bims-mideyd 2024-06-30 papers

bims-mideyd

Biomed News

on Mitochondrial dysfunction in eye diseases

Issue of 2024–06–30
seven papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Reduced Retinal Pigment Epithelial Autophagy Due to Loss of Rab12 Prenylation in a Human iPSC-RPE Model of Choroideremia.
The microRNA Let-7f Induces Senescence and Exacerbates Oxidative Stress in Retinal Pigment Epithelial Cells.
Administration of Bicarbonate Protects Mitochondria, Rescues Retinal Ganglion Cells, and Ameliorates Visual Dysfunction Caused by Oxidative Stress.
The effect of Fernblock® in preventing blue-light-induced oxidative stress and cellular damage in retinal pigment epithelial cells is associated with NRF2 induction.
Immune modulatory and anti-angiogenic effects of cathepsin S knockdown in ARPE-19 cells.
Vitamin D and Sulforaphane Decrease Inflammatory Oxidative Stress and Restore the Markers of Epithelial Integrity in an In Vitro Model of Age-Related Macular Degeneration.
VDAC in Retinal Health and Disease.

Cells. 2024 Jun 19. pii: 1068. [Epub ahead of print]13(12):

Reduced Retinal Pigment Epithelial Autophagy Due to Loss of Rab12 Prenylation in a Human iPSC-RPE Model of Choroideremia.

Maide Ö Raeker, Nirosha D Perera, Athanasios J Karoukis, Lisheng Chen, Kecia L Feathers, Robin R Ali, Debra A Thompson, Abigail T Fahim.

  Choroideremia is an X-linked chorioretinal dystrophy caused by mutations in CHM, encoding Rab escort protein 1 (REP-1), leading to under-prenylation of Rab GTPases (Rabs). Despite ubiquitous expression of CHM, the phenotype is limited to degeneration of the retina, retinal pigment epithelium (RPE), and choroid, with evidence for primary pathology in RPE cells. However, the spectrum of under-prenylated Rabs in RPE cells and how they contribute to RPE dysfunction remain unknown. A CRISPR/Cas-9-edited CHM-/- iPSC-RPE model was generated with isogenic control cells. Unprenylated Rabs were biotinylated in vitro and identified by tandem mass tag (TMT) spectrometry. Rab12 was one of the least prenylated and has an established role in suppressing mTORC1 signaling and promoting autophagy. CHM-/- iPSC-RPE cells demonstrated increased mTORC1 signaling and reduced autophagic flux, consistent with Rab12 dysfunction. Autophagic flux was rescued in CHM-/- cells by transduction with gene replacement (ShH10-CMV-CHM) and was reduced in control cells by siRNA knockdown of Rab12. This study supports Rab12 under-prenylation as an important cause of RPE cell dysfunction in choroideremia and highlights increased mTORC1 and reduced autophagy as potential disease pathways for further investigation.

Keywords:  autophagy; choroideremia; disease modeling; human pluripotent stem cells; inherited retinal disease; retinal degeneration; retinal pigment epithelium

DOI:  https://doi.org/10.3390/cells13121068
Antioxidants (Basel). 2024 May 25. pii: 646. [Epub ahead of print]13(6):

The microRNA Let-7f Induces Senescence and Exacerbates Oxidative Stress in Retinal Pigment Epithelial Cells.

Christina Ortiz, Houda Tahiri, Chun Yang, Claudia Gilbert, Carl Fortin, Pierre Hardy.

  This study aims to investigate the role of microRNA let-7f in the dysfunction and degeneration of retinal pigment epithelium (RPE) cells through the induction of senescence and oxidative stress. Furthermore, we explore whether let-7f inhibition can protect these cells against sodium iodate (SI)-induced oxidative stress. Oxidative stress and let-7f expression are reciprocally regulated in retinal pigment epithelial cells. Overexpression of let-7f in ARPE-19 cells induced oxidative stress as demonstrated by increased reactive oxygen species (ROS) production as well as senescence. Inhibition of let-7f successfully protected RPE cells from the detrimental effects induced by SI. In addition, let-7f overexpression induced RPE cellular dysfunction by diminishing their migratory capabilities and reducing the phagocytosis of porcine photoreceptor outer segments (POS). Results were further confirmed in vivo by intravitreal injections of SI and let-7f antagomir in C57BL/6 mice. Our results provide strong evidence that let-7f is implicated in the dysfunction of RPE cells through the induction of senescence and oxidative injury. These findings may help to uncover novel and relevant processes in the pathogenesis of dry AMD.

Keywords:  dry age-related macular degeneration; microRNA let-7f; oxidative stress; senescence

DOI:  https://doi.org/10.3390/antiox13060646
Antioxidants (Basel). 2024 Jun 19. pii: 743. [Epub ahead of print]13(6):

Administration of Bicarbonate 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 a key regulator of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway, which is known to protect mitochondria and promote RGC survival. However, the precise molecular mechanisms connecting the sAC-mediated signaling pathway with mitochondrial protection in RGCs against 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 induced by ischemic injury and paraquat administration, we found that administration of bicarbonate, as an activator of 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. Notably, the administration of bicarbonate 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.

Keywords:  glaucoma; mitochondria; oxidative stress; retinal ganglion cells (RGCs); soluble adenylyl cyclase (sAC)

DOI:  https://doi.org/10.3390/antiox13060743
Photochem Photobiol Sci. 2024 Jun 23.

The effect of Fernblock® in preventing blue-light-induced oxidative stress and cellular damage in retinal pigment epithelial cells is associated with NRF2 induction.

María Gallego-Rentero, Ana López Sánchez, Jimena Nicolás-Morala, Paula Alcaraz-Laso, Noelia Zhang, Ángeles Juarranz, Salvador González, Elisa Carrasco.

  Blue light exposure of the ocular apparatus is currently rising. This has motivated a growing concern about potential deleterious effects on different eye structures. To address this, ARPE-19 cells were used as a model of the retinal pigment epithelium and subjected to cumulative expositions of blue light. The most relevant cellular events previously associated with blue-light-induced damage were assessed, including alterations in cell morphology, viability, cell proliferation, oxidative stress, inflammation, and the induction of DNA repair cellular mechanisms. Consistent with previous reports, our results provide evidence of cellular alterations resulting from repeated exposure to blue light irradiation. In this context, we explored the potential protective properties of the vegetal extract from Polypodium leucotomos, Fernblock® (FB), using the widely known treatment with lutein as a reference for comparison. The only changes observed as a result of the sole treatment with either FB or lutein were a slight but significant increase in γH2AX+ cells and the raise in the nuclear levels of NRF2. Overall, our findings indicate that the treatment with FB (similarly to lutein) prior to blue light irradiation can alleviate blue-light-induced deleterious effects in RPE cells, specifically preventing the drop in both cell viability and percentage of EdU+ cells, as well as the increase in ROS generation, percentage of γH2AX+ nuclei (more efficiently with FB), and TNF-α secretion (the latter restored only by FB to similar levels to those of the control). On the contrary, the induction in the P21 expression upon blue light irradiation was not prevented neither by FB nor by lutein. Notably, the nuclear translocation of NRF2 induced by blue light was similar to that observed in cells pre-treated with FB, while lutein pre-treatment resulted in nuclear NRF2 levels similar to control cells, suggesting key differences in the mechanism of cellular protection exerted by these compounds. These results may represent the foundation ground for the use of FB as a new ingredient in the development of alternative prophylactic strategies for blue-light-associated diseases, a currently rising medical interest.

Keywords:  ARPE-19; Blue light; Fernblock®; NRF2; Retinal damage

DOI:  https://doi.org/10.1007/s43630-024-00606-6
Exp Eye Res. 2024 Jun 22. pii: S0014-4835(24)00202-1. [Epub ahead of print] 109981

Immune modulatory and anti-angiogenic effects of cathepsin S knockdown in ARPE-19 cells.

Umma Hafsa Preya, Shithima Sayed, Ngoc Lan Nguyen, Jee Taek Kim.

  We aimed to determine the role of cathepsin S (CTSS) in modulating oxidative stress-induced immune and inflammatory reactions and angiogenesis in age-related macular degeneration. Human retinal pigment epithelium cells line ARPE-19 (immature) were maintained and treated with H2O2. The expression of CTSS, inflammatory cytokines, and complement factors induced by oxidative stress was compared between cells incubated without (control) and with CTSS knockdown (using small interfering ribonucleic acid; siRNA). To evaluate the role of CTSS in angiogenesis, we assayed tube formation using human umbilical vein endothelial cells and conditioned medium from ARPE-19 cells. We also used a mouse model of laser-induced choroidal neovascularization. CTSS levels were higher in ARPE-19 cells treated with H2O2 than in control cells. Oxidative stress-induced CTSS resulted in significantly elevated transcription of nuclear factor kappa B-dependent inflammatory cytokines, complement factors C3a and C5a, membrane attack complex (C5b-9), and C3a and C5a receptors. siRNA-mediated knockdown of CTSS reduced the number of inflammatory signals. Furthermore, oxidative stress-induced CTSS regulated the expression of peroxisome proliferator-activated receptor γ and vascular endothelial growth factor A/ Akt serine/threonine kinase family signaling, which led to angiogenesis. Tube formation assays and mouse models of choroidal neovascularization revealed that CTSS knockdown ameliorated angiogenesis in vitro and in vivo. The present findings suggest that CTSS modulates the complement pathway, inflammatory reactions, and neovascularization, and that CTSS knockdown induces potent immunomodulatory effects. Hence, it could be a promising target for the prevention and treatment of early- and late-stage age-related macular degeneration.

Keywords:  age-related macular degeneration; cathepsin S; oxidative stress; reactive oxygen species; retinal pigment epithelium

DOI:  https://doi.org/10.1016/j.exer.2024.109981
Int J Mol Sci. 2024 Jun 10. pii: 6404. [Epub ahead of print]25(12):

Vitamin D and Sulforaphane Decrease Inflammatory Oxidative Stress and Restore the Markers of Epithelial Integrity in an In Vitro Model of Age-Related Macular Degeneration.

Loredana Bergandi, Giulia Palladino, Alessandro Meduri, Laura De Luca, Francesca Silvagno.

  Age-related macular degeneration (AMD) is strictly linked to chronic oxidative stress, inflammation, loss of epithelial barrier integrity, and often with abnormal new blood vessel development. In this study, the retinal epithelial cell line ARPE-19 was treated with pro-inflammatory transforming growth factor-beta (TGF-β) to investigate the activity of vitamin D (VD) and sulforaphane (SF) in abating the consequences of oxidative stress and inflammation. The administration of VD and SF lowered reactive oxygen species (ROS) levels, and abated the related expression of the pro-inflammatory cytokines interleukin-6 and interleukin-8 induced by TGF-β. We evaluated mitochondrial respiration as a source of ROS production, and we discovered that the increased transcription of respiratory elements triggered by TGF-β was prevented by VD and SF. In this model of inflamed epithelium, the treatment with VD and SF also reduced the secretion of VEGF, a key angiogenic factor, and restored the markers of epithelial integrity. Remarkably, all the observed biological effects were potentiated by the co-stimulation with the two compounds and were not mediated by VD receptor expression but rather by the ERK 1/2 pathway. Altogether, the results of this study reveal the powerful synergistic anti-inflammatory activity of SF and VD and lay the foundation for future clinical assessment of their efficacy in AMD.

Keywords:  human retinal pigment epithelial cells; inflammation; reactive oxygen species; sulforaphane; transforming growth factor-β (TGF-β); vascular-endothelial growth factor (VEGF); vitamin D receptor

DOI:  https://doi.org/10.3390/ijms25126404
Biomolecules. 2024 Jun 04. pii: 654. [Epub ahead of print]14(6):

VDAC in Retinal Health and Disease.

Ying Xu, Shanti R Tummala, Xiongmin Chen, Noga Vardi.

  The retina, a tissue of the central nervous system, is vital for vision as its photoreceptors capture light and transform it into electrical signals, which are further processed before they are sent to the brain to be interpreted as images. The retina is unique in that it is continuously exposed to light and has the highest metabolic rate and demand for energy amongst all the tissues in the body. Consequently, the retina is very susceptible to oxidative stress. VDAC, a pore in the outer membrane of mitochondria, shuttles metabolites between mitochondria and the cytosol and normally protects cells from oxidative damage, but when a cell's integrity is greatly compromised it initiates cell death. There are three isoforms of VDAC, and existing evidence indicates that all three are expressed in the retina. However, their precise localization and function in each cell type is unknown. It appears that most retinal cells express substantial amounts of VDAC2 and VDAC3, presumably to protect them from oxidative stress. Photoreceptors express VDAC2, HK2, and PKM2-key proteins in the Warburg pathway that also protect these cells. Consistent with its role in initiating cell death, VDAC is overexpressed in the retinal degenerative diseases retinitis pigmentosa, age related macular degeneration (AMD), and glaucoma. Treatment with antioxidants or inhibiting VDAC oligomerization reduced its expression and improved cell survival. Thus, VDAC may be a promising therapeutic candidate for the treatment of these diseases.

Keywords:  HK2; age related macular degeneration; apoptosis; degeneration; ganglion cells; glaucoma; mitochondria; oxidative stress; photoreceptors; retinitis pigmentosa

DOI:  https://doi.org/10.3390/biom14060654