scholarly journals Autophagy Induction by Cyclic Stretch and Its Effect on Cytokines in Retinal Pigment Epithelial Cells

Author(s):  
Zengyi Wang ◽  
Xida Liang ◽  
Shen Wu ◽  
Jingxue Zhang ◽  
Qian Liu ◽  
...  

Abstract Background: Strong evidence of the correlation between age-related macular degeneration (AMD) and vitreomacular interface abnormality (VMIA). Meanwhile, as a crucial mechanism of retinal pigment epithelial (RPE) cells’ homeostasis, autophagy induction by cyclic stretch appears to be particularly significant.Methods: Cultured ARPE-19 cells were subjected to cyclic stretch (20% elongation, 1HZ) for 1h, 2h, 6h, 12h,24h and 48h by FX-5000 Tension System. Then, we observed the expression levels of LC3I, LC3II, Beclin-1, SQSTM1/p62, LAMP-1, mTOR and phosphorylated mTOR(pmTOR), AMPK and pAMPK, NADPH oxidase 4 (NOX4), and vascular endothelial growth factor (VEGF) in RPE cells under stretch by western blot and immunofluorescence.Results: We found autophagic proteins mostly induced by cyclic stretch in a time-dependent fashion via mTOR suppression and AMPK activation, except for SQSTM1/p62. 3-Methyladenine(3-MA), an inhibitor for autophagy, could reduce the up-regulation of autophagy due to cyclic stretch, leading to higher level of VEGF release after 24h cyclic stretch. Rapamycin could narrow the increase degree of VEGF and NOX4 by cyclic stretch by raise autophagic level in RPE cells.Conclusion: Stretch might induce autophagy in RPE cells by mTOR or AMPK pathway. Autophagy might play the protective function for RPE cells away from mechanical stress derived from VMIA-related AMD.

2019 ◽  
Vol 20 (6) ◽  
pp. 1387 ◽  
Author(s):  
Abdulwahab Alamri ◽  
Lincoln Biswas ◽  
David Watson ◽  
Xinhua Shu

Age-related macular degeneration is the main cause of vision loss in the aged population worldwide. Drusen, extracellular lesions formed underneath the retinal pigment epithelial (RPE) cells, are a clinical feature of AMD and associated with AMD progression. RPE cells support photoreceptor function by providing nutrition, phagocytosing outer segments and removing metabolic waste. Dysfunction and death of RPE cells are early features of AMD. The translocator protein, TSPO, plays an important role in RPE cholesterol efflux and loss of TSPO results in increased intracellular lipid accumulation and reactive oxygen species (ROS) production. This study aimed to investigate the impact of TSPO knockout on RPE cellular metabolism by identifying the metabolic differences between wildtype and knockout RPE cells, with or without treatment with oxidized low density lipoprotein (oxLDL). Using liquid chromatography mass spectrometry (LC/MS), we differentiated several metabolic pathways among wildtype and knockout cells. Lipids amongst other intracellular metabolites were the most influenced by loss of TSPO and/or oxLDL treatment. Glucose, amino acid and nucleotide metabolism was also affected. TSPO deletion led to up-regulation of fatty acids and glycerophospholipids, which in turn possibly affected the cell membrane fluidity and stability. Higher levels of glutathione disulphide (GSSG) were found in TSPO knockout RPE cells, suggesting TSPO regulates mitochondrial-mediated oxidative stress. These data provide biochemical insights into TSPO-associated function in RPE cells and may shed light on disease mechanisms in AMD.


2020 ◽  
Vol 2020 ◽  
pp. 1-29 ◽  
Author(s):  
Camille Keisha Mahendra ◽  
Loh Teng Hern Tan ◽  
Priyia Pusparajah ◽  
Thet Thet Htar ◽  
Lay-Hong Chuah ◽  
...  

Retinal pigment epithelial (RPE) cells are an essential part of the human eye because they not only mediate and control the transfer of fluids and solutes but also protect the retina against photooxidative damage and renew photoreceptor cells through phagocytosis. However, their function necessitates cumulative exposure to the sun resulting in UV damage, which may lead to the development of age-related macular degeneration (AMD). Several studies have shown that UVB induces direct DNA damage and oxidative stress in RPE cells by increasing ROS and dysregulating endogenous antioxidants. Activation of different signaling pathways connected to inflammation, cell cycle arrest, and intrinsic apoptosis was reported as well. Besides that, essential functions like phagocytosis, osmoregulation, and water permeability of RPE cells were also affected. Although the melanin within RPE cells can act as a photoprotectant, this photoprotection decreases with age. Nevertheless, the changes in lens epithelium-derived growth factor (LEDGF) and autophagic activity or application of bioactive compounds from natural products can reverse the detrimental effect of UVB. Additionally, in vivo studies on the whole retina demonstrated that UVB irradiation induces gene and protein level dysregulation, indicating cellular stress and aberrations in the chromosome level. Morphological changes like retinal depigmentation and drusen formation were noted as well which is similar to the etiology of AMD, suggesting the connection of UVB damage with AMD. Therefore, future studies, which include mechanism studies via in vitro or in vivo and other potential bioactive compounds, should be pursued for a better understanding of the involvement of UVB in AMD.


2019 ◽  
Vol 20 (23) ◽  
pp. 6028 ◽  
Author(s):  
Hwang ◽  
Kwon ◽  
Woo ◽  
Chung

: (1) Background: Age-related macular degeneration (AMD) is closely related with retinal pigment epithelial (RPE) cell dysfunction. Although the exact pathogenesis of AMD remains largely unknown, oxidative stress-induced RPE damage is believed to be one of the primary causes. We investigated the molecular mechanisms of pentraxin 3 (PTX3) expression and its biological functions during oxidative injury. (2) Methods: Using enzyme-linked immunosorbent assays and real-time reverse transcription-polymerase chain reaction, we analyzed mRNA and protein levels of PTX3 in the presence or absence of oxidative stress inducer, sodium iodate (NaIO3), in primary human H-RPE and ARPE-19 cells. Furthermore, we assessed cell death, antioxidant enzyme expression, and AMD-associated gene expression to determine the biological functions of PTX3 under oxidative stress. (3) Results: NaIO3 increased PTX3 expression, in a dose- and time-dependent manner, in H-RPE and ARPE-19 cells. We found phosphorylated Akt, a downstream target of the PI3 kinase pathway, phosphor- mitogen-activated protein kinase kinase 1/2 (ERK), and intracellular reactive oxygen species (ROS) were predominantly induced by NaIO3. NaIO3-induced PTX3 expression was decreased in the presence of phosphoinositide 3 (PI3) kinase inhibitors, ERK inhibitors, and ROS scavengers. Furthermore, NaIO3 enhanced mRNA expression of antioxidant enzymes such as glucose-6-phosphate dehydrogenase (G6PDH), catalase (CAT), and glutathione S-reductase (GSR) in the control shRNA expressing RPE cells, but not in hPTX3 shRNA expressing RPE cells. Interestingly, NaIO3 did not induce mRNA expression of AMD marker genes, such as complement factor I (CFI), complement factor H (CFH), apolipoprotein E (APOE), and toll-like receptor 4 (TLR4) in hPTX3 shRNA expressing RPE cells. 4) Conclusions: These results suggest that PTX3 accelerates RPE cell death and might be involved in AMD development in the presence of oxidative stress.


2016 ◽  
Vol 94 (2) ◽  
pp. 188-196 ◽  
Author(s):  
Yaron A. Green ◽  
Keren Ben-Yaakov ◽  
Orit Adir ◽  
Ayala Pollack ◽  
Zeev Dvashi

Autophagy is an evolutionarily conserved mechanism for degrading long-lived or malfunctioning proteins and organelles, such as those resulting from oxidative stress. Several publications have demonstrated the importance of the autophagy process in the pathophysiology of dry age-related macular degeneration (AMD). Still, the mechanism underlying this process and its involvement in dry AMD are not fully characterized. Investigating the autophagy process in retinal pigment epithelial (RPE) cells, we identified transforming growth factor β activated kinase 1 (TAK1) as a key player in the process. We found increased TAK1 phosphorylation in ARPE-19 and D407 cells treated with different inducers of autophagy, such as oxidative stress and rapamycin. Moreover, utilizing TAK1 specific inhibitor prior to oxidative stress or rapamycin treatment, we found significant reduction in LC3A/B-II expression. These results point at the involvement of TAK1 in the regulation of autophagy in RPE cells. This study suggests that aberrant activity of this kinase impairs autophagy and subsequently leads to alterations in the vitality of RPE cells. Proper activity of TAK1 may be essential for efficient autophagy, and crucial for the ability of RPE cells to respond to stress and dispose of damaged organelles, thus preventing or delaying retinal pathologies.


2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Liang Ye ◽  
Ting Yu ◽  
Yanqun Li ◽  
Bingni Chen ◽  
Jinshun Zhang ◽  
...  

To gain further insights into the molecular basis of Sulforaphane (SF) mediated retinal pigment epithelial (RPE) 19 cell against oxidative stress, we investigated the effects of SF on the regulation of gene expression on a global scale and tested whether SF can endow RPE cells with the ability to resist apoptosis. The data revealed that after exposure to H2O2, RPE 19 cell viability was increased in the cells pretreated with SF compared to the cell not treated with SF. Microarray analysis revealed significant changes in the expression of 69 genes in RPE 19 cells after 6 hours of SF treatment. Based on the functional relevance, eight of the SF-responsive genes, that belong to antioxidant redox system, and inflammatory responsive factors were validated. The up-regulating translation of thioredoxin-1 (Trx1) and the nuclear translocation of Nuclear factor-like2 (Nrf2) were demonstrated by immunoblot analysis in SF treated RPE cells. Our data indicate that SF increases the ability of RPE 19 cell against oxidative stress through up-regulating antioxidative enzymes and down-regulating inflammatory mediators and chemokines. The results suggest that the antioxidant, SF, may be a valuable supplement for preventing and retarding the development of Age Related Macular Degeneration.


Oncotarget ◽  
2016 ◽  
Vol 7 (8) ◽  
pp. 8532-8545 ◽  
Author(s):  
Ahmed S. Ibrahim ◽  
Suchreet Mander ◽  
Khaled A. Hussein ◽  
Nehal M. Elsherbiny ◽  
Sylvia B. Smith ◽  
...  

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