Comparison of In Vivo Gene Expression Profiling of RPE/Choroid following Intravitreal Injection of Dexamethasone and Triamcinolone Acetonide

Gene network analyses unveil possible molecular basis underlying drug-induced glaucoma

Background

Drug-induced glaucoma (DIG) is a kind of serious adverse drug reaction that can cause irreversible blindness. Up-to-date, the molecular mechanism of DIG largely remains unclear yet due to the medical complexity of glaucoma onset.

Methods

In this study, we conducted data mining of tremendous historical adverse drug events and genome-wide drug-regulated gene signatures to identify glaucoma-associated drugs. Upon these drugs, we carried out serial network analyses, including the weighted gene co-expression network analysis (WGCNA), to illustrate the gene interaction network underlying DIG. Furthermore, we applied pathogenic risk assessment to discover potential biomarker genes for DIG.

Results

As the results, we discovered 13 highly glaucoma-associated drugs, a glaucoma-related gene network, and 55 glaucoma-susceptible genes. These genes likely played central roles in triggering DIGs via an integrative mechanism of phototransduction dysfunction, intracellular calcium homeostasis disruption, and retinal ganglion cell death. Further pathogenic risk analysis manifested that a panel of nine genes, particularly OTOF gene, could serve as potential biomarkers for early-onset DIG prognosis.

Conclusions

This study elucidates the possible molecular basis underlying DIGs systematically for the first time. It also provides prognosis clues for early-onset glaucoma and thus assists in designing better therapeutic regimens.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-00960-9.

Early Transcriptomic Response to OxLDL in Human Retinal Pigment Epithelial Cells

In the sub-retinal pigment epithelium (sub-RPE) space of the aging macula, deposits of oxidized phospholipids, oxidized derivatives of cholesterol and associated oxidized low-density lipoproteins (OxLDL) are considered contributors to the onset and development of age-related macular degeneration (AMD). We investigated the gene expression response of a human-derived RPE cell line exposed for short periods of time to non-cytotoxic levels of OxLDL or LDL. In our cell model, treatment with OxLDL, but not LDL, generated an early gene expression response which affected more than 400 genes. Gene pathway analysis unveiled gene networks involved in the regulation of various cellular functions, including acute response to oxidative stress via up-regulation of antioxidative gene transcripts controlled by nuclear factor erythroid-2 related factor 2 (NRF2), and up-regulation of aryl hydrocarbon receptor-controlled detoxifying gene transcripts. In contrast, circadian rhythm-controlling genes and genes involved in lipid metabolism were strongly down-regulated. Treatment with low-density lipoprotein (LDL) did not induce the regulation of these pathways. These findings show that RPE cells are able to selectively respond to the oxidized forms of LDL via the up-regulation of gene pathways involved in molecular mechanisms that minimize cellular oxidative damage, and the down-regulation of the expression of genes that regulate the intracellular levels of lipids and lipid derivatives. The effect on genes that control the cellular circadian rhythm suggests that OxLDL might also disrupt the circadian clock-dependent phagocytic activity of the RPE. The data reveal a complex cellular response to a highly heterogeneous oxidative stress-causing agent such as OxLDL commonly present in drusen formations.

Glucocorticoid receptor signaling in the eye

Glucocorticoids (GCs) are essential steroid hormones that regulate numerous metabolic and homeostatic functions in almost all physiological systems. Synthetic glucocorticoids are among the most commonly prescribed drugs for the treatment of various conditions including autoimmune, allergic and inflammatory diseases. Glucocorticoids are mainly used for their potent anti-inflammatory and immunosuppressive activities mediated through signal transduction by their nuclear receptor, the glucocorticoid receptor (GR). Emerging evidence showing that diverse physiological and therapeutic actions of glucocorticoids are tissue-, cell-, and sex-specific, suggests more complex actions of glucocorticoids than previously anticipated. While several synthetic glucocorticoids are widely used in the ophthalmology clinic for the treatment of several ocular diseases, little is yet known about the mechanism of glucocorticoid signaling in different layers of the eye. GR has been shown to be expressed in different cell types of the eye such as cornea, lens, and retina, suggesting an important role of GR signaling in the physiology of these ocular tissues. In this review, we provide an update on the recent findings from in vitro and in vivo studies reported in the last 5 years that aim at understanding the role of GR signaling specifically in the eye. Advances in studying the physiological effects of glucocorticoids in the eye are vital for the elaboration of optimized and targeted GC therapies with potent anti-inflammatory potential while minimizing adverse effects.