Abstract
Purpose: :
To identify the endogenous phospholipids of the aqueous humor (AQH) and trabecular meshwork (TM) by mass spectrometric shotgun lipidomics.
Methods: :
The human TM and AQH samples were collected adhering to tenets of declaration of Helsinki under IRB approved protocols. The TM and AQH were obtained from Caucasian donors with mean age of 55 ±8 years (n=10 each). Control TM and AQH were from cadavers and cataract surgery patients respectively. Lipids were extracted using the Bligh and Dyer method, and re-suspended in Isopropanol/Acetonitrile solution. For lipid analyses we have used recently developed shotgun lipidomic methods. Briefly, positive mode precursor ion scan (PIS) for phosphocholines (PC; product m/z of 184) and negative mode PIS for phosphoinositol (PI; product m/z 241) and phosphoethanolamine (PE; product m/z of 196) was used with a TSQ Quantum Access Max instrument. The samples were infused and scanned for one minute between 200 m/z to 1000 m/z. Ratiometric quantification was performed using quantitative standards for each lipid class.
Results: :
All classes of phospholipids (PC, PI and PE) and corresponding lysophospholipids were found in both the AQH and TM. We found variation in lipid profile between AQH and TM. All phospholipid classes showed differences with respect to levels and species between glaucomatous and control groups. Unique phosphopholipids in controls that are absent in glaucomatous AQH and TM are being subjected to further characterization using high resolution mass spectrometry.
Conclusions: :
We found unique phospholipids and lysophospholipids in control AQH and TM that are either absent or present in very low levels in glaucomatous samples. We identified different phospholipid species in AQH and TM using shotgun lipidomics.
Keywords: lipids • trabecular meshwork • aqueous