Airborne particulate collected from central Taiwaninduces DNA strand breaks, Poly(ADP-ribose)polymerase-1 activation, and estrogen-disruptingactivity in human breast carcinoma cell lines

Abstract

The objectives of this investigation were to examine whether airborne particles induceDNA damaging and estrogen-disrupting effectsand to explore the relationships between them. In this study, airborne particulate was collected at an urban, a suburban, and a ruralsite in central Taiwan. The organic solvent extracts of airborne particulate were examined in human MCF-7 and T47D-KBluc breastcancer cells. We observed significant increases in reactive oxygen species (ROS) generation in MCF-7 cells after treatment with theparticulate extracts whereas aryl hydrocarbon receptor (AhR) antagonist blocked the particulate-induced ROS generation in cells.Further, induction of CYP1A1 protein expression was confirmed by immunoblots in cells treated with airborne particles, suggestingthe roles of AhR status in mediating the particulate-induced toxicity. In addition, we observed that at non-cytotoxic concentration(∼0.01m3 air equivalent), airborne particles induced decreases in intracellularNAD(P)H andNAD+ in MCF-7 cells. These decreaseswere completely blocked by three types of poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors. Moreover, we demonstrated increasesin the number of DNA strand breaks in MCF-7 cells exposed to airborne particles as measured by the single-cell gel electrophoresis(Comet) assay. Overall, this evidence confirms that airborne particles induce decreases in intracellular NAD(P)H and NAD+ throughPARP-1 activation mediated by formation of DNA strand breaks. Furthermore, we confirmed that with series dilution airborneparticles (∼10−7–10−2 m3 air equivalent) possess both estrogenic and anti-estrogenic activities as determined by the ERα-mediatedreporter gene assay in human T47D-KBluc breast cancer cells. In conclusions, we confirmed that the DNA-damaging activity andestrogenicity of airborne particles varied considerably with concentration (air equivalent). Our findings add further support to thetheme that ROS formation is a significant determinant factor in mediating the induction of oxidative DNA damage and repair inhuman breast cancer cells exposed to airborne particles and that oxidative stress and the subsequent induction of DNA damage may,in part, contribute to airborne particle-induced carcinogenesis