Effects of a conventional photocoagulator and a 3-ns pulse laser on preconditioning responses and retinal ganglion cell survival after optic nerve crush

Necrostatin-1 Relieves Learning and Memory Deficits in a Zebrafish Model of Alzheimer's Disease Induced by Aluminum

Aluminum (Al) is considered one of the environmental risk factors for Alzheimer's disease (AD). The present study aims to establish a zebrafish AD model induced by Al and explore if necrostation-1 (Nec-1), a specific inhibitor of necroptosis, is effective in relieving learning and memory deficits in the zebrafish AD models. We treated adult zebrafish with aluminum trichloride at various doses for 1 month, followed by a T-maze test to evaluate learning and memory performance. Al concentration, levels of acetylcholine (Ach), and AD-related protein and gene expression in the brain tissue were evaluated in the zebrafish AD models. Our results demonstrated that in the brain tissue of Al-treated zebrafish, Al accumulated, Ach levels decreased, and AD-related genes and proteins increased. As a result, the learning and memory performance of Al-treated zebrafish was impaired. This suggested that a zebrafish AD model was established. To test the effect of Nec-1 on the zebrafish AD model, we added Nec-1 into the culture medium of the Al-treated adult zebrafish. The results demonstrated that Nec-1 could relive the learning and memory deficits, enhance Ach levels and the numbers of neural cells, and impact necroptosis-related gene expression. We concluded that Nec-1 could reverse Al-induced learning and memory impairment and had potential theoretical value in the zebrafish AD model.

Photobiomodulation enhances facial nerve regeneration via activation of PI3K/Akt signaling pathway-mediated antioxidant response

Facial nerve dysfunction is a common clinical condition that leads to disfigurement and emotional distress in the affected individuals. This study aimed to evaluate whether photobiomodulation can enhance regeneration of crushed facial nerves and attempt to investigate the possible underlying mechanism of neuroprotective function and therapeutic target. Various parameters of photobiomodulation were assigned to the facial nerves and Schwann cells (SCs) separately during crushed injury in rats. Axonal regeneration, functional outcomes, and SC apoptosis, proliferation, and underlying mechanisms of action were evaluated by morphological, histopathological, and functional assessments, flow cytometry, western blotting, real-time PCR, and IncuCyte. The results showed that photobiomodulation improved axonal regeneration and functional recovery, and also promoted proliferation, and inhibited apoptosis of SCs, both of these were considered as the most effective parameters in 250mW group. In addition, the neuroprotective effects of photobiomodulation (500mW) were likely associated with oxidative stress-induced SC apoptosis via activation of the PI3K/Akt signaling pathway. Our results revealed that photobiomodulation significantly promoted axonal regeneration, functional recovery, and regeneration of the facial nucleus, and its mechanism was related to the up-regulation of the PI3K/Akt signaling pathway. These findings provide clear experimental evidence of photobiomodulation as an alternative therapeutic strategy for peripheral nerve damage.

Alterations in the expression of Hs1-associated protein X-1 in the rat retina after optic nerve crush

HS-1-associated protein X-1 (Hax-1) has been suggested to be expressed in various rodent and human tissues. Accumulating evidence has demonstrated that Hax‑1 exerts an anti‑apoptotic effect in neurological diseases. Furthermore, it has also been reported that Hax‑1 interacts with various apoptosis‑associated proteins, including high temperature-regulated A2 (HtrA2) and caspase‑3. Previous studies have indicated that abnormal expression of Hax‑1 may be associated with the development of the nervous system and with the pathophysiology of neurological diseases, including traumatic brain injury and cerebral ischemia. The present study reported temporal‑spatial patterns of Hax‑1 in rat retina following optic nerve crush (ONC). Using western blotting and double‑immunofluorescence, significant upregulation of Hax‑1 was observed in retinal ganglion cells (RGCs) in the retina following ONC. Increased Hax‑1 expression was demonstrated to be accompanied by upregulation of active‑caspase‑3 and HtrA2 following ONC. In addition, Hax-1 co‑localized with active caspase‑3 and HtrA2 in RGCs following ONC. Terminal deoxynucleotidyl transferase‑mediated biotinylated-dUTP nick‑end labeling staining suggested that Hax‑1 was involved in RGC apoptosis following ONC. Thus, these results suggested that Hax‑1 may participate in regulating RGC apoptosis via interacting with caspase‑3 and HtrA2 following ONC.

Effect of subconjunctival glucose on retinal ganglion cell survival in experimental retinal ischaemia and contrast sensitivity in human glaucoma

PURPOSE

This study aims to evaluate the effect of subconjunctival glucose on the retinal ganglion cells (RGCs) in experimental retinal ischaemia and contrast sensitivity in humans with primary open-angle glaucoma (POAG).

METHODS

First, we measured the intravitreal concentration of glucose at various time points after a subconjunctival injection of 100 μl of 50% glucose to Sprague-Dawley rats. Next, treatment and control groups received 50% subconjunctival glucose and iso-osmotic (8%) saline, respectively, 1 h prior to a unilateral ischaemic retinal injury; 7 days later, the damage profiles were compared using RGC and axon counts. Subsequently, we conducted a double-blind, crossover, pilot clinical study in seven eyes of five pseudophakic subjects with severe POAG. Subjects received either 0.3 mL of 50% glucose subconjunctivally or iso-osmotic (8%) saline, then vice versa after a 2-3 week 'wash-out' period; change in contrast sensitivity from baseline was the primary outcome.

RESULTS

Subconjunctival glucose preserved approximately 60% of Brn3a-positive RGCs in all retinal zones compared with an 80% loss in control retinas, and rescued approximately 40% of the axonal loss. In the human trial, the contrast sensitivity at 12 cycles/degree was 0.24 log units greater than baseline (95% confidence interval 0.12-0.36; P < 0.001).

CONCLUSIONS

Subconjunctival glucose partially protects RGC somata and axons against an ischaemic insult and temporarily recovers contrast sensitivity in patients with severe POAG. Although an unlikely therapeutic strategy for POAG, the findings motivate further bioenergetic-based research in glaucoma and other optic nerve and retinal diseases, where energy failure may be part of the pathogenesis.