Trolox aids coenzyme Q10 in neuroprotection against NMDA induced damage via upregulation of VEGF in rat model of glutamate excitotoxicity

Glutamate induced damage to retinal ganglion cells (RGCs) requires tight physiological regulation of the N-methyl-D-aspartate (NMDA) receptors. Previously, studies have demonstrated the neuroprotective abilities of antioxidants like coenzyme Q10 (CoQ10) and vitamin E analogs like α-tocopherol against neuropathies resulting from NMDA insult, but have failed to shed light on the effect of CoQ10 and trolox, a hydrophilic analog of vitamin E, on glaucomatous neurodegeneration. In the current study, we wanted to investigate whether the combined effect of trolox with CoQ10 could alleviate NMDA-induced death of retinal cells while also trying to elucidate the underlying mechanism in relation to the yet unexplained role of vascular endothelial growth factor (VEGF) in NMDA-mediated excitotoxicity. After successful NMDA-induced degeneration, we followed it up with the treatment of combination of Trolox and CoQ10. The structural damage by NMDA was repaired significantly and retina retained structural integrity comparable to levels of control in the treatment group of Trolox and CoQ10. Detection of ROS generation after NMDA insult showed that together, Trolox and CoQ10 could significantly bring down the high levels of free radicals while also rescuing mitochondrial membrane potential (MMP). A significant increase in NMDA receptor Grin2A by CoQ10 alone as well as by CoQ10 and trolox was accompanied by a lowered Grin2B receptor expression, suggesting neuroprotective action of Trolox and CoQ10. Subsequently, lowered VEGFR1 and VEGFR2 receptor expression by NMDA treatment also recovered when subjected to combined treatment of Trolox and CoQ10. Western blot analyses also indicated the same whereby Trolox and CoQ10 could increase the diminished levels of phosphorylated VEGFR2. Immunofluorescence studies also indicated a positive correlation between recovered VEGFR2 and NMDAR2A levels and diminished levels of NMDAR2D, confirming the results obtained by RT-PCR analysis. This is the first report in our knowledge that demonstrates the efficacy of trolox in combination with CoQ10 highlighting the importance of maintaining VEGF levels that are lowered in ocular diseases due to NMDA-related toxicities.

A novel and efficient murine model of Bietti crystalline dystrophy

Bietti crystalline dystrophy (BCD) is an autosomal recessive inherited retinal disease, resulting in blindness in most patients. The etiology and development mechanism of it remain unclear. Given the defects in previous mouse models of BCD, we generated a new Cyp4v3-/- mouse model, using CRISPR/Cas9 technology, for investigating the pathogenesis of BCD. We estimated the ocular phenotypes by fundus imaging, optical coherence tomography (OCT) and full-field scotopic electroretinography, and investigated the histological features by Hematoxylin and Eosin staining, Oil Red O staining and immunofluorescence. This model effectively exhibited age-related progression that mimicked the human ocular phenotypes. Moreover, gas chromatography-mass spectrometry and RNA-seq analysis indicated that the defect of Cyp4v3 led to the abnormal lipid metabolism, inflammation activation and oxidative stress of retina. Notably, inflammation activation and oxidative stress could also promote the progression of BCD in light-induced retinal degeneration. In conclusion, our data provided evidence that we established a novel and more effective Cyp4v3 knockout preclinical mouse model for BCD, which served as a useful tool for evaluating the effect of drugs and gene therapy in vivo.

Retinal degeneration in mice lacking the cyclic nucleotide-gated channel subunit CNGA1

Cyclic nucleotide-gated (CNG) channels are important mediators in the transduction pathways of rod and cone photoreceptors. Native CNG channels are heterotetramers composed of homologous A and B subunits. Biallelic mutations in CNGA1 or CNGB1 genes result in autosomal recessive retinitis pigmentosa (RP). To investigate the pathogenic mechanism of CNG channel-associated retinal degeneration, we developed a mouse model of CNGA1 knock-out using CRISPR/Cas9 technology. We observed progressive retinal thinning and a concomitant functional deficit in vivo as typical phenotypes for RP. Immunofluorescence and TUNEL staining showed progressive degeneration in rods and cones. Moreover, microglial activation and oxidative stress damage occurred in parallel. RNA-sequencing analysis of the retinae suggested down-regulated synaptic transmission and phototransduction as early as 9 days postnatal, possibly inducing later photoreceptor degeneration. In addition, the down-regulated PI3K-AKT-mTOR pathway indicated upregulation of autophagic process, and chaperone-mediated autophagy was further shown to coincide with the time course of photoreceptor death. Taken together, our studies add to a growing body of research exploring the mechanisms of photoreceptor death during RP progression and provide a novel CNGA1 knockout mouse model for potential development of therapies.

Different effects of anti-VEGF drugs (Ranibizumab, Aflibercept, Conbercept) on autophagy and its effect on neovascularization in RF/6A cells

INTRODUCTION

Choroidal neovascularization (CNV) is the main pathological change of wet age-related macular degeneration. Anti-VEGF drugs are the most commonly used treatment for CNV. The biggest drawback of anti-VEGF drugs is the recurrence of CNV, which requires repeated therapy several times. Autophagy activation may be involved in reducing the therapeutic effect of anti-VEGF drugs. So, this study aims to elucidate the effect and mechanism of anti-VEGF drugs on endothelial autophagy and neovascularization in vitro.

METHODS

RF/6A cells were randomly divided into five groups: The control group, hypoxia group (1% O₂, 5% CO₂, 94% N₂), anti-VEGF group (group1: Ranibizumab 100 μg/ml; group2: Aflibercept, 400 μg/ml; group3: Conbercept, 100 μg/ml). Autophagy-related proteins were examined by Western blot. RFP-GFP-LC3 was used to detect autophagy and autophagic flow. Subsequently, we used autophagy inhibitors (3-MA or CQ) to inhibit Conbercept induced autophagy and to observe its effect on angiogenesis in vitro. Proliferation, migration, and tube formation of endothelial cells can be used to study neovascularization in vitro. In this research, the CCK-8 assay was used to detect cell proliferation. Cell migration and tube formation were assessed by wound assay and matrix method, respectively. Flow cytometry and Tunel were used to detect cell apoptosis. Finally, the mechanism of Conbercept activated autophagy was studied. Western blot was used to detect the expression of p53 and DRAM (damage-regulated autophagy modulator), upstream activators of autophagy.

RESULTS

The protein levels of Beclin-1 and LC3-2/1 in Ranibizumab and Conbercept groups were significantly higher than in the hypoxia group(P < 0.05). While the expression of P62 was decreased (P < 0.05). The autophagic flux was showed the same results. However, Aflibercept showed the opposite effect on autophagy. Compared with the Conbercept group, autophagy inhibitor 3-MA or CQ can further inhibit cell proliferation and promotes cell apoptosis (P < 0.05). Conbercept significantly inhibited cell migration compared with the hypoxia group (633.08 ± 72.52 vs. 546.33 ± 24.61), while the autophagy inhibitor group (3-MA or CQ) had a more obvious inhibition effect (309.75 ± 86.36 and 263.33 ± 68.67) (P < 0.05). For tube formation, the number of tube formation was decreased significantly in the Conbercept group (32.00 ± 2.00) compared to the hypoxia group (39.00 ± 1.53) and even further reduced in 3-MA or CQ group (24.00 ± 3.61, 20.00 ± 2.65). The length of master segments in the hypoxia group was 15,668.00 ± 894.11. It was decreased in Conbercept (13,885.34 ± 730.03). In 3-MA or CQ group, the length of master segments dropped further (11,997.00 ± 433.66, 10,617.67 ± 543.21). Compare with the hypoxia group, the expression P53 and DRAM were increased in the Conbercept group (P < 0.05). Autophagy-related proteins LC-3, Beclin-1, and DRAM were inhibited by P53 inhibitor Pifithrin-α (PFTα) (P < 0.05).

CONCLUSION

Ranibizumab and Conbercept can trigger the autophagy of vascular endothelial cells while Aflibercept can inhibit it. The combination of Conbercept and autophagy inhibitor can significantly inhibit the formation of angiogenesis in vitro. The mechanism of autophagy activation is related to the activation of the p53/DRAM pathway.

SLC7A11 Reduces Laser-Induced Choroidal Neovascularization by Inhibiting RPE Ferroptosis and VEGF Production

In age-related macular degeneration (AMD), one of the principal sources of vascular endothelial growth factor (VEGF) is retinal pigment epithelium (RPE) cells under hypoxia or oxidative stress. Solute carrier family 7 member 11 (SLC7A11), a key component of cystine/glutamate transporter, regulates the level of cellular lipid peroxidation, and restrains ferroptosis. In our study, we assessed the role of SLC7A11 in laser-induced choroidal neovascularization (CNV) and explored the underlying mechanism. We established a mouse model of CNV to detect the expression level of SLC7A11 and VEGF during disease progression. We found the expression of the SLC7A11 protein in RPE cells peaked at 3 days after laser treatment, which was correlated with the expression of VEGF. Intraperitoneal injection of SLC7A11 inhibitor expanded the area of CNV. We examined functional proteins related to oxidative stress and Fe²⁺ and found laser-induced ferroptosis accompanied by increased Fe²⁺ content and GPX4 expression in the RPE-choroidal complex after laser treatment. We verified the expression of SLC7A11 in the ARPE19 cell line and the effects of its inhibitors on cell viability and lipid peroxidation in vitro. Application of SLC7A11 inhibitor and SLC7A11 knockdown increased the level of lipid peroxidation and reduced the cell viability of ARPE19 which can be rescued by ferroptosis inhibitors ferrostatin-1 (Fer-1) and liproxstatin-1 (Lip-1). Conversely, SLC7A11 overexpression induced resistance to erastin or RSL3-induced ferroptosis. Moreover, we tested the possible regulatory transcription factor NF-E2-related factor 2 (NRF2) of SLC7A11 by Western blot. Knock-down of NRF2 decreased the expression of SLC7A11. Our study suggests that SLC7A11 plays a key role in the laser-induced CNV model by protecting RPE cells from ferroptosis. SLC7A11 provides a new therapeutic target for neovascular AMD patients.