ABSTRACT
We investigated the induction of apoptosis by cadmium in NIH 3T3 murine fibroblasts. Apoptosis was triggered effectively by 10 microM CdCl2 within 24 h, under which conditions cell viability was reduced by 50%. Cadmium-induced apoptosis was demonstrated by both morphological and biochemical analysis. We have shown that cadmium concentrations of 5-20 microM caused nuclear fragmentation. Moreover, internucleosomal DNA fragmentation was evoked by 10-25 microM CdCl2 within 24 h, as detected by the formation of ladder patterns in DNA electrophoresis. Since the induction of programmed cell death occurs together with modifications in the cell cycle, we examined the ability of cadmium to block cell divisions by using a 5-bromo2-deoxy-uridine incorporation assay. Our results indicate that about 40% of treated cells are blocked in G0-G1 phase when exposed to 10 microM cadmium for 27 h. Finally, we addressed the question of whether the effect of cadmium could be prevented by suppressing apoptosis. Over-expression of the anti-apoptotic protein Bcl-2 in NIH 3T3 cells protects against cadmium toxicity, thus suggesting a role for Bcl-2 in the regulation of cadmium-induced apoptosis.
Subject(s)
Apoptosis/drug effects , Cadmium/toxicity , Proto-Oncogene Proteins c-bcl-2/physiology , 3T3 Cells , Animals , Cell Survival/drug effects , DNA Fragmentation/drug effects , Dose-Response Relationship, Drug , Fibroblasts/cytology , Fibroblasts/drug effects , Genetic Vectors , Histocytochemistry , Immunochemistry , Mice , Microscopy, Fluorescence , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/immunology , Transduction, GeneticABSTRACT
The PC3 gene is transiently expressed during neurogenesis in precursor cells of the telencephalic ventricular/subventricular zone, and is rapidly downregulated before cell migration and differentiation. It is thought to have a role in controlling cell proliferation, but its precise function is not known. Here we present evidence that PC3, when overexpressed in vitro by retroviral-mediated gene transfer, acts by interfering with the normal pattern of cell division. Firstly, we report evidence that PC3 overexpression reduces the rate of cell proliferation in both NIH 3T3 cells and embryonic precursor cells from the rat cerebral cortex. Secondly, when studying the pattern of BrdU dilution in clones of cortical precursors, we observe that clones transduced with PC3 show an asymmetric pattern of BrdU dilution more frequently than clones transduced with a control vector. We discuss the hypothesis that the higher number of PC3 transduced clones showing an asymmetric pattern of BrdU dilution may be due to an increase in asymmetric cell divisions.
