ABSTRACT
<p><b>OBJECTIVE</b>To analyze the changes in endogenous small molecule metabolites after benzo[a]pyrene (B[a]P) exposure in rat cerebral cortex and explore the mechanism of B[a]P neurotoxicity.</p><p><b>METHODS</b>Five-day-old SD rats were subjected to gavage administration of 2 mg/kg B[a]P for 7 consecutive weeks. After the exposure, the rats were assessed for spatial learning ability using Morris water maze test, ultrastructural changes of the cortical neurons under electron microscope, and metabolite profiles of the cortex using GC/MS. The differential metabolites between the exposed and control rats were identified with partial least squares discriminant analysis (PLS-DA) and the metabolic pathways related with the differential metabolites were analyzed using Cytoscape software.</p><p><b>RESULTS</b>Compared with the control group, the rats exposed to B[a]P showed significantly increased escape latency (P<0.05) and decreased time spent in the target area (P<0.05). The exposed rats exhibited widened synaptic cleft, thickened endplate membrane and swollen cytoplasm compared with the control rats. Eighteen differential metabolites (VIP>1, P<0.05) in the cortex were identified between the two groups, and 9 pathways associated with B[a]P neurotoxicity were identified involving amino acid metabolism, tricarboxylic acid cycle and Vitamin B3 (niacin and nicotinamide) metabolism.</p><p><b>CONCLUSION</b>B[a]P can cause disturbance in normal metabolisms and its neurotoxicity is possibly related with disorders in amino acid metabolism, tricarboxylic acid cycle and vitamin metabolism.</p>
ABSTRACT
<p><b>OBJECTIVE</b>To observe the effect of chronic arsenic exposure on cerebral cortex and serum metabolics of mice and explore the mechanism of arsenic neurotoxicity.</p><p><b>METHODS</b>Twelve 3-week-old male C57BL/6J mice were randomly assigned into exposure group and control group and exposed to sodium arsenite (50 mg/L) via drinking water and deionized water for 12 weeks, respectively. After the exposure, arsenic level in the cerebrum was determined by hydride generation-atomic fluorescence spectrometry. The metabolites in the cerebral cortex and serum were determined using gas chromatography-mass spectrometry (GC/MS) analysis. Principal component analysis (PCA) was used to analyze the difference of the metabolites between the exposure and the control groups. Online tools for analyzing metabolic pathways were used to identify the related metabolites pathways.</p><p><b>RESULTS</b>Arsenic content in the brain of exposure group was significantly higher than that in the control group (P<0.05). The mice exposed to arsenic had a higher level of citric acid, phenylalanine, tyrosine, histidine and lysine in the cerebral cortex (P<0.05). Serum levels of serine, glycine, proline, aspartate and glutamate were significantly higher while α-ketoglutaric acid level was significantly lower in the exposure group than in the control group (P<0.05). PCA analysis showed a significant difference in cerebral cortex and serum metabolites between the two groups.</p><p><b>CONCLUSION</b>Chronic arsenic exposure may affect the function of the central nervous system by interfering with amino acid metabolism and tricarboxylic acid cycle, which may be one of the mechanisms of arsenic neurotoxicity.</p>