bims-mideyd 2022-11-20 papers

bims-mideyd

Biomed News

on Mitochondrial dysfunction in eye diseases

Issue of 2022–11–20
eight papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Analysis of mitochondrial dynamics and function in the retinal pigment epithelium by high-speed high-resolution live imaging.
m6A modification of circSPECC1 suppresses RPE oxidative damage and maintains retinal homeostasis.
Glaucomatous optic neuropathy: Mitochondrial dynamics, dysfunction and protection in retinal ganglion cells.
Fat mass and obesity-associated protein alleviates Aβ1-40 induced retinal pigment epithelial cells degeneration via PKA/CREB signaling pathway.
The intervention of epithelial-mesenchymal transition in homeostasis of human retinal pigment epithelial cells: a review.
Type 2 Diabetes Mellitus Makes Corneal Endothelial Cells Vulnerable to Ultraviolet A-Induced Oxidative Damage Via Decreased DJ-1/Nrf2/NQO1 Pathway.
Changes in glial cells and neurotrophic factors due to rotenone-induced oxidative stress in Nrf2 knockout mice.
AMPK/MFF Activation: Role in Mitochondrial Fission and Mitophagy in Dry Eye.

Front Cell Dev Biol. 2022 ;10 1044672

Analysis of mitochondrial dynamics and function in the retinal pigment epithelium by high-speed high-resolution live imaging.

Li Xuan Tan, Jianlong Li, Colin J Germer, Aparna Lakkaraju.

  Mitochondrial dysfunction is strongly implicated in neurodegenerative diseases including age-related macular degeneration (AMD), which causes irreversible blindness in over 50 million older adults worldwide. A key site of insult in AMD is the retinal pigment epithelium (RPE), a monolayer of postmitotic polarized cells that performs essential functions for photoreceptor health and vision. Recent studies from our group and others have identified several features of mitochondrial dysfunction in AMD including mitochondrial fragmentation and bioenergetic defects. While these studies provide valuable insight at fixed points in time, high-resolution, high-speed live imaging is essential for following mitochondrial injury in real time and identifying disease mechanisms. Here, we demonstrate the advantages of live imaging to investigate RPE mitochondrial dynamics in cell-based and mouse models. We show that mitochondria in the RPE form extensive networks that are destroyed by fixation and discuss important live imaging considerations that can interfere with accurate evaluation of mitochondrial integrity such as RPE differentiation status and acquisition parameters. Our data demonstrate that RPE mitochondria show localized heterogeneities in membrane potential and ATP production that could reflect focal changes in metabolism and oxidative stress. Contacts between the mitochondria and organelles such as the ER and lysosomes mediate calcium flux and mitochondrial fission. Live imaging of mouse RPE flatmounts revealed a striking loss of mitochondrial integrity in albino mouse RPE compared to pigmented mice that could have significant functional consequences for cellular metabolism. Our studies lay a framework to guide experimental design and selection of model systems for evaluating mitochondrial health and function in the RPE.

Keywords:  RPE; live imaging; mitochondria; pigmented and albino mice; retina

DOI:  https://doi.org/10.3389/fcell.2022.1044672
Cell Rep. 2022 Nov 15. pii: S2211-1247(22)01545-5. [Epub ahead of print]41(7): 111671

m6A modification of circSPECC1 suppresses RPE oxidative damage and maintains retinal homeostasis.

Xue Chen, Ying Wang, Jia-Nan Wang, Qiu-Chen Cao, Ru-Xu Sun, Hong-Jing Zhu, Ye-Ran Zhang, Jiang-Dong Ji, Qing-Huai Liu.

  Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss in the elderly population with unclear pathogenic mechanism. Herein, we detect downregulated circSPECC1 expression in retinal pigment epithelium (RPE) of AMD patients. In RPE cells, circSPECC1 insufficiency leads to oxidative stress-induced ferroptosis, depolarization, and irregular lipid metabolism. Consistently, in mice, circSPECC1 deficiency induces visual impairments and RPE anomalies and interrupts retinal homeostasis. Mechanically, nuclear export of circSPECC1 transcript depends on its N6-methyladenosine (m6A) level with YTHDC1 as the reader. CircSPECC1 directly sponges miR-145-5p to block its interaction with CDKN1A. Overexpressing miR-145-5p aggravates RPE dysfunctions, mimicking circSPECC1 silencing effects. Retinal phenotypes induced by circSPECC1 insufficiency are alleviated by miR-145-5p inhibition and are aggravated by miR-145-5p overexpression. Collectively, circSPECC1, mediated by m6A modification and sponging miR-145-5p, resists oxidative stress injuries and maintains lipid metabolism in RPE. Pharmacological supplementation of circSPECC1 is a promising therapeutic option for atrophic retinopathies like AMD.

Keywords:  CP: Neuroscience; age-related macular degeneration; circular RNA; m(6)A; oxidative stress; retinal pigment epithelium

DOI:  https://doi.org/10.1016/j.celrep.2022.111671
Prog Retin Eye Res. 2022 Nov 15. pii: S1350-9462(22)00096-9. [Epub ahead of print] 101136

Glaucomatous optic neuropathy: Mitochondrial dynamics, dysfunction and protection in retinal ganglion cells.

Won-Kyu Ju, Guy A Perkins, Keun-Young Kim, Tonking Bastola, Woo-Young Choi, Soo-Ho Choi.

  Glaucoma is a leading cause of irreversible blindness worldwide and is characterized by a slow, progressive, and multifactorial degeneration of retinal ganglion cells (RGCs) and their axons, resulting in vision loss. Despite its high prevalence in individuals 60 years of age and older, the causing factors contributing to glaucoma progression are currently not well characterized. Intraocular pressure (IOP) is the only proven treatable risk factor. However, lowering IOP is insufficient for preventing disease progression. One of the significant interests in glaucoma pathogenesis is understanding the structural and functional impairment of mitochondria in RGCs and their axons and synapses. Glaucomatous risk factors such as IOP elevation, aging, genetic variation, neuroinflammation, neurotrophic factor deprivation, and vascular dysregulation, are potential inducers for mitochondrial dysfunction in glaucoma. Because oxidative phosphorylation stress-mediated mitochondrial dysfunction is associated with structural and functional impairment of mitochondria in glaucomatous RGCs, understanding the underlying mechanisms and relationship between structural and functional alterations in mitochondria would be beneficial to developing mitochondria-related neuroprotection in RGCs and their axons and synapses against glaucomatous neurodegeneration. Here, we review the current studies focusing on mitochondrial dynamics-based structural and functional alterations in the mitochondria of glaucomatous RGCs and therapeutic strategies to protect RGCs against glaucomatous neurodegeneration.

Keywords:  Gene therapy; Glaucoma; Mitochondrial bioenergetics; Mitochondrial dynamics; Mitophagy; Retinal ganglion cell

DOI:  https://doi.org/10.1016/j.preteyeres.2022.101136
Cell Biol Int. 2022 Nov 15.

Fat mass and obesity-associated protein alleviates Aβ1-40 induced retinal pigment epithelial cells degeneration via PKA/CREB signaling pathway.

Yifan Hu, Jieqiong Chen, Yuwei Wang, Junran Sun, Peirong Huang, Jingyang Feng, Te Liu, Xiaodong Sun.

  Amyloid-β (Aβ) is thought to be a critical pathologic factor of retinal pigment epithelium (RPE) degeneration in age-related macular degeneration (AMD). Aβ induces inflammatory responses in RPE cells and recent studies demonstrate the N6-methyladenosine (m6A) regulatory role in RPE cell inflammation. m6A is a reversible epigenetic posttranslational modification, but its relationship with Aβ-induced RPE degeneration is yet to be thoroughly investigated. The present study explored the role and mechanism of m6A in Aβ-induced RPE degeneration model. This model was induced via intravitreally injecting oligomeric Aβ and the morphology of its retina was analyzed. One of m6A demethylases, the fat mass and obesity-associated (FTO) gene expression, was assessed. An m6A-messenger RNA (mRNA) epitranscriptomic microarray was employed for further bioinformatic analyses. It was confirmed that Aβ induced FTO upregulation within the RPE. Hypopigmentation alterations and structural disorganization were observed in Aβ-treated eyes, and inhibition of FTO exacerbated retinal degeneration and RPE impairment. Moreover, the m6A-mRNA epitranscriptomic microarray suggested that protein kinase A (PKA) was a target of FTO, and the PKA/cyclic AMP-responsive element binding (CREB) signaling pathway was involved in Aβ-induced RPE degeneration. m6A-RNA binding protein immunoprecipitation confirmed that FTO demethylated PKA within the RPE cells of Aβ-treated eyes. Altered expression of PKA and its downstream targets (CREB and brain-derived neurotrophic factor) was confirmed by quantitative reverse-transcription polymerase chain reaction and Western blot analyses. Hence, this study's findings shed light on FTO-mediated m6A modification in Aβ-induced RPE degeneration and indicate potential therapeutic targets for AMD.

Keywords:  N6-methyladenosine; age-related macular degeneration; amyloid-β; fat mass and obesity-associated protein; m6A-mRNA epi-transcriptomic microarray; retinal pigment epithelium

DOI:  https://doi.org/10.1002/cbin.11959
J Histotechnol. 2022 Nov 15. 1-13

The intervention of epithelial-mesenchymal transition in homeostasis of human retinal pigment epithelial cells: a review.

Brijesh Gelat, Pooja Rathaur, Pooja Malaviya, Binita Patel, Krupali Trivedi, Kaid Johar, Rahul Gelat.

  The health and activity of photoreceptors and Bruch's membrane are promoted by the retinal pigment epithelium (RPE), which is essential for normal vision. Age-related macular degeneration (AMD), diabetic retinopathy (DR), and proliferative vitreoretinopathy (PVR) are examples of retinopathies that result in vision loss. Epithelial-mesenchymal transition (EMT) is a process in which epithelial cells transform into mesenchymal cells as a result of a faulty microenvironment, and it is associated with the oculopathies stated above. Cell differentiation, autophagy, growth factors (GFs), the blood-retinal barrier (BRB), and other complicated signaling pathways all contribute to proper morphology, and their disruption by harmful compounds has an impact on RPE function. The inducer and suppressor of EMT in RPE, on the other hand, are unknown. The current article reviews the experimental research investigations, suggested that certain modulators like glucosamine (Glc-N) and bradykinin (BK) suppress the TGFβ signaling pathway and that other variables like oxidative stress triggered EMT, which is not found in normal RPE homeostasis. Finding molecular targets and treatments to prevent and restore RPE function, as well as understanding how EMT regulators affect RPE degeneration, are therefore crucial.

Keywords:  Retinal pigment epithelial cells; age-related macular degeneration; diabetic retinopathy; epithelial-mesenchymal transition; retinopathy

DOI:  https://doi.org/10.1080/01478885.2022.2137665
Invest Ophthalmol Vis Sci. 2022 Nov 01. 63(12): 25

Type 2 Diabetes Mellitus Makes Corneal Endothelial Cells Vulnerable to Ultraviolet A-Induced Oxidative Damage Via Decreased DJ-1/Nrf2/NQO1 Pathway.

Xueling Zhang, Jini Qiu, Feifei Huang, Kun Shan, Chaoran Zhang.

Purpose: The purpose of this study was to investigate whether type 2 diabetes mellitus (T2DM) makes corneal endothelial cells (CECs) suffer from more severe ultraviolet A (UVA)-induced oxidative damage and explore its mechanisms via measuring the oxidant level and the antioxidant level in vitro.
Methods: Corneas of spontaneous T2DM db/db mice and non-diabetes littermate control mice were irradiated with UVA, leading to oxidative damage of CECs. Anterior segment-optical coherence tomography, corneal image, and CECs immunohistochemistry staining were taken thereafter to measure central corneal thickness, corneal edema degree, and damage extent of CECs. In vitro, human corneal endothelial cells line B4G12 (HCECs) treated with high glucose (HG) and low glucose (LG) were exposed to UVA light separately. Subsequently, cellular proliferation, apoptosis, pro-oxidant factors, such as reactive oxygen species (ROS), antioxidant factors including Parkinson's disease protein 7 (DJ-1), nuclear factor-erythroid 2 related factor 2 (Nrf2), phosphorylated-Nrf2, and NAD(P)H: quinone oxidoreductase 1 (NQO1) were measured.
Results: T2DM mice presented greater oxidant damage of CECs and more distinct corneal edema compared with control mice when they were irradiated with the 150 J/cm2 UVA light. In vitro, HCECs in HG condition showed a significant decrease of proliferation, higher apoptosis extent, more ROS generation, lower expressions of DJ-1/Nrf2/NQO1, and distinct reduction of Nrf2 nuclear translocation compared to those in LG condition after exposing to 5 J/cm2 UVA light.
Conclusions: Increase of ROS, downregulation of DJ-1/Nrf2/NQO1 expressions, and decrease of Nrf2 nuclear translocation could result in that T2DM makes CECs more vulnerable to oxidative damage.

DOI: https://doi.org/10.1167/iovs.63.12.25
Exp Eye Res. 2022 Nov 15. pii: S0014-4835(22)00395-5. [Epub ahead of print] 109314

Changes in glial cells and neurotrophic factors due to rotenone-induced oxidative stress in Nrf2 knockout mice.

Maki Inoue-Yanagimachi, Noriko Himori, Keiko Uchida, Hiroshi Tawarayama, Kota Sato, Masayuki Yamamoto, Kazuhiko Namekata, Takayuki Harada, Toru Nakazawa.

  Glaucoma is one of the most common causes of blindness worldwide. It is thought to be a multifactorial disease with underlying mechanisms that include mitochondrial dysfunction and oxidative stress. Here, we used NF-E2 related factor 2 (Nrf2) knockout (KO) mice, which are vulnerable to oxidative stress, to examine a neuroprotective effect against oxidative stress due to rotenone, a mitochondrial complex I inhibitor. Wild-type (WT) and Nrf2 KO mice received an oral solution of rotenone for 30 days. We then extracted the retinas and performed immunohistochemistry and quantitative RT-PCR. We also prepared a primary Müller cell culture of samples from each mouse, added 30 μM rotenone, and then measured cell viability, cytotoxicity and CellRox absorbance. We also examined gene expression. We found a significant increase in the number of 8-OHdG-positive retinal ganglion cells (RGCs) after rotenone administration in both the WT and Nrf2 KO mice. There was no difference in the number of RNA-binding protein with multiple splicing (RBPMS)-positive RGCs in the WT and Nrf2 KO mice, but Nrf2 KO mice that were given rotenone had significantly less retinal gene expression of RBPMS than Nrf2 KO mice given a control. Moreover, there was significantly higher mRNA gene expression of vimentin and glial fibrillary acidic protein (GFAP) in Nrf2 KO mice that received rotenone than WT mice that received rotenone. A statistical analysis of the in vitro experiment showed that cell viability was lower, cytotoxicity was higher, and oxidative stress was higher in the Müller cells of the Nrf2 KO mice than the WT mice. Finally, brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF) were significantly higher in the Müller cells of the Nrf2 KO mice than the WT mice. These findings suggest that in Nrf2 KO mice under oxidative stress caused by rotenone, temporary neurotrophic factors are secreted from the Müller cells, conferring neuroprotection in these cells.

Keywords:  BDNF; Glaucoma; Müller cells; Neuroprotection; Nrf2; Oxidative stress; Retinal ganglion cell; Rotenone

DOI:  https://doi.org/10.1016/j.exer.2022.109314
Invest Ophthalmol Vis Sci. 2022 Nov 01. 63(12): 18

AMPK/MFF Activation: Role in Mitochondrial Fission and Mitophagy in Dry Eye.

Fangli Peng, Dan Jiang, Wei Xu, Yining Sun, Zhiwei Zha, Xiying Tan, Jinjie Yu, Chengjie Pan, Qinxiang Zheng, Wei Chen.

Purpose: To assess the role of mitochondrial morphology and adenosine monophosphate-activated protein kinase (AMPK)/mitochondrial fission factor (MFF) in dry eye and the underlying mechanisms.
Methods: Immortalized human corneal epithelial cells (HCECs) and primary HCECs were cultured under high osmotic pressure (HOP). C57BL/6 female mice were injected subcutaneously with scopolamine. Quantitative real-time PCR was used to measure mRNA expression. Protein expression was assessed by western blot and immunofluorescence staining. Mitochondrial morphology was observed by confocal microscopy and transmission electron microscopy.
Results: First, HOP induced mitochondrial oxidative damage to HCECs, accompanied by mitochondrial fission and increased mitophagy. Then, AMPK/MFF pathway proteins were increased consequent to HOP-induced energy metabolism dysfunction. Interestingly, the AMPK pathway promoted mitochondrial fission and mitophagy by increasing the recruitment of dynamin-related protein 1 (DRP1) to the mitochondrial outer membrane in the HOP group. Moreover, AMPK knockdown attenuated mitochondrial fission and mitophagy due to HOP in HCECs. AMPK activation triggered mitochondrial fission and mitophagy. Mitochondrial fission of HCECs stressed by HOP was mediated via MFF phosphorylation. MFF knockdown reversed mitochondrial fragmentation and mitophagy in HCECs treated with HOP. Inhibition of MFF protected HCECs against oxidative damage, cell death, and inflammation in the presence of HOP. Finally, we detected mitochondrial fission and AMPK pathway activation in vivo.
Conclusions: The AMPK/MFF pathway mediates the development of dry eye by positively regulating mitochondrial fission and mitophagy. Inhibition of mitochondrial fission can alleviate oxidative damage and inflammation in dry eye and may provide experimental evidence for treating dry eye.

DOI: https://doi.org/10.1167/iovs.63.12.18