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Biomedical subjects

A Kappas

Publications and source records attributed to A Kappas.

At least 37 records · Page 2Linked to original sources
PubMed1999

Differential effects of heme oxygenase isoforms on heme mediation of endothelial intracellular adhesion molecule 1 expression.

Heme oxygenase (HO), by catabolizing heme to bile pigments, down-regulates cellular hemoprotein, hemoglobin, and heme; the latter generates pro-oxidant products, including free radicals. Two HO isozymes, the products of distinct genes, have been described; HO-1 is the inducible isoform, whereas HO-2 is suggested to be constitutively expressed. We studied the inducing effect of several metal compounds (CoCl(2), stannic mesoporphyrin, and heme) on HO activity. Additionally, we studied HO-1 expression in experimental models of adhesion molecule expression produced by heme in endothelial cells, and the relationship of HO-1 expression to the induced adhesion molecules. Flow cytometry analysis showed that heme induces intracellular adhesion molecule 1 (ICAM-1) expression in a concentration (10-100 microM)- and time (1-24 h)-dependent fashion in human umbilical vein endothelial cells. Pretreatment with stannic mesoporphyrin, an inhibitor of HO activity, caused a 2-fold increase in heme-induced ICAM-1 expression. In contrast, HO induction by CoCl(2) decreased heme-induced ICAM-1 expression by 33%. To examine the contribution of HO-1 and HO-2 to endothelial HO activity, specific antisense oligonucleotides (ODNs) of each isoform were tested for their specificity to inhibit HO activity in cells exposed to heme. Endothelial cells exposed to heme elicited increased HO activity, which was prevented (70%) by HO-1 antisense ODNs. HO-2 antisense ODN inhibited heme-induced HO activity by 21%. Addition of HO-1 antisense ODNs prevented heme degradation and resulted in elevation of microsomal heme. Western blot analysis showed that HO-1 antisense ODNs selectively inhibited HO-1 protein and failed to inhibit HO-2 protein. Incubation of endothelial cells with HO-1 antisense enhanced heme-dependent increase of ICAM-1. In contrast, addition of HO-2 antisense to endothelial cells failed to increase adhesion molecules. The role of glutathione, an important antioxidant, was examined on heme-induced ICAM-1 expression. Endothelial cells pretreated with a glutathione precursor, N-acetylcysteine, or glutathione ester, showed a decrease in heme-induced ICAM-1 expression of 37 and 44%, respectively, suggesting that the mechanism of ICAM-1 induction by heme may be partly dependent on the levels of antioxidant. It is possible that amelioration of the heme-induced oxidative stress and expression of ICAM-I is due, in part, to the induction of HO-1 activity. Regulation of HO activity in this manner may have clinical applications.

Cells, Cultured↗
PubMed1999

Induction of micronuclei in human lymphocytes by organic solvents in vitro.

Our work is focused on identifying micronuclei (MN) induced in whole blood lymphocyte cultures after treatment with the organic solvents toluene, benzene, and acetone. We used the micronucleus test as a cytogenetic biomarker for genotoxicity and treated whole blood cultures with different concentrations of these solvents (0.1 to 5 mM) and mixtures of them (toluene plus acetone, toluene plus benzene). Our results did not show a significant increase in the number of micronuclei in binucleated lymphocytes after 48 hr of in vitro treatment. The addition of an external metabolic factor (10% S9 mix for 2 hr) in blood cultures treated with the organic solvents or their mixtures did not cause induction of MN. These results indicate the lack of genotoxic activity of toluene, benzene, and acetone in vitro.

Acetone↗
PubMed1998

Specific recombinogenic activity of a new polyene antibiotic.

A new antibiotic from Streptomyces sp., tetrapol A159, active against various fungi, a promising compound for the control of plant diseases, was studied for its genotoxic effects. It was produced at the Institute of Microbiological Preparations for Agriculture, Sofia, Bulgaria. The chemical was tested in three different test systems: a bacterial system, the Ames test for point mutations, the micronucleus test in bone marrow cells of rats for chromosomal aberrations and the fungal system of Aspergillus nidulans for mitotic recombination and aneuploidy. No increase in histidine revertants was observed in any of the TA100, TA98, TA1535 and TA1537 strains of Salmonella at concentrations ranging from 1 to 4000 mg/plate. The results were also negative in the micronucleus test of bone marrow cells at concentrations from 124 to 600 mg/kg b.w., whereas a statistically significant threefold increase of mitotic crossovers was found in Aspergillus, at concentrations from 0.5 to 2.5 mg/ml.

Animals↗
PubMed1998

Sn-mesoporphyrin suppression of hyperbilirubinemia in EHBR/Eis rats, an animal model of Dubin-Johnson syndrome.

Sn-mesoporphyrin (SnMP), a potent inhibitor of heme oxygenase (HO), controlled hyperbilirubinemia in rats of the mutant strain EHBR/Eis. This mutant strain displays pronounced conjugated hyperbilirubinuria and dark pigmentation of hepatocytes, characteristics of the Dubin-Johnson syndrome. SnMP administered at a dose of 10 mumol/kg body weight produced an immediate decrease in plasma bilirubin concentrations which could be maintained by weekly injections of this synthetic heme analogue. Marked inhibition of HO activity was demonstrated in liver, kidney and spleen but not in brain. These results demonstrate that SnMP can lower plasma bilirubin concentrations for extended periods in a new mutant rat model of Dubin-Johnson syndrome.

Animals↗
PubMed1998

Control of hyperbilirubinemia in glucose-6-phosphate dehydrogenase-deficient newborns using an inhibitor of bilirubin production, Sn-mesoporphyrin.

BACKGROUND: Hyperbilirubinemia in new-borns with glucose-6-phosphate dehydrogenase (G6PD) deficiency is a serious clinical problem because of the severity and unpredictability of its course. An innovative approach to this problem is suggested by previous experience with Sn-mesoporphyrin (SnMP), a potent inhibitor of bilirubin production, in moderating neonatal hyperbilirubinemia caused by ABO incompatibility, immaturity, and unspecified mechanisms. OBJECTIVE: To compare the effectiveness of the preventive and therapeutic uses of SnMP in ameliorating the course of bilirubinemia of G6PD-deficient neonates. METHODS: Neonates born at the Metera Maternity Hospital, Athens, Greece, and found to be G6PD-deficient by cord blood testing were stratified by sex and gestational age (210-265 days and >265 days) and randomized in pairs to receive SnMP (6 micromol/kg birth weight, intramuscularly) either on the first day of life (preventive use) or if and when the plasma bilirubin concentration (PBC) level reached an age-specific threshold level for intervention (therapeutic use). In the case of failure of SnMP to control the rise of PBC levels, the protocol defined precisely the threshold PBC levels for switchover to phototherapy (PT) and, if necessary, exchange transfusion. PBC was measured daily until a declining value was obtained and the case was closed. RESULTS: A total of 86 G6PD-deficient neonates were randomized: 42 in the preventive arm and 44 in the therapeutic arm. Of the latter, 20 (45%) reached PBC levels requiring therapeutic intervention and thus received SnMP. Regardless of the trial arm, none of the 86 neonates required PT, whereas in a previous study in the same population, 33% of G6PD-deficient neonates required PT. In the intrapair sequential analysis, the favored arm was decided on the criterion of the age at closure of the case being shorter by at least 1 day. After plotting 30 untied pairs in the sequential analysis graph, the preventive use of SnMP proved to be the favored arm, and the trial was stopped. At this point, there were 2 unpaired neonates, 12 tied pairs, 22 pairs in which the preventive use of SnMP was favored and 8 pairs in which the therapeutic use of SnMP was favored. In the group analysis, infants in the preventive group, compared with those in the therapeutic group, had a lower maximum PBC level (8.2 +/- 3.1 and 10.9 +/- 2.8 mg/dL, respectively), which was reached at an earlier age (63.5 +/- 34.8 and 82.2 +/- 24.7 hours, respectively) as well as a lower closing PBC level (7.2 +/- 2.9 and 9.6 +/- 2.5 mg/dL, respectively) and an earlier age at closing (89.1 +/- 35.6 and 110.8 +/- 23.6 hours, respectively). Moreover, a PBC level of >/=8.0 mg/dL, a level at which jaundice is clearly visible, was not reached by 52% of the neonates in the preventive arm and 16% of the neonates in the therapeutic arm. CONCLUSIONS: In G6PD-deficient neonates, a single dose of SnMP administered preventively or therapeutically entirely supplanted the need for PT to control hyperbilirubinemia. The preventive use of SnMP offers practical advantages in populations with a high enough prevalence of G6PD deficiency to justify cord blood screening.

Bilirubin↗
PubMed1997

Heme oxygenase induction with attenuation of experimentally induced corneal inflammation.

Heme oxygenase (HO), by catabolizing heme to bile pigments, down-regulates cellular levels of heme and hemeproteins; certain of the latter, i.e. cytochrome P450s, generate pro-inflammatory products from endogenous substrates. Two HO isozymes, the products of distinct genes, have been described; HO-1 is the inducible one, whereas HO-2 is believed to be constitutively expressed. We studied the inducing effects of several metal compounds [CoCl2, SnCl2, ZnCl2, heme, and cobalt protoporphyrin (CoPP)] on HO-1 mRNA content and enzyme activity in cultures of rabbit corneal epithelial (RCE) cells; these metal compounds are known to induce HO in other tissues. Additionally, we studied HO-1 expression in an experimental model of ocular inflammation produced in rabbit corneas by extended contact lens wear, and the relation of HO expression to the induced inflammatory process. SnCl2 added to RCE cells in vitro produced marked time- and concentration-dependent increases in HO-1 mRNA and HO-1 enzyme activity; CoCl2, ZnCl2, and CoPP were inducers of HO as well, though to a lesser degree than SnCl2. Corneas treated for 6 days with contact lenses impregnated with SnCl2 displayed substantially less corneal inflammation, swelling, and new vessel invasion than did controls; attenuation of ocular inflammation was paralleled by SnCl2-induced increases in HO mRNA and HO activity in corneal epithelial cells from treated eyes. It is suggested that amelioration of the inflammatory response produced by extended contact lens wear is due, in part, to the induction of high levels of HO-1 activity by SnCl2, which results in diminished production of pro-inflammatory mediators generated through heme-dependent metabolic processes. Regulation of HO activity in this manner may have clinical applications.

Animals↗
PubMed1997

Zinc porphyrins: potent inhibitors of hematopoieses in animal and human bone marrow.

The effects of selected heme analogues on heme oxygenase activity in tissues and on human and rabbit bone marrow hematopoietic colony growth were examined. Zinc protoporphyrin (ZnPP) and zinc mesoporphyrin (ZnMP), at concentrations ranging between 1 and 20 microM, produced significant inhibition of human and rabbit bone marrow erythroid (CFU-E, BFU-E) and myeloid (CFU-GM) colony growth. The growth inhibition produced by ZnPP or ZnMP was not overcome with exposure of cultures to elevated levels of the growth factors erythropoietin and granulocyte-macrophage colony stimulating factor. In contrast, tin protoporphyrin and tin mesoporphyrin did not display any significant bone marrow toxicity when used at similar concentrations. In other studies, differential effects of tin mesoporphyrin and ZnMP administered intravenously on kidney heme oxygenase were demonstrated. Chromium mesoporphyrin administered intravenously proved lethal to animals. These results indicate that exposure of bone marrow to ZnPP and ZnMP can be deleterious to hematopoietic cells and raise the possibility that ZnPP, which is endogenously formed and found in high concentration in red blood cells in lead-poisoned children, may itself participate in the bone marrow toxicity produced by this metal.

Animals↗
PubMed1997

The effect of environmental aneuploidy-inducing agents on the microtubule architecture of mitotic meristematic root cells in Hordeum vulgare.

Microtubules are the prime components involved in chromosomal segregation, their functional accuracy ensuring maintenance of the normal karyotype in the progeny. Chemically-induced disruption of microtubules during mitosis can lead to aneuploidy. In this study, seven environmental chemicals, i.e. cadmium chloride (CD), econazole nitrate (EZ), benomyl (BM), thiabendazole (TB), griseofulvin (GF), thimerosal (TM) and hydroquinone (HQ), were tested for their ability to induce microtubule disruption in mitotic meristematic root cells of the higher plant Hordeum vulgare, with the use of anti-tubulin indirect immunofluorescence microscopy. All chemicals tested in this study, with the exception of TB and HQ, produced modifications in the morphology of microtubule organization and reduced the fidelity of the spindle apparatus in Hordeum vulgare.

Aneuploidy↗
PubMed1996

Contingency detection and the contingent organization of behavior in interactions: implications for socioemotional development in infancy.

In this report, the authors review studies addressing the issue of contingencies in social and nonsocial contexts during infancy. The review is divided into 4 groups of studies that suggest that (a) young infants detect contingencies unrelated to their behavior; (b) infants detect contingencies involving their behavior; (c) the study of contingency is pertinent for addressing behavioral organization within parent-infant interaction; and (d) there is a link between behavioral contingency in early infancy and global measures of socioemotional development that are predictive of social functioning at later points during childhood. Throughout the report, the pertinence of infant emotional responses during contingency-related tasks is emphasized. Finally, the authors delineate certain enduring questions regarding contingency experience in infancy and suggest ways of organizing research to address some of them.

Emotions↗
PubMed1996

Effects of a series of metalloporphyrins on adrenal, testicular and thyroid function in rats.

We have extended our earlier studies [Pharmacology 1986;34:9-16] on the effects of certain synthetic heme analogues and cobalt chloride (CoCl2) on endocrine functions mediated by the hypothalamic-pituitary axis to examine specifically the ability of Sn-protoporphyrin (SnPP) and Sn-mesoporphyrin (SnMP) to perturb adrenal, testicular and thyroid function since there is interest in the use of Sn(tin)-porphyrins in the treatment of hyperbilirubinemia of the newborn. SnPP and SnMP when administered to adult male rats did not alter serum corticosterone, testosterone, thyroxine or triiodothyronine levels when compared to control animals. In addition, administration of exogenous adrenocorticotrophic hormone produced an increase in serum corticosterone levels that was comparable in placebo-treated and SnPP- and SnMP-treated animals. These studies involved doses of both compounds substantially greater than those used clinically. The results clearly indicate that SnMP, presently the compound of choice for use in newborns, and SnPP do not in the doses studied impair adrenal, testicular and thyroid function in vivo.

Adrenal Glands↗
PubMed1996

Tissue distribution of synthetic heme analogues: studies with tin, chromium, and zinc mesoporphyrins.

The uptake in tissue of Sn-mesoporphyrin (SnMP), Cr-mesoporphyrin (CrMP) and Zn-mesoporphyrin (ZnMP) administered at doses ranging from 1 to 10 mu mol/kg BW and the effects of these compounds on heme oxygenase activity were examined in both adult and neonatal rats. SnMP and CrMP, but not ZnMP, were rapidly cleared from blood and taken up by liver, spleen and kidney where marked inhibition of heme oxygenase activity was demonstrated. None of the metalloporphyrins were detectable in brain, and no inhibition of heme oxygenase activity was demonstrable in this tissue after administration of the compounds to both adult and neonatal rats. These results demonstrate that SnMP, CrMP and ZnMP do not cross the blood brain barrier, a fact of interest in relation to the potential use of these compounds clinically.

Animals↗
PubMed1996

Inhibition of human immunodeficiency virus-1 reverse transcriptase by heme and synthetic heme analogs.

Heme and a series of synthetic heme analogs were tested for inhibition of human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT) activity. Heme and the protoporphyrin complexes of cadmium, magnesium, and tin significantly inhibited HIV-1 RT, whereas other metalloporphyrins had a lesser or no effect on the enzyme. The mechanism of inhibition was examined with respect to heme and tin protoporphyrin (SnPP), as both compounds have been utilized clinically as treatment for noninfectious disorders. Heme and SnPP inhibited HIV-1 RT in a noncompetitive manner with respect to deoxythymidine triphosphate. Inhibition depended in part on the protoporphyrin structure, because the mesoderivatives of the heme analogs essentially were without effect. Heme also markedly enhanced the inhibitory effect of azidothymidine (zidovudine, AZT) on HIV-1 RT, and the combination of the two compounds showed synergy in inhibiting HIV-1 RT. HIV-1 RT was used to reverse transcribe the glyceraldehyde phosphate dehydrogenase (GAPDH) gene from human kidney. Subsequently, GAPDH cDNA was amplified with Taq polymerase, and electrophoresis showed that HIV-1 RT catalyzed the reverse transcription of human mRNA at a rate comparable to that of Moloney murine leukemia virus. Heme and SnPP prevented cDNA synthesis by HIV-1 RT in this RT-polymerase chain reaction assay. We also examined the effects of these compounds on normal human bone marrow function. Heme stimulated both erythroid and myeloid progenitor colony formation, whereas SnPP was essentially without effect. In contrast, ZnPP had a suppressive effect on hematopoiesis. Finally, we show that heme has a sparing effect against the myelotoxicity of AZT. The results of these studies raise the possibility that combination therapy with AZT and heme, or heme plus an inhibitor of heme catabolism, might have therapeutic potential in the acquired immunodeficiency syndrome.

Antiviral Agents↗
PubMed1995

Transfection of the human heme oxygenase gene into rabbit coronary microvessel endothelial cells: protective effect against heme and hemoglobin toxicity.

Heme oxygenase (HO) is a stress protein and has been suggested to participate in defense mechanisms against agents that may induce oxidative injury such as metals, endotoxin, heme/hemoglobin, and various cytokines. Overexpression of HO in cells might therefore protect against oxidative stress produced by certain of these agents, specifically heme and hemoglobin, by catalyzing their degradation to bilirubin, which itself has antioxidant properties. We report here the successful in vitro transfection of rabbit coronary microvessel endothelial cells with a functioning gene encoding the human HO enzyme. A plasmid containing the cytomegalovirus promoter and the human HO cDNA complexed to cationic liposomes (Lipofectin) was used to transfect rabbit endothelial cells. Cells transfected with human HO exhibited an approximately 3.0-fold increase in enzyme activity and expressed a severalfold induction of human HO mRNA as compared with endogenous rabbit HO mRNA. Transfected and nontransfected cells expressed factor VIII antigen and exhibited similar acetylated low-density lipoprotein uptake (two important features that characterize endothelial cells) with > 85% of cells staining positive for each marker. Moreover, cells transfected with the human HO gene acquired substantial resistance to toxicity produced by exposure to recombinant hemoglobin and heme as compared with nontransfected cells. The protective effect of HO overexpression against heme/hemoglobin toxicity in endothelial cells shown in these studies provides direct evidence that the inductive response of human HO to such injurious stimuli represents an important tissue adaptive mechanism for moderating the severity of cell damage produced by these blood components.

Animals↗
PubMed1995

Differential heme oxygenase induction by stannous and stannic ions in the heart.

Heme oxygenase is the rate-limiting enzyme in heme catabolism, and is induced by oxidative stress, foreign and endogenous chemicals, and many trace elements and heavy metals. This study examined the effect of the oxidative state of the heavy metal tin, on heme oxygenase-1 induction in cardiac tissue. Subcutaneous administration of stannous and stannic chloride failed to induce the enzyme in this tissue. Atomic absorption spectroscopy revealed the absence of tin in the heart cells. Investigation of several metal formulations showed that both stannous and stannic citrate were able to enter the bloodstream from the injection site and into heart tissue. Northern blot analysis revealed that heme oxygenase-1 mRNA was elevated several-fold in rat hearts from animals which received either stannous or stannic citrate, and that mRNA levels corresponded with the increase in enzyme activity. The presence of citrate facilitated the transport of the tin ion into the blood stream and possibly across cardiac cell membrane. The stannous ion was more potent as an inducer of heme oxygenase than was the stannic ion.

Analysis of Variance↗
PubMed1995

Modulation of corneal heme oxygenase expression by oxidative stress agents.

Heme oxygenase, the rate-limiting enzyme in the degradation of heme to bile-pigments and carbon monoxide, is induced in response to increased oxidative stress and is believed to provide a cytoprotective effect. We investigated the role of heme oxygenase in cultured rabbit corneal epithelial cells (RCE), and its potential to alleviate oxidative stress-induced cell damage. Heme oxygenase in RCE was effectively and potently induced by most metals tested, including tin, silver, and gold, and cytokines such as IL-6, and TGF beta. Stannous chloride and heme-induced heme oxygenase mRNA by 40 and 100 fold within 1-3 hours and increased enzyme activity by 9.2- and 10-fold, respectively, over a 24 hour period. IL-6, TGF beta and H2O2 induced heme oxygenase by 2-3 fold. Zinc protoporphyrins were effective inhibitors of heme oxygenase activity in vitro. However, when incubated with cells for 24 h they induced heme oxygenase mRNA but decreased or had no effect on its activity. Administration of heme, SnCl2, and H2O2 resulted in some degree of glutathione perturbation (GSH/GSSG). However, in all cases, depletion of glutathione was exacerbated if heme oxygenase was simultaneously inhibited. Conversely, perturbation of glutathione levels was minimized if heme oxygenase was induced by heme or stannous chloride. These results demonstrate that RCE cells exhibit functional heme oxygenase activity which is inducible in response to inflammatory cytokines and oxidative stress agents and suggest a cytoprotective role for heme oxygenase against cell injury.

Animals↗
PubMed1995

The comparative abilities of inorganic cobalt and cobalt-protoporphyrin to affect copper metabolism and elevate plasma ceruloplasmin.

A comparison of the effects of the trace element cobalt and the protoporphyrin chelate of this metal, cobalt-protoporphyrin, on copper and zinc metabolism in male Sprague-Dawley rats was made. Following subcutaneous treatment (250 mumol/kg body weight), inorganic cobalt elicited only a moderate (25-30%) and transient (48 h) increase in plasma copper levels and a concomitant elevation (up to 2-fold) in ceruloplasmin (ferroxidase) activity. Treatment with cobalt-protoporphyrin (25 mumol/kg), however, produced substantial (2- to 3-fold) and prolonged (up to 4 weeks) increases in plasma copper levels and ceruloplasmin. This effect on ceruloplasmin was specific to cobalt-protoporphyrin, since equimolar doses (25 mumol/kg body weight) of both tin-protoporphyrin and iron-protoporphyrin did not produce changes in the levels of circulating ceruloplasmin. Both inorganic cobalt and cobalt-protoporphyrin produced an elevation in liver cytosolic zinc levels at 48 h. This zinc associated with a fraction that coelutes with authentic metallothionein standard. These differential effects of inorganic cobalt and cobalt-protoporphyrin on copper and zinc metabolism represent newly defined biological properties of this trace element and point to the importance of chemical speciation as an underlying factor in the ultimate biological actions of metals.

Analysis of Variance↗