Extraction and quantitation of cytokine mRNA from human epidermal blister roofs

Genomic-scale analysis of psoriatic skin reveals differentially expressed insulin-like growth factor-binding protein-7 after phototherapy

BACKGROUND

Phototherapy is an effective therapy for psoriasis. The molecular mechanisms underlying its efficacy are not yet understood.

OBJECTIVES

To compare the expression profiles of psoriatic epidermis in patients before and after undergoing phototherapy with the purpose of expounding the molecular mechanisms underlying the efficacy of this therapeutic modality.

METHODS

Patients with psoriasis were investigated before and after full courses of phototherapy: three patients completed 3 weeks of heliotherapy at the Dead Sea; three patients received narrowband ultraviolet B (NB-UVB) for a total of 20-27 treatments. Epidermal samples were analysed using oligonucleotide microarrays. Our microarray results led us to explore further and to quantify a specific gene, insulin-like growth factor-binding protein-7 (IGFBP7), using real-time quantitative reverse transcriptase-polymerase chain reaction assays and immunohistochemical protein expression.

RESULTS

We identified 315 genes modulated by phototherapy: the expressions of 248 genes (142 up; 106 down) were changed by Dead Sea treatment, 116 (71 up; 45 down) by NB-UVB and 49 (37 up; 12 down) were modulated regardless of treatment. The differentially changed genes include S100 calcium-binding proteins, dendritic cell markers, tumour necrosis factor-alpha target genes, matrix metalloproteinases and NFkappaB target genes. We also found that IGFBP7 mRNA and protein were significantly underexpressed in psoriatic compared with normal epidermis, and that phototherapy significantly increased their expression.

CONCLUSIONS

IGFBP7 is underexpressed in psoriatic epidermis but is inducible by UVB.

The UVB-induced gene expression profile of human epidermis in vivo is different from that of cultured keratinocytes

In order to obtain a comprehensive picture of the molecular events regulating cutaneous photodamage of intact human epidermis, suction blister roofs obtained after a single dose of in vivo ultraviolet (UV)B exposure were used for microarray profiling. We found a changed expression of 619 genes. Half of the UVB-regulated genes had returned to pre-exposure baseline levels at 72 h, underscoring the transient character of the molecular cutaneous UVB response. Of special interest was our finding that several of the central p53 target genes remained unaffected following UVB exposure in spite of p53 protein accumulation. We next compared the in vivo expression profiles of epidermal sheets to that of cultured human epidermal keratinocytes exposed to UVB in vitro. We found 1931 genes that differed in their expression profiles between the two groups. The expression profile in intact epidemis was geared mainly towards DNA repair, whereas cultured keratinocytes responded predominantly by activating genes associated with cell-cycle arrest and apoptosis. These differences in expression profiles might reflect differences between mature differentiating keratinocytes in the suprabasal epidermal layers versus exponentially proliferating keratinocytes in cell culture. Our findings show that extreme care should be taken when extrapolating from findings based on keratinocyte cultures to changes in intact epidermis.

Gene expression profiling of in vivo UVB-irradiated human epidermis

BACKGROUND

Several recent studies have employed microarray profiling to study UVB-regulated gene expression in human skin. These studies are all based on UV-irradiated cultured cells that differ substantially from the intact tissues they are supposed to imitate. The purpose of the present study was to analyze the differential expression of UVB-regulated genes in intact human epidermis following in vivo UV irradiation.

METHODS

The forearms of human volunteers were exposed to 4 MED of UVB in vivo, followed by removal of epidermal samples from exposed and non-exposed areas after 24 h. RNA samples were analyzed using oligonucleotide microarray (Affymetrix) technology analyzing 12 500 genes simultaneously. Verification of selected genes was performed by semi-quantitative reverse transcriptase polymerase chain reaction.

RESULTS

Gene expression patterns clearly distinguished UV-exposed epidermis from unexposed skin. Classification of these genes into functional categories revealed that several biological processes are globally affected by UVB. Significant changes were seen in more than 800 genes.

CONCLUSION

Human intact epidermis responds to a single low dose of in vivo UVB irradiation by differential regulation of numerous genes. Our results illustrate the power of global gene expression analysis of human epidermis to identify molecular pathways involved in UV-induced photodamage.

Effect of midazolam on interleukin-6 mRNA expression in human peripheral blood mononuclear cells in the absence of lipopolysaccharide

Midazolam, a benzodiazepine, has an hypnotic effect via benzodiazepine receptors and is widely used as an anaesthetic. Recently, it has been suggested that benzodiazepines modulate cytokine responses. The purpose of the present study was to evaluate the effect of midazolam on interleukin-6 (IL-6) response by observing mRNA expression levels in human peripheral blood mononuclear cells (PBMCs) in the absence of lipopolysaccharide (LPS). PBMCs were isolated from healthy volunteers in endotoxin-free 0.9% sodium chloride solution. The cells were incubated for 2 h at 37 degrees C immediately after isolation. IL-6 mRNA expression levels in the cells were quantified using reverse transcription and competitive polymerase chain reaction. It was found that midazolam time-dependently inhibited the IL-6 mRNA expression in PBMCs in the absence of LPS, and significantly inhibited the IL-6 mRNA expression at 1 microg/ml (P<0.05) or 10 microg/ml (P<0.01) in the absence of LPS. However, neither a specific agonist of peripheral-type benzodiazepine receptors, Ro5-4864, nor a specific agonist of central-type benzodiazepine receptors, clonazepam, inhibited IL-6 mRNA expression. These findings indicated a suppression of the IL-6 response in human PBMCs by midazolam in the absence of LPS, and suggests that midazolam has its effect not via benzodiazepine receptors, but by another mechanism.

Cytokine gene expression during the elicitation phase of contact sensitivity: regulation by endogenous IL-4

Recent studies have focused on characterizing the cytokine profile produced in the epidermis during the sensitization phase of contact sensitivity (CS). Some prior studies have also identified altered individual cytokine mRNA profiles in skin or draining lymph nodes (or several cytokine mRNA profiles in the epidermis) during the elicitation phase of CS. In this study we determined the dynamics of appearance of a battery of cytokine mRNA levels in both the epidermis and dermis during the elicitation phase of CS. We isolated mRNA from dispase-separated epidermis and dermis of TNCB-sensitized and naive BALB/c mice at various times after TNCB challenge. Changes in IFN-gamma and IL-4 mRNA levels (by semiquantitative RT-PCR) were more reproducible and dramatic than those of other cytokines studied (IL-1beta, IL-2, IL-10, and IL-12 p40). Compared to naive mice, sensitized mice had significantly elevated IL-4 mRNA signals 9 and 24 h (dermis), and 24 h (epidermis), after TNCB challenge. The increased IL-4 mRNA levels were mast-cell-independent, because sensitized mast-cell-deficient mice showed similar increases in IL-4 mRNA. To examine the role of endogenous IL-4 in CS elicitation, sensitized mice were treated with anti-IL-4 mAb 1 h before challenge. In accord with prior studies, anti-IL-4 mAb-pretreated mice showed increased ear swelling 24 h after challenge compared to mice pretreated with isotype control mAb. Anti-IL-4 mAb pretreatment also enhanced IFN-gamma, IL-2, IL-12 p40, and IL-1beta (but not IL-10) mRNA signals in the dermis of sensitized and challenged mice. These data indicate that IL-4 is produced in murine skin during the elicitation phase of CS and is an important down-modulator of inflammation. IL-4 may blunt CS by regulating local production of proinflammatory cytokines.

Interleukin-15 mRNA is expressed by human keratinocytes Langerhans cells, and blood-derived dendritic cells and is downregulated by ultraviolet B radiation

Interleukin (IL)-15 is a recently described cytokine that shares many functional activities with IL-2; however, unlike IL-2, IL-15 is produced by monocytes/macrophages, and not by lymphocytes. In this report, we assessed IL-15 mRNA expression by freshly isolated human epidermal cells, as well as by negatively selected keratinocytes and positively selected Langerhans cells, utilizing reverse transcription and polymerase chain reaction. In addition, cultured keratinocytes, immortalized keratinocytes (HaCaT cells), and dendritic cells expanded from adult peripheral blood in the presence of granulocyte/macrophage-colony stimulating factor and IL-4 were examined for IL-15 transcripts. Using cultured keratinocytes, we also studied the regulation of IL-15 mRNA expression by ultraviolet B radiation in vitro. Freshly isolated keratinocytes, HaCaT cells, and cultured keratinocytes all constitutively expressed IL-15 mRNA, and IL-15 expression was downregulated by ultraviolet B radiation in cultured keratinocytes in a time- and dose-dependent manner. In addition, IL-15 transcripts were constitutively expressed by freshly isolated Langerhans cells. IL-15 produced by keratinocytes, Langerhans cells, and other tissue-specific dendritic cells may be important in attracting and activating antigen-specific Th1 T cells. Furthermore, ultraviolet B-induced downregulation of keratinocyte IL-15 production may contribute to the relative state of immunosuppression induced by sun exposure.