Biomedical subjects

G Poli

Publications and source records attributed to G Poli.

At least 163 records · Page 9Linked to original sources

PubMed1995

Acetaldehyde involvement in ethanol-induced potentiation of rat hepatocyte damage due to the carcinogen 1,2-dibromoethane.

Previous experiments with hepatocytes isolated from ethanol-treated rats showed that alcohol potentiates the toxic action of 1,2-dibromoethane (DBE) by inhibiting its metabolism via glutathione-S-transferase. The aim of this study was to investigate whether acetaldehyde, the main product of ethanol metabolism, may be responsible for such inactivation. By pretreatment with 4-methylpyrazole, an inhibitor of acetaldehyde formation, the ethanol inactivation of glutathione transferase was actually prevented. As a consequence of this protective action, 4-methylpyrazole also prevented the high basal lipid peroxidation and the potentiated DBE toxicity observed in hepatocytes from ethanol-dosed animals. Finally, the inactivation of glutathione-S-transferase by concentrations of acetaldehyde likely to occur in the ethanol-intoxicated animal was confirmed in an in vitro model by direct aldehyde addition to hepatocyte suspensions.

Acetaldehyde↗

PubMed1995

Yeasts: from genetics to biotechnology.

Yeasts have been known and used in food and alcoholic fermentations ever since the Neolithic Age. In more recent times, on the basis of their peculiar features and history, yeasts have become very important experimental models in both microbiological and genetic research, as well as the main characters in many fermentative production processes. In the last 40 years, advances in molecular biology and genetic engineering have made possible not only the genetic selection of organisms, but also the genetic modification of some of them, especially the simplest of them, such as bacteria and yeasts. These discoveries have led to the availability of new yeast strains fit to fulfill requests of industrial production and fermentation. Moreover, genetically modified and transformed yeasts have been constructed that are able to produce large amounts of biologically active proteins and enzymes. Thus, recombinant yeasts make it easier to produce drugs, biologically active products, diagnostics, and vaccines, by inexpensive and relatively simple techniques. Yeasts are going to become more and more important in the "biotechnological revolution" by virtue of both their features and their very long and safe use in human nutrition and industry.

Biotechnology↗

PubMed1994

A family of serine proteases expressed exclusively in myelo-monocytic cells specifically processes the nuclear factor-kappa B subunit p65 in vitro and may impair human immunodeficiency virus replication in these cells.

Two groups of U937 promonocytic cells were obtained by limiting dilution cloning which differed strikingly in their ability to support human immunodeficiency virus 1 (HIV-1) replication. "Plus" clones replicated the virus efficiently, whereas "minus" clones did not. We examined these clones for differences in nuclear factor (NF)-kappa B activity which might account for the observed phenomenon. Stimulation of plus clones liberated the classical p50-p65 complex from cytoplasmic pools, whereas minus clones produced an apparently novel, faster-migrating complex, as judged by electrophoretic mobility shift assays. It is surprising that the faster-migrating complex was composed also of p50 and p65. However, the p65 subunit was COOH-terminally truncated, as shown by immunoprecipitation. The truncation resulted from limited proteolysis of p65 during cellular extraction which released particular lysosomal serine proteases, such as elastase, cathepsin G, and proteinase 3. These specific proteases are coordinately expressed and were present exclusively in the minus U937 clones, but not in the plus clones, as demonstrated in the case of cathepsin G. In addition, these proteases were detected in certain subclones of THP-1 and HL-60 cells and in primary monocytes, in each case correlating with the truncated from of p65. We demonstrate in vitro cleavage of p65 by purified elastase and cathepsin G. It is possible that particular serine proteases may have inhibiting effects on the replication of HIV-1 in myelo-monocytic cells. The data also demonstrate that special precautions must be taken when making extracts from myelo-monocytic cells.

Animals↗

PubMed1994

NF-kappa B-dependent and -independent pathways of HIV activation in a chronically infected T cell line.

J delta K cells were isolated as a chronically infected survivor cell line, following infection of Jurkat CD4+ T cells with dl-NF, a mutated strain of human immunodeficiency virus type 1 (HIV-1) containing a deletion of the long terminal repeat (LTR) NF-kappa B sites. J delta K cells exhibited very low levels of constitutive HIV production. HIV-1 expression was activated from J delta K cells by treatment with phorbol myristate acetate (PMA), sodium butyrate (NaB), or hexamethylene bisacetamide (HMBA), but not tumor necrosis factor alpha (TNF-alpha), confirming the role of NF-kappa B in mediating TNF-alpha induction of HIV transcription. The strong induction of HIV expression by NaB or HMBA in J delta K cells clearly demonstrates the existence of NF-kappa B-independent mechanisms of HIV activation in chronically infected cells. J delta K cells may provide a useful model for characterizing NF-kappa B-independent transcriptional activation of the HIV LTR.

Acetamides↗

PubMed1994

Codon usage and evolutionary rates of proteins.

The 61 codons and the three terminators were counted in the coding sequences of 31 families of proteins of higher vertebrates. The protein families were ordered according to their evolutionary rate. In each family, the ratio between the Observed and Expected frequency of each codon was obtained (O/E ratio). A strong and significant positive correlation was observed between the O/E ratio of the eight codons AAC, TAT, ATA, GAA, ACA, AAT, ATG and CGA and the evolutionary rate of the protein. A negative and significant correlation was observed for codons AAG and GAG. It was advanced that the functional constraints of proteins can influence the usage of codons, particularly for those trimers which are components of signal sequences. It was also observed that the O/E ratios of the terminators are negatively correlated with the evolutionary rate of the protein they terminate, and the correlation is significant for TAA and TGA, which in vertebrates might be older than TAG.

Animals↗

PubMed1994

Interleukin 1 induces expression of the human immunodeficiency virus alone and in synergy with interleukin 6 in chronically infected U1 cells: inhibition of inductive effects by the interleukin 1 receptor antagonist.

In the present study we have observed that interleukin (IL) 1 alpha or IL-1 beta directly induced expression of human immunodeficiency virus (HIV) in the latently infected human promonocytic cell line U1. In addition, IL-1 synergized with IL-6, but not with tumor necrosis factor, in the upregulation of virus expression in U1 cells as measured by accumulation of steady-state mRNAs and production of reverse transcriptase activity. The HIV inductive effect of IL-1 was blocked by transforming growth factor beta, anti-IL-1 antibodies, or monoclonal antibodies directed to the type 1, but not to the type 2, cell surface receptor for IL-1; the latter actually caused enhancement of the IL-1-mediated effect. Unlike tumor necrosis factor alpha, IL-1 either alone or in combination with IL-6 did not induce activation of the transcription activating factor NF-kappa B above the constitutive levels of unstimulated U1 cells. Finally, the IL-1 receptor antagonist effectively blocked IL-1-mediated direct and synergistic inductive effects on virus production. Thus, IL-1 may be an important mediator of HIV expression, and blocking of IL-1 expression and/or its effects may have a potential therapeutic role in the inhibition of HIV expression in infected individuals.

Base Sequence↗

PubMed1994

Regulation of HIV expression by viral genes and cytokines.

The human immunodeficiency virus (HIV) is the causative agent of the acquired immunodeficiency syndrome (AIDS), a leading cause of death among young individuals. As a complex pathogenic retrovirus, HIV is characterized in vitro and in vivo by the ability to establish either a latent or productive infection of CD4+ T lymphocytes and mononuclear phagocytes (MPs). Viral latency and expression are under the control of both viral genes and several host-related factors. Among these latter, several proinflammatory and immunoregulatory cytokines profoundly affect HIV replication in T lymphocytes and MPs in vitro. Because many of these cytokines have been found to be elevated in HIV-infected individuals, it is likely that they act as regulators of viral expression in vivo. Both viral genes and cytokines regulate transcriptional and posttranscriptional steps in HIV replication. Thus, it is likely that common regulatory pathways between these two distinct classes of regulator molecules will be identified in the near future and will provide potential targets for pharmacologic intervention and treatment of HIV disease.

Cytokines↗

PubMed1994

Ultraviolet irradiation and cytokines as regulators of HIV latency and expression.

The ability of the human immunodeficiency virus (HIV) to persist and replicate in human CD4+ T lymphocytes and mononuclear phagocytes is under the control of both virally encoded proteins and a variety of host-related factors. Ultraviolet (UV) light has been shown to induce transcription and expression of HIV. Both DNA damage and repair and DNA damage/repair-independent pathways caused by UV irradiation lead to expression of proviral HIV genomes via activation of the cellular transcription factor NF-kappa B. Transgenic mice that contain either long terminal repeat (LTR)-reporter genes or HIV genomes, either full length or deleted in the gag-pol region, express RNA and proteins at the epidermal level, particularly after UV irradiation. Furthermore, UV-triggered release of soluble factors capable of inducing expression of HIV in non-irradiated cells has been observed. Among other host factors, the functional network of pro-inflammatory and immunoregulatory cytokines has been demonstrated to act as a potent regulator of HIV replication, at least in different in vitro systems of infection.

Animals↗

PubMed1994

Interferons in the pathogenesis and treatment of human immunodeficiency virus infection.

There still remains several unanswered questions concerning the pathogenesis of human immunodeficiency virus (HIV) infection. Interferons (IFNs), as well as other cytokines, are both dysregulated in HIV infection and serve as effector molecules that modulate the replicative capacity of HIV. Acid-labile IFN-alpha, an aberrant form of interferon earlier described in certain autoimmune diseases, has been detected in HIV-infected individuals. Conversely, a deficient expression of IFN-alpha may occur usually associated with HIV disease. Although conflicting findings have been reported on whether IFN-gamma, a product of activated T and natural killer (NK) cells, is elevated in the peripheral blood (PB) compartment, high levels of its expression have been observed in the germinal centers of the lymph nodes during HIV disease. IFN-alpha and IFN-beta have shown potent anti-retroviral effects in several in vitro systems of both acute and chronic HIV infection. These findings have served as the basis of the rationale for their therapeutic application, resulting in some positive effects at least in those patients with relatively high CD4+ T cell counts and healthy immune functions. Furthermore, IFN-alpha has shown important therapeutic effects on HIV-associated Kaposi's sarcoma (KS). Both suppressive and inductive effects on HIV replication in vitro have been described for IFN-gamma, whereas no clear clinical benefits have been reported following its administration to HIV-infected individuals. In conclusion, IFNs are involved in several pathogenic aspects of HIV infection and AIDS, and certain IFNs may serve as important tools to limit the spread of the virus and the progression of disease.

HIV↗

PubMed1994

Oxidative stress in the development of human ischemic hepatitis during circulatory shock.

An increasing number of studies support the involvement of free radical-mediated oxidative reactions in the pathogenesis of tissue injury following ischemia reperfusion. In particular, a condition of oxidative stress is evident in patients with circulatory shock, a disease process often complicated by progressive organ failure sustained by inflammatory reactions. In all shock patients without signs of organ failure, a consistent increase of intermediate and final products of lipid peroxidation (lipid peroxides and aldehydes respectively) was observed. Impairment of the redox equilibrium in the tissues of these patients was confirmed by a significant reduction of glutathione and vitamin E hematic concentrations. Moreover, a selective increase of plasma aldehyde-protein adducts, actual proof of oxidative damage of macromolecules, is only present in the shock patients who, in addition, show hepatic cytolysis (ischemic hepatitis) as estimated by plasma levels of LDH5 isoenzyme. Aldehyde adducts well mark the progression of the disease towards multiple organ failure. Finally, the good statistical correlation between aldehyde-modified proteins and LDH5, as well as their distinct behaviour in control and ischemic hepatitis, support the involvement of oxidative damage in the expression and worsening of circulatory shock.

Alanine Transaminase↗

PubMed1994

Interleukin 10 blocks HIV replication in macrophages by inhibiting the autocrine loop of tumor necrosis factor alpha and interleukin 6 induction of virus.

Human interleukin 10 is a pleiotropic cytokine capable of suppressing cytokine production from macrophages and T cells; in addition, it exerts complex regulatory effects on CD8+ T cells, natural killer cells, vascular endothelial cells, and B lymphocytes. Levels of IL-10 are elevated in HIV-infected individuals, suggesting that this cytokine may play a role in the suppression of T cell and monocyte/macrophage function typical of HIV disease. In this article, IL-10 blocked HIV-induced tumor necrosis factor alpha and interleukin 6 secretion and inhibited HIV replication in monocyte-derived macrophages (MDMs). The inhibition by IL-10 was correlated with a block in endogenous TNF-alpha and IL-6 secretion from HIV-infected MDMs.

Antiviral Agents↗

PubMed1994

Role of aldehyde metabolizing enzymes in mediating effects of aldehyde products of lipid peroxidation in liver cells.

It is well established that many types of tumor cells have reduced lipid peroxidation capacity compared to their normal counterparts. Changes in the activity of enzymes metabolizing aldehydes produced by lipid peroxidation have also been reported in a variety of tumor cells. We have investigated the relationship between changes in lipid peroxidation and changes in aldehyde-metabolizing enzymes in normal hepatocytes and two representative rat hepatoma cell lines, McA-RH-7777 and JM2. Compared to hepatocytes, both 7777 and JM2 cells have significantly lower basal and prooxidant-induced levels of lipid peroxidation than normal hepatocytes. Using 4-hydroxynonenal (4-HNE) as substrate, both cell lines also have significantly reduced activities of alcohol dehydrogenase (ADH) and glutathione S-transferase (GST) compared to hepatocytes. JM2 cells have significantly increased aldehyde dehydrogenase (ALDH) and aldehyde reductase (ALRD) activities with 4-HNE. In 7777 cells the ALDH and ALRD activities are not different from hepatocytes. The changes in enzyme activity are inversely correlated with the sensitivity of cells to 4-HNE. JM2 cells, with increased ALDH and ALRD and decreased ADH and GST, are much more resistant to the toxic effects of 4-HNE than 7777 cells. Normal hepatocytes and JM2 cells are approximately equally resistant to 4-HNE even though hepatocytes rely primarily on GST-mediated aldehyde conjugation to metabolize 4-HNE. Coupled with previous results from our laboratories, the overall increased sensitivity of certain hepatoma cells to lipid aldehydes appears due to decreased ability of these hepatoma cells to remove toxic products of lipid peroxidation. Moreover, hepatoma cells with increased levels of aldehyde dehydrogenase and aldehyde reductase appear most like hepatocytes in their ability to metabolize lipid aldehydes.

Aldehyde Dehydrogenase↗

PubMed1994

Elevated levels of tumor necrosis factor-alpha in Zairian neonate plasmas: implications for perinatal infection with the human immunodeficiency virus.

Plasma levels of tumor necrosis factor-alpha (TNF alpha) and the ability of plasmas to induce HIV expression in chronically infected cell lines were measured in samples from adults, cord blood, and neonates from Zaire and North America. Plasma levels of TNF alpha were higher in Zairian neonates born to HIV-negative and -positive mothers than in uninfected Zairian adults (612 vs. 128 vs. 8 pg/mL, P < .001); this dichotomy persisted until children were 9 months old. Plasmas from neonates of HIV-negative Zairian mothers also stimulated higher levels of reverse transcriptase from HIV-infected cell lines than did plasma from HIV-negative Zairian adults (1339 vs. 110 cpm, P < .001). Similar patterns were noted in plasmas from HIV-negative North American adults and neonates; however, TNF alpha levels were markedly lower, and smaller differences were noted among North American adults and neonates than those in the Zairian cohort. Markedly elevated plasma TNF alpha levels in Zairian neonates and infants may play a role in the pathogenesis and progression of HIV disease in this patient population.

Adult↗

PubMed1994

Cytokine-mediated induction of human immunodeficiency virus (HIV) expression and cell death in chronically infected U1 cells: do tumor necrosis factor alpha and gamma interferon selectively kill HIV-infected cells?

Infection with several DNA or RNA viruses induces a state of increased sensitivity to cell lysis mediated by tumor necrosis factor (TNF), particularly in the presence of gamma interferon (IFN-gamma). Infection of human cells with the human immunodeficiency virus (HIV) may induce a similar phenomenon. However, TNF and IFN-gamma are known upregulators of HIV replication, raising the question of the potential role of these cytokines in the selective elimination of cells infected with this virus. The present study demonstrates that chronically infected U1 cells were killed with much greater efficiency by costimulation with TNF-alpha and IFN-gamma than their uninfected parental cell line U937. However, synergistic induction of viral expression also occurred in U1 cells as a consequence of treatment with the two cytokines. Cell death in U1 cells was not caused by the massive production of virions, in that costimulation with glucocorticoid hormones and TNF-alpha or IFN-gamma resulted in high levels of virion production without cytopathicity. To investigate the nature of the selective cytotoxic effect observed in U1 cells costimulated with TNF-alpha plus IFN-gamma, a panel of uninfected cell clones was generated by limiting dilution of U937 cells and tested for response to TNF-alpha and/or IFN-gamma. In contrast to the uncloned bulk parental U937 cell line, most uninfected cell clones showed a very high susceptibility to being killed by TNF-alpha and IFN-gamma. Similar findings were obtained when both infected U1 cells and several uninfected U937 cell clones were costimulated with an anti-Fas monoclonal antibody in the presence of IFN-gamma, although, unlike cells stimulated with TNF-alpha, cells treated with anti-Fas antibody did not express virus. Therefore, the increased susceptibility to cytokine-mediated lysis observed in cell lines infected with HIV is likely due to the selection of preexisting cell clones rather than viral infection.

Antibodies, Monoclonal↗

PubMed1993

Lack of stereospecificity of suid pseudorabies virus thymidine kinase.

We have partially purified suid pseudorabies virus (PRV) thymidine kinase from infected thymidine kinase- mouse cells, and cytosolic swine thymidine kinase from lymphatic glands, and we have found that PRV thymidine kinase, unlike the host enzyme, shows no stereospecificity for D- and L-beta-nucleosides. In vitro, unnatural L-enantiomers, except L-deoxycytidine, function as specific inhibitors for the viral enzyme in the order: L-thymidine >> L-deoxyguanosine > L-deoxyuridine > L-deoxyadenosine. Contrary to human and swine thymidine kinases and like herpes simplex virus-1 and -2 thymidine kinases, PRV thymidine kinase phosphorylates both the natural (D-) and the unnatural (L-) thymidine enantiomers to their corresponding monophosphates with comparable efficiency. The kinetic parameters Vmax/Km for D- and L-thymidine are 3.7 and 2.3 respectively. Our results demonstrate that the lack of stereospecificity might be a common feature of the thymidine kinases that are encoded by human and animal herpes viruses. These observations could lead to the development of a novel class of antiviral drugs.

Binding, Competitive↗

PubMed1993

Stimulation of lipid peroxidation or 4-hydroxynonenal treatment increases procollagen alpha 1 (I) gene expression in human liver fat-storing cells.

Hepatic fat-storing cells (FSC) play a key role in the development of fibrosis as a major source of collagen and other extracellular matrix (ECM) proteins in the injured liver. Both experimental and clinical studies have shown that lipid peroxidation is often associated with the development of liver fibrosis. Here we report that exposure of cultured human liver FSC to the pro-oxidant system ascorbate/iron results in an early induction of lipid peroxidation, as monitored in terms of MDA and fluorescent aldehyde/protein adducts production, and in a significant increase of the constitutive expression of procollagen type I mRNA paralleled by the accumulation of the protein in cell culture media. This fibrogenic effect is almost completely abolished by pretreatment of FSC cultures with the antioxidants alpha-tocopherol (Vitamin E) or diphenylphenylendiamine (DPPD). Moreover, treatment of FSC with 1.0 microM 4-hydroxynonenal (HNE), a highly reactive aldehydic end-product of lipid peroxidation, results in a significant stimulation of procollagen type I gene expression and synthesis, suggesting that this aldehyde also exerts profibrogenic activity. These findings indicate that oxidative reactions can directly influence procollagen I gene expression and synthesis in FSC, thus contributing to the development of liver fibrosis.

Adipose Tissue↗

PubMed1993

Modulation of rat liver protein kinase C during "in vivo" CC14-induced oxidative stress.

Rat intoxication with a single dose of the hepatotoxin carbon tetrachloride induces a significant modification of liver protein kinase C total activity which depends on the degree of the intrahepatocyte oxidative unbalance provoked by various concentrations of the haloalkane. Low carbon tetrachloride amounts stimulate total protein kinase C activity, while one order of magnitude higher amounts exert strong enzyme inhibition. The latter effect is due to an early inactivation followed with progress of time by a proteolytic degradation of the enzyme. A pathological recruitment of the calcium-dependent protein kinase C regulatory enzymes calpain and calpastatin appears responsible for protein kinase C loss. The prolonged excess of cytosolic calcium which characterizes the single high dose carbon tetrachloride poisoning also leads to inactivation of calpain II and calpastatin in a time-dependent manner.

Animals↗

PubMed1993

A platelet-activating factor antagonist, RP 55778, inhibits cytokine-dependent induction of human immunodeficiency virus expression in chronically infected promonocytic cells.

A platelet-activating factor antagonist, RP 55778, potently suppressed the induction of human immunodeficiency virus (HIV) expression in chronically infected promonocytic U1 cells. RP 55778 inhibited the production of reverse transcriptase activity in U1 cells stimulated with the transcriptionally active inducers of virus production, tumor necrosis factor alpha and phorbol 12-myristate 13-acetate. This effect was correlated only in part with a reduction in the levels of HIV RNA, suggesting that this agent was also affecting posttranscriptional levels of virus production. In this regard, RP 55778 effectively blocked the induction of HIV expression in U1 cells stimulated with interleukin 6 and granulocyte-macrophage colony-stimulating factor, which act predominantly as posttranscriptional activators of HIV expression. Finally, RP 55778 inhibited the production of endogenous tumor necrosis factor alpha in phorbol 12-myristate 13-acetate-stimulated cells, thereby interfering with an autocrine pathway of virus expression. The suppressive effects of RP 55778 on HIV expression appeared to be independent of the platelet-activating factor cell surface receptor on U1 cells. RP 55778 inhibited acute HIV replication in primary T-cell blasts and the proliferative capacity of these cells. This study suggests that RP 55778 may represent potentially useful compounds in the treatment of HIV infection.

Cell Line↗