Ultrastructural and confocal laser scanning microscopical aspects of apoptosis in cultured human neuroblastoma SH-SY5Y cells

Programmed cell death or apoptosis is a physiological process that plays an important role during development and maintains tissue homeostasis during adult life. In pathological conditions, such as cancer, apoptosis may be the mechanism by which cancer proliferation is hampered. Many antineoplastic drugs act by inducing apoptosis. SH-SY5Y human neuroblastoma cells undergo apoptosis when exposed to cisplatin, an effective antineoplastic drug. The occurrence of cell death by the apoptotic process is evidenced by the typical electrophoretic laddering of DNA, which begins 24 h after cisplatin exposure and becomes even more apparent at 3-4 days after exposure. Concomitantly, ultrastructural changes of the nucleus and nucleolar organization occur, followed by nuclear membrane disruption and, finally, by cytoplasm degeneration. These last two aspects are present in cultured cells detached from the substrate and predominate in long-term cultures after drug exposure. Confocal laser scanning microscopy (CLSM) of orange-acridine stained nuclei also clearly demonstrates the fragmentation of the chromatin into 3-5 domains. The CLSM, therefore can clearly demonstrate the occurrence of apoptosis in a much simpler, but equally accurate way than electron microscopy.