Lactoferrin Expression in Human and Murine Ocular Tissue

Abstract

Purpose Lactoferrin (LF) is a multifunctional protein known to provide innate defense due to its antimicrobial and anti-inflammatory properties. In the eye, LF has been identified in the tears and vitreous humor. Its presence in other ocular tissues has not been determined. Our aim is to assess the presence of LF in the cornea, iris, retina and retinal pigment epithelium (RPE) of humans and mice. Methods To test for the endogenous production of LF, reverse transcription polymerase chain reaction was performed in cultured human cells from the cornea and RPE and in murine tissues. To confirm LF localization in specific ocular tissue, immunohistochemistry was performed on flat mounts of cornea, retina and RPE in human donor eyes. The presence of LF was assessed by western blotting in human and mouse ocular tissue and human culture cells (cornea and RPE). To verify antibody specificity, purified human LF and transferrin (TF) were used on 1D and 2D western blots. Results LF gene expression was confirmed in the cornea and RPE cell cultures from humans, suggesting that LF is an endogenously produced protein. PCR results from mouse ocular tissue showed LF expression in cornea, iris, RPE, but not in retina. These results were also consistent with immunohistochemical localization of LF in human donor tissue. Antibody reaction for human LF was specific and western blotting showed its presence in the cornea, iris and RPE tissues. A faint reaction for the retina was observed but was likely due to contamination from other ocular tissues. Multiple commercially available antibodies for murine LF cross-reacted with TF, so no reliable results were obtained for murine western blot. Conclusion LF is expressed in multiple eye tissues of humans and mice. This widespread expression and multifunctional activity of LF suggests that it may play an important role in protecting eye tissues from inflammation-associated diseases.

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“… 23 Lactoferrin is an important multifunctional tear protein that has antimicrobial and anti-inflammatory effects and has been found to be reduced in the tear of patients with dry eye. 24 It was unclear if patients with dry eye in that study 23 had yin-deficiency.…”

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“…Another protein possibly involved in iron transport is lactoferrin (LF), a multifunctional protein which shares 65% of homology with TF. It is synthesized in various human ocular tissues mainly in the RPE but not in the neural retina [18]. LF receptors have not been studied in the eye but are present in the brain [48].…”