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Biomedical subjects

M Seman

Publications and source records attributed to M Seman.

At least 19 recordsLinked to original sources
PubMed2001

Rapid induction of naive T cell apoptosis by ecto-nicotinamide adenine dinucleotide: requirement for mono(ADP-ribosyl)transferase 2 and a downstream effector.

Lymphocytes express a number of NAD-metabolizing ectoenzymes, including mono(ADP-ribosyl)transferases (ART) and ADP ribosylcyclases. These enzymes may regulate lymphocyte functions following the release of NAD in injured or inflammatory tissues We report here that extracellular NAD induces apoptosis in BALB/c splenic T cells with an IC(50) of 3-5 microM. Annexin V staining of cells was observed already 10 min after treatment with NAD in the absence of any additional signal. Removal of GPI-anchored cell surface proteins by phosphatidylinositol-specific phospholipase C treatment rendered cells resistant to NAD-mediated apoptosis. RT-PCR analyses revealed that resting BALB/c T cells expressed the genes for GPI-anchored ART2.1 and ART2.2 but not ART1. ART2-specific antisera blocked radiolabeling of cell surface proteins with both [(32)P]NAD and NAD-mediated apoptosis. Further analyses revealed that natural knockout mice for Art2.a (C57BL/6) or Art2.b (NZW) were resistant to NAD-mediated apoptosis. Labeling with [(32)P]NAD revealed strong cell surface ART activity on T cells of C57BL/6 and little if any activity on cells of NZW mice. T cells of (C57BL/6 x NZW)F(1) animals showed strong cell surface ART activity and were very sensitive to NAD-induced apoptosis. As in BALB/c T cells, ART2-specific antisera blocked cell surface ART activity and apoptosis in (C57BL/6 x NZW)F(1) T cells. The fact that T cells of F(1) animals are sensitive to rapid NAD-induced apoptosis suggests that this effect requires the complementation of (at least) two genetic components. We propose that one of these is cell surface ART2.2 activity (defective in the NZW parent), the other a downstream effector of ADP-ribosylation (defective in the C57BL/6 parent).

ADP Ribose Transferases↗
PubMed2001

Synthesis and anti-HIV activity of thymidine analogues bearing a 4'-cyanovinyl group and some derivatives thereof.

Treatment of 3'-O-tert-butyldimethylsilyl-2',5'-dideoxy-5'-oxothymidine (4) with potassium or magnesium nitromethanide afforded in good yield the resolvable epimeric mixture of the expected blocked nitronucleosides 5 which upon dehydration led to the corresponding E-nitroenofuranosylthymidine 6. Nucleophilic attack of cyanide onto the nitrovinyl group led to a nucleoside analogue bearing a terminal 1-cyanovinyl group (7), a soft electrophilic group which, upon reaction with benzeneselenol, underwent a conjugate addition to the phenylselenonucleoside derivative 9. All these compounds, eventually de-O-silylated, were subject of in vitro biological testing, some exhibiting interesting cytotoxic or antiviral properties.

Animals↗
PubMed2001

Resistance to melanoma metastases in mice selected for high acute inflammatory response.

The role of innate immunity in natural resistance to tumor progression was investigated in two mouse lines, AIRmax and AIRmin, selected by bi-directional selective breeding on the basis of high or low acute inflammatory response. Compared with AIRmin, AIRmax mice were shown to be resistant to 7,12-dimethylbenz[a]anthracene (DMBA)/12-O:-tetradecanoylphorbol-13-acetate-induced skin cancers and here we demonstrate that AIRmax are also able to restrain the development of metastases upon transfer of MHC compatible, incompatible or xenogeneic melanomas. An acute inflammatory response to melanoma cells was observed in AIRmax mice only, although both lines were found to mount similar specific immune responses to melanoma antigens. The genetically selected lines therefore represent a model system to analyze the positive correlation between multiple resistance to tumorigenesis and host inflammatory responsiveness.

Animals↗
PubMed2000

CD3 activation induces concentrative nucleoside transport in human T lymphocytes.

Nucleoside transport, assessed by measuring deoxythymidine influx, was investigated in normal and CD3-activated human peripheral blood mononuclear cells (PBMC) and in the CEM cell line. On both cell types, an equilibrative nitrobenzylmercaptopurine (NBMPR)-sensitive (es) transporter encoded by the hENT(1) gene was identified on resting cells, although the expression level was about 20-fold higher on CEM cells than on resting peripheral T lymphocytes. After stimulation with anti-CD3, a strong increase of nucleoside transport was observed in PBMC accompanied by a mild augmentation of NBMPR binding sites on the cell surface. Most of this improved transport capacity was NBMPR insensitive, dependent on Na(+) concentration in the medium, and displayed the features of a concentrative process. Similar results were obtained with CEM cells despite their high basal es level, indicating that the induction of a concentrative process for nucleoside salvage is a specific metabolic response associated with antigen-driven stimulation. In CEM cells, this induction did not affect the growth rate. The concentrative transporter involved does not correspond to any of those which have been cloned so far. Molecular characterization of this transporter should provide a new marker of antigen stimulation and will allow to define whether activation of the corresponding gene is under the control of TCR-CD3-induced second messengers.

Biological Transport↗
PubMed2000

MS-8209, an amphotericin B analogue, delays the appearance of spongiosis, astrogliosis and PrPres accumulation in the brain of scrapie-infected hamsters.

The histopathological response of scrapie-infected hamsters treated at the late stage of the infection with an "anti-scrapie" drug, a polyene macrolide antibiotic designated MS-8209, was evaluated in the brain. The results showed that (1) MS-8209 prolonged significantly the incubation time of the experimental disease, (2) MS-8209 delayed the appearance of spongiosis and astrogliosis in the brain, (3) immunodetection of abnormal prion protein and glial fibrillary acidic protein was significantly reduced in the central nervous system. In addition, this report indicates that polyene antibiotics markedly delay the development of the classical brain lesions that result from scrapie infection.

Amphotericin B↗
PubMed2000

Highly stereoselective synthesis and biological properties of nucleoside analogues bearing a spiro inserted oxirane ring.

Starting from 2',5'-di-O-TBDMS-3'-ketouridine 1 or its thymine analogue 2, both xylo (3-10) and ribo (20) epimers of a series of 3"-substituted 3'-spironucleosides have been obtained in good yields and with a total stereoselectivity. Most new compounds were moderately cytotoxic with in some cases slightly selective antiproliferative activities. None of these compounds was active against HIV, but some other antiviral activities against HSV-2, CMV, EBV, or VZV, in the micromolar range, were noted in specific cases.

Antibody-Dependent Cell Cytotoxicity↗
PubMed2000

Effects of MS-8209, an amphotericin B derivative, on tumor necrosis factor alpha synthesis and human immunodeficiency virus replication in macrophages.

Amphotericin B derivatives, such as MS-8209, have been evaluated as a therapeutic approach to human immunodeficiency virus (HIV) infection. We show that MS-8209, like amphotericin B, increases tumor necrosis factor alpha (TNF-alpha) mRNA expression and TNF-alpha production and consequently HIV replication in human macrophages. These effects confirm the pharmacological risk associated with the administration of amphotericin B or its derivatives to HIV-infected patients.

Amphotericin B↗
PubMed2000

Autocloning and amplification of LIP2 in Yarrowia lipolytica.

We synthesized a Yarrowia lipolytica strain overproducing lipase for industrial applications by using long terminal repeat (zeta) of the Y. lipolytica retrotransposon Ylt1 and an allele of URA3 with a promoter deletion to construct JMP3. JMP3 is a derivative of plasmid pHSS6 carrying a NotI-NotI cassette which contains a defective URA3 allele, a polylinker sequence, and the zeta region for targeting to multiple sites in the genome of the recipient. We inserted the LIP2 gene (encoding extracellular lipase) under the control of the strong POX2 promoter into JMP3 to generate JMP6. The pHSS6 region was removed by NotI digestion prior to transformation. Two Y. lipolytica strains transformed with the JMP6 LIP2 cassette had a mean of 10 integrated copies devoid of the Escherichia coli region, corresponding to an autocloning event. The copy number in the transformants was stable even after 120 generations in nonselective and lipase-inducing conditions. The resulting strains could produce 0.5 g of active lipase per liter in the supernatant, 40 times more than the single-copy strain with the LIP2 promoter. This work provides a new expression system in Y. lipolytica that results in strains devoid of bacterial DNA and in strains producing a high level of lipase for industrial uses, waste treatment, and pancreatic insufficiency therapy.

Bacterial Proteins↗
PubMed2000

Characterization of an extracellular lipase encoded by LIP2 in Yarrowia lipolytica.

We isolated the LIP2 gene from the lipolytic yeast Yarrowia lipolytica. It was found to encode a 334-amino-acid precursor protein. The secreted lipase is a 301-amino-acid glycosylated polypeptide which is a member of the triacylglycerol hydrolase family (EC 3.1.1.3). The Lip2p precursor protein is processed by the KEX2-like endoprotease encoded by XPR6. Deletion of the XPR6 gene resulted in the secretion of an active but less stable proenzyme. Thus, the pro region does not inhibit lipase secretion and activity. However, it does play an essential role in the production of a stable enzyme. Processing was found to be correct in LIP2(A) (multiple LIP2 copy integrant)-overexpressing strains, which secreted 100 times more activity than the wild type, demonstrating that XPR6 maturation was not limiting. No extracellular lipase activity was detected with the lip2 knockout (KO) strain, strongly suggesting that extracellular lipase activity results from expression of the LIP2 gene. Nevertheless, the lip2 KO strain is still able to grow on triglycerides, suggesting an alternative pathway for triglyceride utilization in Y. lipolytica.

Amino Acid Sequence↗
PubMed2000

Cardiovascular and pulmonary response to oral administration of ATP in rabbits.

Extracellular purines such as ATP and adenosine participate in the regulation of cardiovascular and respiratory functions through specific P1 and P2 purine receptors. These properties have mainly been described after intravenous infusion. Experiments reported herein were designed to explore the possible effect of oral ATP administration (3 or 20 mg. kg(-1). day(-1)) on vascular, cardiac, and pulmonary functions in rabbits. Whereas a unique oral dose of ATP has no effect, chronic supplementation during 14 days reduces peripheral vascular resistance, pulmonary resistance, and respiratory frequency and increases arterial PO(2). No effect on central blood pressure and heart rate is observed, but an increase of the left ventricular work index is noticed subsequent to the diminution of vascular resistance. Rather similar cardiovascular modifications are observed in rabbits given 20 mg. kg(-1). day(-1) adenosine for 14 days but without variation of respiratory parameters. These original effects of repeated oral treatment with ATP may result from an adaptive metabolic response to nucleoside supplementation that might affect the turnover of extracellular purines leading to P1- and/or P2-receptor activation.

Adenosine↗
PubMed2000

Chronic oral administration of ATP modulates nucleoside transport and purine metabolism in rats.

The effect of repeated oral administration of ATP on purine transport and metabolism was investigated in rats. An increased ability of the gut to capture intraluminal purine nucleosides and to export ATP and nucleosides toward portal bloodstream was observed in rats after 30 days of treatment with 5 mg/kg/day ATP. This was accompanied in erythrocytes by an increased transport of adenosine rapidly transformed into ATP, which in turn was exported toward extracellular fluid. However, these metabolic changes were associated with a paradoxical and progressive diminution of plasma ATP level below that found in control rats and that was not strictly dependent on the ATP dose administered, whereas plasma adenosine concentration remained unchanged. This diminution likely resulted from an increased ectonucleotidase activity, suggesting that the chronic administration of ATP seems to induce a progressive adaptation of purine metabolism. This adaptive response to free purine supplementation affects both intracellular metabolism and purine exchange between intracellular and extracellular compartments. This modification of free purine turnover and delivery may affect physiological parameters under the control of P(1) and P(2) purinoceptors described in different experimental models.

Adenosine↗
PubMed2000

Synthesis and antiproliferative activity of O-silylated nucleoside triazene N-oxide derivatives.

A series of modified nucleosides bearing at varied positions of the sugar moiety one 3-aryl-1-triazeno N1-oxide group and a variable number of O-TBDMS groups have been prepared and their cytotoxicities and cytostaticities measured on different cell lines. Nucleosides bearing an aryltriazeno N-oxide group and O-TBDMS groups are either devoid of cytotoxicity or possess a selective cytotoxicity. On the other hand, nucleosides bearing one triazeno group and no silyl group are devoid of cytotoxicity and silylated nucleosides without triazeno group are generally either devoid of cytotoxicity or unselectively cytotoxic. This indicates that the O-TBDMS group per se is not cytotoxic.

Animals↗
PubMed1999

[Therapeutic prospects for subacute transmissible spongiform encephalopathies].

There is currently no effective therapy available for Creutzfeldt-Jakob disease. However, a limited number of drugs such as polyanions, the amyloid-binding dye Congo red, amphotericin B and anthracyclines have been found to delay the appearance of the clinical signs in experimental prion diseases. Today, the most promising agent appears to be less toxic derivative the amphotericin B, MS-8209. Indeed this compound has a wide spectrum of anti-prion activity and constitute the unique molecule able to prolong survival time when treatment is performed at the late stages of infection. This result represents an important progress in therapeutical approaches of prion diseases and justify the development of new polyene antibiotic derivatives.

Amphotericin B↗
PubMed1999

MS-8209, a water-soluble amphotericin B derivative, affects both scrapie agent replication and PrPres accumulation in Syrian hamster scrapie.

Amphotericin B (AmB) has been shown to delay hamster scrapie. Infectivity studies have been performed previously using AmB in order to understand the relationship between the accumulation of an abnormal isoform (PrPres) of the prion protein and 263K scrapie agent replication in the brain. The first study reported that AmB had no effect upon agent replication, although it delayed the development of both clinical signs and PrPres accumulation. However, subsequent experiments using the same model showed a significant effect both on agent replication and PrPres accumulation early in infection. This fundamental discrepancy was assumed to be linked to differences in experimental protocols. In order to unravel the issue, a new experiment has been performed encompassing different protocols and using an AmB derivative, MS-8209, that can be used at higher doses because of its lower toxicity. The findings of this study exclude the suspected differences in the protocols as the reason for previous conflicting results, and suggest strongly that these discrepancies were due to a low dose of AmB causing a 'threshold effect'. Overall, this study indicates that, in this model, PrPres cannot be dissociated from infectivity by polyene antibiotics.

Amphotericin B↗
PubMed1999

Inhibiting scrapie neuroinvasion by polyene antibiotic treatment of SCID mice.

The polyene antibiotic MS-8209 is currently one of the most effective drugs in the treatment of experimental scrapie. However, its mechanism of action and its site of intervention in the pathogenetical process of scrapie infection are largely unknown. It has been shown previously that the infection of immunodeficient SCID mice by the peripheral route provides a reliable model for direct scrapie neuroinvasion, bypassing the lymphoreticular system. Indeed, a proportion of SCID mice develop scrapie after a similar time to immunocompetent mice, despite their severe immune impairment. This model is now used to clarify the targets of MS-8209. In SCID mice, MS-8209 treatment protected against infection but did not prolong survival time. In SCID mice immunologically reconstituted prior to inoculation, the drug delayed the disease without an effect on the attack rate. These findings strongly suggest that MS-8209 acts by hampering the first step of the neuroinvasion process, i.e. the uptake of the infectious agent by peripheral nerve endings. The mechanism leading to the inhibition of agent propagation to nervous cells is discussed with regard to the properties of polyene antibiotics.

Amphotericin B↗
PubMed1998

Innate resistance to infection by intracellular bacterial pathogens differs in mice selected for maximal or minimal acute inflammatory response.

The intensity of nonspecific immune reaction and the host resistance to facultative intracellular pathogens are found to be associated in lines of mice selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory reactivity. AIRmax are more resistant than AIRmin mice to Salmonella typhimurium and Listeria monocytogenes infection, the differences between lines in LD50 being > 1000 and 100 times, respectively. This difference was shown to be related to the initial bacterial containment at the infectious focus, and to the control of bacterial multiplication in the spleen during the 1st week after s. c. inoculation of the bacteria. Specific immune responses were not deeply affected by the selective process: antibody production and delayed-type hypersensitivity were both of similar intensity in AIRmax and AIRmin mice. The differential susceptibility to infection seems independent of the Nramp-1 locus polymorphism; therefore, these two lines represent a powerful model for investigating the role of other genetic loci regulating the nonspecific immunity effectors in the course of infectious diseases.

Acute-Phase Reaction↗
PubMed1997

Identification of a chemokine receptor encoded by human cytomegalovirus as a cofactor for HIV-1 entry.

The human cytomegalovirus encodes a beta-chemokine receptor (US28) that is distantly related to the human chemokine receptors CCR5 and CXCR4, which also serve as cofactors for the entry into cells of human immunodeficiency virus-type 1 (HIV-1). Like CCR5, US28 allowed infection of CD4-positive human cell lines by primary isolates of HIV-1 and HIV-2, as well as fusion of these cell lines with cells expressing the viral envelope proteins. In addition, US28 mediated infection by cell line-adapted HIV-1 for which CXCR4 was an entry cofactor.

AIDS-Related Opportunistic Infections↗