Intravitreal ketamine promotes neuroprotection in rat eyes after experimental ischemia

Intravitreal CBD-Loaded niosomes enhance retinal neuroprotection in ischemic injury

Cannabidiol (CBD) has emerged as a promising treatment for conditions like retinal ischemia, characterized by reduced blood flow to the retina and significant vision loss. Despite its therapeutic potential, CBD's clinical application could be limited by due to its low bioavailability. This study investigates the efficacy of CBD-loaded niosomes as a neuroprotective formulation for the use in ocular therapies related to retinal ischemia. We investigated the neuroprotective effects of CBD using a nanodispersed system (niosomes) administered via intravitreal injection in rats' eyes. Niosomes underwent characterization for size, distribution, zeta potential, morphology, and encapsulation efficiency. Safety and neuroprotective activity were assessed by electroretinography (ERG), confocal and transmission microscopy and histology. Niosomes exhibited nanometric size (100-400 nm) and stability, showing good tolerance in animals. ERG results demonstrated higher b-wave amplitudes in animals pre-treated with niosomes + CBD compared to the control group following ischemic injury induced by a sudden increase in IOP. Histological and confocal microscopy analyses of retinas from the niosomes + CBD group showed preserved structure compared to the ischemic control group, suggesting significant retinal protection by intravitreally injected niosomes + CBD before ischemia. CBD-loaded niosomes effectively preserved retinal function, highlighting the neuroprotective potential of CBD against retinal ischemia. This formulation presents a promising and innovative treatment for ischemic retinal diseases.

A Polytherapy Intervention in an Experimental Traumatic Optic Neuropathy Mouse Model

PURPOSE

To test a novel early polytherapy treatment strategy targeting mitochondrial bioenergetics, glutamate excitotoxicity, and sterile inflammatory response molecular pathways associated with retinal ganglion cell survival following optic nerve trauma.

METHODS

Twenty C57BL/6J mice were subjected to sonication-induced traumatic optic neuropathy injury. The control group (n = 10) received intravitreal, retrobulbar, and subcutaneous phosphate buffered saline injections on days 0 and 3 (no repeat retrobulbar vehicle). On day 0, the treatment group (n = 10) received injections of intravitreal interleukin-1 receptor antagonist with ketamine, retrobulbar ropivacaine, and subcutaneous etanercept. Treatment group animals had 1% (wt/vol) N-acetylcysteine ad libitum supplemented in drinking water from day 1. On day 3, intravitreal pan-ephrin receptor antagonist peptide and subcutaneous elamipretide and etanercept injections were given. Pattern electroretinogram assessments continued at weeks 0, 1, 2, 4, 6, 8, 10, and 12. Optical coherence tomography retinal layer thickness was measured on naive, control, and treatment groups at week 12. The whole mount retinas were harvested for retinal ganglion cell quantitation.

RESULTS

At 12 weeks, the averaged retinal ganglion cell density count in the control group was lower (413.37 ± 41.77 cells/mm 2 ) compared with treatment (553.97 ± 18.00 cells/mm 2 ; p < 0.001) and naive (595.94 ± 30.67cells/mm 2 ; p < 0.001) groups. Ganglion cell complex layer thicknesses showed control group (49.29 ± 5.48 μm) thinner than the treated (61.00 ± 2.57 μm; p = 0.004) and naive (67.00 ± 6.12 μm; p = 0.004) groups. No significant difference was seen at 12 weeks between the treated and naive groups. Pattern electroretinogram recordings in the control group revealed a statistically significant decrease in amplitudes for all time points. Apart from week 8, the amplitudes in the treatment group did not significantly differ from the baseline at any time point.

CONCLUSIONS

Early combinatorial therapeutic intervention to address disparate molecular pathways following optic nerve trauma effectively halts retinal neurons' progressive structural and functional degeneration.

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Retinal cell-targeted liposomal ginsenoside Rg3 attenuates retinal ischemia-reperfusion injury via alleviating oxidative stress and promoting microglia/macrophage M2 polarization

Retinal ischemia-reperfusion (RIR) injury remains a major challenge that is detrimental to retinal cell survival in a variety of ocular diseases. However, current clinical treatments focus on a single pathological mechanism, making them unable to provide comprehensive retinal protection. A variety of natural products including ginsenoside Rg3 (Rg3) exhibit potent antioxidant and anti-inflammatory activities. Unfortunately, the hydrophobicity of Rg3 and the presence of various intraocular barriers limit its effective application in clinical settings. Hyaluronic acid (HA)- specifically binds to cell surface receptors, CD44, which is widely expressed in retinal pigment epithelial cells and M1-type macrophage. Here, we developed HA-decorated liposomes loaded with Rg3, termed Rg3@HA-Lips, to protect against retinal damage caused by RIR injury. Treatment with Rg3@HA-Lips significantly inhibited the oxidative stress induced by RIR injury. In addition, Rg3@HA-Lips promoted the transition of M1-type macrophage to the M2 type, ultimately reversing the pro-inflammatory microenvironment. The mechanism of Rg3@HA-Lips was further investigated and found that they can regulateSIRT/FOXO3a, NF-κB and STAT3 signaling pathways. Together with as well demonstrated good safety profiles, this CD44-targeted platform loaded with a natural product alleviates RIR injury by modulating the retinal microenvironment and present a potential clinical treatment strategy.

Sodium butyrate-loaded nanoparticles coated with chitosan for the treatment of neovascularization in age-related macular degeneration: ocular biocompatibility and antiangiogenic activity

Sodium butyrate-loaded nanoparticles coated chitosan (NaBu-loaded nanoparticles/CS) were developed to treat the choroidal neovascularization in wet age-related macular degeneration (AMD). The nanoparticles were produced by double emulsification and solvent evaporation technique, optimized by experimental statistical design, characterized by analytical methods, investigated in terms of in vitro and in vivo ocular biocompatibility, and evaluated as an antiangiogenic system in vivo. The NaBu-loaded nanoparticles/CS were 311.1 ± 3.1 nm in diameter with a 0.208 ± 0.007 polydispersity index; had a +56.3 ± 2.6 mV zeta potential; showed a 92.3% NaBu encapsulation efficiency; and sustained the drug release over 35 days. The NaBu-loaded nanoparticles/CS showed no toxicity to human retinal pigment epithelium cells (ARPE-19 cells); was not irritant to the chorioallantoic membrane (CAM); did not interfere in the integrity of the retinal layers of rat's eyes, as detected by the Optical Coherence Tomography and histopathology; and inhibited the angiogenesis in CAM assay. The NaBu-loaded nanoparticles/CS could be a therapeutic alternative to limit the neovascularization in AMD.

Lentiviral vector-mediated expression of C3 transferase attenuates retinal ischemia and reperfusion injury in rats

AIMS

Our previous study showed that intravitreal delivery of self-complementary AAV2 (scAAV2)-mediated exoenzyme C3 transferase (C3) can attenuate retinal ischemia/reperfusion (I/R) injury. The current study investigated the neuroprotective effects of lentivirus (LV)-mediated C3 transgene expression on rat retinal I/R injury.

MAIN METHODS

The LV encoding C3 and green fluorescent protein (GFP) together (LV-C3-GFP) or GFP only (LV-GFP) was intravitreally injected to SPRAGUE-DAWLEY rats. On day 5 post-intravitreal injection, eyes were evaluated by slit-lamp examination. The GFP expression on retina was confirmed by in vivo and ex vivo assessments. RhoA GTPase expression in retina was examined by western blot. Retinal I/R injury was generated by transiently increasing intraocular pressure (110 mmHg, 90 min). Eyes were then enucleated, and retinas processed for morphological analysis and TdT-dUTP terminal nick-end labeling (TUNEL) assay.

KEY FINDINGS

No obvious inflammatory reactions or surgical complications were observed after intravitreal injection of LV vectors. There was a significant decrease of total RhoA GTPase level in the retina treated with LV-C3-GFP. Compared to the blank control group, LV-C3-GFP and LV-GFP did not affect the retinal thickness, cell density in ganglion cell layer (GCL), or numbers of apoptotic cells in retinal flat-mounts. In the LV-GFP-treated retinas, I/R decreased the retinal thickness and GCL cell density and increased apoptotic retinal cell numbers. LV-C3-GFP significantly protected against all these degenerative effects of I/R.

SIGNIFICANCE

This study indicated that LV-mediated C3 transgene expression exhibits neuroprotective effects on the retinal I/R injury and holds potential as a novel neuroprotective approach targeting certain retinopathies.