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Human & Experimental Toxicology Jan 2021Methylphenidate (MPH) is used as the first-line treatment for attention-deficit hyperactivity disorder. However, there are concerns that this treatment may be associated...
Methylphenidate (MPH) is used as the first-line treatment for attention-deficit hyperactivity disorder. However, there are concerns that this treatment may be associated with increased risk of retinal damage. This study was to investigate cytotoxicity of MPH on photoreceptor cells and explore its underlying mechanisms. MPH-caused cell toxicity was established in 661 W cells. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium-bromid and lactate dehydrogenase assays. Oxidative stress was measured by the markers: glutathione (GSH) reductase, catalase, and superoxide dismutase activities as well as GSH, reactive oxygen species, and malondialdehyde levels. Gene and protein expression was detected by real-time polymerase chain reaction (PCR) and western blot, respectively. Results showed that MPH decreased 661 W cell viability, increased caspase-3/9 activities, and induced oxidative stress. Furthermore, MPH treatment increased messenger RNA (mRNA) expression of and microtubule-associated protein 1A/1B-light chain 3B (LC3B) protein expression in 661 W cells, suggesting autophagy was induced. MPH treatment also upregulated p-JAK1/p-STAT1 protein expression. These data demonstrated that MPH could increase oxidative stress in photoreceptor cells to cause cell toxicity via autophagy, providing the scientific rationale for the photoreceptor cell damage caused by the MPH administration.
Topics: Animals; Autophagy; Glutathione; Malondialdehyde; Methylphenidate; Oxidative Stress; Photoreceptor Cells; Reactive Oxygen Species
PubMed: 32748667
DOI: 10.1177/0960327120940357 -
The FEBS Journal Sep 2023The endoplasmic reticulum membrane protein complex (EMC) plays a critical role in the synthesis of multipass membrane proteins. Genetic studies indicated that mutations...
The endoplasmic reticulum membrane protein complex (EMC) plays a critical role in the synthesis of multipass membrane proteins. Genetic studies indicated that mutations in EMC1 gene were associated with retinal degeneration diseases; however, the role of EMC1 in photoreceptor has not been confirmed. Here, we show that Emc1 ablation in the photoreceptor cells of mice recapitulated the retinitis pigmentosa phenotypes, including an attenuated scotopic electroretinogram response and the progressive degeneration of rod cells and cone cells. Histopathological examination of tissues from rod-specific Emc1 knockout mice revealed mislocalized rhodopsin and irregularly arranged cone cells at the age of 2 months. Further immunoblotting analysis revealed decreased levels of membrane proteins and endoplasmic reticulum chaperones in 1-month-old rod-specific Emc1 knockout mice retinae, and this led us to speculate that the loss of membrane proteins is the main cause of the degeneration of photoreceptors. EMC1 most likely regulated the membrane protein levels at an earlier step in the biosynthetic process before the proteins translocated into the endoplasmic reticulum. The present study demonstrates the essential roles of Emc1 in photoreceptor cells, and reveals the mechanism through which EMC1 mutations are linked to retinitis pigmentosa.
Topics: Animals; Mice; Disease Models, Animal; Membrane Proteins; Mice, Knockout; Photoreceptor Cells; Retinal Degeneration; Retinitis Pigmentosa; Endoplasmic Reticulum
PubMed: 37098815
DOI: 10.1111/febs.16807 -
Biological Chemistry Apr 2020Photoreceptors are polarized neurons, with specific subcellular compartmentalization and unique requirements for protein expression and trafficking. Each photoreceptor... (Review)
Review
Photoreceptors are polarized neurons, with specific subcellular compartmentalization and unique requirements for protein expression and trafficking. Each photoreceptor contains an outer segment (OS) where vision begins, an inner segment (IS) where protein synthesis occurs and a synaptic terminal for signal transmission to second-order neurons. The OS is a large, modified primary cilium attached to the IS by a slender connecting cilium (CC), the equivalent of the transition zone (TZ). Daily renewal of ~10% of the OS requires massive protein biosynthesis in the IS with reliable transport and targeting pathways. Transport of lipidated ('sticky') proteins depends on solubilization factors, phosphodiesterase δ (PDEδ) and uncoordinated protein-119 (UNC119), and the cargo dispensation factor (CDF), Arf-like protein 3-guanosine triphosphate (ARL3-GTP). As PDE6 and transducin still reside prominently in the OS of PDEδ and UNC119 germline knockout mice, respectively, we propose the existence of an alternate trafficking pathway, whereby lipidated proteins migrate in rhodopsin-containing vesicles of the secretory pathway.
Topics: Animals; Diffusion; Humans; Lipid Metabolism; Photoreceptor Cells; Protein Transport
PubMed: 31811799
DOI: 10.1515/hsz-2019-0375 -
Journal of the American Association For... Jan 2023Light is an extrinsic factor that exerts widespread influence on the regulation of circadian, physiologic, hormonal, metabolic, and behavioral systems of all animals,... (Review)
Review
Light is an extrinsic factor that exerts widespread influence on the regulation of circadian, physiologic, hormonal, metabolic, and behavioral systems of all animals, including those used in research. These wide-ranging biologic effects of light are mediated by distinct photoreceptors, the melanopsin-containing intrinsically photosensitive retinal ganglion cells of the nonvisual system, which interact with the rods and cones of the conventional visual system. Here, we review the nature of light and circadian rhythms, current industry practices and standards, and our present understanding of the neurophysiology of the visual and nonvisual systems. We also consider the implications of this extrinsic factor for vivarium measurement, production, and technological application of light, and provide simple recommendations on artificial lighting for use by regulatory authorities, lighting manufacturers, designers, engineers, researchers, and research animal care staff that ensure best practices for optimizing animal health and wellbeing and, ultimately, improving scientific outcomes.
Topics: Animals; Lighting; Retinal Ganglion Cells; Photoreceptor Cells; Circadian Rhythm
PubMed: 36755210
DOI: 10.30802/AALAS-JAALAS-23-000003 -
The Journal of Biological Chemistry Feb 2022The breakdown of all-trans-retinal (atRAL) clearance is closely associated with photoreceptor cell death in dry age-related macular degeneration (AMD) and autosomal...
The breakdown of all-trans-retinal (atRAL) clearance is closely associated with photoreceptor cell death in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt's disease (STGD1), but its mechanisms remain elusive. Here, we demonstrate that activation of gasdermin E (GSDME) but not gasdermin D promotes atRAL-induced photoreceptor damage by activating pyroptosis and aggravating apoptosis through a mitochondria-mediated caspase-3-dependent signaling pathway. Activation of c-Jun N-terminal kinase was identified as one of the major causes of mitochondrial membrane rupture in atRAL-loaded photoreceptor cells, resulting in the release of cytochrome c from mitochondria to the cytosol, where it stimulated caspase-3 activation required for cleavage of GSDME. Aggregation of the N-terminal fragment of GSDME in the mitochondria revealed that GSDME was likely to penetrate mitochondrial membranes in photoreceptor cells after atRAL exposure. ABC (subfamily A, member 4) and all-trans-retinol dehydrogenase 8 are two key proteins responsible for clearing atRAL in the retina. Abca4Rdh8 mice exhibit serious defects in atRAL clearance upon light exposure and serve as an acute model for dry AMD and STGD1. We found that N-terminal fragment of GSDME was distinctly localized in the photoreceptor outer nuclear layer of light-exposed Abca4Rdh8 mice. Of note, degeneration and caspase-3 activation in photoreceptors were significantly alleviated in Abca4Rdh8Gsdme mice after exposure to light. The results of this study indicate that GSDME is a common causative factor of photoreceptor pyroptosis and apoptosis arising from atRAL overload, suggesting that repressing GSDME may represent a potential treatment of photoreceptor atrophy in dry AMD and STGD1.
Topics: ATP-Binding Cassette Transporters; Animals; Caspase 3; Mice; Photoreceptor Cells; Pore Forming Cytotoxic Proteins; Retina; Retinaldehyde; Stargardt Disease
PubMed: 34973334
DOI: 10.1016/j.jbc.2021.101553 -
Progress in Retinal and Eye Research Jul 2022The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive... (Review)
Review
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
Topics: Blood-Retinal Barrier; Humans; Lipids; Photoreceptor Cells; Retinal Diseases; Retinal Pigment Epithelium
PubMed: 34971765
DOI: 10.1016/j.preteyeres.2021.101037 -
Eye (London, England) Nov 2021In human retina, photoreceptor cell death (PCD) is a slow but conspicuous event, which continues with aging. Rods die earlier than cones, the latter continue to alter in... (Review)
Review
In human retina, photoreceptor cell death (PCD) is a slow but conspicuous event, which continues with aging. Rods die earlier than cones, the latter continue to alter in a subtle manner until advanced aging. This review summarizes the existing information on age-related changes in photoreceptor cells, especially cones and analyses the possible associated factors. Oxidative and nitrosative stress are involved in photoreceptor alterations, which may stem from light and iron toxicity and other sources. Lipid peroxidation in macular photoreceptor outer segments and mitochondrial aberrations are prominent in aging. It is important to understand how those changes ultimately trigger PCD. The redistribution of calbindin D-28K and long/middle-wavelength-sensitive opsin in the parafoveal and perifoveal cones, anomalies in their somata and axons are strong predictors of their increasing vulnerability with aging. Signs of reduced autophagy, with autophagosomes containing organelle remnants are seen in aging photoreceptor cells. Currently, mechanisms that lead to human PCD are unknown; some observations favour apoptosis as a pathway. Since cones appear to change slowly, there is an opportunity to reverse those changes before they die. Therefore, a full understanding of how cones alter and the molecular pathways they utilize for survival must be the future research goal. Recent approaches to prevent PCD in aging and diseases are highlighted.
Topics: Aging; Humans; Immunohistochemistry; Retina; Retinal Cone Photoreceptor Cells; Retinal Rod Photoreceptor Cells
PubMed: 34079093
DOI: 10.1038/s41433-021-01602-1 -
Biotechnology Journal Feb 2015Molecular signals are sensed by their respective receptors and information is transmitted and processed by a sophisticated intracellular network controlling various... (Review)
Review
Molecular signals are sensed by their respective receptors and information is transmitted and processed by a sophisticated intracellular network controlling various biological functions. Optogenetic tools allow the targeting of specific signaling nodes for a precise spatiotemporal control of downstream effects. These tools are based on photoreceptors such as phytochrome B (PhyB), cryptochrome 2, or light-oxygen-voltage-sensing domains that reversibly bind to specific interaction partners in a light-dependent manner. Fusions of a protein of interest to the photoreceptor or their interaction partners may enable the control of the protein function by light-mediated dimerization, a change of subcellular localization, or due to photocaging/-uncaging of effectors. In this review, we summarize the photoreceptors and the light-based mechanisms utilized for the modulation of signaling events in mammalian cells focusing on non-neuronal applications. We discuss in detail optogenetic tools and approaches applied to control signaling events mediated by second messengers, Rho GTPases and growth factor-triggered signaling cascades namely the RAS/RAF and phosphatidylinositol-3-kinase pathways. Applying the latest generation of optogenetic tools allows to control cell fate decisions such as proliferation and differentiation or to deliver therapeutic substances in a spatiotemporally controlled manner.
Topics: Animals; Cell Differentiation; Cell Proliferation; Cryptochromes; Humans; Models, Molecular; Optogenetics; Photoreceptor Cells; Phytochrome B; Signal Transduction
PubMed: 25216399
DOI: 10.1002/biot.201400077 -
Ophthalmic Genetics Jun 2022Rods and cones are photoreceptor neurons in the retina that are required for visual sensation in vertebrates, wherein the perception of vision is initiated when these...
BACKGROUND
Rods and cones are photoreceptor neurons in the retina that are required for visual sensation in vertebrates, wherein the perception of vision is initiated when these neurons respond to photons in the light stimuli. The photoreceptor cell is structurally studied as outer segments (OS) and inner segments (IS) where proper protein sorting, localization, and compartmentalization are critical for phototransduction, visual function, and survival. In human retinal diseases, improper protein transport to the OS or mislocalization of proteins to the IS and other cellular compartments could lead to impaired visual responses and photoreceptor cell degeneration that ultimately cause loss of visual function.
RESULTS
Therefore, studying and identifying mechanisms involved in facilitating and maintaining proper protein transport in photoreceptor cells would help our understanding of pathologies involving retinal cell degeneration in inherited retinal dystrophies, age-related macular degeneration, and Usher Syndrome.
CONCLUSIONS
Our mini-review will discuss mechanisms of protein transport within photoreceptors and introduce a novel role for an unconventional motor protein, MYO1C, in actin-based motor transport of the visual chromophore Rhodopsin to the OS, in support of phototransduction and visual function.
Topics: Animals; Humans; Protein Transport; Retina; Retinal Cone Photoreceptor Cells; Retinal Degeneration; Retinal Rod Photoreceptor Cells; Vision, Ocular
PubMed: 35470760
DOI: 10.1080/13816810.2022.2062391 -
Bulletin of Experimental Biology and... Aug 2022Immunohistochemical and ultrastructural analysis revealed signs of structural alterations in neurons and autophagy in all layers of the human retina at the end-stage...
Immunohistochemical and ultrastructural analysis revealed signs of structural alterations in neurons and autophagy in all layers of the human retina at the end-stage glaucoma. The most pronounced destructive changes associated with swelling and destruction of mitochondria, endoplasmic reticulum, and Golgi apparatus, as well as structural signs of impaired synaptic activity and apoptosis were noted in ganglion, bipolar, and amacrine neurons. In the structure of photoreceptor cells, alone with destructive processes associated with structural alterations of rods and cones in the outer membrane discs, as well as swelling of organelles, we observed processes aimed at the maintenance of cell homeostasis. Structural signs of autophagy (mainly mitophagy) and changes of the ultrastructural organization in rod neurons were more pronounced than in cones.
Topics: Autophagy; Glaucoma; Humans; Photoreceptor Cells; Retina; Retinal Neurons; Synapses
PubMed: 36058974
DOI: 10.1007/s10517-022-05563-7