Yu Tezuka, Yusuke Oku, Naoyuki Nishiya, Atsushi Sanbe, Daijiro Kurosaka.

Purpose: To investigate the effect of yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) on connective tissue growth factor (CTGF) expression in adult retinal pigment epithelial (ARPE)-19 cells. We also studied the inhibitory effect of K-975, a new pan-transcriptional enhanced associate domain (TEAD) inhibitor, and luteolin, a plant-derived flavonoid on CTGF expression. Methods: ARPE-19 cells were transfected with either YAP or TAZ overexpression plasmid or treated with transforming growth factor (TGF)-β2. The cells were cultured either with or without K-975 or luteolin. The expression of YAP, TAZ, and CTGF was examined using real-time PCR. Results: ARPE-19 cells overexpressing YAP or TAZ exhibited significantly increased CTGF expression. This increase was attenuated by K-975 or luteolin alone. TGF-β2 treatment significantly raised the expression of not just YAP and TAZ, but also CTGF in ARPE-19 cells. TGF-β2 treatment-enhanced CTGF expression was considerably lowered by the addition of K-975 or luteolin. Conclusions: Overexpression of YAP or TAZ and treatment with TGF-β2 led to an increase in the expression of CTGF in ARPE-19 cells. These increases were attenuated by treatment with K-975 and luteolin. These findings suggest that YAP and TAZ may be related to the expression of CTGF in ARPE-19 cells and that K-975 and luteolin can be explored as potential therapeutic agents for preventing CTGF production in vitreoretinal fibrosis.

Keywords: K-975; TAZ; YAP; connective tissue growth factor; luteolin; retinal pigment epithelial cells

DOI: https://doi.org/10.1089/jop.2023.0141