RESUMO
BACKGROUND: Iron is an essential metal element for organisms, whose metabolism is regulated by many genes and also dietary iron sources. However, the characterization, distribution and the responses of iron metabolism-related genes to different iron sources were not clear in fish. METHODS: The full-length cDNA sequences of fifteen iron metabolism-relevant genes (tf, tfr1, hp, fpn1, ho1, ho2, tfr2, hjv, hepcidin, fth, ftl, ftm, irp1, irp2 and hif2α.) were obtained via 3' and 5' RACE PCR from yellow catfish, a widely distributed freshwater teleost in China and other Asian countries. Their molecular characterizations were analyzed via the bioinformatic methods. Real-time quantitative PCR was used to explore their mRNA distribution in nine tissues. Their mRNA expression responses in four tissues (heart, brain, kidney and gill) were explored in yellow catfish fed diets with five iron sources, including ferrous sulfate (FeSO4), ferrous bisglycinate (Fe-Gly), ferrous chloride (FeCl2), ferric citrate (Fe-CA) and ferric oxide nanoparticles (Fe2O3NPs). RESULTS: Compared with mammals and other teleost, these members shared similar domains. Their mRNAs were expressed in nine tested tissues, but mRNA levels varied. Yellow catfish fed the diets containing Fe-Gly and Fe2O3NPs had higher iron contents in heart, brain, kidney and gill. Meantime, different dietary iron sources addition affected their mRNA expression differentially in brain, heart, kidney and gill. It should be pointed out that only three biological replicate tanks were used in the present feeding treatment, and more biological replicate tanks (more than five) should be emphasized in further researches. CONCLUSION: Taken together, our study identified fifteen iron metabolism-relevant genes, explored their mRNA expression in nine tissues, and their mRNA expression in the responses to different dietary iron sources in four tissues, indicating their important regulatory function in iron metabolism and homeostasis.
Assuntos
Peixes-Gato , Ferro da Dieta , Animais , Peixes-Gato/genética , Receptores da Transferrina/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ferro/metabolismo , Mamíferos/genética , Mamíferos/metabolismoRESUMO
Excessive copper (Cu) intake leads to hepatic lipotoxicity disease, which has adverse effects on health, but the underlying mechanism is unclear. We found that Cu increased lipotoxicity by promoting Nrf2 recruitment to the ARE site in the promoters of five lipogenic genes (g6pd, 6pgd, me, icdh and pparγ). We also found that Cu affected the Nrf2 expression via different pathways: metal regulatory transcription factor 1 (MTF-1) mediated the Cu-induced Nrf2 transcriptional activation; Cu also enhanced the expression of Nrf2 by inhibiting the SP1 expression, which was achieved by inhibiting the negative regulator Fyn of Nrf2. These promoted the enrichment of Nrf2 in the nucleus and ultimately affected lipotoxicity. Thus, for the first time, we elucidated that Cu induced liver lipotoxicity disease by up-regulating Nrf2 expression via the MTF-1 activation and the inhibition of SP1/Fyn pathway. Our study elucidates the Cu-associated obesity and NAFLD for fish and possibly humans.
Assuntos
Cobre , Hepatopatia Gordurosa não Alcoólica , Humanos , Animais , Cobre/toxicidade , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo , Hepatopatia Gordurosa não Alcoólica/genética , Fator de Transcrição Sp1/genética , Fator de Transcrição Sp1/metabolismoRESUMO
Here, we characterized the function of ctr1, ctr2 and atox1 promoters in yellow catfish Pelteobagrus fulvidraco, a common freshwater teleost in Asian countries. We obtained 1359 bp, 1842 bp and 1825 bp sequences of ctr1, ctr2 and atox1 promoters, and predicted key transcription factor binding sites on their promoters, including MRE, SREBP1, NRF2, KLF4 and STAT3. Cu differentially influenced the activities of ctr1, ctr2 and atox1 promoters from different regions. We found that the -326/-334 bp and -1232/-1240 bp locus in the atox1 promoter were functional NRF2 binding sites, which negatively controlled the activity of the atox1 promoter. The -91/-100 bp locus in the ctr1 promoter and -232/-241 bp and -699/-708 bp locus in the atox1 promoter were functional SREBP1 binding sites, which positively controlled the activities of ctr1 and atox1 promoters. Cu inhibited the NRF2 binding ability to the atox1 promoter, but promoted the SREBP1 binding ability to the ctr1 and atox1 promoters. Dietary Cu excess significantly down-regulated hepatic mRNA and total protein expression of CTR1, CTR2 and ATOX1 of yellow catfish, compared to the adequate dietary Cu group. The subcellular localization showed that CTR1 was mainly localized on the cell membrane, CTR2 in the cell membrane and the lysosome, and ATOX1 in the cytoplasm. In conclusion, we demonstrated the regulatory mechanism of three Cu transporters at the transcription levels, and found the functional NRF2 and SREBP1 response elements in ctr1, ctr2 and atox1 promoters, which provided new insights into their roles in the regulation of Cu homeostasis in fish.
Assuntos
Peixes-Gato , Animais , Peixes-Gato/genética , Peixes-Gato/metabolismo , Cobre/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Homeostase , RNA Mensageiro/genéticaRESUMO
Iron is an essential micro-element, involved in multiple biological activities in vertebrates. Excess iron accumulation has been identified as an important mediator of lipid deposition. However, the underlying mechanisms remain unknown. In the present study, we found that a high-iron diet significantly increased intestinal iron content and upregulated the mRNA expression of two iron transporters (zip14 and fpn1). Intestinal iron overload increased lipogenesis, reduced lipolysis and promoted oxidative stress and mitochondrial dysfunction. Iron-induced lipid accumulation was mediated by hypoxia-inducible factor-1 α (HIF1α), which was induced in response to mitochondrial oxidative stress following inhibition of prolyl hydroxylase 2 (PHD2). Mechanistically, iron promoted lipid deposition by enhancing the DNA binding capacity of HIF1α to the pparγ and fas promoters. Our results provide experimental evidence that oxidative stress, mitochondrial dysfunction and the HIF1α-PPARγ pathway are critical mediators of iron-induced lipid deposition.
Assuntos
Ferro , PPAR gama , Animais , Lipídeos , Mitocôndrias , Estresse Oxidativo , PPAR gama/genéticaRESUMO
Oxidative stress can induce occurrence of non-alcoholic fatty liver disease (NAFLD). Nrf2 is a central regulator of cellular oxidative stress and also participates in the control of lipid deposition and metabolism. Here, we hypothesize that oxidative stress-mediated Nrf2 activation participates in the regulation of the Cu-induced lipid deposition. We found that Cu excess activated oxidative stress and autophagy, up-regulated lipogenesis and lipid metabolism, suppressed Keap1 expression and activated Nrf2 signaling. Moreover, Cu induced lipid deposition via oxidative stress and the mitochondrial dysfunction. Oxidative stress mediated Cu-induced activation of Nrf2 and autophagy. The activation of autophagy helps to alleviate Cu-induced lipid deposition and accordingly provided a protective role against Cu-induced NAFLD. Meantime, Cu-induced oxidative stress promoted Nrf2 recruitment to the PPARγ promoter, inducing target gene transcription, and subsequent lipogenesis. Our findings, for the first time, provide direct evidences for Nrf2 function in the modulation of lipogenic metabolism via the transcriptional activation of PPARγ, and elucidate the mechanisms by which Nrf2 functions as the central regulator of lipogenic genes and highlights the significance of Nrf2 as potential therapeutic targets for oxidative stress-associated obesity and NAFLD for fish and human beings.
Assuntos
Autofagia , Cobre/administração & dosagem , Hepatócitos/metabolismo , Metabolismo dos Lipídeos , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo , PPAR gama/metabolismo , Animais , Peixes-Gato , Células Cultivadas , Cobre/metabolismo , Cobre/farmacologia , Dieta , Células HEK293 , Hepatócitos/efeitos dos fármacos , Humanos , Lipogênese , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de SinaisRESUMO
B-cell lymphoma 2 (Bcl-2) and cytochrome c (Cycs) are two important proteins relevant to cellular apoptosis. In this study, we characterized the functions of the promoter regions of two apoptosis-related genes, Bcl-2 and Cycs, in yellow catfish Pelteobagrus fulvidraco. We obtained a 1989 bp Bcl-2 promoter and an 1830 bp Cycs promoter and predicted several key transcription factor binding sites (TFBSs) on the promoters, such as Kruppel-like factor 4 (KLF4), signal transducer and activator of transcription factor 3 (STAT3), forkhead box O (FOXO), metal-responsive element (MRE) and hepatocyte nuclear factor 1α (HNF-1α). Zinc (Zn) increased the activities of the Bcl-2 promoter but decreased the activities of the Cycs promoter. Metal-responsive transcription factor 1 (MTF-1) and HNF-1α directly bound with Bcl-2 and Cycs promoters, and they positively regulated the activity of the Bcl-2 promoter but negatively regulated the activity of the Cycs promoter. Zn promoted the binding ability of HNF-1α to the Bcl-2 promoter but decreased its binding ability to the Cycs promoter. However, Zn had no significant effect on the binding capability of MTF-1 to the regions of Bcl-2 and Cycs promoters. Zn upregulated the mRNA and total protein expression of Bcl-2 but downregulated the mRNA and total protein expression of Cycs. At the same time, Annexin V-FITC/PI staining showed that Zn significantly reduced the apoptosis of primary hepatocytes. For the first time, our study provides evidence for the MRE and HNF-1α response elements on the Bcl-2 and Cycs promoters, offering new insight into the mechanism by which Zn affects apoptosis in vertebrates.
Assuntos
Apoptose/genética , Peixes-Gato/genética , Citocromos c/genética , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-bcl-2/genética , Zinco/farmacologia , Animais , Apoptose/efeitos dos fármacos , Sequência de Bases , Sítios de Ligação , Citocromos c/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Deleção de SequênciaRESUMO
The study characterized their regulatory functions of four znt members (znt1, znt2, znt6 and znt8) in Zn homeostasis in vertebrates. We found that the -1281/-1296 bp locus on the znt1 promoter, the -1/-16 bp locus on the znt2 promoter, the -825/-839 bp locus on the znt6 promoter, the -165/-180 bp locus and the -274/-292 bp STAT3 locus on the znt8 promoter were functional MTF-1 binding sites and had metal responsive element (MRE). Zn incubation increased activities of four znt promoters, which was mediated by MRE sites on znt1, znt2, znt6 and znt8 promoters and by STAT3 binding site on znt8 promoter. Moreover, Zn activated the transcription of these znts genes through MTF-1-MRE-dependent pathway. Zn incubation up-regulated the mRNA and total protein expression of ZnT1, ZnT2 and ZnT8 at both 24 h and 48 h. Overall, for the first time, this study offered novel insights for regulatory mechanism of Zn homeostasis in vertebrates.
Assuntos
Peixes-Gato/genética , Proteínas de Transporte de Cátions/genética , Proteínas de Peixes/genética , Ativação Transcricional , Zinco/metabolismo , Animais , Sítios de Ligação , Peixes-Gato/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Células Cultivadas , Proteínas de Ligação a DNA/metabolismo , Proteínas de Peixes/metabolismo , Células HEK293 , Homeostase , Humanos , Mutação , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Fator de Transcrição STAT3/metabolismo , Fatores de Transcrição/metabolismo , Fator MTF-1 de TranscriçãoRESUMO
The steroid hormones are required for gonadal development in fish. The present study was undertaken to characterize the cDNA and promoter sequences of TSPO and SMAD4 genes in yellow catfish Pelteobagrus fulvidraco, explored the mRNA tissue expression and deciphered their promoter regions. Yellow catfish TSPO and SMAD4 shared the similar domains to the corresponding genes from other vertebrates. The TSPO and SMAD4 mRNAs were widely expressed in the detected tissues, but at different levels. Several transcription factors were predicted, such as Sp, GATA, AP1, SOX1, SRY, STAT, HNF4α, PPARγ, Pu.1 and FOXL2. PPARγ overexpression increased but STAT3 overexpression reduced TSPO promoter activity, and FOXL2 overexpression inhibited the promoter activity of TSPO and SMAD4. The site mutation and EMSA analysis indicated that TSPO promoter possessed STAT3 and FOXL2 sites. Overall, our provided the novel understanding into the transcriptionally regulatory mechanisms of TSPO and SMAD4 in fish.