Effects of Fine Particulate Matter (PM2.5) on Systemic Oxidative Stress and Cardiac Function in ApoE-/- Mice

Aim: In this study, we aimed to explore the toxic mechanisms of cardiovascular injuries induced by ambient fine particulate matter (PM2.5) in atherosclerotic-susceptible ApoE(-/-) mice. An acute toxicological animal experiment was designed with PM2.5 exposure once a day, every other day, for three days. Methods: ApoE(-/-) and C57BL/6 mice were randomly categorized into four groups, respectively (n = 6): one control group, three groups exposed to PM2.5 alone at low-, mid-, and high-dose (3, 10, or 30 mg/kg b.w.). Heart rate (HR) and electrocardiogram (ECG) were monitored before instillation of PM2.5 and 24 h after the last instillation, respectively. Cardiac function was monitored by echocardiography (Echo) after the last instillation. Biomarkers of systemic oxidative injuries (MDA, SOD), heart oxidative stress (MDA, SOD), and NAD(P)H oxidase subunits (p22phox, p47phox) mRNA and protein expression were analyzed in mice. The results showed that PM2.5 exposure could trigger the significant increase of MDA, and induce the decrease of heart rate variability (HRV), a marker of cardiac autonomic nervous system (ANS) function with a dose-response manner. Meanwhile, abnormal ECG types were monitored in mice after exposure to PM2.5. The expression of cytokines related with oxidative injuries, and mRNA and protein expression of NADPH, increased significantly in ApoE(-/-) mice in the high-dose group when compared with the dose-matched C57BL6 mice, but no significant difference was observed at Echo. In conclusion, PM2.5 exposure could cause oxidative and ANS injuries, and ApoE(-/-) mice displayed more severe oxidative effects induced by PM2.5.