13-cis retinoic acid (13-cis RA; also known as isotretinoin), is the most potent agent available for treatment of acne. It is known that the drug induces apoptosis in cells cultured from human sebaceous glands, but its mechanism of action has not been determined. In this study, skin biopsies were taken from 7 patients with acne prior to and at 1 week of treatment with 13-cis RA. TUNEL staining confirmed that 13-cis RA induced apoptosis in sebaceous glands. Transcriptional profiling of patient skin and cultured human sebaceous gland cells (SEB-1 sebocytes) indicated that lipocalin 2 was among the genes most highly upregulated by 13-cis RA. Lipocalin 2 encodes neutrophil gelatinase–associated lipocalin (NGAL), which functions in innate immune defense and induces apoptosis of murine B lymphocytes. Increased immunolocalization of NGAL was noted in patients’ sebaceous glands following treatment with 13-cis RA, and recombinant NGAL induced apoptosis in SEB-1 sebocytes. Furthermore, apoptosis in response to 13-cis RA was inhibited in the presence of siRNA to lipocalin 2. These data indicate that NGAL mediates the apoptotic effect of 13-cis RA and suggest that agents that selectively induce NGAL expression in sebaceous glands might represent therapeutic alternatives to the use of 13-cis RA to treat individuals with acne.
Amanda M. Nelson, Wei Zhao, Kathryn L. Gilliland, Andrea L. Zaenglein, Wenlei Liu, Diane M. Thiboutot
Effective reepithelialization after injury is essential for correct wound healing. The upregulation of keratinocyte α3β1 integrin during reepithelialization suggests that this adhesion molecule is involved in wound healing; however, its precise role in this process is unknown. We have shown here that retarded reepithelialization in Itga3–/– mouse skin wounds is due predominantly to repressed TGF-β1–mediated responses. Specifically, expression of the inhibitor of TGF-β1–signaling Smad7 was elevated in Itga3–/– keratinocytes. Indeed, in vivo blockade of Smad7 increased the rate of reepithelialization in Itga3–/– and WT wounds to similar levels. Our data therefore indicate that the function of α3β1 integrin as a mediator of keratinocyte migration is not essential for reepithelialization but suggest instead that α3β1 integrin has a major new in vivo role as an inhibitor of Smad7 during wound healing. Moreover, our study may identify a previously undocumented function for Smad7 as a regulator of reepithelialization in vivo and implicates Smad7 as a potential novel target for the treatment of cutaneous wounds.
Louise E. Reynolds, Francesco J. Conti, Rita Silva, Stephen D. Robinson, Vandana Iyer, Rob Rudling, Barbara Cross, Emma Nye, Ian R. Hart, C. Michael DiPersio, Kairbaan M. Hodivala-Dilke
Psoriasis is a chronic skin disease resulting from the dysregulated interplay between keratinocytes and infiltrating immune cells. We report on a psoriasis-like disease model, which is induced by the transfer of CD4+CD45RBhiCD25– cells to pathogen-free scid/scid mice. Psoriasis-like lesions had elevated levels of antimicrobial peptide and proinflammatory cytokine mRNA. Also, similar to psoriasis, disease progression in this model was dependent on the p40 common to IL-12 and IL-23. To investigate the role of IL-22, a Th17 cytokine, in disease progression, mice were treated with IL-22–neutralizing antibodies. Neutralization of IL-22 prevented the development of disease, reducing acanthosis (thickening of the skin), inflammatory infiltrates, and expression of Th17 cytokines. Direct administration of IL-22 into the skin of normal mice induced both antimicrobial peptide and proinflammatory cytokine gene expression. Our data suggest that IL-22, which acts on keratinocytes and other nonhematopoietic cells, is required for development of the autoreactive Th17 cell–dependent disease in this model of skin inflammation. We propose that IL-22 antagonism might be a promising therapy for the treatment of human psoriasis.
Hak-Ling Ma, Spencer Liang, Jing Li, Lee Napierata, Tom Brown, Stephen Benoit, Mayra Senices, Davinder Gill, Kyriaki Dunussi-Joannopoulos, Mary Collins, Cheryl Nickerson-Nutter, Lynette A. Fouser, Deborah A. Young
Glucocorticoids (GCs) are widely used in the treatment of allergic skin conditions despite having numerous side effects. Here we use Cre/loxP-engineered tissue- and cell-specific and function-selective GC receptor (GR) mutant mice to identify responsive cell types and molecular mechanisms underlying the antiinflammatory activity of GCs in contact hypersensitivity (CHS). CHS was repressed by GCs only at the challenge phase, i.e., during reexposure to the hapten. Inactivation of the GR gene in keratinocytes or T cells of mutant mice did not attenuate the effects of GCs, but its ablation in macrophages and neutrophils abolished downregulation of the inflammatory response. Moreover, mice expressing a DNA binding–defective GR were also resistant to GC treatment. The persistent infiltration of macrophages and neutrophils in these mice is explained by an impaired repression of inflammatory cytokines and chemokines such as IL-1β, monocyte chemoattractant protein-1, macrophage inflammatory protein-2, and IFN-γ–inducible protein 10. In contrast TNF-α repression remained intact. Consequently, injection of recombinant proteins of these cytokines and chemokines partially reversed suppression of CHS by GCs. These studies provide evidence that in contact allergy, therapeutic action of corticosteroids is in macrophages and neutrophils and that dimerization GR is required.
Jan P. Tuckermann, Anna Kleiman, Richard Moriggl, Rainer Spanbroek, Anita Neumann, Anett Illing, Björn E. Clausen, Brenda Stride, Irmgard Förster, Andreas J.R. Habenicht, Holger M. Reichardt, François Tronche, Wolfgang Schmid, Günther Schütz
An essential element of the innate immune response to injury is the capacity to recognize microbial invasion and stimulate production of antimicrobial peptides. We investigated how this process is controlled in the epidermis. Keratinocytes surrounding a wound increased expression of the genes coding for the microbial pattern recognition receptors CD14 and TLR2, complementing an increase in cathelicidin antimicrobial peptide expression. These genes were induced by 1,25(OH)2 vitamin D3 (1,25D3; its active form), suggesting a role for vitamin D3 in this process. How 1,25D3 could participate in the injury response was explained by findings that the levels of CYP27B1, which converts 25OH vitamin D3 (25D3) to active 1,25D3, were increased in wounds and induced in keratinocytes in response to TGF-β1. Blocking the vitamin D receptor, inhibiting CYP27B1, or limiting 25D3 availability prevented TGF-β1 from inducing cathelicidin, CD14, or TLR2 in human keratinocytes, while CYP27B1-deficient mice failed to increase CD14 expression following wounding. The functional consequence of these observations was confirmed by demonstrating that 1,25D3 enabled keratinocytes to recognize microbial components through TLR2 and respond by cathelicidin production. Thus, we demonstrate what we believe to be a previously unexpected role for vitamin D3 in innate immunity, enabling keratinocytes to recognize and respond to microbes and to protect wounds against infection.
Jürgen Schauber, Robert A. Dorschner, Alvin B. Coda, Amanda S. Büchau, Philip T. Liu, David Kiken, Yolanda R. Helfrich, Sewon Kang, Hashem Z. Elalieh, Andreas Steinmeyer, Ulrich Zügel, Daniel D. Bikle, Robert L. Modlin, Richard L. Gallo
Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease associated with autoantibodies directed against the hemidesmosomal proteins BP180 and BP230 and inflammation. Passive transfer of antibodies to the murine BP180 (mBP180) induces a skin disease that closely resembles human BP. In the present study, we defined the roles of the different complement activation pathways in this model system. Mice deficient in the alternative pathway component factor B (Fb) and injected with pathogenic anti-mBP180 IgG developed delayed and less intense subepidermal blisters. Mice deficient in the classical pathway component complement component 4 (C4) and WT mice pretreated with neutralizing antibody against the first component of the classical pathway, C1q, were resistant to experimental BP. These mice exhibited a significantly reduced level of mast cell degranulation and polymorphonuclear neutrophil (PMN) infiltration in the skin. Intradermal administration of compound 48/80, a mast cell degranulating agent, restored BP disease in C4–/– mice. Furthermore, C4–/– mice became susceptible to experimental BP after local injection of PMN chemoattractant IL-8 or local reconstitution with PMNs. These findings provide the first direct evidence to our knowledge that complement activation via the classical and alternative pathways is crucial in subepidermal blister formation in experimental BP.
Kelly C. Nelson, Minglang Zhao, Pamela R. Schroeder, Ning Li, Rick A. Wetsel, Luis A. Diaz, Zhi Liu
Mast cells are involved in many disorders where the triggering mechanism that leads to degranulation and/or cytokine secretion has not been defined. Several chronic inflammatory diseases are associated with increased mast cell numbers and upregulation of the TNF receptor family member CD30, but the role of elevated CD30 expression is poorly understood. Here we report what we believe to be a novel way to activate mast cells with CD30 that leads to degranulation-independent secretion of chemokines. CD30 induced a de novo synthesis and secretion of the chemokines IL-8, macrophage inflammatory protein-1α (MIP-1α), and MIP-1β, a process involving the MAPK/ERK pathway. Mast cells were found to be the predominant CD30 ligand–positive (CD30L-positive) cell in the chronic inflammatory skin diseases psoriasis and atopic dermatitis, and both CD30 and CD30L expression were upregulated in lesional skin in these conditions. Furthermore, the number of IL-8–positive mast cells was elevated both in psoriatic and atopic dermatitis lesional skin as well as in ex vivo CD30-treated healthy skin organ cultures. In summary, characterization of CD30 activation of mast cells has uncovered an IgE-independent pathway that is of importance in understanding the entirety of the role of mast cells in diseases associated with mast cells and CD30 expression. These diseases include Hodgkin lymphoma, atopic dermatitis, and psoriasis.
Marie Fischer, Ilkka T. Harvima, Ricardo F.S. Carvalho, Christine Möller, Anita Naukkarinen, Gunilla Enblad, Gunnar Nilsson
Transgenic mice overexpressing PKCα in the epidermis (K5-PKCα mice) exhibit an inducible severe intraepidermal neutrophilic inflammation and systemic neutrophilia when PKCα is activated by topical 12-O-tetradecanoylphorbol-13-acetate (TPA). This inducible model of cutaneous inflammation was used to define mediators of skin inflammation that may have clinical relevance. Activation of cutaneous PKCα increased the production of the chemotactic factors cytokine-induced neutrophil chemoattractant (KC) and macrophage inflammatory protein 2 (MIP-2) in murine plasma. TPA treatment of cultured K5-PKCα keratinocytes also released KC and MIP-2 into culture supernatants through an NF-κB–dependent pathway. MIP-2 and KC mediated the infiltration of neutrophils into the epidermis, since this was prevented by ablating CXCR2 in K5-PKCα mice or administering neutralizing antibodies against KC or MIP-2. The neutrophilia resulted from PKCα-mediated upregulation of cutaneous G-CSF released into the plasma independent of CXCR2. These responses could be inhibited by topical treatment with a PKCα-selective inhibitor. Inhibiting PKCα also reduced the basal and TNF-α– or TPA-induced expression of CXCL8 in cultured psoriatic keratinocytes, suggesting that PKCα activity may contribute to psoriatic inflammation. Thus, skin can be the source of circulating factors that have both local and systemic consequences, and these factors, their receptors, and possibly PKCα could be therapeutic targets for inhibition of cutaneous inflammation.
Christophe Cataisson, Andrea J. Pearson, Margaret Z. Tsien, Francesca Mascia, Ji-Liang Gao, Saveria Pastore, Stuart H. Yuspa
Psoriasis is a common skin disease, the pathogenesis of which has not yet been resolved. In mice, epidermis-specific deletion of inhibitor of NF-κB (IκB) kinase 2 (IKK2) results in a skin phenotype that mimics human psoriasis in several aspects. Like psoriasis, this skin disease shows pronounced improvement when mice are treated with a TNF-neutralizing agent. We have found previously that this phenotype does not depend on the presence of αβ T lymphocytes. In order to evaluate contributions of other immune cell populations to the skin disease, we selectively eliminated macrophages and granulocytes from the skin of mice with epidermis-specific deletion of IKK2 (K14-Cre-IKK2fl/fl mice). Elimination of skin macrophages by subcutaneous injection of clodronate liposomes was accompanied by inhibition of granulocyte migration into the skin and resulted in a dramatic attenuation of psoriasis-like skin changes. The hyperproliferative, inflammatory skin disease in K14-Cre-IKK2fl/fl mice was a direct consequence of the presence of macrophages in the skin, as targeted deletion of CD18, which prevented accumulation of granulocytes but not macrophages, did not lead to major changes in the phenotype. Targeted deletion of the receptor for IFN-γ revealed that the pathogenesis of the skin disease does not depend on classical IFN-γ–mediated macrophage activation. Our results demonstrate that in mice epidermal keratinocytes can initiate a hyperproliferative, inflammatory, IFN-γ–independent, psoriasis-like skin disease whose development requires essential contributions from skin macrophages but not from granulocytes or αβ T lymphocytes.
Athanasios Stratis, Manolis Pasparakis, Rudolf A. Rupec, Doreen Markur, Karin Hartmann, Karin Scharffetter-Kochanek, Thorsten Peters, Nico van Rooijen, Thomas Krieg, Ingo Haase
The CD18 hypomorphic (CD18hypo) PL/J mouse model clinically resembling human psoriasis is characterized by reduced expression of the common chain of β2 integrins (CD11/CD18) to only 2–16% of WT levels. Previously we found that this chronic psoriasiform skin inflammation also depends on the presence of CD4+ T cells. Herein we investigated the role of macrophages in this CD18hypo mouse model. Activated macrophages were significantly increased in lesional skin as well as in inflamed skin draining lymph nodes (DLNs) of affected CD18hypo mice and were identified as being an important source of TNF-α in vivo. Both depletion of macrophages and neutralization of TNF-α resulted in a significant alleviation of psoriasiform skin inflammation. As monocyte chemotactic protein 1 was enhanced in lesional skin of affected CD18hypo mice, we intradermally injected recombinant murine monocyte chemotactic protein-1 (rJE/MCP-1) alone or in combination with rTNF-α into the skin of healthy CD18hypo mice. Only simultaneous injection of rJE/MCP-1 and rTNF-α, but neither substance alone, resulted in the induction of psoriasiform skin inflammation around the injection sites with recruitment and activation of macrophages. Collectively, our data suggest that maintenance of psoriasiform skin inflammation critically depends on efficient recruitment and activation of macrophages with sufficient release of TNF-α.
Honglin Wang, Thorsten Peters, Daniel Kess, Anca Sindrilaru, Tsvetelina Oreshkova, Nico Van Rooijen, Athanasios Stratis, Andreas C. Renkl, Cord Sunderkötter, Meinhard Wlaschek, Ingo Haase, Karin Scharffetter-Kochanek