Abstract
Purpose :
Secretory phospholipase A2 (sPLA2) is a potent antimicrobial enzyme found in the tear film that protects the ocular surface from microbial pathogens. The enzyme may also play a role in the degradation of tear phospholipids, which might cause lipid layer disruption and tear instability. Increased sPLA2 activity may also lead to increased formation of pro-inflammatory lipid mediators responsible for ocular surface inflammation. To our knowledge, the enzyme’s activity and concentration have not been correlated with patient-reported outcomes. Our purpose was to evaluate the potential relation between the activity and concentration of sPLA2-IIA and subjective outcomes.
Methods :
Ten µL of tears were collected from each eye of 20 normal subjects using glass microcapillaries, pooled, and stored at -80 °C until analysis. sPLA2-IIA activity was calculated using 1,2-dithio analog of diheptanoyl phosphatidylcholine as substrate. A double-antibody sandwich ELISA was used to determine the sPLA2-IIA concentrations. Subjects also completed the Ocular Surface Disease Index (OSDI) which was scored per recommended guidelines. The activity and concentration were then correlated with the OSDI using Spearman’s rank correlation coefficient. A p-value of less than 0.05 was considered significant.
Results :
The mean sPLA2-IIA activity in normal human tears was found to be 0.014 ± 0.028 µmol/min/ml while the mean sPLA2-IIA concentration was found to be 8111.098 ± 7.662 pg/ml. A moderate but non-significant negative correlation was found between the sPLA2-IIA activity and OSDI scores (ρ= - 0.42, p=0.06). sPLA2-IIA concentration had a strong negative correlation with the OSDI scores (ρ=-0.67, p=0.001).
Conclusions :
The results indicate that tears contain low activity and concentration of sPLA2-IIA which may be due to the fact that all the tear samples came from normal individuals. The significant negative correlation between OSDI scores and the sPLA2-IIA concentration suggests increased activity in the tears may protect the ocular surface, thereby leading to lower subjective scores.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.