Showing papers on "Heme oxygenase published in 1992"

Induction of heme oxygenase is a rapid, protective response in rhabdomyolysis in the rat

Abstract: Heme proteins such as myoglobin or hemoglobin, when released into the extracellular space, can instigate tissue toxicity. Myoglobin is directly implicated in the pathogenesis of renal failure in rhabdomyolysis. In the glycerol model of this syndrome, we demonstrate that the kidney responds to such inordinate amounts of heme proteins by inducing the heme-degradative enzyme, heme oxygenase, as well as increasing the synthesis of ferritin, the major cellular repository for iron. Prior recruitment of this response with a single preinfusion of hemoglobin prevents kidney failure and drastically reduces mortality (from 100% to 14%). Conversely, ablating this response with a competitive inhibitor of heme oxygenase exacerbates kidney dysfunction. We provide the first in vivo evidence that induction of heme oxygenase coupled to ferritin synthesis is a rapid, protective antioxidant response. Our findings suggest a therapeutic strategy for populations at a high risk for rhabdomyolysis.

Heme Oxygenase: Clinical Applications and Functions

Abstract: AN OVERVIEW OF PORPHYRINS AND HEMES AND THEIR BIOSYNTHETIC PATHWAY. Introduction. Porphyrins and Metalloporphyrins-General Properties. d-Aminolevulinate Synthetase. d-Aminolevulinate Dehydratase. Porphobilinogen Deaminase and Uroporphyrinogen III Synthetase. Uroporphyrinogen III Decarboxylase. Coproporphyrinogen Oxidase. Protoporphyrin Oxidase. Ferrochelatase. Disorders of Porphyrin Metabolism (Porphyrias). References. BILIVERDIN REDUCTASE. Introduction. References. HEME OXYGENASE AND HEME DEGRADING SYSTEMS. Introduction. Nonenzymatic Degradation of Heme by Heme Oxygenase. Enzymatic Degradation of Heme by Heme Oxygenase. References. CHARACTERIZATION AND REGULATION OF HEME OXYGENASE ISOZYMES AT THE MOLECULAR LEVEL. Background. Molecular and Biochemical Properties of Heme Oxygenase Isozymes. Molecular Cloning and Characterization of HO-1 and HO-2. References. REGULATION OF HEME OXYGENASE ACTIVITY. RESULTANT MODULATING EFFECT ON HEMOPROTEIN-DEPENDENT FUNCTIONS. Introduction. Mechanisms of Heme Oxygenase Regulation. Consequences of Induction of Heme Oxygenase on Drug Steroid and Prostaglandin Metabolic Systems. References. NEONATAL JAUNDICE. Introduction: Jaundice in the Newborn. Factors Influencing Serum Bilirubin Levels in the Newborn. Toxicity of Bilirubin to the Newborn. Developmental Changes in Cellular Ability to Produce Bilirubin in the Newborn. Possible Physiological Importance of Bilirubin. Treatment of Hyperbilirubinemia. References.

Endogenous glutathione levels modulate both constitutive and UVA radiation/hydrogen peroxide inducible expression of the human heme oxygenase gene.

Abstract: Induction of the expression of the mammalian heme oxygenase gene appears to be a general response to oxidant stress. In view of the role of glutathione in protecting cells against solar UVA radiation and other forms of oxidant stress, we have investigated the relationship between intracellular glutathione levels and the inducibility of the human heme oxygenase gene after treatment of populations of cultured skin fibroblasts with either UVA radiation or hydrogen peroxide. We observe a clear relationship between cellular glutathione status and both the constitutive and oxidant-inducible accumulation of heme oxygenase mRNA. Glutathione depletion may lead to enhanced gene expression either as a result of the potentiated accumulation of active oxygen intermediates or as a result of the direct influence of glutathione on a critical target involved in signal transduction.

Normal and heat-induced patterns of expression of heme oxygenase-1 (HSP32) in rat brain: hyperthermia causes rapid induction of mRNA and protein.

Abstract: Most cells possess a variety of mechanisms, such as high levels of glutathione, that guard against cytotoxic free radicals, which are suspected in the etiology of various neurological deficits. Neurons, however, are deficient in this antioxidant source. The list of other potent antioxidants includes the bile pigments biliverdin and bilirubin. Heme oxygenase (HO) isozymes, HO-1 (HSP32) and HO-2, catalyze the rate-limiting step in the only biological pathway by which bile pigments are produced. In this study, heat shock is identified as the only stimulus reported to date that can alter expression in brain HO-1 of protein and mRNA in vivo. Using a HO-1 cDNA probe, we examined the level of HO-1 mRNA in normal rat brain and in brain 1 and 6 h following heat shock. Exposure of male rats to 42 degrees C for 20 min caused a 20-fold increase in brain HO-1 1.8-kb mRNA within 1 h after treatment. Quantification of brain HO-1 protein by HO-1 radioimmunoassay revealed a fourfold increase at 6 h posttreatment. In normal brain, HO-1 protein was sparsely expressed in few select neuronal and nonneuronal cell populations in forebrain, diencephalon, cerebellum, and brainstem regions. Six hours following heat shock, an intense increase in HO-1 protein in glia throughout the brain, ependyma lining the ventricles of the brain, paraventricular nucleus, Purkinje cell layer of the cerebellum, and cochlear nucleus of brainstem was observed. We suggest that increases in HO-1 transcript and protein reflect a means to elevate levels of antioxidants in cells with compromised defense mechanisms caused by stress.

Heme oxygenase is a heat shock protein and PEST protein in rat astroglial cells.

Abstract: Cultured rat forebrain astrocytes contained significant amounts of immunostainable heme oxygenase-1 (HO-1) isozyme, whereas HO-1 was undetectable in spontaneously transformed rat astroglial cells (ATs). HO-1 was inducible in both cell types by heat shock and by submicromolar amounts of H2O2. Inhibition of RNA synthesis with actinomycin D or protein synthesis with cycloheximide resulted in the rapid loss of immunostainable heme oxygenase in astrocytes. Analysis of the primary structure of heme oxygenase suggests that it is a PEST protein, i.e., targeted for rapid turnover. © 1992 Wiley-Liss, Inc.

Suppression of bilirubin production in the Crigler-Najjar type I syndrome: studies with the heme oxygenase inhibitor tin-mesoporphyrin.

Abstract: The heme oxygenase inhibitor tin-mesoporphyrin was used to moderate hyperbilirubinemia in two 17-year-old boys with Crigler-Najjar type I syndrome. Both patients had histories of recent, progressive neurological deterioration and plasma bilirubin concentrations on admission to the hospital were 34.5 and 28.5 mg/dL. Throughout hospitalization lasting more than 400 days, both patients underwent 10 hours of phototherapy nightly and consumed constant weight-maintaining diets. They were treated with intermittent plasmapheresis and two periods of tin-mesoporphyrin therapy comprising, in the first study period, 40 doses of 0.5 mumol/kg body weight and in the second study period, 70 doses of 1.0 mumol/kg body weight. Plasma bilirubin concentrations were decreased in both patients to varying degrees as was the rebound hyperbilirubinemia which occurs after plasmapheresis. The prolonged treatments with the inhibitor were well-tolerated and no progression of the preexisting neurological impairments occurred during the clinical trials. The results of this study suggest that the clinical application of an effective heme oxygenase inhibitor can provide a potentially useful, pharmacological adjunct to presently available therapeutic modalities for controlling episodes of acute, severe jaundice in this but lethal disorder.

Endothelial cell heme oxygenase and ferritin induction by heme proteins: a possible mechanism limiting shock damage.

Abstract: Acutely, hemin sensitizes endothelial cells to oxidants but chronically protects the endothelium through the induction of ferritin. By releasing its heme, methemoglobin can sensitize endothelial cells in a fashion similar to free hemin. Furthermore, prolonged incubation with the endothelium allows methemoglobin to induce heme oxygenase and ferritin and concomitantly to modulate oxidant-mediated cytotoxicity. Methemoglobin but not hemoglobin, metmyoglobin or cytochrome c induces heme oxygenase and ferritin. Heme needs to be released from methemoglobin, since sodium cyanide, haptoglobin, and hemopexin inhibit the induction of these proteins. Neutrophils can oxidize hemoglobin to methemoglobin, which can subsequently induce both heme oxygenase and ferritin. We speculate that in shock with disseminated intravascular coagulation, marginated PMNs oxidize hemoglobin to heme-releasing methemoglobin. If critical defenses such as haptoglobin and hemopexin are overwhelmed, heme enters the endothelin cells, sensitizing them to oxidant damage. Endothelial cell adaptation via heme-induced heme oxygenase and ferritin production might limit ultimate progression to pulmonary and other vascular leak syndromes.

Differential induction of heme oxygenase in the hepatocarcinoma cell line (Hep3B) by environmental agents

Abstract: In situ hybridization and Northern analysis of heme oxygenase (HO) mRNA was used to determine the induction and expression of HO by various environmental agents. Exposure of Hep3B cells to hemin (10 μM) for as little as 5 min resulted in significant production of HO transcripts and mRNA expression as seen by in situ hybridization. We followed the pattern of HO transcript accumulation by heme and results indicate that the peak of induction of HO by heme was reached between 10 and 20 minutes. Other metalloporphyrins were all effective in inducing HO mRNA after 1 h exposure. On the other hand, CoCl2 caused accumulation of HO mRNA at a later time than seen with the metalloporphyrins. However, lipopolysaccharide (LPS) gave a more immediate effect on HO induction which was somewhat similar to heme in its time course. Direct measurements of HO activity revealed that enzyme activity could be detected after about 20 min exposure to hemin, and this activity was inhibited by tin protoporphyrin (SnPP). The different pattern of HO mRNA induction by LPS as contrasted with CoCl2 suggests that LPS may act through a different translational factor, or stimulate free radical formation and the subsequent release of heme and induction of HO. These results indicate that heme causes accumulation of HO mRNA by a different mechanism than that of CoCl2. Finally, LPS shares a concomitant effect on induction of HO as an acute phase reactant type protein.

Tin-protoporphyrin-mediated disruption in vivo of heme oxygenase-2 protein integrity and activity in rat brain.

Abstract: The ability of synthetic metalloporphyrins to suppress heme oxygenase activity and bilirubin formation has recently become of considerable clinical and experimental interest for suppression of jaundice in humans, including neonatal hyperbilirubinemia. The present investigation compares the biochemical effects of Sn- and Znprotoporphyrins on the predominant heme oxygenase iso-zyme present in the brain (HO-2) at activity, protein, and transcript levels and describes the ability of Sn-protopor-phyrin to adversely affect this isozyme. Specifically, 6 h after a modest dose (50 μmol/kg, i.v.) of Sn-protoporphyrin, heme oxygenase activity in rat brain was nearly undetectable. In addition, as revealed by Western blot analysis, HO-2 protein level was decreased by 20% and the electrophoretic behavior of the protein in the microsomal membranes was altered. Moreover, the activity of NADPH-cytochrome P-450 reductase, which is required for the oxidation of heme molecule, was markedly decreased (60% of control). Western immunoblot analysis revealed also a pronounced decrease in the reductase protein level. The inducible form of heme oxygenase, HO-1, was not detectable by immunoblotting in brain microsomes of either control or Sn-protoporphyrin-treated animals. Northern blot analyses did not reveal decreases in the levels of the single HO-1 mRNA (1.8 kb) or the two HO-2 transcripts (1.3 and 1.9 kb), suggesting that Sn-protoporphyrin mediates its effects on heme oxygenase isozymes at the protein level. Zn-protoporphyrin, on the other hand, had no deleterious effect on brain parameters presently investigated. The data suggest that Sn-protoporphyrin exerts its inhibitory effects on heme oxygenase activity in the brain through multiple mechanisms involving direct effect on HO-2 protein and its cellular level, inhibiting NADPH-cytochrome P-450 reductase activity, decreasing the cellular content of the reductase, as well as inhibiting heme oxygenase activity by serving as a competitive inhibitor. We suggest that Zn-protoporphyrin may be the safer alternative if metalloporphyrins are to be used to control hyperbilirubinemia.

Comparative effects of tin- and zinc-protoporphyrin on steroidogenesis: tin-protoporphyrin is a potent inhibitor of cytochrome P-450-dependent activities in the rat adrenals.

Abstract: Synthetic metalloporphyins inhibit formation of bilirubin by the heme oxygenase system, an ability that is of considerable experimental and clinical interest for suppression of jaundice in the newborn. The present investigation compares the consequences of treatment with Sn- and Zn-protoporphyrin on hemoprotein-dependent enzymes of the rat adrenals and corticosterone production and defines Sn-protoporphyrin as a potent toxin to adrenal functions. Treatment of rats with Sn-protoporphyrin (two doses of 50 μmol/kg, in 7 d) resulted in a marked reduction of 30–40% in cytochrome P-450-dependent adrenal microsomal 21α-hydroxylase and mitochondrial 11β-hydroxylase activities. In the serum, the levels of corticosterone were reduced to about 70% of the control value. In addition, the mitochondrial cytochrome P-450SCC activity was decreased by about 50%. This decrease, however, could not be attributed to a reduced total heme level or an accelerated heme degradatory activity. Disruption by Sn-protoporphyrin of adrenal hemoprotein-dependent functions was not restricted to steroidogenic activities and encompassed drug metabolism activity of the organ; benzo(a)pyrene hydroxylase activity of both the microsomal and the mitochondrial fractions, as well as the microsomal NADPH-cytochrome P-450 reductase activity, were significantly reduced. Zn-protoporphyrin did not cause significant alterations in the above measured parameters although it too was effective in inhibiting the hepatic microsomal heme oxygenase activity. In light of the presently defined adverse effects of Sn-protoporphyrin on adrenal Steroidogenesis, we suggest Zn-protoporphyrin is the agent of choice for potential use in treatment of hyperbilirubinemia in humans.

Heme oxygenase: expression in human retina and modulation by stress agents in a human retinoblastoma cell model system.

Abstract: PCR and Southern blot analyses demonstrate that mRNA for heme oxygenase (HO), a well known “stress protein” in a number of tissues, is present in human retina. Western and northern blots show that the protein and mRNA are also expressed in human Y-79 retinoblastoma cells in culture and that the HO enzyme is rapidly induced by its substrate, heme. Moreover, HO is also induced by two chemicals, sodium arsenite and menadione, that act as agents of oxidative stress. HO is the regulatory enzyme in the heme degradative pathway and an increase in its activity could lead to the accumulation of bilirubin, an antioxidant, in the cell at the expense of heme, a prooxidant. The HO pathway may thus be of importance in protecting the retina against oxidative stress in vivo. Moreover, the Y-79 culture system should provide an excellent model for use in examining stress mechanisms in retinal cells at a molecular level.

Tributyltin is a potent inducer of the heat shock response in human diploid fibroblasts.

Abstract: Submicromolar concentrations of tributyltin (TBT), a commercially used organotin compound, were found to induce the expression of several stress proteins, most notably HSP89 and HSP70, in IMR-90 human diploid fibroblats in a time- and dose-dependent manner. This induction can be demonstrated by quantitation of 1) synthesis of the heat shock proteins (HSPs), 2) relative abundance of mRNA of hsp70, and 3) transient expression of a human hsp70 promoter driven reporter gene. TBT also increased the abundance of mRNA of heme oxygenase, whereas heat shock was without effect. Analysis of protein binding to a consensus heat shock element (HSE)by electrophoretic mobility shift assay suggests that the induction of the heat shock response by TBT was attributable to activation of the heat shock transcription factor (HSTF). © 1992 Wiley-Liss, Inc.

Nucleotide sequence of cDNA for porcine heme oxygenase and its expression in Escherichia coli.

Abstract: The nucleotide sequence of a cDNA for porcine heme oxygenase was determined The open reading frame encoded a polypeptide of 288 amino acid residues with a molecular mass of 33,074 Da A prokaryotic expression plasmid carrying porcine heme oxygenase cDNA was constructed and transfected into Escherichia coli cells The full-length heme oxygenase expressed was localized in the bacterial membranes Two small-sized heme oxygenases with no membrane-bound properties were also detected, suggesting that in E coli cells a considerable amount of the enzyme expressed was degraded

Regulation of heme pathway in regenerating mouse liver.

Abstract: 1. 1. δ-Aminolevulinic acid synthetase (ALA-S), rhodanese and microsomal heme oxygenase (MHO), were quantitated in Cl4C induced regenerating mouse liver. 2. 2. Maximal hepatomegalia was observed at 48 hr after i.p. injection of a single dose of the toxin. 3. 3. ALA-S activity decreased on day 2, and then significantly increased (50%) between days 3 and 7, returning afterwards to control values. 4. 4. Cytoplasmic rhodanese, as well as MHO activities, exhibited a clear correlation as compared with the ALA-S activity profile. 5. 5. Porphyrin biosynthesis from precursor δ-aminolevulinic acid (ALA) was significantly increased even after 15 days of intoxication. 6. 6. Present results would indicate that Cl4C is acting in a dual fashion.