Gas chromatography-mass spectrometry based metabolomics profile of hippocampus and cerebellum in mice after chronic arsenic exposure.

Intake of arsenic (As) via drinking water has been a serious threat to global public health. Though there are numerous reports of As neurotoxicity, its pathogenesis mechanisms remain vague especially its chronic effects on metabolic network. Hippocampus is a renowned area in relation to learning and memory, whilst recently, cerebellum is argued to be involved with process of cognition. Therefore, the study aimed to explore metabolomics alternations in these two areas after chronic As exposure, with the purpose of further illustrating details of As neurotoxicity. Twelve 3-week-old male C57BL/6J mice were divided into two groups, receiving deionized drinking water (control group) or 50 mg/L of sodium arsenite (via drinking water) for 24 weeks. Learning and memory abilities were tested by Morris water maze (MWM) test. Pathological and morphological changes of hippocampus and cerebellum were captured via transmission electron microscopy (TEM). Metabolic alterations were analyzed by gas chromatography-mass spectrometry (GC-MS). MWM test confirmed impairments of learning and memory abilities of mice after chronic As exposure. Metabolomics identifications indicated that tyrosine increased and aspartic acid (Asp) decreased simultaneously in both hippocampus and cerebellum. Intermediates (succinic acid) and indirect involved components of tricarboxylic acid cycle (proline, cysteine, and alanine) were found declined in cerebellum, indicating disordered energy metabolism. Our findings suggest that these metabolite alterations are related to As-induced disorders of amino acids and energy metabolism, which might therefore, play an important part in mechanisms of As neurotoxicity.

Integrated Epigenetics, Transcriptomics, and Metabolomics to Analyze the Mechanisms of Benzo[a]pyrene Neurotoxicity in the Hippocampus.

Benzo[a]pyrene (B[a]P) is a common environmental pollutant that is neurotoxic to mammals, which can cause changes to hippocampal function and result in cognitive disorders. The mechanisms of B[a]P-induced impairments are complex .To date there have been no studies on the association of epigenetic, transcriptomic, and metabolomic changes with neurotoxicity after B[a]P exposure. In the present study, we investigated the global effect of B[a]P on DNA methylation patterns, noncoding RNAs (ncRNAs) expression, coding RNAs expression, and metabolites in the rat hippocampus. Male Sprague Dawley rats (SD rats) received daily gavage of B[a]P (2.0 mg/kg body weight [BW]) or corn oil for 7 weeks. Learning and memory ability was analyzed using the Morris water maze (MWM) test and change to cellular ultrastructure in the hippocampus was analyzed using electron microscope observation. Integrated analysis of epigenetics, transcriptomics, and metabolomics was conducted to investigate the effect of B[a]P exposure on the signaling and metabolic pathways. Our results suggest that B[a]P could lead to learning and memory deficits, likely as a result of epigenetic and transcriptomic changes that further affected the expression of CACNA1C, Tpo, etc. The changes in expression ultimately affecting LTP, tyrosine metabolism, and other important metabolic pathways.

[Changes of cerebral cortical metabolomics in rats following benzo[a]pyrene exposure].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

[Effect of Benzo [α]pryene and Butylated Hydroxylanisole on Learning and Memory in Rats].

OBJECTIVE: To investigate the neurotoxic effect of benzo[α]pryene (B[α]P) and protective effect of butylated hydroxyl anisole (BHA) on learning and memory in hippocampus of rats. METHODS: Ninety male, SD rats were randomly divided into blank control group, solvent control group, B[α]P exposed group [(2 mg/(kg x d)], BRA group [50 mg/(kg x d)] and B[α]P + BHA combined group. Rats were given the appropriate dose oral treatment according to body mass and group (the same volume of saline and peanut oil were given to blank and solvent control group, respectively) for 90 d. After 90 d exposer, Morris water maze (MWM) was conducted to estimate rats' learning and memory ability. The level of malonaldehyde (MDA), superoxide dismutase (SOD) activity, Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activity and Ca2+ concentration were measured after rats were sacrificed and brain tissue were removed. RESULTS: Behavioral test results showed that the escape latency of B[α]P exposed group were significantly increased than other groups (P < 0.05); however, the number of crossing platform (4.13 ± 0.78) were decreased significant. The level of MDA [( 2.46 ± 0.39) nmol/mg prot.] and Ca2+ concentration [(146.3 ± 16.68) nmol/L] in the B[α]P exposed group increased significant, while the activity of Na(+)-K(+)-ATPase and SOD [(76.1 ± 11.42) nmol/mg prot.] were significantly decreased. Compared with B[α]P group, each index in B[α]P+ BHA combined group improved significantly (P < 0.05), besides, there were no statistically difference when compared with solvent control group. CONCLUSION: The neurotoxic effect of B[α]P may be related to the decrease of ATPase activity and the increase of Ca2+ concentration in hippocampus, while BHA can prevent these damages.

[Effects of benzo(a)pyrene exposure on oxidative stress and ATPase in the hippocampus of rats].

OBJECTIVE: To investigate the effects of benzo[a]pyrene (B[a]P) exposure on the behaviors and hippocampal oxidative stress and ATPase in rats and the molecular mechanism of neurobehavioral toxicity of B[a]P. METHODS: A total of 120 male SD rats (21 days old) were randomly and equally assigned to five groups: blank control group, vegetable oil (solvent control) group, and 2.5, 5, and 10 mg/kg B[a]P exposure groups. The rats in B[a]P exposure groups were injected intraperitoneally with B[a]P once a day for 4 consecutive weeks. Then, Morris water maze and shuttle box were used to evaluate the learning and memory abilities of rats; colorimetric assay was used to measure the activities of superoxide dismutase (SOD), Na(+)/K(+)-ATPase, and Ca(2+)/Mg(2+)-ATPase and the content of malonaldehyde (MDA) in the hippocampus; the concentration of Ca(2+) in the hippocampus was measured by fluorescent labeling. RESULTS: Compared with the blank control group and solvent control group, the B[a]P exposure groups exhibited significant increases in escape latency, active avoidance response latency, and passive avoidance response latency and significant decreases in number of platform crossings and active avoidance response frequency in the last test (P < 0.05 for all comparisons), with a dose-effect relationship. In addition, the B[a]P exposure groups had significantly lower activities of SOD, Na(+)/K(+)-AT-Pase, and Ca(2+)/Mg(2+)-ATPase and significantly higher MDA level and Ca(2+) concentration than the blank control group and solvent control group (P < 0.05 for all comparisons), with a dose-effect relationship. CONCLUSION: The neurobehavioral toxicity of B[a]P may be related to increased oxidative stress and decreased activities of Na(+)/K(+)-ATPase and Ca(2+)/Mg(2+)-ATPase in the hippocampus of rats.

Neurotoxic effect of subacute benzo(a)pyrene exposure on gene and protein expression in Sprague-Dawley rats.

Benzo(a)pyrene (B[a]P) is an environmental carcinogen that induces tumors in many animal species, but the neurotoxic effects of B[a]P have not been well studied. In the present study, we investigated the effects of subacute exposure to B[a]P in Sprague-Dawley (SD) rats. Male rats received daily injections of either B[a]P (0, 1, 2.5, or 6.25mg/kg, i.p.) or vehicle for 45 days. Exposure to B[a]P affected the behavior of rats in the Morris water maze test. Gene microarray and real-time PCR analyses revealed that exposure to B[a]P affected signal transduction in the rat hippocampus. Protein microarray analysis revealed that altered protein expression played a role in cell death in the functional annotation cluster analysis. Finally, major vault protein was found to display low cDNA and protein expression levels. The present study explored some of the possible mechanisms underlying B[a]P neurotoxicity and provided evidence that B[a]P plays a neurotoxic role in rats.