Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reduction of iron is important in promoting xenobiotic-enhanced, microsomal lipid peroxidation, yet there is little evidence that Fe3+ chelates that promote lipid peroxidation can be reduced by the microsomal system. We have shown that rat liver microsomes catalyse NADPH-dependent reduction of Fe3+ without chelator, as well as Fe3+(ADP), Fe3+(ATP), Fe3+(citrate), Fe3+(EDTA), and ferrioxamine in N2. The NADPH oxidation that accompanied Fe3+ reduction was inhibited by CO for all chelates, except Fe3+ (EDTA). This implies that, except for Fe3+ (EDTA), cytochrome P450 was involved in reduction of the complexes. Adriamycin, paraquat, and anthraquinone 2-sulfonate (AQS) enhanced reduction of all the Fe3+ chelates, whereas menadione enhanced reduction only of Fe3+(ADP) and Fe3+(citrate). All the compounds enhanced oxidation of NADPH in the presence or absence of iron. This was not inhibited by CO, and the results are compatible with Fe3+ reduction occurring via the xenobiotic radicals produced by cytochrome P450 reductase. Microsomal reduction of the xenobiotics, except menadione, enabled the reduction and release of iron from ferritin. Fe3+ chelate reduction, both with and without xenobiotic, was inhibited by O2, although it still proceeded in air at 10-20% of the rate in N2. Iron-dependent lipid peroxidation was promoted by ADP and ATP, inhibited 50% by citrate, and completely inhibited by EDTA and desferrioxamine. Of the xenobiotics, only Adriamycin enhanced microsomal lipid peroxidation. These results indicate that the effects of chelators and xenobiotics on Fe3+ reduction do not correlate with lipid peroxidation and, although reduction is necessary, there must be other factors involved.
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PMID:Microsomal reduction of low-molecular-weight Fe3+ chelates and ferritin: enhancement by adriamycin, paraquat, menadione, and anthraquinone 2-sulfonate and inhibition by oxygen. 285 Jul 67

Estrogens induce hydroxyl radical-mediated DNA and protein damage and lipid peroxidation. As part of a study of the mechanism of hydroxyl radical generation by estrogens, we investigated the in vitro mobilization of Fe2+ from ferritin by redox cycling of the stilbene or steroid estrogen metabolites diethylstilbestrol-4',4"-quinone (DESQ), equilenin-3,4-quinone (EQ), or estrone-3,4-quinone (3,4EQ). Aerobic cytochrome P450 reductase-mediated redox cycling of 35.50 microM DESQ, 0.35 microM EQ, or 3.55 microM 3,4EQ increased the reduction of succinoylated cytochrome c, a measure of superoxide radical formation, by 19-20% over control values (24.5+/-0.3 microM) in the absence of estrogen quinone substrate. Rates of Fe2+ release from horse spleen ferritin by cytochrome P450 reductase-mediated redox cycling of 35.50 microM DESQ, 0.35 microM EQ, or 3.55 microM 3,4EQ were 94.4+/-0.6, 117.2+/-9.4, or 137.7+/-19.9 pmol Fe2+/min, respectively, compared to 67.3 + 2.3 pmol Fe2+/min in the absence of estrogen substrates. Redox cycling of 35.5 microM DESQ, EQ, or 3,4EQ mediated by microsomes of hamster kidney, a target organ of estrogen-induced carcinogenesis, released 511+/-30.10, 516.91+/-22.90, or 410.27+/-28.49 pmol Fe2+/min, respectively. Corresponding values with microsomes of hamster liver, where tumors do not develop by estrogen treatment, were 272.27+/-43.10, 222.25+/-21.78, or 91.36+/-8.54 pmol Fe2-/min, respectively. Diethylstilbestrol, equilenin, and 4-hydroxyestrone do not induce detectable iron release from ferritin under these conditions. The cytochrome P450 reductase-mediated redox cycling of DESQ, EQ, or 3,4EQ in the presence of iron resulted in the hydroxylation of benzoic acid by hydroxyl radical attack. These data demonstrate that redox cycling of estrogen metabolites releases Fe2+ from ferritin, which in turn generates hydroxyl radicals by a Fenton reaction. This estrogen-induced hydroxyl radical damage may contribute to tumor initiation in hormone target tissues, including breast cancer.
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PMID:Release of iron from ferritin storage by redox cycling of stilbene and steroid estrogen metabolites: a mechanism of induction of free radical damage by estrogen. 934 64

NADPH-P450 oxidoreductase (CPR) is essential for the activity of cytochrome P450 (P450). Previous studies demonstrated that CPR regulates the levels of various P450 isoforms in vitro. We investigated the mechanistic basis for this regulation. By transfection of Chinese hamster ovary DUKXB11 cells we obtained the cell line DUKX/2D6, which expressed human CYP2D6, a P450 isoform. Subsequently, DUKX/2D6 cells were transfected with human CPR cDNA to generate the cell line DUKX/2D6/CPR-3. Expression of recombinant CPR decreased the level of spectrally detectable CYP2D6 holoprotein in DUKX/2D6/CPR-3 cells by 70%, whereas the level of immunodetectable apoprotein remained unchanged. Addition of the radical scavenger DMSO increased levels of CYP2D6 holoenzyme in DUKX/2D6/CPR-3 cells but not in DUKX/2D6 cells. A similar effect was noted when cells were grown in the presence of hemin. Importantly, combined treatment with DMSO and hemin increased levels of CYP2D6 holoenzyme in DUKX/2D6/CPR-3 but not in DUKX/2D6 cells even further than either treatment alone. None of these treatments affected the level of immunodetectable CYP2D6. This demonstrates that expression of CPR increases production of damaging radicals but also that CPR may alter haem homoeostasis. In agreement with this, the activity of haem oxygenase, a rate-limiting enzyme in haem metabolism, was compared with that in DUKX/DHFR control cells (expressing dihydrofolate reductase), and was 3-fold higher in DUKX/2D6/CPR-3 but similar in DUKX/2D6 cells. Furthermore, treatment of cells with sodium arsenite increased levels of haem oxygenase concomitant with a marked decrease of spectrally detectable CYP2D6 and a rise in levels of ferritin, which sequesters free iron released from the destruction of haem. These data demonstrate that CPR regulates P450 activity by supplying electrons and also by altering P450 levels via radical-and haem oxygenase-mediated pathways.
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PMID:Human NADPH-P450 oxidoreductase modulates the level of cytochrome P450 CYP2D6 holoprotein via haem oxygenase-dependent and -independent pathways. 1136 92