bims-mideyd 2023-06-04 papers

Issue of 2023‒06‒04
six papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Front Neurosci. 2023 ;17 1198343

Mitochondria-associated endoplasmic reticulum membranes (MAMs) and their role in glaucomatous retinal ganglion cell degeneration-a mini review.

Jennifer H Pham, Dorota L Stankowska.

Glaucoma is a leading cause of blindness worldwide, commonly associated with elevated intraocular pressure (IOP), leading to degeneration of the optic nerve and death of retinal ganglion cells, the output neurons in the eye. In recent years, many studies have implicated mitochondrial dysfunction as a crucial player in glaucomatous neurodegeneration. Mitochondrial function has been an increasingly researched topic in glaucoma, given its vital role in bioenergetics and propagation of action potentials. One of the most metabolically active tissues in the body characterized by high oxygen consumption is the retina, particularly the retinal ganglion cells (RGCs). RGCs, which have long axons that extend from the eyes to the brain, rely heavily on the energy generated by oxidative phosphorylation for signal transduction, rendering them more vulnerable to oxidative damage. In various glaucoma models, mitochondrial dysfunction and stress from protein aggregates in the endoplasmic reticulum (ER) have been observed in the RGCs. However, it has been shown that the two organelles are connected through a network called mitochondria-associated ER membranes (MAMs); hence this crosstalk in a pathophysiological condition such as glaucoma should be evaluated. Here, we review the current literature suggestive of mitochondrial and ER stress related to glaucoma, indicating potential cross-signaling and the potential roles of MAMs.

Keywords: ER stress; MAMs; endoplasmic reticulum; glaucoma; inflammation; mitochondria; oxidative stress; retinal ganglion cells

DOI: https://doi.org/10.3389/fnins.2023.1198343

FASEB J. 2023 Jul;37(7): e23002

Investigating the effects of 7-ketocholesterol on retinal pigment epithelium bioenergetics.

Sanchareeka Dey, Timothy Catchpole, Alison Takacs, Karl G Csaky.

Age-related macular degeneration (AMD) is associated with formation of drusen, clusters of lipids, and oxidized lipid products under the retinal pigment epithelium (RPE). 7-Ketocholesterol (7KC) is a form of oxidized cholesterol present in drusen and is hypothesized to play a role in AMD pathogenesis. The association of 7KC with cellular toxicity and inflammation, key elements of AMD pathology, has been demonstrated. However, the effects of 7KC on altering RPE bioenergetics, a potentially important pathologic process in AMD, are unclear. Herein, we describe the effects of non-lethal doses of 7KC on the bioenergetics and phenotype of RPE cells in culture. Metabolic analysis demonstrated a significant dose-dependent increase in total ATP production rates that was driven primarily by an increase in glycolysis. The increase in glycolysis was accompanied by an increase in glucose uptake and increased expression of hexokinase 1. Increased levels of Translocase of Outer Mitochondrial Membrane 20 and NADH:Ubiquinone Oxidoreductase Core Subunit S1, Succinate dehydrogenase, Ubiquinol-Cytochrome C Reductase Core Protein 2, Cytochrome C Oxidase II, and ATP synthase subunit beta, proteins involved in oxidative phosphorylation (OXPHOS), were also seen. However, specific electron transport chain activity remained unchanged. 7KC-treated cells also demonstrated a change in cellular morphology with decreased expression of epithelial markers. In summary, 7KC has significant effects on the bioenergetics and morphology of RPE cells reflective of findings seen in clinical AMD.

Keywords: 7-ketocholesterol; age related macular degeneration; cellular bioenergetics; retinal pigment epithelium

DOI: https://doi.org/10.1096/fj.202300101R

Exp Eye Res. 2023 May 31. pii: S0014-4835(23)00117-3. [Epub ahead of print] 109496

Acteoside inhibits high glucose-induced oxidative stress injury in RPE cells and the outer retina through the Keap1/Nrf2/ARE pathway.

Jingfei Yang, Zhijuan Hua, Zhikun Zheng, Xuan Ma, Liang Zhu, Yan Li.

Diabetes retinopathy (DR) is one of the most common microvascular complications of diabetes. Retinal pigment epithelial (RPE) cells exposed to a high glucose environment experience a series of functional damages, which is an important factor in promoting the progression of DR. Acteoside (ACT) has strong antioxidant and anti-apoptotic properties, but the mechanism of ACT in DR is not completely clear. Therefore, the purpose of the present study was to explore whether ACT inhibits the damage to RPE cells in a high glucose environment through antioxidative effects to alleviate the DR process. The DR in vitro cell model was constructed by treating RPE cells with high glucose, and the DR in vivo animal model was constructed by injecting streptozotocin (STZ) into the peritoneal cavity of mice to induce diabetes. The proliferation and apoptosis of RPE cells were detected by CCK-8 and flow cytometry assays, respectively. The expression changes in Nrf2, Keap1, NQO1 and HO-1 were evaluated by qRT‒PCR, Western blot and immunohistochemistry analyses. The MDA, SOD, GSH-Px and T-AOC contents were detected by kits. The changes in ROS and nuclear translocation of Nrf2 were observed by immunofluorescence assays. HE staining was used to measure the thickness of the outer nuclear layer (ONL) of the retina, and TUNEL staining was used to detect the number of apoptotic cells in the retinas of mice. In the present study, ACT effectively ameliorated outer retina damage in diabetic mice. In high glucose (HG)-induced RPE cells, ACT treatment had the following effects: improved proliferation, decreased apoptosis, inhibited Keap1 expression, promoted the nuclear translocation and expression of Nrf2, upregulated NQO1 and HO-1 (the target genes of Nrf2) expression, decreased ROS concentration, and increased the levels of the SOD, GSH-Px and T-AOC antioxidant indicators. However, knockdown of Nrf2 reversed the above phenomena, which indicated that the protective function of ACT in HG-induced RPE cells are closely related to Nrf2. In summary, the present study demonstrated that HG-induced oxidative stress injury is inhibited by ACT in RPE cells and the outer retina through the Keap1/Nrf2/ARE pathway.

Keywords: Acteoside; Diabetic retinopathy; Keap1-Nrf2-ARE pathway; Oxidative stress; Retinal pigment epithelial cells

DOI: https://doi.org/10.1016/j.exer.2023.109496

Life Sci. 2023 May 30. pii: S0024-3205(23)00449-6. [Epub ahead of print] 121815

The alleviation effects of n-butylidenephthalide on apoptosis, senescence, and tight junction impairment of retinal pigment epithelium by activating Nrf-2/HO-1 signaling pathway in early diabetic retinopathy.

Ya-Chih Huang, Bo-Chun Chen, Kai-Fu Chang, Ming-Chang Hsieh, Gwo-Tarng Sheu, Chih-Yen Hsiao, Nu-Man Tsai.

AIMS: Diabetic retinopathy (DR) is a common complication of diabetes that causes visual impairment and blindness in adults. This study aimed to explore the protective effects of n-Butylidenephthalide (BP) on hyperglycemia-treated RPE in vitro and in vivo.MAIN METHODS: C57BL/6 mice were injected with STZ by intraperitoneal to induce early DR and orally administrated with 2 mg/kg BP every day for twelve weeks. Body weight and blood glucose were measured once a week. The level of retina damage was determined by TUNEL assay and H&E staining. The outer blood-retinal barrier integrity and RPE65 expression of retina were evaluated by immunofluorescence. In in vitro study, ARPE-19 cells were long-term cultured with high glucose and BP for 8 days and studied for cell survival, tight junction integrity, RPE65 expression, angiogenic factors, mitochondria membrane potential (MMP), and ROS by MTT assay, Western blot, β-galactosidase staining, immunofluorescence, JC-1, or DCFH-DA.
KEY FINDINGS: The results indicate that BP suppressed the hyperglycemic effect and maintained retina anatomy normalization, as well as protected RPE cell survival, tight junction integrity, and RPE65 expression in vitro and in vivo. In vitro results showed BP stimulated high glucose-treated ARPE-19 cell proliferation and suppressed senescence via ERK pathway. Numerous ROS production and MMP imbalance were prevented by BP through Nrf-2/HO-1 pathway. BP inhibited high glucose-induced RPE neovascularization by VEGF dysregulation.
SIGNIFICANCE: BP significantly protected tight junction integrity and RPE cellular physiology through ERK/Nrf-2/HO-1 pathway to prevent DR progression. Thus, BP has great potential to be developed therapeutic agents or adjuvants for DR.

Keywords: Anti-oxidant; Diabetic retinopathy; Neovascularization; Retinal pigment epithelium senescence; Tight junction impairment; n-Butylidenephthalide

DOI: https://doi.org/10.1016/j.lfs.2023.121815

Sci Rep. 2023 05 27. 13(1): 8647

RNA-Seq-based transcriptome analysis of corneal endothelial cells derived from patients with Fuchs endothelial corneal dystrophy.

Tatsuya Nakagawa, Yuichi Tokuda, Masakazu Nakano, Yuya Komori, Naoya Hanada, Theofilos Tourtas, Ursula Schlötzer-Schrehardt, Friedrich Kruse, Kei Tashiro, Noriko Koizumi, Naoki Okumura.

Fuchs endothelial corneal dystrophy (FECD) is the most common inherited corneal disease. Fibrillar focal excrescences called guttae and corneal edema due to corneal endothelial cell death result in progressive vision loss. Multiple genetic variants have been reported, but the pathogenesis of FECD is not fully understood. In this study, we used RNA-Seq to analyze differential gene expression in the corneal endothelium obtained from patients with FECD. Differential expression analysis of transcriptomic profiles revealed that expression of 2366 genes (1092 upregulated and 1274 downregulated genes) was significantly altered in the corneal endothelium of patients with FECD compared to healthy subjects. Gene ontology analysis demonstrated an enrichment of genes involved in extracellular matrix (ECM) organization, response to oxidative stress, and apoptotic signaling. Several pathway analyses consistently indicated the dysregulation of ECM-associated pathways. Our differential gene expression findings support the previously proposed underlying mechanisms, including oxidative stress and apoptosis of endothelial cells, as well as the phenotypic clinical FECD hallmark of ECM deposits. Further investigation focusing on differentially expressed genes related to these pathways might be beneficial for elucidating mechanisms and developing novel therapies.

DOI: https://doi.org/10.1038/s41598-023-35468-y

Biochem Soc Trans. 2023 May 30. pii: BST20230121. [Epub ahead of print]

Caveolae and the oxidative stress response.

Yeping Wu, Ye-Wheen Lim, Robert G Parton.

Oxidative stress is a feature of many disease conditions. Oxidative stress can activate a number of cellular pathways leading to cell death, including a distinct iron-dependent pathway involving lipid peroxidation, termed ferroptosis, but cells have evolved complex mechanisms to respond to these stresses. Here, we briefly summarise current evidence linking caveolae to the cellular oxidative stress response. We discuss recent studies in cultured cells and in an in vivo model suggesting that lipid peroxidation driven by oxidative stress causes disassembly of caveolae to release caveola proteins into the cell where they regulate the master transcriptional redox controller, nuclear factor erythroid 2-related factor 2. These studies suggest that caveolae maintain cellular susceptibility to oxidative stress-induced cell death and suggest a crucial role in cellular homeostasis and the response to wounding.

Keywords: Cavin1; NRF2; caveolae; cell death; lipid peroxidation; oxidative stress

DOI: https://doi.org/10.1042/BST20230121