bims-mideyd 2021-11-28 papers

bims-mideyd

Biomed News

on Mitochondrial dysfunction in eye diseases

Issue of 2021–11–28
eight papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Deletion of transcription factor AP-2β from the developing murine trabecular meshwork region leads to progressive glaucomatous changes.
Receptor interacting protein 3 kinase, not 1 kinase, through MLKL-mediated necroptosis is involved in UVA-induced corneal endothelium cell death.
Complement Factor H-Related 3 Enhanced Inflammation and Complement Activation in Human RPE Cells.
PKM2 Is a Potential Diagnostic and Therapeutic Target for Retinitis Pigmentosa.
A coarse-grained NADH redox model enables inference of subcellular metabolic fluxes from fluorescence lifetime imaging.
Loss of Caveolin-1 Impairs Light Flicker-Induced Neurovascular Coupling at the Optic Nerve Head.
Differential Responses of Neural Retina Progenitor Populations to Chronic Hyperglycemia.
Role of the Phospholipase C Pathway and Calcium Mobilization in Oxytocin-Induced Contraction of Lacrimal Gland Myoepithelial Cells.

J Neurosci Res. 2021 Nov 25.

Deletion of transcription factor AP-2β from the developing murine trabecular meshwork region leads to progressive glaucomatous changes.

Aftab Taiyab, Monica Akula, Japnit Dham, Paula Deschamps, Heather Sheardown, Trevor Williams, Teresa Borrás, Judith A West-Mays.

  Glaucoma is one of the leading causes of irreversible blindness and can result from abnormalities in anterior segment structures required for aqueous humor outflow, including the trabecular meshwork (TM) and Schlemm's canal (SC). Transcription factors such as AP-2β play critical roles in anterior segment development. Here, we show that the Mgp-Cre knock-in (Mgp-Cre.KI) mouse can be used to target the embryonic periocular mesenchyme giving rise to the TM and SC. Fate mapping of male and female mice indicates that AP-2β loss causes a decrease in iridocorneal angle cells derived from Mgp-Cre.KI-expressing populations compared to controls. Moreover, histological analyses revealed peripheral iridocorneal adhesions in AP-2β mutants that were accompanied by a decrease in expression of TM and SC markers, as observed using immunohistochemistry. In addition, rebound tonometry showed significantly higher intraocular pressure (IOP) that was correlated with a progressive significant loss of retinal ganglion cells, reduced retinal thickness, and reduced retinal function, as measured using an electroretinogram, in AP-2β mutants compared with controls, reflecting pathology described in late-stage glaucoma patients. Importantly, elevated IOP in AP-2β mutants was significantly reduced by treatment with latanoprost, a prostaglandin analog that increases unconventional outflow. These findings demonstrate that AP-2β is critical for TM and SC development, and that these mutant mice can serve as a model for understanding and treating progressive human primary angle-closure glaucoma.

Keywords:  RRID:AB_143157; RRID:AB_2058198; RRID:AB_2077527; RRID:AB_2534074; RRID:AB_2534102; RRID:AB_2536161; RRID:AB_2749865; RRID:AB_476701; RRID:AB_626765; glaucoma; outflow pathways; periocular mesenchyme

DOI:  https://doi.org/10.1002/jnr.24982
Cell Death Discov. 2021 Nov 23. 7(1): 366

Receptor interacting protein 3 kinase, not 1 kinase, through MLKL-mediated necroptosis is involved in UVA-induced corneal endothelium cell death.

Zhen Yu, Nikolaos E Efstathiou, Victor S M C Correa, Xiaohong Chen, Kenji Ishihara, Yasuhiro Iesato, Toshio Narimatsu, Dimitrios Ntentakis, Yanyun Chen, Demetrios G Vavvas.

Ultraviolet (UV) is one of the most energetic radiations in the solar spectrum that can result in various tissue injury disorders. Previous studies demonstrated that UVA, which represents 95% of incident photovoltaic radiation, induces corneal endothelial cells (CECs) death. Programmed cell death (PCD) has been implicated in numerous ophthalmologic diseases. Here, we investigated receptor-interacting protein 3 kinase (RIPK3), a key signaling molecule of PCD, in UVA-induced injury using a short-term corneal endothelium (CE) culture model. UVA irradiation activated RIPK3 and mediated necroptosis both in mouse CE and primary human CECs (pHCECs). UVA irradiation was associated with upregulation of key necroptotic molecules (DAI, TRIF, and MLKL) that lie downstream of RIPK3. Moreover, RIPK3 inhibition or silencing in primary corneal endothelial cells suppresses UVA-induced cell death, along with downregulation of MLKL in pHCECs. In addition, genetic inhibition or knockout of RIPK3 in mice (RIPK3K51A and RIPK3-/- mice) similarly attenuates cell death and the levels of necroptosis in ex vivo UVA irradiation experiments. In conclusion, these results identify RIPK3, not RIPK1, as a critical regulator of UVA-induced cell death in CE and indicate its potential as a future protective target.

DOI: https://doi.org/10.1038/s41420-021-00757-w
Front Immunol. 2021 ;12 769242

Complement Factor H-Related 3 Enhanced Inflammation and Complement Activation in Human RPE Cells.

Nicole Schäfer, Anas Rasras, Delia M Ormenisan, Sabine Amslinger, Volker Enzmann, Herbert Jägle, Diana Pauly.

  Complement Factor H-Related 3 (FHR-3) is a major regulator of the complement system, which is associated with different diseases, such as age-related macular degeneration (AMD). However, the non-canonical local, cellular functions of FHR-3 remained poorly understood. Here, we report that FHR-3 bound to oxidative stress epitopes and competed with FH for interaction. Furthermore, FHR-3 was internalized by viable RPE cells and modulated time-dependently complement component (C3, FB) and receptor (C3aR, CR3) expression of human RPE cells. Independently of any external blood-derived proteins, complement activation products were detected. Anaphylatoxin C3a was visualized in treated cells and showed a translocation from the cytoplasm to the cell membrane after FHR-3 exposure. Subsequently, FHR-3 induced a RPE cell dependent pro-inflammatory microenvironment. Inflammasome NLRP3 activation and pro-inflammatory cytokine secretion of IL-1ß, IL-18, IL-6 and TNF-α were induced after FHR-3-RPE interaction. Our previously published monoclonal anti-FHR-3 antibody, which was chimerized to reduce immunogenicity, RETC-2-ximab, ameliorated the effect of FHR-3 on ARPE-19 cells. Our studies suggest FHR-3 as an exogenous trigger molecule for the RPE cell "complosome" and as a putative target for a therapeutic approach for associated degenerative diseases.

Keywords:  AMD; FHR-3; RETC-2; RPE cells FHR-3 alters RPE cell complosome; complement activation; complosome; inflammation; oxidative stress epitopes

DOI:  https://doi.org/10.3389/fimmu.2021.769242
Dis Markers. 2021 ;2021 1602797

PKM2 Is a Potential Diagnostic and Therapeutic Target for Retinitis Pigmentosa.

Peiwen Zhu, Qian Yang, Gang Li, Qing Chang.

Retinitis pigmentosa (RP) is a major cause of blindness that is difficult to diagnose and treat. PKM2, a subtype of pyruvate kinase, is strongly associated with oxidative stress and is expressed in photoreceptors. We investigated whether PKM2 reduces photoreceptor cell apoptosis and evaluated possible antiapoptotic mechanisms in RP. We established RP models by exposing 661W cells to blue light and modulated PKM2 activity using a PKM2 inhibitor. We measured the apoptosis rates using calcein-acetoxymethyl ester/propidium iodide double staining and Cell Counting Kit-8, the oxidative stress levels using a reactive oxygen species assay, and the changes in protein expression by western blotting. Photodamage increased PKM2 expression, cellular oxidative stress, and apoptosis of 661W cells. PKM2 inhibition significantly reduced the levels of apoptosis and oxidative stress induced by photodamage. Our data suggest that PKM2 is a potential disease marker and therapeutic target for RP.

DOI: https://doi.org/10.1155/2021/1602797
Elife. 2021 Nov 22. pii: e73808. [Epub ahead of print]10

A coarse-grained NADH redox model enables inference of subcellular metabolic fluxes from fluorescence lifetime imaging.

Xingbo Yang, Gloria Ha, Dan Needleman.

  Mitochondrial metabolism is of central importance to diverse aspects of cell and developmental biology. Defects in mitochondria are associated with many diseases, including cancer, neuropathology, and infertility. Our understanding of mitochondrial metabolism in situ and dysfunction in diseases are limited by the lack of techniques to measure mitochondrial metabolic fluxes with sufficient spatiotemporal resolution. Herein, we developed a new method to infer mitochondrial metabolic fluxes in living cells with subcellular resolution from fluorescence lifetime imaging of NADH. This result is based on the use of a generic coarse-grained NADH redox model. We tested the model in mouse oocytes and human tissue culture cells subject to a wide variety of perturbations by comparing predicted fluxes through the electron transport chain (ETC) to direct measurements of oxygen consumption rate. Interpreting the FLIM measurements of NADH using this model, we discovered a homeostasis of ETC flux in mouse oocytes: perturbations of nutrient supply and energy demand of the cell do not change ETC flux despite significantly impacting NADH metabolic state. Furthermore, we observed a subcellular spatial gradient of ETC flux in mouse oocytes and found that this gradient is primarily a result of a spatially heterogeneous mitochondrial proton leak. We concluded from these observations that ETC flux in mouse oocytes is not controlled by energy demand or supply, but by the intrinsic rates of mitochondrial respiration.

Keywords:  biochemistry; chemical biology; human; mouse; physics of living systems

DOI:  https://doi.org/10.7554/eLife.73808
Front Neurosci. 2021 ;15 764898

Loss of Caveolin-1 Impairs Light Flicker-Induced Neurovascular Coupling at the Optic Nerve Head.

Jing Hong Loo, Ying Shi Lee, Chang Yi Woon, Victor H K Yong, Bingyao Tan, Leopold Schmetterer, Rachel S Chong.

  Glaucoma is a neurodegenerative disease, which results in characteristic visual field defects. Intraocular pressure (IOP) remains the main risk factor for this leading cause of blindness. Recent studies suggest that disturbances in neurovascular coupling (NVC) may be associated with glaucoma. The resultant imbalance between vascular perfusion and neuronal stimulation in the eye may precede retinal ganglion cell (RGC) loss and increase the susceptibility of the eye to raised IOP and glaucomatous degeneration. Caveolin-1 (Cav-1) is an integral scaffolding membrane protein found abundantly in retinal glial and vascular tissues, with possible involvement in regulating the neurovascular coupling response. Mutations in Cav-1 have been identified as a major genetic risk factor for glaucoma. Therefore, we aim to evaluate the effects of Cav-1 depletion on neurovascular coupling, retinal vessel characteristics, RGC density and the positive scotopic threshold response (pSTR) in Cav-1 knockout (KO) versus wild type C57/Bl6 mice (WT). Following light flicker stimulation of the retina, Cav-1 KO mice showed a smaller increase in perfusion at the optic nerve head and peripapillary arteries, suggesting defective neurovascular coupling. Evaluation of the superficial capillary plexus in Cav-1 KO mice also revealed significant differences in vascular morphology with higher vessel density, junction density and decreased average vessel length. Cav-1 KO mice exhibited higher IOP and lower pSTR amplitude. However, there was no significant difference in RGC density between Cav-1 KO and wild type mice. These findings highlight the role of Cav-1 in regulating neurovascular coupling and IOP and suggest that the loss of Cav-1 may predispose to vascular dysfunction and decreased RGC signaling in the absence of structural loss. Current treatment for glaucoma relies heavily on IOP-lowering drugs, however, there is an immense potential for new therapeutic strategies that increase Cav-1 expression or augment its downstream signaling in order to avert vascular dysfunction and glaucomatous change.

Keywords:  caveolin; glaucoma; neuroprotection; neurovascular coupling; neurovascular dysfunction

DOI:  https://doi.org/10.3389/fnins.2021.764898
Cells. 2021 Nov 22. pii: 3265. [Epub ahead of print]10(11):

Differential Responses of Neural Retina Progenitor Populations to Chronic Hyperglycemia.

Nicole Schmitner, Christina Recheis, Jakob Thönig, Robin A Kimmel.

  Diabetic retinopathy is a frequent complication of longstanding diabetes, which comprises a complex interplay of microvascular abnormalities and neurodegeneration. Zebrafish harboring a homozygous mutation in the pancreatic transcription factor pdx1 display a diabetic phenotype with survival into adulthood, and are therefore uniquely suitable among zebrafish models for studying pathologies associated with persistent diabetic conditions. We have previously shown that, starting at three months of age, pdx1 mutants exhibit not only vascular but also neuro-retinal pathologies manifesting as photoreceptor dysfunction and loss, similar to human diabetic retinopathy. Here, we further characterize injury and regenerative responses and examine the effects on progenitor cell populations. Consistent with a negative impact of hyperglycemia on neurogenesis, stem cells of the ciliary marginal zone show an exacerbation of aging-related proliferative decline. In contrast to the robust Müller glial cell proliferation seen following acute retinal injury, the pdx1 mutant shows replenishment of both rod and cone photoreceptors from slow-cycling, neurod-expressing progenitors which first accumulate in the inner nuclear layer. Overall, we demonstrate a diabetic retinopathy model which shows pathological features of the human disease evolving alongside an ongoing restorative process that replaces lost photoreceptors, at the same time suggesting an unappreciated phenotypic continuum between multipotent and photoreceptor-committed progenitors.

Keywords:  Notch; diabetes; hyperglycemia; neurod; photoreceptors; progenitor cell; regeneration; retinal degeneration; zebrafish

DOI:  https://doi.org/10.3390/cells10113265
Invest Ophthalmol Vis Sci. 2021 Nov 01. 62(14): 25

Role of the Phospholipase C Pathway and Calcium Mobilization in Oxytocin-Induced Contraction of Lacrimal Gland Myoepithelial Cells.

Angela Gárriz, Salome Aubry, Quentin Wattiaux, Jeffrey Bair, Michael Mariano, Georgios Hatzipetrou, Maytal Bowman, Junji Morokuma, Gustavo Ortiz, Pedram Hamrah, Darlene A Dartt, Driss Zoukhri.

Purpose: We reported that oxytocin (OXT), added to freshly prepared lacrimal gland lobules, induced myoepithelial cell (MEC) contraction. In other systems, OXT activates phospholipase C (PLC) generating Inositol 1,4,5-trisphosphate (IP3) which increases intracellular calcium concentration ([Ca2+]i) causing contraction. The aim of the current study was to investigate the role of this pathway in OXT-induced contraction of MEC.
Methods: Tear volume was measured using the cotton thread method. Lacrimal gland MEC were isolated and propagated from α-smooth muscle actin (SMA)-green fluorescent protein (GFP) mice, in which MEC express GFP making them easily identifiable. RNA and protein samples were prepared for RT-PCR and Western blotting for G protein expression. Changes in [Ca2+]i were measured in Fura-2 loaded MEC using a ratio imaging system. MEC contraction was monitored in real time and changes in cell size were quantified using ImageJ software.
Results: OXT applied either topically to surgically exposed lacrimal glands or delivered subcutaneously resulted in increased tear volume. OXT stimulated lacrimal gland MEC contraction in a dose-dependent manner, with a maximum response at 10-7 M. MEC express the PLC coupling G proteins, Gαq and Gα11, and their activation by OXT resulted in a concentration-dependent increase in [Ca2+]i with a maximum response at 10-6 M. Furthermore, the activation of the IP3 receptor to increase [Ca2+]i is crucial for OXT-induced MEC contraction since blocking the IP3 receptor with 2-APB completely abrogated this response.
Conclusions: We conclude that OXT uses the PLC/Ca2+ pathway to stimulate MEC contraction and increase lacrimal gland secretion.

DOI: https://doi.org/10.1167/iovs.62.14.25