Physical state changes of membrane lipids in human lung adenocarcinoma A 549 cells and their resistance to cisplatin

Abstract

The properties of membrane lipids in sensitive A 549 and resistant A 549/DDP cells to cis-dichlorodiammine platinum[II] (cisplatin) were examined by combining different approaches. The results showed that fluorescence intensity (Δ F) of Merocyanine 540 (MC540) was 93.5±21.8 for the sensitive A 549 cells and 49.5±11.2 for the resistive A 549/DDP cells, monitored by flow cytometry, which may indicate that membrane lipid packing of the sensitive A 549 cells were looser than that of the resistant A 549/DDP cells. Diffusion rate of N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-1,2-hexadecanoyl-Sn-glycero-3-phosphatidyl-ethanolamine (NBD-PE) was slower in A 549/DDP cells than in A 549 cells as detected by fluorescence recovery after photobleaching (FRAP) technique. Fatty acid analysis of the membrane lipids showed 21.6, 27.0 and 31.8% increase in the amount of C 18:1, C 18:2 and C 18:3 fatty acid, respectively, in A 549 cells as compared to A 549/DDP cells. The total amount of unsaturated fatty acids in the plasma membrane lipid is 69.13%±2.2% for A 549, and 55.08%±1.8% for A 549/DDP cells, respectively. The resistance to cisplatin in A 549/DDP cells was confirmed by the measurements of the transmembrane influx of Rhodamine-123, cisplatin or Bodipy-cisplatin by fluorescence assay and inductively coupled plasma mass spectrometry (ICP-MS). From the results described previously, it is concluded that changes in the membrane lipids “composition” cause a change in the physical state of the plasma membrane lipids and that this may be associated with the resistance of A 549/DDP cells to cisplatin.