The effect of inhibition of Ca 2+-independent phospholipase A 2 on chemotherapeutic-induced death and phospholipid profiles in renal cells

Abstract

We demonstrate that cells derived from primary cultures of rabbit proximal tubules (RPTC), human embryonic kidney (HEK293) and human kidney carcinomas (Caki-1) express microsomal Ca 2+-independent phospholipase A 2 (iPLA 2γ) and cytosolic Ca 2+-independent phospholipase A 2 (iPLA 2β). Inhibition of iPLA 2 activity in these cells using the iPLA 2 inhibitor bromoenol lactone (BEL) (0–5.0 μM) for 24 h did not induce cell death as determined by annexin V and propidium iodide (PI) staining. However, BEL treatment prior to cisplatin (50 μM) or vincristine (2 μM) exposure reduced apoptosis 30–50% in all cells tested (RPTC, HEK293 and Caki-1 cells). To identify the phospholipids altered during cell death electrospray ionization-mass spectrometry and lipidomic analysis of HEK293 and Caki-1 cells was performed. Cisplatin treatment reduced 14:0–16:0 and 16:0–16:0 phosphatidylcholine (PtdCho) 50% and 35%, respectively, in both cell lines, 16:0–18:2 PtdCho in Caki-1 cells and increased 16:1–22:6 plasmenylcholine (PlsCho). BEL treatment prior to cisplatin exposure further decreased 14:0–16:0 PtdCho, 16:0–16:1 PlsCho and 16:0–18:1 PlsCho in HEK293 cells, and inhibited cisplatin-induced increases in 16:1–22:6 PlsCho in Caki-1 cells. Treatment of cells with BEL prior to cisplatin exposure also increased the levels of several arachidonic containing phospholipids including 16:0–20:4, 18:1–20:4, and 18:0–20:4 PtdCho, compared to cisplatin only treated cells. These data demonstrate that inhibition of iPLA 2 protects against chemotherapeutic-induced cell death in multiple human renal cell models, identifies specific phospholipids whose levels are altered during cell death, and demonstrates that alterations in these phospholipids correlate to the protection against cell death in the presence of iPLA 2 inhibitors.