Diesel Exhaust Particles Induce Impairment of Vascular and Cardiac Homeostasis in Mice: Ameliorative Effect of Emodin

Abstract

Background/aim: There is strong epidemiological and clinical evidence that components of the cardiovascular system are adversely affected by particulate air pollutants through the generation of inflammation and oxidative stress. Emodin (1,3,8-trihydroxy-6- methylanthraquinone), which is commonly found in the roots of rhubarb plant, has strong antioxidant and anti-inflammatory effects. However, its possible protective effect on the cardiovascular effect of particulate air pollutants has never been reported before.

Methods: We tested, in Tuck-Ordinary mice, the possible ameliorative effect of emodin on the acute (24h) cardiovascular effects of diesel exhaust particles (DEP, 1 mg/kg) or saline (control). Emodin (4 mg/kg) was administered intraperitoneally 1h before and 7h after pulmonary exposure to DEP. Twenty four h following DEP exposure, several cardiovascular endpoints were assessed.

Results: Emodin significantly prevented the increase of leukocyte (n=8, P<0.001) and erythrocyte (n=8, P<0.01) numbers caused by DEP. Likewise, emodin abrogated DEP-induced increase of heart tissue levels of interleukin 1β (n=8, P<0.01) and tumour necrosis factor α (n=8, P<0.05), and significantly mitigated the change of the activities of antioxidant enzymes superoxide dismutase (n=8, P<0.001) and glutathione reductase (n=8, P<0.05). Emodin abolished the in vivo prothrombotic effect of DEP in pial arterioles (n=6, P<0.01) and venules (n=6, P<0.001). Similarly, emodin prevented platelet aggregation in vitro in whole blood (n=4-5, P<0.01), and the shortening of activated partial thromboplastin time (n=4, P<0.001) and prothrombin time (n=4, P<0.01) caused by DEP.

Conclusion: We conclude that emodin treatment has consistently protected against DEP-induced impairment of vascular and cardiac homeostasis in mice. Our study provides experimental evidence that the use of functional food such as emodin, pending further studies, can be considered a useful agent and may have the potential to protect or mitigate the cardiovascular detrimental effects observed in people living in cities with high concentrations of particulate air pollution.