Publication Date
1-1-2022
Journal
Experimental Eye Research
DOI
10.1016/j.exer.2021.108895
PMID
34910926
PMCID
PMC8908478
PubMedCentral® Posted Date
1-1-2023
PubMedCentral® Full Text Version
Author MSS
Published Open-Access
yes
Keywords
Aging, Animals, Cathepsins, Cells, Cultured, Conjunctiva, Drug Delivery Systems, Dry Eye Syndromes, Epithelium, Corneal, Goblet Cells, Lacrimal Apparatus, Mice, Mice, Inbred C57BL, Occludin, Spleen, Tears, Tight Junction Proteins, Zonula Occludens-1 Protein, Cathepsin S, dry eye, aging, inflammaging, corneal barrier, goblet cells, tight junction proteins
Abstract
Cathepsin S (CTSS) is a protease that is proinflammatory on epithelial cells. The purpose of this study was to investigate the role of CTSS in age-related dry eye disease. Ctss−/− mice [in a C57BL/6 (B6) background] of different ages were compared to B6 mice. CTSS activity in tears and lacrimal gland (LG) lysates was measured. The corneal barrier function was investigated in naïve mice or after topical administration of CTSS eye drops 5X/day for two days. Eyes were collected, and conjunctival goblet cell density was measured in PAS-stained sections. Immunoreactivity of the tight junction proteins, ZO-1 and occludin, was investigated in primary human cultured corneal pithelial cells (HCEC) without or with CTSS with or without a CTSS inhibitor. A significant increase in CTSS activity was observed in the tears and LG lysates in aged B6 compared to young mice. This was accompanied by higher Ctss transcripts and protein expression in LG and spleen. Compared to B6, 12 and 24-month-old Ctss−/− mice did not display age-related corneal barrier disruption and goblet cell loss. Treatment of HCEC with CTSS for 48 hours disrupted occludin and ZO-1 immunoreactivity compared to control cells. This was prevented by the CTSS inhibitor LY3000328 or CTSS-heat inactivation. Topical reconstitution of CTSS in Ctss−/− mice for two days disrupted corneal barrier function. Aging on the ocular surface is accompanied by increased expression and activity of the protease CTSS. Our results suggest that CTSS modulation might be a novel target for age-related dry eye disease.