In vitro studies of the inhibition of protein kinase C from rat brain by di-(2-ethylhexyl)phthalate

Di-(2-ethylhexyl)-phthalate affects lipid profiling in fetal rat brain upon maternal exposure

Lipids, especially essential fatty acids (EFAs), play critical roles in guiding proper fetal development. Exposure to xenobiotics that may alter the fetal supply of EFAs/lipids could potentially lead to fetotoxicity. In this study, we investigated the effects of the peroxisome proliferator chemical, di-(2-ethylhexyl)-phthalate (DEHP), on the lipid metabolomic profile of the rat fetal brain upon maternal exposure during gestation. Female Sprague-Dawley rats were orally gavaged with a control vehicle or DEHP (1,500 mg/kg) from gestational day (GD) 0 to GD 19 and fetal brain tissue was isolated at GD 20. The concentrations of 11 lipid classes [free fatty acid, free cholesterol (FC), cholesterol ester (CE), diacylglycerol (DAG), triacylglyceride, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine (PS), lysophosphatidylcholine (LYPC), cardiolipin, and sphingomyelin (SM)] were determined, as well as the differences in the composition of individual fatty acids. The total lipid concentration decreased with DEHP exposure, particularly for FC and SM, by 33 and 54%, respectively. The same trend was observed in the fatty acid compositions, particularly the unsaturated fatty acids, where a greater decrease was observed with longer fatty acid chain length. The compositions of docosahexaenoic acid decreased significantly in five lipid classes (P < 0.05), including CE (43%), DAG (60%), PS (33%), LYPC (35%), and SM (40%). In contrast, the most remarkable reduction of arachidonic acid presented in two lipid classes, CE and LYPC, with a decrease of up to 33%. These results suggest that in utero exposure to DEHP alters the lipid metabolome in the fetal brain, which may lead to aberrant neurodevelopment.

A plasticizer released from IV drip chambers elevates calcium levels in neurosecretory terminals

We report that intracellular calcium levels rise in mammalian neurosecretory terminals and in cultured pheochromocytoma cells during acute exposure to physiological medium incubated in IV drip chambers. The agent responsible for this effect is shown to be di(2-ethylhexyl)phthalate (DEHP). DEHP (800 nM) added to saline solution caused a rise in [Ca(2+)](i) similar to that elicited by the contaminant-containing solution. The extraction of this contaminant from the IV drip chamber, as measured by spectrophotometry, was time-dependent and was markedly accelerated by the presence of 50 mM ethanol in the solution. Larger [Ca(2+)](i) increases were observed in terminals exposed to solutions incubated in IV drip chambers for greater durations. The rise in calcium requires transmembrane calcium flux through membrane channels, as the response is blocked by either 100 microM cadmium or by lowering the extracellular free Ca(2+) concentration to 10 microM. Our results suggest that acute alterations in intracellular calcium should be considered in addition to long-term effects when determining the safety of phthalate-containing plastics and that laboratory researchers using plastic perfusion materials consider this potential source of artifactual results.

Plasticisers, another burden for asthmatics?

The widely used plasticiser di(2-ethylhexyl)phthalate (DEHP) has been reported to have some toxicological effects on pulmonary tissue. Inhalation of DEHP may cause pulmonary edema and bronchial asthma. Moreover intravenous injection of DEHP induces pulmonary inflammation and hemorrhage of the lungs. We now report that DEHP might cause bronchial hyperresponsiveness. The metabolite of DEHP mono(2-ethylhexyl)phthalate (MEHP) induces in vitro a dose-dependent increase in -log EC50 for methacholine dose response curves in rat tracheal tissue. Moreover MEHP induces a decrease in maximal effect of the methacholine dose response curve. We concluded that DEHP due to the formation of MEHP in vivo, may cause bronchial hyperresponsiveness.