CYP7A1
Cytochrome P450 7A1 (24-hydroxycholesterol 7-alpha-hydroxylase) (EC 1.14.14.26) (CYPVII) (Cholesterol 7-alpha-hydroxylase) (Cholesterol 7-alpha-monooxygenase) (EC 1.14.14.23) [CYP7]
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Cytochrome P450s (CYPs) are phase-I metabolic enzymes playing important roles in drug metabolism, dietary chemicals and endogenous molecules. Age is a key factor influencing P450s expression. Thus, age-related changes of CYP 1-4 families and bile acid homeostasis-related CYPs, the corresponding nuclear receptors and a few phase-II genes were examined. Livers from male Sprague-Dawley rats at fetus (-2 d), neonates (1, 7, and 14 d), weanling (21 d), puberty (28 and 35 d), adulthood (60 and 180 d), and aging (540 and 800 d) were collected and subjected to qPCR analysis. Liver proteins from 14, 28, 60, 180, 540 and 800 days of age were also extracted for selected protein analysis by western blot. In general, there were three patterns of their expression: Some of the drug-metabolizing enzymes and related nuclear receptors were low in fetal and neonatal stage, increased with liver maturation and decreased quickly at aging (AhR, Cyp1a1, Cyp2b1, Cyp2b2, Cyp3a1, Cyp3a2, Ugt1a2); the majority of P450s (Cyp1a2, Cyp2c6, Cyp2c11, Cyp2d2, Cyp2e1, CAR, PXR, FXR, Cyp7a1, Cyp7b1. Cyp8b1, Cyp27a1, Ugt1a1, Sult1a1, Sult1a2) maintained relatively high levels throughout the adulthood, and decreased at 800 days of age; and some had an early peak between 7 and 14 days (CAR, PXR, PPARα, Cyp4a1, Ugt1a2). The protein expression of CYP1A2, CYP2B1, CYP2E1, CYP3A1, CYP4A1, and CYP7A1 corresponded the trend of mRNA changes. In summary, this study characterized three expression patterns of 16 CYPs, five nuclear receptors, and four phase-II genes during development and aging in rat liver, adding to our understanding of age-related CYP expression changes and age-related disorders.
Keywords
- Aging
- Cytochrome P450’s
- Nuclear receptors
- Ontogeny
- Rat liver
- mRNA/protein expression
Individual and combined toxicities of endosulfan (ENDO) with phenanthrene (PHE) were evaluated using zebrafish (Danio rerio) adults. The 96-h LC values for ENDO and PHE were 4.6 μg L and 920 μg L , respectively. To evaluate the mixture toxicity, LC and LC concentrations were grouped into four combinations as ENDO-LC PHE-LC , ENDO-LC PHE-LC , ENDO-LC PHE-LC , and ENDO-LC PHE-LC , and their acute toxicities were determined. The combination of LC -ENDO and LC -PHE exhibited a synergistic effect. In addition, acetylcholinesterase activity decreased in zebrafish bodies exposed to ENDO with or without PHE. Combined treatments induced higher glutathione S-transferase activity compared to individual treatments. Carboxylesterase activity increased in both heads and bodies of ENDO-treated fishes compared with PHE-treated fishes. Using RT-qPCR technique, CYP1A gene expression significantly up-regulated in all combinations, whereas CYP3A was unchanged, suggesting that enzymes involved in defense may play different roles in the detoxification. CYP7A1 gene responsible for bile acid biosynthesis is dramatically down-regulated after exposure to the synergistic combination exposure, referring that the synergistic effect may be resulted from the reduction of bile production in zebrafishes. Among gender-related genes, CYP11A1 and CYP17A1 genes in female zebrafish decreased after treatment with ENDO alone and combination of LC -ENDO and LC -PHE. This might be related to a reduction in cortisol production. The overall results indicated that ENDO and PHE were toxic to zebrafish adults both individually and in combination, and that their co-presence induced changes in the expression of genes responsible for metabolic processes and defense mechanisms.
MeSH Terms
- Acetylcholinesterase
- Aging
- Animals
- Carboxylesterase
- Cytochrome P-450 Enzyme System
- Drug Synergism
- Endosulfan
- Female
- Glutathione Transferase
- Insecticides
- Male
- Phenanthrenes
- Water Pollutants, Chemical
- Zebrafish
Keywords
- Endosulfan
- Enzyme activity
- Gene expression
- Mixture toxicity
- Phenanthrene
- Zebrafish
n-3 PUFA such as EPA and DHA as well as oestrogen have been reported to decrease blood levels of cholesterol, but their underlying mechanism is unclear. The purpose of this study was to determine the effects of the combination of n-3 PUFA supplementation and oestrogen injection on hepatic cholesterol metabolism. Rats were fed a modified AIN-93G diet with 0, 1 or 2 % n-3 PUFA (EPA DHA) relative to the total energy intake for 12 weeks. Rats were surgically ovariectomised at week 8, and, after 1-week recovery, rats were injected with 17β-oestradiol-3-benzoate (E2) or maize oil for the last 3 weeks. Supplementation with n-3 PUFA and E2 injection significantly increased the ratio of the hepatic expression of phosphorylated AMP activated protein kinase (p-AMPK):AMP activated protein kinase (AMPK) and decreased sterol regulatory element-binding protein-2, 3-hydroxy-3-methylglutaryl coenzyme A reductase and proprotein convertase subtilisin/kexin type 9. Supplementation with n-3 PUFA increased hepatic expression of cholesterol 7α-hydroxylase (CYP7A1), sterol 12α-hydroxylase (CYP8B1) and sterol 27-hydroxylase (CYP27A1); however, E2 injection decreased CYP7A1 and CYP8B1 but not CYP27A1. Additionally, E2 injection increased hepatic expression of oestrogen receptor-α and β. In conclusion, n-3 PUFA supplementation and E2 injection had synergic hypocholesterolaemic effects by down-regulating hepatic cholesterol synthesis (n-3 PUFA and oestrogen) and up-regulating bile acid synthesis (n-3 PUFA) in ovariectomised rats.
MeSH Terms
- Aging
- Animals
- Anticholesteremic Agents
- Cholestanetriol 26-Monooxygenase
- Cholesterol 7-alpha-Hydroxylase
- Combined Modality Therapy
- Diet, Fat-Restricted
- Dietary Supplements
- Estradiol
- Estrogens
- Fatty Acids, Omega-3
- Female
- Hydroxymethylglutaryl CoA Reductases
- Hypercholesterolemia
- Liver
- Ovariectomy
- Proprotein Convertase 9
- Random Allocation
- Rats, Wistar
- Serine Endopeptidases
- Steroid 12-alpha-Hydroxylase
- Sterol Regulatory Element Binding Protein 2
Keywords
- n-3 PUFA
- AMPK AMP activated protein kinase
- CYP27A1 sterol 27-hydroxylase
- CYP7A1 cholesterol 7α-hydroxylase
- CYP8B1 sterol 12α-hydroxylase
- Cholesterol metabolism
- E2 17β-oestradiol-3-benzoate
- ER-α oestrogen receptor-α
- ER-β oestrogen receptor-β
- HMG-CoA reductase 3-hydroxy-3-methylglutaryl coenzyme A reductase
- Oestrogen
- Ovariectomised rats
- Proprotein convertase subtilisin/kexin type 9
- SREBP-2 sterol regulatory element-binding protein-2
- TC total cholesterol
- p-AMPK phosphorylated AMP activated protein kinase
The fetoprotein transcription factor (FTF) gene was inactivated in the mouse, with a lacZ gene inserted inframe into exon 4. LacZ staining of FTF /- embryos shows that the mFTF gene is activated at initial stages of zygotic transcription. FTF gene activity is ubiquitous at the morula and blastocyst stages and then follows expression patterns indicative of multiple FTF functions in fetal development. FTF-/- embryos die at E6.5-7.5, with features typical of visceral endoderm dysfunction. Adult FTF /- mice are hypocholesterolemic, and express liver FTF at about 40% of the normal level. Overexpression of liver FTF in transgenic mice indicates in vivo that FTF is an activator of CYP7A1. However, CYP7A1 expression is increased in FTF /- liver. Gene expression profiles indicate that higher CYP7A1 expression is caused by attenuated liver cell stress signaling. Diet experiments support a model where FTF is quenched both by activated c-Jun, and by SHP as a stronger feedback mechanism to repress CYP7A1. A DR4 element is conserved in the FTF gene promoter and activated by LXR-RXR and TR-RXR, qualifying the FTF gene as a direct metabolic sensor. Liver FTF increases in rats treated with thyroid hormone or a high cholesterol diet. The FTF DR4 element tightens functional links between FTF and LXRalpha in cholesterol homeostasis and can explain transient surges of FTF gene activities during development and FTF levels lower than predicted in FTF /- liver. The FTF-lacZ mouse establishes a central role for FTF in developmental, nutritive, and metabolic functions from early embryogenesis through adulthood.
MeSH Terms
- Aging
- Animals
- Base Sequence
- Cholesterol
- DNA Primers
- DNA-Binding Proteins
- Embryonic and Fetal Development
- Fetal Death
- Gene Deletion
- Gene Expression Regulation, Developmental
- Genes, Essential
- Homeostasis
- Liver
- Mice
- Mice, Knockout
- Mice, Transgenic
- Polymerase Chain Reaction
- Receptors, TNF-Related Apoptosis-Inducing Ligand
- Receptors, Tumor Necrosis Factor
- Stem Cells
- Transcription Factors
- beta-Galactosidase
The developmental variation of cytochrome P450 (CYP)7A1, CYP7B1, CYP27A1, and 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase, key enzymes in bile acid biosynthesis, were investigated in pigs of different ages. As part of these studies, peptide sequences from a purified pig liver oxysterol 7alpha-hydroxylase were analyzed. The sequences showed a high degree of identity with those of murine and human CYP7B1. Enzymatic activities and mRNA levels of CYP27A1 and 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase were similar in livers of newborn and 6-month-old pigs. Enzymatic activity mediated by CYP7A1 increased several-fold between infancy and adolescence. Hepatic CYP7A1 and CYP7B1 mRNA levels increased several-fold with age. Hepatic microsomal 7alpha-hydroxylation of 27-hydroxycholesterol and dehydroepiandrosterone, substrates typical for CYP7B1, increased about 5-fold between infancy and adolescence whereas the activities in kidney microsomes decreased at least 10-fold. In conclusion, the results indicate that the expression of CYP27A1 and 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase are similar in livers of newborn and 6-month-old pigs whereas the levels of CYP7A1 increase. The finding that the levels of CYP7B1 increase with age in the liver but decrease in the kidney suggest a tissue-specific developmental regulation of CYP7B1. The age-dependent variation in the liver and kidney suggests that hormonal factors are involved in the regulation of CYP7B1.
MeSH Terms
- Aging
- Amino Acid Sequence
- Animals
- Animals, Newborn
- Base Sequence
- Bile Acids and Salts
- Cytochrome P-450 Enzyme System
- Cytochrome P450 Family 7
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Humans
- Kinetics
- Male
- Mice
- Mitochondria, Liver
- Molecular Sequence Data
- Orchiectomy
- Organ Specificity
- Peptide Fragments
- Polymerase Chain Reaction
- Progesterone Reductase
- RNA, Messenger
- Sequence Alignment
- Sequence Homology, Amino Acid
- Steroid Hydroxylases
- Swine
- Transcription, Genetic