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Phospholipid transfer protein is present in human tear fluid
Matti Jauhiainen1, Niko L Setälä, Christian Ehnholm
1Department of Molecular Medicine, National Public Health Institute, Biomedicum, Helsinki, Finland.
Biochemistry
|June 1, 2005
Summary
Human tear fluid contains active phospholipid transfer protein (PLTP), with higher concentrations and activity than in plasma. This suggests PLTP plays a role in tear film formation and lipid balance.
Area of Science:
- Ophthalmology
- Biochemistry
- Lipid Metabolism
Background:
- The tear film's lipid layer is crucial for ocular surface protection.
- Dysregulation of tear film lipids can lead to ocular dryness.
- Phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein (CETP) are key in systemic lipid transport.
Purpose of the Study:
- To investigate the presence and activity of PLTP and CETP in human tear fluid.
- To understand the potential role of these proteins in tear film physiology.
Main Methods:
- Tear fluid collection using microcapillaries.
- Western blotting for protein detection.
- ELISA for PLTP quantification.
- Lipid transfer assays for enzymatic activity assessment.
- Chromatographic techniques (size-exclusion, heparin-affinity) for molecular characterization.
Main Results:
- PLTP was detected in human tear fluid, but CETP was absent.
- Tear fluid PLTP concentration was approximately double that of plasma (10.9 ± 2.4 μg/mL).
- PLTP exhibited significantly higher phospholipid transfer activity in tears compared to plasma.
- Activity was abolished by heat inactivation or immunoinhibition, confirming PLTP's role.
Conclusions:
- Human tear fluid contains catalytically active PLTP.
- The active form of PLTP in tears is similar to that found in plasma.
- PLTP likely contributes to tear film formation by facilitating phospholipid transfer.