ToxSci Advance Access originally published online on January 6, 2007
Toxicological Sciences 2007 96(2):268-278; doi:10.1093/toxsci/kfl198
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In Vitro Toxicity of Tetrabromobisphenol-A on Cerebellar Granule Cells: Cell Death, Free Radical Formation, Calcium Influx and Extracellular Glutamate
* Norwegian Defence Research Establishment, Division for Protection, PO Box 25, N-2027 Kjeller, Norway
Norwegian Institute for Air Research, PO Box 100, N-2027 Kjeller, Norway
Department of Biochemistry, Institute of Basic Medical Science, University of Oslo, PO Box 1112, Blindern, N-0317 Oslo, Norway
1 To whom correspondence should be addressed. Fax: + 47 63807509. E-mail: trine.reistad{at}ffi.no.
Received November 7, 2006; accepted December 20, 2006
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Abstract |
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Tetrabromobisphenol-A (TBBPA) is one of the worlds most widely used brominated flame retardant. The present study reports effects of TBBPA on primary cultures of cerebellar granule cells (CGC). Using the trypan blue exclusion assay, we show that TBBPA induces death of CGC at low micro molar concentrations. Cell death was reduced by the NMDA receptor antagonist MK-801 (3µM), the antioxidant vitamin E (50µM), and in calcium-free buffer. We further demonstrate that TBBPA's toxicity was accompanied by apoptosis-like nuclear shrinkage, chromatin condensation, and DNA fragmentation. Other hallmarks of apoptosis such as caspase activity were, however, absent, indicating an atypical form of apoptosis. TBBPA increased intracellular free calcium in a concentration-dependent manner. TBBPA also induced an increase in extracellular glutamate in a time-dependent manner. TBBPA gave a concentration-dependent increase information reactive oxygen species (ROS) of measured with 2,7-dichlorofluorescein diacetate. The ROS formation was inhibited by the extracellular signal-regulated protein kinase (ERK) inhibitor U0126 (10µM), the tyrosine kinase inhibitor erbstatin-A (25µM), eliminating calcium from the buffer and by the superoxide dismutase inhibitor diethyldithio-carbamic acid (DDC, 100µM). Further analysis with Western blot confirmed phosphorylation of ERK1/2 after exposure to TBBPA. We found that TBBPA induces ROS formation, increases intracellular calcium, extracellular glutamate, and death of CGC in vitro at concentrations comparable to those of polychlorinated biphenyl. These findings implicate TBBPA as a predicted environmental toxin and bring out the importance of awareness of its hazardous effects.
Key Words: tetrabromobisphenol-A (TBBPA); cerebellar granule cells (CGC); reactive oxygen species (ROS); cell death; glutamate; calcium.
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