Evaluation of the ToxRTool's ability to rate the reliability of toxicological data for human health hazard assessments.

Regulatory agencies often utilize results from peer reviewed publications for hazard assessments. A problem in doing so is the lack of well-accepted tools to objectively, efficiently and systematically assess the quality of published toxicological studies. Herein, we evaluated the publicly available software-based ToxRTool (Toxicological data Reliability assessment Tool) for use in human health hazard assessments. The ToxRTool was developed by the European Commission's Joint Research Center in 2009. It builds on Klimisch categories, a rating system established in 1997, by providing additional criteria and guidance for assessing the reliability of toxicological studies. It also transparently documents the study-selection process. Eight scientists used the ToxRTool to rate the same 20 journal articles on thyroid toxicants. Results were then compared using the Finn coefficient and "AC1" to determine inter-rater consistency. Ratings were most consistent for high-quality journal articles, but less consistent as study quality decreased. Primary reasons for inconsistencies were that some criteria were subjective and some were not clearly described. It was concluded, however, that the ToxRTool has potential and, with refinement, could provide a more objective approach for screening published toxicology studies for use in health risk evaluations, although the ToxRTool ratings are primarily based on study reporting quality.

Alterations in glutamatergic and gabaergic ion channel activity in hippocampal neurons following exposure to the abused inhalant toluene.

Toluene, a representative member of the large class of abused inhalants, decreases neuronal activity and depresses behavior in both animals and humans. The sites of action of toluene are not completely known but recent studies suggest that ion channels that regulate neuronal excitability may be particularly sensitive. Previous studies with recombinant receptors showed that toluene decreases currents carried by N-methyl-D-aspartate (NMDA)-glutamate receptors without affecting those gated by non-NMDA receptors. In addition, toluene increases currents generated by GABA and glycine receptors. In the present study, primary cultures of rat hippocampal neurons were used to investigate the effects of acute and chronic toluene exposure on native excitatory and inhibitory ligand-gated ion channels. Toluene dose-dependently inhibited NMDA-mediated currents (IC50 1.5 mM) but had no effect on responses evoked by the non-NMDA agonist kainic acid. Prolonged treatment of neurons with toluene (1 mM; 4 days) increased whole-cell responses to exogenously applied NMDA, reduced those evoked by GABA but did not alter responses generated by kainic acid. Immunoblot analysis revealed that prolonged toluene exposure increased levels of NR2A and NR2B NMDA receptor subunits with no change in NR1. Immunohistochemical analysis with confocal imaging showed that toluene-treated neurons had significant increases in the density of NR1 subunits as compared with control neurons. Toluene exposure increased the amplitude of synaptic NMDA currents and decreased those activated by GABA. The results from this study suggest that toluene induces compensatory responses in the functional expression of ion channels that regulate neuronal excitability.