RNA Aptamer Delivery through Intact Human Skin.

It is generally recognized that only relatively small molecular weight (typically < ∼ 500 Da) drugs can effectively permeate through intact stratum corneum. Here, we challenge this orthodoxy using a 62-nucleotide (molecular weight = 20,395 Da) RNA-based aptamer, highly specific to the human IL-23 cytokine, with picomolar activity. Results demonstrate penetration of the aptamer into freshly excised human skin using two different fluorescent labels. A dual hybridization assay quantified aptamer from the epidermis and dermis, giving levels far exceeding the cellular half maximal inhibitory concentration values (>100,000-fold), and aptamer integrity was confirmed using an oligonucleotide precipitation assay. A T helper 17 response was stimulated in freshly excised human skin resulting in significantly upregulated IL-17f, and IL-22; topical application of the IL-23 aptamer decreased both IL-17f and IL-22 by approximately 45% but did not result in significant changes to IL-23 mRNA levels, confirming that the aptamer did not globally suppress mRNA levels. This study demonstrates that very-large-molecular-weight RNA aptamers can permeate across the intact human skin barrier to therapeutically relevant levels into both the epidermis and dermis and that the skin-penetrating aptamer retains its biologically active conformational structure capable of binding to endogenous IL-23.

Tapinarof Is a Natural AhR Agonist that Resolves Skin Inflammation in Mice and Humans.

Tapinarof (GSK2894512) is a naturally derived topical treatment with demonstrated efficacy for patients with psoriasis and atopic dermatitis, although the biologic target and mechanism of action had been unknown. We demonstrate that the anti-inflammatory properties of tapinarof are mediated through activation of the aryl hydrocarbon receptor (AhR). We show that tapinarof binds and activates AhR in multiple cell types, including cells of the target tissue-human skin. In addition, tapinarof moderates proinflammatory cytokine expression in stimulated peripheral blood CD4+ T cells and ex vivo human skin, and impacts barrier gene expression in primary human keratinocytes; both of these processes are likely to be downstream of AhR activation based on current evidence. That the anti-inflammatory properties of tapinarof derive from AhR agonism is conclusively demonstrated using the mouse model of imiquimod-induced psoriasiform skin lesions. Topical treatment of AhR-sufficient mice with tapinarof leads to compound-driven reductions in erythema, epidermal thickening, and tissue cytokine levels. In contrast, tapinarof has no impact on imiquimod-induced skin inflammation in AhR-deficient mice. In summary, these studies identify tapinarof as an AhR agonist and confirm that its efficacy is dependent on AhR.

Early Activation of Th2/Th22 Inflammatory and Pruritogenic Pathways in Acute Canine Atopic Dermatitis Skin Lesions.

Determining inflammation and itch pathway activation in patients with atopic dermatitis (AD) is fraught with the inability to precisely assess the age of skin lesions, thus affecting the analysis of time-dependent mediators. To characterize inflammatory events occurring during early experimental acute AD lesions, biopsy samples were collected 6, 24, and 48 hours after epicutaneous application of Dermatophagoides farinae house dust mites to sensitized atopic dogs. The skin transcriptome was assessed using a dog-specific microarray and quantitative PCR. Acute canine AD skin lesions had a significant up-regulation of genes encoding T helper (Th) 2 (e.g., IL4, IL5, IL13, IL31, and IL33), Th9 (IL9), and Th22 (IL22) cytokines as well as Th2-promoting chemokines such as CCL5 and CCL17. Proinflammatory (e.g., IL6, LTB, and IL18) cytokines were also up-regulated. Other known pruritogenic pathways were also activated: there was significant up-regulation of genes encoding proteases cathepsin S (CTSS), mast cell chymase (CMA1), tryptase (TPS1) and mastin, neuromedin-B (NMB), nerve growth factor (NGF), and leukotriene-synthesis enzymes (ALOX5, ALOX5AP, and LTA4H). Experimental acute canine house dust mite-induced AD lesions exhibit an activation of innate and adaptive immune responses and pruritogenic pathways similar to those seen in humans with acute AD, thereby validating this model to test innovative therapeutics modalities for this disease.

Development of a Topical Treatment for Psoriasis Targeting RORγ: From Bench to Skin.

BACKGROUND: Psoriasis is a chronic inflammatory skin disorder involving marked immunological changes. IL-17-targeting biologics have been successful in reducing the disease burden of psoriasis patients with moderate-to-severe disease. Unfortunately, the stratum corneum prevents penetration of large molecule weight proteins, including monoclonal antibodies. Thus, for the majority of psoriasis patients ineligible for systemic treatments, a small molecule targeting RORγt, the master regulator of IL-17 family cytokines, may represent an alternative topical medicine with biologic-like efficacy. METHODS AND FINDINGS: The preclinical studies described in this manuscript bridge the gap from bench to bedside to provide the scientific foundation for a compound entering clinical trials for patients with mild to moderate psoriasis. In addition to several ex vivo reporter assays, primary T cell cultures, and the imiquimod mouse model, we demonstrate efficacy in a newly developed human ex vivo skin assay, where Th17-skewed cytokine expression is induced from skin-resident immune cells. Importantly, the skin barrier remains intact allowing for the demonstration of topical drug delivery. With the development of this novel assay, we demonstrate potent compound activity in the target tissue: human skin. Finally, target engagement by this small molecule was confirmed in ex vivo lesional psoriatic skin. CONCLUSIONS: Our work describes a progressive series of assays to demonstrate the potential clinical value of a novel RORγ inverse agonist small molecule with high potency and selectivity, which will enter clinical trials in late 2015 for psoriasis patients.

IL-33 amplifies an innate immune response in the degenerating retina.

Age-related macular degeneration (AMD), a leading cause of vision impairment in the ageing population, is characterized by irreversible loss of retinal pigment epithelial (RPE) cells and photoreceptors and can be associated with choroidal neovascularization. Mononuclear phagocytes are often present in AMD lesions, but the processes that direct myeloid cell recruitment remain unclear. Here, we identify IL-33 as a key regulator of inflammation and photoreceptor degeneration after retina stress or injury. IL-33(+) Müller cells were more abundant and IL-33 cytokine was elevated in advanced AMD cases compared with age-matched controls with no AMD. In rodents, retina stress resulted in release of bioactive IL-33 that in turn increased inflammatory chemokine and cytokine expression in activated Müller cells. Deletion of ST2, the IL-33 receptor α chain, or treatment with a soluble IL-33 decoy receptor significantly reduced release of inflammatory mediators from Müller cells, inhibited accumulation of mononuclear phagocytes in the outer retina, and protected photoreceptor rods and cones after a retina insult. This study demonstrates a central role for IL-33 in regulating mononuclear phagocyte recruitment to the photoreceptor layer and positions IL-33 signaling as a potential therapeutic target in macular degenerative diseases.

Altered subcellular localization of IL-33 leads to non-resolving lethal inflammation.

Non-resolving inflammation is a major contributor to chronic disease pathogenesis, including that of cancer, chronic obstructive pulmonary disease, asthma, arthritis, inflammatory bowel disease, multiple sclerosis and obesity. Some cytokines, such as IL-1α and IL-33, may act as endogenous alarmins that contribute to non-resolving inflammation. These cytokines are constitutively expressed in the nucleus and are thought to promote inflammation only upon release during tissue damage or cell necrosis. However, the importance of their nuclear localization in immune homeostasis is not fully understood. We describe herein a novel mouse model in which the nuclear localization signal of IL-33 is abolished and demonstrate for the first time that, alone, altered subcellular localization of IL-33 dramatically affects immune homeostasis. Heterozygous IL33(tm1/+) mice display elevated serum IL-33 levels, indicating that IL-33 is constitutively released when not actively targeted to the nucleus. IL33(tm1/+) mice succumb to lethal inflammation characterized by eosinophil-dominated immune cell infiltration of multiple organs. The profound inflammatory phenotype is dependent on mediators downstream of ST2 as ST2-null mice are protected in spite of high serum IL-33 levels. Importantly, IL-33 transcript levels in this knock-in mouse model remain under endogenous control. We adopt the term "nuclear alarmin" to describe a danger signal that is primarily regulated by nuclear compartmentalization in this fashion.

Flt3L-mobilized dendritic cells bearing H2-Kbm1 apoptotic cells do not induce cross-tolerance to CD8+ T cells across a class I MHC mismatched barrier.

Tolerization of allogeneic CD8(+) T cells is still a pending issue in the field of transplantation research to achieve long-term survival. To test whether dendritic cells (DC) bearing allogeneic major histocompatibility complex (MHC) class I mismatched apoptotic cells could induce cross-tolerance to alloreactive CD8(+) T cells, the following experimental strategy was devised. Rag2/γ(c) KO B6 mice were treated with Fms-like tyrosine kinase 3 ligand (Flt3L)-transduced B16 melanoma cells to drive a rapid expansion and mobilization of DC in vivo. Of all DC populations expanded, splenic CD11c(+) CD103(+) CD8α(+) DC were selectively involved in the process of antigen clearance of X-ray irradiated apoptotic thymocytes in vivo. Considering that CD11c(+) CD103(+) CD8α(+) DC selectively take up apoptotic cells and that they are highly specialized in cross-presenting antigen to CD8(+) T cells, we investigated whether B6 mice adoptively transferred with Flt3L-derived DC loaded with donor-derived apoptotic thymocytes could induce tolerance to bm1 skin allografts. Our findings on host anti-donor alloresponse, as revealed by skin allograft survival and cytotoxic T lymphocyte assays, indicated that the administration of syngeneic DC presenting K(bm1) donor-derived allopeptides through the indirect pathway of antigen presentation was not sufficient to induce cross-tolerance to alloreactive CD8(+) T cells responding to bm1 alloantigens in a murine model of skin allograft transplantation across an MHC class I mismatched barrier.

KU812 cells provide a novel in vitro model of the human IL-33/ST2L axis: functional responses and identification of signaling pathways.

Activation of interleukin-1 family receptor ST2L by its ligand interleukin-33 (IL-33) is an important component in inflammatory responses. Peripheral blood basophils, recognized as major effector cells in allergic inflammation that play a role in both innate and adaptive immunity, are activated by IL-33 through ST2L. However, studies are challenging due to the paucity of this cell population, representing less than 1% of peripheral blood leukocytes. We identified a basophil-like chronic myelogenous leukemia cell line, KU812, that constitutively expresses ST2L and demonstrates functional responses to IL-33 stimulation. IL-33 induced production of multiple inflammatory mediators in KU812 cells that were blocked by anti-ST2L and anti-IL-33 antibodies. The interaction of IL-33 and ST2L activated NF-kappaB, JNK, and p38 MAPK, but not ERK1/2 signaling pathways. Studies using pharmacological inhibitors to IKK-2 and MAP kinases revealed that one of the functional responses, IL-33-induced IL-13 production, was regulated through NF-kappaB, but not JNK or p38 MAPK signaling. The requirement of NF-kappaB was confirmed by IKK-2 knockdown using shRNA. KU812 represents the first human cell line-based in vitro model of the IL-33/ST2L axis and provides a valuable tool to aid in understanding the mechanism and significance of IL-33 and ST2L interaction and function.

Coordinated involvement of mast cells and T cells in allergic mucosal inflammation: critical role of the CC chemokine ligand 1:CCR8 axis.

CCL1 is the predominant chemokine secreted from IgE-activated human and mouse mast cells in vitro, colocalizes to mast cells in lung biopsies, and is elevated in asthmatic airways. CCR8, the receptor for CCL1, is expressed by approximately 70% of CD4(+) T lymphocytes recruited to the asthmatic airways, and the number of CCR8-expressing cells is increased 3-fold in the airways of asthmatic subjects compared with normal volunteers. In vivo, CCL1 expression in the lung is reduced in mast cell-deficient mice after aeroallergen provocation. Neutralization of CCL1 or CCR8 deficiency results in reduced mucosal lung inflammation, airway hyperresponsiveness, and mucus hypersecretion to a similar degree as detected in mast cell-deficient mice. Adenoviral delivery of CCL1 to the lungs of mast cell-deficient mice restores airway hyperresponsiveness, lung inflammation, and mucus hypersecretion to the degree observed in wild-type mice. The consequences of CCR8 deficiency, including a marked reduction in Th2 cytokine levels, are comparable with those observed by depletion of CD4(+) T lymphocytes. Thus, mast cell-derived CCL1- and CCR8-expressing CD4(+) effector T lymphocytes play an essential role in orchestrating lung mucosal inflammatory responses.

CCR8 expression identifies CD4 memory T cells enriched for FOXP3+ regulatory and Th2 effector lymphocytes.

CD4+ Th2 cells are important regulators of allergic inflammation. CCR8 is thought to play a role in Th2-mediated responses, however, expression of CCR8 in peripheral blood has not been fully characterized. Using a fluorescent form of the ligand selective for CCR8 (F-CCL1), we identified the leukocytes expressing CCR8 in human, monkey, and mouse peripheral blood. CCR8 expression is primarily restricted to a subset of human CD4 memory T lymphocytes (15%). Approximately 40% of CCR8+CD4+ T cells express Th2 cytokines IL-4 or IL-13 while 13% express the Th1 cytokine IFN-gamma. In fact, 50% of all Th2, but only 5% of Th1, cells express CCR8. Upon anti-CD3/anti-CD28 mAb-mediated activation, CCR8+CD4+ T cells secrete 3- to 7-fold higher levels of IL-4, IL-5, IL-9, and IL-13 and 10- to 20-fold lower levels of IFN-gamma or IL-17, compared with CCR8-CD4+ memory T cells. Two-thirds of CCR8+CD4 T cells express cutaneous lymphocyte-associated Ag while the majority lack gut-homing receptors. CCR8+CD4+ cells express CCR7 and CD62L and are present in spleen and lymph nodes of mice. Approximately 25% of CCR8+CD4 T cells express CD25high while 20% of CCR8+CD4+ express the T regulatory cell transcription factor FOXP3 accounting for 60% of all FOXP3-expressing CD4+ T cells. In conclusion, CCR8 marks a diverse subset of CD4 memory T cells enriched for T regulatory and Th2 cells which have the potential for recruitment into sites of allergic inflammation where they could participate in the induction and regulation of the allergic response.

GATA-3 promotes Th2 responses through three different mechanisms: induction of Th2 cytokine production, selective growth of Th2 cells and inhibition of Th1 cell-specific factors.

Naïve CD4 T cells can differentiate into at least two different types of T helpers, Th1 and Th2 cells. Th2 cells, capable of producing IL-4, IL-5 and IL-13, are involved in humoral immunity against extracellular pathogens and in the induction of asthma and other allergic diseases. In this review, we summarize recent reports regarding the transcription factors involved in Th2 differentiation and cell expansion, including Stat5, Gfi-1 and GATA-3. Stat5 activation is necessary and sufficient for IL-2-mediated function in Th2 differentiation. Enhanced Stat5 signaling induces Th2 differentiation independent of IL-4 signaling; although it does not up-regulate GATA-3 expression, it does require the presence of GATA-3 for its action. Gfi-1, induced by IL-4, promotes the expansion of GATA-3-expressing cells. Analysis of conditional Gata3 knockout mice confirmed the critical role of GATA-3 in Th2 cell differentiation (both IL-4 dependent and IL-4 independent) and in Th2 cell proliferation and also showed the importance of basal GATA-3 expression in inhibiting Th1 differentiation.

Interleukin 2 plays a central role in Th2 differentiation.

Differentiation of naïve CD4 T cells into T helper (Th) 2 cells requires signaling through the T cell receptor and an appropriate cytokine environment. IL-4 is critical for such Th2 differentiation. We show that IL-2 plays a central role in this process. The effect of IL-2 on Th2 generation does not depend on its cell growth or survival effects. Stat5a(-/-) cells show diminished differentiation to IL-4 production, and forced expression of a constitutively active form of Stat5a replaces the need for IL-2. In vivo IL-2 neutralization inhibits IL-4 production in two models. Studies of restriction enzyme accessibility and binding of Stat5 to chromatin indicate that IL-2 mediates its effect by stabilizing the accessibility of the Il4 gene. Thus, IL-2 plays a critical role in the polarization of naive CD4 T cells to the Th2 phenotype.

Stat5 activation plays a critical role in Th2 differentiation.

Upon TCR engagement, naive CD4 T cells differentiate toward the Th1 or Th2 phenotype. IL-4, acting through Stat6, plays a major role in Th2 differentiation; IL-2 has also been reported to be essential. Here, we report that retroviral (RV)-mediated expression of a constitutively active Stat5A mutant (STAT5A1*6) can fully restore IL-4 production when naive CD4 T cells are primed in the absence of IL-2. Furthermore, STAT5A1*6 expression causes Th2 differentiation in the absence of IL-4 or in Stat6- or IL-4Ralpha-deficient cells. Infection with STAT5A1*6-NGFR-RV does not enhance GATA-3 expression. STAT5A1*6-NGFR-RV and GATA-3-GFP-RV each render the Il4 gene accessible, but the sites of restriction enzyme accessibility are different. Stat5A binds to HSII and HSIII sites of the Il4 gene. Coinfection with STAT5A1*6-NGFR-RV and GATA-3-GFP-RV results in optimal Th2 priming.

Bacterial lipoprotein-based vaccines induce tumor necrosis factor-dependent type 1 protective immunity against Leishmania major.

Immunity against Leishmania major requires rapid induction of a type 1 immune response in which tumor necrosis factor alpha (TNF-alpha) plays an essential role. Hence, vaccination strategies that simulate the protective immune response found in hosts that have recovered from natural infection provide a rational approach to combat leishmaniasis. One method for optimizing the qualitative and quantitative immune responses after vaccination is to use an adjuvant. In this study we demonstrate that the OprI lipoprotein (L-OprI) from Pseudomonas aeruginosa induces a long-term cellular (gamma interferon [IFN-gamma]) and humoral (immunoglobulin G2a) type 1 immune response against a truncated 32-kDa version (COOHgp63) of the 63-kDa major cell surface glycoprotein gp63. By contrast, immunization with COOHgp63 either fused to OprI nonlipoprotein or with no adjuvant did not result in the induction of type 1 immune responses. The adjuvanticity of L-OprI is strongly dependent on its capacity to induce TNF-alpha, since generation of type 1 immune responses is clearly delayed and impaired in TNF-alpha(-/-) mice. Vaccination with L-OprICOOHgp63 fusion protein protected BALB/c mice against L. major infection for at least 19 weeks. Vaccinated mice were largely free of lesions or clearly controlled lesion size on termination of the experiment. The control of disease progression in mice vaccinated with L-OprICOOHgp63 was associated with enhancement of antigen-specific IFN-gamma production. These data indicate that bacterial lipoproteins constitute appropriate adjuvants to include in vaccines against diseases in which type 1 immune responses are important for protection.