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PubMed2004

The effect of LIGHT in inducing maturation of monocyte-derived dendritic cells from MDS patients.

LIGHT is a recently cloned novel cytokine belonging to the TNF family that is selectively expressed on immature dendritic cells (iDCs) generated from monocytes isolated from human PBMCs. In these studies, we demonstrate that exogenous soluble LIGHT or soluble CD40 ligand (CD40L) can promote monocyte-derived dendritic cell maturation in vitro by the up-regulation of CD86, CD80, CD83, and HLA-DR antigen expression. Immature dendritic cells differentiated from monocytes of MDS patients displayed lower levels of costimulatory and HLA-DR molecules compared with iDCs differentiated from monocytes of normal subjects. However, upon induction of maturation by LIGHT or CD40L, the expression of costimulatory and HLA-DR molecules is comparable between DCs from MDS and normal subjects. Exogenous LIGHT- and CD40L-stimulated mature DCs (mDCs) also displayed increased antigen presentation to autologous T lymphocytes (tetanus toxin) or allogeneic T lymphocytes in mixed lymphocyte reactions. DCs matured by LIGHT showed increased secretion of IL-6, IL-12p75, and TNF-alpha, but not IL-1beta. We conclude that both LIGHT and CD40L are immunoregulating factors that induce monocyte-derived iDCs from MDS patients to undergo maturation resulting in increased antigen presentation and T-cell activation. Monocyte-derived DCs can be stimulated to undergo phenotypic and functional changes with LIGHT that might be applied in the development of a DC-based vaccine for MDS treatment.

Antigen Presentation↗

PubMed1999

Chromosome aberrations induced by light ions: Monte Carlo simulations based on a mechanistic model.

PURPOSE: To investigate the mechanisms underlying the induction of chromosome aberrations by ionizing radiation, focusing attention on DNA damage severity, interphase chromosome geometry and the distribution of DNA strand breaks. METHODS: An ab initio biophysical model of aberration induction in human lymphocytes specific for light ions was developed, based on the assumption that 'complex lesions' (clustered DNA breaks) produce aberrations, whereas less severe breaks are repaired. It was assumed that interphase chromosomes are spatially localized and that chromosome break free-ends rejoin pairwise randomly; the unrejoining of a certain fraction of free-ends was assumed to be possible, and small fragments were neglected in order to reproduce experimental conditions. The yield of different aberrations was calculated and compared with some data obtained using Giemsa or FISH techniques. RESULTS: Dose-response curves for dicentrics and centric rings (Giemsa) and for reciprocal, complex and incomplete exchanges (FISH) were simulated; the ratio between complex and reciprocal exchanges was also calculated as a function of particle type and LET. The results showed agreement with data from lymphocyte irradiation with light ions. CONCLUSIONS: The results suggest that clustered DNA breaks are a critical damage type for aberration induction and that interphase chromosome localization plays an important role. Moreover, the effect of a given particle type is related both to the number of induced complex lesions and to their spatial distribution.

Alpha Particles↗

PubMed1978

Effects of caffeine on sister chromatid exchange (SCE) after exposure to UV light or triaziquone studied with a fluorescence plus giemsa (FPG) technique.

Studies are reported that are designed to analyze the mechanism by which caffeine reduces the induction of SCE by UV light or alkylating agents. The substantial points are (1) caffeine does not inhibit SCE formation, and (2) the caffeine-mediated apparent decrease of SCE induction after UV or triaziquone exposure is due to a selective destruction of those metaphases otherwise exhibiting a high number of SCE. These findings and their relevance to the ascertainment of the SCE-forming process are discussed.

Animals↗

PubMed1994

Signal transduction in the sexual life of Chlamydomonas.

Several signal transduction pathways play important roles in the sexual life cycle of Chlamydomonas. Nitrogen deprivation, perhaps sensed as a drop in intracellular [NH4+], triggers a signal transduction pathway that results in altered gene expression and the induction of the gametogenic pathway. Blue light triggers a second signalling cascade which also culminates in gene induction and completion of gametogenesis. New screens have uncovered several mutants in these pathways, but so far we know little about the biochemical events that transduce the environmental signals of nitrogen deprivation and blue light into the changes in gene transcription that produce gametes. Cell-cell contact of mature, complementary gametes elicits a number of responses that prepare the cells for fusion. Contact is sensed by the agglutinin-mediated cross-linking of flagellar membrane proteins. An increase in [cAMP] couples protein cross-linking to the mating responses. In C. reinhardtii the cAMP signal appears to be generated by the sequential stimulation of as many as 3 distinct adenylyl cyclase activities. Although the molecular mechanisms of adenylyl cyclase activations are poorly understood, Ca2+ may play a role. Most of the mating responses appear to be triggered by a cAMP-dependent protein kinase, but here too, Ca2+ may play a role. Numerous mutants are facilitating studies of the signalling pathways that trigger the mating responses. Cell fusion triggers another series of events that culminate in the expression of zygote specific genes. The mature zygote is sensitive to a light signal which stimulates the expression of genes whose products are essential for germination. The signal transduction pathways that trigger zygospore formation and germination are ripe for investigation in this experimentally powerful system.

Animals↗

PubMed2003

Late immature B cells (IgMhighIgDneg) undergo a light chain receptor editing response to soluble self-antigen.

Receptor editing is an important mechanism to modify the Ag specificity of newly developing B cells that are reactive with self-Ags. Previous studies have suggested that late immature B cells, bearing high levels of IgM on their cell surface, are unable to initiate receptor editing and instead are deleted by apoptosis. Using the hen egg lysozyme transgenic system, we show that IgM(high) late-immature B cells are fully capable of receptor editing to soluble self-Ag. This was demonstrated by the induction of new endogenous light chain locus rearrangements and by a single-cell flow cytometric assay using a recombination-activating gene 2-green fluorescence protein reporter transgene. These studies suggest that the developmental window available for immature B cells to edit their Ig receptors, at least in response to certain soluble Ags, extends through the IgM(high) late immature B cell stage.

Animals↗

PubMed1985

[The role of histones H3 and H1 in the formation of thymine-lysine cross-links during UV-irradiation of deoxyribonucleoprotein].

The effect of UV light (lambda = 254 nm) on calf thymus DNP at low ionic strengths was studied. It was found that at the irradiation doses used the protein in the DNA-protein complex increases as the irradiation dose rises. Thermal treatment and acid hydrolysis resulted in a predominant release of histones H3 and H1 from the complex. Data from liquid high performance chromatography, amino acid analysis, thin-layer chromatography point to the induction by UV-light of a thymine-lysine bond, whose formation involves DNA thymines and histone lysine residues, predominantly H3 and H1 fractions.

Animals↗

PubMed1999

Environmental factors in nonmelanoma and melanoma skin cancer.

We discuss the role of sunlight, mostly ultraviolet light (UV), in the induction of nonmelanoma and melanoma skin cancer. Whilst the former seems to be correlated with accumulated exposure, the causation of melanoma is more complex, and may also involve the pattern of, and age at, exposure. The efficacy of sunscreens is debatable; while they protect against UVB wavelengths (290-320 nm), and so extend the time that may be spent in the sun before becoming sunburnt, their use may subject wearers to excessive exposure to UVA (320-400 nm) and visible light. Both epidemiological surveys and experiments with animal models suggest that UVA, and perhaps the visible, may induce melanomas. Although Japanese have a much lower incidence of skin cancer than Caucasians, the dramatic rise in skin cancer in Japanese-Americans in Hawaii exposed to high-intensity irradiation raises concerns. If the Japanese people adopt sun-seeking behavior, or should the levels of UV irradiation rise significantly through depletion of the ozone layer, then this could become an important health problem in future.

Animals↗

PubMed2000

Antiproliferative properties of sphingosine 1-phosphate in human hepatic myofibroblasts. A cyclooxygenase-2 mediated pathway.

Proliferation of hepatic myofibroblasts (hMF) is central for the development of fibrosis during liver injury, and factors that may limit their growth are potential antifibrotic agents. Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid with growth-regulating properties, either via Edg receptors or through intracellular actions. In this study, we examined the effects of S1P on the proliferation of human hMF. Human hMF expressed mRNAs for the S1P receptors Edg1, Edg3, and Edg5. These receptors were functional at nanomolar concentrations and coupled to pertussis toxin-sensitive and -insensitive G proteins, as demonstrated in guanosine 5'-3-O-(thio)triphosphate binding assays. S1P potently inhibited hMF growth (IC(50) = 1 microm), in a pertussis toxin-insensitive manner. Analysis of the mechanisms involved in growth inhibition revealed that S1P rapidly increased prostaglandin E(2) production and in turn cAMP, two growth inhibitory messengers for hMF; C(2)-ceramide and sphingosine, which inhibited hMF proliferation, did not affect cAMP levels. Production of cAMP by S1P was abolished by NS-398, a selective inhibitor of COX-2. Also, S1P potently induced COX-2 protein expression. Blocking COX-2 by NS-398 blunted the antiproliferative effect of S1P. We conclude that S1P inhibits proliferation of hMF, probably via an intracellular mechanism, through early COX-2-dependent release of prostaglandin E(2) and cAMP, and delayed COX-2 induction. Our results shed light on a novel role for S1P as a growth inhibitory mediator and point out its potential involvement in the negative regulation of liver fibrogenesis.

Base Sequence↗

PubMed1995

Positive and negative selection events during B lymphopoiesis.

Early in B-cell development, large numbers of cells have to be generated, each of which expresses only one type of B-cell receptor (i.e. Ig) on its surface. This is achieved by the surface expression of a pre-B cell receptor containing a mu heavy chain/surrogate light chain which differentially provides signals for two responses of precursor B cells at this stage of development. On the one hand, it signals inhibition of further rearrangements of variable heavy chain to diverse-joining heavy chain loci to achieve allelic exclusion at the heavy-chain locus. On the other hand, it signals proliferative expansion by factors between 20 and 100. Later in B-cell development, tolerance to autoantigens must be established and maintained. Tolerance is achieved by developmental arrest and induction of secondary light-chain gene rearrangements in those IgM+ immature B cells that are reactive to autoantigens presented in the primary B-cell generating organs. Even later in development, when mature surface (s)IgM+/sIgD+ B cells encounter autoantigens presented to them in the periphery, either deletion or anergy of the autoantigen-reactive cells occurs. Anergic cells have a sIg-dependent, sIg-proximal defect in signaling and are short-lived. Anergy can be broken in vitro by polyclonal activation via ligation of CD40 in the presence of IL-4. A small part of the remaining immature B cells not reactive to autoantigens are selected to become mature, antigen-reactive sIgM+/sIgD+ B cells. Molecules which might guide such positive selection of B cells still remain to be identified.

Animals↗

PubMed1992

Glutathione and tissue amino acid responses to light-exposed parenteral nutrients.

Effects of infusion of light-exposed (+L) or light-protected (-L) total parenteral nutrition solutions were investigated in rats. The parenteral infusions were carried out for 7 days through jugular cannulas in freely moving rats in metabolic cages. Plasma tyrosine and citrulline, hepatic methionine, valine, isoleucine, leucine and tyrosine, and biliary cystathionine were significantly greater in the -L than +L rats, whereas biliary arginine was significantly lower in the -L compared to +L rats. Bile flow, biliary inorganic phosphate and glucose were significantly lower, whereas biliary total glutathione (GSH+GSSG) was significantly greater in the -L compared to +L animals. These data suggest adverse effects on hepatobiliary function due to light exposure of parenteral nutrients. The endogenous markers used suggest that tight junction permeability, bile acid-independent flow, glutathione and amino acid homeostasis are altered by light exposure and that these changes can be minimized by light protection. The mechanisms involved in the induction of these changes need to be elucidated. The role of light exposure of parenteral nutrients during routine clinical use in the induction of hepatic dysfunction, a common metabolic complication of parenteral nutrition, needs to be considered.

Amino Acids↗

PubMed1985

Structural determination of the ultraviolet light-induced thymine-cytosine pyrimidine-pyrimidone (6-4) photoproduct.

Ultraviolet light induces damage to DNA, with the majority of the damage expressed as the formation of cyclobutane dimers and pyrimidine-pyrimidone (6-4) photoproducts. The (6-4) photoproducts have been implicated as important UV light-induced premutagenic DNA lesions. The most abundant of the (6-4) products is the thymine-cytosine pyrimidine-pyrimidone (6-4) photoproduct, or TC (6-4) product. The structure of the TC (6-4) product was deduced by proton NMR, IR, and fast atom bombardment mass spectroscopy, and the product was found to differ from the previously described photoadduct, Thy(6-4)Pyo, by the presence of an amino group at the 5 position of the 5' pyrimidine. The implications of this structure on DNA base pairing and the induction of ultraviolet light-induced mutations are discussed.

Cytosine↗

PubMed1978

Conditions for establishment of reflex ovulation in light estrous rats.

Continual anovulatory state associating with persistent vaginal cornification (light estrus) was induced by placing 4-day cycling rats under continuous lighting (LL). Uterine cervical stimulation was applied at arbitrary solar hours to light estrous rats showing continual vaginal estrus for more than 2 weeks. The ovulation was induced between 14 and 16 hr after the stimulation dissociating entirely with solar hours. Injection of anti-LHRH serum 5 min after the stimulation but not later than 20 min blocked this ovulation. Ovulation thus induced was always followed by pseudopregnancy with continual leucocytic vaginal smear lasting 10.70 days. The change in concentrations of peripheral serum progesterone during this period was almost similar to that of normal pseudopregnancy except extremely low levels observed at the start and end. Effectiveness of the cervical stimulation for induction of ovulation in light estrous rats was related to not only the duration of light estrus but also the time after transfer to LL, suggesting that the neural mechanism of ovulation in light estrous rats shifted from that of the spontaneous to reflex ovulators due to the extinction of environmental photic cue.

20-alpha-Dihydroprogesterone↗

PubMed1996

Apurinic/apyrimidinic (AP) endonuclease from Dictyostelium discoideum: cloning, nucleotide sequence and induction by sublethal levels of DNA damaging agents.

We have cloned an AP endonuclease gene (APEA) from Dictyostelium discoideum, along with 1.8 kb of the 5' flanking region. There are no introns. The sequence predicts a protein of 361 amino acids, showing high homology to the major human/Escherichia coli exonuclease III family of AP endonucleases. There is 47% identity and 64% similarity to the Ape endonuclease of human cells using the C-terminal 257 amino acids of the Dictyostelium protein. The 104 amino acids on the N-terminus show only low homology with other AP endonucleases. Instead, this region shows high homology with the acid-rich regions of proteins associated with chromatin, such as nucleolins and HMG proteins. The gene is transcriptionally activated up to 7-fold after treatment of cells with sublethal levels of DNA damaging agents, including ultraviolet light, MNNG and bleomycin. Induction does not occur following blocking of replication fork polymerases with aphidicolin. It is not eliminated by treatment with kinase or phosphatase inhibitors. Four DNA damage-sensitive mutants all retained the DNA damage-induced up-regulation.

Animals↗

PubMed1996

Moloney murine leukemia virus activates NF-kappa B.

Nonacutely transforming retroviruses, such as Moloney murine leukemia virus (M-MuLV), differ from transforming viruses in their mechanisms of tumor induction. While the transforming viruses cause tumors by transduction of oncogenes, the leukemia retroviruses, lacking oncogenes, employ other mechanisms, including promoter insertion and enhancer activation. Although these two mechanisms occur in many tumors induced by leukemia viruses, a substantial proportion of such tumors do not show site-specific proviral insertions. Thus, other, unidentified virus-driven mechanisms may participate in tumorigenesis. In these studies, we show that infection of cells by M-MuLV activates expression of Rel family transcription factors. In murine cells chronically infected with M-MuLV, gel shift analyses with kappaB DNA-binding motifs from the murine immunoglobulin kappa light chain enhancer demonstrated induction of at least two distinct kappaB enhancer-binding complexes. Supershifting and immunoblotting analyses defined p50, p52, RelB, and c-Rel subunits as constituents of these virus-induced protein complexes. Transient transfections performed with kappaB-dependent reporter plasmids showed transcriptional activation in M-MuLV-infected cells relative to uninfected cells. Induction of Rel/NF-kappaB transcription factor activity by M-MuLV infection may prove relevant to the mechanism of M-MuLV-induced leukemia.

3T3 Cells↗

PubMed2003

Synchronization of the molecular clockwork by light- and food-related cues in mammals.

The molecular clockwork in mammals involves various clock genes with specific temporal expression patterns. Synchronization of the master circadian clock located in the suprachiasmatic nucleus (SCN) is accomplished mainly via daily resetting of the phase of the clock by light stimuli. Phase shifting responses to light are correlated with induction of Per1, Per2 and Dec1 expression and a possible reduction of Cry2 expression within SCN cells. The timing of peripheral oscillators is controlled by the SCN when food is available ad libitum. Time of feeding, as modulated by temporal restricted feeding, is a potent 'Zeitgeber' (synchronizer) for peripheral oscillators with only weak synchronizing influence on the SCN clockwork. When restricted feeding is coupled with caloric restriction, however, timing of clock gene expression is altered within the SCN, indicating that the SCN function is sensitive to metabolic cues. The components of the circadian timing system can be differentially synchronized according to distinct, sometimes conflicting, temporal (time of light exposure and feeding) and homeostatic (metabolic) cues.

ARNTL Transcription Factors↗

PubMed1985

Induction of in vitro transformation by near-u.v. light and its interaction with beta-propiolactone.

The ability of u.v.-A light (320-400 nm) to induce cellular transformation in vitro and to modify chemical carcinogen-induced cellular transformation was investigated in BALB/c 3T3 cell cultures. When administered as a series of nontoxic exposures, u.v.-A alone was found to induce cellular transformation as a linear function of the numbers of u.v-A exposures. Possible interactions of u.v.-A with environmentally encountered chemical carcinogens were studied by examining the effects of u.v.-A light exposures on cellular transformation in cells exposed to the direct acting carcinogen, beta-propiolactone (BPL), an alkylating agent, with a standard initiation/promotion protocol. Twenty-four hours after a single treatment with 2.5 micrograms/ml of beta-propiolactone, cells were exposed to 3.0 kJ/m2 of u.v.-A light. U.v.-A exposures were repeated weekly for up to 5 weeks, after which cells were fixed, stained and dishes were scored for type III transformed foci. Weekly exposures to u.v.-A alone for 5 weeks induced approximately 3 foci/dish. Treatment with BPL alone induced approximately 1 focus/dish (background was 0.17 foci/dish). A combination of the two treatments resulted in a marked increase in the yield of transformed foci/dish, with the u.v.-A enhancement increasing with increasing numbers of exposures (approximately 10 foci/dish after a single exposure to BPL and five u.v.-A exposures). These results suggest a synergistic interaction between BPL and subsequent u.v.-A exposures in the induction of in vitro neoplastic transformation.

Animals↗

PubMed1985

Arginine reversion and lambda induction in E. coli with benzothiadiazine diuretics irradiated with near-ultraviolet light.

Photoinduced genotoxicity of benzothiadiazine diuretics was studied with regard to mutagenic and lambda prophage-inducing activities in E. coli. Irradiation of E. coli with near-ultraviolet light in the presence of hydrochlorothiazide or methyclothiazide caused mutations of strain Hs30R argF(Am) to the prototrophic phenotype and induction of lambda from the lysogenic bacteria AB1157(lambda). Both drugs showed nearly the same amount of activity. Penfluzide showed much less mutagenic and much less prophage-inducing activity than did hydrochlorothiazide and methyclothiazide.

Bacteriophage lambda↗

PubMed1998

A light-independent developmental mechanism potentiates flavonoid gene expression in Arabidopsis seedlings.

Throughout the plant kingdom expression of the flavonoid biosynthetic pathway is precisely regulated in response to developmental signals, nutrient status, and environmental stimuli such as light, heat and pathogen attack. Previously we showed that, in developing Arabidopsis seedlings, flavonoid genes are transiently expressed during germination in a light-dependent manner, with maximal mRNA levels occurring in 3-day-old seedlings. Here we describe the relationship between developmental and environmental regulation of flavonoid biosynthesis by examining phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) mRNA levels in germinating Arabidopsis seedlings as a function of light, developmental stage and temperature. We show that seedlings exhibit a transient potential for induction of these four genes, which is distinct from that observed for chlorophyll a/b-binding protein(CAB). The potential for flavonoid gene induction was similar in seedlings grown in darkness and red light, indicating that induction potential is not linked to cotyledon expansion or the development of photosynthetic capacity. The evidence for metabolic regulation of flavonoid genes during seedling development is discussed.

Acyltransferases↗