Pollen Enzymes Degrade Human Tear Fluid and Conjunctival Cells: An Approach to Understanding Seasonal Non-Allergic Conjunctivitis

Background: During pollen seasons, allergy-like symptoms can be observed in proven non-allergy sufferers. Pollen enzymes are thought to be responsible for conjunctival irritation. We investigated the influence of the well-known aggressive pollen species hazelnut (Corylus avellana) and birch pollen (Betula pendula) on both human tear fluid and conjunctival cell cultures. This study is an approach to seasonal non-allergic conjunctivitis (SNAC) syndrome. Methods: Zymography was carried out in order to investigate the proteolytic activity of the pollen. Thereafter, human tear fluid was incubated with pollen extract, and the results were studied by polyacrylamide gel electrophoresis. In addition, cultivated conjunctival cells (CHANG cells) were incubated with pollen extracts. Cytomorphological changes were analyzed using the CASY1 Cell Counter. Cell viability was quantified via MTS assay. The viability of the cells which were incubated with pollen extract was compared to the viability of control cells. Results: Pollen proteases destroy tear fluid proteins, as observed by polyacrylamide gel electrophoresis. The treatment of CHANG cells with pollen extract induced a statistically significant decrease in cell viability, depending on the pollen extract concentration and the incubation period. Conclusion: Evidence of the destruction of tear fluid proteins and damage to human conjunctival cells by pollen proteases explains conjunctival irritation in proven non-allergic people during the pollen season. One reason why not all people are affected by SNAC syndrome to the same extent could be differences in the concentrations of antiproteases present on the ocular surface.