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J C Simon

Publications and source records attributed to J C Simon.

At least 37 records · Page 2Linked to original sources
PubMed2001

CD44 is the principal mediator of hyaluronic-acid-induced melanoma cell proliferation.

Interactions of the extracellular matrix component hyaluronic acid and its cellular receptors CD44 and RHAMM/IHABP have been linked to tumor progression and metastasis formation. We investigated the expression and hyaluronic-acid-dependent functions of CD44 and RHAMM/IHABP in human melanoma. Immunohistochemistry of tumor specimens at different stages of melanoma progression revealed an increased expression of CD44 and RHAMM/IHABP. High mRNA expression of CD44 was found in three highly tumorigenic melanoma cell lines compared with less tumorigenic melanoma cells or nontransformed melanocytes. RHAMM/IHABP expression was upregulated in all cell lines analyzed but not in melanocytes. In contrast to the cell surface localization of CD44, RHAMM/IHABP was detected exclusively within the cytoplasm of melanoma cells. Binding and adhesion of melanoma cells to hyaluronic acid is mainly CD44 dependent as it was inhibited to 60%--80% by an anti-CD44 monoclonal antibody whereas anti-RHAMM/IHABP sera had no effect. Culture of melanoma cells in the presence of hyaluronic acid resulted in a dose-dependent, CD44-mediated increase of melanoma cell proliferation and enhanced release of basic fibroblast growth factor and transforming growth factor beta 1. We conclude that (i) the expression of CD44 and RHAMM/IHABP is increased during melanoma progression, (ii) CD44 is the principal hyaluronic acid surface receptor on melanoma cells, and (iii) the hyaluronic-acid-induced increase of the proliferative capacity of melanoma cells is mainly dependent on CD44--hyaluronic acid interactions.

Antigens, Surface↗
PubMed2001

UVB-irradiated dendritic cells are impaired in their APC function and tolerize primed Th1 cells but not naive CD4+ T cells.

We have shown that low-dose UVB radiation converts Langerhans cells (LC) from immunogenic to tolerogenic APC. Therefore, we questioned whether low-dose UVB irradiation of bone marrow-derived dendritic cells (DC) alters their APC function, thereby inducing tolerance in T cells. To address this issue, cocultures of DC; and naive, allogeneic T cells; naïve, OVA-specific TCR-transgenic T cells from DO11.10 mice; or primed, antigen-specific T cells using the Th1 clone AE7 were analyzed. First, we found low-dose UVB-irradiated DC (UVB-DC) to dose-dependently (50-200 J/m2) inhibit T-cell proliferation of naive and primed T cells. In addition, supernatants harvested from cocultures of UVB-DC and naive T cells showed markedly reduced levels of IL-2 and IFN-gamma and to a lesser degree of IL-4 and IL-10, suggesting a preferential down-regulation of Th1 responses by UVB-DC. FACS analysis of UVB-DC revealed no changes in surface expression of MHC, costimulatory, and adhesion molecules. To test tolerance induction, allo- or antigen-specific T cells isolated from cocultures with unirradiated DC and UVB-DC were restimulated with unirradiated DC or IL-2. It is interesting that UVB-DC induced antigen-specific tolerance in the Th1 clone AE7. In contrast, UVB-DC induced a partial inhibition of allogeneic T-cell proliferation but no tolerance with similar unresponsiveness to restimulation with IL-2 and unirradiated DC irrespective of their haplotype. Similar observations were made when naive, TCR-transgenic T cells from DO11.10 mice were used. In conclusion, UVB-DC are impaired in their APC function and tolerize the primed antigen-specific Th1 clone AE7 but not naive allo- or OVA-specific T cells.

Animals↗
PubMed2001

Microsatellite allele sizing: difference between automated capillary electrophoresis and manual technique.

By comparing data collected with different automated sequencers and a manual technique (fragment separation in a silver-stained polyacrylamide gel), we found strong discrepancies in allele size of microsatellite loci. To quantify the sizing bias generated by automated capillary electrophoresis, we typed 51 alleles at seven loci andfound that differences between actual (manual) and called (automated) sizing were inversely related to locus size. This result seems independent of the fluorescent dye but might be due to different migration patterns of the size standard and the microsatellite loci. Thus, it is essential to distinguish between actual (that can only be confirmed by sequencing) and called (obtained with automated sequencer) allele sizes. To enable the comparison of data collected by different laboratories on different instruments, the greatest attention should be paid to material and protocol descriptions used for allele sizing, and reference standard DNA genotypes should be shared between collaborating laboratories. Without these precautions, scoring errors in allele size might result in important misleading conclusions.

Alleles↗
PubMed2001

The role of CD44 during CD40 ligand-induced dendritic cell clustering and maturation.

The interaction between CD40 on dendritic cells (DC) and its ligand CD154 has been recognized to be an important feature in the maturation of DC. Here, we were interested in the role of CD44 a surface receptor shown to mediate cell-cell adhesion and binding to Hyaluronic acid (HA). Western blot analysis of human DC stimulated for 3-12 h with CD154 revealed the rapid induction of the 85 kDa standard form of CD44 and an increased HA-binding affinity. Time-lapse video-imaging microscopy of human DC co-cultured on CD154-transfected murine fibroblasts showed that the CD44 up-regulation coincided with the rapid induction of homotypic DC clustering, which did not occur on empty vector-transfected fibroblasts. In this system, addition of anti-CD44s mAbs abrogated DC-cluster formation, thereby inhibiting further maturation, as shown by a reduced TNF-alpha production and inhibition of CD154-induced MHC class II up-regulation. However, co-incubation with HA-degrading enzymes induced no changes in the CD154-mediated DC clustering and maturation.

Animals↗
PubMed2000

Oligosaccharides of hyaluronan are potent activators of dendritic cells.

The extracellular matrix component hyaluronan (HA) exists physiologically as a high m.w. polymer but is cleaved at sites of inflammation, where it will be contacted by dendritic cells (DC). To determine the effects of HA on DC, HA fragments of different size were established. Only small HA fragments of tetra- and hexasaccharide size (sHA), but not of intermediate size (m.w. 80, 000-200,000) or high m.w. HA (m.w. 1,000,000-600,000) induced immunophenotypic maturation of human monocyte-derived DC (up-regulation of HLA-DR, B7-1/2, CD83, down-regulation of CD115). Likewise, only sHA increased DC production of the cytokines IL-1beta, TNF-alpha, and IL-12 as well as their allostimulatory capacity. These effects were highly specific for sHA, because they were not induced by other glycosaminoglycans such as chondroitin sulfate or heparan sulfate or their fragmentation products. Interestingly, sHA-induced DC maturation does not involve the HA receptors CD44 or the receptor for hyaluronan-mediated motility, because DC from CD44-deficient mice and wild-type mice both responded similarly to sHA stimulation, whereas the receptor for hyaluronan-mediated motility is not detectable in DC. However, TNF-alpha is an essential mediator of sHA-induced DC maturation as shown by blocking studies with a soluble TNFR1. These findings suggest that during inflammation, interaction of DC with small HA fragments induce DC maturation.

Adjuvants, Immunologic↗
PubMed2000

Downregulation of platelet-activating factor responsiveness during maturation of human dendritic cells.

Dendritic cells (DCs) are specialized antigen-presenting cells characterized by their ability to migrate into target sites, process antigens, and activate naive T-cells. Biological activities of platelet-activating factor (PAF) and the cytokine macrophage inflammatory protein-3beta (MIP-3beta) as well as the mRNA expression of their receptors were characterized in human DCs during lipopolysaccharide (LPS)-promoted maturation. Platelet-activating factor induced calcium transients, migration-associated actin polymerization response, and chemotaxis in immature human dendritic cells differentiated in vitro from monocytes with interleukin-4 and granulocyte macrophage colony stimulating factor. In addition, RT-PCR experiments indicated mRNA expression of the PAF receptor in these immature DCs. Cell studies and mRNA analyses further revealed that immature DCs neither respond to MIP-3beta nor express its specific receptor, CCR7. Induction of cell differentiation by LPS led to the loss of the mRNA expression of the PAF receptor, accompanied by decreasing intracellular calcium release, actin polymerization, and migration after stimulation with PAF. In contrast, LPS treatment induced increasing responsiveness toward MIP-3beta and mRNA expression of CCR7. Comparable data regarding mRNA expression of PAF receptor and PAF responsiveness were also obtained with another maturation protocol using TNFalpha instead of LPS. The direct comparison between the two different protocols showed a slower decrease of PAF responsiveness induced by TNFalpha than by LPS. These results show the loss of PAF responsiveness associated with downregulation of PAF receptor mRNA expression during LPS- and TNFalpha-induced maturation in human DCs. Therefore, these findings point to a functional relevance of PAF in recruiting immature DCs, whereas MIP-3beta might regulate the migration of DCs at a later stage of maturation.

Antigen Presentation↗
PubMed2000

Human dendritic cells are a physiological source of the chemotactic arachidonic acid metabolite 5-oxo-eicosatetraenoic acid.

OBJECTIVE: The arachidonic acid metabolite, 5-oxo-eicosatetraenoic acid (5-oxo-ETE), is a potent chemotaxin for neutrophils and eosinophils. The aim of this study was to identify physiological conditions and stimulators of 5-oxo-ETE synthesis, because no such conditions have yet been identified. METHODS: Human neutrophils and monocyte-derived dendritic cells were prepared and 5-oxo-ETE synthesis analyzed using precolumn/reversed-phase HPLC under different conditions and with several physiological and unphysiological stimuli. RESULTS: Incubation of neutrophils with 5-hydroxyeicosatetraenoic acid (5-HETE) resulted in the synthesis of about 3.4 nM 5-oxo-ETE per 10(6) cells in 1 ml under optimal conditions. The synthesis was enhanced about 8-fold with the unphysiological stimuli calcium ionophore A23187 and phorbol 12-myristate 13-acetate (PMA). No significant effect was observed with different physiological activators. Under optimal conditions, human dendritic cells produced about 50 nM 5-oxo-ETE per 10(6) cells in 1 ml. The synthesis could be increased with PMA and A23187 by about 50%. Again, no effect could be observed with physiological agents for dendritic cells such as complement fragment C5a, platelet activating factor, N-formyl peptides and interleukin-5. CONCLUSIONS: These data identified dendritic cells as the only yet known physiological source of relevant amounts of 5-oxo-ETE. This suggests a regulatory function of dendritic cells in the induction of inflammatory neutrophil and eosinophil infiltration caused by 5-oxo-eicosatetraenoic acid.

Arachidonic Acids↗
PubMed2000

Effect of topical application of Hypericum perforatum extract (St. John's wort) on skin sensitivity to solar simulated radiation.

St. John's wort (Hypericum perforatum) is a tradional folk remedy that is used for the topical treatment of superficial wounds, scars and burns. A characteristic metabolite of St. John's wort is the photodynamic active plant pigment hypericin. It is known that hypericin may cause a severe photodermatitis called hypericism when higher amounts of St. John's wort are ingested orally. To date, no reports on the photosensitizing capacity of topical application of St. John's wort are available. Here, we investigated the effects of Hypericum oil (hypericin 110 microg/mL) and Hypericum ointment (hypericin 30 microg/mL) on skin sensitivity to solar simulated radiation. Sixteen volunteers of the skin types II and III were tested on their volar forearms with solar simulated radiation for photosensitizing effects of Hypericum oil (n=8) and Hypericum ointment (n=8). The minimal erythema dose (MED) was determined by visual assessment, and skin erythema was evaluated photometrically. With the visual erythema score, no change of the MED could be detected after application of either Hypericum oil or Hypericum ointment (P>0.05). With the more sensitive photometric measurement, an increase of the erythema-index after treatment with the Hypericum oil could be detected (P< or =0.01). The results do not provide evidence for a severe phototoxic potential of Hypericum oil and Hypericum ointment, detectable by the clinically relevant visual erythema score. However, the trend towards increased photosensitivity detected with the more sensitive photometric measurement could become relevant in fair-skinned individuals, in diseased skin or after extended solar irradiation.

Administration, Cutaneous↗
PubMed2000

Topical application of St John's wort (Hypericum perforatum L.) and of its metabolite hyperforin inhibits the allostimulatory capacity of epidermal cells.

St John's wort (Hypericum perforatum) is a traditional herbal medicine that is used for the topical treatment of superficial wounds, burns and dermatitis. The characteristic metabolites of St John's wort are the photodynamic active plant pigment hypericin and the phloroglucin-derivative hyperforin. To date, no studies on immunomodulatory properties of topical preparations of St John's wort have been performed. Here, we investigated the alloantigen presenting function of human epidermal cells (EC) exposed to Hypericum ointment in vivo in a mixed EC lymphocyte reaction (MECLR). The effect of Hypericum ointment was compared with the immunosuppressive effect of solar-simulated radiation (SSR). Subsequently, we tested purified hyperforin in vivo and in vitro in a MECLR to evaluate its possible contribution to the effect of the Hypericum ointment. Furthermore, we assessed the effect of hyperforin on the proliferation of peripheral blood mononuclear cells (PBMC) in vitro. Compared with untreated skin, treatment with Hypericum ointment resulted in a significant suppression of the MECLR (P </= 0.001) that was similar to the effect of SSR. The combination of Hypericum ointment plus SSR was not significantly different from either treatment alone. EC isolated from skin treated with the hyperforin containing ointment also showed a reduced capacity to stimulate the proliferation of allogeneic T cells (P </= 0.001). Similarly, in vitro incubation of EC with hyperforin suppressed the proliferation of alloreactive T cells (P </= 0.001). Furthermore, hyperforin inhibited the proliferation of PBMC in a dose-dependent manner, without displaying pronounced toxic effects as determined by Trypan blue staining. The results demonstrate an inhibitory effect of Hypericum extract and of its metabolite hyperforin on the MECLR and on the proliferation of T lymphocytes that may provide a rationale for the traditional treatment of inflammatory skin disorders with Hypericum extracts.

Adjuvants, Immunologic↗
PubMed2000

Evidence for predominant clones in a cyclically parthenogenetic organism provided by combined demographic and genetic analyses.

Aphids are particularly interesting models in the study of genetic and demographic components of plant adaptation because of their breeding system which combines parthenogenesis and sexual reproduction (i.e. cyclical parthenogenesis), and the frequent emergence of host-adapted races reported in this group. In this paper, patterns of host adaptation were assessed on local populations of the aphid Sitobion avenae by following their demographic and genetic structure in a maize field for two consecutive years. The existence of putative generalist (polyphagous) or specialized (host-adapted) genotypes was also investigated by comparing the genotypic distribution of this aphid on maize and other cultivated host plants, using five microsatellite loci. Although population dynamics revealed strong variation in aphid abundance during the colonization period on maize, two genotypes identified at seven additional microsatellite loci were predominant and exhibited stable frequencies over cropping season and between years. Based on present and earlier studies, these two prevalent genotypes were shown to survive on different host plants other than maize, to colonize large geographical zones and to persist parthenogenetically for several years. All these data strongly suggest that these two genotypes are asexual generalist clones that could have been favoured by agricultural practices encountered in western Europe. Besides these two clones, a continual replacement of rare genotypes was observed on maize in both years. Hypotheses involving selection via aphid-plant interactions and natural enemies were proposed for explaining the disappearance of these genotypes on maize.

Alleles↗
PubMed2000

Peptide immunization indicates that CD8+ T cells are the dominant effector cells in trinitrophenyl-specific contact hypersensitivity.

The identity of the effector T cell population involved in contact hypersensitivity is still questionable with evidence promoting both CD4+ or CD8+ T cells. Previous experimental studies have relied on the in vivo depletion of T cell subsets using antibody, or the use of knock-out mice with deficiencies in either CD4+ or CD8+ T cell-mediated immunity. To address the role of the class I- and class II-mediated pathways of T cell activation in contact hypersensitivity responses in mice with an intact immune system, we utilized various trinitrophenyl-derivatized peptides, which bind specifically with H-2Kb (major histocompatibility complex class I) or H-2I-Ab (major histocompatibility complex class II). The subcutaneous injection of major histocompatibility complex class II-specific, but not of class I-binding, hapten-derivatized peptides in incomplete Freund's adjuvant induced specific, albeit low, contact hypersensitivity responsiveness to trinitrochlorobenzene. When bone-marrow-derived dendritic cells, however, were pulsed with the same peptides and administered intradermally, the opposite result was observed, namely that the class I binding peptides induced contact hypersensitivity responses similar to that observed after epicutaneous trinitrochlorobenzene application. In contrast, dendritic cells pulsed with major histocompatibility complex class II binding peptides did not reproducibly sensitize for contact hypersensitivity responses. Surprisingly, both immunization protocols efficiently induced CD8+ effector T cells. These results support the notion that CD8+ T cells are the dominant effector population mediating contact hypersensitivity responsiveness and that the CD4+ T cell subset only contributes little if at all.

Animals↗
PubMed2000

Magnesium ions inhibit the antigen-presenting function of human epidermal Langerhans cells in vivo and in vitro. Involvement of ATPase, HLA-DR, B7 molecules, and cytokines.

The combination of seawater baths and solar radiation at the Dead Sea is known as an effective treatment for patients with psoriasis and atopic dermatitis. Dead Sea water is particularly rich in magnesium ions. In this study we wished to determine the effects of magnesium ions on the capacity of human epidermal Langerhans cells to stimulate the proliferation of alloreactive T cells. Twelve subjects were exposed on four subsequent days on the volar aspects of their forearms to 5% MgCl2, 5% NaCl, ultraviolet B (1 minimal erythemal dose), MgCl2 + ultraviolet B, and NaCl + ultraviolet B. Epidermal sheets were prepared from punch biopsies and were stained for ATPase and HLA-DR. Compared with untreated skin, the number of ATPase+/HLA-DR+ Langerhans cells was significantly reduced after treatment with MgCl2 (p = 0.0063) or ultraviolet B (p = 0.0005), but not after NaCl (p = 0.7744). We next questioned whether this reduced expression of ATPase and HLA-DR on Langerhans cells bears a functional relevance. Six subjects were treated on four subsequent days with 5% MgCl2, ultraviolet B (1 minimal erythemal dose), and MgCl2 + ultraviolet B. Epidermal cell suspensions from treated and untreated skin were assessed for their antigen-presenting capacity in a mixed epidermal lymphocyte reaction with allogeneic naive resting T cells as responder cells. Treatment with MgCl2, similarly to ultraviolet B, significantly reduced the capacity of epidermal cells to activate allogeneic T cells (p = 0.0356). Magnesium ions also suppressed Langerhans cells function when added to epidermal cell suspensions in vitro. The reduced antigen-presenting capacity of Langerhans cells after treatment with MgCl2 was associated with a reduced expression by Langerhans cells of HLA-DR and costimulatory B7 molecules, and with a suppression of the constitutive tumor necrosis factor-alpha production by epidermal cells in vitro. These findings demonstrate that magnesium ions specifically inhibit the antigen-presenting capacity of Langerhans cells and may thus contribute to the efficacy of Dead Sea water in the treatment of inflammatory skin diseases.

Adenosine Triphosphatases↗
PubMed2000

Long-wave UVA offers partial protection against UVB-induced immune suppression in human skin.

Ultraviolet-B (UVB, 280-320 nm) interferes with the generation of cell-mediated immunity to contact allergens applied epicutaneously on the irradiated site. To investigate whether pretreatment with UVA-1 (340-400 nm) protects against the UVB-induced immune suppression we sensitized human volunteers with diphenylcyclopropenone (DPCP) on normal buttock skin (n= 12), on UVB-irradiated buttock skin (n=21), on buttock skin pretreated with UVA-1 (n= 12), and on buttock skin pretreated with UVA-1 and thereafter irradiated with UVB (n=22). Sensitization on UVB-irradiated skin reduced the immunization rate to DPCP compared with sensitization on non-irradiated skin (p<0.01) and skin pretreated with UVA-1 (p<0.01). In contrast, the immunization rate in the group of volunteers sensitized on skin pretreated with UVA-1 before UVB irradiation was significantly higher than the immunization rate in the group of volunteers sensitized on UVB-irradiated skin alone (p<0.05). These results indicate that pretreatment with UVA-1 under certain conditions offers partial protection against the UVB-induced reduction in the immunization rates to epicutaneous allergens.

Adult↗
PubMed2000

Clones of pea aphid, Acyrthosiphon pisum (Hemiptera: aphididae) distinguished using genetic markers, differ in their damaging effect on a resistant alfalfa cultivar.

CUF 101, a resistant cultivar of alfalfa, was exposed to 15 clones of Acyrthosiphon pisum Harris collected from alfalfa fields in three regions of France (east, south, central west) to determine whether the level of resistance varied across the different clones. The survival of alfalfa seedlings infested at the cotyledon stage was assessed using a standardized method. Although no difference in seedling mortality was detected between clones grouped by region, there was a significant variation among the 15 pea aphid clones. In particular, two clones of southern origin were more aggressive. In addition, the different pea aphid clones were characterized using allozyme and RAPD-PCR markers. Among the 15 clones, seven allozyme genotypes (plus one when adding colour polymorphism) and 12 RAPD-PCR genotypes were distinguished. The two southern clones differing by their aggressiveness on the resistant alfalfa belonged to the same allozyme and RAPD genotype which was distinct from the other pea aphid clones. Our results reinforce the need to take into account aphid genetic diversity in breeding programmes for resistance in cultivated plants.

Agriculture↗
PubMed2000

Recent advances in phototherapy.

This synopsis reviews recent developments in dermatological phototherapy. UVA1 phototherapy (340-400 nm) is effective in the treatment of inflammatory skin diseases such as acutely exacerbated atopic dermatitis, localized scleroderma, urticaria pigmentosa and disseminated granuloma annulare. Narrowband UVB radiation (311-313 nm) is used successfully as monotherapy or combined with dithranol, oral retinoids or 8-MOP in psoriasis, atopic dermatitis (AD) or photosensitivity disorders such as polymorphic light eruption. Bath water delivery of 8-methoxypsoralen and subsequent UVA-irradiation (PUVA bath therapy) for the treatment of psoriasis as well as for mycosis fungoides, localized scleroderma, urticaria pigmentosa or lichen planus is an effective alternative to its systemic application. The combination of salt water brine baths in different concentrations and subsequent UVA/B irradiation is used increasingly for the treatment of psoriasis or AD. Extracorporeal photopheresis (ECP) has proven to be a very effective treatment modality for cutaneous T cell lymphoma, chronic graft-versus-host disease and certain autoimmune diseases such as systemic scleroderma or pemphigus. However, despite the documented benefits of these new treatment modalities, little data exist as of yet on potential long-term side effects, thus the indications for these therapies should be considered carefully and patients should be followed up at regular intervals.

Female↗