Therapeutic Potential of Antioxidants and Hybrid TEMPOL Derivatives in Ocular Neurodegenerative Diseases: A Glimpse into the Future

Optimized PLGA encapsulated SA-2 nanosuspension exhibits sustained intraocular pressure reduction in the mouse microbead occlusion model of ocular hypertension

Elevated intraocular pressure (IOP) is implicated in the structural and functional damage to the retinal ganglion cells (RGCs) in primary open-angle glaucoma (POAG). Topical IOP lowering agents provide short-term relief, necessitating frequent dosing. Moreover, non-adherence to frequent eyedrops administration contributes significantly to visual field loss and worsens the disease outcome. We optimized the poly (lactic-co-glycolic acid) (PLGA) nanoparticles encapsulation of hybrid antioxidant-nitric oxide donor SA-2 (SA-2NP), investigated its bioavailability, duration of IOP lowering efficacy, and effects on retinal function in the microbead model of ocular hypertension (OHT). SA-2 was bioavailable in the anterior and posterior segments after 1, 8, and 24 h post-single topical eyedrop administration. SA-2NP significantly lowered IOP (∼25-34%) and preserved the RGC function after weekly eyedrop administration for 3 weeks in C57BL/6J mice. In conclusion, the optimized SA-2NP formulation demonstrated optimal bioavailability, ocular safety, and prolonged IOP-lowering efficacy in the mouse microbead occlusion model of OHT.

Tert-butyl hydroperoxide induces trabecular meshwork cells injury through ferroptotic cell death

Trabecular meshwork (TM) tissue has a crucial role in regulating aqueous humor circulation in the eye, thus maintaining normal intraocular pressure (IOP). TM dysfunction causes IOP elevation, which leads to glaucoma. To investigate biological changes in TM tissue in patients with glaucoma, we analyzed the mRNA expression microarray dataset, GSE27276. Gene ontology analysis indicated that redox microenvironment imbalance is among the main changes of TM tissue in patients with glaucoma. Subsequently, we induced oxidative stress in TM cells using the tert-butyl hydroperoxide (tBHP) treatment, to generate in vivo and in vitro models, and conducted mRNA sequencing to identify genes with critical roles in maintaining the redox microenvironment balance. We found that the tBHP caused TM dysfunction in vivo, characterized by aqueous humor circulation resistance, IOP elevation, and TM cell death. Further, Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that ferroptosis signaling was enriched in tBHP-treated TM cells. Consistently, in vitro analyses showed that levels of reactive oxygen species, ferric ion, and malondialdehyde were increased after the tBHP treatment, indicating TM cell ferroptosis. Furthermore, inhibiting ferroptosis alleviated tBHP-induced TM cell injury. This study provides new insights suggesting that inhibition of ferroptosis has potential as a treatment for glaucoma.

The Role and Mechanism of Nicotinamide Riboside in Oxidative Damage and a Fibrosis Model of Trabecular Meshwork Cells

Purpose

To investigate the potential effects and mechanism of nicotinamide riboside (NR) on the oxidative stress and fibrosis model of human trabecular meshwork (HTM) cell line cells.

Methods

HTM cells were pretreated with NR, followed by the induction of oxidative injury and fibrosis by hydrogen peroxide (H2O2) and TGF-β2, respectively. Cell viability was tested using Hoechst staining and MTT assays, cell proliferation was assessed by EdU assay, and cell apoptosis was detected by flow cytometry and western blotting. DCFH-DA and DHE probes were used to measure the level of reactive oxygen species (ROS), and MitoTracker staining was used to measure the mitochondrial membrane potential (MMP). Fibrotic responses, including cell migration and deposition of extracellular matrix (ECM) proteins, were detected via Transwell assays, qRT-PCR, and immunoblotting.

Results

NR pretreatment improved the viability, proliferation, and MMP of H2O2-treated HTM cells. Compared to cells treated solely with H2O2, HTM cells treated with both NR and H2O2, exhibited a reduced rate of apoptosis and generation of ROS. Compared with H2O2 pretreatment, NR pretreatment upregulated expression of the JAK2/Stat3 pathway but inhibited mitogen-activated protein kinase (MAPK) pathway expression. Moreover, 10-ng/mL TGF-β2 promoted cell proliferation and migration, which were inhibited by NR pretreatment. Both qRT-PCR and immunoblotting showed that NR inhibited the expression of fibronectin in a TGF-β2-induced fibrosis model.

Conclusions

NR has a protective effect on oxidative stress and fibrosis in HTM cells, which may be related to the JAK2/Stat3 pathway and MAPK pathway.

Translational Relevance

Our research provides the ongoing data for potential therapy of NAD+ precursors in glaucoma.