The effect of tissue plasminogen activator on corticosteroid-induced ocular hypertension in guinea pig–a next generation proteomic study

Abstract

Purpose : This project studied the reaction of tissue plasminogen activator (tPA) on corticosteroid-induced ocular hypertension (CIH) and glaucoma using a guinea pig animal model. The molecular mechanism underlying was also explored.

Methods : Ocular hypertension in guinea pigs was induced by sub-conjunctival injection of 5% dexamethasone (DEX) into both eyes. After 6 weeks, tPA was then injected into the treated eyes while PBS was used to inject into contralateral eyes. Trabecular meshwork (TM) tissue in both eyes of the guinea pigs were then collected for proteomic analysis after intraocular pressure (IOP) measurement. Differentially expressed proteins were quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS) using SWATH^TM technologies.

Results : The average IOP at baseline was 18.5 ± 2.8 mmHg (mean ± SD) and 18.7 ± 2.8 mmHg (mean ± SD) in both eyes respectively. After 6 weeks of DEX treatment, IOPs increased to 22.9 ± 2.2 mmHg (mean ± SD) and 23.1 ± 2.8 mmHg (mean ± SD) in both eyes respectively. The average inter-ocular difference (IOD, treated minus control IOP) of IOP between 2 eyes was, at day 0 of injection, - 0.2 ± 0.8 mmHg (mean ± SD) while it reached - 6.7 ± 1.6 mmHg (mean ± SD) after 2 days of tPA treatment. IOPs of the tPA-treated eyes were lower than the contralateral eyes. Eight differentially expressed proteins (p-value ≤ 0.05 and fold-change ≥1.3 or ≤ 0.77) were identified by SWATH-MS. Among them, phospholipid scramblase (PLSCR3) was found to be regulated by tPA in CIH TM tissue of guinea pigs. It was found that phospholipid scramblase activity was regulated in a genome-wide association study of glaucoma subjects.

Conclusions : An albino guinea pig CIH model was successfully developed and IOP could be induced after 6 weeks of DEX injection via subconjunctiva. tPA was found to significantly reduce the IOP in CIH guinea pig’s eyes. Our results revealed that tPA can also regulate multiple differentially expressed proteins. Furthermore, our result will inform new clinical study to assess the development of a novel therapeutic drug in patients with glaucoma.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.