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Proteinase-activated receptor 2 belongs to a new G protein-coupled receptor subfamily activated by various serine proteases. It has been demonstrated to play a role during inflammation of many tissues including the skin. Proteinase-activated receptor 2 is expressed by endothelial cells and regulates cutaneous inflammation in vivo. The underlying mechanisms of proteinase-activated receptor 2 activation in the skin and the effects on human dermal microvascular endothelial cells, however, are still unknown. Agonists of proteinase-activated receptor 2 such as mast cell tryptase induce widespread inflammation in many organs including the skin. Trypsinogen is generated by endothelial cells during inflammation or tumor growth. Therefore we tested whether human dermal microvascular endothelial cells express functional proteinase-activated receptor 2 and whether agonists of proteinase-activated receptor 2 regulate inflammatory responses in these cells. Calcium mobilization studies revealed that proteinase-activated receptor 2 is functional in human dermal microvascular endothelial cells. Interleukin-6 and interleukin-8 were upregulated as detected by reverse transcription polymerase chain reaction or enzyme-linked immunosorbent assay indicating a role of proteinase-activated receptor 2 in stimulating human dermal microvascular endothelial cells. Electromobility shift assays revealed proteinase-activated-receptor-2-induced activation of nuclear transcription factor kappaB with a maximum after 1 h. In conclusion, agonists of proteinase-activated receptor 2 upregulate interleukin-6 and interleukin-8 expression and release in human dermal microvascular endothelial cells. Thus, proteinase-activated receptor 2 may play an important role in cutaneous inflammation by mediating inflammatory responses on dermal microvascular endothelial cells and activation of nuclear transcription factor kappaB.

Many lines of evidence indicate that the activity of sebaceous glands can be modulated by neuropeptides. Direct evidence in man, however, is still missing. We show that SZ95 sebocytes, an immortalized human sebaceous gland cell line, express receptors for α-melanocyte-stimulating hormone. Reverse transcription polymerase chain reaction with primers against the five melanocortin receptors and immunofluorescence studies using an antibody directed against a peptide corresponding to the amino acids 2–18 of the human melanocortin-1 receptor disclosed specific transcripts and immunoreactivity for melanocortin-1 receptor in these cells. Melanocortin-1 receptor expression was confirmed in sebocytes of normal human skin by immunohistochemistry. In contrast, no immunostaining for the melanocortin-5 receptor could be detected in sebocytes in situ , in accordance with the lack of specific transcripts for this melanocortin receptor in SZ95 sebocytes. As cytokines play an important role in the recruitment of inflammatory cells in acne and related disorders and α-melanocyte-stimulating hormone exerts immunomodulatory effects in many other cell types, we investigated the effect of α-melanocyte-stimulating hormone on interleukin-8 secretion by SZ95 sebocytes. Treatment with interleukin-1β resulted in a marked increase in interleukin-8 release that was partially blocked by coincubation with α-melanocyte-stimulating hormone in a dose-dependent manner. Taken together, we show here that the melanocortin-1 receptor is expressed in vitro and in situ in human sebocytes. By modulating interleukin-8 secretion, α-melanocyte-stimulating hormone may act as a modulator of inflammatory responses in the pilosebaceous unit. [ABSTRACT FROM AUTHOR]

Exposure of the skin to ultraviolet (UV) light causes DNA damage, inflammation, and impairment of local as well as systemic immune responses. Dermal microvascular endothelial cells are key elements for the recruitment of inflammatory cells during the pathogenesis of inflammatory skin diseases via the expression of adhesion molecules and the release of cytokines. Because UVB may directly affect the function of dermal cells it was investigated whether UVB irradiation alters the production of proinflammatory and chemotactic cytokines by endothelial cells. UVB exposure of transformed human microvascular endothelial cells (HMEC‐1) resulted in a dose dependently increased mRNA expression as well as release of interleukin (IL)‐1β, IL‐6, IL‐8, and growth‐regulated oncogene alpha (GROα). Maximum cytokine production was observed 16–24 h after irradiation when 7.5–12.5 mJ UVB per cm2 were used. In addition, it was examined whether IL‐10, which is upregulated in keratinocytes following UVB irradiation and accounts for UV mediated immunosuppression such as inhibition of contact hypersensitivity, also affects endothelial cell cytokine production. Treatment of HMEC‐1 with IL‐10 significantly enhanced IL‐6 and IL‐8 release and further upregulated UVB‐induced IL‐6 and IL‐8 mRNA expression. These findings demonstrate that UVB both directly and indirectly via the release of IL‐10 stimulates microvascular endothelial cells to produce proinflammatory cytokines and chemokines that are required for the migration and activation of inflammatory cells in UV‐mediated inflammatory skin reactions. [ABSTRACT FROM AUTHOR]