Disease relevance of HYDROP

• Survival of mice receiving melanoma transplants is promoted by hydroquinone [1].
• Restoration of a lost metal-binding site: construction of two different copper sites into a subunit of the E. coli cytochrome o quinol oxidase complex [2].
• Mutations conferring resistance to quinol oxidation (Qz) inhibitors of the cyt bc1 complex of Rhodobacter capsulatus [3].
• A considerable amount of evidence suggests that Proteobacteria (Purple bacteria) acquired quinol oxidase through a lateral gene transfer from Gram-positive bacteria [4].
• Nitrogen Fixation Special Feature: Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state [5].

Psychiatry related information on HYDROP

• Hence, when the presence of the HRP marker of the immunoassay was determined using hydroquinone, the production of electroactive quinone was shown to permeate faster to the electrode, thus providing a faster response time [6].

High impact information on HYDROP

• Phenidone and hydroquinone blockers of endothelium-dependent vasodilation, inhibited arteriolar dilation to ACH without affecting that to NP [7].
• A novel family of cytochrome c quinol dehydrogenases that play an important role in bacterial respiratory chains was recognised in recent years [8].
• X-ray structure of the membrane-bound cytochrome c quinol dehydrogenase NrfH reveals novel haem coordination [8].
• The operon coding for a respiratory quinol oxidase was cloned from thermoacidophilic archaebacterium Sulfolobus acidocaldarius [9].
• Here we demonstrate that, after replacement of Glu-C180 with Gln or Ile by site-directed mutagenesis, the resulting mutants are unable to grow on fumarate, and the membrane-bound variant enzymes lack quinol oxidation activity [10].

Chemical compound and disease context of HYDROP

• The nonphotosynthetic mutant R126 of Rhodobacter capsulatus has a cytochrome (cyt) bc1 complex (EC 1.10.2.2) with a defective quinol oxidation Qz(o,p) site but a functional quinone reduction Qc(i,n) site [11].
• Thus, the formation of catechol and hydroquinone is the most likely cause of benzene toxicity [12].
• Groups of 15 rats were given three i.p. injections of 25 mg/kg of body weight of MNAN within the initial 2-wk period, and commencing 1 wk thereafter they were administered 0.8% catechol, 0.8% resorcinol, or 0.8% hydroquinone in powdered basal diet or were given basal diet alone for 49 wk [13].
• Bacillus subtilis contains two aa3-type terminal oxidases (caa3-605 and aa3-600) catalyzing cytochrome c and quinol oxidation, respectively, with the concomitant reduction of O2 to H2O (Lauraeus, M., Haltia, T., Saraste, M., and Wikström, M. (1991) Eur. J. Biochem. 197, 699-705) [14].
• Probing substrate binding site of the Escherichia coli quinol oxidases using synthetic ubiquinol analogues [15].

Biological context of HYDROP

• Oxidation of membrane-bound quinol molecules is a central step in the respiratory electron transport chains used by biological cells to generate ATP by oxidative phosphorylation [8].
• Femtosecond resolution of ligand-heme interactions in the high-affinity quinol oxidase bd: A di-heme active site [16]?
• We have studied the kinetics of the oxygen reaction of the fully reduced quinol oxidase, cytochrome bo3, using flow-flash and stopped flow techniques [17].
• In this work, Gly-158 was changed by oligonucleotide-mediated mutagenesis to several other amino acids to define its role on quinol oxidation catalyzed by the cyt bc1 complex [11].
• Interestingly, overexpression of Nrf1 and Nrf2 individually in Hep-G2 and monkey kidney (COS1) cells significantly increased CAT gene expression from reporter plasmid hARE-thymidine kinase-CAT in transfected cells that were inducible by beta-naphthoflavone and teri-butyl hydroquinone [18].

Anatomical context of HYDROP

• The human promyeloblastic cell line, KG-1a, was used to investigate the ability of the benzene metabolite hydroquinone (HQ) to induce NQO1 [19].
• Pretreatment with hydroquinone (HQ) at concentrations ranging from picomolar to micromolar for 30 min resulted in a 1.5- to 4.6-fold enhancement in colonies formed in response to rGM-CSF that was due to an increase in granulocyte/macrophage colonies [20].
• Induced differentiation of HL-60 promyelocytic leukemia cells to monocyte/macrophages is inhibited by hydroquinone, a hematotoxic metabolite of benzene [21].
• We studied the effect of hydroquinone (HQ), a toxic metabolite of benzene found in the bone marrow, on the human promyelocytic leukemia cell line (HL-60), which can be induced to differentiate to both monocyte and myeloid cells, and thus has been used as a surrogate for a granulocyte/macrophage progenitor cell [21].
• Combinations of phenol, catechol, and hydroquinone also resulted in significant increases in steady state levels of oxidative DNA damage in the mouse bone marrow but were not effective when administered individually [22].

Associations of HYDROP with other chemical compounds

• Polymeric melanins undergo reversible oxidation-reduction reactions between cell wall-penetrating quinone and hydroquinone oxidation states and thus represent polymeric redox buffers; using strong oxidants, it is possible to titrate the melanin on living cells and thereby demonstrate protection conferred by melanin in several species [23].
• In isolated mutant RCs, the kinetics of the first electron transfer, leading to formation of the semiquinone, QB-, and the proton-linked second electron transfer, leading to the formation of fully reduced quinol, were both greatly retarded, as observed previously in the Asp L213 --> Asn mutant [24].
• Because benzene is metabolized to a variety of intermediate compounds and two of these, catechol and hydroquinone, have been reported to be potent SCE-inducers, it is possible that other known and proposed metabolites could have chromosome-damaging effects in lymphocytes [25].
• The hydroquinone-containing cytostatic compound avarol inhibits predominantly growth of those cell lines which have a low level of superoxide dismutase [26].
• Molecular modeling predicted covalent irreversible binding between quinol analogues and cysteine residues 32 and 35 of thioredoxin, thereby inhibiting enzyme activity [27].

Gene context of HYDROP

• The Bacillus subtilis genome contains a homologue of yeast Sco1, YpmQ (hereafter termed BSco), deletion of which leads to a phenotype lacking in caa3 (CuA-containing) oxidase activity but expressing normal levels of aa3 (quinol) oxidase activity [28].
• Hydroquinone and tert-butyl hydroquinone, prototypes of phenolic antioxidants, block lipopolysaccharide (LPS)-induced transcription of TNFalpha and a nuclear factor (NF)-kappaB-mediated reporter gene expression, suggesting NF-kappaB as a target in the inhibition [29].
• Treatment of normal murine stromal macrophages in culture with hydroquinone (HQ) also showed an inhibition in processing of pre-IL-1 alpha [30].
• The properties of MG in vitro, including (1) pigmentation inhibition in melanocytes, (2) tyrosinase inhibition and selectivity, (3) reduced cytotoxicity relative to HQ, and (4) lack of mutagenic potential in mammalian cells, establish MG as a superior candidate skin-lightening agent [31].
• Results: Tissue sections stained with cresyl violet did not reveal any gross differences between HQ-treated Eker (Tsc2Ek/+) rats and siblings (Tsc2+/+) [32].

Analytical, diagnostic and therapeutic context of HYDROP

• Treatment with hydroquinone and 1,2,4,-benzenetriol produced DNA adducts not detected after treatment with either metabolite alone [33].
• The hyperthermophilic archaeon Acidianus ambivalens expresses a membrane-bound aa(3)-type quinol oxidase, when grown aerobically, that we have studied by resonance Raman spectroscopy [34].
• Molecular cloning, sequencing, and physiological characterization of the qox operon from Bacillus subtilis encoding the aa3-600 quinol oxidase [14].
• Sequence alignments indicate only six totally conserved histidine residues among all known sequences of subunit I of the cytochrome c oxidases of various species plus the E. coli quinol oxidase [35].
• In cancer bioassays, HQ has reproducibly produced renal adenomas in male F344 rats [36].

References