bims-mideyd 2022-03-27 papers

Issue of 2022‒03‒27
five papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Cell Death Dis. 2022 Mar 21. 13(3): 255

Deficiency of thyroid hormone receptor protects retinal pigment epithelium and photoreceptors from cell death in a mouse model of age-related macular degeneration.

Hongwei Ma, Fan Yang, Xi-Qin Ding.

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly. Progressive dystrophy of the retinal pigment epithelium (RPE) and photoreceptors is the characteristic of dry AMD, and oxidative stress/damage plays a central role in the pathogenic lesion of the disease. Thyroid hormone (TH) regulates cell growth, differentiation, and metabolism, and regulates development/function of photoreceptors and RPE in the retina. Population-/patient-based studies suggest an association of high free-serum TH levels with increased risk of AMD. We recently showed that suppressing TH signaling by antithyroid treatment reduces cell damage/death of the RPE and photoreceptors in an oxidative-stress/sodium iodate (NaIO3)-induced mouse model of AMD. This work investigated the effects of TH receptor (THR) deficiency on cell damage/death of the RPE and photoreceptors and the contribution of the receptor subtypes. Treatment with NaIO3 induced RPE and photoreceptor cell death/necroptosis, destruction, and oxidative damage. The phenotypes were significantly diminished in Thrα1-/-, Thrb-/-, and Thrb2-/- mice, compared with that in the wild-type (C57BL/6 J) mice. The involvement of the receptor subtypes varies in the RPE and retina. Deletion of Thrα1 or Thrb protected RPE, rods, and cones, whereas deletion of Thrb2 protected RPE and cones but not rods. Gene-expression analysis showed that deletion of Thrα1 or Thrb abolished/suppressed the NaIO3-induced upregulation of the genes involved in cellular oxidative-stress responses, necroptosis/apoptosis signaling, and inflammatory responses. In addition, THR antagonist effectively protected ARPE-19 cells and hRPE cells from NaIO3-induced cell death. This work demonstrates the involvement of THR signaling in cell damage/death of the RPE and photoreceptors after oxidative-stress challenge and the receptor-subtype contribution. Findings from this work support a role of THR signaling in the pathogenesis of AMD and the strategy of suppressing THR signaling locally in the retina for protection of the RPE/retina in dry AMD.

DOI: https://doi.org/10.1038/s41419-022-04691-2

Int J Mol Sci. 2022 Mar 16. pii: 3194. [Epub ahead of print]23(6):

Regulation of ABCA1 by AMD-Associated Genetic Variants and Hypoxia in iPSC-RPE.

Florian Peters, Lynn J A Ebner, David Atac, Jordi Maggi, Wolfgang Berger, Anneke I den Hollander, Christian Grimm.

Age-related macular degeneration (AMD) is a progressive disease of the macula characterized by atrophy of the retinal pigment epithelium (RPE) and photoreceptor degeneration, leading to severe vision loss at advanced stages in the elderly population. Impaired reverse cholesterol transport (RCT) as well as intracellular lipid accumulation in the RPE are implicated in AMD pathogenesis. Here, we focus on ATP-binding cassette transporter A1 (ABCA1), a major cholesterol transport protein in the RPE, and analyze conditions that lead to ABCA1 dysregulation in induced pluripotent stem cell (iPSC)-derived RPE cells (iRPEs). Our results indicate that the risk-conferring alleles rs1883025 (C) and rs2740488 (A) in ABCA1 are associated with increased ABCA1 mRNA and protein levels and reduced efficiency of cholesterol efflux from the RPE. Hypoxia, an environmental risk factor for AMD, reduced expression of ABCA1 and increased intracellular lipid accumulation. Treatment with a liver X receptor (LXR) agonist led to an increase in ABCA1 expression and reduced lipid accumulation. Our data strengthen the homeostatic role of cholesterol efflux in the RPE and suggest that increasing cellular cholesterol export by stimulating ABCA1 expression might lessen lipid load, improving RPE survival and reducing the risk of developing AMD.

Keywords: ABCA1; LXR agonist; age-related macular degeneration; hypoxia; iPSC-RPE; lipid accumulation; reverse cholesterol transport

DOI: https://doi.org/10.3390/ijms23063194

Biomedicines. 2022 Feb 22. pii: 516. [Epub ahead of print]10(3):

Early-Onset Glaucoma in egl1 Mice Homozygous for Pitx2 Mutation.

Bindu Kodati, Shawn A Merchant, J Cameron Millar, Yang Liu.

Mutations in PITX2 cause Axenfeld-Rieger syndrome, with congenital glaucoma as an ocular feature. The egl1 mouse strain carries a chemically induced Pitx2 mutation and develops early-onset glaucoma. In this study, we characterized the glaucomatous features in egl1 mice. The eyes of egl1 and C57BL/6J control mice were assessed by slit lamp examination, total aqueous humor outflow facility, intraocular pressure (IOP) measurement, pattern electroretinography (PERG) recording, and histologic and immunohistochemistry assessment beginning at 3 weeks and up to 12 months of age. The egl1 mice developed elevated IOP as early as 4 weeks old. The IOP elevation was variable and asymmetric within and between the animals. The aqueous humor outflow facility was significantly reduced in 12-month-old animals. PERG detected a decreased response at 2 weeks after the development of IOP elevation. Retinal ganglion cell (RGC) loss was detected after 8 weeks of IOP elevation. Slit lamp and histologic evaluation revealed corneal opacity, iridocorneal adhesions (anterior synechiae), and ciliary body atrophy in egl1 mice. Immunohistochemistry assessment demonstrated glial cell activation and RGC axonal injury in response to IOP elevation. These results show that the eyes of egl1 mice exhibit anterior segment dysgenesis and early-onset glaucoma. The egl1 mouse strain may represent a useful model for the study of congenital glaucoma.

Keywords: Pitx2; glaucoma; mouse model

DOI: https://doi.org/10.3390/biomedicines10030516

Sci Rep. 2022 Mar 24. 12(1): 5122

Oxidative stress facilitates exogenous mitochondria internalization and survival in retinal ganglion precursor-like cells.

Michal Aharoni-Simon, Keren Ben-Yaakov, Maya Sharvit-Bader, Daniel Raz, Yasmin Haim, Waleed Ghannam, Noga Porat, Hana Leiba, Arie Marcovich, Avital Eisenberg-Lerner, Ziv Rotfogel.

Ocular cells are highly dependent on mitochondrial function due to their high demand of energy supply and their constant exposure to oxidative stress. Indeed, mitochondrial dysfunction is highly implicated in various acute, chronic, and genetic disorders of the visual system. It has recently been shown that mitochondrial transplantation (MitoPlant) temporarily protects retinal ganglion cells (RGCs) from cell death during ocular ischemia. Here, we characterized MitoPlant dynamics in retinal ganglion precursor-like cells, in steady state and under oxidative stress. We developed a new method for detection of transplanted mitochondria using qPCR, based on a difference in the mtDNA sequence of C57BL/6 and BALB/c mouse strains. Using this approach, we show internalization of exogenous mitochondria already three hours after transplantation, and a decline in mitochondrial content after twenty four hours. Interestingly, exposure of target cells to moderate oxidative stress prior to MitoPlant dramatically enhanced mitochondrial uptake and extended the survival of mitochondria in recipient cells by more than three fold. Understanding the factors that regulate the exogenous mitochondrial uptake and their survival may promote the application of MitoPlant for treatment of chronic and genetic mitochondrial diseases.

DOI: https://doi.org/10.1038/s41598-022-08747-3

Antioxidants (Basel). 2022 Mar 12. pii: 543. [Epub ahead of print]11(3):

Oxidative Stress, Vascular Endothelium, and the Pathology of Neurodegeneration in Retina.

Xin Shi, Panpan Li, Hanhan Liu, Verena Prokosch.

Oxidative stress (OS) is an imbalance between free radicals/ROS and antioxidants, which evokes a biological response and is an important risk factor for diseases, in both the cardiovascular system and central nervous system (CNS). The underlying mechanisms driving pathophysiological complications that arise from OS remain largely unclear. The vascular endothelium is emerging as a primary target of excessive glucocorticoid and catecholamine action. Endothelial dysfunction (ED) has been implicated to play a crucial role in the development of neurodegeneration in the CNS. The retina is known as an extension of the CNS. Stress and endothelium dysfunction are suspected to be interlinked and associated with neurodegenerative diseases in the retina as well. In this narrative review, we explore the role of OS-led ED in the retina by focusing on mechanistic links between OS and ED, ED in the pathophysiology of different retinal neurodegenerative conditions, and how a better understanding of the role of endothelial function could lead to new therapeutic approaches for neurodegenerative diseases in the retina.

Keywords: endothelium; neurodegeneration; oxidative stress; retina

DOI: https://doi.org/10.3390/antiox11030543