Involvement of Upregulated P53-Induced Death Domain Protein in Retinal Ganglion Cells Apoptosis After Optic Nerve Crush

Total recall: the role of PIDDosome components in neurodegeneration

The PIDDosome is a multiprotein complex that includes p53-induced protein with a death domain 1 (PIDD1), receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (RAIDD), and caspase-2, the activation of which is driven by PIDDosome assembly. In addition to the key role of the PIDDosome in the regulation of cell differentiation, tissue homeostasis, and organogenesis and regeneration, caspase-2, RAIDD and PIDD1 engagement in neuronal development was shown. Here, we focus on the involvement of PIDDosome components in neurodegenerative disorders, including retinal neuropathies, different types of brain damage, and Alzheimer's disease (AD), Huntington's disease (HD), and Lewy body disease. We also discuss pathogenic variants of PIDD1, RAIDD, and caspase-2 that are associated with intellectual, behavioral, and psychological abnormalities, together with prospective PIDDosome inhibition strategies and their potential clinical application.

Optic nerve injury models under varying forces

PURPOSE

To explore the pathological changes in optic nerve injury models under varying forces.

METHODS

The rats were classified into 4 groups: sham operation (SH), 0.1, 0.3, and 0.5 N. Modeling was performed using the lateral optic nerve pulling method. Seven days after modeling, Brn3a immunofluorescence was used to detect retinal ganglion cell (RGC) number, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to detect RGC apoptosis, and flash visual evoked potential (FVEP) was used to detect the optic nerve function on days 1, 3, and 7 after modeling. In addition, LC3 II and P62 expression levels in retinal tissues were detected by western blotting to observe the changes in autophagy levels.

RESULTS

RGC number decreased 7 d after modeling, and it showed a downward trend with increasing damaging force. The number of apoptotic RGCs in ganglion cell layer in the 0.3 and 0.5 N groups was increased and was higher than that in the 0.1 N group. The difference in FVEP of rats in each group was mainly reflected in the P2 peak latency. LC3 II and P62 expression levels in retinal tissue of 0.3 and 0.5 N groups were higher than those of the SH and 0.1 groups; however, the difference between the 0.1 N and SH groups was not statistically significant.

CONCLUSION

Precisely controlling the force of the optic nerve clamping injury model is necessary because different forces acting on the optic nerve will lead to differences in the loss of optic neurons, the conduction function of the optic nerve, and autophagy level in retinal tissues.

Diterpene Ginkgolides Meglumine Injection inhibits apoptosis induced by optic nerve crush injury via modulating MAPKs signaling pathways in retinal ganglion cells

ETHNOPHARMACOLOGICAL RELEVANCE

Diterpene Ginkgolides Meglumine Injection (DGMI) is made of extracts from Ginkgo biloba L, including Ginkgolides A, B, and K and some other contents, and has been widely used as the treatment of cerebral ischemic stroke in clinic. It can be learned from the "Compendium of Materia Medica" that Ginkgo possesses the effect of "dispersing toxin". The ancient Chinese phrase "dispersing toxin" is now explained as elimination of inflammation and oxidative state in human body. And it led to the original ideas for today's anti-oxidation studies of Ginkgo in apoptosis induced by optic nerve crush injury.

AIM OF THE STUDY

To investigate the underlying molecular mechanism of the DGMI in retinal ganglion cells (RGCs) apoptosis.

MATERIALS AND METHODS

TUNEL staining was used to observe the anti-apoptotic effects of DGMI on the adult rat optic nerve injury (ONC) model, and flow cytometry and hoechst 33,342 staining were used to observe the anti-apoptotic effects of DGMI on the oxygen glucose deprivation (OGD) induced RGC-5 cells injury model. The regulation of apoptosis and MAPKs pathways were investigated with Immunohistochemistry and Western blotting.

RESULTS

This study demonstrated that DGMI is able to decrease the conduction time of F-VEP and ameliorate histological features induced by optic nerve crush injury in rats. Immunohistochemistry and TUNEL staining results indicated that DGMI can also inhibit cell apoptosis via modulating MAPKs signaling pathways. In addition, treatment with DGMI markedly improved the morphological structures and decreased the apoptotic index in RGC-5 cells. Mechanistically, DGMI could significantly inhibit cell apoptosis by inhibiting p38, JNK and Erk1/2 activation.

CONCLUSION

The study shows that DGMI and ginkgolides inhibit RGCs apoptosis by impeding the activation of MAPKs signaling pathways in vivo and in vitro. Therefore, the present study provided scientific evidence for the underlying mechanism of DGMI and ginkgolides on optic nerve crush injury.