Diabetic retinopathy (DR), a sight-threatening neurovasculopathy, is the leading cause of irreversible blindness in the developed world. DR arises as the result of prolonged hyperglycemia and is characterized by leaky retinal vasculature, retinal ischemia, retinal inflammation, angiogenesis, and neovascularization. The number of DR patients is growing with an increase in the elderly population, and therapeutic approaches are limited, therefore, new therapies to prevent retinal injury and enhance repair are a critical unmet need. Besides vascular endothelial growth factor (VEGF)-induced vascular proliferation, several other mechanisms are important in the pathogenesis of diabetic retinopathy, including vascular inflammation. Thus, combining anti-VEGF therapy with other new therapies targeting these pathophysiological pathways of DR may further optimize treatment outcomes. Technological advancements have allowed for high-throughput proteomic studies examining biofluids such as aqueous humor, vitreous humor, tear, and serum. Many DR biomarkers have been identified, especially proteins involved in retinal inflammatory processes. This review attempts to summarize the proteomic biomarkers of DR-associated retinal inflammation identified over the last several years.

Elevated intraocular pressure (IOP) is the only modifiable risk factor for primary open-angle glaucoma (POAG). Herein we sought to prioritize a set of previously identified IOP-associated genes using novel and previously published datasets. We identified several genes for future study, including several involved in cytoskeletal/extracellular matrix reorganization, cell adhesion, angiogenesis, and TGF-β signaling. Our differential correlation analysis of IOP-associated genes identified 295 pairs of 201 genes with differential correlation. Pathway analysis identified β-estradiol as the top upstream regulator of these genes with ESR1 mediating 25 interactions. Several genes (i.e., EFEMP1, FOXC1, and SPTBN1) regulated by β-estradiol/ESR1 were highly expressed in non-glaucomatous human trabecular meshwork (TM) or Schlemm’s canal (SC) cells and specifically expressed in TM/SC cell clusters defined by single-cell RNA-sequencing. We confirmed ESR1 gene and protein expression in human TM cells and TM/SC tissue with quantitative real-time PCR and immunofluorescence, respectively. 17β-estradiol was identified in bovine, porcine, and human aqueous humor (AH) using ELISA. In conclusion, we have identified estrogen receptor signaling as a key modulator of several IOP-associated genes. The expression of ESR1 and these IOP-associated genes in TM/SC tissue and the presence of 17β-estradiol in AH supports a role for estrogen signaling in IOP regulation.

SPI1, a transcription factor implicated in myeloid cell development, has emerged as a genetic risk factor for Alzheimer's disease (AD). Recent in vivo studies reveal that Spi1 knockdown in mice exacerbates AD pathology by increasing amyloid-β aggregation and gliosis while Spi1 overexpression ameliorates these features. Transcriptomic analyses suggest that Spi1 regulates microglial immune response, complement activation, and phagocytosis. SPI1 regulation of these processes may explain how SPI1 affects AD risk. Further studies, including human validation, are needed to explore the dynamic influence of SPI1 across AD stages, its applicability to clinical settings, and its potential as a therapeutic target.

Mutations in the myocilin olfactomedin (OLF) domain can cause vision loss in glaucoma by inducing protein misfolding in trabecular meshwork cells. However, not all mutations are causal for the disease. Here, we compare the cellular behaviors of two variants with uncertain contribution to glaucoma – namely, the missense variant A427T and premature stop variant Q368X – to those of wild type (WT) and disease variant Y437H. When expressed in an inducible immortalized trabecular meshwork cell line, inhibition of the proteasome rerouted WT myocilin from endoplasmic reticulum-associated degradation to autophagy. By contrast, neither Y437H, A427T nor Q368X could be rerouted for degradation. Conversely, inhibition of autophagy caused accumulation of WT myocilin and did not promote clearance of any tested mutant myocilins. Although the Q368X OLF mutant is misfolded, the crystal structure of the A427T OLF mutant showed modest perturbations that were largely confined to the mutation site. Our study demonstrates that a full range of misfolded states of mutant myocilin can present challenges for protein quality control clearance pathways and expands the range of defects known to impair mutant myocilin clearance.