| Lead is the toxic heavy metal, which was widely found in our living environment, causing the damage to the body. The impact of lead mainly focused on the nervous system, but it also affects on other systems, such as the digestive system. Recent studies of our group found that high concentration of lead inhibits the expression of pancreatic exocrine gene ela2l, which may affect the digestive system of zebrafish.The nuclear factor-erythroid-2 (nfe2)-related factor (Nrf) can regulate genes involving in antioxidative stress response, anti-inflammatory response, detoxification of heavy metals, ect.. Six nrf genes (nfe2, nrf1a, nrf1b, nrf1a, nrf2b, and nrf3) were found in zebrafish by blasting in the GenBank and Ensembl. The phylogenetic analysis indicated that the vertebrate Nrf proteins were conserved during the evolution of species, in spite of the fact that the nrfl and nrf2 respectively have two duplicates, resulted from the whole-genome duplication in teleosts. The spatial-temporal expressions of six nrf genes in early development of zebrafish embryos were examined in this study by whole mount in situ hybridization. All the genes have expression signals from the one cell stage, and their expressions were ubiquitous in early stage of embryonic development. After 72 hpf, the expression of nrflb?nrf1a?nrf2b?nrf3 and nfe2 were tissue-specific in head, part of the trunk and gut, while slight expression of nrf2b was observed in the spinal cord. It is obvious that the expressional sites of six nrf gene were overlap, coinciding to their function superposition and replacement.It was found that the difference or contrary of expressional regulations of the paralogs of bach and nrf on pancreatic exocrine gene tryl in a dose-dependent manner via dual-luciferase system. Over expressions of bachla?bach2a?nrf1a?nrf2a?nrf2b and nfe2 up-regulated transcription of tryl, however, Bachlb?Bach2b?Nrf1b and Nrf3 down-regulated transcriptions of tryl. Strikingly, nrf1a and nrf1b were found to have the contrary role in regulating the expression of tryl, suggesting that the functions of Nrf1a and Nrflb were divergent. These studies provided foundational data to research functional superposition and complementarities among these six nrf and four bach paralogs. The five combinations of bach/nrf paralogs, such as bach2a/nr/3, nfe2/bach2b, nrf2a/bach2b, nrf2b/bach2b and nrf2a/bach1b, were found to have co-effects on the expression of tryl, which enriched the Bach/Nrf-MafK pathway, and benefitted to explore the network architecture among these transcription factors.After transfecting tryl into human 293 cells and treating with lead acetate 48 h, it was found that high concentration of lead acetate (2×10-1g/L) down-regulated the expression of tryl, however, a low concentration of lead acetate(2×10-3 g/L) could up-regulate the expression of tryl, compared with the control group. Compared with single transfection of nrf2a, the treatment of activating factor nrf2a and 2 × 10-1 g/L lead acetate was found to inhibit significantly the expression of tryl. However, the treatments of inhibiting factor bach1b and lead acetate were found to up-regulate the expression of tryl, with the increase of lead concentrations, While mafk together with different concentrations of lead acetate led to the expression of tryl significantly rise, compared with the single carrying mafk, We presumed that with the increase of the concentration of lead acetate, lead abated the combining ability of Nrf2a-MafK, Bachlb-MafK and MafK-MafK dimers with the recongnized element (MARE) of the down control gene. These above results showed that Bach/Nrf-MafK signaling pathway or net was involved in the process of the lead toxicity, which enriched the researches of lead molecular toxicology. |
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