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Biomedical subjects

S Sassa

Publications and source records attributed to S Sassa.

At least 109 records · Page 6Linked to original sources
PubMed1990

Activation of heme oxygenase and heat shock protein 70 genes by stress in human hepatoma cells.

Effects of various stresses were examined on the accumulation of mRNA for microsomal heme oxygenase and a heat shock protein, hsp70, in three human hepatoma cell lines. By heat shock, hsp70 mRNA was induced in all three hepatoma lines, Hep G2, Hep 3B and Hep G2f, while heme oxygenase mRNA was increased only in Hep 3B. Time-courses of the heat shock induction of both mRNAs in Hep 3B were similar. Arsenite caused induction of both mRNAs in all three cell lines, while cadmium increased them in Hep G2 and Hep 3B, but not in Hep G2f cells. These findings suggest that, although both hsp70 and heme oxygenase are heat shock proteins, the mode of induction of mRNAs for these proteins is different.

Arsenic↗
PubMed1990

Regulation of the genes for heme pathway enzymes in erythroid and in non-erythroid cells.

There are eight enzymes in the heme biosynthetic pathway and three enzymes in the heme catabolic pathway. Enzymatic defects in heme biosynthesis lead to clinical conditions termed porphyrias. cDNAs for five of the eight enzymes in the heme biosynthetic pathway and two of the three enzymes in the heme catabolic pathway have been cloned and characterized in mammalian cells. At least two enzymes exist as isozymes between erythroid and non-erythroid tissues. One is delta-aminolevulinic acid synthase (ALAS), and the erythroid and hepatic isozymes are coded by two separate genes. The other is porphobilinogen deaminase (PBGD), and both the erythroid and the non-erythroid PBGD mRNA are transcribed from a single PBGD gene by alternate transcription and splicing. There is also a significant tissue-specific control of expression of the uroporphyrinogen decarboxylase gene which is expressed as a unique mRNA in all tissues.

5-Aminolevulinate Synthetase↗
PubMed1990

Phenotypic variation in human HepG2 hepatoma cells: alterations in cell growth, plasma protein synthesis and heme pathway enzymes.

1. Growth rates, morphology, plasma protein synthesis and the level of heme pathway enzymes were examined in six sublines of HepG2 cells obtained from various laboratories. 2. Five sublines represented by G2a display the known characteristics of HepG2 cell type, including morphology, plasma protein synthesis and an increase in delta-aminolevulinic acid (ALA) dehydratase activities in response to Me2SO treatment. 3. In contrast, cells of the G2f subline failed to secrete significant quantities of plasma proteins. There was also no increase in ALA dehydratase activity following Me2SO treatment. These findings suggest that G2f cells represent a variant of HepG2 cells with an altered phenotype.

Blood Proteins↗
PubMed1990

The effects of early treatment of hereditary tyrosinemia type I in infancy by orthotopic liver transplantation.

Two infants with hereditary tyrosinemia secondary to fumarylacetoacetate hydrolase (FAH) deficiency underwent orthotopic liver transplantation at 14 and 16 weeks of age due to poor clinical and biochemical response to medical therapy. Prompt clearance of abnormal metabolites with improved mental alertness and appetite occurred with minimal perioperative complications. Both infants tolerated rapid institution of normal diets and have shown progressive growth and development in the first 36 months after transplantation. Early liver transplantation should be considered as an option for infants with certain inherited metabolic disorders with poor prognosis, such as tyrosinemia type I, who fail to respond to medical therapy.

Amino Acid Metabolism, Inborn Errors↗
PubMed1990

Succinylacetone and delta-aminolevulinic acid dehydratase in hereditary tyrosinemia: immunochemical study of the enzyme.

Immunochemical determinations of delta-aminolevulinic acid (ALA) dehydratase were performed in erythrocytes and in liver of a patient with hereditary tyrosinemia who underwent liver transplantation for correction of this metabolic disorder. Both erythrocytic and hepatic ALA dehydratase activities were extremely low before liver transplantation, but they appeared normal after transplantation. According to results of immunochemical quantification of ALA dehydratase, the level of the enzyme protein in erythrocytes was not different before, during, and after liver transplantation. Immunoquantifiable enzyme concentrations were not substantially different in the patient's own liver as compared with the transplanted liver. These findings indicate that although succinylacetone, an abnormal metabolite produced in tyrosinemia, is a potent inhibitor of the activity of ALA dehydratase, it has a far less effect on the synthesis of the enzyme protein.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

Heat shock induction of heme oxygenase mRNA in human Hep 3B hepatoma cells.

Heat shock treatment of human Hep 3B hepatoma cells led to the induction of mRNA for microsomal heme oxygenase. The maximum induction of heme oxygenase mRNA (5----7-fold) was observed with treatment of cells at 43.5 degrees C, for 60 min. The heat-mediated induction of heme oxygenase mRNA was blocked by simultaneous treatment of cells with actinomycin D or cycloheximide. In contrast to Hep 3B cells, cells of another human hepatoma line, Hep G2, showed little induction of heme oxygenase mRNA by heat treatment. These findings suggest that heat shock treatment induces heme oxygenase mRNA in certain human hepatoma cells, but not in others.

Carcinoma, Hepatocellular↗
PubMed1989

delta-Aminolaevulinate synthase in human HepG2 hepatoma cells. Repression by haemin and induction by chemicals.

delta-Aminolaevulinate (ALA) synthase, the rate-limiting enzyme in haem biosynthesis in the normal liver, was examined in human HepG2 hepatoma cells. Haemin, up to 100 microM, had no effect on ALA synthase activity in vitro; it did, however, exhibit a dose-dependent inhibitory action when added to cells growing in culture (half-maximal inhibition at 1 microM). The half-life of ALA synthase activity after haemin treatment was 2 h, which was similar to that found after treatment with cycloheximide. Cells treated with actinomycin D showed a longer half-life of the enzyme activity, i.e. 4 h, compared with haemin or cycloheximide treatment. Treatment of cells with succinylacetone markedly inhibited the activity of ALA dehydratase and 59Fe incorporation into haem, but in increased ALA synthase activity. Both the haemin-induced repression and the succinylacetone-mediated de-repression of ALA synthase activity were reversible within 4 h after replacing the medium with fresh medium without the chemical. In addition to succinylacetone, dimethyl sulphoxide and 3-methylcholanthrene induced the enzyme. Induction of ALA synthase by these chemicals was also suppressed by treatment of cells with haemin. These findings indicate that the level of ALA synthase in HepG2 cells is maintained by both synthesis and degradation of the enzyme, and that the synthesis of the enzyme is regulated by the concentration of regulatory free haem in the cell.

5-Aminolevulinate Synthetase↗
PubMed1989

The effects of acute-phase inducers and dimethyl sulphoxide on delta-aminolaevulinate synthase activity in human HepG2 hepatoma cells.

The effects of acute-phase inducers and dimethyl sulphoxide (Me2SO) on delta-aminolaevulinate (ALA) synthase in HepG2 cells were examined. Treatment of cells with Me2SO resulted in a significant increase in ALA synthase activity. Interleukin-6 increased ALA synthase activity only slightly, but it substantially potentiated the induction of ALA synthase by Me2SO. These data suggest that ALA synthase activity in liver is altered during acute-phase reactions.

5-Aminolevulinate Synthetase↗
PubMed1989

The effect of dimethyl sulfoxide on heme synthesis and the acute phase reaction in human HepG2 hepatoma cells.

Effects of DMSO on heme synthesis and enzymes of the heme biosynthetic pathway were examined in human HepG2 hepatoma cells. HepG2 cells contain measurable levels of ALA synthase and ALA dehydratase, and their levels are increased after treatment of cells with DMSO. DMSO treatment also led to increases in heme content and the synthesis of haptoglobin, while it decreased the synthesis of albumin and AFP. Changes in plasma protein synthesis after DMSO treatment are characteristic of those known to occur in the acute phase reaction. These findings suggest that profound changes in heme synthesis may occur during the acute phase reaction.

5-Aminolevulinate Synthetase↗
PubMed1989

The rapid and decremental change in haem oxygenase mRNA during erythroid differentiation of murine erythroleukaemia cells.

Changes in mRNA for haem oxygenase (HO), the rate-limiting enzyme for haem catabolism, were examined in murine Friend-virus transformed erythroleukaemia (MEL) cells while they were induced to undergo erythroid cell differentiation by treatment with dimethyl sulfoxide (DMSO). When MEL cells were treated with 1.5% (v/v) DMSO, a rapid decrease in HO mRNA content was observed (less than 12 h) which reached the lowest value at 18 h (18% of the untreated control). HO mRNA levels remained at substantially lower levels (approximately 50%) than those in untreated controls thereafter. A rapid decline in HO mRNA may be involved in the cellular events that determine the onset of erythroid differentiation.

Animals↗
PubMed1989

Erythrocyte uroporphyrinogen decarboxylase activity in porphyria cutanea tarda: a study of 40 consecutive patients.

We measured uroporphyrinogen decarboxylase (UROD) activity in erythrocyte lysates obtained from 40 consecutive patients with porphyria cutanea tarda (PCT) without selection for family history. Enzyme determinations indicated that 28% of the patients had abnormally decreased UROD activity in erythrocytes; this finding did not always correlate with family history. Two siblings with PCT and normal erythrocytic, but abnormally decreased hepatic UROD activities, were encountered. This finding suggests that familial PCT may occur not only with decreased erythrocyte UROD activity, but also with a normal UROD activity in erythrocytes.

Adult↗