Hydrolysis of Phosphatidylserine-exposing Red Blood Cells by Secretory Phospholipase A2 Generates Lysophosphatidic Acid and Results in Vascular Dysfunction

• Published in: The Journal of biological chemistry Vol. 281; no. 2; pp. 775 - 781
• Main Authors: Neidlinger, Nikole A., Larkin, Sandra K., Bhagat, Amrita, Victorino, Gregory P., Kuypers, Frans A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 13.01.2006; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Cell Line; Cells, Cultured; Dose-Response Relationship, Drug; Endothelium, Vascular - cytology; Endothelium, Vascular - metabolism; Erythrocytes - cytology; Erythrocytes - metabolism; Group II Phospholipases A2; Hemolysis; Humans; Hydrolysis; Inflammation; Lipids - chemistry; Lysophospholipids - chemistry; Palmitates - pharmacology; Phosphatidic Acids - chemistry; Phosphatidylserines - chemistry; Phospholipases A - metabolism; Phospholipases A - physiology; Phospholipases A2; Phosphoserine - analogs & derivatives; Phosphoserine - pharmacology; Rats; Time Factors; Umbilical Veins - cytology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M505790200

Secretory phospholipase A2 (sPLA2) type IIa, elevated in inflammation, breaks down membrane phospholipids and generates arachidonic acid. We hypothesized that sPLA2 will hydrolyze red blood cells that expose phosphatidylserine (PS) and generate lysophosphatidic acid (LPA) from phosphatidic acid that is elevated in PS-exposing red blood cells. In turn, LPA, a powerful lipid mediator, could affect vascular endothelial cell function. Although normal red blood cells were not affected by sPLA2, at levels of sPLA2 observed under inflammatory conditions (100 ng/ml) PS-exposing red blood cells hemolyzed and generated LPA (1.2 nm/108 RBC). When endothelial cell monolayers were incubated in vitro with LPA, a loss of confluence was noted. Moreover, a dose-dependent increase in hydraulic conductivity was identified in rat mesenteric venules in vivo with 5 μm LPA, and the combination of PS-exposing red blood cells with PLA2 caused a similar increase in permeability. In the presence of N-palmitoyl l-serine phosphoric acid, a competitive inhibitor for the endothelial LPA receptor, loss of confluence in vitro and the hydraulic permeability caused by 5 μm LPA in vivo were abolished. The present study demonstrates that increased sPLA2 activity in inflammation in the presence of cells that have lost their membrane phospholipid asymmetry can lead to LPA-mediated endothelial dysfunction and loss of vascular integrity.