AAV-NDI1 Therapy Provides Significant Benefit to Murine and Cellular Models of Glaucoma

Glaucoma, a leading cause of blindness, is a multifactorial condition that leads to progressive loss of retinal ganglion cells (RGCs) and vision. Therapeutic interventions based on reducing ocular hypertension are not always successful. Emerging features of glaucoma include mitochondrial dysfunction and oxidative stress. In the current study, NDI1-based gene therapy, which improves mitochondrial function and reduces reactive oxygen species, was delivered intraocularly via an adeno-associated viral vector (AAV). This AAV-NDI1 therapy protected RGCs from cell death in treated (1552.4 ± 994.0 RGCs/mm2) versus control eyes (1184.4 ± 978.4 RGCs/mm2, p < 0.05) in aged DBA/2J mice, a murine model of glaucoma. The photonegative responses (PhNRs) of RGCs were also improved in treated (6.4 ± 3.3 µV) versus control eyes (5.0 ± 3.1 µV, p < 0.05) in these mice. AAV-NDI1 also provided benefits in glaucomatous human lamina cribrosa (LC) cells by significantly increasing basal and maximal oxygen consumption rates and ATP production in these cells. Similarly, NDI1 therapy significantly protected H2O2-insulted primary porcine LC cells from oxidative stress. This study highlights the potential utility of NDI1 therapies and the benefits of improving mitochondrial function in the treatment of glaucoma.

Three genes expressed in relation to lipid metabolism considered as potential biomarkers for the diagnosis and treatment of diabetic peripheral neuropathy

Diabetic neuropathy is one of the most common chronic complications and is present in approximately 50% of diabetic patients. A bioinformatic approach was used to analyze candidate genes involved in diabetic distal symmetric polyneuropathy and their potential mechanisms. GSE95849 was downloaded from the Gene Expression Omnibus database for differential analysis, together with the identified diabetic peripheral neuropathy-associated genes and the three major metabolism-associated genes in the CTD database to obtain overlapping Differentially Expressed Genes (DEGs). Gene Set Enrichment Analysis and Functional Enrichment Analysis were performed. Protein-Protein Interaction and hub gene networks were constructed using the STRING database and Cytoscape software. The expression levels of target genes were evaluated using GSE24290 samples, followed by Receiver operating characteristic, curve analysis. And Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed on the target genes. Finally, mRNA-miRNA networks were constructed. A total of 442 co-expressed DEGs were obtained through differential analysis, of which 353 expressed up-regulated genes and 89 expressed down-regulated genes. The up-regulated DEGs were involved in 742 GOs and 10 KEGG enrichment results, mainly associated with lipid metabolism-related pathways, TGF-β receptor signaling pathway, lipid transport, and PPAR signaling pathway. A total of 4 target genes (CREBBP, EP300, ME1, CD36) were identified. Analysis of subject operating characteristic curves indicated that CREBBP (AUC = 1), EP300 (AUC = 0.917), ME1 (AUC = 0.944) and CD36 (AUC = 1) may be candidate serum biomarkers for DPN. Conclusion: Diabetic peripheral neuropathy pathogenesis and progression is caused by multiple pathways, which also provides clinicians with potential therapeutic tools.

Differential Activation of Glioprotective Intracellular Signaling Pathways in Primary Optic Nerve Head Astrocytes after Treatment with Different Classes of Antioxidants

Optic nerve head astrocytes are the specialized glia cells that provide structural and trophic support to the optic nerve head. In response to cellular injury, optic nerve head astrocytes undergo reactive astrocytosis, the process of cellular activation associated with cytoskeletal remodeling, increases in the rate of proliferation and motility, and the generation of Reactive Oxygen Species. Antioxidant intervention has previously been proposed as a therapeutic approach for glaucomatous optic neuropathy, however, little is known regarding the response of optic nerve head astrocytes to antioxidants under physiological versus pathological conditions. The goal of this study was to determine the effects of three different antioxidants, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin (Mn-TM-2-PyP), resveratrol and xanthohumol in primary optic nerve head astrocytes. Effects on the expression of the master regulator nuclear factor erythroid 2-related factor 2 (Nrf2), the antioxidant enzyme, manganese-dependent superoxide dismutase 2 (SOD2), and the pro-oxidant enzyme, nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), were determined by quantitative immunoblotting. Furthermore, efficacy in preventing chemically and reactive astrocytosis-induced increases in cellular oxidative stress was quantified using cell viability assays. The results were compared to the effects of the prototypic antioxidant, Trolox. Antioxidants elicited highly differential changes in the expression levels of Nrf2, SOD2, and NOX4. Notably, Mn-TM-2-PyP increased SOD2 expression eight-fold, while resveratrol increased Nrf2 expression three-fold. In contrast, xanthohumol exerted no statistically significant changes in expression levels. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) uptake and lactate dehydrogenase (LDH) release assays were performed to assess cell viability after chemically and reactive astrocytosis-induced oxidative stress. Mn-TM-2-PyP exerted the most potent glioprotection by fully preventing the loss of cell viability, whereas resveratrol and xanthohumol partially restored cell viability. Our data provide the first evidence for a well-developed antioxidant defense system in optic nerve head astrocytes, which can be pharmacologically targeted by different classes of antioxidants.

Early and Late Induction of KRAS and HRAS Proto-Oncogenes by Reactive Oxygen Species in Primary Astrocytes

Astrocytes, one of the predominant types of glial cells, function as both supportive and metabolic cells for the brain. Among mammalian tissues, the highest levels of p21^Ras protein are detected in the brain. Here, we investigated the expression of KRAS and HRAS proto-oncogenes in primary astrocytes following acute oxidative stimulation. Reactive oxygen species (ROS) changed the expression of proto-oncogenes at both transcriptional and translational levels. De novo protein synthesis analysis measured approximate values of proteins half-life, ranging from 1–4 h, of the different H- and K- isoforms by western blot analysis. Quantitative gene expression analysis of KRAS and HRAS revealed an unexpected short-term induction of KRAS mRNA in primary astrocytes in response to acute stimulation. Indeed, cultured astrocytes responded to proteasomal inhibition by preventing the reduction of c-K-Ras. A fraction of K-Ras protein accumulated in the presence of ROS and cycloheximide, while a substantial proportion was continuously synthesized. These data indicate that ROS regulate in a complementary fashion p21^Ras isoforms in primary astrocytes: K-Ras is rapidly and transiently induced by post-translational and post-transcriptional mechanisms, while H-Ras is stably induced by mRNA accumulation. We suggest that K-Ras and H-Ras are ROS sensors that adapt cells to metabolic needs and oxidative stress.

The role of lamina cribrosa cells in optic nerve head fibrosis in glaucoma

Glaucoma is a chronic progressive optic neuropathy. There are extracellular matrix (ECM) changes associated with optic disc cupping in the optic nerve head (ONH) and subsequent visual field defects. The primary risk factor for onset and progression of glaucoma is raised intraocular pressure (IOP). Elevated IOP causes deformation at the ONH specifically at the lamina cribrosa (LC) region where there is also deposition of ECM causing the LC to initially undergo thickening and posterior migration with eventual shearing and collapse of the LC plates leading to a thin fibrotic connective tissue structure/scar. Cells that populate the LC region of the ONH are those cells that are positive for GFAP (the astrocytes) and those negative for GFAP (the LC cells). The LC cell plays an integral role in ECM remodelling producing ECM when exposed to high level mechanical stretch, TGF- β1 and a hypoxic environment.

Crystallins and neuroinflammation: The glial side of the story

BACKGROUND

There is an abundance of evidence to support the association of damaging neuroinflammation and neurodegeneration across a multitude of diseases. One of the links between these pathological phenomena is the role of chaperone proteins as both neuroprotective and immune-regulatory agents.

SCOPE OF REVIEW

Chaperone proteins are highly expressed at sites of neuroinflammation both in glial cells and in the injured neurons that initiate the immune response. For this reason, the use of chaperones as treatment for various diseases associated with neuroinflammation is a highly active area of investigation. This review explores the various ways that the small heat shock protein chaperones, α-crystallins, can affect glial cell function with a specific focus on their implication in the inflammatory response associated with neurodegenerative disorders, and their potential as therapeutic treatment.

MAJOR CONCLUSIONS

Although the mechanisms are still under investigation, a clear link has now been established between alpha-crystallins and neuroinflammation, especially through their roles in microglial and macroglial cells. Interestingly, similar to inflammation in itself, crystallins can have a beneficial or detrimental impact on the CNS based on the context and duration of the condition.

GENERAL SIGNIFICANCE

Overall this review points out the novel roles that chaperones such as alpha-crystallins can play outside of the classical protein folding pathways, and their potential in the development of new therapies for the treatment of neuroinflammatory/neurodegenerative diseases. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.