RNA Interference Reveals the Coregulatory Effects of Cylindromatosis on Apoptosis and Necroptosis of Photoreceptor Cells in Experimental Retinal Detachment

CDR1as Deficiency Prevents Photoreceptor Degeneration by Regulating miR-7a-5p/α-syn/Parthanatos Pathway in Retinal Detachment

Retinal detachment (RD) is the separation of the neural retina from the retinal pigment epithelium, with photoreceptor degeneration being a major cause of irreversible vision loss. Herein, ischemia and hypoxia after RD decreased the level of miR-7a-5p (miR-7) and promoted the expression of its main target, α-synuclein (α-syn), which activated the parthanatos pathway and led to photoreceptor damage. Circular RNA CDR1as is an antisense transcript of cerebellar degeneration-associated protein 1, which functions as a "sponge" for miR-7, thereby regulating the abundance and activity of miR-7. In this study, CDR1as expression was elevated after RD. Adeno-associated virus serotype 9 vector containing the shRNA-CDR1as sequence was used to inhibit CDR1as expression via subretinal injection. Hematoxylin and eosin staining and transmission electron microscopy revealed that the morphology and outer nuclear layer thickness of the retina were preserved and photoreceptor cell death was decreased after experimental RD in mice. Mechanistically, CDR1as deficiency significantly increased the expression of miR-7, then decreased the expression of α-syn, poly (ADP-ribose) polymerase 1, apoptosis-inducing factor, and migration inhibitory factor. Furthermore, visual function was improved as shown by Morris water maze experiments in the mouse model of RD. These findings suggest a surprisingly neuroprotective role for CDR1as deficiency, which is probably mediated by enhancing miR-7 activity and inhibiting α-syn/poly (ADP-ribose) polymerase 1/apoptosis-inducing factor pathway, thereby preventing photoreceptor degeneration.

Deferiprone protects photoreceptors by inhibiting ferroptosis after experimental retinal detachment

The detachment of the retinal neuroepithelium from the retinal pigment epithelium (RPE), often due to a retinal tear and subsequent subretinal fluid (SRF) accumulation, is a critical factor leading to photoreceptor cells (PR) death and permanent vision impairment in retinal detachment (RD) scenarios. Predicting postoperative visual recovery is challenging, even with surgical reattachment. Research has indicated that increased iron and transferrin (TF) saturation in the vitreous fluid (VF) correlates with poorer visual outcomes, suggesting a potential role for ferroptosis, a form of regulated cell death, in PR following RD. To explore this hypothesis, we analyzed the VF of RD patients for ferroptosis markers, revealing reduced levels of glutathione peroxidase 4 (GPX4), glutathione (GSH), and reduced nicotinamide adenine dinucleotide phosphate (NADPH), alongside elevated levels of Long-chain acyl-CoA synthetase 4(ACSL4), malondialdehyde (MDA), and ferrous iron. We then developed a mouse model to simulate RD and administered the iron chelator deferiprone (DFP) as a treatment. Our findings indicated that DFP mitigated ferroptosis in the retina, thereby preserving retinal architecture and function. Collectively, our study establishes the occurrence of ferroptosis in RD and demonstrates the therapeutic potential of DFP in protecting PR and treating RD.

The Expression of Parthanatos Markers and miR-7 Mimic Protects Photoreceptors from Parthanatos by Repressing α-Synuclein in Retinal Detachment

Retinal detachment (RD) refers to the separation between the neuroepithelium and the pigment epithelium layer. It is an important disease leading to irreversible vision damage worldwide, in which photoreceptor cell death plays a major role. α-Synuclein (α-syn) is reportedly involved in numerous mechanisms of neurodegenerative diseases, but the association with photoreceptor damage in RD has not been studied. In this study, elevated transcription levels of α-syn and parthanatos proteins were observed in the vitreous of patients with RD. The expression of α-syn- and parthanatos-related proteins was increased in experimental rat RD, and was involved in the mechanism of photoreceptor damage, which was related to the decreased expression of miR-7a-5p (miR-7). Interestingly, subretinal injection of miR-7 mimic in rats with RD inhibited the expression of retinal α-syn and down-regulated the parthanatos pathway, thereby protecting retinal structure and function. In addition, interference with α-syn in 661W cells decreased the expression of parthanatos death pathway in oxygen and glucose deprivation model. In conclusion, this study demonstrates the presence of parthanatos-related proteins in patients with RD and the role of the miR-7/α-syn/parthanatos pathway in photoreceptor damage in RD.

RNA interference targeting NOX4 protects visual function in an experimental model of retinal detachment by alleviating blood-retinal barrier damage

AIM

To observe the effects of the inhibition of NADPH oxidase 4 (NOX4) expression on the retinal vascular barriers and visual function after retinal detachment (RD).

METHODS

RD model was established 3wk after adeno-associaned virus vector injection. The retinal tissue was harvested 3d after RD, and the death of retinal vascular endothelial cells and photoreceptors was observed using electron microscopy. The NOX4 expression was detected by Western blot. Confocal microscopy was used to observe a retinal patch that had been perfused with Evans blue. A modified water maze test was used to detect the time required to find the platform on the water surface. The visual function of the rats was evaluated and reactive oxygen species (ROS) expression was detected by a fluorescence microplate reader.

RESULTS

The retinal patch showed that NOX4 interference significantly reduced the destruction of the tight junctions between the retinal endothelium of RD rats and reduced leakage. Western blotting showed decreased expression of the NOX4 protein and decreased expression of ROS in retinal tissue; the Morris water maze test results showed that NOX4 interference significantly decreased the escape latency of the rats.

CONCLUSION

NOX4 interference reduces the production of ROS in retinal vascular endothelial cells after experimental RD, thereby protecting the blood-retinal barrier and protecting visual function.

Experimental models and examination methods of retinal detachment

Retinal detachment refers to the separation of the retinal neuroepithelium and pigment epithelium, usually involving the death of photoreceptor cells. Severe detachment may lead to permanent visual impairment if not treated properly and promptly. According to the underlying causes, retinal detachment falls into one of three categories: exudative retinal detachment, traction detachment, and rhegmatogenous retinal detachment. Like many other diseases, it is difficult to study the pathophysiology of retinal detachment directly in humans, because the human retinal tissues are precious, scarce and non-regenerative; thus, establishing experimental models that better mimic the disease is necessary. In this review, we summarize the existing models of the three categories of retinal detachment both in vivo and in vitro, along with an overview of their examination methods and the major strengths and weaknesses of each model.

TRPML1 Inhibited Photoreceptor Apoptosis and Protected the Retina by Activation of Autophagy in Experimental Retinal Detachment

OBJECTIVE

In this study, we used a rat model of retinal detachment (RD) to investigate the effects of transient receptor potential mucolipin 1 (TRPML1) on photoreceptor cells and the underlying mechanism.

METHODS

An RD model was established by subretinal injection of sodium hyaluronate, and mucolipin synthetic agonist 1 (ML-SA1) and dimethyl sulphoxide were subretinally injected after RD induction. Retinal morphology was observed using haematoxylin-eosin staining, and the apoptosis of photoreceptor cells was detected by transmission electron microscopy. Reactive oxygen species (ROS) were examined with an ROS detection kit. The retinal expression levels of TRPML1, the autophagy-related protein microtubule-associated protein 1 light chain 3 (LC3), Beclin 1, and cleaved caspase 3 were detected by Western blotting. The Morris water maze was used to test vision-dependent behaviour.

RESULTS

We found that retinal structure and the outer nuclear layer were improved and that the apoptosis of photoreceptor cells was reduced after ML-SA1 injection. The expression of ROS was reduced, and the loss of TRPML1 was inhibited after ML-SA1 treatment. The LC3-II to LC3-I ratio and Beclin 1 expression were enhanced, and cleaved caspase 3 expression was decreased after ML-SA1 treatment. Treatment with ML-SA1 also improved vision-dependent behaviour.

CONCLUSIONS

Our findings suggest that ML-SA1 attenuates photoreceptor apoptosis and improves vision-dependent behaviour by activation of autophagy.

Photoreceptors Degenerate Through Pyroptosis After Experimental Retinal Detachment

Purpose

Gasdermin D (GSDMD) is crucial in neuronal pyroptosis. GSDMD-N and GSDMD-C are two subdomains of the protein GSDMD. GSDMD-N is an executor of pyroptosis, and GSDMD-C has an inhibitory effect on pyroptotic cell death. This study evaluated the role of GSDMD in photoreceptor cell pyroptosis caused by retinal detachment (RD).

Methods

RD models were established in rats, and GSDMD cleavage was detected by western blotting. The morphology of photoreceptors was assessed by transmission electron microscopy. Some rats were given subretinal injections of recombinant adeno-associated virus 2/8 (rAAV2/8)–GSDMD-C before RD surgery. We documented the expression of caspase-1 and GSDMD-N in retinas by western blot. Levels of IL-1β, TNF-α, and monocyte chemoattractant protein-1 (MCP-1) were detected by quantitative RT-PCR. The membrane integrity of photoreceptors was evaluated by TOTO-3 iodide staining. Retinal function was measured by electroretinography, and the thickness of the outer nuclear layer was also recorded. We measured the activation of glial fibrillary acidic protein (GFAP), F4/80, and ionized calcium binding adaptor molecule 1 (Iba-1) by immunofluorescence.

Results

The cleavage of GSDMD peaked at 1 day after RD. The administration of rAAV2/8–GSDMD-C reduced the pyroptosis and subsequent apoptosis of photoreceptors and preserved the retinal function after RD. Expression of IL-1, TNF-α, and MCP-1 was decreased in the rAAV2/8–GSDMD-C group. In addition, the activation of GFAP, Iba-1, and F4/80 in retinas was alleviated by administering rAAV2/8–GSDMD-C after RD.

Conclusions

GSDMD participates in the pyroptosis of photoreceptor after RD. Overexpression of GSDMD-C may block GSDMD cleavage and attenuate photoreceptor degeneration.

PJ34 Protects Photoreceptors from Cell Death by Inhibiting PARP-1 Induced Parthanatos after Experimental Retinal Detachment

PURPOSE

Our previous study discoveredreactive oxygen species (ROS) and apoptosis inducing factor (AIF) increased after retinal detachment. Parthanatos is a cell death form involving ROS and AIF, which is induced by poly (ADP-ribose) polymerase-1 (PARP-1). Therefore, we investigated whether PJ34 (a PARP-1 inhibitor) could inhibit parthanatos and protect the photoreceptors from cell death after retinal detachment (RD).

METHODS

Experimental retinal detachment modelswere created in Sprague-Dawley rats by subretinal injection of sodium hyaluronate.PJ34 orDMSO were introduced into subretinal space at RD induction, respectively. The structure of retinas and the morphology of photoreceptors were observed by hematoxylin eosin (H&E) staining and transmission electron microscope (TEM). Parthanatos related proteins (PARP-1, PAR,AIF) were detected by Western blot. The vision-dependent behavior of rat was tested by Morris water maze.

RESULTS

H&E staining and TEM results indicated that the structure and outer nuclear layer (ONL) thickness of retinas were preserved, and the photoreceptors death decreasedwith PJ34 treatment. Western blot showed that the expression of PARP-1, PAR and AIF were decreased withPJ34 treatment. In addition, administration of PJ34 also improved the vision-dependent behavior of rat.

CONCLUSIONS

These findings suggested that PJ34 is a potential therapeutic agent that attenuated photoreceptor parthanatos death in retinal detachment through inhibition of PARP-1/AIF pathway.