The potential of metabolomic approaches for investigating mode(s) of action of xenobiotics: Case study with carbon tetrachloride
Both experimental animals and humans exhibit complex cellular responses upon exposure to xenobiotics and may undergo similar types of metabolic changes leading to adverse outcomes. Exposure to xenobiotics results in perturbation of many cellular events (e.g. oxidative stress, lipid peroxidation, inflammation, genotoxicity, cytotoxicity, etc.), and during this process biochemicals (endogenous metabolites) of a given metabolic pathway are increased, decreased or unaffected. Metabolomics is an emerging medium to high-throughput technology that can automatically identify, quantify and characterize hundreds to thousands of low molecular weight biochemicals simultaneously, using targeted or global analytical approaches, yielding a metabolic fingerprint and understanding of biochemical pathway perturbations. Herein, we illustrate how metabolomics can be utilized to explore the mechanisms of action of xenobiotics which affect different 'key events' contributing to different mode(s) of action. The extensively studied hepatotoxicant carbon tetrachloride (CCl(4)) is specifically described.
Available from: Thomas C Schmitt
- "Metabolite changes also indicated altered TCA cycle and nucleotide metabolism. Several biomarkers of CCl 4 -induced hepatotoxicity have been identified, which are related to specific modes of action (Vulimiri et al. 2011). Specifically, lipids, amino acids, and metabolites related to energy metabolism have been reported to be altered coincidently with liver injury after exposure to CCl 4 . "
[Show abstract] [Hide abstract]
ABSTRACT: Understanding mechanisms of liver injury can enable better preclinical testing and clinical management of patients. Carbon tetrachloride (CCl4), used extensively as a model hepatotoxicant, induces lipid perturbation and increases in plasma bile acids (BAs). An integrated transcriptomics and metabolomics approach was employed to investigate CCl4-induced alterations in lipid and BA metabolism. Sprague-Dawley rats were treated orally with corn oil, 50 (low dose, LD) or 2,000 mg CCl4/kg/d (high dose, HD). Animals were sacrificed at 6, 24 or 72 h. Terminal blood was collected for clinical chemistry and metabolomics analyses. Livers were harvested for histopathology, metabolomics and transcriptomics analyses. Both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the treated groups with the greatest increases observed in the HD group at 24 and 72 h. Blood cholesterol and triglycerides (TGs) were significantly decreased in the HD group at both 24 and 72 h, and hepatocyte vacuolization was observed at these timepoints. Consistent with the clinical chemistry and histopathological data, metabolomics results showed that levels of total fatty acids increased in the liver but decreased in the blood in the HD group at the 24 and 72 h timepoints. This suggested that lipids accumulate in the liver. Primary BAs increased in both liver and blood, while secondary and conjugated BAs decreased in the liver and increased in the blood, which indicated that the BA conjugation pathway and that BA uptake by the liver were inhibited by CCl4. Results from this study provide a better understanding of the mechanisms of CCl4-induced hepatotoxicity.
- "This method compares the concentrations of endogenous metabolites in a tissue or biofluid (identified and quantified by NMR) collected under varied environmental conditions (Viant, 2008). Interpretation of changes in the metabolic profile ('metabolome') can reveal information about the organism's response to contaminant exposure at the metabolic level (Hines et al., 2010; Viant, 2008; Vulimiri et al., 2011). To date, many metabolomic studies of earthworm responses to contaminated soil have used soil exposure periods comparable to or longer than the >50 day exposure required for the earthworm reproduction test (i.e., 21e110 days in Bundy et al., 2004, 2008; Gibb et al., 1997; Guo et al., 2009; Jones et al., 2008). "
[Show abstract] [Hide abstract]
ABSTRACT: (1)H NMR metabolomics and conventional ecotoxicity endpoints were used to examine the response of earthworms exposed to petroleum hydrocarbons (PHCs) in soil samples collected from a site that was contaminated with crude oil from a pipeline failure in the mid-1990s. The conventional ecotoxicity tests showed that the soils were not acutely toxic to earthworms (average survival ≥90%), but some soil samples impaired reproduction endpoints by >50% compared to the field control soil. Additionally, metabolomics revealed significant relationships between earthworm metabolic profiles (collected after 2 or 14 days of exposure) and soil properties including soil PHC concentration. Further comparisons by partial least squares regression revealed a significant relationship between the earthworm metabolomic data (collected after only 2 or 14 days) and the reproduction endpoints (measured after 63 days). Therefore, metabolomic responses measured after short exposure periods may be predictive of chronic, ecologically relevant toxicity endpoints for earthworms exposed to soil contaminants.
Available from: Sarantos Kostidis
- "Animal models of acute and chronic liver injury induced by different toxicants have been studied by NMR-based metabonomics like hydrazine, acetaminophen, thioacetamide, etc. (Bollard et al., 2005a; Coen et al., 2003; Constantinou et al., 2007a; Dyrby et al., 2005; Waters et al., 2005). In this aspect CCl 4 induced acute liver injury has been recently approached by different -omics methods (Vulimiri et al., 2011) such as genomics (Chung et al., 2005), proteomics (Wong et al., 2010). The metabonomic approach has employed both NMR (urine and serum Robertson, 2005; Kim et al., 2008; Sanins et al., 1990; Wu et al., 2005) and MS (urine, and plasma Huang et al., 2008; Lin et al., 2009), in order to better delineate the metabolic changes of the CCl 4 -induced injury. "
[Show abstract] [Hide abstract]
ABSTRACT: The administration of carbon tetrachloride (CCl(4)) has been established as a model of toxin-induced acute and chronic liver injury. In the present study, we investigate the progression of the biochemical response to acute CCl(4)-induced liver injury, capturing metabolic variations during both toxic insult and regeneration using NMR-based metabonomic analysis of liver tissue and plasma. A single dose of CCl(4) (1mL/kg BW) was intraperitoneally administered to male Wister rats sacrificed every 12hours up to 72h post treatment, while healthy animals served as controls. Acquired (1)H NMR spectra of liver tissue extracts and plasma samples were explored with multivariate analysis and the resulted models were correlated with conventional biochemical and histopathological indices of toxicity for monitoring the progression of experimental injury. The metabonomic analysis resulted in discrimination between the subjects under toxic insult (up to 36h) and those at the regenerative phase (peaked at 48h). At 72h normalization of liver's pathology similar to the controls group was apparent. Principal Component Analysis (PCA) trajectories highlighted the time points of the greater degree of toxic insult and the regenerative state. A number of metabolites such as glucose, lactate, choline, formate exhibited variations suggesting CCl(4) induced impairment in essential biochemical pathways as energy metabolism, lipid biosynthesis and transmethylation reactions. The latter provides new evidence of B12 and folate pathways deficiency, indicative of new mechanistic implications possibly by direct inhibition of B12 dependent enzymes by the chlorinated radicals of CCl(4) metabolism.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.