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Biomedical subjects

A Kappas

Publications and source records attributed to A Kappas.

At least 19 recordsLinked to original sources
PubMed1992

Interleukin-6 down regulates the expression of transcripts encoding cytochrome P450 IA1, IA2 and IIIA3 in human hepatoma cells.

Effects of human interleukin-6 (hIL-6), the major acute phase inducer, on the expression of transcripts encoding cytochrome P450s were examined in human hepatoma-derived cells. Using reverse-transcription polymerase chain reaction, it was demonstrated that three hepatoma cell lines, HepG2, HepG2f and Hep3B, express P450 mRNAs encoding IA1, IA2 and IIIA3, the major P450 isozymes involved in carcinogen metabolism, and that they also show induction responses to treatment with their specific inducers. When hepatoma cells were treated with hIL-6, the levels of IA1, IA2 and IIIA3 mRNAs were markedly suppressed. These findings suggest that significant down regulation of cytochrome P450s may occur during the acute phase reaction, which may result in alterations in drug biotransformation.

Base Sequence↗
PubMed1992

Heme oxygenase is a positive acute-phase reactant in human Hep3B hepatoma cells.

The effects of human interleukin-6 (hIL-6), the major acute-phase inducer, on the level of the transcript of microsomal heme oxygenase (HO) were examined in a human hepatoma cell line, Hep3B. Messenger RNAs (mRNAs) encoding HO and haptoglobin (Hpt) increased after hIL-6 treatment in a time- and dose-dependent manner. hIL-6 had no effect on the induction of heat-shock protein 70 (hsp70) mRNA, suggesting that the induction of HO by hIL-6 is regulated by a different mechanism from that which mediates the heat-shock induction of this enzyme. The hIL-6-mediated induction of HO mRNA was completely abrogated by simultaneous treatment of cells with actinomycin D, but not with cycloheximide, suggesting that the induction occurs at the level of transcription. A nuclear factor was shown both in untreated, and in the hIL-6-treated Hep3B cells that binds specifically to the IL-6-responsive element (IL6-RE) of the human HO gene. These findings suggest that HO is a positive acute-phase reactant in this human liver-derived cell line, and that the nuclear factor specific to the IL6-RE may be involved in the activation of the HO gene after hIL-6 treatment.

Acute-Phase Proteins↗
PubMed1992

The molecular defect of ferrochelatase in a patient with erythropoietic protoporphyria.

The molecular basis of an inherited defect of ferrochelatase in a patient with erythropoietic protoporphyria (EPP) was investigated. Ferrochelatase is the terminal enzyme in the heme biosynthetic pathway and catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. In Epstein-Barr virus-transformed lymphoblastoid cells from a proband with EPP, enzyme activity, an immunochemically quantifiable protein, and mRNA content of ferrochelatase were about one-half the normal level. In contrast, the rate of transcription of ferrochelatase mRNA in the proband's cells was normal, suggesting that decreased ferrochelatase mRNA is due to an unstable transcript. cDNA clones encoding ferrochelatase in the proband, isolated by amplification using the polymerase chain reaction, were found to be classified either into those encoding the normal protein or into those encoding an abnormal protein that lacked exon 2 of the ferrochelatase gene, indicating that the proband is heterozygous for the ferrochelatase defect. Genomic DNA analysis revealed that the abnormal allele had a point mutation, C----T, near the acceptor site of intron 1. This point mutation appears to be responsible for the post-transcriptional splicing abnormality resulting in an aberrant transcript of ferrochelatase in this patient.

Amino Acid Sequence↗
PubMed1992

The facilitative effect of facial expression on the self-generation of emotion.

Twenty-seven female undergraduates completed three tasks: (1) feel four emotions (happiness, sadness, anger, peacefulness); (2) express these emotions, without trying to feel them; and (3) feel and express clearly these four emotions. During each trial subjects pressed a button to indicate when they had reached the required state, and the latency from emotion cue to button press was measured. Heart rate, skin conductance and EMG from four facial sites (brow, cheek, jaw and mouth) were recorded for 15 s before and after the button press and during a baseline period prior to each trial. Self-reports were obtained after each trial. Facial EMG and patterns of autonomic arousal differentiated among the four emotions within each task. Shorter self-generation latency in the Feel-and-Show versus the Feel condition indicated the facilitative effect of facial expression on the self-generation of emotion. Furthermore, the presence of autonomic changes and self-reported affect in the Show condition supports the sufficiency version of the facial feedback hypothesis. The self-generation method employed as an emotion elicitor was shown to reliably induce emotional reactions and is proposed as a useful technique for the elicitation of various emotional states in the laboratory.

Adult↗
PubMed1992

Hypothalamic mechanism for cobalt protoporphyrin-induced hypophagia and weight loss: inhibition of the feeding response to NPY.

The mechanism whereby neurally or peripherally administered cobalt-protoporphyrin (CoPP) leads to transient hypophagia and prolonged weight reduction in normal and genetically obese animals is unknown. Neuropeptide Y (NPY) is a known endogenous stimulator of feeding behavior and is elevated in the hypothalamus of food-deprived rats. Accordingly, we examined the interaction between CoPP and NPY in the central nervous system. Concentrations of NPY mRNA in the hypothalami of rats treated intracerebroventricularly with vehicle or CoPP responded to decreased food intake with comparable increases. However, intracerebroventricular infusions of NPY elicited increased intake of food in vehicle-treated rats but were without effect in CoPP-treated animals. The results suggest that CoPP acts, at least in part, by blocking the feeding response to NPY.

Animals↗
PubMed1992

Injection of cobalt protoporphyrin into the medial nuclei of the hypothalamus elicits weight loss.

Intracerebroventricular administration of small amounts (0.1 mumol/kg body wt) of cobalt protoporphyrin (CoPP), a synthetic analogue of heme, results in transient hypophagia and prolonged reduction in body weight of rats. Statistically significant hypophagia is detectable within 3 h of CoPP infusion. These changes are accompanied by prompt and sustained reductions in running wheel revolutions, a measure of spontaneous locomotor activity. Bilateral intrahypothalamic injections of CoPP at far lower doses (4 nmol/rat) resulted in similar findings following infusion into the paraventricular, dorsomedial, and ventromedial nuclei, but the compound had no such effect when injected into the thalamus or the lateral hypothalamic area. These effects were also observed following microinjection of the natural metalloporphyrin, heme, into the medial hypothalamic nuclei. Inorganic cobalt, iron, protoporphyrin, and magnesium protoporphyrin injected similarly were without such effect. These findings provide further evidence that the site of the previously described actions of CoPP in reducing food intake and body weight in rats resides, at least in part, in the medial hypothalamus. Furthermore, this study expands the spectrum of metalloporphyrins that act in the central nervous system to elicit these changes from synthetic compounds such as CoPP to heme, the natural, physiological metalloporphyrin.

Animals↗
PubMed1992

Cloning and expression of the defective genes from a patient with delta-aminolevulinate dehydratase porphyria.

Cloning and expression of the defective genes for delta-aminolevulinate dehydratase (ALAD) from a patient with inherited ALAD deficiency porphyria (ADP) were carried out. Cloning of cDNAs for the defective ALAD were performed from EBV-transformed lymphoblastoid cells of the proband, and nucleotide sequences were determined. Two separate point mutations resulting in a single amino acid change in each ALAD allele were identified. One, C718----T, termed 'G1', occurred in the allele within the substrate-binding site, producing an Arg240----Trp substitution; the other, G820----A, termed 'G2', occurred downstream of this site in the other allele, resulting in an Ala274----Thr substitution. Using the reverse transcription-polymerase chain reaction, the mother, the brother, and the sister were shown to have the G1 defect. Expression of the G1 cDNA in Chinese hamster ovary cells produced ALAD protein with little activity; the G2 cDNA produced the enzyme with approximately 50% normal activity. Pulse-labeling studies demonstrated that the G1 enzyme had a normal half life, while the G2 enzyme had a markedly decreased half life. These data thus define the separate point mutations in each ALAD allele, as well as the altered properties of the two enzymic proteins encoded by the mutant genes in a patient with ADP.

Alleles↗
PubMed1992

Cloning and expression of the defective genes in delta-aminolevulinate dehydratase porphyria: compound heterozygosity in this hereditary liver disease.

Cloning and expression of the defective genes for ALAD from a patient with inherited ADP were carried out. Two separate point mutations, termed G1 and G2, resulting in a single amino acid change in each ALAD allele, were identified. The G1 mutation (C718-->T) occurred in the allele within the substrate-binding site, producing an Arg240-->Trp substitution; the G2 mutation (G820-->A) occurred downstream of this site in the other allele, resulting in an Ala274-->Thr substitution. Using RT-PCR, the mother, the brother, and the sister were shown to have the G1 defect. Expression of the G1 cDNA in CHO cells produced ALAD protein with little activity; the G2 cDNA produced the enzyme with approximately 50% normal activity. Pulse-labeling studies demonstrated that the G1 enzyme had a normal half-life, while the G2 enzyme had a markedly decreased half-life. These data thus define two separate point mutations, one in each ALAD allele, as well as the altered properties of the two enzymic proteins encoded by the mutant genes in this patient.

Adolescent↗
PubMed1992

Intestinal heme oxygenase inhibition and increased biliary iron excretion by metalloporphyrins.

The effects of synthetic metalloporphyrins on heme oxygenase activity in the epithelium of the proximal region of the small intestine were examined both in vitro and in vivo in male Sprague-Dawley rats. Metalloporphyrins, which inhibit hepatic heme oxygenase in vitro, also inhibit intestinal heme oxygenase. Chromium and tin porphyrins are the most potent inhibitors of the intestinal enzyme in vitro. Oral administration of Sn-protoporphyrin (25 mumol/kg body weight) resulted in inhibition of intestinal heme oxygenase; however, no effect was observed on the splenic, hepatic, or renal enzymes. Metal analyses in these tissues showed essentially no intestinal absorption of the metalloporphyrin. Oral administration of Cr-mesoporphyrin (25 mumol/kg body wt) also resulted in inhibition of intestinal heme oxygenase activity. Zinc and manganese mesoporphyrin did not inhibit intestinal heme oxygenase activity when administered orally. Microsomal intestinal heme oxygenase activity was inhibited in a dose-dependent manner by antiserum raised in rabbit against rat hepatic heme oxygenase. The parenteral administration of metalloporphyrin inhibitors of heme oxygenase to bile duct-cannulated rats resulted in a significant increase in iron levels in the bile.

Animals↗
PubMed1992

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

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.

Adolescent↗
PubMed1991

A heat-inducible nuclear factor that binds to the heat-shock element of the human haem oxygenase gene.

Haem oxygenase is a heat-shock protein in several rat tissues, as well as in certain human cells such as Hep3B hepatoma cells. In common with other heat-shock-protein genes, both the human and the rat haem oxygenase genes contain a heat-shock element (HSE) in their promoter regions. In the present study we have identified a factor in nuclear extracts of human Hep3B cells which binds specifically to the HSE of the human haem oxygenase gene. The factor in Hep3B cells was significantly induced within 1 h after heat-shock treatment, and the induction was blocked by treatment of cells with actinomycin D or cycloheximide. The factor was not detected in human HepG2 hepatoma cells, which exhibit the heat-mediated induction of heat-shock protein 70 mRNA, but not that of haem oxygenase mRNA. These findings suggest that the heat-inducible nuclear factor is increased at the level of transcription and that it may activate the human haem oxygenase gene via the HSE after heat treatment.

Base Sequence↗
PubMed1991

Induction of heme oxygenase in the small intestinal epithelium: a response to oral cadmium exposure.

The effects of oral cadmium administration on heme oxygenase activity and cytochrome P-450-dependent drug metabolism in intestinal epithelium were examined in male Sprague-Dawley rats. Cadmium chloride was administered via drinking water (0, 5 or 50 ppm cadmium) for 5 or 30 days, and heme oxygenase, 7-ethoxycoumarin O-deethylase (ECOD), 7-ethoxyresorufin O-deethylase (EROD) and cytochrome P-450 were measured in the liver and in the epithelium of the proximal region of the small intestine. Cadmium exposure produced a marked, dose-related induction of intestinal heme oxygenase (up to 300% of control levels) in the small intestine at both time points examined. Concomitant decreases in intestinal ECOD (70%) and EROD (65%) activities were also observed, with a 65% decline in cytochrome P-450 levels at 30 days as compared with controls. Oral cadmium exposure, however, did not affect heme catabolism or cytochrome P-450 function in the liver, even at the highest concentration (50 ppm) administered, although cadmium levels accumulated in a dose-related manner in the liver as well as in the small intestine. Systemic absorption of cadmium was limited, as reflected by the relatively low accumulation of cadmium in the liver at 5 days (approximately 20 micrograms/g), as compared with the levels present in small intestine at this time ponit (approximately 100 micrograms/g). These findings emphasize the sensitivity of cytochrome P-450-dependent drug metabolism in small intestinal epithelium to orally ingested cadmium, and highlight the vulnerability of this tissue to low-dose exposure to this metal.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1991

Heme inhibits human immunodeficiency virus 1 replication in cell cultures and enhances the antiviral effect of zidovudine.

The effects of heme alone and heme administered together with 3'-azido-3'-deoxythymidine (AZT) on human immunodeficiency virus replication in human peripheral blood lymphocytes and in the H9 cell line were studied. Heme enhanced the antiviral action of AZT against both drug-resistant and drug-sensitive viral strains; the heme effect was more pronounced against the latter. Moreover, heme alone displayed a significant ability to inhibit viral replication in concentrations markedly smaller than those required to inhibit the reverse transcriptase of Rauscher murine leukemia virus. The results of this study extend the range of pharmacological actions that metalloporphyrins exert in biological systems and suggest that further study of the interactions of the natural compound heme and human immunodeficiency virus chemotherapeutic agents such as AZT may be useful.

Antiviral Agents↗
PubMed1991

UV-irradiation potentiates the antimutagenicity of p-aminobenzoic and p-aminosalicylic acids in Salmonella typhimurium.

UV-irradiation (254 nm, 10 or 20 J/cm2) of p-aminobenzoic acid (PABA) and p-aminosalicylic acid (NaPAS) potentiated their antimutagenicity towards N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis in Salmonella typhimurium. Their inhibitory action towards the formation of the mutagen N-methyl-N-nitrosourea from the nitrosation mixture of N-methylurea and nitrite was also increased by UV-irradiation. In contrast, UV-irradiated PABA exhibited no inhibitory effects towards the mutagenicity of sodium azide or 3-azidoglycerol. Neither PABA nor NaPAS nor their UV-irradiation products were themselves mutagenic in the Ames assay.

4-Aminobenzoic Acid↗
PubMed1991

Effects of protein and carbohydrate content of diet on drug conjugation.

Eight healthy subjects were fed a high-protein-low-carbohydrate diet and, after a 3-day washout period, an isocaloric low-protein-high-carbohydrate diet. They received acetaminophen and oxazepam, drugs metabolized primarily by conjugation, on days 11 and 13, respectively, of each diet. Changing the diets of subjects from the high-protein-low-carbohydrate diet to the low-protein-high-carbohydrate diet resulted in a 14% increase in urinary recovery of acetaminophen glucuronide and a 32% increase in urinary recovery of oxazepam glucuronide (p less than 0.05). The increases in glucuronidation were at the expense of other pathways of metabolism, and there were no significant changes in the metabolic clearance rates of acetaminophen and oxazepam. Mean renal clearances of acetaminophen glucuronide, acetaminophen sulfate, and oxazepam glucuronide decreased 45%, 32%, and 54%, respectively (p less than 0.05), when the subjects were switched to the low-protein-high-carbohydrate diet.

Acetaminophen↗
PubMed1991

Hereditary hepatic porphyria due to homozygous delta-aminolevulinic acid dehydratase deficiency: studies in lymphocytes and erythrocytes.

Activities of delta-aminolevulinic acid (ALA) dehydratase and porphobilinogen (PBG) deaminase, and haem content were determined in EB-virus transformed lymphocytes from two patients with homozygous ALA dehydratase deficiency, and their family members to determine the expression of the specific gene defect in this cell type. ALA dehydratase activity, but not PBG deaminase activity or haem content, was markedly decreased in lymphocyte preparations from both patients with homozygous enzyme deficiency, and moderately decreased in subjects heterozygous for enzyme deficiency. Immunochemical quantitation of erythrocyte ALA dehydratase suggested the presence of a cross-reactive material in a patient with a late-onset of acute hepatic porphyria due to the homozygous enzyme deficiency.

Adult↗
PubMed1991

Comparative photoactivity of tin and zinc porphyrin inhibitors of heme oxygenase: pronounced photolability of the zinc compounds.

Metalloporphyrin inhibitors of heme oxygenase may also have photosensitizing properties in vivo. To assess photoactivity in serum, the relative ability to mediate photooxidation of tryptophan or other oxidizable targets, presumably by singlet oxygen production, was measured for tin mesoporphyrin, zinc mesoporphyrin, and zinc deuteroporphyrin bisglycol in aqueous solution and when bound to human serum albumin. While tin mesoporphyrin sensitized at the greatest initial rate in aqueous solution, the zinc compounds sensitized at a greater initial rate in detergent micelles or when bound to albumin. There was minimal alteration of the tin mesoporphyrin during the time course of illumination in the Soret or visible absorption regions. The zinc compounds, however, proved to be extremely photolabile and were extensively destroyed by light; the photooxidized forms were found to be ineffective as inhibitors of heme oxygenase.

Animals↗