Retinal ganglion cell loss in an ex vivo mouse model of optic nerve cut is prevented by curcumin treatment

Abstract

Retinal ganglion cell (RGC) loss is a pathologic feature common to several retinopathies associated to optic nerve damage, leading to visual loss and blindness. Although several scientific efforts have been spent to understand the molecular and cellular changes occurring in retinal degeneration, an effective therapy to counteract the retinal damage is still not available. Here we show that eyeballs, enucleated with the concomitant optic nerve cut (ONC), when kept in PBS for 24 h showed retinal and optic nerve degeneration. Examining retinas and optic nerves at different time points in a temporal window of 24 h, we found a thinning of some retinal layers especially RGC’s layer, observing a powerful RGC loss after 24 h correlated with an apoptotic, MAPKs and degradative pathways dysfunctions. Specifically, we detected a time-dependent increase of Caspase-3, -9 and pro-apoptotic marker levels, associated with a strong reduction of BRN3A and NeuN levels. Importantly, a powerful activation of JNK, c-Jun, and ERK signaling (MAPKs) were observed, correlated with a significant augmented SUMO-1 and UBC9 protein levels. The degradation signaling pathways was also altered, causing a significant decrease of ubiquitination level and an increased LC3B activation. Notably, it was also detected an augmented Tau protein level. Curcumin, a powerful antioxidant natural compound, prevented the alterations of apoptotic cascade, MAPKs, and SUMO-1 pathways and the degradation system, preserving the RGC survival and the retinal layer thickness. This ex vivo retinal degeneration model could be a useful method to study, in a short time window, the effect of neuroprotective tools like curcumin that could represent a potential treatment to contrast retinal cell death.

Protective Effect of Curcuma Extract in an Ex Vivo Model of Retinal Degeneration via Antioxidant Activity and Targeting the SUMOylation

“…The total number of animals used in this study was 60. Animals were sacrificed, and their eyes were harvested according to our ex vivo model of retinal degeneration induction [ 15 ]. The enucleated eyeballs were used freshly (WT) or injected with different treatments: Ctr: dimethyl sulfoxide (DMSO, 0.05%), or Curcuma extracts: Cur 5 or 10 μ M (Linnea, cat# CUM 1259), or memantine: Mem 10 μ M (ChemCruz, cat# SC-203628), or citicoline: Cit 100 μ M (Santa Cruz, cat# SC-300380), or ginkgolic acid: GA 20 μ M (Calbiochem, cat# 345887).…”

“…Different methods are mimicking retina degeneration and RGC death. Recently, in our lab, we optimized an ex vivo model of retinal degeneration by cutting the optic nerve (ONC) that could replicate the retinal degeneration and represents a valuable model for primary screening of different compounds against retinal degeneration and RGC death [ 15 ].…”

“…Later, we found that cutting the optic nerve induces retinal degeneration in a time-dependent manner, and curcumin was able to prevent these pathological processes [ 15 ]. In accordance with these results, Ke et al showed that pretreatment with curcumin significantly augmented the cell viability of BV-2 microglia in an in vivo rat model of chronic high intraocular pressure.…”

Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update

“…In the same study, it was also observed that curcumin inhibited pro-apoptotic factors, such as caspase-3 and Bax, and upregulated the anti-apoptotic factor Bcl-2 [169]. In an ex vivo optic nerve injury model, thinning of retinal layers, especially the GCL, and strong RGC apoptosis were observed after 24 h post-injury, which correlated with a time-dependent increase in caspase-3 and -9 and pro-apoptotic marker levels, and a powerful activation of the JNK, c-Jun and ERK signaling (MAPK) pathways [170]. Curcumin prevented alterations in the apoptotic cascade and MAPK pathways, preserving RGC survival and retinal thickness [170].…”

“…In an ex vivo optic nerve injury model, thinning of retinal layers, especially the GCL, and strong RGC apoptosis were observed after 24 h post-injury, which correlated with a time-dependent increase in caspase-3 and -9 and pro-apoptotic marker levels, and a powerful activation of the JNK, c-Jun and ERK signaling (MAPK) pathways [170]. Curcumin prevented alterations in the apoptotic cascade and MAPK pathways, preserving RGC survival and retinal thickness [170]. In another experimental study in a rat retinal I/R injury model, curcumin supplementation in the diet for 2 days before I/R was able to protect the retina from ischemic injury [171].…”