CCL27 expression is regulated by both p38 MAPK and IKKβ signalling pathways

UBE2N Is Essential for Maintenance of Skin Homeostasis and Suppression of Inflammation

UBE2N, a Lys63 ubiquitin-conjugating enzyme, plays critical roles in embryogenesis and immune system development and function. However, its roles in adult epithelial tissue homeostasis and pathogenesis are unclear. We generated conditional mouse models that deleted Ube2n in skin cells in a temporally and spatially controlled manner. We found that Ube2n knockout in the adult skin keratinocytes induced a range of inflammatory skin defects characteristic of psoriatic and actinic keratosis. These included inflammation, epidermal and dermal thickening, parakeratosis, and increased immune cell infiltration as well as signs of edema and blistering. Single-cell transcriptomic analyses and RT-qPCR showed that Ube2n-knockout keratinocytes expressed elevated myeloid cell chemoattractants such as Cxcl1 and Cxcl2 and decreased the homeostatic T lymphocyte chemoattractant Ccl27a. Consistently, the infiltrating immune cells were predominantly myeloid-derived cells, including neutrophils and M1-like macrophages, which expressed high levels of inflammatory cytokines such as Il1β and Il24. Pharmacological blockade of the IL-1 receptor associated kinases (IRAK1/4) alleviated inflammation, epidermal and dermal thickening, and immune infiltration of the Ube2n-mutant skin. Together, these findings highlight a key role of keratinocyte UBE2N in maintenance of epidermal homeostasis and skin immunity and identify IRAK1/4 as potential therapeutic target for inflammatory skin disorders.

UBE2N is essential for maintenance of skin homeostasis and suppression of inflammation

UBE2N, a Lys63-ubiquitin conjugating enzyme, plays critical roles in embryogenesis and immune system development and function. However, its roles in adult epithelial tissue homeostasis and pathogenesis are unclear. We generated conditional mouse models that deleted Ube2n in skin cells in a temporally and spatially controlled manner. We found that Ube2n-knockout (KO) in the adult skin keratinocytes induced a range of inflammatory skin defects characteristic of psoriatic and actinic keratosis. These included eczematous inflammation, epidermal and dermal thickening, parakeratosis, and increased immune cell infiltration, as well as signs of edema and blistering. Single cell transcriptomic analyses and RT-qPCR showed that Ube2n KO keratinocytes expressed elevated myeloid cell chemo-attractants such as Cxcl1 and Cxcl2 and decreased the homeostatic T lymphocyte chemo-attractant, Ccl27a. Consistently, the infiltrating immune cells of Ube2n-KO skin were predominantly myeloid-derived cells including neutrophils and M1-like macrophages that were highly inflammatory, as indicated by expression of Il1β and Il24. Pharmacological blockade of the IL-1 receptor associated kinases (IRAK1/4) alleviated eczema, epidermal and dermal thickening, and immune infiltration of the Ube2n mutant skin. Together, these findings highlight a key role of keratinocyte-UBE2N in maintenance of epidermal homeostasis and skin immunity and identify IRAK1/4 as potential therapeutic target for inflammatory skin disorders.

CCL27 is a crucial regulator of immune homeostasis of the skin and mucosal tissues

Abundant immune cells reside in barrier tissues. Understanding the regulation of these cells can yield insights on their roles in tissue homeostasis and inflammation. Here, we report that the chemokine CCL27 is critical for establishment of resident lymphocytes and immune homeostasis in barrier tissues. CCL27 expression is associated with normal skin and hair follicle development independent of commensal bacterial stimulation, indicative of a homeostatic role for the chemokine. Accordingly, in the skin of CCL27-knockout mice, there is a reduced presence and dysregulated localization of T cells that express CCR10, the cognate receptor to CCL27. Besides, CCL27-knockout mice have overreactive skin inflammatory responses in an imiquimod-induced model of psoriasis. Beyond the skin, CCL27-knockout mice have increased infiltration of CCR10⁺ T cells into lungs and reproductive tracts, the latter of which also exhibit spontaneous inflammation. Our findings demonstrate that CCL27 is critical for immune homeostasis across barrier tissues.

The ERK-p38MAPK-STAT3 Signalling Axis Regulates iNOS Expression and Salmonella Infection in Senescent Cells

The cellular changes occurring due to senescence like proliferation arrest, increase in free radical levels, and secretion of pro-inflammatory cytokines have been well studied, but its associated alteration in intracellular signalling networks has been scarcely explored. In this study, we examine the roles of three major kinases viz. p38 MAPK, ERK, and STAT3 in regulating iNOS expression and thereby the levels of the free radical Nitric oxide in senescent cells. Our study revealed that these kinases could differentially regulate iNOS in senescent cells compared to non-senescent cells. Further, we tested the physiological relevance of these alterations with Salmonella infection assays and established an inter-regulatory network between these kinases unique to infected senescent cells. Overall, our findings show how key signalling networks may be rewired in senescent cells rendering them phenotypically different.

Regulation of connexin 43 by interleukin 1β in adult rat cardiac fibroblasts and effects in an adult rat cardiac myocyte: fibroblast co-culture model

Connexin 43 expression (Cx43) is increased in cardiac fibroblasts (CFs) following myocardial infarction. Here, potential mediators responsible for increasing Cx43 expression and effects of differential CF phenotype on cardiac myocyte (CM) function were investigated. Stimulating adult rat CFs with proinflammatory mediators revealed that interleukin 1β (IL-1β) significantly enhanced Cx43 levels through the IL-1β pathway. Additionally, IL-1β reduced mRNA levels of the myofibroblast (MF) markers: (i) connective tissue growth factor (CTGF) and (ii) α smooth muscle actin (αSMA), compared to control CFs. A co-culture adult rat CM:CF model was utilised to examine cell-to-cell interactions. Transfer of calcein from CMs to underlying CFs suggested functional gap junction formation. Functional analysis revealed contraction duration (CD) of CMs was shortened in co-culture with CFs, while treatment of CFs with IL-1β reduced this mechanical effect of co-culture. No effect on action potential rise time or duration of CMs cultured with control or IL-1β-treated CFs was observed. These data demonstrate that stimulating CFs with IL-1β increases Cx43 and reduces MF marker expression, suggesting altered cell phenotype. These changes may underlie the reduced mechanical effects of IL-1β treated CFs on CD of co-cultured CMs and therefore have an implication for our understanding of heterocellular interactions in cardiac disease.

Silkworm dropping extract ameliorate trimellitic anhydride-induced allergic contact dermatitis by regulating Th1/Th2 immune response

Allergic contact dermatitis (ACD) is an inflammatory skin disease caused by hapten-specific immune response. Silkworm droppings are known to exert beneficial effects during the treatment of inflammatory diseases. Here, we studied whether topical treatment and oral administration of silkworm dropping extract (SDE) ameliorate trimellitic anhydride (TMA)-induced ACD. In ACD mice model, SDE treatment significantly suppressed the increase in both ear thickness and serum IgE levels. Furthermore, IL-1β and TNF-α levels were reduced by SDE. In allergic responses, SDE treatment significantly attenuated the production of the Th2-associated cytokine IL-4 in both ear tissue and draining lymph nodes. However, it increased the production of the Th1-mediated cytokine IL-12. Thus, these results showed that SDE attenuated TMA-induced ACD symptoms through regulation of Th1/Th2 immune response. Taken together, we suggest that SDE treatment might be a potential agent in the prevention or therapy of Th2-mediated inflammatory skin diseases such as ACD and atopic dermatitis.

ABBREVIATIONS

ACD: allergic contact dermatitis; AD: atopic dermatitis; APC: antigen presenting cells; CCL: chemokine (C-C motif) ligand; CCR: C-C chemokine receptor; Dex: dexamethasone; ELISA: enzyme-linked immunosorbent assay; IFN: interferon; Ig: immunoglobulin; IL: interleukin; OVA: ovalbumin; PS: prednisolone; SDE: silkworm dropping extract; Th: T helper; TMA: trimellitic anhydride; TNF: tumor necrosis factor.

CCR10/CCL27 crosstalk contributes to failure of proteasome-inhibitors in multiple myeloma

The bone marrow microenvironment plays a decisive role in multiple myeloma progression and drug resistance. Chemokines are soluble mediators of cell migration, proliferation and survival and essentially modulate tumor progression and drug resistance. Here we investigated bone marrow-derived chemokines of naive and therapy-refractory myeloma patients and discovered that high levels of the chemokine CCL27, known so far for its role in skin inflammatory processes, correlated with worse overall survival of the patients. In addition, chemokine levels were significantly higher in samples from patients who became refractory to bortezomib at first line treatment compared to resistance at later treatment lines.

In vitro as well as in an in vivo model we could show that CCL27 triggers bortezomib-resistance of myeloma cells. This effect was strictly dependent on the expression of the respective receptor, CCR10, on stroma cells and involved the modulation of IL-10 expression, activation of myeloma survival pathways, and modulation of proteasomal activity. Drug resistance could be totally reversed by blocking CCR10 by siRNA as well as blocking IL-10 and its receptor.

From our data we suggest that blocking the CCR10/CCL27/IL-10 myeloma-stroma crosstalk is a novel therapeutic target that could be especially relevant in early refractory myeloma patients.

Establishment and function of tissue-resident innate lymphoid cells in the skin

Innate lymphoid cells (ILCs) are a newly classified family of immune cells of the lymphoid lineage. While they could be found in both lymphoid organs and non-lymphoid tissues, ILCs are preferentially enriched in barrier tissues such as the skin, intestine, and lung where they could play important roles in maintenance of tissue integrity and function and protection against assaults of foreign agents. On the other hand, dysregulated activation of ILCs could contribute to tissue inflammatory diseases. In spite of recent progress towards understanding roles of ILCs in the health and disease, mechanisms regulating specific establishment, activation, and function of ILCs in barrier tissues are still poorly understood. We herein review the up-to-date understanding of tissue-specific relevance of ILCs. Particularly we will focus on resident ILCs of the skin, the outmost barrier tissue critical in protection against various foreign hazardous agents and maintenance of thermal and water balance. In addition, we will discuss remaining outstanding questions yet to be addressed.

NF-κB and STAT3 inhibition as a therapeutic strategy in psoriasis: in vitro and in vivo effects of BTH

Benzo[b]thiophen-2-yl-3-bromo-5-hydroxy-5H-furan-2-one (BTH) is a simple and interesting synthetic derivative of petrosaspongiolide M, a natural compound isolated from a sea sponge with demonstrated potent anti-inflammatory activity through inhibition of the NF-κB signaling pathway. In the present study, we report the in vitro and in vivo pharmacological effect of BTH on some parameters related to the innate and adaptive response in the pathogenesis of psoriasis. BTH inhibited the release of some of the key psoriatic cytokines such as tumor necrosis factor α, IL-8, IL-6, and CCL27 through the downregulation of NF-κB in normal human keratinocytes. Moreover, it impaired signal transducers and activators of transcription 3 (STAT3) phosphorylation and translocation to the nucleus, which resulted in decreased keratinocyte proliferation. These results were confirmed in vivo in two murine models of psoriasis: the epidermal hyperplasia induced by 12-O-tetradecanoylphorbol-13-acetate and the imiquimod-induced skin inflammation model. In both cases, topical administration of BTH prevented skin infiltration and hyperplasia through suppression of NF-κB and STAT3 phosphorylation. Our results confirm the pivotal role of both transcriptional factors in skin inflammation, as occurs in psoriasis, and highlight the potential of small molecules as therapeutic agents for the treatment of this skin disease, with BTH being a potential candidate for future drug research.

CCR10 and its ligands in regulation of epithelial immunity and diseases

Epithelial tissues covering the external and internal surface of a body are constantly under physical, chemical or biological assaults. To protect the epithelial tissues and maintain their homeostasis, multiple layers of immune defense mechanisms are required. Besides the epithelial tissue-resident immune cells that provide the first line of defense, circulating immune cells are also recruited into the local tissues in response to challenges. Chemokines and chemokine receptors regulate tissue-specific migration, maintenance and functions of immune cells. Among them, chemokine receptor CCR10 and its ligands chemokines CCL27 and CCL28 are uniquely involved in the epithelial immunity. CCL27 is expressed predominantly in the skin by keratinocytes while CCL28 is expressed by epithelial cells of various mucosal tissues. CCR10 is expressed by various subsets of innate-like T cells that are programmed to localize to the skin during their developmental processes in the thymus. Circulating T cells might be imprinted by skin-associated antigen- presenting cells to express CCR10 for their recruitment to the skin during the local immune response. On the other hand, IgA antibody-producing B cells generated in mucosa-associated lymphoid tissues express CCR10 for their migration and maintenance at mucosal sites. Increasing evidence also found that CCR10/ligands are involved in regulation of other immune cells in epithelial immunity and are frequently exploited by epithelium-localizing or -originated cancer cells for their survival, proliferation and evasion from immune surveillance. Herein, we review current knowledge on roles of CCR10/ligands in regulation of epithelial immunity and diseases and speculate on related important questions worth further investigation.