Inflammation is a physiological response of the body to tissue injury, pathogen invasion and irritants. In the course of inflammation, immune cells of the innate and/or adaptive immune system are ...activated and recruited to the site of inflammation. Attraction and activation of immune cells is regulated by a variety of different cytokines and chemokines, which are predominantly regulated by transcription factors such as AP-1, NF-κB, NFATs and STATs. The evidence that Jun/AP-1 proteins control inflammation in the skin is summarised in this article. Genetic mouse models have demonstrated that a loss of Jun/AP-1 expression in epidermal cells controls cytokine expression through transcriptional and post-transcriptional pathways. The absence of JunB in epithelial K5-expressing tissues leads to a multiorgan disease, which is characterised by increased levels of granulocyte colony-stimulating factor and interleukin 6. Deletion of both JunB and c-Jun, in a constitutive or inducible manner, leads to perinatal death of newborn pups and to a psoriasis-like disease in adults, in which tumour necrosis factor α and the TIMP-3/TACE pathway have central roles. The loss or reduction of Jun expression in the epidermis relieves a block on cytokine expression. As a consequence, the increased levels of cytokines in mice lead to diseases reminiscent of psoriasis and systemic lupus erythematosus in human patients. New targets identified in mouse models, together with investigations on human samples, will provide important new avenues for therapeutic interventions in psoriasis and other inflammatory skin diseases.
The molecular control of inflammation and epidermal thickening in skin lesions of patients with atopic dermatitis (AD) is not known. Sequestosome 1/p62 is a multifunctional adapter protein implicated ...in the control of key regulators of cellular homeostasis, such as proinflammatory and mechanistic target of rapamycin signaling.
We sought to determine whether p62 plays a role in the cutaneous and systemic manifestations of an AD-like mouse model.
AD-like skin lesions were induced by deletion of JunB/AP-1, specifically in epidermal keratinocytes (JunBΔep). The contribution of p62 to pathological changes was determined by inactivation of p62 in JunBΔepp62−/− double knockout mice.
Expression of p62 was elevated in skin lesions of JunBΔep mice, resembling upregulation of p62 in AD and psoriasis. When p62 was inactivated, JunBΔep-associated defects in the differentiation of keratinocytes, epidermal thickening, skin infiltration by mast cells and neutrophils, and the development of macroscopic skin lesions were significantly reduced. p62 inactivation had little effect on circulating cytokines, but decreased serum IgE. Signaling through mechanistic target of rapamycin and natural factor kappa B was increased in JunBΔep but not in JunBΔepp62−/− double knockout skin, indicating an important role of p62 in enhancing these signaling pathways in the skin during AD-like inflammation.
Our results provide the first in vivo evidence for a proinflammatory role of p62 in skin and suggest that p62-dependent signaling pathways may be promising therapeutic targets to ameliorate the skin manifestations of AD and possibly psoriasis.
NFATc1 and NFATc2 are functionally redundant in the immune system, but it was suggested that NFATc1 is required exclusively for differentiation of osteoclasts in the skeletal system. Here we provide ...genetic evidence that NFATc1 is essential for osteoclast differentiation in vivo by adoptive transfer of NFATc1(-/-) hematopoietic stem cells to osteoclast-deficient Fos(-/-) mice, and by Fos(-/-) blastocyst complementation, thus avoiding the embryonic lethality of NFATc1(-/-) mice. However, in vitro osteoclastogenesis in NFATc1-deficient cells was rescued by ectopic expression of NFATc2. The discrepancy between the in vivo essential role of NFATc1 and the in vitro effect of NFATc2 was attributed to selective autoregulation of the NFATc1 gene by NFAT through its promoter region. This suggested that an epigenetic mechanism contributes to the essential function of NFATc1 in cell lineage commitment. Thus, this study establishes that NFATc1 represents a potential therapeutic target for bone disease and reveals a mechanism that underlies the essential role of NFATc1 in bone homeostasis.
The molecular basis underlying glioblastoma (GBM) heterogeneity and plasticity is not fully understood. Using transcriptomic data of human patient-derived brain tumor stem cell lines (BTSCs), ...classified based on GBM-intrinsic signatures, we identify the AP-1 transcription factor
as a key regulator of the mesenchymal (MES) subtype. We provide a mechanistic basis to the role of the neurofibromatosis type 1 gene (
), a negative regulator of the RAS/MAPK pathway, in GBM mesenchymal transformation through the modulation of
expression. Depletion of
in
-mutant human BTSCs and
-mutant mouse neural stem cells results in loss of the mesenchymal gene signature and reduction in stem cell properties and in vivo tumorigenic potential. Our data demonstrate that
controls GBM plasticity and aggressiveness in response to
alterations.
Squamous cell carcinomas (SCCs) are highly heterogeneous tumours, resulting from deranged expression of genes involved in squamous cell differentiation. Here we report that microRNA‐34a (miR‐34a) ...functions as a novel node in the squamous cell differentiation network, with SIRT6 as a critical target. miR‐34a expression increases with keratinocyte differentiation, while it is suppressed in skin and oral SCCs, SCC cell lines, and aberrantly differentiating primary human keratinocytes (HKCs). Expression of this miRNA is restored in SCC cells, in parallel with differentiation, by reversion of genomic DNA methylation or wild‐type p53 expression. In normal HKCs, the pro‐differentiation effects of increased p53 activity or UVB exposure are miR‐34a‐dependent, and increased miR‐34a levels are sufficient to induce differentiation of these cells both in vitro and in vivo. SIRT6, a sirtuin family member not previously connected with miR‐34a function, is a direct target of this miRNA in HKCs, and SIRT6 down‐modulation is sufficient to reproduce the miR‐34a pro‐differentiation effects. The findings are of likely biological significance, as SIRT6 is oppositely expressed to miR‐34a in normal keratinocytes and keratinocyte‐derived tumours.
Dotto and colleagues identify miR‐34a as novel determinant of keratinocyte differentiation, at the same time establishing SIRT6 as crucial miR‐34a target in this context.
Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death. HCC incidence is on the rise, while treatment options remain limited. Thus, a better understanding of the molecular pathways ...involved in HCC development has become a priority to guide future therapies. While previous studies implicated the Activator Protein-1 (AP-1) (Fos/Jun) transcription factor family members c-Fos and c-Jun in HCC formation, the contribution of Fos-related antigens (Fra-) 1 and 2 is unknown. Here, we show that hepatocyte-restricted expression of a single chain c-Jun~Fra-2 protein, which functionally mimics the c-Jun/Fra-2 AP-1 dimer, results in spontaneous HCC formation in c-Jun~Fra-2
mice. Several hallmarks of human HCC, such as cell cycle dysregulation and the expression of HCC markers are observed in liver tumors arising in c-Jun~Fra-2
mice. Tumorigenesis occurs in the context of mild inflammation, low-grade fibrosis, and Pparγ-driven dyslipidemia. Subsequent analyses revealed increased expression of c-Myc, evidently under direct regulation by AP-1 through a conserved distal 3' enhancer. Importantly, c-Jun~Fra-2-induced tumors revert upon switching off transgene expression, suggesting oncogene addiction to the c-Jun~Fra-2 transgene. Tumors escaping reversion maintained c-Myc and c-Myc target gene expression, likely due to increased c-Fos. Interfering with c-Myc in established tumors using the Bromodomain and Extra-Terminal motif inhibitor JQ-1 diminished liver tumor growth in c-Jun~Fra-2 mutant mice. Thus, our data establish c-Jun~Fra-2
mice as a model to study liver tumorigenesis and identify the c-Jun/Fra-2-Myc interaction as a potential target to improve HCC patient stratification and/or therapy.
Toll‐like receptor (TLR) stimulation induces innate immune responses involved in many inflammatory disorders including psoriasis. Although activation of the AP‐1 transcription factor complex is ...common in TLR signaling, the specific involvement and induced targets remain poorly understood. Here, we investigated the role of c‐Jun/AP‐1 protein in skin inflammation following TLR7 activation using human psoriatic skin, dendritic cells (DC), and genetically engineered mouse models. We show that c‐Jun regulates CCL2 production in DCs leading to impaired recruitment of plasmacytoid DCs to inflamed skin after treatment with the TLR7/8 agonist Imiquimod. Furthermore, deletion of c‐Jun in DCs or chemical blockade of JNK/c‐Jun signaling ameliorates psoriasis‐like skin inflammation by reducing IL‐23 production in DCs. Importantly, the control of IL‐23 and CCL2 by c‐Jun is most pronounced in murine type‐2 DCs. CCL2 and IL‐23 expression co‐localize with c‐Jun in type‐2/inflammatory DCs in human psoriatic skin and JNK‐AP‐1 inhibition reduces the expression of these targets in TLR7/8‐stimulated human DCs. Therefore, c‐Jun/AP‐1 is a central driver of TLR7‐induced immune responses by DCs and JNK/c‐Jun a potential therapeutic target in psoriasis.
Synopsis
Based on genetically engineered mouse models (GEMMs) and human psoriasis biopsies, this study suggests that c‐Jun in Dendritic Cells (DC) contributes to psoriasis by controlling CCL2 and IL‐23 production, and further identifies the JNK/c‐Jun axis as a druggable target.
TLR7 (IMQ)‐induced skin inflammation was attenuated in mice lacking c‐Jun in DCs.
TLR7/JNK/c‐Jun signalling was required for CCL2 and IL‐23 transcription in human and murine DCs.
c‐Jun was co‐expressed with CCL2 and IL‐23 in type‐2/inflammatory DCs of human psoriatic skin.
Treatment with JNK inhibitor alleviated skin inflammation in mouse models of psoriasis.
Based on genetically engineered mouse models (GEMMs) and human psoriasis biopsies, this study suggests that c‐Jun in Dendritic Cells (DC) contributes to psoriasis by controlling CCL2 and IL‐23 production, and further identifies the JNK/c‐Jun axis as a druggable target.
Although, vascular remodeling is a hallmark of many chronic inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease, and psoriasis, anti-vascular strategies to treat these ...conditions have received little attention to date. We investigated the anti-inflammatory activity of systemic blockade of VEGF-A by the inhibitory monoclonal antibody G6-31, employing a therapeutic trial in a mouse model of psoriasis. Simultaneous deletion of JunB and c-Jun (DKO*) in the epidermis of adult mice leads to a psoriasis-like phenotype with hyper- and parakeratosis and increased subepidermal vascularization. Moreover, an inflammatory infiltrate and elevated levels of cytokines/chemokines including TNFα, IL-1α/β, IL-6, and the innate immune mediators IL-22, IL-23, IL-23R, and IL-12p40 are detected. Here we show that anti-VEGF antibody treatment of mice already displaying disease symptoms resulted in an overall improvement of the psoriatic lesions leading to a reduction in the number of blood vessels and a significant decrease in the size of dermal blood and lymphatic vessels. Importantly, anti-VEGF-treated mice showed a pronounced reduction of inflammatory cells within the dermis and a normalization of epidermal differentiation. These results demonstrate that systemic blockade of VEGF by an inhibitory antibody might be used to treat patients who have inflammatory skin disorders such as psoriasis.
Cancer-associated cachexia (CAC) is a hypermetabolic syndrome characterized by unintended weight loss due to the atrophy of adipose tissue and skeletal muscle. A phenotypic switch from white to beige ...adipocytes, a phenomenon called browning, accelerates CAC by increasing the dissipation of energy as heat. Addressing the mechanisms of white adipose tissue (WAT) browning in CAC, we now show that cachexigenic tumors activate type 2 immunity in cachectic WAT, generating a neuroprotective environment that increases peripheral sympathetic activity. Increased sympathetic activation, in turn, results in increased neuronal catecholamine synthesis and secretion, β-adrenergic activation of adipocytes, and induction of WAT browning. Two genetic mouse models validated this progression of events. 1) Interleukin-4 receptor deficiency impeded the alternative activation of macrophages, reduced sympathetic activity, and restrained WAT browning, and 2) reduced catecholamine synthesis in peripheral dopamine β-hydroxylase (DBH)-deficient mice prevented cancer-induced WAT browning and adipose atrophy. Targeting the intraadipose macrophage-sympathetic neuron cross-talk represents a promising therapeutic approach to ameliorate cachexia in cancer patients.
Fibroblasts for all seasons Wagner, Erwin F
Nature (London),
02/2016, Letnik:
530, Številka:
7588
Journal Article
Recenzirano
Odprti dostop
Koliaraki and colleagues used a constitutive gene-deletion approach. Because this leads to much earlier IKKβ inhibition, the cell population had a chance to adapt to the loss of IKKβ. Besides these ...differences, the most exciting aspect of the two studies is that they raise the possibility that fibroblast subpopulations in the tumour stroma may have fundamentally different and even opposing functions in regulating tumour formation and development.
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