Chronic itch, or pruritus, is associated with a wide range of skin abnormalities. The mechanisms responsible for chronic itch induction and persistence remain unclear. We developed a mouse model in which a constitutively active form of the serine/threonine kinase BRAF was expressed in neurons gated by the sodium channel Nav1.8 (BRAFNav1.8 mice). We found that constitutive BRAF pathway activation in BRAFNav1.8 mice results in ectopic and enhanced expression of a cohort of itch-sensing genes, including gastrin-releasing peptide (
Zhong-Qiu Zhao, Fu-Quan Huo, Joseph Jeffry, Lori Hampton, Shadmehr Demehri, Seungil Kim, Xian-Yu Liu, Devin M. Barry, Li Wan, Zhong-Chun Liu, Hui Li, Ahu Turkoz, Kaijie Ma, Lynn A. Cornelius, Raphael Kopan, James F. Battey Jr., Jian Zhong, Zhou-Feng Chen
Retinoids are structurally related derivatives of vitamin A and are required for normal vision as well as cell proliferation and differentiation. Clinically, retinoids are effective in treating many skin disorders and cancers. Application of retinoids evokes substantial irritating side effects, including pain and inflammation; however, the precise mechanisms accounting for the sensory hypersensitivity are not understood. Here we show that both naturally occurring and synthetic retinoids activate recombinant or native transient receptor potential channel vanilloid subtype 1 (TRPV1), an irritant receptor for capsaicin, the pungent ingredient of chili peppers. In vivo, retinoids produced pain-related behaviors that were either eliminated or significantly reduced by genetic or pharmacological inhibition of TRPV1 function. These findings identify TRPV1 as an ionotropic receptor for retinoids and provide cellular and molecular insights into retinoid-evoked hypersensitivity. These findings also suggest that selective TRPV1 antagonists are potential therapeutic drugs for treating retinoid-induced sensory hypersensitivity.
Shijin Yin, Jialie Luo, Aihua Qian, Junhui Du, Qing Yang, Shentai Zhou, Weihua Yu, Guangwei Du, Richard B. Clark, Edgar T. Walters, Susan M. Carlton, Hongzhen Hu
Although a host of intracellular signals is known to contribute to wound healing, the role of the cell microenvironment in tissue repair remains elusive. Here we employed 2 different mouse models of genetic skin fragility to assess the role of the basement membrane protein collagen VII (COL7A1) in wound healing. COL7A1 secures the attachment of the epidermis to the dermis, and its mutations cause a human skin fragility disorder coined recessive dystrophic epidermolysis bullosa (RDEB) that is associated with a constant wound burden. We show that COL7A1 is instrumental for skin wound closure by 2 interconnected mechanisms. First, COL7A1 was required for re-epithelialization through organization of laminin-332 at the dermal-epidermal junction. Its loss perturbs laminin-332 organization during wound healing, which in turn abrogates strictly polarized expression of integrin α6β4 in basal keratinocytes and negatively impacts the laminin-332/integrin α6β4 signaling axis guiding keratinocyte migration. Second, COL7A1 supported dermal fibroblast migration and regulates their cytokine production in the granulation tissue. These findings, which were validated in human wounds, identify COL7A1 as a critical player in physiological wound healing in humans and mice and may facilitate development of therapeutic strategies not only for RDEB, but also for other chronic wounds.
Alexander Nyström, Daniela Velati, Venugopal R. Mittapalli, Anja Fritsch, Johannes S. Kern, Leena Bruckner-Tuderman
In pemphigus vulgaris, a life-threatening autoimmune skin disease, epidermal blisters are caused by autoantibodies primarily targeting desmosomal cadherins desmoglein 3 (DSG3) and DSG1, leading to loss of keratinocyte cohesion. Due to limited insights into disease pathogenesis, current therapy relies primarily on nonspecific long-term immunosuppression. Both direct inhibition of DSG transinteraction and altered intracellular signaling by p38 MAPK likely contribute to the loss of cell adhesion. Here, we applied a tandem peptide (TP) consisting of 2 connected peptide sequences targeting the DSG adhesive interface that was capable of blocking autoantibody-mediated direct interference of DSG3 transinteraction, as revealed by atomic force microscopy and optical trapping. Importantly, TP abrogated autoantibody-mediated skin blistering in mice and was effective when applied topically. Mechanistically, TP inhibited both autoantibody-induced p38 MAPK activation and its association with DSG3, abrogated p38 MAPK-induced keratin filament retraction, and promoted desmosomal DSG3 oligomerization. These data indicate that p38 MAPK links autoantibody-mediated inhibition of DSG3 binding to skin blistering. By limiting loss of DSG3 transinteraction, p38 MAPK activation, and keratin filament retraction, which are hallmarks of pemphigus pathogenesis, TP may serve as a promising treatment option.
Volker Spindler, Vera Rötzer, Carina Dehner, Bettina Kempf, Martin Gliem, Mariya Radeva, Eva Hartlieb, Gregory S. Harms, Enno Schmidt, Jens Waschke
Psoriasis is a chronic inflammatory disorder of the skin affecting approximately 2% of the world’s population. Accumulating evidence has revealed that the IL-23/IL-17/IL-22 pathway is key for development of skin immunopathology. However, the role of keratinocytes and their crosstalk with immune cells at the onset of disease remains poorly understood. Here, we show that IL-36R–deficient (Il36r–/–) mice were protected from imiquimod-induced expansion of dermal IL-17–producing γδ T cells and psoriasiform dermatitis. Furthermore, IL-36R antagonist-deficient (Il36rn–/–) mice showed exacerbated pathology. TLR7 ligation on DCs induced IL-36–mediated crosstalk with keratinocytes and dermal mesenchymal cells that was crucial for control of the pathological IL-23/IL-17/IL-22 axis and disease development. Notably, mice lacking IL-23, IL-17, or IL-22 were less well protected from disease compared with Il36r–/– mice, indicating an additional distinct activity of IL-36 beyond induction of the pathological IL-23 axis. Moreover, while the absence of IL-1R1 prevented neutrophil infiltration, it did not protect from acanthosis and hyperkeratosis, demonstrating that neutrophils are dispensable for disease manifestation. These results highlight a central and unique IL-1–independent role for IL-36 in control of the IL-23/IL-17/IL-22 pathway and development of psoriasiform dermatitis.
Luigi Tortola, Esther Rosenwald, Brian Abel, Hal Blumberg, Matthias Schäfer, Anthony J. Coyle, Jean-Christoph Renauld, Sabine Werner, Jan Kisielow, Manfred Kopf
Psoriasis is a common, relapsing inflammatory skin disease characterized by erythematous scaly plaques. Histological manifestations of psoriasis include keratinocyte dysregulation and hyperproliferation, elongated rete ridges, and inflammatory infiltrates consisting of T cells, macrophages, dendritic cells, and neutrophils. Despite the availability of new effective drugs to treat psoriasis, the underlying mechanisms of pathogenesis are still poorly understood. Recent studies have shown that Aldara cream, used to treat benign skin abnormalities, triggers psoriasis-like disease in humans and mice and have implicated Th17 cells in disease initiation. Using this as a model, we found a predominant role for the Th17 signature cytokines IL-17A, IL-17F, and IL-22 in psoriasiform plaque formation in mice. Using gene-targeted mice, we observed that loss of Il17a, Il17f, or Il22 strongly reduced disease the severity of psoriasis. However, we found that Th17 cells were not the primary source of these pathogenic cytokines. Rather, IL-17A, IL-17F, and IL-22 were produced by a skin-invading population of γδ T cells and RORγt+ innate lymphocytes. Furthermore, our findings establish that RORγt+ innate lymphocytes and γδ T cells are necessary and sufficient for psoriatic plaque formation in an experimental disease model that closely resembles human psoriatic plaque formation.
Stanislav Pantelyushin, Stefan Haak, Barbara Ingold, Paulina Kulig, Frank L. Heppner, Alexander A. Navarini, Burkhard Becher
Spontaneous gene repair, also called revertant mosaicism, has been documented in several genetic disorders involving organs that undergo self-regeneration, including the skin. Genetic reversion may occur through different mechanisms, and in a single individual, the mutation can be repaired in various ways. Here we describe a disseminated pattern of revertant mosaicism observed in 6 patients with Kindler syndrome (KS), a genodermatosis caused by loss of kindlin-1 (encoded by FERMT1) and clinically characterized by patchy skin pigmentation and atrophy. All patients presented duplication mutations (c.456dupA and c.676dupC) in FERMT1, and slipped mispairing in direct nucleotide repeats was identified as the reversion mechanism in all investigated revertant skin spots. The sequence around the mutations demonstrated high propensity to mutations, favoring both microinsertions and microdeletions. Additionally, in some revertant patches, mitotic recombination generated areas with homozygous normal keratinocytes. Restoration of kindlin-1 expression led to clinically and structurally normal skin. Since loss of kindlin-1 severely impairs keratinocyte proliferation, we predict that revertant cells have a selective advantage that allows their clonal expansion and, consequently, the improvement of the skin condition.
Dimitra Kiritsi, Yinghong He, Anna M.G. Pasmooij, Meltem Onder, Rudolf Happle, Marcel Jonkman, Leena Bruckner-Tuderman, Cristina Has
Zinc deficiency can be an inherited disorder, in which case it is known as acrodermatitis enteropathica (AE), or an acquired disorder caused by low dietary intake of zinc. Even though zinc deficiency diminishes cellular and humoral immunity, patients develop immunostimulating skin inflammation. Here, we have demonstrated that despite diminished allergic contact dermatitis in mice fed a zinc-deficient (ZD) diet, irritant contact dermatitis (ICD) in these mice was more severe and prolonged than that in controls. Further, histological examination of ICD lesions in ZD mice revealed subcorneal vacuolization and epidermal pallor, histological features of AE. Consistent with the fact that ATP release from chemically injured keratinocytes serves as a causative mediator of ICD, we found that the severe ICD response in ZD mice was attenuated by local injection of soluble nucleoside triphosphate diphosphohydrolase. In addition, skin tissue from ZD mice with ICD showed increased levels of ATP, as did cultured wild-type keratinocytes treated with chemical irritants and the zinc-chelating reagent TPEN. Interestingly, numbers of epidermal Langerhans cells (LCs), which play a protective role against ATP-mediated inflammatory signals, were decreased in ZD mice as well as samples from ZD patients. These findings suggest that upon exposure to irritants, aberrant ATP release from keratinocytes and impaired LC-dependent hydrolysis of nucleotides may be important in the pathogenesis of AE.
Tatsuyoshi Kawamura, Youichi Ogawa, Yuumi Nakamura, Satoshi Nakamizo, Yoshihiro Ohta, Hajime Nakano, Kenji Kabashima, Ichiro Katayama, Schuichi Koizumi, Tatsuhiko Kodama, Atsuhito Nakao, Shinji Shimada
BM-derived endothelial progenitor cells (EPCs) are critical and essential for neovascularization in tissue repair and tumorigenesis. EPCs migrate from BM to tissues via the bloodstream, but specific chemotactic cues have not been identified. Here we show in mice that the absence of CCR5 reduced vascular EPC accumulation and neovascularization, but not macrophage recruitment, and eventually delayed healing in wounded skin. When transferred into Ccr5–/– mice, Ccr5+/+ BM cells, but not Ccr5–/– cells, accumulated in the wound site, were incorporated into the vasculature, and restored normal neovascularization. Consistent with these observations, CCL5 induced in vitro EPC migration in a CCR5-dependent manner. Moreover, expression of VEGF and TGF-β was substantially diminished at wound sites in Ccr5–/– mice, which suggests that EPCs are important not only as the progenitors of endothelial cells, but also as the source of growth factors during tissue repair. Taken together, these data identify the CCL5/CCR5 interaction as what we believe to be a novel molecular target for modulation of neovascularization and eventual tissue repair.
Yuko Ishida, Akihiko Kimura, Yumi Kuninaka, Masanori Inui, Kouji Matsushima, Naofumi Mukaida, Toshikazu Kondo
Wounds that fail to heal in a timely manner, for example, diabetic foot ulcers, pose a health, economic, and social problem worldwide. For decades, conventional wisdom has pointed to growth factors as the main driving force of wound healing; thus, growth factors have become the center of therapeutic developments. To date, becaplermin (recombinant human PDGF-BB) is the only US FDA-approved growth factor therapy, and it shows modest efficacy, is costly, and has the potential to cause cancer in patients. Other molecules that drive wound healing have therefore been sought. In this context, it has been noticed that wounds do not heal without the participation of secreted Hsp90α. Here, we report that a 115-aa fragment of secreted Hsp90α (F-5) acts as an unconventional wound healing agent in mice. Topical application of F-5 peptide promoted acute and diabetic wound closure in mice far more effectively than did PDGF-BB. The stronger effect of F-5 was due to 3 properties not held by conventional growth factors: its ability to recruit both epidermal and dermal cells; the fact that its ability to promote dermal cell migration was not inhibited by TGF-β; and its ability to override the inhibitory effects of hyperglycemia on cell migration in diabetes. The discovery of F-5 challenges the long-standing paradigm of wound healing factors and reveals a potentially more effective and safer agent for healing acute and diabetic wounds.
Chieh-Fang Cheng, Divya Sahu, Fred Tsen, Zhengwei Zhao, Jianhua Fan, Rosie Kim, Xinyi Wang, Kathryn O’Brien, Yong Li, Yuting Kuang, Mei Chen, David T. Woodley, Wei Li