Background: Glaucoma, the major cause of irreversible blindness worldwide, is characterized by progressive degeneration of retinal ganglion cells (RGCs). Current treatments for glaucoma only slow or partially prevent the disease progression, failing to prevent RGCs death and visual field defects completely. Glutamate excitotoxicity via N-methyl-d-aspartic acid (NMDA) receptors plays a vital role in RGCs death in glaucoma, which is often accompanied by oxidative stress and NLRP3 inflammasome activation. However, the exact mechanisms remain unclear. Methods: The glutamate-induced R28 cell excitotoxicity model and NMDA-induced mouse glaucoma model were established in this study. Cell counting kit-8, Hoechst 33342/PI dual staining and lactate dehydrogenase release assay were performed to evaluate cell viability. Annexin V-FITC/PI double staining was used to detect apoptosis and necrosis rate. Reactive oxygen species (ROS) and glutathione (GSH) were used to detect oxidative stress in R28 cells. Levels of proinflammatory cytokines were measured by qRT-PCR. Transmission electron microscopy (TEM) was used to detect necroptotic morphological changes in RGCs. Retinal RGCs numbers were detected by immunofluorescence. Hematoxylin and eosin staining was used to detect retinal morphological changes. The expression levels of RIP1, RIP3, MLKL and NLRP3 inflammasome-related proteins were measured by immunofluorescence and western blotting. Results: We found that glutamate excitotoxicity induced necroptosis in RGCs through activation of the RIP1/RIP3/MLKL pathway in vivo and in vitro. Administration of the RIP3 inhibitor GSK872 and RIP1 inhibitor necrostatin-1 (Nec-1) prevented glutamate-induced RGCs loss, retinal damage, neuroinflammation, overproduction of ROS and a decrease in GSH. Furthermore, after suppression of the RIP1/RIP3/MLKL pathway by GSK872 and Nec-1, glutamate-induced upregulation of key proteins involved in NLRP3 inflammasome activation, including NLRP3, pro-caspase-1, cleaved-caspase-1, and interleukin-1β (IL-1β), was markedly inhibited. Conclusions: Our findings suggest that the RIP1/RIP3/MLKL pathway mediates necroptosis of RGCs and regulates NLRP3 inflammasome activation induced by glutamate excitotoxicity. Moreover, GSK872 and Nec-1 can protect RGCs from necroptosis and suppress NLRP3 inflammasome activation through inhibition of RIP1/RIP3/MLKL pathway, conferring a novel neuroprotective treatment for glaucoma.

Radiation-induced optic neuropathy (RION) is a devastating complication following external beam radiation therapy (EBRT) that leads to acute vision loss. To date, no efficient, available treatment for this complication, due partly to the lack of understanding regarding the developmental processes behind RION. Here, we report radiation caused changes in mitochondrial dynamics by regulating the mitochondrial fission proteins dynamin-related protein 1 (Drp1) and fission-1 (Fis1). Concurrent with an excessive production of reactive oxygen species (ROS), both neuronal injury and visual dysfunction resulted. Further, our findings delineate an important mechanism by which cyclin-dependent kinase 5 (Cdk5)-mediated phosphorylation of Drp1 (Ser616) regulates defects in mitochondrial dynamics associated with neuronal injury in the development of RION. Both the pharmacological inhibition of Cdk5 by roscovitine and the inhibition of Drp1 by mdivi-1 inhibited mitochondrial fission and the production of ROS associated with radiation-induced neuronal loss. Taken together, these findings may have clinical significance in preventing the development of RION.

The death of retinal ganglion cells (RGCs) is a key factor in the pathophysiology of all types of glaucoma, but the mechanism of pathogenesis of glaucoma remains unclear. RGCs are a group of central nervous system (CNS) neurons whose soma are in the inner retina. The axons of RGCs form the optic nerve and converge at the optic chiasma; from there, they project to the visual cortex via the lateral geniculate nucleus (LGN). In recent years, there has been increasing interest in the dysfunction and death of CNS and retinal neurons caused by transneuronal degeneration of RGCs, and the view that glaucoma is a widespread neurodegenerative disease involving CNS damage appears more and more frequently in the literature. In this review, we summarize the current knowledge of LGN and visual cortex neuron damage in glaucoma and possible mechanisms behind the damage. This review presents an updated and expanded view of neuronal damage in glaucoma, and reveals new and potential targets for neuroprotection and treatment.

Glaucoma is an irreversible blinding eye disease characterized by retinal ganglion cell (RGC) death.Previous studies have demonstrated that protecting mitochondria and activating the CaMKII/CREB signaling pathway can effectively protect RGC and axon. However, currently treatments are often unsatisfactory, and the pathogenesis of glaucoma requires further elucidation. In this study, a ROS‐responsive dual drug conjugate (OLN monomer) is first designed that simultaneously bonds nicotinamide and oleic acid. The conjugate self‐assembled into nanoparticles (uhOLN‐NPs) through the aggregation of multiple micelles and possesses ROS scavenging capability. Then, a polymer with a hypoxic response function is designed, which encapsulates uhOLN‐NPs to form nanoparticles with hypoxic and ROS responses (HOLN‐NPs). Under hypoxia in RGCs, the azo bond of HOLN‐NPs breaks and releases uhOLN‐NPs. Meanwhile, under high ROS conditions, the thioketone bond broke, leading to the dissociation of nano‐prodrug. The released nicotinamide and oleic acid co‐scavenge ROS and activate the CaMKII/CREB pathway, protecting mitochondria in RGCs. HOLN‐NPs exhibit a significantly superior protective effect on R28 cells in glutamate models of glaucoma. The accumulation of HOLN‐NPs in retinal RGCs lead to significant inhibition of RGC apoptosis and axonal damage in vivo. Notably, HOLN‐NPs provide a new therapeutic approach for patients with neurodegenerative disease.