Differences in DNA damage pathways induced by two ceramic nanoparticles.

Area of Science:

• Biomaterials Science
• Toxicology
• Molecular Biology

Background:

• Hydroxyapatite (HAP) and tricalcium phosphate (TCP) nanoparticles exhibit cytotoxicity in rat macrophages.
• Understanding the molecular mechanisms of DNA damage induced by these nanoparticles is crucial.

Purpose of the Study:

• To investigate the DNA damage mechanisms induced by HAP and TCP nanoparticles in rat macrophages.
• To analyze the differential responses of gene expression related to DNA damage and cell cycle arrest.

Main Methods:

• Primary rat peritoneal macrophages were cultured and exposed to HAP and TCP nanoparticles in vitro.
• Gene expression analysis of P53, P21, growth arrest and DNA damage 45 (Gadd45), and heat shock protein 70 (HSP70) was performed using reverse transcription polymerase chain reaction.

Main Results:

• HAP nanoparticles increased P53, P21, and HSP70 expression in a dose-dependent manner, with significant effects at 100 microg/mL, but P21 decreased at 200 microg/mL. Gadd45 expression remained unaffected.
• TCP nanoparticles at 20 microg/mL markedly induced the expression of all four genes, though expression decreased with higher concentrations.
• DNA damage was irreversible at nanoparticle concentrations exceeding 200 microg/mL.

Conclusions:

• TCP nanoparticles at 20 microg/mL induced DNA damage, whereas HAP nanoparticles at 100 microg/mL induced cell cycle arrest for DNA repair.
• HAP and TCP nanoparticles trigger distinct DNA damage responses at the molecular level.
• The concentration of nanoparticles significantly influences the reversibility and outcome of DNA damage.