Heavy metal pollution is one of the most serious environmental problems in China and a large number of people are threatened by heavy metal pollution. Extensive damage to human organs, such as liver, kidney, digestion system, and nervous system can be caused by uptake of excess heavy metals. Heavy metals in the environment can originate from both natural and anthropogenic sources. Although contamination of heavy metals has been known to be a severe environmental problem for decades, it is still getting worse in recent years and there are few feasible approaches to resolve this problem. Due to their high toxicity, prevalent existence and persistence in the environment, lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr) and arsenic (As) are commonly considered as the priority heavy metals which should be concerned and their emission should be controlled in China. This paper reviewed the pollution of heavy metals in China, focusing on the following four aspects: current status of heavy metal pollution in China, sources of heavy metals in China, toxicity and potential risk, and possible reduction strategies.
The impact of silver nanoparticles (AgNPs) on the central nervous system is a topic with mounting interest and concern and the facts remain elusive. In the current study, the neurotoxicity of commercial AgNPs to rat cerebellum granule cells (CGCs) and the corresponding molecular mechanism are closely investigated. It is demonstrated that AgNPs induce significant cellular toxicity to CGCs in a dose-dependent manner without damaging the cell membrane. Flow cytometry analysis with the Annexin V/propidium iodide (PI) staining indicates that the apoptotic proportion of CGCs upon treatment with AgNPs is greatly increased compared to the negative control. Moreover, the activity of caspase-3 is largely elevated in AgNP-treated cells compared to the negative control. AgNPs are demonstrated to induce oxidative stress, reflected by the massive generation of reactive oxygen species (ROS), the depletion of antioxidant glutathione (GSH), and the increase of intracellular calcium. Histological examination suggests that AgNPs provoke destruction of the cerebellum granular layer in rats with concomitant activation of caspase-3, in parallel to the neurotoxicity of AgNPs observed in vitro. Taken together, it is demonstrated for the first time that AgNPs substantially impair the survival of primary neuronal cells through apoptosis coupled to oxidative stress, depending on the caspase activation-mediated signaling.
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