Dysregulated Tear Film Proteins in Macular Edema Due to the Neovascular Age-Related Macular Degeneration Are Involved in the Regulation of Protein Clearance, Inflammation, and Neovascularization

Abstract

Macular edema and its further complications due to the leakage from the choroidal neovascularization in course of the age-related macular degeneration (AMD) is a leading cause of blindness among elderly individuals in developed countries. Changes in tear film proteomic composition have been reported to occur in various ophthalmic and systemic diseases. There is an evidence that the acute form of neovascular AMD may be reflected in the tear film composition. Tear film was collected with Schirmer strips from patients with neovascular AMD and sex- and age-matched control patients. Two-dimensional electrophoresis was performed followed by MALDI-TOF mass spectrometry for identification of differentially expressed proteins. Quantitative analysis of the differential electrophoretic spots was performed with Delta2D software. Altogether, 11 significantly differentially expressed proteins were identified; of those, 8 were downregulated, and 3 were upregulated in the tear film of neovascular AMD patients. The differentially expressed proteins identified in tear film were involved in signaling pathways associated with impaired protein clearance, persistent inflammation, and neovascularization. Tear film protein analysis is a novel way to screen AMD-related biomarkers.

Targeted Analysis of Tears Revealed Specific Altered Metal Homeostasis in Age-Related Macular Degeneration

“…Recently, the tear film of 15 patients with wet AMD and 15 age-matched healthy controls was comparatively analyzed by two-dimensional gel electrophoresis and MALDI-TOF/TOF, which identified altered proteins belong to pathways involving oxidative stress, protein clearance and chronic inflammation pathways, highlighting annexins A1 and A4 are part of the calcium-dependent phospholipid-binding family that regulate inflammation and autophagy. 52 , 53 However, none of the identified altered proteins in those works coincide with those evaluated in our study showing significant variations.…”

Presbyopia: An outstanding and global opportunity for early detection of pre-frailty and frailty states

“…Some data support the concept of age-related eye diseases as biomarkers of frailty phenotype and predictors of poor health outcomes ( 8 , 22 , 27 , 31 , 34 , 35 , 42 , 67 ). Equally, data back the concept of the eye and its tear as a source of diagnostic biomarkers of ocular and systemic diseases, including age-related ones ( 57 , 59 – 63 ). Thus, it would not be surprising that tears would contain frailty biomarkers.…”

“…Among these conditions are age-related diseases, including eye diseases. So, tears have provided several potential biomarkers for cataracts, glaucoma, AMD, DR, Alzheimer's, and Parkinson's diseases ( 57 , 59 – 63 ). Conversely, the presence of specific frailty biomarkers in tears is unknown.…”

Changes in Tear Proteomic Profile in Ocular Diseases

“…For protein extraction, our team used 8 M of urea buffer containing dithiothreitol and CHAPS in the presence of protease inhibitor cocktail. The process lasted for 3 h in 4 °C and was ended by centrifuging (5000× g for 20 min) [ 23 , 24 , 25 ]. Moreover, Ihnatko chose the addition of urea in solubilization buffer for protein extraction [ 26 ].…”

“…NanoDrop was used to determine protein level in studies correlated with age-related changes to human tear composition [ 33 ] and with a prediction of vernal keratoconjunctivitis reactivation [ 34 ]. MaestroNano was applied by our team for the protein measurements of tear fluid in macular edema, due to the neovascular age-related macular degeneration and analysis of tear film obtained from diabetic dogs [ 24 , 25 ]. In terms of protein concentration determination, infrared electromagnetic radiation is also suitable.…”