Project description:Dysregulation and abnormal expression of inflammatory mediators by keratinocytes promote the pathogenesis of the skin inflammation such as allergic contact dermatitis (ACD). High-mobility group box 1 (HMGB1) protein, a prototypical damage-associated molecular pattern (DAMP), that is expressed in the nucleus but released extracellularly upon inflammation has gained attention as an accelerator for skin inflammation. However, in vivo role of HMGB1 in ACD and other skin disorders remains to be elusive. In this study, we generated conditional knockout mice in which HMGB1 is deleted in keratinocytes and examined its role in skin inflammation models including 2,4-dinitrofluorobenezene (DNFB)-induced ACD. Unexpectedly, deletion of HMGB1 in keratinocytes exacerbated skin inflammation, accompanied by increased ear thickening. Elevated mRNA expression of interleukin-24 (IL-24), a known cytokine which promotes the pathogenesis of ACD, was also observed in the skin lesion of the mice. In accordance with above observations, both constitutive and IL-4-induced Il24 mRNA expression in vitro was augmented in hmgb1-deficient primary mouse keratinocytes and keratinocyte cell line PAM212 cells. Chromatin immunoprecipitation (ChIP) analysis revealed increased binding of tri-methyl histone H3 (lys4) (H3K4me3), a well-known histone mark for transcription active genes, to the promoter region of the Il24 gene in the hmgb1-deficient cells. ChIP-sequencing data also showed broad changes of H3K4me3 mark in the cells. Thus, HMGB1 in the nucleus dictates histone modifications. In conclusion, our study demonstrated a key role for HMGB1 in keratinocytes in the maintenance of chromatin modification status to protect from exuberant skin inflammation.
Project description:Regenerative responses predispose tissues to tumor formation by largely unknown mechanisms. High-mobility group box 1 (HMGB1) is a danger-associated molecular pattern contributing to inflammatory pathologies. Here, we show that HMGB1 derived from keratinocytes, but not myeloid cells, delays cutaneous wound healing and drives skin tumor formation. In wounds of mice lacking HMGB1 selectively in keratinocytes, a marked reduction in neutrophil extracellular trap (NET) formation is observed. Pharmacological targeting of HMGB1 or NETs prevents skin tumorigenesis and accelerates wound regeneration. HMGB1-dependent NET formation and skin tumorigenesis is orchestrated by the cytokine TNF and requires RIPK1 kinase activity. NETs are present in the microenvironment of keratinocyte-derived tumors in mice and lesional and tumor skin of patients suffering from Recessive Dystrophic Epidermolysis Bullosa (RDEB), a disease in which skin blistering predisposes to tumorigenesis. We conclude that tumorigenicity of the wound microenvironment depends on epithelial-derived HMGB1 regulating NET formation, thereby establishing a mechanism linking reparative inflammation to tumor initiation.
Project description:The DEAD-box (DDX) proteins function in diverse cellular processes including RNA alternative splicing, and are linked to immune-mediated diseases. However, little is known about the roles of DDXs in skin inflammatory diseases. Here, we show that DDX5, one of the founding members of the DDX RNA helicase family, controls skin inflammation and participates in the pathogenesis of psoriasis via regulating IL-36R pre-mRNA splicing. We found that both mRNA and protein of DDX5 are decreased in lesional skin from patients with psoriasis and psoriasis-like mice, and that mice with keratinocyte-specific ablation of DDX5 spontaneously develop psoriasis-like phenotypes. Mechanistically, DDX5 complexes with serine/arginine-rich splicing factor 1(SRSF1) to typically regulate IL-36R pre-mRNA splicing in keratinocytes, which generates mRNAs encoding full-length IL-36R and a previously unknown soluble form of IL-36R (sIL-36R). sIL-36R controls IL-36/IL-36R signaling by competing with IL-36R for IL-36γ ligation. The reduction or deficiency of DDX5 leads to IL-36R pre-mRNA splicing preferring to the generation of IL-36R but not sIL-36R, thereby selectively amplifying inflammatory responses of keratinocytes to IL-36γ and then aggravating cutaneous inflammation in psoriasis. Genetic restoration or intradermal administration of sIL-36R in psoriasis-like mice suppresses IL-36R signaling and alleviates the disease phenotype of psoriasis. Altogether, these data reveal a pathogenic role of DDX5 during psoriasis, and provide mechanistic insights into the regulation of IL-36R splicing and its impact on psoriasis development.
Project description:FGFs are key orchestrators of development, tissue homeostasis and repair. FGFR deficiency in mouse keratinocytes causes an inflammatory skin phenotype resembling atopic dermatitis (AD). To determine the human relevance of this finding, we generated human keratinocytes with a CRISPR/Cas9-induced knockout of FGFR2. Loss of this receptor promoted the expression of interferon-stimulated genes and other genes involved in inflammation under homeostatic conditions and in particular in response to inflammatory mediators without affecting cell viability. Bioinformatics analyses and functional studies showed strong down-regulation of FGFR2 expression in cultured keratinocytes exposed to various pro-inflammatory stimuli and in keratinocytes of lesional AD skin, which is likely to further aggravate the inflammatory phenotype. These results reveal a key function of FGFR2 in human keratinocytes in the suppression of skin inflammation and suggests a role of FGFR2 down-regulation in AD pathogenesis.
Project description:The epidermis, outermost layer of the skin, forms a barrier and is involved in innate and adaptive immunity in an organism. Keratinocytes participate in all these three protective processes. However, a regulator of keratinocyte protective responses against external dangers and stresses remains elusive. We found that upregulation of the orphan gene 2610528A11Rik was a common factor in the skin of mice with several types of inflammation. In the human epidermis, peptide expression of G protein-coupled receptor 15 ligand (GPR15L), encoded by the human ortholog C10orf99, was highly induced in the lesional skin of patients with atopic dermatitis or psoriasis. C10orf99 gene transfection into normal human epidermal keratinocytes (NHEKs) induced the expression of inflammatory mediators and reduced the expression of barrier-related genes. Gene ontology analyses showed its association with translation, mitogen-activated protein kinase (MAPK), mitochondria, and lipid metabolism. Treatment with GPR15L reduced the expression levels of filaggrin and loricrin in human keratinocyte 3D cultures. Instead, their expression levels in mouse primary cultured keratinocytes did not show significant differences between the wild-type and 2610528A11Rik deficient keratinocytes. Lipopolysaccharide-induced expression of Il1b and Il6 was less in 2610528A11Rik deficient mouse keratinocytes than in wild-type, and imiquimod-induced psoriatic dermatitis was blunted in 2610528A11Rik deficient mice. Furthermore, repetitive subcutaneous injection of GPR15L in mouse ears induced skin inflammation in a dose-dependent manner. These results suggest that C10orf99/GPR15L is a primary inducible regulator that reduces the barrier formation and induces the inflammatory response of keratinocytes.
Project description:Psoriasis is a chronic inflammatory skin disorder underpinned by dysregulated cytokine signaling. Drugs neutralizing the common p40 subunit of IL-12 and IL-23 represented a therapeutic breakthrough; however, new drugs that block the IL-23p19 subunit and spare IL-12 are more effective, suggesting a regulatory function of IL-12. In order to pinpoint the cell type and underlying mechanism of IL-12 mediated immune-regulation in psoriasis we generated a conditional Il12rb2-knockout (KO)/reporter mouse strain. We detected Il12rb2 expression in T cells and a specific subset of interfollicular (IF) keratinocytes. Analysis of scRNAseq data from psoriasis patients confirmed this expression pattern in the human skin. Mechanistically, deletion of Il12rb2 in the keratinocyte compartment led to exacerbated psoriasiform inflammation. Protective IL-12 signaling blocked the hyperproliferation of keratinocytes, maintained skin barrier integrity, and, importantly, diminished disease-driving IL-23/type 3 immune circuits. Collectively, we provide a potential explanation for the superior efficacy of IL-23p19 inhibitors in psoriasis and describe an unperceived role of IL-12 in maintaining skin epithelial cell homeostasis.
Project description:Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from human skin keratinocytes derived from healthy donors, as well as from telomerase immortalised human skin keratinocytes (N/TERT), transduced with mock, EGFP, or EGFP-GLI2DeltaN transgenes to compare chromosomal ploidy status. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from human skin keratinocytes derived from healthy donors, as well as from telomerase immortalised human skin keratinocytes (N/TERT) to compare chromosomal ploidy status
Project description:Strong inhibition of NF-kB signaling in the epidermis results in spontaneous skin inflammation in mice and men. Since there is evidence for linkage between polymorphisms within the NF-kB signaling pathway and human inflammatory skin phenotypes, we asked whether partial functional inhibition of NF-kB signaling in epidermal keratinocytes can modulate clinically relevant skin inflammation. We therefore mutated rela specifically in the epidermis of mice (RelAE-MUT mice). These mice show no inflammatory phenotype. Induction of contact allergy, but not croton oil induced irritant dermatitis, resulted in stronger ear swelling and increased epidermal thickness in RelAE-MUT mice. Both contact allergen and croton oil treatment led to increase expression of calgranulins A and B (S100A8/ A9) in RelAE-MUT mice. Epidermal hyperproliferation in RelAE-MUT mice was non-cell autonomous since cultured primary epidermal keratinocytes from RelAE-MUT mice showed reduced proliferation compared to controls. These results demonstrate that epidermal RelA specifically regulates DTH-induced skin inflammation. In addition, we here describe an essential but non- specific function of RelA in the protection of epidermal keratinocytes from apoptosis. Our study identifies new functions of NF-kB signaling in the epidermis and corroborates a specific role of epidermal keratinocytes in the regulation of skin inflammation