Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.14.99.3 (heme oxygenase)
 4,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 Zn-protoporphyrins on the predominant heme oxygenase isozyme present in the brain (HO-2) at activity, protein, and transcript levels and describes the ability of Sn-protoporphyrin to adversely affect this isozyme. Specifically, 6 h after a modest dose (50 mumol/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.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tin-protoporphyrin-mediated disruption in vivo of heme oxygenase-2 protein integrity and activity in rat brain. 140 70

We show by Northern blot analysis that human HO-2 is encoded by two transcripts (1.3 and 1.7 kb) and is a single-copy gene as judged by Southern blot analysis. We further provide evidence based on Northern blot and sequence analysis of a cDNA representing the larger transcript that the transcripts differ in the 3' untranslated region. A 274-base-pair DNA fragment from the rat heme oxygenase-2 gene (I. Cruse and M.D. Maines, 1988, J. Biol. Chem. 263, 3348-3353) was used to isolate a human HO-2 cDNA from a fetal kidney library in lambda gt11. The clone, designated hK-1, was sequenced and the cDNA insert was determined to be 1625 base pairs in length, encoding a protein of 313 amino acids. Two consensus polyadenylation signals separated by 440 nucleotides were identified in the 3' untranslated region. The size of the cDNA insert closely approximated the larger of two mRNAs. The nucleotide sequence was 88% identical to the rat HO-2 gene within the predicted coding region and the putative translation product was also estimated to be 88% identical to the rat gene product (M. O. Rotenberg and D. Maines, 1990, J. Biol. Chem. 265, 7501). The predicted size, 36 kDa, corresponded well with HO-2 detected in human testis microsomes by Western blot analysis. Further, the fusion protein expressed in Escherichia coli displayed significant heme oxygenase activity, which was inhibited by Zn- and Sn-protoporphyrins, known inhibitors of eukaryotic heme oxygenase, but not by sulfhydryl reagents.
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PMID:Human heme oxygenase-2: characterization and expression of a full-length cDNA and evidence suggesting that the two HO-2 transcripts may differ by choice of polyadenylation signal. 157 8

Synthetic metalloporphyrins decrease heme oxygenase (HO)-dependent bilirubin formation. Presently, the effects in vivo and in vitro of Sn- and Zn-protoporphyrins on HO-1 (HSP-32) and HO-2 at the protein and transcript levels were examined. Western blot analysis of HO-2 in testes microsomes of Sn-protoporphyrin-treated rats revealed a dramatic disruption of the integrity of the HO-2 protein. Similar observations were made with the liver and adrenal HO-2 and the NADPH-cytochrome P-450 reductase of treated rats. Northern blot analysis, however, suggested unaltered tissue levels of HO-2 transcripts (approximately 1.9 and approximately 1.3 kb). The HO-1 protein integrity in organs of treated rats was less dramatically affected by the metalloporphyrin and an increase in its 1.8 kb mRNA level in the testes was detected. Zn-protoporphyrin also increased HO-1 mRNA level in the testes, but did not affect HO-2 protein integrity. In in vitro studies with purified HO-1 and HO-2, both Sn- and Zn-protoporphyrins were equally inhibitory to HO-1 activity; Sn-protoporphyrin, however, was by far more inhibitory to HO-2-dependent activity than to that of HO-1. Together, these findings and the fact that HO-2 under normal conditions is the predominant form of the enzyme in most organs suggest that loss of HO-2 protein integrity may to a significant degree account for suppression of bilirubin formation by Sn-protoporphyrin. These in turn may reflect differences between HO-1 and HO-2, both at the transcriptional level with HO-2 being noninducible, and in structure/composition of the isozymes, with HO-2 being more labile.
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PMID:Differential regulation of heme oxygenase isozymes by Sn- and Zn-protoporphyrins: possible relevance to suppression of hyperbilirubinemia. 161 Aug 97

Chinese hamster ovary cells cultured in vitro were used to assess the role of glutathione metabolism in the induction of the 32-kDa stress protein. Enhanced synthesis of the 32-kDa protein was observed after cells were incubated with CdCl2 or diethylmaleate and protein was subjected to SDS-PAGE followed by fluorography. Concomitantly, in both cell preparations an increase in heme oxygenase activity was observed. Proteins from CdCl2- and diethylmaleate-treated cells were subjected to Western blotting and protein crossreacting with either rabbit antibody to rat liver heme oxygenase-1 (32,000 Mr) or rat testis heme oxygenase-2 (36,000 Mr) quantitated. The analysis indicated that the CdCl2 treatment increased the intensity of the HO-1 band 5.5-fold while the diethylmaleate treatment increased it three-fold relative to control. Neither treatment affected the intensity of HO-2 antibody binding. Incubation of cells with buthionine sulfoximine, under conditions which resulted in greater than or equal to 90% of the intracellular glutathione being depleted, enhanced synthesis of a 32-kDa protein when assayed by SDS-PAGE. This protein exhibited a Mr similar to the 32-kDa protein induced by either CdCl2 or diethylmaleate treatment. Proteins from buthionine sulfoximine and diethylmaleate-treated cells were mixed together and subjected to 2D PAGE. The resulting fluorograph demonstrated that both treatments produced identical patterns. In contrast, incubation of cells in diamide, a thiol oxidizing compound, resulted in enhanced synthesis of the 110-, 90-, and 73-kDa heat shock proteins but not the 32-kDa protein. The data presented have shown that depletion of glutathione by two independent methods, conjugation and inhibition of synthesis, enhances the synthesis of a 32-kDa protein identified as heme oxygenase-1; oxidation of glutathione, on the other hand did not. We interpret this to indicate that glutathione depletion rather than conjugation or oxidation represents one pathway for induction of heme oxygenase-1.
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PMID:Enhancement of heme oxygenase-1 synthesis by glutathione depletion in Chinese hamster ovary cells. 189 36

In Cebus apella monkey, as with other mammalian species tested to date, two different forms of haem oxygenase, HO-1 and HO-2, are detected. With the use of cDNA fragment corresponding to HO-1 nucleotides +71 to +833, blot hybridization of RNA revealed the presence of only one HO-1 mRNA of approx. 1.8 kb in both rat and monkey liver, kidney and brain. With the use of a full-length HO-2 DNA probe, blot hybridization of RNA isolated from the same rat organs revealed the presence of two HO-2 homologous transcripts of approx. 1.3 kb and approx. 1.9 kb. The same probe detected only one message of approx. 1.7 kb in monkey organs. The rat 1.3 kb mRNA has been previously shown [Rotenberg & Maines (1990) J. Biol. Chem. 265, 7501-7506] to encode HO-2 (36 kDa). The monkey 1.7 kb mRNA and the rat 1.3 kb mRNA encode proteins with similar molecular masses and immunochemical properties as indicated by Western-immunoblotting analysis. In rat organs the relative abundance of the two mRNAs differed as follows: in the liver the 1.3 kb mRNA was by far the most abundant form; in the brain equal amounts of the two mRNAs were detected, whereas in the kidney the 1.3 kb mRNA was somewhat more abundant. The protein encoded by the 1.8 kb HO-1 mRNA in the monkey did not exhibit immunochemical reactivity with antibody to rat HO-1 in Western blotting and direct e.l.i.s.a. analysis. The data suggest that, at the primary structural level, both HO-1 and HO-2 share extensive base sequence similarity in the rat and the Cebus apella monkey. The HO-1 protein, however, appears to undergo differential post-translational and/or conformational modifications in the two species, whereas the secondary structure of HO-2 protein and antigenic epitopes are conserved among the two mammalian species.
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PMID:Heterogeneity of haem oxygenase 1 and 2 isoenzymes. Rat and primate transcripts for isoenzyme 2 differ in number and size. 201 71

Catalytic activity of heme oxygenase (heme, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.3) isozymes, HO-1 and HO-2, permits production of physiologic isomers of bile pigments. In turn, bile pigments biliverdin and bilirubin are effective antioxidants in biological systems. In the rat brain we have identified only the HO-1 isozyme of heme oxygenase as a heat shock protein and defined hyperthermia as a stimulus that causes an increase in brain HO-1 protein. Exposure of male rats to 42 degrees C for 20 min caused a rapid and marked increase in brain 1.8-kilobase HO-1 mRNA. Specifically, a 33-fold increase in brain HO-1 mRNA was observed within 1 h and sustained for at least 6 h posttreatment. In contrast, the two HO-2 homologous transcripts (1.3 and 1.9 kilobases) did not respond to heat shock; neither the ratio nor the level of the two messages differed from that of the control when measured either at 1, 6, or 24 h after hyperthermia. The induction of a 1.8-kilobase HO-1 mRNA resulted in a pronounced increase in HO-1 protein 6 h after hyperthermia, as detected by both Western immunoblot and RIA. Immunocytochemistry of rat brain showed discrete localization of HO-1-like protein only in neurons of select brain regions. Six hours after heat shock, an intense increase in HO-1-like protein was observed in both Purkinje cells of the cerebellum and epithelial cells lining the cerebral aqueduct of the brain. We suggest that the increase in HO-1 protein, hence increased capacity to form bile pigments, represents a neuronal defense mechanism against heat shock stress.
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PMID:Rapid induction of heme oxygenase 1 mRNA and protein by hyperthermia in rat brain: heme oxygenase 2 is not a heat shock protein. 205 13

Blot hybridization of RNA isolated from rat brain revealed the presence of two HO-2 homologous transcripts (1.3 and 1.9 kilobases (kb] at all stages of development ranging from 1 day before birth to adulthood. The level of both HO-2 messages appeared to be developmentally regulated and a gradual increase was observed from prenatal day 1 to adulthood. The two transcripts were highly homologous as assayed through hybridization studies using probes derived from the 5' end, middle, and 3' end of a cloned rat testis HO-2 cDNA. The 1.3-kb mRNA was essentially identical in size to the testis HO-2 cDNA. The message was efficiently translated in the brain, and is believed to encode the HO-2 protein. It seems unlikely that the 1.9-kb species represents a precursor of the 1.3-kb mRNA, as it was also translated in vivo, although less efficiently than the smaller mRNA species. Neither of the two HO-2 mRNA species were induced by bacterial endotoxin. Unlike HO-2, only one HO-1 transcript of approximately 1.8 kb could be detected. This transcript was of very low abundance and was not developmentally regulated, but could be increased by bacterial endotoxin. The product of this induced message, however, was not detectable by Western immunoblot analysis using antibody raised against liver HO-1. An immunoprecipitate could be detected in brain microsomes by radioimmunoassay using the same antibody. This protein, however, exhibited antigenic properties different from that of the purified liver HO-1 or that of spleen microsomal HO-1. Brain heme oxygenase activity correlated well with the amount of immunoreactive HO-2 protein and both reflect the abundance of the 1.3-kb mRNA message over the course of development.
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PMID:Developmental expression of heme oxygenase isozymes in rat brain. Two HO-2 mRNAs are detected. 218 37

We have previously identified two isozymes of heme oxygenase, HO-1 and HO-2, in the rat liver exhibiting vastly different molecular biochemical properties, including their responses to various chemical inducers. In the present study of the livers of fetal and newborn rats (-1 day to 21 days) we observed marked differences in the developmental pattern of expression of the transcripts for the two forms of heme oxygenase. In addition, the transcripts for HO-1 and HO-2 vary in their number and response to treatment with cobalt chloride. Specifically, using a full length cDNA probe for HO-2, we observed the 1.3-kb mRNA previously shown to encode HO-2 in the testis, as well as a second less abundant transcript of 1.9 kb. An HO-1 cDNA probe detected only the anticipated single transcript of 1.8 kb. The abundance of each HO-2 homologous transcript was unaffected by cobalt chloride treatment (4 or 24 h) in newborn (7 days old) and adult rats. The 1.8-kb HO-1 mRNA, however, was markedly increased in abundance in both age groups by this treatment. The 1.3-kb HO-2 mRNA level nearly doubled after parturition, but remained essentially unchanged during the first 2 weeks of life, and only modestly increased by age 21 days. At all stages of development, the relative abundance of the 1.3- and 1.9-kb transcripts remained unchanged. In the case of 1.8-kb HO-1 mRNA, the level of mRNA was relatively constant during the first week of life, but was substantially reduced by age 14 days, and was further decreased by age 21 days and in the adult animals. In adult rats, the abundance of the 1.3-kb HO-2 mRNA did not markedly increase over that detected in the course of the early postparturition developmental period. The data suggest that the abundance of the two HO-2 homologous transcripts is not readily subject to regulation by chemicals at any stage of development. The expression of HO-1, on the other hand, is subject to such regulation throughout life, and its high transcript abundance in newborn rats may well reflect availability of an endogenous inducer.
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PMID:Heme oxygenase-2 mRNA: developmental expression in the rat liver and response to cobalt chloride. 224 Nov 54

We report on the detection and characterization of two forms of heme oxygenase in rabbit tissues and provide data suggesting that heme oxygenases in rat and rabbit are not identical and constitute a group of heterogenous proteins. Certain molecular properties, however, are shared by the isozymes in rat and rabbit; the predominant form of the enzyme in control liver and testis is HO-2, in the liver HO-1 is the inducible form, and in the brain HO-1 is not detectable. HO-1 was purified from liver of rabbits treated with bromobenzene to near homogeneity with a specific activity of 8,270 nmol of bilirubin/mg/h and compared with a homogenous preparation of rat HO-1 with a specific activity of 6,220, also obtained from bromobenzene-treated animals. Rat and rabbit HO-1, on sodium dodecyl sulfate-polyacrylamide gel, had molecular weights of 30,000 and 30,700, respectively. Rabbit HO-2 was partially purified from testis to a specific activity of 386 nmol of bilirubin/mg/h and compared with a purified preparation of rat testis HO-2 with a specific activity of 5,700. Using Western immunoblotting, rabbit HO-2 displayed intense cross-reactivity with antibody raised in rabbit to sodium dodecyl sulfate-denatured rat HO-2, and had a substantially larger molecular weight than the rat HO-2 (42,000 versus 36,000). Rabbit HO-1 did not cross-react with antibody to rat HO-1 which was also raised in rabbit. Unlike the rat enzymes, rabbit HO-1 and HO-2 did not differ in thermolability. It is speculated that HO-1 in rat and rabbit, and possibly HO-2, have evolved from divergent evolution of a common ancestral gene(s).
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PMID:Multiplicity of heme oxygenase isozymes. HO-1 and HO-2 are different molecular species in rat and rabbit. 291 Aug 57

A radioimmunoassay was developed to assess the response of testicular HO-1 to agents known to increase the microsomal heme oxygenase activity. Treatment of rats with human chorionic gonadotropin (hCG) increased the microsomal heme oxygenase activity in rat testis. The following data suggest that the increase was specific to the HO-1 isozyme: (a) The elution profile of heme oxygenase activity from a DEAE-Sephacel column showed an increase in the HO-1 peak, but not in the HO-2 peak, (b) the Western immunoblot of the testis microsomes showed an increase in HO-1 protein, and (c) the amount of HO-1 protein that was present in the microsomes, when measured by radioimmunoassay, was doubled. Using radioimmunoassay, it was shown that other agents known to increase the testicular heme oxygenase, sodium arsenate and sodium arsenite, also increased the microsomal content of HO-1. An inhibitor of the testicular microsomal heme oxygenase activity, cadmium, also increased the microsomal HO-1 protein. The findings suggest that inducibility of HO-1 extends to tissues other than the liver, in this instance, the testis, and further support the possibility that HO-1 is the only inducible form of heme oxygenase.
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PMID:Selective induction of heme oxygenase-1 isozyme in rat testis by human chorionic gonadotropin. 291 70


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