p53 reaction to apoptosis induced by hydroxyapatite nanoparticles in rat macrophages

The effects and mechanism of hydroxyapatite (HAP) nanoparticles (NPs) on the induction of cytotoxicity and apoptosis in rat macrophages was evaluated by testing the antiproliferative effect of HAP NPs with agar overlay and direct contact methods. The apoptotic phenotype of the macrophages was observed by transmission electron microscopy (TEM), and the variation of transcription and expression of a cell apoptosis related gene (p53) was determined by semiquantitative RT-PCR and western blotting. The results showed that a dose-dependent proliferative inhibition of macrophages was induced by HAP NPs (30-80 nm) at concentrations between 20 and 200 microg/mL. The characteristic morphological changes of apoptosis were observed in macrophages after treatment with HAP NPs for 24 h. Furthermore, p53 mRNA levels significantly increased when macrophages were incubated with 200 microg/mL HAP NPs (p < 0.01). Western blot analysis showed that 100 microg/mL HAP NPs upregulated p53. The conclusion is that HAP NPs can induce p53 expression through phosphorylation, which promotes downstream genes and finally results in cell apoptosis. Moreover, p53 may be one of the ideal indictors to evaluate the biological safety of ceramic nanoparticles.