Methyl tertiary-butyl ether inhibits THP-1 macrophage cholesterol efflux in vitro and accelerates atherosclerosis in ApoE-deficient mice in vivo

The biosafety of methyl tertiary-butyl ether(MTBE),mainly used as a gasoline additive,has long been a contentious topic.In addition to its routine toxicities,MTBE has been demonstrated to disrupt glucose and lipid metabolism and contribute to the development of type2 diabetes as well as obesity.As one of the morbidities related to dyslipidemia,atherosclerosis is worthy of being investigated under MTBE exposure.Since foam cells derived from macrophages play pivotal roles during atherosclerosis development,we studied the effects of MTBE on macrophages in vitro and assessed the effect of MTBE on atherosclerosis plaque formation with the ApoE^(-/-)mouse model in uiuo for the first time.Our results demonstrated that exposure to MTBE at environmentally relevant concentrations decreased the expression of ABCA1 and ABCG1,which are responsible for macrophage cholesterol efflux,at both mRNA and protein levels in THP-1 macrophages.Consequently,treatment with MTBE inhibited the transport of cholesterol from macrophages to High-density lipoprotein.ApoE^(-/-)mice exposed to MTBE at environmentally relevant concentrations(100,1000μg/kg)displayed significant increases in lesion area in the aorta and aortic root compared to vehicletreated ones.Further analysis indicated that MTBE exposure enhanced the macrophagespecific marker Mac-2 contents within plaques in the aortic root,implying that MTBE could promote macrophage-derived foam cell formation and thus accelerate atherosclerosis plaque formation.We for the first time demonstrated the pro-atherogenic effect of MTBE via eliciting disruption of macrophage cholesterol efflux and accelerating foam cell formation and atherosclerosis plaque development.

Mass Transfer of MTBE in Groundwater During Air Sparging

A one-dimensional column is set up to study the mass transfer during air sparging process for methyl tertiary butyl ether（MTBE） removal in saturated soil and groundwater, with the condition of different airflow and soil penetrability. It is shown that the removal rate of MTBE can reach 80%, 90% and 95% when airflow is 0.05 m^3/h, 0. 085 m^3/h and 0. 10 m^3/h, respectively. Increasing airflow will help to increase the removal rate of dissolved MTBE, but eventually a threshold removal rate is reached, above which further increasing air injection rates does not increase the removal rate. Fine sand allows the injected air to travel in bubble form, while coarse sand and medium sand allow the injected air to travel in the form of discrete channels; the greater the soil grain size is, the more extensive the channel net work forms, which in turn leads to higher removal rate. A tailing effect of lingering residual contaminant concentrations occur within the fine sand. About 20% of MTBE cannot be removed.