Metal induction of haem oxygenase without concurrent degradation of cytochrome P-450. Protective effects of compound SKF 525A on the haem protein.
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ABSTRACT:
SUBMITTER: Drummond GS
PROVIDER: S-EPMC1158074 | biostudies-other | 1982 Jan
REPOSITORIES: biostudies-other
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Project description:The administration of organotin compounds to rats in single doses causes a significant and prolonged induction of haem oxygenase and a sustained decrease in haemoprotein content in the liver. The extent of induction of hepatic haem oxygenase varied between 3 and 5-fold at 72h after a single injection of water-insoluble organotins of differing structure. The alterations in haem metabolism produced by tricyclohexyltin hydroxide were studied in detail. The effects were dose-dependent, with doses as low as 3.75 mg/kg body wt. resulting in significant induction of haem oxygenase and a decrease in cytochrome P-450 and cytochrome b5 contents at 72h in the liver. The effects with time of a single dose of tricyclohexyltin on various parameters of liver haem metabolism were also examined. The organotin produced a substantial and very prolonged induction of haem oxygenase accompanied by a steady decline in cytochrome P-450 content for periods up to 8 days. The long duration of action of these organotins with respect to induction of haem oxygenase and depletion of cellular haemoprotein content provides a highly sensitive metabolic system with which to define further the toxic potential of organometals as well as to study the adaptive responses in liver to long-term perturbations of haem metabolism by foreign chemicals.
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Project description:Haem oxygenase 1 (HO-1) is an inducible protein that plays a major protective role in conditions such as ischaemia-reperfusion injury and inflammation. In this study, we have investigated the role of haem arginate (HA) in human male subjects in the modulation of HO-1 expression and its correlation with the GT length polymorphism (GT(n)) in the promoter of the HO-1 gene.In a dose-escalation, randomized, placebo-controlled trial, seven healthy male subjects with a homozygous short (S/S) and eight with a long (L/L) GT(n) genotype received intravenous HA. HO-1 protein expression and mRNA levels in peripheral blood monocytes, bilirubin, haptoglobin, haemopexin and haem levels were analysed over a 48?h observation period.We found that the baseline mRNA levels of HO-1 were higher in L/L subjects, while protein levels were higher in S/S subjects. HA induced a dose-dependent increase in the baseline corrected area under the curve values of HO-1 mRNA and protein over 48?h. The response of HO-1 mRNA was more pronounced in L/L subjects but the protein level was similar across the groups.HA is an effective inducer of HO-1 in humans irrespective of the GT(n) genotype. The potential therapeutic application of HA needs to be evaluated in clinical trials.
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Project description:Cyanide is a well known potent inhibitor of haem proteins, including haem oxygenase (HO). Generally, cyanide coordinates to the ferric haem iron with a linear binding geometry; the Fe-C-N angle ranges from 160 to 180 degrees . The Fe-C-N angle observed in the crystal structure of haem-HO bound to cyanide prepared at alkaline pH was 166 degrees . Here, it is reported that cyanide can bind to the haem iron in HO in a bent mode when the ternary complex is prepared at neutral pH; a crystal structure showed that the Fe-C-N angle was bent by 47 degrees . Unlike the ternary complex prepared at alkaline pH, in which the haem group, including the proximal ligand and the distal helix, was displaced upon cyanide binding, the positions of the haem group and the distal helix in the complex prepared at neutral pH were nearly identical to those in haem-HO. Cyanide that was bound to haem-HO with a bent geometry was readily photodissociated, whereas that bound with a linear geometry was not photodissociated. Thus, alternative cyanide-binding modes with linear and bent geometries exist in the crystalline state of haem-HO.
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Project description:By using 3-amino-1,2,4-triazole, an inhibitor of haem synthesis, and 2-allyl-2-isopropylacetamide, a drug that degrades the haem moiety of cytochrome P-450, the involvement of haem in cytochrome P-450 synthesis and assembly was investigated. Phenobarbital was used to stimulate apo-(cytochrome P-450) synthesis. Degradation of preformed cytochrome P-450 haem does not result in a concomitant release of the apoprotein from the endoplasmic reticulum. The availability of haem for cytochrome P-450 synthesis in the normal animal is not rate-limiting. Prolonged inhibition of haem synthesis in vivo decreases the rate of apo-(cytochrome P-450) synthesis, although this effect is not discernible under conditions of short-term inhibition of haem synthesis. Under the former conditions exogenous haemin is able to counteract the decrease in the rate of apoprotein synthesis. In animals receiving successive injections of phenobarbital plus 3-amino-1,2,4-triazole, compared with those receiving phenobarbital only, the holo-(cytochrome P-450) content measured spectrally shows a greater decrease than could be accounted for by the decrease in the content of the total apoprotein. In addition to less haem being available under these conditions, the free apoprotein appears to have undergone some modification, such that its haem-binding capacity is considerably decreased. This particular effect could be due to a direct interaction of 3-amino-1,2,4-triazole or its metabolites with cytochrome P-450 rather than a consequence of haem deficiency. Apo-(cytochrome P-450) is capable of binding to the endoplasmic reticulum in a form and at a site, which can be reconstituted with haemin to yield the functional protein.
| S-EPMC1164794 | biostudies-other
Project description:The present work shows that the ability of pyridines e.g. metyrapone, to maintain the cytochrome P-450 concentration in cultured hepatocytes is not due to their ability to alter the 5-aminolaevulinate synthase and haem oxygenase activities of the hepatocytes. Since ligands such as metyrapone will prevent the cobalt-mediated loss of hepatic cytochrome P-450 in rats, the hypothesis that ligand formation is the mechanism of maintenance of the cytochrome in hepatocyte culture was tested. The observation that non-pyridine ligands will maintain the cytochrome P-450 concentration supports this hypothesis.
| S-EPMC1154299 | biostudies-other
Project description:Bacterial cytochrome c maturation occurs at the outside of the cytoplasmic membrane, requires transport of haem b across the membrane, and depends on membrane-bound cytochrome c haem lyase (CCHL), an enzyme that catalyses covalent attachment of haem b to apocytochrome c. Epsilonproteobacteria such as Wolinella succinogenes use the cytochrome c biogenesis system II and contain unusually large CCHL proteins of about 900 amino acid residues that appear to be fusions of the CcsB and CcsA proteins found in other bacteria. CcsBA-type CCHLs have been proposed to act as haem transporters that contain two haem b coordination sites located at different sides of the membrane and formed by histidine pairs. W. succinogenes cells contain three CcsBA-type CCHL isoenzymes (NrfI, CcsA1 and CcsA2) that are known to differ in their specificity for apocytochromes and apparently recognize different haem c binding motifs such as CX(2)CH (by CcsA2), CX(2)CK (by NrfI) and CX(15)CH (by CcsA1). In this study, conserved histidine residues were individually replaced by alanine in each of the W. succinogenes CCHLs. Characterization of NrfI and CcsA1 variants in W. succinogenes demonstrated that a set of four histidines is essential for maturing the dedicated multihaem cytochromes c NrfA and MccA, respectively. The function of W. succinogenes CcsA2 variants produced in Escherichia coli was also found to depend on each of these four conserved histidine residues. The presence of imidazole in the growth medium of both W. succinogenes and E. coli rescued the cytochrome c biogenesis activity of most histidine variants, albeit to different extents, thereby implying the presence of two functionally distinct histidine pairs in each CCHL. The data support a model in which two conserved haem b binding sites are involved in haem transport catalysed by CcsBA-type CCHLs.
| S-EPMC3068706 | biostudies-literature
Project description:Cytochrome P450 (CYP) proteins constitute a large ancient family of oxidative enzymes essential for the efficient elimination of a wide variety of clinically used drugs. Polymorphic variants of human CYP2D6 are associated with the conversion rate and efficacy of several drugs such as antidepressants. Polymorphisms of the canine orthologue CYP2D15 are of interest because these antidepressants are also used in dogs with behavioral problems and the outcome of the treatment is variable. However, the annotated CYP2D15 gene is incomplete and inaccurately assembled in CanFam3.1, hampering DNA sequence analysis of the gene in individual dogs. We elucidated the complete exon-intron structure of CYP2D15 to enable comprehensive genotyping of the gene using genomic DNA. We surveyed variations of the gene in four diverse dog breeds and identified novel polymorphisms in exon 2 in border collies. Further investigation to establish the impact of these canine CYP2D15 polymorphisms on interindividual variability in expression and function of this metabolizing enzyme is now feasible. Further knowledge of CYP pharmacogenetics will help individualize therapy and thereby increase therapeutic efficacy, especially in the use of antidepressants in veterinary behavioral medicine.
| S-EPMC7689907 | biostudies-literature
Project description:Cytochrome P-450 was purified to apparent homogeneity from the brain microsomes of phenobarbital-treated rats. The specific content of the purified P-450 was 12.7 nmol/mg of protein. NADPH-cytochrome P-450 reductase (reductase) was also purified to apparent homogeneity from brain microsomes. The specific content was 34.7 mumol of cytochrome c reduced/min per mg of protein. The reduced carbon monoxide spectrum of purified P-450 exhibited a peak at 450 nm. Both the P-450 and the reductase moved as single bands on SDS/PAGE. The molecular masses of the purified P-450 and the reductase were determined to be 53.3 and 72.0 kDa respectively. The purified brain P-450 cross-reacted with antibodies to rat liver P-450IIB1/IIB2 when examined by Western immunoblotting, but no immunological similarity was observed with rat liver P-450IA1/IA2 or P-450IIE1. Purified rat brain reductase cross-reacted with antibodies to rat liver reductase. Further, immunoblot experiments with untreated rat and human brain microsomes using antisera to the purified rat brain P-450 and reductase indicated that these forms of P-450 and NADPH-cytochrome P-450 reductase exist constitutively in rat and human brain. Purified rat brain P-450 was reconstituted with purified NADPH-cytochrome P-450 reductase, deoxycholate and dilauroyl glyceryl 3-phosphocholine. NADPH-dependent N-demethylation of aminopyrine and morphine was observed in the reconstituted system. The catalytic-centre activities were 80.25 and 38.2 nmol of formaldehyde formed/min per nmol of P-450 respectively. The reconstituted system had a comparatively lower catalytic-centre activity for 7-ethoxycoumarin O-de-ethylase (10.5 nmol of product formed/min per nmol of P-450).
| S-EPMC1132036 | biostudies-other
Project description:Background and purposeUlinastatin (UTI), a serine protease inhibitor, was recently found to have an anti-inflammatory action. However, the mechanisms mediating this anti-inflammatory effect are not well understood. This study tested the hypothesis that UTI suppresses allergic inflammation by inducing the expression of haem oxygenase 1 (HO1).Experimental approachControl mice and mice sensitized (on days 1, 9 and 14) and challenged (on days 21 to 27) with ovalbumin (OVA) were treated with UTI. The effects of UTI on basal expression of HO1 and that induced by OVA challenge were examined. The involvement of UTI-induced HO1 expression in anti-inflammatory and antioxidant effects of UTI was also evaluated.Key resultsUTI markedly increased basal HO1 protein expression in lungs of control mice in a time- and dose-dependent manner, and augmented HO1 protein expression induced by OVA. The up-regulation of HO1 mediated by UTI in sensitized and OVA-challenged mice was associated with reduced airway inflammation, alleviated tissue injury, reduced oxidant stress and enhanced antioxidant enzyme activities. Inhibition of HO1 activity using HO1 inhibitor, zinc protoporphyrin, attenuated inhibitory effects of UTI on inflammation and oxidant stress, and its stimulant effects on antioxidant enzyme activities. Mechanistic analysis showed that UTI increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), stimulated Nrf2 DNA binding activity and concomitantly up-regulated HO1 mRNA expression.Conclusions and implicationsUTI is a potent and naturally occurring inducer of HO1 expression. HO1 up-regulation contributes significantly to the anti-inflammatory and organ-protective effects of UTI, which has important research and therapeutic implications.
| S-EPMC4209147 | biostudies-literature
Project description:Mn2+ and Zn2+ exhibit a striking ability to block the induction by Sn2+ and Ni2+ of haem oxygenase (EC 1.14.99.3) in kidney. The blocking effects of Mn2+ and Zn2+ were found to be greatest on simultaneous administration, time-dependent when administered up to 8 h before the inducing metal ions, and ineffective when administered as little as 10 min after the inducing metal ions. The decreases in cytochrome P-450 and haem contents and the sequential changes in delta-aminolaevulinate synthase (EC 2.3.1.37) activity that occur concomitant with haem oxygenase induction were largely eliminated with simultaneous or prior treatment with Mn2+ or Zn2+, but not when Mn2+ or Zn2+ was administered after Sn2+ or Ni2+. Mn2+ and Zn2+ did not increase the catabolism of the enzyme in vivo. Zn2+ on simultaneous administration was also able substantially to block the induction of haem oxygenase by Co2+, Cd2+ and Ni2+ in liver. The Zn2+ blockade of Cd2+ induction was examined in detail, and prior or simultaneous administration of Zn2+ was found to be effective in blocking the induction of haem oxygenase and the concomitant decreases in cytochrome P-450 and haem contents, ethylmorphine demethylase activity and the sequential changes in delta-aminolaevulinate synthase activity. Zn2+ administration 10 min or more after Cd2+ was ineffective in preventing the occurrence of these perturbations in haem metabolism. These findings describe a new and striking biological property of Mn2+ and Zn2+, and indicate the existence of significant metal ion interactions in the control of haem metabolism.
| S-EPMC1162380 | biostudies-other