Effects of oxidative stress on plasma membrane fluidity: Biological consequences
- Autores: Carlos de la Haba Fonteboa
- Directores de la Tesis: Paz Martínez Ramírez (dir. tes.), Antoni Morros (codir. tes.), José Ramón Palacio Cornide (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2015
- Idioma: inglés
- Tribunal Calificador de la Tesis: Dolores Jaraquemada Pérez de Guzmán (presid.), Angel Mozo Villarias (secret.), Jordi Hernández Borrell (voc.)
- Materias:
- Enlaces
- Resumen
Oxidative stress is present in many diseases and it is generated in cells and tissues when an imbalance between oxidants and antioxidants occurs, favouring an oxidant status with high concentrations of reactive oxygen and nitrogen species. Lipids in plasma membrane are one of the preferential targets giving rise to lipid peroxidation. This process modifies membrane properties and may modulate cell function.
Aims: 1) To evaluate the effect of oxidative stress on plasma membrane fluidity regionalization of single living THP-1 macrophages and MEC-1 lymphocytes. 2) To analyse, in these cells, the relationship between lipid peroxidation and membrane fluidity. 3) To study the effect of oxidative stress on receptor-ligand binding and membrane fluidity: toll-like receptors (TLR2-4)/lipopolysaccharide in macrophages and progesterone-induced blocking factor (PIBF) receptor/PIBF in lymphocytes.
Material and Methods: Two-photon microscopy was standardized for the first time in the Universitat Autònoma de Barcelona by our laboratory, to analyse membrane fluidity in single living cells with the fluorescent probe Laurdan. Cellular oxidative stress was induced by H2O2. A new software application was also developed to analyse membrane lipid domain size and number. LPS for macrophages, or PIBF for lymphocytes, were used to analyse receptor-ligand interactions under oxidative stress.
Results: Macrophages showed a significant H2O2 concentration dependent increase in the frequency of rigid lipid regions. Under oxidative stress conditions, an increase in number, but not in size, of pseudo-raft domains was detected. Macrophage activation by LPS increases the frequency of fluid regions, which was inhibited by oxidative stress. Concerning macrophage function, secretion of TNF¿ under oxidative conditions was decreased.
Lymphocytes showed a significant H2O2 concentration dependent increase in the frequency of rigid lipid regions. Upon PIBF binding to its receptor, lymphocyte plasma membrane becomes more rigid due to clustering of lipid rafts. However, when PIBF bound lymphocytes were placed under oxidative stress conditions, lipid raft clustering did not occur and PIBF binding to its receptor decreased.
Conclusions: 1) An important general consequence of oxidative stress is that both in macrophages and lymphocytes plasma membrane becomes more rigid. 2) Receptor-ligand interactions have an effect on membrane fluidity, which vary greatly between the two cell types studied: macrophages and lymphocytes. 3) Upon LPS complex/TLR2-4 binding, macrophage plasma membrane became more fluid. Our results in macrophages suggest that membrane fluidification is in accordance with some macrophage functions. However, upon PIBF/PIBF-R binding, lymphocyte plasma membrane became more rigid. Our results in lymphocytes suggest that lipid raft clustering may be linked to lymphocyte function. 4) Nevertheless, the above-described effects induced by receptor-ligand binding on membrane fluidity do not occur under oxidative stress in both types of cells. Results showed that another consequence of oxidative stress was an impaired cell function in both cases.
