Biomedical subjects

J O Funk

Publications and source records attributed to J O Funk.

28 records · Page 2Linked to original sources

PubMed1996

Protein kinase C activation is involved in ultraviolet B irradiation-induced endothelial cell ICAM-1 up-regulation and lymphocyte-endothelium interaction in vitro.

Lymphocyte-endothelium interactions are pivotal steps in mediating inflammatory responses. The authors have analysed the influence of ultraviolet B (UVB) irradiation on intercellular adhesion molecule (ICAM)-1 expression on cells of the human microvascular endothelial cell line (HMEC)-1 and the intracellular signalling pathways involved. Flow cytometry revealed dose-dependent ICAM-1 up-regulation with maximum induced expression 24h after sublethal UVB irradiation of 10 mJ/cm2. While anti-tumour necrosis factor (TNF)-alpha antibodies or recombinant human interleukin (IL)-10 did not influence this response, anti-interferon (IFN)-gamma antibodies blocked the UVB-induced ICAM-1 up-regulation. Significant induction of intracellular/membrane-bound IFN-gamma was measured as early as 6 h post-UVB. Since previous work has shown a differential role of protein kinase C (PKC) in cytokine induced ICAM-1 expression, the effect of a selective bisindolylmaleimide-derived PKC-inhibitor (GF109203X) was studied. Ultraviolet B-induced ICAM-1 up-regulation was effectively blocked by the PKC-inhibitor, whereas a PKA-inhibitor was ineffective. Moreover, immunofluorescence analysis showed a radiation-induced membrane translocation of PKC-alpha, indicative of enzyme activation, in HMEC-1 cells already 30 min post-UVB. The functional relevance of the UVB-induced ICAM-1 expression and involvement of PKC in this process was demonstrated in an adhesion assay with peripheral blood mononuclear cells. In conclusion, UVB-induced ICAM-1 expression on human endothelial cells involves PKC-dependent pathways and can be prevented by a PKC-inhibitor. The use of PKC-inhibitors as additive modulators in immune reactions may bear clinical potential. The mechanisms of IFN-gamma induction in endothelial cells by UVB deserve further investigation.

Cell Adhesion↗

PubMed1995

Ultraviolet B irradiation-induced G2 cell cycle arrest in human keratinocytes by inhibitory phosphorylation of the cdc2 cell cycle kinase.

In response to genotoxic stress, cell cycle progression can be arrested at certain checkpoints which serve to maintain genomic integrity. We have investigated the mechanism of ultraviolet B (UVB) irradiation-induced cell cycle arrest in normal human keratinocytes and in the HaCaT keratinocyte cell line which carries mutant p53 tumour suppressor protein. While only normal keratinocytes showed a delay in G1 following sublethal UVB irradiation both cell types exhibited prolonged G2 arrest attributable to rapid inhibition of cyclin B-associated cdc2 kinase activity. This inhibition coincided with increased tyrosine phosphorylation of cdc2 and was reversed by the cdc25C phosphatase in vitro. The data indicate that UVB-induced G2 arrest in mammalian cells is mediated by inhibitory tyrosine phosphorylation of cdc2 and acts as a defense mechanism against DNA damage irrespective of the cells' p53 status.

CDC2 Protein Kinase↗

PubMed1995

Abrogation of p53-induced cell cycle arrest by c-Myc: evidence for an inhibitor of p21WAF1/CIP1/SDI1.

The tumor-suppressor p53 inhibits cell cycle progression by direct transactivation of the p21WAF1/CIP1/SDI1 gene, which encodes a universal inhibitor of cyclin dependent kinases (cdk). The proto-oncogene product c-Myc induces cell cycle progression and, in the absence of survival factors, apoptosis. However, a direct link between the cell cycle machinery and c-Myc has not yet been established. We show that c-Myc has not yet been established. We show that c-Myc abrogates a p53-induced G1-arrest without elevating the expression of cdks or cyclins involved in the G1/S-transition. Instead, the results suggest that c-Myc interferes with the inhibitory action of p21 on cdk/cyclin-complexes by inducing a heat-labile inhibitor of p21. The inactivation of p21 and related cdk-inhibitors may explain several of the oncogenic actions of c-Myc, including the induction of proliferation, immortalisation and the inhibition of differentiation. Modulation of cdk activity by the induction of an inhibitor of cdk-inhibitors represents a novel mechanism of cell cycle regulation in mammalian cells.

3T3 Cells↗

PubMed1995

Pentoxifylline exerts synergistic immunomodulatory effects in combination with dexamethasone or cyclosporin A.

The methylxanthine derivative pentoxifylline (PTX) is an immunomodulatory agent with incompletely characterized effects on cytokine production. To analyse these effects and to delineate new combination strategies in immunotherapy, we have investigated immunomodulatory properties of PTX in combination with dexamethasone (DEX) or cyclosporin A (CsA). Stimulated human peripheral blood mononuclear cells were treated with clinically relevant concentrations of PTX (12.5-100 micrograms/ml), DEX (0.01-10 microM) or CsA (12.5-50 ng/ml), alone or in combination. With increasing doses of PTX the maximum supernatant titres of tumour necrosis factor (TNF)-alpha, interleukin (IL)-2 and interferon (IFN)-gamma decreased concomitantly, and all cultures co-treated with DEX showed synergism. Release of IL-6 was not consistently altered under PTX treatment. Similarly, PTX and CsA synergistically inhibited the release of IL-2, IFN-gamma and, to a lesser degree, TNF-alpha. Although PTX alone did not significantly reduce lymphoproliferation, both combinations of drugs synergistically inhibited this process. Furthermore, to demonstrate that the key mechanism of PTX-induced effects is an increase in intracellular cyclic adenosine 3':5'-monophosphate (cAMP) levels, identical experiments were performed using dibutyryl-cAMP instead of PTX. In cultures treated with PTX and DEX, expression of different cell receptors was analysed. Expression of IL-2 receptor (IL-2R) was reduced in cultures treated with PTX, and combination with DEX led to further reduction. Expression of intercellular adhesion molecule (ICAM)-1 and of leucocyte function antigen (LFA)-1 alpha was also synergistically reduced, though to a lesser degree. HLA-DR expression remained unchanged. In conclusion, we demonstrate that clinically relevant levels of PTX exert profound immunomodulatory effects in vitro, and that the combined treatment with DEX or CsA has synergistic effects.

Adjuvants, Immunologic↗

PubMed1995

Sunscreen intolerance. Contact sensitization, photocontact sensitization, and irritancy of sunscreen agents.

Reports of contact sensitization and photocontact sensitization induced by various sunscreening agents are reviewed. Current knowledge about the most often used sunscreening agents is summarized. The problems of cross-sensitization and sensitization in photodermatoses are discussed. Strategies for patch and photopatch testing, as well as immediate-type testing, are critically evaluated.

4-Aminobenzoic Acid↗

PubMed1994

Horizons in pharmacologic intervention in allergic contact dermatitis.

The treatment of allergic contact dermatitis remains a major challenge. Current management strategies consist of elimination of the allergen when possible and therapy for symptoms with topical or systemic corticosteroids. With increasing exposure of the human skin to environmental antigens and haptens, more selective treatment options are needed. Advances in the elucidation of the skin immune system and of the cellular and molecular events in immunologic processes may allow targeted methods of controlling delayed hypersensitivity reactions. This review focuses on mechanisms of established therapeutic agents and new developments, such as FK 506 (tacrolimus), pentoxifylline, and vitamin D3 derivative, for suppression of any phase of allergic contact dermatitis.

Allergens↗

PubMed1994

Propylene glycol dermatitis: re-evaluation of an old problem.

Evaluation of dermatitis associated with propylene glycol application or ingestion remains a challenge. The research dealing with skin reactions to propylene glycol is revisited and new aspects for future research are outlined. Based on literature review and our own observations, we propose classifying skin reactions to propylene glycol into 4 mechanisms: (a) irritant contact dermatitis, (b) allergic contact dermatitis, (c) non-immunologic contact urticaria, and (d) subjective or sensory irritation. This concept allows a partial explanation of effects observed by different authors. Despite attempts to define objective criteria, biologically, histopathologically, or clinically, the distinction between irritant and allergic reactions remains unclear. Furthermore, the irritation threshold of propylene glycol, and likewise the optimal standard concentration in patch tests, is sub judice. Future studies on propylene glycol dermatitis should include repeated patch tests with serial dose dilutions, repeated open application tests/provocative use tests, oral challenge tests, and biopsies for a more complete evaluation of mechanisms and clinical significance.

Algorithms↗

PubMed1993

Helium-neon laser irradiation induces effects on cytokine production at the protein and the mRNA level.

The construction of an in vitro model allowed an investigation of the basic functions of immunocompetent cells after laser irradiation. Among low-energy laser sources, the helium-neon (He-Ne) laser, with a wavelength of 632.8 nm, has often been found to produce photobiological effects including evidence of interference with immunological functions. Previous experiments revealed an influence of He-Ne laser irradiation on concentrations of interleukin-1 alpha (IL-1 alpha), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) in supernatants of cultures of human peripheral blood mononuclear cells (PBMC) with increased cytokine concentrations after irradiation of 18.9 J/cm2 and decreased concentrations after irradiation of 37.8 J/cm2. Now, the mechanisms involved were studied. Results showed that cytokine production of cells stimulated with phytohemagglutinin (PHA), concanavalin A (Con A), or bacterial lipopolysaccharide (LPS) was altered significantly after laser irradiation but not after stimulation with staphylococcus aureus enterotoxin B (SEB). In situ hybridization of IFN-gamma mRNA producing PBMC revealed that the number of positive cells was modulated similarly. The results were identical in cultures of enriched monocytes (M phi) or enriched T cells. Cells of the human monocytic cell line Mono Mac 6 were also influenced after LPS stimulation, whereas constitutively IL-2-producing Jurkat cells were not influenced by laser irradiation at any energy density. Analysis of the IL-2 receptor (IL-2R) and intercellular adhesion molecule-1 (ICAM-1) expression in PBMC showed partial down-regulation of both receptors at 37.8 J/cm2, but only after stimulation with PHA.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion Molecules↗

PubMed1992

Cytokine production after helium-neon laser irradiation in cultures of human peripheral blood mononuclear cells.

The effects of laser light on the immune system have not been extensively characterized. Low-power laser sources, such as the helium-neon (He-Ne) laser with a wavelength of 632.8 nm, have been found to produce photobiological effects with evidence of interference with immunological functions. We have investigated the effects of He-Ne laser irradiation on Ficoll-Hypaque-isolated human peripheral blood mononuclear cells (PBMC). Cultured cells were irradiated for various times at two selected intensities and then stimulated with different mitogens. The rate of incorporation of 3H-thymidine into the DNA of stimulated cells decreased with increasing energy density. The levels of interleukin-1 alpha (IL-1 alpha), interleukin-2 (IL-2), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in supernatants of the cultures were determined (irradiated either before or after stimulation). When stimulating cells after irradiation, significantly increased levels of all cytokines were detected after 30 min of irradiation (18.9 J cm-2), whereas after 60 min of irradiation (37.8 J cm-2) cytokine levels were found to be significantly decreased.

Cell Division↗

PubMedDate not supplied

Cancer cell cycle control.

The cell cycle is controlled by multiple mechanisms on which exogenous and endogenous stimuli converge. The pathways governing the different cell cycle phases are central for the cells' decisions when to commit to DNA synthesis and proliferation versus growth arrest, DNA repair or apoptosis. Consequently, these pathways incorporate various oncogenes and tumor suppressors and are therefore a central target for genetic alterations in human cancers. These events may ultimately lead to aberrant cell proliferation and increased genetic instability. Unraveling these regulatory networks provides an important insight into the balance of normal and cancerous cell proliferation and is pivotal for the design of novel anticancer strategies.

Cell Cycle↗