Age-related differences in pulmonary and cardiovascular responses to SiO2 nanoparticle inhalation: nanotoxicity has susceptible population.

Epidemiologic studies have revealed that pollution by ambient particulates is associated with respiratory and cardiovascular diseases, particularly in older people. Toxicologic sensitivity of nanoparticles in different ages was investigated for the first time to demonstrate and explain an age-related difference in response to manufactured nanoparticles. Young, adult, and old rats physiologically inhaled air containing aerosol of manufactured SiO2 nanoparticles (24.1 mg/m3; 40 min/day) for four weeks. Changes in serum biomarkers, hemorheologic, pulmonary inflammation, heart injury, and pathology in rats of different ages and their corresponding controls were compared. Inhalation of SiO2 nanoparticles under identical conditions caused pulmonary and cardiovascular alterations in old rats, yet less change in young and adult rats, including pulmonary inflammation, myocardial ischemic damage, atrio-ventricular blockage, and increase in fibrinogen concentration and blood viscosity. Old individuals were more sensitive to nanoparticle exposure than the young and adult rats. The risk of causing pulmonary damages was: old > young > adult The risk of cardiovascular disorder was observed only in old age. Our results suggest that different ages may require different biomarkers for identifying pulmonary toxicity during inhalation of nanoparticles.