Sulfur Mustard Exposure Disrupts Transmembrane Water Channel Proteins In Rabbit Corneas in vivo

Abstract

Purpose : Aquaporins (AQPs), transmembrane water channel proteins, play an important role in corneal homeostasis and hydration maintenance in vivo. We investigated changes in AQPs levels during acute mustard gas keratopathy condition in vivo by measuring transcript levels in normal and damaged rabbit corneas collected 3-, 7- and 14-days post SM exposure.

Methods : New Zealand White Rabbits were used. The study was approved by the ICUC committee and performed following ARVO guidelines. Rabbits were exposed to vehicle (air) or SM vapor (200 mg-min/m³ for 8 mins) once at the MRI Global, Kansas City, Missouri, USA. Eyes were subjected to clinical exams with the slit-lamp microscope and in vivo confocal microscope. Also, Fante's grading system, fluorescein test, Schirmer’s test, pachymetry, applanation tonometry, and optical coherence tomography were used to grade corneal haze, inflammation, epithelial integrity, and eye pressure in -/+ SM exposed eyes in live rabbits. Corneas collected 3-, 7- and 14-days post euthanasia were used to isolate total RNA and generate cDNA. Quantitative real-time RT-PCR was used to measure levels of AQPs gene expression. One-way analysis of variance (ANOVA) followed by Tukey-Kramer multiple comparisons using the GraphPad 8 program was used for statistical analysis. The p < 0.05 was considered statistically significant

Results : The SM-exposed rabbit eyes showed significant corneal epithelial defect (day-3=p<0.0001; day-7=p=0.0002), corneal haze (day-3=1.5-1.7; day-7=1.7-2.2), corneal oedema/thickness (day-3=495-520um; day-7=520-550mm) and increased tear flow (day-3=8.8-9.3mm/Hg; day-7=8.1-8.6mm/Hg) compared to naïve. These effects were not so pronounced on day -14 between naïve and SM-exposed corneas. The six AQP isoforms, AQP1, AQP3, AQP4, AQP5, AQP7, and AQP11 were detected the cornea. The SM-exposed rabbit corneas showed statistically significant mRNA expression of AQP1, AQP3, and AQP5 on day-3, day-7, and day-14 compared to naive (p<0.01 or p<0.001).

Conclusions : Alterations in transmembrane water channel proteins may be contributing, at least in part, in acute mustard gas keratopathy in vivo. More studies are warranted.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.