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Y. Wei, S. P. Epstein, S. Fukuoka, P. A. Asbell; The Role of sPLA2-IIa in the Experimental Dry Eye Mouse Model. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4314.
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© ARVO (1962-2015); The Authors (2016-present)
Group II secretory phospholipase sPLA-IIa has been shown an inflammatory mediator in human dry eye disease. Studies utilizing a murine model have confirmed that mice with scopolamine-induced dry eye develop T-cell dominant ocular surface immune responses. This study analyzed the change in expression of sPLA2-IIa and inflammatory cytokines in this experimental dry eye mouse model.
Forty-five 6-8 week old female BALB/c mice, 5 mice/group, were injected with scopolamine, 2.5 mg/day and placed in specially designed environmentally controlled cages with daytime fan-circulated air for 5-10 days. Control mice received no scopolamine and no fan. Tear samples at Days 1, 5, 10 were collected for quantification of tear production by pheno-red thread and tear inflammatory cytokine quantification by MILLIPLEX cytokine panel. Biopsy samples of cornea, conjunctiva and lacrimal gland were analyzed for inflammation and goblet cell density by standard H&E and PAS staining. sPLA2-IIa protein expression was assayed by immunofluorescence (IF), immunohistochemistry(IHC) and qRT-PCR.
Tear thread measurement showed a significant decrease in tear production at Day 5 of scopolamine injection (treated: 2.17 ± 0.75 mm, control: 7.08 ± 3.14 mm, p<0.0001), a deficiency maintained through Day 10 (treated: 2.44 ± 1.08 mm, control: 7.20 ± 3.08 mm, p<0.0001). Corneal staining with fluorescein confirmed heavy staining only in treated eyes, indicating ocular surface compromise. Compared to non-treated controls, the goblet cell densities in the conjunctivae of scopolamine-treated mice were significantly reduced (treated: 76.3 ± 35.2, control: 142.7 ± 18.9, p<0.001), while inflammatory cell densities increased. Multiple inflammatory cytokine changes were detected, especially Th2-type, in agreement with others. An increase in expression of sPLA2-IIa in both goblet cells and conjunctiva epithelia cells was noted by ICH and IF. mRNA expression of sPLA2-IIa was found to increase in only conjunctival epithelial cells, no changes were found in cornea epithelia cells or lacrimal gland, consistent with reports in human corneal epithelium.
Our results indicate scopolamine-induced tear deficiency not only triggers Th-2-dominant ocular surface inflammation, but also promotes expression of sPLA2-IIa, suggesting sPLA2-IIa is involved in the immune modulation of conjunctival epithelium, especially inflammatory responses. Studies elucidating the role(s) and mechanism of sPLA2-IIa in ocular surface inflammation, such as dry eye diseases, may provide new therapeutic strategies to treat these diseases.
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