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Biomedical subjects

G Poli

Publications and source records attributed to G Poli.

At least 181 records · Page 10Linked to original sources
PubMed1993

Change of liver metabolism of 1,2-dibromoethane during simultaneous treatment with carbon tetrachloride.

The combination of carbon tetrachloride (CCl4) and 1,2-dibromoethane (DBE) in isolated rat hepatocytes led to a significant potentiation of both lipid peroxidation and of plasma membrane damage observed after a single treatment with CCl4. Such a synergistic effect appeared to be related to the CCl4-induced shift of DBE metabolism from the cytosolic conjugation with glutathione towards the microsomal transformation into toxic intermediates. In fact, CCl4 significantly inactivated hepatocyte total GSH-transferase, i.e. the DBE detoxification pathway. Furthermore, while the microsomal metabolism of CCl4 was not affected by the simultaneous presence of DBE, the amount of DBE reactive metabolites covalently bound to hepatocyte protein was significantly enhanced in the presence of CCl4.

Animals↗
PubMed1993

Ability of different hepatoma cells to metabolize 4-hydroxynonenal.

4-Hydroxynonenal (4-HNE), produced during the oxidative lipid breakdown of biological membranes, modulates various biochemical processes in normal liver and in hepatoma cells. It is very probable that the effects of 4-HNE are related to the quantity formed in the cells and to the cells' ability to metabolize it. Aldehyde catabolism takes place within the cells through oxidative and reductive enzymes, and through conjugation with intracellular glutathione. In this paper, the various enzymatic pathways involved in the metabolism of 4-HNE were studied in normal hepatocytes and in hepatoma cells. The hepatocyte pathway undergoes a complex variety of change during neoplastic transformation. In hepatoma cells, generally, 4-HNE metabolism was due mainly to aldehyde dehydrogenases, whereas in normal hepatocytes 4-HNE metabolism was mainly due to alcohol dehydrogenase and glutathione-S-transferase. The increase in oxidative enzymes compared to normal tissue was not the same in all types of hepatoma: in HTC hepatoma cells, the enzyme levels were considerably higher; in AH-130 hepatoma cells of Yoshida, they were lower in subcellular particles and similar in the cytosol. Indeed, consumption of externally-added 4-HNE in hepatoma cells was proportional to their content of 4-HNE metabolizing enzymes.

Alcohol Dehydrogenase↗
PubMed1993

Cytokine modulation of HIV expression.

Cytokines, the peptide hormones which control the homeostasis of the immune system and also play a fundamental role in inflammatory and immune mediated reactions, have been involved at multiple levels in the pathogenesis of the acquired immune deficiency syndrome (AIDS). Infection with the human immunodeficiency virus (HIV) has been shown to induce production of several cytokines both in vitro and in vivo. Conversely, several cytokines modulate the levels of HIV expression in infected cells of both T lymphocytic and mononuclear phagocytic lineage. Activated mononuclear cells, particularly B cells which are in a state of chronic activation in HIV infected individuals, release HIV-inductive cytokines and thus play a potentially important role in the pathogenesis of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Expression and modulation of a mononuclear phagocyte differentiation antigen (PAM-1) during in vitro maturation of peripheral blood monocytes.

Human macrophages obtained by in vitro maturation of peripheral blood monocytes express a surface antigen, PAM-1, recognized by a monoclonal antibody and typical of pulmonary alveolar and tissue macrophages. PAM-1, undetectable in freshly isolated peripheral blood monocytes, was expressed in monocyte-derived macrophages after 3 days of in vitro adherent culture and was maximal after 14-15 days (50%-60% of positive cells). Similar levels of PAM-1 positivity were observed in non-adherent monocyte-derived macrophages suggesting that cell adhesion was not a critical requisite for the expression of this antigen. Bacterial lipopolysaccharide and a monocyte chemotactic protein preparation respectively suppressed and upregulated PAM-1 expression in monocyte-derived macrophages. In contrast, interferon-gamma, although enhancing the levels of class II HLA-DR antigen in monocyte-derived macrophages, did not influence the kinetics of appearance and the levels of PAM-1 in these cells. Thus, expression of PAM-1, which is restricted to certain stages of the monocyte-macrophage differentiation pathway, is also differentially modulated by activation signals, which can be present in the micro-environment of inflammed tissues.

Antigens, Differentiation↗
PubMed1993

Modulation of hepatic fibrogenesis by antioxidants.

The oxidative damage of liver tissue appears to favour a fibrogenic process, through the stimulation of TGF beta 1 and procollagen gene expression. The latter effect has been also showed by a well defined end-product of lipid peroxidation, 4-hydroxy-2,3-nonenal in human Ito cell culture. "In vivo" and "in vitro" data give evidence of a strong down modulation of TGF beta 1 and collagen expression afforded by supplementation with different antioxidant molecules.

Animals↗
PubMed1993

Glucocorticoids synergize with tumor necrosis factor alpha in the induction of HIV expression from a chronically infected promonocytic cell line.

In this study we have investigated the effects of glucocorticoids (GCs) on the expression of human immunodeficiency virus (HIV) in a chronically infected promonocytic cell line, U1. Although no increase in virus production was observed in U1 cells stimulated with physiological concentrations of GC alone, costimulation with dexamethasone plus tumor necrosis factor alpha (TNF-alpha) synergistically enhanced TNF-alpha-dependent HIV expression. Molecular analysis demonstrated that GCs plus TNF-alpha resulted in an accumulation of steady state HIV RNA secondary to either an increase in transcription or an increase in message stability. These findings may be of physiological relevance because GCs are used in the treatment of certain disorders associated with HIV infection and TNF-alpha levels have been reported to be elevated in the plasma and cerebrospinal fluid of certain HIV-infected individuals.

Cell Line↗
PubMed1993

Liver damage due to free radicals.

The involvement of free radical reactions in the pathogenesis of liver injury has been investigated for many years in a few defined experimental systems using carbon tetrachloride, excess iron or ethanol as prooxidant agents. More recently, the hepatotoxicity of several other free radical-generating compounds has been characterised mainly in the rat hepatocyte model. In particular, the mechanisms by which drugs like paracetamol, halothane, paraquat or conditions such as ischemia-reperfusion exert their damaging activity to the liver have mostly been clarified. Since we are not trying to cure diseases occurring only in rats, the likely relevance of free radical reactions also in the genesis and progression of human liver injury has been carefully considered. Increasing evidence of free radical involvement is reported for chronic ethanol intoxication and iron overload, but the most striking proof of a causative role of ree radical chain reactions, namely lipid peroxidation, in the acute lethal damage of the hepatocyte has been obtained so far in ischemic hepatitis.

Alcoholism↗
PubMed1993

Rat hepatocytes in single cell suspension: a still suitable system for lipid peroxidation studies.

The investigation of toxic compounds which need a previous metabolic activation often gets advantage by the employment of cell suspensions, in most of the cases rat hepatocytes. In particular, this model system allows the characterization of lipid peroxidation kinetics, the evaluation of its pathogenetic role in the induction of cell death and the analysis of the interaction among different prooxidant compounds in bringing about both oxidative damage and cytolysis.

Aldehydes↗
PubMed1993

Immunopathogenesis of human immunodeficiency virus infection.

Infection with human immunodeficiency virus (HIV) causes AIDS. As a consequence of the interaction of gp120 envelope with the CD4 receptor molecule expressed by a subset of T lymphocytes and by mononuclear phagocytes (MPs), a second envelope protein (gp41) mediates fusion of the virion membrane with the target membrane. In these events the role of adhesion molecules such as LFA-1 has recently been highlighted. Following viral entry, reverse transcription of the virion-associated RNA and integration of proviral DNA into the host genome are crucial steps in HIV infection, which can lead to expression of high levels of new HIV or to silent infection for indefinite periods, a condition defined as viral latency. Several factors in addition to endogenous viral regulatory proteins have been reported as capable of modulating the state of viral latency and expression in vitro, including the cytokine network that normally modulates immune homeostasis as well as the immune response to inflammatory stimuli. Finally, recent studies have underscored the observation that the CD4+ T lymphocytes are the major reservoir of HIV in the peripheral blood compartment and in the lymphoid tissues, which are characterized by a greater viral burden, whereas in nonlymphoid organs such as the brain and the lung, local infection is predominantly sustained by MPs.

CD4-Positive T-Lymphocytes↗
PubMed1993

Use of polymerase chain reaction to diagnose bovine leukemia virus infection in calves at birth.

A specific polymerase chain reaction (PCR) assay was devised, allowing detection of 1 bovine leukemia virus (BLV)-infected cell in 10(4) bovine lymphocytes. The efficacy of field application of the developed method was verified by evaluating the rate of viral transmission to calves from infected cows, whether they have persistent lymphocytosis. With this objective, 43 calves were simultaneously tested at birth and at 6 months of age for viral antibodies in serum and for proviral DNA in lymphocytes. At birth, 36 calves were BLV-negative and 3 were BLV-positive by results of serologic and DNA-based assays. Conversely, results for 4 calves had lack of correlation between the diagnostic methods. In particular, 2 calves were DNA-positive and antibody-negative for BLV and 2 other calves had the opposite test results. At 6 months of age, when the immunologic pattern more closely reflects the status of calves' immune response, independent of maternal antibodies, all calves DNA-negative for BLV at birth (n = 38), were consistently PCR- and antibody-negative for BLV. On the contrary, the cattle DNA-positive for BLV at birth (n = 5), whether seropositive or not, were PCR- and antibody-positive for BLV, at the time of the second screening. Thus, these results indicate reliability of the PCR to diagnose perinatal BLV infection. Furthermore, the observation that all calves found to be infected at birth were born to BLV-positive cows with persistent lymphocytosis, indicates that the persistent lymphocytosis status of the cow may represent a factor associated with BLV infection in utero.

Animals↗
PubMed1992

Interferon gamma induces the expression of human immunodeficiency virus in persistently infected promonocytic cells (U1) and redirects the production of virions to intracytoplasmic vacuoles in phorbol myristate acetate-differentiated U1 cells.

Interferon gamma (IFN-gamma), a lymphokine that exerts multiple immunoregulatory effects, has been found to be elevated in the plasma, cerebrospinal fluid, and lymph nodes of human immunodeficiency virus (HIV)-infected individuals and has shown variable effects on HIV replication in acutely infected cells. In the present study, we have demonstrated that IFN-gamma is a potent modulator of HIV expression in persistently infected U1 promonocytic cells in which virus production is characterized by a constitutive state of relative latency. Direct stimulation of U1 cells with IFN-gamma (10-1,000 U/ml) activated HIV expression, as measured by reverse transcriptase (RT) activity in the culture supernatant and increased levels of cell-associated viral protein and mRNAs. These effects on virus expression were not accounted for by the induction of endogenous TNF-alpha secretion, as previously described in U1 cells stimulated with phorbol myristate acetate (PMA). At the ultrastructural level, the stimulatory activity of IFN-gamma was correlated with HIV particle production in intracytoplasmic vacuoles along with the differentiation of U1 into macrophage-like cells. Furthermore, costimulation of U1 cells with IFN-gamma and PMA significantly increased the accumulation of vacuole-associated HIV concomitant with decreasing membrane-associated particles and RT activity production, as compared with cells stimulated with PMA alone. No evidence of spontaneous secretion of intracellular vacuole-associated virus was obtained by kinetic analysis of the RT activity released in the supernatants throughout the culture period unless cells were deliberately disrupted. These findings suggest that vacuole-associated virions likely represent a relatively stable intracellular reservoir of HIV, as previously described in primary macrophages infected in vitro or in infected macrophages in the brains of patients with acquired immune deficiency syndrome. The reduced levels of RT activity observed in the culture supernatants of U1 cells stimulated with PMA in the presence of IFN-gamma were not indicative of a suppressive effect of IFN-gamma on PMA-induced expression of HIV proteins and mRNAs, either directly or mediated by the release of IFN-alpha/beta. This study suggests that IFN-gamma may play an important role as an inducer of HIV expression in infected mononuclear phagocytes.

Cell Differentiation↗
PubMed1992

Vitamin E dietary supplementation inhibits transforming growth factor beta 1 gene expression in the rat liver.

Overexpression of transforming growth factor beta 1 (TGF beta 1) and increased transcription of pro-collagen type I, are known to represent major events implicated in the development of liver fibrosis under either experimental or clinical conditions. Here we report that long-term dietary vitamin E supplementation in animals undergoing an experimental model of liver fibrosis (induced by chronic treatment of rats with carbon tetrachloride) results in a net inhibition of both hepatic TGF beta 1 and alpha 2 (I) procollagen mRNA levels. Moreover, of striking interest is the observation that vitamin E supplementation per so down-modulates basal levels of TGF beta 1 mRNA in the liver of untreated animals, suggesting that a dietary regimen rich in vitamin E may potentially interfere with both the initiation and progression of the fibrosclerotic processes.

Animals↗
PubMed1992

Lipid peroxidation and irreversible damage in the rat hepatocyte model. Protection by the silybin-phospholipid complex IdB 1016.

IdB 1016 is a new silybin-phospholipid complex which is more bioavailable than the flavonoid silybin itself and displays free radical scavenging and antioxidant properties in liver microsomes. We report here that the addition of increasing concentrations of IdB 1016 to isolated rat hepatocytes caused a dose-dependent inhibition of lipid peroxidation induced by ADP-Fe3+ or cumene hydroperoxide. Moreover, IdB 1016 at the concentration which completely prevented MDA formation also protected isolated hepatocytes against the toxicity of pro-oxidant agents such as allyl alcohol, cumene hydroperoxide and bromotrichloromethane, without interfering with the activation mechanism of these xenobiotics. Similar protection was also obtained in hepatocytes prepared from animals pretreated in vivo with IdB 1016 while rat supplementation with pure silybin was totally inefficient. These results indicate IdB 1016 as being a potentially useful protective agent against free radical-mediated toxic liver injury.

1-Propanol↗
PubMed1992

Highly concentrated urine-purified Tac peptide fails to inhibit IL-2-dependent cell proliferation in vitro.

Tac peptide, i.e., the p55 chain of the human interleukin-2 receptor (IL-2R) complex, is detectable as a soluble from (sIL-2R) in normal sera and, at increased levels, in patients with different diseases. Since several immunological abnormalities are observed in most conditions associated with an increase in sIL-2R levels, a down-regulatory effect on IL-2-dependent functions has been postulated as a consequence of binding and functional block of IL-2 by the excess of sIL-2R. To test this hypothesis, we purified sIL-2R from the urine of a patient with hairy cell leukemia and investigated the possible inhibitory effect of this peptide on the in vitro IL-2-induced cell proliferation. The urine-purified molecule was detectable by the specific immunoassay utilized to measure the serum Tac peptide and was constructed by a single polypeptide of about 50 kDa which was able to bind IL-2. Experiments performed with the IL-2-dependent murine CTLL-2 cell line and with PHA-stimulated human peripheral blood mononuclear cells showed that the purified sIL-2R at concentrations up to about 300 nM was unable to block IL-2-dependent cell proliferation. According to these data, which can be explained by the low affinity for IL-2 of the p55 IL-2R chain, it seems unlikely that in vivo the soluble Tac peptide can exert a down regulatory effect on IL-2-induced phenomena through a functional block of IL-2.

Animals↗
PubMed1992

Retinoic acid mimics transforming growth factor beta in the regulation of human immunodeficiency virus expression in monocytic cells.

Retinoic acid (RA) exerts potent suppressive and upregulatory effects on human immunodeficiency virus (HIV) expression in mononuclear phagocytes, strikingly similar to the effects of the cytokine transforming growth factor beta (TGF-beta). RA significantly inhibited phorbol ester-mediated, but not tumor necrosis factor alpha-mediated, induction of HIV transcription in the chronically infected promonocytic U1 cell line. RA and TGF-beta also completely suppressed the induction of virus production in U1 cells by interleukin 6 alone or in combination with glucocorticoids, which predominantly upregulate virus expression at the posttranscriptional level. Despite the close parallel to TGF-beta-induced effects, no evidence was obtained that RA mediated its effect by inducing secretion of active TGF-beta 1, -beta 2, or -beta 3. As with chronically infected U1 cells, similar inhibitory effects were also observed in primary monocyte-derived macrophages previously infected with HIV and then exposed to either RA or TGF-beta. In contrast, stimulation of monocyte-derived macrophages or U937 cells (the parental cell line of U1) with either RA or TGF-beta prior to in vitro infection resulted in the enhancement of virus production. Given the already successful use of retinoids in the treatment of several malignancies and the present demonstration of their capability of blocking the induction of HIV expression in infected mononuclear phagocytes, it would be of interest to pursue the potential role of this class of compounds in the development of strategies aimed at the pharmacologic regulation of HIV expression.

HIV↗
PubMed1992

Selenium and glutathione peroxidase variations induced by polyunsaturated fatty acids oral supplementation in humans.

Serum and erythrocyte selenium, erythrocyte and platelet glutathione-peroxidase (GSH-Px) activities, and erythrocyte reduced glutathione (GSH) content were measured in 25 healthy adult individuals before and after daily supplementation with 20 ml of fish oil for 10 weeks. Serum-Se decreased from 0.83 +/- 0.01 mumol/l to 0.75 +/- 0.02 mumol/l (mean +/- S.E.M.) (P less than 0.01); erythrocyte-Se decreased from 4.39 +/- 0.17 nmol/g hemoglobin (Hb) to 2.83 +/- 0.15 nmol/g (P less than 0.001). GSH-Px activities increased both in erythrocytes (6.93 +/- 0.24 iu/g vs 8.18 +/- 0.27 iu/g Hb, P less than 0.01) and in platelets (69.2 +/- 2.8 iu/g vs 90.9 +/- 3.6 iu/g protein, P less than 0.001). The concentration of GSH in erythrocytes fell from 9.56 +/- 0.29 mumol/g Hb to 5.90 +/- 0.30 mumol/g Hb (P less than 0.001). The effects on plasma lipids were evident only for triglycerides (before 1.96 +/- 0.16 mmol/l, after 1.75 +/- 0.14 mmol/l, P less than 0.001). We hypothesise the enrichment of erythrocyte and platelet membranes with polyunsaturated fatty acids (PUFAs), following fish oil intake, can generate increased amounts of lipid peroxides and thus allosterically activate GSH-Px: with time this is harmful for the integrity of the enzyme molecule and Se release may result. We suggest that the Se status of individuals given PUFAs is assessed before and during intake; Se supplements should only be given when serum and/or erythrocyte Se are reduced.

Administration, Oral↗
PubMed1992

Use of purified dermatan sulfate for heparin cofactor II (HC II) assay.

HC II functional assays are generally preferred with respect to immunochemical assays. Nevertheless functional assays can be biased by the antithrombin III (AT III)-heparin complex activity; in fact trace amounts of heparin generally contaminate dermatan sulfate (DS) commercial preparations used as HC II reaction activators. We have employed a purified DS preparation showing these features: DS concentration 94.4%, chondroitin sulfate 5.6%, M.W. 21.4 kDa. The absence of any interference due to AT III-heparin complexes was verified in a kinetic HC II assay of some human plasma pools. The immunological inhibition of AT III by anti-AT III caused a minimal decrease (6-8%) of the reaction slope, attributable to AT III activity. Progressive increase of heparin concentration in the assay was effective only starting from 30 U/ml (the assay was carried out in the presence of polybrene to prevent any AT III activation). The reference interval (mean +/- SD) obtained from 157 normal subjects was 100.8 +/- 20.2%; there was a good correlation with immunoreactive HC II. The purified DS we have used seems suitable for routinary assays of HC II where a minimal interference due to AT III-heparin is required.

Amino Acid Sequence↗