Studies on haem alpha-methenyl oxygenase. Isomeric structure of formylbiliverdin, a possible precursor of biliverdin.
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ABSTRACT:
SUBMITTER: Nakajima O
PROVIDER: S-EPMC1270541 | biostudies-other | 1967 Jul
REPOSITORIES: biostudies-other
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Project description:Conversion of four isomers of meso-oxyprotohaem IX into the corresponding biliverdin IX was attempted with a reconstituted haem oxygenase system in the presence of NADPH-cytochrome c reductase and NADPH. Only the alpha-isomer of meso-oxyprotohaem IX was converted effectively into biliverdin IX alpha, which was further reduced to bilirubin IX alpha by biliverdin reductase. Only trace amounts of biliverdins IX beta, IX gamma and IX delta were respectively formed from the incubation mixture of the corresponding oxyprotohaemin IX isomers with the complete haem oxygenase system under the same conditions. In a kinetic study, the Km for alpha-meso-oxyprotohaem IX was 3.6 microM, which was 2-fold higher than that for protohaem IX. The maximum velocity (Vmax.) of the conversion of alpha-meso-oxyprotohaem IX into biliverdin IX alpha was twice as fast as that of protohaem IX. These results demonstrate that alpha-meso-oxyprotohaem IX is an intermediate of haem degradation and it was converted stereospecifically into biliverdin IX alpha via verdohaem IX alpha.
| S-EPMC1131782 | biostudies-other
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.
| S-EPMC3010580 | biostudies-literature
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.
| S-EPMC2335079 | biostudies-literature
Project description:Monospecific polyclonal rabbit antibodies to a purified form of haem oxygenase of chick liver, showing sequence similarity to mammalian haem oxygenase-1, were raised and used to study characteristics of the oxygenase. The antibodies inhibited activity of the purified oxygenase, but not other enzyme components (NADPH:cytochrome reductase and biliverdin reductase) of the standard assay mixture of haem oxygenase. In addition, the antibodies inhibited activity of haem oxygenase in microsomes (microsomal fractions) from Cd(2+)-treated chick liver, spleen, testis and brain. Western (immuno-) blots of microsomal proteins of selected organs from chick, rat and man, and homogenates of chick-embryo liver-cell cultures, probed with the antibodies, showed a major protein with a molecular mass of 33-34 kDa and a lower-molecular-mass protein (28-29 kDa) of variable intensity. Studies with trypsin and selected proteinase inhibitors established that the smaller peptide was a proteolytic product of the larger. Treatment of chick-embryo liver-cell cultures with CdCl2, a potent inducer of haem oxygenase, increased the degree of proteinase-mediated cleavage of the 33 kDa protein to the lower-molecular-mass form. These results indicate that, under at least some conditions, such cultures should be homogenized in the presence of trypsin inhibitor to prevent proteolytic degradation of the enzyme and allow maximal expression of haem oxygenase activity. The antibodies also reacted with haem oxygenase from spleen, testis and brain of both chicks and rats, and the spleen of humans. A method for quantifying the amount of haem oxygenase protein was developed with use of slot-blots and laser densitometry; linearity was observed from 0 to 5 ng of haem oxygenase protein per slot, and the method was applied to sonicated cultured chick-embryo liver cells treated with Cd2+ (0.3 mM) or iron plus glutethimide. In both cases, increases in enzyme activity were of similar magnitude to increases in amounts of enzyme protein. Approximate amounts of haem oxygenase protein in microsomes of several organs from intact animals could also be estimated by the use of slot-blot-laser densitometry, and the amounts measured were increased by the addition of purified haem oxygenase to the microsomal preparations. Results of these studies indicated that haem oxygenase-1 could be detected in microsomes from all chick or rat organs studied, including testis and brain.(ABSTRACT TRUNCATED AT 400 WORDS)
| S-EPMC1151524 | biostudies-other
Project description:A library of isomeric 2,4-diaminoquinazoline (DAQ) derivatives were synthesized and evaluated for antiaggregation potential toward A?40/42. Structure-activity relationship data identified compound 3k (N (4)-(4-bromobenzyl)quinazoline-2,4-diamine) with a 4-bromobenzyl substituent as the most potent inhibitor (A?40 IC50 = 80 nM) and was almost 18-fold more potent compared to the reference agent curcumin (A?40 IC50 = 1.5 ?M). The corresponding N (2)-isomer 4k (N (2)-(4-bromobenzyl)quinazoline-2,4-diamine) was also able to prevent A? aggregation (A?40 IC50 = 1.7 ?M). However, compound 4k exhibited superior inhibition of A?42 aggregation (A?42 IC50 = 1.7 ?M) compared to compound 3k (A?42 IC50 = 14.8 ?M) and was ?1.8-fold more potent compared to curcumin (A?42 IC50 = 3.1 ?M). These results were supported by A? aggregation kinetics investigations and transmission electron microscopy studies, which demonstrate the suitability of DAQ ring system to develop antiamyloid agents as pharmacological tools to study A? aggregation.
| S-EPMC4867481 | biostudies-literature
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:We previously reported that the activation of the nuclear factor of activated T-lymphocyte-3 (NFAT3) by carboplatin leads to renal apoptosis as a result of oxidative stress, which is reversed by N-acetylcysteine. Herein, we extend our previous work to provide evidence of the molecular mechanisms of haem oxygenase (HO)-1 in protecting against injury.Protective mechanisms of HO-1 in carboplatin-mediated renal apoptosis were examined in C57BL/6 mice and rat renal tubular cells (RTC) with HO-1 induction or inactivation/knockdown.The HO-1, induced by cobalt protoporphyrin, protected against carboplatin-induced renal injury in vivo. This protection was decreased by an inhibitor of HO-1 action, tin protoporphyrin. In cultures of RTC, carboplatin-induced apoptosis was similarly affected by HO-1 overexpression or knockdown. Carboplatin-mediated NFAT3 activation and apoptosis involve activation of the signalling kinases, extracellular signal regulated kinase, Jun N-terminal kinase and protein kinase C, and such activation was reversed in cells overexpressing HO-1. Both products of the HO-1 reaction, CO and bilirubin, inhibited (by 30-40%) NFAT3 activation and production of the pro-apoptotic proteins Bcl-XS/Bax. Additionally, the activation of NF?B was markedly decreased by HO-1 induction.HO-1 and its reaction products show anti-apoptotic effects in carboplatin-mediated renal injury. A novel functional NFAT3 binding site identified in the rat HO-1 promoter region was involved in producing a 1.5-fold to 2.5-fold increase in HO-1 induction by carboplatin. Nevertheless, only HO-1 overexpression and activation prior to the carboplatin challenge provided protection against carboplatin-induced injury.
| S-EPMC3081116 | biostudies-literature
Project description:Background and purposePrevious studies demonstrated that intraplaque haemorrhage increased the contents of cholesterol and oxidants in atherosclerotic plaques. The present study was aimed to test the hypothesis that enhanced expression of haem oxygenase-1 (HO-1) may stabilize vulnerable plaques.Experimental approachIntravascular ultrasound (IVUS) was performed to identify three similar abdominal aortic plaques in each of 58 fat-fed New Zealand rabbits after aortic balloon injury. With the guidance of IVUS, 50 microL autologous erythrocytes (RBC) or normal saline (NS) were injected from adventitia into two of the pre-selected plaques, respectively, whereas the third plaque served as a blank control. All rabbits were randomly divided into two groups, receiving intraperitoneal injection of haemin and saline respectively.Key resultsCompared with NS or control plaques, RBC plaques had more macrophage infiltration and lipid content, thinner plaque fibrous cap, and higher expression of inflammatory factors and incidence of plaque rupture. RBC plaques in the haemin group had about a 50% lower incidence of plaque rupture than those in the control group.Conclusions and implicationsHaem oxygenase-1 may eliminate haem or other oxidants, exert unexpected anti-oxidative and anti-inflammatory effects and serve as a promising approach to the direct inhibition of erythrocyte-induced plaque instability.
| S-EPMC2938819 | biostudies-literature
Project description:Certain selenoproteins such as GPX-1 (glutathione peroxidase-1) and TrxR1 (thioredoxin reductase-1) possess important antioxidant defence functions in vascular endothelial cells. Reduced selenoprotein activity during dietary selenium (Se) deficiency can result in a compensatory increase of other non-Se-dependent antioxidants, such as HO-1 (haem oxygenase-1) that may help to counteract the damaging effects of oxidant stress. However, the role of individual selenoproteins in regulating vascular-derived protective gene responses such as HO-1 is less understood. Using an oxidant stress model based on Se deficiency in BAECs (bovine aortic endothelial cells), we sought to determine whether TrxR1 activity may contribute to the differential regulation of HO-1 expression as a function of altered redox environment. Se-sufficient BAECs up-regulated HO-1 expression following stimulation with the pro-oxidant, 15-HPETE (15-hydroperoxyeicosatetraenoic acid), and levels of this antioxidant inversely correlated with EC apoptosis. While Se-deficient BAECs exhibited higher basal levels of HO-1, it was not up-regulated upon 15-HPETE treatment, which resulted in significantly higher levels of pro-apoptotic markers. Subsequent results showed that HO-1 induction depended on the activity of TrxR1, as proved with chemical inhibitor studies and direct inhibition with TrxR1 siRNA. Finally, restoring intracellular levels of the reduced substrate Trx (thioredoxin) in Sedeficient BAECs was sufficient to increase HO-1 activation following 15-HPETE stimulation. These data provide evidence for the involvement of the Trx/TrxR system, in the regulation of HO-1 expression in BAECs during pro-oxidant challenge.
| S-EPMC1386018 | biostudies-literature
Project description:Subarachnoid hemorrhage is a specific, life-threatening form of hemorrhagic stroke linked to high morbidity and mortality. It has been found that the choroid plexus of the brain ventricles forming the blood-cerebrospinal fluid barrier plays an important role in subarachnoid hemorrhage pathophysiology. Heme oxygenase-1 and biliverdin reductase are two of the key enzymes of the hemoglobin degradation cascade. Therefore, the aim of present study was to investigate changes in protein levels of heme oxygenase-1 and biliverdin reductase in the rat choroid plexus after experimental subarachnoid hemorrhage induced by injection of non-heparinized autologous blood to the cisterna magna. Artificial cerebrospinal fluid of the same volume as autologous blood was injected to mimic increased intracranial pressure in control rats. Immunohistochemical and Western blot analyses were used to monitor changes in the of heme oxygenase-1 and biliverdin reductase levels in the rat choroid plexus after induction of subarachnoid hemorrhage or artificial cerebrospinal fluid application for 1, 3, and 7 days. We found increased levels of heme oxygenase-1 and biliverdin reductase protein in the choroid plexus over the entire period following subarachnoid hemorrhage induction. The level of heme oxygenase-1 was the highest early (1 and 3 days) after subarachnoid hemorrhage indicating its importance in hemoglobin degradation. Increased levels of heme oxygenase-1 were also observed in the choroid plexus epithelial cells at all time points after application of artificial cerebrospinal fluid. Biliverdin reductase protein was detected mainly in the choroid plexus epithelial cells, with levels gradually increasing during subarachnoid hemorrhage. Our results suggest that heme oxygenase-1 and biliverdin reductase are involved not only in hemoglobin degradation but probably also in protecting choroid plexus epithelial cells and the blood-cerebrospinal fluid barrier from the negative effects of subarachnoid hemorrhage.
| S-EPMC7732689 | biostudies-literature