Regulation of the neutrophil chemoattractant, AcPGP, in open and closed eye tears

Cameron Postnikoff

Abstract

Purpose: In eye closure, a massive neutrophil influx can be observed at the ocular surface. The exact mechanisms responsible for neutrophil recruitment have yet to be determined. Extracellular matrix turnover may be partially responsible, through the production of the collagen fragment and neutrophil chemoattractant proline-glycine-proline (PGP). The mechanisms of increased matrix turnover and neutrophil infiltration are also thought to be implicated in dry eye disease.

Methods: Ten subjects were recruited (ages 22-57) and were trained for the self-collection of tears using a microcapillary tube. Subjects collected unstimulated basal tears from the lateral canthus per each eye, and two separate collections were performed: immediately upon awakening and between 11am and 2pm. Tears were frozen at -80°C following collection. For peptide quantification, PGP and the acetylated version of PGP (AcPGP) were measured using a MDS Sciex API-4000 mass spectrometer (Concord, ON) equipped with a Shimadzu HPLC (Columbia, MD). PGP/AcPGP peptide concentrations were calculated using a relative standard curve method.

Results: All samples showed no presence of PGP, which is hypothesized to be rapidly degraded ex vivo by the enzyme LTA4H. However, the downstream acetylated PGP product, AcPGP was detected in 60% of samples. At awakening, the overall concentration of AcPGP was higher (2.8 ng/mL) compared to mid-day, open eye tears (1.37 ng/mL).

Conclusions: This pilot investigation demonstrated that PGP could not be easily recovered from closed eye tears. Higher levels of AcPGP suggest increased extracellular matrix turnover in the closed eye, and its properties as a stronger neutrophil chemoattractant than PGP warrant further investigation in a larger cohort. Study of this pathway in the closed eye could aid in understanding of dry eye pathogenesis.

Details

Year: 2016

Program Number: 160120

Author Affiliation: University of Alabama at Birmingham

Co-Authors: Patricia Jackson, Taylor Berryhill, Landon Wilson, Stephen Barnes, J. Blalock, Kelly Nichols

Co-Author Affiliation: University of Alabama at Birmingham, University of Alabama at Birmingham, University of Alabama at Birmingham, University of Alabama at Birmingham, University of Alabama at Birmingham, University of Alabama at Birmingham, School of Optometry

Room: 211AB