Biochemical and Biophysical Research Communications
Titanium dioxide nanoparticles induce apoptosis through the JNK/p38-caspase-8-Bid pathway in phytohemagglutinin-stimulated human lymphocytes
Section snippets
Materials and methods
Isolation, culturing, and stimulation of peripheral blood lymphocytes. Heparinized (50 U/mol sodium heparin) whole blood was obtained, with consent, from young, healthy, non-smoking adult donors. Peripheral blood lymphocytes were isolated by buoyancy density centrifugation at 400g using Ficoll-Hypaque™ (Amersham Biosciences, Uppsala, Sweden). The isolated lymphocytes were cultured in RPMI 1640 medium (Gibco, Invitrogen, Carlsbad, CA) that contained 10% fetal bovine serum (FBS) and 100 U/ml each
Nano-TiO2-induced apoptosis of PHA-activated lymphocytes
Recently, we demonstrated that nano-TiO2 causes lymphocyte death [4]. To determine whether nano-TiO2-induced cell death involves apoptosis, the sub-G1 cell fractions were analyzed by staining the cellular DNA with propidium iodide. The proportion of sub-G1 cells was significantly higher in the cell population that was exposed to nano-TiO2 for 30 h than in the untreated cell population (Fig. 1A).
Cleavage of poly(ADP-ribose) polymerase by caspase cascade activation after nano-TiO2 treatment
We evaluated the apoptosis-inducing effect of nano-TiO2 by examining the changes in the levels of
Discussion
Recently, we reported that nano-TiO2 activates the p53-mediated DNA damage checkpoints in human lymphocytes [4]. We observed that the transcription factor p63, which is structurally similar to p53 and the expression of which is implicated in apoptosis, was also up-regulated by nano-TiO2[4]. Given that a link between DNA damage and apoptosis is supported by a large body of evidence, it seemed reasonable to assume that nano-TiO2 causes the apoptosis of human lymphocytes. Although a recent study
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These authors contributed equally to this work.