Genetic regulation of the heme pathway.
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Animals↗
Biomedical subjects
S Sassa
Publications and source records attributed to S Sassa.
Immunochemical study of uroporphyrinogen decarboxylase in a patient with mild hepatoerythropoietic porphyria.
Hepatoerythropoietic porphyria (HEP) is due to a marked deficiency of uroporphyrinogen (URO) decarboxylase, a cytosolic enzyme in the heme biosynthetic pathway. Using a radioimmunoassay method, we determined the concentration of URO decarboxylase protein in erythrocytes from a patient with mild HEP and found that the enzyme protein concentration had markedly decreased to less than 7% of the normal controls. This finding, however, was in contrast to the enzyme activity in the patient's erythrocytes, which was 16% of normal control levels and different from previously reported HEP cases in that erythrocytes in our patient contained disproportionately elevated URO decarboxylase activity in comparison to its immunoreactive material. Our findings suggests the possibility of a mutant isozyme in this patient that is not immunoreactive with an antibody raised against the normal enzyme.
Adult↗
Inhibition of erythroid differentiation of mouse erythroleukemia cells by a macrophage product(s).
Conditioned media from established murine macrophage cell lines (RAW264.7, P388D1, and WEHI-3) incubated with endotoxin in a serum-free medium contain an erythroid inhibitory activity (EIA) that inhibited dimethylsulfoxide-induced erythroid differentiation of mouse Friend virus-transformed erythroleukemia cells. Endotoxin itself has no EIA activity. Partial purification of EIA demonstrated that it is distinct from other macrophage products such as IL-1, TGF beta, ECGF, FGF, G-CSF, hepatocyte stimulating factor, interferon, PDGF, and cachectin/TNF. These findings indicate that EIA is a macrophage product distinct from other monokines.
Animals↗
Enzymatic defect in a child with hereditary hepatic porphyria due to homozygous delta-aminolevulinic acid dehydratase deficiency: immunochemical studies.
Immunochemical studies of the enzyme defect in the first reported child with acute hepatic porphyria due to homozygous delta-aminolevulinic acid dehydratase deficiency are described. This enzyme activity was markedly decreased (approximately 2% of the normal control level) in the proband, a 3-year-old boy, and intermediately decreased (23% to 57%) in both parents, in both grandfathers, and in a sister, but it was normal in two siblings and in both grandmothers. In contrast to the profound decrease in delta-aminolevulinic acid dehydratase activity, the immunoreactive enzyme protein in the child's erythrocytes was decreased to only 28% of the normal control level, suggesting the presence of positive cross-reactive material. In other family members with abnormally decreased delta-aminolevulinic acid dehydratase activity, and in the proband immediately after transfusion of normal RBCs, the positive cross-reactive material was not detectable. The immunochemical and enzyme activity data support the idea that delta-aminolevulinic acid dehydratase deficiency in this porphyric child is associated with the production of a catalytically abnormal enzyme protein.
Blood Proteins↗
Chloro-substituent sites and probability of co-planarity in polychlorinated biphenyls in determining uroporphyrin formation in cultured liver cells.
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Cells, Cultured↗
Induction of haem synthesis in Hep G2 human hepatoma cells by dimethyl sulphoxide. A transcriptionally activated event.
Exposure of cultured human hepatoma cells (Hep G2) to medium containing 2% (v/v) dimethyl sulphoxide resulted in an approximate doubling in the activity of delta-aminolaevulinate dehydratase, an increase in the haem content and a decreased growth rate; induced enzyme activity was decrease by 50% after treatment with alpha-amanitin. The findings are strikingly similar to those seen in murine Friend-virus-transformed erythroleukaemia cells.
Amanitins↗
Studies of the influence of chloro-substituent sites and conformational energy in polychlorinated biphenyls on uroporphyrin formation in chick-embryo liver cell cultures.
Treatment of cultured chick-embryo liver cells with polychlorinated biphenyls (PCB) results in decreased uroporphyrinogen decarboxylase activity and increased uroporphyrin accumulation. In the present study we examined the effect of the chloro- or bromo-substituent sites in biphenyls (BP) on uroporphyrin accumulation in cultured hepatocytes and the three-dimensional structure of these congeners determined by molecular orbital calculations using a MNDO ('modified neglect of diatomic overlap') method. Among 20 congeners examined, those which were effective in stimulating porphyrin accumulation contained at least two Cl or Br atoms at the lateral adjacent positions in each phenyl ring, e.g. 3,4,3',4'-tetrachloro-, 2,4,3',4'-tetrachloro-, 3,4,5,3',4',5'-hexachloro- and 3,4,5,3',4',5'-hexabromobiphenyl, whereas those which contained less than two halogen atoms or more than three halogen atoms in each phenyl ring or those which contained halogen atoms at 2,2'-positions were not effective. On the basis of the conformational energy (delta E, difference from the most stable conformational energy), which is calculated as a function of the dihedral angle (theta) between the two phenyl rings, biphenyl congeners can be classified into four groups with different conformations. The conformation of active PCB was relatively flexible, whereas inactive species had a rigidly angulated conformation. Furthermore, the calculated probability of the conformation distribution for each congener indicated that the probability of co-planarity was higher for active biphenyls than for inactive congeners. These structural characteristics suggest the significance of both the chloro-substituent sites and the conformational energy reflecting the phenyl-ring twist angles in determining the inhibitory effect of PCB on uroporphyrinogen decarboxylase activity.
Animals↗
Priming procedure and cell isolation for study on luteal cell response to peptide hormone in the rat.
The objective of this study was to develop a method of isolating luteal cells from the ovaries of immature rats pretreated with pregnant mare serum gonadotrophin (PMSG). After the ovaries were digested by collagenase and trypsin, the corpora lutea were obtained from the tissues, gently pressed in a test tube, and then placed on a sucrose density gradient. The two bands that appeared in the tube after centrifugation were designated S1 (top band) and S2 (bottom band). Progesterone and 20 alpha-dihydroprogesterone (20 alpha-DHP) secreted by the isolated cells during short-term incubation were measured by radioimmunoassay (RIA). A larger amount of progesterone, i.e., 60 to 260 ng/10(5) cells, was secreted by S1 cells than by S2 cells during the 18-h incubation. These results suggest that this simple procedure for isolation of luteal cells may provide a suitable model for in vitro studies of the luteal function.
20-alpha-Dihydroprogesterone↗
Heme binding to murine erythroleukemia cells. Evidence for a heme receptor.
Friend virus transformed murine erythroleukemia (MEL) cells are known to take up heme from the surrounding medium and to incorporate it into newly synthesized hemoglobin (Granick, J. L., and Sassa, S. (1978) J. Biol. Chem. 253, 5402-5406), but the mechanism of its uptake is unknown. We hypothesized the existence of a specific receptor for heme in the plasma membrane. Using [55Fe]heme, we examined the characteristics of its interaction with MEL cells at 4 degrees C. [55Fe]heme binding reached equilibrium within 4 h, was 80% dissociable by 16 h, and was independent of pH over the range 7.0-8.2. Specific heme binding was linear with cell number, and competitive binding studies with various heme analogues, such as free protoporphyrin IX, metal-substituted protoporphyrin IX, Fe-mesoporphyrin IX, and Fe-deuteroporphyrin IX, revealed significant stereospecificity for Fe-protoporphyrin IX. The dissociation constant of the interaction was 0.03 nM-1 with no evidence of cooperativity or multiple classes of sites. The average number of sites/cell was approximately 10,300. Reduction of binding following preincubation with trypsin, in conjunction with the above data, suggests that this cell type may display a receptor for heme which is comprised, as least in part, of protein.
Animals↗
Hereditary tyrosinemia. Formation of succinylacetone-amino acid adducts.
Succinylacetone (SA) (4,6-dioxoheptanoic acid) is an abnormal metabolite produced in patients with hereditary tyrosinemia as a consequence of an inherited deficiency of fumaryl acetoacetate hydrolase activity. Patients with this disease are associated with a number of abnormalities, including aminoaciduria, proteinuria, liver failure, commonly hepatoma, and decreased GSH concentration in the liver. In the course of our studies of tyrosinemia, we found that the urine of patients with this disorder contains material(s) that absorbs light at 315 nm. We investigated the nature of the 315 nm material in detail. SA was found to react with amino acids and protein nonenzymatically, to form stable adducts at physiological temperature and pH. All SA adducts with amino acids and/or proteins exhibited an absorption peak at 315 nm. Although all amino acids reacted with SA, the most reactive amino acid was lysine (Lys), followed, in order, by glycine, methionine, phenylalanine, serine, alanine, and glutamine. SA-adducts were unstable at pH below 6, while they were made considerably more stable after reduction with NaBH4, suggesting that SA forms an adduct via Schiff base formation. High-performance liquid chromatography (HPLC) analysis of urines from patients with tyrosinemia revealed the existence of SA-glycine, SA-methionine, SA-tyrosine, and SA-phenylalanine. After digestion of urines with proteinase K, three more HPLC peaks appeared, which all corresponded to SA-Lys adducts. TLC analysis of SA-Lys showed that SA-Lys could form as many as seven different adducts. No SA-adduct peaks were observed in HPLC in urines from normal subjects, patients with other forms of aminoaciduria, or patients with the nephrotic syndrome. In addition to amino acids and proteins, SA reacted with reduced glutathione (GSH) and formed a stable adduct. These findings suggest that SA adduct formation with amino acids, GSH, and proteins is a significant process occurring in tyrosinemia, and may account for certain of the pathologic findings in this hereditary disorder.
Amino Acid Metabolism, Inborn Errors↗
Long-term administration of massive doses of Sn-protoporphyrin in anemic mutant mice (sphha/sphha).
The effects of long-term administration of very large doses of Sn-protoporphyrin on hematological indices, histological changes, plasma bilirubin levels, tissue heme oxygenase activity, and activities of heme biosynthetic enzymes, were examined in genetically anemic mutant mice with hemolytic anemia (sphha/sphha). Long-term weekly treatment with Sn-protoporphyrin (100 mumol/kg body weight for 32 wk) did not alter hematological indices, histological findings, or enzyme activities related to heme biosynthesis, even though it resulted in sustained decreases in microsomal heme oxygenase activity in the liver, kidney, and spleen, and a prolonged decrease in plasma bilirubin concentration. Inhibition of heme oxygenase did not alter the level of cytochrome P-450 in the liver and the kidney. The results indicate that long-term treatment with massive doses of Sn-protoporphyrin suppresses bilirubin formation but does not produce significant histopathological changes or appreciably interfere with heme synthesis, in this strain of genetically anemic mice. These findings provide further support for the idea that suppression of heme degradation to bile pigment by the inhibition of heme oxygenase may prove useful to the prevention of severe hyperbilirubinemia in humans.
5-Aminolevulinate Synthetase↗
Hormonal regulation of heme oxygenase induction in avian hepatocyte culture.
The effects of various hormones were examined on the induction of heme oxygenase in monolayer cultures in chick embryo hepatocytes maintained in a chemically defined medium. Addition of insulin to the cultured cells markedly suppressed the activity of basal as well as Co2+-induced heme oxygenase. Treatment of cells with hydrocortisone also suppressed the basal enzyme activity, while the Co2+-induced enzyme activity was enhanced slightly. In contrast, triiodothyronine addition to the culture caused a slight increase of both uninduced and induced levels of the enzyme. This stimulatory effect of triiodothyronine was enhanced significantly by prolonged incubation of cells (48-96 hr) in the serum-free medium. These findings indicate that heme oxygenase synthesis can be substantially altered by changing the hormonal environment of the hepatocytes. Furthermore, the induction of heme oxygenase by Co2+ was inhibited by glucagon, dibutyryl cAMP and theophylline in a dose-dependent manner, suggesting that the enzyme induction may also be controlled by changes in cAMP levels.
5-Aminolevulinate Synthetase↗
Modulation of cell attachment to culture support by pH, fibronectin, hemin, and cobalt protoporphyrin.
When chick embryo fibroblasts were seeded in the presence of minimum essential medium supplemented with 1% (v/v) horse serum, the rate of cell attachment, after 1 hr incubation, was less than 5% at pH 6.5 and about 50% and 80% at pH 7.5 and pH 8.3, respectively. If, however, cultures were pretreated with fibronectin, a substance that promotes cell adhesion, a high rate of cell attachment was also observed at pH 6.5. Two other compounds of totally different chemical nature, cobalt-protoporphyrin (CoPP) and hemin, also enhanced cell attachment at pH 6.5. CoPP was shown to increase the synthesis of proteins, but it did not affect the intracellular heme content of cells incubated at pH 6.5. The possibility that CoPP, and presumably also hemin, induce cell attachment by promoting the synthesis of a fibronectin like protein is discussed.
Animals↗
Polychlorinated aromatic hydrocarbon lethality, mixed-function oxidase induction, and uroporphyrinogen decarboxylase inhibition in the chick embryo: dissociation of dose-response relationships.
Effects on survival of chick embryos and on the activity of hepatic enzymes involved in heme biosynthesis and hemoprotein function were compared as a function of dose of 3,4,3',4'-tetrachlorobiphenyl (TCB), 3,4,5,3',4',5'-hexachlorobiphenyl (HCB), 2,3,6,2',3',6'-HCB, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at 24 hr and at 9 days after polyhalogenated aromatic hydrocarbon (PAH) administration. 2,3,6,2',3',6'-HCB did not alter enzyme activities or survival. The other PAH increased delta-aminolevulinic acid synthetase up to 10- to 20-fold after 24 hr or 9 days of exposure. Hepatic porphyrins and uroporphyrinogen decarboxylase (Uro-D) activity were unaffected except by 3,4,3',4'-TCB which after 9 days of exposure increased porphyrins slightly (less than 2-fold) at 500 and 1000 nmol/egg and decreased Uro-D by 20% at 1000 nmol/egg. 3,4,3',4'-TCB, 3,4,5,3',4',5'-HCB, and TCDD preferentially induced cytochrome P-448-mediated mixed-function oxidases. The degree of induction was the same or greater after 9 days of exposure than after 24 hr. The three PAH increased aminopyrine demethylase and 7-ethoxycoumarin deethylase up to 2-fold and aryl hydrocarbon hydroxylase (AHH) 10- to 12-fold. 7-Ethoxyresorufin deethylase (7-ER) was increased 45-fold by 3,4,3',4'-TCB, 28-fold by 3,4,5,3',4',5'-HCB, and 55-fold by TCDD. The three PAH decreased survival after 9 days but not after 24 hr. Decreases in survival were accompanied by decreased thymus weights and increased incidences of pericardial and subcutaneous edema in surviving embryos. 3,4,3',4'-TCB caused dose-related decreases in survival at 100 to 1000 nmol/egg. 3,4,5,3',4',5'-HCB decreased survival at 500 and 1000 nmol/egg and TCDD at 6 nmol/egg. The effects on survival were greatest for 3,4,3',4',-TCB and least for TCDD, notwithstanding that all three PAH induced AHH to the same degree and that TCDD caused the greatest induction of 7-ER. The results demonstrate that the dose-response relationships for hepatic induction and lethality are dissociated and that the maximal induction levels are not correlated with the incidence of lethality. The findings indicate that the induction per se does not lead directly to toxicity and that other factors must intervene. The results further show that PAH lethality occurs independently of effects on hepatic Uro-D.
5-Aminolevulinate Synthetase↗
The liver excretes large amounts of heme into bile when heme oxygenase is inhibited competitively by Sn-protoporphyrin.
TinIV-protoporphyrin IX (Sn-protoporphyrin) potently inhibits heme degradation to bilirubin in vitro and in vivo, and it completely suppresses neonatal hyperbilirubinemia in experimental animals, including primates. It also reduces plasma bilirubin levels in certain naturally occurring or induced forms of jaundice in animals and man. We have examined in this study the fate of that fraction of heme whose degradation to bile pigment is inhibited in vivo by administration of this heme oxygenase (EC 1.14.99.3) inhibitor. In bile-duct-cannulated rats, infused exogenous heme is rapidly converted to biliary bilirubin; a small amount of the infused heme is excreted into bile as well. Sn-protoporphyrin, administered with the exogenous heme, markedly increased (3- to 4-fold) the amount of heme excreted into bile and greatly diminished biliary output of bilirubin. The increase in biliary heme output exceeded the decrease in bilirubin excretion elicited by the inhibitor metalloporphyrin. In the same experimental model, Sn-protoporphyrin substantially decreased the conversion of heme, derived from heat-damaged erythrocytes, to biliary bilirubin. This decrease in biliary bilirubin output was accounted for entirely by a prompt and marked increase in biliary excretion of unmetabolized heme. The enhanced biliary excretion of unmetabolized heme following administration of Sn-protoporphyrin is a newly defined and biologically important response associated with use of this synthetic heme analogue. The features of the action of this compound in vivo--suppression of formation of the potentially neurotoxic metabolite, bilirubin; enhancement of disposal of the untransformed substrate (heme) of the enzyme that it inhibits; and its own elimination without metabolic alteration--define some of the characteristics of a therapeutically useful chemical.
Animals↗
delta-Aminolevulinate dehydratase in human erythroleukemia cells: an immunologically distinct enzyme.
Physicochemical and immunologic properties of delta-aminolevulinate (ALA) dehydratase in human K562 erythroleukemia cells were examined. ALA dehydratase activity was found to increase in K562 cells after treatment with butyric acid or selenium oxide. Enzyme activity in untreated K562 cells was comparable to that in normal adult erythrocytes but was increased three- to six-fold in K562 cells treated with 1.2 mmol/L butyric acid or 0.03 mmol/L selenium oxide. The Michaelis-Menten constant (Km), the inhibitor constant (Ki), and elution profile by diethylaminoethyl (DEAE) cellulose chromatography were similar for ALA dehydratase from K562 cells and normal human adult and human fetal erythrocytes. However, ALA dehydratase from K562 cells did not react with a monospecific rabbit antibody against ALA dehydratase purified from normal adult erythrocytes, although the antibody reacted with the enzyme from normal adult and fetal red cells. These findings indicate that ALA dehydratase in K562 cells is immunologically distinct from the normal enzyme.
Antibodies↗
[The extraction of biologically active substances from hop].
Substances which suppressed the effect of gonadotropin in the rat were obtained from hop. These biologically active substances were fractionated from the hop cone, from which lipophilic components (total resins) were removed with acetone. They were water soluble, 70,000-80,000 in molecular weight and were composed mainly of neutral sugars and uronic acid. Administration of the substances to immature rats primed with pregnant mare's serum gonadotropin (PMS) resulted in the following: a significant decrease of ovarian weight gain, whereas there was no change in uterine weight gain, and significant reductions of serum LH and progesterone from cultured luteal rat cells.
Animals↗
Prevention of cyclical attacks of acute intermittent porphyria with a long-acting agonist of luteinizing hormone-releasing hormone.
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Acute Disease↗