In Vitro Models for Biochemical Investigations on Programmed Cell Death

Abstract

Isolated rat thymocytes treated with methylprednisolone (MPS), cultured human synovial (McCoy's) cells exposed to cold shock and human mammary adenocarcinoma (BT-20) cells treated with Tumour Necrosis Factor (TNF), all showed DNA fragmentation and the morphological and biochemical features of cell death characteristic of a process known as apoptosis. DNA fragmentation in MPS-treated thymocytes and in cold shock-exposed McCoy's cells was preceded by a marked increase in cytosolic free Ca2+ concentration resulting either from a sustained influx of Ca2+ from the extracellular medium or from the release of Ca2+ from intracellular pools. On the other hand, in TNF-treated BT-20 cells, DNA fragmentation was not associated with any early, marked increase in the cytosolic free Ca2+ level. In all three models, however, DNA fragmentation was efficiently prevented by intracellular Ca2+ chelators, calmodulin inhibitors and activators of protein kinase C (PKC). These results suggest that the activation of common mechanisms involving Ca2+ and PKC may be essential for the development of apoptosis.