Secreted leukocyte protease inhibitor is present in aqueous humours from cataracts and other eye pathologies

Differential expression of proteome in aqueous humor in patients with and without glaucoma

OBJECTIVE

To determine quantitative and qualitative differences of aqueous humor proteome in patients with and without glaucoma.

METHOD

Observational, descriptive and cross-sectional study of 12 patients (8 men; 4 women) with and without glaucoma. There are 3 groups of minority proteins with serum equimolar contribution of each of the patients. Specimens were obtained during cataract surgery from patients without glaucoma (performed with retrobulbar anaesthesia [cataract retrobulbar patient -CRP-;n=4] or topical [cataract topical patient -CTP-; n=4]), or from patients with glaucoma (performed with retrobulbar anaesthesia [glaucoma retrobulbar patient -GRP-; n=4]). The humor proteome samples were frozen at -80°C until processing by trypsin digestion to obtain tryptic peptides, and then performing liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) to obtain the proteome and its differential expression between groups. Statistical analysis was performed using the SPSS v.17 program.

RESULTS

The study included 12 patients, aged (mean±standard deviation) 74.50±9.53 years. Concentrations obtained: 0.48±0.25μg/μl for CRP, 0.28±0.04μg/μl for CTP, and 0.35±0.16μg/μl for GRP. A total of 309 proteins were identified, of which 205, 210, and 182 were in CRP, CTP, and GRP, respectively. A total of 114 proteins were common to all three groups, 50 were exclusive to CRP, 58 to CTP, and 27 to GRP.

CONCLUSIONS

In this pilot study, a quantitative difference was found in the protein expression of humor among patients with glaucoma, there being 27 proteins unique to patients with glaucomatous disease.

Biofluid proteases profiling in diabetes mellitus

The investigation of protease relevance in biologic systems beyond catabolism of proteins and peptides to amino acids has stimulated interest as to their role in the pathogenesis of several disorders including diabetes mellitus (DM). Evaluation of proteases and the assessment of their activity in biofluids are fundamental to elucidate these proteolytic systems in DM and its related complications. In contrast to traditional immunoassay or substrate based approaches that targeted specific proteases and their inhibitors, the field of degradomics has provided a comprehensive approach to study these enzymes. Although the degradome contains over 500 proteases, very few have been associated with DM and its micro- and macrovascular complications. In this paper, we review these proteases and their respective inhibitors with emphasis on DM. It is likely that future research will expand these initial studies and look to develop high throughput automated technologies to identify and characterize biofluid proteases of diagnostic and prognostic value in other pathologies.

Proteomic analysis of the aqueous humor in age-related macular degeneration (AMD) patients

Age-related macular degeneration (AMD) can lead to irreversible central vision loss in the elderly. Although large number of growth factor pathways, including the vascular endothelial growth factor (VEGF), has been implicated in the pathogenesis of AMD, no study has directly assessed the whole proteomic composition in the aqueous humor (AH) among AMD patients. The AH contains proteins secreted from the anterior segment tissue, and these proteins may play an important role in the pathogenesis of AMD. Thus, comparisons between the AH proteomic profiles of AMD patients and non-AMD controls may lead to the verification of novel pathogenic proteins useful as potential clinical biomarkers. In this study, we used discovery-based proteomics and Multiple Reaction Monitoring Mass Spectrometry (MRM-MS) to analyze AH from AMD patients and AH from controls who underwent cataract surgery. A total of 154 proteins with at least two unique peptides were identified in the AH. Of these 154 proteins identified by discovery-based proteomics, 10 AH proteins were novel identifications. The protein composition in the AH was different between AMD patients and non-AMD controls. Subsequently, a systematic MRM-MS assay was performed in seven highly abundant differentially expressed proteins from these groups. Differential expression of three proteins was observed in the AH of AMD patients compared with that of cataract controls (p<0.0312). Elucidation of the aqueous proteome will establish a foundation for protein function analysis and identify differentially expressed markers associated with AMD. This study demonstrates that integrated proteomic technologies can yield novel biomarkers to detect exudative AMD.

Proteomics of the aqueous humor in healthy New Zealand rabbits

There are several physiological roles postulated for aqueous humor, a liquid located in the anterior and posterior chamber of the eye, such as maintenance of the intraocular pressure, provision of nutrients, and removal of metabolic waste from neighboring tissues and provision of an immune response and protection during inflammation and infection. To link these function to specific or classes of proteins, identification of the aqueous humor proteome is essential. Aqueous humor obtained from healthy New Zealand white rabbits was analyzed using three synergistic protein separation methods: 1-D gel electrophoresis, 2-DE, and 1-DLC (RPLC) prior to protein identification by MS. As each of these separation methods separates intact proteins based on different physical properties (pIs, molecular weights, hydrophobicity, solubility, etc.) the proteome coverage is expanded. This was confirmed, since overlap between all three separation technologies was only about 8.2% with many proteins found uniquely by a single method. Although the most dominant protein presented in normal aqueous humor is albumin, by using this extensive separation/MS strategy, additional proteins were identified in total amount of 98 nonredundant proteins (plus an additional ten proteins for consideration). This expands the current protein identifications by approximately 65%. The aqueous humor proteome comprises a specific selection of cellular and plasma based proteins and can almost exclusively be divided into four functional groups: cell-cell interactions/wound healing, proteases and protease inhibitors, antioxidant protection, and antibacterial/anti-inflammatory proteins.