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Acne is a chronic disease hallmarked by sebaceous hyperplasia, follicular hyperkeratosis, and inflammation. Parallel targeting of these factors is required to treat acne effectively. Inhibitors of dipeptidyl peptidase IV (DP IV) and aminopeptidase N (APN) show strong anti-inflammatory effects on immune cells and therapeutic efficacy in autoimmune disorders. Our investigation focused on the expression and functional relevance of these ectopeptidases in three cell types which exhibit an altered phenotype in early acne lesions. We showed for the first time expression of DP IV and APN on human sebocytes. In the SZ95 sebocyte cell line, the DP IV inhibitors Lys[Z(NO2)]-thiazolidide and Lys[Z(NO2)]-pyrrolidide and the APN inhibitors actinonin and bestatin suppressed proliferation, enhanced terminal differentiation, and slightly decreased total neutral lipid production. The anti-inflammatory and differentiation-restoring cytokine IL-1 receptor antagonist was significantly upregulated in SZ95 sebocytes and the HaCaT keratinocyte cell line in the presence of inhibitors. Furthermore, the inhibitors suppressed proliferation and IL-2 production of Propionibacterium acnes-stimulated T cells ex vivo and enhanced the expression of the immunosuppressive cytokine transforming growth factor-beta1. Our data provide first evidence for a functional role of DP IV and APN in the sebaceous gland apparatus and for their inhibitors, used alone or in combination, as completely new substances possibly affecting acne pathogenesis in a therapeutic manner.

Aminopeptidase inhibitors strongly affect proliferation, differentiation, and function of immune cells and show therapeutic potential in inflammatory disorders. In psoriatic lesions, keratinocytes display increased cellular turnover and disturbed differentiation, leading to epidermal hyperplasia accompanied by the loss of stratum granulosum. Here, we report in the HaCaT hyperproliferative keratinocyte cell line as well as in two primary keratinocyte strains in vitro a molecular and biochemical analysis of the expression of both membrane and cytosol alanyl aminopeptidase (cAAP) on the mRNA, protein, and enzymatic activity level. We found a clear dose-dependent suppression of DNA synthesis in vitro in the presence of the inhibitors actinonin, bestatin, and the cAAP-specific inhibitor PAC-22 correlating well with the simultaneous decrease in enzyme activity. In vivo, actinonin dose-dependently restored the stratum granulosum and ameliorated the impaired keratinocyte differentiation in the mouse tail model of psoriasis. Taken together, these data suggest that targeting alanyl aminopeptidases may be beneficial for psoriasis and other inflammatory skin disorders.

Various studies have shown that the membrane ectoenzyme dipeptidyl peptidase IV (DP IV, CD26), expressed on T, NK, and B cells in the human immune system, is involved in the regulation of DNA synthesis and cytokine production. Here, we clearly demonstrate that this enzyme is highly expressed also on human epidermal foreskin and split-skin keratinocytes and that the specific DP IV inhibitors Lys[Z(NO2)]-thiazolidide, Lys[Z(NO2)]-pyrrolidide inhibit the enzymatic activity as well as the DNA synthesis of these cells. These data demonstrate that CD26 plays a role also in regulation of DNA synthesis of epidermal keratinocytes and that the enzymatic activity is required for mediating these effects.

Objective To assess the type of severe skin reactions caused by valdecoxib treatment. Design Case registry of severe skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. Setting All hospitals in Germany that treat patients with severe skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. Patients Five case notifications of Stevens-Johnson syndrome after the use of valdecoxib were reevaluated following the withdrawal of valdecoxib on April 7, 2005. Results A thorough review of all reported cases of severe skin reactions caused by valdecoxib revealed extensive erythematous, targetlike skin eruptions in addition to facial edema and dyspnea. Histologic changes, clinical pattern, and outcome demonstrated a distinct disease entity. Conclusion Valdecoxib induces severe skin reactions different from those of Stevens-Johnson syndrome and toxic epidermal necrolysis in clinical and histopathologic findings, course, and outcome.

The presented data provide evidence that DP IV is expressed on human sebocytes and most likely involved in regulation of sebocyte proliferation and cytokine production. The aminopeptidase inhibitors Lys[Z(NO2)]-thiazolidide and Lys[Z(NO2)]-pyrrolidide suppress proliferation of three cells types involved in acne initiation; moreover, they induce the anti-inflammatory cytokine IL-1RA in sebocytes and keratinocytes being capable to follicular hyperkeratosis, and they up-regulate the immunosuppressive cytokine transforming growth factor-β1 in P. acnes-stimulated T cells.

The ectopeptidase dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) is present on most mammalian cells. Using specific inhibitors of DP IV, it has been shown that this enzyme is involved in the regulation of DNA synthesis and in production of various cytokines in lymphocytes. The aim of the present work was to investigate the expression of DP IV/CD26 on human keratinocytes and to answer the question, whether the proliferation (DNA synthesis) of human keratinocytes is influenced by inhibition of the enzymatic activity of DP IV. Using flow cytometry, RT-PCR, and specific enzymatic activity assays, expression of DP IV-mRNA and CD26 antigen were shown on primary keratinocyte strains and on the HaCaT keratinocyte cell line. The synthetic DP IV inhibitors Lys[Z(NO2)]-thiazolidide and -pyrrolidide suppress the DNA-synthesis of these cells in a dose-dependent manner. These data demonstrate that CD26 is also involved in the regulation of DNA synthesis of keratinocytes and that the enzymatic activity is required for mediating these effects.

Auteur(s) : Carl Meissner1, Marc Hoefeld-Fegeler1, Robert Vetter1, Michael Bellutti1, Artem Vorobyev3, Harald Gollnick1, Martin Leverkus1,2 1Department of Dermatology and Venereology, Otto-von-Guericke-University Magdeburg, Germany 2Department of Dermatology, Venereology, and Allergology, Medical Faculty Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany 3Department of Dermatology, University of Lubeck Epidermolysis bullosa acquisita [...]

The ectopeptidase dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) is present on most mammalian cells. Using specific inhibitors of DP IV, it has been shown that this enzyme is involved in the regulation of DNA synthesis and in production of various cytokines in lymphocytes. The aim of the present work was to investigate the expression of DP IV/CD26 on human keratinocytes and to answer the question, whether the proliferation (DNA synthesis) of human keratinocytes is influenced by inhibition of the enzymatic activity of DP IV. Using flow cytometry, RT-PCR, and specific enzymatic activity assays, expression of DP IV-mRNA and CD26 antigen were shown on primary keratinocyte strains and on the HaCaT keratinocyte cell line. The synthetic DP IV inhibitors Lys[Z(NO2)]-thiazolidide and -pyrrolidide suppress the DNA synthesis of these cells in a dose-dependent manner. These data demonstrate that CD26 is also involved in the regulation of DNA synthesis of keratinocytes and that the enzymatic activity is required for mediating these effects.

Suppression of collagen and matrix synthesis and inhibition of the fibrogenic cytokine transforming growth factor-beta(1) (TGF-beta(1)) is a major therapeutic goal in the treatment of fibrosis and keloids. Inhibitors of dipeptidyl peptidase IV (DP IV)-like activity affect cell growth and cytokine production and are currently under investigation for the treatment of metabolic, autoimmune and inflammatory diseases. We show here that the inhibitors of DP IV-like activity, Lys[Z(NO(2))]-thiazolidide and Lys[Z(NO(2))]-pyrrolidide, suppress proliferation in human skin fibroblasts and keloid-derived skin fibroblasts in vitro. They significantly decrease TGF-beta(1) expression and secretion of procollagen type I C-terminal peptide in supernatants of both cell types. Furthermore, they abrogate the TGF-beta(1)-induced stimulation of collagen synthesis, matrix deposition, and TGF-beta(1) and fibronectin expression. Both inhibitors lead to dephosphorylation of mitogen-activated protein kinases pp38 and pERK1/2, which are activated upon TGF-beta1 stimulation and have been implicated in fibrogenesis. In a mouse model of dermal fibrosis, induced by repetitive intracutaneous injections of TGF-beta(1), the profibrotic effect of TGF-beta(1) detected by dermal thickening, collagen I, and alpha-smooth muscle actin expression, is significantly suppressed in the presence of inhibitors. Inhibition of DP IV-like enzymatic activity may therefore represent a promising therapeutic approach for the treatment of fibrotic skin disorders and keloids.