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C. Kindler, K. Recker, M. Risch, S. Hawgood, B. Nölle, F. Paulsen; Structural And Functional Aspects Of Surfactant Proteins In The Lacrimal Apparatus And At The Ocular Surface . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5434.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the presence and role of surfactant proteins (SP)–A and D in the lacrimal apparatus, at the ocular surface and in tears in healthy and pathologic states.
Expression of mRNA for SP–A and SP–D was analyzed by RT–PCR in healthy lacrimal gland, conjunctiva, cornea and nasolacrimal ducts as well as in a conjunctival epithelial cell line (HCjE; IOBA–NHC) and a corneal epithelial cell line (HCE). Deposition of SP–A and SP–D was determined by Western blot, dot blot and immunohistochemistry in healthy tissues, in tears, aqueous humor as well as in different corneal pathologys including keratoconus, herpetic keratitis, and Staphylococcus aureus based ulceration. mRNA of both peptides was quantified by real time PCR in cases of functional dacryostenosis. Cell lines were stimulated with lipopolysaccharid (LPS), tumor necrosis factor alpha (TNFa), interferone gamma (INFg), and peptidoglycane (PGN) and analysed for expression and production of SP–A by real–time PCR, dot blot and immunohistochemistry.
Expression and protein of both SP–A and SP–D were detected in all healthy tissues. Moreover, both proteins were present in tears but were absent in aqueous humor. Immunohistochemistry revealed production of both peptides by acinar epithelial cells of the lacrimal gland as well as epithelial cells of the conjunctiva and nasolacrimal ducts. Healthy cornea revealed only on epithelial surface cells weak reactivity. In contrast, SP–A and SP–D revealed strong reactivity in cases of herpetic keratitis, corneal ulceration, and weak reactivity in keratokonus. Real time PCR revealed upregulated expression of both proteins in dacryosenosis. Cell culture experiments revealed that TNFa, INFg, LPS and PGN upregulated the expression and production of SP–A significantly in HCjE but not in HCE.
Our data suggest that SP–A and SP–D play an important role in innate immunity of the lacrimal apparatus and at the ocular surface and may also influence the rheological properties of the tear film by lowering surface tension and during tear drainage. Based on their direct and indirect antimicrobial effects, their possible functions in the reduction of surface tension and their modulating functions with regard to T–cells and dendritic cell functions, SP–A and SP–D seem to be involved in several ocular surface diseases.
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