Human aqueous humor proteome in cataract, glaucoma, and pseudoexfoliation syndrome

Abstract

Twenty-nine human aqueous humor samples from patients with eye diseases such as cataract and glaucoma with and without pseudoexfoliation syndrome were characterized by LC-high resolution MS analysis. In total, 269 protein groups were identified with 1% false discovery rate including 32 groups that were not reported previously for this biological fluid. Since the samples were analyzed individually, but not pooled, 36 proteins were identified in all samples, comprising the constitutive proteome of the fluid. The most dominant molecular function of aqueous humor proteins as determined by GO analysis is endopeptidase inhibitor activity. Label-free protein quantification showed no significant difference between glaucoma and cataract aqueous humor proteomes. At the same time, we found decrease in the level of apolipoprotein D as a marker of the pseudoexfoliation syndrome. The data are available from ProteomeXchange repository (PXD002623).

LC-MS-Based Metabolic Fingerprinting of Aqueous Humor

“…However, during the method development not only the number of metabolites detected but also the reproducibility of measured intensities of metabolic features and the number of features in the blank extractions were taken into account. AH is to some extent similar to blood plasma as it contains plasma proteins and metabolites which are filtered to AH through fenestrated capillaries of the ciliary body stroma via the iris root [14]. Although the total concentration of proteins in AH seems to be low (five times lower than in blood plasma [14]), protein depletion in AH sample was performed before metabolite analysis.…”

“…AH is to some extent similar to blood plasma as it contains plasma proteins and metabolites which are filtered to AH through fenestrated capillaries of the ciliary body stroma via the iris root [14]. Although the total concentration of proteins in AH seems to be low (five times lower than in blood plasma [14]), protein depletion in AH sample was performed before metabolite analysis. This step was used to eliminate potential enzymatic reactions between proteins and metabolites.…”

“…It supplies nutrients and removes metabolic waste from avascular tissues in the eye [13]. Homeostasis of AH is required to maintain adequate intraocular pressure as well as optical and refractive properties of the eye [14]. AH is a complex mixture known to contain electrolytes, glucose, urea, antioxidants (e.g., glutathione and ascorbic acid), organic solutes, several proteins (e.g., growth factors and cytokines), and oxygen and carbon dioxide [12, 14].…”

“…Homeostasis of AH is required to maintain adequate intraocular pressure as well as optical and refractive properties of the eye [14]. AH is a complex mixture known to contain electrolytes, glucose, urea, antioxidants (e.g., glutathione and ascorbic acid), organic solutes, several proteins (e.g., growth factors and cytokines), and oxygen and carbon dioxide [12, 14]. Until now, only a few articles in which metabolomics has been applied to analyze AH have been published [12, 15–18].…”

Changes to the Aqueous Humor Proteome during Glaucoma

“…However, as some patients (two in the glaucoma, one in the control group) received cholesterol-lowering drugs, an influence of systemic medication on this finding cannot completely ruled out. Interestingly, Kliuchnikova and coworkers also identified cholesterol metabolism to be influenced during glaucoma, with apolipoprotein D down-regulated during pseudoexfoliation syndrome [6]. Furthermore, GO analysis revealed that significantly enriched proteins are related to the acute phase response with Scavenger receptor cysteine-rich type 1 protein M130, Alpha-2-antiplasmin, Alpha-1-antichymotrypsin, Inter-alpha-trypsin inhibitor heavy chain H4, Alpha-2-HS-glycoprotein, and Prothrombin upregulated in glaucomatous aqueous humor.…”