@article {70, title = {Mercury-induced hepatotoxicity in zebrafish: in vivo mechanistic insights from transcriptome analysis, phenotype anchoring and targeted gene expression validation.}, journal = {BMC Genomics}, volume = {11}, year = {2010}, month = {2010}, pages = {212}, abstract = {

BACKGROUND: Mercury is a prominent environmental contaminant that causes detrimental effects to human health. Although the liver has been known to be a main target organ, there is limited information on in vivo molecular mechanism of mercury-induced toxicity in the liver. By using transcriptome analysis, phenotypic anchoring and validation of targeted gene expression in zebrafish, mercury-induced hepatotoxicity was investigated and a number of perturbed cellular processes were identified and compared with those captured in the in vitro human cell line studies.

RESULTS: Hepato-transcriptome analysis of mercury-exposed zebrafish revealed that the earliest deregulated genes were associated with electron transport chain, mitochondrial fatty acid beta-oxidation, nuclear receptor signaling and apoptotic pathway, followed by complement system and proteasome pathway, and thereafter DNA damage, hypoxia, Wnt signaling, fatty acid synthesis, gluconeogenesis, cell cycle and motility. Comparative meta-analysis of microarray data between zebrafish liver and human HepG2 cells exposed to mercury identified some common toxicological effects of mercury-induced hepatotoxicity in both models. Histological analyses of liver from mercury-exposed fish revealed morphological changes of liver parenchyma, decreased nucleated cell count, increased lipid vesicles, glycogen and apoptotic bodies, thus providing phenotypic evidence for anchoring of the transcriptome analysis. Validation of targeted gene expression confirmed deregulated gene-pathways from enrichment analysis. Some of these genes responding to low concentrations of mercury may serve as toxicogenomic-based markers for detection and health risk assessment of environmental mercury contaminations.

CONCLUSION: Mercury-induced hepatotoxicity was triggered by oxidative stresses, intrinsic apoptotic pathway, deregulation of nuclear receptor and kinase activities including Gsk3 that deregulates Wnt signaling pathway, gluconeogenesis, and adipogenesis, leading to mitochondrial dysfunction, endocrine disruption and metabolic disorders. This study provides important mechanistic insights into mercury-induced liver toxicity in a whole-animal physiology context, which will help in understanding the syndromes caused by mercury poisoning. The molecular conservation of mercury-induced hepatotoxicity between zebrafish and human cell line reveals the feasibility of using zebrafish to model molecular toxicity in human for toxicant risk assessments.

}, keywords = {Animals, Apoptosis, Arsenic, Cell Adhesion, Cell Line, Gene Expression Profiling, Hepatocytes, Humans, Liver, Mercury, Oligonucleotide Array Sequence Analysis, Zebrafish}, issn = {1471-2164}, doi = {10.1186/1471-2164-11-212}, author = {Ung, Choong Yong and Lam, Siew Hong and Hlaing, Mya Myintzu and Winata, Cecilia L and Korzh, Svetlana and Mathavan, Sinnakaruppan and Gong, Zhiyuan} } @article {65, title = {Transcriptome kinetics of arsenic-induced adaptive response in zebrafish liver.}, journal = {Physiol Genomics}, volume = {27}, year = {2006}, month = {2006 Nov 27}, pages = {351-61}, abstract = {

Arsenic is a prominent environmental toxicant and carcinogen; however, its molecular mechanism of toxicity and carcinogenicity remains poorly understood. In this study, we performed microarray-based expression profiling on liver of zebrafish exposed to 15 parts/million (ppm) arsenic [As(V)] for 8-96 h to identify global transcriptional changes and biological networks involved in arsenic-induced adaptive responses in vivo. We found that there was an increase of transcriptional activity associated with metabolism, especially for biosyntheses, membrane transporter activities, cytoplasm, and endoplasmic reticulum in the 96 h of arsenic treatment, while transcriptional programs for proteins in catabolism, energy derivation, and stress response remained active throughout the arsenic treatment. Many differentially expressed genes encoding proteins involved in heat shock proteins, DNA damage/repair, antioxidant activity, hypoxia induction, iron homeostasis, arsenic metabolism, and ubiquitin-dependent protein degradation were identified, suggesting strongly that DNA and protein damage as a result of arsenic metabolism and oxidative stress caused major cellular injury. These findings were comparable with those reported in mammalian systems, suggesting that the zebrafish liver coupled with the available microarray technology present an excellent in vivo toxicogenomic model for investigating arsenic toxicity. We proposed an in vivo, acute arsenic-induced adaptive response model of the zebrafish liver illustrating the relevance of many transcriptional activities that provide both global and specific information of a coordinated adaptive response to arsenic in the liver.

}, keywords = {Adaptation, Physiological, Animals, Arsenic, Down-Regulation, Gene Expression Profiling, Gene Expression Regulation, Genomics, Liver, Male, Metabolic Networks and Pathways, Oligonucleotide Array Sequence Analysis, Transcription, Genetic, Up-Regulation, Zebrafish}, issn = {1531-2267}, doi = {10.1152/physiolgenomics.00201.2005}, author = {Lam, Siew Hong and Winata, Cecilia L and Tong, Yan and Korzh, Svetlana and Lim, Wen San and Korzh, Vladimir and Spitsbergen, Jan and Mathavan, Sinnakarupan and Miller, Lance D and Liu, Edison T and Gong, Zhiyuan} }