Aqueous humor phospholipids of DBA/2J and DBA/2J-Gpnmb(+)/SjJ mice

To compare phospholipid profiles [phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI)] of normotensive and hypertensive aqueous humor (AH) from DBA/2J and compare them with phospholipid profiles of DBA/2J-Gpnmb(+)/SjJ mice.

AH was obtained from young-normotensive DBA/2J, old -hypertensive DBA/2J mice, young and old DBA/2J-Gpnmb(+)/SjJ mice (aging control). Lipids were extracted using modified Bligh and Dyer method and subjected to mass spectrometric identification using appropriate class-specific lipid standards and ratiometric quantification. Corresponding aqueous phase (of extraction) protein concentrations were measured using Bradford method.

The total amount of phospholipids showed a decrease in the hypertensive state compared to normotensive state. The total PE and total PS contributed over 50% of the total amount. Total PS showed a remarkable decrease in hypertensive compared to normotensive state. In contrast, total PE in the hypertensive stage presented an increase in amount. Unique lipid species were found encompassing all four phospholipid classes in normotensive as well as in the hypertensive state. Several phospholipid species were found common to both states but with remarkable differences in amount in individual states. The ratio of lysophospholipids to total phospholipids is significantly reduced in the hypertensive state. Commensurate with reduced level of lysophospholipids, we found an increased level of lysophospholipase D (Autotaxin) in the hypertensive state. The difference of total phospholipids between young and old was 35.4% in DBA/2J group but 10% in DBA/2J-Gpnmb(+)/SjJ mice.

The significant change of phospholipids including lysophospholipids was found commensurate with the elevated intraocular pressure (IOP).