bims-mideyd 2023-12-10 papers

Issue of 2023‒12‒10
four papers selected by
Rajalekshmy “Raji” Shyam, Indiana University Bloomington

Graefes Arch Clin Exp Ophthalmol. 2023 Dec 07.

Metformin protects retinal pigment epithelium cells against H2O2-induced oxidative stress and inflammation via the Nrf2 signaling cascade.

Qiting Feng, Xiangcai Ruan, Min Lu, Shimiao Bu, Yuehong Zhang.

PURPOSE: Dysfunctions of retinal pigment epithelium (RPE) attributed to oxidative stress and inflammation are implicated with age-related macular degeneration (AMD). A debate on the curative role of metformin in AMD has been raised, though several recent clinical studies support the lower odds by using metformin. This study aimed to determine whether metformin could exert cytoprotection against RPE oxidative damages and the potential mechanisms.METHODS: A cellular AMD model was established by treating ARPE-19 cells with hydrogen peroxide (H2O2) for 24 h. The reactive oxygen species (ROS) generation, expression of antioxidant enzymes, and levels of pro-inflammatory cytokines were monitored under administrations with H2O2 with/without metformin. The expression and DNA-binding activity of transcription factor erythroid-related factor 2 (Nrf2) were determined by western blot, immunofluorescence, and electrophoretic mobility shift assay. Knockout of Nrf2 was conducted by CRISPR/Cas9 gene deletion system.
RESULTS: Metformin pretreatment significantly improved the H2O2-induced low viability of ARPE-19 cells, reduced ROS production, and increased contents of antioxidative molecules. Concurrently, metformin also suppressed levels of pro-inflammatory cytokines caused by H2O2. The metformin-augmented nuclear translocation and DNA-binding activity of Nrf2 were further verified by the increased expression of its downstream targets. Genetic deletion of Nrf2 blocked the cytoprotective role of metformin.
CONCLUSION: Metformin possesses antioxidative and anti-inflammatory properties in ARPE-19 cells by activating the Nrf2 signaling. It supports the potential use for the control and prevention of AMD.

Keywords: Age-related macular degeneration; Inflammation; Metformin; Nrf2; Oxidative stress; Retinal pigment epithelial cells

DOI: https://doi.org/10.1007/s00417-023-06321-9

Invest Ophthalmol Vis Sci. 2023 Dec 01. 64(15): 6

HO-1-Mediated Autophagic Restoration Protects Lens Epithelial Cells Against Oxidative Stress and Cellular Senescence.

Lijun Wang, Wei Lou, Yao Zhang, Ziang Chen, Yang Huang, Haiying Jin.

Purpose: Oxidative stress and cellular senescence are risk factors for age-related cataract. Heme oxygenase 1 (HO-1) is a critical antioxidant enzyme and related to autophagy. Here, we investigate the crosstalk among HO-1, oxidative stress, and cellular senescence in mouse lens epithelial cells (LECs).Methods: The gene expression of HO-1, p21, LC3, and p62 was measured in human samples. The protective properties of HO-1 were examined in hydrogen peroxide (H2O2)-damaged LECs. Autophagic flux was examined by Western blot and mRFP-GFP-LC3 assay. Western blotting and lysotracker staining were used to analyze lysosomal function. Flow cytometry was used to detect intracellular reactive oxygen species and analyze cell cycle. Senescence-associated β-galactosidase assay was used to determine cellular senescence. The crosstalk between HO-1 and transcription factor EB (TFEB) was further observed in TFEB-knockdown cells. The TFEB binding site in the promoter region of Hmox1 was predicted by the Jasper website and was confirmed by chromatin immunoprecipitation assay.
Results: HO-1 gene expression decreased in LECs of patients with age-related nuclear cataract, whereas mRNA expression levels of p21, LC3, and p62 increased. Upon H2O2-induced oxidative stress, LECs showed the characteristics of autophagic flux blockade, lysosomal dysfunction, and premature senescence. Interestingly, HO-1 significantly restored the impaired autophagic flux and lysosomal function and delayed cellular senescence. TFEB gene silencing greatly reduced the HO-1-mediated autophagic restoration, leading to a failure to prevent LECs from oxidative stress and premature senescence.
Conclusions: We demonstrated HO-1 effects on restoring autophagic flux and delaying cellular senescence under oxidative stress in LECs, which are dependent on TFEB.

DOI: https://doi.org/10.1167/iovs.64.15.6

Proc Natl Acad Sci U S A. 2023 Dec 12. 120(50): e2302845120

Pathologic vs. protective roles of hypoxia-inducible factor 1 in RPE and photoreceptors in wet vs. dry age-related macular degeneration.

Savalan Babapoor-Farrokhran, Yu Qin, Miguel Flores-Bellver, Yueqi Niu, Imran A Bhutto, Silvia Aparicio-Domingo, Chuanyu Guo, Murilo Rodrigues, Timothy Domashevich, Monika Deshpande, Haley Megarity, Rakesh Chopde, Charles G Eberhart, Valeria Canto-Soler, Silvia Montaner, Akrit Sodhi.

It has previously been reported that antioxidant vitamins can help reduce the risk of vision loss associated with progression to advanced age-related macular degeneration (AMD), a leading cause of visual impairment among the elderly. Nonetheless, how oxidative stress contributes to the development of choroidal neovascularization (CNV) in some AMD patients and geographic atrophy (GA) in others is poorly understood. Here, we provide evidence demonstrating that oxidative stress cooperates with hypoxia to synergistically stimulate the accumulation of hypoxia-inducible factor (HIF)-1α in the retinal pigment epithelium (RPE), resulting in increased expression of the HIF-1-dependent angiogenic mediators that promote CNV. HIF-1 inhibition blocked the expression of these angiogenic mediators and prevented CNV development in an animal model of ocular oxidative stress, demonstrating the pathological role of HIF-1 in response to oxidative stress stimulation in neovascular AMD. While human-induced pluripotent stem cell (hiPSC)-derived RPE monolayers exposed to chemical oxidants resulted in disorganization and disruption of their normal architecture, RPE cells proved remarkably resistant to oxidative stress. Conversely, equivalent doses of chemical oxidants resulted in apoptosis of hiPSC-derived retinal photoreceptors. Pharmacologic inhibition of HIF-1 in the mouse retina enhanced-while HIF-1 augmentation reduced-photoreceptor apoptosis in two mouse models for oxidative stress, consistent with a protective role for HIF-1 in photoreceptors in patients with advanced dry AMD. Collectively, these results suggest that in patients with AMD, increased expression of HIF-1α in RPE exposed to oxidative stress promotes the development of CNV, but inadequate HIF-1α expression in photoreceptors contributes to the development of GA.

Keywords: age-related macular degeneration; choroidal neovascularization; geographic atrophy; hypoxia-inducible factor-1; oxidative stress

DOI: https://doi.org/10.1073/pnas.2302845120

J Microbiol Biotechnol. 2023 Nov 13. 34(3): 1-10

Anthocyanins Inhibits Oxidative Injury in Human Retinal Pigment Epithelial ARPE-19 Cells via Activating Heme Oxygenase-1.

Cheol Park, Hyun Hwangbo, Sung Ok Kim, Jeong Sook Noh, Shin-Hyung Park, Su Hyun Hong, Sang Hoon Hong, Gi-Young Kim, Yung Hyun Choi.

Anthocyanins belong to phenolic pigments and are known to have various pharmacological activities. This study aimed to investigate whether anthocyanins could inhibit hydrogen peroxide (H2O2)-induced oxidative damage in human retinal pigment epithelial ARPE-19 cells. Our results indicated that anthocyanins suppressed H2O2-induced genotoxicity, while inhibiting reactive oxygen species (ROS) production and preserving diminished glutathione. Anthocyanins also suppressed H2O2-induced apoptosis by reversing the Bcl-2/Bax ratio and inhibiting caspase-3 activation. Additionally, anthocyanins attenuated the release of cytochrome c into the cytosol, which was achieved by interfering with mitochondrial membrane disruption. Moreover, anthocyanins increased the expression of heme oxygenase-1 (HO-1) as well as its activity, which was correlated with the phosphorylation and nuclear translocation of nuclear factor-erythroid-2 related factor 2 (Nrf2). However, the cytoprotective and anti-apoptotic effects of anthocyanins were significantly attenuated by the HO-1 inhibitor, demonstrating that anthocyanins promoted Nrf2-induced HO-1 activity to prevent ARPE-19 cells from oxidative stress. Therefore, our findings suggest that anthocyanins, as Nrf2 activators, have potent ROS scavenging activity and may have the potential to protect ocular injury caused by oxidative stress.

Keywords: Anthocyanins; Nrf2/HO-1; ROS; apoptosis; genotoxicity

DOI: https://doi.org/10.4014/jmb.2310.10011