Study of immune-associated antigens (IL-1 and ICAM-1) in normal human keratinocytes treated by sodium lauryl sulphate

Cyclic nucleotide phosphodiesterase 4 subtypes are differentially expressed by primary keratinocytes and human epidermoid cell lines

Cyclic AMP phosphodiesterase (PDE) type 4 has been the subject of considerable interest as a potential molecular target for treating cutaneous inflammatory and allergic disorders; however, little is known regarding the expression of PDE 4 isogenes in human keratinocytes, the predominant cell type present in the epidermis. In this study, we investigated the expression of PDE 4 subtypes in epidermal cells (primary keratinocytes derived from breast skin, epidermoid cell lines A431, KB, and HaCaT) using reverse transcriptase polymerase chain reaction. Analysis of the amplified cDNA showed that there were differences in the expression of PDE 4 isogenes in the epidermal cells. Constitutive expression of the PDE 4 isozymes was detected in untreated epidermal cells at different levels. Transcripts for PDE 4B and 4D were abundantly expressed in breast skin-derived keratinocytes, whereas transcripts for PDE 4A, 4C, and 4D were present in HaCaT cells and transcripts for all the PDE 4 isotypes were present in A431 and KB. PDE 4A and 4C were detectable in HaCaT cells in equal amounts, but PDE 4C was only marginally expressed in the other cells. Of the four isogenes, PDE 4D was abundantly expressed in all the cells. Elevation of intracellular levels of cAMP by forskolin increased the expression of all the hPDE 4 isogenes 2-3-fold as revealed by semiquantitative reverse transcriptase polymerase chain reaction. Western blot analysis of extracts from control and forskolin or dibutyryl cAMP-treated A431 and KB cells demonstrated the presence of proteins with a molecular mass identical to that corresponding to recombinant human PDE 4B. Together, these findings show that PDE 4 isogenes are expressed in keratinocytes to a different degree and that their expression can be modulated by intracellular levels of cAMP.

ICAM-1 expression on keratinocytes in mechanically-injured skin of a patient with atopic dermatitis

The expression of intercellular adhesion molecule-1 (ICAM-1) on keratinocytes was studied in skin specimens of patch- or scratch-test using Dermatophagoides farinae (DF) antigen in atopic dermatitis (AD). Positive patch test reaction showed exocytosis of lymphocytes and focal expression of ICAM-1 on keratinocytes. Similar lymphocyte infiltration and keratinocyte expression of ICAM-1 were observed in tape-stripped skin which was subjected as the control. In addition, focal ICAM-1 expression on keratinocytes was also observed without exocytosis of lymphocytes. By scratch-test with DF antigen, ICAM-1 expression on keratinocytes was observed in eight out of eleven patients. One specimen showed ICAM-1 expression in spite of the absence of exocytosis of lymphocytes. Two out of three specimens from negative scratch-test sites with control liquid (mixture of equal amount of saline and glycerine) showed ICAM-1 expression in a similar manner to that of the positive scratch tests. In normal control skin, patch-test sites showed focal and weak expression of ICAM-1. Normal appearing skin of AD also showed no ICAM-1 expression. Therefore, in patients with atopic dermatitis, keratinocytes may express ICAM-1 prior to infiltration of lymphocytes into the epidermis and this expression might be induced not only by cytokines produced by lymphocytes but also by mechanically injured (tape-stripped or scratched) epidermal cells.

Epidermal cell proliferation and terminal differentiation in skin organ culture after topical exposure to sodium dodecyl sulphate

Epidermal cell proliferation and differentiation were investigated in vitro after exposure to the anionic surfactant sodium dodecyl sulfate (SDS). Human skin organ cultures were exposed topically to various concentrations of SDS for 22 h, after which the irritant was removed. Cell proliferation was measured immunohistochemically by incorporation of bromodeoxyuridine (BrdU) into the DNA of cells during S-phase, while the expression of transglutaminase and involucrin were used as markers of differentiation. Cell proliferation was moderately increased at concentrations of SDS that did not affect the histomorphology (0.1% and 0.2% SDS). A marked increase of cell proliferation was observed 22 to 44 h after removal of SDS at a concentration (0.4%) that induced slight cellular damage. Exposure of human skin organ cultures to a toxic concentration of SDS 91.0% led to decreased cell proliferation. Transglutaminase and involucrin were expressed in the more basal layers of the epidermis after exposure to 0.4% or 1.0% SDS. Moreover, intra-epidermal sweat gland ducts were positive for transglutaminase at these irritant concentrations. These in vitro data demonstrate that SDS-induced alterations of epidermal cell kinetics, as described in vivo are at least partly due to local mechanisms and do not require the influx of infiltrate cells. However, we were unable to relate to altered cell kinetics to the release of interleukin-1 alpha or interleukin-6. Furthermore, supplementation of the culture medium with 12-hydroxyeicosantetraenoic acid did not affect epidermal cell proliferation. Rabbit skin cultures appeared more sensitive to SDS than human skin. At nontoxic doses, the irritant induced an increase of epidermal cell proliferation, similar to that observed in human skin discs.

Expression of integrin receptors and ICAM-1 on keratinocytes in vivo and in an in vitro reconstructed epidermis: effect of sodium dodecyl sulphate

Several integrin heterodimers such as alpha 2 beta 1, alpha 6 beta 4 and alpha v beta 5 are expressed on basal keratinocytes of the epidermis. Because overexpression of these integrins as well as induction of the intercellular adhesion molecule-1 (ICAM-1) have been found in inflammatory dermatoses, we sought to determine whether these modulations could be used as markers of skin irritation. In normal epidermis, topical application of 1% sodium dodecyl sulphate (SDS) for 24 h caused an upregulation of alpha 3, beta 1, alpha 6, beta 4, alpha v, beta 5 and to a lesser extent alpha 2 integrin chains as well as an induction of ICAM-1. To investigate whether these parameters could also be used for evaluation of skin irritancy in vitro, SDS was applied for 24 h to reconstructed epidermis on de-epidermized dermis (RE-DED). In RE-DED, integrin overexpression and aberrant alpha 5 expression was seen under normal in vitro culture conditions and topical application of SDS caused only marginal additional upregulation. We could not detect any ICAM-1 reactivity on either normal or irritated RE-DED. Our results demonstrate that the modulation of integrin and ICAM-1 expression can be used as markers of irritation of the epidermis in vivo, but not in vitro.

Effect of various metals on intercellular adhesion molecule-1 expression and tumour necrosis factor alpha production by normal human keratinocytes

Nickel, cobalt and chromium are metals very often implicated in allergic contact dermatitis. In vivo, keratinocytes, which are the first target cells, can be directly activated to participate in the local reaction, especially through the expression of the membrane antigen ICAM-1, a ligand of the leucocyte antigen LFA-1, and the production of cytokines. Our aim was to assess the effects of sensitizing metal haptens (nickel, cobalt and chromium) compared with the toxic metal cadmium on the induction of ICAM-1 and the production of TNF alpha by epidermal cells. For this purpose, normal human keratinocytes obtained during plastic skin surgery were cultured in low-calcium defined medium (MCDB153) and the metals were used in non-toxic concentrations. Using FACS analysis, ICAM-1 expression was found to be induced only by nickel. This stimulation appeared as early as 24 h after stimulation. All the metals induced a low expression of TNF alpha detectable by immunocytochemistry correlating with the induction of the nuclear stress protein Hsp72 which is closely linked genetically with the TNF alpha locus. However, only Ni2+, Co2+ and Cr2+ induced a significant release of TNF alpha detectable by ELISA after 48 h stimulation. This secretion was lower than that observed with known stimulants such as lipopolysaccharide. These results indicate that the metals studied are able to induce an aggressive cellular effect, and that nickel, by its ICAM-1 induction, may play a major role in the keratinocyte activation state during allergic contact dermatitis.

Effect of nickel on the activation state of normal human keratinocytes through interleukin 1 and intercellular adhesion molecule 1 expression

Patch tests with nickel on sensitive subjects induce a characteristic allergic reaction involving epidermal and dermal cells, as well as modulation of cytokines and adhesion molecule production. In order to gain further insight into the role of keratinocytes in this phenomenon, we assessed their activation state induced by Ni2+ by studying interleukin 1 (IL-1) production and intercellular adhesion molecule 1 (ICAM-1) expression, using normal human keratinocytes cultured in defined medium. In comparison with controls, the addition of subtoxic NiSO4 concentrations (0.1-20 micrograms/ml) to keratinocyte cultures induced a significant, but low release of IL-1 alpha and IL-1 beta at 24 and 48 h, detectable by enzyme-linked immunosorbent assay of the supernatants of treated cells. Moreover, IL-1 receptor antagonist was significantly increased in the supernatants and the cell extracts. Using fluorescence-activated cell sorter analysis, ICAM-1 expression at 24 h was found to be induced in a dose-dependent manner, reaching a level comparable with that obtained upon interferon-gamma (10 IU/ml) stimulation. Overall, these data confirm the existence of direct interactions between Ni2+ and keratinocytes, which generate immunological signals of major importance in the pathophysiology of allergic contact dermatitis.