NMR studies of the relationship between the changes of membrane lipids and the cisplatin-resistance of A549/DDP cells

Abstract

Changes of membrane lipids in cisplatin-sensitive A549 and cisplatin-resistant A549/DDP cells during the apoptotic process induced by a clinical dose of cisplatin (30 &mgr;M) were detected by 1H and 31P-NMR spectroscopy and by membrane fluidity measurement. The apoptotic phenotypes of the two cell lines were monitored with flow cytometry. The assays of apoptosis showed that significant apoptotic characteristics of the A549 cells were induced when the cells were cultured for 24 hours after treatment with cisplatin, while no apoptotic characteristic could be detected for the resistant A549/DDP cells even after 48 hours. The results of 1H-NMR spectroscopy demonstrated that the CH2/CH3 and Glu/Ct ratios of the membrane of A549 cells increased significantly, but those in A549/DDP cell membranes decreased. In addition, the Chol/CH3 and Eth/Ct ratios decreased for the former but increased for the latter cells under the same conditions. 31P-NMR spectroscopy indicated levels of phosphomonoesters (PME) and ATP decreased in A549 but increased in A549/DDP cells after being treated with cisplatin. These results were supported with the data obtained from 1H-NMR measurements. The results clearly indicated that components and properties of membrane phospholipids of the two cell lines were significantly different during the apoptotic process when they were treated with a clinical dose of cisplatin. Plasma membrane fluidity changes during cisplatin treatment as detected with the fluorescence probe TMA-DPH also indicate marked difference between the two cell lines. We provided evidence that there are significant differences in plasma membrane changes during treatment of cisplatin sensitive A549 and resistant A549/DDP cells.

Figure 1

Flow cytometry histograms of A549 and A549/DDP cells treated with a clinical dose of 30 μM cisplatin. a, b, c stands for A549 cells treated and cultured for 0, 24, and 48 h, respectively, and d, e, f for A549/DDP cells under the same conditions.

Figure 2

¹H-NMR spectra of A549 cells (A) and A549/DDP cells (B) treated with a clinical dose of 30 μM cisplatin and cultured for 0 h, 24 h, and 48 h. The cell concentrations are comparable (1 × 10⁷ cells/mL) for each sample. The peak assignments are shown in the figures. Number of scans was 128.

Figure 3

³¹P-NMR spectra of A549 cells (A), A549/DDP cells (B) treated with a clinical dose of 30 μM cisplatin and cultured for 0 h, 24 h, and 48 h. The cell concentrations are comparable (5 × 10⁸ cells/mL) for each sample. The peak assignments are shown in the figures. 2000 transients were accumulated for each spectrum.

Figure 4

The microviscosity of the plasma membranes of A549 and A549/DDP cells treated with a clinical dose of 30 μM cisplatin and cultured for different time periods. Microviscosity was measured by the fluorescence probe TMA-DPH (2 μM) as given as .