Tài liệu Báo cáo khoa học: Characterization of 1H NMR detectable mobile lipids in cells from human

Characterization of 1H NMR detectable mobile lipids

in cells from human adenocarcinomas

Anna Maria Luciani1

, Sveva Grande1

, Alessandra Palma1

, Antonella Rosi1

, Claudio Giovannini2

,

Orazio Sapora3

, Vincenza Viti1 and Laura Guidoni1

1 Dipartimento di Tecnologie e Salute and INFN Gruppo Collegato Sanita`, Istituto Superiore di Sanita`, Rome, Italy

2 Dipartimento di Sanita` Pubblica Veterinaria e Sicurezza Alimentare, Istituto Superiore di Sanita`, Rome, Italy

3 Dipartimento di Ambiente e Connessa Prevenzione Primaria, Istituto Superiore di Sanita`, Rome, Italy

Among the different molecules showing intense and

narrow peaks in the 1

H magnetic resonance spectra,

much attention has been devoted to the fatty acid sig￾nals from mobile lipids (MLs), which are characterized

by high mobility and, thus, differently from most cell

lipids, are visible in high resolution magnetic resonance

spectra. High-intensity MLs are often observed in pro￾liferating cells and in tumour cells [1–4]. Many studies

have found that the onset of apoptosis is accompanied

by an increase in ML intensity [5–7], although other

studies have not [8,9].

A number of studies have been performed in view of

the possible use of MLs as spectroscopic markers of

cell fate, although a clear explanation of their behav￾iour has not yet been provided. Essentially, two differ￾ent localizations have been proposed. In mammalian

cells, ML resonances arise from lipids that are either

present as microdomains with high mobility embedded

in the plasma membrane bilayer [9] or exist in cytosolic

lipid droplets, mostly consisting of triglycerides (TGs)

[10,11]. Some studies have found that the concentra￾tion of total cell TGs was consistent with the intensity

of ML signals [11], whereas, more recently, changes in

the size of lipid droplets were suggested [12].

In the present study, we examined the 1

H NMR ML

signals of cultured tumour cells, specifically HeLa and

Keywords

cell cycle; cell metabolism; lipids; magnetic

resonance spectroscopy; tumour cell lines

Correspondence

L. Guidoni, Dipartimento di Tecnologie e

Salute, Istituto Superiore di Sanita`, 00161

Rome, Italy

Fax: +39 06 4938 7075

Tel: +39 06 4990 2804

E-mail: [email protected]

(Received 5 November 2008, revised 15

December 2008, accepted 22 December

2008)

doi:10.1111/j.1742-4658.2009.06869.x

Magnetic resonance spectroscopy studies are often carried out to provide

metabolic information on tumour cell metabolism, aiming for increased

knowledge for use in anti-cancer treatments. Accordingly, the presence of

intense lipid signals in tumour cells has been the subject of many studies

aiming to obtain further insight on the reaction of cancer cells to external

agents that eventually cause cell death. The present study explored the rela￾tionship between changes in neutral lipid signals during cell growth and

after irradiation with gamma rays to provide arrest in cell cycle and cell

death. Two cell lines from human tumours were used that were differently

prone to apoptosis following irradiation. A sub-G1 peak was present only

in the radiosensitive HeLa cells. Different patterns of neutral lipids changes

were observed in spectra from intact cells, either during unperturbed cell

growth in culture or after radiation-induced growth arrest. The intensities

of triglyceride signals in the spectra from extracted total lipids changed

concurrently. The increase in lipid peak intensities did not correlate with

the apoptotic fate. Modelling to fit the experimental data revealed a

dynamic equilibrium between the production and depletion of neutral

lipids. This is observed for the first time in cells that are different from

adipocytes.

Abbreviations

GPC, glycerophosphorylcholine; IR, intensity ratio; ML, mobile lipid; PC, phosporylcholine; PCA, perchloric acid; PL, phospholipids;

TG, triglycerides.

FEBS Journal 276 (2009) 1333–1346 ª 2009 The Authors Journal compilation ª 2009 FEBS 1333