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Biomedical subjects

T A Luger

Publications and source records attributed to T A Luger.

At least 73 records · Page 4Linked to original sources
PubMed2000

The role of melanocortins in skin homeostasis.

Melanocortins are structurally related bioactive peptides which are produced by many extra-neural tissues including the skin. All of the melanocortins (alpha, beta, and gamma-melanocyte-stimulating hormone and adrenocorticotropin) have melanotropic activity but can elicit many other effects on skin cells. On the basis of in vitro and in vivo findings melanocortins have been shown to regulate immune and inflammatory responses, hair growth, exocrine gland activity and extracellular matrix composition. These effects are mediated by melanocortin receptors among which the melanocortin-1 receptor is most ubiquitously expressed by human skin cells. Simultaneous expression of melanocortins and their receptors suggest a complex autocrine and/or paracrine regulatory network whose disruption invariably affects skin homeostasis. Expression of melanocortin receptors on various skin cell types further indicates novel pharmacological targets for the treatment of skin diseases.

Animals↗
PubMed1999

Reduced ultraviolet-induced carcinogenesis in mice with a functional disruption in B7-mediated costimulation.

Immunosuppression by UV light contributes significantly to the induction of skin cancer by suppressing the cell-mediated immune responses which control the development of carcinogenesis. The B7/CD28-CTLA-4 signaling pathway provides costimulatory signals essential for Ag-specific T cell activation. To investigate the role of this pathway in photocarcinogenesis, we utilized transgenic (Tg) mice which constitutively express CTLA-4Ig, a high-affinity CD28/CTLA-4 antagonist that binds to both B7-1 and B7-2. The transgene is driven by a skin-specific promoter yielding high levels of CTLA-4Ig in the skin and serum. Chronic UV exposure of CTLA-4Ig Tg mice resulted in significantly reduced numbers of skin tumors, when compared to control mice. In addition, Tg mice were resistant to UV-induced suppression of delayed-type hypersensitivity responses to alloantigens. Most importantly, upon stimulation with mitogens and alloantigens, T cells isolated from CTLA-4Ig Tg mice produced significantly less IL-4 but more IFN-gamma compared to control T cells, suggesting an impaired Th2 response and a relative increase of Th1-type immunity. Together, these data show that overall B7 engagement directs immune responses toward the Th2 pathway. Moreover, they point out the crucial role of Th1 immune reactions in the protection against photocarcinogenesis.

Abatacept↗
PubMed1999

Human peripheral blood-derived dendritic cells express functional melanocortin receptor MC-1R.

The neuropeptide, alpha-melanocyte-stimulating hormone (alpha-MSH) is well known for its immunomodulating capabilities. alpha-MSH antagonizes the activity of numerous proinflammatory mediators; for example, Interleukin-1 (IL-1), IL-6, tumor necrosis factor alpha (TNF alpha), and bacterial endotoxin. In vivo alpha-MSH has been shown to suppress a contact hypersensitivity reaction in mice, and to induce hapten-specific tolerance. Since antigen presenting cells (APC) represent key elements for tolerance induction, the effect of alpha-MSH, and the expression of its receptor-melanocortin receptor-1 (MC-1R), on human peripheral blood-derived monocytes and dendritic cells (DC), was investigated. Semiquantitative RT-PCR demonstrated that monocytes and DC express MC-1R, but none of the other members of the MC-receptor family. Moreover, the extent of MC-1R expression correlated with the state of activation of these cells. Since the major ligand of MC-1R is alpha-MSH the question of whether alpha-MSH affects the function of monocyte derived DC was further investigated. We found that the expression of the costimulatory molecules CD 86 and CD 40 was downregulated on DC in the presence of alpha-MSH. Thus, alpha-MSH may exert its immunosuppressive effects by altering the function of APC.

Animals↗
PubMed1999

Role of epidermal cell-derived alpha-melanocyte stimulating hormone in ultraviolet light mediated local immunosuppression.

Irradiation of the skin with ultraviolet light (UV) results in profound alterations of both local and systemic immune responses. These effects are largely mediated by soluble mediators released from epidermal cells in response to UV. It is well known that keratinocytes release increased amounts of cytokines upon UV-irradiation. UV-light also induces the release of the proopiomelanocortin (POMC)-derived peptide, alpha-melanocyte-stimulating hormone (alpha MSH), from keratinocytes, and upregulates the expression of POMC mRNA. alpha MSH exerts a variety of immunomodulating and antiinflammatory effects, mainly by virtue of its capacity to alter the function of antigen presenting cells and vascular endothelial cells. Within an in vivo mouse-model, both intravenous and topical application of alpha MSH resulted in inhibiting the induction, eliciting a contact hypersensitivity reaction, and inducing hapten-specific tolerance. These findings indicate that alpha MSH, released in the epidermis after UV irradiation, may contribute to UV-mediated immunosuppression. The therapeutic application of alpha MSH or alpha MSH-derived peptides may prove to be a useful approach for treating inflammatory skin diseases.

Animals↗
PubMed1999

Molecular basis of the alpha-MSH/IL-1 antagonism.

The neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) is recognized as a potent mediator of immune and inflammatory reactions. Accordingly, alpha-MSH in vitro, as well as in vivo, antagonizes the proinflammatory activities of cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor alpha (TNF alpha). Since the molecular basis of these antiinflammatory effects is not well known, the influence of alpha-MSH on IL-1 beta-induced chemokine production and transcription factor activation was investigated in human keratinocytes. alpha-MSH, in a dose-dependent manner, after 48 h, significantly reduced the IL-1 beta mediated secretion of the C-X-C chemokines IL-8 and Gro alpha. This was confirmed by semiquantitative RT-PCR, which revealed a marked down-regulation in IL-8 and Gro alpha mRNA expression. Furthermore, we determined the effect of alpha-MSH on the IL-1 beta-induced activation of the nuclear factor kappa B (NF kappa B)--a major transcription factor for chemokine genes. Electrophoretic mobility-shift-assays showed that alpha-MSH, in a dose range from 10(-6) to 10(-12) M, significantly downregulated the IL-1 beta-induced activation of NF kappa B 10 minutes after stimulation. Therefore, NF kappa B inactivation by alpha-MSH appears to be a crucial event, one that is responsible for the downregulation of cytokine gene transcription.

Cell Line↗
PubMed1999

Expression of functional melanocortin receptors and proopiomelanocortin peptides by human dermal microvascular endothelial cells.

Human dermal microvascular endothelial cells (HDMEC) are capable of mediating leukocyte-endothelial interactions by the expression of cellular adhesion molecules and the release of proinflammatory cytokines and chemokines during cutaneous inflammation. Recent studies support the important role for proopiomelanocortin (POMC) peptides, such as alpha-melanocyte stimulating hormone (alpha-MSH), as immunomodulators in the cutaneous immune system. The purpose of the studies described here was to determine whether HDMEC serves as both target and source for POMC peptides. RT-PCR and Northern blot studies demonstrated the constitutive expression of mRNA for the adrenocorticotropin (ACTH) and alpha-MSH-specific melanocortin receptor 1 (MC-1R) in HDMEC, and the microvascular endothelial cell line HMEC-1 that could be upregulated by stimulation with IL-1 beta and alpha-MSH. HDMEC responded to stimulation by alpha-MSH with a dose- and time-dependent synthesis and release of the CXC chemokines, IL-8 and GRO alpha. Likewise, alpha-MSH augmented HDMEC chemokine release induced by TNF or IL-1. HD-MEC were found to constitutively express POMC and prohormone convertase 1 (PC-1); the latter being required to generate ACTH from the POMC prohormone. POMC and PC-1 mRNA expression are increased as a result of stimulation with UVB and UVA1 radiation, IL-1, and alpha-MSH. In addition, UV-radiation is capable of inducing the release of HDMEC, ACTH, and alpha-MSH in a time- and dose-dependent fashion. Thus, these data provide evidence that HDMEC are capable of expressing functional MC-1R, POMC, and PC-1 mRNA; and of releasing POMC peptides with UV light, IL-1, and alpha-MSH as regulatory factors. The expression and regulation of these peptides may be of importance, not only for the autocrine or paracrine regulation of physiologic functions of dermal endothelial cells, but also for the regulation of certain microvascular-mediated cutaneous or systemic inflammatory responses.

Animals↗
PubMed1999

Mechanisms of the antiinflammatory effects of alpha-MSH. Role of transcription factor NF-kappa B and adhesion molecule expression.

The recruitment of leukocytes from the circulation to inflamed tissue is regulated by the expression of adhesion molecules on both leukocytes and endothelial cells. The proopiomelanocortin-derived peptide alpha-melanocyte stimulating hormone (alpha-MSH) is known to modulate inflammation. Thus, we investigated the influence of alpha-MSH on the LPS-induced expression of the adhesion molecules E-selectin and VCAM-1 on endothelial cells. Human microvascular endothelial cells (HMEC-1) were treated with LPS (100 ng/ml) alone or in the presence of alpha-MSH (10(-8) to 10(-16) M). RT-PCR analysis showed that alpha-MSH significantly reduced LPS-induced expression of VCAM-1 and E-selectin. Since many adhesion molecules contain regulatory NF-kappa B sites in their promoter region, the role of alpha-MSH in the activation of the transcription factor NF-alpha B was also investigated. alpha-MSH significantly downregulated the LPS-mediated activation of NF-kappa B, in a dose-dependent manner. These findings indicate that modulation of the transcription factor NF-kappa B is a crucial molecular event, one that seems to be responsible for the antiinflammatory effects of alpha-MSH.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Alpha-melanocyte-stimulating hormone modulates activation of NF-kappa B and AP-1 and secretion of interleukin-8 in human dermal fibroblasts.

Alpha-melanocyte-stimulating hormone (alpha-MSH) has evolved as a mediator of diverse biological activities in an ever-growing number of non-melanocytic cell types. One mechanism by which alpha-MSH exerts its effects is modulation of AP-1 and NF-kappa B. These two transcription factors also play an important role in fibroblasts, in extracellular matrix composition, and in cytokine expression. By use of electric mobility shift assays, we demonstrate that alpha-MSH (10(-6) to 10(-14) M) activates AP-1 in human dermal fibroblasts, whereas coincubation with interleukin-1 beta (IL-1 beta) results in suppression of its activation. alpha-MSH also induces activation of NF-kappa B but does not modulate DNA binding on costimulation with IL-1 beta. Since AP-1 and NF-kappa B are key elements in controlling interleukin-8 (IL-8) transcription, human fibroblasts were treated with alpha-MSH and IL-1 beta for 24 hours, and cytokine levels in the supernatants were measured by ELISA. alpha-MSH alone had little effect, whereas coincubation with IL-1 beta led to marked downregulation of IL-8 secretion (at most 288 +/- 152 ng/mL) when compared to treatment with IL-1 beta alone (919 +/- 157 ng/mL). Our results indicate that alpha-MSH exerts modulatory effects on the activation of NF-kappa B and AP-1, and that it can regulate chemokine secretion in human dermal fibroblasts. These effects of alpha-MSH may have important regulatory functions in extracellular matrix composition, wound healing, or angiogenesis.

Cells, Cultured↗
PubMed1999

Characterization of a polyclonal antibody raised against the human melanocortin-1 receptor.

We have generated a polyclonal antibody raised against a synthetic peptide corresponding to the amino acids 2-18 of the extracellular, N-terminal domain of the human melanocortin-1 receptor (MC-1R). Specificity of the affinity-purified anti-MC-1R antibody was confirmed by dot blot analysis with the antigenic peptide. The antibody detected MC-1R antigenicity on the surface of normal human melanocytes and WM35 melanoma cells, as shown by FACS and immunofluorescence analysis. The antibody was suitable for immunoperoxidase staining of deparaffinized skin sections, revealing prominent MC-1R staining of a cutaneous melanoma as opposed to undiseased skin in which normal melanocytes were only occasionally immunoreactive. Distinct adnexal structures in normal skin also displayed MC-1R immunostaining. Specificity of the MC-1R immunoreactivity in each technique was confirmed by preabsorption with the immunogenic peptide, omission, or substitution of the primary antibody with preimmune serum. Our results provide a baseline for future studies on MC-1R expression in diseased human skin.

Amino Acid Sequence↗
PubMed1999

Interleukin-1 protects transformed keratinocytes from tumor necrosis factor-related apoptosis-inducing ligand- and CD95-induced apoptosis but not from ultraviolet radiation-induced apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a new member of the tumor necrosis factor (TNF) family, induces apoptosis primarily of transformed cells. Interleukin-1 was previously found to protect the keratinocyte cell line KB from TRAIL-induced apoptosis, thus we studied whether interleukin-1 also protects from other apoptotic stimuli (ultraviolet radiation (UV), CD95-ligand). Interleukin-1 rescued KB cells from TRAIL- and CD95-induced apoptosis, which was critically dependent on nuclear factor kappaB, because cells transfected with a super-repressor form of the nuclear factor kappaB inhibitor IkappaB were less protected. In contrast, UV-mediated apoptosis was not only not prevented by interleukin-1 but even enhanced. This opposite effect of interleukin-1 was also observed for the expression of the inhibitor of apoptosis proteins (IAP). Whereas TRAIL- and CD95-mediated suppression of IAP expression was partially reversed by interleukin-1, UV-mediated down-regulation of IAPs was not reversed but even further enhanced. Increased apoptosis induced by interleukin-1 plus UV was accompanied by excessive TNFalpha release, implying that enhanced cytotoxicity is due to the additive effect of these two apoptotic stimuli. Accordingly, enhanced apoptosis was reduced by blocking the TNF receptor-1. The opposite effects of interleukin-1 indicate that different mechanisms are involved in UV-induced apoptosis compared with CD95- and TRAIL-mediated apoptosis. Furthermore, the data suggest that whether a signal acts in an antiapoptotic way or not does not only depend on the signal itself but also on the stimulus causing apoptosis.

Apoptosis↗
PubMed1999

Nuclear and cell membrane effects contribute independently to the induction of apoptosis in human cells exposed to UVB radiation.

UVB-induced DNA damage is a crucial event in UVB-mediated apoptosis. On the other hand, UVB directly activates death receptors on the cell surface including CD95, implying that UVB-induced apoptosis can be initiated at the cell membrane through death receptor clustering. This study was performed to measure the relative contribution of nuclear and membrane effects in UVB-induced apoptosis of the human epithelial cell line HeLa. UVB-mediated DNA damage can be reduced by treating cells with liposomes containing the repair enzyme photolyase followed by exposure to photoreactivating light. Addition of photolyase followed by photoreactivation after UVB reduced the apoptosis rate significantly, whereas empty liposomes had no effect. Likewise, photoreactivating treatment did not affect apoptosis induced by the ligand of CD95, CD95L. UVB exposure at 4 degrees C, which prevents CD95 clustering, also reduced the apoptosis rate, but to a lesser extent. When cells were exposed to UVB at 4 degrees C and treated with photolyase plus photoreactivating light, UVB-induced apoptosis was almost completely prevented. Inhibition of caspase-3, a downstream protease in the CD95 signaling pathway, blocked both CD95L and UVB-induced apoptosis, whereas blockage of caspase-8, the most proximal caspase, inhibited CD95L-mediated apoptosis completely, but UVB-induced apoptosis only partially. Although according to these data nuclear effects seem to be slightly more effective in mediating UVB-induced apoptosis than membrane events, both are necessary for the complete apoptotic response. Thus, this study shows that nuclear and membrane effects are not mutually exclusive and that both components contribute independently to a complete response to UVB.

Antigens, CD↗
PubMed1999

Transfection of immature murine bone marrow-derived dendritic cells with the granulocyte-macrophage colony-stimulating factor gene potently enhances their in vivo antigen-presenting capacity.

Ag presentation by dendritic cells (DC) is crucial for induction of primary T cell-mediated immune responses in vivo. Because DC culture from blood or bone marrow-derived progenitors is now clinically applicable, this study investigated the effectiveness of in vitro-generated murine bone marrow-derived DC (Bm-DC) for in vivo immunization protocols. Previous studies demonstrated that GM-CSF is an essential growth and differentiation factor for DC in culture and that in vivo administration of GM-CSF augments primary immune responses, which renders GM-CSF an attractive candidate to further enhance the effectiveness of DC-based immunotherapy protocols. Therefore, immature Bm-DC were transiently transfected with the GM-CSF gene and tested for differentiation, migration, and Ag-presenting capacity in vitro and in vivo. In vitro, GM-CSF gene-transfected Bm-DC were largely unaltered with regard to MHC and costimulatory molecule expression as well as alloantigen or peptide Ag-presenting capacity. When used for in vivo immunizations, however, the Ag-presenting capacity of GM-CSF gene-transfected Bm-DC was greatly enhanced compared with mock-transfected or untransfected cells, as determined by their effectiveness to induce primary immune reactions against hapten, protein Ag, and tumor Ag, respectively. Increased effectiveness in vivo correlated with the better migratory capacity of GM-CSF gene-transfected Bm-DC. These results show that GM-CSF gene transfection significantly enhances the capacity of DC to induce primary immune responses in vivo, which might also improve DC-based vaccines currently under clinical investigation.

Adjuvants, Immunologic↗
PubMed1999

Generation of tumor immunity by bone marrow-derived dendritic cells correlates with dendritic cell maturation stage.

Bone marrow-derived dendritic cells (BmDC) are potent APC and can promote antitumor immunity in mice when pulsed with tumor Ag. This study aimed to define the culture conditions and maturation stages of BmDC that enable them to optimally function as APC in vivo. BmDC cultured under various conditions (granulocyte-macrophage CSF (GM-CSF) or GM-CSF plus IL-4 alone or in combination with Flt3 ligand, TNF-alpha, LPS, or CD40 ligand (CD40L)) were analyzed morphologically, phenotypically, and functionally and were tested for their ability to promote prophylactic and/or therapeutic antitumor immunity. Each of the culture conditions generated typical BmDC. Whereas cells cultured in GM-CSF alone were functionally immature, cells incubated with CD40L or LPS were mature BmDC, as evident by morphology, capacity to internalize Ag, migration into regional lymph nodes, IL-12 secretion, and alloantigen or peptide Ag presentation in vitro. The remaining cultures exhibited intermediate dendritic cell maturation. The in vivo Ag-presenting capacity of BmDC was compared with respect to induction of both protective tumor immunity and immunotherapy of established tumors, using the poorly immunogenic squamous cell carcinoma, KLN205. In correspondence to their maturation stage, BmDC cultured in the presence of CD40L exhibited the most potent immunostimulatory effects. In general, although not entirely, the capacity of BmDC to induce an antitumor immune response in vivo correlated to their degree of maturation. The present data support the clinical use of mature, rather than immature, tumor Ag-pulsed dendritic cells as cancer vaccines and identifies CD40L as a potent stimulus to enhance their in vivo Ag-presenting capacity.

Animals↗
PubMed1999

[Embolia cutis medicamentosa (Nicolau syndrome) after intra-articular injection].

Embolia cutis medicamentosa (Nicolau Syndrome) is a very rare complication of intramuscular injections which presents with extensive necrosis of the injected skin area. Intra-arteria and/or para-arterial injections after prior perforation of certain vessels are discussed as possible pathogenetic mechanisms. We describe the occurrence of embolia cutis medicamentosa after intra-articular injections into the knee.

Anti-Inflammatory Agents↗