Secretory Leukocyte Protease Inhibitor in Innate and Adaptive Ocular Immunity: One Glove, Many Fingers

Abstract

Purpose:: Secretory leukocyte protease inhibitor (SLPI) is a cationic protein and a member of the innate immunity-associated protein family. The main function of SLPI is to protect local tissue against the detrimental consequences of inflammation. We undertook this study to investigate the expression of SLPI in ocular tissues and to determine its function as an antimicrobial and antiprotease agent.

Methods:: We used immunohistochemistry to localize SLPI and MMPs in normal and inflamed-infected rat eye tissues. The expression levels of SLPI mRNA and protein were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. Eighty female Lewis rats (200g) were randomly divided into four test groups as follows: 1) Staphylococcus aureus endophthalmitis, 2) S. aureus keratitis, 3) HSV I keratitis, 4) Photorefractive keratectomy. The animals were sacrificed at different time points and the eyes processed for the experimental studies.

Results:: RT-PCR showed that SLPI mRNA levels in pathological tissues were noticeably increased on average as compared with normal rat eye. Western blotting analysis showed that SLPI protein expression in inflamed-infected eyes is up-regulated versus normal samples. Immunohistochemical staining for SLPI and MMPs showed that SLPI is expressed mainly in the inflamed and compromised tissues associated to inflammatory cells recruitment.

Conclusions:: These findings imply that SLPI contributes to host protection against inflammatory cell and destructive enzymes in the inflammatory state of ocular tissues by modulate immune response.

Keywords: inflammation • cornea: basic science • wound healing