Proteases and Proteolysis in the tears of people with Keratoconus

Abstract

AbstractPurpose Keratoconus is a degenerating disease of the eye which causes an irregularly shaped cornea leading to impairment of vision.The role of proteases in keratoconus has been a topic of substantial discussion and speculation over many years.This study was designed to examine the levels and activity of proteases in the tear film of people with keratoconus.Methods A case‐controlled study was performed studying the tear proteome of keratoconus patients(K) and controls(N).Basal tears were collected using a capillary tube.Total protein(TP)in tears was estimated using BCA assay;the levels of lactoferrin(Lf),secretory immunoglobin A(sIgA) and serum albumin were measured using specific ELISAs.Levels and activity of tear proteases were studied using Raybiotech® Antibody Array and EnzChek® Assay Kits respectively.Results There was a two‐fold (p=0.0001) decrease in TP levels between K(3.86+1.62 mg/ml) and N(7.00+1.58 mg/ml). Levels of Lf(0.67+0.28 vs. 1.13+0.29 mg/ml) and sIgA(0.78+0.36 vs. 1.70+0.66 mg/ml) were also significantly(p=0.0001) reduced in K. The expression levels of matrix metalloproteinases(MMP)‐1,‐2,‐3,‐7,‐13,interleukins(IL)‐1α,‐3,‐4,‐5,‐6,‐8,‐10 and tumour necrosis factor(TNF)‐α,‐β were significantly(p=0.01)altered between K and N. Tear proteolysis(gelatinase/collagenase)was expressed as Fluorescence Intensity(FI).The activity of gelatinases(87.54+33.57 vs. 45.79+24.60 FI,p=0.0002)and collagenases(6.11+3.18 vs. 3.56+2.03 FI,p=0.03)were significantly increased in K.Conclusion The tears of people with keratoconus expressed high levels of proteases, increased proteolysis and a profoundly altered protein profile, which might change with the severity of the disease.These findings may lead the way to understanding or monitoring disease progression.