Aluminum Affects Membrane Physical Properties in Human Neuroblastoma (IMR-32) Cells Both before and after Differentiation

The capacity of Al3+ to induce changes in the physical properties of plasma membrane from human neuroblastoma cells (IMR-32) was investigated, and the magnitude of the changes was compared with that obtained after cell differentiation to a neuronal phenotype. Similarly to our previous results in liposomes, Al3+ (10 to 100 μM) caused a significant loss of membrane fluidity, being the differentiated cells more affected than the nondifferentiated cells. Al3+ also increased the relative content of lipids in gel phase and promoted lipid rearrangement through lateral phase separation, with the magnitude of this effect being similar in nondifferentiated and differentiated cells. Since membrane physical properties depend on bilayer composition, we characterized the content of proteins, phospholipids, cholesterol, and fatty acids in the IMR-32 cells before and after differentiation. Differentiated cells had a significantly higher content of unsaturated fatty acids, creating an environment that favors Al3+-mediated effects on the bilayer fluidity. The neurotoxic effects of Al3+ may be, at least in part, due to alterations of neuronal membrane physical properties, with potential consequences on the normal functioning of membrane-related cellular processes.