Abstract
Purpose:
The purpose of this study is to determine whether lipids derived from omega-3 and omega-6 polyunsaturated fatty acids (PUFA) are present in human aqueous humor.
Methods:
Undiluted aqueous humor samples were collected from 10 patients who underwent either elective cataract surgery and/or non-elective glaucoma surgery. Samples were removed from the anterior chamber following the initial paracenthesis and prior to any further intervention. The samples were immediately packed in dry ice and stored at -80 °C. The samples were analyzed in a masked fashion for the presence of poly-unsaturated fatty acids. Lipids were extracted from aqueous humor by solid phase exaction, and analyzed via liquid chromatography tandem mass spectrometry (LC-MS/MS, Thermo Scientific) in negative-ion mode. Deuterium-labeled prostglandin D2 (PGD2-d4) and/or docosahexaenoic acid (DHA-d5) were added to each sample as the internal standard for quantification.
Results:
The analysis of ten samples of aqueous humor demonstrated the presence of the omega-6 fatty acid linoleic acid (LA), the omega-3 fatty acid-alpha linolenic acid (ALA), with its metabolites DHA and EPA. A one-way repeated measures ANOVA demonstrated a significant difference between the concentration levels of the 8 lipids identified in the aqueous humor [F (7, 27) = 634.2, p<.0001. A Tukey post-hoc pairwise comparison analysis demonstrated that LA was significantly highest in concentration. The mean concentrations were 0.88 ng/uL for LA, 0.09 ng/uL for ALA, and 0.10 ng/uL for both DHA and EPA. There were no intra-operative or post-operative complications related to aqueous humor sample collection.
Conclusions:
We demonstrate the presence of omega-3 and omega-6 PUFAs in human aqueous humor. The omega-6 fatty acid, linoleic acid, is highest in concentration of the lipids we identified. The omega-6 metabolic pathway gives rise to arachidonic acid pro-inflammatory bioactive lipids. The omega-3 PUFAs, DHA and EPA, are identified in our analysis and serve as precursors for a novel class of mediators termed Resolivins and Protectins possessing pro-anti-inflammatory, pro-resolving and neuro-protective properties. The identification of PUFAs in human aqueous humor helps build a foundation for the development of novel therapeutic agents and diagnostic tests.
Keywords: 427 aqueous •
583 lipids •
420 anterior chamber