Abstract
Purpose :
Dry eye is one of the leading causes for individuals to seek eye care. Treatment is focused on enhancing ocular surface lubrication and/or blunting immune cell recruitment. Proteoglycan 4 (PRG4, or lubricin) is a mucin-like glycoprotein present on the ocular surface and in tears. While initially classified as a lubricant, recent studies have shown PRG4 has anti-inflammatory properties. Here, we examined the ability of exogenous recombinant human PRG4 (rhPRG4) to modulate chemokine secretion in response to dry eye associated inflammatory stimuli in human corneal epithelial (HCE) cells, and characterized PRG4 expression in a widely used experimental dry eye (EDE) mouse model.
Methods :
Telomerase-immortalized HCE cells were cultured in media alone (control), +IL1β (10ng/ml), or +TNFα (100ng/ml); all ±300µg/ml rhPRG4 (Lubris BioPharma). After 48hr, media was collected and chemokine (IP10, RANTES, and ENA78) levels were quantitated by ELISA. Dry eye was induced in 6-10 week-old C57Bl/6 mice for 5 days via subcutaneous scopolamine hydrobromide and environmental desiccation. Age and sex matched control mice were housed under normal conditions. PRG4 expression was quantified in corneal epithelium and in lacrimal gland lysate by immunohistochemistry and quantitative western blotting, respectively. Data reflects Mean±SEM of 3-5 animals/group.
Results :
rhPRG4 significantly reduced (p<0.05) IL1β and TNFα induced levels of IP10 (564±43 to 436±31; 1371±90 to 438±8pg/ml), RANTES (123±9 to 73±4; 76±2 to 33±11 pg/ml), and ENA78 (225±28 to 110±18; 141±45 to 64±9 pg/ml). EDE resulted in 2.96-fold reduction of pixel intensity (p<0.05) in PRG4 immunostaining on the corneal epithelium compared to control animals, and decreased protein expression in lacrimal gland cell lysate (1.2±0.2 to 0.5±0.2 au, p<0.05).
Conclusions :
In addition to PRG4’s well-known lubricating properties, here we demonstrate PRG4’s anti-inflammatory activity in HCE cells in response to dry eye associated conditions. Additionally, reduced ocular surface expression of PRG4 in a murine model of dry eye was observed. Both results are consistent with rhPRG4’s previously demonstrated efficacy in a dry eye small clinical trial. Collectively, these findings provide the foundation for elucidating the biological mechanism of action of PRG4 on the ocular surface in maintaining homeostasis and treating dry eye disease.
This is a 2020 ARVO Annual Meeting abstract.